Control method and system of grid-type flywheel energy storage system

Abstract

The embodiment of the present invention provides a control method and system for a grid-type flywheel energy storage system, which belongs to the technical field of flywheel energy storage. The flywheel energy storage system is connected in parallel with a corresponding auxiliary energy storage system on the AC and DC busbars, and the method includes: real-time acquisition of grid-connected circuit information and DC-side voltage information of the flywheel energy storage system, and acquisition of real-time grid conditions based on the grid-connected circuit information; based on the real-time grid conditions and power control instructions issued by the operator; generating control loop instructions for the grid-side converter and control loop instructions for the machine-side converter; reading the topological structure between the auxiliary energy storage system and the flywheel energy storage system, and generating and executing control schemes for the flywheel energy storage system and the auxiliary energy storage system based on the control loop instructions. The scheme of the present invention solves the problem that the existing scheme cannot properly solve the problem of frequency stability caused by insufficient inertia of the grid and cannot meet the demand for rapid response support when the grid fails.

Description

Technical Field

[0001] The present invention relates to the technical field of flywheel energy storage, and in particular to a control method of a grid-type flywheel energy storage system and a control system of a grid-type flywheel energy storage system. Background Art

[0002] With the continuous increase in the proportion of new energy in my country and the rapid development of UHV DC, the grid structure and operating characteristics of the power system have undergone tremendous changes, and a new power system with a high proportion of new energy and a high proportion of power electronics is gradually taking shape. In areas with a high proportion of new energy transmission, the lack of system short-circuit capacity and rotational inertia has greatly reduced the ability of the power grid to resist risks. The fluctuations in grid voltage and frequency are likely to cause large-scale new energy units to be disconnected from the grid, which will lead to an expansion of the scope of faults and is not conducive to the safe and stable operation of the power grid. In order to improve the strength of the power grid, increase the short-circuit ratio and short-circuit capacity of the power grid, and solve the safety problems of new energy consumption and UHV DC transmission, a new generation of large-capacity synchronous phase regulators and new distributed phase regulators have been proposed. At present, many phase regulator projects have been put into engineering application, playing an important role in improving cross-regional transmission capacity and supporting new energy consumption. It has become a key equipment to ensure the sustainable development of new energy and promote the transformation of energy structure.

[0003] As the proportion of new energy units in some regions exceeds that of conventional generating units, the short-circuit ratio of new energy stations has further decreased. The insufficient short-circuit capacity, rotational inertia or dynamic reactive power regulation capacity of new energy stations has repeatedly caused large-scale chain disconnection of new energy units. For this reason, local power grids require new energy stations to be equipped with storage and to install grid-forming devices to increase the short-circuit capacity of new energy stations and increase the inertia of the system. At present, a number of grid-forming energy storage power stations based on electrochemical energy storage have been put into engineering application, and grid-forming new energy units based on grid-forming technology have also entered the research and development stage, while the research on grid-forming flywheel energy storage systems lags behind.

[0004] At present, in order to improve the short-circuit capacity of the power grid, enhance the strength of the power grid, increase the rotational inertia and damping of the power grid, the power grid company has added distributed phase regulators and grid-type energy storage systems to the new energy stations and the sending end system of high-voltage direct current transmission to increase the new energy grid connection rate and direct current transmission power. There are mainly two solutions:

[0005] 1) The new distributed phase regulator can be forcibly excited at 3.5 times the voltage, and its leading phase operation capability is close to its rated reactive capacity. Especially during the rapid drop of system voltage after a fault, its instantaneous reactive support capability far exceeds that of other reactive compensation equipment, and has a significant support effect. However, this solution has the following disadvantages: the construction and operation and maintenance costs of the phase regulator are high, and the economy is not good; the existing new distributed phase regulator lacks inertia support capacity and cannot properly solve the frequency stability problem caused by insufficient inertia of the power grid.

[0006] 2) Grid-type energy storage system, using grid-type technology to make the energy storage converter present voltage source external characteristics, replace the synchronous motor, respond quickly when the grid voltage and frequency fluctuate, and can provide inertia support, frequency and voltage regulation, increase short-circuit capacity and other functions of conventional units. A few existing grid-type electrochemical energy storage power stations have good control effects after testing. However, this scheme has the following disadvantages: in the transient control process of pure grid-type electrochemical energy storage system, the electrochemical energy storage battery discharges quickly, and the battery safety and service life are not clear, which poses a safety risk; the grid-type new energy unit based on grid-type technology sacrifices steady-state power generation in exchange for grid-type support energy when the grid fails, affecting the economic benefits of new energy power generation; if the grid-type technology is simply integrated into the grid-side converter control of the flywheel energy storage system, because the flywheel energy storage itself has a small capacity, and the energy stored in the flywheel rotor is converted and output by a two-stage converter, when the grid voltage fluctuates, the support energy is small and the response is slow, which cannot meet the demand for rapid response support when the grid fails.

