A variable frequency transformer fault ride-through control method for regulating voltage balance and related device

Abstract

The application discloses a variable-frequency transformer fault ride-through control method for regulating voltage balance and related devices, and the method is applied to a fault ride-through circuit. Grid voltage, stator winding parameters, three-phase converter parameters, capacitor voltage and rotor phase angle are collected. The stator winding parameters and three-phase converter positive sequence current direct current components are calculated based on the collected parameters. The preset voltage control equation is used to calculate the direct current components according to the above parameters, and the three-phase converter positive sequence and negative sequence voltage reference value direct current components are obtained. The obtained direct current components are subjected to coordinate transformation according to the grid voltage phase angle and the rotor phase angle, and the three-phase converter voltage vector reference value in the two-phase stationary coordinate system is obtained. The reference value is subjected to space vector modulation, and a control signal is generated. The variable-frequency transformer fault ride-through control is realized based on the control signal. The application can realize grid voltage imbalance regulation control by using at least two three-phase converters, and the technical problems of obvious material consumption and complex operation are solved.

Description

Technical Field

[0001] This application relates to the field of power grid control technology, and in particular to a method and related apparatus for fault ride-through control of variable frequency transformers for regulating voltage balance. Background Technology

[0002] The power grid is a crucial backbone of the energy internet, and grid interconnection is an inevitable trend in future power grid development. Variable frequency transformers (VFDs) are a new type of grid interconnection device. When the voltage across the VFD becomes unbalanced, the current flowing through it will also be unbalanced, leading to fluctuations in torque and power of the VFD at twice the rotor's electrical angular velocity, twice the stator's synchronous angular velocity, and twice the rotor's synchronous angular velocity. Torque fluctuations reduce the mechanical life of the shaft, while power fluctuations degrade the power quality of the power system.

[0003] Existing technologies typically require at least two three-phase converters to stabilize the DC capacitor voltage and resolve the voltage imbalance between the two grids. From a material cost perspective, this undoubtedly results in more materials and higher costs. From an operational perspective, too many devices increase operational complexity, reduce actual control efficiency, and are not conducive to practical applications. Summary of the Invention

[0004] This application provides a method and related apparatus for regulating voltage balance in a variable frequency transformer fault ride-through control system, which addresses the technical problems of existing technologies requiring at least two three-phase converters to regulate and control grid voltage imbalance, resulting in significant material consumption and operational complexity.

[0005] In view of this, the first aspect of this application provides a fault ride-through control method for a variable frequency transformer to regulate voltage balance. The control method is applied in a fault ride-through circuit of a variable frequency transformer, the circuit including: a first power grid, a second power grid, a three-phase transformer, a three-phase converter, a variable frequency transformer, an H-bridge converter, a DC capacitor, and a control circuit.

[0006] One end of the AC output terminal of the three-phase transformer is connected to the first power grid, and the other end is connected to the stator winding of the variable frequency transformer.

[0007] The rotor winding of the variable frequency transformer is connected to the second power grid;

[0008] The AC input terminal of the three-phase transformer is connected to the AC terminal of the three-phase converter;

[0009] The DC terminal of the three-phase converter is connected to the DC input terminal of the H-bridge converter and the DC capacitor;

[0010] The DC output terminal of the H-bridge converter is connected to the DC motor of the variable frequency transformer;

[0011] The control circuit is connected to the control signal input terminals of the three-phase converter and the H-bridge converter, respectively;

[0012] The control method includes:

[0013] The system collects grid voltage, stator winding parameters, three-phase converter parameters, capacitor voltage, and rotor phase angle. The grid voltage includes the voltages of the first grid and the second grid. The stator winding parameters and the three-phase converter parameters both include voltage and current.

[0014] The grid voltage, stator winding parameters, three-phase converter parameters, and rotor phase angle are analyzed and processed to obtain stator winding reactive power, three-phase converter positive sequence current DC component, and stator winding negative sequence DC component. The stator winding negative sequence DC component includes voltage DC component and current DC component.

[0015] The capacitor voltage, the stator winding reactive power, the DC component of the positive sequence current of the three-phase converter, and the DC component of the stator winding are analyzed and processed using a preset voltage control equation to obtain the DC component of the reference value of the positive sequence voltage of the three-phase converter and the DC component of the reference value of the negative sequence voltage of the three-phase converter. The DC component of the reference value of the negative sequence voltage of the three-phase converter includes a first negative sequence component and a second negative sequence component.

[0016] Based on the grid voltage phase angle and the rotor phase angle, the DC component of the positive sequence voltage reference value and the DC component of the negative sequence voltage reference value of the three-phase converter are analyzed and processed to obtain the voltage vector reference value of the three-phase converter in the two-phase stationary coordinate system.

[0017] The voltage vector reference value of the three-phase converter is spatially vector modulated to generate the control signal for the three-phase converter switch, and the fault ride-through control of the variable frequency transformer is realized based on the control signal.

[0018] Preferably, the analysis and processing of the grid voltage, the stator winding parameters, the three-phase converter parameters, and the rotor phase angle yields the stator winding reactive power, the positive-sequence DC component of the three-phase converter current, and the negative-sequence DC component of the stator winding. The negative-sequence DC component of the stator winding includes a voltage DC component and a current DC component, comprising:

[0019] The power is calculated based on the stator winding parameters to obtain the reactive power of the stator winding;

[0020] Based on the grid voltage, the stator winding parameters, the three-phase converter parameters, and the rotor phase angle, the three-phase stationary to two-phase stationary coordinate transformation, positive and negative sequence separation calculation, phase angle calculation, and two-phase stationary to two-phase rotating coordinate transformation processes are performed to obtain the positive sequence DC component of the three-phase converter current and the negative sequence DC component of the stator winding.

[0021] Preferably, the step of performing three-phase stationary to two-phase stationary coordinate transformation, positive and negative sequence separation calculation, phase angle calculation, and two-phase stationary to two-phase rotating coordinate transformation based on the grid voltage, the stator winding parameters, the three-phase converter parameters, and the rotor phase angle to obtain the positive sequence DC component of the three-phase converter current and the negative sequence DC component of the stator winding includes:

[0022] Based on the grid voltage, the stator winding parameters, and the three-phase converter parameters, a three-phase stationary to two-phase stationary coordinate transformation is performed to obtain the grid voltage vector, the stator winding vector, and the three-phase converter vector. The three-phase converter vector includes the three-phase converter voltage vector and the three-phase converter current vector.

[0023] The positive and negative sequence separation calculations are performed on the grid voltage vector, the stator winding vector, and the three-phase converter vector to obtain the grid positive and negative sequence voltage vector, the stator winding negative sequence vector, and the three-phase converter positive sequence vector. The three-phase converter positive sequence vector includes the voltage positive sequence vector and the current positive sequence vector.

