NL2021568B1 - SYSTEM FOR CONTROLLING BALANCE OF SOC IN A CASCADED ENERGY STORAGE SYSTEM - Google Patents

SYSTEM FOR CONTROLLING BALANCE OF SOC IN A CASCADED ENERGY STORAGE SYSTEM Download PDF

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Publication number
NL2021568B1
NL2021568B1 NL2021568A NL2021568A NL2021568B1 NL 2021568 B1 NL2021568 B1 NL 2021568B1 NL 2021568 A NL2021568 A NL 2021568A NL 2021568 A NL2021568 A NL 2021568A NL 2021568 B1 NL2021568 B1 NL 2021568B1
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Netherlands
Prior art keywords
energy storage
storage module
controlled
angular frequency
module
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NL2021568A
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Dutch (nl)
Inventor
Han Hua
Shi Guangze
Su Mei
Sun Yao
Liu Zhangjie
Hou Xiaocao
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Univ Central South
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/0013—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries acting upon several batteries simultaneously or sequentially
    • H02J7/0014—Circuits for equalisation of charge between batteries
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J15/00—Systems for storing electric energy
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/28—Arrangements for balancing of the load in a network by storage of energy
    • H02J3/32—Arrangements for balancing of the load in a network by storage of energy using batteries with converting means
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/0013—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries acting upon several batteries simultaneously or sequentially
    • H02J7/0014—Circuits for equalisation of charge between batteries
    • H02J7/0019—Circuits for equalisation of charge between batteries using switched or multiplexed charge circuits
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/0068—Battery or charger load switching, e.g. concurrent charging and load supply
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/0047—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with monitoring or indicating devices or circuits
    • H02J7/0048—Detection of remaining charge capacity or state of charge [SOC]

Abstract

The present disclosure provides a system for controlling SOC balance of a cascaded energy storage system, comprising multiple control devices each being in connection With a 5 corresponding one of energy storage modules in the cascaded energy storage system and independently controlling SOC balance of the corresponding one of energy storage modules. The system for controlling the SOC balance is a distributed control system, and devices for controlling SOC balance corresponding to each energy storage module can control the SOC balance of the energy storage module merely by means of local 10 information without communicating with other external devices. Therefore, compared with the existing system for controlling SOC balance, the cost of the present system is greatly reduced. (Fig. 2) 15 21The present disclosure provides a system for controlling SOC balance of a cascaded energy storage system, including multiple control devices each being in connection With a 5 corresponding one of energy storage modules in the cascaded energy storage system and independently controlling SOC balance of the corresponding one of energy storage modules. The system for controlling the SOC balance is a distributed control system, and devices for controlling SOC balance corresponding to each energy storage module can control the SOC balance of the energy storage module merely by means of local 10 information without communicating with other external devices. Therefore, compared to the existing system for controlling SOC balance, the cost of the present system is greatly reduced. (Fig. 2)

Description

Technical Field
The present disclosure relates to the technical field of power electronics, in particular to a system for controlling balance of SOC in a cascaded energy storage system and a centralized large-capacity energy storage system.
Technical Background
In the applications of energy storage engineering, in order that an energy storage system can be charged and discharged synchronously, such that the service life of the energy storage system can be prolonged, the state of charge (SOC for short) in each energy storage module should be balanced. However, the SOC between each energy storage module of a system might be unbalanced due to such reasons as different initial SOCs of the system and different output power during operation of the system, then some individual energy storage modules will be charged or discharged excessively, and further the service life and system efficiency of the energy storage module will be influenced.
Along with continuous improvement of our consciousness on sustainable development of energy and environmental protection, renewable energy sources and electric automobiles have been developed rapidly, and traditional small-capacity energy storage systems cannot meet the existing demands. With gradual enlargement of energy storage scales, in medium- and high-voltage application occasions, the cascaded energy storage system has been valued on the market. The voltage of a single energy storage unit is low, while a higher voltage level can be directly obtained through a cascaded inverter, with no need of a large and expensive transformer. Meanwhile, each energy storage module can be separately controlled, such that each energy storage unit can be managed more conveniently.
The existing methods for controlling SOC balance of a cascaded energy storage system depend on centralized high-bandwidth communications. With the increase in the number of energy storage modules, on the one hand, the cost of communication bandwidths is constantly increased, on the other hand, system robustness will be greatly lowered due to such conditions as packet loss and failure of communications.
