Grid active support type doubly-fed wind turbine generator control system and method

Abstract

This invention provides a grid-actively supported doubly-fed induction generator (DFIG) wind turbine control system, comprising: a DFIG converter power generation system, a wind turbine primary frequency regulation control module, a wind turbine autonomous inertia response control module, a wind turbine autonomous voltage control module, a rotor-side converter current command generation module, a rotor-side converter current control module, a rotor-side converter signal processing module, a grid-side converter synchronization angle control module, a grid-side converter AC voltage amplitude control module, a grid-side converter current command generation module, a grid-side converter current control module, and a grid-side converter signal processing module. Based on the principle that both the turbine-side and grid-side converters of the DFIG wind turbine employ amplitude and phase control, this invention achieves active support control of the grid frequency and voltage by the DFIG wind turbine unit through active primary frequency regulation, inertia response, and autonomous voltage regulation control strategies, without relying on communication with the power station controller.

Description

Technical Field

[0001] This invention relates to the fields of wind power generation technology and power electronic converter control technology in power systems. Specifically, it relates to a grid-supported doubly-fed induction generator (DFIG) wind turbine control system and method, which aims to achieve active support control of grid frequency and voltage by the DFIG wind turbine unit without relying on communication with the station controller. Background Technology

[0002] With the rapid development of new energy sources such as wind and solar power, a large amount of wind and solar power is connected to the grid through power electronic converters. The power system is gradually exhibiting the "dual high" characteristics of a high proportion of clean energy and a high proportion of power electronic devices. Under this dual-high grid, the key problems currently facing the development of new energy are insufficient system equivalent inertia and decreased short-circuit current. This is mainly because current new energy power generation units are grid-connected power sources. In steady-state operation, they control active power based on the maximum captured wind power and receive reactive power commands from the power station controller for reactive power control. In transient operation, they output reactive current based on the grid voltage drop depth, but due to the capacity limitations of power devices, they can only output a maximum of approximately 1.1 times the short-circuit current. Therefore, in terms of external port characteristics, they do not possess the inherent autonomous inertia response capability and strong short-circuit current support capability of synchronous machines. With a high proportion of new energy connected, these operating characteristics of new energy will seriously affect the frequency and voltage stability of the power system, preventing new energy from becoming the main power source in future new power systems.

[0003] Grid-based control technology can effectively change the power characteristics of new energy power generation units, realizing a fundamental transformation of new energy from current source characteristics to voltage source characteristics. Existing grid-based doubly-fed induction generator (DFIG) wind turbines mainly achieve grid-based control by modifying the control architecture of the wind power converter. The converter uses power / torque closed-loop control for frequency and reactive power closed-loop control for voltage. The unit receives active and reactive power commands from the power station controller, and can achieve primary frequency regulation under the condition of reserved power capacity. However, under this control method, the DFIG wind turbine relies on the power station controller to achieve frequency and voltage regulation functions. The communication delay between the power station controller and the wind turbine's main controller is relatively large, resulting in slow frequency and voltage response speeds for the wind turbine, making it unable to provide effective frequency and voltage support to the grid. Therefore, wind turbines under this grid-based control method cannot assume the responsibility of being the main power source.

[0004] Therefore, in view of the shortcomings of the existing technology, there is an urgent need in this field to propose a grid-supported doubly-fed wind turbine control system and method. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this invention is to provide a grid-supported doubly-fed wind turbine control system.

[0006] According to the present invention, a grid-supported doubly-fed induction generator (DFIG) wind turbine control system includes: a DFIG converter power generation system, a wind turbine primary frequency regulation control module, a wind turbine autonomous inertia response control module, a wind turbine autonomous voltage control module, a rotor-side converter current command generation module, a rotor-side converter current control module, a rotor-side converter signal processing module, a grid-side converter synchronization angle control module, a grid-side converter AC voltage amplitude control module, a grid-side converter current command generation module, a grid-side converter current control module, and a grid-side converter signal processing module.

[0007] The doubly-fed wind turbine converter power generation system includes: a doubly-fed wind turbine generator, a turbine-side converter, a DC capacitor, a DC unloader, a grid-side converter, and an AC filter circuit.

[0008] The primary frequency regulation control module of the wind turbine is used to control the grid frequency deviation of the doubly fed wind turbine converter power generation system;

[0009] The wind turbine autonomous inertia response control module is used to control the grid frequency change rate of the doubly fed wind turbine converter power generation system.

[0010] The wind turbine autonomous voltage control module is used to realize the active control of the grid voltage by the doubly fed wind turbine converter power generation system;

[0011] The rotor-side converter current command generation module is used to generate rotor current command values;

[0012] The rotor-side converter current control module is used to control the rotor current tracking command value;

[0013] The rotor-side converter signal processing module is used to process the signals required for rotor converter control.

[0014] The grid-side converter synchronization angle control module is used to generate the rotation angle of the grid-side converter electrical signal while achieving constant DC voltage.

[0015] The AC voltage amplitude control module of the grid-side converter is used to realize the active support control of the grid voltage by the grid-side converter.

[0016] The grid-side converter current command generation module is used to generate grid-side converter current command values;

[0017] The grid-side converter current control module is used to control the grid-side converter current tracking command value;

[0018] The grid-side converter signal processing module is used to process the signals required for grid-side converter control.

[0019] Preferably, the primary frequency control module of the wind turbine obtains the frequency regulation power of the unit by proportionally adjusting the deviation between the desired frequency and the actual frequency of the power grid;

[0020] (1)

[0021] in, This refers to the frequency regulation power of the generator unit; The rated frequency of the power grid; The actual frequency of the power grid; This refers to the frequency regulation coefficient of the generator unit; This is the frequency regulation dead zone of the generator unit.

