Power conversion system and power updating control method

Abstract

The invention discloses a power conversion system and a power update control method, and the system comprises N power conversion units and a control unit, and the control unit selects a target power conversion unit and a cooperative power conversion unit in a control period. Controlling the working mode of the target power conversion unit to perform mode switching according to the sequence of a power reservation (PR) mode and a maximum power point tracking (MPPT) mode, updating the reference power according to the maximum power obtained in the MPPT mode, and enabling the working power of the target power conversion unit in the PR mode to be the updated reference power, and the updated reference power is smaller than or equal to the maximum power. And the control unit controls the working power of the cooperative power conversion units to perform cooperative adjustment, so that the total variable quantity of the working power of the N power conversion units is smaller than a variable quantity threshold value, the total variable quantity of the working power of the N power conversion units becomes smaller, and fluctuation of the total output power and the output voltage of the power conversion units is reduced.

Description

Technical Field

[0001] The present application relates to the field of power electronics technology, and in particular to a power conversion system and a power update control method. Background Art

[0002] The power supply system is a new type of power generation system that uses the photovoltaic effect of photovoltaic modules to convert solar radiation energy into electrical energy. The power converter is the core component of the power supply system, which is mainly responsible for converting the direct current generated by the photovoltaic module into alternating current and outputting the alternating current to the power grid. The inverter usually includes a power conversion unit. By controlling the power conversion unit to work in the maximum power point tracking (MPPT) mode, the maximum power of the photovoltaic module can be tracked, so that the power supply system can work at the maximum power point in real time.

[0003] In practical applications, the voltage amplitude, frequency, and phase on the power grid will have dynamic fluctuations, and the power conversion unit works in the MPPT mode, which makes the power supply system unable to freely adjust the power to support the power during the dynamic fluctuation of the power grid (it can only reduce the power in one direction, but cannot increase the power). Based on this, by reserving power (power reserve, PR) for the output power of the photovoltaic module, that is, controlling the power conversion unit to work in the PR mode, so that the output power of the photovoltaic module is lower than the maximum power, the power supply system can increase and reduce the output power based on the reserved power during the period when the voltage amplitude, frequency, and phase of the power grid are in dynamic fluctuations, so as to meet the needs of the power grid. In addition, when the power conversion unit works in the PR mode, it is also necessary to rely on the MPPT mode to detect the maximum power of the photovoltaic module, which causes the power conversion unit to switch between the PR mode and the MPPT mode, resulting in fluctuations in the total output power and output voltage of the power conversion unit, endangering the stability and control accuracy of the power supply system, and even increasing the mechanical stress and thermal stress of the equipment. Summary of the invention

[0004] The embodiments of the present application provide a power conversion system and a power update control method, which are used to timely and accurately update the working power of the power conversion unit in the PR mode through maximum power tracking, and reduce the fluctuation of the total output power and output voltage of the power conversion unit.

[0005] In the first aspect, an embodiment of the present application provides a power conversion system, which includes: N power conversion units and a control unit, N is an integer and N≥2; the first end of each power conversion unit is used to connect to a DC power supply or an AC power supply, the second end of each power conversion unit is used to connect to a load or an energy storage unit or a power generation unit or a power grid, and each power conversion unit is used to convert the DC power input by the DC power supply or the AC power input by the AC power supply and then output it. In addition, the control unit controls the working mode of one or more target power conversion units in the N power conversion units to switch between the power reservation PR mode and the maximum power point tracking MPPT mode during the control cycle, and after the working mode of the target power conversion unit is switched to the MPPT mode, the maximum power can be obtained in the MPPT mode. Therefore, the reference power can be updated according to the maximum power obtained in the MPPT mode to obtain the updated reference power, so that the working power of the target power conversion unit after switching from the MPPT mode to the PR mode can be changed to the updated reference power, and the updated reference power is less than or equal to the maximum power. And, in the control cycle, the working modes of the cooperative power conversion units except the target power conversion unit among the N power conversion units are controlled to remain unchanged, so that the cooperative power conversion unit does not switch modes. In addition, the control unit also controls the cooperative adjustment of the working power of the cooperative power conversion unit according to the working power change of the target power conversion unit during the mode switching process, so that the total change of the working power of the N power conversion units is less than the change threshold. With this arrangement, the working power change of the cooperatively adjusted cooperative power conversion unit and the working power change of the target power conversion unit during the mode switching process are offset as much as possible, so that the total change of the working power of the N power conversion units is as small as possible, thereby reducing the fluctuation of the total output power and output voltage of the power conversion unit, and improving the stability and control accuracy of the power supply system.

[0006] It is understandable that the updated reference power P res ' is less than the maximum power P mpp , in order to realize photovoltaic grid construction. Of course, in practical applications, it is also possible to make P res '=P mpp , which is not limited here. In addition, the change threshold may be 0±ΔPth. When the total change of the working power of the N power conversion units is less than the change threshold, it can be indicated that the total change of the working power of the N power conversion units is as small as possible or negligible. Among them, ΔPth may be a value such as 0, 0.01, 0.05, etc. Alternatively, ΔPth may also be an allowable error range.

[0007] Furthermore, through the above-mentioned embodiments, the mechanical and thermal stresses of the power conversion system equipment can be reduced, thereby improving the overall stability of the power conversion system.

[0008] In specific applications, when the target power conversion unit operates in the MPPT mode, the corresponding maximum power P mpp will be greater than the original reference power P res . Since the updated reference power P res ' is less than or equal to the maximum power P mpp , the updated reference power P res ' and the original reference power P res have the following relationship: P res ' > P res , or P res ' < P res , or, P res ' = P res .

[0009] In some embodiments, the N power conversion units include k target power conversion units and m cooperative power conversion units, and k is an integer and 1 ≤ k ≤ N - 1, m is an integer and 1 ≤ m ≤ N - 1, 2 ≤ k + m ≤ N. Wherein, k can select a suitable value from 1, 2, 3,..., N - 1, and m can also select a suitable value from 1, 2, 3,..., N - 1, but k and m need to satisfy 2 ≤ k + m ≤ N. For example, when k + m = N, the cooperative power conversion units are all the remaining power conversion units among the N power conversion units except the target power conversion units. When m + k < N, the cooperative power conversion units are some of the N power conversion units except the target power conversion units. Based on this, the part of the N power conversion units except the target power conversion units and the cooperative power conversion units can operate in the PR mode. It can be understood that the value of k in each control cycle can be the same, or the value of k in some control cycles can be the same, and the value of k in some control cycles can be different, or the value of k in each control cycle can be different. And, the value of m in each control cycle can be the same, or the value of m in some control cycles can be the same, and the value of m in some control cycles can be different, or the value of m in each control cycle can be different. In addition, m = k or m > k or m < k can also be set in the same control cycle.

[0010] In some embodiments, the working power variation of each target power conversion unit during the mode switching process includes a target power variation, which is the variation between the instantaneous working power of the target power conversion unit during the mode switching process and the reference power. In addition, the working power variation of each cooperative power conversion unit during the cooperative adjustment process includes a cooperative power variation, which is the variation between the instantaneous working power of the cooperative power conversion unit during the cooperative adjustment process and the set power. By making the sum of the cooperative power variation opposite to the sum of the target power variation, and the difference between the absolute value of the sum of the cooperative power variation and the absolute value of the sum of the target power variation is less than the variation threshold. Thus, the total variation of the working power of the N power conversion units is made as small as possible or even negligible, thereby reducing the fluctuation of the output power and output voltage of the power conversion unit, and improving the stability and control accuracy of the power supply system.

[0011] Exemplarily, the difference between the absolute value of the sum of the coordinated power variations and the absolute value of the sum of the target power variations may be a difference or a ratio between the absolute value of the sum of the coordinated power variations and the absolute value of the sum of the target power variations.

[0012] In the present application, since the sum of the coordinated power changes is related to the sum of the target power changes, based on this, each coordinated power change is determined according to the sum of the target power changes.

[0013] Exemplarily, the coordinated power change corresponding to the yth coordinated power conversion unit among the m coordinated power conversion units is: y *ΔP msm , ΔP msm represents the sum of the target power changes, and y is an integer and y∈[1,m]. And α y represents the allocation weight corresponding to the y-th cooperative power conversion unit, and α y ∈[0, 1]. By setting this, the sign of the cooperative power change corresponding to each cooperative power conversion unit can be opposite to the sum of the target power change, and the distribution weight α can be used to y , ΔP msm Distributed to different collaborative power conversion units.

[0014] It is understandable that each assigned weight α y The configuration can be performed offline or online. In addition, the sum of the allocation weights corresponding to the m coordinated power conversion units can be 1, that is, It is understandable that the sum of the allocation weights corresponding to the m collaborative power conversion units is 1, which is a theoretical value. In specific applications, since there may be an error between the sum of the collaborative power changes and the sum of the target power changes when the test equipment outputs power, the sum of the allocation weights corresponding to the m collaborative power conversion units may not be 1, but it only needs to meet the error tolerance condition.

[0015] In the present application, each cooperative power variation can also be determined according to a constant cooperative power setting value. syn0 It is a preset parameter of power coordination, which can be configured not only as a required fixed value or variable value online or offline, but also according to the maximum power obtained in MPPT mode.

[0016] Exemplarily, the coordinated power change corresponding to the zth coordinated power conversion unit among the m coordinated power conversion units is: z *ΔP syn0 , α z represents the allocation weight corresponding to the zth cooperative power conversion unit, and α z ∈[0, 1], ΔP syn0 Represents a constant cooperative power setting value. By setting this, the sign of the cooperative power change corresponding to each cooperative power conversion unit can be opposite to the sum of the target power change, and the distribution weight α can be used to z , ΔP syn0 Distributed to different coordinated power conversion units. It can be understood that α z The implementation method can refer to α y The specific implementation method will not be described here.

[0017] In some embodiments, each coordinated power variation and each target power variation are made to appear in the same stage. That is, the appearance time of each coordinated power variation is made the same as the appearance time of each target power variation, and the end time of each coordinated power variation is made the same as the end time of each target power variation. With this arrangement, the timeliness of coordinated control can be improved, so that when the working power variation appears in the target power conversion unit, the coordinated power conversion unit can be timely controlled to coordinately adjust the occurrence of coordinated power variation, so as to offset the working power variation through the coordinated power variation, thereby reducing the fluctuation of the output power and output voltage of the power conversion unit.

[0018] In some embodiments, the stage at which each coordinated power variation occurs is later than the stage at which each working power variation occurs, that is, the stage at which each coordinated power variation occurs is delayed as a whole compared to the stage at which each working power variation occurs. For example, the stage at which each coordinated power variation occurs is delayed as a whole compared to the stage at which each working power variation occurs by a delay time parameter T delay That is, the occurrence time of each coordinated power variation is later than the occurrence time of each target power variation by a certain delay time parameter T delay , and the end time of each coordinated power variation is also later than the end time of each target power variation by a certain delay time parameter T delay It is understandable that, due to the fact that during the actual operation of the power conversion system, there will be a certain delay in signal transmission, so the delay time parameter T delay It may refer to the delay that occurs when the power conversion system is running, which is not set manually online or offline. Of course, in order to match the delay of the power conversion system, the delay time parameter T can also be set manually online or offline. delay Can be a fixed value or a changing value.

[0019] In some embodiments, a reference threshold can also be set so that the sum of the target power changes is compared with the reference threshold, and the control unit controls the coordinated power conversion unit to perform corresponding work according to the comparison result. For example, in response to the sum of the target power changes being greater than or equal to the reference threshold, the control unit controls the working power of the coordinated power conversion unit to be coordinated and adjusted based on the set power according to the working power change of the target power conversion unit during the mode switching process. The target power change is the change between the instantaneous working power of the target power conversion unit during the mode switching process and the reference power.

[0020] In the present application, the working mode of the collaborative power conversion unit remains unchanged, which means that the working mode of the collaborative power conversion unit does not switch modes, but works constantly in one working mode. For example, the working mode of the collaborative power conversion unit is PR mode. With this setting, all power conversion units can work in PR mode to realize photovoltaic network construction. In addition, some power conversion units are used as target power conversion units to switch between PR mode and MPPT mode, and one or part or all of the remaining power conversion units are used as collaborative power conversion units and are constantly in PR mode, which can reduce the fluctuation of the total output power and output voltage of the power conversion unit and improve the stability and control accuracy of the power supply system. And, when the target power conversion unit works in MPPT mode, the working power of the collaborative power conversion unit in PR mode is the original reference power. In order to enable the reference power of the collaborative power conversion unit in PR mode to be updated accordingly, after the target power conversion unit updates the reference power, the working power of the collaborative power conversion unit is also switched to the updated reference power. It is understandable that after the target power conversion unit updates the reference power, there is no need to update the reference power of the collaborative power conversion unit in the PR mode. Instead, the reference power of the collaborative power conversion unit in the PR mode is controlled to continue to work using the reference power in the previous control cycle.

[0021] In some embodiments, the target power conversion unit and / or the collaborative power conversion unit are randomly selected. Specifically, the target power conversion unit is randomly selected from N power conversion units. The collaborative power conversion unit can also be randomly selected from N power conversion units. With this arrangement, the target power conversion unit and / or the collaborative power conversion unit can be selected by random selection.

[0022] Exemplarily, each power conversion unit has the same probability of being selected as the target power conversion unit.

[0023] Exemplarily, the probabilities of at least some of the power conversion units being selected as target power conversion units are different.

[0024] Exemplarily, each power conversion unit has the same probability of being selected as a cooperative power conversion unit.

[0025] Exemplarily, the probability of at least some of the power conversion units being selected as cooperative power conversion units is different.

