A method for indirect measurement of system impedance based on high voltage fault generation device

Abstract

The present invention discloses a method for indirectly measuring system impedance based on a high voltage fault generating device, wherein a high voltage fault generating device is used to perform a no-load test, and the no-load test data is used to list the system impedance Z. sx The resistance R sx and inductor X sx Solve the quadratic equations with two unknown variables to get the resistance R sx and inductor X sx value, and finally obtain the system impedance Z sx ; In view of the fact that there is a certain deviation between the measured value and the true value, in order to improve the accuracy of the system impedance, multiple no-load tests are carried out for different test conditions, and the equation groups are listed in pairs to solve the system impedance under each test condition. The system impedance is averaged to obtain a more accurate system impedance value. Based on the system impedance value, the high-voltage fault generating device can efficiently and accurately select the current limiting impedance, boost branch capacitor and boost branch resistor, accurately control the voltage increase amplitude, and reduce the damage of high voltage to the wind turbine and converter.

Description

Technical Field

[0001] The present invention relates to the technical field of high voltage ride-through capability testing of wind turbine generator sets, and in particular to a method for indirectly measuring system impedance based on a high voltage fault generating device. Background Art

[0002] Fault voltage ride-through capability refers to the ability of a wind turbine or photovoltaic power generation system to continue operating and support grid recovery when the grid voltage drops or rises to a certain value. As a prerequisite for renewable energy grid connection, new energy power plants must conduct fault voltage ride-through capability testing and meet test requirements. When conducting fault voltage ride-through capability testing, system impedance is one of the key factors affecting voltage changes and phase jumps. Quickly and accurately obtaining the actual system impedance value at the test site is of great practical significance for fault voltage ride-through capability testing. Based on accurate system impedance values, high-voltage fault generators can efficiently and accurately select current-limiting impedances and boost capacitors and resistors, precisely control the voltage rise amplitude, and reduce high voltage damage to wind turbines and converters. Summary of the Invention

[0003] The purpose of the present invention is to address the deficiencies in the prior art and provide a method for indirectly measuring system impedance based on a high-voltage fault generating device. A no-load test is performed using the high-voltage fault generating device, and the resistance and inductance values of the system impedance are obtained based on the no-load test data. In order to improve the accuracy of the system impedance, multiple no-load tests are performed for different test conditions, and the system impedance is averaged.

[0004] To achieve the above objectives, the present invention provides a technical solution: a method for indirectly measuring system impedance based on a high voltage fault generating device, wherein the high voltage fault generating device is connected in series to the high voltage side of the wind turbine step-up transformer, and the method comprises the following steps:

[0005] S1. Perform multiple no-load tests using a high-voltage fault generator for different test conditions to obtain multiple sets of no-load test data corresponding to different test conditions.

[0006] S2. Calculate, based on each set of no-load test data, multiple system impedances corresponding to different test conditions and the resistance and inductance values corresponding to each system impedance;

[0007] S3. Calculate the average resistance and inductance values based on the resistance and inductance values corresponding to each system impedance, and ultimately determine the system impedance of the access point between the high-voltage fault generating device and the high-voltage side of the wind turbine step-up transformer, thereby controlling the voltage rise amplitude during the high-voltage ride-through capability test of the wind turbine fault.

[0008] Furthermore, the high voltage fault generating device is electrically connected to the external power grid, which includes a system impedance Z in series. sx , current limiting impedance Z sr , boost branch capacitor and boost branch resistor; the current limiting impedance Zsr is used to limit the impact of the fault voltage on the power grid and other operating wind turbines in the wind farm, and its calculation formula is:

[0009] Z sr =R sr +jX sr ,

[0010] Among them, R sr The resistor of the current limiting impedance, X sr is the inductor of the current-limiting impedance;

[0011] The system impedance Z sx The calculation formula is:

[0012] Z sx =R sx +jX sx ,

[0013] Among them, R sx is the resistance of the system impedance, X sx The inductance is the system impedance.

[0014] Furthermore, in step S1, the following operations are specifically performed:

[0015] Under various test conditions, a high-voltage fault generating device was used to perform two no-load tests with different voltage increase amplitudes. That is, under the premise of the same system impedance and two different voltage increase amplitudes, two different sets of current limiting impedances, boost branch capacitors, and boost branch resistors were calculated, which are a set of no-load test data under the corresponding test conditions.