[0022] Preferably, the wind turbine autonomous inertia response control module obtains the frequency deviation value by passing the unit torque deviation through a first-order inertial control loop, and adds the frequency deviation value to the actual grid frequency to obtain the angular frequency of the doubly-fed motor stator control signal. The angle of the doubly-fed motor stator control signal is obtained by integrating the angular frequency.

[0023] The angular frequency and angle of the stator control signal for a doubly-fed induction generator (DFIG) include:

[0024] (2)

[0025] in, The angular frequency of the stator control signal; This is the actual angular frequency of the power grid; The inertial time constant; The damping coefficient; The set active power of the generator unit; This represents the actual active power value of the unit; The mechanical angular velocity of the doubly-fed generator; The angle of the stator control signal; For the Laplace operator;

[0026] The slip angle of the doubly-fed motor is obtained from the angular frequency of the stator control signal and the rotor angular velocity. The calculation formula is as follows:

[0027] (3)

[0028] In the formula, This is the slip frequency of the doubly-fed generator; This represents the number of pole pairs in a doubly-fed generator. This represents the slip angle of the doubly-fed generator.

[0029] Preferably, the wind turbine autonomous voltage control module obtains the reactive power command value by passing the difference between the grid voltage setpoint and the actual value through a proportional controller, and then passes it through a reactive power control loop and adds the grid voltage setpoint to obtain the desired amplitude of the stator voltage.

[0030] The grid voltage setpoint includes the voltage deviation value given by the power station, as well as the unit's own voltage compensation and stator voltage rating. The calculation formula is as follows:

[0031] (4)

[0032] in, Set the grid voltage value; This is the stator voltage rating; The voltage deviation value given by the station; This is the voltage compensation amount for the generator unit itself;

[0033] The unit's own voltage compensation amount It is calculated based on the active power of the generator unit, and its expression is:

[0034] (5)

[0035] in, This is the voltage compensation value when the unit power is zero. This is the voltage compensation value when the unit power is at its rated power.

[0036] The reactive power command value is obtained by outputting the difference between the grid voltage setpoint and the actual value through a proportional controller, and its expression is:

[0037] (6)

[0038] in, This is the reactive power command value for the doubly-fed motor; This refers to the phase voltage amplitude of the power grid. This refers to the AC voltage droop coefficient.

[0039] The desired amplitude of the stator voltage is obtained by outputting the difference between the grid voltage setpoint and the actual value through a proportional controller, and its expression is as follows:

[0040] (7)

[0041] in, This represents the expected amplitude of the stator voltage. This represents the actual value of the stator reactive power of the doubly-fed motor. This is the proportional coefficient of the reactive power loop; This is the integral coefficient of the reactive power loop.

[0042] Preferably, the rotor-side converter current command generation module uses the desired amplitude of the stator voltage and the stator voltage to determine the grid voltage setpoint and the grid voltage at the stator control signal angle. The first-stage rotor current command value is obtained by calculating the component differences in the rotating coordinate system.

[0043] (8)

[0044] in, and The d-axis and q-axis components of the first-stage rotor current command value; and The actual value of the stator voltage at the stator control signal angle Components in the rotating coordinate system; Virtual resistance value for rotor-side converter control; The virtual inductance value is used for rotor-side converter control; The rated angular frequency of the power grid;

[0045] The first-stage rotor current command value is vector-limited to prevent the rotor command current from exceeding the limit. The formula for calculating the d-axis current after limiting is:

[0046] (9)

[0047] in, This is the d-axis command value for the rotor current; This is the maximum limit of the rotor current;

[0048] The formula for calculating the q-axis current after limiting is:

[0049] (10)

[0050] in, This is the q-axis command value for the rotor current.

[0051] Preferably, the rotor-side converter current control module obtains the rotor modulation voltage by passing the deviation between the command value and the actual value of the rotor current through a proportional-integral controller and adding a compensation voltage in a rotating coordinate system.

[0052] (11)

[0053] in, and This is the rotor voltage control value; This is the proportional coefficient of the rotor current controller; The integral coefficient of the rotor current controller; and These are the actual values ​​of the rotor current along the d-axis and q-axis. and This is the first compensation amount for the rotor voltage; and This is the second compensation amount for the rotor voltage;

[0054] The formula for calculating the first compensation amount of rotor voltage is:

[0055] (12)

[0056] in, This refers to the rotor inductance of a doubly-fed induction generator. This refers to the stator inductance of a doubly-fed motor. Mutual inductance for a doubly-fed motor;

[0057] The formula for calculating the second compensation amount of rotor voltage is:

[0058] (13)

[0059] in, The virtual impedance for rotor current control;

[0060] The expression for the virtual impedance used for rotor current control is:

[0061] (14).

[0062] Preferably, the stator voltage signal coordinate transformation in the rotor-side converter signal processing module includes:

[0063] (15)

[0064] in, , and The instantaneous values ​​of the phase voltages of the three-phase stator voltage;

[0065] The calculation formula used for the coordinate transformation of the stator current signal is:

[0066] (16)

[0067] in, , , This represents the instantaneous value of the three-phase stator current;

[0068] The calculation formula used for rotor current signal coordinate transformation is:

[0069] (17)

[0070] in, , and This represents the instantaneous value of the three-phase phase current of the rotor;

[0071] The formula used for calculating stator power is:

[0072] (18).

[0073] Preferably, the grid-side converter synchronization angle control module obtains the rotation angular frequency of the grid-side converter electrical signal by normalizing the DC voltage, and then integrates it to obtain the rotation angle of the grid-side converter electrical signal;

[0074] (19)

[0075] in, The rotational angular frequency of the control signal for the grid-side converter; This is the rated angular frequency value of the mains voltage; Set DC voltage value; This is the actual value of the DC voltage; The gain of the DC voltage synchronization circuit; This is the filtering time constant of the DC voltage synchronization circuit; This refers to the rotation angle of the control signal for the grid-side converter.

