Direct current network construction type distributed photovoltaic power supply system

Abstract

The invention discloses a direct-current networking type distributed photovoltaic power supply system which comprises a photovoltaic array, a DC / DC converter, a direct-current bus, a power controller, a droop controller and a power compensation controller. The power compensation controller determines a control parameter associated with mapping according to the illumination intensity, and obtains a first compensation amount through a PI controller; obtaining node output voltage corresponding to each photovoltaic power supply, calculating an output voltage difference value between different nodes, and obtaining a second compensation amount through a PI controller; the power compensation controller inputs the comprehensive compensation amount of the first compensation amount and the second compensation amount into a droop controller; the droop controller obtains the direct-current bus voltage and corrects the reference voltage to be corrected according to the comprehensive compensation amount; and the power controller carries out regulation and control according to the corrected power reference value. According to the invention, distributed secondary cooperative control of the photovoltaic power supply is realized based on # imgabs0 # droop control, and a photovoltaic power supply output voltage consistency control strategy is combined.

Description

Technical Field

[0001] The present invention relates to the field of distributed power generation, and in particular to a DC grid-type distributed photovoltaic power supply system. Background Art

[0002] With the development of renewable energy technologies, distributed photovoltaic power generation systems are increasingly being used in power systems due to their clean, environmentally friendly, flexible, and reliable nature. As a new power system architecture, DC microgrids connect multiple distributed photovoltaic power sources via a DC bus. With advantages such as high transmission efficiency and a simple system structure, they have become a key application of distributed photovoltaic power generation systems.

[0003] In a DC microgrid, power distribution control of distributed photovoltaic power sources is one of the key technologies to ensure stable system operation. Traditional distributed photovoltaic power control methods mainly use the VI droop control strategy to achieve power distribution by adjusting the droop coefficient.

[0004] In photovoltaic power generation systems, maximum power point tracking (MPPT) technology is widely used to improve the energy efficiency of photovoltaic power sources. However, when photovoltaic systems need to operate in coordination with the power grid, relying solely on MPPT control cannot meet system stability requirements.

[0005] The main problem with the existing technology is that in DC grid-type distributed photovoltaic power supply systems, the traditional VI droop control strategy only considers the droop coefficient and fails to fully consider the differences in the actual power generation capacity of each photovoltaic power supply under different lighting conditions. This results in the system being unable to achieve fair power distribution according to the maximum available power ratio of each photovoltaic power supply under uneven lighting conditions, thereby affecting the overall power generation efficiency and stability of the system. Specifically, when each photovoltaic power supply is affected by different light intensities, the traditional droop control method will cause the photovoltaic power supply with stronger light to be unable to fully realize its power generation potential, while the photovoltaic power supply with weaker light may be forced to operate beyond its actual capacity range, which not only reduces the energy utilization efficiency of the system, but may also cause system instability or even failure.

[0006] Furthermore, existing technologies lack an effective mechanism to coordinate voltage differences between different nodes, resulting in large fluctuations in the DC bus voltage and affecting the system's stable operation. Maintaining smooth transitions and stable operation, especially under rapidly changing lighting conditions, remains a pressing technical challenge.

[0007] The disclosure of the above background technology content is only used to assist in understanding the concept and technical solution of this application. It does not necessarily belong to the prior art of this application, nor does it necessarily provide technical guidance. In the absence of clear evidence that the above content has been disclosed before the filing date of this application, the above background technology should not be used to evaluate the novelty and creativity of this application. Summary of the Invention

[0008] The purpose of the present invention is to provide a system that solves the problem of uneven power distribution of DC grid-connected photovoltaic power sources under different lighting conditions, compensates for voltage deviations caused by droop control, and realizes fair power distribution among photovoltaic power sources based on consistency control of photovoltaic output ratio.