[0024] The phase angles of the positive and negative sequence voltage vectors of the power grid and the positive sequence voltage vector of the three-phase converter are calculated respectively to obtain the phase angles of the power grid voltage and the positive sequence voltage of the three-phase converter.

[0025] Based on the grid voltage phase angle, the positive sequence voltage phase angle of the three-phase converter, and the rotor phase angle, the positive sequence current vector of the three-phase converter and the negative sequence vector of the stator winding are transformed from two-phase stationary to two-phase rotating coordinates to obtain the DC component of the positive sequence current of the three-phase converter and the DC component of the negative sequence of the stator winding.

[0026] Preferably, the step of analyzing and processing the DC components of the positive-sequence voltage reference value and the negative-sequence voltage reference value of the three-phase converter based on the grid voltage phase angle and the rotor phase angle to obtain the three-phase converter voltage vector reference value in a two-phase stationary coordinate system includes:

[0027] Based on the grid voltage phase angle, the DC component of the positive sequence voltage reference value of the three-phase converter is subjected to a coordinate transformation from two-phase rotation to two-phase stationary to obtain the positive sequence voltage vector reference value of the three-phase converter in the two-phase stationary coordinate system.

[0028] Based on the grid voltage phase angle, the first negative sequence component of the DC component of the three-phase converter negative sequence voltage reference value is subjected to a coordinate transformation from two-phase rotation to two-phase stationary to obtain the first negative sequence voltage vector reference value of the three-phase converter in the two-phase stationary coordinate system.

[0029] Based on the grid voltage phase angle and the rotor phase angle, the second negative sequence component of the DC component of the three-phase converter negative sequence voltage reference value is transformed from two-phase rotation to two-phase stationary coordinate system to obtain the second negative sequence voltage vector reference value of the three-phase converter in the two-phase stationary coordinate system.

[0030] The positive-sequence voltage vector reference value, the first negative-sequence voltage vector reference value, and the second negative-sequence voltage vector reference value of the three-phase converter are summed to obtain the voltage vector reference value of the three-phase converter in a two-phase stationary coordinate system.

[0031] The second aspect of this application provides a variable frequency transformer fault ride-through control device for regulating voltage balance. The control device is applied in a variable frequency transformer fault ride-through circuit, the circuit including: a first power grid, a second power grid, a three-phase transformer, a three-phase converter, a variable frequency transformer, an H-bridge converter, a DC capacitor, and a control circuit.

[0032] One end of the AC output terminal of the three-phase transformer is connected to the first power grid, and the other end is connected to the stator winding of the variable frequency transformer.

[0033] The rotor winding of the variable frequency transformer is connected to the second power grid;

[0034] The AC input terminal of the three-phase transformer is connected to the AC terminal of the three-phase converter;

[0035] The DC terminal of the three-phase converter is connected to the DC input terminal of the H-bridge converter and the DC capacitor;

[0036] The DC output terminal of the H-bridge converter is connected to the DC motor of the variable frequency transformer;

[0037] The control circuit is connected to the control signal input terminals of the three-phase converter and the H-bridge converter, respectively;

[0038] The control device includes:

[0039] The parameter acquisition unit is used to acquire grid voltage, stator winding parameters, three-phase converter parameters, capacitor voltage and rotor phase angle. The grid voltage includes the voltages of the first grid and the second grid. The stator winding parameters and the three-phase converter parameters both include voltage and current.

[0040] The first analysis unit is used to analyze and process the grid voltage, the stator winding parameters, the three-phase converter parameters and the rotor phase angle to obtain the stator winding reactive power, the positive sequence DC component of the three-phase converter current and the stator winding negative sequence DC component. The stator winding negative sequence DC component includes voltage DC component and current DC component.

[0041] The second analysis unit is used to analyze and process the capacitor voltage, the stator winding reactive power, the DC component of the positive sequence current of the three-phase converter and the DC component of the stator winding using a preset voltage control equation, so as to obtain the DC component of the reference value of the positive sequence voltage of the three-phase converter and the DC component of the reference value of the negative sequence voltage of the three-phase converter. The DC component of the reference value of the negative sequence voltage of the three-phase converter includes a first negative sequence component and a second negative sequence component.

[0042] The third analysis unit is used to analyze and process the DC component of the positive sequence voltage reference value and the DC component of the negative sequence voltage reference value of the three-phase converter according to the grid voltage phase angle and the rotor phase angle, so as to obtain the three-phase converter voltage vector reference value in the two-phase stationary coordinate system.

[0043] The modulation and control unit is used to perform space vector modulation on the voltage vector reference value of the three-phase converter, generate control signals for the switching of the three-phase converter, and realize fault ride-through control of the variable frequency transformer based on the control signals.

[0044] Preferably, the first analysis unit specifically includes:

[0045] The power calculation subunit is used to perform power calculation based on the stator winding parameters to obtain the reactive power of the stator winding.

[0046] The coordinate transformation subunit is used to perform three-phase stationary to two-phase stationary coordinate transformation, positive and negative sequence separation calculation, phase angle calculation, and two-phase stationary to two-phase rotating coordinate transformation processing according to the grid voltage, the stator winding parameters, the three-phase converter parameters, and the rotor phase angle, respectively, to obtain the positive sequence DC component of the three-phase converter current and the negative sequence DC component of the stator winding.

[0047] Preferably, the coordinate transformation subunit is specifically used for:

[0048] Based on the grid voltage, the stator winding parameters, and the three-phase converter parameters, a three-phase stationary to two-phase stationary coordinate transformation is performed to obtain the grid voltage vector, the stator winding vector, and the three-phase converter vector. The three-phase converter vector includes the three-phase converter voltage vector and the three-phase converter current vector.

[0049] The positive and negative sequence separation calculations are performed on the grid voltage vector, the stator winding vector, and the three-phase converter vector to obtain the grid positive and negative sequence voltage vector, the stator winding negative sequence vector, and the three-phase converter positive sequence vector. The three-phase converter positive sequence vector includes the voltage positive sequence vector and the current positive sequence vector.

[0050] The phase angles of the positive and negative sequence voltage vectors of the power grid and the positive sequence voltage vector of the three-phase converter are calculated respectively to obtain the phase angles of the power grid voltage and the positive sequence voltage of the three-phase converter.

[0051] Based on the grid voltage phase angle, the positive sequence voltage phase angle of the three-phase converter, and the rotor phase angle, the positive sequence current vector of the three-phase converter and the negative sequence vector of the stator winding are transformed from two-phase stationary to two-phase rotating coordinates to obtain the DC component of the positive sequence current of the three-phase converter and the DC component of the negative sequence of the stator winding.

