CN116111619A - SOC (system on chip) balance control method and system for distributed energy storage battery optimizer - Google Patents
SOC (system on chip) balance control method and system for distributed energy storage battery optimizer Download PDFInfo
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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
- H02J1/00—Circuit arrangements for dc mains or dc distribution networks
- H02J1/10—Parallel operation of dc sources
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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
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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
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/381—Dispersed generators
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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
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- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/0029—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or 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
- H02J7/0047—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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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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Abstract
The invention discloses a distributed energy storage battery optimizer SOC balance control method and system, and belongs to the field of battery energy storage system control. The invention obtains the secondary voltage compensation quantity by carrying out secondary voltage compensation on the output voltage of the battery optimizer; performing improved droop control on the value of superposition of the secondary voltage compensation quantity and the rated voltage of the bus to obtain a reference value of the output voltage of the battery optimizer; performing voltage closed-loop control on a reference value of the output voltage of the battery optimizer to obtain a frequency difference signal; superposing the output frequency difference signal with the initial resonant frequency to obtain an actual switching frequency value; and carrying out pulse frequency modulation on the actual switching frequency value to obtain a driving signal of the power device of the battery optimizer. Therefore, the equalization control method provided by the invention can realize parallel control when the plurality of battery optimizers are charged and discharged, and can realize coordination control on the plurality of battery optimizers when the plurality of battery optimizers are simultaneously subjected to output power control.
Description
Technical Field
The invention belongs to the technical field of battery energy storage system control, and relates to a distributed energy storage battery optimizer SOC balance control method and system.
Background
In order to realize the effect of peak clipping and valley filling on the power of a direct current bus in an energy storage system, a battery is generally connected into the direct current bus through a bidirectional DC/DC converter, and bidirectional flow of energy is realized through switching of charge and discharge modes of the bidirectional DC/DC converter, so that the bidirectional DC/DC converter has good working performance and is an important precondition for maintaining stable operation of the system.
In the prior art, a non-isolated bidirectional DC-DC converter is mostly adopted as a bidirectional DC-DC converter topology, and as in the published documents of distributed energy storage bidirectional DC-DC converter and SOC balance control and coordination control strategy research based on an improved droop method in an independent direct current micro-grid, a suspension staggered parallel bidirectional DC-DC converter and a bidirectional Buck/Boost converter are respectively adopted, so that the bidirectional DC-DC converter has the advantages of simple structure, no transformer and fewer components. However, the non-isolated bidirectional DC/DC converter topology used in the above document cannot be adapted to the situation of high voltage level, and works in the hard switching state, the efficiency and the power density are limited.
Each energy storage module in the energy storage system is connected in parallel with a direct current bus in a distributed mode. However, because of the difference of components, parameters of each energy storage module connected in parallel on the direct current bus are difficult to be kept consistent, if effective control measures are not adopted, the output current of each module is larger, and a circulation phenomenon is generated among the modules when serious, so that the service life of the energy storage module is seriously influenced, and even the safety and the reliability of the system are endangered. In order to avoid over-charging or over-discharging of the energy storage modules and realize reasonable distribution of power among the energy storage modules, the energy storage modules need to output or absorb power according to the charge states of the energy storage modules by utilizing an effective power distribution strategy, so that the purposes of balancing the power and efficiently utilizing the energy storage units are achieved.
Disclosure of Invention
The invention aims to solve the problems that in the prior art, components in an energy storage system are different, parameters of energy storage modules connected in parallel on a direct current bus are difficult to keep consistent, and the output current of each module has larger phase difference, and provides a distributed energy storage battery optimizer SOC balance control method and system.
