CN109067003B - SOC balance control system for cascade energy storage system - Google Patents
SOC balance control system for cascade energy storage system Download PDFInfo
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- CN109067003B CN109067003B CN201810923122.6A CN201810923122A CN109067003B CN 109067003 B CN109067003 B CN 109067003B CN 201810923122 A CN201810923122 A CN 201810923122A CN 109067003 B CN109067003 B CN 109067003B
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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
- H02J15/00—Systems for storing electric energy
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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
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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
- 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
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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
- H02J7/0019—Circuits for equalisation of charge between batteries using switched or multiplexed charge circuits
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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
- H02J7/0068—Battery or charger load switching, e.g. concurrent charging and load supply
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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
- H02J7/0047—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]
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Abstract
The SOC balance control system for the cascade energy storage system comprises a plurality of control devices with the same structure, wherein each control device is connected with each energy storage module in the cascade energy storage system in a one-to-one correspondence mode and can independently perform SOC balance control on the corresponding energy storage modules. The system is a distributed control system, the SOC balance control device corresponding to each energy storage module can realize SOC balance control on the energy storage module only through local information, and other external communication is not required. Therefore, compared with the conventional SOC balance control system, the system has the advantage that the cost is greatly reduced.
Description
Technical Field
The invention relates to the technical field of power electronics, in particular to an SOC balance control system and a centralized high-capacity energy storage system for a cascade energy storage system.
Background
In the application of energy storage engineering, in order to enable an energy storage system to be charged and discharged simultaneously so as to increase the service life of the energy storage system, the State of Charge (SOC) of each energy storage module needs to be balanced. The SOC imbalance among the energy storage modules of the system can be caused by different initial SOCs of the system, different output powers during operation and the like, so that the individual energy storage modules are overcharged or overdischarged, and the service life of the energy storage modules and the system efficiency are further reduced.
With the continuous improvement of people's consciousness on sustainable development of energy and environmental protection, renewable energy and electric vehicles have been vigorously developed, and the traditional small-capacity energy storage system has been unable to meet the current demand. With the continuous expansion of the energy storage scale, the value of the cascade energy storage system is accepted by the market in medium and high voltage application occasions. The voltage of a single energy storage unit is low, and a higher voltage level can be directly obtained in the form of cascading inverters without expensive and bulky transformers. Simultaneously, every energy storage module can both be controlled alone for it is more convenient to manage each energy storage unit.
At present, SOC balance control methods for a cascade energy system all depend on high-bandwidth centralized communication, and as the number of energy storage modules increases, on one hand, the cost of communication bandwidth also increases continuously, and on the other hand, the robustness of the system is greatly reduced under the conditions of communication packet loss, communication failure and the like.
Disclosure of Invention
In order to solve the above problems, the present invention provides an SOC balance control system for a cascaded energy storage system, wherein the system includes a plurality of control devices having the same structure, each control device is connected to each energy storage module in the cascaded energy storage system in a one-to-one correspondence manner and can independently perform SOC balance control on the corresponding energy storage module, and for an energy storage module to be controlled, the corresponding control device includes:
the output voltage reference value generating module is used for generating an output voltage reference value aiming at the energy storage module to be controlled according to the acquired state of charge and output power of the energy storage module to be controlled;
a closed-loop control module for generating a corresponding modulation reference signal from the output voltage reference value based on a closed-loop control strategy;
and the pulse modulation module is used for generating a corresponding switching pulse signal according to the modulation reference signal so as to adjust the charge state of the energy storage module to be controlled through the switching pulse signal.
According to an embodiment of the invention, when the energy storage modules in the cascaded energy storage system share the filter circuit, the output voltage reference value generation module is configured to determine the output power of the energy storage module to be controlled according to the acquired current flowing through the filter circuit and a preset reference voltage corresponding to the energy storage module to be controlled.
