High and low voltage ride-through control method and device of inverter, controller and photovoltaic system

Abstract

The invention provides a high and low voltage ride-through control method and device of an inverter, a controller and a photovoltaic system. The method comprises the following steps: judging whether a power grid recovers from a high-low voltage ride-through state or not; if it is monitored that the power grid recovers from the high-low voltage ride-through state, determining a reactive power compensation value based on the voltage change of the power grid in the high-low voltage ride-through state; obtaining a reactive power given value of the inverter; compensating the reactive power given value by adopting the reactive power compensation value to obtain a compensated reactive power given value, and generating a switch control quantity by adopting the compensated reactive power given value; the switch control quantity is used for generating a pulse signal for controlling the inverter after modulation. According to the method, the reactive response speed can be increased when the power grid is recovered by directly adjusting the reactive power given value, and the reactive loop parameters do not need to be changed, so that the stability of the system is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of inverters, and in particular to a high and low voltage ride-through control method, device, controller and photovoltaic system for an inverter. Background Art

[0002] With the continuous increase in the proportion of renewable energy connected to the power grid, its impact on weak power grids has become more and more significant. Specifically, the grid-connected operation of renewable energy power generation systems will significantly affect the short-circuit ratio (LCR) index of weak power grids, thereby deteriorating the dynamic stability of the power grid.

[0003] According to the technical regulations for photovoltaic power stations connected to the power system, when a grid fault occurs, the reactive power response time of the photovoltaic inverter needs to be within the standard time. To meet this technical requirement, in related technologies, the loop response speed is usually increased by adjusting the inverter loop parameters. However, blindly increasing the loop response speed by adjusting the loop parameters will damage the stability when the system resumes normal operation. Summary of the Invention

[0004] Embodiments of the present invention provide a high and low voltage ride-through control method, device, controller and photovoltaic system for an inverter to solve the problem of slow reactive power output response of the inverter.

[0005] In a first aspect, an embodiment of the present invention provides a high and low voltage ride-through control method for an inverter, which is applied to a new energy power generation system. The new energy power generation system includes at least one inverter, and the AC terminals of each inverter are all used to connect to the power grid. The method includes:

[0006] Determine whether the power grid has recovered from the high and low voltage ride-through state;

[0007] If it is monitored that the power grid has recovered from the high and low voltage ride-through state, determine the reactive power compensation value based on the voltage change of the power grid in the high and low voltage ride-through state;

[0008] Obtain the reactive power reference value of the inverter;

[0009] Compensate the reactive power reference value with the reactive power compensation value to obtain a compensated reactive power reference value, and generate a switch control quantity with the compensated reactive power reference value. The switch control quantity is used to generate a pulse signal for controlling the inverter after modulation.

[0010] In a second aspect, an embodiment of the present invention provides a high and low voltage ride-through control device for an inverter, which is applied to a new energy power generation system. The new energy power generation system includes at least one inverter, and the AC terminals of each inverter are all used to connect to the power grid. The device includes:

[0011] A power grid monitoring module, configured to determine whether the power grid has recovered from a high-low voltage ride-through state;

[0012] A reactive power compensation value calculation module, configured to, if it is monitored that the power grid has recovered from the high-low voltage ride-through state, determine a reactive power compensation value based on the voltage change of the power grid in the high-low voltage ride-through state;

[0013] A reactive power reference value calculation module, configured to obtain the reactive power reference value of the inverter;

[0014] A control quantity acquisition module, configured to compensate the reactive power reference value with the reactive power compensation value to obtain a compensated reactive power reference value, and generate a switching control quantity by using the compensated reactive power reference value; the switching control quantity is used to generate a pulse signal for controlling the inverter after modulation.

[0015] 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 method in any possible implementation manner of the first aspect above are implemented.

[0016] In a fourth aspect, an embodiment of the present invention provides a photovoltaic system, including the controller described in the third aspect above.