[0016] Furthermore, in step S2, the following operations are specifically performed:

[0017] The equation group is established based on each group of no-load test data obtained:

[0018]

[0019] Where n is a positive number, representing the total number of test conditions; U S is the voltage increase amplitude; R sr The resistor of the current limiting impedance, X sr is the inductor of the current limiting impedance; R d is the boost branch resistance, is the boost branch capacitor; R sx is the resistance of the system impedance, X sx The inductance is the system impedance;

[0020] According to the above equations, the resistance of the system impedance corresponding to all test conditions is {R sx1 ,R sx2 ,…,R sxn}, the inductance of the system impedance corresponding to all test conditions is {X sx1 ,X sx2 ,...,X sxn}.

[0021] Furthermore, in step S3, the following operations are specifically performed:

[0022] According to the resistance value {R sx1 ,R sx2 ,...,R sxn} and the inductance {X sx1 ,X sx2 ,...,X sxn}, calculate the average resistance R and the average inductance X:

[0023]

[0024]

[0025] Where i is a positive number; n is a positive number representing the total number of test conditions;

[0026] Finally determine the system impedance Z of the connection point between the high voltage fault generating device and the high voltage side of the wind turbine step-up transformer:

[0027] Z=R+jX.

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

[0029] The present invention can improve the accuracy of system impedance. In the high-voltage ride-through capability test of a wind turbine fault, the current-limiting impedance and boost capacitor and boost resistor can be selected efficiently and accurately based on a more accurate system impedance, thereby precisely controlling the voltage increase amplitude and reducing the damage of high voltage to the wind turbine and converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a structural diagram of a high voltage fault generating device.

[0031] Figure 2 This is the equivalent circuit diagram of the high voltage fault generating device. DETAILED DESCRIPTION

[0032] The present invention will be further described below with reference to specific embodiments.

[0033] See also Figures 1 to 2As shown, the high voltage fault generating device provided by this embodiment is connected in series to the high voltage side of the wind turbine step-up transformer 2, and the high voltage fault generating device is electrically connected to the external power grid 1, which includes a system impedance Z in series. sx , current limiting impedance Z sr , boost branch capacitor C L and the boost branch resistor R d ; Close the short-circuit switch CB3 to increase the boost branch capacitor C L , boost branch resistor R d Three or two phases are connected together at the test point U TP The voltage rise required by the test is generated. The current limiting impedance Zsr is used to limit the impact of the fault voltage on the power grid and other operating wind turbines in the wind farm. Its calculation formula is:

[0034] Z sr =R sr +jX sr ,

[0035] Among them, R sr The resistor of the current limiting impedance, X sr is the inductor of the current-limiting impedance;

[0036] The system impedance Z sx The calculation formula is:

[0037] Z sx =R sx +jX sx ,

[0038] Among them, R sx is the resistance of the system impedance, X sx The inductance is the system impedance.

[0039]

[0040]

[0041]

[0042]

[0043] in, is the grid voltage; is the system impedance voltage; is the current limiting impedance voltage; is the boost voltage; is the grid current; U S is the voltage increase amplitude.

[0044] The method for indirectly measuring system impedance based on a high voltage fault generating device includes the following steps:

[0045] S1. For different test conditions, use a high voltage fault generating device to perform multiple no-load tests to obtain multiple sets of no-load test data corresponding to different test conditions. Specifically, perform the following operations:

[0046] Under each test condition, a high voltage fault generator was used to perform two no-load tests with different voltage increase amplitudes. That is, under the premise of the same system impedance and two different voltage increase amplitudes, two different sets of current limiting impedances, boost branch capacitors, and boost branch resistors were calculated. This is a set of no-load test data under the corresponding test condition, as shown in the following table:

[0047]

[0048] S2. Based on each set of no-load test data, calculate multiple system impedances corresponding to different test conditions and the resistance and inductance values corresponding to each system impedance. Specifically, perform the following operations:

[0049] The equation group is established based on each group of no-load test data obtained:

[0050]

[0051] Where n is a positive number, representing the total number of test conditions; U S is the voltage increase amplitude; R sr The resistor of the current limiting impedance, X sr is the inductor of the current limiting impedance; R d is the boost branch resistance, is the boost branch capacitor; R sx is the resistance of the system impedance, X sx The inductance is the system impedance;

[0052] According to the above equations, the resistance of the system impedance corresponding to all test conditions is {R sx1 ,R sx2 ,...,R sxn}, the inductance of the system impedance corresponding to all test conditions is {X sx1 ,X sx2 ,...,X sxn}.

