Method and system for low voltage ride through control of power electronic equipment based on negative sequence current

Abstract

This invention patent application provides a low-voltage ride-through control method and system for power electronic equipment based on negative-sequence current, comprising: performing primary and secondary limiting on the command values ​​of positive and negative sequence currents in the outer loop according to a predetermined positive and negative sequence current command threshold range; obtaining positive and negative sequence voltage reference values ​​through the transfer function of the inner loop controller based on the command value of the positive sequence current obtained after primary limiting, the command value of the negative sequence current obtained after secondary limiting, and the corresponding measured values ​​of the positive and negative sequence currents; generating positive and negative sequence command values ​​based on the positive and negative sequence voltage reference values ​​using coordinate system transformation; and controlling the power electronic equipment to complete low-voltage ride-through according to the positive and negative sequence command values. The negative sequence current command protection range of this invention is a reasonable limitation of the negative sequence current command value during a fault, achieving the effect of reducing the negative sequence component of the system, enabling rapid recovery to the pre-fault state, and not conflicting with new energy control.

Description

Technical Field

[0001] This invention patent application belongs to the field of power electronic device technology, specifically relating to a low-voltage ride-through control method and system for power electronic equipment based on negative sequence current. Background Technology

[0002] Power electronic fault ride-through after renewable energy integration refers to the ability of renewable energy equipment (such as photovoltaic power plants and wind turbines) to maintain continuous operation without disconnecting from the grid and smoothly transition to normal operation when the voltage or frequency at the renewable energy grid connection point exceeds the standard allowable normal operating range due to power system faults or disturbances. When a power system fault occurs or is disturbed, the voltage or frequency at the grid connection point may change. In this case, renewable energy equipment needs to use certain control strategies and technical means to ensure continuous operation without disconnecting from the grid. This requires the equipment to have a certain fault ride-through capability, including the ability to cope with transient processes such as overcurrent, undervoltage, and overspeed. To achieve power electronic fault ride-through after renewable energy integration, a series of technical and management measures need to be adopted. For example, for photovoltaic power plants, inverter control strategies can be used to dynamically adjust the inverter's output voltage and current according to changes in grid voltage and frequency to ensure continuous operation without disconnecting from the grid. For wind turbines, doubly-fed induction generator control strategies can be used to control the voltage and current on the stator and rotor sides of the generator to ensure the wind turbine can continue to operate under grid fault conditions. To improve the fault ride-through capability of renewable energy equipment, it is also necessary to strengthen equipment maintenance and management. For example, regular inspections and maintenance of equipment can promptly identify and address potential hazards and malfunctions, ensuring the healthy operation of the equipment.

[0003] Existing power electronic device control strategies often encounter difficulties in quickly restoring to normal operation during low-voltage ride-through. This is mainly because the power electronic control strategy does not reasonably limit the negative sequence current during the fault, making recovery difficult after the fault. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, this patent application proposes a low-voltage ride-through control method for power electronic equipment based on negative sequence current, comprising:

[0005] According to the predetermined positive and negative sequence current command threshold range, the command values ​​of the positive and negative sequence currents of the outer loop are limited once; the command values ​​of the positive and negative sequence currents include the command values ​​of the positive sequence current and the command values ​​of the negative sequence current.

[0006] According to the preset negative sequence current command protection range, the command value of the negative sequence current after the first limit is subjected to a second limit.

[0007] Based on the commanded value of the positive sequence current obtained after the first limiting, the commanded value of the negative sequence current obtained after the second limiting, and the corresponding measured values ​​of the positive and negative sequence currents, the reference values ​​of the positive and negative sequence voltages are obtained through the transfer function of the inner loop controller.

[0008] Based on the positive and negative sequence voltage reference values, coordinate system transformation is used to generate positive and negative sequence command values. According to the positive and negative sequence command values, the power electronic equipment is controlled to complete the low voltage ride-through.

[0009] Preferably, the positive and negative sequence current command threshold range includes a negative sequence current command threshold range and a positive sequence current command threshold range; the step of limiting the command values ​​of the positive and negative sequence currents of the outer loop according to the predetermined positive and negative sequence current command threshold range includes:

[0010] Based on the command value of the negative sequence current of the outer loop, the command value of the negative sequence current after one limit is obtained by using a pre-set negative sequence current command threshold range.

[0011] Based on the command value of the positive sequence current of the outer loop, the command value of the positive sequence current after one limit is obtained by using a pre-set positive sequence current command threshold range.

[0012] The command values ​​for the positive sequence current include positive sequence d-axis current command values ​​and positive sequence q-axis current command values; the command values ​​for the negative sequence current include negative sequence d-axis current command values ​​and negative sequence q-axis current command values; the command values ​​for the positive sequence current after first-stage limiting include positive sequence d-axis current command values ​​and positive sequence q-axis current command values ​​after first-stage limiting; the command values ​​for the negative sequence current after first-stage limiting include negative sequence d-axis current command values ​​and negative sequence q-axis current command values ​​after first-stage limiting.

[0013] Preferably, the step of performing a secondary limit on the command value of the negative sequence current after the first limit, based on a pre-set negative sequence current command protection range, includes:

[0014] When a fault voltage drop is detected, the command value of the negative sequence current after the first limit is adjusted to the negative sequence current command protection range according to the preset negative sequence current command protection range.

[0015] After the fault voltage is cleared, the command value of the negative sequence current in the negative sequence current command range is limited by the positive sequence current command threshold range to obtain the command value of the negative sequence current after secondary limiting.

[0016] The command value of the negative sequence current after the second-stage limiting includes: the command value of the negative sequence d-axis current after the second-stage limiting and the command value of the negative sequence q-axis current after the second-stage limiting.

[0017] Preferably, the negative sequence current command protection range is greater than 0.05 pu and less than 0.5 pu.

[0018] Preferably, before limiting the command value of the positive and negative sequence current of the outer loop based on a predetermined positive and negative sequence current command threshold range, the method further includes:

[0019] Determine if the outer loop control exists. If it exists, set the outer loop control strategy to network-type control and simultaneously set the inner loop control.

[0020] If it does not exist, then directly set the inner loop control;

[0021] The inner loop control includes negative sequence current control.