[0009] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0010] A DC grid-type distributed photovoltaic power supply system includes a power circuit and a control circuit, wherein the power circuit includes a photovoltaic array, a DC / DC converter and a DC bus, and the control circuit includes a power controller, a droop controller, a power compensation controller and a light sensor;

[0011] The light sensor is configured to detect the light intensity of each photovoltaic power source of the photovoltaic array;

[0012] The power compensation controller determines a control parameter associated with the mapping according to the light intensity, and calculates a first compensation amount through a first PI controller; obtains the node output voltage corresponding to each photovoltaic power source, calculates the output voltage difference between different nodes, and calculates a second compensation amount through a second PI controller;

[0013] The power compensation controller inputs a comprehensive compensation amount of the first compensation amount and the second compensation amount into the droop controller;

[0014] The droop controller obtains the DC bus voltage and corrects the reference voltage to be corrected according to the comprehensive compensation amount as follows: in, To correct the power reference value, is the nominal power value, m is the droop coefficient, is the reference voltage value to be corrected, v dc is the DC bus voltage, Δv is the comprehensive compensation output by the power compensation controller;

[0015] The power controller regulates the DC / DC converter of the power circuit according to the power reference value corrected by the droop controller.

[0016] Furthermore, based on any one of the above technical solutions or a combination of multiple technical solutions, the power controller further calculates the duty cycle of the DC / DC converter in the following manner:

[0017] Sampling the output of the photovoltaic array to calculate the output power of the photovoltaic array;

[0018] Calculating a ratio of the power reference value to the output power of the photovoltaic array as a duty cycle;

[0019] And the power controller dynamically controls the control end of the DC / DC converter according to the duty cycle and the power reference value.

[0020] Further, based on any one of the above technical solutions or a combination of multiple technical solutions, the DC / DC converter includes a capacitor branch, a diode branch, and an LC branch connected in parallel at both ends of the photovoltaic array, wherein the capacitor branch includes at least one capacitor, the positive plate of the capacitor is connected to the positive electrode of the DC bus, and the negative plate of the capacitor is connected to the negative electrode of the DC bus;

[0021] The diode branch includes at least one diode, the cathode of the diode is connected to the cathode of the DC bus, and the anode of the diode is connected to the anode of the DC bus;

[0022] The LC branch includes an inductor and a capacitor connected in series, the middle connection point between the capacitor and the inductor on the LC branch is connected to the positive electrode of the DC bus, and the negative plate of the capacitor on the LC branch is connected to the negative electrode of the DC bus.

[0023] Further, based on any one of the above technical solutions or a combination of multiple technical solutions, the DC / DC converter further includes a controllable switch, which is arranged between the capacitor branch and the cathode of the diode;

[0024] The control end of the controllable switch is connected to the output end of the power controller.

[0025] Further, based on any one of the above technical solutions or a combination of multiple technical solutions, the DC / DC converter further includes a current loop and a voltage loop, wherein the current loop is provided on the input side of the DC / DC converter and is configured to detect the output current of the photovoltaic array and send the current detection result to the power controller;

[0026] The voltage loop is provided at the input side of the DC / DC converter and is configured to detect the output voltage of the photovoltaic array and send the voltage detection result to the power controller;

[0027] The power controller is equipped with a power calculation module, which is configured to calculate the output power of the photovoltaic array according to the detection results of the current loop and the voltage loop.

[0028] Furthermore, based on any one of the above technical solutions or a combination of multiple technical solutions, the calculation method of the first compensation amount includes:

[0029] The output power ratio of a photovoltaic power source is defined as the ratio of the current output power of the photovoltaic power source to its maximum available power. The output power ratio of each photovoltaic power source in the photovoltaic array is calculated.

[0030] Calculate the difference between the output power ratio of one photovoltaic power source and the output power ratio of its corresponding adjacent photovoltaic power source;

[0031] The difference in the output power ratio is subjected to PI control to obtain the first compensation amount.

[0032] Furthermore, based on any one of the above technical solutions or a combination of multiple technical solutions, the calculation method of the second compensation amount includes:

[0033] One of the photovoltaic power sources is preset as the photovoltaic power source corresponding to the virtual leader node, which is configured with a preset reference voltage, and the other photovoltaic power sources are used as follower nodes;

[0034] Calculating a first difference between a local output voltage of the photovoltaic power source corresponding to the virtual leader node and a local output voltage of an adjacent photovoltaic power source corresponding to the virtual leader node, and calculating a second difference between the reference voltage and the local output voltage of the photovoltaic power source corresponding to the virtual leader node;

[0035] The sum of the first difference and the second difference is calculated and PI control is performed on the sum to obtain the second compensation amount.

