Current harmonic optimization method and device of converter, controller and photovoltaic system

Abstract

The invention provides a current harmonic optimization method and device of a converter, a controller and a photovoltaic system. The method comprises the following steps: when the voltage of a power grid is greater than a preset voltage threshold value, reducing an initial active current given value of the converter, and generating a switching control quantity based on the adjusted active current given value, thereby controlling the converter. According to the method, when the voltage of the power grid suddenly increases, the actual value of the bus voltage can be increased by reducing the given value of the active current on the premise of ensuring the output of the active power, so that the actual value of the bus voltage quickly changes along with the given value of the bus voltage; and the problem that the output current harmonic wave of the converter is relatively large because the actual bus voltage value is lower than the power grid voltage is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of converters, and particularly to a method, device, controller and photovoltaic system for optimizing current harmonics of a converter. Background Art

[0002] In today's era, new energy power generation systems are booming. They have significant advantages. Solar and wind energy are inexhaustible, which can greatly alleviate the traditional energy crisis, reduce carbon emissions, and contribute to environmental protection. At the same time, the decentralized layout can reduce transmission losses. However, the output power of new energy power generation systems is intermittent and volatile due to factors such as light intensity / wind level, etc., which is prone to the drawback of causing grid voltage fluctuations.

[0003] Taking the photovoltaic power generation system as an example, the applicant has found that when a high voltage ride-through occurs in the grid, the output current of the converter in the photovoltaic power generation system will generate harmonics, and moreover, the more severe the high voltage ride-through is, the greater the harmonics generated by its output current will be, affecting the load balance and power quality of the grid, and bringing difficulties to the reactive power compensation and voltage regulation of the grid. Summary of the Invention

[0004] Embodiments of the present invention provide a method, device, controller and photovoltaic system for optimizing current harmonics of a converter to solve the problem of large current harmonics in the output current of the converter when a severe high voltage ride-through event occurs in the grid.

[0005] In a first aspect, embodiments of the present invention provide a method for optimizing current harmonics of a converter, which is applied to a new energy power generation system. The new energy power generation system includes at least one converter, and one end of each converter is connected to a common bus, and the common bus is used to connect to the grid. The method includes:

[0006] Obtain the grid voltage in real time;

[0007] If the grid voltage is greater than a preset voltage threshold, then reduce the initial active current given value of the converter;

[0008] Generate a switching control quantity based on the adjusted active current given value, and the switching control quantity generates a pulse signal for controlling the converter after modulation.

[0009] In a second aspect, embodiments of the present invention provide a device for optimizing current harmonics of a converter, which is applied to a new energy power generation system. The new energy power generation system includes at least one converter, and one end of each converter is connected to a common bus, and the common bus is used to connect to the grid. The device includes:

[0010] A grid voltage acquisition module for obtaining the grid voltage in real time;

[0011] The active current compensation module is used to reduce the initial given value of the active current of the converter if the grid voltage is greater than the preset voltage threshold.

[0012] The switch control module is used to generate a switch control quantity based on the adjusted given value of the active current, and the switch control quantity generates a pulse signal for controlling the converter after modulation.

[0013] In a third aspect, an embodiment of the present invention provides a controller, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps of the current harmonic optimization method of the converter in any possible implementation manner of the first aspect above are implemented.

[0014] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium storing a computer program, and when the computer program is executed by a processor, the steps of the current harmonic optimization method of the converter in any possible implementation manner of the first aspect above are implemented.

[0015] In a fifth aspect, an embodiment of the present invention provides a photovoltaic system, which includes the controller described in the third aspect above.