[0026] In some embodiments, the target power conversion unit can also be selected from the N power conversion units in sequence. The cooperative power conversion unit can also be selected from the N power conversion units in sequence.

[0027] Exemplarily, the N power conversion units include the 1st unit group to the Mth unit group arranged in sequence, and any unit group includes one or more power conversion units, M is an integer and M≥2. The continuous multiple cycle periods include one or a combination of the first cycle period and the second cycle period. Among them, in the first cycle period, a unit group selected in sequence from the 1st unit group to the Mth unit group is used as the target power conversion unit. And, in the second cycle period, a unit group selected in sequence from the Mth unit group to the 1st unit group is used as the target power conversion unit.

[0028] In some examples, the power conversion unit includes a direct current-direct current (DC-DC) conversion circuit, and the power conversion system also includes a direct current-alternating current (DC-AC) conversion circuit. Wherein, the first end of the direct current-direct current conversion circuit is used to connect to a direct current power supply, the second end of the direct current-direct current conversion circuit is connected to the first end of the direct current-alternating current conversion circuit, and the second end of the direct current-alternating current conversion circuit is used to connect to a load or a power grid. Exemplarily, the DC-DC conversion circuit is used to convert the direct current input by the direct current power supply into alternating current and output it to the load or the power grid.

[0029] In some other examples, the power conversion unit includes a direct current-alternating current (DC-AC) conversion circuit. The first end of the direct current-alternating current conversion circuit is used to connect to a direct current power source, and the second end of the direct current-alternating current conversion circuit is used to connect to a load or a power grid or an alternating current system. Exemplarily, the DC-AC conversion circuit is used to convert direct current input from a direct current power source into alternating current and then output it to a load or a power grid or an alternating current system.

[0030] In some other examples, the power conversion unit includes a direct current-to-direct current (DC-DC) conversion circuit. The first end of the direct current-to-direct current conversion circuit is used to connect a direct current power supply, and the second end of the direct current-to-direct current conversion circuit is used to connect a load or an energy storage unit or a power generation unit. Exemplarily, the DC-DC conversion circuit is used to convert the direct current input by the direct current power supply into power and output it to the load or the energy storage unit or the power generation unit. Alternatively, the DC-DC conversion circuit can also be used to convert the direct current input by the energy storage unit or the power generation unit into power and output it to the direct current power supply.

[0031] In some other examples, the power conversion unit includes an alternating current-direct current (AC-DC) conversion circuit. The first end of the AC-DC conversion circuit is used to connect to an AC power source, and the second end of the AC-DC conversion circuit is used to connect to a load or an energy storage unit or a power generation unit. Exemplarily, the AC-DC conversion circuit is used to convert the AC power input from the AC power source into DC power and then output it to the load or the energy storage unit or the power generation unit. Alternatively, the AC-DC conversion circuit can also be used to convert the DC power input from the energy storage unit or the power generation unit into AC power and then output it to the AC power source.

[0032] In some other examples, the power conversion system includes an AC-DC (AC-DC) conversion circuit, and the power conversion system also includes a DC-AC (DC-AC) conversion circuit. Wherein, the first end of the AC-DC conversion circuit is used to connect to an AC power supply, the second end of the AC-DC conversion circuit is connected to the first end of the DC-AC conversion circuit, and the second end of the DC-AC conversion circuit is used to connect to a load or a power grid. Exemplarily, the AC-DC conversion circuit is used to convert the AC power input from the AC power supply into DC power and then output it to the DC-AC conversion circuit, and the DC-AC conversion circuit is used to convert the input DC power into AC power and then output it to a load or an energy storage unit or a power generation unit. Alternatively, the DC-AC conversion circuit can also convert the AC power input from the energy storage unit or the power generation unit into DC power and then output it to the AC-DC conversion circuit, and the AC-DC conversion circuit can convert the input DC power into AC power and then output it to the AC power supply.

[0033] In a specific implementation, the control unit can be a field programmable gate array (FPGA), a central processing unit (CPU), a general-purpose processor, a digital signal processing (DSP), an application specific integrated circuit (ASIC), or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. It can implement or execute various exemplary logic blocks, modules, and circuits described in conjunction with the disclosure of this application. The above-mentioned control unit can also be a combination that implements computing functions, such as a combination of one or more microprocessors, a combination of a DSP and a microprocessor, etc.

[0034] In the second aspect, the embodiment of the present application also provides a power update control method, which is applied to a power conversion system, wherein the power conversion system includes N power conversion units, where N is an integer and N≥2; the first end of each power conversion unit is used to connect to a DC power supply or an AC power supply, and the second end of each power conversion unit is used to connect to a load or an energy storage unit or a power grid, and the power conversion unit is used to convert the DC power input by the DC power supply or the AC power input by the AC power supply and output it. In addition, the power update control method includes: controlling the working mode of one or more target power conversion units among the N power conversion units to switch between the power reservation PR mode and the maximum power point tracking MPPT mode, updating the reference power according to the maximum power obtained in the MPPT mode, so that the working power of the target power conversion unit after switching from the MPPT mode to the PR mode is the updated reference power; wherein the updated reference power is less than or equal to the maximum power. In addition, the working modes of the cooperative power conversion units except the target power conversion unit among the N power conversion units are controlled to remain unchanged, and according to the change in the working power of the target power conversion unit during the mode switching process, the working power of the cooperative power conversion unit is controlled to be cooperatively adjusted based on the set power, so that the total change in the working power of the N power conversion units is less than the change threshold.

[0035] In a third aspect, an embodiment of the present application further provides a power supply system, which includes a power conversion system, wherein the first end of the power conversion unit in the power conversion system is connected to a DC power supply or an AC power supply, and the second end of the power conversion system is used to connect a load or an energy storage unit or a power generation unit or a power grid. In addition, the power conversion system is used to convert the direct current input by the DC power supply or the alternating current input by the AC power supply and then output it. Among them, the power conversion system is the power conversion system in the first aspect or any embodiment of the first aspect.

[0036] The above power supply system can be configured as a photovoltaic system, then the power supply system further includes a photovoltaic component, and the first end of the power conversion unit in the power conversion system is connected to the photovoltaic component, and the photovoltaic component serves as a DC power supply.

[0037] In addition, the technical effects of the corresponding schemes in the second and third aspects can refer to the technical effects that can be obtained by the corresponding schemes in the first aspect, and the repeated parts will not be described in detail. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 A schematic diagram of an application scenario of a power supply system provided in an embodiment of the present application;

[0039] Figure 2a A schematic diagram of a structure of a power conversion system provided in an embodiment of the present application;

[0040] Figure 2b A schematic diagram of a specific structure of a power conversion system provided in an embodiment of the present application;

[0041] Figure 3 A schematic diagram of the working power of the power conversion unit provided in an embodiment of the present application;

[0042] Figure 4 A schematic diagram of the working mode of the power conversion unit in the embodiment of the present application in the control cycle;

[0043] Figure 5 It is another schematic diagram of the working mode of the power conversion unit in the embodiment of the present application in the control cycle;

[0044] Figure 6 It is another schematic diagram of the working mode of the power conversion unit in the embodiment of the present application in the control cycle;

[0045] Figure 7 It is another schematic diagram of the working mode of the power conversion unit in the embodiment of the present application in the control cycle;

[0046] Figure 8 It is another schematic diagram of the working mode of the power conversion unit in the embodiment of the present application in the control cycle;

[0047] Fig. 9 This is another schematic diagram of the cycle in the embodiment of the present application;

[0048] Fig.10 Another schematic diagram of the working power of the power conversion unit provided in the embodiment of the present application;

[0049] Fig.11 Another schematic diagram of the working power of the power conversion unit provided in the embodiment of the present application;

[0050] Fig.12 Another schematic diagram of the working power of the power conversion unit provided in the embodiment of the present application;

[0051] Fig.13 Another schematic diagram of the working power of the power conversion unit provided in the embodiment of the present application;

[0052] Fig.14 Another schematic diagram of the working power of the power conversion unit provided in the embodiment of the present application;

[0053] Fig.15a A schematic diagram of another structure of a power conversion system provided in an embodiment of the present application;

[0054] Fig.15b A schematic diagram of another structure of a power conversion system provided in an embodiment of the present application.

[0055] Reference numerals:

[0056] 100-photovoltaic module; 200-power conversion system; 300-grid-connected transformer; 400-grid; 210_1~210_N-power conversion unit; 211-DC-DC conversion circuit; 220-DC-AC conversion unit; 212 / 221-DC-AC conversion circuit; 230-control unit; Bus+-positive DC bus; Bus--negative DC bus. DETAILED DESCRIPTION

[0057] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings. The specific operating methods in the method embodiments can also be applied to device embodiments or system embodiments. It should be noted that in the description of the present application, "multiple" can be understood as "at least two". In addition, it should be understood that in the description of the present application, words such as "first" and "second" are only used to distinguish the purpose of description, and cannot be understood as indicating or implying relative importance, nor can they be understood as indicating or implying order.

[0058] It should be noted that the same reference numerals in the drawings of this application represent the same or similar structures, and thus their repeated description will be omitted. The words expressing positions and directions described in this application are all explained using the drawings as examples, but they can be changed as needed, and the changes are included in the protection scope of this application. The drawings of this application are only used to illustrate the relative position relationship and do not represent the true proportion.

[0059] In order to facilitate the understanding of the technical solution provided by the embodiment of the present application, the application scenario of the solution of the present application is first described below. The power conversion system provided by the embodiment of the present application can be applied to the power supply system. The power supply system can be a photovoltaic system based on solar power generation or a wind power generation system based on wind power generation, or it can also be other energy conversion products and power generation products. Among them, the power conversion system is suitable for outputting electric energy to the power grid through a grid-connected transformer, and is also suitable for powering base station equipment (such as base station equipment in remote areas without mains power or poor mains power), or for powering batteries, or for powering power generation units (such as motors), or for powering various types of electrical equipment such as household appliances (such as refrigerators, air conditioners, etc.) in the power grid. Alternatively, the power conversion system is also suitable for transmitting the electric energy generated by the power generation unit to a DC power supply or an AC power supply, and reversely providing electric energy to the DC power supply or the AC power supply. Of course, in actual applications, the specific implementation of the power conversion system can be determined according to the actual application scenario, and is not limited here.

[0060] The following is a detailed description of the application of the power conversion system provided by the embodiment of the present application in the photovoltaic system scenario. For the working process of the power conversion system provided by the embodiment of the present application in other scenarios, the working process applied to the power supply system can be referred to, and the repetitions are not discussed.

[0061] Figure 1 This is a schematic diagram of an application scenario of a power supply system provided in an embodiment of the present application. Figure 1 , the power supply system includes: a photovoltaic module 100 and a power conversion system 200, the input end of the power conversion system 200 is connected to the photovoltaic module 100, the output end of the power conversion system 200 is connected to the input end of the grid-connected transformer 300, and the output end of the grid-connected transformer 300 is connected to the power grid 400 (for example, an AC power grid). In specific applications, the power conversion system 200 converts the direct current input by the photovoltaic module 100 into alternating current and outputs it to the grid-connected transformer 300, and the grid-connected transformer 300 performs step-up or step-down conversion and outputs it to the power grid 400. Of course, in actual applications, it is also possible not to set up the grid-connected transformer 300, but to directly connect the output end of the power conversion system 200 to the power grid 400. In addition, the output end of the power conversion system can also be connected to a load to supply power to the load. Alternatively, the output end of the power conversion system can also be connected to an AC system.

[0062] Figure 2a A schematic diagram of a power conversion system provided in an embodiment of the present application. Figure 2aThe power conversion system 200 includes: N power conversion units 210_1 to 210_N (N is an integer and N≥2), a DC-AC conversion unit 220 and a control unit 230, so that the power conversion system is set as a bipolar photovoltaic inverter. The input end of each power conversion unit 210_1 to 210_N is respectively connected to the photovoltaic module 100 as a DC power supply, the output end of each power conversion unit 210_1 to 210_N is connected to the input end of the DC-AC conversion unit 220 through a DC bus (including a positive DC bus Bus+ and a negative DC bus Bus-), and the output end of the DC-AC conversion unit 220 is connected to the power grid 400 through a grid-connected transformer 300. In specific applications, each power conversion unit 210_1 to 210_N converts the DC power input by the photovoltaic module 100 and outputs it to the DC bus (including the positive DC bus Bus+ and the negative DC bus Bus-), and the DC-AC conversion unit 220 converts the DC power on the DC bus (including the positive DC bus Bus+ and the negative DC bus Bus-) into AC power and outputs it to the grid-connected transformer 300, and the grid-connected transformer 300 performs step-up or step-down conversion and outputs it to the power grid 400. Alternatively, the output end of the DC-AC conversion unit is connected to the load to supply power to the load. It is understandable that N can be set to 2, 3, 4, 5 or more, and the specific value of N can be determined according to the needs of the actual application scenario, which is not limited here. In addition, the control unit can also be set to 1, 2, 3 or more, and the specific value of the control unit can also be determined according to the needs of the actual application scenario, which is not limited here.