Summary of the Invention
In order to solve the above problem, the present disclosure provides a system for controlling SOC balance of a cascaded energy storage system, including multiple control devices each being in connection with a corresponding one of energy storage modules in the cascaded energy storage system and independently controlling SOC balance of the corresponding one of energy storage modules, wherein for an energy storage module to be controlled, the corresponding one of the multiple control devices includes:
an output voltage reference generating module, configured to generate an output voltage reference with respect to the energy storage module to be controlled according to an acquired state of charge and output power of the energy storage module to be controlled;
a closed-loop control module, configured to generate a corresponding modulated reference signal based on the output voltage reference according to a closed-loop control strategy; and a pulse modulation module, configured to correspondingly generate a switching pulse signal according to the modulated reference signals, so as to adjust the state of charge of the energy storage module to be controlled through the switching pulse signal.
According to one embodiment of the present disclosure, when the energy storage modules in the cascaded energy storage system share a filter circuit, the output voltage reference generating module is configured to determine the output power of the energy storage module to be controlled according to an acquired current flowing through the filter circuit and a preset reference voltage corresponding to the energy storage module to be controlled.
According to one embodiment of the present disclosure, the output voltage reference generating module includes:
a phase angle reference generating unit, configured to determine an angular frequency reference of the output voltage according to the state of charge and output 5 power of the energy storage module to be controlled and generate a phase angle reference according to the angular frequency reference.
an amplitude reference generating unit, configured to determine the amplitude reference of the output voltage according to the voltage amplitude reference at a neutral point of the cascaded energy storage system; and a reference voltage generating unit, configured to generate an output voltage reference of the energy storage module to be controlled according to the phase angle reference and the amplitude reference of the output voltage.
According to one embodiment of the present disclosure, the amplitude reference 15 generating unit is configured to:
determine a weight reference of the voltage amplitude of the energy storage module to be controlled based on maximum power capacity of the cascaded energy storage system and maximum power capacity of the energy storage module to be controlled; and determine the amplitude reference of the output voltage of the energy storage module to be controlled based on the weight reference of the voltage amplitude and the voltage amplitude reference at a neutral point of the cascaded energy storage system.
According to one embodiment of the present disclosure, the amplitude reference generating unit is configured to determine the amplitude reference of the output voltage of the energy storage module to be controlled according to the following
equations: r=v(e7v'
30 <ρ(ε„._, )=/Σ £.»_.
wherein ' represents the amplitude reference of the output voltage of energy
storage module i, which is used as the energy storage module to be controlled, represents the weight reference of the voltage amplitude of energy storage module z, represents the voltage amplitude reference at the neutral point of the cascaded energy storage system, and
E V' E urax_, ancj 2-j max_/ respectively represent the maximum power capacity of the energy storage module i and the maximum power capacity of the cascaded energy storage system.
According to one embodiment of the present disclosure, the phase angle reference generating unit is configured to generate a correction term of an angular frequency of the energy storage module to be controlled according to the state of charge of the energy storage module to be controlled, generate the angular frequency reference of the energy storage module to be controlled according to the correction term of the angular frequency and the output power, and perform integration on the angular frequency reference to obtain the phase angle reference.
According to one embodiment of the present disclosure, the phase angle reference generating unit is configured to generate the correction term of the angular frequency of the energy storage module to be controlled according to the following equation:
Αω, =k,-SOC, wherein represents the correction term of the angular frequency of energy storage module z, ' represents a coefficient of the correction term of the angular frequency of energy storage module z, and
SOC ' represents the state of charge of energy storage module z.
According to one embodiment of the present disclosure, the coefficient of the correction term of the angular frequency of each energy storage module in the cascaded energy storage system is constant.
According to one embodiment of the present disclosure, the phase angle reference generating unit is configured to generate the angular frequency reference according to the following equation:
0, = 0* + sgn (Q,) (- Am,) wherein Θ' represents the angular frequency reference of energy storage module z, ω represents the angular frequency of energy storage module i with no load, and m' respectively represent reactive power and a coefficient of droop control of energy storage module z, p
j represents output power of energy storage module z, and ^a>' represents the correction term of the angular frequency of energy storage module z.
The present disclosure further provides a centralized large-capacity energy storage system, including a cascaded energy storage system and any of the above system for controlling SOC balance.