[0016] An embodiment of the present invention provides a method, device, controller, and photovoltaic system for optimizing the current harmonics of a converter. When the grid voltage is greater than the preset voltage threshold, the method reduces the initial given value of the active current of the converter; and generates a switch control quantity based on the adjusted given value of the active current, thereby controlling the converter. When the grid voltage increases above the preset voltage threshold, on the premise of ensuring that the active power output value remains unchanged, the actual value of the bus voltage is increased by reducing the given value of the active current, so that the actual value of the bus voltage quickly follows the given value of the bus voltage, avoiding the problem that the actual value of the bus voltage is lower than the grid voltage, resulting in large output current harmonics of the converter. Description of the Drawings

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the following drawings are only some embodiments of the present invention, and those of ordinary skill in the art can obtain other drawings without creative efforts based on these drawings.

[0018] Figure 1 is an application scenario diagram of the current harmonic optimization method of the converter provided by the embodiment of the present invention;

[0019] Figure 2 is an implementation flowchart of the current harmonic optimization method of the converter provided by the embodiment of the present invention;

[0020] Figure 3 is a schematic structural diagram of a current harmonic optimization device for a converter provided by an embodiment of the present invention;

[0021] Figure 4 is a schematic diagram of a controller provided by an embodiment of the present invention. Detailed implementation manners

[0022] In the following description, for the purpose of illustration rather than limitation, specific details such as specific system structures and technologies are presented in order to thoroughly understand the embodiments of the present invention. However, those skilled in the art should understand that the present invention can also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to avoid unnecessary details from interfering with the description of the present invention.

[0023] In the description of the specification of this application and the appended claims, the terms "first", "second", "third", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.

[0024] The reference to "an embodiment" or "some embodiments" etc. described in the specification of this application means that a specific feature, structure, or characteristic described in connection with the embodiment is included in one or more embodiments of this application. Thus, the statements "in an embodiment", "in some embodiments", "in other some embodiments", "in still other embodiments", etc. that appear in different places in this specification do not necessarily refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. The terms "include", "comprise", "have" and their variants all mean "including but not limited to", unless otherwise specifically emphasized in other ways.

[0025] In addition, the "multiple" mentioned in the embodiments of this application should be construed as two or more.

[0026] To make the objectives, technical solutions, and advantages of the present invention clearer, the following will be described in detail through specific embodiments with reference to the accompanying drawings.

[0027] Refer to Figure 1 , Figure 1 is an application scenario diagram of a current harmonic optimization method for a converter provided by an embodiment of the present invention. As Figure 1 shown, this application scenario can be a photovoltaic system or other new energy power generation systems, such as a wind power generation system. Hereinafter, taking the photovoltaic system as an example, the method provided by the embodiments of this application will be described in detail.

[0028] Specifically, the photovoltaic system includes at least one photovoltaic module (PV1 to PVn), at least one converter, and a controller corresponding to each converter. At least one photovoltaic module (PV1 to PVn) is connected to the first end of the converter, the second ends of at least one converter are all connected to a common bus, and the common bus is connected to the power grid.

[0029] Among them, the converter can be a photovoltaic inverter or a battery energy storage converter. Taking the photovoltaic inverter as an example, the photovoltaic inverter can adjust the bus voltage of the common bus in real time according to the change of the grid voltage, so that the actual value of the bus voltage is always greater than the grid line voltage, thereby ensuring that the photovoltaic system can successfully output an electrical signal to the power grid. The applicant found that when a voltage surge event such as high voltage ride-through occurs in the power grid, the actual value of the bus voltage cannot keep up with the change of the given value of the bus voltage, and the situation where the actual value of the bus voltage is less than the grid line voltage will occur, resulting in harmonics in the active output current of the photovoltaic inverter, and this harmonic will increase as the high voltage ride-through event intensifies.

[0030] To solve the above problems, this embodiment provides a method for optimizing the current harmonics of a converter to solve the problem of large current harmonics output by the converter when a high voltage ride-through event occurs in the power grid.

[0031] See Figure 2 , which shows the implementation flowchart of the method for optimizing the current harmonics of the converter provided by the embodiment of the present invention, and is described in detail as follows:

[0032] S101: Obtain the grid voltage in real time.