[0017] An embodiment of the present invention provides a high-low voltage ride-through control method, device, controller, and photovoltaic system for an inverter. The method first determines whether the power grid has recovered from a high-low voltage ride-through state; if it is monitored that the power grid has recovered from the high-low voltage ride-through state, a reactive power compensation value is determined based on the voltage change of the power grid in the high-low voltage ride-through state; then the reactive power reference value of the inverter is obtained; the reactive power reference value is compensated with the reactive power compensation value to obtain a compensated reactive power reference value, and a switching control quantity is generated by using the compensated reactive power reference value; the switching control quantity is used to generate a pulse signal for controlling the inverter after modulation. The above method can accelerate the reactive power response speed when the power grid recovers by directly adjusting the reactive power reference value, enable the reactive power control loop to return to the state before the fault, and does not need to change the reactive loop parameters, thereby ensuring the stability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] 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. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0019] Figure 1 is a schematic structural diagram of a photovoltaic grid-connected system provided by an embodiment of the present invention;

[0020] Figure 2 is a flowchart for implementing a high and low voltage ride-through control method of an inverter provided by an embodiment of the present invention;

[0021] Figure 3 is a schematic structural diagram of a high and low voltage ride-through control device of an inverter provided by an embodiment of the present invention;

[0022] Figure 4 is a schematic diagram of a controller provided by an embodiment of the present invention. Detailed implementation manners

[0023] In the following description, for the purpose of illustration rather than limitation, specific details such as specific system structures and technologies are presented 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.

[0024] In the description of the specification and the appended claims of the present application, the terms "first", "second", "third", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.

[0025] In the description of the present application, referring to "one embodiment" or "some embodiments" etc. means that a specific feature, structure, or characteristic described in combination with the embodiment is included in one or more embodiments of the present application. Thus, the statements "in one 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.

[0026] In addition, "a plurality" mentioned in the embodiments of the present application should be construed as two or more.

[0027] To make the purpose, technical solution, and advantages of the present invention clearer, the following will be described through specific embodiments with reference to the accompanying drawings.

[0028] See Figure 1, which shows an application scenario of the high and low voltage ride-through control method of the inverter provided by the embodiment of the present invention. 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 embodiment of the present application will be described in detail.

[0029] Specifically, the photovoltaic system includes at least one photovoltaic module (PV1~PVn), at least one photovoltaic inverter, and a controller corresponding to each photovoltaic inverter. At least one photovoltaic module is connected to the DC side of the photovoltaic inverter, the AC sides of at least one photovoltaic inverter are all connected to the AC bus, and the AC bus is connected to the power grid.

[0030] The photovoltaic inverter can adjust the reactive power output in real time according to the change of the grid voltage. When the grid voltage rises, it absorbs reactive power, and when the grid voltage drops, it outputs reactive power, thereby effectively reducing voltage fluctuations and maintaining the stability of the grid voltage. According to the technical regulations for grid connection of photovoltaic power stations, when a grid fault occurs, the reactive power response time of the photovoltaic inverter needs to be within 30ms. To meet this requirement, the prior art usually adopts the method of adjusting the parameters of the reactive power control loop (such as PID parameters) to accelerate the reactive power response speed. However, this method will damage the control stability due to excessive changes in the reactive power loop parameters when the grid returns to normal.

[0031] To avoid the above problems, this embodiment provides a high and low voltage ride-through control method for an inverter. The execution subject of this method can be the high and low voltage ride-through controller of the above photovoltaic inverter.

[0032] See Figure 2 , which shows the implementation flowchart of the high and low voltage ride-through control method of the inverter provided by the embodiment of the present invention, and is described in detail as follows:

[0033] S101: Determine whether the grid has recovered from the high and low voltage ride-through state.

[0034] In this embodiment, the controller of the photovoltaic inverter can obtain the grid electrical parameters and determine whether the grid has experienced high and low voltage ride-through or whether the grid has recovered from the high and low voltage ride-through state according to the magnitude of the grid electrical parameters.

