A control method and system for an inertia-adjustable grid-connected device capable of independent phase adjustment

Abstract

The present invention discloses a control method and system for an inertia-adjustable grid-connected device capable of independent phase adjustment. The method of the present invention comprises adopting three-loop control to generate a dq axis reference voltage instruction. The outer loop of the three-loop control generates a stator reactive power reference value and a rotor speed reference value based on the deviation of the DC bus voltage and the grid-side frequency. The middle loop generates a dq axis current reference value based on the output of the outer loop and the stator reactive power and the rotor speed. The inner loop generates a dq axis reference voltage instruction based on the output of the middle loop and the dq axis current to control the DC / AC converter of the control winding of the doubly-fed motor in the inertia-adjustable grid-connected device, so that the doubly-fed motor enters an overexcitation or underexcitation state and outputs inductive or capacitive reactive power to the grid to realize an independent phase adjustment function. The present invention aims to realize independent phase adjustment by using an inertia-adjustable grid-connected device to increase the system inertia, realize greater control flexibility, play a greater supporting role in transient state, and improve system stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of grid connection of new energy power stations, and in particular relates to a control method and system for an inertia-adjustable grid-connected device capable of independent phase adjustment. Background Art

[0002] In recent years, the scale of renewable energy power generation in my country has grown rapidly. Building a new power system with microgrids based on new energy is an inevitable trend in the current power system. At present, the microgrids using new energy power generation are connected to the grid mainly by power electronic converters. Power electronic converters are used to convert the electric energy generated by microgrids using new energy power generation into AC power and then integrate it into the grid. However, with the continuous increase in the penetration rate of new energy, the inertia of the entire power system is relatively insufficient, and the frequency and voltage characteristics of the entire network are also deteriorating. Although some scholars have adopted synchronous phase condensers to increase the rotational inertia of the system, and as a reactive compensation device, it can play a role in voltage support for the new energy system. However, on the one hand, the inertia constant of its traditional synchronous phase condensers is small, and the inertia release cannot be actively controlled; on the other hand, it mainly provides reactive support for the power grid, and can only provide short-term frequency support capabilities, and the support capacity is limited. Summary of the invention

[0003] Technical problem to be solved by the present invention: In view of the above-mentioned problems in the prior art, a control method and system for an adjustable inertia type grid-connected device capable of independent phase adjustment are provided. The present invention aims to utilize the adjustable inertia type grid-connected device to achieve independent phase adjustment to increase the system inertia, achieve greater control flexibility, play a greater supporting role in transient conditions, and improve system stability.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0005] A control method for an inertia-adjustable grid-connected device capable of independent phase adjustment comprises the following steps:

[0006] S1, the DC bus voltage and bus voltage reference value The deviation is used as the input of the outer loop of the three-loop control to obtain Stator reactive power reference value at time , the grid side frequency and power frequency The deviation is used as the input of the outer loop of the three-loop control to obtain The rotor speed reference value at time ;

[0007] S2, Stator reactive power reference value at time Grid-connected device with adjustable inertia Reactive power at the moment The deviation is used as the input of the middle loop of the three-loop control to obtain The d-axis current reference value at time ,Will The rotor speed reference value at time Double-fed machine with inertia-adjustable grid-connected device Rotor speed at time The deviation is used as the input of the middle loop of the three-loop control to obtain The q-axis current reference value at time ;

[0008] S3, The dq axis current reference value at the moment and the dq axis current of the doubly-fed motor control winding As the input of the inner loop of the three-loop control, we can obtain The dq axis reference voltage command at the moment ;

[0009] S4, The dq axis reference voltage command at the moment After the coordinates are converted, space vector pulse width modulation is performed to generate a control signal to control the DC / AC converter of the control winding of the doubly-fed motor in the inertia-type grid-connected device, so that the doubly-fed motor enters an over-excitation or under-excitation state to output inductive or capacitive reactive power to the grid to achieve an independent phase modulation function.

