Grid-type converter voltage source characteristic test device and test and evaluation method thereof

Abstract

The present invention discloses a grid-type converter voltage source characteristic test device and a test and evaluation method thereof, comprising: a variable power frequency load Load and a control switch S load The variable frequency load Load is used to simulate loads with different characteristics. Its control switch S load Used to control the variable frequency load Load to be connected to or off the grid; simulate the grid and its control switch S Grid The simulated grid is used to provide a stable voltage for the variable frequency load Load and simulate a fault. Its control switch S Grid Used to control the state of the simulated power grid; data acquisition device, used to collect the instantaneous value of the three-phase voltage on the GFC side of the grid-forming converter (v GFC,a 、v GFC,b 、v GFC,c The present invention can verify the control performance and the ability to ensure stable operation of the system according to the voltage source characteristics of the grid-type converter, and clarify the control performance index of the voltage source characteristics of the grid-type converter. The device has a simple and reliable structure and is easy to operate, which can save a lot of testing time and cost.

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 voltage source characteristic testing device and a testing and evaluation method thereof, which are suitable for wind turbine generator sets connected to the grid using full-power converters. 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 has shown a trend of reduced inertia and weakened strength. In order to ensure the stability and safe operation of the power grid, power electronic converters need to realize or even replace the functions and roles of traditional synchronous motors. Grid-type converters have emerged and gradually become the mainstream development trend. However, there is no consensus on the dynamic characteristics of grid-type converters, especially the accurate definition and standardization of voltage source characteristics. Therefore, a set of standardized test methods is needed to define its control performance indicators to evaluate the dynamic stability of its voltage source 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 to provide a grid-type converter voltage source characteristic testing device, which can verify the control performance and the ability to ensure stable operation of the system based on the voltage source characteristics of the grid-type converter. The device has a simple and reliable structure, is easy to operate, and can save a lot of testing time and cost.

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

[0005] The third object of the present invention is to provide an evaluation method for a grid-type converter voltage source characteristic testing device.

[0006] The first object of the present invention is achieved by the following technical solution: a grid-type converter voltage source characteristic testing device, comprising:

[0007] Variable power frequency load Load and its control switch S load The variable frequency load Load is used to simulate loads with different characteristics. Its control switch S load Used to control variable frequency load Load to be connected to or off the grid;

[0008] Simulated power grid Grid and its control switch S Grid The simulated grid is used to provide a stable voltage for the variable frequency load Load and simulate a fault. Its control switch S Grid Used to control the state of the simulated power grid;

[0009] Data acquisition device, used to collect the instantaneous value of three-phase voltage on the GFC side of the grid-connected converter (v GFC,a 、vGFC,b 、v GFC,c );

[0010] The grid-connected converter GFC is equipped with a grid-connected switch S for controlling its own grid-connected / off-grid state. GFC The grid-type converter GFC and the variable power frequency load are connected in parallel through cables and then in series with the simulated power grid Grid through cables. Due to its voltage source characteristics, the grid-type converter GFC can provide voltage support for the variable power frequency load Load when a power grid fails. The data acquisition device is connected to the signal acquisition point on the grid-type converter GFC side through a signal line.

[0011] Preferably, the characteristic load simulated by the variable power frequency load Load is one of a pure resistive load, an inductive load, a capacitive load, or a combination of any two or three of them.

[0012] Preferably, the capacity of the variable power frequency load Load is 0.25, 0.5, 0.75 or 1 times the rated capacity of the grid-type converter GFC.

[0013] Preferably, the sampling frequency of the data acquisition device is not less than 4 kHz.

[0014] The second object of the present invention is achieved by the following technical solution: A test method for a grid-type converter voltage source characteristic test device comprises the following steps:

[0015] 1) Set the characteristics and capacity of the variable power frequency load;

[0016] 2) Close S in sequence Grid , S load , S GFC , connect the variable frequency load Load and the grid-forming converter GFC to the simulated grid;

[0017] 3) Turn on the data acquisition device and record the data;

[0018] 4) Gradually increase the power set point P of the grid-connected converter GFC with a specific step size GFC,set , until the power set point P GFC,set The rated power of the grid-connected converter GFC is reached, and the grid-connected converter GFC is at the rated power set point P n Stable operation, at this time, disconnect the grid control switch S Grid , and record this time as t step ;

[0019] 5) Set the power set point P of the grid-connected converter GFC GFC,set = 0, after the grid-type converter GFC stops running completely, stop the data acquisition device, disconnect Sload , S GFC ;

[0020] 6) Data analysis;

[0021] 7) Determine whether all the characteristics and capacity combinations of the variable power frequency load simulation have been tested; if completed, end the test; if not, repeat steps 1)-6).

