Power grid simulation method and device with non-ideal grid-connected impedance compensation capability

Abstract

The invention belongs to the technical field of wind turbine generator grid-connected tests, and discloses a power grid simulation method and device with non-ideal grid-connected impedance compensation capability. The method comprises the steps of obtaining a three-phase voltage waveform of a power grid fault point, and obtaining a three-phase voltage reference value reflecting a fault voltage; fitting equivalent grid-connected impedance characteristics from a power grid fault point to a tested new energy equipment terminal by adopting a low-order transfer function; and performing non-ideal grid-connected impedance simulation on the equivalent grid-connected impedance characteristics, and correcting the voltage output by the power grid to the tested new energy equipment based on a simulation result for a grid-connected test of the tested new energy equipment. By utilizing the method, the defect that only fault voltage characteristics are reproduced and grid-connected impedance characteristics are neglected in a fault voltage ride-through test of new energy equipment such as a wind turbine generator can be overcome. Through the method provided by the invention, grid-connected impedance characteristics can be compensated, so that fault characteristics can be more accurately reproduced, and key capabilities such as fault voltage ride-through of new energy equipment can be more effectively verified.

Description

Technical Field

[0001] The present invention belongs to the technical field of wind turbine grid-connected test, and in particular relates to a grid simulation method and device with non-ideal grid-connected impedance compensation capability. Background Art

[0002] The grid connection of new energy units refers to the connection of the electric energy generated by new energy power generation equipment to the power grid, so that it can transmit electricity to the power grid and realize the effective utilization and distribution of new energy electricity. Faults in the power grid will cause voltage waveform distortion at the machine end of the grid-connected new energy equipment, which may affect its normal operation. To this end, new energy equipment needs to verify its ability to maintain grid-connected operation in the event of a voltage drop in the power grid through a fault voltage ride-through test. The fault voltage ride-through test usually uses an impedance voltage divider test device and test method, using resistors, inductors and capacitors to divide the voltage at the grid connection point to generate voltage drops / rises of different depths for testing. In addition, in recent years, power grid operation simulation devices based on power electronic equipment can also be used to simulate power grid fault / disturbance voltage waveforms to carry out relevant tests.

[0003] The invention patent application with application number 201410734345.X discloses a high and low voltage continuous process fault ride-through test method, which is based on the high and low voltage ride-through capability detection system of the wind turbine. The method includes the following steps: I. The high and low voltage ride-through capability detection system of the wind turbine generates an uninterrupted and continuous output of grid voltage drop and voltage rise; II. Non-electrical quantity data and electrical quantity data are obtained during high and low voltage fault ride-through; III. The non-electrical quantity data and the electrical quantity data are processed; IV. The non-electrical quantity data and the electrical quantity data are analyzed. The method can continuously and truly simulate the voltage drop and rise characteristics during grid faults, ensure that when low voltage and high voltage are generated, the changes in the voltage phase angle and power quality are consistent with the real grid fault characteristics, and can realize the continuous low voltage and high voltage ride-through capability detection of the wind turbine in one test process.

[0004] This invention application proposes a corresponding test method based on the impedance-divider fault voltage ride-through test equipment. However, this method can only generate a deterministic and idealized fault voltage waveform, and cannot flexibly generate a fault voltage curve that is consistent with the actual grid characteristics and takes into account key factors such as grid impedance characteristics, which limits the effectiveness of the fault ride-through test.

[0005] The invention patent application with application number 201310334718.X discloses a wind farm power grid operation simulation device, and provides a wind farm power grid operation simulation device including a step-down transformer, a power grid disturbance simulation generating device and a power grid fault simulation generating device; one end of the step-down transformer is connected to the medium and high voltage power grid, and the other end is connected to the input end of the power grid disturbance simulation generating device, the output end of the power grid disturbance simulation generating device is connected to the input end of the power grid fault simulation generating device, and the output end of the power grid fault simulation generating device is connected to the medium and high voltage power grid; a circuit breaker is connected in parallel between the input end and the output end of the power grid disturbance simulation generating device. The present invention can realize online hybrid simulation of power grid disturbance and fault, collect and analyze actual operation data during the test of wind turbines, and can perform power grid adaptability test, low voltage ride-through capability test and high voltage ride-through capability test and detection on wind turbines, and conduct comprehensive test and evaluation on power grid disturbance anti-interference capability and power grid fault ride-through capability of wind turbines.

[0006] The invention application proposes the overall structure of a power grid operation simulation device, which can generate a relatively flexible voltage waveform at the end of the wind turbine unit under test for relevant test tests. However, the invention does not propose how to simulate the fault voltage characteristics of the power grid, and lacks a specific method that can reflect different fault voltage characteristics under complex power grid conditions.

[0007] The invention patent application with application number 202410208637.3 discloses a power grid simulation device and control method with power grid voltage reproduction function, wherein the input end of the power grid simulation device is connected to the power grid, the output end is connected to the device under test, and is connected to the controller to provide a test voltage for the device under test. The three-phase voltage information of the power grid to be reproduced is obtained as the voltage data to be reproduced, and the voltage data to be reproduced is imported into the controller. The controller controls the output voltage three-phase modulation wave through the control strategy with the voltage data to be reproduced, and the voltage three-phase modulation wave is sent to the pulse width modulation module to generate a switching signal of the power grid simulation device; this method increases the timeliness of power grid analysis, realizes the waveform reproduction function based on the power grid simulation device, increases the means of realizing the power grid waveform, can verify the effectiveness of the test of the device under test, and improves the test efficiency.

[0008] This invention application proposes a control algorithm for a power grid operation simulation device to track a reference voltage, but the invention still does not propose a specific simulation method for the fault characteristic voltage under different power grid conditions, such as different fault locations, different fault types, etc.

[0009] Whether using an impedance voltage divider test device or a power grid simulation device for testing, the current focus is on reproducing only the physical and chemical fault voltage waveform, while ignoring the consideration of the non-ideal power grid broadband impedance. In this regard, there is currently no specific simulation method that can clearly give consideration to the non-ideal power grid fault voltage characteristics and the broadband impedance of the tested new energy equipment. Summary of the invention

[0010] The purpose of the present invention is to provide a power grid simulation method and device with the ability to compensate for non-ideal grid-connected impedance, so as to realize the simulation and compensation functions of the non-ideal grid-connected impedance of new energy equipment, thereby reproducing the broadband equivalent impedance between the fault point and the tested new energy equipment in the fault voltage ride-through test, accurately reflecting the comprehensive effect of the power grid fault and the output current of the tested new energy equipment at the grid connection point, so as to more effectively test the key characteristics of the new energy equipment such as the fault voltage ride-through.

[0011] In order to achieve the above object, the present invention adopts the following technical solution: In a first aspect, the present invention provides a power grid simulation method with non-ideal grid-connected impedance compensation capability, comprising: Obtain the three-phase voltage waveform at the fault point of the power grid and obtain the three-phase voltage reference value reflecting the fault voltage V fault ; The three-phase voltage reference value V fault When a power grid fault occurs, it is obtained based on on-site recording data or electromagnetic transient simulation methods; Obtain the broadband impedance characteristics of the tested new energy equipment connected to the power grid environment; use low-order transfer functions to fit the grid impedance characteristics within the preset frequency band to obtain the equivalent grid-connected impedance characteristics ; Equivalent grid impedance characteristics The non-ideal grid-connected impedance is simulated, and based on the simulation results, the voltage output by the power grid to the tested new energy equipment is corrected for the grid-connected test of the tested new energy equipment.