[0035] Specifically, the grid electrical parameters include the actual power value of the grid and the actual voltage value of the grid. Taking the actual voltage value as an example, when the controller monitors that the actual voltage value of the grid exceeds the corresponding high and low voltage ride-through threshold, it determines that the grid has entered the high and low voltage ride-through state. Among them, the high and low voltage ride-through state includes the low voltage ride-through state and the high voltage ride-through state.

[0036] In this embodiment, the low-high voltage ride-through threshold includes a lower voltage limit value and an upper voltage limit value. When the actual voltage value of the power grid is less than the lower voltage limit value, it is determined that the power grid enters the low voltage ride-through state. When the actual voltage value of the power grid is greater than the upper voltage limit value, it is determined that the power grid enters the high voltage ride-through state. When the power grid is in the high voltage ride-through state or the low voltage ride-through state, if it is detected that the actual voltage value of the power grid enters the normal voltage range (the actual voltage value is greater than the lower voltage limit value and less than the upper voltage limit value), it is determined that the power grid recovers from the low-high voltage ride-through state.

[0037] It can be understood that in this embodiment, the actual power value of the power grid can also be compared with the low-high voltage ride-through power threshold to determine whether the power grid enters the low-high voltage ride-through state. When the actual power value of the power grid enters the normal power range (the actual power value is greater than the lower power limit value and less than the upper power limit value), it is determined that the power grid recovers from the low-high voltage ride-through state.

[0038] In a possible implementation manner, the specific implementation process of S101 includes:

[0039] Judge whether the difference between the actual voltage value of the power grid and the per-unit voltage value is less than a preset difference threshold. If the difference is less than the preset difference threshold, it is determined that the power grid recovers from the low-high voltage ride-through state.

[0040] In this embodiment, when the power grid electrical parameter is voltage, the controller obtains the positive sequence component of the three-phase actual voltage value of the voltage. The per-unit voltage value can be the rated voltage of the power grid. When the difference between the positive sequence component of the power grid voltage and the positive sequence component of the rated voltage is greater than the preset difference threshold, it indicates that the power grid enters the low-high voltage ride-through state.

[0041] Specifically, when the difference between the positive sequence component of the actual power grid voltage value and the positive sequence component of the per-unit voltage value is greater than the first preset difference threshold, it is determined that the power grid enters the high voltage ride-through state. When the difference between the positive sequence component of the three-phase actual voltage value of the power grid and the positive sequence component of the per-unit voltage value is less than the second preset difference threshold, it is determined that the power grid enters the low voltage ride-through state, where the first preset difference threshold is greater than zero and the second preset difference threshold is less than zero.

[0042] When the absolute value of the difference between the actual voltage value of the power grid and the per-unit voltage value is less than the preset difference threshold, it is determined that the power grid recovers from the low-high voltage ride-through state. The preset difference threshold can be the absolute value of the first preset difference threshold or the second preset difference threshold.

[0043] S102: If it is monitored that the power grid recovers from the low-high voltage ride-through state, determine the reactive power compensation value based on the voltage change of the power grid in the low-high voltage ride-through state.

[0044] In this embodiment, when it is detected that the power grid recovers from the high and low voltage ride-through state, the magnitude of the reactive power compensation value can be determined based on the high and low voltage ride-through conditions of the power grid voltage. When the power grid enters the low voltage ride-through state, the photovoltaic inverter is used to output positive reactive power to the power grid to support the power grid voltage; when the power grid recovers from the low voltage ride-through state, the reactive power compensation value is negative, and the reactive power compensation value decreases as the degree of the low voltage ride-through state increases, so that the photovoltaic inverter quickly reduces the reactive power output and returns to the normal state. When the power grid enters the high voltage ride-through state, the photovoltaic inverter is used to absorb the reactive power of the power grid, so the reactive power set value is negative; when the power grid recovers from the high voltage ride-through state, the reactive power compensation value is positive, and the reactive power compensation value increases as the degree of the high voltage ride-through state increases, so that the photovoltaic inverter quickly reduces the absorption of reactive power and returns to the normal state.

