Direct current bus voltage control method and system of flywheel energy storage system

Abstract

The invention belongs to the field of new energy, and particularly discloses a direct-current bus voltage control method and system of a flywheel energy storage system. Comprising the following steps: if DC bus voltage is in a normal range, DC voltage forms a q-axis current reference signal after being adjusted by a PI controller, the q-axis current reference signal generates a q-axis voltage instruction signal after being adjusted by a current control loop PI, and a dq-axis voltage instruction value is generated through decoupling; if the current control loop slightly deviates from the normal range, parameters of a PI controller are adjusted, so that an integration link plays a leading role in control output, a virtual impedance link connected to the current control loop in parallel is adjusted, and a dq-axis voltage instruction value is generated; and if the voltage is seriously deviated from the normal range, a grid-side power signal is fed forward to a machine-side direct-current voltage control loop, virtual resistance in a virtual impedance link is adjusted, and a dq-axis voltage instruction value is generated. According to the invention, the control mode is automatically switched according to different conditions of the DC bus voltage by adopting a threshold-grading regulation and control strategy, and the adaptability to large disturbance is improved while the steady-state precision of the system is maintained.

Description

Technical Field

[0001] This application belongs to the field of new energy technology, specifically to the field of power supply control technology, and more specifically, to a DC bus voltage control method and system for a flywheel energy storage system. Background Technology

[0002] Taking PWM (Pulse Width Modulation) energy storage systems as an example, their typical grid connection method often adopts a two-stage circuit topology with inverters (DC / AC) and rectifiers (AC / DC) back-to-back. In this structure, the DC bus, as the intermediate link of energy, plays a core role in connecting the two power conversion units, and its voltage stability directly affects the system's energy transmission efficiency and operational safety.

[0003] Among various energy storage forms, flywheel energy storage has become an important solution for supporting the dynamic regulation of power systems due to its moderate energy density, fast charging and discharging speed, long cycle life, and rapid power response. Especially when there are large power fluctuations and load disturbances on the grid side (such as the access of new energy sources, grid faults, or rapid load changes), flywheels can quickly release or absorb energy in millisecond-level response, thus playing a significant supporting role in the stability of grid voltage and frequency.

[0004] However, in the energy release process of a flywheel energy storage system, the kinetic energy stored during its high-speed rotation is essentially output as mechanical power via the shaft system through deceleration, and then converted into electromagnetic energy as the mechanical input power of the motor. The dynamic change in instantaneous output power during this process depends not only on the rate of change of the flywheel speed but also on the combined constraints of load power demand and the regulation characteristics of the control system. When the external load changes abruptly or the control command is rapidly adjusted, a transient imbalance occurs between the mechanical power output by the flywheel and the electromagnetic power on the grid side. Furthermore, the excessively rapid energy release from the flywheel generates significant instantaneous power fluctuations, which can easily accumulate as voltage overshoot on the bus. If not properly controlled, this can easily lead to DC bus voltage instability. This not only threatens the safe operation of power devices but may also reduce the system's dynamic support capability. Therefore, how to achieve efficient and stable control of the DC bus voltage of a flywheel energy storage system in a complex power grid environment has become a key technical issue for ensuring the stable operation of the flywheel energy storage system and leveraging its rapid support advantages. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this application is to provide a DC bus voltage control method and system for a flywheel energy storage system, which aims to solve the problem of DC bus voltage instability caused by improper control when the external load changes suddenly or the control command is adjusted rapidly.

[0006] To achieve the above objectives, in a first aspect, this application provides a DC bus voltage control method for a flywheel energy storage system, applied to a generator-side converter. The control method includes: if the DC bus voltage is within the normal range, the DC voltage is adjusted by a PI controller to form a q-axis current reference signal; the q-axis current reference signal is adjusted by a current control loop PI to generate a q-axis voltage command signal, and a dq-axis voltage command value for the converter modulation wave is generated accordingly; if the DC bus voltage slightly deviates from the normal range, the parameters of the PI controller are adjusted so that the integral element plays a dominant role in the control output, and the virtual impedance element connected in parallel with the current control loop is adjusted to generate the dq-axis voltage command value for the converter modulation wave; if the DC bus voltage severely deviates from the normal range, the grid-side power signal is fed forward to the generator-side DC voltage control loop, and the virtual resistance in the virtual impedance element is further adjusted to generate the dq-axis voltage command value for the converter modulation wave.