[0033] In this embodiment, in order to monitor whether the situation where the actual value of the bus voltage is less than or equal to the actual value of the grid voltage occurs in the photovoltaic system, the controller of the photovoltaic inverter in this embodiment can obtain the grid voltage in real time, and judge whether a high voltage ride-through fault occurs in the grid voltage according to the magnitude of the grid voltage, so as to determine whether harmonics will be generated in the active output current of the photovoltaic inverter.

[0034] S102: If the grid voltage is greater than a preset voltage threshold, reduce the initial active current given value of the converter.

[0035] In this embodiment, when the grid voltage is greater than the preset voltage threshold, it is considered that the grid voltage may be greater than the actual value of the bus voltage. At this time, in order to match the actual value of the bus voltage, the controller will automatically increase the given value of the bus voltage. However, the actual value of the bus voltage cannot quickly follow the change of the given value of the bus voltage, and this deviation will cause harmonics in the active current signal. In order to accelerate the following speed of the actual value of the bus voltage, based on the principle that reducing the active current can increase the bus voltage when the given value of the active power remains unchanged, this embodiment reduces the given value of the active current of the photovoltaic inverter to further increase the actual value of the output voltage of the photovoltaic inverter, thereby providing sufficient voltage support for the bus voltage and ensuring that the actual value of the bus voltage can quickly follow the change of the given value of the bus voltage, avoiding the generation of larger harmonics in the active current signal.

[0036] S103: Generate a switching control quantity based on the adjusted given value of the active current, and the switching control quantity generates a pulse signal for controlling the converter after modulation.

[0037] As can be seen from the above embodiments, when the grid voltage is greater than the preset voltage threshold, that is, when the grid enters the high voltage ride-through state, on the premise of ensuring the active power output, the actual value of the bus voltage is increased by reducing the given value of the active current, so that the actual value of the bus voltage can quickly follow the change of the given value of the bus voltage, avoiding the problem that the actual value of the bus voltage is lower than the grid voltage, resulting in a large harmonic in the output current of the converter.

[0038] In a possible implementation manner, the specific implementation process of S102 includes:

[0039] If the grid voltage is greater than the preset voltage threshold and the load rate of the new energy power generation system exceeds the preset load threshold, then reduce the initial given value of the active current of the converter; where the preset voltage threshold is the product of the grid rated voltage and a preset coefficient, and the preset coefficient is greater than 1.1.

[0040] In this embodiment, the preset coefficient can be from 1.1 times to 1.3. Exemplarily, the preset coefficient can be 1.2. When the preset coefficient is 1.2, if the grid voltage is greater than the preset voltage threshold, it means that the grid is in a severe high voltage ride-through state at this time, and the harmonics of the output current of the converter will be relatively large. At the same time, when the load of the photovoltaic system is large, it will exacerbate the generation of larger harmonics in the output current.

[0041] Therefore, in order to avoid large harmonics in the output current and improve the accuracy and efficiency of harmonic optimization in this embodiment, when it is recognized that the power grid is in a severe high-voltage crossing state and the load is large, the actual output voltage can be increased by reducing the initial active current reference value of the converter, so as to provide sufficient voltage support for the bus voltage, ensure that the actual value of the bus voltage can quickly follow the change of the bus voltage reference value, and avoid large harmonics in the active current signal.

[0042] Exemplarily, the preset load threshold can be from 0.7 to 0.9.

[0043] In a possible implementation manner, the specific implementation process of S102 further includes:

[0044] If the grid voltage is greater than the preset voltage threshold and the change rate of the grid voltage in the most recent N sampling periods is greater than the preset change rate threshold, then reduce the initial active current reference value of the converter.

[0045] Specifically, since the problem that the actual value of the bus voltage cannot quickly follow the change of the bus voltage reference value is more likely to occur when the power grid undergoes a mutation, this embodiment can monitor the magnitude of the grid voltage change rate while monitoring the magnitude of the grid voltage, so as to improve the accuracy of the harmonic optimization startup condition.

