Inverter reactive current control method, device, equipment and medium

Abstract

The invention discloses an inverter reactive current control method, device and equipment and a medium, and the method comprises the steps: obtaining an output port voltage and an output port current of an inverter, and estimating the equivalent impedance between the inverter and a grid connection point based on the output port voltage and the output port current; calculating the amplitude and phase of the grid-connected point voltage based on the output port voltage, the output port current and the equivalent impedance; based on the amplitude of the voltage of the grid-connected point and the recorded value of the reactive current phasing by the voltage of the high-voltage side before the fault ride-through occurs, the target value of the reactive current which should be injected into the grid-connected point by the inverter during the fault ride-through is calculated; on the basis of the phase of the grid-connected point voltage and the reactive current target value, a reactive current instruction value phasing by the inverter output port voltage is obtained through calculation; and taking the reactive current instruction value as a current given value of the inverter, enabling the inverter to carry out closed-loop tracking on the reactive current instruction value, and outputting reactive current. Reactive current output by the inverter can accurately respond to the voltage change of the grid-connected point.

Description

Technical Field

[0001] This invention relates to the field of power technology, and in particular to a method, device, equipment and medium for controlling reactive current in an inverter. Background Technology

[0002] With the large-scale grid connection of new energy sources, represented by photovoltaic power generation, the power system has placed clear requirements on the fault ride-through capability of photovoltaic power plants. According to relevant standards (such as GB / T 19964-2012 "Technical Regulations for Photovoltaic Power Plants Connected to the Power System"), during voltage faults in the power grid, photovoltaic power plants should dynamically inject reactive current into the grid connection point to support the recovery and stabilization of the grid connection voltage. This dynamic reactive current command should directly respond to changes in the amplitude and phase of the grid connection voltage.

[0003] However, in mainstream implementations of existing technologies, when a photovoltaic inverter performs fault ride-through control, its output dynamic reactive current is typically phased and controlled using the voltage at its own grid connection port as a reference. Because photovoltaic power plants contain impedances such as step-up transformers (panel substations) and collector lines, significant voltage drops and phase shifts occur across these impedances when fault current flows through them. This results in a significant difference between the voltage amplitude and phase at the grid connection point (PCC) and the voltage measured at the inverter port.

[0004] Therefore, existing control strategies based on the inverter's local port voltage struggle to ensure that the inverter's output reactive current accurately responds to actual changes in the grid connection point voltage. This inconsistency between the control target (grid connection point voltage) and the measurement feedback point (local port voltage) can lead to insufficient reactive power support or inaccurate response from the photovoltaic power plant during faults, failing to fully meet the grid standards' requirements for reactive power compensation effectiveness, and consequently affecting the transient stability of the grid. How to enable more precise reactive current control of the inverter in response to changes in the grid connection point voltage has become a pressing technical problem requiring improvement in this field. Summary of the Invention

[0005] This invention provides a method, apparatus, device, and medium for controlling reactive current in an inverter, aiming to solve the problem that the reactive current output of existing photovoltaic inverters cannot accurately respond to changes in the phase and amplitude of the grid connection voltage.

[0006] In a first aspect, embodiments of the present invention provide a reactive current control method for an inverter, comprising: Obtain the inverter output port voltage and output port current, and estimate the equivalent impedance between the inverter and the grid connection point based on the output port voltage and output port current; The amplitude and phase of the grid connection point voltage are calculated based on the output port voltage, the output port current, and the equivalent impedance. The target value of reactive current that the inverter should inject into the grid connection point during fault ride is calculated based on the amplitude of the grid connection point voltage and the reactive current recorded value with the high voltage side voltage phase determined before the fault ride-through. The reactive current command value, which is phased by the output port voltage, is calculated based on the phase of the grid connection point voltage and the target value of the reactive current. The reactive current command value is used as the current setpoint of the inverter so that the inverter can perform closed-loop tracking of the reactive current command value and output reactive current.