In order to achieve the purpose, the invention is realized by adopting the following technical scheme:
the invention provides a distributed energy storage battery optimizer SOC balance control method, which comprises the following steps:
the bus output voltage of the battery optimizer is differed from the bus rated voltage of the battery optimizer, and then the secondary voltage compensation quantity of the battery optimizer is obtained through the PI controller;
obtaining bus voltage after secondary voltage compensation according to the secondary voltage compensation quantity of the battery optimizer and the bus rated voltage of the battery optimizer;
obtaining a reference value of the output voltage of the battery optimizer according to the bus voltage after secondary voltage compensation, the dynamic sagging coefficient and the output current of the battery optimizer;
the reference value of the output voltage of the battery optimizer is differed from the bus output voltage of the battery optimizer, and then a frequency difference signal is obtained through a PI controller and a limiter;
and acquiring an actual switching frequency value according to the frequency difference signal and the initial resonant frequency of the CLLC resonant converter, and performing pulse frequency modulation on the actual switching frequency value to acquire a driving signal of the power device of the battery optimizer.
Preferably, the secondary voltage compensation amount δu of the battery optimizer is calculated as follows:
wherein ,uoref U for the bus voltage rating of a given battery optimizer o Bus output voltage, k, of battery optimizer for sampling p_b For compensating proportional control parameters, k, of a PI controller for voltage i_b The integral control parameters of the PI controller are compensated for the voltage.
Preferably, the bus voltage u 'after the secondary voltage compensation' oref The calculation method of (2) is as follows:
u' oref ＝u oref +δu
wherein ,uoref For a given bus voltage rating of the battery optimizer, δu is the amount of secondary voltage compensation of the battery optimizer.
Preferably, the reference value u 'of the output voltage of the battery optimizer' orefi The following are provided:
u' orefi ＝u' oref -i oi R i
wherein when the system reaches a steady state, the output voltage of the battery optimizer satisfies u oi ＝u' orefi ，i oi For the output current of the ith battery optimizer, R i Is a dynamic sag factor;
dynamic sag coefficient R determined from state of charge parameters of each cell i In the charging process, the battery with higher charge state parameters absorbs less electric energy, and the battery with lower charge state parameters absorbs more electric energy; in the discharging process, the battery with higher charge state parameter releases more electric energy, and the battery with lower charge state parameter releases less electric energy.
Preferably, the battery optimizer output current i is obtained from sampling oi Judging the battery state;
dynamic sag factor R in charge or discharge state i The calculation method of (2) is as follows:
when the battery optimizer outputs current i oi <0, the battery is in a charged state, and the dynamic sagging coefficient R i The formula of (2) is:
when the battery optimizer outputs current i oi >0, the battery is in a discharge state, and the dynamic sagging coefficient R i The formula of (2) is:
when the battery optimizer outputs current i oi =0, at which time the battery optimizer is out of operation;
wherein ,R0 For the initial sag factor of the energy storage module,when selected, satisfy
Δu omax For sampling the maximum value of allowable deviation of bus output voltage, deltau omin Minimum allowable deviation value of bus output voltage obtained by sampling, i omax Is the maximum value of the output current of the battery optimizer, i omin Is the minimum value of the output current of the battery optimizer, n is the equalizing speed regulating factor of the energy storage module and SOC i For the state of charge of the battery connected to the ith battery optimizer, A SOC The average value of the charge states of all batteries is that alpha and beta are constants; the value of alpha is required to be the current SOC i alpha|SOC when the value of (a) is large i -A SOC |>The value of 10 beta, beta is required to be beta<1。
Preferably, the frequency difference signal Δf is calculated as follows:
wherein ,kp_u Is the proportional control parameter k of the voltage ring PI controller i_u U is the integral control parameter of the voltage ring PI controller o Bus output voltage of battery optimizer obtained by sampling, u' orefi Outputting a reference value of voltage for the battery optimizer;
actual switching frequency value f of driving signal of power device of battery optimizer s The method comprises the following steps:
wherein ,
for the initial resonant frequency of the CLLC resonant converter, Δf is the frequency difference signal.