[0052] Preferably, the third analysis unit is specifically used for:

[0053] Based on the grid voltage phase angle, the DC component of the positive sequence voltage reference value of the three-phase converter is subjected to a coordinate transformation from two-phase rotation to two-phase stationary to obtain the positive sequence voltage vector reference value of the three-phase converter in the two-phase stationary coordinate system.

[0054] Based on the grid voltage phase angle, the first negative sequence component of the DC component of the three-phase converter negative sequence voltage reference value is subjected to a coordinate transformation from two-phase rotation to two-phase stationary to obtain the first negative sequence voltage vector reference value of the three-phase converter in the two-phase stationary coordinate system.

[0055] Based on the grid voltage phase angle and the rotor phase angle, the second negative sequence component of the DC component of the three-phase converter negative sequence voltage reference value is transformed from two-phase rotation to two-phase stationary coordinate system to obtain the second negative sequence voltage vector reference value of the three-phase converter in the two-phase stationary coordinate system.

[0056] The positive-sequence voltage vector reference value, the first negative-sequence voltage vector reference value, and the second negative-sequence voltage vector reference value of the three-phase converter are summed to obtain the voltage vector reference value of the three-phase converter in a two-phase stationary coordinate system.

[0057] The third aspect provides a variable frequency transformer fault ride-through control device for regulating voltage balance, the device including a processor and a memory;

[0058] The memory is used to store program code and transmit the program code to the processor;

[0059] The processor is used to execute the variable frequency transformer fault ride-through control method for adjusting voltage balance as described in the first aspect, according to the instructions in the program code.

[0060] The fourth aspect provides a computer-readable storage medium for storing program code for executing the variable frequency transformer fault ride-through control method for adjusting voltage balance as described in the first aspect.

[0061] As can be seen from the above technical solutions, the embodiments of this application have the following advantages:

[0062] This application provides a fault ride-through control method for a variable frequency transformer to regulate voltage balance. The method is applied in a fault ride-through circuit of the variable frequency transformer. The circuit includes: a first power grid, a second power grid, a three-phase transformer, a three-phase converter, a variable frequency transformer, an H-bridge converter, a DC capacitor, and a control circuit. One end of the AC output terminal of the three-phase transformer is connected to the first power grid, and the other end is connected to the stator winding of the variable frequency transformer. The rotor winding of the variable frequency transformer is connected to the second power grid. The AC input terminal of the three-phase transformer is connected to the AC terminal of the three-phase converter. The DC terminal of the three-phase converter is connected to the DC input terminal of the H-bridge converter and the DC capacitor. The DC output terminal of the H-bridge converter is connected to the DC motor of the variable frequency transformer. The control circuit is connected to the control signal input terminals of the three-phase converter and the H-bridge converter, respectively.

[0063] The control method includes: acquiring grid voltage, stator winding parameters, three-phase converter parameters, capacitor voltage, and rotor phase angle; grid voltage includes the voltages of both the first and second grids; and stator winding parameters and three-phase converter parameters include both voltage and current; analyzing and processing the grid voltage, stator winding parameters, three-phase converter parameters, and rotor phase angle to obtain stator winding reactive power, the DC component of the positive-sequence current of the three-phase converter, and the negative-sequence DC component of the stator winding; and using preset voltage control equations to control the capacitor voltage, stator winding reactive power, the DC component of the positive-sequence current of the three-phase converter, and the stator winding... The negative-sequence DC component is analyzed and processed to obtain the DC component of the positive-sequence voltage reference value and the DC component of the negative-sequence voltage reference value of the three-phase converter. The DC component of the negative-sequence voltage reference value of the three-phase converter includes the first negative-sequence component and the second negative-sequence component. The DC component of the positive-sequence voltage reference value and the DC component of the negative-sequence voltage reference value of the three-phase converter are analyzed and processed according to the grid voltage phase angle and the rotor phase angle to obtain the voltage vector reference value of the three-phase converter in a two-phase stationary coordinate system. The voltage vector reference value of the three-phase converter is spatially vector modulated to generate the control signal of the three-phase converter switch, and the fault ride-through control of the variable frequency transformer is realized based on the control signal.

[0064] The fault ride-through control method for variable frequency transformers provided in this application is applied to a fault ride-through circuit of a variable frequency transformer. This fault ride-through circuit only requires a three-phase converter connected in series to simultaneously solve the DC capacitor voltage control problem and the problem of voltage imbalance between the two grid sides. Based on this circuit, a detailed and explicit fault ride-through control method is designed. It can still accurately calculate the control signal without relying on more three-phase converters. While ensuring the reliability of variable frequency transformer ride-through control, it also reduces circuit complexity, avoids large material consumption and more complex operation, and can meet practical fault ride-through control requirements. Therefore, this application addresses the technical problems of existing technologies that require at least two three-phase converters to achieve grid voltage imbalance regulation and control, which have significant drawbacks in terms of large material consumption and complex operation. Attached Figure Description

[0065] Figure 1 A schematic diagram of a variable frequency transformer fault ride-through circuit used in a variable frequency transformer fault ride-through control method for adjusting voltage balance, provided in an embodiment of this application.

[0066] Figure 2 A flowchart illustrating a variable frequency transformer fault ride-through control method for adjusting voltage balance, provided in an embodiment of this application;

[0067] Figure 3 A schematic diagram illustrating the overall calculation and analysis process of the variable frequency transformer fault ride-through control method for adjusting voltage balance provided in the embodiments of this application;

[0068] Figure 4 This application provides a schematic diagram of the structure of a variable frequency transformer fault ride-through control device for adjusting voltage balance. Detailed Implementation

[0069] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0070] For easier understanding, please refer to Figure 1 An embodiment of a variable frequency transformer fault ride-through control method for adjusting voltage balance provided in this application includes: the method is applied in a variable frequency transformer fault ride-through circuit, the circuit including: a first power grid, a second power grid, a three-phase transformer, a three-phase converter, a variable frequency transformer, an H-bridge converter, a DC capacitor, and a control circuit.

[0071] One end of the AC output terminal of the three-phase transformer is connected to the first power grid, and the other end is connected to the stator winding of the variable frequency transformer.

[0072] The rotor winding of the variable frequency transformer is connected to the second power grid;

[0073] The AC input terminal of the three-phase transformer is connected to the AC terminal of the three-phase converter;

[0074] The DC terminal of the three-phase converter is connected to the DC input terminal and the DC capacitor of the H-bridge converter.