[0012] Further improvement of the present invention: the step of obtaining the broadband impedance characteristics of the tested new energy equipment connected to the power grid environment specifically includes: Use broadband impedance measurement, simulated impedance scanning or modeling analysis to obtain the second-order impedance characteristics of the power grid environment in a broadband environment. Z dq ( s ): (2) in, Z dd ( s ), Z dq ( s ), Z qd ( s ), Z qq ( s ) represent dqThe broadband impedance characteristic elements of the power grid in the axis coordinate system.

[0013] Further improvement of the present invention: the equivalent grid impedance characteristic is obtained by fitting the grid impedance characteristic with a low-order transfer function within a preset frequency band. The steps include: According to the preset frequency range [ f min , f max ] and the fitting order N , the least squares method is used for iteration, with the order being N The frequency range of the low-order rational transfer function simulation is [ f min , f max The second-order impedance characteristics of the power grid within Z dq ( s ), and obtain the equivalent grid-connected impedance characteristics : (3) in, f dd ( s ), f dq ( s ), f qd ( s ), f qq ( s ) represent dq The equivalent impedance elements obtained by low-order fitting in the axis coordinate system are in the form of N Subrational transfer function; f min , f max They are the minimum and maximum values ​​of the preset frequency band range respectively.

[0014] Further improvement of the present invention: the equivalent grid-connected impedance characteristic The steps of simulating non-ideal grid-connected impedance and correcting the voltage output by the grid to the tested new energy equipment based on the simulation results specifically include: Based on three-phase voltage reference V fault and equivalent grid impedance characteristics Calculate the virtual impedance control d Axis and q Shaft voltage control reference value V d,ref * andV q,ref * : (4) (5) in, (1) in, V fault To reflect the three-phase voltage reference value of the fault voltage; V a,ref , V b,ref , V c,ref They are respectively the fault voltage a Mutually, b Harmony c Phase voltage reference value; V d,ref and V q,ref Respectively by V a,ref , V b,ref , V c,ref The Park transformation is obtained d Axis and q Shaft voltage reference value, I d and I q They are abc Three-phase current of power grid in coordinate system I a 、I b 、I c The Park transformation is obtained d Axis and q Shaft current value; based on d Axis and q Shaft voltage control reference value V d,ref * and V q,ref * Perform voltage and current dual-loop control to obtain a corrected PWM modulation signal; control the inverter-side subsystem based on the corrected PWM modulation signal to correct the voltage output by the power grid to the tested new energy equipment.

[0015] Further improvement of the present invention: the equivalent grid-connected impedance characteristic Simulate non-ideal grid impedance, including: Using equivalent RLC actual impedance series and parallel connection to compare equivalent grid impedance characteristics Simulate non-ideal grid impedance.

[0016] In a second aspect, the present invention provides a power grid simulation device capable of compensating for non-ideal grid-connected impedance, comprising: The acquisition unit is used to obtain the three-phase voltage waveform of the power grid fault point and obtain the three-phase voltage reference value reflecting the fault voltage V fault ; The three-phase voltage reference value V fault When a power grid fault occurs, it is obtained based on on-site recording data or electromagnetic transient simulation methods; The fitting unit is used to obtain the broadband impedance characteristics of the tested new energy equipment connected to the power grid environment; the low-order transfer function is used to fit the grid impedance characteristics within the preset frequency band to obtain the equivalent grid-connected impedance characteristics. ; Analog correction unit for equivalent grid impedance characteristics The non-ideal grid-connected impedance is simulated, and based on the simulation results, the voltage output by the power grid to the tested new energy equipment is corrected for the grid-connected test of the tested new energy equipment.

[0017] Further improvement of the present invention: the step of obtaining the broadband impedance characteristics of the tested new energy equipment connected to the power grid environment specifically includes: Use broadband impedance measurement, simulated impedance scanning or modeling analysis to obtain the second-order impedance characteristics of the power grid environment in a broadband environment. Z dq ( s ): (2) in, Z dd ( s ), Z dq ( s ), Z qd ( s ), Z qq ( s ) represent dq The broadband impedance characteristic elements of the power grid in the axis coordinate system.

[0018] Further improvement of the present invention: the equivalent grid impedance characteristic is obtained by fitting the grid impedance characteristic with a low-order transfer function within a preset frequency band. The steps include: According to the preset frequency range [ f min ,f max ] and the fitting order N , the least squares method is used for iteration, with the order being N The frequency range of the low-order rational transfer function simulation is [ f min , f max The second-order impedance characteristics of the power grid within Z dq ( s ), and obtain the equivalent grid-connected impedance characteristics : (3) in, f dd ( s ), f dq ( s ), f qd ( s ), f qq ( s ) represent dq The equivalent impedance elements obtained by low-order fitting in the axis coordinate system are in the form of N Subrational transfer function; f min , f max They are the minimum and maximum values ​​of the preset frequency band range respectively.

[0019] Further improvement of the present invention: the equivalent grid-connected impedance characteristic The steps of simulating non-ideal grid-connected impedance and correcting the voltage output by the grid to the tested new energy equipment based on the simulation results specifically include: Based on three-phase voltage reference V fault and equivalent grid impedance characteristics Calculate the virtual impedance control d Axis and q Shaft voltage control reference value V d,ref * and V q,ref * : (4) (5) in, (1) in, Vfault To reflect the three-phase voltage reference value of the fault voltage; V a,ref , V b,ref , V c,ref They are respectively the fault voltage a Mutually, b Harmony c Phase voltage reference value; V d,ref and V q,ref Respectively by V a,ref , V b,ref , V c,ref The Park transformation is obtained d Axis and q Shaft voltage reference value, I d and I q They are abc Three-phase current of power grid in coordinate system I a 、I b 、I c The Park transformation is obtained d Axis and q Shaft current value; based on d Axis and q Shaft voltage control reference value V d,ref * and V q,ref * Perform voltage and current dual-loop control to obtain a corrected PWM modulation signal; control the inverter-side subsystem based on the corrected PWM modulation signal to correct the voltage output by the power grid to the tested new energy equipment.

[0020] Further improvement of the present invention: the equivalent grid-connected impedance characteristic Simulate non-ideal grid impedance, including: Using equivalent RLC actual impedance series and parallel connection to compare equivalent grid impedance characteristics Simulate non-ideal grid impedance.

