A control method, device and equipment for a distributed hybrid energy storage system

Abstract

The present application discloses a control method, device and equipment for a distributed hybrid energy storage system, which relates to the field of power system control. The method includes: obtaining the DC bus voltage, average DC bus voltage, operating data of the flywheel energy storage unit and operating data of the battery unit of each hybrid energy storage system; using a consistency algorithm to determine the voltage correction amount of each hybrid energy storage system according to the communication status between multiple hybrid energy storage systems, the DC bus voltage and average DC bus voltage of each hybrid energy storage system; using virtual resistance droop control and voltage and current dual closed-loop control strategy to control the bidirectional DC / DC converter corresponding to the battery unit; using virtual capacitor droop control and voltage and current dual closed-loop control strategy to control the AC / DC converter corresponding to the flywheel energy storage unit. The present application realizes compensation for the power imbalance between renewable energy and load, and improves the stability of the distributed hybrid energy storage system.

Description

Technical Field

[0001] The present application relates to the field of power system control, and in particular to a control method, device and equipment for a distributed hybrid energy storage system. Background Art

[0002] In recent years, renewable clean energy such as photovoltaics and wind power has developed rapidly, and its share of power generation has continued to increase. However, due to its intermittent, random and volatile characteristics, it poses a hidden danger to the safe and stable operation of the power system. Configuring an energy storage system is an effective means to smooth out the fluctuations in the output power of new energy and maintain the stable operation of the power system. However, due to its own limitations, a single type of energy storage system is difficult to simultaneously meet the requirements of service life, response speed, power density and other aspects. Therefore, different types of energy storage forms are often combined to form a hybrid energy storage system for configuration and use.

[0003] Hybrid energy storage usually combines energy-type energy storage (such as lithium batteries, lead-acid batteries, etc.) with power-type energy storage (supercapacitors, flywheel energy storage, superconducting magnetic energy storage, etc.) to meet various needs through the complementary advantages of their respective advantages. However, the current research and application of hybrid energy storage are mostly concentrated on the combination of batteries and supercapacitors. There are relatively few studies and applications on flywheel energy storage as a hybrid energy storage form that combines power-type energy storage with batteries. Flywheel energy storage has a fast response speed, long service life, high power density, and low maintenance cost. It is suitable for dealing with high-frequency power fluctuations with small change cycles in power systems. It is combined with batteries to form a hybrid energy storage system, which not only has the advantages of high power output and high storage capacity, but also can cooperate with each other to smooth out power fluctuations of different frequencies in the system. It has certain development prospects.

[0004] At present, hybrid energy storage composed of flywheels and batteries is often applied to DC microgrids composed of renewable energy generation in a distributed structure. In this application process, the key to determining the effect of multiple hybrid energy storage systems in the distributed network on smoothing power fluctuations and maintaining the stability of the DC microgrid lies in: how to design the control strategy of the hybrid energy storage system so that the flywheel as power-type energy storage and the battery as energy-type energy storage can reasonably distribute the unbalanced power of different frequencies in the system, so as to give full play to their respective advantages and maintain the stability of the DC bus voltage level during the regulation process. At present, for hybrid energy storage composed of flywheels and batteries, the power distribution control of multiple groups of hybrid energy storage systems is mostly centralized control and decentralized control. Centralized control directly distributes unbalanced power by relying on filtering devices to process power instructions, but this method has high communication requirements, is prone to single point failures, and has poor control flexibility and reliability; while decentralized control uses local control based on extended droop control to distribute power within the hybrid energy storage system, lacking coordination between hybrid energy storage systems and global control of the entire system.

[0005] Therefore, for the distributed hybrid energy storage system composed of flywheel batteries, it is necessary to design an effective distributed control strategy to achieve the stable operation of the entire DC microgrid system and the reasonable distribution of unbalanced power within the hybrid energy storage system. Summary of the invention

[0006] The purpose of this application is to provide a control method, device and equipment for a distributed hybrid energy storage system, which can compensate for the power imbalance between renewable energy and load and improve the stability of the distributed hybrid energy storage system.

[0007] To achieve the above objectives, this application provides the following solutions:

[0008] In a first aspect, the present application provides a control method for a distributed hybrid energy storage system, wherein each hybrid energy storage system includes a flywheel energy storage unit and a battery unit, wherein the flywheel energy storage unit is connected to a DC bus via an AC / DC converter, and the battery unit is connected to a DC bus via a bidirectional DC / DC converter, and the control method for the distributed hybrid energy storage system includes:

[0009] Obtaining the DC bus voltage, average DC bus voltage, operating data of the flywheel energy storage unit and operating data of the battery unit of each hybrid energy storage system;

[0010] According to the communication status among the multiple hybrid energy storage systems, the DC bus voltage of each hybrid energy storage system and the average DC bus voltage, a consistency algorithm is used to determine the voltage correction amount of each hybrid energy storage system;

[0011] For any hybrid energy storage system, according to the voltage correction amount of the hybrid energy storage system and the operating data of the battery unit of the hybrid energy storage system, a virtual resistance droop control and a voltage and current dual closed-loop control strategy are adopted to control the bidirectional DC / DC converter corresponding to the battery unit of the hybrid energy storage system;

[0012] According to the voltage correction amount of the hybrid energy storage system and the operating data of the flywheel energy storage unit of the hybrid energy storage system, a virtual capacitor droop control and a voltage and current dual closed-loop control strategy are adopted to control the AC / DC converter corresponding to the flywheel energy storage unit of the hybrid energy storage system.