[0045] S103: Obtain the reactive power set value of the inverter.

[0046] S104: Compensate the reactive power set value with the reactive power compensation value to obtain the compensated reactive power set value, and generate a switch control quantity with the compensated reactive power set value; the switch control quantity is used to generate a pulse signal for controlling the inverter after modulation.

[0047] In this embodiment, after compensating the reactive power set value with the reactive power compensation value, the compensated reactive power set value can be limited based on the upper limit value of the reactive power of the inverter, so as to avoid the compensated reactive power set value exceeding the rated capacity range of the inverter, resulting in damage or unstable operation of the inverter.

[0048] In this embodiment, the reactive power compensation value is added to the reactive power set value to obtain the compensated reactive power set value.

[0049] As can be seen from the above embodiments, in this embodiment, when it is detected that the power grid recovers from the fault state, the reactive power set value is compensated by setting the reactive power compensation value to accelerate the adjustment speed of the reactive power loop, and there is no need to change the reactive power loop parameters, thereby ensuring the stability of the system.

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

[0051] Determine the reactive power compensation value according to the voltage abnormality degree of the power grid.

[0052] In this embodiment, the degree of voltage abnormality is the degree to which the grid voltage deviates from the normal voltage threshold after entering the high and low voltage ride-through state. Determining the reactive power compensation value according to the degree of voltage abnormality can not only shorten the time for the reactive power output of the inverter to return to zero and reduce the reactive power response time of the high and low voltage ride-through to the standard time, but also avoid the problem of overcompensation damaging the control stability of the inverter.

[0053] In a possible implementation manner, the high and low voltage ride-through state includes a low voltage ride-through state; the reactive power compensation value includes a first reactive power compensation value; the specific implementation process of S102 further includes:

[0054] Determine the first reactive power compensation value according to the voltage dip depth of the grid, and the voltage dip depth is negatively correlated with the first reactive power compensation value.

[0055] In this embodiment, the first reactive power compensation value is negative. In this embodiment, it can be set that the voltage dip depth is inversely proportional to the first reactive power compensation value, that is, the greater the voltage dip depth, the smaller the first reactive power compensation value, and the smaller the voltage dip depth, the greater the first reactive power compensation value. Through this setting, the response speed of the reactive power loop can be adaptively adjusted so that the response time of the reactive power loop when the grid recovers from the low voltage ride-through state just meets the standard time. That is, the response time of the reactive power control loop executed using the compensated reactive power given value is less than or equal to the standard time, and the maximum first reactive power compensation value that can make the response time of the reactive power control loop less than or equal to the standard time is taken.

[0056] In a possible implementation manner, the specific implementation process of S102 further includes:

[0057] According to the formula Determine the first reactive power compensation value;

[0058] wherein, ΔU1 represents the first reactive power compensation value, H min represents the grid dip threshold value; U f represents the actual value of the grid voltage, U e represents the rated voltage of the grid, I e represents the rated current of the grid, K1 represents the first preset coefficient, and k0 represents the preset adjustment value.

[0059] In this embodiment, when the grid voltage returns to normal from the low voltage ride-through state, that is, when it is monitored that the difference between the actual voltage value and the per-unit voltage value is less than the negative preset difference threshold, the above formula is used to calculate the low voltage reactive power compensation value. In this formula, H min represents the grid dip threshold value, and this value is a value after normalization processing, that is wherein, Umin1 It can be the lower limit value of the conventional voltage range, that is, the value obtained by subtracting the preset difference threshold from the grid rated voltage.

[0060] In this embodiment, both K1 and k0 are preset values, and this value can be determined through actual experiments. Exemplarily, the value range of K1 can be from 1 to 5. The value range of k0 can be from 0.02 to 0.08.