[0046] Exemplarily, N is greater than or equal to 1 and less than or equal to 5, and the preset change rate threshold can be 20% - 30%.

[0047] In a possible implementation manner, S102 can also combine the above three conditions to determine the startup timing of the harmonic optimization method, specifically as follows:

[0048] If the grid voltage is greater than the preset voltage threshold, and the change rate of the grid voltage in the most recent N sampling periods is greater than the preset change rate threshold, and the load rate of the new energy power generation system exceeds the preset load threshold, then reduce the initial active current reference value of the converter.

[0049] The above method can further optimize the startup timing of the harmonic optimization method, thereby improving the accuracy of the active current harmonic optimization.

[0050] In a possible implementation manner, the specific implementation process of S102 includes:

[0051] S201: If the grid voltage is greater than the preset voltage threshold, then determine the current compensation value based on the difference between the bus voltage reference value and the actual value of the common bus.

[0052] Specifically, subtract the actual bus voltage value from the given value of the bus voltage of the common bus to obtain a bus voltage difference, and determine a current compensation value based on the bus voltage difference. When the current compensation value is positive, the bus voltage difference and the current compensation value can be positively correlated, that is, the larger the bus voltage difference, the larger the current compensation value, and the smaller the bus voltage difference, the smaller the current compensation value.

[0053] Optionally, when the current compensation value is negative, the bus voltage difference and the current compensation value can also be negatively correlated.

[0054] S202: Compensate the initial active current given value of the converter with the current compensation value to reduce the initial active current given value.

[0055] In this embodiment, when the current compensation value is positive, subtract the current compensation value from the initial active current given value to obtain a compensated active current given value. The compensated active current given value is less than the initial active current given value, so as to quickly reduce the actual active current value, further increase the actual bus voltage value, and make the actual bus voltage value quickly follow the given bus voltage value.

[0056] On the other hand, when the current compensation value is negative, the controller adds the current compensation value to the initial active current given value to obtain a compensated active current given value, which can also achieve the effect of reducing the active current given value.

[0057] In a possible implementation manner, the difference is positively correlated with the current compensation value;

[0058] Correspondingly, the specific implementation process of S202 includes:

[0059] Subtract the current compensation value from the initial active current given value to obtain an adjusted active current given value.

[0060] In a possible implementation manner, the specific implementation process of S201 includes:

[0061] Determine the current compensation value according to the formula ΔI = (U bus_s - U bus_f )·k 1 , where ΔI represents the current compensation value, U bus_s represents the given value of the bus voltage, U bus_f represents the actual value of the bus voltage, and k 1 represents a preset threshold.

[0062] In a possible implementation manner, before the grid voltage is acquired in real time, the method provided in this embodiment further includes:

[0063] Conduct multiple photovoltaic system experiments. When the grid voltage is greater than the preset voltage threshold, determine the difference between the actual value and the given value of the bus voltage.

[0064] Adjust the corresponding current compensation value under different differences, determine whether the active current signal after compensation for each current compensation value still has harmonic components, and take the minimum current compensation value corresponding to when the active current signal no longer has harmonic components as the target current compensation value; this current compensation value is a positive value.

[0065] Based on the formula ΔI = (U bus_s -U bus_f )·k 1 , determine the initial threshold corresponding to the target current compensation value.

[0066] Calculate the mean value of each initial threshold to obtain the preset threshold.

[0067] In a possible implementation manner, the specific implementation process of S103 includes:

[0068] Obtain the given value of the reactive current output by the reactive power loop of the converter.

[0069] Based on the adjusted given value of the active current and the given value of the reactive current, obtain the given value of the current loop.

[0070] Obtain the actual value of the output current of the converter, and subtract the actual value of the output current from the given value of the current loop to obtain a first difference.

