A power grid simulation method and device with the ability to compensate for non-ideal grid connection impedance

Abstract

The present invention belongs to the technical field of grid connection tests for wind turbines, and discloses a power grid simulation method and device with the ability to compensate for non-ideal grid connection impedance; the method includes: obtaining the three-phase voltage waveforms at the power grid fault point to obtain the three-phase voltage reference values reflecting the fault voltage; fitting the equivalent grid connection impedance characteristics from the power grid fault point to the machine terminal of the new energy device under test using a low-order transfer function; simulating the non-ideal grid connection impedance for the equivalent grid connection impedance characteristics, and correcting the voltage output from the power grid to the new energy device under test based on the simulation results for the grid connection test of the new energy device under test. Using the method of the present invention, it is possible to make up for the deficiency in the previous fault voltage ride-through tests of new energy devices such as wind turbines, where only the fault voltage characteristics are reproduced while ignoring the grid connection impedance characteristics. Through the method proposed by the present invention, the grid connection impedance characteristics can be compensated to reproduce the fault characteristics more accurately and verify the key capabilities such as the fault voltage ride-through of new energy devices more effectively.

Description

Technical Field

[0001] The present invention belongs to the technical field of grid connection tests for wind turbines, and particularly relates to a power grid simulation method and device with the ability to compensate for non-ideal grid connection impedance. Background Art

[0002] The grid connection of new energy units refers to connecting the electric energy generated by new energy power generation equipment to the power grid, enabling it to transmit electricity to the power grid and realizing the effective utilization and distribution of new energy power. Faults in the power grid can cause voltage waveform distortion at the machine terminals of grid-connected new energy equipment, which may in turn affect its normal operation. Therefore, new energy equipment needs to verify its ability to maintain grid connection during voltage dips and other situations in the power grid through fault voltage ride-through tests. Fault voltage ride-through tests usually adopt impedance voltage division test devices and test methods, using resistors, inductors, and capacitor devices to divide the voltage at the grid connection point to generate voltage dips / rises of different depths for testing. In addition, in recent years, grid operation simulation devices based on power electronic equipment can also be used to simulate grid fault / disturbance voltage waveforms to conduct relevant tests.

[0003] The invention patent application with the application number 201410734345.X discloses a high and low voltage continuous process fault ride-through test method, based on a wind turbine high and low voltage ride-through ability detection system. The method includes the following steps: I. Generating uninterrupted and continuous output of grid voltage dips and voltage rises through the wind turbine high and low voltage ride-through ability detection system; II. Obtaining non-electrical quantity data and electrical quantity data during high and low voltage fault ride-through; III. Processing the non-electrical quantity data and the electrical quantity data; IV. Analyzing the non-electrical quantity data and the electrical quantity data. This method can truly simulate the voltage dip and rise characteristics in grid faults without interruption, ensuring that when generating low voltage and high voltage, the changes in voltage phase angle and power quality are consistent with the actual grid fault characteristics, and it can realize the coherent detection of the high and low voltage ride-through abilities of wind turbines in one test process.

[0004] Based on the impedance voltage division type fault voltage ride-through test equipment, this invention application proposes a corresponding test method. However, this method can only generate deterministic and idealized fault voltage waveforms, and cannot flexibly generate fault voltage curves that are consistent with actual grid characteristics and consider key factors such as grid impedance characteristics, which limits the effectiveness of fault ride-through tests.

[0005] The invention patent application with the application number 201310334718.X discloses a wind farm power grid operation simulation device, providing 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-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-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 the online hybrid simulation of power grid disturbances and faults, collect and analyze the actual operation data during the test of wind turbines, and can conduct power grid adaptability tests, low voltage ride-through ability tests, high voltage ride-through ability tests and detections on wind turbines, and conduct comprehensive tests and evaluations on the power grid disturbance anti-interference ability and power grid fault ride-through ability of wind turbines.

[0006] This invention application proposes the overall structure of a power grid operation simulation device, which can generate relatively flexible voltage waveforms at the machine terminal of the wind turbine under test for carrying out relevant test measurements. However, this invention does not propose how to simulate the power grid fault voltage characteristics and lacks a specific method that can reflect different fault voltage characteristics under complex power grid conditions.

[0007] The invention patent application with the application number 202410208637.3 discloses a power grid simulation device with a power grid voltage reproduction function and a control method. 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 it is connected to a controller for providing a test voltage for the device under test. Obtain the three-phase voltage information of the power grid to be reproduced as the voltage data to be reproduced, import the voltage data to be reproduced into the controller, and the controller controls the output voltage three-phase modulation wave through a control strategy for the voltage data to be reproduced, and sends the voltage three-phase modulation wave into the pulse width modulation module to generate the switching signal of the power grid simulation device; this method improves 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 the reference voltage, but this 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 a test device with impedance voltage division or a power grid simulation device for testing, currently both focus only on reproducing the physical and chemical fault voltage waveforms and ignore the consideration of the broadband impedance of the non-ideal power grid. In this regard, there is currently no specific simulation method that can clearly give the fault voltage characteristics considering the non-ideal power grid and the broadband impedance of the new energy device under test for grid connection. Summary of the Invention

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

[0011] To achieve the above object, the present invention adopts the following technical solutions:

[0012] In a first aspect, the present invention provides a power grid simulation method with the ability to compensate for non-ideal grid connection impedance, including:

[0013] Obtain the three-phase voltage waveforms at the power grid fault point to obtain the three-phase voltage reference values reflecting the fault voltage V fault ; The three-phase voltage reference values V fault In the event of a power grid fault, be obtained based on on-site recorded wave data or based on electromagnetic transient simulation methods;

[0014] Obtain the broadband impedance characteristics of the power grid environment where the new energy equipment under test is connected; Obtain the equivalent grid connection impedance characteristics by fitting the power grid impedance characteristics with a low-order transfer function within a preset frequency band ;

[0015] Simulate the non-ideal grid connection impedance for the equivalent grid connection impedance characteristics Based on the simulation results, correct the voltage output by the power grid to the new energy equipment under test for the grid connection test of the new energy equipment under test.

[0016] A further improvement of the present invention: The step of obtaining the broadband impedance characteristics of the power grid environment where the new energy equipment under test is connected specifically includes:

[0017] Adopt methods such as broadband impedance measurement, simulation impedance scanning, or modeling analysis to obtain the second-order impedance characteristics of the power grid environment in the broadband range Z dq ( s )

[0018] (2)

[0019] Among them, Z dd ( s ) Z dq ( s )Z qd ( s )、 Z qq ( s ) respectively represent dq the broadband impedance characteristic elements of the power grid in the axis coordinate system.

[0020] A further improvement of the present invention: the step of obtaining the equivalent grid-connected impedance characteristic by fitting the power grid impedance characteristic with a low-order transfer function within a preset frequency band specifically includes:

[0021] According to the preset frequency band range f min , f max and the fitting order N , use the least squares method for iteration, and use a low-order rational transfer function of order N times to simulate the second-order impedance characteristic of the power grid within the frequency band range f min , f max to obtain the equivalent grid-connected impedance characteristic Z dq ( s ) and obtain the equivalent grid-connected impedance characteristic :

[0022] (3)

[0023] Wherein, f dd ( s )、 f dq ( s )、 f qd ( s )、 f qq ( s ) respectively represent dq the equivalent impedance elements obtained by low-order fitting in the axis coordinate system, and the form is N times rational transfer function; f min , f max are respectively the minimum value and the maximum value of the preset frequency band range.