[0007] In a second aspect, embodiments of the present invention provide an inverter reactive current control device for implementing the inverter reactive current control method described in the first aspect. The device is configured in a controller of a power generation system and includes: Impedance estimation unit is used to obtain the inverter output port voltage and output port current, and estimate the equivalent impedance between the inverter and the grid connection point based on the output port voltage and output port current. The first calculation unit is used to calculate the amplitude and phase of the grid connection point voltage based on the output port current and the equivalent impedance. The second calculation unit is used to calculate the target value of reactive current that the inverter should inject into the grid connection point during fault ride based on the amplitude of the grid connection point voltage and the reactive current record value with the high voltage side voltage phase determined before the fault ride-through occurs. The third calculation unit is used to calculate the reactive current command value with the output port voltage as the phase based on the phase of the grid connection point voltage and the reactive current target value. The instruction sending unit is used to use the reactive current instruction value as the current setpoint of the inverter, so that the inverter can perform closed-loop tracking of the reactive current instruction value and output reactive current.

[0008] Thirdly, embodiments of the present invention provide a control device, the device including a processor, a communication interface, a memory and a communication bus, wherein the processor, the communication interface and the memory communicate with each other through the communication bus; Memory, used to store computer programs; When a processor executes a program stored in a memory, it implements the steps of the inverter reactive current control method described in the first aspect.

[0009] Fourthly, embodiments of the present invention provide a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of the inverter reactive current control method as described in the first aspect.

[0010] This invention provides a method, apparatus, device, and medium for controlling reactive current in an inverter. The method involves acquiring the inverter's output port voltage and current, estimating the equivalent impedance between the inverter and the grid connection point based on these parameters, calculating the amplitude and phase of the grid connection point voltage based on the output port voltage, current, and equivalent impedance, calculating the target reactive current value that the inverter should inject into the grid connection point during fault ride-through based on the grid connection point voltage amplitude and the reactive current record value (phased with the high-voltage side voltage) before fault ride-through, calculating the reactive current command value (phased with the output port voltage) based on the grid connection point voltage phase and the target reactive current value, and using the reactive current command value as the inverter's current setpoint to enable closed-loop tracking of the reactive current command value and output reactive current. This ensures that during fault ride-through, the inverter's reactive current output accurately responds to changes in the phase and amplitude of the grid connection point voltage. Attached Figure Description

[0011] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 A flowchart of an inverter reactive current control method provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the power generation system provided in an embodiment of the present invention; Figure 3 A simplified structural diagram of the power generation system provided in an embodiment of the present invention; Figure 4 This is a voltage and current vector diagram of a power generation system during fault ride-through, provided in an embodiment of the present invention. Figure 5 (a) is a control logic closed-loop diagram of the inverter reactive current control method provided in the embodiment of the present invention; wherein, (b) is a control logic closed-loop diagram of the actual implementation of the inverter reactive current control method provided in the embodiment of the present invention; and (a) is an equivalent control logic closed-loop diagram of the actual implementation of the inverter reactive current control method provided in the embodiment of the present invention. Figure 6 A schematic block diagram of an inverter reactive current control device provided in an embodiment of the present invention; Figure 7 A schematic block diagram of a control device provided in an embodiment of the present invention. Detailed Implementation

[0013] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0014] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0015] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0016] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0017] It should also be noted that, unless otherwise explicitly specified and limited, terms such as "installation," "connection," "linking," "fixing," and "setting" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. When an component is referred to as being "on" or "below" another component, the component can be located "directly" or "indirectly" on the other component, or there may be one or more intermediary components. The terms "first," "second," "third," etc., are only for the convenience of describing this technical solution and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, features defined with "first," "second," "third," etc., may explicitly or implicitly include one or more of that feature. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0018] Please see Figure 1 and Figure 2This invention provides a reactive current control method for an inverter, applicable to the controller of a power generation system. Specifically, the power generation system can be a photovoltaic (PV) power generation system, which may include an inverter and a box-type transformer (box-type transformer). The inverter may be an inverter array, with its output port connected to the low-voltage side of the box-type transformer, and the high-voltage side of the box-type transformer connected to the grid connection point of the power generation system. This reactive current control method addresses the problem that existing PV inverters cannot accurately respond to changes in the phase and amplitude of the grid connection point voltage. The method may include steps S1 to S5.