[0013] In a second aspect, the present application provides a control device for a distributed hybrid energy storage system, wherein the distributed hybrid energy storage system includes a plurality of hybrid energy storage systems, each of which includes a flywheel energy storage unit and a battery unit, wherein the flywheel energy storage unit is connected to a DC bus via an AC / DC converter, and the battery unit is connected to a DC bus via a bidirectional DC / DC converter, wherein the control device for the distributed hybrid energy storage system includes:

[0014] A data acquisition module, connected to the flywheel energy storage unit and the battery unit of each hybrid energy storage system, for acquiring the DC bus voltage, average DC bus voltage, operating data of the flywheel energy storage unit and operating data of the battery unit of each hybrid energy storage system;

[0015] A voltage correction module, connected to the data acquisition module, is used to determine the voltage correction amount of each hybrid energy storage system using a consistency algorithm according to the communication status between the multiple hybrid energy storage systems, the DC bus voltage of each hybrid energy storage system and the average DC bus voltage;

[0016] A battery control module, connected to the data acquisition module and the voltage correction module respectively, for controlling the bidirectional DC / DC converter corresponding to the battery unit of any hybrid energy storage system by adopting virtual resistance droop control and voltage and current dual closed-loop control strategies according to the voltage correction amount of the hybrid energy storage system and the operation data of the battery unit of the hybrid energy storage system;

[0017] The flywheel control module is connected to the data acquisition module and the voltage correction module respectively, and is used for controlling the AC / DC converter corresponding to the flywheel energy storage unit of any hybrid energy storage system by adopting virtual capacitor droop control and voltage and current dual closed-loop control strategy according to the voltage correction amount of the hybrid energy storage system and the operating data of the flywheel energy storage unit of the hybrid energy storage system.

[0018] In a third aspect, the present application provides a computer device, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the above-mentioned distributed hybrid energy storage system control method.

[0019] According to the specific embodiments provided in this application, this application discloses the following technical effects:

[0020] The present application provides a control method, device and equipment for a distributed hybrid energy storage system, which applies droop control to a hybrid energy storage system composed of a flywheel and a battery, wherein the battery unit adopts virtual resistance droop control, and the flywheel energy storage unit adopts virtual capacitance droop control, so that the entire hybrid energy storage system can automatically complete dynamic disturbance power distribution and realize compensation for power imbalance between renewable energy and load. The battery unit mainly compensates for unbalanced power in steady state, while the flywheel energy storage unit compensates for dynamic high-frequency unbalanced power. At the same time, consistency control is applied to the distributed hybrid energy storage system, and through the mutual communication of each hybrid energy storage system, the DC bus voltage deviation caused by the inherent characteristics of droop control is compensated, and the coordination between the hybrid energy storage systems is realized, so as to maintain the whole system more stable, without single point failure problems, and with high reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 This is an application environment diagram of a control method for a distributed hybrid energy storage system in one embodiment of the present application;

[0023] Figure 2 This is the structural diagram of the entire DC microgrid;

[0024] Figure 3 A schematic flow chart of a control method for a distributed hybrid energy storage system provided in one embodiment of the present application;

[0025] Figure 4 A structural diagram of a hierarchical control strategy provided in an embodiment of the present application;

[0026] Figure 5 An equivalent circuit diagram of a hybrid energy storage system provided in one embodiment of the present application;

[0027] Figure 6 is the step disturbance under ofi and i obi Schematic diagram of the response situation;

[0028] Figure 7 A schematic diagram of functional modules of a control device for a distributed hybrid energy storage system provided in one embodiment of the present application;

[0029] Figure 8 A schematic diagram of the structure of a computer device provided in one embodiment of the present application. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0031] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0032] The control method of the distributed hybrid energy storage system provided in the embodiment of the present application can be applied to Figure 1 In the application environment shown. Among them, the terminal 102 communicates with the server 104 through the network. A distributed hybrid energy storage system is deployed in the server 104. The terminal 102 can send a control instruction to the server 104. After the server 104 receives the control instruction, the server 104 starts to control the on and off of the switching devices in the distributed hybrid energy storage system according to the relevant operating data of the distributed hybrid energy storage system. The server 104 can feedback the control result or the relevant operating data of the distributed hybrid energy storage system to the terminal 102. In addition, in some embodiments, the control method of the distributed hybrid energy storage system can also be implemented by the server 104 or the terminal 102 alone.

[0033] The terminal 102 may be, but is not limited to, various desktop computers, laptop computers, smart phones, tablet computers, IoT devices, and portable wearable devices. The IoT devices may be smart speakers, smart TVs, smart air conditioners, smart vehicle-mounted devices, etc. The portable wearable devices may be smart watches, smart bracelets, head-mounted devices, etc. The server 104 may be implemented as an independent server or a server cluster consisting of multiple servers, or may be a cloud server.