[0021] In a third aspect, the present invention provides a power grid simulation device capable of compensating for non-ideal grid-connected impedance, comprising: A power grid, for providing a three-phase power grid voltage; Rectifier subsystem, used to convert three-phase grid voltage into stable DC voltage V dc ; The inverter subsystem is used to convert the DC voltage V dc Invert into controlled three-phase grid-connected voltage; A non-ideal grid-connected impedance simulation unit, used for adopting a grid simulation method with non-ideal grid-connected impedance compensation capability as described in any one of claims 1 to 4 to simulate the equivalent grid-connected impedance characteristic. Simulate non-ideal grid-connected impedance, control the inverter-side subsystem based on the simulation results, and output a corrected three-phase grid-connected voltage for grid-connected test of the tested new energy equipment; or, use a grid simulation method with non-ideal grid-connected impedance compensation capability as described in claim 5 to compare equivalent grid-connected impedance characteristics by connecting equivalent RLC actual impedances in series and parallel. The non-ideal grid-connected impedance is simulated, and the three-phase grid-connected voltage output by the inverter-side subsystem is corrected based on the simulation results to obtain the corrected three-phase grid-connected voltage for the grid-connected test of the tested new energy equipment.

[0022] Further improvement of the present invention: the non-ideal grid-connected impedance simulation unit includes a virtual impedance control unit, a medium voltage RLC impedance network and a circuit breaker K; The virtual impedance control unit is used to use a power grid simulation method with non-ideal grid-connected impedance compensation capability as described in any one of claims 1 to 4 to calculate the equivalent grid-connected impedance characteristic. Simulate non-ideal grid-connected impedance, control the inverter-side subsystem based on the simulation results, and output the corrected three-phase grid-connected voltage for grid-connected test of the tested new energy equipment; The medium voltage RLC impedance network is used to connect the equivalent RLC actual impedance in series and parallel to the equivalent grid impedance characteristics. Simulate non-ideal grid-connected impedance, and based on the simulation results, correct the three-phase grid-connected voltage output by the inverter-side subsystem to obtain the corrected three-phase grid-connected voltage for grid-connected test of the tested new energy equipment; The output end of the inverter-side subsystem is connected to the tested new energy equipment through a medium-voltage RLC impedance network; a circuit breaker K is connected in parallel to the medium-voltage RLC impedance network.

[0023] A further improvement of the present invention is that a virtual impedance control unit is used to control the inverter side subsystem, output a corrected three-phase grid-connected voltage, and when the tested new energy equipment is connected to the grid, the circuit breaker K is closed to bypass the medium voltage RLC impedance network.

[0024] A further improvement of the present invention is that a medium voltage RLC impedance network is used to correct the three-phase grid-connected voltage output by the inverter side subsystem to obtain a corrected three-phase grid-connected voltage for grid-connected testing of the tested new energy equipment, and the virtual impedance control unit is turned off and the circuit breaker K is disconnected.

[0025] In a fourth aspect, the present invention provides an electronic device, comprising a processor and a memory, wherein the processor is used to execute a computer program stored in the memory to implement a power grid simulation method having the capability of compensating for non-ideal grid-connected impedance.

[0026] In a fifth aspect, the present invention provides a computer-readable storage medium, wherein the computer-readable storage medium stores at least one instruction, and when the at least one instruction is executed by a processor, the power grid simulation method with non-ideal grid-connected impedance compensation capability is implemented.

[0027] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a power grid simulation method with non-ideal grid-connected impedance compensation capability, comprising: obtaining a three-phase voltage waveform at a power grid fault point, obtaining a three-phase voltage reference value reflecting the fault voltage V fault ; Use low-order transfer function to fit the equivalent grid-connected impedance characteristics from the grid fault point to the tested new energy equipment terminal ; Equivalent grid impedance characteristics The non-ideal grid-connected impedance is simulated, and the voltage output by the power grid to the tested new energy equipment is corrected based on the simulation results, so as to provide the tested new energy equipment with a grid-connected test. The method of the present invention can make up for the shortcomings of only reproducing the fault voltage characteristics and ignoring the grid-connected impedance characteristics in the previous fault voltage ride-through test of new energy equipment such as wind turbines. The method proposed by the present invention can compensate for the grid-connected impedance characteristics, so as to more accurately reproduce the fault characteristics and more effectively verify the key capabilities of new energy equipment such as fault voltage ride-through.

[0028] Furthermore, the method proposed in the present invention can be applied in the fault voltage ride-through grid-connected test of new energy equipment, improve the empirical capability of the grid simulation device for wind turbine grid-connected test, and enrich the test equipment for wind turbine fault voltage test, so as to more effectively verify the fault voltage ride-through capability of wind turbines, ensure the safe and stable operation of new energy after grid connection, and support the reliable operation of the power system under fault transient state after large-scale new energy is connected to the grid.

[0029] Furthermore, the method of the present invention can simulate the non-ideal grid-connected characteristics of new energy equipment such as wind turbines through virtual impedance control or additional RLC series-parallel impedance, thereby accurately characterizing the impact of power grid faults / disturbance and the output current of the test object on the grid connection point voltage, so as to more effectively carry out the simulation and verification of the grid-connected characteristics of new energy equipment.

[0030] Furthermore, the method proposed in the present invention includes three links: voltage curve generation, equivalent impedance fitting and equivalent impedance construction. Among them, the voltage curve generation link determines the output voltage of the power grid simulation device according to the fault recording and other data. Furthermore, the equivalent impedance fitting link fits the broadband impedance characteristics of the power grid within the frequency band of interest to the power grid environment to which the tested new energy equipment is connected as a low-order transfer function. Finally, the equivalent impedance construction link can use virtual impedance control to achieve grid-connected impedance compensation on the one hand; on the other hand, according to the impedance transfer function expression, the equivalent structure of the resistor, inductor, and capacitor series-parallel connection of the grid impedance can be obtained, thereby using actual passive impedance equipment to achieve simulation and compensation of the grid-connected impedance. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings: Figure 1 This is a schematic diagram of simulating the access of the tested new energy equipment to the power grid environment based on "equivalent impedance"; Figure 2 A schematic flow chart of a power grid simulation method with non-ideal grid-connected impedance compensation capability according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the equivalent impedance fitting process according to an embodiment of the present invention; Figure 4 This is a schematic diagram of equivalent impedance characteristics after fitting in an embodiment of the present invention; Figure 5 A schematic diagram of a virtual impedance control function according to an embodiment of the present invention; Figure 6 is the real number pole term in the embodiment of the present invention " c n / ( sd n )” is converted into a schematic diagram of RC parallel branches; Figure 7 is the real number pole term in the embodiment of the present invention " c n / ( sd n )” is converted into a schematic diagram of RL series branches; Figure 8 is the conjugate complex pole term "[ c n1 / ( sd n1 )]+[ c n2 / ( sd n2)]” as a schematic diagram of impedance conversion into RLC hybrid branch; Fig. 9 is the conjugate complex pole term "[ c n1 / ( sd n1 )]+[ c n2 / ( sd n2 )]” as a schematic diagram of the admittance conversion into the RLC hybrid branch; Fig.10 is the constant term and the first-order term in the embodiment of the present invention e + sh Schematic diagram of conversion to RL series branch; Fig.11 is the constant term and the first-order term in the embodiment of the present invention e + sh Schematic diagram of conversion to RC parallel branch; Fig.12 It is a flow chart of a power grid simulation method with non-ideal grid-connected impedance compensation capability in an embodiment of the present invention; Fig.13 It is a structural block diagram of a power grid simulation device with non-ideal grid-connected impedance compensation capability in an embodiment of the present invention; Fig.14 It is a structural block diagram of another power grid simulation device with non-ideal grid-connected impedance compensation capability in an embodiment of the present invention; Fig.15 The present invention is a structural block diagram of an electronic device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0032] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that the embodiments and features in the embodiments of the present invention can be combined with each other without conflict.