[0019] S1. Obtain the inverter output port voltage and output port current, and estimate the equivalent impedance between the inverter and the grid connection point based on the output port voltage and output port current.

[0020] In this embodiment, the power generation system may further include a voltage sampling device and a current sampling device. The voltage sampling device is used to collect the output port voltage U of the inverter. L The current sampling device collects the inverter's output port current I and sends it to the controller. The controller can then estimate the equivalent impedance between the inverter and the grid connection point based on the inverter's output port voltage and current.

[0021] See also Figure 3 In one embodiment, estimating the equivalent impedance between the inverter and the grid connection point based on the output port voltage and the output port current includes: The inverter output port voltage and output port current are collected under two operating conditions to obtain the first port voltage, first port current, second port voltage, and second port current. The first port voltage, first port current, second port voltage, and second port current are then subjected to Clark-Park transformation to obtain the active and reactive components of the first port voltage, first port current, second port voltage, and second port current. The equivalent impedance is calculated based on the active and reactive components of the first port voltage, first port current, second port voltage, and second port current.

[0022] In this embodiment, the controller acquires the output port voltage U at two different operating points through a voltage sampling device and a current sampling device. L And the output port current I, for example, by changing the voltage and current data of the active or reactive power output of the inverter, i.e., two operating conditions, to obtain two sets of output port voltage and output port current data, specifically including: the first port voltage U L1 First port current I1, second port voltage U L2 And the second port current I2. Regarding the output port voltage U...L The output port current I is phase-locked using the port voltage, and the active component U of the output port voltage is obtained by Clark-Park transformation. Ld reactive component U Lq The active component I of the output port current d Reactive component I q .in accordance with Figure 3 The grid connection point voltage U shown in the figure H With equivalent impedance and inverter output port voltage U L Based on the relationship between the voltage and current, we can obtain the following equation 1 for the voltage and current under the two operating conditions: ; Where R is the equivalent resistance component, X is the equivalent reactance component, and j is the imaginary unit; Equation 2 is obtained by subtracting the two equations in the voltage-current relationship (assuming the grid connection point voltage U under two operating conditions). H (Unchanged or very little changed): ; Through the voltage U at the first port L1 First port current I1, second port voltage U L2 Furthermore, by using the same phase for the second port current I2 and performing Clark and Park transformations, the active component U of the first port voltage can be obtained. 1d The reactive component U of the first port voltage 1q The active component U of the second port voltage 2d The reactive component U of the second port voltage 2q The active component I of the first port current 1d The reactive component I of the first port current 1q The active component I of the second port current 2d The reactive component I of the second port current 2q Converting the vectors in relation 2 into dq component expressions, we obtain relation 3: ; Therefore, we obtain relation 4: ; In this way, the equivalent impedance between the inverter and the grid connection point can be estimated.

[0023] S2. The amplitude and phase of the grid connection point voltage are calculated based on the output port voltage, the output port current, and the equivalent impedance.

[0024] In this embodiment, the amplitude and phase of the grid connection point voltage are calculated using the inverter's output port voltage and current, as well as the equivalent impedance between the inverter and the grid connection point. This quantifies the core characteristics of grid faults and builds a data bridge for the accurate response of reactive current to voltage changes, ensuring that the reactive current command given to the inverter can respond accordingly to changes in the amplitude and phase of the grid connection point voltage. Furthermore, during fault ride-through, the grid is under complex conditions of voltage abrupt changes, harmonic distortion, and strong electromagnetic interference. Directly acquiring the grid connection point voltage is susceptible to interference, while calculating the grid connection point voltage by acquiring the inverter's port voltage avoids this problem.