[0034] In an exemplary embodiment, the control method proposed in this application is applied to a distributed hybrid energy storage system in a DC microgrid. The structure of the entire DC microgrid is as follows: Figure 2 As shown, the distributed hybrid energy storage system includes multiple hybrid energy storage systems, and each power generation unit in the DC microgrid is equipped with a hybrid energy storage system consisting of a flywheel and a battery. The power generation unit is connected to the DC bus through a converter 202 matched therewith, and the DC load and line resistance are directly connected to the DC bus. Each hybrid energy storage system includes a flywheel energy storage unit and a battery unit, the flywheel energy storage unit is connected to the DC bus through an AC / DC converter, and the battery unit is connected to the DC bus through a bidirectional DC / DC converter.

[0035] In an exemplary embodiment, Figure 3 As shown, a control method for a distributed hybrid energy storage system is provided. The method is executed by a computer device, and can be executed by a computer device such as a terminal or a server alone, or by a terminal and a server together. In the embodiment of the present application, the method is applied to Figure 1 The server 104 in the example is used for explanation, and the steps include the following steps 301 to 308.

[0036] Since the photovoltaic module works in the maximum power point tracking mode, it can be equivalent to a constant power supply. The bus voltage stability of the DC microgrid and the dynamic distribution of the unbalanced power inside the hybrid energy storage system mainly rely on hierarchical control based on consistency algorithm and droop control. The hierarchical control strategy provided in this application is as follows Figure 4As shown, it relies on the coordination of the physical layer, the primary control layer and the secondary control layer of the hybrid energy storage system to work. In this application, step 301 corresponds to the physical layer, step 302 corresponds to the secondary control layer, and steps 303 and 304 correspond to the sequential control layer.

[0037] Step 301 , obtaining the DC bus voltage, average DC bus voltage, operating data of the flywheel energy storage unit and operating data of the battery unit of each hybrid energy storage system.

[0038] Specifically, the operating data of the flywheel energy storage unit includes the three-phase AC current of the flywheel motor stator, the output voltage of the AC / DC converter, the output current of the AC / DC converter and the angular velocity of the permanent magnet synchronous motor.

[0039] The operation data of the battery unit includes the output current of the battery, the output voltage of the bidirectional DC / DC converter, and the output current of the bidirectional DC / DC converter.

[0040] In this application, at the physical layer, the flywheel energy storage unit in the hybrid energy storage system i uses sensors to respectively transmit the three-phase AC current i abci 、AC / DC converter output voltage v ofi , the output current i of the AC / DC converter ofi and the angular velocity ω of the permanent magnet synchronous motor m The battery unit transmits the output current i of the battery to the primary control layer and the secondary control layer through the sensor. bati , the output voltage v of the bidirectional DC / DC converter obi and the output current i obi Transmitted to the primary control layer and the secondary control layer.

[0041] Step 302 : According to the communication status among the multiple hybrid energy storage systems, the DC bus voltage of each hybrid energy storage system and the average DC bus voltage, a consistency algorithm is used to determine the voltage correction amount of each hybrid energy storage system.

[0042] The function of step 302 is to calculate and generate a voltage correction value output to the battery and the flywheel primary control layer. The calculation of the voltage correction value is based on the communication network and consistency algorithm of each hybrid energy storage system.

[0043] In a DC microgrid, due to the existence of line impedance, there will be differences in the DC bus voltages at each hybrid energy storage system. If the DC bus voltages of each hybrid energy storage system are made equal during voltage control, power flow and exchange cannot be achieved between the hybrid energy storage systems. Therefore, in this application, the purpose of secondary control is mainly to output voltage correction to ensure that the average DC bus voltages of each hybrid energy storage system are consistent and reach the corresponding rated value.

[0044] Specifically, step 302 includes the following (21) to (23):

[0045] (21) Determine an adjacency matrix based on the communication status among the plurality of hybrid energy storage systems. The adjacency matrix includes a set of neighboring nodes of each hybrid energy storage system. The set of neighboring nodes of each hybrid energy storage system includes hybrid energy storage systems that can receive information about the hybrid energy storage system.

[0046] For a communication network with N nodes, its structure is usually represented by a graph G = (V, E), where V represents the set of N nodes in the network. Represents the set of edges between nodes. For a communication network G, the adjacency matrix A is used to describe the connections between nodes in G. The elements in the adjacency matrix A are a ij , if (ν j ,ν i )∈E, that is, when node j can receive the information of node i, a ij =1, otherwise, a ij = 0. In the present application, the nodes in the communication network are hybrid energy storage systems.

[0047] (22) For any hybrid energy storage system, an average DC bus voltage update value of the hybrid energy storage system is determined based on the DC bus voltage of the hybrid energy storage system, the average DC bus voltage of the hybrid energy storage system, and the average DC bus voltages of each hybrid energy storage system in a neighboring node set of the hybrid energy storage system.

[0048] In order to make the average DC bus voltage of each hybrid energy storage system consistent, this application adopts a consistency algorithm, that is, the following formula to determine the average DC bus voltage update value of hybrid energy storage system i:

[0049]

[0050] Among them, v avg i ' is the average DC bus voltage update value of hybrid energy storage system i, v busi is the DC bus voltage of hybrid energy storage system i, v avg i is the average DC bus voltage of hybrid energy storage system i, v avg j is the average DC bus voltage of hybrid energy storage system j, N i is the set of neighboring nodes of hybrid energy storage system i, N i ={j|(ν j ,ν i )∈E}.