[0024] A further improvement of the present invention: the step of simulating the non-ideal grid-connected impedance for the equivalent grid-connected impedance characteristic and correcting the voltage output by the power grid to the tested new energy device based on the simulation result, specifically including:

[0025] Based on the three-phase voltage reference value V fault and the equivalent grid-connected impedance characteristics calculate and obtain the d axis and q axis voltage control reference values V d,ref * and V q,ref * :

[0026] (4)

[0027] (5)

[0028] wherein, (1)

[0029] wherein, V fault is the three-phase voltage reference value reflecting the fault voltage; V a,ref 、 V b,ref 、 V c,ref are respectively the a phase, b phase and c phase voltage reference values reflecting the fault voltage; V d,ref and V q,ref are respectively the V a,ref 、 V b,ref 、 V c,ref axis and d axis voltage reference values obtained through Park transformation, q and I d and I q are respectively the abc axis and I a 、I b 、I c axis current values obtained through Park transformation; d axis and q axis current values;

[0030] Based on the d axis and q axis voltage control reference values V d,ref* and V q,ref * Perform voltage and current double-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 from the power grid to the new energy device under test.

[0031] A further improvement of the present invention: the simulation of the equivalent grid connection impedance characteristics for simulating non-ideal grid connection impedance, specifically including:

[0032] Use equivalent RLC actual impedance series and parallel to simulate the equivalent grid connection impedance characteristics for simulating non-ideal grid connection impedance.

[0033] In a second aspect, the present invention provides a power grid simulation device with non-ideal grid connection impedance compensation ability, including:

[0034] An acquisition unit for obtaining the three-phase voltage waveforms at the power grid fault point to obtain the three-phase voltage reference values reflecting the fault voltage V fault ; the three-phase voltage reference values V fault are obtained based on on-site recorded wave data or based on electromagnetic transient simulation methods when the power grid fails;

[0035] A fitting unit for obtaining the broadband impedance characteristics of the power grid environment where the new energy device under test is connected; using a low-order transfer function to fit the power grid impedance characteristics within a preset frequency band to obtain the equivalent grid connection impedance characteristics ;

[0036] A simulation correction unit for simulating non-ideal grid connection impedance characteristics and correcting the voltage output from the power grid to the new energy device under test based on the simulation results for the grid connection test of the new energy device under test.

[0037] A further improvement of the present invention: the step of obtaining the broadband impedance characteristics of the power grid environment where the new energy device under test is connected specifically includes:

[0038] Using methods such as broadband impedance measurement, simulation impedance scanning, or modeling analysis to obtain the second-order impedance characteristics of the power grid environment in the broadband Z dq ( s ):

[0039] (2)

[0040] wherein, Z dd ( s )、Z dq ( s )、 Z qd ( s )、 Z qq ( s ) respectively represent dq the grid broadband impedance characteristic elements in the axis coordinate system.

[0041] A further improvement of the present invention: the step of obtaining the equivalent grid connection impedance characteristic by fitting the grid impedance characteristic with a low-order transfer function within a preset frequency band specifically includes:

[0042] According to the preset frequency band range f min , f max and the fitting order N , use the least squares method for iteration, and use a low-order rational transfer function of order N times to simulate the second-order impedance characteristic of the grid within the frequency band range f min , f max to obtain the equivalent grid connection impedance characteristic Z dq ( s ) to obtain the equivalent grid connection impedance characteristic :

[0043] (3)

[0044] Among them, f dd ( s )、 f dq ( s )、 f qd ( s )、 f qq ( s ) respectively represent dq the equivalent impedance elements obtained by low-order fitting in the axis coordinate system, and the form is N th-order rational transfer function; f min , f max are respectively the minimum and maximum values of the preset frequency band range.

[0045] A further improvement of the present invention: the said equivalent grid connection impedance characteristic Steps for simulating a non-ideal grid connection impedance and correcting the voltage output from the grid to the new energy device under test based on the simulation results, specifically including:

[0046] Based on the three-phase voltage reference values V fault and the equivalent grid connection impedance characteristics calculate the d axis and q axis voltage control reference values obtained through virtual impedance control V d,ref * and V q,ref * :

[0047] (4)

[0048] (5)

[0049] Wherein, (1)

[0050] Wherein, V fault is the three-phase voltage reference value reflecting the fault voltage; V a,ref , V b,ref , V c,ref are respectively the a phase, b phase and c phase voltage reference values reflecting the fault voltage; V d,ref and V q,ref are respectively the V a,ref , V b,ref , V c,ref axis and d axis voltage reference values obtained through Park transformation, q d I q and I q are respectively the abc axis and I a 、I b 、I c axis current values obtained through Park transformation of the three-phase grid currents in the d axis and q axis in the

[0051] Based on d axis and q axis voltage control reference value V d,ref * and V q,ref * Perform voltage and current double-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 from the power grid to the new energy device under test.

[0052] A further improvement of the present invention: the simulation of the equivalent grid connection impedance characteristic for simulating the non-ideal grid connection impedance, specifically including:

[0053] Use an equivalent RLC actual impedance series-parallel connection to simulate the equivalent grid connection impedance characteristic for simulating the non-ideal grid connection impedance.

[0054] In a third aspect, the present invention provides a grid simulation device with non-ideal grid connection impedance compensation ability, including:

[0055] A power grid for providing three-phase grid voltage;

[0056] A rectifier-side subsystem for converting the three-phase grid voltage into a stable DC voltage V dc ;

[0057] An inverter-side subsystem for inverting the DC voltage V dc into a controlled three-phase grid connection voltage;

[0058] A non-ideal grid connection impedance simulation unit for using a grid simulation method with non-ideal grid connection impedance compensation ability described in any one of claims 1 to 4 to simulate the equivalent grid connection impedance characteristic for simulating the non-ideal grid connection impedance, controlling the inverter-side subsystem based on the simulation result, and outputting a corrected three-phase grid connection voltage for the grid connection test of the new energy device under test; or, for using a grid simulation method with non-ideal grid connection impedance compensation ability described in claim 5 to simulate the equivalent grid connection impedance characteristic through an equivalent RLC actual impedance series-parallel connection for simulating the non-ideal grid connection impedance, and correcting the three-phase grid connection voltage output by the inverter-side subsystem based on the simulation result to obtain a corrected three-phase grid connection voltage for the grid connection test of the new energy device under test.

[0059] A further improvement of the present invention: the non-ideal grid connection impedance simulation unit includes a virtual impedance control unit, a medium-voltage RLC impedance network, and a circuit breaker K;

[0060] The virtual impedance control unit is used to simulate the equivalent grid connection impedance characteristics by using the grid simulation method with the ability to compensate for non-ideal grid connection impedance described in any one of claims 1 to 4 perform the simulation of non-ideal grid connection impedance, control the inverter-side subsystem based on the simulation results, and output the corrected three-phase grid connection voltage for the grid connection test of the new energy device under test;

[0061] The medium-voltage RLC impedance network is used to simulate the equivalent grid connection impedance characteristics by using the series and parallel connection of equivalent RLC actual impedances perform the simulation of non-ideal grid connection impedance, correct the three-phase grid connection voltage output by the inverter-side subsystem based on the simulation results, and obtain the corrected three-phase grid connection voltage for the grid connection test of the new energy device under test;

[0062] The output end of the inverter-side subsystem is connected to the new energy device under test through a medium-voltage RLC impedance network; a circuit breaker K is connected in parallel on the medium-voltage RLC impedance network.