[0076] Preferably, the grid-side converter AC voltage amplitude control module obtains the grid-side converter reactive power command value by passing the difference between the grid voltage set value and the actual value through a proportional controller, and then passes it through a reactive power control loop and adds the grid voltage set value to obtain the desired amplitude of the stator voltage.

[0077] The reactive power command value of the grid-side converter is obtained by outputting the difference between the grid voltage setpoint and the actual value through a proportional controller. Its expression is:

[0078] (20)

[0079] in, This is the reactive power command value for the grid-side converter. This refers to the AC voltage droop coefficient of the grid-side converter.

[0080] The magnitude of the grid voltage that the grid-side converter aims to control is obtained by the difference between the grid voltage setpoint and the actual value, output by a proportional controller. Its expression is as follows:

[0081] (twenty one)

[0082] in, This represents the expected amplitude of the grid voltage. This represents the actual reactive power value of the grid-side converter. This is the proportional coefficient of the reactive power loop; The integral coefficient of the reactive power loop; For grid-side converter control compensation voltage;

[0083] The expression for the control compensation voltage of the grid-side converter is:

[0084] (twenty two)

[0085] in, These are the stabilization control coefficients for the grid-side converter; The filtering time constant of the stabilization control circuit.

[0086] Preferably, the grid-side converter current command generation module uses the desired amplitude of the grid voltage and the grid voltage at the grid-side converter control signal angle... The current command value of the first-stage grid-side converter is obtained by calculating the component difference in the rotating coordinate system.

[0087] (twenty three)

[0088] in, and These are the d-axis and q-axis components of the current command value for the first-stage grid-side converter. and The actual grid voltage value is at the angle of the grid-side converter control signal. Components in the rotating coordinate system; Virtual resistor value for grid-side converter control; Virtual inductance value for grid-side converter control;

[0089] The current command value of the first-stage grid-side converter is vector-limited to prevent the grid-side converter command current from exceeding the limit. The formula for calculating the d-axis current after limiting is as follows:

[0090] (25)

[0091] in, This represents the d-axis command value for the grid-side converter current. This is the maximum limit of the grid-side converter current.

[0092] The formula for calculating the q-axis current after limiting is:

[0093] (26)

[0094] in, This represents the q-axis command value for the grid-side converter current.

[0095] The grid-side converter current control module obtains the grid-side converter modulation voltage by passing the deviation between the command value and the actual value of the grid-side converter current through a proportional-integral controller and adding a compensation voltage in a rotating coordinate system.

[0096] (27)

[0097] in, and This refers to the voltage control value of the grid-side converter; The proportional gain of the grid-side converter current controller; For the integral coefficient of the grid-side converter current controller; and These are the actual d-axis and q-axis values ​​of the grid-side converter current; and This is the first compensation amount of the grid-side converter control voltage in the d-axis and q-axis. and This is the second compensation amount for the grid-side converter control voltage in the d-axis and q-axis.

[0098] The formula for calculating the first compensation amount of the grid-side converter control voltage is:

[0099] (28)

[0100] in, This refers to the filter inductance value of the grid-side converter;

[0101] The formula for calculating the second compensation amount of the grid-side converter control voltage is as follows:

[0102] (29)

[0103] in, Virtual impedance for current control of the grid-side converter;

[0104] The expression for the virtual impedance used for current control of the grid-side converter is:

[0105] (30)

[0106] The calculation formula used for coordinate transformation of the grid-side voltage signal in the grid-side converter signal processing module is as follows:

[0107] (31)

[0108] in, , and These are the instantaneous values ​​of the three-phase phase voltages of the power grid.

[0109] The calculation formula used for coordinate transformation of the current signal in the grid-side converter is as follows:

[0110] (32)

[0111] in, , and This represents the instantaneous value of the three-phase phase current of the grid-side converter;

[0112] The formula used for calculating the power of the grid-side converter is as follows:

[0113] (33).

[0114] Compared with the prior art, the present invention has the following beneficial effects:

[0115] 1. The present invention enables doubly-fed wind turbines to have active inertia response, primary frequency regulation downregulation and transient voltage support functions, so that the doubly-fed wind turbines can exhibit voltage source characteristics externally and achieve active support for the transient frequency and voltage of the power grid.

[0116] 2. This invention innovates the control strategy of the doubly-fed induction generator converter and adopts an active support control strategy to realize the change of the doubly-fed induction generator's characteristics from a grid-following power source to a grid-supported power source without increasing any hardware costs. It is especially suitable for upgrading and retrofitting existing current-source doubly-fed induction generators and can effectively solve the oscillation problem of existing current-source doubly-fed induction generators under weak grid conditions. Attached Figure Description

[0117] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0118] Figure 1 This is a schematic diagram of the control system for a self-synchronizing voltage source doubly fed wind turbine.

[0119] Figure 2 This is a schematic diagram of the primary frequency control module of a self-synchronizing voltage source doubly fed wind turbine.

[0120] Figure 3 This is a schematic diagram of the autonomous inertia response control module of a self-synchronizing voltage source doubly fed wind turbine.

[0121] Figure 4 This is a schematic diagram of the autonomous voltage control module of a self-synchronizing voltage source doubly fed wind turbine.

[0122] Figure 5 This is a schematic diagram of the rotor-side converter current command generation module in a self-synchronizing voltage source doubly fed wind turbine.

[0123] Figure 6 This is a schematic diagram of the rotor-side converter current control module in a self-synchronizing voltage source doubly fed wind turbine.

[0124] Figure 7This is a schematic diagram of the signal processing module of the rotor-side converter in a self-synchronizing voltage source doubly fed wind turbine.