[0022] Preferably, in step 4), the specific step length is 0.25S N , where S N is the rated apparent power of the grid-connected converter GFC.

[0023] The third object of the present invention is achieved by the following technical solution: an evaluation method for a grid-type converter voltage source characteristic test device, the method is used to determine the characteristic parameter of the grid-type converter voltage source characteristic, that is, the voltage response time t VR , which is defined as the time t when the effective value of the fundamental positive sequence voltage last enters the error band of the new operating point set With t step The difference between set With t step If the difference between t and t is within the threshold, it can be determined that the voltage source characteristics of the grid-connected converter meet the requirements; where t step is the power set point P of the grid converter GFC GFC,set The rated power of the grid-connected converter GFC is reached, and the grid-connected converter GFC is at the rated power set point P n After stable operation, disconnect the grid control switch S Grid moment.

[0024] Preferably, the evaluation method of the grid-type converter voltage source characteristic test device comprises the following steps: first, according to the instantaneous value of the three-phase phase voltage (v GFC ,a、v GFC ,b、v GFC ,c), perform Fourier transform on it and the calculation method is as follows;

[0025] Calculate the Fourier coefficients of the fundamental component within one fundamental period:

[0026]

[0027]

[0028] Where: f1 is the fundamental frequency; v j,cos is the cosine component of the fundamental voltage of one phase in the three-phase; v j,sin is the sinusoidal component of the fundamental voltage of one phase in the three-phase; v GFC，jis the instantaneous value of the voltage of one phase in the three-phase system; j = a, b, c; t is the actual time series; T is the fundamental wave period;

[0029] Calculate the fundamental positive sequence voltage component as follows:

[0030]

[0031]

[0032] 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;

[0033] Then, according to v 1+,cos and v 1+,sin , and combined with Calculate the fundamental positive sequence voltage effective value V pos , according to V pos At the steady-state value of the new operating point, draw its error band and judge t set The value of set After the determination, the positive sequence voltage value should be within the error band at this moment. VR =t set -t step Calculate t VR The value of .

[0034] Preferably, the error of the error band is ±5%.

[0035] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0036] 1. The present invention can effectively target the voltage source characteristics of the grid-type converter, verify its control performance and the ability to ensure stable operation of the system, and clarify the control performance indicators of the voltage source characteristics of the grid-type converter.

[0037] 2. The device has a simple and reliable structure and is easy to operate, which can save a lot of testing time and cost.

[0038] 3. The present invention provides a systematic approach for testing and evaluating grid-type converters, which is conducive to the rapid development of grid-type converters and even grid-type new energy power generation technologies. At the same time, it can enhance the grid-friendliness of new energy power generation based on power electronic equipment and strengthen the stability of the grid system. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 Schematic diagram of the device of the present invention.

[0040] Figure 2 It is a test flow chart of the device of the present invention.

[0041] Figure 3 Schematic diagram for determining the response time of the voltage source characteristic of a grid-connected converter. DETAILED DESCRIPTION

[0042] The present invention is further described in detail below in conjunction with embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0043] like Figure 1 As shown, this embodiment provides a grid-type converter voltage source characteristic testing device, including:

[0044] Variable power frequency load Load and its control switch S load The variable frequency load Load is used to simulate loads with different characteristics. Its control switch S load Used to control variable frequency load Load to be connected to or off the grid;

[0045] Simulated power grid Grid and its control switch S Grid The simulated grid is used to provide a stable voltage for the variable frequency load Load and simulate a fault. Its control switch S Grid Used to control the state of the simulated power grid;

[0046] Data acquisition device, used to collect the instantaneous value of three-phase voltage on the GFC side of the grid-connected converter (v GFC,a 、v GFC,b 、v GFC,c );

[0047] The grid-connected converter GFC is equipped with a grid-connected switch S for controlling its own grid-connected / off-grid state. GFC The grid-type converter GFC and the variable power frequency load are connected in parallel through cables and then in series with the simulated power grid Grid through cables. Due to its voltage source characteristics, the grid-type converter GFC can provide voltage support for the variable power frequency load Load when a power grid fails. The data acquisition device is connected to the signal acquisition point on the grid-type converter GFC side through a signal line.