[0063] The power conversion unit in the embodiment of the present application can operate in the MPPT mode to output the maximum power P of the photovoltaic module. mpp Tracking, at this time the working power of the power conversion unit is also the maximum power P mpp In order to enable the power supply system in this application to have the output capability of increasing power and decreasing power and realize photovoltaic grid construction, it is necessary to make the power conversion unit work in PR mode. When the power conversion unit works in PR mode, the working power of the power conversion unit is the reference power P res , which is less than or equal to the maximum power P mpp At the same time, the output power of the photovoltaic module is approximately equal to the reference power P res (Equipment losses are ignored). However, as the environment in which the photovoltaic module is located changes, its power output characteristics change, and the maximum power P mpp Therefore, the reference power P needs to be adjusted accordingly. res Therefore, the power conversion unit can be controlled to work in MPPT mode, detect the current maximum power of the photovoltaic module, and then adjust the reference power P based on the detected current maximum power. resUpdate to get the updated reference power P res ', so that the working power of the power conversion unit when working in PR mode is the updated reference power P res '. Based on this, in order to realize photovoltaic grid construction, the power conversion unit needs to work in PR mode, and also relies on MPPT mode to detect the maximum power of the photovoltaic module to update the reference power. This causes the power conversion unit to switch between PR mode and MPPT mode, which leads to fluctuations in the output power and output voltage of the power conversion unit, endangering the stability and control accuracy of the power supply system, and even increasing the mechanical stress and thermal stress of the equipment.

[0064] To this end, in the present application, in each control cycle, the control unit 230 controls the working mode of one or more target power conversion units among the N power conversion units to switch between the PR mode and the MPPT mode. After the working mode of the target power conversion unit is switched to the MPPT mode, the maximum power P output by the photovoltaic module can be obtained in the MPPT mode. mpp . Thus, the maximum power P obtained in the MPPT mode in the kth control cycle can be mpp For the original reference power P in the k-1th control cycle res Update to obtain the updated reference power P in the kth control cycle res ', and then in the kth control cycle, the working power of the target power conversion unit after switching from the MPPT mode to the PR mode changes to the updated reference power P res '. Since the working mode of the target power conversion unit switches between the PR mode and the MPPT mode, its working power will also be in the original reference power P res , maximum power P mpp And the reference power P res', so that the target power conversion unit will have a working power change during the mode switching process, which will cause the total output power and output voltage of the power conversion unit to fluctuate. In order to reduce the fluctuation of the total output power and output voltage of the power conversion unit, in each control cycle, the control unit 230 also controls the working mode of the cooperative power conversion unit other than the target power conversion unit among the N power conversion units to remain unchanged, so that the cooperative power conversion unit does not switch the mode. In addition, the control unit 230 also controls the working power of the cooperative power conversion unit to be coordinated and adjusted according to the working power change of the target power conversion unit during the mode switching process, so that the total change of the working power of the N power conversion units is less than the change threshold. With this setting, the working power change of the cooperatively adjusted cooperative power conversion unit and the working power change of the target power conversion unit during the mode switching process are offset as much as possible, so that the total change of the working power of the N power conversion units is as small as possible, thereby reducing the fluctuation of the total output power and output voltage of the power conversion unit, and improving the stability and control accuracy of the power supply system.

[0065] Understandably, P res ' <P mpp , in order to realize photovoltaic grid construction. Of course, in practical applications, P res '=P mpp , which is not limited here. In addition, the change threshold may be 0±ΔPth. When the total change of the working power of the N power conversion units is less than the change threshold, it can be indicated that the total change of the working power of the N power conversion units is as small as possible or negligible. Among them, ΔPth may be a value such as 0, 0.01, 0.05, etc. Alternatively, ΔPth may also be an allowable error range.

[0066] Furthermore, through the above-mentioned embodiments, the mechanical and thermal stresses of the power conversion system equipment can be reduced, thereby improving the overall stability of the power conversion system.

[0067] Figure 2b A specific structural diagram of a power conversion system provided in an embodiment of the present application. Figure 2bEach power conversion unit 210_1~210_N can be set as a direct current-direct current (DC-DC) conversion circuit 211, the direct current-alternating current conversion unit 220 can be set as a direct current-alternating current (DC-AC) conversion circuit 221, and the control unit 230 can be a field programmable gate array (FPGA), a general-purpose central processing unit (CPU), a general-purpose processor, a digital signal processing (DSP), an application-specific integrated circuit (ASIC), or other programmable logic devices, transistor logic devices, hardware components or any combination thereof. It can implement or execute various exemplary logic blocks, modules and circuits described in conjunction with the disclosure of this application. The above-mentioned control unit can also be a combination that implements computing functions, such as a combination of one or more microprocessors, a combination of DSP and microprocessors, etc.

[0068] And, refer to Figure 2b , the first end of the DC-DC conversion circuit 211 is connected to the photovoltaic module 100 as a DC power source, the second end of the DC-DC conversion circuit 211 is connected to the first end of the DC-AC conversion circuit 221 through the DC bus, and the second end of the DC-AC conversion circuit 221 is used to connect to the power grid. Exemplarily, the DC-DC conversion circuit 211 converts the DC power input by the photovoltaic module 100 and outputs it to the DC-AC conversion circuit 221, and the DC-AC conversion circuit 221 converts the input DC power into AC power and outputs it to the power grid 400. In addition, the second end of the DC-AC conversion circuit 221 can also be connected to a load to supply power to the load.

[0069] In this application, the working mode of the cooperative power conversion unit remaining unchanged means that: the working mode of the cooperative power conversion unit does not switch modes, but operates constantly in one working mode. For example, the working mode of the cooperative power conversion unit is the PR mode. With this setting, all power conversion units 210_1 to 210_N can operate in the PR mode to achieve photovoltaic grid formation. Moreover, some power conversion units 210_1 to 210_k are used as target power conversion units to switch between the PR mode and the MPPT mode, and one or part or all of the remaining power conversion units 210_k + 1 to 210_N are used as cooperative power conversion units and are constantly in the PR mode, which can reduce the fluctuations of the total output power and output voltage of the power conversion units and improve the stability and control accuracy of the power supply system. Also, when the target power conversion unit operates in the MPPT mode, the working power of the cooperative power conversion unit in the PR mode is the original reference power P res , in order to enable the reference power of the cooperative power conversion unit in the PR mode to be updated accordingly, after the target power conversion unit updates the reference power, the working power of the cooperative power conversion unit is also switched to the updated reference power P res '. It can be understood that k is an integer, and 1 ≤ k < N, and k needs to be determined according to the actual application scenario. It can be understood that after the target power conversion unit updates the reference power, it is not necessary to update the reference power of the cooperative power conversion unit in the PR mode accordingly, but to control the reference power of the cooperative power conversion unit in the PR mode to continue to work with its reference power in the previous control cycle.

[0070] In each control period, the N power conversion units include: k target power conversion units and m cooperative power conversion units, where k is an integer and 1 ≤ k ≤ N - 1, m is an integer and 1 ≤ m ≤ N - 1, and 2 ≤ k + m ≤ N. Among them, k can select a suitable value from 1, 2, 3, …… N - 1, and m can also select a suitable value from 1, 2, 3, …… N - 1, but k and m need to satisfy 2 ≤ k + m ≤ N. With this setting, at least one target power conversion unit and at least one cooperative power conversion unit are selected from the N power conversion units. For example, when k + m = N, the cooperative power conversion units are all the remaining power conversion units among the N power conversion units except the target power conversion units. When m + k < N, the cooperative power conversion units are some of the N power conversion units except the target power conversion units. Based on this, the part of the power conversion units among the N power conversion units except the target power conversion units and the cooperative power conversion units can operate in the PR mode. It can be understood that the value of k in each control period can be the same, or the value of k in some control periods can be the same, and the value of k in some control periods can be different, or the value of k in each control period can be different. Also, the value of m in each control period can be the same, or the value of m in some control periods can be the same, and the value of m in some control periods can be different, or the value of m in each control period can be different. In addition, m = k or m > k or m < k can also be set in the same control period.

[0071] In specific applications, when the target power conversion unit operates in the MPPT mode, the maximum power P mpp will be greater than the original reference power P res . Since the updated reference power P res ’ is less than or equal to the maximum power P mpp , the updated reference power P res ’ and the original reference power P res have the following relationship: P res ’ > P res , or P res ’ < P res , or, P res ’ = P res .

[0072] Figure 3 is a schematic diagram of the operating power of the power conversion unit provided by the embodiment of the present application. Refer to Figure 3, taking the power conversion unit 210_1 as the target power conversion unit and 210_2 to 210_N as the collaborative power conversion units as an example, P210_1 represents the working power of the power conversion unit 210_1, P210_2 represents the working power of the power conversion unit 210_2, ... P210_N represents the working power of the power conversion unit 210_N. Specifically, the working mode of the target power conversion unit 210_1 runs in the PR mode before switching to the MPPT mode (i.e., before the Tm stage), and at this time, the working power of the target power conversion unit 210_1 is the original reference power P before the update. res Then, the mode switching process (i.e., the Txh1 stage and the Txh2 stage) is entered. In the Tm stage (i.e., the Txh1 stage), the control unit 230 controls the working mode of the target power conversion unit 210_1 to switch from the PR mode to the MPPT mode, and obtains the maximum power P that the photovoltaic assembly 100 can output in the MPPT mode. mpp , and then according to the maximum power P mpp Get the updated reference power P res '. And in the Tm stage (i.e., the Txh1 stage), the working power of the cooperative power conversion units 210_2 to 210_N is controlled to be coordinated and adjusted. Thereafter, in the Txh2 stage within the Tr stage, the control unit 230 controls the working mode of the target power conversion unit 210_1 to switch from the MPPT mode to the PR mode, and the working power of the target power conversion unit 210_1 is changed from the maximum power P mpp Transformed into the updated reference power P res '. And in the Txh2 stage, the control unit 230 controls the working power of the coordinated power conversion units 210_2 to 210_N to be coordinated and adjusted. Based on this, the target power conversion unit 210_1 will experience power changes during its mode switching process (i.e., the Txh1 and Txh2 stages). For example, taking any moment TS0 in the Txh1 and Txh2 stages as an example, in the Txh1 stage, the working power change amount of the target power conversion unit 210_1 at the moment TS0 is the target power change amount ΔP ms _1, the target power change ΔP ms1_1 It can be the instantaneous working power P of the target power conversion unit 210_1 at time TS0. ss1_1 Compared with the reference power P before updating res In the Txh2 stage, the target power conversion unit 210_1 at TS0' has a target power change ΔP ms2 _1, the target power change ΔP ms2_1 It can be the instantaneous working power P of the target power conversion unit 210_1 at time TS0' ss2_1 With the updated reference power Pres Of course, the target power change ΔP ms2_1 It can also be the instantaneous working power P of the target power conversion unit 210_1 at time TS0'. ss2_1 Compared with the reference power P before updating res The amount of change between them is not limited here.

[0073] Moreover, taking the collaborative power conversion units 210_2 to 210_N working in the PR mode in the Tm stage and the Tr stage as an example, taking the collaborative power conversion unit 210_2 as an example, before the working mode of the target power conversion unit 210_1 is switched to the MPPT mode, the working power of the collaborative power conversion unit 210_2 is the original reference power P before the update. res , the power of the cooperative power conversion unit 210_2 will change during its cooperative adjustment process (ie, the Txh1 stage and the Txh2 stage). Specifically, the working power change amount of the cooperative power conversion unit 210_2 at time TS0 is the cooperative power change amount ΔP xs1_2 , and the coordinated power change ΔP xs1_2 is the instantaneous working power P of the coordinated power conversion unit 210_2 at time TS0 ss1_2 With the set power (such as the original reference power P res The change in the working power of the cooperative power conversion unit 210_2 at time TS0' is the cooperative power change ΔP xs2_2 , coordinated power change ΔP xs2_2 is the instantaneous working power P of the coordinated power conversion unit 210_2 at time TS0′ ss2_2 and the set power (e.g. the updated reference power P res Of course, the coordinated power change ΔP xs2_2 It can also be the instantaneous working power P of the cooperative power conversion unit 210_2 at time TS0'. ss2_2 With the set power (such as the original reference power P res ). Similarly, the coordinated power change ΔP xs1_3 ~ΔP xs1_N , ΔP xs2_3 ~ΔP xs2_N The same can be said for many other reasons, so I will not elaborate on them here.

[0074] And, refer to Figure 3 , the target power change amount ΔP of the target power conversion unit 210_1 during the mode switching process ms_1 Relatively speaking, it increases, so the target power change ΔP ms_1 is a positive value, that is, its sign is positive, so the sum of the target power changes ΔPmsm (At this time, ΔP msm =ΔP ms_1 ) is also positive and its sign is also positive. In order to reduce the fluctuation of the total output power and output voltage of the power conversion unit, the coordinated power change ΔP xs_2 ~ΔP xs_N Offset target power change ΔP ms_1 , it is necessary to control the coordinated power conversion unit to be at the reference power (for example, the original reference power P before updating) res ) based on the coordinated reduction of the corresponding power, so that the coordinated power change ΔP xs_2 ~ΔP xs_N is a negative value, that is, ΔP xs_2 ~ΔP xs_N The sign is negative, so that the coordinated power change ΔP xs_2 ~ΔP xs_N The sum is also negative and its sign is also negative.

[0075] It is understandable that the sum of the target power changes is: the sum of the target power changes that occur in each target power conversion unit at the same moment. And, the sum of the coordinated power changes is: the sum of the coordinated power changes that occur in each coordinated power conversion unit at the same moment. It is understandable that in the actual operation of the power conversion system, there are factors such as control errors. Therefore, if the difference between the moment when the above-mentioned target power change occurs and the moment when the coordinated power change occurs is within a certain time threshold, it can be considered to be the same moment. Exemplarily, the above-mentioned time threshold can be a value such as 1ns. The connotation of the same moment in the following embodiments is consistent and will not be repeated one by one.