[0051] Before mutual communication, the initial value of the average DC bus voltage of each hybrid energy storage system is equal to its DC bus voltage. Then, the secondary control layer of hybrid energy storage system i obtains the average DC bus voltage and DC bus voltage through mutual communication with other hybrid energy storage systems and local sensors, and calculates the updated value of the average bus voltage using the above formula.

[0052] (23) According to the average DC bus voltage update value and the voltage reference value of the hybrid energy storage system, a PI controller is used to determine the voltage correction amount of the hybrid energy storage system.

[0053] Specifically, the voltage correction amount of the hybrid energy storage system i is determined by the following formula:

[0054]

[0055] in, is the voltage correction of hybrid energy storage system i, v ref is the voltage reference value, k PU is the proportional coefficient of the secondary control, k IU is the integral coefficient of the secondary control.

[0056] The present application adopts double closed-loop control based on droop control at the primary control layer of the flywheel energy storage unit and the battery unit respectively.

[0057] Step 303, for any hybrid energy storage system, according to the voltage correction value of the hybrid energy storage system and the operating data of the battery unit of the hybrid energy storage system, a virtual resistance droop control and a voltage and current dual closed-loop control strategy are adopted to control the bidirectional DC / DC converter corresponding to the battery unit of the hybrid energy storage system.

[0058] Specifically, step 303 includes the following (31) to (34):

[0059] (31) Determine a given value of the battery voltage of the hybrid energy storage system based on a voltage reference value, a voltage correction value of the hybrid energy storage system, a virtual resistance droop coefficient of the battery of the hybrid energy storage system, and an output current of a bidirectional DC / DC converter corresponding to the hybrid energy storage system.

[0060] In this embodiment, the following formula is used to determine the battery voltage setpoint of the hybrid energy storage system i:

[0061]

[0062] in, is the battery voltage set value of the hybrid energy storage system i, indicating the voltage set value of the battery unit voltage outer loop, v ref is the voltage reference value, is the voltage correction of hybrid energy storage system i, R i is the virtual resistance droop coefficient of the battery in the hybrid energy storage system i, obi is the output current of the bidirectional DC / DC converter corresponding to the hybrid energy storage system i.

[0063] (32) According to the battery voltage set value of the hybrid energy storage system and the output voltage of the bidirectional DC / DC converter corresponding to the hybrid energy storage system, a PI controller is used to determine the battery current set value of the hybrid energy storage system.

[0064] The voltage outer loop of the battery unit adopts a PI controller. The input of the PI controller is the difference between the battery voltage set value and the output voltage of the bidirectional DC / DC converter. The output of the PI controller is the battery current set value, that is, the current set value of the current inner loop:

[0065]

[0066] in, is the given value of the battery current of hybrid energy storage system i, v obi is the output voltage of the bidirectional DC / DC converter corresponding to the hybrid energy storage system i, k PUB is the proportional coefficient of the battery voltage loop, k IUB is the integral coefficient of the battery voltage loop.

[0067] (33) According to the given value of the battery current of the hybrid energy storage system and the output current of the battery unit, a PI controller is used to determine the battery duty cycle signal.

[0068] The following formula is used to determine the battery duty cycle signal, that is, the duty cycle signal of the current inner loop:

[0069]

[0070] Among them, d bi is the battery duty cycle signal of hybrid energy storage system i, i bati is the output current of the battery unit of the hybrid energy storage system i, k PCB is the proportional coefficient of the battery current loop, k ICB is the integral coefficient of the battery current loop

[0071] (34) Pulse width modulation is performed on the battery duty cycle signal to obtain a battery pulse signal sequence to control the on and off of switching devices in the bidirectional DC / DC converter corresponding to the hybrid energy storage system.

[0072] After the battery duty cycle signal is pulse-width modulated by the pulse width modulation module (PWM), a pulse signal sequence with a fixed frequency is generated. The two switching devices in the bidirectional DC / DC converter receive opposite pulse signal sequences respectively. The switching devices are all fully controlled devices. They are turned on when the amplitude of the received pulse signal sequence is 1, and turned off when the amplitude of the received signal is 0. When one of the two switching devices in the bidirectional DC / DC converter is turned on, the other is in the off state. Under the continuous on and off of the two switching devices, the output current and voltage of the entire bidirectional DC / DC converter are controlled.

[0073] Step 304, according to the voltage correction amount of the hybrid energy storage system and the operating data of the flywheel energy storage unit of the hybrid energy storage system, a virtual capacitor droop control and a voltage and current dual closed-loop control strategy are adopted to control the AC / DC converter corresponding to the flywheel energy storage unit of the hybrid energy storage system.

[0074] Specifically, step 304 includes the following (41) to (46):

[0075] (41) Determine a given flywheel energy storage voltage of the hybrid energy storage system based on a voltage reference value, a voltage correction value of the hybrid energy storage system, a flywheel energy storage virtual capacitor droop coefficient of the hybrid energy storage system, and an output current of an AC / DC converter corresponding to the hybrid energy storage system.

[0076] In this embodiment, the following formula is used to determine the flywheel energy storage voltage set value of the hybrid energy storage system i:

[0077]

[0078] in, is the flywheel energy storage voltage given value of hybrid energy storage system i, v ref is the voltage reference value, is the voltage correction of hybrid energy storage system i, C i is the flywheel energy storage virtual capacitor droop coefficient of hybrid energy storage system i, i ofi is the output current of the AC / DC converter corresponding to the hybrid energy storage system i.