[0048] Preferably, the characteristic load simulated by the variable power frequency load Load is one of a pure resistive load, an inductive load, a capacitive load, or a combination of any two or three of them.

[0049] Preferably, the capacity of the variable power frequency load Load is 0.25, 0.5, 0.75 or 1 times the rated capacity of the grid-type converter GFC.

[0050] Preferably, the sampling frequency of the data acquisition device is not less than 4 kHz.

[0051] like Figure 2As shown, this embodiment provides a test method for the above-mentioned grid-type converter voltage source characteristic test device, comprising the following steps:

[0052] 1) Set the characteristics and capacity of the variable power frequency load;

[0053] 2) Close S in sequence Grid , S load , S GFC , connect the variable frequency load Load and the grid-forming converter GFC to the simulated grid;

[0054] 3) Turn on the data acquisition device and record the data;

[0055] 4) 0.25S N The step size of (rated apparent power of grid-type converter) gradually increases the power set point P of the grid-type converter GFC. GFC,set , until the power set point P GFC,set The rated power of the grid-connected converter GFC is reached, and the grid-connected converter GFC is at the rated power set point P n Stable operation, at this time, disconnect the grid control switch S Grid , and record this time as t step ;

[0056] 5) Set the power set point P of the grid-connected converter GFC GFC,set = 0, after the grid-type converter GFC stops running completely, stop the data acquisition device, disconnect S load , S GFC ;

[0057] 6) Data analysis;

[0058] 7) Determine whether all the characteristics and capacity combinations of the variable power frequency load simulation (3 characteristics and 4 capacity levels, a total of 12 combinations) have been tested; if completed, end the test; if not, repeat steps 1)-6).

[0059] Furthermore, this embodiment provides an evaluation method for the above-mentioned grid-type converter voltage source characteristic test device, which is used to determine the characteristic parameter of the grid-type converter voltage source characteristic, namely, the voltage response time t VR , which is defined as the time t when the effective value of the fundamental positive sequence voltage enters the error band of the new operating point for the last time (the error is ±5%) set With t step (t step is the power set point P of the grid converter GFC GFC,set The rated power of the grid-connected converter GFC is reached, and the grid-connected converter GFC is at the rated power set point P nAfter stable operation, disconnect the grid control switch S Grid The difference between the moments of set With t step If the difference is within the threshold, it can be determined that the voltage source characteristics of the grid-connected converter meet the requirements. The specific operations are as follows:

[0060] First, according to the instantaneous value of the three-phase voltage on the GFC side of the grid-connected converter (v GFC,a 、v GFC,b 、v GFC,c ), perform Fourier transform on it, and the calculation method is as follows;

[0061] Calculate the Fourier coefficients of the fundamental component within one fundamental period:

[0062]

[0063]

[0064] Where: f1 is the fundamental frequency; v j,cos is the cosine component of the fundamental voltage of one phase in the three-phase; v j,sin is the sinusoidal component of the fundamental voltage of one phase in the three-phase; v GFC，j is the instantaneous value of the voltage of one phase in the three-phase system; j = a, b, c; t is the actual time series; T is the fundamental wave period;

[0065] Calculate the fundamental positive sequence voltage component as follows:

[0066]

[0067]

[0068] 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;

[0069] Then, according to v 1+,cos and v 1+,sin , and combined with Calculate the fundamental positive sequence voltage effective value V pos , according to V pos At the steady-state value at the new operating point, draw its error band, according to Figure 3 The judgment method is to judge t set The value of set After the determination, the positive sequence voltage value should be within the error band at this moment. VR =t set -t step Calculate t VR The value of .