[0076] Based on this, the sum of the coordinated power changes can be made to have opposite signs to the sum of the target power changes. Moreover, by making the difference between the absolute value of the sum of the coordinated power changes and the absolute value of the sum of the target power changes smaller than the change threshold, the total change of the working power of the N power conversion units can be made as small as possible or even negligible, thereby reducing the fluctuation of the output power and output voltage of the power conversion unit and improving the stability and control accuracy of the power supply system.

[0077] It is understandable that the difference between the absolute value of the sum of the coordinated power variations and the absolute value of the sum of the target power variations may be the difference or ratio between the absolute value of the sum of the coordinated power variations and the absolute value of the sum of the target power variations.

[0078] In the present application, since the sum of the cooperative power changes is related to the sum of the target power changes, each cooperative power change can be determined according to the sum of the target power changes. For example, the cooperative power change corresponding to the yth cooperative power conversion unit among the m cooperative power conversion units is:y *ΔP msm , ΔP msm represents the sum of the target power changes, and y is an integer and y∈[1,m]. And α y represents the allocation weight corresponding to the y-th cooperative power conversion unit, and α y ∈[0, 1]. By setting this, the sign of the cooperative power change corresponding to each cooperative power conversion unit can be opposite to the sum of the target power change, and the distribution weight α can be used to y , ΔP msm Distributed to different collaborative power conversion units.

[0079] For example, refer to Figure 3 , taking TS0 as an example, ΔP msm =ΔP ms_1 , the collaborative power conversion unit 210_2 is the first collaborative power conversion unit, and the collaborative power conversion unit 210_2 corresponds to the allocation weight α1, then the collaborative power change amount ΔP corresponding to the collaborative power conversion unit 210_2 xs_2 = -α1*ΔP msm , that is, ΔP xs_2 = -α1*ΔP ms_1 The coordinated power conversion unit 210_3 is used as the second coordinated power conversion unit, and the coordinated power conversion unit 210_3 is assigned a weight α2. Then the coordinated power change amount ΔP corresponding to the coordinated power conversion unit 210_3 is xs _3 is: -α2*ΔP msm , that is, ΔP xs_3 = -α2*ΔP ms_1 The coordinated power conversion unit 210_4 is the third coordinated power conversion unit, and the coordinated power conversion unit 210_4 is assigned a weight α3. Then the coordinated power change amount ΔP corresponding to the coordinated power conversion unit 210_4 is xs_4 = -α3*ΔP msm , that is, ΔP xs_4 = -α3*ΔP ms_1 ... The coordinated power conversion unit 210_N is used as the mth coordinated power conversion unit, and the coordinated power conversion unit 210_N is assigned a corresponding weight α m , then the coordinated power conversion unit 210_N corresponds to the coordinated power change ΔP xs_N is: -α m *ΔP msm , that is, ΔP xs_N =-α m *ΔP ms_1 .

[0080] It is understandable that each assigned weight α yThe configuration can be performed offline or online. In addition, the sum of the allocation weights corresponding to the m coordinated power conversion units can be 1, that is, It is understandable that the sum of the allocation weights corresponding to the m collaborative power conversion units is 1, which is a theoretical value. In specific applications, since there may be an error between the sum of the collaborative power changes and the sum of the target power changes when the test equipment outputs power, the sum of the allocation weights corresponding to the m collaborative power conversion units may not be 1, but it only needs to meet the error tolerance condition.

[0081] Continue to refer to Figure 3 , each coordinated power variation and each target power variation can appear in the same stage, that is, the appearance time of each coordinated power variation is the same as the appearance time of each target power variation, and the end time of each coordinated power variation is the same as the end time of each target power variation. For example, the coordinated power variation ΔP xs_2 ~ΔP xs_N The target power change ΔP ms_1 This setting can improve the timeliness of the coordinated control, so that when the target power conversion unit has a target power change, the coordinated power conversion unit can be controlled in time to coordinately adjust the coordinated power change, so as to offset the target power change through the coordinated power change, thereby reducing the fluctuation of the output power and output voltage of the power conversion unit.

[0082] In this application, multiple updating methods can be used to obtain the updated reference power P res '. Next, we get the updated reference power P res ' is updated with an example.

[0083] Update method 1: In a control cycle, if the control unit 230 selects a power conversion unit (for example, 210_1) from the N power conversion units as the target power conversion unit, after the working mode of the power conversion unit 210_1 is switched to the MPPT mode, the maximum power P output by the photovoltaic assembly 100 can be obtained in the MPPT mode. mpp _1, so that the maximum power P mpp _1 as the target maximum power P a1 , that is, P a1 =P mpp _1. Based on this, the updated reference power P res 'Equal to the target maximum power P a1 Subtract the reserved power ΔP, that is, P res '=P a1-ΔP. A constant power threshold can be set as the reserved power ΔP based on experimental data or experience. Alternatively, the maximum power P mpp _1 obtains a power threshold value that can be updated accordingly as the reserved power ΔP. For example, before the working mode of the power conversion unit 210_1 is switched to the MPPT mode, its working mode is still the PR mode. At this time, the power conversion unit 210_1 corresponds to a reserved power ΔP'. After the control unit 230 controls the working mode of the power conversion unit 210_1 to switch to the MPPT mode, it can control the maximum power P obtained by the power conversion unit 210_1 in the MPPT mode. mpp _1, so that according to the maximum power P mpp _1 updates the reserved power ΔP' to obtain the updated reserved power ΔP", so that P res '=P a1 -ΔP". For example, the maximum power P mpp _1 multiplied by the percentage C C As the reserved power ΔP", that is, ΔP" = P mpp _1*C C , where 0%≤C C ≤100%, 70%≤C C ≤100%, e.g. 80%≤C C ≤100%, e.g. 85%≤C C ≤95%. In specific applications, C C The settings are 70%, 75%, 80%, 85%, 90%, 95%, etc., and are not limited here.

[0084] Update method 2: In a control cycle, if the control unit 230 selects multiple power conversion units from N power conversion units as target power conversion units, for example, taking two power conversion units 210_1 and 210_2 as target power conversion units, after the working mode of the power conversion unit 210_1 is switched to the MPPT mode, the maximum power P output by the photovoltaic module can be obtained in the MPPT mode. mpp _1, after the working mode of the power conversion unit 210_2 is switched to the MPPT mode, the maximum power P output by the photovoltaic module can be obtained in the MPPT mode. mpp _2, so that the maximum power P mpp _1 and P mpp The average value (e.g., arithmetic mean, weighted mean) of _2 is taken as the target maximum power P b1 , that is, P b1 Equal to P mpp _1 and P mppBased on this, the updated reference power P res 'Equal to the target maximum power P b1 Subtract the reserved power ΔP, that is, P res '=P b1 -ΔP. A constant power threshold can be set as the reserved power ΔP based on experimental data or experience. Alternatively, the maximum power P mpp _1 or P mpp _2 obtains a power threshold that can be updated accordingly as the reserved power ΔP. For example, with the maximum power P mpp _1 as an example, according to the maximum power P mpp _1 Update the reserved power ΔP' to obtain an updated reserved power ΔP" (for example, the maximum power P mpp _1 or P mpp _2 multiplied by the percentage as the reserved power ΔP”), so that P res '=P b1 -ΔP". For example, the maximum power P mpp _1 or P mpp _2 times the percentage C C As the reserved power ΔP", that is, ΔP" = P mpp _1*C C Or, ΔP” = P mpp _2*C C Alternatively, the target maximum power P b1 A power threshold that can be updated accordingly is obtained as the reserved power ΔP, and then the target maximum power P b1 Update the reserved power ΔP' to obtain the updated reserved power ΔP", so that P res '=P b1 -ΔP". For example, the target maximum power P b1 Multiply by the percentage to get the reserved power ΔP”, that is, ΔP” = P b1 *C C .

[0085] Update method three: In a control cycle, if the control unit 230 selects a power conversion unit (for example, 210_1) from the N power conversion units as the target power conversion unit, after the working mode of the power conversion unit 210_1 is switched to the MPPT mode, the maximum power P output by the photovoltaic module can be obtained in the MPPT mode. mpp _1, so that the maximum power P mpp _1 as the target maximum power P a2 , that is, P a2 =P mppBased on this, the updated reference power P res 'Equal to the target maximum power P a2 Multiply by the reference percentage C A , that is, P res '=P a2* C A Among them, 70% ≤ C A <100%, e.g. 80%≤C A <100%, e.g. 85%≤C A ≤95%. In specific applications, C A The settings are 70%, 75%, 80%, 85%, 90%, 95%, etc., and are not limited here.

[0086] Update method 4: In a control cycle, if the control unit 230 selects multiple power conversion units from N power conversion units as target power conversion units, for example, taking two power conversion units 210_1 and 210_2 as target power conversion units, after the working mode of the power conversion unit 210_1 is switched to the MPPT mode, the maximum power P output by the photovoltaic module can be obtained in the MPPT mode. mpp _1, after the working mode of the power conversion unit 210_2 is switched to the MPPT mode, the maximum power P output by the photovoltaic module can be obtained in the MPPT mode. mpp _2, so that the maximum power P mpp _1 and P mpp The average value (e.g., arithmetic mean, weighted mean) of _2 is taken as the target maximum power P b2 , that is, P b2 Equal to P mpp _1 and P mpp Based on this, the updated reference power P res 'Equal to the target maximum power P b2 Multiply by the reference percentage C B , that is, P res '=P a2* C B Among them, 70% ≤ C B <100%, e.g. 80%≤C B <100%, e.g. 85%≤C B ≤95%. In specific applications, C B The settings are 70%, 75%, 80%, 85%, 90%, 95%, etc., and are not limited here.

[0087] It is understandable that, in each of the multiple consecutive control cycles, any one of the above-mentioned updating modes 1 to 4 can be used to obtain the updated reference power. Alternatively, two, three, or four of the above-mentioned updating modes 1 to 4 can be combined to obtain the updated reference power in the multiple consecutive control cycles.

[0088] It is understandable that the reference power updated in the kth control cycle may be the same as the reference power in the k-1th control cycle. Alternatively, the reference power updated in the kth control cycle may be greater than the reference power in the k-1th control cycle. Alternatively, the reference power updated in the kth control cycle may be less than the reference power in the k-1th control cycle. Wherein, k is an integer greater than 0.

[0089] It is understandable that the reserved power after update in the kth control cycle may be the same as the reserved power in the k-1th control cycle. Alternatively, the reserved power after update in the kth control cycle may be greater than the reserved power in the k-1th control cycle. Alternatively, the reserved power after update in the kth control cycle may be less than the reserved power in the k-1th control cycle.

[0090] In some examples, a target power conversion unit and a collaborative power conversion unit can be randomly selected from N power conversion units. Specifically, in one or more control cycles within a plurality of consecutive control cycles, one or more power conversion units are randomly selected from N power conversion units as target power conversion units, and one or more power conversion units are randomly selected from N power conversion units as collaborative power conversion units. With this arrangement, it is possible to select a target power conversion unit and / or a collaborative power conversion unit by random selection. The working process of randomly selecting a target power conversion unit in an embodiment of the present application is described in detail below in conjunction with an embodiment of a specific random selection method.

[0091] In the present application, the probabilities of at least some of the power conversion units being selected as the target power conversion units can be made different. Exemplarily, the probabilities of all the power conversion units being selected as the target power conversion units can be made different, or the probabilities of some of the power conversion units being selected as the target power conversion units can be made different, while the probabilities of the remaining power conversion units being selected as the target power conversion units are the same. And, the probabilities of at least some of the power conversion units being selected as the collaborative power conversion units can be made different. Exemplarily, the probabilities of all the power conversion units being selected as the collaborative power conversion units can be made different, or the probabilities of some of the power conversion units being selected as the collaborative power conversion units can be made different, while the probabilities of the remaining power conversion units being selected as the collaborative power conversion units are the same.

[0092] Random selection method 1:

[0093] When randomly selecting a target power conversion unit, the probability χA of each power conversion unit being selected as the target power conversion unit is made the same. And, when randomly selecting a collaborative power conversion unit, the probability χB of each power conversion unit being selected as the collaborative power conversion unit is made the same. With this arrangement, it is possible to randomly select a power conversion unit with equal probability as the target power conversion unit, and to randomly select a power conversion unit with equal probability as the collaborative power conversion unit. Further, in each control cycle, a power conversion unit is randomly selected with equal probability as the target power conversion unit, and a power conversion unit is randomly selected with equal probability as the collaborative power conversion unit.

[0094] The following takes the continuous control period T_c~T_c+d+2 as an example, and selects a power conversion unit as the target power conversion unit in each control period. Figure 4 Detailed description is given. Figure 4 Schematic diagram of the working mode of the power conversion unit in the embodiment of the present application in the control cycle. Figure 4In the cth control cycle T_c, the control unit 230 randomly selects the power conversion unit 210_1 from the power conversion units 210_1 to 210_N as the target power conversion unit according to the same probability χA, and randomly selects the power conversion units 210_2 to 210_N from the power conversion units 210_1 to 210_N as the collaborative power conversion units according to the same probability χB. In addition, the working process of the target power conversion unit 210_1 and the collaborative power conversion units 210_1 to 210_N can refer to the working process described above, and the details are not repeated here. Similarly, in the c+1th control cycle T_c+1, the control unit 230 selects the power conversion unit 210_3 as the target power conversion unit, and selects the power conversion units 210_1, 210_2, 210_4 to 210_N as the collaborative power conversion units. In the c+2th control cycle T_c+2, the control unit 230 selects the power conversion unit 210_2 as the target power conversion unit, and selects the power conversion units 210_1, 210_3 to 210_N as the collaborative power conversion units. In the c+3th control cycle T_c+3, the control unit 230 selects the power conversion unit 210_N as the target power conversion unit, and selects the power conversion units 210_1 to 210_N-1 as the collaborative power conversion units. In the c+dth control cycle T_c+d, the control unit 230 selects the power conversion unit 210_4 as the target power conversion unit, and selects the power conversion units 210_1 to 210_3, 210_5 to 210_N as the collaborative power conversion units. In the c+d+1th control cycle T_c+d+1, the control unit 230 selects the power conversion unit 210_2 as the target power conversion unit, and selects the power conversion units 210_1, 210_3 to 210_N as the cooperative power conversion units. In the c+d+2th control cycle T_c+d+2, the control unit 230 selects the power conversion unit 210_2 as the target power conversion unit, and selects the power conversion units 210_1, 210_3 to 210_N as the cooperative power conversion units. In addition, the remaining working processes in the c+1th control cycle to the c+d+2th control cycle T_c+1 to T_c+d+2 can refer to the working process in the cth control cycle T_c, which will not be repeated here.