[0007] In view of the fact that the existing solutions cannot properly solve the problem of frequency stability caused by insufficient inertia of the power grid and cannot meet the problem of rapid response support needs when the power grid fails, it is necessary to create a new control solution for the grid-connected flywheel energy storage system. Summary of the invention

[0008] The purpose of the embodiments of the present invention is to provide a grid-type flywheel energy storage system control method and system to solve the problem that the existing solutions cannot properly solve the frequency stability problem caused by insufficient inertia of the power grid and cannot meet the problem of rapid response support requirements when the power grid fails.

[0009] In order to achieve the above-mentioned purpose, the first aspect of the present invention provides a control method for a grid-type flywheel energy storage system, wherein the flywheel energy storage system is connected in parallel with a corresponding auxiliary energy storage system on the AC / DC bus, and the method comprises: collecting grid-connected circuit information and DC-side voltage information of the flywheel energy storage system in real time, and obtaining the real-time working condition of the power grid based on the grid-connected circuit information; executing power control based on the real-time working condition of the power grid and the power control instructions issued by the operator to obtain the output virtual voltage source amplitude and phase angle; generating a control loop instruction of the grid-side converter based on the output virtual voltage source amplitude and the phase angle, and generating a control loop instruction of the machine-side converter based on the DC-side voltage information and the real-time working condition of the power grid; reading the topological structure between the auxiliary energy storage system and the flywheel energy storage system, and generating and executing a control scheme of the flywheel energy storage system and its auxiliary energy storage system based on the topological structure, the control loop instruction of the grid-side converter and the control loop instruction of the machine-side converter.

[0010] Optionally, the grid-connected side circuit information includes: phase voltage and line current of the grid access point; wherein the positive direction of the line current is the direction of flowing into the grid.

[0011] Optionally, acquiring the real-time operating condition of the power grid based on the grid-connected side circuit information includes: calculating the voltage amplitude and frequency of the power grid based on the grid-connected side circuit information; and calculating the real-time active power and real-time reactive power exchanged between the power grid and the flywheel energy storage system based on the grid-connected side circuit information; and acquiring the real-time operating condition of the power grid based on the real-time active power and the real-time reactive power.

[0012] Optionally, the power control is performed based on the real-time working condition of the power grid and the power control instruction issued by the operator to obtain the amplitude and phase angle of the virtual voltage source output by the grid-side converter, including: determining the target active power and the target reactive power in response to the power control instruction issued by the operator; adjusting the real-time active power to the target active power, and adjusting the real-time reactive power to the target reactive power, and obtaining the amplitude and phase angle of the virtual voltage source output by the grid-side converter based on the adjustment process; wherein the expression of the adjustment process is:

[0013]

[0014] in, is the target active power, is the real-time active power; is the target reactive power, is the real-time reactive power; θ is the equivalent phase angle of the voltage source; =2*π*f, which is the equivalent angular frequency; is the rated angular frequency; J is the virtual inertia; is the equivalent active damping coefficient; is the equivalent reactive power-voltage droop coefficient; is the rated grid voltage amplitude; K is the simulated excitation regulation inertia coefficient.

[0015] Optionally, based on the DC side voltage information and the real-time operating condition of the power grid, generating a control loop instruction for the machine-side converter includes: obtaining a current control loop instruction value based on the output virtual voltage source amplitude and the phase angle; using a DC bus voltage control method including an AC voltage frequency response to generate a DC bus voltage loop instruction and an AC voltage frequency control loop instruction; and constructing a control loop instruction for the machine-side converter based on the current control loop instruction value, the DC bus voltage loop instruction and the AC voltage frequency control loop instruction.

[0016] Optionally, the generation rule expressions of the DC bus voltage loop instruction and the AC voltage frequency control loop instruction are:

[0017]

[0018] in, Positioning the q-axis current reference value for the machine-side converter flux vector; is the DC voltage reference value; is the measured value of DC bus voltage; is the rated grid frequency; , They are the PI parameters of the DC bus voltage loop and the grid frequency loop respectively.