[0022] Preferably, the step of obtaining positive and negative sequence voltage reference values ​​through the transfer function of the inner loop controller based on the commanded value of the positive sequence current obtained after the first limiting, the commanded value of the negative sequence current obtained after the second limiting, and the corresponding measured values ​​of the positive and negative sequence currents includes:

[0023] The difference between the negative sequence d-axis current command value and the corresponding measured negative sequence d-axis current value after secondary limiting is calculated, and the difference is input into the transfer function of the inner loop controller of the d-axis current to calculate the negative sequence d-axis command value. Based on the negative sequence d-axis command value and the negative sequence d-axis voltage related parameters, the negative sequence d-axis voltage reference value is calculated using the negative sequence d-axis voltage reference value calculation formula.

[0024] Calculate the difference between the positive sequence d-axis current command value after one limit and the corresponding measured positive sequence d-axis current value, and input the difference into the transfer function of the inner loop controller of the d-axis current to calculate the positive sequence d-axis command value. Based on the positive sequence d-axis command value and the positive sequence d-axis voltage related parameters, use the positive sequence d-axis voltage reference value calculation formula to calculate the positive sequence d-axis voltage reference value.

[0025] The difference between the negative-sequence q-axis current command value and the corresponding measured negative-sequence q-axis current value after secondary limiting is calculated, and the difference is input into the transfer function of the inner loop controller of the q-axis current to calculate the negative-sequence q-axis command value. Based on the negative-sequence q-axis command value and the negative-sequence q-axis voltage related parameters, the negative-sequence q-axis voltage reference value is calculated using the negative-sequence q-axis voltage reference value calculation formula.

[0026] The difference between the positive-sequence q-axis current command value after one limit is calculated and the corresponding positive-sequence q-axis current measured value is input into the transfer function of the inner loop controller of the q-axis current to calculate the positive-sequence q-axis command value. Based on the positive-sequence q-axis command value and the positive-sequence q-axis voltage related parameters, the positive-sequence q-axis voltage reference value is calculated using the positive-sequence q-axis voltage reference value calculation formula.

[0027] The positive-sequence q-axis voltage-related parameters include one or more of the following: angular velocity, equivalent inductance, and measured values ​​of positive-sequence d-axis current.

[0028] Preferably, the expression for the transfer function is as follows:

[0029] G(S) = KP + Ki ÷ S

[0030] Where G(S) is the transfer function, KP is the proportional coefficient, Ki is the integral coefficient, and S is the Laplace operator.

[0031] Preferably, the formula for calculating the positive-sequence q-axis voltage reference value is as follows:

[0032]

[0033] in, Here, ω is the positive-sequence q-axis voltage reference value, ω is the angular velocity, and L is the equivalent inductance. This represents the measured value of the positive-sequence d-axis current. The measured value of the positive-sequence q-axis current is qrr. + This is the positive sequence q-axis command value.

[0034] Preferably, the step of generating positive and negative sequence command values ​​based on the positive and negative sequence voltage reference values ​​using coordinate system transformation, and controlling the power electronic equipment to complete low-voltage ride-through according to the positive and negative sequence command values, includes:

[0035] Based on the positive sequence d-axis voltage reference value and the positive sequence q-axis voltage reference value, coordinate transformation is used to transform from the dq coordinate system to the abc coordinate system to generate a positive sequence command value;

[0036] Based on the negative sequence d-axis voltage reference value and the negative sequence q-axis voltage reference value, coordinate transformation is used to transform from the dq coordinate system to the abc coordinate system to generate a negative sequence command value;

[0037] Based on the positive and negative sequence command values, the power electronic equipment is controlled to complete the low voltage ride-through.

[0038] Based on the same inventive concept, this patent application also provides a low-voltage ride-through control system for power electronic equipment based on negative sequence current, including: a primary limiting module, a secondary limiting module, a positive and negative sequence voltage reference value calculation module, and a low-voltage ride-through module.

[0039] The primary limiting module is used to limit the command values ​​of the positive and negative sequence currents of the outer loop according to a predetermined positive and negative sequence current command threshold range; the command values ​​of the positive and negative sequence currents include the command values ​​of the positive sequence current and the command values ​​of the negative sequence current.

[0040] The secondary limiting module is used to perform secondary limiting on the command value of the negative sequence current after the primary limiting, according to the preset negative sequence current command protection range.

[0041] The positive and negative sequence voltage reference value calculation module is used to obtain the positive and negative sequence voltage reference values ​​based on the command value of the positive sequence current obtained after the first limiting, the command value of the negative sequence current obtained after the second limiting, and the corresponding measured values ​​of the positive and negative sequence currents, through the transfer function of the inner loop controller.

[0042] The low-voltage ride-through module is used to generate positive and negative sequence command values ​​based on the positive and negative sequence voltage reference values ​​by using coordinate system transformation, and to control the power electronic equipment to complete the low-voltage ride-through according to the positive and negative sequence command values.

[0043] Preferably, the positive and negative sequence current command threshold intervals include a negative sequence current command threshold interval and a positive sequence current command threshold interval; the primary limiting module is used for:

[0044] Based on the command value of the negative sequence current of the outer loop, the command value of the negative sequence current after one limit is obtained by using a pre-set negative sequence current command threshold range.

[0045] Based on the command value of the positive sequence current of the outer loop, the command value of the positive sequence current after one limit is obtained by using a pre-set positive sequence current command threshold range.

[0046] The command values ​​for the positive sequence current include positive sequence d-axis current command values ​​and positive sequence q-axis current command values; the command values ​​for the negative sequence current include negative sequence d-axis current command values ​​and negative sequence q-axis current command values; the command values ​​for the positive sequence current after first-stage limiting include positive sequence d-axis current command values ​​and positive sequence q-axis current command values ​​after first-stage limiting; the command values ​​for the negative sequence current after first-stage limiting include negative sequence d-axis current command values ​​and negative sequence q-axis current command values ​​after first-stage limiting.

[0047] Preferably, the secondary limiting module is used for:

[0048] When a fault voltage drop is detected, the command value of the negative sequence current after the first limit is adjusted to the negative sequence current command protection range according to the preset negative sequence current command protection range.

[0049] After the fault voltage is cleared, the command value of the negative sequence current in the negative sequence current command range is limited by the positive sequence current command threshold range to obtain the command value of the negative sequence current after secondary limiting.

[0050] The command value of the negative sequence current after the second-stage limiting includes: the command value of the negative sequence d-axis current after the second-stage limiting and the command value of the negative sequence q-axis current after the second-stage limiting.

[0051] Preferably, the negative sequence current command protection range is greater than 0.05 pu and less than 0.5 pu.