[0095] It is understandable that χA∈[0,1], wherein the sum of the probabilities χA corresponding to the power conversion units 210_1 to 210_N may be 1, or the sum of the probabilities χA corresponding to the power conversion units 210_1 to 210_N may also be greater than or less than 1. In a specific implementation, the selection probabilities χAA corresponding to the power conversion units 210_1 to 210_N may be stored in a storage unit of the power supply system. The control unit 230 can obtain the selection probability χAA corresponding to each power conversion unit 210_1 to 210_N from the storage unit, and randomly select the corresponding power conversion unit as the target power conversion unit. Among them, the selection probability χAA corresponding to each power conversion unit 210_1 to 210_N can be configured as a fixed value in an offline or online manner. For example, if the operator needs to configure the selection probability χAA in an online manner, the probability adjustment instruction of the selection probability of the corresponding part or all of the power conversion units can be input through the user interface (UI). When the control unit 230 receives the probability adjustment instruction, it can adjust the selection probability of some or all of the power conversion units according to the probability adjustment instruction. For example, if the target power conversion unit is selected from all the power conversion units 210_1 to 210_N by random equal probability, the selection probability χAA corresponding to each power conversion unit 210_1 to 210_N can be configured to the same value χAA_1 according to the probability adjustment instruction. For example, if the target power conversion unit is selected from some of the power conversion units 210_2 to 210_N by random equal probability, the selection probability χAA corresponding to each of the power conversion units 210_2 to 210_N can be configured to the same value χAA_2 according to the probability adjustment instruction. For example, if the target power conversion unit is selected from some of the power conversion units 210_3 to 210_N by random equal probability, the selection probability χAA corresponding to each of the power conversion units 210_3 to 210_N can be configured to the same value χA_3 according to the probability adjustment instruction.

[0096] Similarly, χB∈[0,1], wherein the sum of the probabilities χB corresponding to the power conversion units 210_1 to 210_N may be 1, or the sum of the probabilities χB corresponding to the power conversion units 210_1 to 210_N may be greater than or less than 1. In a specific implementation, the implementation of probability χB may refer to the implementation of probability χA, and will not be described in detail herein.

[0097] It is understandable that each control cycle includes the MPPT mode stage Tm and the PR mode stage Tr, that is, the MPPT mode stage Tm and the PR mode stage Tr constitute a control cycle. In addition, the cycle durations of the control cycles may be the same or different. Also, the cycle duration of the control cycle may be a fixed constant or may not be a fixed constant, that is, the cycle duration is not fixed. In practical applications, the cycle duration may be adjusted and changed in real time according to the duration of the MPPT mode stage Tm and the duration of the PR mode stage Tr. The control cycles in the following embodiments may be set similarly, and will not be described one by one below.

[0098] Random selection method 2:

[0099] When randomly selecting a target power conversion unit, the probability of at least some of the power conversion units being selected as the target power conversion unit is different. Thus, it is possible to randomly select power conversion units as target power conversion units with different probabilities. Exemplarily, the probabilities of all power conversion units being selected as target power conversion units can be different. For example, the probability of power conversion unit 210_1 being selected as the target power conversion unit is χ0A_1, the probability of power conversion unit 210_2 being selected as the target power conversion unit is χ0A_2, ... the probability of power conversion unit 210_N being selected as the target power conversion unit is χ0A_N, and χ0A_1 to χ0A_N are different from each other. Alternatively, the probabilities of some power conversion units being selected as target power conversion units can be different, and the probabilities of the remaining power conversion units being selected as target power conversion units are the same. For example, the probability that the power conversion unit 210_1 is selected as the target power conversion unit is χ0A_1, the probability that the power conversion unit 210_2 is selected as the target power conversion unit is χ0A_2, the probability that the power conversion unit 210_3 is selected as the target power conversion unit is χ0A_3, ... the probability that the power conversion unit 210_N is selected as the target power conversion unit is χ0A_N, and χ0A_1=χ0A_2, and χ0A_3~χ0A_N are different. Exemplarily, in each control cycle, a power conversion unit is randomly selected as the target power conversion unit with different probabilities.

[0100] Furthermore, when randomly selecting a collaborative power conversion unit, the probability of at least some of the power conversion units being selected as collaborative power conversion units is made different. With this arrangement, it is possible to randomly select power conversion units as collaborative power conversion units with different probabilities. Exemplarily, the probabilities of all power conversion units being selected as collaborative power conversion units can be made different. For example, the probability of power conversion unit 210_1 being selected as a collaborative power conversion unit is χ0B_1, the probability of power conversion unit 210_2 being selected as a collaborative power conversion unit is χ0B_2, ... the probability of power conversion unit 210_N being selected as a collaborative power conversion unit is χ0B_N, and χ0B_1 to χ0B_N are different from each other. Alternatively, the probabilities of some power conversion units being selected as collaborative power conversion units can be made different, and the probabilities of the remaining power conversion units being selected as collaborative power conversion units can be made the same. For example, the probability that the power conversion unit 210_1 is selected as the collaborative power conversion unit is χ0B_1, the probability that the power conversion unit 210_2 is selected as the collaborative power conversion unit is χ0B_2, the probability that the power conversion unit 210_3 is selected as the collaborative power conversion unit is χ0B_3, ... the probability that the power conversion unit 210_N is selected as the collaborative power conversion unit is χ0B_N, and χ0B_1=χ0B_2, and χ0B_3~χ0B_N are different. Exemplarily, in each control cycle, power conversion units are randomly selected as collaborative power conversion units with different probabilities.

[0101] The following takes the continuous control period T_c~T_c+d+2 as an example, and selects a power conversion unit as the target power conversion unit in each control period. Figure 5 Detailed description is given. Figure 5 FIG. 1 is another schematic diagram of the working mode of the power conversion unit in the embodiment of the present application in the control cycle. Figure 5 In the cth control cycle T_c, the control unit 230 randomly selects the power conversion unit 210_1 from the power conversion units 210_1 to 210_N as the target power conversion unit according to the set selection probabilities χ0AA_1 to χ0AA_N. And, the control unit 230 randomly selects the power conversion units 210_2 to 210_N from the power conversion units 210_1 to 210_N as the cooperative power conversion units according to the set selection probabilities χ0BA_1 to χ0BA_N. And, the working process of the target power conversion unit 210_1 and the cooperative power conversion units 210_1 to 210_N can refer to the working process described above, and will not be described in detail here.

[0102] Similarly, in the c+1th control cycle T_c+1, the control unit 230 selects the power conversion unit 210_1 as the target power conversion unit, and selects the power conversion units 210_2 to 210_N as the collaborative power conversion units. In the c+2th control cycle T_c+2, the control unit 230 selects the power conversion unit 210_2 as the target power conversion unit, and selects the power conversion units 210_1, 210_3 to 210_N as the collaborative power conversion units. In the c+3th control cycle T_c+3, the control unit 230 selects the power conversion unit 210_3 as the target power conversion unit, and selects the power conversion units 210_1 to 210_2, 210_4 to 210_N-1 as the collaborative power conversion units. In the c+dth control cycle T_c+d, the control unit 230 selects the power conversion unit 210_4 as the target power conversion unit, and selects the power conversion units 210_1 to 210_3, 210_5 to 210_N as the cooperative power conversion units. In the c+d+1th control cycle T_c+d+1, the control unit 230 selects the power conversion unit 210_2 as the target power conversion unit, and selects the power conversion units 210_1, 210_3 to 210_N as the cooperative power conversion units. In the c+d+2th control cycle T_c+d+2, the control unit 230 selects the power conversion unit 210_2 as the target power conversion unit, and selects the power conversion units 210_1, 210_3 to 210_N as the cooperative power conversion units. Furthermore, the remaining working processes in the c+1th control cycle to the c+d+2th control cycle T_c+1 to T_c+d+2 can refer to the working process in the cth control cycle T_c, which will not be described in detail here.

[0103] It is understandable that any one of χ0A_1~χ0A_N is in [0, 1], wherein the sum of the probabilities χ0A_1~χ0A_N may be 1, or the sum of the probabilities χ0A_1~χ0A_N may also be greater than or less than 1. Moreover, in a specific application, the storage unit of the power supply system also stores the probabilities χ0A_1~χ0A_N corresponding to the power conversion units 210_1~210_N. The control unit 230 can obtain the selection probability χ0AA_1~χ0AA_N of each power conversion unit from the storage unit, and randomly select the corresponding power conversion unit from the power conversion units 210_1~210_N as the target power conversion unit. Among them, any one of the selection probabilities χ0AA_1~χ0AA_N corresponding to each power conversion unit 210_1~210_N can also be configured as an arbitrary fixed value in an offline or online manner. For example, if the operator needs to configure one or more of the selection probabilities χ0AA_1 to χ0AA_N online, the operator can input a probability adjustment instruction through a user interface (UI). When the control unit 230 receives the probability adjustment instruction, it can adjust the selection probability of some or all power conversion units according to the probability adjustment instruction. For example, if the selection probability χ0AA_1 needs to be adjusted, the operator inputs the probability adjustment instruction to the control unit 230 through the user interface to change χ0AA_1 to χ0AA_1'. Or, for example, if the selection probabilities χ0A_1 to χ0A_3 need to be adjusted, the operator inputs the probability adjustment instruction to the control unit 230 through the user interface to change χ0AA_1 to χ0AA_1', χ0AA_2 to χ0AA_2', and χ0AA_3 to χ0AA_3'.

[0104] Similarly, any one of χ0B_1 to χ0B_N is in [0, 1], wherein the sum of the probabilities χ0B_1 to χ0B_N may be 1, or the sum of the probabilities χ0B_1 to χ0B_N may be greater than or less than 1. In specific applications, the implementation of the probabilities χ0B_1 to χ0B_N may refer to the implementation of the probabilities χ0A_1 to χ0A_N, and will not be described in detail herein.

[0105] Random selection method three:

[0106] When randomly selecting the target power conversion unit and the cooperative power conversion unit, the probability χA of each power conversion unit being selected as the target power conversion unit can also be made the same, and the probability of at least some power conversion units being selected as the cooperative power conversion units can be made different. The specific working process of this embodiment can refer to the above-mentioned random selection method 1 and random selection method 2, and will not be described in detail here.

[0107] Random selection method 4:

[0108] When randomly selecting the target power conversion unit and the cooperative power conversion unit, the probability of at least some of the power conversion units being selected as the target power conversion unit is different. In addition, the probability of each power conversion unit being selected as the cooperative power conversion unit is the same. The specific working process of this embodiment can also refer to the above-mentioned random selection method 1 and random selection method 2, and will not be described in detail here.

[0109] It is understandable that when randomly selecting a target power conversion unit, it is also possible not to randomly select a cooperative power conversion unit, but to directly use all the remaining power conversion units except the target power conversion unit as cooperative power conversion units, which is not limited here.

[0110] In some other examples, the target power conversion unit and / or the collaborative power conversion unit may also be selected in a fixed order. Specifically, in one or more control cycles within a plurality of consecutive control cycles, the target power conversion unit is one or more power conversion units selected from N power conversion units in a fixed order, and / or the collaborative power conversion unit is one or more power conversion units selected from N power conversion units in a fixed order. With this arrangement, the target power conversion unit and / or the collaborative power conversion unit can be selected in a specific selection order. The working process of selecting the target power conversion unit in a fixed order in an embodiment of the present application is described in detail below in conjunction with an embodiment of a specific fixed order selection method.

[0111] Fixed order selection method 1:

[0112] Each control cycle selects a unit group as the target power conversion unit according to a unidirectional fixed timing (for example, a positive sequence) cycle. Based on this, each M control cycle constitutes a cycle, so that multiple continuous cycles can appear, and the multiple cycles have a first cycle. Specifically, the power conversion units 210_1~210_N are divided into the first unit group Z_1 to the Mth unit group Z_M arranged in sequence, and any unit group Z_1~Z_M includes one or more power conversion units, M is an integer and M≥2. Among them, the power conversion units in different unit groups are different. Exemplarily, each unit group Z_1~Z_M can include a power conversion unit, then M=N, for example, unit group Z_1 includes power conversion unit 210_1, unit group Z_2 includes power conversion unit 210_2,...unit group Z_N includes power conversion unit 210_N. Alternatively, each unit group Z_1 to Z_M includes a plurality of power conversion units. For example, when each unit group Z_1 to Z_M includes two power conversion units, then M=N / 2, unit group Z_1 includes power conversion units 210_1 to 210_2, unit group Z_2 includes power conversion units 210_3 to 210_4, ... unit group Z_M includes power conversion units 210_N-1 to 210_N. Alternatively, some unit groups may include one power conversion unit, and the rest may include a plurality of power conversion units. It is understandable that the power conversion units in different units may also be partially identical, which is not limited here.