The system for controlling SOC balance in the cascaded energy storage system provided in the present disclosure is a distributed control system, and devices for controlling SOC balance corresponding to each energy storage module can control the SOC balance of the energy storage module merely by means of local information without communicating with other external devices. Therefore, compared with the existing system for controlling SOC balance, the cost of the present system is greatly reduced.
Other features and advantages of the present disclosure will be further explained in the following description, and will partly become self-evident therefrom, or be understood through the implementation of the present disclosure. The objectives and advantages of the present disclosure will be achieved through the structures specifically pointed out in the description, claims, and the accompanying drawings.
Brief Description of the Drawings
The accompanying drawings, together with the embodiments, are provided for a further understanding of the present disclosure, and constitute a part of the description, and are not intended to limit the present disclosure, wherein
Fig. 1 is a structural diagram of a cascaded energy storage system;
Fig. 2 is a structural diagram of a control device corresponding to energy storage module i according to one embodiment of the present disclosure;
Fig. 3 is a structural diagram of an output voltage reference generating module according to one embodiment of the present disclosure;
Fig. 4 and Fig. 5 are Ρ-ω curve graphs of two energy storage modules with the same maximum power capacity in different modes according to one embodiment of the present disclosure;
Fig. 6 is a block diagram of a simulation model of a cascaded energy storage system according to one embodiment of the present disclosure;
Fig. 7 to Fig. 10 are curve graphs of changes of SOC values and active power of each energy storage module when operating under four different modes in one embodiment of the present disclosure;
Fig. 11 and Fig. 12 are curve graphs of changes of SOC values and power of each energy storage module in one embodiment of the present disclosure when being switched between a charging mode and a discharging mode;
Fig. 13 is a curve graphs of changes of SOC and a power when load characteristics of an energy storage module in one embodiment of the present disclosure changes.
Detailed Description of the Embodiments
The present disclosure will be explained in detail below with reference to the accompanying drawings, so that the objective, technical solutions and advantages thereof can be understood more clearly. It should be noted that each embodiment and feature thereof can be combined each other if there is no conflict, and the technical solutions formed thereby are all fallen in the scope of the present disclosure.
In the meantime, many specifics are illustrated for purpose of interpretation, such that the embodiments of the present disclosure can be thoroughly understood. However, it is apparent for the ones skilled in the art that the present disclosure is not necessarily implemented by the specifics or particular manners described herein.
Aiming at the above problems existing in the prior art, the present disclosure provides a novel distributed system for controlling SOC balance of a cascaded energy storage system, and a centralized large-capacity energy storage system applying the same. The distributed system for controlling SOC balance can realize the SOC balance of the cascaded energy system without communications.
Fig. 1 is a structural diagram of a cascaded energy storage system. As shown in Fig. 1, the cascaded energy storage system can include N (N is greater than or equal to 2) cascaded energy storage modules (namely, energy storage module 1011 to energy storage module 10 I N) with a same structure. Each energy storage module is composed of an energy storage unit, a switching circuit and a filter circuit which are connected each other, wherein N energy storage modules are connected in series and then as a whole connected to a public bus via a feeder line, so that it can provide power for a load 102 through the public bus. Further, the public bus is connected with other types of micro power sources 103 (for example, photovoltaic power generation equipment or wind power generation equipment), such that the load 102 can get the power provided by these micro power sources.
In accordance with different load characteristics and different energy storage operating modes, the operating modes of a cascaded energy storage system can be divided into four types: quadrant I (a discharging mode and an inductive load), a quadrant II (a charging mode and an inductive load), a quadrant III (a charging mode and a capacitive load) and a quadrant IV (a discharging mode and a capacitive load).
The control system provided herein can realize SOC balance between each energy storage module in a cascaded energy storage system under four different modes, and can realize unified control of four different operating modes.
The system for controlling SOC balance of the cascaded energy storage system provided herein is a distributed control system, which includes multiple control devices with the same structure. Each control device is in connection with a corresponding one of energy storage modules in the cascaded energy storage system, and can independently control SOC balance of the corresponding energy storage module.
Since a structure and working principle of each control device in the system for controlling SOC balance are the same, in order to only one control device will be illustrated in more detail as an example for more clearly describing implementation concept and advantages of the system for controlling SOC balance provided herein.
Taking energy storage module i in the cascaded energy storage system as the energy storage module to be controlled, a control device corresponding to energy storage module i is control device i in the system for controlling SOC balance. Fig. 2 is a structural diagram of the control device in the embodiment.