[0033] The following detailed description is an exemplary description, which is intended to provide further detailed description of the present invention. Unless otherwise specified, all technical terms used in the present invention have the same meaning as those generally understood by those skilled in the art to which the present invention belongs. The terms used in the present invention are only for describing specific embodiments, and are not intended to limit the exemplary embodiments according to the present invention.

[0034] See also Figure 1 As shown, the embodiment of the present invention proposes a power grid simulation method with non-ideal grid-connected impedance compensation capability, which is based on the Thevenin equivalent concept and adopts "equivalent impedance Z eq"Simulate the non-ideal impedance of the power grid to which the tested new energy equipment is connected, so as to carry out relevant tests such as fault voltage ride-through.

[0035] See also Figure 2 As shown, an embodiment of the present invention provides a power grid simulation method with non-ideal grid-connected impedance compensation capability, including: S101, voltage curve generation: using on-site recording or simulation method to determine the three-phase voltage waveform at the fault point; S102, equivalent impedance fitting: use low-order transfer function to fit the equivalent grid-connected impedance from the fault point to the tested new energy equipment terminal; S103, equivalent impedance construction: virtual impedance control or access to equivalent RLC series-parallel impedance is used to simulate and compensate for the equivalent grid-connected impedance.

[0036] Specifically, the steps of generating the voltage curve include: The voltage curve generation link is based on the on-site recording data or the electromagnetic transient simulation method to determine the three-phase voltage waveform at the fault point when the power grid fails. Figure 1 Equivalent voltage source V fault The control reference; specific equivalent voltage source V fault The formula is shown in formula (1).

[0037] (1) in, V fault is the three-phase voltage reference value reflecting the fault voltage; specifically, V a,ref , V b,ref , V c,ref They are respectively the fault voltage a Mutually, b Harmony c Phase voltage reference value.

[0038] Specifically, the steps of equivalent impedance fitting include: S201, obtaining the broadband impedance characteristics of the tested new energy equipment when connected to the power grid; S202. Use a low-order transfer function to fit the impedance characteristics of the power grid within the frequency band of interest.

[0039] See also Figure 3 As shown in the figure, the equivalent impedance fitting link converts the broadband impedance characteristics of the power grid into a low-order transfer function within the frequency band of interest according to the power grid environment to which the tested new energy equipment is connected.

[0040] First, for the grid environment to which the tested new energy equipment is connected, the second-order impedance characteristics of the grid environment under a wide bandwidth are obtained by using broadband impedance measurement, simulated impedance scanning or modeling analysis. Z dq ( s ), as shown in formula (2), where Z dd ( s ), Z dq ( s ), Z qd ( s ), Z qq ( s ) represent dq The broadband impedance characteristic elements of the power grid in the axis coordinate system.

[0041] (2) In a specific embodiment, the broadband frequency band may be 1-1000 Hz.

[0042] Then, according to the preset frequency range [ f min , f max ] and the fitting order N , the least squares method is used for iteration, with the order being N The frequency range of the low-order rational transfer function simulation is [ f min , f max The second-order impedance characteristics of the power grid within Z dq ( s ), and obtain the equivalent impedance characteristics obtained by fitting , where each element is fitted using a rational transfer function of a certain order, as shown in formula (3). f dd ( s ), f dq ( s ), f qd ( s ), f qq ( s ) represent dq The equivalent impedance elements obtained by low-order fitting in the axis coordinate system are in the form of N Subrational transfer function; f min , fmax They are the minimum and maximum values ​​of the preset frequency band range respectively.

[0043] (3) In a specific embodiment, f min =10Hz, f max =30Hz.

[0044] In one embodiment, the fitting order N 3 or 5 。

[0045] See also Figure 4 As shown, the equivalent impedance characteristics after fitting in the embodiment of the present invention coincide with the original high-order impedance characteristics, and the original high-order impedance can be well simulated. Figure 4 In the figure, the solid line represents the original broadband impedance characteristics of the power grid, and the dotted line represents the equivalent impedance characteristics obtained by fitting the fifth-order rational transfer function. Within the preset frequency range [10Hz, 30Hz], the equivalent impedance characteristics are consistent with the original impedance characteristics of the power grid in amplitude and phase.

[0046] Specifically, the steps of constructing equivalent impedance include: The equivalent impedance construction step is based on the equivalent impedance characteristics obtained by fitting. , impedance simulation and compensation are performed on the equivalent impedance characteristics. Among them, the impedance simulation and compensation method can be implemented by virtual impedance control, or by equivalent RLC actual impedance series-parallel connection.

[0047] 1) Using virtual impedance control Equivalent impedance characteristics The simulation adopts the virtual impedance control method and is implemented in the control system of the power grid simulation device. When the virtual impedance control method is adopted, according to equations (2) and (3), the additional Figure 5 The virtual impedance control is mainly achieved by Figure 5 The virtual impedance voltage drop calculation link in the implementation is realized. When the virtual impedance voltage drop calculation link is not added, the attached Figure 5 The remaining control links in the system can be regarded as the conventional voltage and current dual-loop control links of the power grid simulation device.

[0048] The virtual impedance voltage drop calculation process can be expressed as shown in equations (4) and (5).

[0049] (4) (5) in, V d,ref* and V q,ref * They are respectively obtained after correction in the virtual impedance voltage drop calculation link d Axis and q Shaft voltage control reference value, V d,ref and V q,ref Respectively by V a,ref , V b,ref , V c,ref The Park transformation is obtained d Axis and q Shaft voltage reference value, f dd ( s ), f dq ( s ), f qd ( s ), f qq ( s ) are the equivalent impedances of the power grid obtained by fitting in formula (3), I d and I q They are abc Three-phase current of power grid in coordinate system I a 、I b 、I c The Park transformation is obtained d Axis and q Shaft current value.

[0050] based on d Axis and q Shaft voltage control reference value V d,ref * and V q,ref * Perform voltage and current dual-loop control to obtain the corrected PWM modulation signal PWM a 、PWM b 、PWM c , based on the modified PWM modulation signal PWM a 、PWM b 、PWM c Control the inverter side subsystem and output the corrected three-phase grid-connected voltage for grid-connected test of the tested new energy equipment. Figure 5 middle, V d and V q They are abc Three-phase voltage of power grid in coordinate system V a 、V b 、V c The Park transformation is obtained d Axis and q Shaft voltage value; based on d Axis and q Shaft voltage control reference value V d,ref * and V q,ref * Respectively V d and V q Correction is performed, and then voltage and current dual-loop control is performed to obtain the corrected PWM modulation signal PWM a 、PWM b 、PWM c .

[0051] 2) Use equivalent RLC actual impedance series and parallel When using equivalent RLC actual impedance series and parallel connection, firstly, according to formula (6), dq The equivalent impedance transfer function (3) in the coordinate system is converted into the comprehensive equivalent impedance Z eq ( s ),in Z dd ( s ), Z dq ( s ), Z qd ( s ), Z qq ( s ) represent the dq The broadband impedance characteristic element of the power grid in the axis coordinate system, f dd ( s ), f dq ( s ), f qd ( s ), f qq (s ) are the equivalent impedances of the power grid obtained by fitting in formula (3), j Is an imaginary unit.