[0052] Preferably, the system further includes: an inner and outer loop control module, used for:

[0053] Determine if the outer loop control exists. If it exists, set the outer loop control strategy to network-type control and simultaneously set the inner loop control.

[0054] If it does not exist, then directly set the inner loop control;

[0055] The inner loop control includes negative sequence current control.

[0056] Preferably, the positive and negative sequence voltage reference value calculation module is used for:

[0057] The difference between the negative sequence d-axis current command value and the corresponding measured negative sequence d-axis current value after secondary limiting is calculated, and the difference is input into the transfer function of the inner loop controller of the d-axis current to calculate the negative sequence d-axis command value. Based on the negative sequence d-axis command value and the negative sequence d-axis voltage related parameters, the negative sequence d-axis voltage reference value is calculated using the negative sequence d-axis voltage reference value calculation formula.

[0058] Calculate the difference between the positive sequence d-axis current command value after one limit and the corresponding measured positive sequence d-axis current value, and input the difference into the transfer function of the inner loop controller of the d-axis current to calculate the positive sequence d-axis command value. Based on the positive sequence d-axis command value and the positive sequence d-axis voltage related parameters, use the positive sequence d-axis voltage reference value calculation formula to calculate the positive sequence d-axis voltage reference value.

[0059] The difference between the negative-sequence q-axis current command value and the corresponding measured negative-sequence q-axis current value after secondary limiting is calculated, and the difference is input into the transfer function of the inner loop controller of the q-axis current to calculate the negative-sequence q-axis command value. Based on the negative-sequence q-axis command value and the negative-sequence q-axis voltage related parameters, the negative-sequence q-axis voltage reference value is calculated using the negative-sequence q-axis voltage reference value calculation formula.

[0060] The difference between the positive-sequence q-axis current command value after one limit is calculated and the corresponding positive-sequence q-axis current measured value is input into the transfer function of the inner loop controller of the q-axis current to calculate the positive-sequence q-axis command value. Based on the positive-sequence q-axis command value and the positive-sequence q-axis voltage related parameters, the positive-sequence q-axis voltage reference value is calculated using the positive-sequence q-axis voltage reference value calculation formula.

[0061] The positive-sequence q-axis voltage-related parameters include one or more of the following: angular velocity, equivalent inductance, and measured values ​​of positive-sequence d-axis current.

[0062] Preferably, the expression for the transfer function is as follows:

[0063] G(S) = KP + Ki ÷ S

[0064] Where G(S) is the transfer function, KP is the proportional coefficient, Ki is the integral coefficient, and S is the Laplace operator.

[0065] Preferably, the formula for calculating the positive-sequence q-axis voltage reference value is as follows:

[0066]

[0067] in, Here, ω is the positive-sequence q-axis voltage reference value, ω is the angular velocity, and L is the equivalent inductance. This represents the measured value of the positive-sequence d-axis current. The measured value of the positive-sequence q-axis current is qrr. + This is the positive sequence q-axis command value.

[0068] Preferably, the low voltage ride-through module is used for:

[0069] Based on the positive sequence d-axis voltage reference value and the positive sequence q-axis voltage reference value, coordinate transformation is used to transform from the dq coordinate system to the abc coordinate system to generate a positive sequence command value;

[0070] Based on the negative sequence d-axis voltage reference value and the negative sequence q-axis voltage reference value, coordinate transformation is used to transform from the dq coordinate system to the abc coordinate system to generate a negative sequence command value;

[0071] Based on the positive and negative sequence command values, the power electronic equipment is controlled to complete the low voltage ride-through.

[0072] Based on the same inventive concept, this patent application also provides an electronic device, comprising: at least one processor and a memory; wherein the memory and the processor are connected via a bus.

[0073] The memory is used to store one or more programs;

[0074] When the one or more programs are executed by the at least one processor, a low-voltage ride-through control method for power electronic equipment based on negative sequence current is implemented as described above.

[0075] Based on the same inventive concept, this patent application also provides a readable storage medium on which an executable program is stored, which, when executed, implements the aforementioned low-voltage ride-through control method for power electronic equipment based on negative sequence current.

[0076] Compared with the closest prior art, the beneficial effects of this invention patent application are as follows:

[0077] This invention patent application provides a low-voltage ride-through control method and system for power electronic equipment based on negative-sequence current, comprising: firstly limiting the command values ​​of positive and negative sequence currents in the outer loop according to a predetermined positive and negative sequence current command threshold range; the command values ​​of positive and negative sequence currents include command values ​​of positive sequence current and negative sequence current; secondly limiting the command values ​​of negative sequence currents after the first limiting according to a predetermined negative sequence current command protection range; obtaining positive and negative sequence voltage reference values ​​through the transfer function of the inner loop controller based on the command values ​​of positive sequence currents obtained after the first limiting, the command values ​​of negative sequence currents obtained after the second limiting, and the corresponding measured values ​​of positive and negative sequence currents; generating positive and negative sequence command values ​​based on the positive and negative sequence voltage reference values ​​using coordinate system transformation; and controlling the power electronic equipment to complete low-voltage ride-through according to the positive and negative sequence command values. The negative sequence current command protection range of this invention is a reasonable restriction of the negative sequence current command value during a fault, achieving the effect of reducing the negative sequence component of the system, realizing rapid recovery to the pre-fault state, and not conflicting with the control of new energy sources. Attached Figure Description

[0078] Figure 1 A schematic flowchart of a low-voltage ride-through control method for power electronic equipment based on negative sequence current, provided for this patent application.

[0079] Figure 2 A schematic diagram of a low-voltage ride-through control system for power electronic equipment based on negative sequence current, provided for this patent application.

[0080] Figure 3 This is a schematic diagram of the structure of an electronic device provided in this patent application. Detailed Implementation

[0081] The specific embodiments of this patent application will be further described in detail below with reference to the accompanying drawings.

[0082] Example 1:

[0083] This invention patent application provides a low-voltage ride-through control method for power electronic equipment based on negative sequence current, such as... Figure 1 As shown, it includes:

[0084] Step 1: Based on the predetermined positive and negative sequence current command threshold range, limit the command values ​​of the positive and negative sequence currents of the outer loop once; the command values ​​of the positive and negative sequence currents include the command values ​​of the positive sequence current and the negative sequence current.