[0010] Optionally, the outer loops of the three-loop control in step S1 all use PI controllers, and the DC bus voltage and bus voltage reference value The deviation is used as the input of the outer loop of the three-loop control to obtain Stator reactive power reference value at time The DC bus voltage and bus voltage reference value The deviation is used as the input of the PI controller, and then the output of the PI controller is amplified times to get Stator reactive power reference value at time ; The grid side frequency and power frequency The deviation is used as the input of the outer loop of the three-loop control to obtain The rotor speed reference value at time Including the grid side frequency and power frequency The deviation is used as the input of the PI controller to obtain the speed deviation , the speed deviation and initial speed setting The deviation between The rotor speed reference value at time .

[0011] Optionally, the middle loops of the three-loop control in step S2 all adopt PI controllers.

[0012] Optionally, the inner loop of the three-loop control in step S3 is a model-free predictive controller, and the function expression of the model-free predictive controller is:

[0013] ,

[0014] ,

[0015] In the above formula, and They are The q-axis current reference value at time The d and q axis reference voltage instructions in and are the dq axis coefficients, To control the cycle, and They are The d-axis and q-axis current reference values ​​at the moment, and They are the dq axis currents of the double-fed motor control windings respectively The d and q axis currents in and are the d-axis and q-axis disturbance terms respectively.

[0016] Optionally, the d-axis and q-axis disturbance terms are obtained by observing a noise suppression extended state observer, and the function expression of the d-axis and q-axis disturbance terms obtained by observing the noise suppression extended state observer is:

[0017] ,

[0018] In the above formula, for The error in time, and They are and Additional state observations at time , for Additional state at the moment, To control the cycle, and They are and The rotor current vector observation value at time , , and is the coefficient, and , superscript represents the transpose operation, is the observer bandwidth, is the d and q axis coefficient vector, , and are the d and q axis coefficients respectively, for Voltage vector at time , and there is , and is the d-axis and q-axis voltage of the control winding of the doubly-fed machine, and They are and The d and q axis disturbance terms at time , and there are , .

[0019] Optionally, the inertia-adjustable grid-connected device includes a doubly-fed motor and a synchronous motor coaxially connected to the doubly-fed motor via a mechanical shaft.

[0020] Optionally, the control method for the adjustable inertia type grid-connected device is executed when the new energy station to which the adjustable inertia type grid-connected device is connected does not generate power or the new energy station is offline.

[0021] In addition, the present invention also provides a control system for an independently phase-adjustable inertia-type grid-connected device, comprising a microprocessor and a memory connected to each other, wherein the microprocessor is programmed or configured to execute the independently phase-adjustable inertia-type grid-connected device control method.

[0022] In addition, the present invention also provides a computer-readable storage medium, in which a computer program or instruction is stored, and the computer program or instruction is programmed or configured to execute the control method of the independently phase-adjustable inertia-type grid-connected device through a processor.

[0023] In addition, the present invention also provides a computer program product, including a computer program or instructions, which are programmed or configured to execute the control method of the inertia-adjustable grid-connected device capable of independent phase adjustment through a processor.

[0024] Compared with the prior art, the present invention mainly has the following advantages: the method of the present invention comprises adopting three-loop control to generate dq axis reference voltage instructions, the outer loop of the three-loop control is for generating stator reactive power reference value and rotor speed reference value based on the deviation of DC bus voltage and grid side frequency, the middle loop is for generating dq axis current reference value based on the output of the outer loop and stator reactive power and rotor speed, the inner loop is for generating dq axis reference voltage instructions based on the output of the middle loop and dq axis current to control and adjust the DC / AC converter of the control winding of the doubly fed motor in the inertia-type grid-connected device, so that the doubly fed motor enters an overexcitation or underexcitation state to output inductive or capacitive reactive power to the grid to realize independent phase modulation function, the present invention can make the doubly fed motor enter an overexcitation or underexcitation state by controlling the magnitude of the rotor excitation current, thereby outputting inductive or capacitive reactive power to the system, when the grid encounters disturbance, the speed change of the phase regulator can be realized by adjusting the excitation current frequency of the rotor, thereby releasing or absorbing energy, increasing the inertia of the system, realizing greater control flexibility, playing a greater supporting role in transient state, and improving the stability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the basic flow of the method of the embodiment of the present invention.