[0075] The DC output terminal of the H-bridge converter is connected to the DC motor of the variable frequency transformer;

[0076] The control circuit is connected to the control signal input terminals of the three-phase converter and the H-bridge converter, respectively.

[0077] It should be noted that, Figure 1 The variable frequency transformer (5) includes a stator winding (51), a rotor winding (52), and a DC motor (53); the first power grid (1) is connected to one end of the AC output terminal of the three-phase transformer (3). It can be observed that... Figure 1 The proposed variable frequency transformer fault ride-through circuit only requires a three-phase converter (4) in series to achieve fault ride-through. Compared with the existing technology, it is simpler and clearer in circuit design, which can reduce circuit complexity, reduce circuit design cost, and avoid complex operation caused by complex circuit.

[0078] Please see Figure 2 The control methods include:

[0079] Step 101: Collect grid voltage, stator winding parameters, three-phase converter parameters, capacitor voltage and rotor phase angle. Grid voltage includes the voltage of the first grid and the second grid. Stator winding parameters and three-phase converter parameters include both voltage and current.

[0080] It should be noted that, based on the variable frequency transformer fault ride-through circuit provided above, the voltages of the first power grid (1) and the second power grid (2), i.e., the grid voltages, can be collected and expressed as follows: , The stator winding parameters specifically include the stator winding voltage. and stator winding current The specific parameters of the three-phase converter include the three-phase converter voltage. and three-phase converter current The capacitor voltage is the voltage of the DC capacitor (7), expressed as... The rotor phase angle is expressed as .

[0081] Step 102: Analyze and process the grid voltage, stator winding parameters, three-phase converter parameters and rotor phase angle to obtain the stator winding reactive power, the positive sequence DC component of the three-phase converter current, and the stator winding negative sequence DC component. The stator winding negative sequence DC component includes voltage DC component and current DC component.

[0082] Further, step 102 includes:

[0083] The power is calculated based on the stator winding parameters to obtain the reactive power of the stator winding.

[0084] Based on the grid voltage, stator winding parameters, three-phase converter parameters, and rotor phase angle, the three-phase stationary to two-phase stationary coordinate transformation, positive and negative sequence separation calculation, phase angle calculation, and two-phase stationary to two-phase rotating coordinate transformation processes are performed to obtain the positive sequence DC component of the three-phase converter current and the negative sequence DC component of the stator winding.

[0085] Furthermore, based on the grid voltage, stator winding parameters, three-phase converter parameters, and rotor phase angle, three-phase stationary to two-phase stationary coordinate transformation, positive and negative sequence separation calculation, phase angle calculation, and two-phase stationary to two-phase rotating coordinate transformation are performed to obtain the positive sequence DC component of the three-phase converter current and the negative sequence DC component of the stator winding, including:

[0086] Based on the grid voltage, stator winding parameters, and three-phase converter parameters, a coordinate transformation from three-phase stationary to two-phase stationary is performed to obtain the grid voltage vector, stator winding vector, and three-phase converter vector. The three-phase converter vector includes the three-phase converter voltage vector and the three-phase converter current vector.

[0087] The positive and negative sequence separation calculations are performed on the grid voltage vector, stator winding vector, and three-phase converter vector to obtain the grid positive and negative sequence voltage vector, stator winding negative sequence vector, and three-phase converter positive sequence vector. The three-phase converter positive sequence vector includes the voltage positive sequence vector and the current positive sequence vector.

[0088] The phase angles of the positive and negative sequence voltage vectors of the power grid and the positive sequence voltage vector of the three-phase converter are calculated respectively to obtain the phase angles of the power grid voltage and the positive sequence voltage of the three-phase converter.

[0089] Based on the grid voltage phase angle, the positive sequence voltage phase angle of the three-phase converter, and the rotor phase angle, the positive sequence current vector of the three-phase converter and the negative sequence vector of the stator winding are transformed from two-phase stationary to two-phase rotating coordinates to obtain the DC component of the positive sequence current of the three-phase converter and the DC component of the negative sequence current of the stator winding.

[0090] It should be noted that, based on the stator winding voltage and stator winding current The power can be directly calculated to obtain the reactive power of the stator winding, i.e., the reactive power of the stator winding. And the first grid voltage Second grid voltage Stator winding voltage Stator winding current Three-phase converter voltage and three-phase converter current By performing coordinate transformations from three-phase stationary to two-phase stationary coordinates, we can obtain the grid voltage vector, stator winding vector, and three-phase converter vector in the two-phase stationary coordinate system. The grid voltage vector includes the first grid voltage vector. Second grid voltage vector The stator winding vector includes the stator winding voltage vector. and stator winding current vector The three-phase converter vector includes the three-phase converter voltage vector. and the current vector of the three-phase converter .

[0091] The first grid voltage vector Second grid voltage vector Stator winding voltage vector Stator winding current vector Three-phase converter voltage vector and the current vector of the three-phase converter Separate calculations were performed to separate the positive and negative sequence voltage vectors, yielding the grid positive and negative sequence voltage vectors, the stator winding negative sequence vector, and the three-phase converter positive sequence vector in a two-phase stationary coordinate system. The grid positive and negative sequence voltage vectors include the first grid positive sequence voltage vector. First grid negative sequence voltage vector Second grid negative sequence voltage vector The stator winding negative sequence vector includes the stator winding negative sequence voltage vector. and stator winding negative sequence current vector The positive sequence vector of a three-phase converter includes the positive sequence voltage vector of the three-phase converter. and the positive sequence current vector of the three-phase converter .

[0092] Based on the first grid positive sequence voltage vector First grid negative sequence voltage vector Second grid negative sequence voltage vector and the positive sequence voltage vector of the three-phase converter Phase angles were calculated separately to obtain the grid voltage phase angle and the positive-sequence voltage phase angle of the three-phase converter. The grid voltage phase angle includes the first grid positive-sequence voltage phase angle. Phase angle of negative sequence voltage in the first power grid Phase angle of negative sequence voltage in the second power grid The phase angle of the positive sequence voltage of a three-phase converter is expressed as follows: .

[0093] Based on the negative sequence voltage phase angle of the first power grid Phase angle of negative sequence voltage in the second power grid Three-phase converter positive sequence voltage phase angle and rotor phase angle The positive sequence current vector of the three-phase converter Stator winding negative sequence voltage vector and stator winding negative sequence current vector By performing two-phase stationary to two-phase rotating coordinate transformations, the DC component of the positive sequence current of the three-phase converter in the stator positive sequence synchronous rotating coordinate system is obtained. And the stator winding negative sequence DC component. The stator winding negative sequence DC component includes the stator winding negative sequence voltage DC component. DC component of stator winding negative sequence current .