[0085] Step 2: Based on the preset negative sequence current command protection range, perform a second limit on the command value of the negative sequence current after the first limit;

[0086] Step 3: Based on the commanded value of the positive sequence current obtained after the first limiting, the commanded value of the negative sequence current obtained after the second limiting, and the corresponding measured values ​​of the positive and negative sequence currents, the reference values ​​of the positive and negative sequence voltages are obtained through the transfer function of the inner loop controller.

[0087] Step 4: Based on the positive and negative sequence voltage reference values, coordinate system transformation is used to generate positive and negative sequence command values. According to the positive and negative sequence command values, the power electronic equipment is controlled to complete the low voltage ride-through.

[0088] Before step 1 above, the following is also included:

[0089] Determine if the outer loop control exists. If it exists, set the outer loop control strategy to network-type control and simultaneously set the inner loop control.

[0090] If it does not exist, then directly set the inner loop control;

[0091] The inner loop control includes negative sequence current control.

[0092] For example, the relationship between the outer loop control strategy and the negative sequence current limiting link is set as follows: determine whether the outer loop control exists, and if it exists, set the outer loop control strategy to grid-type control; when the outer loop control strategy is grid-type, the inner loop is simultaneously set to include the negative sequence current limiting link; the present invention limits the outer loop to adopt grid-type control, but in order to ensure that the grid-type control does not conflict with the grid-type control of wind power, negative sequence current control is set in the power inner loop.

[0093] The positive and negative sequence current command threshold range mentioned in step 1 above includes a negative sequence current command threshold range and a positive sequence current command threshold range; the step of limiting the command values ​​of the positive and negative sequence currents of the outer loop according to the predetermined positive and negative sequence current command threshold range includes:

[0094] Based on the command value of the negative sequence current of the outer loop, the command value of the negative sequence current after one limit is obtained by using a pre-set negative sequence current command threshold range.

[0095] For example, the command value of the negative sequence current needs to be limited by a pre-set negative sequence current command threshold range before it is given as the inner loop control.

[0096] The command value for negative sequence current must meet the negative sequence current command threshold range, as follows:

[0097]

[0098]

[0099] in, This is the commanded value for the negative sequence d-axis current. L3 is the command value for the negative sequence q-axis current, L4 is the upper limit of the negative sequence current command threshold range, and L5 is the lower limit of the negative sequence current command threshold range.

[0100] When the command value of the negative sequence d-axis current and the command value of the negative sequence q-axis current exceed the limit of the negative sequence current command threshold range, L3 or L4, the outer loop controller limits its output to the limit value corresponding to the time L3 or L4 at that time.

[0101] Before implementing inner-loop control, it must be ensured that the commanded value of the negative-sequence current is within the permissible range. Specifically, this range is defined by two boundaries: L4 (the lower limit of the negative-sequence current command threshold range) and L3 (the upper limit of the negative-sequence current command threshold range), both of which must satisfy the range from L4 to L3. If either commanded value exceeds this range, the outer-loop controller will limit its output, selecting the closest boundary value (L3 or L4) as the output. This is done to protect the power system and equipment from potential problems caused by negative-sequence current command values ​​that exceed the range. In summary, this is a limiting process to ensure that the negative-sequence current command value is within a reasonable range.

[0102] Based on the command value of the positive sequence current of the outer loop, the command value of the positive sequence current after one limit is obtained by using a pre-set positive sequence current command threshold range.

[0103] For example, the commanded values ​​for the positive-sequence current and the negative-sequence current need to be limited before being given as the inner-loop control.

[0104] The command value for the positive sequence current must satisfy the following formula:

[0105]

[0106]

[0107] in, This is the commanded value for the positive-sequence d-axis current. L1 is the upper limit of the positive sequence q-axis current command value, and L2 is the lower limit of the positive sequence current command threshold range.

[0108] When the command value of the positive sequence d-axis current and the command value of the positive sequence q-axis current exceed the limit of the positive sequence current command threshold range, i.e., L1 or L2, the outer loop controller limits its output to the limit value corresponding to the time L1 or L2 at that time.

[0109] Both the commanded values ​​for positive-sequence and negative-sequence currents need to be limited before being given by the inner-loop control. This is to ensure that the current command values ​​are within a reasonable range, thereby protecting the power system and equipment. This means that the commanded value for the positive-sequence current must be between L2 and L1. When the commanded value for the positive-sequence current exceeds this range—that is, exceeds L1 or falls below L2—the outer-loop controller intervenes and limits its output. The outer-loop controller selects the closest limit value (L1 or L2) as the output to ensure that the current command value does not exceed the set safe range. Similarly, the commanded value for the negative-sequence current also needs to meet similar limiting conditions and is limited by the outer-loop controller when it exceeds the range. In summary, both the commanded values ​​for positive-sequence and negative-sequence currents need to be limited to ensure that they remain within allowable ranges before inner-loop control. If the commanded value exceeds this range, the outer-loop controller will take appropriate measures to limit the output, thereby protecting the safe operation of the power system and equipment.

[0110] The command values ​​for the positive-sequence current include positive-sequence d-axis current command values ​​and positive-sequence q-axis current command values; the command values ​​for the negative-sequence current include negative-sequence d-axis current command values ​​and negative-sequence q-axis current command values; the command values ​​for the positive-sequence current after the first limiting include positive-sequence d-axis current command values ​​and positive-sequence q-axis current command values ​​after the first limiting; the command values ​​for the negative-sequence current after the first limiting include negative-sequence d-axis current command values ​​and negative-sequence q-axis current command values ​​after the first limiting. This invention obtains the command values ​​for the positive and negative-sequence currents after the limiting by first limiting the command values ​​of the positive and negative-sequence currents of the outer loop, providing data for subsequent second limiting.

[0111] Step 2 above, which describes performing a secondary limit on the command value of the negative sequence current after the first limit, based on a pre-set negative sequence current command protection range, includes:

[0112] When a fault voltage drop is detected, the command value of the negative sequence current after the first limit is adjusted to the negative sequence current command protection range according to the preset negative sequence current command protection range.

[0113] After the fault voltage is cleared, the command value of the negative sequence current in the negative sequence current command range is limited by the positive sequence current command threshold range to obtain the command value of the negative sequence current after secondary limiting.