[0025] See also Figure 4 In one embodiment, calculating the amplitude and phase of the grid-connected point voltage based on the output port voltage, the output port current, and the equivalent impedance includes: A complex plane coordinate system constructed with the vector direction of the output port voltage as the positive real axis is used as the low-voltage side coordinate system, and a complex plane coordinate system constructed with the vector direction of the grid connection point voltage as the positive real axis is used as the high-voltage side coordinate system. The output port voltage and the port current are subjected to Clark-Park transformation to obtain the real and imaginary components of the output port voltage and the port current in the low-voltage side coordinate system. Based on the real and imaginary components of the output port voltage and the port current in the low-voltage side coordinate system, and the equivalent impedance, the real and imaginary components of the grid connection point voltage in the low-voltage side coordinate system are calculated. Based on the real and imaginary components of the grid connection point voltage in the low-voltage side coordinate system, the phase and amplitude of the grid connection point voltage in the low-voltage side coordinate system are calculated.

[0026] In this embodiment, in the low-voltage side coordinate system and the high-voltage side coordinate system, the real axis is the d-axis, the imaginary axis is the q-axis, the real axis component is the active component, and the imaginary axis component is the reactive component. Hd with I Hq Line current Real and imaginary axis components in the high-pressure side coordinate system; I Ld with I Lq Line current Real and imaginary axis components in the low-pressure side coordinate system; U Ld with U Lq The output port voltage of the inverter The real and imaginary components of U in the low-pressure side coordinate system Hd with U Hq Voltage at grid connection point The real and imaginary axis components are defined in the low-voltage side coordinate system. This transforms the AC electrical quantity (vector form) into a DC component (algebraic form).

[0027] Specifically, the equivalent impedance R+jX is transformed into R+jω0L, where ω0 is the rated angular frequency, a known fixed parameter, and L is the main inductance of the filter inductance of the line between the inverter output port and the box-type transformer, also a known fixed value. For example... Figure 4 As shown, and The vector relationship is shown in Relation 5: ; The grid connection point voltage is obtained based on equation 5. With the inverter's output port voltage Equation 6 for the dq axis components in the low-pressure side coordinate system: ; in, , I represents a transient quantity. Ld with I Lq U Ld with U Lq It can be obtained by using the same phase (low-voltage side voltage phase) and performing Clark-Park transformation on the output port voltage and port current. In this way, the real axis component and imaginary axis component of the grid connection point voltage in the low-voltage side coordinate system can be calculated by relation 6.

[0028] Transient quantities decay rapidly, and fault traversal focuses on the steady-state response. To simplify calculations while maintaining core accuracy, transient quantities are ignored, resulting in steady-state equation 7: ; This transforms the complex AC vector relationships into simple dq-axis algebraic equations, simplifying steady-state operations to focus on the core requirement of fault ride-through, avoiding redundant calculations, and improving engineering practicality. Based on steady-state equation 7, the grid connection point voltage can be obtained. Phase in the low-pressure side coordinate system Formula 8: ; Grid connection point voltage Formula 9 for the magnitude (i.e., amplitude): .

[0029] Thus, the amplitude and phase of the grid connection point voltage can be calculated using the inverter's output port voltage, output port current, and equivalent impedance. The core issue of fault ride-through is "responding to changes in the phase and amplitude of the grid connection point voltage." This step directly quantifies these two key parameters: the phase reflects the change in the direction of the voltage vector, and the magnitude reflects the change in the voltage amplitude, providing a clear basis for subsequent reactive current adjustments.

[0030] After calculating the phase and amplitude of the grid connection point voltage in the low-voltage side coordinate system based on the real axis and imaginary axis components of the grid connection point voltage in the low-voltage side coordinate system, the method further includes: Based on the phase, the low-voltage side coordinate system, and the high-voltage side coordinate system, the transformation relationship of current on the low-voltage side and the high-voltage side is obtained as Equation 10: ; in, It is the reactive component of the line current on the low-voltage side; It is the active component of the line current on the low-voltage side; It is the phase of the grid connection point voltage. It is the reactive component of the line current on the high-voltage side.

[0031] Specifically, based on the low-pressure side coordinate system and the high-pressure side coordinate system, we can obtain... The relationships between the dq components in different coordinate systems are shown in Equation 11 (including Transformation Equation 10): ; Thus, the active component I of the line current on the high-voltage side can be calculated. Hd Reactive component I Hq With the active component I of the line current on the low-voltage side Ld Reactive component I Lq The equivalent relationship between currents means that the reactive current given or fed back for the high-voltage side phase-locked loop can be obtained from the reactive current given or fed back for the low-voltage side phase-locked loop through this equivalent relationship.