[0026] Figure 2 Schematic diagram of the control principle of the method according to an embodiment of the present invention.

[0027] Figure 3 1 is a Bode diagram of the transfer function of the disturbance estimation error of the noise immune extended state observer in an embodiment of the present invention.

[0028] Figure 4 1 is a Bode diagram of an estimated disturbance transfer function of a noise-immune extended state observer in an embodiment of the present invention.

[0029] Figure 5 It is a structural schematic diagram of a new energy station connected to the grid using an inertia-adjusting grid-connected device in an embodiment of the present invention.

[0030] Figure 6 It is a schematic diagram of the independent phase adjustment structure of the inertia-adjusting grid-connected device when the new energy station is not doing work in an embodiment of the present invention. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0032] like Figure 1 As shown, the control method of the inertia-adjustable grid-connected device capable of independent phase adjustment in this embodiment includes the following steps:

[0033] S1, the DC bus voltage and bus voltage reference value The deviation is used as the input of the outer loop of the three-loop control to obtain Stator reactive power reference value at time , the grid side frequency and power frequency The deviation is used as the input of the outer loop of the three-loop control to obtain The rotor speed reference value at time ;

[0034] S2, Stator reactive power reference value at time Grid-connected device with adjustable inertia Reactive power at the moment The deviation is used as the input of the middle loop of the three-loop control to obtain The d-axis current reference value at time ,Will The rotor speed reference value at time Double-fed machine with inertia-adjustable grid-connected device Rotor speed at time The deviation is used as the input of the middle loop of the three-loop control to obtain The q-axis current reference value at time ;

[0035] S3, The dq axis current reference value at the moment and the dq axis current of the doubly-fed motor control winding As the input of the inner loop of the three-loop control, we can obtain The dq axis reference voltage command at the moment ;

[0036] S4, The dq axis reference voltage command at the moment After the coordinates are converted, space vector pulse width modulation is performed to generate a control signal to control the DC / AC converter of the control winding of the doubly-fed motor in the inertia-type grid-connected device, so that the doubly-fed motor enters an over-excitation or under-excitation state to output inductive or capacitive reactive power to the grid to achieve an independent phase modulation function.

[0037] like Figure 2 As shown, in step S1 of this embodiment, the outer loops of the three-loop control all adopt PI controllers, and the DC bus voltage and bus voltage reference value The deviation is used as the input of the outer loop of the three-loop control to obtain Stator reactive power reference value at time (Abbreviated as ) refers to the DC bus voltage and bus voltage reference value The deviation is used as the input of the PI controller, and then the output of the PI controller is amplified times to get Stator reactive power reference value at time ; The grid side frequency and power frequency The deviation is used as the input of the outer loop of the three-loop control to obtain The rotor speed reference value at time Including the grid side frequency and power frequency The deviation is used as the input of the PI controller to obtain the speed deviation , the speed deviation and initial speed setting The deviation between The rotor speed reference value at time (Abbreviated as ). In addition, the outer loop can also use other closed-loop controllers as needed. Figure 2 Middle,U pabc Represents the voltage of the stator winding of the doubly-fed machine, U rabc represents the voltage of the control winding of the doubly-fed machine, i pabc represents the current of the stator winding of the doubly-fed machine, i rabc represents the current of the control winding of the doubly-fed machine, is the electrical angular velocity of the doubly-fed machine rotor, is the rotor angle of the doubly-fed generator, is the rotor speed of the doubly-fed generator. rabc The phase-locked loop can be used to obtain the direction angle of the power winding of the doubly-fed machine , Indicates the direction angle of the control winding, U pabc and i pabc By coordinate transformation, the dq axis voltage U of the power winding of the doubly fed machine can be obtained. pdq and dq axis current i pdq . Will U rabc and i rabc By coordinate transformation, the dq axis voltage U of the control winding of the doubly fed machine can be obtained. rdq and dq axis current i rdq .