[0094] Step 103: Using a preset voltage control equation, analyze and process the capacitor voltage, stator winding reactive power, DC component of positive sequence current of the three-phase converter, and DC component of negative sequence current of the stator winding to obtain the DC component of reference value of positive sequence voltage of the three-phase converter and the DC component of reference value of negative sequence voltage of the three-phase converter. The DC component of reference value of negative sequence voltage of the three-phase converter includes the first negative sequence component and the second negative sequence component.

[0095] The preset voltage control equation in this embodiment is expressed as follows:

[0096]

[0097] in, Represents the Laplace operator. This is the reference value for DC capacitor voltage; This is the reference value for the reactive power of the stator winding; and These are the d-axis and q-axis components of the DC component of the positive sequence current reference value of the three-phase converter, respectively. and These are the d-axis and q-axis components of the DC component of the positive sequence current of the three-phase converter, respectively. and These are the d-axis and q-axis components of the DC component of the positive sequence voltage reference value of the three-phase converter, respectively. and These are the d-axis and q-axis components of the DC component of the negative sequence voltage of the stator winding, respectively. and These are the d-axis and q-axis components of the DC component of the first negative sequence voltage reference value of the three-phase converter, respectively. and These are the d-axis and q-axis components of the DC component of the negative sequence current in the stator winding, respectively. and These are the d-axis and q-axis components of the DC component of the second negative sequence voltage reference value of the three-phase converter, respectively. and These are the proportional and integral coefficients of the DC capacitor voltage controller, respectively. and These are the proportional coefficient and integral coefficient of the stator winding reactive power controller, respectively. and These are the proportional and integral coefficients of the d-axis positive sequence current controller of the three-phase converter; and These are the proportional and integral coefficients of the q-axis positive sequence current controller of the three-phase converter; and These are the proportional coefficient and integral coefficient of the stator winding d-axis negative sequence voltage controller, respectively. and These are the proportional coefficient and integral coefficient of the stator winding q-axis negative sequence voltage controller, respectively. and These are the proportional coefficient and integral coefficient of the stator winding d-axis negative sequence current controller, respectively. and These are the proportional coefficient and integral coefficient of the stator winding q-axis negative sequence current controller, respectively.

[0098] DC capacitor voltage Stator winding reactive power DC component of positive sequence current in three-phase converter DC component of stator winding negative sequence voltage DC component of stator winding negative sequence current By performing calculations and analysis according to the preset voltage control equations, the DC component of the positive sequence voltage reference value of the three-phase converter can be obtained. And the DC component of the negative sequence voltage reference value of the three-phase converter. The DC component of the negative sequence voltage reference value of the three-phase converter can be further divided into the DC component of the first negative sequence voltage reference value of the three-phase converter. DC component of the second negative sequence voltage reference value of the three-phase converter .

[0099] Step 104: Analyze and process the DC components of the positive sequence voltage reference value and the negative sequence voltage reference value of the three-phase converter based on the grid voltage phase angle and the rotor phase angle to obtain the voltage vector reference value of the three-phase converter in the two-phase stationary coordinate system.

[0100] Further, step 104 includes:

[0101] Based on the grid voltage phase angle, the DC component of the positive sequence voltage reference value of the three-phase converter is transformed from a two-phase rotation to a two-phase stationary coordinate system to obtain the positive sequence voltage vector reference value of the three-phase converter in the two-phase stationary coordinate system.

[0102] Based on the grid voltage phase angle, the first negative sequence component of the DC component of the three-phase converter negative sequence voltage reference value is transformed from two-phase rotation to two-phase stationary coordinates to obtain the first negative sequence voltage vector reference value of the three-phase converter in the two-phase stationary coordinate system.

[0103] Based on the grid voltage phase angle and rotor phase angle, the second negative sequence component of the DC component of the three-phase converter negative sequence voltage reference value is transformed from two-phase rotation to two-phase stationary coordinates to obtain the second negative sequence voltage vector reference value of the three-phase converter in the two-phase stationary coordinate system.

[0104] The reference values ​​of the positive-sequence voltage vector, the first negative-sequence voltage vector, and the second negative-sequence voltage vector of the three-phase converter are summed to obtain the reference values ​​of the three-phase converter voltage vector in the two-phase stationary coordinate system.

[0105] It should be noted that, based on the phase angle of the positive sequence voltage of the first power grid... The DC component of the positive sequence voltage reference value of the three-phase converter can be used. By performing a two-phase rotational to two-phase stationary coordinate transformation, the positive sequence voltage vector reference value of the three-phase converter in the two-phase stationary coordinate system can be obtained. .

[0106] Based on the negative sequence voltage phase angle of the first power grid The DC component of the first negative sequence voltage reference value of the three-phase converter can be used. By performing a two-phase rotational to two-phase stationary coordinate transformation, the reference value of the first negative sequence voltage vector of the three-phase converter in the two-phase stationary coordinate system is obtained. According to the negative sequence voltage phase angle of the second power grid and rotor phase angle Then the DC component of the second negative sequence voltage reference value of the three-phase converter can be... By performing a two-phase rotational to two-phase stationary coordinate transformation, the reference value of the second negative sequence voltage vector of the three-phase converter in the two-phase stationary coordinate system is obtained. .

[0107] The positive sequence voltage vector reference value of the three-phase converter Reference value of the first negative sequence voltage vector of the three-phase converter and the second negative sequence voltage vector reference value of the three-phase converter By performing summation calculations, the reference value of the three-phase converter voltage vector in the two-phase stationary coordinate system is obtained. .

[0108] Step 105: Perform space vector modulation on the three-phase converter voltage vector reference value to generate control signals for the three-phase converter switch, and realize fault ride-through control of the variable frequency transformer based on the control signals.

[0109] For the overall calculation and analysis process of the variable frequency transformer fault ride-through control in this embodiment, please refer to [link / reference needed]. Figure 3 The calculated reference value of the three-phase converter voltage vector The control signal for the three-phase converter switch can be obtained through space vector modulation (SVPWM). , , Fault ride-through control of variable frequency transformers can be achieved based on control signals.

[0110] The fault ride-through control method for variable frequency transformers providing voltage balance adjustment in this application is applied to a fault ride-through circuit of a variable frequency transformer. This fault ride-through circuit only requires a three-phase converter connected in series to simultaneously solve the DC capacitor voltage control problem and the problem of voltage imbalance between the two grid sides. Based on this circuit, a detailed and explicit fault ride-through control method is designed. It can still accurately calculate the control signal without relying on more three-phase converters. While ensuring the reliability of variable frequency transformer ride-through control, it also reduces circuit complexity, avoids large material consumption and more complex operations, and can meet practical fault ride-through control requirements. Therefore, the embodiments of this application address the technical problems of existing technologies that require at least two three-phase converters to achieve grid voltage imbalance adjustment and control, which have significant problems of large material consumption and complex operation.