[0071] Input the first difference into a proportional controller, output a first control quantity, and add the first control quantity to the actual value of the grid voltage to obtain a voltage control quantity.

[0072] Divide the voltage control quantity by the actual value of the bus voltage to obtain the switch control quantity.

[0073] In this embodiment, the control loop of the photovoltaic inverter includes an active power loop and a reactive power loop. In the reactive power loop, the controller subtracts the reactive power feedback value from the reactive power given value to obtain a reactive power difference, and inputs the reactive power difference into a PI controller to obtain a reactive current control quantity I q ; on the other hand, within the active power loop, the controller subtracts the active power feedback value from the active power given value to obtain an active power difference, inputs the active power difference into a PI controller to obtain a given value of the active current I d , after compensating the given value of the active current through S101 to S102, use the formula I set =I q ·cosθ-I d ·sinθ to calculate the given value of the current loop Iset , where θ represents the phase of the grid voltage output by the phase-locked loop. Then, subtract the actual output current value of the photovoltaic inverter from the current-loop set value to obtain the current-loop difference. Input the current-loop difference into a proportional controller to obtain a first control quantity. Add the first control quantity to the actual value of the grid voltage to obtain a voltage control quantity. Finally, divide the voltage control quantity by the actual value of the bus voltage of the AC bus to obtain the switching control quantity of the photovoltaic inverter. Input the switching control quantity into a modem to generate a pulse signal for controlling the photovoltaic inverter. The pulse signal can be a PWM (Pulse Width Modulation) signal, a PFM (Pulse Frequency Modulation) signal, or a combination of the two.

[0074] In a possible implementation, the specific implementation process of S102 includes:

[0075] Continuously reduce the initial active current set value of the converter for N consecutive cycles starting from the first moment; the first moment is the initial moment when the grid voltage is greater than the preset voltage threshold in this time;

[0076] After N cycles of the first moment, then according to Calculate the active current set value of the converter;

[0077] where I d represents the active current set value of the converter, P d represents the active power of the converter before the first moment, and V grid represents the grid voltage at the current moment.

[0078] In this embodiment, since the moments when the output current of the photovoltaic inverter generates large harmonics mainly occur in the initial N cycles of a severe high-voltage crossing event, this embodiment can start from the initial moment of this severe high-voltage crossing event and reduce the initial active power current set value in the subsequent N cycles. And after N cycles of the first moment, if the grid voltage is still greater than the preset voltage threshold, calculate the active current set value according to the processing method of the high-voltage crossing event, that is, use the formula to calculate the active current set value of the converter, so as to perform targeted compensation on the output current set value and improve the accuracy of current harmonic optimization. Wherein, N takes a value of 2 to 5; specifically, N can be made equal to 4.

[0079] Specifically, the method of reducing the initial active current set value of the converter in each cycle after the first moment can refer to the method steps disclosed in S201-S202, which will not be elaborated here.

[0080] As can be seen from the above embodiments, in this embodiment, when the grid voltage suddenly increases, on the premise of ensuring that the active power output value remains unchanged, the actual value of the bus voltage is increased by reducing the given value of the active current, and the pulse signal for controlling the photovoltaic inverter is generated through the above power loop and current loop. After adjustment, the photovoltaic inverter reduces the output voltage, so that the actual value of the bus voltage quickly follows the change of the given value of the bus voltage, avoiding the problem that the output current harmonic of the converter is large due to the actual value of the bus voltage being lower than the grid voltage.

[0081] It should be understood that the magnitudes of the sequence numbers of the steps in the above embodiments do not mean the order of execution. The order of execution of each process should be determined according to its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present invention.

[0082] The following is an embodiment of the device of the present invention. For the details not described in detail, reference may be made to the corresponding method embodiments above.