Preferably, pulse frequency modulation is carried out on the actual switching frequency value to obtain PFM waves under the actual switching frequency value;
output current i to battery optimizer oi Detecting the state of the battery, and judging that the battery is in a charging or discharging state:
when the battery optimizer outputs current i oi <When 0, PFM wave driving switch tube S under actual switch frequency value 1 -S 4 When the battery optimizer outputs current i oi >When 0, PFM wave driving switch tube S under actual switch frequency value 5 -S 8 When the battery optimizer outputs current i oi When=0, no driving signal is input to the switching transistor.
The invention provides a distributed energy storage battery optimizer SOC balance control system, which comprises:
the secondary voltage compensation quantity acquisition module is used for making a difference between the bus output voltage of the battery optimizer and the bus rated voltage of the battery optimizer and then obtaining the secondary voltage compensation quantity of the battery optimizer through the PI controller;
the secondary voltage compensated bus voltage acquisition module is used for acquiring the secondary voltage compensated bus voltage according to the secondary voltage compensation quantity of the battery optimizer and the bus rated voltage of the battery optimizer;
the reference value acquisition module of the output voltage of the battery optimizer is used for acquiring the reference value of the output voltage of the battery optimizer according to the bus voltage after secondary voltage compensation, the dynamic sagging coefficient and the output current of the battery optimizer;
the frequency difference signal acquisition module is used for making a difference between a reference value of the output voltage of the battery optimizer and the bus output voltage of the battery optimizer, and then passing through the PI controller and the limiter to obtain a frequency difference signal;
the driving signal acquisition module is used for acquiring an actual switching frequency value according to the frequency difference signal and the initial resonant frequency of the CLLC resonant converter, and carrying out pulse frequency modulation on the actual switching frequency value to obtain a driving signal of the power device of the battery optimizer.
A computer device comprising a memory storing a computer program and a processor implementing the steps of a distributed energy storage battery optimizer, SOC, equalization control method when the computer program is executed.
A computer readable storage medium storing a computer program which when executed by a processor implements the steps of a distributed energy storage battery optimizer, SOC, equalization control method.
Compared with the prior art, the invention has the following beneficial effects:
compared with the bidirectional DC/DC converter in the prior art, the distributed energy storage battery optimizer SOC balance control method provided by the invention adopts the CLLC resonant converter to obtain parameters, and solves the problems that the topology of the non-isolated bidirectional DC/DC converter cannot be suitable for occasions with high voltage levels and works in a hard switching state. The secondary voltage compensation is carried out on the busbar voltage drop, the problem that the busbar voltage deviates from a given value to a certain extent due to sagging control is solved, and the busbar voltage fluctuation range is reduced. According to the dynamic sagging coefficient determined by the real-time state-of-charge parameters of each battery, the output power of the energy storage module can be adjusted in real time according to the real-time state-of-charge parameters of the battery, so that the bus power is reasonably distributed among the energy storage modules, and the state-of-charge balance speed of each energy storage module is improved. And when the output power of the plurality of battery optimizers is controlled simultaneously, the coordination control of the plurality of battery optimizers can be realized. Therefore, the control method provided by the invention can solve the problems that in the prior art, components in the energy storage system have differences, parameters of energy storage modules connected in parallel on the direct current bus are difficult to keep consistent, and the output current of each module has larger difference.
Further, by combining with an idle starting strategy, the overshoot of the resonance current in the starting process is reduced; setting a discharge threshold and a charge threshold, and avoiding oscillation phenomenon of the converter during back and forth switching.
The invention provides a system for a distributed energy storage battery optimizer SOC balance control method, which is divided into a secondary voltage compensation quantity acquisition module, a bus voltage acquisition module after secondary voltage compensation, a reference value acquisition module, a frequency difference signal acquisition module and a driving signal acquisition module for output voltage of a battery optimizer, wherein the modules are mutually independent by adopting a modularized idea, so that unified management of the modules is facilitated.
Drawings
For a clearer description of the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present invention and should not be considered as limiting the scope, and other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a flowchart of a distributed energy storage battery optimizer SOC equalization control method of the present invention.