[0111] For easier understanding, please refer to Figure 4 This application provides an embodiment of a variable frequency transformer fault ride-through control device for regulating voltage balance. The control device is applied in a variable frequency transformer fault ride-through circuit, and the circuit includes: a first power grid, a second power grid, a three-phase transformer, a three-phase converter, a variable frequency transformer, an H-bridge converter, a DC capacitor, and a control circuit.

[0112] One end of the AC output terminal of the three-phase transformer is connected to the first power grid, and the other end is connected to the stator winding of the variable frequency transformer.

[0113] The rotor winding of the variable frequency transformer is connected to the second power grid;

[0114] The AC input terminal of the three-phase transformer is connected to the AC terminal of the three-phase converter;

[0115] The DC terminal of the three-phase converter is connected to the DC input terminal and the DC capacitor of the H-bridge converter.

[0116] The DC output terminal of the H-bridge converter is connected to the DC motor of the variable frequency transformer;

[0117] The control circuit is connected to the control signal input terminals of the three-phase converter and the H-bridge converter, respectively.

[0118] The control device includes:

[0119] The parameter acquisition unit 201 is used to acquire grid voltage, stator winding parameters, three-phase converter parameters, capacitor voltage and rotor phase angle. The grid voltage includes the voltage of the first grid and the second grid. The stator winding parameters and the three-phase converter parameters both include voltage and current.

[0120] The first analysis unit 202 is used to analyze and process the grid voltage, stator winding parameters, three-phase converter parameters and rotor phase angle to obtain stator winding reactive power, three-phase converter positive sequence current DC component and stator winding negative sequence DC component. The stator winding negative sequence DC component includes voltage DC component and current DC component.

[0121] The second analysis unit 203 is used to analyze and process the capacitor voltage, stator winding reactive power, DC component of positive sequence current of three-phase converter and DC component of negative sequence current of stator winding using a preset voltage control equation, so as to obtain DC component of reference value of positive sequence voltage of three-phase converter and DC component of reference value of negative sequence voltage of three-phase converter. The DC component of reference value of negative sequence voltage of three-phase converter includes first negative sequence component and second negative sequence component.

[0122] The third analysis unit 204 is used to analyze and process the DC component of the positive sequence voltage reference value and the DC component of the negative sequence voltage reference value of the three-phase converter according to the grid voltage phase angle and the rotor phase angle, so as to obtain the voltage vector reference value of the three-phase converter in the two-phase stationary coordinate system.

[0123] The modulation control unit 205 is used to perform space vector modulation on the voltage vector reference value of the three-phase converter, generate control signals for the three-phase converter switching, and realize fault ride-through control of the variable frequency transformer based on the control signals.

[0124] Furthermore, the first analysis unit 202 specifically includes:

[0125] The power calculation subunit 2021 is used to perform power calculations based on the stator winding parameters to obtain the reactive power of the stator winding.

[0126] The coordinate transformation subunit 2022 is used to perform three-phase stationary to two-phase stationary coordinate transformation, positive and negative sequence separation calculation, phase angle calculation, and two-phase stationary to two-phase rotating coordinate transformation based on the grid voltage, stator winding parameters, three-phase converter parameters, and rotor phase angle, respectively, to obtain the positive sequence DC component of the three-phase converter current and the negative sequence DC component of the stator winding.

[0127] Furthermore, the coordinate transformation subunit 2022 is specifically used for:

[0128] Based on the grid voltage, stator winding parameters, and three-phase converter parameters, a coordinate transformation from three-phase stationary to two-phase stationary is performed to obtain the grid voltage vector, stator winding vector, and three-phase converter vector. The three-phase converter vector includes the three-phase converter voltage vector and the three-phase converter current vector.

[0129] The positive and negative sequence separation calculations are performed on the grid voltage vector, stator winding vector, and three-phase converter vector to obtain the grid positive and negative sequence voltage vector, stator winding negative sequence vector, and three-phase converter positive sequence vector. The three-phase converter positive sequence vector includes the voltage positive sequence vector and the current positive sequence vector.

[0130] The phase angles of the positive and negative sequence voltage vectors of the power grid and the positive sequence voltage vector of the three-phase converter are calculated respectively to obtain the phase angles of the power grid voltage and the positive sequence voltage of the three-phase converter.

[0131] Based on the grid voltage phase angle, the positive sequence voltage phase angle of the three-phase converter, and the rotor phase angle, the positive sequence current vector of the three-phase converter and the negative sequence vector of the stator winding are transformed from two-phase stationary to two-phase rotating coordinates to obtain the DC component of the positive sequence current of the three-phase converter and the DC component of the negative sequence current of the stator winding.

[0132] Furthermore, the third analysis unit 204 is specifically used for:

[0133] Based on the grid voltage phase angle, the DC component of the positive sequence voltage reference value of the three-phase converter is transformed from two-phase rotation to two-phase stationary coordinate system to obtain the positive sequence voltage vector reference value of the three-phase converter in the two-phase stationary coordinate system.

[0134] Based on the grid voltage phase angle, the first negative sequence component of the DC component of the three-phase converter negative sequence voltage reference value is transformed from two-phase rotation to two-phase stationary coordinate system to obtain the first negative sequence voltage vector reference value of the three-phase converter in the two-phase stationary coordinate system.

[0135] Based on the grid voltage phase angle and rotor phase angle, the second negative sequence component of the DC component of the three-phase converter negative sequence voltage reference value is transformed from two-phase rotation to two-phase stationary coordinate system to obtain the second negative sequence voltage vector reference value of the three-phase converter in the two-phase stationary coordinate system.

[0136] The reference values ​​of the positive-sequence voltage vector, the first negative-sequence voltage vector, and the second negative-sequence voltage vector of the three-phase converter are summed to obtain the reference values ​​of the three-phase converter voltage vector in the two-phase stationary coordinate system.

[0137] This application also provides a variable frequency transformer fault ride-through control device for regulating voltage balance, the device including a processor and a memory;

[0138] The memory is used to store program code and transfer the program code to the processor;

[0139] The processor is used to execute the variable frequency transformer fault ride-through control method for adjusting voltage balance in the above method embodiment according to the instructions in the program code.

[0140] This application also provides a computer-readable storage medium for storing program code for executing the variable frequency transformer fault ride-through control method for adjusting voltage balance in the above method embodiments.