[0113] Moreover, for the M control cycles in the first cycle, the target power conversion unit in each control cycle is a unit group selected in the order of the first unit group Z_1 to the Mth unit group Z_M. Figure 6 Detailed description is given. Figure 6It is another schematic diagram of the working mode of the power conversion unit in the control cycle in the embodiment of the present application. Referring to the figure, there are N control cycles in the first cycle X1: the 1st control cycle to the Nth control cycle T1_1~T1_N. Specifically, in the first control cycle T1_1, the control unit 230 selects the power conversion unit 210_1 as the target power conversion unit, and selects the power conversion units 210_2~210_N as the collaborative power conversion units. In the second control cycle T1_2, the control unit 230 selects the power conversion unit 210_2 as the target power conversion unit, and selects the power conversion units 210_1, 210_3~210_N as the collaborative power conversion units. ... In the Nth control cycle T1_N, the control unit 230 selects the power conversion unit 210_N as the target power conversion unit, and selects the power conversion units 210_1~210_N-1 as the collaborative power conversion units. Furthermore, the remaining working processes in the first control cycle to the Nth control cycle T1_1-T1_N can refer to the working processes described above, which will not be described in detail. Also, after the first cycle X1 is completed, the power conversion unit 210_1 restarts the selection process, which will not be described in detail here.

[0114] It is understandable that part of the cycle period may be set as the first cycle period, or all of the cycle period may be set as the first cycle period.

[0115] Fixed order selection method 2:

[0116] Each control cycle selects a unit group as the target power conversion unit in a unidirectional fixed time sequence (for example, in reverse order). Based on this, each M control cycles can constitute a cycle, so that multiple continuous cycles can appear, and the multiple cycles have a second cycle. Specifically, the power conversion units 210_1~210_N are divided into the first unit group Z_1 to the Mth unit group Z_M arranged in sequence. For the M control cycles in the second cycle, the target power conversion unit in each control cycle is a unit group selected in the order of the Mth unit group Z_M to the first unit group Z_1. In addition, the implementation of the unit groups Z_1~Z_M can refer to the above description and will not be repeated here.

[0117] In the following, any unit group Z_1 to Z_M includes a power conversion unit and the second cycle X2 as an example. Figure 7 Detailed description is given. Figure 7 This is another schematic diagram of the working mode of the power conversion unit in the embodiment of the present application in the control cycle, referring to Figure 7, the second cycle X2 has N control cycles: the 1st control cycle to the Nth control cycle T1_1~T1_N. Specifically, in the 1st control cycle T1_1, the control unit 230 selects the power conversion unit 210_N as the target power conversion unit, and selects the power conversion units 210_1~210_N-1 as the cooperative power conversion units. ... In the N-1th control cycle T1_N-1, the control unit 230 selects the power conversion unit 210_2 as the target power conversion unit, and selects the power conversion units 210_1, 210_3~210_N as the cooperative power conversion units. In the Nth control cycle T1_N, the control unit 230 selects the power conversion unit 210_1 as the target power conversion unit, and selects the power conversion units 210_2~210_N as the cooperative power conversion units. In addition, the remaining working processes in the 1st control cycle to the Nth control cycle T1_1~T1_N can refer to the working processes described above, and will not be repeated here. And, after the second cycle X2 is completed, the power conversion unit 210_N restarts the selection process, which will not be described in detail here.

[0118] It is understandable that part of the cycle period may be set as the second cycle period, or the entire cycle period may be set as the second cycle period.

[0119] Fixed order selection method three:

[0120] The first cycle and the second cycle are combined with each other, and the first cycle and the second cycle appear alternately. In this way, a bidirectional fixed timing cycle can be realized. Specifically, the implementation of the unit groups Z_1 to Z_M can refer to the above description, and will not be repeated here. And, taking any unit group Z_1 to Z_M including a power conversion unit, and the first cycle X1_1 to X2_1 and the second cycle X1_2 to X2_2 as an example, combined Figure 8 Detailed description is given. Figure 8 This is another schematic diagram of the working mode of the power conversion unit in the embodiment of the present application in the control cycle, referring to Figure 8 First, the working process in the first cycle X1_1 is performed. Then, the working process in the second cycle X1_2 is performed. Then, the working process in the first cycle X2_1 is performed. Then, the working process in the second cycle X2_2 is performed. The rest is similar, and can be deduced in sequence, which will not be described in detail here. In addition, the working processes in the first cycle X1_1~X2_1 and the second cycle X1_2~X2_2 can refer to the above embodiment, which will not be described in detail here.

[0121] Fixed order selection method 4:

[0122] The first cycle and the second cycle are combined with each other, and at least two adjacent first cycle and at least two adjacent second cycle appear alternately. Thus set, a bidirectional fixed timing cycle can also be realized. Specifically, the implementation of the unit group Z_1~Z_M can refer to the above description, which is not repeated here. In the specific implementation, the number of adjacent first cycle periods can be made the same as the number of adjacent second cycle periods, for example, two adjacent first cycle periods and two adjacent second cycle periods appear alternately. Or, three adjacent first cycle periods and three adjacent second cycle periods appear alternately. Or, four adjacent first cycle periods and four adjacent second cycle periods appear alternately. It is also possible to make the number of adjacent first cycle periods different from the number of adjacent second cycle periods, for example, two adjacent first cycle periods and three adjacent second cycle periods appear alternately. Or, two adjacent first cycle periods and four adjacent second cycle periods appear alternately. Or, three adjacent first cycle periods and four adjacent second cycle periods appear alternately.

[0123] The following takes the alternation of two adjacent first cycles and two adjacent second cycles as an example. Fig. 9 Detailed description is given. Fig. 9 This is another schematic diagram of the cycle period in the embodiment of the present application. Fig. 9 , first, perform the working process in the first cycle X1_1. Afterwards, perform the working process in the first cycle X2_1. Afterwards, perform the working process in the second cycle X1_2. Afterwards, perform the working process in the second cycle X2_2. Afterwards, perform the working process in the first cycle X3_1. Afterwards, perform the working process in the first cycle X4_1. Afterwards, perform the working process in the second cycle X3_2. Afterwards, perform the working process in the second cycle X4_2. The rest are similar, and can be deduced successively, which will not be elaborated here. Moreover, the working processes in the first cycle X1_1~X4_1 and the second cycle X1_2~X4_2 can refer to the above description, which will not be elaborated here.

[0124] It can be understood that the above-mentioned random selection method and the fixed order selection method can be performed independently of each other, or the above-mentioned random selection method and the fixed order selection method can be combined with each other, which is not limited here.

[0125] Fig.10 Another schematic diagram of the working power of the power conversion unit provided in the embodiment of the present application is a variation of the implementation method in the above embodiment. The following only describes the differences between this embodiment and the above embodiment, and the similarities are not repeated here. Fig.10, taking the power conversion unit 210_1 as the target power conversion unit and 210_2 to 210_N as the cooperative power conversion units as an example, P210_1 represents the working power of the power conversion unit 210_1, P210_2 represents the working power of the power conversion unit 210_2, ... P210_N represents the working power of the power conversion unit 210_N. Moreover, the specific working process of the power conversion units 210_1 to 210_N can refer to the above description, which will not be repeated here. In specific applications, the maximum power P mpp Less than the original reference power P res In the case of res 'Less than or equal to the maximum power P mpp , then the updated reference power P res 'will be less than the original reference power P res Moreover, at the end of the Tm phase, the working power of the coordinated power conversion units 210_2 to 210_N is directly switched to the updated reference power P res ', but in actual operation, the working power switching will have a change process, and the time of the change process is usually short. Of course, under ideal conditions, the working power of the coordinated power conversion units 210_2 to 210_N can also be directly changed to the updated reference power P res Based on this, in the Txh2 phase, the working power of the coordinated power conversion units 210_2 to 210_N is controlled to be within the updated reference power P res Based on this, the target power change ΔP ms1_1 is the instantaneous working power P of the target power conversion unit 210_1 at time TS1 ss1_1 Compared with the reference power P before updating res The target power change ΔP ms2_1 is the instantaneous working power P of the target power conversion unit 210_1 at time TS2 ss2_1 Compared with the reference power P before updating res The change between the two. Coordinated power change ΔP xs1_2 is the instantaneous working power P of the coordinated power conversion unit 210_2 at time TS1 ss1_2 The coordinated adjustment of the set power (i.e. the original reference power P res ) between the two. Coordinated power change ΔP xs2_2 is the instantaneous working power P of the coordinated power conversion unit 210_2 at time TS2 ss2_2 With the updated reference power P res '. Similarly, the coordinated power change ΔP xs1 _3~ΔP xs1 _N , ΔP xs2 _3~ΔP xs2_N The same can be said for many other reasons, so I will not elaborate on them here.

[0126] And, refer to Fig.10 Taking time TS1 as an example, the target power change ΔP of the target power conversion unit 210_1 during the mode switching process is ms1_1 Relatively speaking, it is reduced, so the target power change ΔP ms1_1 is a negative value, that is, its sign is negative, so the sum of the target power changes ΔP msm (At this time, ΔP msm =ΔP ms1_1 ) is also a negative value and its sign is also negative. In order to reduce the fluctuation of the total output power and output voltage of the power conversion unit, the coordinated power change ΔP xs1_2 ~ΔP xs1_N Offset target power change ΔP ms1_1 , it is necessary to control the coordinated power conversion unit to be at the reference power (for example, the original reference power P before updating) res ) based on the coordinated increase of the corresponding power, so that the coordinated power change ΔP xs1_2 ~ΔP xs1_N is a positive value, that is, ΔP xs1_2 ~ΔP xs1_N The sign of is positive, so that the coordinated power change ΔP xs1_2 ~ΔP xs1_N The sum of is also a positive value and its sign is also positive. In addition, at the end of the Tm phase, the working power of the coordinated power conversion units 210_2 to 210_N is directly switched to the updated reference power P res ', in order to continue the coordinated adjustment in the Txh2 stage, the control unit also controls the working power of the coordinated power conversion units 210_2 to 210_N in the Txh2 stage, and the updated reference power P res Based on this, taking TS2 as an example, the target power change ΔP of the target power conversion unit 210_1 during the mode switching process is ms2_1 Relatively speaking, it is also reduced, so the target power change ΔP ms2_1 is a negative value, that is, its sign is negative, so the sum of the target power changes ΔP msm (At this time, ΔP msm =ΔP ms2_1 ) is also a negative value and its sign is also negative. In order to reduce the fluctuation of the total output power and output voltage of the power conversion unit, the coordinated power change ΔP xs2_2 ~ΔP xs2_N Offset target power change ΔP ms2_1, it is necessary to control the coordinated power conversion unit to be at the reference power (e.g. the updated reference power P res ') based on the coordinated increase of the corresponding power, so that the coordinated power change ΔP xs2_2 ~ΔP x2_N is a positive value, that is, ΔP xs2_2 ~ΔP xs2_N The sign of is positive, so that the coordinated power change ΔP xs2_2 ~ΔP xs2_N The sum is also positive and its sign is also positive.

[0127] For example, refer to Fig.10 , taking TS1 as an example, ΔP msm =ΔP ms1_1 , the collaborative power conversion unit 210_2 is the first collaborative power conversion unit, and the collaborative power conversion unit 210_2 corresponds to the allocation weight α1, then the collaborative power change amount ΔP corresponding to the collaborative power conversion unit 210_2 xs1_2 = -α1*ΔP msm , that is, ΔP xs1_2 = -α1*ΔP ms1_1 The coordinated power conversion unit 210_3 is used as the second coordinated power conversion unit, and the coordinated power conversion unit 210_3 is assigned a weight α2. Then the coordinated power change amount ΔP corresponding to the coordinated power conversion unit 210_3 is xs1 _3 is: -α2*ΔP msm , that is, ΔP xs1_3 = -α2*ΔP ms1_1 The coordinated power conversion unit 210_4 is the third coordinated power conversion unit, and the coordinated power conversion unit 210_4 is assigned a weight α3. Then the coordinated power change amount ΔP corresponding to the coordinated power conversion unit 210_4 is xs1_4 = -α3*ΔP msm , that is, ΔP xs1_4 = -α3*ΔP ms1_1 ... The coordinated power conversion unit 210_N is used as the mth coordinated power conversion unit, and the coordinated power conversion unit 210_N is assigned a corresponding weight α m , then the coordinated power conversion unit 210_N corresponds to the coordinated power change ΔP xs1_N is: -α m *ΔP msm , that is, ΔP xs1_N =-α m *ΔP ms1_1 .

[0128] Taking TS2 as an example, ΔP msm =ΔP ms2_1, the collaborative power conversion unit 210_2 is the first collaborative power conversion unit, and the collaborative power conversion unit 210_2 corresponds to the allocation weight α1, then the collaborative power change amount ΔP corresponding to the collaborative power conversion unit 210_2 xs2_2 = -α1*ΔP msm , that is, ΔP xs2_2 = -α1*ΔP ms2_1 The coordinated power conversion unit 210_3 is used as the second coordinated power conversion unit, and the coordinated power conversion unit 210_3 is assigned a weight α2. Then the coordinated power change amount ΔP corresponding to the coordinated power conversion unit 210_3 is xs2_3 = -α2*ΔP msm , that is, ΔP xs2_3 = -α2*ΔP ms2_1 The coordinated power conversion unit 210_4 is the third coordinated power conversion unit, and the coordinated power conversion unit 210_4 is assigned a weight α3. Then the coordinated power change amount ΔP corresponding to the coordinated power conversion unit 210_4 is xs2_4 = -α3*ΔP msm , that is, ΔP xs2_4 = -α3*ΔP ms2_1 ... The coordinated power conversion unit 210_N is used as the mth coordinated power conversion unit, and the coordinated power conversion unit 210_N is assigned a corresponding weight α m , then the coordinated power conversion unit 210_N corresponds to the coordinated power change ΔP xs2_N is: -α m *ΔP msm , that is, ΔP xs2_N =-α m *ΔP ms2_1 .