[0079] (42) According to the given value of the flywheel energy storage voltage of the hybrid energy storage system and the output voltage of the AC / DC converter corresponding to the hybrid energy storage system, a PI controller is used to determine the q-axis current reference value of the hybrid energy storage system.

[0080] Specifically, the following formula is used to determine the quadrature-axis current reference value of the hybrid energy storage system i:

[0081]

[0082] in, is the quadrature axis current reference value of the hybrid energy storage system i, that is, the quadrature axis current reference value in the current inner loop, v ofi is the output voltage of the AC / DC converter corresponding to the hybrid energy storage system i, k PUQ is the proportional coefficient of the flywheel energy storage voltage loop, k IUQ is the integral coefficient of the flywheel energy storage voltage loop.

[0083] (43) Converting the three-phase alternating current of the flywheel motor stator corresponding to the hybrid energy storage system into quadrature-axis current and direct-axis current.

[0084] Specifically, the three-phase AC current i of the flywheel motor stator corresponding to the hybrid energy storage system i is abci Through coordinate transformation, it is converted into quadrature axis current i qi and the direct axis current i di .

[0085] (44) A PI controller is used to determine a given value of the direct-axis voltage of the hybrid energy storage system according to the angular velocity of the permanent magnet synchronous motor corresponding to the hybrid energy storage system, the direct-axis current, the quadrature-axis current and a given value of the direct-axis current.

[0086] In this application, the direct axis current is adopted control strategy, is the given value of direct axis current.

[0087] Specifically, the direct-axis voltage set value of the hybrid energy storage system i is determined by the following formula:

[0088]

[0089] in, is the given value of the direct-axis voltage of the hybrid energy storage system i, n p is the number of pole pairs of the flywheel motor, ω m is the angular velocity of the permanent magnet synchronous motor, L q is the quadrature axis inductance of the motor stator, k PCF is the proportional coefficient of the flywheel energy storage current loop, k ICF is the integral coefficient of the flywheel energy storage current loop.

[0090] (45) According to the angular velocity of the permanent magnet synchronous motor corresponding to the hybrid energy storage system, the quadrature-axis current, the direct-axis current and the quadrature-axis current reference value, a PI controller is used to determine a quadrature-axis voltage set value of the hybrid energy storage system.

[0091] exist Under the control strategy, the power output or absorbed by the flywheel energy storage unit is changed mainly by controlling the quadrature axis current. The quadrature axis voltage set value of the hybrid energy storage system i is determined by the following formula:

[0092]

[0093] in, is the given value of the quadrature axis voltage of the hybrid energy storage system i, L d is the direct axis inductance of the motor stator, ψ f is the permanent magnet flux of the motor.

[0094] (46) Converting the direct-axis voltage set value and the quadrature-axis voltage set value of the hybrid energy storage system into voltage set values ​​in a stationary two-phase coordinate system, and performing space vector pulse width modulation to obtain a flywheel energy storage pulse signal sequence to control the on and off of switching devices in the AC / DC converter corresponding to the hybrid energy storage system.

[0095] Specifically, the direct-axis voltage of the hybrid energy storage system i is given as And the quadrature axis voltage given value After the inverse PARK transformation, it is converted into the voltage given value in the stationary two-phase coordinate system and Will and After being input into the Space Vector Pulse Width Modulation (SVPWM) module for space vector pulse width modulation, 6 groups of pulse signals for controlling the switch state are output. The 6 fully controlled switch devices in the AC / DC converter with a three-phase bridge fully controlled rectifier structure receive the 6 groups of pulse signals output by the SVPWM module respectively. When the pulse signal amplitude is 1, the switch device is turned on, and vice versa, when the amplitude is 0, the switch device is turned off. The two switch devices on the same bridge arm receive opposite pulse signals, that is, when one is turned on, the other switch device is turned off. The pulse signal sequence output by the SVPWM module controls the on and off of the switch devices on each bridge arm, thereby realizing the control of the output current and output voltage of the AC / DC converter.

[0096] The present application realizes dynamic frequency distribution of unbalanced power in a hybrid energy storage unit by adding virtual resistance droop control and virtual capacitance droop control to the primary control links of the battery unit and the flywheel energy storage unit respectively, that is, the flywheel responds to the high-frequency part of the unbalanced power, while the battery responds to the low-frequency part.

[0097] The specific implementation principle is as follows:

[0098] Each hybrid energy storage system in the distributed microgrid relies on droop control to control the battery unit and the flywheel energy storage unit. When its voltage loop control achieves fast tracking, the output voltages of the bidirectional DC / DC converter corresponding to the battery unit and the AC / DC converter corresponding to the flywheel energy storage unit satisfy the following relationships:

[0099]

[0100] make Then the equivalent circuit diagram of the hybrid energy storage system can be obtained, such as Figure 5 shown.

[0101] The output voltage / current relationship of the battery unit and the flywheel energy storage unit can then be expressed in the frequency domain as:

[0102]

[0103] Among them, V obi 、V ofi ,I obi ,I ofi Respectively represent v obi 、v ofi 、i obi 、i ofi Represented in the frequency domain, for In the frequency domain, s represents the Laplace operator.