As shown in Fig. 2, in the embodiment, control device 200 includes: an output voltage reference generating module 201, a closed-loop control module 202 and a pulse modulation module 203, wherein the output voltage reference generating module 201 can generate an output voltage reference of energy storage module 101_i to be controlled according to the acquired state of charge and output power of energy storage module 101_i to be controlled.
In the present embodiment, energy storage module 101_i to be controlled preferably includes an energy storage unit, a bridge switching circuit and a filter circuit. Output voltage reference generating module 201 preferably determines output power of energy storage module 101_i to be controlled according to the voltage and current of the filter circuit.
It should be noted that, in other embodiments of the present disclosure, output voltage reference generating module 201 can also determine the output power of energy storage module 101_i to be controlled by adopting other reasonable manners according to actual conditions, which is not limited herein. For example, in one embodiment, when the energy storage modules in a cascaded energy storage system have a filter circuit in common, output voltage reference generating module 201 can determine the output power of energy storage module 101_i to be controlled based on the acquired current flowing through the filter circuit and a preset voltage reference (for example, a nominal voltage) corresponding to energy storage module 101_i to be controlled.
Closed-loop control module 202, being connected with output voltage reference generating module 201, is configured to generate corresponding modulated reference signals based on a closed-loop control strategy and according to the output voltage reference, and transmit the modulated reference signals to pulse modulation module 203 which is connected therewith.
Pulse modulation module 203, being connected with the closed-loop control module and energy storage module 101_i to be controlled, is configured to generate corresponding switching pulse signals according to the modulated reference signals, so as to adjust the state of charge of energy storage module 10l i to be controlled by the switching pulse signals.
Specifically, in the present embodiment, pulse modulation module 203 preferably controls on/off state of controllable switches in a bridge switching circuit by switching pulse signals generated and output by the pulse modulation module itself, and thus realizing adjustment of the charge of state of the energy storage module.
Fig. 3 is a structural schematic diagram of an output voltage reference generating module 201 in the present embodiment.
As shown in Fig. 3, in the present embodiment, output voltage reference generating module 201 preferably includes: phase angle reference generating unit 301, amplitude reference generating unit 302 and voltage reference generating unit 303.
Phase angle reference generating unit 301, being connected with the energy storage unit in energy storage module 101_i to be controlled and the fdter circuit, can acquire
SOC the state of charge ' of energy storage module 101_i to be controlled through p detecting the energy storage unit, and the output power ' of energy storage module 101_i to be controlled through detecting voltage and current output from the fdter circuit.
SOC P
According to the state of charge ' and the output power ' of energy storage module 101_i to be controlled, phase angle reference generating unit 301 can determine angular frequency reference of the output voltage of energy storage module 101_i to be controlled and generate a phase angle reference of the output voltage according to the angular frequency reference.
Specifically, in the present embodiment, the phase angle reference generating unit 301 can generate a correction for angular frequency of energy storage module SOC
101_i to be controlled according to the state of charge ' of energy storage module 101_i to be controlled, and can further generate an angular frequency reference of energy storage module 101_i to be controlled according to the angular p frequency correction and the output power ' of energy storage module 101_i to be controlled.
For example, phase angle reference generating unit 301 is preferably configured to generate the correction for angular frequency of energy storage module 101_i to be controlled according to the following formula:
wherein represents the correction for angular frequency of energy storage module i (namely, the energy storage module to be controlled), and represents a coefficient of correction for the angular frequency of energy storage module i.
In the present embodiment, in order to control the balance of SOC, the coefficient of the correction for angular frequency correction terms of each energy storage module in the cascaded energy storage system should be preferably equal, namely, and the following formula should be satisfied:
A =ki =... = kN = K wherein N represents the total number of energy storage modules in the cascaded energy storage system, and K represents a positive constant.
In the present embodiment, the phase angle reference generating unit 301 preferably generates the angular frequency reference according to the following formula:
ω, = o* + sgn(Q)(m,P, - Αω,) (3) wherein ω' represents the angular frequency reference of energy storage module i, ω represents the angular frequency of energy storage module i with no A) /ƒ/ load, represents reactive power energy storage module i, and ' represents a droop control coefficient of energy storage module i.
It should be noted that, in order to ensure stable operation of the system, the droop control coefficient ' should preferably satisfy the following formula:
2arcsin i )\z-load\ < \^load (4) wherein · , and
- are respectively phase angle references of energy /9 7 ioa,> represents an impedance angle of a load, and l,,aJ storage module i, j, and k, represents an impedance modulus value of the load. It can be seen that, a smaller Kim, value easily enables the system to be stable. Therefore, in the present embodiment, selection of the value of the droop control coefficient 7 should refer to the value of k .