[0053] S3. Calculate the average resistance and inductance values based on the resistance and inductance values corresponding to each system impedance, and ultimately determine the system impedance at the access point between the high-voltage fault generating device and the high-voltage side of the wind turbine step-up transformer. This will then control the voltage rise amplitude during the high-voltage ride-through capability test of the wind turbine fault. Specifically, perform the following operations:

[0054] According to the resistance value {Rsx1 ,R sx2 ,…,R sxn} and the inductance {X sx1 ,X sx2 ,...,X sxn}, calculate the average resistance R and the average inductance X:

[0055]

[0056]

[0057] Where i is a positive number; n is a positive number representing the total number of test conditions;

[0058] Finally determine the system impedance Z of the connection point between the high voltage fault generating device and the high voltage side of the wind turbine step-up transformer:

[0059] Z=R+jX.

[0060] The embodiments described above are only preferred embodiments of the present invention and are not intended to limit the scope of implementation of the present invention. Therefore, any changes made based on the shape and principle of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for indirectly measuring system impedance based on a high voltage fault generating device, wherein the high voltage fault generating device is connected in series to the high voltage side of a step-up transformer of a wind turbine generator set, characterized in that: The high voltage fault generating device is electrically connected to the external power grid and includes a system impedance Z in series. sx , current limiting impedance Z sr , boost branch capacitor and boost branch resistor; the current limiting impedance Zsr is used to limit the impact of the fault voltage on the power grid and other operating wind turbines in the wind farm, and its calculation formula is: Z sr =R sr +jX sr , Among them, R sr The resistor of the current limiting impedance, X sr is the inductor of the current-limiting impedance; The system impedance Z sx The calculation formula is: Z sx =R sx +jX sx , Among them, R sx is the resistance of the system impedance, X sx The inductance is the system impedance; The method comprises the following steps: S1. For different test conditions, use a high voltage fault generating device to perform multiple no-load tests to obtain multiple sets of no-load test data corresponding to different test conditions. Specifically, perform the following operations: Under each test condition, a high-voltage fault generator was used to perform two no-load tests with different voltage increase amplitudes. That is, under the premise of the same system impedance and two different voltage increase amplitudes, two different sets of current limiting impedances, boost branch capacitors, and boost branch resistors were calculated, which were the no-load test data under the corresponding test condition. S2. Calculate, based on each set of no-load test data, multiple system impedances corresponding to different test conditions and the resistance and inductance values corresponding to each system impedance; S3. Calculate the average resistance and inductance values based on the resistance and inductance values corresponding to each system impedance, and ultimately determine the system impedance of the access point between the high-voltage fault generating device and the high-voltage side of the wind turbine step-up transformer, thereby controlling the voltage rise amplitude during the high-voltage ride-through capability test of the wind turbine fault.

2. The method for indirect measurement of system impedance based on a high voltage fault generating device according to claim 1, characterized in that: In step S2, the following operations are specifically performed: The equation group is established based on each group of no-load test data obtained: Where n is a positive number, representing the total number of test conditions; U S is the voltage increase amplitude; R sr The resistor of the current limiting impedance, X sr is the inductor of the current limiting impedance; R d is the boost branch resistance, is the boost branch capacitor; R sx is the resistance of the system impedance, X sx The inductance is the system impedance; According to the above equations, the resistance of the system impedance corresponding to all test conditions is {R sx1 ,R sx2 ,...,R sxn }, the inductance of the system impedance corresponding to all test conditions is {X sx1 ,X sx2 ,...,X sxn }.

3. The method for indirect measurement of system impedance based on a high voltage fault generating device according to claim 1, characterized in that: In step S3, the following operations are specifically performed: According to the resistance value {R sx1 ,R sx2 ,...,R sxn } and the inductance {X sx1 ,X sx2 ,...,X sxn }, calculate the average resistance R and the average inductance X: Where i is a positive number; n is a positive number representing the total number of test conditions; Finally determine the system impedance Z of the connection point between the high voltage fault generating device and the high voltage side of the wind turbine step-up transformer: Z=R+jX.

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