[0063] A further improvement of the present invention: when using the virtual impedance control unit to control the inverter-side subsystem and output the corrected three-phase grid connection voltage for the grid connection test of the new energy device under test, close the circuit breaker K to bypass the medium-voltage RLC impedance network.

[0064] A further improvement of the present invention: when using the medium-voltage RLC impedance network to correct the three-phase grid connection voltage output by the inverter-side subsystem and obtain the corrected three-phase grid connection voltage for the grid connection test of the new energy device under test, turn off the virtual impedance control unit and disconnect the circuit breaker K.

[0065] Fourthly, the present invention provides an electronic device, including a processor and a memory. The processor is used to execute a computer program stored in the memory to implement the grid simulation method with the ability to compensate for non-ideal grid connection impedance.

[0066] Fifthly, the present invention provides a computer-readable storage medium. The computer-readable storage medium stores at least one instruction, and when the at least one instruction is executed by a processor, the grid simulation method with the ability to compensate for non-ideal grid connection impedance is implemented.

[0067] Compared with the prior art, the present invention has the following beneficial effects:

[0068] The present invention provides a grid simulation method with the ability to compensate for non-ideal grid connection impedance, including: obtaining the three-phase voltage waveforms at the grid fault point to obtain the three-phase voltage reference values reflecting the fault voltage V fault ; using a low-order transfer function to fit the equivalent grid connection impedance characteristics from the grid fault point to the machine terminal of the new energy device under test ; for the equivalent grid connection impedance characteristics Simulate the non-ideal grid connection impedance, and correct the voltage output from the power grid to the new energy device under test based on the simulation results for the grid connection test of the new energy device under test. Using the method of the present invention, it is possible to make up for the deficiency in the previous fault voltage ride-through test of new energy devices such as wind turbines, where only the fault voltage characteristics are reproduced while ignoring the grid connection impedance characteristics. Through the method proposed by the present invention, the grid connection impedance characteristics can be compensated to more accurately reproduce the fault characteristics and more effectively verify the key capabilities such as the fault voltage ride-through of new energy devices.

[0069] Furthermore, the method proposed by the present invention can be applied in the grid connection test of new energy devices for fault voltage ride-through, improving the empirical ability of the grid simulation device for wind turbine grid connection testing, enriching the testing equipment for wind turbine fault voltage tests, thus more effectively verifying the fault voltage ride-through ability of wind turbines, ensuring the safe and stable operation of the power grid after new energy grid connection, and supporting the reliable operation of the power system under fault transients after large-scale new energy grid connection.

[0070] Furthermore, the method of the present invention can simulate the non-ideal grid connection characteristics of new energy devices such as wind turbines by virtual impedance control or adding series-parallel RLC impedance, so as to accurately describe the impact of grid faults / disturbances and the output current of the device under test on the grid connection point voltage, and more effectively carry out the simulation and verification of the grid connection characteristics of new energy devices.

[0071] Furthermore, the method proposed by the present invention includes three links: voltage curve generation, equivalent impedance fitting, and equivalent impedance construction. Among them, in the voltage curve generation link, the output voltage of the grid simulation device is determined based on data such as fault recordings. Furthermore, in the equivalent impedance fitting link, for the grid environment to which the new energy device under test is connected, the broadband impedance characteristics of the grid are fitted into a low-order transfer function within the frequency band of interest. Finally, in the equivalent impedance construction link, on the one hand, virtual impedance control can be used to achieve grid connection impedance compensation; on the other hand, according to the impedance transfer function expression, the series-parallel equivalent structure of the resistance, inductance, and capacitance of the grid connection impedance can be obtained, and thus an actual passive impedance device can be used to simulate and compensate the grid connection impedance. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] The accompanying drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic 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 drawings:

[0073] Figure 1 It is a schematic diagram for simulating the connection of the new energy device under test to the grid environment based on the "equivalent impedance";

[0074] Figure 2Schematic flowchart of a power grid simulation method with non-ideal grid connection impedance compensation ability according to an embodiment of the present invention;

[0075] Figure 3 Schematic flowchart of the equivalent impedance fitting process according to an embodiment of the present invention;

[0076] Figure 4 Schematic diagram of the characteristics of the equivalent impedance after fitting according to an embodiment of the present invention;

[0077] Figure 5 Schematic diagram of the virtual impedance control function according to an embodiment of the present invention;

[0078] Figure 6 In the embodiment of the present invention, the real pole term " c n / ( s-d n )" is converted into a schematic diagram of an RC parallel branch;

[0079] Figure 7 In the embodiment of the present invention, the real pole term " c n / ( s-d n )" is converted into a schematic diagram of an RL series branch;

[0080] Figure 8 In the embodiment of the present invention, the conjugate complex pole term " c n1 / ( s-d n1 )]+ c n2 / ( s-d n2 )]" is converted into a schematic diagram of an RLC series-parallel branch as impedance;

[0081] Figure 9 In the embodiment of the present invention, the conjugate complex pole term " c n1 / ( s-d n1 )]+ c n2 / ( s-d n2 )]" is converted into a schematic diagram of an RLC series-parallel branch as admittance;

[0082] Figure 10 In the embodiment of the present invention, the constant term and the first-order term e + sh are converted into a schematic diagram of an RL series branch;

[0083] Figure 11 In the embodiment of the present invention, the constant term and the first-order term e +sh Schematic diagram converted into an RC parallel branch;

[0084] Figure 12 Schematic flow diagram of a power grid simulation method with non-ideal grid connection impedance compensation ability in an embodiment of the present invention;

[0085] Figure 13 Structural block diagram of a power grid simulation device with non-ideal grid connection impedance compensation ability in an embodiment of the present invention;

[0086] Figure 14 Structural block diagram of another power grid simulation device with non-ideal grid connection impedance compensation ability in an embodiment of the present invention;

[0087] Figure 15 Structural block diagram of an electronic device in an embodiment of the present invention. Detailed implementation manners

[0088] 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, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0089] The following detailed descriptions are all exemplary descriptions, aiming to provide further detailed descriptions of the present invention. Unless otherwise specified, all technical terms adopted by the present invention have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs. The terms used in the present invention are only for describing specific implementation manners and are not intended to limit the exemplary embodiments according to the present invention.

[0090] Please refer to Figure 1 As shown, an embodiment of the present invention provides a power grid simulation method with non-ideal grid connection impedance compensation ability, which is based on the Thevenin equivalent idea and uses "equivalent impedance Z eq " to simulate the non-ideal impedance of the power grid connected to the new energy device under test, so as to carry out relevant tests such as fault voltage ride-through.

