A method for simulating the strength and weakness of power systems based on real-time digital simulator for STATCOM access

Abstract

The present invention provides a method for simulating the strength of a power system based on a real-time digital simulator for STATCOM access, the method comprising the following steps: step 1, by building a power system simulation model based on a real-time digital simulator, and accessing a reactive compensation device STATCOM in the power system; step 2, introducing an equivalent simulated impedance between the generator set grid connection point and the power system side, the parameters required for the equivalent simulated impedance are the values ​​of resistance and inductance; step 3, accurately simulating the strength of the power grid by calculating the value of the introduced equivalent simulated impedance. The present invention can simulate the strength of the power system, and provide a feasible method for conducting stability analysis of power electronic equipment access under different strengths of the power system, thereby solving the current problem that the penetration rate of new energy and the proportion of power electronic equipment continue to increase, making the power grid present weak grid characteristics, leading to problems such as wide-band oscillation and overvoltage.

Description

Technical Field

[0001] The present invention relates to the technical field of management systems, and in particular to a method for simulating the strength and weakness of a power system based on a real-time digital simulator for STATCOM access. Background Art

[0002] At present, driven by the "dual carbon" goal, with the continuous increase in the penetration rate of new energy and the proportion of power electronic equipment, the power grid has gradually transformed from a synchronous machine-dominated system to a power electronic equipment-dominated system, which will lead to a reduction in system inertia and a significant decrease in the short-circuit ratio of the common coupling point, making the power grid present a weak grid characteristic, which is an important influencing factor for the emergence of problems such as wide-band oscillation and overvoltage. Therefore, the support capacity of the STATCOM of the new energy power station to the power grid becomes increasingly important, and it is urgent to analyze the operating stability of the STATCOM in the station and its support capacity to the power system when the new energy power station is connected under the weak power grid. Therefore, a strong and weak simulation method for the power system connected to STATCOM based on a real-time digital simulator is proposed to solve the above problems. Summary of the invention

[0003] In view of this, the object of the present invention is to provide a method for simulating the strength and weakness of a power system connected to STATCOM based on a real-time digital simulator, so as to at least solve the above problems.

[0004] The technical solution adopted by the present invention is as follows:

[0005] A method for simulating the strength and weakness of a power system connected to a STATCOM based on a real-time digital simulator, the method comprising the following steps:

[0006] Step 1: Building a power system simulation model based on a real-time digital simulator and connecting a reactive power compensation device STATCOM to the power system;

[0007] Step 2: introducing an equivalent simulated impedance between the generator set grid connection point and the power system side, the parameters required for the equivalent simulated impedance are the values ​​of resistance and inductance;

[0008] Step 3: Accurately simulate the strength of the power grid by calculating the value of the introduced equivalent simulated impedance.

[0009] Furthermore, in step S3, the equivalent simulated impedance is specifically:

[0010] By defining the power system strength coefficient K as a constant greater than 0, the larger the K, the stronger the power grid strength, and vice versa. The calculation formula is expressed as:

[0011]

[0012] Where U1 represents the effective value of the line voltage when the generator is connected to the high-voltage side of the transformer and connected to the grid, Z eq It represents the total equivalent simulated impedance between the generator set grid connection point and the system side, S G Indicates the apparent power of the generator.

[0013] Furthermore, for Z eq The calculation can be expressed by the following formula:

[0014]

[0015] Where: Z eq1 Represents the introduced equivalent impedance, Z T It represents the equivalent impedance of the transformer connected between the generator set grid connection point and the system side.

[0016] Furthermore, for Z eq The calculation can be expressed by the following formula:

[0017] Z eq =Z eq1 +Z T (2)

[0018] Where: Z eq1 Represents the introduced equivalent impedance, Z T It represents the equivalent impedance of the transformer connected between the generator set grid connection point and the system side.