[0061] In a possible implementation manner, the high and low voltage ride-through state includes a high voltage ride-through state; the reactive power compensation value includes a second reactive power compensation value; the specific implementation process of S102 includes:

[0062] Determine the second reactive power compensation value according to the overvoltage depth of the power grid, and the voltage overvoltage depth is positively correlated with the second reactive power compensation value.

[0063] In this embodiment, the second reactive power compensation value is a positive value. In this embodiment, it can be set that the voltage overvoltage depth is proportional to the second reactive power compensation value, that is, the greater the voltage overvoltage depth, the greater the second reactive power compensation value, and the smaller the voltage drop depth, the smaller the second reactive power compensation value. Through this setting, the response speed of the reactive power loop can be adaptively adjusted so that the response time of the reactive power loop when the power grid recovers from the high voltage state just meets the standard time. That is, the response time of the reactive power control loop executed by using the compensated reactive power given value is less than or equal to the standard time, and the minimum second reactive power compensation value that can make the response time of the reactive power control loop less than or equal to the standard time is taken.

[0064] In a possible implementation manner, the specific implementation process of S102 further includes:

[0065] According to the formula Determine the second reactive power compensation value;

[0066] Wherein, ΔU2 represents the second reactive power compensation value, H max represents the overvoltage threshold value of the power grid; U f represents the actual value of the power grid voltage, U e represents the rated voltage of the power grid, I e represents the rated current of the power grid, K2 represents the second preset coefficient, and k0 represents the preset adjustment value.

[0067] In this embodiment, when the power grid voltage recovers to normal from the high voltage ride-through state, that is, when it is monitored that the difference between the actual voltage value and the voltage per unit value is less than the preset difference threshold, the low-voltage reactive power compensation value is calculated by using the above formula. In this formula, H max represents the overvoltage threshold value of the power grid, and this value is a value after normalization processing, that is Among them, U max1 can be the upper limit value of the conventional voltage range, that is, the value after adding the preset difference threshold to the grid rated voltage.

[0068] In this embodiment, both K2 and k0 are preset values, and this value can be determined through actual experiments. Exemplarily, the value range of K2 can be from 1 to 5. The value range of k0 can be from 0.02 to 0.08.

[0069] In a possible implementation manner, the specific implementation process of S104 includes:

[0070] Taking the difference between the compensated reactive power reference value and the actual reactive power value as the reactive power difference;

[0071] Based on the reactive power difference, determining the reactive current control amount;

[0072] Obtaining the active current control amount output by the active power control loop of the inverter;

[0073] Based on the reactive current control amount and the active current control amount, generating the switch control amount.

[0074] Specifically, the high and low voltage ride-through control loop of the photovoltaic inverter includes an active power loop and a reactive power loop. After obtaining the compensated reactive power reference value, the controller subtracts the reactive power feedback value from the reactive power reference value to obtain the reactive power difference, and inputs the reactive power difference into the PI controller to obtain the reactive current control amount I q ; on the other hand, within the active power loop, the controller subtracts the active power feedback value from the active power reference value to obtain the active power difference, and inputs the active power difference into the PI controller to obtain the active current control amount I d , after limiting the current of the active current control amount I d , using the formula I set = I q ·cosθ - I d ·sinθ to calculate the current loop reference value I set, where θ represents the phase of the grid voltage output by the phase-locked loop. Then, subtract the actual value of the output current from the given value of the current loop of the photovoltaic inverter to obtain the current loop difference. Input the current loop difference into the proportional controller to obtain the first control quantity. Add the first control quantity to the actual value of the grid voltage to obtain the 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 the 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.