[0036] Furthermore, based on any one of the above technical solutions or a combination of multiple technical solutions, the calculation method of the second compensation amount includes:

[0037] Calculating the difference between the local output voltage of one photovoltaic power source and the local output voltage of its corresponding adjacent photovoltaic power source;

[0038] PI control is performed on the difference in the local output voltage to obtain the second compensation amount, wherein, if there are multiple photovoltaic power sources adjacent to the photovoltaic power source, the difference in the local output voltage between the photovoltaic power source and each of the adjacent photovoltaic power sources is calculated, and the sum of the differences in the multiple local output voltages is calculated, and PI control is performed on the sum of the differences in the multiple local output voltages.

[0039] Furthermore, based on any one of the above technical solutions or a combination of multiple technical solutions, the system has a DC bus voltage regulation mode and a maximum power point tracking mode;

[0040] If the photovoltaic capacity is greater than the load, the system operates in a DC bus voltage regulation mode: each photovoltaic power source of the photovoltaic array outputs power according to a preset output power ratio;

[0041] If the photovoltaic capacity is less than the load, the system runs the maximum power point tracking mode: each photovoltaic power source of the photovoltaic array enters the maximum power point tracking mode to maintain the maximum output.

[0042] Furthermore, based on any one of the technical solutions or a combination of multiple technical solutions mentioned above, the control frequency range of the power controller and the droop controller is 3k to 4k Hz, and the calculation period of the power compensation controller is between 20 and 100 ms.

[0043] The beneficial effects brought about by the technical solution provided by the present invention are as follows:

[0044] a. Under different lighting conditions, reasonable and fair distribution of power generation can be achieved;

[0045] b. Based on Droop control realizes distributed secondary coordinated control of photovoltaic power sources. Compared with traditional VI droop control, it directly controls power parameters Compared with traditional control, there is one less PI controller, so the control structure is simpler; at the same time, The maximum reference value is zero, which corresponds to the maximum photovoltaic power. After the reference value reaches zero, it no longer changes with the output voltage. The voltage can be reduced until it meets the port output characteristics and reaches a new balance. This droop mechanism avoids overload problems and enhances the robustness of photovoltaic power generation.

[0046] c. Under different load levels, the photovoltaic power supply can flexibly switch operating modes according to system requirements, taking into account bus voltage stability and power generation efficiency, thereby improving the flexibility and adaptability of system operation;

[0047] d. Adopt the photovoltaic power supply output voltage consistency control strategy to achieve the output voltage recovery of each photovoltaic power supply and improve the steady-state performance and voltage support capability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in this application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0049] Figure 1 A schematic diagram of a DC grid-type distributed photovoltaic power supply system provided by an exemplary embodiment of the present invention;

[0050] Figure 2 A schematic diagram of information interaction for coordinated control of four photovoltaic power sources provided by an exemplary embodiment of the present invention;

[0051] Figure 3 A schematic diagram of the output power ratio of each photovoltaic power source under different illumination conditions provided by an exemplary embodiment of the present invention;

[0052] Figure 4 A schematic diagram of DC bus voltage under different illumination conditions provided for an exemplary embodiment of the present invention;

[0053] Figure 5 A schematic diagram of the output power of each photovoltaic power source under different illumination conditions provided by an exemplary embodiment of the present invention. DETAILED DESCRIPTION

[0054] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0055] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, apparatus, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0056] Control strategies for DC-grid photovoltaic power sources based on droop control are gaining popularity. This strategy adjusts the output of the photovoltaic power source according to the droop coefficient based on bus voltage deviation. This strategy automatically distributes power among multiple photovoltaic power sources without requiring global information exchange, improving the system's plug-and-play capabilities and operational stability. However, existing droop control strategies primarily focus on power balancing under identical lighting conditions. This involves balancing the load power between photovoltaic power sources of varying installed capacities based on their installed capacity. These strategies fail to consider power distribution under varying light intensities, leading to poor system stability and even safety incidents.