[0091] Please refer to Figure 2 As shown, an embodiment of the present invention provides a power grid simulation method with non-ideal grid connection impedance compensation ability, including:

[0092] S101. Voltage curve generation: Determine the three-phase voltage waveforms at the fault point by using on-site waveform recording or simulation methods;

[0093] S102. Equivalent impedance fitting: Fit the equivalent grid connection impedance from the fault point to the machine terminal of the new energy device under test by using a low-order transfer function;

[0094] S103. Equivalent impedance construction: The equivalent grid connection impedance is simulated and compensated by using virtual impedance control or connecting equivalent RLC series-parallel impedance.

[0095] Specifically, the steps of voltage curve generation specifically include:

[0096] Based on on-site recorded wave data or electromagnetic transient simulation methods, the three-phase voltage waveforms at the fault point are determined during grid faults in the voltage curve generation section, and used as the control reference for the equivalent voltage source; specifically, the formula for the equivalent voltage source Figure 1 is as follows V fault of the control reference; specifically, the equivalent voltage source V fault is shown in Equation (1).

[0097] (1)

[0098] Where V fault is the three-phase voltage reference value reflecting the fault voltage; specifically, V a,ref , V b,ref , V c,ref are respectively the a phase, b phase and c phase voltage reference values reflecting the fault voltage.

[0099] Specifically, the steps of equivalent impedance fitting specifically include:

[0100] S201. Obtain the broadband impedance characteristics of the grid environment where the new energy device under test is connected to the grid;

[0101] S202. Fit the grid impedance characteristics with a low-order transfer function within the frequency band of interest.

[0102] Please refer to Figure 3 shown. The equivalent impedance fitting section equivalent the broadband impedance characteristics of the grid to a low-order transfer function within the frequency band of interest according to the grid environment where the new energy device under test is connected.

[0103] First, for the grid environment where the new energy device under test is connected, methods such as broadband impedance measurement, simulation impedance scanning or modeling analysis are used to obtain the second-order impedance characteristics of the grid environment under broadband Z dq ( s ), as shown in Equation (2), where Z dd ( s ), Z dq ( s)、 Z qd ( s )、 Z qq ( s ) respectively represent dq the power grid broadband impedance characteristic elements in the axis coordinate system.

[0104] (2)

[0105] In a specific embodiment, the broadband can be 1 - 1000 Hz.

[0106] Furthermore, according to the preset frequency band range f min , f max and the fitting order N , using the least squares method for iteration, a low - order rational transfer function with an order of N times is used to simulate the second - order impedance characteristic of the power grid within the frequency band range f min , f max to obtain the equivalent impedance characteristic Z dq ( s ) obtained by fitting, where each element is fitted using a rational transfer function under a determined order, as shown in Equation (3). Among them , where f dd ( s )、 f dq ( s )、 f qd ( s )、 f qq ( s ) respectively represent dq the equivalent impedance elements obtained by low - order fitting in the axis coordinate system, and their forms are all N - order rational transfer functions; f min , f max are respectively the minimum and maximum values of the preset frequency band range.

[0107] (3)

[0108] In a specific embodiment, take f min = 10 Hz, f max = 30 Hz.

[0109] In a specific embodiment, the fitting order N is 3 or 5 。

[0110] Please refer to 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. In Figure 4 , the solid line represents the original broadband impedance characteristics of the power grid, and the dashed line represents the equivalent impedance characteristics obtained by fitting with a 5th-order rational transfer function. Within the preset frequency band range [10 Hz, 30 Hz], the equivalent impedance characteristics are consistent with the original impedance characteristics of the power grid in terms of amplitude and phase.

[0111] Specifically, the steps for constructing the equivalent impedance include:

[0112] The equivalent impedance construction link performs impedance simulation and compensation on the equivalent impedance characteristics obtained by fitting . Among them, the impedance simulation and compensation method can be implemented by virtual impedance control or by the series-parallel connection of equivalent RLC actual impedances.

[0113] 1) Adopting virtual impedance control

[0114] The simulation of the equivalent impedance characteristics is implemented by the virtual impedance control method 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 control block diagram shown in Appendix Figure 5 is used for control. Among them, the virtual impedance control is mainly implemented through the virtual impedance voltage drop calculation link in Appendix Figure 5 . When the virtual impedance voltage drop calculation link is not added, the remaining control links in Appendix Figure 5 can be regarded as the conventional voltage and current double-loop control links of the power grid simulation device.

[0115] Among them, the virtual impedance voltage drop calculation link can be expressed as shown in Equations (4) and (5).

[0116] (4)

[0117] (5)

[0118] Among them, V d,ref * and V q,ref * are respectively the voltage control reference values of the d axis and the q axis corrected by the virtual impedance voltage drop calculation link, Vd,ref and V q,ref are respectively the V a,ref and V b,ref and V c,ref axis voltage reference values obtained through Park transformation, d axis and q axis voltage reference value, f dd ( s )、 f dq ( s )、 f qd ( s )、 f qq ( s ) are respectively the equivalent impedance of the power grid obtained by fitting in Equation (3), I d and I q are respectively abc the three-phase current of the power grid in the I a 、I b 、I c axis current values obtained through Park transformation, d axis and q axis current value.

[0119] Based on d axis and q axis voltage control reference values V d,ref * and V q,ref * perform voltage and current double-loop control to obtain the corrected PWM modulation signals PWM a 、PWM b 、PWM c ,Based on the corrected PWM modulation signals PWM a 、PWM b 、PWM c control the inverter-side subsystem to output the corrected three-phase grid-connected voltage for the grid-connected test of the new energy equipment under test. In Appendix Figure 5 In, V d and V q are respectively abc the three-phase voltage of the power grid in the V a、V b 、V c Obtained by Park transformation d axis and q axis voltage value; Based on d axis and q axis voltage control reference value V d,ref * and V q,ref * respectively correct V d and V q and then perform dual-loop control of voltage and current to obtain the corrected PWM modulation signals PWM a 、PWM b 、PWM c .

[0120] 2) Adopt equivalent RLC actual impedance series-parallel

[0121] When adopting equivalent RLC actual impedance series-parallel, first according to Equation (6), convert the equivalent impedance transfer function (3) in the dq coordinate system into the comprehensive equivalent impedance Z eq ( s ), where Z dd ( s ), Z dq ( s ), Z qd ( s ), Z qq ( s ) respectively represent the grid broadband impedance characteristic elements in the dq axis coordinate system in Equation (2), f dd ( s ), f dq ( s ), f qd ( s ), f qq ( s ) are respectively the grid equivalent impedances obtained by fitting in Equation (3), j is the imaginary unit.

[0122] (6)

[0123] Furthermore, the comprehensive equivalent impedance shown in Equation (6) is converted into the form described in Equation (7). Among them a k ( k = 0, 1, …, n ) represents each order s k ( k = 0, 1, …, n ) of the coefficients in the denominator of the impedance transfer function, and its highest order is n order; b k ( k =0, 1, …, m ) are the coefficients of each order s k ( k = 0, 1, …, m ) in the numerator of the impedance transfer function, and its highest order is m order. After equivalent transformation, c n , d n , e, h respectively represent the coefficients to be fitted. If h is 0 after fitting, the impedance expression is retained. If h is not equal to 0, it is converted into an admittance expression so that the denominator order is higher than the numerator order.