[0075] As can be seen from the above embodiments, in this embodiment, by directly compensating the reactive power given value with the reactive power compensation value, the response speed of the reactive power loop can be accelerated by increasing the adjustment amount, so that the reactive power output by the reactive power loop can quickly recover to the state before the grid fault. On this basis, it is no longer necessary to adjust the PID parameters in the reactive power control loop, thus avoiding the problem of poor system stability caused by excessive changes in the PID parameters after the grid returns to normal. The effect of accelerating the response speed of the reactive power loop is achieved on the premise of ensuring the stability of the high and low voltage ride-through control of the photovoltaic inverter, so as to meet the increasingly strict technical standards of the power system.

[0076] 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 by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present invention.

[0077] The following is an apparatus embodiment of the present invention. For details not described in detail herein, reference may be made to the corresponding method embodiments above.

[0078] Figure 3 The structural schematic diagram of the high and low voltage ride-through control device of the inverter 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:

[0079] As Figure 3 shown, the high and low voltage ride-through control device 100 of the inverter includes:

[0080] A grid monitoring module 110, configured to determine whether the grid has recovered from the high and low voltage ride-through state;

[0081] A reactive power compensation value calculation module 120, configured to, if it is detected that the grid has recovered from the high and low voltage ride-through state, determine a reactive power compensation value based on the voltage change of the grid in the high and low voltage ride-through state;

[0082] A reactive power reference value calculation module 130, configured to obtain the reactive power reference value of the inverter;

[0083] A control quantity acquisition module 140, configured to compensate the reactive power reference value with the reactive power compensation value to obtain a compensated reactive power reference value, and generate a switch control quantity by using the compensated reactive power reference value; the switch control quantity is used to generate a pulse signal for controlling the inverter after modulation.

[0084] In a possible implementation manner, the reactive power compensation value calculation module 120 is configured to:

[0085] Determine the reactive power compensation value according to the voltage abnormality degree of the power grid.

[0086] In a possible implementation manner, the high and low voltage ride-through state includes a low voltage ride-through state; the reactive power compensation value includes a first reactive power compensation value; specifically, the reactive power compensation value calculation module 120 is configured to:

[0087] Determine the first reactive power compensation value according to the voltage dip depth of the power grid, and the voltage dip depth is negatively correlated with the first reactive power compensation value.

[0088] In a possible implementation manner, the reactive power compensation value calculation module 120 is further configured to:

[0089] According to the formula Determine the first reactive power compensation value;

[0090] Wherein, ΔU1 represents the first reactive power compensation value, H min Represents the dip threshold of the power grid; U f Represents the actual value of the power grid voltage, U e Represents the rated voltage of the power grid, I e Represents the rated current of the power grid, K1 represents a first preset coefficient, and k0 represents a preset adjustment value.

[0091] In a possible implementation manner, the high and low voltage ride-through state includes a high voltage ride-through state; the reactive power compensation value includes a second reactive power compensation value; specifically, the reactive power compensation value calculation module 120 is configured to:

[0092] Determine the second reactive power compensation value according to the overvoltage depth of the power grid, and the voltage overvoltage depth is positively correlated with the second reactive power compensation value.

[0093] In a possible implementation manner, the reactive power compensation value calculation module 120 is further configured to:

[0094] According to the formula determine the second reactive power compensation value;

[0095] wherein, ΔU2 represents the second reactive power compensation value, and H max represents the overvoltage threshold of the power grid; U f represents the actual value of the power grid voltage, and U e represents the rated voltage of the power grid, and I e represents the rated current of the power grid, K2 represents the second preset coefficient, and k0 represents the preset adjustment value.

[0096] In a possible implementation manner, the control quantity acquisition module 140 is configured to:

[0097] Take the difference between the compensated reactive power set value and the actual reactive power value as the reactive power difference;

[0098] Based on the reactive power difference, determine the reactive current control quantity;

[0099] Obtain the active current control quantity output by the active power control loop of the inverter;

[0100] Based on the reactive current control quantity and the active current control quantity, generate the switch control quantity.