[0057] In one embodiment of the present invention, a DC grid-type distributed photovoltaic power supply system is provided, such as Figure 1 As shown, the power supply system includes a power circuit and a control circuit, wherein the power circuit includes a photovoltaic array, a DC / DC converter and a DC bus, and the control circuit includes a power controller, a droop controller, a power compensation controller (i.e., a controller that executes Figure 1 Secondary control in ) and light sensor;

[0058] The light sensor is configured to detect the light intensity of each photovoltaic power source of the photovoltaic array;

[0059] Pre-built with a control parameter and light intensity G(w / m 2 ) mapping table, the power compensation controller determines its mapping-associated control parameter ( That is, the minimum power voltage derivative), and calculating the first compensation amount through the first PI controller; and obtaining the node output voltage corresponding to each photovoltaic power source, calculating the output voltage difference between different nodes, and calculating the second compensation amount through the second PI controller;

[0060] The power compensation controller inputs a comprehensive compensation amount of the first compensation amount and the second compensation amount into the droop controller;

[0061] The droop controller obtains the DC bus voltage and corrects the reference voltage to be corrected according to the comprehensive compensation amount as follows: in, To correct the power reference value, is the nominal power value, m is the droop coefficient, is the reference voltage value to be corrected, v dc is the DC bus voltage, Δv is the comprehensive compensation value output by the power compensation controller, that is, the sum of the first compensation value and the second compensation value;

[0062] The power controller regulates the DC / DC converter of the power circuit according to the power reference value corrected by the droop controller.

[0063] Specifically, if Figure 1 As shown, the DC / DC converter in the power circuit includes a capacitor branch, a diode branch and an LC branch connected in parallel at both ends of the photovoltaic array, wherein the capacitor branch includes at least one capacitor C PV , the capacitor C PV The positive plate is connected to the positive electrode of the DC bus, and the negative plate is connected to the negative electrode of the DC bus;

[0064] The diode branch includes at least one diode, the cathode of the diode is connected to the cathode of the DC bus, and the anode of the diode is connected to the anode of the DC bus;

[0065] The LC branch includes an inductor L and a capacitor C connected in series. The middle connection point between the capacitor C and the inductor L on the LC branch is connected to the positive electrode of the DC bus, and the negative plate of the capacitor C on the LC branch is connected to the negative electrode of the DC bus.

[0066] Continue to see Figure 1 The DC / DC converter further includes a current loop, a voltage loop and a controllable switch. The current loop is provided at the input side of the DC / DC converter and is configured to detect the output current i of the photovoltaic array. PV and sends the current detection result to the power controller; the voltage loop is set at the input side of the DC / DC converter, which is configured to detect the output voltage v of the photovoltaic array PV The power controller is provided with a power calculation module, which is configured to calculate the output power of the photovoltaic array according to the detection results of the current loop and the voltage loop. The controllable switch is arranged between the capacitor branch and the cathode of the diode; the control end of the controllable switch is connected to the output end of the power controller.

[0067] The power controller also calculates the duty cycle of the DC / DC converter in the following manner:

[0068] The output of the photovoltaic array is sampled, that is, the output current of the photovoltaic array detected by the current loop and the output voltage of the photovoltaic array detected by the voltage loop to calculate the output power of the photovoltaic array

[0069] Calculate the corrected power reference value The output power of the photovoltaic array The ratio of is taken as the duty cycle d;

[0070] The power controller is based on the duty cycle d and the corrected power reference value. Dynamically control the control end of the controllable switch of the DC / DC converter.

[0071] In one embodiment, the control frequency range of the power controller and the droop controller is 3k to 4k Hz, the calculation period of the power compensation controller is between 20 and 100 ms, and the calculation frequency of the power compensation controller is much smaller than the control frequency of the power controller and the droop controller. This setting can reduce the communication frequency and the calculation burden.

[0072] In one embodiment of the present invention, the calculation method of the first compensation amount v1 includes:

[0073] The output power ratio of the photovoltaic power source is defined as the current output power P of the photovoltaic power source. i Its maximum available power The ratio R i , calculate the output power ratio of each photovoltaic power source in the photovoltaic array;

[0074] Calculate the difference between the output power ratio of one photovoltaic power source and the output power ratio of its corresponding adjacent photovoltaic power source; if a photovoltaic power source has several adjacent photovoltaic power sources, calculate the difference between the output power ratio of the photovoltaic power source and each of the adjacent photovoltaic power sources, and find the sum of the differences in the output power ratios, which is recorded as R total ; Take two adjacent photovoltaic power sources as an example, and calculate the difference between the two output power ratios as R diff1 and R diff2 , then R total =R diff1 +R diff2 , the difference R of the output power ratio total Perform PI control to obtain the first compensation amount, and the calculation formula is as follows:

[0075] v1=k*K p1 *R total +K i1 *(∫R diff1 dt+∫R diff2 dt)

[0076] Among them, k is the preset amplification factor, K p1 is the proportional coefficient of the first PI controller, K i1 is the integral coefficient of the first PI controller.