According to an embodiment of the invention, the output voltage reference generation module comprises:
the phase angle reference value generating unit is used for determining an angular frequency reference value of the output voltage according to the state of charge and the output power of the energy storage module to be controlled and generating a phase angle reference value of the output voltage according to the angular frequency reference value;
the amplitude reference value generating unit is used for determining an amplitude reference value of the output voltage according to a voltage amplitude reference value at a common point of the cascade energy storage system;
and the reference voltage generating unit is used for generating an output voltage reference value of the energy storage module to be controlled according to the phase angle reference value and the amplitude reference value of the output voltage.
According to an embodiment of the invention, the amplitude reference value generation unit is configured to:
determining a voltage amplitude reference weight of the energy storage module to be controlled according to the maximum electric energy capacity of the cascade energy storage system and the maximum electric energy capacity of the energy storage module to be controlled;
and determining the amplitude reference value of the output voltage of the energy storage module to be controlled according to the voltage amplitude reference weight and the voltage amplitude reference value at the common point of the cascade energy storage system.
According to an embodiment of the present invention, the amplitude reference value generating unit is configured to determine the amplitude reference value of the output voltage of the energy storage module to be controlled according to the following expression:
wherein, ViThe amplitude reference value of the output voltage of the ith energy storage module is represented, the ith energy storage module is used as the energy storage module to be controlled,representing the voltage amplitude reference weight, V, of the ith energy storage module*Representing a reference value, E, representing the voltage amplitude at a common point of the cascaded energy storage systemmax_iAnd ∑ Emax_iRespectively represents the ith energy storage module and the cascade energy storage systemThe maximum power capacity of the system.
According to an embodiment of the present invention, the phase angle reference value generating unit is configured to generate an angular frequency correction term of the energy storage module to be controlled according to a state of charge of the energy storage module to be controlled, generate an angular frequency reference value of the energy storage module to be controlled according to the angular frequency correction term and an output power, and obtain the phase angle reference value by integrating the angular frequency reference value.
According to an embodiment of the present invention, the phase angle reference value generating unit is configured to generate an angular frequency correction term of the energy storage module to be controlled according to the following expression:
Δωi=ki·SOCi
wherein, Δ ωiRepresenting the angular frequency correction term, k, of the ith energy storage moduleiCorrection coefficient, SOC, representing an angular frequency correction term for the ith energy storage moduleiIndicating the state of charge of the ith energy storage module.
According to one embodiment of the invention, the correction coefficients of the angular frequency correction terms of the energy storage modules in the cascaded energy storage system are all equal.
According to an embodiment of the present invention, the phase angle reference value generation unit is configured to generate the angular frequency reference value according to the following expression:
ωi=ω*+sgn(Qi)(miPi-Δωi)
wherein, ω isiRepresenting the angular frequency reference, ω, of the ith energy storage module*Representing the angular frequency, Q, of the ith energy storage module at no loadiAnd miRespectively representing the reactive power and the droop control coefficient, P, of the ith energy storage moduleiRepresenting the output power, Δ ω, of the ith energy storage moduleiRepresenting the angular frequency correction term for the ith energy storage module.
The invention also provides a centralized high-capacity energy storage system which is characterized by comprising a cascade energy storage system and the SOC balance control system.
The SOC balance control system for the cascade energy storage system is a distributed control system, the SOC balance control device corresponding to each energy storage module can realize SOC balance control on the energy storage module only through local information, and other external communication is not needed. Therefore, compared with the conventional SOC balance control system, the system has the advantage that the cost is greatly reduced.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required in the description of the embodiments or the prior art:
FIG. 1 is a schematic diagram of a cascaded energy storage system;
FIG. 2 is a schematic structural diagram of a control device for an ith energy storage switch according to an embodiment of the invention;
FIG. 3 is a block diagram of an output voltage reference generation module according to an embodiment of the invention;
fig. 4 and 5 are schematic P- ω curves of two energy storage modules of the same maximum power capacity in different modes according to an embodiment of the invention;
FIG. 6 is a schematic diagram of a simulation model of a cascaded energy storage system according to an embodiment of the invention;
fig. 7 to 10 are schematic diagrams of SOC values and active power variation curves of each energy storage module operating in four different modes according to an embodiment of the present invention;
fig. 11 to 12 are schematic diagrams of SOC variation curves and power variation curves of the energy storage modules under charging and discharging switching according to an embodiment of the invention;
fig. 13 is a schematic diagram of an SOC conversion curve and a power change curve when the load characteristics of the energy storage module are switched according to an embodiment of the invention.