[0019] Optionally, the reading of the topological structure between the auxiliary energy storage system and the flywheel energy storage system, and the generation and execution of a control scheme for the flywheel energy storage system and its auxiliary energy storage system based on the topological structure and the control loop instruction, include: if the topological structure between the auxiliary energy storage system and the flywheel energy storage system is a first topological structure, directly executing the flywheel energy storage system control based on the control loop instruction; if the topological structure between the auxiliary energy storage system and the flywheel energy storage system is a second topological structure, integrating the AC voltage frequency response loop in the control loop instruction to obtain a first corrected control loop instruction , and based on the first corrected control loop instruction, the flywheel energy storage system and the auxiliary energy storage system are controlled in linkage; if the topological structure between the auxiliary energy storage system and the flywheel energy storage system is the third topological structure, the virtual inertia and the damping coefficient are determined based on the capacity of the flywheel energy storage system, the capacity of the auxiliary energy storage system and the output priority of each energy storage system, and the control loop instruction is corrected based on the virtual inertia and the damping coefficient to obtain a second corrected control loop instruction, and the flywheel energy storage system and the auxiliary energy storage system are controlled in linkage based on the second corrected control loop instruction.

[0020] Optionally, the first topology structure is: the auxiliary energy storage system is directly connected in parallel to the DC bus of the flywheel energy storage system; the second topology structure is: the auxiliary energy storage system is connected in parallel to the DC bus of the flywheel energy storage system through a DC converter; the third topology structure is: the auxiliary energy storage system is connected in parallel to the AC bus of the flywheel energy storage system through a PCS converter.

[0021] The second aspect of the present invention provides a grid-type flywheel energy storage system control system, wherein the flywheel energy storage system is connected in parallel with a corresponding auxiliary energy storage system on the DC bus, a collection unit, which collects grid-connected circuit information and DC-side voltage information of the flywheel energy storage system in real time, and obtains the real-time working condition of the power grid based on the grid-connected circuit information; a control unit, which performs power control based on the real-time working condition of the power grid and the power control instructions issued by the operator, and obtains the output virtual voltage source amplitude and phase angle; an instruction generation unit, which generates a control loop instruction of the grid-side converter based on the output virtual voltage source amplitude and the phase angle, and generates a control loop instruction of the machine-side converter based on the DC-side voltage information and the real-time working condition of the power grid; an execution unit, which reads the topological structure between the auxiliary energy storage system and the flywheel energy storage system, and generates and executes a control scheme for the flywheel energy storage system and its auxiliary energy storage system based on the topological structure, the control loop instruction of the grid-side converter and the control loop instruction of the machine-side converter.

[0022] On the other hand, the present invention provides a computer-readable storage medium having instructions stored thereon, which, when executed on a computer, enables the computer to execute the above-mentioned control method of the grid-type flywheel energy storage system.

[0023] Through the above technical scheme, the flywheel system machine-side converter of the present invention superimposes AC voltage frequency control on the basis of the existing control of DC bus voltage stability, maintains the DC bus voltage constant, and actively responds to AC voltage frequency changes, speeds up the flywheel energy storage system fault response speed, and meets the grid-side converter's demand for DC bus power. In order to provide more energy to support grid voltage fault response and improve grid stability, this application adds an auxiliary energy storage system to the flywheel energy storage system, enhances the inertia support capacity of the grid-type flywheel energy storage system, and proposes different control schemes according to different access points of the energy storage system.

[0024] Other features and advantages of the embodiments of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings are used to provide a further understanding of the embodiments of the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the embodiments of the present invention, but do not constitute a limitation on the embodiments of the present invention. In the accompanying drawings:

[0026] Figure 1 It is a flowchart of the steps of a control method of a grid-type flywheel energy storage system provided by an embodiment of the present invention;

[0027] Figure 2 is a control block diagram of a grid-side converter provided by an embodiment of the present invention;

[0028] Figure 3 is a schematic structural diagram of a first topological structure provided by an embodiment of the present invention;

[0029] Figure 4 is a schematic structural diagram of a second topological structure provided by an embodiment of the present invention;

[0030] Figure 5 is a schematic structural diagram of a third topological structure provided by an embodiment of the present invention;

[0031] Figure 6 is a control block diagram of a machine-side converter provided by an embodiment of the present invention;

[0032] Figure 7 It is a system structure diagram of a grid-type flywheel energy storage system control system provided by one embodiment of the present invention. DETAILED DESCRIPTION

[0033] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0034] With the increasing proportion of new energy in my country and the rapid development of UHV DC, the grid structure and operation characteristics of the power system have undergone tremendous changes, and a new power system with a high proportion of new energy and a high proportion of power electronics is gradually taking shape. In areas with a high proportion of new energy transmission, the lack of system short-circuit capacity and rotational inertia has greatly reduced the ability of the power grid to resist risks. The fluctuations in the voltage and frequency of the power grid are likely to cause large-scale new energy units to disconnect from the grid, which will lead to an expansion of the scope of faults and is not conducive to the safe and stable operation of the power grid.