[0077] In a specific embodiment, a weak communication method is used between nodes of the photovoltaic power source, such as Figure 2 As shown, each photovoltaic power source has only one adjacent photovoltaic power source, namely R total =R diff , v1=k*K p1 *Rdiff +K i1 *∫R diff dt.

[0078] The first compensation amount is calculated to compensate for the voltage deviation caused by the droop control, thereby stabilizing the DC bus voltage.

[0079] In one embodiment of the present invention, the calculation method of the second compensation amount v2 includes:

[0080] One of the photovoltaic power sources is preset as the photovoltaic power source corresponding to the virtual leader node, which is configured with a preset reference voltage v ref , other photovoltaic power sources serve as follower nodes;

[0081] Calculate the local output voltage of the photovoltaic power source corresponding to the virtual leader node ( Figure 1 v in dc_i ) and its corresponding local output voltage of the adjacent photovoltaic power source ( Figure 1 v in dc_j )'s first difference v diff1 , and calculate the reference voltage v ref The second difference value v of the local output voltage of the photovoltaic power source corresponding to the virtual leader node diff2 ;

[0082] Calculate the sum of the first difference and the second difference, that is, v total =v diff1 +v diff2 , and perform PI control on it to obtain the second compensation amount, which is calculated as follows:

[0083] v2=K p2 ×v total +K i2 ×∫v total dt

[0084] Among them, K p2 is the proportional coefficient of the second PI controller, K i2 is the integral coefficient of the second PI controller.

[0085] In other embodiments, each photovoltaic power source has multiple adjacent photovoltaic power sources. Taking two adjacent photovoltaic power sources as an example, the local output voltage of the photovoltaic power source corresponding to the virtual leader node is calculated by calculating the sum of the first difference and the second difference corresponding to the first adjacent photovoltaic power source, which is recorded as v total1 The local output voltage of the photovoltaic power source corresponding to the virtual leader node corresponds to the sum of the first difference and the second difference calculated by the second adjacent photovoltaic power source, recorded as v total2 ; The second PI controller controls v total1 +v total2 , denoted as Vsum , accordingly, the calculation formula of the second compensation amount is as follows:

[0086] v2=K p2 ×V sum +K i2 ×(∫v total1 dt+∫v total2 dt)

[0087] In another embodiment of calculating the second compensation amount, the virtual leader node and the follower node are not distinguished, and the calculated parameter does not involve the preset reference voltage v ref :

[0088] When a photovoltaic power source has only one adjacent photovoltaic power source, calculate the difference in local output voltages between the two. d , then the calculation formula of the second compensation amount is as follows:

[0089] v2=K p2 ×v d +K i2 ×∫v d dt

[0090] When a photovoltaic power source has multiple adjacent photovoltaic power sources, taking two adjacent photovoltaic power sources as an example, the difference in local output voltage between the target photovoltaic power source and the first adjacent photovoltaic power source is calculated, which is recorded as v d1 , calculate the difference in local output voltage between the target PV source and the second adjacent PV source, denoted as v d2 , which is controlled by the second PI controller is v d1 +v d2 , denoted as V d-sum , then the calculation formula of the second compensation amount is as follows:

[0091] v2=K p2 ×V d-sum +K i2 ×(∫v d1 dt+∫v d2 dt)

[0092] The second compensation amount is calculated to ensure that all photovoltaic power sources operate at the same photovoltaic output power ratio, that is, based on the current maximum output power distribution rather than the installed power distribution, thereby achieving fair power distribution.

[0093] Under different load levels, the system can flexibly switch between DC bus voltage regulation mode and maximum power point tracking mode according to demand:

[0094] If the photovoltaic capacity is greater than the load, the system operates in a DC bus voltage regulation mode: each photovoltaic power source of the photovoltaic array outputs power according to a preset output power ratio;

[0095] If the photovoltaic capacity is less than the load, the system runs the maximum power point tracking mode: each photovoltaic power source of the photovoltaic array enters the maximum power point tracking mode to maintain the maximum output.