[0032] S3. Based on the amplitude of the grid connection point voltage and the reactive current recorded value with the high-voltage side voltage phase determined before the fault ride-through, calculate the target value of reactive current that the inverter should inject into the grid connection point during the fault ride-through.

[0033] In this embodiment, when a fault ride-through occurs, the reactive current injected by the inverter into the grid connection point must satisfy the following formula 12: ; Among them, I Hq The target value of reactive current to be injected into the grid connection point; K is the dynamic reactive current proportional coefficient; I represents the per-unit value of the high-voltage side voltage modulus; N This is the inverter's rated current; The reactive current recorded before the fault ride-through occurs, with the high-voltage side voltage as the phase reference. = U Hm / Rated amplitude.

[0034] In one embodiment, calculating the target reactive current value that the inverter should inject into the grid connection point during fault ride-through based on the amplitude of the grid connection point voltage and the reactive current recorded value phased by the high-voltage side voltage before the fault ride-through occurs includes: obtaining the active current recorded value and reactive current recorded value phased by the low-voltage side voltage before the fault ride-through occurs; obtaining the active component recorded value and reactive component recorded value of the low-voltage side voltage before the fault ride-through occurs; and calculating the reactive current recorded value phased by the high-voltage side voltage based on the active current recorded value and reactive current recorded value phased by the low-voltage side voltage, the active component recorded value and reactive component recorded value of the low-voltage side voltage, and the transformation relationship.

[0035] In this embodiment, the low-voltage side voltage and low-voltage side current records before the fault ride-through are obtained, and based on the low-voltage side voltage phase-locked loop and Clark-Park transform, the active current record I, phased by the low-voltage side voltage, before the fault ride-through is obtained. Ld_pre And reactive current recorded value I Lq_pre Recorded value of the active component of the low-voltage side voltage U Ld_pre And reactive component recording value U Lq_pre Based on formulas 8 and 9 in the above embodiments and transformation relation 10, the reactive current recorded value with high-voltage side voltage phase determined before the fault ride-through is obtained. Formula 13: ; Therefore, by combining Formula 13 and Formula 12, the target value of reactive current I to be injected into the grid connection point when a fault ride-through occurs can be calculated. Hq .

[0036] S4. Calculate the reactive current command value with the output port voltage as the phase based on the phase of the grid connection point voltage and the reactive current target value.

[0037] In this embodiment, the phase of the grid connection point voltage is used as a basis. Target value of reactive current The reactive current command value, phased by the output port voltage, is calculated using Formula 12.

[0038] In one embodiment, the reactive current command value phased by the output port voltage is calculated based on the phase of the grid connection point voltage and the target reactive current value, including: Substitute the phase of the grid connection point voltage into the transformation formula, replace the reactive component of the current on the high-voltage side with the reactive current target value, calculate the reactive component of the current on the low-voltage side, and use it as the reactive current command value with the output port voltage as the phase.

[0039] In this embodiment, the grid connection point voltage Substituting the phase into transformation equation 10, the reactive component of the current on the high-voltage side in transformation equation 10 is replaced with the target value of reactive current. This yields the reactive power command value I output by the inverter in response to changes in the phase and amplitude of the grid connection point voltage when a fault ride-through occurs. Lqref Formula 14 must be satisfied: ; Thus, when a fault ride-through occurs, the magnitude and phase of the grid connection point voltage are calculated using the port current and the estimated equivalent impedance between the grid connection point and the photovoltaic inverter. Based on the grid connection point voltage magnitude, the target value of reactive current to be injected into the grid connection point during fault ride-through is calculated. This target value of reactive current is the target setpoint of reactive current for the high-voltage side phase-locked loop. Based on the grid connection point voltage phase and the target value of reactive current, the reactive current command value with the output port voltage as the phase is calculated.