[0038] like Figure 2 As shown, the middle loop of the three-loop control in step S2 of this embodiment adopts a PI controller, and other closed-loop controllers can also be used as needed. Figure 2 ,Will Stator reactive power reference value at time (Abbreviated as ) and the inertia-adjustable grid-connected device Reactive power at the moment The deviation is used as the input of the PI controller to obtain The d-axis current reference value at time (Abbreviated as ),Will The rotor speed reference value at time (Abbreviated as ) and double-fed machines with adjustable inertia type grid-connected devices Rotor speed at time The deviation is used as the input of the PI controller to obtain The q-axis current reference value at time (Abbreviated as ).

[0039] like Figure 2 As shown, the inner loop of the three-loop control in step S3 of this embodiment is a model-free predictive controller, and the function expression of the model-free predictive controller is:

[0040] ,

[0041] ,

[0042] In the above formula, and They are The q-axis current reference value at time The d and q axis reference voltage instructions in Figure 2 Abbreviated as and ), and are the dq axis coefficients, To control the cycle, and They are The d-axis and q-axis current reference values ​​at the moment, and They are the dq axis currents of the double-fed motor control windings respectively The d and q axis currents in and are the d-axis and q-axis disturbance terms respectively. Figure 1 and Figure 2 It can be seen that in order to control the reactive power, speed, and DC bus voltage of the doubly-fed generator, a three-loop control strategy is designed. At the same time, in order to improve the system response speed, the current inner loop adopts predictive control.

[0043] The mathematical model of the doubly-fed machine in the dq coordinate system is as follows:

[0044] ,

[0045] ,

[0046] ,

[0047] ,

[0048] ,

[0049] ,

[0050] ,

[0051] ,

[0052] ,

[0053] In the above formulas, and are the dq axis voltages of the control winding (denoted by the subscript r), and are the dq axis voltages of the stator winding (denoted by the subscript p) respectively; and are the dq axis currents of the control winding respectively, and are the dq axis currents of the stator winding respectively; and are the dq axis flux of the control winding, and are the dq axis flux of the stator winding respectively; and are the resistances of the control winding and stator winding respectively; and are the inductances of the control winding and the stator winding respectively; is the magnetizing inductance; is the electrical angular velocity of the power winding, which is equal to the synchronous electrical angular velocity on the grid side; is the rotor electrical angular velocity. is the electromagnetic torque.

[0054] Substituting the flux equation into the voltage equation, the current components of the stator and rotor of the doubly fed generator are sorted out as follows:

[0055] ,

[0056] ,

[0057] Therefore, the predicted reference voltage of the control winding can be expressed as:

[0058] ,

[0059] ,

[0060] Since the predictive control is based on the above prediction model, accurate motor parameters are required. When the motor is running, its actual parameters are often different from the parameters given on the nameplate, which will cause a deviation between the predicted reference voltage and the actual reference voltage. In order to solve this problem, a robust predictive control method is proposed. According to the equations obtained by sorting out the current components of the stator and rotor of the doubly fed motor, the super-local model of the doubly fed motor can be described as:

[0061] ,

[0062] In the above formula, and are the input dq axis coefficients. and is the dq axis disturbance, which can be expressed as follows:

[0063] ,

[0064] In actual situations, and can be obtained by the disturbance observer. As an optional implementation, in order to further suppress parameter disturbances and noise disturbances, a model-free predictive current control based on a noise suppression extended state observer is designed. Figure 2 As shown, in this embodiment, the d-axis and q-axis disturbance terms are obtained by observing the noise suppression extended state observer, and the function expression of the d-axis and q-axis disturbance terms obtained by observing the noise suppression extended state observer is:

[0065] ,

[0066] In the above formula, for The error in time, and They are and Additional state observations at time , for Additional state at the moment, To control the cycle, and They are and The rotor current vector observation value at time , , and is the coefficient, and , superscript represents the transpose operation, is the observer bandwidth, is the d and q axis coefficient vector, , and are the d and q axis coefficients respectively, for Voltage vector at time , and there is , and is the d-axis and q-axis voltage of the control winding of the doubly-fed machine, and They are and The d and q axis disturbance terms at time , and there are , In this embodiment, the additional state satisfy ,in is the starting time, For the current moment, is the rotor current vector, are the d-axis and q-axis currents of the control winding of the doubly-fed motor.

[0067] In this embodiment, the transfer function of the disturbance estimation error is It is expressed as:

[0068] ,

[0069] Estimated disturbance transfer function representation for:

[0070] ,

[0071] In the above formula, is the observed value of the disturbance term on the d and q axes, is the d and q axis disturbance term, is the observer bandwidth. Figure 3 1 is a Bode diagram of the transfer function of the disturbance estimation error of the noise immune extended state observer in an embodiment of the present invention. Figure 4 : is a Bode diagram of the estimated disturbance transfer function of the noise immune extended state observer in the embodiment of the present invention. Figure 3 and Figure 4 It can be seen that, compared with the traditional linear extended state observer, the noise immune extended state observer in this embodiment has similar disturbance suppression capability and stronger noise suppression capability.

[0072] like Figure 5 and Figure 6As shown, the adjustable inertia type grid-connected device in this embodiment includes a doubly-fed motor and a synchronous motor coaxially connected to the doubly-fed motor through a mechanical shaft, the doubly-fed motor is a brushless doubly-fed motor or a brushed doubly-fed motor, the control winding of the doubly-fed motor is connected to the DC grid of the new energy power station through a DC / AC converter, and the output end of the power winding of the doubly-fed motor is connected in series to the grid; the synchronous motor is coaxially connected to the rotor of the doubly-fed motor, and the input end of the synchronous motor is connected in series with a DC / AC converter for converting the DC power output from the DC grid of the new energy power station into AC power.

[0073] The power generation equipment of the new energy station includes a double-fed DC fan based on diode rectification, a permanent magnet DC fan, a photovoltaic power station, a hydropower station and an energy storage station. The power output of the new energy power station is rectified and then boosted and collected with the energy storage output power in the DC network to form an integrated new energy station of wind, light and water storage. The power output of the new energy power station is rectified and then boosted and collected with the energy storage output power in the DC network and then connected to the grid through one or more inertia-adjusting grid-connected devices, which have an independent phase adjustment function. The double-fed motor can be made to enter an over-excitation or under-excitation state by controlling the magnitude of the rotor excitation current, thereby outputting inductive or capacitive reactive power to the system. On the one hand, by controlling the magnitude of the rotor excitation current, the double-fed motor can be made to enter an over-excitation or under-excitation state, thereby outputting inductive or capacitive reactive power to the system. On the other hand, when the power grid encounters a disturbance, the speed change of the phase regulator can be achieved by adjusting the excitation current frequency of the rotor, thereby releasing or absorbing energy and increasing the inertia of the system. The control method of the inertia-adjusting grid-connected device in this embodiment is executed when the new energy station connected to the inertia-adjusting grid-connected device does not generate power or the new energy station is offline. When the new energy station does not generate power, the inertia-adjusting grid-connected device can still work as an independent phase regulator. In this embodiment, the speed of the double-fed motor is controlled to be the grid side frequency. f g and rotor excitation current frequency f r The frequency difference between times, where p is the number of pole pairs of the doubly-fed generator. When the power grid encounters disturbances, the speed of the phase regulator can be changed by adjusting the frequency of the rotor's excitation current, thereby releasing or absorbing energy and increasing the system inertia.