[0125] Figure 8 This is a schematic diagram of the synchronization angle control module of the grid-side converter in a self-synchronizing voltage source doubly fed wind turbine.

[0126] Figure 9 This is a schematic diagram of the AC voltage amplitude control module of the grid-side converter in a self-synchronizing voltage source doubly fed wind turbine generator.

[0127] Figure 10 This is a schematic diagram of the current command generation module of the grid-side converter in a self-synchronizing voltage source doubly fed wind turbine generator.

[0128] Figure 11 This is a schematic diagram of the grid-side converter current control module in a self-synchronizing voltage source doubly fed wind turbine.

[0129] Figure 12 This is a schematic diagram of the signal processing module of the grid-side converter in a self-synchronizing voltage source doubly fed wind turbine.

[0130] Among them, 100-Doubly-fed induction generator (DFIG) converter power generation system; 101-Wind turbine primary frequency regulation control module; 102-Wind turbine autonomous inertia response control module; 103-Wind turbine autonomous voltage control module; 104-Rotor-side converter current command generation module; 105-Rotor-side converter current control module; 106-Rotor-side converter signal processing module; 107-Grid-side converter synchronization angle control module; 108-Grid-side converter AC voltage amplitude control module; 109-Grid-side converter current command generation module; 110-Grid-side converter current control module; 111-Grid-side converter signal processing module. Detailed Implementation

[0131] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0132] To address the shortcomings of existing technologies, the present invention aims to provide a grid-actively supported doubly-fed induction generator (DFIG) wind turbine control system and method. This system obtains the primary frequency regulation power deviation value by sending the deviation between the grid's rated frequency and the actual grid frequency to a dead-zone controller. This deviation is then summed with the wind turbine's desired output power to generate the converter power setpoint, thereby achieving autonomous response to grid frequency deviations. The system further obtains the torque deviation by dividing the converter power setpoint and the converter power feedback value by the generator's mechanical angular velocity. This torque deviation is then processed through a virtual synchronization control loop to obtain the frequency deviation value. The frequency deviation value is summed with the actual grid frequency to obtain the angular frequency of the DFIG stator current. Integrating the stator angular frequency yields the rotation angle of the stator electrical signal. Integrating the rotor angular velocity yields the rotor position rotation angle. Finally, the system integrates the stator current... The rotor current rotation angle is obtained by subtracting the rotor position rotation angle from the rotation angle. The stator voltage deviation value is obtained by using the relationship between the stator power and the stator voltage compensation value of the doubly-fed generator. The stator voltage reference value is obtained by adding the stator voltage rated value. The stator voltage reference value and the set value are passed through the voltage droop controller and the limiting circuit to the reactive power set value. The deviation between the reactive power set value and the actual value is passed through the proportional-integral controller and added to the grid voltage set value to obtain the desired amplitude of the stator voltage. The stator and rotor electrical signals are transformed into coordinates by using the stator and rotor rotation angles respectively. The command value of the rotor current in the rotating coordinate system is obtained according to the amplitude and actual value of the stator voltage. The autonomous support control of the doubly-fed wind turbine for grid frequency and voltage can be realized by controlling the deviation between the rotor current command value and the actual value.

[0133] Example 1

[0134] According to the present invention, a grid-supported doubly-fed wind turbine control system is provided, such as... Figure 1-12 As shown, it includes: a doubly fed wind turbine converter power generation system 100 and a grid-actively supported doubly fed wind turbine control system, which can realize the wind power generation unit's autonomous support for grid frequency and voltage.

[0135] The doubly-fed wind turbine converter power generation system 100 includes a doubly-fed wind turbine generator, a turbine-side converter, a DC capacitor bank, a DC unloader, a grid-side converter, and an AC filter circuit; wherein, the turbine-side converter and the grid-side converter can be selected as two-level converters and three-level converters.

[0136] The grid-supported doubly-fed induction generator (DFIG) control system includes: a primary frequency regulation control module 101, an autonomous inertia response control module 102, an autonomous voltage control module 103, a rotor-side converter current command generation module 104, a rotor-side converter current control module 105, a rotor-side converter signal processing module 106, a grid-side converter synchronization angle control module 107, a grid-side converter AC voltage amplitude control module 108, a grid-side converter current command generation module 109, a grid-side converter current control module 110, and a grid-side converter signal processing module 111.

[0137] The primary frequency regulation control module 101 for the wind turbine is used to control the frequency deviation of the power grid.

[0138] The wind turbine autonomous inertia response control module 102 is used to realize the control of the unit's grid frequency change rate, i.e., inertia response control.

[0139] The wind turbine autonomous voltage control module 103 is used to realize the active control of the grid voltage by the unit.

[0140] The rotor-side converter current command generation module 104 is used to generate rotor current command values.

[0141] The rotor-side converter current control module 105 is used to control the rotor current to track command values.

[0142] The rotor-side converter signal processing module 106 is used to process the signals required for the control of the rotor-side converter.

[0143] The grid-side converter synchronization angle control module 107 is used to generate the rotation angle of the grid-side converter electrical signal while achieving constant DC voltage.

[0144] The grid-side converter AC voltage amplitude control module 108 is used to realize the active support control of the grid voltage by the grid-side converter.

[0145] The grid-side converter current command generation module 109 is used to generate grid-side converter current command values.

[0146] The grid-side converter current control module 110 is used to control the grid-side converter current tracking command value.

[0147] The grid-side converter signal processing module 111 is used to process the signals required for grid-side converter control.

[0148] More specifically, the primary frequency regulation control module 101 of the wind turbine adopts the following method: the frequency regulation power of the unit is obtained by proportionally adjusting the deviation between the desired frequency and the actual frequency of the power grid. The calculation formula for the frequency regulation power is as follows:

[0149] ;

[0150] In the formula, This refers to the frequency regulation power of the generator unit; The rated frequency of the power grid; The actual frequency of the power grid; This refers to the frequency regulation coefficient of the generator unit; This is the frequency regulation dead zone of the generator unit.