[0096] In order to demonstrate the control effect of the present invention, the present invention builds a four-photovoltaic power supply photovoltaic DC network model in Matlab / Simulink. The specific parameters of the model are shown in Table 1:

[0097] Table 1 Model specific parameters

[0098]

[0099] The system switches to secondary control at 2s, changes the light intensity at 4s and 6s, switches on a 3Ω load at 8s, and switches off the load at 10s. Figure 3 As shown in the figure, before the secondary control is switched on, the power distribution of the photovoltaic power sources follows the traditional droop control strategy, that is, power is distributed according to the inverse ratio of the droop coefficient. At this time, the output power of each photovoltaic power source depends only on the bus voltage deviation, without considering the influence of lighting conditions, which may lead to uneven power distribution among the photovoltaic power sources. After the secondary control is switched on, through power sharing control, the photovoltaic power sources adjust the power according to the photovoltaic output power ratio, so that their output power is proportional to their maximum available power, thereby achieving more equitable power distribution. In addition, when there are drastic changes in lighting or sudden changes in load, the photovoltaic output power ratio can be controlled consistently within 0.5 seconds, allowing the system to quickly adjust to a new steady state, ensuring that each photovoltaic power source can still output according to its maximum available power ratio, and achieving fair power distribution in dynamic environments.

[0100] Combine Figure 4 As shown in the figure, before the secondary control is turned on, the DC bus voltage of the system fluctuates due to the influence of droop control. After the secondary control is turned on, the DC bus voltage recovers to 570V, realizing the recovery of the DC bus voltage and improving the steady-state performance and voltage support capability of the system.

[0101] Combine Figure 5 As shown in the figure, before the secondary control is implemented, each PV source still distributes power according to the droop control strategy. The power distribution relationship is affected by the droop coefficient, and it cannot ensure fairness among different PV sources under different lighting conditions. After the secondary control is implemented, the PV sources distribute power according to the photovoltaic output power ratio, so that the power output is adjusted according to the maximum available power ratio of each PV source, eliminating the power imbalance caused by different lighting conditions. When the system finally stabilizes, the power distribution error is controlled within 1%, indicating that the proposed secondary control strategy can effectively improve the accuracy of power sharing and make power sharing between PV sources more reasonable.

[0102] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply the existence of any such actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or device comprising the element.

[0103] The above is only a specific implementation method of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. A DC grid-type distributed photovoltaic power supply system, characterized in that: The system comprises a power circuit and a control circuit, wherein the power circuit comprises a photovoltaic array, a DC / DC converter and a DC bus, and the control circuit comprises a power controller, a droop controller, a power compensation controller and a light sensor; The light sensor is configured to detect the light intensity of each photovoltaic power source of the photovoltaic array; The power compensation controller determines a control parameter associated with the mapping according to the light intensity, and calculates a first compensation amount through a first PI controller; obtains the node output voltage corresponding to each photovoltaic power source, calculates the output voltage difference between different nodes, and calculates a second compensation amount through a second PI controller; The power compensation controller inputs a comprehensive compensation amount of the first compensation amount and the second compensation amount into the droop controller; The droop controller obtains the DC bus voltage and corrects the reference voltage to be corrected according to the comprehensive compensation amount as follows: in, To correct the power reference value, is the nominal power value, m is the droop coefficient, is the reference voltage value to be corrected, v dc is the DC bus voltage, Δv is the comprehensive compensation output by the power compensation controller; The power controller regulates the DC / DC converter of the power circuit according to the power reference value corrected by the droop controller.

2. The DC grid-type distributed photovoltaic power supply system according to claim 1, characterized in that: The power controller also calculates the duty cycle of the DC / DC converter in the following manner: Sampling the output of the photovoltaic array to calculate the output power of the photovoltaic array; Calculating a ratio of the power reference value to the output power of the photovoltaic array as a duty cycle; And the power controller dynamically controls the control end of the DC / DC converter according to the duty cycle and the power reference value.