[0007] Preferably, if the DC bus voltage is at [first low voltage threshold, first high voltage threshold], it is considered that the DC bus voltage is within the normal range; if the DC bus voltage is at [second low voltage threshold, first low voltage threshold] or [first high voltage threshold, second high voltage threshold], it is considered that the DC bus voltage slightly deviates from the normal range; if the DC bus voltage exceeds the second high voltage threshold or is lower than the second low voltage threshold, it is considered that the DC bus voltage seriously deviates from the normal range. The second low-voltage threshold is set based on the peak value of the grid-side AC voltage and the rated voltage of the DC bus, taking the maximum value of the two; the first high-voltage threshold is set based on the rated value of the DC bus voltage; the first low-voltage threshold is greater than the second low-voltage threshold, and the second high-voltage threshold is greater than the first high-voltage threshold.

[0008] Preferably, if the DC bus voltage is within the normal range, the dq axis voltage command value is determined as follows:

[0009]

[0010] in,

[0011]

[0012] in, , These are the voltage command values ​​for the d and q axes, respectively. , , , These are the PI gains of the current control loop; This is the reference value for the q-axis current of the current control loop. , These are the dq-axis currents on the motor side, , , These are the stator resistance and inductance, respectively. The equivalent magnetic flux of a permanent magnet. Electric angular velocity, , These represent the proportional / integral gain of the DC voltage control loop. This represents the error value of the DC voltage control loop. This is a control mode switching status flag. This indicates that the situation is within the normal range; This is the virtual impedance value, which is zero at this point.

[0013] Preferably, if the DC bus voltage deviates slightly from the normal range, the dq-axis voltage command value is determined as follows:

[0014]

[0015] in,

[0016]

[0017] in, , These are the voltage command values ​​for the d and q axes, respectively. , , , These are the PI gains of the current control loop; This is the reference value for the q-axis current of the current control loop. , These are the dq-axis currents on the motor side, , , These are the stator resistance and inductance, respectively. The equivalent magnetic flux of a permanent magnet. Electric angular velocity, , These represent the proportional / integral gain of the DC voltage control loop, respectively, and α is the adjustment coefficient of the integral element of the DC voltage control loop, where α > 1. This represents the error value of the DC voltage control loop. This is a control mode switching status flag. This indicates a slight deviation from the normal range; This is a virtual impedance value, which is not zero at this point. The first virtual resistance value is taken as 5% to 15% of the rated system impedance; The first virtual reactance value is taken as 10% to 20% of the rated system reactance.

[0018] Preferably, if the DC bus voltage deviates significantly from the normal range, the dq-axis voltage command value is determined as follows:

[0019]

[0020] in,

[0021]

[0022] in, , These are the voltage command values ​​for the d and q axes, respectively. , , , These are the PI gains of the current control loop; This is the reference value for the q-axis current of the current control loop. , These are the dq-axis currents on the motor side, , , These are the stator resistance and inductance, respectively. The equivalent magnetic flux of a permanent magnet. Electric angular velocity, , These represent the proportional / integral gain of the DC voltage control loop, respectively, and α is the adjustment coefficient of the integral element of the DC voltage control loop, where α > 1. This represents the error value of the DC voltage control loop. Add a current signal to the q-axis; This is a control mode switching status flag. This indicates a significant deviation from the normal range; This is a virtual impedance value, which is not zero at this point. The second virtual resistance value is taken as 10% to 20% of the rated system impedance, and is greater than the first virtual resistance value used when there is a slight deviation from the normal range. The first virtual reactance value is taken as 10% to 20% of the rated system reactance.

[0023] Preferably, the grid-side power is introduced into the DC voltage control branch as an additional feedforward quantity. The calculation method for the additional feedforward branch is as follows:

[0024] in, ; This is the proportional coefficient of the feedforward stage. Add a current signal to the q-axis; and These are the grid-side power setpoint and actual value, respectively. This is the power feedforward command value on the grid side.

[0025] To achieve the above objectives, in a second aspect, this application provides a DC bus voltage control system for a flywheel energy storage system, including at least one processor and at least one memory; the at least one memory is used to store computer instructions; the at least one processor is used to execute at least a portion of the computer instructions to implement the control method described in the first aspect.