[0052] (6) Then, the comprehensive equivalent impedance shown in equation (6) is converted into the form described in equation (7). a k ( k = 0, 1,… , n ) represents the order of the denominator of the impedance transfer function s k ( k = 0, 1, … , n ) coefficient, the highest order of which is n Second-rate; b k ( k =0, 1, … , m ) is the impedance transfer function numerator s k ( k = 0, 1, … , m ) coefficient, the highest order of which is m times. After equivalent transformation, c n , d n ,e,h Respectively represent the coefficients to be fitted. h is 0, retaining the impedance expression, if h If it is not equal to 0, convert it into an admittance expression so that the denominator has a higher order than the numerator.

[0053] (7) For each item in equation (7), the equivalent RLC impedance branch is constructed in the following manner. Where: In formula (7), when d n When is a real number, the first term is a real pole term " c n / ( sd n )”, which can be converted into an RC parallel branch as an impedance, as shown in the attached Figure 6 As shown, including the parallel resistor R 1k and capacitor C 1k ; can be converted into RL series branch as admittance, as shown in the attached Figure 7 As shown, including the series resistor R 1k and inductor L 1k .

[0054] In formula (7), when d n When it is a conjugate complex number, it can be expressed as a pair of conjugate complex numbers d n1 and d n2 , then the first term is the conjugate complex pole term "[ c n1 / ( sd n1 )]+[ c n2 / ( sd n2 )]”, which can be converted into a hybrid branch mainly composed of RLC parallel connection as an impedance, as shown in the attached Figure 8 As shown, it includes three branches in parallel: capacitor C 1k Branch, resistor R 2k branch, and the series resistor R 1k and inductor L 1k branch; as an admittance, it can be converted into a hybrid branch mainly composed of RLC series, as shown in the attached Fig. 9 As shown, including resistors R connected in series 1k 、Inductance L 1k and the capacitor C connected in parallel 1k and resistor R 2k .

[0055] In formula (7), the second and third terms are constant terms and linear terms. e + sh , which can be converted into an RL series branch as an impedance, as shown in the attached Fig.10 As shown, it includes a series resistor R1 and an inductor L1; as an admittance, it can be converted into an RC parallel branch, as shown in the attached Fig.11 As shown, it includes a resistor R1 and a capacitor C1 connected in parallel.

[0056] According to the transfer function form represented by equation (7), the overall circuit structure reflected by equation (7) can be constructed based on the equivalent circuit conversion by using the series form of the actual RLC impedance or the parallel form of the admittance. Furthermore, the actual RLC impedance series-parallel structure can be used to realize the construction of the equivalent grid-connected impedance.

[0057] See also Fig.12 As shown, an embodiment of the present invention provides a power grid simulation method with non-ideal grid-connected impedance compensation capability, including: S1. Obtain the three-phase voltage waveform at the fault point of the power grid and obtain the three-phase voltage reference value reflecting the fault voltage V fault ; S2. Use low-order transfer function to fit the equivalent grid-connected impedance characteristics from the grid fault point to the tested new energy equipment terminal ; S3. Equivalent grid-connected impedance characteristics The non-ideal grid-connected impedance is simulated, and based on the simulation results, the voltage output by the power grid to the tested new energy equipment is corrected for the grid-connected test of the tested new energy equipment.

[0058] In a specific implementation, the tested new energy equipment is a wind turbine.

[0059] In a specific implementation manner, the three-phase voltage waveform at the fault point of the power grid is obtained to obtain a three-phase voltage reference value reflecting the fault voltage. V fault The steps include: When a power grid fault occurs, the three-phase voltage waveform at the fault point is obtained based on the on-site recording data or the electromagnetic transient simulation method as the three-phase voltage reference value. V fault ; (1) in, V fault To reflect the three-phase voltage reference value of the fault voltage; V a,ref , V b,ref , V c,ref They are respectively the fault voltage a Mutually, b Harmony c Phase voltage reference value.

[0060] In a specific implementation, the low-order transfer function is used to fit the equivalent grid-connected impedance characteristics from the fault point to the tested new energy equipment terminal. The steps include: Obtain the broadband impedance characteristics of the tested new energy equipment when connected to the power grid environment; The low-order transfer function is used to fit the grid impedance characteristics in the preset frequency band to obtain the equivalent grid impedance characteristics. .

[0061] In a specific implementation, the step of obtaining the broadband impedance characteristics of the tested new energy device connected to the power grid environment specifically includes: Use broadband impedance measurement, simulated impedance scanning or modeling analysis to obtain the second-order impedance characteristics of the power grid environment in a broadband environment. Z dq ( s ): (2) in, Z dd ( s), Z dq ( s ), Z qd ( s ), Z qq ( s ) represent dq The broadband impedance characteristic elements of the power grid in the axis coordinate system.

[0062] In a specific embodiment, the low-order transfer function is used to fit the grid impedance characteristics in the preset frequency band to obtain the equivalent grid impedance characteristics. The steps include: According to the preset frequency range [ f min , f max ] and the fitting order N , the least squares method is used for iteration, with the order being N The frequency range of the low-order rational transfer function simulation is [ f min , f max The second-order impedance characteristics of the power grid within Z dq ( s ), and obtain the equivalent grid-connected impedance characteristics : (3) in, f dd ( s ), f dq ( s ), f qd ( s ), f qq ( s ) represent dq The equivalent impedance elements obtained by low-order fitting in the axis coordinate system are in the form of N Subrational transfer function; f min , f max They are the minimum and maximum values ​​of the preset frequency band range respectively.

[0063] In a specific embodiment, the equivalent grid-connected impedance characteristic The steps of simulating non-ideal grid-connected impedance and correcting the voltage output by the grid to the tested new energy equipment based on the simulation results specifically include: Based on three-phase voltage reference V fault and equivalent grid impedance characteristics Calculate the virtual impedance control d Axis and q Shaft voltage control reference value V d,ref * and V q,ref * : (4) (5) in, V d,ref and V q,ref Respectively by V a,ref , V b,ref , V c,ref The Park transformation is obtained d Axis and q Shaft voltage reference value, I d and I q They are abc Three-phase current of power grid in coordinate system I a 、I b 、I c The Park transformation is obtained d Axis and q Shaft current value; based on d Axis and q Shaft voltage control reference value V d,ref * and V q,ref * Perform voltage and current dual-loop control to obtain a corrected PWM modulation signal; control the inverter-side subsystem based on the corrected PWM modulation signal to correct the voltage output by the power grid to the tested new energy equipment.

[0064] In a specific embodiment, the equivalent grid-connected impedance characteristic Simulate non-ideal grid impedance, including: using equivalent RLC actual impedance series and parallel to compare equivalent grid impedance characteristics Simulate non-ideal grid impedance.