3. The DC grid-type distributed photovoltaic power supply system according to claim 1, characterized in that: The DC / DC converter includes a capacitor branch, a diode branch, and an LC branch connected in parallel at both ends of the photovoltaic array, wherein the capacitor branch includes at least one capacitor, a positive plate of the capacitor is connected to the positive electrode of the DC bus, and a negative plate of the capacitor is connected to the negative electrode of the DC bus; The diode branch includes at least one diode, the cathode of the diode is connected to the cathode of the DC bus, and the anode of the diode is connected to the anode of the DC bus; The LC branch includes an inductor and a capacitor connected in series, the middle connection point between the capacitor and the inductor on the LC branch is connected to the positive electrode of the DC bus, and the negative plate of the capacitor on the LC branch is connected to the negative electrode of the DC bus.

4. The DC grid-type distributed photovoltaic power supply system according to claim 3, characterized in that: The DC / DC converter further includes a controllable switch, which is arranged between the capacitor branch and the cathode of the diode; The control end of the controllable switch is connected to the output end of the power controller.

5. The DC grid-type distributed photovoltaic power supply system according to claim 3, characterized in that: The DC / DC converter further includes a current loop and a voltage loop, wherein the current loop is provided at the input side of the DC / DC converter and is configured to detect the output current of the photovoltaic array and send the current detection result to the power controller; The voltage loop is provided at the input side of the DC / DC converter and is configured to detect the output voltage of the photovoltaic array and send the voltage detection result to the power controller; The power controller is equipped with a power calculation module, which is configured to calculate the output power of the photovoltaic array according to the detection results of the current loop and the voltage loop.

6. The DC grid-type distributed photovoltaic power supply system according to claim 1, characterized in that: The calculation method of the first compensation amount includes: The output power ratio of a photovoltaic power source is defined as the ratio of the current output power of the photovoltaic power source to its maximum available power. The output power ratio of each photovoltaic power source in the photovoltaic array is calculated. Calculate the difference between the output power ratio of one photovoltaic power source and the output power ratio of its corresponding adjacent photovoltaic power source; The difference in the output power ratio is subjected to PI control to obtain the first compensation amount.

7. The DC grid-type distributed photovoltaic power supply system according to claim 1, characterized in that: The calculation method of the second compensation amount includes: One of the photovoltaic power sources is preset as the photovoltaic power source corresponding to the virtual leader node, which is configured with a preset reference voltage, and the other photovoltaic power sources are used as follower nodes; Calculating a first difference between a local output voltage of the photovoltaic power source corresponding to the virtual leader node and a local output voltage of an adjacent photovoltaic power source corresponding to the virtual leader node, and calculating a second difference between the reference voltage and the local output voltage of the photovoltaic power source corresponding to the virtual leader node; The sum of the first difference and the second difference is calculated and PI control is performed on the sum to obtain the second compensation amount.

8. The DC grid-type distributed photovoltaic power supply system according to claim 1, characterized in that: The calculation method of the second compensation amount includes: Calculating the difference between the local output voltage of one of the photovoltaic power sources and the local output voltage of its corresponding adjacent photovoltaic power source; PI control is performed on the difference in the local output voltage to obtain the second compensation amount, wherein, if there are multiple photovoltaic power sources adjacent to the photovoltaic power source, the difference in the local output voltage between the photovoltaic power source and each of the adjacent photovoltaic power sources is calculated, and the sum of the differences in the multiple local output voltages is calculated, and PI control is performed on the sum of the differences in the multiple local output voltages.

9. The DC grid-type distributed photovoltaic power supply system according to claim 1, characterized in that: The system has a DC bus voltage regulation mode and a maximum power point tracking mode; If the photovoltaic capacity is greater than the load, the system operates in a DC bus voltage regulation mode: each photovoltaic power source of the photovoltaic array outputs power according to a preset output power ratio; If the photovoltaic capacity is less than the load, the system runs the maximum power point tracking mode: each photovoltaic power source of the photovoltaic array enters the maximum power point tracking mode to maintain the maximum output.

10. The DC grid-type distributed photovoltaic power supply system according to any one of claims 1 to 9, characterized in that: The control frequency range of the power controller and the droop controller is 3k Hz to 4k Hz, and the calculation period of the power compensation controller is between 20 and 100 ms.

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