[0151] Frequency regulation power is used to control the frequency deviation of the power grid.

[0152] More specifically, the wind turbine autonomous inertia response control module 102 adopts the following approach: by passing the unit torque deviation through a first-order inertial control loop to obtain the frequency deviation value, the frequency deviation value is added to the actual grid frequency to obtain the angular frequency of the doubly fed motor stator control signal, and then the angular frequency is integrated to obtain the angle of the doubly fed motor stator control signal.

[0153] The formulas for calculating the angular frequency and angle of the stator control signal of a doubly-fed induction generator are as follows:

[0154] ;

[0155] In the formula, The angular frequency of the stator control signal; This is the actual angular frequency of the power grid; The inertial time constant; The damping coefficient; The set active power of the generator unit; This represents the actual active power value of the unit; The mechanical angular velocity of the doubly-fed generator; The angle of the stator control signal; For the Laplace operator.

[0156] The slip angle of the doubly-fed induction generator can be obtained from the angular frequency of the stator control signal and the angular velocity of the rotor. The calculation formula is as follows:

[0157] ;

[0158] In the formula, This is the slip frequency of the doubly-fed generator; This represents the number of pole pairs in a doubly-fed generator. This represents the slip angle of the doubly-fed generator.

[0159] More specifically, the wind turbine autonomous voltage control module 103 adopts the following approach: by passing the difference between the grid voltage setpoint and the actual value through a proportional controller to obtain the reactive power command value, and then passing it through a reactive power control loop and adding the grid voltage setpoint to obtain the desired amplitude of the stator voltage.

[0160] The grid voltage setpoint consists of three parts: the voltage deviation value given by the power station, the unit's own voltage compensation, and the stator voltage rating. The calculation formula is as follows:

[0161] ;

[0162] in, Set the grid voltage value; This is the rated value of the mains voltage; The voltage deviation command given to the station; This is the voltage compensation value generated by the unit itself.

[0163] Voltage compensation value generated by the unit itself The expression is calculated based on the active power of the unit:

[0164] ;

[0165] in, This is the voltage compensation value when the unit power is zero. This is the voltage compensation value when the unit power is at its rated power.

[0166] The reactive power command value of the doubly-fed induction generator is obtained by outputting the difference between the grid voltage setpoint and the actual value through a proportional controller. Its expression is:

[0167] ;

[0168] in, This is the reactive power command value for the doubly-fed motor; This refers to the phase voltage amplitude of the power grid. This is the AC voltage droop coefficient.

[0169] The desired amplitude of the stator voltage of the doubly-fed induction generator is obtained by outputting the difference between the grid voltage setpoint and the actual value through a proportional controller, and its expression is:

[0170] ;

[0171] in, This represents the expected amplitude of the stator voltage. This represents the actual value of the stator reactive power of the doubly-fed motor. This is the proportional coefficient of the reactive power loop; This is the integral coefficient of the reactive power loop.

[0172] Active control of grid voltage is achieved by utilizing the desired amplitude of stator voltage.

[0173] More specifically, the rotor-side converter current command generation module 104 employs: by comparing the desired amplitude of the stator voltage with the stator voltage at the stator control signal angle, and comparing the grid voltage setpoint with the grid voltage at the stator control signal angle. The first-stage rotor current command value is obtained by calculating the component differences in the rotating coordinate system. The corresponding calculation formula is as follows:

[0174] ;

[0175] in, and The d-axis and q-axis components of the first-stage rotor current command value; and The actual value of the stator voltage at the stator control signal angle Components in the rotating coordinate system; Virtual resistance value for rotor-side converter control; The virtual inductance value is used for rotor-side converter control; This is the rated angular frequency of the power grid.

[0176] The first-stage rotor current command value is vector-limited to prevent the rotor command current from exceeding the limit. The formula for calculating the d-axis current after limiting is:

[0177] ;

[0178] in, This is the d-axis command value for the rotor current; This is the maximum limit of the rotor current.

[0179] The formula for calculating the q-axis current after limiting is:

[0180] ;

[0181] in, This is the q-axis command value for the rotor current.

[0182] More specifically, the rotor-side converter current control module 105 employs the following method: in a rotating coordinate system, the deviation between the commanded value and the actual value of the rotor current is processed by a proportional-integral controller and a compensation voltage is applied to obtain the rotor modulation voltage. The calculation formula is as follows:

[0183] ;

[0184] in, and This is the rotor voltage control value; This is the proportional coefficient of the rotor current controller; The integral coefficient of the rotor current controller; and These are the actual values ​​of the rotor current along the d-axis and q-axis. and This is the first compensation amount for the rotor voltage; and This is the second compensation amount for the rotor voltage.

[0185] The formula for calculating the first compensation amount of rotor voltage is:

[0186] ;

[0187] in, This refers to the rotor inductance of a doubly-fed induction generator. This refers to the stator inductance of a doubly-fed motor. The mutual inductance is for a doubly fed motor.

[0188] The formula for calculating the second compensation amount of rotor voltage is:

[0189]

[0190] in, This is the virtual impedance controlled by the rotor current.

[0191] The expression for the virtual impedance used for rotor current control is:

[0192] ;

[0193] More specifically, the rotor-side converter signal processing module 106 processes the signals required for rotor converter control in a rotating coordinate system, wherein the calculation formula used for the coordinate transformation of the stator voltage signal is:

[0194] ;

[0195] in, , and This refers to the instantaneous values ​​of the three-phase stator voltage and the phase voltage.