[0065] When using equivalent RLC actual impedance series and parallel connection, firstly, according to formula (6), dq The equivalent impedance transfer function (3) in the coordinate system is converted into the comprehensive equivalent impedance Z eq ( s ),in Z dd ( s ), Z dq ( s ), Z qd ( s ), Z qq ( s ) represent the dq The broadband impedance characteristic element of the power grid in the axis coordinate system, f dd ( s ), f dq ( s ), f qd ( s ), f qq ( s ) are the equivalent impedances of the power grid obtained by fitting in formula (3), j Is an imaginary unit.

[0066] (6) Then, the comprehensive equivalent impedance shown in equation (6) is converted into the form described in equation (7). a k ( k = 0, 1,… , n ) represents the order of the denominator of the impedance transfer function s k ( k = 0, 1, … , n ) coefficient, the highest order of which is n Second-rate; b k ( k =0, 1, … , m ) is the impedance transfer function numerator s k ( k = 0, 1, … , m ) coefficient, the highest order of which is m times. After equivalent transformation, c n , d n ,e,h Respectively represent the coefficients to be fitted. h is 0, retaining the impedance expression, if h If it is not equal to 0, convert it into an admittance expression so that the denominator has a higher order than the numerator.

[0067] (7) For each item in equation (7), the equivalent RLC impedance branch is constructed in the following manner. Where: when d n When is a real number, the first term is a real pole term " c n / ( sd n )”, which can be converted into an RC parallel branch as an impedance, as shown in the attached Figure 6 As shown, it can be converted into an RL series branch as an admittance. Figure 7 shown.

[0068] when d n When it is a conjugate complex number, it can be expressed as a pair of conjugate complex numbers d n1 and d n2 , then the first term is the conjugate complex pole term "[ c n1 / ( sd n1 )]+[ c n2 / ( sd n2 )]”, which can be converted into a hybrid branch mainly composed of RLC parallel connection as an impedance, as shown in the attached Figure 8 As shown, the admittance can be converted into a hybrid branch mainly composed of RLC series, as shown in the attached Fig. 9 shown.

[0069] In formula (7), the second and third terms are constant terms and linear terms. e + sh , which can be converted into an RL series branch as an impedance, as shown in the attached Fig.10 As shown, it can be converted into an RC parallel branch as an admittance, as shown in the attached Fig.11 shown.

[0070] According to the transfer function form represented by equation (7), the overall circuit structure reflected by equation (7) can be constructed based on the equivalent circuit conversion by using the series form of the actual RLC impedance or the parallel form of the admittance. Furthermore, the actual RLC impedance series-parallel structure can be used to realize the construction of the equivalent grid-connected impedance.

[0071] See also Fig.13 As shown, an embodiment of the present invention further provides a power grid simulation device with non-ideal grid-connected impedance compensation capability, comprising: The acquisition unit is used to obtain the three-phase voltage waveform of the power grid fault point and obtain the three-phase voltage reference value reflecting the fault voltage V fault ; The three-phase voltage reference value V fault When a power grid fault occurs, it is obtained based on on-site recording data or electromagnetic transient simulation methods; The fitting unit is used to obtain the broadband impedance characteristics of the tested new energy equipment connected to the power grid environment; the low-order transfer function is used to fit the grid impedance characteristics within the preset frequency band to obtain the equivalent grid-connected impedance characteristics. ; Analog correction unit for equivalent grid impedance characteristics The non-ideal grid-connected impedance is simulated, and based on the simulation results, the voltage output by the power grid to the tested new energy equipment is corrected for the grid-connected test of the tested new energy equipment.

[0072] See also Fig.14 As shown, an embodiment of the present invention further provides a power grid simulation device with non-ideal grid-connected impedance compensation capability, comprising: A power grid, for providing a three-phase power grid voltage; Rectifier subsystem, used to convert three-phase grid voltage into stable DC voltage V dc ; The inverter subsystem is used to convert the DC voltage V dc Invert into controlled three-phase grid-connected voltage; A non-ideal grid-connected impedance simulation unit is used to simulate the equivalent grid-connected impedance characteristics using a grid simulation method with non-ideal grid-connected impedance compensation capability. Simulate non-ideal grid-connected impedance, control the inverter-side subsystem based on the simulation results, and output the corrected three-phase grid-connected voltage for grid-connected test of the tested new energy equipment; or, use the grid simulation method with non-ideal grid-connected impedance compensation capability to compare the equivalent grid-connected impedance characteristics by connecting equivalent RLC actual impedance in series and parallel. The non-ideal grid-connected impedance is simulated, and the three-phase grid-connected voltage output by the inverter-side subsystem is corrected based on the simulation results to obtain the corrected three-phase grid-connected voltage for the grid-connected test of the tested new energy equipment.

[0073] In a specific implementation, the non-ideal grid-connected impedance simulation unit includes a virtual impedance control unit, a medium voltage RLC impedance network and a circuit breaker K; The virtual impedance control unit is used to use the power grid simulation method with non-ideal grid-connected impedance compensation capability to calculate the equivalent grid-connected impedance characteristic. Simulate non-ideal grid-connected impedance, control the inverter-side subsystem based on the simulation results, and output the corrected three-phase grid-connected voltage for grid-connected test of the tested new energy equipment; The medium voltage RLC impedance network is used to connect the equivalent RLC actual impedance in series and parallel to the equivalent grid impedance characteristics. Simulate non-ideal grid-connected impedance, and based on the simulation results, correct the three-phase grid-connected voltage output by the inverter-side subsystem to obtain the corrected three-phase grid-connected voltage for grid-connected test of the tested new energy equipment; The output end of the inverter-side subsystem is connected to the tested new energy equipment through a medium-voltage RLC impedance network; a circuit breaker K is connected in parallel to the medium-voltage RLC impedance network.

[0074] In a specific implementation, a virtual impedance control unit is used to control the inverter side subsystem to output a corrected three-phase grid-connected voltage for grid-connected testing of the tested new energy equipment, close the circuit breaker K, and bypass the medium voltage RLC impedance network.

[0075] In a specific implementation, a medium voltage RLC impedance network is used to correct the three-phase grid-connected voltage output by the inverter side subsystem to obtain a corrected three-phase grid-connected voltage for grid-connected testing of the tested new energy equipment. The virtual impedance control unit is turned off and the circuit breaker K is disconnected.

[0076] The embodiment of the present invention is a power grid simulation device with non-ideal grid impedance compensation capability. The rectifier side subsystem adopts DC voltage control, and its function is to convert the three-phase grid voltage into a stable DC voltage. V dc The inverter side subsystem is responsible for converting the DC voltage V dc The inverter is converted into a controlled three-phase grid-connected voltage for grid-connected testing of the tested new energy equipment. The broadband impedance compensation for grid-connected simulation equipment can be achieved in one of the following two ways: (1) The inverter side subsystem adopts the following Figure 5 The virtual impedance control shown in FIG. 1 combines equations (2) and (3) to compensate for the broadband impedance of the grid while closing the circuit breaker. K , bypass the medium voltage RLC impedance network.

[0077] (2) The inverter subsystem is usually controlled in a conventional manner, that is, the attached Figure 5 The virtual impedance voltage drop calculation link in the circuit breaker is disconnected at the same time. K , connected to the medium voltage RLC impedance network. In the medium voltage RLC impedance network, combining equation (7) and the attached Figure 6-11Set the access impedance, build an equivalent RLC impedance series-parallel structure, and realize grid-connected impedance simulation.