[0114] For example, after the fault is cleared, the limiting of the negative sequence inner loop is restored to the limiting limits L1 and L2. The reason for the secondary limiting of the command value of the negative sequence current after the first limiting is that if the negative sequence current is set to 0 during the setting process, it may cause a conflict with the control strategy of the wind turbine and make it impossible to balance the voltage. However, if the negative sequence current is reduced, it can cooperate with the wind turbine to achieve the purpose of suppressing the negative sequence voltage. Finally, the negative sequence voltage will be reduced to 0. This is because, with the same control objective, different controllers may not be able to truly stabilize to a unified timing.

[0115] The command value of the negative sequence current after the second-stage limiting includes: the command value of the negative sequence d-axis current after the second-stage limiting and the command value of the negative sequence q-axis current after the second-stage limiting.

[0116] In one implementation, the negative sequence current command protection range is greater than 0.05 pu and less than 0.5 pu; the specific value of the negative sequence current command protection range of the present invention further illustrates the numerical range of the negative sequence current command protection range; the negative sequence current command protection range is an additional fault suppression strategy added to the negative sequence current in the inner loop control, which is a reasonable restriction on the negative sequence current command during the fault period, and can achieve rapid fault ride-through recovery.

[0117] Step 3 above describes obtaining positive and negative sequence voltage reference values ​​based on the commanded value of the positive sequence current obtained after the first limiting, the commanded value of the negative sequence current obtained after the second limiting, and the corresponding measured values ​​of the positive and negative sequence currents, through the transfer function of the inner loop controller. This includes:

[0118] The difference between the negative sequence d-axis current command value and the corresponding measured negative sequence d-axis current value after secondary limiting is calculated, and the difference is input into the transfer function of the inner loop controller of the d-axis current to calculate the negative sequence d-axis command value. Based on the negative sequence d-axis command value and the negative sequence d-axis voltage related parameters, the negative sequence d-axis voltage reference value is calculated using the negative sequence d-axis voltage reference value calculation formula.

[0119] For example, the formula for calculating the negative-sequence d-axis voltage reference value is as follows:

[0120]

[0121] in, Here, ω is the negative-sequence d-axis voltage reference value, ω is the angular velocity, and L is the equivalent inductance. This represents the measured value of the negative sequence q-axis current. The measured value of the negative sequence d-axis current is drr. - The negative d-axis command value;

[0122] Calculate the difference between the positive sequence d-axis current command value after one limit and the corresponding measured positive sequence d-axis current value, and input the difference into the transfer function of the inner loop controller of the d-axis current to calculate the positive sequence d-axis command value. Based on the positive sequence d-axis command value and the positive sequence d-axis voltage related parameters, use the positive sequence d-axis voltage reference value calculation formula to calculate the positive sequence d-axis voltage reference value.

[0123] For example, the formula for calculating the positive-sequence d-axis voltage reference value is as follows:

[0124]

[0125] in, Here, ω is the positive-sequence d-axis voltage reference value, ω is the angular velocity, and L is the equivalent inductance. This represents the measured value of the positive-sequence q-axis current. The measured value of the positive sequence d-axis current is drr. + This is the command value for the positive d-axis;

[0126] The difference between the negative-sequence q-axis current command value and the corresponding measured negative-sequence q-axis current value after secondary limiting is calculated, and the difference is input into the transfer function of the inner loop controller of the q-axis current to calculate the negative-sequence q-axis command value. Based on the negative-sequence q-axis command value and the negative-sequence q-axis voltage related parameters, the negative-sequence q-axis voltage reference value is calculated using the negative-sequence q-axis voltage reference value calculation formula.

[0127] For example, the formula for calculating the negative-sequence q-axis voltage reference value is as follows:

[0128]

[0129] in, Here, ω is the negative-sequence q-axis voltage reference value, ω is the angular velocity, and L is the equivalent inductance. This represents the measured value of the negative sequence q-axis current. The measured value of the negative sequence q-axis current is qrr. - This is the negative q-axis command value.

[0130] The difference between the positive-sequence q-axis current command value after one limit is calculated and the corresponding positive-sequence q-axis current measured value is input into the transfer function of the inner loop controller of the q-axis current to calculate the positive-sequence q-axis command value. Based on the positive-sequence q-axis command value and the positive-sequence q-axis voltage related parameters, the positive-sequence q-axis voltage reference value is calculated using the positive-sequence q-axis voltage reference value calculation formula.

[0131] The positive-sequence q-axis voltage-related parameters include one or more of the following: angular velocity, equivalent inductance, and measured values ​​of positive-sequence d-axis current.

[0132] For example, the implementation of current inner-loop control, specifically how the difference between the commanded and measured current values ​​of the d-axis and q-axis is used to calculate the voltage reference value, is illustrated by calculations based on transfer functions and Laplace transforms, as well as some basic electrical parameters of the motor. First, we calculate the difference between the commanded and measured current values ​​of the d-axis and q-axis. These differences are used as inputs to the d-axis and q-axis transfer functions, which describe how the inner-loop controller adjusts the voltage reference value based on the current error. In general, this process describes how the voltage reference value is adjusted by the inner-loop controller based on the difference between the commanded and measured current values, thereby achieving precise current control.

[0133] In one implementation, the expression for the transfer function is as follows:

[0134] G(S) = KP + Ki ÷ S

[0135] Where G(S) is the transfer function, KP is the proportional coefficient, Ki is the integral coefficient, and S is the Laplace operator.

[0136] In one implementation, the positive-sequence q-axis voltage reference value is calculated as follows:

[0137]

[0138] in, Here, ω is the positive-sequence q-axis voltage reference value, ω is the angular velocity, and L is the equivalent inductance. This represents the measured value of the positive-sequence d-axis current. The measured value of the positive-sequence q-axis current is qrr. + The current is the positive-sequence q-axis command value. This invention uses the difference between the current command value and the measured value to adjust the positive and negative sequence voltage reference values ​​through the inner loop controller, thereby achieving precise current control.

[0139] Step 4 above, based on the positive and negative sequence voltage reference values, uses coordinate system transformation to generate positive and negative sequence command values, and controls the power electronic equipment to complete low-voltage ride-through according to the positive and negative sequence command values, includes:

[0140] Based on the positive sequence d-axis voltage reference value and the positive sequence q-axis voltage reference value, coordinate transformation is used to transform from the dq coordinate system to the abc coordinate system to generate a positive sequence command value;

[0141] Based on the negative sequence d-axis voltage reference value and the negative sequence q-axis voltage reference value, coordinate transformation is used to transform from the dq coordinate system to the abc coordinate system to generate a negative sequence command value;

[0142] Based on the positive and negative sequence command values, the power electronic equipment is controlled to complete the low voltage ride-through.