[0104] In each hybrid energy storage system, the fluctuation of photovoltaic power output and the sudden change of load lead to the power imbalance inside the hybrid energy storage system, which will generate unbalanced current i oi , and the current i output by the converter of the battery unit and flywheel energy storage unit in the hybrid energy storage system obi and i ofi Can be used to compensate for unbalanced current i obi +i ofi =i oi , thereby maintaining the power balance within the hybrid energy storage system and ensuring the stability of the DC bus voltage.

[0105] The distribution current of the battery unit and the flywheel energy storage unit can be expressed in the frequency domain as:

[0106]

[0107] Among them, I oi is the unbalanced current i oi Representation in the frequency domain, I obi for i obi Representation in the frequency domain, I ofi for i ofiRepresentation in the frequency domain. From the form of G1(s) and G2(s), it can be seen that G1(s) exhibits the characteristics of low-pass filtering, while G2(s) exhibits the characteristics of high-pass filtering. The low-frequency part and the high-frequency part of the unbalanced current can be respectively allocated to the battery unit and the flywheel energy storage unit, thus realizing the dynamic frequency division distribution of the unbalanced power.

[0108] Figure 6 Shows that when R i C i =1, unbalanced current i oi The ideal response of the output current of the flywheel energy storage unit and the battery unit in the hybrid energy storage system when it is in step form, where the output current of the flywheel energy storage unit i ofi The response is fast, and it mainly responds in the dynamic stage, and decreases to 0 in the steady state stage; the battery unit output current i obi The response is relatively slow, and the unbalanced current is fully compensated in the steady state stage. Under the power distribution of this method, the flywheel responds to the high-frequency components in the disturbance, giving full play to the advantage of the flywheel's fast response speed, while the battery mainly responds to the low-frequency components, improving the situation where the frequent charging and discharging of the battery caused by high-frequency disturbances reduces its service life.

[0109] In addition, the present application adopts a consistency algorithm based on mutual communication among distributed hybrid energy storage systems. The secondary control layer can output a voltage correction value to the primary control layer. Relying on this voltage correction value, the average DC bus voltage of each hybrid energy storage system can be made consistent during the control process, and the average DC bus voltage level can reach the corresponding rated value level.

[0110] The present application also provides an application scenario, which applies the control method of the above-mentioned distributed hybrid energy storage system. Specifically: The control method of the distributed hybrid energy storage system provided in this embodiment can be applied in the stable operation control process of the DC microgrid. In the stable operation control process of the DC microgrid, the control method of the above-mentioned distributed hybrid energy storage system is used to control the distributed hybrid energy storage system in the DC microgrid, so as to achieve the stable operation of the entire DC microgrid and the reasonable distribution of unbalanced power within the hybrid energy storage system.

[0111] Based on the same inventive concept, the embodiment of the present application also provides a control device for a distributed hybrid energy storage system for implementing the control method of the distributed hybrid energy storage system involved above. The implementation scheme for solving the problem provided by the device is similar to the implementation scheme recorded in the above method, so the specific limitations in the embodiments of the control device for one or more distributed hybrid energy storage systems provided below can refer to the limitations of the control method for the distributed hybrid energy storage system above, and will not be repeated here.

[0112] In an exemplary embodiment, Figure 7 As shown, a control device for a distributed hybrid energy storage system is provided, including: a data acquisition module 701, a voltage correction module 702, a battery control module 703 and a flywheel control module 704. Among them:

[0113] The data acquisition module 701 is connected to the flywheel energy storage unit and the battery unit of each hybrid energy storage system, and is used to obtain the DC bus voltage, average DC bus voltage, operating data of the flywheel energy storage unit and operating data of the battery unit of each hybrid energy storage system.

[0114] The voltage correction module 702 is connected to the data acquisition module 701, and is used to determine the voltage correction amount of each hybrid energy storage system using a consistency algorithm according to the communication status between multiple hybrid energy storage systems, the DC bus voltage of each hybrid energy storage system and the average DC bus voltage.

[0115] The battery control module 703 is connected to the data acquisition module 701 and the voltage correction module 702 respectively. The battery control module 703 is used for any hybrid energy storage system. According to the voltage correction amount of the hybrid energy storage system and the operating data of the battery unit of the hybrid energy storage system, the virtual resistance droop control and the voltage and current dual closed-loop control strategy are adopted to control the bidirectional DC / DC converter corresponding to the battery unit of the hybrid energy storage system.

[0116] The flywheel control module 704 is connected to the data acquisition module 701 and the voltage correction module 702 respectively. The flywheel control module 704 is used for any hybrid energy storage system, according to the voltage correction amount of the hybrid energy storage system and the operating data of the flywheel energy storage unit of the hybrid energy storage system, to control the AC / DC converter corresponding to the flywheel energy storage unit of the hybrid energy storage system by adopting virtual capacitor droop control and voltage and current dual closed-loop control strategy.

[0117] In an exemplary embodiment, a computer device is provided. The computer device may be a server or a terminal. The internal structure diagram thereof may be as follows: Figure 8As shown. The computer device includes a processor, a memory, an input / output interface (Input / Output, referred to as I / O) and a communication interface. The processor, the memory and the input / output interface are connected through a system bus, and the communication interface is connected to the system bus through the input / output interface. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program and a database. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The database of the computer device is used to store the structure of the distributed hybrid energy storage system. The input / output interface of the computer device is used to exchange information between the processor and an external device. The communication interface of the computer device is used to communicate with an external terminal through a network connection. When the computer program is executed by the processor, a control method for a distributed hybrid energy storage system is implemented.