[0124] (7)

[0125] For each term in Equation (7), equivalent RLC impedance branches are constructed respectively in the following manner. Among them:

[0126] In Equation (7), when d n is a real number, the first term is the real pole term " c n / ( s-d n )", which can be converted into an RC parallel branch as an impedance, as shown in Appendix Figure 6 , including the parallel resistor R 1k and capacitor C 1k ; and can be converted into an RL series branch as an admittance, as shown in Appendix Figure 7 , including the series resistor R 1k and inductor L 1k .

[0127] In Equation (7), when d n is a conjugate complex number, it can be expressed as a pair of conjugate complex numbers dn1 and d n2 , the first term is the conjugate complex pole term " c n1 / ( s-d n1 )]+ c n2 / ( s-d n2 )]". As impedance, it can be converted into a series-parallel branch mainly composed of RLC in parallel. As shown in the appendix Figure 8 , it includes three parallel branches: the capacitor C 1k branch, the resistor R 2k branch, and the series-connected resistor R 1k and inductor L 1k branch; as admittance, it can be converted into a series-parallel branch mainly composed of RLC in series. As shown in the appendix Figure 9 , it includes the mutually series-connected resistor R 1k , inductor L 1k and the mutually parallel capacitor C 1k and resistor R 2k .

[0128] In Equation (7), the second and third terms are the constant term and the first-order term e + sh . As impedance, it can be converted into an RL series branch. As shown in the appendix Figure 10 , it includes the series-connected resistor R1 and inductor L1; as admittance, it can be converted into an RC parallel branch. As shown in the appendix Figure 11 , it includes the parallel-connected resistor R1 and capacitor C1.

[0129] According to the transfer function form represented by Equation (7), based on the equivalent circuit conversion, the overall circuit structure reflected by Equation (7) can be constructed by using the series form of the actual impedance of RLC or the parallel form of admittance. Furthermore, the equivalent grid-connected impedance can be constructed by adopting the actual series-parallel structure of RLC impedance.

[0130] Please refer to Figure 12 shown. The embodiment of the present invention provides a power grid simulation method with the ability to compensate for non-ideal grid-connected impedance, including:

[0131] S1. Obtain the three-phase voltage waveforms at the power grid fault point to obtain the three-phase voltage reference values reflecting the fault voltage V fault ;

[0132] S2. Fit the equivalent grid-connected impedance characteristics from the power grid fault point to the machine terminal of the new energy device under test by using a low-order transfer function ;

[0133] S3. For the equivalent grid-connected impedance characteristics Simulate the non-ideal grid connection impedance, and correct the voltage output from the grid to the new energy device under test based on the simulation results for the grid connection test of the new energy device under test.

[0134] In a specific embodiment, the new energy device under test is a wind turbine.

[0135] In a specific embodiment, the step of obtaining the three-phase voltage waveforms at the grid fault point to obtain the three-phase voltage reference values reflecting the fault voltage V fault specifically includes:

[0136] When a grid fault occurs, obtain the three-phase voltage waveforms at the fault point as the three-phase voltage reference values based on on-site recorded wave data or based on electromagnetic transient simulation methods V fault ;

[0137] (1)

[0138] Wherein, V fault is the three-phase voltage reference value reflecting the fault voltage; V a,ref , V b,ref , V c,ref are respectively the a phase, b phase and c phase voltage reference values reflecting the fault voltage.

[0139] In a specific embodiment, the step of using a low-order transfer function to fit the equivalent grid connection impedance characteristics from the fault point to the machine terminal of the new energy device under test specifically includes:

[0140] Obtain the broadband impedance characteristics of the grid environment where the new energy device under test is connected;

[0141] Use a low-order transfer function to fit the grid impedance characteristics within a preset frequency band to obtain the equivalent grid connection impedance characteristics .

[0142] In a specific embodiment, the step of obtaining the broadband impedance characteristics of the grid environment where the new energy device under test is connected specifically includes:

[0143] Use methods such as broadband impedance measurement, simulation impedance scanning or modeling analysis to obtain the second-order impedance characteristics of the grid environment in the broadband Z dq ( s )

[0144] (2)

[0145] Among them, Z dd ( s )、 Z dq ( s )、 Z qd ( s )、 Z qq ( s ) respectively represent dq the grid broadband impedance characteristic elements in the axis coordinate system.

[0146] In a specific embodiment, the step of obtaining the equivalent grid connection impedance characteristic by fitting the grid impedance characteristic with a low-order transfer function within a preset frequency band specifically includes:

[0147] According to the preset frequency band range f min , f max and the fitting order N , use the least squares method for iteration, and use a low-order rational transfer function of order N to simulate the second-order impedance characteristic of the grid within the frequency band range f min , f max , and obtain the equivalent grid connection impedance characteristic Z dq ( s ): :

[0148] (3)

[0149] Among them, f dd ( s )、 f dq ( s )、 f qd ( s )、 f qq ( s ) respectively represent dq the equivalent impedance elements obtained by low-order fitting in the axis coordinate system, and the form is N -order rational transfer function; f min , f max are respectively the minimum and maximum values of the preset frequency band range.

[0150] In a specific embodiment, the step of simulating the equivalent grid connection impedance characteristic and correcting the voltage output by the power grid to the new energy device under test based on the simulation results specifically includes:

[0151] Based on the three-phase voltage reference value V fault and the equivalent grid connection impedance characteristic calculate the d axis and q axis voltage control reference values V d,ref * and V q,ref * :

[0152] (4)

[0153] (5)

[0154] wherein, V d,ref and V q,ref are respectively the V a,ref , V b,ref , V c,ref axis and d axis voltage reference values obtained through Park transformation, q d and I q are respectively abc the I axis and 、I a 、I b d c axis current values obtained through Park transformation of the three-phase grid current in the q axis and coordinate system;

[0155] d Based on the q axis and V axis voltage control reference values V d,ref * and q,ref *Perform voltage and current double-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 from the power grid to the new energy device under test.

[0156] In a specific embodiment, the equivalent grid connection impedance characteristics are simulated for non-ideal grid connection impedance, specifically including: using equivalent RLC actual impedance series and parallel to simulate the equivalent grid connection impedance characteristics for non-ideal grid connection impedance.

[0157] When using equivalent RLC actual impedance series and parallel, first, according to Equation (6), convert the dq equivalent impedance transfer function (3) in the coordinate system to the comprehensive equivalent impedance Z eq ( s ), where Z dd ( s ), Z dq ( s ), Z qd ( s ), Z qq ( s ) respectively represent the grid broadband impedance characteristic elements in the dq axis coordinate system in Equation (2), f dd ( s ), f dq ( s ), f qd ( s ), f qq ( s ) are respectively the grid equivalent impedance obtained by fitting in Equation (3), j is the imaginary unit.

[0158] (6)

[0159] Furthermore, convert the comprehensive equivalent impedance shown in Equation (6) to the form described in Equation (7). Among them, a k ( k = 0, 1, …, n ) represents the coefficients of each order s k ( k = 0, 1, …, n ) in the denominator of the impedance transfer function, and its highest order isn times; b k ( k = 0, 1, …, m ) are the coefficients of each order in the numerator of the impedance transfer function. s k ( k = 0, 1, …, m ) with the highest order being m times;. After equivalent transformation, c n , d n , e, h respectively represent the coefficients to be fitted. If h is 0 after fitting, the impedance expression is retained. If h is not equal to 0, it is converted to an admittance expression such that the denominator order is higher than the numerator.