[0196] The calculation formula used for the coordinate transformation of the stator current signal is:

[0197] ;

[0198] in, , , This represents the instantaneous value of the three-phase stator current;

[0199] The calculation formula used for rotor current signal coordinate transformation is:

[0200] ;

[0201] in, , and This represents the instantaneous value of the three-phase phase current of the rotor.

[0202] The formula used for calculating stator power is:

[0203] ;

[0204] More specifically, the grid-side converter synchronization angle control module 107 employs the following method: The rotation angular frequency of the grid-side converter electrical signal is obtained by normalizing the DC voltage, and then the rotation angle of the grid-side converter electrical signal is obtained by integration. The calculation formula is as follows:

[0205] ;

[0206] in, The rotational angular frequency of the control signal for the grid-side converter; This is the rated angular frequency value of the mains voltage; Set DC voltage value; This is the actual value of the DC voltage; The gain of the DC voltage synchronization circuit; This is the filtering time constant of the DC voltage synchronization circuit; This refers to the rotation angle of the control signal for the grid-side converter.

[0207] More specifically, the grid-side converter AC voltage amplitude control module 108 adopts the following approach: by passing the difference between the grid voltage setpoint and the actual value through a proportional controller to obtain the grid-side converter reactive power command value, and then passing it through a reactive power control loop and adding the grid voltage setpoint to obtain the desired amplitude of the stator voltage; the desired amplitude of the stator voltage is used to realize the grid-side converter's active support control of the grid voltage.

[0208] The reactive power command value of the grid-side converter is obtained by outputting the difference between the grid voltage setpoint and the actual value through a proportional controller. Its expression is:

[0209] ;

[0210] in, This is the reactive power command value for the grid-side converter. This is the AC voltage droop coefficient for the grid-side converter.

[0211] The magnitude of the grid voltage that the grid-side converter aims to control is obtained by the difference between the grid voltage setpoint and the actual value, output by a proportional controller. Its expression is as follows:

[0212] ;

[0213] in, This represents the expected amplitude of the grid voltage. This represents the actual reactive power value of the grid-side converter. This is the proportional coefficient of the reactive power loop; The integral coefficient of the reactive power loop; The control compensation voltage is used for the grid-side converter.

[0214] The expression for the control compensation voltage of the grid-side converter is:

[0215] ;

[0216] in, These are the stabilization control coefficients for the grid-side converter; The filtering time constant of the stabilization control circuit.

[0217] More specifically, the grid-side converter current command generation module 109 employs: by comparing the desired amplitude of the grid voltage with the grid voltage at the grid-side converter control signal angle. The current command value of the first-stage grid-side converter is obtained by calculating the component difference in the rotating coordinate system. The corresponding calculation formula is as follows:

[0218] ;

[0219] in, and These are the d-axis and q-axis components of the current command value for the first-stage grid-side converter. and The actual grid voltage value is at the angle of the grid-side converter control signal. Components in the rotating coordinate system; Virtual resistor value for grid-side converter control; This is the virtual inductance value used for grid-side converter control.

[0220] The current command value of the first-stage grid-side converter is vector-limited to prevent the grid-side converter command current from exceeding the limit. The formula for calculating the d-axis current after limiting is as follows:

[0221] ;

[0222] in, This represents the d-axis command value for the grid-side converter current. This is the maximum limit of the grid-side converter current.

[0223] The formula for calculating the q-axis current after limiting is:

[0224] ;

[0225] in, This is the q-axis command value for the grid-side converter current.

[0226] More specifically, the grid-side converter current control module 110 employs the following method: in a rotating coordinate system, the deviation between the commanded value and the actual value of the grid-side converter current is processed by a proportional-integral controller and a compensation voltage is applied to obtain the grid-side converter modulation voltage. The calculation formula is as follows:

[0227] ;

[0228] in, and This refers to the voltage control value of the grid-side converter; The proportional gain of the grid-side converter current controller; For the integral coefficient of the grid-side converter current controller; and These are the actual d-axis and q-axis values ​​of the grid-side converter current; and This is the first compensation amount of the grid-side converter control voltage in the d-axis and q-axis. and This is the second compensation amount for the grid-side converter control voltage on the d-axis and q-axis.

[0229] The formula for calculating the first compensation amount of the grid-side converter control voltage is:

[0230] ;

[0231] in, This represents the filter inductance value of the grid-side converter.

[0232] The formula for calculating the second compensation amount of the grid-side converter control voltage is as follows:

[0233]

[0234] in, This is a virtual impedance used for current control of the grid-side converter.

[0235] The expression for the virtual impedance used for current control of the grid-side converter is:

[0236] ;

[0237] More specifically, the grid-side converter signal processing module 111 processes the signals required for grid-side converter control in a rotating coordinate system, wherein the calculation formula used for the coordinate transformation of the grid-side voltage signal is:

[0238] ;

[0239] in, , and These are the instantaneous values ​​of the three-phase voltages of the power grid.

[0240] The calculation formula used for coordinate transformation of the current signal in the grid-side converter is as follows:

[0241] ;

[0242] in, , and This represents the instantaneous value of the three-phase phase current of the grid-side converter.

[0243] The formula used for calculating the power of the grid-side converter is as follows:

[0244] ;

[0245] The present invention also provides a grid-supported doubly-fed induction generator (DFIG) wind turbine control system. The grid-supported DFIG wind turbine control system can be implemented by executing the process steps of the grid-supported DFIG wind turbine control method. That is, those skilled in the art can understand the grid-supported DFIG wind turbine control method as a preferred embodiment of the grid-supported DFIG wind turbine control system.