Of course, in other embodiments of the present disclosure, phase angle reference generating unit 301 can also determine the angular frequency reference 0' according to other reasonable manners, which is not limited herein.
After obtaining the angular frequency reference , phase angle reference generating unit 301 can perform integration on the angular frequency reference to β obtain the phase angle reference '.
Referring to Fig. 3 again, in the present embodiment, amplitude reference jy generating unit 302 can determine the amplitude reference ' of the output voltage of energy storage module to be controlled according to the voltage amplitude reference 1 at a neutral point of the cascaded energy storage system.
Specifically, in the present embodiment, amplitude reference generating unit 302 will preferably firstly determine a weight of the voltage amplitude reference of the energy storage module to be controlled according to the maximum power capacity of the cascaded energy storage system and the maximum power capacity of the energy storage module to be controlled, and then determine the amplitude reference of the output voltage of the storage module to be controlled energy according to the weight t r* of the voltage amplitude reference and the voltage amplitude reference y at the neutral point of the cascaded energy storage system.
Preferably, the amplitude reference generating unit 302 can determine the amplitude reference of the output voltage of the to-be-controlled energy storage module according to the following formulas:
(5) (6) wherein ! represents the amplitude reference of the output voltage of energy storage module i, ) represents the weight of the voltage amplitude reference
E VE of energy storage module i, and max-' and m/ respectively represent the maximum power capacity of energy storage module i and the maximum power capacity of the cascaded energy storage system.
Of course, in other embodiments of the present disclosure, amplitude reference generating unit 302 can also determine the amplitude reference ' of the output voltage of the energy storage module to be controlled according to other reasonable manners, which is not limited herein.
As shown in Fig. 3, in the present embodiment, reference voltage generating unit 303, being connected with phase angle reference generating unit 301 and amplitude reference generating unit 302, can generate an output voltage reference for energy storage module 101_i to be controlled according to the above phase angle reference ί ' and the amplitude reference '. Specifically, the output voltage reference can be represented as ' S*n .
Fig. 4 and Fig. 5 show Ρ-ω curves of two energy storage modules with the same maximum power capacity in different modes. Curve 1 represents an uncorrected Ρ-ω curve, curve 2 represents a Ρ-ω curve of an energy storage module with a larger SOC, and curve 3 represents a Ρ-ω curve of an energy storage module with a smaller SOC. It can be seen from Fig. 3 and Fig. 4 that, in a discharging mode, the unit capacity power output from the energy storage module with a larger SOC is greater than the unit capacity power output from the energy storage module with a smaller SOC, while in a charging mode, the unit capacity power input to the energy storage module with a larger SOC is greater than the unit capacity power input to the energy storage module with a smaller SOC.
Fig. 6 shows a simulation model of a cascaded energy storage system in the present embodiment. As shown in Fig. 6, the simulation model in the cascaded energy storage system includes three energy storage modules (the maximum power capacity of the three energy storage modules is the same), a common load and a line impedance. In the simulation model, the initial SOC values of the first energy storage module, the second energy storage module and the third energy storage module in a discharging mode are respectively 90%, 80% and 70%, and the initial SOC values in a charging mode are respectively 10%, 20% and 30%.
Fig. 7 to Fig. 10 respectively show curves of changes of SOC values and active power of each energy storage module in the cascaded energy storage system when operating in four operating modes including a quadrant I (a discharging mode and an inductive load), a quadrant II (a charging mode and an inductive load), a quadrant III (a charging mode and a capacitive load) and a quadrant IV (a discharging mode and a capacitive load).
It can be seen from Fig. 7 to Fig. 10 that, when the system for controlling SOC balance provided herein operates, the output active power and the SOC values of the energy storage module under the four-quadrant modes are gradually converged, an error ASOC of SOC and an error of power at the moment of 40s are approximately equal to 0. In this case, the cascaded energy storage system is in a steady state, and both the SOC values and the output power of the energy storage module are in balance. Therefore, it can be seen that the system for controlling SOC balance provided herein can enable the cascaded energy storage system to operate stably in four different modes, thereby realizing SOC balance between each energy storage module in the cascaded energy storage system and realizing equipartition of the active power.