[0026] It is understandable that the beneficial effects of the second aspect mentioned above can be found in the relevant descriptions in the first aspect mentioned above, and will not be repeated here.

[0027] Overall, the technical solutions conceived in this application have the following beneficial effects compared with the prior art: This application proposes a DC bus voltage control method for a flywheel energy storage system, comprising: if the DC bus voltage is within the normal range, the DC voltage is regulated by a PI controller to form a q-axis current reference signal; the q-axis current reference signal is regulated by a current control loop PI controller to generate a q-axis voltage command signal, and a dq-axis voltage command value for the converter modulation wave is generated accordingly; if the DC bus voltage slightly deviates from the normal range, the parameters of the PI controller are adjusted to make the integral element play a dominant role in the control output, and the virtual impedance element connected in parallel with the current control loop is adjusted to generate the dq-axis voltage command value for the converter modulation wave; if the DC bus voltage severely deviates from the normal range, the grid-side power signal is fed forward to the generator-side DC voltage control loop, and the virtual resistance in the virtual impedance element is further adjusted to generate the dq-axis voltage command value for the converter modulation wave. This application adopts the above-mentioned threshold-based hierarchical control strategy, sets multiple threshold ranges for the DC bus voltage, and automatically switches the control mode according to different DC bus voltage conditions, thereby maintaining the steady-state accuracy of the system while improving the system's adaptability to large disturbances. On the one hand, it can achieve rapid and stable control of the DC bus voltage of flywheel energy storage in scenarios with severe power fluctuations; on the other hand, it can effectively improve the safety and stability of flywheel energy storage systems. Attached Figure Description

[0028] Figure 1 This is a flowchart of a DC bus voltage control method for a flywheel energy storage system provided in an embodiment of this application.

[0029] Figure 2 This is a working area threshold distribution map provided in the embodiments of this application.

[0030] Figure 3This is a block diagram of the generator-side converter control for a flywheel energy storage system provided in an embodiment of this application.

[0031] Figure 4 This is a control block diagram of the grid-side converter of the flywheel energy storage system provided in the embodiments of this application. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0033] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A existing alone, A and B existing simultaneously, and B existing alone. In this application, the symbol " / " indicates that the related objects are in an "or" relationship, for example, A / B means A or B.

[0034] In this application, the terms "first" and "second," etc., are used to distinguish different objects, not to describe a specific order of objects. For example, "first response message" and "second response message," etc., are used to distinguish different response messages, not to describe a specific order of response messages.

[0035] In the embodiments of this application, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or design that is described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design. Specifically, the use of the terms "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0036] In the description of the embodiments of this application, unless otherwise stated, "multiple" means two or more, for example, multiple processing units means two or more processing units, multiple elements means two or more elements, etc.

[0037] The embodiments of this application are described below with reference to the accompanying drawings.

[0038] Firstly, such as Figure 1As shown, this application provides a DC bus voltage control method for a flywheel energy storage system, applied to a generator-side converter. The control method includes: if the DC bus voltage is within the normal range, the DC voltage is regulated by a PI controller to form a q-axis current reference signal; the q-axis current reference signal is regulated by a current control loop PI controller to generate a q-axis voltage command signal, and based on this, a dq-axis voltage command value for the converter modulation wave is generated; if the DC bus voltage slightly deviates from the normal range, the parameters of the PI controller are adjusted so that the integral element plays a dominant role in the control output, and the virtual impedance element connected in parallel with the current control loop is adjusted to generate the dq-axis voltage command value for the converter modulation wave; if the DC bus voltage severely deviates from the normal range, the grid-side power signal is fed forward to the generator-side DC voltage control loop, and the virtual resistance in the virtual impedance element is further adjusted to generate the dq-axis voltage command value for the converter modulation wave.

[0039] Preferably, such as Figure 2 As shown, if the DC bus voltage is at [first low voltage threshold, first high voltage threshold], it is considered to be within the normal range; if the DC bus voltage is at [second low voltage threshold, first low voltage threshold] or [first high voltage threshold, second high voltage threshold], it is considered to be slightly deviating from the normal range; if the DC bus voltage exceeds the second high voltage threshold or falls below the second low voltage threshold, it is considered to be seriously deviating from the normal range. This application achieves hierarchical regulation and protection of DC voltage by triggering different control modes in zones.