[0083] Figure 3 The structural schematic diagram of the current harmonic optimization device of the converter provided by the embodiment of the present invention is shown. For the sake of convenience of description, only the parts related to the embodiment of the present invention are shown and are described in detail as follows:

[0084] As Figure 3 shown, the current harmonic optimization device 100 of the converter includes:

[0085] A grid voltage acquisition module for acquiring the grid voltage in real time;

[0086] An active current compensation module for reducing the initial given value of the active current of the converter if the grid voltage is greater than a preset voltage threshold;

[0087] A switch control module for generating a switch control quantity based on the adjusted given value of the active current, and the switch control quantity generates a pulse signal for controlling the converter after modulation.

[0088] In a possible implementation manner, the active current compensation module is used for:

[0089] If the grid voltage is greater than the preset voltage threshold and the load rate of the new energy power generation system exceeds a preset load threshold, reducing the initial given value of the active current of the converter; the preset voltage threshold is the product of the grid rated voltage and a preset coefficient, and the preset coefficient is greater than 1.1.

[0090] In a possible implementation manner, the active current compensation module is used for:

[0091] A current compensation value calculation unit, configured to determine a current compensation value based on a difference between a given value of the bus voltage of the common bus and an actual value of the bus voltage if the grid voltage is greater than a preset voltage threshold;

[0092] An active current given value compensation unit, configured to compensate an initial active current given value of the converter by using the current compensation value to reduce the initial active current given value.

[0093] In a possible implementation manner, the difference is positively correlated with the current compensation value;

[0094] Correspondingly, the active current given value compensation unit is specifically configured to:

[0095] Subtract the current compensation value from the initial active current given value to obtain an adjusted active current given value.

[0096] In a possible implementation manner, the current compensation value calculation unit is specifically configured to:

[0097] Determine the current compensation value according to the formula ΔI=(U bus_s -U bus_f )·k 1 , where ΔI represents the current compensation value, U bus_s represents the given value of the bus voltage, U bus_f represents the actual value of the bus voltage, and k 1 represents a preset threshold.

[0098] In a possible implementation manner, the switch control module includes:

[0099] Obtain a reactive current given value output by a reactive power loop of the converter;

[0100] Based on the adjusted active current given value and the reactive current given value, obtain a current loop given value;

[0101] Obtain an actual value of the output current of the converter, and subtract the actual value of the output current from the current loop given value to obtain a first difference;

[0102] Input the first difference into a proportional controller, output a first control quantity, and add the first control quantity to an actual value of the grid voltage to obtain a voltage control quantity;

[0103] Divide the voltage control quantity by the actual value of the bus voltage to obtain the switch control quantity.

[0104] In a possible implementation manner, the active current compensation module includes:

[0105] Reduce the initial active current reference value of the converter continuously for N cycles starting from the first moment; the first moment is the initial moment when the grid voltage is greater than the preset voltage threshold value in this time.

[0106] After N cycles of the first moment, then according to Calculate the active current reference value of the converter.

[0107] Where, I d Represents the active current reference value of the converter, P d Represents the active power of the converter before the first moment, V grid Represents the grid voltage at the current moment.

[0108] As can be seen from the above embodiments, when the grid voltage surges, the device provided in this embodiment, on the premise of ensuring that the active power output value remains unchanged, raises the actual value of the bus voltage by reducing the active current reference value, and generates a pulse signal for controlling the photovoltaic inverter through the above power loop and current loop. After adjustment, the photovoltaic inverter reduces the output voltage, so that the actual value of the bus voltage quickly follows the change of the bus voltage reference value, avoiding the problem that the actual value of the bus voltage is lower than the grid voltage, resulting in a large harmonic of the output current of the converter.

[0109] Figure 4 Is a schematic diagram of the terminal provided by the embodiment of the present invention. As Figure 4 Shown, the controller 4 of this embodiment includes: a processor 40 and a memory 41. The memory 41 is used to store a computer program 42, and the processor 40 is used to call and run the computer program 42 stored in the memory 41, and execute the steps in the above embodiments of the current harmonic optimization method of each converter, such as Figure 2 The steps S101 to S103 shown. Or, the processor 40 is used to call and run the computer program 42 stored in the memory 41 to implement the functions of each module / unit in the above device embodiments, such as Figure 3 The functions of the modules 110 to 130 shown.