[0160] (7)

[0161] For each term in Equation (7), equivalent RLC impedance branches are constructed as follows. Among them:

[0162] When d n is a real number, the first term is the real pole term " c n / ( s-d n )", which can be converted to an RC parallel branch as an impedance, as shown in Appendix Figure 6 and can be converted to an RL series branch as an admittance, as shown in Appendix Figure 7 .

[0163] When d n 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 / ( s-d n1 )]+ c n2 / ( s-d n2 )]", which can be converted to a mixed series - parallel branch mainly composed of RLC in parallel as an impedance, as shown in Appendix Figure 8 , and can be converted to a mixed series - parallel branch mainly composed of RLC in series as an admittance, as shown in Appendix Figure 9 .

[0164] In Equation (7), the second and third terms are constant and linear terms e + sh , which can be converted into an RL series branch as impedance, as shown in the appendix Figure 10 , and can be converted into an RC parallel branch as admittance, as shown in the appendix Figure 11 .

[0165] According to the transfer function form represented by Equation (7), based on the equivalent circuit conversion, the overall circuit structure reflected by Equation (7) can be constructed by using the series form of the actual impedance of RLC or the parallel form of admittance. Furthermore, the actual RLC impedance series-parallel structure can be adopted to realize the construction of the equivalent grid-connected impedance.

[0166] Please refer to Figure 13 . The embodiment of the present invention also provides a power grid simulation device with the ability to compensate for non-ideal grid-connected impedance, including:

[0167] An acquisition unit for obtaining the three-phase voltage waveforms at the power grid fault point to obtain the three-phase voltage reference values reflecting the fault voltage V fault ; the three-phase voltage reference values V fault are obtained based on on-site recorded wave data or electromagnetic transient simulation methods when a fault occurs in the power grid;

[0168] A fitting unit for obtaining the broadband impedance characteristics of the grid environment where the new energy device under test is connected to the power grid; the equivalent grid-connected impedance characteristics are obtained by fitting the power grid impedance characteristics with a low-order transfer function within a preset frequency band ;

[0169] A simulation correction unit for simulating non-ideal grid-connected impedance for the equivalent grid-connected impedance characteristics , and correcting the voltage output from the power grid to the new energy device under test based on the simulation results for the grid connection test of the new energy device under test.

[0170] Please refer to Figure 14 . The embodiment of the present invention also provides a power grid simulation device with the ability to compensate for non-ideal grid-connected impedance, including:

[0171] A power grid for providing three-phase power grid voltages;

[0172] A rectifier side subsystem for converting the three-phase power grid voltages into stable DC voltages V dc ;

[0173] An inverter side subsystem for inverting the DC voltage V dc into controlled three-phase grid-connected voltages;

[0174] The non-ideal grid connection impedance simulation unit is used to simulate the equivalent grid connection impedance characteristics by using the grid simulation method with the ability to compensate for non-ideal grid connection impedance to simulate the non-ideal grid connection impedance, control the inverter side subsystem based on the simulation results, and output the corrected three-phase grid connection voltage for the grid connection test of the new energy equipment under test; or, it is used to simulate the equivalent grid connection impedance characteristics by using the grid simulation method with the ability to compensate for non-ideal grid connection impedance through the series-parallel connection of equivalent RLC actual impedances to simulate the non-ideal grid connection impedance, correct the three-phase grid connection voltage output by the inverter side subsystem based on the simulation results, and obtain the corrected three-phase grid connection voltage for the grid connection test of the new energy equipment under test.

[0175] In a specific embodiment, the non-ideal grid connection impedance simulation unit includes a virtual impedance control unit, a medium-voltage RLC impedance network, and a circuit breaker K;

[0176] The virtual impedance control unit is used to simulate the non-ideal grid connection impedance by using the grid simulation method with the ability to compensate for non-ideal grid connection impedance to simulate the non-ideal grid connection impedance, control the inverter side subsystem based on the simulation results, and output the corrected three-phase grid connection voltage for the grid connection test of the new energy equipment under test;

[0177] The medium-voltage RLC impedance network is used to simulate the non-ideal grid connection impedance by using the series-parallel connection of equivalent RLC actual impedances to simulate the non-ideal grid connection impedance, correct the three-phase grid connection voltage output by the inverter side subsystem based on the simulation results, and obtain the corrected three-phase grid connection voltage for the grid connection test of the new energy equipment under test;

[0178] The output end of the inverter side subsystem is connected to the new energy equipment under test through the medium-voltage RLC impedance network; a circuit breaker K is connected in parallel on the medium-voltage RLC impedance network.

[0179] In a specific embodiment, when using the virtual impedance control unit to control the inverter side subsystem and output the corrected three-phase grid connection voltage for the grid connection test of the new energy equipment under test, close the circuit breaker K to bypass the medium-voltage RLC impedance network.

[0180] In a specific embodiment, when using the medium-voltage RLC impedance network to correct the three-phase grid connection voltage output by the inverter side subsystem and obtain the corrected three-phase grid connection voltage for the grid connection test of the new energy equipment under test, turn off the virtual impedance control unit and open the circuit breaker K.

[0181] In an embodiment of the present invention, a grid simulation device with the ability to compensate for non-ideal grid connection impedance, the rectifier side subsystem adopts DC voltage control, and its function is to convert the three-phase grid voltage into a stable DC voltageV dc The inverter-side subsystem is responsible for converting the DC voltage V dc into a controlled three-phase grid-connected voltage for the grid-connection test of the new energy equipment under test. For the grid-connected broadband impedance compensation of the grid simulation equipment, one of the following two methods can be used to achieve it:

[0182] (1) The inverter-side subsystem adopts the virtual impedance control as shown in the appendix Figure 5 to compensate the grid-connected broadband impedance by combining Equation (2) and Equation (3), and at the same time close the circuit breaker K , and bypass the medium-voltage RLC impedance network.

[0183] (2) The inverter subsystem commonly uses the conventional control method, that is, the virtual impedance voltage drop calculation link in the appendix Figure 5 is not enabled, and at the same time the circuit breaker K is disconnected, and the medium-voltage RLC impedance network is connected. In the medium-voltage RLC impedance network, the access impedance is set by combining Equation (7) and the appendix Figure 6-11 to construct an equivalent RLC impedance series-parallel structure to realize the grid impedance simulation.

[0184] Through the solution proposed by the present invention, the grid simulation device can compensate for the non-ideal grid-connection impedance of the new energy equipment under test, so that it can reflect the influence of factors such as the grid and the output current of the new energy equipment on the grid-connection point voltage under the influence of the grid-connection impedance, and more accurately simulate the harmonic, oscillation and other machine-grid interaction characteristics of the grid-connection point voltage of the new energy equipment under faults and disturbances.

[0185] Accordingly, by more realistically simulating the fault grid environment, the fault voltage crossing ability of the new energy equipment can be tested more effectively to better ensure the transient safety and stability of the wind turbine and its connection to the grid.

[0186] Please refer to Figure 15 as shown. An electronic device 100 for implementing a grid simulation method with non-ideal grid-connection impedance compensation ability is provided in an embodiment of the present invention; 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.

