A grid-type converter inertia response test device and its testing and evaluation method

Abstract

The present invention discloses a grid-connected converter inertia response testing device and its testing and evaluation method. The device comprises a synchronous motor (SG) and its grid-connected switch (S1), two transformers, a controllable simulated grid, and a data acquisition device. The controllable simulated grid simulates grid frequency changes for inertia testing. The synchronous motor (SG) and a grid-connected converter (GFC) with battery energy storage are each connected to a transformer and then to their respective grid-connected switches. The grid-connected switches (S1 and S2) are then connected in parallel to the controllable simulated grid. The data acquisition device is connected via signal lines to voltage signal acquisition points on the synchronous motor (SG) and the grid-connected converter (GFC) with battery energy storage, respectively, to collect instantaneous three-phase voltages on the synchronous motor (SG) and the grid-connected converter (GFC) with battery energy storage. The device is easy to operate, improves testing efficiency, shortens testing time, and reduces costs. The method defines the control performance indicators of the grid-connected converter's inertia response.

Description

Technical Field

[0001] The present invention relates to the technical field of grid-type converter testing, and in particular to a grid-type converter inertia response testing device and a testing and evaluation method thereof. Background Art

[0002] With the development of renewable energy generation, the proportion of power electronic equipment in the power grid has gradually increased, and the overall power grid is showing trends such as reduced inertia and weakening strength. To ensure the stable and safe operation of the power grid, power electronic converters need to fulfill or even replace the functions and roles of traditional synchronous motors. Grid-connected converters have emerged as a mainstream development trend. However, there is no consensus on the dynamic characteristics of grid-connected converters, especially the precise definition and standardization of inertia response. Therefore, a set of standardized test methods is needed to define their control performance indicators and evaluate their dynamic stability against inertia response suppression characteristics. Summary of the Invention

[0003] The first purpose of the present invention is to overcome the shortcomings and deficiencies of the prior art and provide a grid-type converter inertia response test device, which has a simple and reliable structure, is easy to operate, can improve test efficiency, shorten test time and reduce costs.

[0004] A second object of the present invention is to provide a testing method for a grid-type converter inertia response testing device.

[0005] A third object of the present invention is to provide an evaluation method for a grid-type converter inertia response testing device.

[0006] The first objective of the present invention is achieved by the following technical solution: a device for testing the inertia response of a grid-connected converter, wherein the grid-connected converter has battery energy storage and is equipped with a grid-connected switch S2 for controlling its connection to or disconnection from the grid; the device includes a synchronous generator SG and its grid-connected switch S1, two transformers, a controllable simulated grid, and a data acquisition device;

[0007] For synchronous motors (SG), when the grid frequency decreases at a constant rate, they experience near-constant inertia power during steady-state periods. At this point, the inertia response of the synchronous motor (SG) can be compared with the inertia response of a grid-connected converter (GFC) with battery energy storage. This allows the error in the GFC inertia response test to be determined. The grid-connected switch (S1) is used to control the synchronous motor's connection to or disconnection from the grid.

[0008] The controllable simulated power grid is used to simulate power grid frequency changes and perform inertia testing;

[0009] The data acquisition device is used to collect the instantaneous value of the three-phase voltage (vSG,a 、v SG,b 、v SG,c )、(v GFC,a 、v GFC,b 、v GFC,c );

[0010] The synchronous motor SG and the grid-connected converter GFC with battery energy storage are respectively connected to a transformer and then connected to their respective corresponding grid-connected switches. The grid-connected switches S1 and S2 are then connected in parallel to a controllable simulated power grid. The data acquisition device is respectively connected to the voltage signal collection points on the synchronous motor SG and the grid-connected converter GFC with battery energy storage through signal lines.

[0011] Preferably, the sampling frequency of the data acquisition device is not less than 10 kHz.

[0012] The second object of the present invention is achieved by the following technical solution: a testing method for a grid-type converter inertia response testing device, comprising the following steps:

[0013] 1) Close the grid-connected switch S1, connect the synchronous motor SG to the grid, start the synchronous motor SG, and run it at rated power;

[0014] 2) Turn on the data acquisition device and record the data;

[0015] 3) At a certain moment, record the moment as t step1 , and adjust the frequency of the controllable simulated power grid to a specific frequency for a preset time;

[0016] 4) Disconnect the grid-connected switch S1;

[0017] 5) Close the grid-connected switch S2 to connect the GFC with battery energy storage to the grid. Gradually increase the power of the GFC in specific steps until the rated power of the GFC is reached and stable operation is achieved.