[0078] Through the scheme proposed in the present invention, the power grid simulation device can compensate for the non-ideal grid-connected impedance of the tested new energy equipment, thereby being able to reflect the influence of factors such as the output current of the power grid and new energy equipment on the grid-connected point voltage under the influence of the grid-connected impedance, and more accurately simulate the harmonics, oscillations and other machine-grid interaction characteristics of the grid-connected point voltage of the new energy equipment under faults and disturbances.

[0079] Based on this, by simulating the faulty power grid environment more realistically, the fault voltage ride-through capability of new energy equipment can be tested more effectively to better ensure the transient safety and stability of wind turbines and their access to the power grid.

[0080] See also Fig.15 As shown, an embodiment of the present invention provides an electronic device 100 for implementing a power grid simulation method with non-ideal grid-connected impedance compensation capability; the electronic device 100 includes a memory 101, at least one processor 102, a computer program 103 stored in the memory 101 and executable on the at least one processor 102, and at least one communication bus 104.

[0081] The memory 101 can be used to store the computer program 103, and the processor 102 implements the steps of the power grid simulation method with non-ideal grid-connected impedance compensation capability by running or executing the computer program stored in the memory 101 and calling the data stored in the memory 101. The memory 101 can mainly include a program storage area and a data storage area, wherein the program storage area can store an operating system, an application required for at least one function (such as a sound playback function, an image playback function, etc.), etc.; the data storage area can store data (such as audio data) created according to the use of the electronic device 100, etc. In addition, the memory 101 can include a non-volatile memory, such as a hard disk, a memory, a plug-in hard disk, a smart memory card (Smart Media Card, SMC), a secure digital (Secure Digital, SD) card, a flash card (Flash Card), at least one disk storage device, a flash memory device, or other non-volatile solid-state storage devices.

[0082] The at least one processor 102 may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The processor 102 may be a microprocessor or any conventional processor, etc. The processor 102 is the control center of the electronic device 100, and uses various interfaces and lines to connect various parts of the entire electronic device 100.

[0083] The memory 101 in the electronic device 100 stores a plurality of instructions to implement a power grid simulation method with non-ideal grid-connected impedance compensation capability, and the processor 102 can execute the plurality of instructions to implement: Obtain the three-phase voltage waveform at the fault point of the power grid and obtain the three-phase voltage reference value reflecting the fault voltage V fault ; The three-phase voltage reference value V fault When a power grid fault occurs, it is obtained based on on-site recording data or electromagnetic transient simulation methods; Obtain the broadband impedance characteristics of the tested new energy equipment connected to the power grid environment; use low-order transfer functions to fit the grid impedance characteristics within the preset frequency band to obtain the equivalent grid-connected impedance characteristics ; Equivalent grid impedance characteristics The non-ideal grid-connected impedance is simulated, and based on the simulation results, the voltage output by the power grid to the tested new energy equipment is corrected for the grid-connected test of the tested new energy equipment.

[0084] If the module / unit integrated in the electronic device 100 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, the present invention implements all or part of the process in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium, and the computer program can implement the steps of the above-mentioned method embodiments when executed by the processor. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium may include: any entity or device that can carry the computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory and read-only memory (ROM, Read-Only Memory).

[0085] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0086] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0087] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0088] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A power grid simulation method with non-ideal grid-connected impedance compensation capability, characterized in that: include: Obtain the three-phase voltage waveform at the fault point of the power grid and obtain the three-phase voltage reference value reflecting the fault voltage V fault ; The three-phase voltage reference value V fault When a power grid fault occurs, it is obtained based on on-site recording data or electromagnetic transient simulation methods; Obtain the broadband impedance characteristics of the tested new energy equipment when connected to the power grid environment; The low-order transfer function is used to fit the grid impedance characteristics in the preset frequency band to obtain the equivalent grid impedance characteristics. ; Equivalent grid impedance characteristics The non-ideal grid-connected impedance is simulated, and based on the simulation results, the voltage output by the power grid to the tested new energy equipment is corrected for the grid-connected test of the tested new energy equipment.

2. A power grid simulation method with non-ideal grid-connected impedance compensation capability according to claim 1, characterized in that: The step of obtaining the broadband impedance characteristics of the tested new energy equipment connected to the power grid environment specifically includes: Use broadband impedance measurement, simulated impedance scanning or modeling analysis to obtain the second-order impedance characteristics of the power grid environment in a broadband environment. Z dq ( s ): (2) in, Z dd ( s ), Z dq ( s ), Z qd ( s ), Z qq ( s ) represent dq The broadband impedance characteristic elements of the power grid in the axis coordinate system.

3. A power grid simulation method with non-ideal grid-connected impedance compensation capability according to claim 2, characterized in that: The method uses a low-order transfer function to fit the grid impedance characteristics within the preset frequency band to obtain the equivalent grid-connected impedance characteristics. The steps include: According to the preset frequency range [ f min , f max ] and the fitting order N , the least squares method is used for iteration, with the order being N The frequency range of the low-order rational transfer function simulation is [ f min , f max The second-order impedance characteristics of the power grid within Z dq ( s ), and obtain the equivalent grid-connected impedance characteristics : (3) in, f dd ( s ), f dq ( s ), f qd ( s ), f qq ( s ) represent dq The equivalent impedance elements obtained by low-order fitting in the axis coordinate system are in the form of N Subrational transfer function; f min , f max They are the minimum and maximum values ​​of the preset frequency band range respectively.

4. A power grid simulation method with non-ideal grid-connected impedance compensation capability according to claim 3, characterized in that: The equivalent grid-connected impedance characteristics The steps of simulating non-ideal grid-connected impedance and correcting the voltage output by the grid to the tested new energy equipment based on the simulation results specifically include: Based on three-phase voltage reference V fault and equivalent grid impedance characteristics Calculate the virtual impedance control d Axis and q Shaft voltage control reference value V d,ref * and V q,ref * : (4) (5) in, (1) in, V fault To reflect the three-phase voltage reference value of the fault voltage; V a,ref , V b,ref , V c,ref They are respectively the fault voltage a Mutually, b Harmony c Phase voltage reference value; V d,ref and V q,ref Respectively by V a,ref , V b,ref , V c,ref The Park transformation is obtained d Axis and q Shaft voltage reference value, I d and I q They are abc Three-phase current of power grid in coordinate system I a 、I b 、I c The Park transformation is obtained d Axis and q Shaft current value; based on d Axis and q Shaft voltage control reference value V d,ref * and V q,ref * Perform voltage and current dual-loop control to obtain a corrected PWM modulation signal; control the inverter-side subsystem based on the corrected PWM modulation signal to correct the voltage output by the power grid to the tested new energy equipment.

5. A power grid simulation method with non-ideal grid-connected impedance compensation capability according to claim 4, characterized in that: The equivalent grid-connected impedance characteristics Simulate non-ideal grid impedance, including: Using equivalent RLC actual impedance series and parallel connection to compare equivalent grid impedance characteristics Simulate non-ideal grid impedance.