[0035] In order to enhance the strength of the power grid, increase the short-circuit ratio and short-circuit capacity of the power grid, and solve the safety issues of new energy consumption and ultra-high voltage direct current transmission, a new generation of large-capacity synchronous phase-shifting devices and new distributed phase-shifting devices have been proposed. At present, many phase-shifting devices have been put into engineering application, which has played an important role in improving cross-regional power transmission capacity and supporting new energy consumption. It has become a key equipment to ensure the sustainable development of new energy and promote the transformation of energy structure.

[0036] As the proportion of new energy units in some regions exceeds that of conventional generating units, the short-circuit ratio of new energy stations has further decreased. The insufficient short-circuit capacity, rotational inertia or dynamic reactive power regulation capacity of new energy stations has repeatedly caused large-scale chain disconnection of new energy units. For this reason, local power grids require new energy stations to be equipped with storage and to install grid-forming devices to increase the short-circuit capacity of new energy stations and increase the inertia of the system. At present, a number of grid-forming energy storage power stations based on electrochemical energy storage have been put into engineering application, and grid-forming new energy units based on grid-forming technology have also entered the research and development stage, while the research on grid-forming flywheel energy storage systems lags behind.

[0037] At present, the commonly used flywheel energy storage system includes key equipment such as high-speed flywheel, permanent magnet synchronous motor, flywheel side converter, DC bus capacitor, grid side converter, RLC filter, AC transformer, etc. The flywheel side converter, DC bus capacitor, and grid side converter together constitute a back-to-back dual PWM converter, which is the key control device for energy transmission of the flywheel energy storage system and completes the charge and discharge control of the flywheel energy storage system; the flywheel side converter RLC filter is used to suppress the harmonics injected into the grid current by the flywheel energy storage system.

[0038] At present, in order to improve the short-circuit capacity of the power grid, enhance the strength of the power grid, and increase the rotational inertia and damping of the power grid, the power grid company has added distributed phase-shifting condensers and grid-type energy storage systems to the sending-end systems of new energy stations and high-voltage direct current transmission to increase the new energy grid connection rate and direct current transmission power.

[0039] 1) The new distributed phase regulator can be forcibly excited at 3.5 times the voltage, and its leading phase operation capability is close to its rated reactive capacity. Especially during the rapid drop of system voltage after a fault, its instantaneous reactive support capability far exceeds that of other reactive compensation equipment, and has a significant support effect. However, this solution has the following disadvantages: the construction and operation and maintenance costs of the phase regulator are high, and the economy is not good; the existing new distributed phase regulator lacks inertia support capacity and cannot properly solve the frequency stability problem caused by insufficient inertia of the power grid.

[0040] 2) Grid-type energy storage system, using grid-type technology to make the energy storage converter present voltage source external characteristics, replace the synchronous motor, respond quickly when the grid voltage and frequency fluctuate, and can provide inertia support, frequency and voltage regulation, increase short-circuit capacity and other functions of conventional units. A few existing grid-type electrochemical energy storage power stations have good control effects after testing. However, this scheme has the following disadvantages: in the transient control process of pure grid-type electrochemical energy storage system, the electrochemical energy storage battery discharges quickly, and the battery safety and service life are not clear, which poses a safety risk; the grid-type new energy unit based on grid-type technology sacrifices steady-state power generation in exchange for grid-type support energy when the grid fails, affecting the economic benefits of new energy power generation; if the grid-type technology is simply integrated into the grid-side converter control of the flywheel energy storage system, because the flywheel energy storage itself has a small capacity, and the energy stored in the flywheel rotor is converted and output by a two-stage converter, when the grid voltage fluctuates, the support energy is small and the response is slow, which cannot meet the demand for rapid response support when the grid fails.