[0040] S5. Use the reactive current command value as the current setpoint of the inverter so that the inverter can perform closed-loop tracking of the reactive current command value and output reactive current.

[0041] In this embodiment, the reactive current command value is used as the current setpoint of the inverter so that the inverter can perform closed-loop tracking of the reactive current command value and output reactive current. This allows the inverter to accurately respond to changes in the phase and amplitude of the grid connection voltage and output reactive current when a short circuit, voltage drop or rise occurs in the power system, thus enabling the photovoltaic power generation system to maintain grid connection operation.

[0042] See also Figure 5 In one embodiment, the step of using the reactive current command value as the current setpoint of the inverter, so that the inverter performs closed-loop tracking of the reactive current command value and outputs reactive current, includes: Collect the real-time current value at the inverter port; calculate the difference between the real-time current value and the current setpoint; and send a current output command to the inverter based on the difference.

[0043] In this embodiment, Figure 5 The regulator, part of the controller, is used to determine the difference between the real-time current value and the current setpoint. This is achieved by acquiring the real-time current value I at the inverter port. LqAct Calculate the current setpoint I that is phased with the output port voltage. Lqref The difference is used to send a current output command to the inverter to achieve reactive current feedback, thereby enabling the inverter to output current in real time according to the current setpoint I of the output port voltage. Lqref Output reactive current. The solution in this embodiment is as follows: Figure 5(b) The reactive current feedback uses the actual value I of the low-voltage side phase-locked loop reactive current. LqAct With low-voltage side current setpoint I Lqref Comparison, due to the low-voltage side current given value I Lqref It is derived from the reactive current target setpoint, i.e., the reactive current target value, based on the high-voltage side phase-locked loop. Therefore, the scheme in this embodiment is similar to... Figure 5 Scheme (a) shows the actual value of reactive current I using high-voltage side phase-locked loop for reactive current feedback. HqAct (The actual value of reactive current I from the low-voltage side phase-locked loop) LqAct The reactive current target setpoint I obtained by transforming relation 10 and locking with the high-voltage side is obtained. Hqref The comparison is completely equivalent, meaning that it can accurately respond to changes in the phase and amplitude of the grid connection point voltage without collecting the high-voltage side voltage and current.

[0044] This invention also provides an inverter reactive current control device, which can be configured in the controller of a power generation system. This device is used to execute any of the aforementioned embodiments of the inverter reactive current control method. Specifically, please refer to... Figure 6 , Figure 6 This is a schematic block diagram of an inverter reactive current control device provided in an embodiment of the present invention.

[0045] like Figure 6 As shown, the inverter reactive current control device 100 includes: Impedance estimation unit 110 is used to obtain the inverter output port voltage and output port current, and estimate the equivalent impedance between the inverter and the grid connection point based on the output port voltage and output port current. The first calculation unit 120 is used to calculate the amplitude and phase of the grid connection point voltage based on the output port current and the equivalent impedance. The second calculation unit 130 is used to calculate the target value of reactive current that the inverter should inject into the grid connection point during fault ride based on the amplitude of the grid connection point voltage and the reactive current record value with the high voltage side voltage phase determined before the fault ride-through occurs. The third calculation unit 140 is used to calculate the reactive current command value with the output port voltage as the phase based on the phase of the grid connection point voltage and the reactive current target value. The instruction sending unit 150 is used to use the reactive current instruction value as the current setpoint value of the inverter, so that the inverter performs closed-loop tracking of the reactive current instruction value and outputs reactive current.

[0046] The aforementioned inverter reactive current control device can be implemented as a computer program, which can be used in, for example... Figure 7 It runs on the control device shown.

[0047] Please see Figure 7 , Figure 7 This is a schematic block diagram of the control device provided in an embodiment of the present invention.

[0048] The control device 500 includes a processor 502, a memory, and a network interface 505 connected via a communication bus 501. The memory may include a storage medium 503 and internal memory 504.

[0049] The storage medium 503 may store an operating system 5031 and a computer program 5032. When the computer program 5032 is executed, it enables the processor 502 to execute an inverter reactive current control method. The storage medium 503 may be a volatile storage medium or a non-volatile storage medium.