[0070] 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 equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A grid-type converter voltage source characteristic test device, comprising: Variable power frequency load Load and its control switch S load The variable frequency load Load is used to simulate loads with different characteristics. Its control switch S load Used to control variable frequency load Load to be connected to or off the grid; Simulated power grid Grid and its control switch S Grid The simulated grid is used to provide a stable voltage for the variable frequency load Load and simulate a fault. Its control switch S Grid Used to control the state of the simulated power grid; Data acquisition device, used to collect the instantaneous value of three-phase voltage on the GFC side of the grid-connected converter (v GFC,a 、v GFC,b 、v GFC,c ); The grid-connected converter GFC is equipped with a grid-connected switch S for controlling its own grid-connected / off-grid state. GFC The grid-forming converter GFC and the variable power frequency load are connected in parallel through cables and then connected in series with the simulated power grid Grid through cables. Due to its voltage source characteristics, the grid-forming converter GFC can provide voltage support for the variable power frequency load Load when a power grid fails. The data acquisition device is connected to the signal acquisition point on the grid-forming converter GFC side through a signal line; The evaluation method of the grid-type converter voltage source characteristic test device is used to determine the characteristic parameter of the grid-type converter voltage source characteristic, that is, the voltage response time t VR , which is defined as the time t when the effective value of the fundamental positive sequence voltage last enters the error band of the new operating point set With t step The difference between set With t step If the difference between t and t is within the threshold, it can be determined that the voltage source characteristics of the grid-connected converter meet the requirements; where t step is the power set point P of the grid converter GFC GFC,set The rated power of the grid-connected converter GFC is reached, and the grid-connected converter GFC is at the rated power set point P n After stable operation, disconnect the grid control switch S Grid moment; First, according to the instantaneous value of the three-phase voltage on the GFC side of the grid-connected converter (v GFC,a 、v GFC,b 、v GFC,c ), perform Fourier transform on it, and the calculation method is as follows; Calculate the Fourier coefficients of the fundamental component within one fundamental period: Where: f1 is the fundamental frequency; v j,cos is the cosine component of the fundamental voltage of one phase in the three-phase; v j,sin is the sinusoidal component of the fundamental voltage of one phase in the three-phase; v GFC，j is the instantaneous value of the voltage of one phase in the three-phase system; j = a, b, c; t is the actual time series; T is the fundamental wave period; Calculate the fundamental positive sequence voltage component as follows: 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; Then, according to v 1+,cos and v 1+,sin , and combined with Calculate the fundamental positive sequence voltage effective value V pos , according to V pos At the steady-state value of the new operating point, draw its error band and judge t set The value of set After the determination, the positive sequence voltage value should be within the error band at this moment. VR =t set -t step Calculate t VR The value of .

2. The grid-type converter voltage source characteristic testing device according to claim 1, characterized in that: The error band is ±5%.

3. The grid-type converter voltage source characteristic testing device according to claim 1, characterized in that: The characteristic load simulated by the variable power frequency load Load is one of pure resistive load, inductive load, capacitive load, or a combination of any two or three of them.

4. The grid-type converter voltage source characteristic testing device according to claim 1, characterized in that: The capacity of the variable power frequency load Load is 0.25, 0.5, 0.75 or 1 times the rated capacity of the grid-type converter GFC.

5. The grid-type converter voltage source characteristic testing device according to claim 1, characterized in that: The sampling frequency of the data acquisition device is not less than 4 kHz.

6. The testing method of the grid-type converter voltage source characteristic testing device according to any one of claims 1 to 5, characterized in that: The following steps are involved: 1) Set the characteristics and capacity of the variable power frequency load; 2) Close S in sequence Grid , S load , S GFC , connect the variable frequency load Load and the grid-forming converter GFC to the simulated grid; 3) Turn on the data acquisition device and record the data; 4) Gradually increase the power set point P of the grid-connected converter GFC with a specific step size GFC,set , until the power set point P GFC,set The rated power of the grid-connected converter GFC is reached, and the grid-connected converter GFC is at the rated power set point P n Stable operation, at this time, disconnect the grid control switch S Grid , and record this time as t step ; 5) Set the power set point P of the grid-connected converter GFC GFC,set = 0, after the grid-type converter GFC stops running completely, stop the data acquisition device, disconnect S load , S GFC ; 6) Data analysis; 7) Determine whether all the characteristics and capacity combinations of the variable power frequency load simulation have been tested; if completed, end the test; if not, repeat steps 1)-6).

7. The test method of the grid-type converter voltage source characteristic test device according to claim 6, characterized in that: In step 4), the specific step length is 0.25S N , where S N is the rated apparent power of the grid-connected converter GFC.

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