[0040] The second low-voltage threshold is set based on the peak value of the grid-side AC voltage and the rated voltage of the DC bus, taking the maximum value of the two; the first high-voltage threshold is set based on the rated value of the DC bus voltage; the first low-voltage threshold is greater than the second low-voltage threshold, and the second high-voltage threshold is greater than the first high-voltage threshold.

[0041] As one illustrated embodiment, the first low-voltage threshold may be set to 1.05 times the second low-voltage threshold, and the first high-voltage threshold may be set to 1.025 times the rated value of the DC bus voltage, but is not limited thereto.

[0042] Preferably, such as Figure 3 As shown, if the DC bus voltage is within the normal range, based on conventional DC voltage PI control, the virtual impedance link connected in parallel to the current control loop does not actually participate in the control, thus achieving stable operation. The method for determining the dq axis voltage command value is as follows:

[0043]

[0044] in,

[0045]

[0046] in, , These are the voltage command values ​​for the d and q axes, respectively. , , , These are the PI gains of the current control loop; This is the reference value for the q-axis current of the current control loop. , These are the dq-axis currents on the motor side, , , These are the stator resistance and inductance, respectively. The equivalent magnetic flux of a permanent magnet. The electric angular velocity is obtained from the phase-locked loop. , These represent the proportional / integral gain of the DC voltage control loop. This represents the error value of the DC voltage control loop. This is a control mode switching status flag. This indicates that the situation is within the normal range; This is the virtual impedance value, which is zero at this point.

[0047] DC voltage control loop error The calculation method is as follows: ,in, and These are the given and actual values ​​of the DC bus voltage, respectively. This represents the error value of the DC voltage control loop.

[0048] The dynamics of the DC bus (ignoring losses and taking the generator-side power as positive) are shown in the following formula:

[0049] in, For bus capacitors, This is the actual value of the DC bus voltage. This refers to the current injected into the grid-side converter.

[0050] Preferably, such as Figure 3 As shown, if the DC bus voltage deviates slightly from the normal range, the system automatically switches from DC voltage PI control to I-dominant control mode. That is, by adjusting the PI controller parameters, the integral element dominates the control output, and the virtual impedance is increased to quickly offset the energy imbalance. The dq-axis voltage command value is determined as follows:

[0051]

[0052] in,

[0053]

[0054] in, , These are the voltage command values ​​for the d and q axes, respectively. , , , These are the PI gains of the current control loop; This is the reference value for the q-axis current of the current control loop. , These are the dq-axis currents on the motor side, , , These are the stator resistance and inductance, respectively. The equivalent magnetic flux of a permanent magnet. Electric angular velocity, , These represent the proportional / integral gain of the DC voltage control loop, respectively, and α is the adjustment coefficient of the integral element of the DC voltage control loop, where α > 1. This represents the error value of the DC voltage control loop. This is a control mode switching status flag. This indicates a slight deviation from the normal range; This is a virtual impedance value, which is not zero at this point. The first virtual resistance value is taken as 5% to 15% of the rated system impedance; The first virtual reactance value is taken as 10% to 20% of the rated system reactance.

[0055] It should be noted that allowing the integral loop to dominate the control loop is equivalent to controlling the error value of the DC voltage control loop. The system is treated with a "low-pass filter" to keep it stable during slow convergence.

[0056] Preferably, the value of α is in the range of 1.5 to 3.

[0057] Preferably, such as Figure 3 As shown, if the DC bus voltage deviates significantly from the normal range, a protection strategy is triggered, including power feedforward and adjustment of the virtual resistor, to prevent the bus voltage from exceeding the limit significantly. The method for determining the dq-axis voltage command value is as follows:

[0058]

[0059] in,

[0060]

[0061] in, , These are the voltage command values ​​for the d and q axes, respectively. , , , These are the PI gains of the current control loop; This is the reference value for the q-axis current of the current control loop. , These are the dq-axis currents on the motor side, , , These are the stator resistance and inductance, respectively. The equivalent magnetic flux of a permanent magnet. Electric angular velocity, , These represent the proportional / integral gain of the DC voltage control loop, respectively, and α is the adjustment coefficient of the integral element of the DC voltage control loop, where α > 1. This represents the error value of the DC voltage control loop. Add a current signal to the q-axis; This is a control mode switching status flag. This indicates a significant deviation from the normal range; This is a virtual impedance value, which is not zero at this point. The second virtual resistance value is taken as 10% to 20% of the rated system impedance, and is greater than the first virtual resistance value used when there is a slight deviation from the normal range. The first virtual reactance value is taken as 10% to 20% of the rated system reactance.