Detailed Description
The following detailed description of the embodiments of the present invention will be provided with reference to the drawings and examples, so that how to apply the technical means to solve the technical problems and achieve the technical effects can be fully understood and implemented. It should be noted that, as long as there is no conflict, the embodiments and the features of the embodiments of the present invention may be combined with each other, and the technical solutions formed are within the scope of the present invention.
In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without some of these specific details or with other methods described herein.
Aiming at the problems in the prior art, the invention provides a novel distributed SOC balance control system aiming at a cascade energy storage system and a centralized large-capacity energy storage system applying the distributed SOC balance control system, wherein the distributed SOC balance control system can realize SOC balance of the cascade energy storage system under the condition of no communication.
Fig. 1 shows a schematic diagram of a cascaded energy storage system. As shown in fig. 1, the cascaded energy storage system may include N (N is greater than or equal to 2) cascaded energy storage modules having the same structure (i.e., the first energy storage module 101_1 to the nth energy storage module 101_ N). Each energy storage module is formed by connecting an energy storage unit, a conversion circuit and a filter circuit, and N energy storage modules are connected in series and then are connected to a common bus through a feeder line, and the common bus supplies electric energy to the load 102. Wherein the common bus bar is also connected to other types of micro sources 103, such as photovoltaic power plants or wind power plants, for obtaining the electrical energy provided by these micro sources.
According to the difference between the load characteristic and the energy storage working mode, the working operation mode of the cascade energy storage system can be divided into four types: the control system provided by the invention can realize SOC balance among the energy storage modules in the cascade energy storage system in four different modes, and can realize unified control for four different operation modes.
The SOC balance control system for the cascade energy storage system is a distributed control system, and comprises a plurality of control devices with the same structure, wherein each control device is connected with each energy storage module in the cascade energy storage system in a one-to-one correspondence mode. Wherein, these controlling means can carry out SOC balance control to corresponding energy storage module independently.
Since the structure and the operation principle of each control device in the SOC balance control system are the same, in order to more clearly illustrate the implementation principle and the advantages of the SOC balance control system provided by the present invention, the following will further illustrate one of the control devices as an example.
Taking the ith energy storage module in the cascade energy storage system as the energy storage module to be controlled, the control device corresponding to the energy storage module is the ith control device in the SOC balance control system, and fig. 2 shows a schematic structural diagram of the control device in this embodiment.
As shown in fig. 2, in the present embodiment, the control device 200 includes: an output voltage reference generation module 201, a closed loop control module 202, and a pulse modulation module 203. The output voltage reference value generating module 201 can generate an output voltage reference value for the energy storage module to be controlled 101_ i according to the acquired state of charge and the acquired output power of the energy storage module to be controlled 101_ i.
In this embodiment, the energy storage module to be controlled 101_ i preferably includes: the circuit comprises an energy storage unit, a bridge type conversion circuit and a filter circuit. The output voltage reference value generation module 201 determines the output power of the energy storage module 101_ i to be controlled according to the voltage and the current flowing through the filter circuit.
It should be noted that in other embodiments of the present invention, the output voltage reference value generating module 201 also determines the output power of the energy storage module 101_ i to be controlled in other reasonable manners according to actual situations, which is not limited to this. For example, in an embodiment of the present invention, when the energy storage modules in the cascaded energy storage system share a filter circuit, the output voltage reference value generating module 201 may determine the output power of the energy storage module to be controlled 101_ i according to the acquired current flowing through the filter circuit and a preset reference voltage (e.g., a rated voltage) corresponding to the energy storage module to be controlled 101_ i.