[0118] Those skilled in the art will understand that Figure 8 The structure shown in the figure is only a block diagram of a part of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components.

[0119] In an exemplary embodiment, a computer device is further provided, including a memory and a processor, wherein a computer program is stored in the memory, and the processor implements the steps in the above-mentioned method embodiments when executing the computer program.

[0120] In an exemplary embodiment, a computer-readable storage medium is provided, storing a computer program, and when the computer program is executed by a processor, the steps in the above method embodiments are implemented.

[0121] In an exemplary embodiment, a computer program product is provided, including a computer program, and when the computer program is executed by a processor, the steps in the above method embodiments are implemented.

[0122] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, stored data, displayed data, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of relevant data must comply with relevant regulations.

[0123] Those of ordinary skill in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to the memory, database or other medium used in the embodiments provided in the present application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM may be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM).

[0124] The database involved in each embodiment provided in this application may include at least one of a relational database and a non-relational database. The non-relational database may include a distributed database based on blockchain, etc., but is not limited thereto. The processor involved in each embodiment provided in this application may be a general-purpose processor, a central processing unit, a graphics processor, a digital signal processor, a programmable logic device, a data processing logic device based on quantum computing, etc., but is not limited thereto.

[0125] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0126] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A control method for a distributed hybrid energy storage system, wherein the distributed hybrid energy storage system comprises a plurality of hybrid energy storage systems, each of which comprises a flywheel energy storage unit and a battery unit, wherein the flywheel energy storage unit is connected to a DC bus via an AC / DC converter, and the battery unit is connected to a DC bus via a bidirectional DC / DC converter, wherein: The control method of the distributed hybrid energy storage system includes: Obtaining the DC bus voltage, average DC bus voltage, operating data of the flywheel energy storage unit and operating data of the battery unit of each hybrid energy storage system; According to the communication status among the multiple hybrid energy storage systems, the DC bus voltage of each hybrid energy storage system and the average DC bus voltage, a consistency algorithm is used to determine the voltage correction amount of each hybrid energy storage system; For any hybrid energy storage system, according to the voltage correction amount of the hybrid energy storage system and the operating data of the battery unit of the hybrid energy storage system, a virtual resistance droop control and a voltage and current dual closed-loop control strategy are adopted to control the bidirectional DC / DC converter corresponding to the battery unit of the hybrid energy storage system; According to the voltage correction amount of the hybrid energy storage system and the operating data of the flywheel energy storage unit of the hybrid energy storage system, a virtual capacitor droop control and a voltage and current dual closed-loop control strategy are adopted to control the AC / DC converter corresponding to the flywheel energy storage unit of the hybrid energy storage system.

2. The control method of the distributed hybrid energy storage system according to claim 1, characterized in that: According to the communication status among multiple hybrid energy storage systems, the DC bus voltage of each hybrid energy storage system and the average DC bus voltage, a consistency algorithm is used to determine the voltage correction amount of each hybrid energy storage system, including: Determine an adjacency matrix according to the communication status among the plurality of hybrid energy storage systems; the adjacency matrix includes a set of neighboring nodes of each hybrid energy storage system; the set of neighboring nodes of each hybrid energy storage system includes a hybrid energy storage system that can receive information of the hybrid energy storage system; For any hybrid energy storage system, determine an updated average DC bus voltage value of the hybrid energy storage system according to the DC bus voltage of the hybrid energy storage system, the average DC bus voltage of the hybrid energy storage system, and the average DC bus voltages of each hybrid energy storage system in a neighboring node set of the hybrid energy storage system; A PI controller is used to determine a voltage correction amount of the hybrid energy storage system according to an average DC bus voltage update value and a voltage reference value of the hybrid energy storage system.

3. The control method of the distributed hybrid energy storage system according to claim 2, characterized in that: The average DC bus voltage update value of the hybrid energy storage system i is determined by the following formula: Among them, v avgi ' is the average DC bus voltage update value of hybrid energy storage system i, v busi is the DC bus voltage of hybrid energy storage system i, v avgi is the average DC bus voltage of hybrid energy storage system i, v avgj is the average DC bus voltage of hybrid energy storage system j, N i is the set of neighboring nodes of hybrid energy storage system i.

4. The control method of the distributed hybrid energy storage system according to claim 1, characterized in that: The operating data of the flywheel energy storage unit includes the three-phase AC current of the flywheel motor stator, the output voltage of the AC / DC converter, the output current of the AC / DC converter and the angular velocity of the permanent magnet synchronous motor; The operation data of the battery unit includes the output current of the battery, the output voltage of the bidirectional DC / DC converter, and the output current of the bidirectional DC / DC converter.

5. The control method of the distributed hybrid energy storage system according to claim 4, characterized in that: According to the voltage correction amount of the hybrid energy storage system and the operation data of the battery unit of the hybrid energy storage system, a virtual resistance droop control and a voltage and current double closed-loop control strategy are adopted to control the bidirectional DC / DC converter corresponding to the battery unit of the hybrid energy storage system, specifically including: Determine a given value of the battery voltage of the hybrid energy storage system according to a voltage reference value, a voltage correction amount of the hybrid energy storage system, a virtual resistance droop coefficient of the battery of the hybrid energy storage system, and an output current of a bidirectional DC / DC converter corresponding to the hybrid energy storage system; According to the battery voltage given value of the hybrid energy storage system and the output voltage of the bidirectional DC / DC converter corresponding to the hybrid energy storage system, a PI controller is used to determine the battery current given value of the hybrid energy storage system; According to the given value of the battery current of the hybrid energy storage system and the output current of the battery unit, a PI controller is used to determine the battery duty cycle signal; The battery duty cycle signal is pulse-width modulated to obtain a battery pulse signal sequence to control the on-off of a switch device in a bidirectional DC / DC converter corresponding to the hybrid energy storage system.