[0019] Furthermore, Z eq1 Vector representation, Z eq1 Vector expression:

[0020]

[0021] In the formula, R eq1 Represents the introduced equivalent resistance, X eq1 Indicates the equivalent reactance introduced, L eq represents the introduced equivalent inductance, f represents the grid frequency, and is set to 50Hz, then Z eq1 The calculation formula is:

[0022]

[0023] By setting R eq1 With X eq1 The numerical ratio is:

[0024] X eq1 =10·R eq1 (6)

[0025] Then from formula (6) we can get:

[0026]

[0027] Furthermore, the simulated impedance value calculated in formula (8) can be used to simulate the strength of STATCOM access to the power system.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The present invention proposes a method for simulating the strength of a power system based on a real-time digital simulator for STATCOM access. The method can simulate the strength of a power system and provide a feasible method for stability analysis of power electronic equipment access under different strengths of the power system, by targeting the increasing penetration rate of new energy sources and the proportion of power electronic equipment, which makes the power grid present weak grid characteristics, leading to problems such as wide-band oscillation and overvoltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only preferred embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0031] Figure 1 It is a schematic diagram of the strong and weak simulation of a single-machine infinite power system;

[0032] Figure 2 The results of the strong and weak tests of the single-machine infinite power system under different K factors are shown; DETAILED DESCRIPTION

[0033] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The enumerated embodiments are only used to explain the present invention and are not used to limit the scope of the present invention.

[0034] Reference Figure 1-Figure 2 The present invention provides a method for simulating the strength and weakness of a power system connected to a STATCOM based on a real-time digital simulator, the method comprising the following steps:

[0035] Step 1: Building a power system simulation model based on a real-time digital simulator and connecting a reactive power compensation device STATCOM to the power system;

[0036] Step 2: introducing an equivalent simulated impedance between the generator set grid connection point and the power system side, the parameters required for the equivalent simulated impedance are the values ​​of resistance and inductance;

[0037] Step 3: Accurately simulate the strength of the power grid by calculating the value of the introduced equivalent simulated impedance.

[0038] In step S3, the equivalent simulated impedance is specifically:

[0039] By defining the power system strength coefficient K as a constant greater than 0, the larger the K, the stronger the power grid strength, and vice versa. The calculation formula is expressed as:

[0040]

[0041] Where U1 represents the effective value of the line voltage when the generator is connected to the high-voltage side of the transformer and connected to the grid, Z eq It represents the total equivalent simulated impedance between the generator set grid connection point and the system side, S G Indicates the apparent power of the generator.

[0042] For Z eq The calculation can be expressed by the following formula:

[0043] Z eq =Z eq1 +Z T (2)

[0044] Where: Z eq1 Represents the introduced equivalent impedance, Z T It represents the equivalent impedance of the transformer connected between the generator set grid connection point and the system side.

[0045] For Z eq The calculation can be expressed by the following formula:

[0046] Z eq =Z eq1 +Z T (2)

[0047] Where: Z eq1 Represents the introduced equivalent impedance, Z T It represents the equivalent impedance of the transformer connected between the generator set grid connection point and the system side.

[0048] Z eq1 Vector representation, Z eq1 Vector expression:

[0049]

[0050] In the formula, R eq1 Represents the introduced equivalent resistance, X eq1 Indicates the equivalent reactance introduced, L eq represents the introduced equivalent inductance, f represents the grid frequency, and is set to 50Hz, then Z eq1 The calculation formula is:

[0051]

[0052] By setting R eq1 With X eq1 The numerical ratio is:

[0053] X eq1 =10·R eq1 (6)

[0054] Then from formula (6) we can get:

[0055]

[0056] The simulated impedance value calculated in formula (8) can be used to simulate the strength of STATCOM access to the power system.