The closed-loop control module 202 is connected to the output voltage reference value generation module 201, and is capable of generating a corresponding modulation reference signal according to the output voltage reference value based on a closed-loop control strategy, and transmitting the modulation reference signal to the pulse modulation module 203 connected thereto.
The pulse modulation module 203 is connected to the closed-loop control module and the energy storage module to be controlled 101_ i, and is configured to generate a corresponding switching pulse signal according to the modulation reference signal, so as to adjust the state of charge of the energy storage module to be controlled 101_ i through the switching pulse signal.
Specifically, in this embodiment, the pulse modulation module 203 preferably controls the on-off state of the controllable switching tube in the bridge conversion circuit with the switching pulse signal generated and output by itself, so as to adjust the state of charge of the energy storage module.
Fig. 3 shows a schematic structural diagram of the output voltage reference value generation module 201 in this embodiment.
As shown in fig. 3, in the present embodiment, the output voltage reference value generating module 201 preferably includes: a phase angle reference value generation unit 301, a magnitude reference value generation unit 302, and a reference voltage generation unit 303. The phase angle reference value generation unit 301 is connected to the energy storage unit and the filter circuit in the energy storage module to be controlled 101_ i, and can acquire the state of charge SOC of the energy storage module to be controlled 101_ i by detecting the energy storage unitiMeanwhile, the output power P of the energy storage module 101_ i to be controlled can be obtained by detecting the output voltage and the output current of the filter circuiti。
According to the state of charge SOC of the energy storage module 101_ i to be controllediAnd output powerPiThe phase angle reference value generation unit 301 can determine an angular frequency reference value of the output voltage of the energy storage module to be controlled 101_ i, and generate a phase angle reference value of the output voltage according to the angular frequency reference value.
Specifically, in this embodiment, the phase angle reference value generation unit 301 can generate the phase angle reference value according to the state of charge SOC of the energy storage module 101_ i to be controllediGenerating an angular frequency correction term of the energy storage module to be controlled 101_ i, and then generating an output power P of the energy storage module to be controlled 101_ i according to the angular frequency correction term and the output power PiAnd generating an angular frequency reference value of the energy storage module 101_ i to be controlled.
For example, the phase angle reference value generation unit 301 is preferably configured to generate an angular frequency correction term for the energy storage module to be controlled 101 — i according to the following expression:
Δωi=ki·SOCi(1)
wherein, Δ ωiRepresenting the angular frequency correction term, k, of the ith energy storage module (i.e. the energy storage module to be controlled)iAnd a correction coefficient representing an angular frequency correction term of the ith energy storage module.
In this embodiment, in order to control the SOC balance, the correction coefficients of the angular frequency correction terms of the energy storage modules in the cascaded energy storage system are preferably all equal. Namely, the existence of:
k1=k2=...=kN=K (2)
wherein N represents the total number of energy storage modules included in the cascaded energy storage system, and K represents a normal number.
In the present embodiment, the phase angle reference value generation unit 301 preferably generates the angular frequency reference value according to the following expression:
ωi=ω*+sgn(Qi)(miPi-Δωi) (3)
wherein, ω isiRepresenting the angular frequency reference, ω, of the ith energy storage module*Representing the angular frequency, Q, of the ith energy storage module at no loadiRepresenting the reactive power of the i-th energy storage module, miAnd the droop control coefficient of the ith energy storage module is shown.
Need to make sure thatNote that, in order to ensure stable operation of the system, the droop control coefficient miThe following conditions preferably need to be satisfied:
wherein, thetai、θjAnd thetakThe phase angle reference values theta of the ith, j and k energy storage modules respectivelyloadRepresenting the impedance angle, Z, of the loadloadRepresenting the load impedance modulus. From this, a smaller K/miThe value makes it easier to stabilize the system, so in this embodiment, the droop control coefficient m is selectediIn the process of taking the value, the value of K needs to be referred to.
Of course, in other embodiments of the present invention, the phase angle reference value generating unit 301 may also determine the angular frequency reference value ω according to other reasonable mannersiThe present invention is not limited thereto.