Fig. 11 and Fig. 12 respectively show curves of changes of SOC values and power of each energy storage module in the cascaded energy storage system when each energy storage module is switched between a charging mode and a discharging mode, in which the curve in Fig. 11 represents changes during the switching from the discharging mode to the charging mode, and the curve in Fig. 12 represents changes during the switching from the charging mode to the discharging mode.
It can be seen from Fig. 11 and Fig. 12 that, no matter the mode is switched from discharging to charging or from charging to discharging, the output active power and SOC values of each energy storage module are gradually converged, and SOC errors and power errors before and after switching keep no change. Moreover, it can also be seen from the figures that, dynamic response of the energy storage module is rapid and overshoot is small during switching, and thus the system for controlling SOC balance has a favorable response performance.
Fig. 13 shows curves of changes of SOC and power when load characteristics of an energy storage module changes. It can be seen from Fig. 13 that, during switching of the load characteristic, the cascaded energy storage system initially operates under inductive load conditions, the load characteristics of the cascaded energy storage system are switched at the moment of 20s (namely, switching from an inductive load to a capacitive load). Before and after switching of the load characteristics, the SOC errors of an energy storage module are almost unchanged, and are continuously converged until finally the SOC balance between each energy storage module is realized.
Of course, in other embodiments of the present disclosure, according to actual requirements, the system for controlling SOC balance further includes other reasonable modules or devices, which is not limited herein. For example, in one embodiment of the present disclosure, the system for controlling SOC balance can further include an auxiliary service module, which is used to provide such auxiliary services as synchronous starting-up of the system and battery protection. In this way, the system can be started up synchronously and safely, and once one of energy storage modules cannot be operated safely, by-pass switches can be controlled to bypass the energy storage module.
It can be seen from the above description that, the system for controlling SOC balance of a cascaded energy storage system provided herein is a distributed control system, and the devices for controlling SOC balance corresponding to each energy storage module can realize control of SOC balance of the energy storage module merely via local information without depending on other external communications. Therefore, compared with the existing system for controlling SOC balance, the cost of the present system is greatly lowered.
Meanwhile, the system for controlling SOC balance provided by the present disclosure can ensure to realize SOC balance between each energy storage module in a cascaded energy storage system when the system operates in four different modes. Moreover, for the above four different operating modes, the control system can realize unified control.
Additionally, except for controlling SOC balance of each energy storage module in a cascaded energy storage system, the system for controlling SOC balance can also realize equipartition of active power of each energy storage module.
“One embodiment” or “embodiments” mentioned in the description indicate that specific features, structures, or characteristics are involved in at least one embodiment of the present disclosure. Therefore, the phrases “one embodiment” or “embodiments” in each place throughout the description do not always mean the same embodiment.
Although the above examples are intended for explaining a principle of the present disclosure in one or multiple applications, for the person skilled in the art, it is obvious to make various modifications to formations, usages, or details of implementation without departing away from the concept and idea of the present 15 disclosure on the condition that there is no need for inventive labors.

Claims (10)

CONCLUSIESCONCLUSIONS 1. Systeem voor het besturen van een SOC-balans van een cascadeenergieopslagsysteem, omvattende meerdere besturingsinrichtingen die elk in verbinding staan met een corresponderend exemplaar van de energieopslagmodules in het cascadeenergieopslagsysteem en onafhankelijk de SOC-balans van het corresponderende exemplaar van de energieopslagmodules besturen, waarbij, om een energieopslagmodule te besturen, het corresponderende exemplaar van de meerdere besturingsinrichtingen omvat:A system for controlling a SOC balance of a cascade energy storage system, comprising a plurality of control devices each connected to a corresponding copy of the energy storage modules in the cascade energy storage system and independently controlling the SOC balance of the corresponding copy of the energy storage modules, wherein, to control an energy storage module, the corresponding copy of the plurality of control devices comprises: een uitgangsspanningsreferentie genererende module, geconfigureerd om een uitgangsspanningsreferentie te genereren ten opzichte van de te besturen energieopslagmodule volgens