6. The control method of the distributed hybrid energy storage system according to claim 5, characterized in that: The following formula is used to determine the battery voltage setpoint of the hybrid energy storage system i: in, is the battery voltage given value of hybrid energy storage system i, v ref is the voltage reference value, is the voltage correction of hybrid energy storage system i, R i is the virtual resistance droop coefficient of the battery in the hybrid energy storage system i, obi is the output current of the bidirectional DC / DC converter corresponding to the hybrid energy storage system i.

7. The control method of the distributed hybrid energy storage system according to claim 4, characterized in that: According to the voltage correction amount of the hybrid energy storage system and the operating data of the flywheel energy storage unit of the hybrid energy storage system, a virtual capacitor droop control and a voltage and current double closed-loop control strategy are adopted to control the AC / DC converter corresponding to the flywheel energy storage unit of the hybrid energy storage system, specifically including: Determine the flywheel energy storage voltage given value of the hybrid energy storage system according to the voltage reference value, the voltage correction amount of the hybrid energy storage system, the flywheel energy storage virtual capacitor droop coefficient of the hybrid energy storage system and the output current of the AC / DC converter corresponding to the hybrid energy storage system; According to the given value of the flywheel energy storage voltage of the hybrid energy storage system and the output voltage of the AC / DC converter corresponding to the hybrid energy storage system, a PI controller is used to determine the quadrature-axis current reference value of the hybrid energy storage system; Converting the three-phase alternating current of the stator of the flywheel motor corresponding to the hybrid energy storage system into quadrature-axis current and direct-axis current; According to the angular velocity of the permanent magnet synchronous motor corresponding to the hybrid energy storage system, the direct-axis current, the quadrature-axis current and the direct-axis current given value, a PI controller is used to determine the direct-axis voltage given value of the hybrid energy storage system; According to the angular velocity of the permanent magnet synchronous motor corresponding to the hybrid energy storage system, the quadrature-axis current, the direct-axis current and the quadrature-axis current reference value, a PI controller is used to determine a quadrature-axis voltage set value of the hybrid energy storage system; The direct-axis voltage set value and the quadrature-axis voltage set value of the hybrid energy storage system are converted into voltage set values ​​in a stationary two-phase coordinate system, and space vector pulse width modulation is performed to obtain a flywheel energy storage pulse signal sequence to control the on and off of switching devices in the AC / DC converter corresponding to the hybrid energy storage system.

8. The control method of the distributed hybrid energy storage system according to claim 7, characterized in that: The flywheel energy storage voltage setpoint of the hybrid energy storage system i is determined by the following formula: in, is the flywheel energy storage voltage given value of hybrid energy storage system i, v ref is the voltage reference value, is the voltage correction of hybrid energy storage system i, C i is the flywheel energy storage virtual capacitor droop coefficient of hybrid energy storage system i, i ofi is the output current of the AC / DC converter corresponding to the hybrid energy storage system i.

9. A control device for a distributed hybrid energy storage system, applied to the control method for a distributed hybrid energy storage system according to any one of claims 1 to 8, wherein the distributed hybrid energy storage system comprises a plurality of hybrid energy storage systems, each of which comprises a flywheel energy storage unit and a battery unit, wherein the flywheel energy storage unit is connected to a DC bus via an AC / DC converter, and the battery unit is connected to a DC bus via a bidirectional DC / DC converter, wherein: The control device of the distributed hybrid energy storage system comprises: A data acquisition module, connected to the flywheel energy storage unit and the battery unit of each hybrid energy storage system, for acquiring the DC bus voltage, average DC bus voltage, operating data of the flywheel energy storage unit and operating data of the battery unit of each hybrid energy storage system; A voltage correction module, connected to the data acquisition module, is used to determine the voltage correction amount of each hybrid energy storage system by using a consistency algorithm according to the communication status between the multiple hybrid energy storage systems, the DC bus voltage of each hybrid energy storage system and the average DC bus voltage; A battery control module, connected to the data acquisition module and the voltage correction module respectively, for controlling the bidirectional DC / DC converter corresponding to the battery unit of any hybrid energy storage system by adopting virtual resistance droop control and voltage and current dual closed-loop control strategies according to the voltage correction amount of the hybrid energy storage system and the operation data of the battery unit of the hybrid energy storage system; The flywheel control module is connected to the data acquisition module and the voltage correction module respectively, and is used for controlling the AC / DC converter corresponding to the flywheel energy storage unit of any hybrid energy storage system by adopting virtual capacitor droop control and voltage and current dual closed-loop control strategy according to the voltage correction amount of the hybrid energy storage system and the operating data of the flywheel energy storage unit of the hybrid energy storage system.

10. A computer device comprising: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the control method for a distributed hybrid energy storage system according to any one of claims 1 to 8.

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