After obtaining the angular frequency reference value omegaiThen, the phase angle reference value generating unit 301 may obtain the phase angle reference value by integrating the angular frequency reference valuei。
As shown in fig. 3 again, in the present embodiment, the amplitude reference value generating unit 302 can generate the amplitude reference value V according to the voltage at the common point of the cascaded energy storage systems*To determine the amplitude reference value V of the output voltage of the energy storage module to be controlledi。
Specifically, in this embodiment, the amplitude reference value generating unit 302 preferably determines a voltage amplitude reference weight of the energy storage module to be controlled according to the maximum electric energy capacity of the cascaded energy storage system and the maximum electric energy capacity of the energy storage module to be controlled, and then determines a voltage amplitude reference value V at a common point of the cascaded energy storage system according to the voltage amplitude reference weight and the voltage amplitude reference value V at the common point of the cascaded energy storage system*And determining the amplitude reference value of the output voltage of the energy storage module to be controlled.
Preferably, the amplitude reference value generating unit 302 may determine the amplitude reference value of the output voltage of the energy storage module to be controlled according to the following expression:
wherein, ViA magnitude reference value representing the output voltage of the ith energy storage module,representing the voltage amplitude reference weight of the ith energy storage module, Emax_iAnd ∑ Emax_iAnd respectively representing the maximum electric energy capacity of the ith energy storage module and the maximum electric energy capacity of the cascade energy storage system.
Of course, in other embodiments of the present invention, the amplitude reference value generating unit 302 may also determine the amplitude reference value V of the output voltage of the energy storage module to be controlled by using other association methodsiThe present invention is not limited thereto.
As shown in fig. 3, in the present embodiment, the reference voltage generating unit 303 is connected to a phase angle reference value generating unit 301 and a magnitude reference value generating unit 302, which can generate a reference voltage according to the phase angle reference valueiAnd an amplitude reference value ViAn output voltage reference value for the energy storage module 101_ i to be controlled is generated. In particular, the output voltage reference value may be denoted as Visini。
Fig. 4 and 5 show the P- ω curves for two energy storage modules of the same maximum power capacity in different modes. Wherein curve 1 represents the uncorrected P- ω curve, curve 2 represents the P- ω curve for the energy storage module with the larger SOC, and curve 3 represents the P- ω curve for the energy storage module with the smaller SOC. As can be seen from fig. 3 and 4, in the discharging mode, the output power per unit capacity of the energy storage module with the larger SOC is larger than that of the energy storage module with the smaller SOC. And in the charging mode, the unit capacity absorbed power of the energy storage module with the larger SOC is smaller than that of the energy storage module with the smaller SOC.
Fig. 6 shows a simulation model of the cascade energy storage system in the present embodiment. As shown in fig. 6, the simulation model of the cascaded energy storage system includes 3 energy storage modules (the maximum power capacities of the 3 energy storage modules are 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 the discharging mode are respectively 90%, 80% and 70%, and the initial SOC values in the charging mode are respectively 10%, 20% and 30%.
Fig. 7 to fig. 10 respectively show SOC values and active power variation curves of the cascaded energy storage system when each energy storage module operates in four operation modes of quadrant I (discharge mode and load is inductive load), quadrant II (charge mode and load is inductive load), quadrant III (charge mode and load is capacitive load), and quadrant IV (discharge mode and load is capacitive load).
As can be seen from fig. 7 to 10, when the SOC balance control system provided in this embodiment operates, the output active power and the SOC value of the energy storage module in the four-quadrant mode gradually converge, and the SOC error Δ SOC and the power error both approximately equal to 0 at the time of 40 s. At the moment, the cascade energy storage system reaches a steady state, and the SOC value and the output power of the energy storage module reach balance. Therefore, the SOC balance control system provided by the embodiment can enable the cascade energy storage system to stably operate in four different modes, and active power is evenly distributed while SOC balance among the energy storage modules in the cascade energy storage system is achieved.