[0018] 6) At a certain moment, record the moment as t step2 , and adjust the frequency of the controllable simulated power grid to a specific frequency for a preset time;

[0019] 7) Disconnect the grid-connected switch S2;

[0020] 8) Stop the data acquisition device and perform data analysis.

[0021] Preferably, the specific frequency is 0.2 Hz / s, that is, 0.004 pu / s.

[0022] Preferably, the specific step length is 0.25S N , where S Nis the rated apparent power of the grid-type converter GFC.

[0023] The third object of the present invention is achieved by the following technical solution: a method for evaluating an inertia response test device for a grid-type converter, specifically performing the following operations:

[0024] According to the instantaneous values of the three-phase voltages (v SG,a 、v SG,b 、v SG,c )、(v GFC,a 、v GFC,b 、v GFC,c ), perform Fourier transform, and the calculation method is as follows:

[0025]

[0026]

[0027] Where: f1 is the fundamental frequency; v i,cos is the cosine component of the fundamental voltage of one phase in the three-phase; v i,sin is the fundamental sinusoidal component of the voltage of one phase in the three-phase; v i (t) is the instantaneous value of the voltage of one of the three phases; i = a, b, c; t is the actual time series; T is the fundamental wave period;

[0028] The fundamental positive sequence voltage component is calculated using the following formula:

[0029]

[0030]

[0031] Where: v 1+,cos is the cosine component of the fundamental positive sequence voltage; v 1+,sin is the sinusoidal component of the fundamental positive sequence voltage; the active power P of the fundamental positive sequence voltage component 1+ for:

[0032]

[0033] ΔP SG =P SG2 -P SG1

[0034] ΔP GFC =P GFC2 -P GFC1

[0035] Where: P SG2 is the active power after the frequency changes when the synchronous motor SG is connected to the grid, P SG1is the active power before the frequency changes when the synchronous motor SG is connected to the grid, ΔP SG P is the active power increment before and after the frequency changes when the synchronous motor SG is connected to the grid; GFC2 is the active power after frequency change when the grid-connected converter GFC with battery energy storage is connected to the grid, P GFC1 is the active power before frequency change when the grid-connected converter GFC with battery energy storage is connected to the grid, ΔP GFC It is the active power increment before and after the frequency change when the GFC with battery energy storage is connected to the grid;

[0036] The inertia constant is calculated according to the following equation:

[0037]

[0038]

[0039] Where: H SG is the inertia constant of the synchronous motor SG, H GFC is the inertia constant of the grid-connected converter GFC with battery energy storage, S rating is the rated apparent power, f0 is the frequency before the change, and RoCoF is the rate of change of frequency.

[0040] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0041] 1. The present invention addresses the dynamic characteristics of grid-type converters, particularly the current lack of consensus on the precise definition and standardization of inertia response. This invention proposes a simple testing device and test logic to clarify the control performance indicators of the grid-type converter for inertia response, thereby evaluating the dynamic stability of its inertia response suppression characteristics. This will contribute to the rapid development of grid-type converters, while also enhancing the grid-friendliness of renewable energy power generation based on power electronic equipment and strengthening the stability of the grid system.

[0042] 2. The device of the present invention has a simple and reliable structure, is easy to operate and implement, can improve test efficiency and save a lot of test time and cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 Schematic diagram of the device of the present invention.

[0044] Figure 2 4 is a test flow chart of the device of the present invention. DETAILED DESCRIPTION

[0045] The present invention will be described in further detail below with reference to the embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0046] like Figure 1 As shown, this embodiment provides an inertia response test device for a grid-connected converter. The grid-connected converter has battery energy storage and is equipped with a grid-connected switch S2 for controlling its access to or from the grid. The device includes a synchronous generator SG and its grid-connected switch S1, two transformers, a controllable simulated grid, and a data acquisition device.

[0047] For synchronous motors (SG), when the grid frequency decreases at a constant rate, they experience near-constant inertia power during steady-state conditions. Therefore, the inertia response of the synchronous motor (SG) can be compared with the inertia response of a GFC with battery energy storage. This can reveal the error in the GFC's inertia response test. The grid-connected switch (S1) controls the synchronous motor's connection to or disconnection from the grid.