[0246] Those skilled in the art will understand that, besides implementing the system and its various devices, modules, and units provided by this invention in the form of purely computer-readable program code, the same functions can be achieved entirely through logical programming of the method steps, making the system and its various devices, modules, and units of this invention function in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers. Therefore, the system and its various devices, modules, and units provided by this invention can be considered as a hardware component, and the devices, modules, and units included therein for implementing various functions can also be considered as structures within the hardware component; alternatively, the devices, modules, and units for implementing various functions can be considered as both software modules implementing the method and structures within the hardware component.

[0247] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A grid-supported doubly-fed induction generator control system, characterized in that, include: Doubly fed wind turbine converter power generation system (100), wind turbine primary frequency regulation control module (101), wind turbine autonomous inertia response control module (102), wind turbine autonomous voltage control module (103), rotor-side converter current command generation module (104), rotor-side converter current control module (105), rotor-side converter signal processing module (106), grid-side converter synchronization angle control module (107), grid-side converter AC voltage amplitude control module (108), grid-side converter current command generation module (109), grid-side converter current control module (110), and grid-side converter signal processing module (111). The doubly fed wind turbine converter power generation system (100) includes: a doubly fed wind turbine generator, a turbine-side converter, a DC capacitor, a DC unloader, a grid-side converter, and an AC filter circuit; The primary frequency control module (101) of the wind turbine is used to control the frequency deviation of the power grid; The wind turbine autonomous inertia response control module (102) is used to control the rate of change of the power grid frequency; The wind turbine autonomous voltage control module (103) is used to realize active control of the grid voltage; The rotor-side converter current command generation module (104) is used to generate rotor current command values; The rotor-side converter current control module (105) is used to control the rotor current tracking command value; The rotor-side converter signal processing module (106) is used to process the signals required for rotor converter control. The grid-side converter synchronization angle control module (107) is used to generate the rotation angle of the grid-side converter electrical signal while achieving constant DC voltage; The grid-side converter AC voltage amplitude control module (108) is used to realize the active support control of the grid voltage by the grid-side converter; The grid-side converter current command generation module (109) is used to generate grid-side converter current command values; The grid-side converter current control module (110) is used to control the grid-side converter current tracking command value; The grid-side converter signal processing module (111) is used to process the signals required for grid-side converter control; The primary frequency control module (101) of the wind turbine obtains the frequency regulation power of the unit by proportionally adjusting the deviation between the desired frequency and the actual frequency of the power grid. （1） in, This refers to the frequency regulation power of the generator unit; The desired frequency of the power grid; The actual frequency of the power grid; This refers to the frequency regulation coefficient of the generator unit; This is the frequency regulation dead zone of the generator unit; The wind turbine autonomous inertia response control module (102) obtains the frequency deviation value by passing the unit torque deviation through a first-order inertial control loop. The frequency deviation value is added to the actual frequency of the power grid to obtain the angular frequency of the doubly fed motor stator control signal. The angle of the doubly fed motor stator control signal is obtained by integrating the angular frequency. The angular frequency and angle of the stator control signal for a doubly-fed induction generator (DFIG) include: （2） in, The angular frequency of the stator control signal; This is the actual angular frequency of the power grid; The inertial time constant; The damping coefficient; The set active power of the generator unit; This represents the actual active power value of the unit; The mechanical angular velocity of the doubly-fed generator; The angle of the stator control signal; For the Laplace operator; The slip angle of the doubly-fed motor is obtained from the angular frequency of the stator control signal and the rotor angular velocity. The calculation formula is as follows: （3） In the formula, This is the slip frequency of the doubly-fed generator; is the number of pole pairs of the doubly-fed generator; This refers to the slip angle of the doubly-fed generator; The wind turbine autonomous voltage control module (103) obtains the reactive power command value of the doubly fed motor by passing the difference between the grid voltage set value and the actual value through a proportional controller, and then passes it through a reactive power control loop and adds the grid voltage set value to obtain the desired amplitude of the stator voltage. The AC voltage amplitude control module (108) of the grid-side converter obtains the reactive power command value of the grid-side converter by passing the difference between the grid voltage set value and the actual value through the proportional controller, and then passes it through the reactive power control loop and adds the grid voltage set value and the grid-side converter control compensation voltage to obtain the amplitude of the grid voltage to be controlled by the grid-side converter.

2. The grid-supported doubly-fed induction generator control system according to claim 1, characterized in that, The grid voltage setpoint includes: the voltage deviation value given by the substation, the unit's own voltage compensation, and the stator voltage rating, and its calculation formula is as follows: （4） in, Set the grid voltage value; This is the stator voltage rating; The voltage deviation value given by the station; This is the voltage compensation amount for the generator unit itself; The unit's own voltage compensation amount It is calculated based on the active power of the generator unit, and its expression is: （5） in, This is the voltage compensation value when the unit power is zero; This is the voltage compensation value when the unit power is at its rated power. The reactive power command value is obtained by outputting the difference between the grid voltage setpoint and the actual value through a proportional controller, and its expression is: （6） in, This is the reactive power command value for the doubly-fed motor; This refers to the phase voltage amplitude of the power grid. This refers to the AC voltage droop coefficient. The formula for calculating the expected amplitude of the stator voltage is: （7） in, This represents the expected amplitude of the stator voltage; This represents the actual value of the stator reactive power of the doubly-fed motor. This is the proportional coefficient of the reactive power loop; This is the integral coefficient of the reactive power loop.

3. The grid-supported doubly-fed wind turbine control system according to claim 2, characterized in that, The rotor-side converter current command generation module (104) calculates the first-stage rotor current command value, expressed as: （8） in, and The d-axis and q-axis components of the first-stage rotor current command value; and The actual value of the stator voltage at the stator control signal angle Components in the rotating coordinate system; Virtual resistance value for rotor-side converter control; The virtual inductance value is used for rotor-side converter control; The rated angular frequency of the power grid; The first-stage rotor current command value is vector-limited to prevent the rotor command current from exceeding the limit. The formula for calculating the d-axis current after limiting is: （9） in, This is the d-axis command value for the rotor current; This is the maximum limit of the rotor current; The formula for calculating the q-axis current after limiting is: （10） in, This is the q-axis command value for the rotor current.