[0101] In a possible implementation manner, the power grid monitoring module 110 is configured to:

[0102] Judge whether the difference between the actual value of the power grid voltage and the per-unit value of the voltage is less than the preset difference threshold. If the difference is less than the preset difference threshold, it is determined that the power grid has recovered from the high-low voltage ride-through state.

[0103] It can be seen from the above embodiments that the high-low voltage ride-through control device of the inverter provided in this embodiment directly compensates by using the reactive power compensation value, and can accelerate the response speed of the reactive power loop by increasing the adjustment amount. On this basis, it is no longer necessary to adjust the PID parameters in the reactive power control loop, thereby avoiding the problem of poor system stability caused by excessive changes in the PID parameters after the power grid returns to normal, and realizing the effect of accelerating the response speed of the reactive power loop on the premise of ensuring the stability of the high-low voltage ride-through control of the photovoltaic inverter, so as to meet the increasingly strict technical standards of the power system.

[0104] Figure 4 is a schematic diagram of the controller provided by the embodiment of the present invention. As Figure 4As 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 embodiments of the high and low voltage ride-through control methods of the above-mentioned inverters, such as Figure 2 the steps S101 to S104 shown. Alternatively, 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-mentioned device embodiments, such as Figure 3 the functions of the modules 110 to 140 shown.

[0105] 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 performing specific functions, and this instruction segment is used to describe the execution process of the computer program 42 in the controller 4. For example, the computer program 42 can be divided into Figure 3 the modules 110 to 140 shown.

[0106] The controller 4 can be a computing device such as a desktop computer, a notebook, a palm computer, and 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 this is only an example of the controller 4 and does not constitute a limitation on the controller 4. It may include more or fewer components than shown in the figure, or combine some components, or different components. For example, the controller may further include input / output devices, network access devices, buses, etc.

[0107] 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.

[0108] 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 of the controller 4 and external storage devices. The memory 41 is used to store the computer program and other programs and data required by the controller. The memory 41 may also be used to temporarily store the data that has been output or will be output.

[0109] Those skilled in the art can clearly understand that, for the convenience and conciseness of description, only the above-mentioned division of each functional unit and module is used as an example. In actual applications, the above functions can be allocated to different functional units and modules according to needs, that is, the internal structure of the device is 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 in a processing unit, or each unit can exist physically alone, or two or more units can be integrated in one unit. The above-mentioned integrated units can be implemented in the form of hardware or in the form of software functional units. 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 the present 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.

[0110] In the above embodiments, the descriptions of the respective 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.

[0111] 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 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.

[0112] In the embodiments provided by the present invention, it should be understood that the disclosed device / controller and method can be implemented in other ways. For example, the device / controller embodiments described above are merely illustrative. For example, the division of the modules or units is only a logical function division. In actual implementation, there may be other division methods. 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 couplings or direct couplings or communication connections shown or discussed with each other can be through some interfaces. The indirect couplings or communication connections of the devices or units can be in electrical, mechanical or other forms.

[0113] The units described as separate components may or may not be physically separated. The components shown as units may or may not be physical units, that is, they can be located in one place or 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.

[0114] In addition, the functional units in various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically alone, or two or more units can be integrated into one unit. The above integrated units can be implemented in the form of hardware or in the form of software functional units.

[0115] 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 this understanding, to implement all or part of the processes in the above method embodiments of the present invention, it can also be completed by a computer program instructing relevant 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 embodiments of the high and low voltage ride-through control methods of each inverter 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 that can carry the computer program code, recording medium, USB flash drive, mobile hard disk, magnetic disk, optical disk, 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.

[0116] The embodiments described above 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 cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A high and low voltage ride through control method for an inverter, characterized in that: Applied to a new energy power generation system, the new energy power generation system includes at least one inverter, and the AC end of each inverter is used to connect to the power grid; the method includes: Determine whether the power grid has recovered from the high and low voltage ride-through state; If it is monitored that the power grid recovers from the high and low voltage ride through state, determining a reactive power compensation value based on a voltage change of the power grid in the high and low voltage ride through state; Obtaining a reactive power given value of the inverter; The reactive power compensation value is used to compensate the reactive power set value to obtain the compensated reactive power set value, and the compensated reactive power set value is used to generate a switch control quantity; the switch control quantity is used to generate a pulse signal for controlling the inverter after modulation.