[0057] For example, the application example is as follows: the rated capacity of the STATCOM to be tested is S G =30MVar, rated voltage U N1 =35kV, rated current is I N1 =494.9A; rated capacity of step-up transformer S T =100MVA, the rated voltage of high / low voltage side of transformer is 220kV / 35kV respectively, Z k =0.1253;

[0058] Build a STATCOM stand-alone infinite system based on RT-LAB real-time simulator, transmit the instantaneous values ​​of the three-phase voltage and current of the simulation main circuit to the STATCOM controller through DB37 connecting wires, and the STATCOM controller transmits the PWM control signal to the simulator through optical fiber;

[0059] If K is set to 15 and 25 respectively, then according to formulas (6) to (8), we can calculate L eq1 They are 0.1486H, 0.0123H, R eq1 They are 4.6678Ω and 0.3869Ω respectively;

[0060] The test was carried out under the condition that the STATCOM reactive current output was 0.5pu. The test results are as follows Figure 2 As shown;

[0061] according to Figure 2It can be seen that when K is 15 and the STATCOM capacitive reactive current output is 0.5pu, the per-unit value of the average effective value of the transformer high-voltage side line voltage is: 1.0211pu, and the voltage changes by 0.0211pu; when K is 25 and the STATCOM capacitive reactive current output is 0.5pu, the per-unit value of the average effective value of the transformer high-voltage side line voltage is: 1.0090pu, and the voltage changes by 0.0090pu. Therefore, when K=25, the voltage fluctuation caused by the equipment being connected to the grid is smaller, and the grid strength is stronger than when K=15, which verifies that the method of the present invention can simulate the strength of the grid.

[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for simulating the strength of a power system connected to STATCOM based on a real-time digital simulator, characterized in that: The method comprises the following steps: Step 1: Building a power system simulation model based on a real-time digital simulator and connecting a reactive power compensation device STATCOM to the power system; Step 2: introducing an equivalent simulated impedance between the generator set grid connection point and the power system side, the parameters required for the equivalent simulated impedance are the values ​​of resistance and inductance; Step 3: Accurately simulate the strength of the power grid by calculating the value of the introduced equivalent simulated impedance.

2. According to claim 1, a method for simulating the strength and weakness of a power system connected to STATCOM based on a real-time digital simulator, characterized in that: In step S3, the equivalent simulated impedance is specifically: By defining the power system strength coefficient K as a constant greater than 0, the larger the K, the stronger the power grid strength, and vice versa. The calculation formula is expressed as: Where U1 represents the effective value of the line voltage when the generator is connected to the high-voltage side of the transformer and connected to the grid, Z eq It represents the total equivalent simulated impedance between the generator set grid connection point and the system side, S G Indicates the apparent power of the generator.

3. The method for simulating the strength and weakness of a power system connected to STATCOM based on a real-time digital simulator according to claim 2, characterized in that: For Z eq The calculation can be expressed by the following formula: WITH eq =Z eq1 +Z T (2) Where: Z eq1 Represents the introduced equivalent impedance, Z T It represents the equivalent impedance of the transformer connected between the generator set grid connection point and the system side.

4. The method for simulating the strength and weakness of a power system connected to STATCOM based on a real-time digital simulator according to claim 3 is characterized in that: For Z T The calculation can be expressed by the following formula: In the formula, Z k Indicates the short-circuit impedance percentage of the transformer, S T Indicates the apparent power of the transformer.

5. The method for simulating the strength and weakness of a power system connected to STATCOM based on a real-time digital simulator according to claim 4, characterized in that: Z eq1 Vector representation, Z eq1 Vector expression: In the formula, R eq1 Represents the introduced equivalent resistance, X eq1 Indicates the equivalent reactance introduced, L eq represents the introduced equivalent inductance, f represents the grid frequency, and is set to 50Hz, then Z eq1 The calculation formula is: By setting R eq1 With X eq1 The numerical ratio is: X eq1 =10·R eq1 (6) Then from formula (6) we can get:

6. The method for simulating the strength and weakness of a power system connected to STATCOM based on a real-time digital simulator according to claim 5, characterized in that: The simulated impedance value calculated in formula (8) can be used to simulate the strength of STATCOM access to the power system.

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