[0187] The memory 101 can be used to store the computer program 103. By running or executing the computer program stored in the memory 101 and calling the data stored in the memory 101, the processor 102 implements the steps of the grid simulation method with the ability to compensate for non-ideal grid connection impedance. The memory 101 may mainly include a program storage area and a data storage area. Among them, the program storage area can store an operating system, application programs required for at least one function (such as a sound playback function, an image playback function, etc.); the data storage area can store data created according to the use of the electronic device 100 (such as audio data, etc.). In addition, the memory 101 may include non-volatile memory, such as a hard disk, a memory, a plug-in hard disk, a Smart Media Card (SMC), a Secure Digital (SD) card, a Flash Card, at least one magnetic disk storage device, a flash memory device, or other non-volatile solid-state storage devices.

[0188] The at least one processor 102 may be a Central Processing Unit (CPU), or may also be other general-purpose processors, Digital Signal Processors (DSPs), Application Specific Integrated Circuits (ASICs), Field-Programmable Gate Arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The processor 102 may be a microprocessor or the processor 102 may also be any conventional processor, etc. The processor 102 is the control center of the electronic device 100, and connects various parts of the entire electronic device 100 through various interfaces and lines.

[0189] The memory 101 in the electronic device 100 stores multiple instructions to implement a grid simulation method with the ability to compensate for non-ideal grid connection impedance. The processor 102 can execute the multiple instructions to implement:

[0190] Obtain the three-phase voltage waveforms at the grid fault point to obtain the three-phase voltage reference values reflecting the fault voltage V fault ; The three-phase voltage reference values V fault When a grid fault occurs, it is obtained based on on-site recorded wave data or based on an electromagnetic transient simulation method;

[0191] Obtain the broadband impedance characteristics of the power grid environment where the new energy device under test is connected to the grid; within a preset frequency band, use a low-order transfer function to fit the power grid impedance characteristics to obtain the equivalent grid-connected impedance characteristics ;

[0192] For the equivalent grid-connected impedance characteristics Perform simulation of non-ideal grid-connected impedance, and based on the simulation results, correct the voltage output by the power grid to the new energy device under test for the grid-connected test of the new energy device under test.

[0193] If the modules / units integrated in the electronic device 100 are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, to implement all or part of the processes in the above method embodiments of the present invention, it can also be completed by a computer program instructing relevant hardware. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by a processor, the steps of the above method embodiments can be implemented. Among them, the computer program includes computer program code, and the computer program code can be in the form of source code, object code, executable file or some intermediate form, etc. The computer-readable medium can include: any entity or device that can carry the computer program code, recording medium, USB flash drive, mobile hard disk, magnetic disk, optical disc, computer memory and read-only memory (ROM, Read-Only Memory).

[0194] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, system, or computer program product. Therefore, the present invention can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can 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.) that contain computer-usable program code.

[0195] The present invention is described with reference to the 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 can be implemented by computer program instructions, and the combination of the processes and / or blocks in the flowchart and / or block diagram can also be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate a device for implementing the specified functions in Figure 1 one process or multiple processes and / or blocks Figure 1 one block or multiple blocks.

[0196] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to operate in a particular manner, such that the instructions stored in the computer-readable memory produce a manufacture including an instruction device that implements the functions specified in one or more of the processes Figure 1 or sub-processes and / or boxes Figure 1 or boxes specified in one or more of the boxes.

[0197] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus, such that a series of operational steps are performed on the computer or other programmable apparatus to produce a computer-implemented process, whereby the instructions executed on the computer or other programmable apparatus provide steps for implementing the functions specified in one or more of the processes Figure 1 or sub-processes and / or boxes Figure 1 or boxes specified in one or more of the boxes.

[0198] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: it is still possible to modify the specific embodiments of the present invention or make equivalent substitutions, and any modification or equivalent substitution that does not depart from the spirit and scope of the present invention shall be covered by the protection scope of the claims of the present invention.

Claims

1. A power grid simulation method with non-ideal grid connection impedance compensation ability, characterized in that, Comprising: Obtain the three-phase voltage waveforms at the power grid fault point to obtain the three-phase voltage reference values reflecting the fault voltage V fault ; The three-phase voltage reference values V fault are obtained based on on-site oscillographic data or an electromagnetic transient simulation method when a fault occurs in the power grid; Obtaining the broadband impedance characteristics of the power grid environment accessed by the new energy device under test; Obtain the equivalent grid connection impedance characteristics by fitting the grid impedance characteristics with a low-order transfer function within a preset frequency band ; For the characteristics of equivalent grid-connected impedance Simulate the non-ideal grid-connected impedance, and based on the simulation results, correct the voltage output by the power grid to the tested new energy device for the grid-connection test of the tested new energy device; The step of obtaining the equivalent grid connection impedance characteristics by fitting the grid impedance characteristics with a low-order transfer function within a preset frequency band specifically includes: According to the preset frequency band range f min , f max and the fitting order N , perform iteration using the least squares method, and use a low-order rational transfer function of order N to simulate the second-order impedance characteristics of the power grid within the frequency band range f min , f max , and obtain the equivalent grid-connected impedance characteristics Z dq ( s ), and obtain the equivalent grid-connected impedance characteristics : (3) Among them, f dd ( s )、 f dq ( s )、 f qd ( s )、 f qq ( s ) respectively represent dq the equivalent impedance elements obtained by low-order fitting in the axis coordinate system, and the forms are all N sub-rational transfer functions; f min , f max are respectively the minimum and maximum values of the preset frequency band range; The step of simulating the non-ideal grid-connected impedance for the equivalent grid-connected impedance characteristics and correcting the voltage output from the power grid to the new energy device under test based on the simulation results specifically includes: Based on the three-phase voltage reference value V fault and the equivalent grid-connected impedance characteristics Calculate the d axis and q axis voltage control reference values obtained through virtual impedance control V d,ref * and V q,ref * : (4) (5) Among them, (1) Among them, V fault is the three-phase voltage reference value reflecting the fault voltage; V a,ref , V b,ref , V c,ref are respectively the a phase, b phase and c phase voltage reference values reflecting the fault voltage; V d,ref and V q,ref are respectively the V a,ref , V b,ref , V c,ref axis voltage reference values obtained through Park transformation, d axis and q axis voltage reference values, I d and I q are respectively the abc axis and I a 、I b 、I c axis current values obtained through Park transformation of the three-phase grid currents in the d axis and q axis in the Based on d axis and q axis voltage control reference value V d,ref * and V q,ref * perform voltage and current double-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 from the power grid to the new energy device under test.