[0129] Continue to refer to Fig.10 , each coordinated power variation and each target power variation can appear in the same stage, that is, the appearance time of each coordinated power variation is the same as the appearance time of each target power variation, and the end time of each coordinated power variation is the same as the end time of each target power variation. For example, the coordinated power variation ΔP xs1_2 ~ΔP xs1_N The target power change ΔP ms1_1 Appearing at the same time TS1, the coordinated power change ΔP xs2_2 ~ΔP xs2_N The target power change ΔP ms2_1This setting can improve the timeliness of the coordinated control, so that when the target power conversion unit has a working power change, the coordinated power conversion unit can be controlled in time to coordinately adjust the coordinated power change, so as to offset the working power change through the coordinated power change, thereby reducing the fluctuation of the output power and output voltage of the power conversion unit.

[0130] Fig.11 Another schematic diagram of the working power of the power conversion unit provided in the embodiment of the present application is a variation of the implementation method in the above embodiment. The following only describes the differences between this embodiment and the above embodiment, and the similarities are not repeated here. Fig.11 , taking the power conversion unit 210_1 as the target power conversion unit and 210_2~210_N as the collaborative power conversion units as an example, P210_1 represents the working power of the power conversion unit 210_1, P210_2 represents the working power of the power conversion unit 210_2, ... P210_N represents the working power of the power conversion unit 210_N. Moreover, the specific working process of the power conversion units 210_1~210_N can refer to the above description and will not be repeated here. Moreover, at the end of the Txh2 stage, the working power of the collaborative power conversion units 210_2~210_N is directly switched to the updated reference power P res ', but in actual operation, the working power switching will have a change process, and the time of the change process is usually short. Of course, under ideal conditions, the working power of the coordinated power conversion units 210_2 to 210_N can also be directly changed to the updated reference power P res '. In addition, in the Txh1 stage and the Txh2 stage, the working power of the coordinated power conversion units 210_2 to 210_N is controlled to be within the original reference power P res Based on this, the target power change ΔP ms1_1 is the instantaneous working power P of the target power conversion unit 210_1 at time TS1 ss1_1 Compared with the reference power P before updating res The target power change ΔP ms2_1 is the instantaneous working power P of the target power conversion unit 210_1 at time TS2 ss2_1 Compared with the reference power P before updating res The change between the two. Coordinated power change ΔP xs1_2 is the instantaneous working power P of the coordinated power conversion unit 210_2 at time TS1 ss1_2 With the set power (such as the original reference power P res ) between the two. Coordinated power change ΔP xs2_2is the instantaneous working power P of the coordinated power conversion unit 210_2 at time TS2 ss2_2 With the set power (such as the original reference power P res Or the updated reference power P res '). Similarly, the coordinated power change ΔP xs1_3 ~ΔP xs1_N , ΔP xs2_3 ~ΔP xs2_N The same can be said for many other reasons, so I will not elaborate on them here.

[0131] And, refer to Fig.11 Taking time TS1 as an example, the target power change ΔP of the target power conversion unit 210_1 during the mode switching process is ms1_1 Relatively speaking, it is reduced, so the target power change ΔP ms1_1 is a negative value, that is, its sign is negative, so the sum of the target power changes ΔP msm (At this time, ΔP msm =ΔP ms1_1 ) is also a negative value and its sign is also negative. In order to reduce the fluctuation of the total output power and output voltage of the power conversion unit, the coordinated power change ΔP xs1_2 ~ΔP xs1_N Offset target power change ΔP ms1_1 , it is necessary to control the coordinated power conversion unit to be at the reference power (for example, the original reference power P before updating) res ) based on the coordinated increase of the corresponding power, so that the coordinated power change ΔP xs1_2 ~ΔP xs1_N is a positive value, that is, ΔP xs1_2 ~ΔP xs1_N The sign of is positive, so that the coordinated power change ΔP xs1_2 ~ΔP xs1_N The sum of is also a positive value and its sign is also positive. In addition, at the end of the Tm phase, the working power of the coordinated power conversion units 210_2 to 210_N is directly switched to the updated reference power P res ', in order to continue the coordinated adjustment in the Txh2 stage, the control unit also controls the working power of the coordinated power conversion units 210_2 to 210_N in the Txh2 stage, and the updated reference power P res Based on this, taking TS2 as an example, the target power change ΔP of the target power conversion unit 210_1 during the mode switching process is ms2_1 Relatively speaking, it is also reduced, so the target power change ΔP ms2_1 is a negative value, that is, its sign is negative, so the sum of the target power changes ΔP msm (At this time, ΔPmsm =ΔP ms2_1 ) is also a negative value and its sign is also negative. In order to reduce the fluctuation of the total output power and output voltage of the power conversion unit, the coordinated power change ΔP xs2_2 ~ΔP xs2_N Offset target power change ΔP ms2_1 , it is necessary to control the coordinated power conversion unit to be at the reference power (e.g. the updated reference power P res ') based on the coordinated increase of the corresponding power, so that the coordinated power change ΔP xs2_2 ~ΔP x2_N is a positive value, that is, ΔP xs2_2 ~ΔP xs2_N The sign of is positive, so that the coordinated power change ΔP xs2_2 ~ΔP xs2_N The sum is also positive and its sign is also positive.

[0132] Fig.12 Another schematic diagram of the working power of the power conversion unit provided in the embodiment of the present application is a variation of the implementation method in the above embodiment. The following only describes the differences between this embodiment and the above embodiment, and the similarities are not repeated here. Fig.12 , taking the power conversion unit 210_1 as the target power conversion unit and 210_2 to 210_N as the cooperative power conversion units as an example, P210_1 represents the working power of the power conversion unit 210_1, P210_2 represents the working power of the power conversion unit 210_2, ... P210_N represents the working power of the power conversion unit 210_N, and the target power change amount ΔP ms1_1 ~ΔP ms2_1 And the coordinated power change ΔP xs1_2 ~ΔP xs1_N , ΔP xs2_2 ~ΔP xs2_N The implementation method is basically the same as that in the above embodiment, except that: the stage at which each cooperative power change occurs is later than the stage at which each working power change occurs, that is, the stage at which each cooperative power change occurs is delayed as a whole compared to the stage at which each working power change occurs. For example, the stage at which each cooperative power change occurs is delayed as a whole compared to the stage at which each working power change occurs by a delay time parameter T delay That is, the occurrence time of each coordinated power variation is later than the occurrence time of each target power variation by a certain delay time parameter T delay , and the end time of each coordinated power variation is also later than the end time of each target power variation by a certain delay time parameter T delay For example, the target power change ΔP ms1_1It appears at TS1 and starts at TS1 after the delay time parameter T delay After reaching TS3, the coordinated power change ΔP xs1_2 ~ΔP xs1_N Appears at time TS3. Similarly, the target power change ΔP ms2_1 It appears at time TS2 and starts at time TS2 after the delay time parameter T delay After reaching TS4, the coordinated power change ΔP xs2_2 ~ΔP xs2_N It appears at time TS4. It is understandable that the delay time parameter T delay The specific time can be determined according to the needs of the actual application scenario and is not limited here.

[0133] Based on this, the coordinated power change corresponding to the y-th coordinated power conversion unit can be made as follows: ,in, Represents the pull-type transformation expression when delayed, T delay represents the delay time parameter, and its size can be determined by the system characteristics, or can be configured online or offline through control. By setting this, the working power of the yth cooperative power conversion unit can be reduced (or increased) based on the cooperative power change amount, and the delay time parameter T delay Delay is performed so that there is a time interval T between the target power change and the corresponding coordinated power change delay .

[0134] It is understandable that, due to the fact that during the actual operation of the power conversion system, there will be a certain delay in signal transmission, so the delay time parameter T delay It may refer to the delay that occurs when the power conversion system is running, which is not set manually online or offline. Of course, in order to match the delay of the power conversion system, the delay time parameter T can also be set manually online or offline. delay Can be a fixed value or a changing value.

[0135] Fig.13 Another schematic diagram of the working power of the power conversion unit provided in the embodiment of the present application is a variation of the implementation method in the above embodiment. The following only describes the differences between this embodiment and the above embodiment, and the similarities are not repeated here. Fig.13 , taking the power conversion unit 210_1 as the target power conversion unit and 210_2 to 210_N as the cooperative power conversion units as an example, P210_1 represents the working power of the power conversion unit 210_1, P210_2 represents the working power of the power conversion unit 210_2, ... P210_N represents the working power of the power conversion unit 210_N, and the target power change amount ΔPms1 _1~ΔP ms2_1 And the coordinated power change ΔP xs1_2 ~ΔP xs1 _ N , ΔP xs2_2 ~ΔP xs2_N The implementation method is basically the same as that in the above embodiment, except that: the sum of the target power changes ΔP msm With reference threshold ΔP err Compared with the target power change sum ΔP msm Less than the reference threshold ΔP err When , it can be considered that the power change of the target power conversion unit has little effect on the total output power and output voltage, so there is no need to control the working power of the cooperative power conversion unit for coordinated adjustment. msm Greater than or equal to the reference threshold ΔP err When , it can be considered that the power change of the target power conversion unit has a greater impact on the total output power and output voltage, so the working power of the coordinated power conversion unit is controlled to be coordinated and adjusted. Specifically, the control unit can respond to the target power change amount ΔP msm The sum is greater than or equal to the reference threshold ΔP err According to the working power change amount of the target power conversion unit during the mode switching process, the working power of the coordinated power conversion unit is controlled to be coordinated and adjusted based on the set power. msm <ΔP err When ΔP msm ≥ΔP err When the working power of the coordinated power conversion units 210_2 to 210_N is controlled to be coordinated and adjusted based on the set power, the coordinated power change amount corresponding to the yth coordinated power conversion unit is: y *ΔP msm , generating ΔP for each coordinated power conversion unit 210_2 to 210_N xs1_2 ~ΔP xs1 _ N , ΔP xs2_2 ~ΔP xs2_N and make the working power of the coordinated power conversion units 210_2 to 210_N follow ΔP xs1_2 ~ΔP xs1 _ N , ΔP xs2_2 ~ΔP xs2_N To make an adjustment (e.g., increase or decrease). For example, refer to Figure 7 , before TS5, ΔP msm<ΔP err , control the working power of the coordinated power conversion units 210_2 to 210_N to follow the original reference power P res After TS6, ΔP msm <ΔP err , control the working power of the coordinated power conversion units 210_2 to 210_N to follow the updated reference power P res 'Run. Between TS5 and TS6, ΔP msm ≥ΔP err , according to the yth cooperative power conversion unit corresponding to the cooperative power change amount: -α y *ΔP msm The working power of the collaborative power conversion units 210_2 to 210_N is controlled to be collaboratively adjusted (eg, increased or decreased) based on the set power.

[0136] It is understandable that the reference threshold ΔP err The specific value can be configured online or offline according to the actual application requirements.

[0137] Fig.14 Another schematic diagram of the working power of the power conversion unit provided in the embodiment of the present application is a variation of the implementation method in the above embodiment. The following only describes the differences between this embodiment and the above embodiment, and the similarities are not repeated here. Fig.14 , taking the power conversion unit 210_1 as the target power conversion unit and 210_2 to 210_N as the cooperative power conversion units as an example, P210_1 represents the working power of the power conversion unit 210_1, P210_2 represents the working power of the power conversion unit 210_2, ... P210_N represents the working power of the power conversion unit 210_N. In addition, each cooperative power change amount can also be based on the constant cooperative power setting value ΔP syn0 Determine. Among them, the constant coordinated power setting value ΔP syn0 It is a preset parameter of power coordination, which can be configured not only as a required fixed value or variable value online or offline, but also according to the maximum power obtained in MPPT mode.

[0138] Exemplarily, the coordinated power change corresponding to the zth coordinated power conversion unit among the m coordinated power conversion units can be: z *ΔP syn0 , α z represents the allocation weight corresponding to the zth cooperative power conversion unit, and α z ∈[0, 1], ΔP syn0Represents a constant cooperative power setting value. By setting this, the sign of the cooperative power change corresponding to each cooperative power conversion unit can be opposite to the sum of the target power change, and the distribution weight α can be used to z , ΔP syn0 Distributed to different cooperative power conversion units. It can be understood that α z The implementation method can refer to α y The specific implementation method will not be described here.