[0143] For example, the positive-sequence and negative-sequence command values ​​are transformed from the dq coordinate system to the abc coordinate system. The dq coordinate system is typically used to represent rotating coordinate systems, where the d-axis is aligned with the magnetic field direction and the q-axis is perpendicular to the d-axis. The abc coordinate system is a fixed three-phase coordinate system. After the transformation, the positive-sequence and negative-sequence command values ​​in the abc coordinate system are obtained. These command values ​​can be directly used in the PWM control of the motor or other voltage control loops. This invention reduces the negative-sequence component of the system by adding an additional negative-sequence current control strategy during the fault period to the inner loop control. This invention also achieves rapid recovery to the pre-fault state without conflicting with new energy control. To prevent oscillations during low-voltage ride-through, this invention sets a strategy to lower the negative-sequence current command value and reduce the negative-sequence current component of the system. This method can quickly keep the negative-sequence current within a small range, ensuring rapid recovery after the fault ends and effectively suppressing the magnitude of the fault current.

[0144] Example 2:

[0145] Based on the same inventive concept, this patent application also provides a low-voltage ride-through control system for power electronic equipment based on negative sequence current, such as... Figure 2 As shown, it includes: a primary limiting module, a secondary limiting module, a positive and negative sequence voltage reference value calculation module, and a low voltage ride-through module;

[0146] The primary limiting module is used to limit the command values ​​of the positive and negative sequence currents of the outer loop according to a predetermined positive and negative sequence current command threshold range; the command values ​​of the positive and negative sequence currents include the command values ​​of the positive sequence current and the command values ​​of the negative sequence current.

[0147] The secondary limiting module is used to perform secondary limiting on the command value of the negative sequence current after the primary limiting, according to the preset negative sequence current command protection range.

[0148] The positive and negative sequence voltage reference value calculation module is used to obtain the positive and negative sequence voltage reference values ​​based on the command value of the positive sequence current obtained after the first limiting, the command value of the negative sequence current obtained after the second limiting, and the corresponding measured values ​​of the positive and negative sequence currents, through the transfer function of the inner loop controller.

[0149] The low-voltage ride-through module is used to generate positive and negative sequence command values ​​based on the positive and negative sequence voltage reference values ​​by using coordinate system transformation, and to control the power electronic equipment to complete the low-voltage ride-through according to the positive and negative sequence command values.

[0150] Preferably, the positive and negative sequence current command threshold intervals include a negative sequence current command threshold interval and a positive sequence current command threshold interval; the primary limiting module is used for:

[0151] Based on the command value of the negative sequence current of the outer loop, the command value of the negative sequence current after one limit is obtained by using a pre-set negative sequence current command threshold range.

[0152] Based on the command value of the positive sequence current of the outer loop, the command value of the positive sequence current after one limit is obtained by using a pre-set positive sequence current command threshold range.

[0153] The command values ​​for the positive sequence current include positive sequence d-axis current command values ​​and positive sequence q-axis current command values; the command values ​​for the negative sequence current include negative sequence d-axis current command values ​​and negative sequence q-axis current command values; the command values ​​for the positive sequence current after first-stage limiting include positive sequence d-axis current command values ​​and positive sequence q-axis current command values ​​after first-stage limiting; the command values ​​for the negative sequence current after first-stage limiting include negative sequence d-axis current command values ​​and negative sequence q-axis current command values ​​after first-stage limiting.

[0154] Preferably, the secondary limiting module is used for:

[0155] When a fault voltage drop is detected, the command value of the negative sequence current after the first limit is adjusted to the negative sequence current command protection range according to the preset negative sequence current command protection range.

[0156] After the fault voltage is cleared, the command value of the negative sequence current in the negative sequence current command range is limited by the positive sequence current command threshold range to obtain the command value of the negative sequence current after secondary limiting.

[0157] The command value of the negative sequence current after the second-stage limiting includes: the command value of the negative sequence d-axis current after the second-stage limiting and the command value of the negative sequence q-axis current after the second-stage limiting.

[0158] Preferably, the negative sequence current command protection range is greater than 0.05 pu and less than 0.5 pu.

[0159] Preferably, the system further includes: an inner and outer loop control module, used for:

[0160] Determine if the outer loop control exists. If it exists, set the outer loop control strategy to network-type control and simultaneously set the inner loop control.

[0161] If it does not exist, then directly set the inner loop control;

[0162] The inner loop control includes negative sequence current control.

[0163] Preferably, the positive and negative sequence voltage reference value calculation module is used for:

[0164] The difference between the negative sequence d-axis current command value and the corresponding measured negative sequence d-axis current value after secondary limiting is calculated, and the difference is input into the transfer function of the inner loop controller of the d-axis current to calculate the negative sequence d-axis command value. Based on the negative sequence d-axis command value and the negative sequence d-axis voltage related parameters, the negative sequence d-axis voltage reference value is calculated using the negative sequence d-axis voltage reference value calculation formula.

[0165] Calculate the difference between the positive sequence d-axis current command value after one limit and the corresponding measured positive sequence d-axis current value, and input the difference into the transfer function of the inner loop controller of the d-axis current to calculate the positive sequence d-axis command value. Based on the positive sequence d-axis command value and the positive sequence d-axis voltage related parameters, use the positive sequence d-axis voltage reference value calculation formula to calculate the positive sequence d-axis voltage reference value.

[0166] The difference between the negative-sequence q-axis current command value and the corresponding measured negative-sequence q-axis current value after secondary limiting is calculated, and the difference is input into the transfer function of the inner loop controller of the q-axis current to calculate the negative-sequence q-axis command value. Based on the negative-sequence q-axis command value and the negative-sequence q-axis voltage related parameters, the negative-sequence q-axis voltage reference value is calculated using the negative-sequence q-axis voltage reference value calculation formula.

[0167] The difference between the positive-sequence q-axis current command value after one limit is calculated and the corresponding positive-sequence q-axis current measured value is input into the transfer function of the inner loop controller of the q-axis current to calculate the positive-sequence q-axis command value. Based on the positive-sequence q-axis command value and the positive-sequence q-axis voltage related parameters, the positive-sequence q-axis voltage reference value is calculated using the positive-sequence q-axis voltage reference value calculation formula.

[0168] The positive-sequence q-axis voltage-related parameters include one or more of the following: angular velocity, equivalent inductance, and measured values ​​of positive-sequence d-axis current.