[0041] In view of the fact that the existing solutions cannot properly solve the problem of frequency stability caused by insufficient inertia of the power grid and cannot meet the problem of rapid response support requirements when the power grid fails, the present invention proposes a control method and system for a grid-forming flywheel energy storage system. The flywheel system machine-side converter of the present invention superimposes AC voltage frequency control on the basis of the existing control of DC bus voltage stability, maintains the DC bus voltage constant, and actively responds to AC voltage frequency changes, speeds up the flywheel energy storage system fault response speed, and meets the grid-side converter's demand for DC bus power. In order to provide more energy to support the grid voltage fault response and improve the stability of the grid, this application adds an auxiliary energy storage system to the flywheel energy storage system to enhance the inertia support capacity of the grid-forming flywheel energy storage system, and proposes different control schemes according to different access points of the energy storage system.

[0042] The first aspect of the present application provides a flywheel energy storage system for grid connection that can improve the amount of new energy grid connection, including a flywheel energy storage system and an auxiliary energy storage system. The flywheel energy storage system includes a flywheel energy storage system control and protection device and a flywheel energy storage system primary device; the auxiliary energy storage system includes an auxiliary energy storage system control and protection device and an auxiliary energy storage system primary device.

[0043] The auxiliary energy storage system, as an auxiliary setting of the flywheel energy storage system, provides charging and discharging capacity when the flywheel energy storage margin is insufficient or the response capability is insufficient, responds to the voltage fluctuation of the access grid, stabilizes the grid voltage, and ensures that the new energy generator set does not go off the grid. Auxiliary energy storage systems are in various forms, such as electrochemical energy storage devices (including lithium-ion batteries, sodium-ion batteries, flow batteries, supercapacitors and other extended forms), physical energy storage devices (such as gravity energy storage, compressed air energy storage and other extended forms), heat storage devices and other energy storage devices can all construct the auxiliary energy storage system described in this application. The following is an introduction to the specific invention content based on the electrochemical energy storage system as an example, but the described embodiments are only part of the embodiments of the present invention, and related or similar embodiments can achieve the purpose of this application.

[0044] Figure 1 1 is a flow chart of a method for controlling a grid-type flywheel energy storage system provided by an embodiment of the present invention. Figure 1 As shown, an embodiment of the present invention provides a control method for a grid-type flywheel energy storage system, wherein the flywheel energy storage system is connected in parallel with a corresponding auxiliary energy storage system on the AC / DC bus, and the method comprises:

[0045] Step S10: collecting grid-connected circuit information and DC-side voltage information of the flywheel energy storage system in real time, and acquiring real-time grid conditions based on the grid-connected circuit information.

[0046] Specifically, the grid-connected circuit information includes: phase voltage and line current at the grid access point; wherein the positive direction of the line current is the direction of flowing into the grid.

[0047] In the embodiment of the present invention, in order to realize the flywheel energy storage system's ability to perform peak load and frequency regulation based on the real-time situation of the power grid, the scheme of the present invention needs to identify the real-time state of the power grid so as to generate corresponding control instructions based on the identified power grid state.

[0048] Preferably, the acquiring of the real-time working condition of the power grid based on the grid-connected side circuit information includes: calculating the voltage amplitude and frequency of the power grid based on the grid-connected side circuit information; and calculating the real-time active power and real-time reactive power exchanged between the power grid and the flywheel energy storage system based on the grid-connected side circuit information; and acquiring the real-time working condition of the power grid based on the real-time active power and the real-time reactive power.

[0049] In a possible implementation, the real-time measurement system is connected to the grid point, that is, the reference point phase voltage U a / b / c And line current I a / b / c , the line current flows into the grid as the positive direction. a / b / c Calculate the grid voltage amplitude U m and frequency f m . Using the phase voltage U a / b / c And line current I a / b / c Calculate the active power P exchanged between the power grid and the grid-connected flywheel system m and reactive power Q m .

[0050] Step S20: Based on the real-time working condition of the power grid and the power control instruction issued by the operator, power control is performed to obtain the output virtual voltage source amplitude and phase angle.

[0051] Specifically, in response to the power control instruction issued by the operator, the target active power and the target reactive power are determined; the real-time active power is adjusted to the target active power, and the real-time reactive power is adjusted to the target reactive power, and the output virtual voltage source amplitude and phase angle are obtained based on the adjustment process; wherein the expression of the adjustment process is:

[0052]

[0053] in, is the target active power, is the real-time active power; is the target reactive power, is the real-time reactive power; θ is the equivalent phase angle of the voltage source; =2*π*f, which is the equivalent angular frequency; is the rated angular frequency; J is the virtual inertia; is the equivalent active damping coefficient; is the equivalent reactive power-voltage droop coefficient; is the rated grid voltage amplitude; K is the simulated excitation regulation inertia coefficient.