[0048] The controllable simulated power grid is used to simulate power grid frequency changes and perform inertia testing;

[0049] The data acquisition device is used to collect the instantaneous value of the three-phase voltage (v SG,a 、v SG,b 、v SG,c )、(v GFC,a 、v GFC,b 、v GFC,c );

[0050] The synchronous motor SG and the grid-connected converter GFC with battery energy storage are respectively connected to a transformer and then connected to their respective corresponding grid-connected switches. The grid-connected switches S1 and S2 are then connected in parallel to a controllable simulated power grid. The data acquisition device is respectively connected to the voltage signal collection points on the synchronous motor SG and the grid-connected converter GFC with battery energy storage through signal lines.

[0051] Preferably, the sampling frequency of the data acquisition device is not less than 10 kHz.

[0052] like Figure 2 As shown, this embodiment also provides a testing method for the above-mentioned grid-type converter inertia response testing device, comprising the following steps:

[0053] 1) Close the grid-connected switch S1, connect the synchronous motor SG to the grid, start the synchronous motor SG, and run it at rated power;

[0054] 2) Turn on the data acquisition device and record the data;

[0055] 3) At a certain moment (record this moment as t step1 ) Adjust the frequency of the controllable simulated power grid to 0.2 Hz / s (i.e. 0.004 pu / s) for 5 seconds;

[0056] 4) Disconnect the grid-connected switch S1;

[0057] 5) Close the grid-connected switch S2 and connect the grid-connected converter GFC with battery energy storage to the grid. N The step size of (rated apparent power of the grid-type converter GFC) gradually increases the power of the grid-type converter until the rated power of the grid-type converter GFC is reached and stable operation is possible;

[0058] 6) At a certain moment (record this moment as t step2 ) Adjust the frequency of the controllable simulated power grid to 0.2 Hz / s (i.e. 0.004 pu / s) for 5 seconds;

[0059] 7) Disconnect the grid-connected switch S2;

[0060] 8) Stop the data acquisition device and perform data analysis.

[0061] This embodiment also provides an evaluation method for the inertia response test device of the grid-type converter, which specifically performs the following operations:

[0062] According to the instantaneous values of the three-phase voltages (v SG,a 、v SG,b 、v SG,c )、(v GFC,a 、v GFC,b 、v GFC,c ), perform Fourier transform, and the calculation method is as follows:

[0063]

[0064]

[0065] Where: f1 is the fundamental frequency; v i,cos is the cosine component of the fundamental voltage of one phase in the three-phase; v i,sin is the fundamental sinusoidal component of the voltage of one phase in the three-phase; v i (t) is the instantaneous value of the voltage of one of the three phases; i = a, b, c; t is the actual time series; T is the fundamental wave period;

[0066] The fundamental positive sequence voltage component is calculated using the following formula:

[0067]

[0068]

[0069] Where: v 1+,cos is the cosine component of the fundamental positive sequence voltage; v 1+,sinis the sinusoidal component of the fundamental positive sequence voltage;

[0070] Active power P of fundamental positive sequence voltage component 1+ for:

[0071]

[0072] ΔP SG =P SG2 -P SG1

[0073] ΔP GFC =P GFC2 -P GFC1

[0074] Where: P SG2 is the active power after the frequency changes when the synchronous motor SG is connected to the grid, P SG1 is the active power before the frequency changes when the synchronous motor SG is connected to the grid, ΔP SG P is the active power increment before and after the frequency changes when the synchronous motor SG is connected to the grid; GFC2 is the active power after frequency change when the grid-connected converter GFC with battery energy storage is connected to the grid, P GFC1 is the active power before frequency change when the grid-connected converter GFC with battery energy storage is connected to the grid, ΔP GFC It is the active power increment before and after the frequency change when the GFC with battery energy storage is connected to the grid;

[0075] The inertia constant is calculated according to the following equation:

[0076]

[0077]

[0078] Where: H SG is the inertia constant of the synchronous motor SG, H GFC is the inertia constant of the grid-connected converter GFC with battery energy storage, S rating is the rated apparent power, f0 is the frequency before the change, and RoCoF is the rate of change of frequency.