[0169] Preferably, the expression for the transfer function is as follows:

[0170] G(S) = KP + Ki ÷ S

[0171] Where G(S) is the transfer function, KP is the proportional coefficient, Ki is the integral coefficient, and S is the Laplace operator.

[0172] Preferably, the formula for calculating the positive-sequence q-axis voltage reference value is as follows:

[0173]

[0174] in, Here, ω is the positive-sequence q-axis voltage reference value, ω is the angular velocity, and L is the equivalent inductance. This represents the measured value of the positive-sequence d-axis current. The measured value of the positive-sequence q-axis current is qrr. +This is the positive sequence q-axis command value.

[0175] Preferably, the low voltage ride-through module is used for:

[0176] Based on the positive sequence d-axis voltage reference value and the positive sequence q-axis voltage reference value, coordinate transformation is used to transform from the dq coordinate system to the abc coordinate system to generate a positive sequence command value;

[0177] Based on the negative sequence d-axis voltage reference value and the negative sequence q-axis voltage reference value, coordinate transformation is used to transform from the dq coordinate system to the abc coordinate system to generate a negative sequence command value;

[0178] Based on the positive and negative sequence command values, the power electronic equipment is controlled to complete the low voltage ride-through.

[0179] Example 3

[0180] like Figure 3 As shown, the present invention also provides an electronic device, which may be a computer device, a microcontroller device, a smart mobile device, etc. The electronic device in this embodiment may include a processor, a memory, a transceiver component, etc. The memory, processor, and transceiver component are connected via a bus; the memory can be used to store executable programs, and an exemplary executable program may include instructions; the processor is used to execute the instructions stored in the memory. The memory can also be used to store data, which can be accessed and / or modified when instructions are executed.

[0181] The processor may be a Central Processing Unit (CPU), or it may 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. It is the computing and control core of the terminal, and it is suitable for implementing one or more instructions. Specifically, it is suitable for loading and executing one or more instructions in the storage medium to realize the corresponding method flow or corresponding function, so as to realize the steps of the low voltage ride-through control method for power electronic equipment based on negative sequence current in the above embodiments.

[0182] Example 4

[0183] Based on the same inventive concept, this invention also provides a readable storage medium, specifically an electronic device readable storage medium (Memory). This readable storage medium is a memory device within an electronic device used to store programs and data. It is understood that the storage medium here can include both built-in storage media within the electronic device and extended storage media supported by the electronic device. The storage medium provides storage space, which stores the terminal's operating system. Furthermore, this storage space also stores one or more instructions suitable for loading and execution by a processor. These instructions can be one or more executable programs (including program code). It should be noted that the storage medium here can be high-speed RAM or non-volatile memory, such as at least one disk storage device. Loading and executing one or more instructions stored in the storage medium by the processor can implement the steps of the low-voltage ride-through control method for power electronic equipment based on negative sequence current in the above embodiments.

[0184] Those skilled in the art will understand that embodiments of this patent application can be provided as methods, systems, or computer program products. Therefore, this patent application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this patent application can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0185] This patent application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the patent application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing device to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing device, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0186] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0187] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0188] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this patent application and not to limit its scope of protection. Although the patent application has been described in detail with reference to the above embodiments, those skilled in the art should understand that after reading this patent application, they can still make various changes, modifications or equivalent substitutions to the specific implementation of the application, but these changes, modifications or equivalent substitutions are all within the scope of protection of the claims pending approval.

Claims

1. A low-voltage ride-through control method for power electronic equipment based on negative sequence current, characterized in that, include: According to the predetermined positive and negative sequence current command threshold range, the command values ​​of the positive and negative sequence currents of the outer loop are limited once; the command values ​​of the positive and negative sequence currents include the command values ​​of the positive sequence current and the command values ​​of the negative sequence current. According to the preset negative sequence current command protection range, the command value of the negative sequence current after the first limit is subjected to a second limit. Based on the commanded value of the positive sequence current obtained after the first limiting, the commanded value of the negative sequence current obtained after the second limiting, and the corresponding measured values ​​of the positive and negative sequence currents, the reference values ​​of the positive and negative sequence voltages are obtained through the transfer function of the inner loop controller. Based on the positive and negative sequence voltage reference values, coordinate system transformation is used to generate positive and negative sequence command values. According to the positive and negative sequence command values, the power electronic equipment is controlled to complete the low voltage ride-through. The positive and negative sequence current command threshold range includes a negative sequence current command threshold range and a positive sequence current command threshold range; The step of limiting the command values ​​of the positive and negative sequence currents of the outer loop according to a predetermined positive and negative sequence current command threshold range includes: Based on the command value of the negative sequence current of the outer loop, the command value of the negative sequence current after one limit is obtained by using a pre-set negative sequence current command threshold range. Based on the command value of the positive sequence current of the outer loop, the command value of the positive sequence current after one limit is obtained by using a pre-set positive sequence current command threshold range. Wherein, the command value of the positive sequence current includes the command value of the positive sequence d-axis current and the command value of the positive sequence q-axis current; the command value of the negative sequence current includes the command value of the negative sequence d-axis current and the command value of the negative sequence q-axis current; the command value of the positive sequence current after the first limiting includes the command value of the positive sequence d-axis current and the command value of the positive sequence q-axis current after the first limiting; the command value of the negative sequence current after the first limiting includes the command value of the negative sequence d-axis current and the command value of the negative sequence q-axis current after the first limiting. The step of performing a secondary limit on the command value of the negative sequence current after the first limit, based on a pre-set negative sequence current command protection range, includes: When a fault voltage drop is detected, the command value of the negative sequence current after the first limit is adjusted to the negative sequence current command protection range according to the preset negative sequence current command protection range. After the fault voltage is cleared, the command value of the negative sequence current in the negative sequence current command protection range is limited by the positive sequence current command threshold range to obtain the command value of the negative sequence current after secondary limiting. The command value of the negative sequence current after the second-stage limiting includes: the command value of the negative sequence d-axis current after the second-stage limiting and the command value of the negative sequence q-axis current after the second-stage limiting.

2. The method as described in claim 1, characterized in that, The negative sequence current command protection range is greater than 0.05 pu and less than 0.5 pu.

3. The method as described in claim 1, characterized in that, Before limiting the command value of the positive and negative sequence current of the outer loop according to the predetermined positive and negative sequence current command threshold range, the method further includes: Determine if the outer loop control exists. If it exists, set the outer loop control strategy to network-type control and simultaneously set the inner loop control. If it does not exist, then directly set the inner loop control; The inner loop control includes negative sequence current control.