[0074] In summary, the inertia-adjusting grid-connected device in the method of this embodiment includes a doubly-fed motor and a synchronous motor coaxially connected to the doubly-fed motor through a mechanical shaft. The control winding of the doubly-fed motor is connected to the DC grid of the new energy power station through a DC / AC converter, and the output end of the power winding of the doubly-fed motor is connected in series to the grid; the synchronous motor is coaxially connected to the rotor of the doubly-fed motor, and the input end of the synchronous motor is connected in series with a DC / AC converter for converting the DC power output from the DC grid of the new energy power station into AC power. When the new energy station is not working, the inertia-adjusting grid-connected device can be used alone as a phase regulator. The method of this embodiment can make the doubly-fed motor enter an over-excitation or under-excitation state by controlling the magnitude of the rotor excitation current, thereby outputting inductive or capacitive reactive power to the system. When the power grid encounters a disturbance, the method of this embodiment can achieve the speed change of the phase regulator by adjusting the excitation current frequency of the rotor, thereby releasing or absorbing energy, increasing the inertia of the system, achieving greater control flexibility, playing a greater supporting role in transient states, and improving system stability.

[0075] In addition, this embodiment also provides a control system for an independently phase-adjustable inertia-type grid-connected device, comprising a microprocessor and a memory connected to each other, wherein the microprocessor is programmed or configured to execute the independently phase-adjustable inertia-type grid-connected device control method.

[0076] In addition, this embodiment also provides a computer-readable storage medium, in which a computer program or instruction is stored, and the computer program or instruction is programmed or configured to execute the control method of the independently phase-adjustable inertia-type grid-connected device through a processor.

[0077] In addition, this embodiment also provides a computer program product, including a computer program or instructions, which are programmed or configured to execute the control method of the inertia-adjustable grid-connected device capable of independent phase adjustment through a processor.

[0078] Those skilled in the art should understand that the technical solutions provided by the embodiments of the present application may be in the form of methods, systems, or computer program products. Therefore, the present application may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present application may take the form of a computer program product implemented on one or more computer-readable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes. The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the process Figure 1 A process or multiple processes and / or boxes Figure 1 These computer program instructions can also be stored in a computer-readable memory that can guide a computer or other programmable data processing device to work in a specific way, so that the instructions stored in the computer-readable memory produce a product including an instruction device, which implements the functions specified in the process. Figure 1 A process or multiple processes and / or boxes Figure 1 These computer program instructions can also be loaded onto a computer or other programmable data processing device, so that a series of operation steps are executed on the computer or other programmable device to produce a computer-implemented process, so that the instructions executed on the computer or other programmable device provide for implementing the process in the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0079] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A control method for an inertia-adjustable grid-connected device capable of independent phase adjustment, characterized in that: The steps include: S1, the DC bus voltage and bus voltage reference value The deviation is used as the input of the outer loop of the three-loop control to obtain Stator reactive power reference value at time , the grid side frequency and power frequency The deviation is used as the input of the outer loop of the three-loop control to obtain The rotor speed reference value at time ; S2, will Stator reactive power reference value at time Grid-connected device with adjustable inertia Reactive power at the moment The deviation is used as the input of the middle loop of the three-loop control to obtain The d-axis current reference value at time ,Will The rotor speed reference value at time Double-fed machine with inertia-adjustable grid-connected device Rotor speed at time The deviation is used as the input of the middle loop of the three-loop control to obtain The q-axis current reference value at time ; S3, The dq axis current reference value at the moment and the dq axis current of the doubly-fed motor control winding As the input of the inner loop of the three-loop control, we can obtain The dq axis reference voltage command at the moment ; S4, The dq axis reference voltage command at the moment After the coordinates are converted, space vector pulse width modulation is performed to generate a control signal to control the DC / AC converter of the control winding of the doubly-fed motor in the inertia-type grid-connected device, so that the doubly-fed motor enters an over-excitation or under-excitation state to output inductive or capacitive reactive power to the grid to achieve an independent phase modulation function.