[0079] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A grid-type converter inertia response test device, characterized by: The grid-connected converter is equipped with battery energy storage and a grid-connected switch S2 for controlling its access to or from the grid. The device includes a synchronous generator SG and its grid-connected switch S1, two transformers, a controllable simulated grid, and a data acquisition device. For synchronous motors (SG), when the grid frequency decreases at a constant rate, they experience near-constant inertia power during steady-state periods. At this point, the inertia response of the synchronous motor (SG) can be compared with the inertia response of a grid-connected converter (GFC) with battery energy storage. This allows the error in the GFC inertia response test to be determined. The grid-connected switch (S1) is used to control the synchronous motor's connection to or disconnection from the grid. The controllable simulated power grid is used to simulate power grid frequency changes and perform inertia testing; The data acquisition device is used to collect the instantaneous value of the three-phase voltage (v SG,a 、v SG,b 、v SG,c )、(v GFC,a 、v GFC,b 、v GFC,c ); The synchronous motor SG and the grid-connected converter GFC with battery energy storage are respectively connected to a transformer and then connected to their respective corresponding grid-connected switches. The grid-connected switches S1 and S2 are then connected in parallel to a controllable simulated power grid. The data acquisition device is respectively connected to the voltage signal collection points on the synchronous motor SG and the grid-connected converter GFC with battery energy storage through signal lines.

2. The inertia response test device for a grid-type converter according to claim 1, characterized in that: The sampling frequency of the data acquisition device is not less than 10 kHz.

3. The test method of the grid-type converter inertia response test device according to claim 1 or 2, characterized in that: The following steps are involved: 1) Close the grid-connected switch S1, connect the synchronous motor SG to the grid, start the synchronous motor SG, and run it at rated power; 2) Turn on the data acquisition device and record the data; 3) At a certain moment, record the moment as t step1 , and adjust the frequency of the controllable simulated power grid to a specific frequency for a preset time; 4) Disconnect the grid-connected switch S1; 5) Close the grid-connected switch S2 to connect the GFC with battery energy storage to the grid. Gradually increase the power of the GFC in specific steps until the rated power of the GFC is reached and stable operation is achieved. 6) At a certain moment, record the moment as t step2 , and adjust the frequency of the controllable simulated power grid to a specific frequency for a preset time; 7) Disconnect the grid-connected switch S2; 8) Stop the data acquisition device and perform data analysis.

4. The test method of the inertia response test device of the grid-type converter according to claim 3, characterized in that: The specific frequency is 0.2 Hz / s, that is, 0.004 pu / s.

5. The test method of the inertia response test device of the grid-type converter according to claim 3, characterized in that: The specific step length is 0.25S N , where S N is the rated apparent power of the grid-type converter GFC.

6. The evaluation method of the grid-type converter inertia response test device according to claim 1 or 2, characterized in that: Specifically, do the following: According to the instantaneous values of the three-phase voltages (v SG,a 、v SG,b 、v SG,c )、(v GFC,a 、v GFC,b 、v GFC,c ), perform Fourier transform, and the calculation method is as follows: Where: f1 is the fundamental frequency; v i,cos is the cosine component of the fundamental voltage of one phase in the three-phase; v i,sin is the fundamental sinusoidal component of the voltage of one phase in the three-phase; v i (t) is the instantaneous value of the voltage of one of the three phases; i = a, b, c; t is the actual time series; T is the fundamental wave period; The fundamental positive sequence voltage component is calculated using the following formula: Where: v 1+,cos is the cosine component of the fundamental positive sequence voltage; v 1+,sin is the sinusoidal component of the fundamental positive sequence voltage; Active power P of fundamental positive sequence voltage component 1+ for: ΔP SG =P SG2 -P SG1 ΔP GFC =P GFC2 -P GFC1 Where: P SG2 is the active power after the frequency changes when the synchronous motor SG is connected to the grid, P SG1 is the active power before the frequency changes when the synchronous motor SG is connected to the grid, ΔP SG P is the active power increment before and after the frequency changes when the synchronous motor SG is connected to the grid; GFC2 is the active power after frequency change when the grid-connected converter GFC with battery energy storage is connected to the grid, P GFC1 is the active power before frequency change when the grid-connected converter GFC with battery energy storage is connected to the grid, ΔP GFC It is the active power increment before and after the frequency change when the GFC with battery energy storage is connected to the grid; The inertia constant is calculated according to the following equation: Where: H SG is the inertia constant of the synchronous motor SG, H GFC is the inertia constant of the grid-connected converter GFC with battery energy storage, S rating is the rated apparent power, f0 is the frequency before the change, and RoCoF is the rate of change of frequency.

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