[0141] In the several embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0142] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0143] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0144] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for executing all or part of the steps of the methods described in the various embodiments of this application through a computer device (which may be a personal computer, server, or network device, etc.). The aforementioned storage medium includes: USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, optical disks, and other media capable of storing program code.

[0145] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A method for fault ride-through control of a variable frequency transformer for adjusting voltage balance, characterized in that, The control method is applied in a variable frequency transformer fault ride-through circuit, which includes: a first power grid, a second power grid, a three-phase transformer, a three-phase converter, a variable frequency transformer, an H-bridge converter, a DC capacitor, and a control circuit. One end of the AC output terminal of the three-phase transformer is connected to the first power grid, and the other end is connected to the stator winding of the variable frequency transformer. The rotor winding of the variable frequency transformer is connected to the second power grid; The AC input terminal of the three-phase transformer is connected to the AC terminal of the three-phase converter; The DC terminal of the three-phase converter is connected to the DC input terminal of the H-bridge converter and the DC capacitor; The DC output terminal of the H-bridge converter is connected to the DC motor of the variable frequency transformer; The control circuit is connected to the control signal input terminals of the three-phase converter and the H-bridge converter, respectively; The control method includes: The system collects grid voltage, stator winding parameters, three-phase converter parameters, capacitor voltage, and rotor phase angle. The grid voltage includes the voltages of the first grid and the second grid. The stator winding parameters and the three-phase converter parameters both include voltage and current. The grid voltage, stator winding parameters, three-phase converter parameters, and rotor phase angle are analyzed and processed to obtain stator winding reactive power, three-phase converter positive sequence current DC component, and stator winding negative sequence DC component. The stator winding negative sequence DC component includes voltage DC component and current DC component. The capacitor voltage, the stator winding reactive power, the DC component of the positive sequence current of the three-phase converter, and the DC component of the stator winding are analyzed and processed using a preset voltage control equation to obtain the DC component of the reference value of the positive sequence voltage of the three-phase converter and the DC component of the reference value of the negative sequence voltage of the three-phase converter. The DC component of the reference value of the negative sequence voltage of the three-phase converter includes a first negative sequence component and a second negative sequence component. The DC components of the positive-sequence voltage reference value and the negative-sequence voltage reference value of the three-phase converter are analyzed and processed based on the grid voltage phase angle and the rotor phase angle to obtain the three-phase converter voltage vector reference value in a two-phase stationary coordinate system. The grid voltage phase angle includes the first grid positive-sequence voltage phase angle, the first grid negative-sequence voltage phase angle, and the second grid negative-sequence voltage phase angle. The analysis and processing process includes: Based on the first grid positive sequence voltage phase angle, the DC component of the three-phase converter positive sequence voltage reference value is transformed from two-phase rotation to two-phase stationary coordinate system to obtain the three-phase converter positive sequence voltage vector reference value in the two-phase stationary coordinate system. Based on the phase angle of the first grid negative sequence voltage, the first negative sequence component of the DC component of the negative sequence voltage reference value of the three-phase converter is subjected to a coordinate transformation from two-phase rotation to two-phase stationary to obtain the first negative sequence voltage vector reference value of the three-phase converter in the two-phase stationary coordinate system. Based on the phase angle of the second grid negative sequence voltage and the rotor phase angle, the second negative sequence component of the DC component of the three-phase converter negative sequence voltage reference value is transformed from two-phase rotation to two-phase stationary coordinate system to obtain the second negative sequence voltage vector reference value of the three-phase converter in the two-phase stationary coordinate system. The voltage vector reference value of the three-phase converter is spatially vector modulated to generate the control signal for the switching of the three-phase converter, and the fault ride-through control of the variable frequency transformer is realized based on the control signal.

2. The variable frequency transformer fault ride-through control method for adjusting voltage balance according to claim 1, characterized in that, The analysis and processing of the grid voltage, stator winding parameters, three-phase converter parameters, and rotor phase angle yields the stator winding reactive power, the positive-sequence DC component of the three-phase converter current, and the stator winding negative-sequence DC component. The stator winding negative-sequence DC component includes both voltage and current DC components, including: The power is calculated based on the stator winding parameters to obtain the reactive power of the stator winding; Based on the grid voltage, the stator winding parameters, the three-phase converter parameters, and the rotor phase angle, the three-phase stationary to two-phase stationary coordinate transformation, positive and negative sequence separation calculation, phase angle calculation, and two-phase stationary to two-phase rotating coordinate transformation processes are performed to obtain the positive sequence DC component of the three-phase converter current and the negative sequence DC component of the stator winding.

3. The variable frequency transformer fault ride-through control method for adjusting voltage balance according to claim 2, characterized in that, The process involves performing three-phase stationary to two-phase stationary coordinate transformation, positive and negative sequence separation calculation, phase angle calculation, and two-phase stationary to two-phase rotating coordinate transformation based on the grid voltage, stator winding parameters, three-phase converter parameters, and rotor phase angle, respectively, to obtain the positive sequence DC component of the three-phase converter current and the negative sequence DC component of the stator winding, including: Based on the grid voltage, the stator winding parameters, and the three-phase converter parameters, a three-phase stationary to two-phase stationary coordinate transformation is performed to obtain the grid voltage vector, the stator winding vector, and the three-phase converter vector. The three-phase converter vector includes the three-phase converter voltage vector and the three-phase converter current vector. The positive and negative sequence separation calculations are performed on the grid voltage vector, the stator winding vector, and the three-phase converter vector to obtain the grid positive and negative sequence voltage vector, the stator winding negative sequence vector, and the three-phase converter positive sequence vector. The three-phase converter positive sequence vector includes the voltage positive sequence vector and the current positive sequence vector. The phase angles of the positive and negative sequence voltage vectors of the power grid and the positive sequence voltage vector of the three-phase converter are calculated respectively to obtain the phase angles of the power grid voltage and the positive sequence voltage of the three-phase converter. Based on the grid voltage phase angle, the positive sequence voltage phase angle of the three-phase converter, and the rotor phase angle, the positive sequence current vector of the three-phase converter and the negative sequence vector of the stator winding are transformed from two-phase stationary to two-phase rotating coordinates to obtain the DC component of the positive sequence current of the three-phase converter and the DC component of the negative sequence of the stator winding.

4. The variable frequency transformer fault ride-through control method for adjusting voltage balance according to claim 1, characterized in that, The process involves performing a coordinate transformation on the second negative-sequence component of the DC component of the three-phase converter negative-sequence voltage reference value based on the second grid negative-sequence voltage phase angle and the rotor phase angle, rotating it from two phases to two phases stationary, to obtain the second negative-sequence voltage vector reference value of the three-phase converter in a two-phase stationary coordinate system. This process further includes: The positive-sequence voltage vector reference value, the first negative-sequence voltage vector reference value, and the second negative-sequence voltage vector reference value of the three-phase converter are summed to obtain the voltage vector reference value of the three-phase converter in a two-phase stationary coordinate system.