Fig. 11 and 12 show an SOC value variation curve and a power variation curve of each energy storage module in the cascaded energy storage system during charging and discharging switching, respectively. Fig. 11 shows switching from discharging to charging, and fig. 12 shows switching from charging to discharging.
As can be seen from fig. 11 and 12, regardless of whether the switching is from discharging to charging or from charging to discharging, the output active power and the SOC value of each energy storage module gradually converge, and the SOC error and the power error before and after the switching are almost unchanged. Meanwhile, the dynamic response of the energy storage module in the switching process is fast and the overshoot is small as can be seen from the figure, so that the SOC balance control system has good response performance.
Fig. 13 shows the SOC conversion curve and the power change curve at the time of switching the load characteristics of the energy storage module. As can be seen from fig. 13, during the load switching process, the load characteristics of the cascaded energy storage system initially operating under the inductive load condition are changed at 20s (i.e., the inductive load is switched to the capacitive load). The SOC error of the energy storage modules remains almost unchanged before and after the load characteristic switching, and the convergence continues to be maintained, and finally the SOC balance between the respective energy storage modules can be reached.
Of course, in other embodiments of the present invention, the SOC balancing control system further includes other reasonable modules or devices according to actual needs, and the present invention is not limited thereto. For example, in an embodiment of the present invention, the SOC balance control system may further include an auxiliary service module, where the auxiliary service module may implement auxiliary services such as system synchronous start and battery safety protection, so as to ensure that the system can be started synchronously and safely, and on the other hand, a corresponding bypass switch may be controlled to bypass an energy storage module when the energy storage module cannot run safely.
As can be seen from the above description, the SOC balance control system for the cascaded energy storage system provided by the present invention is a distributed control system, and the SOC balance control device corresponding to each energy storage module can realize SOC balance control of the energy storage module only through local information, without relying on other external communication. Therefore, compared with the conventional SOC balance control system, the system has the advantage that the cost is greatly reduced.
Meanwhile, the SOC balance control system provided by the invention can ensure that the SOC balance of each energy storage module in the cascade energy storage system can be realized under four different working modes. And for the four different operation modes, the control system can realize unified control.
In addition, the SOC balance control system can realize the active power uniform division of each energy storage module besides realizing the SOC balance control of each energy storage module in the cascade energy storage system.
Reference in the specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Thus, the appearances of the phrase "one embodiment" or "an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment.
While the above examples are illustrative of the principles of the present invention in one or more applications, it will be apparent to those of ordinary skill in the art that various changes in form, usage and details of implementation can be made without departing from the principles and concepts of the invention. Accordingly, the invention is defined by the appended claims.
Claims (8)
1. The utility model provides a SOC balance control system to cascade energy storage system which characterized in that, the system includes the same controlling means of a plurality of structures, and each controlling means is connected and can independently carry out SOC balance control to the energy storage module that corresponds with each energy storage module one-to-one in the cascade energy storage system respectively, and to an energy storage module that awaits control, its controlling means that corresponds includes:
the output voltage reference value generating module is used for generating an output voltage reference value aiming at the energy storage module to be controlled according to the acquired state of charge and output power of the energy storage module to be controlled;
a closed-loop control module for generating a corresponding modulation reference signal from the output voltage reference value based on a closed-loop control strategy;
the pulse modulation module is used for generating a corresponding switching pulse signal according to the modulation reference signal so as to adjust the charge state of the energy storage module to be controlled through the switching pulse signal;
the simulation model verification module is used for verifying the charge state and the power change of the cascade energy storage system in multiple operation modes through a simulation model of the cascade energy storage system; the operation mode comprises a cascade energy storage system load characteristic switching working condition;
the output voltage reference generation module further comprises:
a phase angle reference value generation unit for generating a phase angle reference value based on the phase angleDetermining an angular frequency reference value of output voltage by combining the charge state and the output power of the energy storage module to be controlled with a droop control coefficient of the energy storage module to be controlled, and generating a phase angle reference value of the output voltage according to the angular frequency reference value; wherein the droop control coefficient miThe following conditions are satisfied:
in the formula, thetai、θjAnd thetakThe phase angle reference values theta of the ith, j and k energy storage modules respectivelyloadRepresenting the impedance angle, Z, of the loadloadRepresenting a load impedance modulus value; SOCiAnd SOCkRespectively representing the charge states of the ith energy storage module and the kth energy storage module, N representing the total number of the energy storage modules in the cascade energy storage system, K representing the correction coefficient of an angular frequency correction term of the energy storage modules, and miThe droop control coefficient of the ith energy storage module is shown, and K/m is set according to the requirementiTaking a preset value to stabilize the system;
the amplitude reference value generating unit is used for determining an amplitude reference value of the output voltage according to the voltage amplitude reference weight of the energy storage module to be controlled and the voltage amplitude reference value at the common point of the cascade energy storage system;
the amplitude reference value generating unit is configured to determine an amplitude reference value of the output voltage of the energy storage module to be controlled according to the following expression:
wherein, ViThe amplitude reference value of the output voltage of the ith energy storage module is represented, the ith energy storage module is used as the energy storage module to be controlled,representing the voltage amplitude reference weight, V, of the ith energy storage module*Representing a reference value, E, representing the voltage amplitude at a common point of the cascaded energy storage systemmax_iAnd ∑ Emax_iRespectively representing the maximum electric energy capacity of the ith energy storage module and the maximum electric energy capacity of the cascade energy storage system;
and the reference voltage generating unit is used for generating an output voltage reference value of the energy storage module to be controlled according to the phase angle reference value and the amplitude reference value of the output voltage.
2. The system according to claim 1, wherein when the energy storage modules in the cascaded energy storage system share the filter circuit, the output voltage reference value generation module is configured to determine the output power of the energy storage module to be controlled according to the acquired current flowing through the filter circuit and a preset reference voltage corresponding to the energy storage module to be controlled.
3. The system of claim 1, wherein the magnitude reference generation unit is configured to:
determining a voltage amplitude reference weight of the energy storage module to be controlled according to the maximum electric energy capacity of the cascade energy storage system and the maximum electric energy capacity of the energy storage module to be controlled;
and determining the amplitude reference value of the output voltage of the energy storage module to be controlled according to the voltage amplitude reference weight and the voltage amplitude reference value at the common point of the cascade energy storage system.
4. The system according to any one of claims 1 to 3, wherein the phase angle reference value generation unit is configured to generate an angular frequency correction term of the energy storage module to be controlled according to the state of charge of the energy storage module to be controlled, generate an angular frequency reference value of the energy storage module to be controlled according to the angular frequency correction term and the output power, and obtain the phase angle reference value by integrating the angular frequency reference value.
5. The system according to claim 4, wherein the phase angle reference value generation unit is configured to generate an angular frequency correction term for the energy storage module to be controlled according to the following expression:
Δωi=ki·SOCi
wherein, Δ ωiRepresenting the angular frequency correction term, k, of the ith energy storage moduleiCorrection coefficient, SOC, representing an angular frequency correction term for the ith energy storage moduleiIndicating the state of charge of the ith energy storage module.
6. The system of claim 5, wherein the correction factors for the angular frequency correction terms of each energy storage module in the cascaded energy storage system are all equal.
7. The system of claim 5, wherein the phase angle reference value generation unit is configured to generate the angular frequency reference value according to the following expression:
ωi=ω*+sgn(Qi)(miPi-Δωi)
wherein, ω isiRepresenting the angular frequency reference, ω, of the ith energy storage module*Representing the angular frequency, Q, of the ith energy storage module at no loadiAnd miRespectively representing the reactive power and the droop control coefficient, P, of the ith energy storage moduleiRepresenting the output power, Δ ω, of the ith energy storage moduleiRepresenting the angular frequency correction term for the ith energy storage module.
8. A centralized high-capacity energy storage system, which is characterized by comprising a cascade energy storage system and the SOC balance control system as claimed in any one of claims 1-7.
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