[0062] It should be noted that the resistive component of the virtual impedance has a more significant effect on suppressing voltage fluctuations. When the DC voltage deviation exceeds the second high-voltage threshold, the system enters a more severe fluctuation range, at which point the resistive component in the virtual impedance... Improved to a greater extent based on the existing foundation This significantly enhances the ability to suppress DC voltage fluctuations and ensures the stability of the bus voltage. If necessary, a limiting / slope restriction can be superimposed in interval ③.

[0063] Preferably, such as Figure 4 As shown, the grid-side power is introduced into the DC voltage control branch as an additional feedforward quantity. The calculation method for the additional feedforward branch is as follows:

[0064] in, ; This is the proportional coefficient of the feedforward stage. Add a current signal to the q-axis; and These are the grid-side power setpoint and actual value, respectively. This is the power feedforward command value on the grid side.

[0065] This application enables rapid stabilization of the DC bus voltage during the energy release process of a flywheel energy storage system, especially under conditions of severe power fluctuations. Flywheel energy storage systems often face voltage surges caused by grid load fluctuations or the integration of new energy sources, resulting in instantaneous voltage overshoot, drop, or oscillation. Under typical operating conditions such as sudden grid load shedding or fluctuations in new energy sources like wind or solar power, the system can respond quickly and take measures to ensure stable operation in the face of these disturbances. By introducing technologies such as power feedforward control and virtual resistance, this application allows the system to quickly adjust the voltage even under scenarios of large-scale load fluctuations and grid faults, preventing equipment damage and improving the overall safety of the system.

[0066] Based on the methods in the above embodiments, this application provides an electronic device that may include a processor, a communications interface, a memory, and a communication bus, wherein the processor, communications interface, and memory communicate with each other via the communication bus. The processor may invoke logical instructions stored in the memory to execute the methods in the above embodiments.

[0067] Furthermore, the logical instructions in the aforementioned memory can be implemented as software functional units and, when sold or used as independent products, can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application.

[0068] Based on the methods in the above embodiments, this application provides a computer-readable storage medium storing a computer program that, when run on a processor, causes the processor to execute the methods in the above embodiments.

[0069] Based on the methods in the above embodiments, this application provides a computer program product that, when run on a processor, causes the processor to execute the methods in the above embodiments.

[0070] It is understood that the processor in the embodiments of this application can be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. A general-purpose processor can be a microprocessor or any conventional processor.

[0071] The method steps in this application embodiment can be implemented in hardware or by a processor executing software instructions. The software instructions can consist of corresponding software modules, which can be stored in random access memory (RAM), flash memory, read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), registers, hard disks, portable hard disks, CD-ROMs, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor, enabling the processor to read information from and write information to the storage medium. Of course, the storage medium can also be a component of the processor. The processor and the storage medium can reside in an ASIC.

[0072] In the above embodiments, implementation can be achieved entirely or partially through software, hardware, firmware, or any combination thereof. When implemented using software, it can be implemented entirely or partially as a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted through the computer-readable storage medium. The computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that integrates one or more available media. The available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium (e.g., solid-state disk (SSD)).

[0073] It is understood that the various numerical designations used in the embodiments of this application are merely for the convenience of description and are not intended to limit the scope of the embodiments of this application.

[0074] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for controlling the DC bus voltage of a flywheel energy storage system, characterized in that, The control method, applied to machine-side converters, includes: If the DC bus voltage is within the normal range, the DC voltage is adjusted by the PI controller to form the q-axis current reference signal. The q-axis current reference signal is adjusted by the current control loop PI to generate the q-axis voltage command signal, and the dq-axis voltage command value used for the converter modulation wave is generated accordingly. If the DC bus voltage deviates slightly from the normal range, adjust the parameters of the PI controller so that the integral element plays a dominant role in the control output, adjust the virtual impedance element connected in parallel with the current control loop, and generate the dq axis voltage command value for the converter modulation wave. If the DC bus voltage deviates significantly from the normal range, the grid-side power signal is fed forward to the generator-side DC voltage control loop, and the virtual resistance in the virtual impedance link is further adjusted to generate the dq-axis voltage command value for the converter modulation wave.