2. The power grid simulation method with non-ideal grid connection impedance compensation ability according to claim 1, characterized in that The steps of obtaining the broadband impedance characteristics of the power grid environment accessed by the new energy device under test specifically include: By using methods such as broadband impedance measurement, simulated impedance scanning, or modeling analysis, the second-order impedance characteristics of the power grid environment in the broadband frequency range are obtained. Z dq ( s ): (2) Among them, Z dd ( s )、 Z dq ( s )、 Z qd ( s )、 Z qq ( s ) respectively 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 connection impedance compensation ability according to claim 1, characterized in that, The equivalent grid-connected impedance characteristics are used to simulate the non-ideal grid-connected impedance, specifically including: Adopt equivalent RLC actual impedance series and parallel pairs to characterize the equivalent grid-connected impedance Simulate the non-ideal grid-connected impedance 4. A power grid simulation device with the ability to compensate for non-ideal grid connection impedance, characterized in that, Comprising: The acquisition unit is used to obtain the three-phase voltage waveforms of the grid fault point and obtain the three-phase voltage reference values reflecting the fault voltage V fault ; The three-phase voltage reference values V fault are obtained based on on-site recorded wave data or an electromagnetic transient simulation method when a grid fault occurs; A fitting unit for obtaining the broadband impedance characteristics of the power grid environment accessed by the new energy device under test; Obtain the equivalent grid connection impedance characteristics by fitting the grid impedance characteristics with a low-order transfer function within a preset frequency band ; The simulation correction unit is used to simulate the equivalent grid-connected impedance characteristics to simulate the non-ideal grid-connected impedance, and correct the voltage output from the grid to the tested new energy device based on the simulation results for the grid connection test of the tested new energy device; The step of obtaining the equivalent grid connection impedance characteristics by fitting the grid impedance characteristics with a low-order transfer function within a preset frequency band specifically includes: According to the preset frequency band range f min , f max and the fitting order N , perform iteration using the least squares method, and use a low-order rational transfer function of order N to simulate the second-order impedance characteristics of the power grid within the frequency band range f min , f max , and obtain the equivalent grid-connected impedance characteristics Z dq ( s ), as follows : (3) Among them, f dd ( s )、 f dq ( s )、 f qd ( s )、 f qq ( s ) respectively represent dq the equivalent impedance elements obtained by low-order fitting in the shaft coordinate system, and the forms are all N sub-rational transfer functions; f min , f max are respectively the minimum and maximum values of the preset frequency band range; The equivalent grid-connected impedance characteristics Performing simulation of non-ideal grid-connected impedance and correcting the voltage output from the grid to the new energy device under test based on the simulation results, specifically including: Based on the three-phase voltage reference value V fault and the equivalent grid-connected impedance characteristics Calculate the d axis and q axis voltage control reference value obtained through virtual impedance control V d,ref * and V q,ref * : (4) (5) Among them, (1) Among them, V fault is the three-phase voltage reference value reflecting the fault voltage; V a,ref , V b,ref , V c,ref are respectively the a phase, b phase and c phase voltage reference values reflecting the fault voltage; V d,ref and V q,ref are respectively the V a,ref , V b,ref , V c,ref axis and d axis voltage reference values obtained through Park transformation, q I d I q and abc are respectively the I axis and 、I a 、I b d c axis current values obtained through Park transformation of the three-phase grid currents in the q coordinate system;​​ Based on d axis and q axis voltage control reference value V d,ref * and V q,ref * perform voltage and current double-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 from the power grid to the new energy equipment under test.

5. The power grid simulation device with non-ideal grid connection impedance compensation ability according to claim 4, characterized in that, The steps of obtaining the broadband impedance characteristics of the power grid environment accessed by the new energy device under test specifically include: By using methods such as broadband impedance measurement, simulation impedance scanning, or modeling analysis, the second-order impedance characteristics of the power grid environment in the broadband frequency range are obtained. Z dq ( s ): (2) Among them, Z dd ( s )、 Z dq ( s )、 Z qd ( s )、 Z qq ( s ) respectively represent dq the broadband impedance characteristic elements of the power grid in the axis coordinate system.

6. The power grid simulation device with the ability to compensate for non-ideal grid connection impedance according to claim 4, characterized in that, The equivalent grid-connected impedance characteristics simulate the non-ideal grid-connected impedance, specifically including: Using equivalent RLC actual impedance series and parallel pairs to characterize the equivalent grid-connected impedance Simulate the non-ideal grid-connected impedance.

7. A power grid simulation device with non-ideal grid connection impedance compensation ability, characterized in that Comprising: A power grid for providing a three-phase power grid voltage; Rectifier side subsystem, used to convert three-phase grid voltage into a stable DC voltage V dc ; The inverter side subsystem is used to invert the DC voltage V dc into a controlled three-phase grid-connected voltage; Non-ideal grid-connected impedance simulation unit, which is used to simulate the equivalent grid-connected impedance characteristics by using the grid simulation method with non-ideal grid-connected impedance compensation ability described in any one of claims 1 to 2 to simulate the 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 the grid connection test of the new energy equipment under test; or, it is used to simulate the equivalent grid-connected impedance characteristics by using the grid simulation method with non-ideal grid-connected impedance compensation ability described in claim 3 through the series-parallel connection of the equivalent RLC actual impedance to simulate the non-ideal grid-connected impedance, correct the three-phase grid-connected voltage output by the inverter-side subsystem based on the simulation results, and obtain the corrected three-phase grid-connected voltage for the grid connection test of the new energy equipment under test.

8. The power grid simulation device with the ability to compensate for non-ideal grid connection impedance according to claim 7, characterized in that, The non-ideal grid connection 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 configured to simulate the non-ideal grid-connected impedance based on the equivalent grid-connected impedance characteristics by using the grid simulation method with the non-ideal grid-connected impedance compensation ability according to any one of claims 1 to 2, and control the inverter-side subsystem based on the simulation results to output corrected three-phase grid-connected voltages for the grid connection test of the new energy device under test; Based on the simulation results, the control of the inverter-side subsystem is carried out to output corrected three-phase grid-connected voltages for the grid connection test of the new energy device under test; The medium-voltage RLC impedance network is used to simulate the characteristics of the equivalent grid-connected impedance by using the series and parallel connections of the actual RLC impedances, and to correct the three-phase grid-connected voltages output by the inverter-side subsystem based on the simulation results to obtain the corrected three-phase grid-connected voltages for the grid connection test of the new energy equipment under test; carry out the simulation of the non-ideal grid-connected impedance, and correct the three-phase grid-connected voltages output by the inverter-side subsystem based on the simulation results to obtain the corrected three-phase grid-connected voltages for the grid connection test of the new energy equipment under test; The output end of the inverter-side subsystem is connected to the new energy device under test through the medium-voltage RLC impedance network; a circuit breaker K is connected in parallel on the medium-voltage RLC impedance network.

9. The power grid simulation device with the ability to compensate for non-ideal grid connection impedance according to claim 8, characterized in that, When using the virtual impedance control unit to control the inverter-side subsystem to output a corrected three-phase grid connection voltage for the grid connection test of the new energy device under test, close the circuit breaker K to bypass the medium-voltage RLC impedance network.

10. A power grid simulation device with non-ideal grid connection impedance compensation ability according to claim 8, characterized in that, When using the medium-voltage RLC impedance network to correct the three-phase grid connection voltage output by the inverter-side subsystem to obtain a corrected three-phase grid connection voltage for the grid connection test of the new energy device under test, turn off the virtual impedance control unit and disconnect the circuit breaker K.

11. An electronic device, characterized in that, Comprising a processor and a memory, the processor is used to execute the computer program stored in the memory to implement a power grid simulation method with non-ideal grid connection impedance compensation ability as described in any one of claims 1 to 3.

12. 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 a power grid simulation method with non-ideal grid connection impedance compensation ability as described in any one of claims 1 to 3.

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