4. The grid-supported doubly-fed wind turbine control system according to claim 3, characterized in that, The rotor-side converter current control module (105) obtains the rotor modulation voltage by passing the deviation between the command value and the actual value of the rotor current in the rotating coordinate system through a proportional-integral controller and adding a compensation voltage. The expression is as follows: （11） in, and This is the rotor voltage control value; This is the proportional coefficient of the rotor current controller; The integral coefficient of the rotor current controller; and These are the actual values ​​of the rotor current along the d-axis and q-axis. and This is the first compensation amount for the rotor voltage; and This is the second compensation amount for the rotor voltage; The formula for calculating the first compensation amount of rotor voltage is: （12） in, This refers to the rotor inductance of a doubly-fed induction generator. This refers to the stator inductance of a doubly-fed motor. Mutual inductance for a doubly-fed motor; The formula for calculating the second compensation amount of rotor voltage is: （13） in, The virtual impedance for rotor current control; The expression for the virtual impedance used for rotor current control is: （14）。 5. The grid-supported doubly-fed induction generator control system according to claim 4, characterized in that, The stator voltage signal coordinate transformation in the rotor-side converter signal processing module (106) includes: （15） in, , and The instantaneous values ​​of the phase voltages of the three-phase stator voltage; The calculation formula used for the coordinate transformation of the stator current signal is: （16） in, , , This represents the instantaneous value of the three-phase stator current; The calculation formula used for rotor current signal coordinate transformation is: （17） in, , and This represents the instantaneous value of the three-phase phase current of the rotor; The formula used for calculating stator power is: （18）。 6. The grid-supported doubly-fed induction generator control system according to claim 5, characterized in that, The grid-side converter synchronization angle control module (107) obtains the rotation angular frequency of the grid-side converter electrical signal by normalizing the DC voltage, and then integrates it to obtain the rotation angle of the grid-side converter electrical signal. The calculation formula is as follows: （19） in, The rotational angular frequency of the control signal for the grid-side converter; This is the rated angular frequency value of the mains voltage; Set the DC voltage value; This is the actual value of the DC voltage; The gain of the DC voltage synchronization circuit; This is the filtering time constant of the DC voltage synchronization circuit; This refers to the rotation angle of the control signal for the grid-side converter.

7. The grid-supported doubly-fed induction generator control system according to claim 6, characterized in that, The reactive power command value of the grid-side converter is obtained by outputting the difference between the grid voltage setpoint and the actual value through a proportional controller. Its expression is: （20） in, This is the reactive power command value for the grid-side converter. This refers to the AC voltage droop coefficient of the grid-side converter. The expression for the grid voltage amplitude that the grid-side converter is expected to control is: （21） in, This represents the expected amplitude of the grid voltage. This represents the actual reactive power value of the grid-side converter. This is the proportional coefficient of the reactive power loop; The integral coefficient of the reactive power loop; For grid-side converter control compensation voltage; The expression for the control compensation voltage of the grid-side converter is: ；（22） in, These are the stabilization control coefficients for the grid-side converter; The filtering time constant of the stabilization control circuit.

8. The grid-supported doubly-fed induction generator control system according to claim 7, characterized in that, The grid-side converter current command generation module (109) uses the desired amplitude of the grid voltage and the grid voltage at the grid-side converter control signal angle. The current command value of the first-stage grid-side converter is obtained by calculating the component difference in the rotating coordinate system. The calculation formula is as follows: （23） in, and These are the d-axis and q-axis components of the current command value for the first-stage grid-side converter. and The actual grid voltage value is at the angle of the grid-side converter control signal. Components in the rotating coordinate system; Virtual resistor value for grid-side converter control; Virtual inductance value for grid-side converter control; The current command value of the first-stage grid-side converter is vector-limited to prevent the grid-side converter current command from exceeding the limit. The formula for calculating the d-axis current after limiting is as follows: （25） in, This represents the d-axis command value for the grid-side converter current. This is the maximum limit of the grid-side converter current. The formula for calculating the q-axis current after limiting is: （26） in, This represents the q-axis command value for the grid-side converter current. The grid-side converter current control module (110) obtains the grid-side converter modulation voltage by passing the deviation between the command value and the actual value of the grid-side converter current in the rotating coordinate system through a proportional-integral controller and adding a compensation voltage. The calculation formula is as follows: （27） in, and This refers to the voltage control value of the grid-side converter; The proportional gain of the grid-side converter current controller; For the integral coefficient of the grid-side converter current controller; and These are the actual d-axis and q-axis values ​​of the grid-side converter current; and This is the first compensation amount of the grid-side converter control voltage in the d-axis and q-axis. and This is the second compensation amount for the grid-side converter control voltage in the d-axis and q-axis. The formula for calculating the first compensation amount of the grid-side converter control voltage is: （28） in, This refers to the filter inductance value of the grid-side converter; The formula for calculating the second compensation amount of the grid-side converter control voltage is as follows: （29） in, Virtual impedance for current control of the grid-side converter; The expression for the virtual impedance used for current control of the grid-side converter is: （30） The calculation formula used for coordinate transformation of the grid-side voltage signal in the grid-side converter signal processing module (111) is as follows: （31） in, , and These are the instantaneous values ​​of the three-phase phase voltages of the power grid. The calculation formula used for coordinate transformation of the current signal in the grid-side converter is as follows: （32） in, , and This represents the instantaneous value of the three-phase phase current of the grid-side converter; The formula used for calculating the power of the grid-side converter is as follows: （33）。

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