[0110] Exemplarily, the computer program 42 can be divided into one or more modules / units. The one or more modules / units are stored in the memory 41 and executed by the processor 40 to complete the present invention. The one or more modules / units can be a series of computer program instruction segments capable of completing specific functions, and this instruction segment is used to describe the execution process of the computer program 42 in the controller 4.

[0111] The controller 4 may be a computing device such as a desktop computer, a notebook, a palm computer, or a cloud server. The controller 4 may include, but is not limited to, a processor 40 and a memory 41. Those skilled in the art can understand that Figure 4 merely examples of the controller 4, which do not constitute a limitation on the controller 4, may include more or fewer components than shown in the figure, or combine certain components, or different components. For example, the terminal may further include input / output devices, network access devices, a bus, etc.

[0112] The so-called processor 40 may be a central processing unit (CPU), or may also be other general-purpose processors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or the processor may also be any conventional processor, etc.

[0113] The memory 41 may be an internal storage unit of the controller 4, such as the hard disk or memory of the controller 4. The memory 41 may also be an external storage device of the controller 4, such as a plug-in hard disk equipped on the controller 4, a smart media card (SMC), a secure digital (SD) card, a flash card, etc. Further, the memory 41 may also include both the internal storage unit and the external storage device of the controller 4. The memory 41 is used to store the computer program and other programs and data required by the terminal. The memory 41 may also be used to temporarily store the data that has been output or will be output.

[0114] Those skilled in the art can clearly understand that, for the convenience and brevity of description, only the above-mentioned division of each functional unit and module is used as an example. In actual applications, the above-mentioned functions can be allocated to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. Each functional unit and module in the embodiment can be integrated into a processing unit, or each unit can exist physically alone, or two or more units can be integrated into one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of a software functional unit. In addition, the specific names of each functional unit and module are only for the convenience of mutual distinction and do not limit the protection scope of this application. The specific working processes of the units and modules in the above system can refer to the corresponding processes in the foregoing method embodiments and will not be elaborated herein.

[0115] In the above embodiments, the descriptions of the various embodiments have their own emphases. For the parts not detailed or recorded in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0116] Those of ordinary skill in the art can realize that the units and algorithm steps of each example described in combination with the embodiments disclosed herein can be implemented by electronic hardware, or by a combination of computer software and electronic hardware. Whether these functions are executed in the form of hardware or software depends on the specific application and design constraints of the technical solution. Professional technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the present invention.

[0117] In the embodiments provided by the present invention, it should be understood that the disclosed device / terminal and method can be implemented in other ways. For example, the device / terminal embodiments described above are merely illustrative. For example, the division of the module or unit is only a logical function division, and there can be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the displayed or discussed coupling or direct coupling or communication connection to each other can be through some interfaces, and the indirect coupling or communication connection of the device or unit can be in an electrical, mechanical or other form.

[0118] The unit described as a separated component may or may not be physically separated, and the component displayed as a unit may or may not be a physical unit, that is, it may be located in one place, or may be distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0119] In addition, in each embodiment of the present invention, each functional unit can be integrated into a processing unit, or each unit can exist physically alone, or two or more units can be integrated into one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of a software functional unit.

[0120] If the integrated module / unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on such an understanding, to implement all or part of the processes in the above-mentioned embodiment methods of the present invention, it can also be completed by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by a processor, the steps of the above-mentioned embodiments of the current harmonic optimization method for each converter can be implemented. Among them, the computer program includes computer program code, and the computer program code can be in the form of source code, object code, executable file or some intermediate form, etc. The computer-readable medium can include: any entity or device capable of carrying the computer program code, recording medium, USB flash drive, mobile hard disk, magnetic disk, optical disc, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signal, telecommunication signal, and software distribution medium, etc. It should be noted that the content included in the computer-readable medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, the computer-readable medium does not include electrical carrier signals and telecommunication signals.