4. The method as described in claim 1, characterized in that, The process of obtaining positive and negative sequence voltage reference values ​​through the transfer function of the inner loop controller, based on the commanded value of the positive sequence current obtained after the first limiting, the commanded value of the negative sequence current obtained after the second limiting, and the corresponding measured values ​​of the positive and negative sequence currents, includes: The difference between the negative sequence d-axis current command value and the corresponding measured negative sequence d-axis current value after secondary limiting is calculated, and the difference is input into the transfer function of the inner loop controller of the d-axis current to calculate the negative sequence d-axis command value. Based on the negative sequence d-axis command value and the negative sequence d-axis voltage related parameters, the negative sequence d-axis voltage reference value is calculated using the negative sequence d-axis voltage reference value calculation formula. Calculate the difference between the positive sequence d-axis current command value after one limit and the corresponding measured positive sequence d-axis current value, and input the difference into the transfer function of the inner loop controller of the d-axis current to calculate the positive sequence d-axis command value. Based on the positive sequence d-axis command value and the positive sequence d-axis voltage related parameters, use the positive sequence d-axis voltage reference value calculation formula to calculate the positive sequence d-axis voltage reference value. The difference between the negative-sequence q-axis current command value and the corresponding measured negative-sequence q-axis current value after secondary limiting is calculated, and the difference is input into the transfer function of the inner loop controller of the q-axis current to calculate the negative-sequence q-axis command value. Based on the negative-sequence q-axis command value and the negative-sequence q-axis voltage related parameters, the negative-sequence q-axis voltage reference value is calculated using the negative-sequence q-axis voltage reference value calculation formula. The difference between the positive-sequence q-axis current command value after one limit is calculated and the corresponding positive-sequence q-axis current measured value is input into the transfer function of the inner loop controller of the q-axis current to calculate the positive-sequence q-axis command value. Based on the positive-sequence q-axis command value and the positive-sequence q-axis voltage related parameters, the positive-sequence q-axis voltage reference value is calculated using the positive-sequence q-axis voltage reference value calculation formula. The positive-sequence q-axis voltage-related parameters include one or more of the following: angular velocity, equivalent inductance, and measured values ​​of positive-sequence d-axis current.

5. The method as described in claim 4, characterized in that, The expression for the transfer function is as follows: G(S) = KP + Ki ÷ S Where G(S) is the transfer function, KP is the proportional coefficient, Ki is the integral coefficient, and S is the Laplace operator.

6. The method as described in claim 4, characterized in that, The formula for calculating the positive-sequence q-axis voltage reference value is as follows: in, This is the reference value for the positive-sequence q-axis voltage. Let L be the angular velocity and L be the equivalent inductance. This represents the measured value of the positive-sequence d-axis current. This represents the measured value of the positive-sequence q-axis current. This is the positive sequence q-axis command value.

7. The method as described in claim 4, characterized in that, Based on the positive and negative sequence voltage reference values, coordinate system transformation is used to generate positive and negative sequence command values. According to these command values, the power electronic equipment is controlled to complete low-voltage ride-through, including: Based on the positive sequence d-axis voltage reference value and the positive sequence q-axis voltage reference value, coordinate transformation is used to transform from the dq coordinate system to the abc coordinate system to generate a positive sequence command value; Based on the negative sequence d-axis voltage reference value and the negative sequence q-axis voltage reference value, coordinate transformation is used to transform from the dq coordinate system to the abc coordinate system to generate a negative sequence command value; Based on the positive and negative sequence command values, the power electronic equipment is controlled to complete the low voltage ride-through.

8. A low-voltage ride-through control system for power electronic equipment based on negative sequence current, characterized in that, include: Primary limiting module, secondary limiting module, positive and negative sequence voltage reference value calculation module, and low voltage ride-through module; The primary limiting module is used to limit the command values ​​of the positive and negative sequence currents of the outer loop according to a predetermined positive and negative sequence current command threshold range; the command values ​​of the positive and negative sequence currents include the command values ​​of the positive sequence current and the command values ​​of the negative sequence current. The secondary limiting module is used to perform secondary limiting on the command value of the negative sequence current after the primary limiting, according to the preset negative sequence current command protection range. The positive and negative sequence voltage reference value calculation module is used to obtain the positive and negative sequence voltage reference values ​​based on the command value of the positive sequence current obtained after the first limiting, the command value of the negative sequence current obtained after the second limiting, and the corresponding measured values ​​of the positive and negative sequence currents, through the transfer function of the inner loop controller. The low-voltage ride-through module is used to generate positive and negative sequence command values ​​based on the positive and negative sequence voltage reference values ​​by coordinate system transformation, and to control the power electronic equipment to complete the low-voltage ride-through according to the positive and negative sequence command values. The positive and negative sequence current command threshold intervals include a negative sequence current command threshold interval and a positive sequence current command threshold interval; the primary limiting module is used for: Based on the command value of the negative sequence current of the outer loop, the command value of the negative sequence current after one limit is obtained by using a pre-set negative sequence current command threshold range. Based on the command value of the positive sequence current of the outer loop, the command value of the positive sequence current after one limit is obtained by using a pre-set positive sequence current command threshold range. Wherein, the command value of the positive sequence current includes the command value of the positive sequence d-axis current and the command value of the positive sequence q-axis current; the command value of the negative sequence current includes the command value of the negative sequence d-axis current and the command value of the negative sequence q-axis current; the command value of the positive sequence current after the first limiting includes the command value of the positive sequence d-axis current and the command value of the positive sequence q-axis current after the first limiting; the command value of the negative sequence current after the first limiting includes the command value of the negative sequence d-axis current and the command value of the negative sequence q-axis current after the first limiting. The secondary limiting module is used for: When a fault voltage drop is detected, the command value of the negative sequence current after the first limit is adjusted to the negative sequence current command protection range according to the preset negative sequence current command protection range. After the fault voltage is cleared, the command value of the negative sequence current in the negative sequence current command protection range is limited by the positive sequence current command threshold range to obtain the command value of the negative sequence current after secondary limiting. The command value of the negative sequence current after the second-stage limiting includes: the command value of the negative sequence d-axis current after the second-stage limiting and the command value of the negative sequence q-axis current after the second-stage limiting.

Images