[0054] Step S30: Generate a control loop instruction for the grid-side converter based on the output virtual voltage source amplitude and the phase angle, and generate a control loop instruction for the generator-side converter based on the DC side voltage information and the real-time operating condition of the power grid.

[0055] Specifically, based on the output virtual voltage source amplitude and the phase angle, a current control loop command value is obtained; a DC bus voltage loop command and an AC voltage frequency control loop command are generated by adopting a DC bus voltage control method including an AC voltage frequency response; and based on the current control loop command value, the DC bus voltage loop command and the AC voltage frequency control loop command, a control loop command of the converter is constructed.

[0056] In a possible implementation, the virtual voltage source amplitude U and phase angle θ are used to obtain the current control loop command value, and the converter modulation pulse is obtained through the current inner loop control to control the converter to output the desired internal potential. Figure 2 The inverter on the side of the wheel energy storage machine adopts a DC bus voltage control method with AC voltage frequency response. On the basis of the DC bus voltage loop, an AC voltage frequency control loop is added to maintain the DC bus voltage constant while actively responding to the change of AC voltage frequency to meet the DC bus power demand of the grid-side inverter.

[0057] Step S40: reading the topology between the auxiliary energy storage system and the flywheel energy storage system, and generating and executing a control scheme for the flywheel energy storage system and its auxiliary energy storage system based on the topology, the control loop instructions of the grid-side converter and the control loop instructions of the generator-side converter.

[0058] Specifically, if the topological structure between the auxiliary energy storage system and the flywheel energy storage system is a first topological structure, the flywheel energy storage system control is directly executed based on the control loop instruction; if the topological structure between the auxiliary energy storage system and the flywheel energy storage system is a second topological structure, the AC voltage frequency response loop is integrated into the control loop instruction to obtain a first corrected control loop instruction, and the flywheel energy storage system and the auxiliary energy storage system are interlockedly controlled based on the first corrected control loop instruction; if the topological structure between the auxiliary energy storage system and the flywheel energy storage system is a third topological structure, the virtual inertia and the damping coefficient are determined based on the capacity of the flywheel energy storage system, the capacity of the auxiliary energy storage system and the output priority of each energy storage system, and the control loop instruction is corrected based on the virtual inertia and the damping coefficient to obtain a second corrected control loop instruction, and the flywheel energy storage system and the auxiliary energy storage system are interlockedly controlled based on the second corrected control loop instruction.

[0059] Preferably, Figure 3 , the first topology structure is: the auxiliary energy storage system is directly connected in parallel to the DC bus of the flywheel energy storage system.

[0060] Specifically, the electrochemical energy storage device is connected in parallel to the DC bus and in parallel to the DC bus capacitor of the flywheel energy storage system as a separate energy supply source.

[0061] Preferably, Figure 4 The second topology structure is: the auxiliary energy storage system is connected in parallel to the DC bus of the flywheel energy storage system through a DC converter.

[0062] Specifically, the electrochemical energy storage device is connected in parallel to the DC bus through a DC / DC converter, and is connected in parallel with the DC bus capacitor of the flywheel energy storage system as a separate energy supply source. The voltage level of the electrochemical energy storage element is changed through the DC / DC converter, which facilitates engineering implementation.

[0063] Preferably, Figure 5 The third topology structure is: the auxiliary energy storage system is connected in parallel to the AC bus of the flywheel energy storage system through a PCS converter.

[0064] Specifically, the electrochemical energy storage device is connected in parallel to the AC bus through the PCS converter AC / DC, and is connected in parallel with the flywheel energy storage system, as a separate energy supply source, to coordinate the charge and discharge of the flywheel energy storage system. The flywheel energy storage system and the electrochemical energy storage system share the same set of AC RLC filter devices, reducing the system hardware cost.

[0065] In a possible implementation, the machine-side converter adopts PI control, the outer loop is the DC bus voltage control with superimposed AC voltage frequency response, and the inner loop is the current loop, and the machine-side converter modulation pulse is obtained through the double closed-loop grid flux vector positioning control method. Figure 6 , is a control block diagram of the machine-side converter. If the auxiliary energy storage system adopts the first topology, there is no need to control the auxiliary energy storage system separately.

[0066] Furthermore, if the auxiliary energy storage system adopts the second topology structure, the DC / DC topology type of the DC converter can adopt the topology form of the existing technical solution. Similar to the control of the machine-side converter, an AC voltage frequency response loop is added to the DC converter control strategy to enable it to actively respond to changes in the AC system frequency, thereby accelerating the overall response speed of the system and actively providing energy support for the grid-side converter.