2. The control method as described in claim 1, characterized in that, If the DC bus voltage is at [first low voltage threshold, first high voltage threshold], it is considered to be within the normal range; if the DC bus voltage is at [second low voltage threshold, first low voltage threshold] or [first high voltage threshold, second high voltage threshold], it is considered to be slightly deviating from the normal range; if the DC bus voltage exceeds the second high voltage threshold or is lower than the second low voltage threshold, it is considered to be seriously deviating from the normal range. The second low-voltage threshold is set based on the peak value of the grid-side AC voltage and the rated voltage of the DC bus, taking the maximum value of the two; the first high-voltage threshold is set based on the rated value of the DC bus voltage; the first low-voltage threshold is greater than the second low-voltage threshold, and the second high-voltage threshold is greater than the first high-voltage threshold.

3. The control method as described in claim 1, characterized in that, If the DC bus voltage is within the normal range, the dq-axis voltage command value is determined as follows: in, in, , These are the voltage command values ​​for the d and q axes, respectively. , , , These are the PI gains of the current control loop; This is the reference value for the q-axis current of the current control loop. , These are the dq-axis currents on the motor side, , , These are the stator resistance and inductance, respectively. The equivalent magnetic flux of a permanent magnet. Electric angular velocity, , These represent the proportional / integral gain of the DC voltage control loop. This represents the error value of the DC voltage control loop. This is a control mode switching status flag. This indicates that the situation is within the normal range; This is the virtual impedance value, which is zero at this point.

4. The control method as described in claim 1, characterized in that, If the DC bus voltage deviates slightly from the normal range, the dq-axis voltage command value is determined as follows: in, in, , These are the voltage command values ​​for the d and q axes, respectively. , , , These are the PI gains of the current control loop; This is the reference value for the q-axis current of the current control loop. , These are the dq-axis currents on the motor side, , , These are the stator resistance and inductance, respectively. The equivalent magnetic flux of a permanent magnet. Electric angular velocity, , These represent the proportional / integral gain of the DC voltage control loop, respectively, and α is the adjustment coefficient of the integral element of the DC voltage control loop, where α >

1. This represents the error value of the DC voltage control loop. This is a control mode switching status flag. This indicates a slight deviation from the normal range; This is a virtual impedance value, which is not zero at this point. The first virtual resistance value is taken as 5% to 15% of the rated system impedance; The first virtual reactance value is taken as 10% to 20% of the rated system reactance.

5. The control method as described in claim 1, characterized in that, If the DC bus voltage deviates significantly from the normal range, the dq-axis voltage command value is determined as follows: in, in, , These are the voltage command values ​​for the d and q axes, respectively. , , , These are the PI gains of the current control loop; This is the reference value for the q-axis current of the current control loop. , These are the dq-axis currents on the motor side, , , These are the stator resistance and inductance, respectively. The equivalent magnetic flux of a permanent magnet. Electric angular velocity, , These represent the proportional / integral gain of the DC voltage control loop, respectively, and α is the adjustment coefficient of the integral element of the DC voltage control loop, where α >

1. This represents the error value of the DC voltage control loop. Add a current signal to the q-axis; This is a control mode switching status flag. This indicates a significant deviation from the normal range; This is a virtual impedance value, which is not zero at this point. The second virtual resistance value is taken as 10% to 20% of the rated system impedance, and is greater than the first virtual resistance value used when there is a slight deviation from the normal range. The first virtual reactance value is taken as 10% to 20% of the rated system reactance.

6. The control method as described in claim 5, characterized in that, The grid-side power is introduced into the DC voltage control branch as an additional feedforward quantity. The calculation method for the additional feedforward branch is as follows: in, ; This is the proportional coefficient of the feedforward stage. Add a current signal to the q-axis; and These are the grid-side power setpoint and actual value, respectively. This is the power feedforward command value on the grid side.

7. A DC bus voltage control system for a flywheel energy storage system, characterized in that, Includes at least one processor and at least one memory; The at least one memory is used to store computer instructions; The at least one processor is configured to execute at least a portion of the computer instructions to implement the control method according to any one of claims 1 to 6.

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