[0050] The processor 502 provides computing and control capabilities to support the operation of the entire control device 500.

[0051] The internal memory 504 provides an environment for the operation of the computer program 5032 in the storage medium 503. When the computer program 5032 is executed by the processor 502, the processor 502 can execute the inverter reactive current control method.

[0052] This network interface 505 is used for network communication, such as providing data transmission. Those skilled in the art will understand that... Figure 7 The structure shown is merely a block diagram of a portion of the structure related to the present invention and does not constitute a limitation on the control device 500 to which the present invention is applied. The specific control device 500 may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0053] The processor 502 is used to run the computer program 5032 stored in the memory to implement the corresponding functions in the inverter reactive current control method described above.

[0054] Those skilled in the art will understand that Figure 7 The embodiments of the control device shown do not constitute a limitation on the specific configuration of the control device. In other embodiments, the control device may include more or fewer components than shown, or combine certain components, or have different component arrangements. For example, in some embodiments, the control device may include only a memory and a processor. In such embodiments, the structure and function of the memory and processor are different from those shown. Figure 7 The embodiments shown are consistent and will not be described again here.

[0055] It should be understood that, in this embodiment of the invention, the processor 502 may be a Central Processing Unit (CPU), or it may 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 any conventional processor.

[0056] In another embodiment of the invention, a computer-readable storage medium is provided. This computer-readable storage medium may be volatile or non-volatile. The computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps included in the above-described inverter reactive current control method.

[0057] Those skilled in the art will readily understand that, for the sake of convenience and brevity, the specific working processes of the devices, apparatuses, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here. Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in terms of function in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this invention.

[0058] In the embodiments provided by this invention, it should be understood that the disclosed devices, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative. For instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. Units with the same function may be grouped into one unit. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. In addition, the mutual coupling or direct coupling or communication connection shown or discussed may be indirect coupling or communication connection through some interfaces, devices, or units, or may be electrical, mechanical, or other forms of connection.

[0059] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of the embodiments of the present invention, depending on actual needs.

[0060] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0061] If the integrated unit is implemented as 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, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a computer-readable storage medium and includes several instructions to cause a control device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned computer-readable storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), magnetic disks, or optical disks.

[0062] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for controlling reactive current in an inverter, characterized in that, include: Obtain the inverter output port voltage and output port current, and estimate the equivalent impedance between the inverter and the grid connection point based on the output port voltage and output port current; The amplitude and phase of the grid connection point voltage are calculated based on the output port voltage, the output port current, and the equivalent impedance. The target value of reactive current that the inverter should inject into the grid connection point during fault ride is calculated based on the amplitude of the grid connection point voltage and the reactive current recorded value with the high voltage side voltage phase determined before the fault ride-through. The reactive current command value, which is phased by the output port voltage, is calculated based on the phase of the grid connection point voltage and the target value of the reactive current. The reactive current command value is used as the current setpoint of the inverter so that the inverter can perform closed-loop tracking of the reactive current command value and output reactive current.

2. The inverter reactive current control method according to claim 1, characterized in that, The estimation of the equivalent impedance between the inverter and the grid connection point based on the output port voltage and the output port current includes: The inverter output port voltage and output port current are collected under two operating conditions to obtain the first port voltage, first port current, second port voltage and second port current; The active and reactive components of the first port voltage, first port current, second port voltage, and second port current are obtained by performing Clark-Park transformation on the first port voltage, first port current, second port voltage, and second port current. The equivalent impedance is calculated based on the active and reactive components of the first port voltage, the first port current, the second port voltage, and the second port current.