een verkregen laadtoestand en uitgangsvermogen van de te besturen energieopslagmodule;an output voltage reference generating module configured to generate an output voltage reference relative to the energy storage module to be controlled according to a obtained charge state and output power of the energy storage module to be controlled; een gesloten-lusbesturingsmodule, geconfigureerd om een corresponderend gemoduleerd referentiesignaal te genereren, gebaseerd op de uitgangsspanningsreferentie volgens een gesloten-lusbesturingsstrategie; en een pulsmodulatiemodule, geconfigureerd om overeenkomstig een schakelpulssignaal volgens de gemoduleerde referentiesignalen te genereren, om de laadtoestand van de te besturen energieopslagmodule door middel van het schakelpulssignaal aan te passen.a closed loop control module configured to generate a corresponding modulated reference signal based on the output voltage reference according to a closed loop control strategy; and a pulse modulation module, configured to correspondingly generate a switching pulse signal according to the modulated reference signals, to adjust the charge state of the energy storage module to be controlled by means of the switching pulse signal. 2. Systeem volgens conclusie 1, waarbij wanneer de energieopslagmodules in het cascade-energieopslagsysteem een gezamenlijk filtercircuit hebben, de uitgangsspanningsreferentie-genererende module is geconfigureerd om het uitgangsvermogen van de te besturen energieopslagmodule te bepalen volgens een verkregen stroom die door het filtercircuit vloeit en een vooraf ingestelde referentiespanning corresponderend met de te besturen energieopslagmodule.The system of claim 1, wherein when the energy storage modules in the cascade energy storage system have a common filter circuit, the output voltage reference generating module is configured to determine the output power of the energy storage module to be controlled according to a obtained current flowing through the filter circuit and a predetermined current set reference voltage corresponding to the energy storage module to be controlled. 3. Systeem volgens conclusie 1 of 2, waarbij de uitgangsspanningsreferentiegenererende module omvat:The system of claim 1 or 2, wherein the output voltage reference generating module comprises: een fasehoekreferentie-genererende eenheid, geconfigureerd om een hoekfrequentiereferentie van de uitgangsspanning te bepalen volgens de laadtoestand en het uitgangsvermogen van de te besturen energieopslagmodule, en om een fasehoekreferentie te genereren volgens de hoekfrequentiereferentie;a phase angle reference generating unit configured to determine an angular frequency reference of the output voltage according to the charging state and the output power of the energy storage module to be controlled, and to generate a phase angular reference according to the angular frequency reference; een amplitudereferentie-genererende eenheid, geconfigureerd om een amplitudereferentie van de uitgangsspanning te bepalen volgens de spanningsamplitudereferentie op een neutraal punt van het cascade-energieopslagsysteem; enan amplitude reference generating unit configured to determine an amplitude reference of the output voltage according to the voltage amplitude reference at a neutral point of the cascade energy storage system; and - 18een referentiespanning-genererende eenheid, geconfigureerd om een uitgangsspanningsreferentie van de te besturen energieopslagmodule te bepalen volgens de fasehoekreferentie en de amplitudereferentie van de uitgangsspanning.18 a reference voltage generating unit configured to determine an output voltage reference of the energy storage module to be controlled according to the phase angle reference and the amplitude reference of the output voltage. 4. Systeem volgens conclusie 3, waarbij de amplitudereferentie-genererende eenheid is geconfigureerd om:The system of claim 3, wherein the amplitude reference generating unit is configured to: een gewichtsreferentie van de spanningsamplitude van de te besturen energieopslagmodule te bepalen, gebaseerd op maximale vermogenscapaciteit van de cascade-energieopslagsysteem en maximum vermogenscapaciteit van de te besturen energieopslagmodule; en de amplitudereferentie van de uitgangsspanning van de te besturen energieopslagmodule te bepalen, gebaseerd op de gewichtsreferentie van de spanningsamplitude en de spanningsamplitudereferentie op het neutrale punt van het cascade-energieopslagsysteem.determine a weight reference of the voltage amplitude of the energy storage module to be controlled, based on maximum power capacity of the cascade energy storage system and maximum power capacity of the energy storage module to be controlled; and determine the amplitude reference of the output voltage of the energy storage module to be controlled based on the weight reference of the voltage amplitude and the voltage amplitude reference at the neutral point of the cascade energy storage system. 