2. The high and low voltage ride through control method of the inverter according to claim 1, characterized in that: The determining of the reactive power compensation value based on the voltage change of the power grid in the high and low voltage ride through state includes: A reactive power compensation value is determined according to the voltage abnormality degree of the power grid.

3. The high and low voltage ride through control method of the inverter according to claim 2, characterized in that: The high and low voltage ride-through state includes a low voltage ride-through state; the reactive power compensation value includes a first reactive power compensation value; Determining the reactive power compensation value according to the voltage abnormality degree of the power grid includes: A first reactive power compensation value is determined according to a voltage drop depth of the power grid, and the voltage drop depth is negatively correlated with the first reactive power compensation value.

4. The high and low voltage ride through control method of the inverter according to claim 3, characterized in that: Determining a first reactive power compensation value according to a voltage drop depth of the power grid includes: According to the formula determining the first reactive power compensation value; Wherein, ΔU1 represents the first reactive power compensation value, H min Indicates the drop threshold value of the power grid; U f Indicates the actual value of the grid voltage, U e Indicates the rated voltage of the grid, I e represents the rated current of the power grid, K1 represents the first preset coefficient, and k0 represents the preset adjustment value.

5. The high and low voltage ride through control method of the inverter according to claim 2, characterized in that: The high and low voltage ride-through state includes a high voltage ride-through state; the reactive power compensation value includes a second reactive power compensation value; Determining the reactive power compensation value according to the voltage abnormality degree of the power grid includes: A second reactive power compensation value is determined according to the overvoltage depth of the power grid, and the voltage overvoltage depth is positively correlated with the second reactive power compensation value.

6. The high and low voltage ride through control method of the inverter according to claim 5, characterized in that: The determining of the second reactive power compensation value according to the overvoltage depth of the power grid comprises: According to the formula determining the second reactive power compensation value; Wherein, ΔU2 represents the second reactive power compensation value, H max represents the overvoltage threshold value of the power grid; U f Indicates the actual value of the grid voltage, U e Indicates the rated voltage of the grid, I e represents the rated current of the power grid, K2 represents the second preset coefficient, and k0 represents the preset adjustment value.

7. The high and low voltage ride through control method of the inverter according to any one of claims 1 to 6, characterized in that: The method of using the compensated reactive power given value to generate a switch control quantity comprises: The difference between the reactive power given value after compensation and the actual reactive power value is taken as the reactive power difference; Determining a reactive current control amount based on the reactive power difference; Obtaining an active current control amount output by an active power control loop of the inverter; The switching control amount is generated based on the reactive current control amount and the active current control amount.

8. A high and low voltage ride through control device for an inverter, characterized in that: Applicable to a new energy power generation system, the new energy power generation system includes at least one inverter, and the AC end of each inverter is used to connect to the power grid; the device includes: The power grid monitoring module is used to determine whether the power grid has recovered from the high and low voltage ride-through state; A reactive power compensation value calculation module is used to determine a reactive power compensation value based on a voltage change of the power grid in the high and low voltage ride-through state if it is monitored that the power grid recovers from the high and low voltage ride-through state; A reactive power given value calculation module, used to obtain a reactive power given value of the inverter; A control quantity acquisition module is used to compensate the reactive power set value with the reactive power compensation value to obtain the compensated reactive power set value, and use the compensated reactive power set value to generate a switch control quantity; the switch control quantity is used to generate a pulse signal for controlling the inverter after modulation.

9. 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 high and low voltage ride-through control method of the inverter as described in any one of claims 1 to 7.

10. A photovoltaic system, characterized in that: include: A controller as claimed in claim 9.

Images