6. A power grid simulation device with non-ideal grid impedance compensation capability, characterized in that: include: The acquisition unit is used to obtain the three-phase voltage waveform of the power grid fault point and obtain the three-phase voltage reference value reflecting the fault voltage V fault ; The three-phase voltage reference value V fault When a power grid fault occurs, it is obtained based on on-site recording data or electromagnetic transient simulation methods; A fitting unit is used to obtain the broadband impedance characteristics of the tested new energy equipment when it is connected to the power grid environment; The low-order transfer function is used to fit the grid impedance characteristics in the preset frequency band to obtain the equivalent grid impedance characteristics. ; Analog correction unit for equivalent grid impedance characteristics The non-ideal grid-connected impedance is simulated, and based on the simulation results, the voltage output by the power grid to the tested new energy equipment is corrected for the grid-connected test of the tested new energy equipment.

7. A power grid simulation device with non-ideal grid-connected impedance compensation capability according to claim 6, characterized in that: The step of obtaining the broadband impedance characteristics of the tested new energy equipment connected to the power grid environment specifically includes: Use broadband impedance measurement, simulated impedance scanning or modeling analysis to obtain the second-order impedance characteristics of the power grid environment in a broadband environment. Z dq ( s ): (2) in, Z dd ( s ), Z dq ( s ), Z qd ( s ), Z qq ( s ) represent dq The broadband impedance characteristic elements of the power grid in the axis coordinate system.

8. A power grid simulation device with non-ideal grid-connected impedance compensation capability according to claim 7, characterized in that: The method uses a low-order transfer function to fit the grid impedance characteristics within the preset frequency band to obtain the equivalent grid-connected impedance characteristics. The steps include: According to the preset frequency range [ f min , f max ] and the fitting order N , the least squares method is used for iteration, with the order being N The frequency range of the low-order rational transfer function simulation is [ f min , f max The second-order impedance characteristics of the power grid within Z dq ( s ), and obtain the equivalent grid-connected impedance characteristics : (3) in, f dd ( s ), f dq ( s ), f qd ( s ), f qq ( s ) represent dq The equivalent impedance elements obtained by low-order fitting in the axis coordinate system are in the form of N Subrational transfer function; f min , f max They are the minimum and maximum values ​​of the preset frequency band range respectively.

9. A power grid simulation device with non-ideal grid-connected impedance compensation capability according to claim 8, characterized in that: The equivalent grid-connected impedance characteristics The steps of simulating non-ideal grid-connected impedance and correcting the voltage output by the grid to the tested new energy equipment based on the simulation results specifically include: Based on three-phase voltage reference V fault and equivalent grid impedance characteristics Calculate the virtual impedance control d Axis and q Shaft voltage control reference value V d,ref * and V q,ref * : (4) (5) in, (1) in, V fault To reflect the three-phase voltage reference value of the fault voltage; V a,ref , V b,ref , V c,ref They are respectively the fault voltage a Mutually, b Harmony c Phase voltage reference value; V d,ref and V q,ref Respectively by V a,ref , V b,ref , V c,ref The Park transformation is obtained d Axis and q Shaft voltage reference value, I d and I q They are abc Three-phase current of power grid in coordinate system I a 、I b 、I c The Park transformation is obtained d Axis and q Shaft current value; based on d Axis and q Shaft voltage control reference value V d,ref * and V q,ref * Perform voltage and current dual-loop control to obtain a corrected PWM modulation signal; control the inverter-side subsystem based on the corrected PWM modulation signal to correct the voltage output by the power grid to the tested new energy equipment.

10. A power grid simulation device with non-ideal grid-connected impedance compensation capability according to claim 9, characterized in that: The equivalent grid-connected impedance characteristics Simulate non-ideal grid impedance, including: Using equivalent RLC actual impedance series and parallel connection to compare equivalent grid impedance characteristics Simulate non-ideal grid impedance.

11. A power grid simulation device with non-ideal grid impedance compensation capability, characterized in that: include: A power grid, for providing a three-phase power grid voltage; Rectifier subsystem, used to convert three-phase grid voltage into stable DC voltage V dc ; The inverter subsystem is used to convert the DC voltage V dc Invert into controlled three-phase grid-connected voltage; A non-ideal grid-connected impedance simulation unit, used for adopting a grid simulation method with non-ideal grid-connected impedance compensation capability as described in any one of claims 1 to 4 to simulate the equivalent grid-connected impedance characteristic. Simulate non-ideal grid-connected impedance, control the inverter-side subsystem based on the simulation results, and output a corrected three-phase grid-connected voltage for grid-connected test of the tested new energy equipment; or, use a grid simulation method with non-ideal grid-connected impedance compensation capability as described in claim 5 to compare equivalent grid-connected impedance characteristics by connecting equivalent RLC actual impedances in series and parallel. The non-ideal grid-connected impedance is simulated, and the three-phase grid-connected voltage output by the inverter-side subsystem is corrected based on the simulation results to obtain the corrected three-phase grid-connected voltage for the grid-connected test of the tested new energy equipment.

12. A power grid simulation device with non-ideal grid-connected impedance compensation capability according to claim 11, characterized in that: The non-ideal grid-connected impedance simulation unit includes a virtual impedance control unit, a medium voltage RLC impedance network and a circuit breaker K; The virtual impedance control unit is used to use a power grid simulation method with non-ideal grid-connected impedance compensation capability as described in any one of claims 1 to 4 to calculate the equivalent grid-connected impedance characteristic. Simulate non-ideal grid-connected impedance, control the inverter-side subsystem based on the simulation results, and output the corrected three-phase grid-connected voltage for grid-connected test of the tested new energy equipment; The medium voltage RLC impedance network is used to connect the equivalent RLC actual impedance in series and parallel to the equivalent grid impedance characteristics. Simulate non-ideal grid-connected impedance, and based on the simulation results, correct the three-phase grid-connected voltage output by the inverter-side subsystem to obtain the corrected three-phase grid-connected voltage for grid-connected test of the tested new energy equipment; The output end of the inverter-side subsystem is connected to the tested new energy equipment through a medium-voltage RLC impedance network; a circuit breaker K is connected in parallel to the medium-voltage RLC impedance network.

13. A power grid simulation device with non-ideal grid-connected impedance compensation capability according to claim 12, characterized in that: A virtual impedance control unit is used to control the inverter side subsystem and output a corrected three-phase grid-connected voltage for grid-connected testing of the tested new energy equipment. The circuit breaker K is closed to bypass the medium voltage RLC impedance network.

14. A power grid simulation device with non-ideal grid-connected impedance compensation capability according to claim 12, characterized in that: The three-phase grid-connected voltage output by the inverter-side subsystem is corrected by a medium-voltage RLC impedance network to obtain a corrected three-phase grid-connected voltage for grid-connected testing of the tested new energy equipment. The virtual impedance control unit is turned off and the circuit breaker K is disconnected.

15. An electronic device, characterized in that: It comprises a processor and a memory, wherein the processor is used to execute a computer program stored in the memory to implement a power grid simulation method with non-ideal grid-connected impedance compensation capability as claimed in any one of claims 1 to 5.

16. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores at least one instruction, and when the at least one instruction is executed by the processor, it implements the power grid simulation method with non-ideal grid-connected impedance compensation capability as described in any one of claims 1 to 5.

Images