5. Systeem volgens conclusie 4, waarbij de amplitudereferentie-genererende eenheid is geconfigureerd om de amplitudereferentie van de uitgangsspanning van de te besturen energieopslagmodule te bepalen volgens de volgende vergelijkingen:The system of claim 4, wherein the amplitude reference generating unit is configured to determine the amplitude reference of the output voltage of the energy storage module to be controlled according to the following equations: waarbij de amplitudereferentie van de uitgangsspanning van energieopslagmodule i representeert, welke als de te besturen energieopslagmodule wordt gebruikt, c(Amaxde gewichtsreferentie van de spanningsamplitude van energieopslagmodule i representeert,wherein represents the amplitude reference of the output voltage of power storage module i, comprising as to control the energy storage module is used, c (A max e d by weight of reference is representative of the voltage amplitude of the energy storage module i, F de spanningsamplitudereferentie op het neutrale punt van het cascadeenergieopslagsysteem representeert, enF represents the voltage amplitude reference at the neutral point of the cascade energy storage system, and E ΎΕ max-' respectievelijk ,nax~' de maximale vermogenscapaciteit van de energieopslagmodule i en de maximale vermogenscapaciteit van het cascadeenergieopslagsysteem representeren.E ΎΕ max - ' , nax ~' respectively represent the maximum power capacity of the energy storage module i and the maximum power capacity of the cascade energy storage system. 6. Systeem volgens een van de conclusies 3 tot en met 5, waarbij de fasehoekreferentie-genererende eenheid is geconfigureerd om een correctieterm van een hoekfrequentie van de te besturen energieopslagmodule te genereren volgens de laadtoestand van de te besturen energieopslagmodule, de hoekfrequentiereferentie van de te besturen energieopslagmodule te genereren volgens de correctieterm van de hoekfrequentie en het uitgangsvermogen, en integratie op de hoekfrequentiereferentie uit te voeren om de fasehoekreferentie te verkrijgen.The system according to any of claims 3 to 5, wherein the phase angle reference generating unit is configured to generate a correction term of an angular frequency of the energy storage module to be controlled according to the loading state of the energy storage module to be controlled, the angular frequency reference of the energy storage module to be controlled generate energy storage module according to the angular frequency and output power correction term, and perform integration on the angular frequency reference to obtain the phase angular reference. 7. Systeem volgens conclusie 6, waarbij de fasehoekreferentie-genererende eenheid is geconfigureerd om de correctieterm van de hoekfrequentie van de te besturen energieopslagmodule te genereren volgens de volgende vergelijking:The system of claim 6, wherein the phase angle reference generating unit is configured to generate the angular frequency correction term of the energy storage module to be controlled according to the following equation: Δλλ = k: SOCt waarbij de correctieterm van de hoekfrequentie van energieopslagmodule i representeert, een coëfficiënt van de correctieterm van de hoekfrequentie van energieopslagmodule i representeert, en ynr ' de laadtoestand van energieopslagmodule i representeert.Δλλ = k : SOC t where the correction term of the angular frequency of energy storage module i represents a coefficient of the correction term of the angular frequency of energy storage module i, and ynr 'represents the loading state of energy storage module i. 8. Systeem volgens conclusie 7, waarbij de coëfficiënt van de correctieterm van de hoekfrequentie van elke energieopslagmodule in het cascade-energieopslagsysteem constant is.The system of claim 7, wherein the coefficient of the angular frequency correction term of each energy storage module in the cascade energy storage system is constant. 9. Systeem volgens een van conclusies 6 tot en met 8, waarbij de fasehoekreferentiegenererende eenheid is geconfigureerd om de hoekfrequentiereferentie te genereren volgens de volgende vergelijking:The system of any of claims 6 to 8, wherein the phase angle reference generating unit is configured to generate the angular frequency reference according to the following equation: <j)t = 0’ + sgn (Q) (mfi - Αω,) waarbij ω· de hoekfrequentiereferentie van energieopslagmodule i representeert, ω de hoekfrequentie van onbelaste energieopslagmodule i representeert, ö respectievelijk m< reactief vermogen en een coëfficiënt van droopbesturing van energieopslagmodule i representeert, p<j) t = 0 '+ sgn (Q) (mfi - Αω,) where ω · represents the angular frequency reference of energy storage module i, ω represents the angular frequency of unloaded energy storage module i, ö respectively m <reactive power and a coefficient of droop control of energy storage module i represents, p i het uitgangsvermogen van energieopslagmodule i representeert, en de correctieterm van de hoekfrequentie van energieopslagmodule i representeert. i represents the output power of energy storage module i, and represents the correction term of the angular frequency of energy storage module i. 10. Gecentraliseerd energieopslagsysteem met grote capaciteit, omvattende een cascade-energieopslagsysteem, en het systeem voor het besturen van de SOC-balans volgens een van conclusies 1 tot en met 9.A large capacity centralized energy storage system comprising a cascade energy storage system, and the SOC balance control system according to any of claims 1 to 9. Public busPublic bus
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