2. The control method of the inertia-adjustable grid-connected device capable of independent phase adjustment according to claim 1, characterized in that: The outer loops of the three-loop control in step S1 all use PI controllers, and the DC bus voltage and bus voltage reference value The deviation is used as the input of the outer loop of the three-loop control to obtain Stator reactive power reference value at time The DC bus voltage and bus voltage reference value The deviation is used as the input of the PI controller, and then the output of the PI controller is amplified times to get Stator reactive power reference value at time ; The grid side frequency and power frequency The deviation is used as the input of the outer loop of the three-loop control to obtain The rotor speed reference value at time Including the grid side frequency and power frequency The deviation is used as the input of the PI controller to obtain the speed deviation , the speed deviation and initial speed setting The deviation between The rotor speed reference value at time .

3. The control method of the inertia-adjustable grid-connected device capable of independent phase adjustment according to claim 1, characterized in that: The middle loops of the three-loop control in step S2 all adopt PI controllers.

4. The control method of the inertia-adjustable grid-connected device capable of independent phase adjustment according to claim 1, characterized in that: The inner loop of the three-loop control in step S3 is a model-free predictive controller, and the function expression of the model-free predictive controller is: ， ， In the above formula, and They are The q-axis current reference value at time The d and q axis reference voltage instructions in and are the dq axis coefficients, To control the cycle, and They are The d-axis and q-axis current reference values ​​at the moment, and They are the dq axis currents of the doubly-fed motor control windings respectively The d and q axis currents in and are the d-axis and q-axis disturbance terms respectively.

5. The control method of the inertia-adjustable grid-connected device capable of independent phase adjustment according to claim 4, characterized in that: The d-axis and q-axis disturbance terms are obtained by observing the noise suppression extended state observer. The function expression of the d-axis and q-axis disturbance terms obtained by observing the noise suppression extended state observer is: ， In the above formula, for The error in time, and They are and Additional state observations at time , for Additional state at the moment, To control the cycle, and They are and The rotor current vector observation value at time , , and is the coefficient, and , superscript represents the transpose operation, is the observer bandwidth, is the d and q axis coefficient vector, , and are the d-axis and q-axis coefficients respectively, for Voltage vector at time , and there is , and is the d-axis and q-axis voltage of the control winding of the doubly-fed machine, and They are and The d and q axis disturbance terms at time , and there are , .

6. The control method of the inertia-adjustable grid-connected device capable of independent phase adjustment according to claim 1, characterized in that: The inertia-adjusting grid-connected device comprises a doubly-fed motor and a synchronous motor coaxially connected to the doubly-fed motor via a mechanical shaft.

7. The control method of the inertia-adjustable grid-connected device capable of independent phase adjustment according to claim 1, characterized in that: The control method of the inertia-adjusting grid-connected device is executed when the new energy station to which the inertia-adjusting grid-connected device is connected does not generate power or the new energy station is offline.

8. An inertia-adjustable grid-connected device control system capable of independent phase adjustment, comprising a microprocessor and a memory connected to each other, characterized in that: The microprocessor is programmed or configured to execute the control method of the inertia-adjustable grid-connected device capable of independent phase adjustment as described in any one of claims 1 to 7.

9. A computer-readable storage medium having a computer program or instruction stored therein, characterized in that: The computer program or instruction is programmed or configured to execute the control method of the inertia-adjustable grid-connected device capable of independent phase adjustment as claimed in any one of claims 1 to 7 through a processor.

10. A computer program product comprising a computer program or instructions, characterized in that The computer program or instruction is programmed or configured to execute the control method of the inertia-adjustable grid-connected device capable of independent phase adjustment as claimed in any one of claims 1 to 7 through a processor.

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