[0139] For example, refer to Fig.14 , the target power change amount of the target power conversion unit 210_1 is ΔP ms_1 , then ΔP msm =ΔP ms_1 . The coordinated power change corresponding to the zth coordinated power conversion unit is: -α z *ΔP syn0 , the collaborative power conversion unit 210_2 is the first collaborative power conversion unit, and the collaborative power conversion unit 210_2 corresponds to the allocation weight α1, then the collaborative power conversion unit 210_2 corresponds to the collaborative power change ΔP xs _2 is: -α1*ΔP syn0 , that is, ΔP xs_2 = -α1*ΔP syn0 , so that the working power of the cooperative power conversion unit 210_2 is within the original reference power P res Adjust (e.g., reduce) ΔP based on xs_2 The coordinated power conversion unit 210_3 is used as the second coordinated power conversion unit, and the coordinated power conversion unit 210_3 is assigned a weight α2. Then the coordinated power change amount ΔP corresponding to the coordinated power conversion unit 210_3 is xs_3 = -α2*ΔP syn0 , that is, ΔP xs_3 = -α2*ΔP syn0 , so that the working power of the cooperative power conversion unit 210_3 is within the original reference power P res Adjust (e.g., reduce) ΔP based on xs_3 The coordinated power conversion unit 210_4 is the third coordinated power conversion unit, and the coordinated power conversion unit 210_4 is assigned a weight α3. Then the coordinated power change amount ΔP corresponding to the coordinated power conversion unit 210_4 is xs_4 = -α3*ΔP syn0 , that is, ΔP xs_4 = -α3*ΔP syn0 , so that the working power of the cooperative power conversion unit 210_4 is within the original reference power P res Adjust (e.g., reduce) ΔP based on xs_4... The coordinated power conversion unit 210_N is used as the mth coordinated power conversion unit, and the coordinated power conversion unit 210_N is assigned a corresponding weight α m , then the coordinated power conversion unit 210_N corresponds to the coordinated power change ΔP xs_N is: -α m *ΔP syn0 , that is, ΔP xs_N =-α m *ΔP syn0 , so that the working power of the cooperative power conversion unit 210_N is within the original reference power P res Adjust (e.g., reduce) ΔP based on xs_N .

[0140] Fig.15a This is another structural diagram of a power conversion system provided in an embodiment of the present application. Fig.15a The power conversion system 200 includes: N power conversion units 210_1 to 210_N (N is an integer and N≥2) and a control unit 230, so that the power conversion system is set as a photovoltaic inverter with a monopolar architecture. Among them, the input end of each power conversion unit 210_1 to 210_N is respectively connected to the photovoltaic module 100 as a DC power supply, and the output end of each power conversion unit 210_1 to 210_N is connected to the power grid 400 through the grid-connected transformer 300. In specific applications, each power conversion unit 210_1 to 210_N converts the DC power input by the photovoltaic module 100 into AC power and outputs it to the grid-connected transformer 300, and the grid-connected transformer 300 performs step-up or step-down conversion and outputs it to the power grid 400. Of course, in actual applications, it is also possible not to set up the grid-connected transformer 300, but to directly connect the output end of the power conversion system 200 to the power grid 400. In addition, the output end of the power conversion unit can also be connected to the load to supply power to the load. Alternatively, the output end of the power conversion unit can also be directly connected to the AC system.

[0141] Fig.15b This is another structural diagram of a power conversion system provided in an embodiment of the present application. Fig.15b , the power conversion unit may be a DC-AC conversion circuit 212, and the first end of the DC-AC conversion circuit 212 is used to connect the photovoltaic module 100 as a DC power source, and the second end of the DC-AC conversion circuit 212 is used to connect the load or the power grid or the AC system. Exemplarily, the DC-AC conversion circuit 212 is used to convert the DC power input by the photovoltaic module into AC power and then output it to the load or the power grid or the AC system. The rest of the content in this embodiment may be basically the same as the content in the above embodiment, and will not be repeated here.

[0142] In some other examples, the power conversion unit can also be configured as a direct current-to-direct current (DC-DC) conversion circuit. Among them, the first end of the direct current-to-direct current conversion circuit is used to connect a direct current power supply, and the second end of the direct current-to-direct current conversion circuit is used to connect a load or an energy storage unit or a power generation unit. Exemplarily, the DC-DC conversion circuit is used to convert the direct current input by the direct current power supply into power and output it to the load or the energy storage unit or the power generation unit. Alternatively, the DC-DC conversion circuit can also be used to convert the direct current input by the energy storage unit or the power generation unit into power and output it to the direct current power supply. For example, the direct current power supply is a photovoltaic module.

[0143] In some other examples, the power conversion unit can also be set as an alternating current-direct current (AC-DC) conversion circuit. Among them, the first end of the AC-DC conversion circuit is used to connect to an AC power supply, and the second end of the AC-DC conversion circuit is used to connect to a load or an energy storage unit or a power generation unit. Exemplarily, the AC-DC conversion circuit is used to convert the AC power input from the AC power supply into DC power and then output it to the load or the energy storage unit or the power generation unit. Alternatively, the AC-DC conversion circuit can also be used to convert the DC power input from the energy storage unit or the power generation unit into AC power and then output it to the AC power supply.

[0144] In some other examples, the power conversion system can also be set as an AC-DC (AC-DC) conversion circuit, and the power conversion system also includes a DC-AC (DC-AC) conversion circuit. Wherein, the first end of the AC-DC conversion circuit is used to connect to the AC power supply, the second end of the AC-DC conversion circuit is connected to the first end of the DC-AC conversion circuit, and the second end of the DC-AC conversion circuit is used to connect to the load or the power grid. Exemplarily, the AC-DC conversion circuit is used to convert the AC power input by the AC power supply into DC power and then output it to the DC-AC conversion circuit, and the DC-AC conversion circuit is used to convert the input DC power into AC power and then output it to the load or energy storage unit or power generation unit. Alternatively, the DC-AC conversion circuit can also convert the AC power input by the energy storage unit or the power generation unit into DC power and then output it to the AC-DC conversion circuit, and the AC-DC conversion circuit can convert the input DC power into AC power and then output it to the AC power supply.

[0145] In addition, when the power conversion unit in the power conversion system provided in the embodiment of the present application is connected to the energy storage unit, the power conversion unit can also be configured as an energy storage inverter to be applied to the energy storage system.

[0146] The embodiment of the present application also provides a power update control method, which is applied to a power conversion system, wherein the power conversion system includes N power conversion units, where N is an integer and N≥2; the first end of each power conversion unit is used to connect to a DC power supply or an AC power supply, and the second end of each power conversion unit is used to connect to a load or an energy storage unit or a power grid, and the power conversion unit is used to convert the DC power input by the DC power supply or the AC power input by the AC power supply and output it. In addition, the power update control method includes: controlling the working mode of one or more target power conversion units among the N power conversion units to switch between a power reservation PR mode and a maximum power point tracking MPPT mode, and updating the reference power according to the maximum power obtained in the MPPT mode, so that the working power of the target power conversion unit after switching from the MPPT mode to the PR mode is the updated reference power; wherein the updated reference power is less than or equal to the maximum power. Furthermore, the working modes of the cooperative power conversion units except the target power conversion unit among the N power conversion units are controlled to remain unchanged, and according to the change in the working power of the target power conversion unit during the mode switching process, the working power of the cooperative power conversion units is controlled to be cooperatively adjusted so that the total change in the working power of the N power conversion units is less than the change threshold.

[0147] The embodiment of the present application also provides a power supply system, a power supply system, which includes a power conversion system, wherein the first end of the power conversion unit in the power conversion system is connected to a DC power supply or an AC power supply, and the second end of the power conversion system is used to connect a load or an energy storage unit or a power generation unit or a power grid. In addition, the power conversion system is used to convert the direct current input by the DC power supply or the alternating current input by the AC power supply for output. The power conversion system is the power conversion system in any of the above-mentioned embodiments. Since the power conversion system provided in the embodiment of the present application can realize the update of the working power of the power conversion unit in the PR mode, and reduce the fluctuation of the output power and output voltage of the power conversion unit, the stability and control accuracy of the power supply system can be improved.

[0148] The above power supply system can be configured as a photovoltaic system, then the power supply system further includes a photovoltaic component, and the first end of the power conversion unit in the power conversion system is connected to the photovoltaic component, and the photovoltaic component serves as a DC power supply.

[0149] The above contents are only specific implementation methods of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be covered by the protection scope of the present application.

Claims

1. A power conversion system, characterized in that: include: N power conversion units and control units, wherein N is an integer and N≥2; the first end of each of the power conversion units is used to connect to a DC power supply or an AC power supply, the second end of each of the power conversion units is used to connect to a load or an energy storage unit or a power grid, and the power conversion unit is used to convert the DC power input by the DC power supply or the AC power input by the AC power supply and then output it; The control unit is used for: In a control cycle, the working mode of one or more target power conversion units among the N power conversion units is controlled to switch between a power reservation PR mode and a maximum power point tracking MPPT mode, and a reference power is updated according to the maximum power obtained in the MPPT mode, so that the working power of the target power conversion unit after switching from the MPPT mode to the PR mode is the updated reference power; wherein the updated reference power is less than or equal to the maximum power; Control the working modes of the cooperative power conversion units among the N power conversion units except the target power conversion unit to remain unchanged, and control the cooperative adjustment of the working power of the cooperative power conversion units according to the change in the working power of the target power conversion unit during the mode switching process, so that the total change in the working power of the N power conversion units is less than the change threshold.

2. The power conversion system according to claim 1, characterized in that: The N power conversion units include: k target power conversion units and m cooperative power conversion units; k is an integer and 1≤k≤N-1, m is an integer and 1≤m≤N-1, and satisfies 2≤k+m≤N; The operating power variation of each target power conversion unit during the mode switching process includes a target power variation, where the target power variation is a variation between the instantaneous operating power of the target power conversion unit during the mode switching process and a reference power; The working power variation of each of the cooperative power conversion units during the cooperative adjustment process includes a cooperative power variation, which is a variation between the instantaneous working power of the cooperative power conversion unit during the cooperative adjustment process and the set power; The sum of the coordinated power changes has an opposite sign to the sum of the target power changes, and a difference between an absolute value of the sum of the coordinated power changes and an absolute value of the sum of the target power changes is smaller than the change threshold.

3. The power conversion system according to claim 2, characterized in that: Each of the coordinated power changes is determined according to the sum of the target power changes.

4. The power conversion system according to claim 3, characterized in that: The coordinated power change corresponding to the yth coordinated power conversion unit among the m coordinated power conversion units is: y *ΔP msm , the α y represents the allocation weight corresponding to the y-th cooperative power conversion unit, and α y ∈[0, 1], ΔP msm Represents the sum of the target power changes.

5. The power conversion system according to claim 2, characterized in that: Each of the cooperative power variation amounts is determined according to a constant cooperative power setting value.

6. The power conversion system according to claim 5, characterized in that: The coordinated power change corresponding to the zth coordinated power conversion unit among the m coordinated power conversion units is: z *ΔP syn0 , the α z represents the allocation weight corresponding to the zth cooperative power conversion unit, and α z ∈[0, 1], ΔP syn0 Represents the constant coordinated power setting value.

7. The power conversion system according to any one of claims 2 to 6, characterized in that: Each of the coordinated power variation amounts and each of the target power variation amounts occur in the same phase.

8. The power conversion system according to any one of claims 2 to 6, characterized in that: The phase at which each of the coordinated power variation amounts appears is later than the phase at which each of the target power variation amounts appears.

9. The power conversion system according to any one of claims 1 to 8, characterized in that: The control unit is further configured to: In response to the sum of the target power changes being greater than or equal to a reference threshold, controlling the working power of the cooperative power conversion unit to be cooperatively adjusted based on the set power according to the target power change of the target power conversion unit during the mode switching process; The target power variation is the variation between the instantaneous working power of the target power conversion unit during the mode switching process and the reference power.

10. The power conversion system according to any one of claims 1 to 9, characterized in that: The working mode of the collaborative power conversion unit is the PR mode, and the working power of the collaborative power conversion unit is updated with the updated reference power.

11. The power conversion system according to any one of claims 1 to 10, characterized in that: The target power conversion unit is randomly selected from the N power conversion units; and / or, The cooperative power conversion unit is randomly selected from the N power conversion units.

12. The power conversion system according to any one of claims 1 to 10, characterized in that: The probability of at least some of the power conversion units being selected as the target power conversion units is different; or, The probability of at least some of the power conversion units being selected as the cooperative power conversion units is different.

13. The power conversion system according to any one of claims 1 to 10, characterized in that: The target power conversion unit is selected from the N power conversion units in order; and / or, The cooperative power conversion unit is selected from the N power conversion units in sequence.

14. The power conversion system according to claim 13, characterized in that: The N power conversion units include a first unit group to an Mth unit group arranged in sequence, any of the unit groups includes one or more power conversion units, and M is an integer and M≥2; The plurality of consecutive cycles include one or a combination of a first cycle and a second cycle; In the first cycle, a unit group is selected in sequence from the first unit group to the Mth unit group as a target power conversion unit; In the second cycle, a unit group is selected in sequence from the Mth unit group to the first unit group as a target power conversion unit.

15. A power update control method, characterized in that: The method is applied to a power conversion system, which includes: N power conversion units, where N is an integer and N≥2; a first end of each of the power conversion units is used to connect to a DC power supply or an AC power supply, a second end of each of the power conversion units is used to connect to a load or an energy storage unit or a power grid, and the power conversion unit is used to convert the DC power input by the DC power supply or the AC power input by the AC power supply and then output it; The power update control method comprises: Controlling the working mode of one or more target power conversion units among the N power conversion units to switch between a power reservation PR mode and a maximum power point tracking MPPT mode, updating a reference power according to the maximum power obtained in the MPPT mode, so that the working power of the target power conversion unit after switching from the MPPT mode to the PR mode is the updated reference power; wherein the updated reference power is less than or equal to the maximum power; Control the working modes of the cooperative power conversion units among the N power conversion units except the target power conversion unit to remain unchanged, and control the cooperative adjustment of the working power of the cooperative power conversion units according to the change in the working power of the target power conversion unit during the mode switching process, so that the total change in the working power of the N power conversion units is less than the change threshold.

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