[0067] Furthermore, if the auxiliary energy storage system adopts the third topology structure, the auxiliary energy storage system converter adopts the flywheel energy storage grid-side converter grid-type control scheme, but different virtual inertias and damping coefficients need to be set according to factors such as the flywheel energy storage capacity, the auxiliary energy storage system capacity, and the output priority.

[0068] In an embodiment of the present invention, if there is an auxiliary control system, the first topology has no controller; the converter of the second topology auxiliary control system is executed according to the control method of the machine-side converter; the converter of the third topology auxiliary control system is executed according to the control method of the grid-side converter, and the control coefficient is coordinated with the grid-side converter.

[0069] In an embodiment of the present invention, the scheme of the present invention utilizes a grid-type control technology to make the flywheel grid-side converter present a voltage source external characteristic, so that the flywheel energy storage system has a grid-type characteristic, thereby improving the stability of the power grid. In the scheme of the present invention, the machine-side converter of the flywheel system, on the basis of the existing control of the DC bus voltage stability, superimposes the AC voltage frequency control, maintains the DC bus voltage constant, and actively responds to the AC voltage frequency change, speeds up the fault response speed of the flywheel energy storage system, and meets the DC bus power demand of the grid-side converter. In order to provide more energy to support the grid voltage fault response and improve the stability of the power grid, the present application adds an auxiliary energy storage system to the flywheel energy storage system, enhances the inertia support capacity of the grid-type flywheel energy storage system, and proposes different control schemes according to different access points of the energy storage system.

[0070] Figure 7 1 is a system structure diagram of a control system of a grid-type flywheel energy storage system provided by an embodiment of the present invention. Figure 7 As shown, an embodiment of the present invention provides a grid-type flywheel energy storage system control system, wherein the flywheel energy storage system is connected in parallel with a corresponding auxiliary energy storage system on the AC / DC bus, and the system comprises: an acquisition unit, for real-time acquisition of grid-connected side circuit information of the flywheel energy storage system, and acquisition of real-time grid conditions based on the grid-connected side circuit information; a control unit, for executing power control based on the real-time grid conditions and power control instructions issued by an operator, and obtaining an output virtual voltage source amplitude and phase angle; an instruction generation unit, for generating a control loop instruction of a converter based on the output virtual voltage source amplitude and the phase angle; an execution unit, for reading a topological structure between the auxiliary energy storage system and the flywheel energy storage system, and generating and executing a control scheme for the flywheel energy storage system and its auxiliary energy storage system based on the topological structure and the control loop instruction.

[0071] The embodiment of the present invention further provides a computer-readable storage medium, on which instructions are stored, which, when executed on a computer, enable the computer to execute the above-mentioned control method of the grid-type flywheel energy storage system.

[0072] Those skilled in the art will understand that all or part of the steps in the method for implementing the above-mentioned embodiments can be completed by instructing the relevant hardware through a program, and the program is stored in a storage medium, including several instructions for making a single-chip microcomputer, a chip or a processor execute all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program codes.

[0073] The optional embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the embodiments of the present invention are not limited to the specific details in the above embodiments. Within the technical concept of the embodiments of the present invention, the technical scheme of the embodiments of the present invention can be subjected to a variety of simple modifications, and these simple modifications all belong to the protection scope of the embodiments of the present invention. It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the embodiments of the present invention will not further describe various possible combinations.

[0074] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the embodiments of the present invention, they should also be regarded as the contents disclosed in the embodiments of the present invention.

Claims

1. A control method for a grid-type flywheel energy storage system, characterized in that: The flywheel energy storage system is connected in parallel with a corresponding auxiliary energy storage system on the AC / DC bus, and the method comprises: Collecting grid-connected circuit information and DC-side voltage information of the flywheel energy storage system in real time, and obtaining real-time grid conditions based on the grid-connected circuit information; Based on the real-time working condition of the power grid and the power control instruction issued by the operator, power control is performed to obtain the amplitude and phase angle of the output virtual voltage source; Based on the output virtual voltage source amplitude and the phase angle, a control loop instruction of the grid-side converter is generated, and based on the DC side voltage information and the real-time working condition of the power grid, a control loop instruction of the machine-side converter is generated; wherein, Based on the DC side voltage information and the real-time working condition of the power grid, generating a machine-side converter control loop instruction includes: A DC bus voltage control method including AC voltage frequency response is adopted to generate a DC bus voltage loop instruction and an AC voltage frequency control loop instruction; Based on the DC bus voltage loop command and the AC voltage frequency control loop command, a control loop command of the machine-side converter is formed; The topology structure between the auxiliary energy storage system and the flywheel energy storage system is read, and based on the topology structure, the control loop instruction of the grid-side converter and the control loop instruction of the generator-side converter, a control scheme of the flywheel energy storage system and its auxiliary energy storage system is generated and executed.