[0121] The above-mentioned embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. A method for optimizing current harmonics of a converter, characterized in that: Applied to a renewable energy power generation system, the renewable energy power generation system comprises at least one converter, and one end of each converter is connected to a common bus, and the common bus is used to connect to a power grid; The method comprises: Obtain grid voltage in real time; If the grid voltage is greater than a preset voltage threshold, reducing the initial active current given value of the converter; A switch control variable is generated based on the adjusted active current set value, and the switch control variable is modulated to generate a pulse signal for controlling the converter.

2. The current harmonic optimization method of the converter according to claim 1, characterized in that: If the grid voltage is greater than a preset voltage threshold, reducing the initial active current given value of the converter comprises: If the grid voltage is greater than the preset voltage threshold and the load rate of the new energy power generation system exceeds the preset load threshold, the initial active current given value of the converter is reduced; the preset voltage threshold is the product of the grid rated voltage and a preset coefficient, and the preset coefficient is greater than 1.

1.

3. The current harmonic optimization method of the converter according to any one of claims 1 to 2, characterized in that: If the grid voltage is greater than a preset voltage threshold, reducing the initial active current given value of the converter comprises: If the grid voltage is greater than a preset voltage threshold, a current compensation value is determined based on a difference between a given bus voltage value and an actual bus voltage value of the common bus; The current compensation value is used to compensate the initial active current given value of the converter to reduce the initial active current given value.

4. The current harmonic optimization method of the converter according to claim 3, characterized in that: The difference is positively correlated with the current compensation value; Correspondingly, the using the current compensation value to compensate the initial active current given value of the converter includes: The current compensation value is subtracted from the initial active current set value to obtain an adjusted active current set value.

5. The current harmonic optimization method of the converter according to claim 3, characterized in that: The determining of the current compensation value based on the difference between the bus voltage set value and the bus voltage actual value of the common bus comprises: According to the formula ΔI=(U bus_s -U bus_f )·k1 determines the current compensation value, where ΔI represents the current compensation value, U bus_s Indicates the bus voltage given value, U bus_f represents the actual value of the bus voltage, and k1 represents the preset threshold value.

6. The current harmonic optimization method of the converter according to claim 1, characterized in that: The reducing the initial active current given value of the converter comprises: reducing the initial active current given value of the converter for N consecutive cycles starting from a first moment; the first moment is the initial moment when the grid voltage is greater than a preset voltage threshold; After N cycles at the first moment, according to Calculating an active current given value of the converter; Among them, I d represents the active current given value of the converter, P d represents the active power of the converter before the first moment, V grid Indicates the grid voltage at the current moment.

7. A current harmonic optimization device for a converter, characterized in that: Applied to a renewable energy power generation system, the renewable energy power generation system includes at least one converter, and one end of each converter is connected to a common bus, and the common bus is used to connect to a power grid; the device includes: A grid voltage acquisition module, used to acquire the grid voltage in real time; An active current compensation module, used for reducing the initial active current given value of the converter if the grid voltage is greater than a preset voltage threshold; The switch control module is used to generate a switch control amount based on the adjusted active current given value, and the switch control amount generates a pulse signal for controlling the converter after modulation.

8. A controller, characterized in that: It comprises a processor and a memory, wherein the memory is used to store a computer program, and the processor is used to call and run the computer program stored in the memory to execute the current harmonic optimization method of the converter according to any one of claims 1 to 6.

9. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of the current harmonic optimization method of the converter as described in any one of claims 1 to 6 are implemented.

10. A photovoltaic system, characterized in that: Comprising a controller as claimed in claim 8.

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