5. A variable frequency transformer fault ride-through control device for regulating voltage balance, characterized in that, The control device is used in a variable frequency transformer fault ride-through circuit, which includes: a first power grid, a second power grid, a three-phase transformer, a three-phase converter, a variable frequency transformer, an H-bridge converter, a DC capacitor, and a control circuit. One end of the AC output terminal of the three-phase transformer is connected to the first power grid, and the other end is connected to the stator winding of the variable frequency transformer. The rotor winding of the variable frequency transformer is connected to the second power grid; The AC input terminal of the three-phase transformer is connected to the AC terminal of the three-phase converter; The DC terminal of the three-phase converter is connected to the DC input terminal of the H-bridge converter and the DC capacitor; The DC output terminal of the H-bridge converter is connected to the DC motor of the variable frequency transformer; The control circuit is connected to the control signal input terminals of the three-phase converter and the H-bridge converter, respectively; The control device includes: The parameter acquisition unit is used to acquire grid voltage, stator winding parameters, three-phase converter parameters, capacitor voltage and rotor phase angle. The grid voltage includes the voltages of the first grid and the second grid. The stator winding parameters and the three-phase converter parameters both include voltage and current. The first analysis unit is used to analyze and process the grid voltage, the stator winding parameters, the three-phase converter parameters and the rotor phase angle to obtain the stator winding reactive power, the positive sequence DC component of the three-phase converter current and the stator winding negative sequence DC component. The stator winding negative sequence DC component includes voltage DC component and current DC component. The second analysis unit is used to analyze and process the capacitor voltage, the stator winding reactive power, the DC component of the positive sequence current of the three-phase converter and the DC component of the stator winding using a preset voltage control equation, so as to obtain the DC component of the reference value of the positive sequence voltage of the three-phase converter and the DC component of the reference value of the negative sequence voltage of the three-phase converter. The DC component of the reference value of the negative sequence voltage of the three-phase converter includes a first negative sequence component and a second negative sequence component. The third analysis unit is used to analyze and process the DC components of the positive-sequence voltage reference value and the negative-sequence voltage reference value of the three-phase converter based on the grid voltage phase angle and the rotor phase angle, to obtain the three-phase converter voltage vector reference value in a two-phase stationary coordinate system. The grid voltage phase angle includes the first grid positive-sequence voltage phase angle, the first grid negative-sequence voltage phase angle, and the second grid negative-sequence voltage phase angle. The analysis and processing process is as follows: Based on the first grid positive sequence voltage phase angle, the DC component of the three-phase converter positive sequence voltage reference value is transformed from two-phase rotation to two-phase stationary coordinate system to obtain the three-phase converter positive sequence voltage vector reference value in the two-phase stationary coordinate system. Based on the phase angle of the first grid negative sequence voltage, the first negative sequence component of the DC component of the negative sequence voltage reference value of the three-phase converter is subjected to a coordinate transformation from two-phase rotation to two-phase stationary to obtain the first negative sequence voltage vector reference value of the three-phase converter in the two-phase stationary coordinate system. Based on the phase angle of the second grid negative sequence voltage and the rotor phase angle, the second negative sequence component of the DC component of the three-phase converter negative sequence voltage reference value is transformed from two-phase rotation to two-phase stationary coordinate system to obtain the second negative sequence voltage vector reference value of the three-phase converter in the two-phase stationary coordinate system. The modulation and control unit is used to perform space vector modulation on the voltage vector reference value of the three-phase converter, generate control signals for the switching of the three-phase converter, and realize fault ride-through control of the variable frequency transformer based on the control signals.

6. The variable frequency transformer fault ride-through control device for adjusting voltage balance according to claim 5, characterized in that, The first analysis unit specifically includes: The power calculation subunit is used to perform power calculation based on the stator winding parameters to obtain the reactive power of the stator winding. The coordinate transformation subunit is used to perform three-phase stationary to two-phase stationary coordinate transformation, positive and negative sequence separation calculation, phase angle calculation, and two-phase stationary to two-phase rotating coordinate transformation processing according to the grid voltage, the stator winding parameters, the three-phase converter parameters, and the rotor phase angle, respectively, to obtain the positive sequence DC component of the three-phase converter current and the negative sequence DC component of the stator winding.

7. The variable frequency transformer fault ride-through control device for adjusting voltage balance according to claim 6, characterized in that, The coordinate transformation subunit is specifically used for: Based on the grid voltage, the stator winding parameters, and the three-phase converter parameters, a three-phase stationary to two-phase stationary coordinate transformation is performed to obtain the grid voltage vector, the stator winding vector, and the three-phase converter vector. The three-phase converter vector includes the three-phase converter voltage vector and the three-phase converter current vector. The positive and negative sequence separation calculations are performed on the grid voltage vector, the stator winding vector, and the three-phase converter vector to obtain the grid positive and negative sequence voltage vector, the stator winding negative sequence vector, and the three-phase converter positive sequence vector. The three-phase converter positive sequence vector includes the voltage positive sequence vector and the current positive sequence vector. The phase angles of the positive and negative sequence voltage vectors of the power grid and the positive sequence voltage vector of the three-phase converter are calculated respectively to obtain the phase angles of the power grid voltage and the positive sequence voltage of the three-phase converter. Based on the grid voltage phase angle, the positive sequence voltage phase angle of the three-phase converter, and the rotor phase angle, the positive sequence current vector of the three-phase converter and the negative sequence vector of the stator winding are transformed from two-phase stationary to two-phase rotating coordinates to obtain the DC component of the positive sequence current of the three-phase converter and the DC component of the negative sequence of the stator winding.

8. The variable frequency transformer fault ride-through control device for adjusting voltage balance according to claim 5, characterized in that, The third analysis unit is also used for: The positive-sequence voltage vector reference value, the first negative-sequence voltage vector reference value, and the second negative-sequence voltage vector reference value of the three-phase converter are summed to obtain the voltage vector reference value of the three-phase converter in a two-phase stationary coordinate system.

9. A variable frequency transformer fault ride-through control device for regulating voltage balance, characterized in that, The device includes a processor and a memory; The memory is used to store program code and transmit the program code to the processor; The processor is used to execute the variable frequency transformer fault ride-through control method for adjusting voltage balance according to any one of claims 1-4, based on the instructions in the program code.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium is used to store program code for executing the variable frequency transformer fault ride-through control method for adjusting voltage balance according to any one of claims 1-4.

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