2. The method according to claim 1, characterized in that The grid-connected side circuit information includes: Phase voltage and line current at the point of access to the grid; where: The positive direction of the line current is the direction of flowing into the power grid.

3. The method according to claim 1, characterized in that The obtaining of the real-time working condition of the power grid based on the grid-connected side circuit information includes: Calculating the grid voltage amplitude and frequency based on the grid-connected side circuit information; and The real-time active power and real-time reactive power exchanged between the power grid and the flywheel energy storage system are calculated based on the grid-connected side circuit information.

4. The method according to claim 1, characterized in that: The generation rule expression of the DC bus voltage loop instruction and the AC voltage frequency control loop instruction is: Among them, i q * Positioning the q-axis current reference value for the machine-side converter flux vector; U dc * is the DC voltage reference value; U dc is the measured value of DC bus voltage; f n is the rated grid frequency; K pu , K pf , K iu , K if They are the PI parameters of the DC bus voltage loop and the grid frequency loop respectively.

5. The method according to claim 1, characterized in that The reading of the topological structure between the auxiliary energy storage system and the flywheel energy storage system, and the generation and execution of a control scheme for the flywheel energy storage system and its auxiliary energy storage system based on the topological structure and the control loop instruction, include: If the topology between the auxiliary energy storage system and the flywheel energy storage system is the first topology, directly executing the flywheel energy storage system control based on the control loop instruction; If the topological structure between the auxiliary energy storage system and the flywheel energy storage system is the second topological structure, the AC voltage frequency response loop is integrated into the control loop instruction to obtain a first correction control loop instruction, and the flywheel energy storage system and the auxiliary energy storage system are controlled in linkage based on the first correction control loop instruction; If the topological structure between the auxiliary energy storage system and the flywheel energy storage system is a third topological structure, the virtual inertia and the damping coefficient are determined based on the capacity of the flywheel energy storage system, the capacity of the auxiliary energy storage system and the output priority of each energy storage system, and the control loop instruction is corrected based on the virtual inertia and the damping coefficient to obtain a second corrected control loop instruction, and the flywheel energy storage system and the auxiliary energy storage system are controlled in linkage based on the second corrected control loop instruction.

6. The method according to claim 5, characterized in that The first topological structure is: The auxiliary energy storage system is directly connected in parallel to the DC bus of the flywheel energy storage system; The second topology is: The auxiliary energy storage system is connected in parallel to the DC bus of the flywheel energy storage system through a DC converter; The third topological structure is: The auxiliary energy storage system is connected in parallel to the AC bus of the flywheel energy storage system through a PCS converter.

7. A control system for a grid-type flywheel energy storage system, characterized in that: The flywheel energy storage system is connected in parallel with a corresponding auxiliary energy storage system on the busbar, and the system includes: A collection unit collects grid-connected circuit information and DC-side voltage information of the flywheel energy storage system in real time, and obtains real-time grid conditions based on the grid-connected circuit information; A control unit, which performs power control based on the real-time working condition of the power grid and the power control instruction issued by the operator to obtain the amplitude and phase angle of the output virtual voltage source; An instruction generation unit generates a control loop instruction for the grid-side converter based on the output virtual voltage source amplitude and the phase angle, and generates a control loop instruction for the generator-side converter based on the DC side voltage information and the real-time working condition of the power grid; wherein, Based on the DC side voltage information and the real-time working condition of the power grid, generating a machine-side converter control loop instruction includes: A DC bus voltage control method including AC voltage frequency response is adopted to generate a DC bus voltage loop instruction and an AC voltage frequency control loop instruction; Based on the DC bus voltage loop command and the AC voltage frequency control loop command, a control loop command of the machine-side converter is formed; The execution unit reads the topological structure between the auxiliary energy storage system and the flywheel energy storage system, and generates and executes a control scheme for the flywheel energy storage system and its auxiliary energy storage system based on the topological structure, the control loop instructions of the grid-side converter and the control loop instructions of the machine-side converter.

8. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores instructions, which, when executed on a computer, enable the computer to execute the control method for a grid-type flywheel energy storage system as described in any one of claims 1 to 6.

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