3. The inverter reactive current control method according to claim 1, characterized in that, The calculation of the amplitude and phase of the grid connection point voltage based on the output port voltage, the output port current, and the equivalent impedance includes: The complex plane coordinate system constructed with the vector direction of the output port voltage as the positive real axis is the low-voltage side coordinate system, and the complex plane coordinate system constructed with the vector direction of the grid connection point voltage as the positive real axis is the high-voltage side coordinate system. The output port voltage and the port current are subjected to Clark-Park transformation to obtain the real axis components and imaginary axis components of the output port voltage and the port current in the low-voltage side coordinate system; The real and imaginary components of the grid connection point voltage in the low-voltage side coordinate system are calculated based on the real and imaginary components of the output port voltage and the port current in the low-voltage side coordinate system, as well as the equivalent impedance. The phase and amplitude of the grid connection point voltage in the low-voltage side coordinate system are calculated based on the real axis and imaginary axis components of the grid connection point voltage in the low-voltage side coordinate system.

4. The inverter reactive current control method according to claim 3, characterized in that, After calculating the phase and amplitude of the grid connection point voltage in the low-voltage side coordinate system based on the real axis and imaginary axis components of the grid connection point voltage in the low-voltage side coordinate system, the method further includes: Based on the phase, the low-voltage side coordinate system, and the high-voltage side coordinate system, the transformation relationship of current on the low-voltage side and the high-voltage side is obtained as follows: ； in, It is the reactive component of the current on the low-voltage side; It is the active component of the current on the low-voltage side; It is the phase of the grid connection point voltage. It is the reactive component of the current on the high-voltage side.

5. The inverter reactive current control method according to claim 4, characterized in that, The target value of reactive current that the inverter should inject into the grid connection point during fault ride-through is calculated based on the amplitude of the grid connection point voltage and the reactive current record value with high-voltage side voltage phase determined before the fault ride-through occurs. This includes: Obtain active current and reactive current records with low-voltage side voltage phase determined before the fault ride-through occurs; Obtain the active and reactive component records of the low-voltage side voltage before the fault ride-through occurs. The reactive current recorded value based on the active and reactive current recorded values ​​phased by the low-voltage side voltage, the active and reactive component recorded values ​​of the low-voltage side voltage, and the transformation formula are used to calculate the reactive current recorded value phased by the high-voltage side voltage.

6. The inverter reactive current control method according to claim 4, characterized in that, Based on the phase of the grid connection point voltage and the target value of the reactive current, a reactive current command value phased with the output port voltage is calculated, including: Substitute the phase of the grid connection point voltage into the transformation formula, replace the reactive component of the current on the high-voltage side with the reactive current target value, calculate the reactive component of the current on the low-voltage side, and use it as the reactive current command value with the output port voltage as the phase.

7. The inverter reactive current control method according to claim 1, characterized in that, The step of using the reactive current command value as the current setpoint of the inverter, so that the inverter performs closed-loop tracking of the reactive current command value and outputs reactive current, includes: Collect the real-time current value at the inverter port; Calculate the difference between the real-time current value and the current setpoint, and send a current output command to the inverter based on the difference.

8. A reactive current control device for an inverter, characterized in that, For performing the inverter reactive current control method according to any one of claims 1-7, the device is configured in the controller of the power generation system, the device comprising: Impedance estimation unit is used to obtain the inverter output port voltage and output port current, and estimate the equivalent impedance between the inverter and the grid connection point based on the output port voltage and output port current. The first calculation unit is used to calculate the amplitude and phase of the grid connection point voltage based on the output port current and the equivalent impedance. The second calculation unit is used to calculate the target value of reactive current that the inverter should inject into the grid connection point during fault ride based on the amplitude of the grid connection point voltage and the reactive current record value with the high voltage side voltage phase determined before the fault ride-through occurs. The third calculation unit is used to calculate the reactive current command value with the output port voltage as the phase based on the phase of the grid connection point voltage and the reactive current target value. The instruction sending unit is used to use the reactive current instruction value as the current setpoint of the inverter, so that the inverter can perform closed-loop tracking of the reactive current instruction value and output reactive current.

9. A control device, characterized in that, The device includes a processor, a communication interface, a memory, and a communication bus, wherein the processor, the communication interface, and the memory communicate with each other through the communication bus; Memory, used to store computer programs; When a processor executes a program stored in a memory, it implements the steps of the inverter reactive current control method according to any one of claims 1-7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the inverter reactive current control method as described in any one of claims 1-7.

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