Fig. 2 is a schematic diagram of a distributed energy storage battery optimizer SOC equalization control method according to the present invention.
Fig. 3 is a block diagram of a distributed energy storage battery optimizer system of the present invention.
Fig. 4 is a diagram showing the charge and discharge U/I control characteristics of the dc bus of the present invention.
Fig. 5 is a control system diagram of the SOC equalization control method of the distributed energy storage battery optimizer of the present invention.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. The components of the embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.
Thus, the following detailed description of the embodiments of the invention, as presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further definition or explanation thereof is necessary in the following figures.
In the description of the embodiments of the present invention, it should be noted that, if the terms "upper," "lower," "horizontal," "inner," and the like indicate an azimuth or a positional relationship based on the azimuth or the positional relationship shown in the drawings, or the azimuth or the positional relationship in which the inventive product is conventionally put in use, it is merely for convenience of describing the present invention and simplifying the description, and does not indicate or imply that the apparatus or element to be referred to must have a specific azimuth, be configured and operated in a specific azimuth, and thus should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and the like, are used merely to distinguish between descriptions and should not be construed as indicating or implying relative importance.
Furthermore, the term "horizontal" if present does not mean that the component is required to be absolutely horizontal, but may be slightly inclined. As "horizontal" merely means that its direction is more horizontal than "vertical", and does not mean that the structure must be perfectly horizontal, but may be slightly inclined.
In the description of the embodiments of the present invention, it should also be noted that, unless explicitly specified and limited otherwise, the terms "disposed," "mounted," "connected," and "connected" should be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.
The invention is described in further detail below with reference to the attached drawing figures:
the invention provides a distributed energy storage battery optimizer SOC balance control method, which is shown in figure 1 and comprises the following steps:
s1, generating a difference between the bus output voltage of the battery optimizer and the bus rated voltage of the battery optimizer, and obtaining a secondary voltage compensation quantity of the battery optimizer through a PI controller;
the secondary voltage compensation amount delta u of the battery optimizer is calculated as follows:
wherein ,uoref U for the bus voltage rating of a given battery optimizer o Bus output voltage, k, of battery optimizer for sampling p_b For compensating proportional control parameters, k, of a PI controller for voltage i_b The integral control parameters of the PI controller are compensated for the voltage.
S2, obtaining bus voltage after secondary voltage compensation according to the secondary voltage compensation quantity of the battery optimizer and the bus rated voltage of the battery optimizer;
bus voltage u 'after secondary voltage compensation' oref The calculation method of (2) is as follows:
u' oref ＝u oref +δu
wherein ,uoref For a given bus voltage rating of the battery optimizer, δu is the amount of secondary voltage compensation of the battery optimizer.
S3, obtaining a reference value of the output voltage of the battery optimizer according to the bus voltage after secondary voltage compensation, the dynamic sagging coefficient and the output current of the battery optimizer;
reference value u 'of output voltage of battery optimizer' orefi The following are provided:
u' orefi ＝u' oref -i oi R i
wherein when the system reaches a steady state, the output voltage of the battery optimizer satisfies u oi ＝u' orefi ，i oi For the output current of the ith battery optimizer, R i Is dynamicSag factor;
dynamic sag coefficient R determined from state of charge parameters of each cell i In the charging process, the battery with higher charge state parameters absorbs less electric energy, and the battery with lower charge state parameters absorbs more electric energy; in the discharging process, the battery with higher charge state parameter releases more electric energy, and the battery with lower charge state parameter releases less electric energy.
Output current i of battery optimizer obtained according to sampling oi Judging the battery state;
dynamic sag factor R in charge or discharge state i The calculation method of (2) is as follows:
when the battery optimizer outputs current i oi <0, the battery is in a charged state, and the dynamic sagging coefficient R i The formula of (2) is:
when the battery optimizer outputs current i oi >0, the battery is in a discharge state, and the dynamic sagging coefficient R i The formula of (2) is:
when the battery optimizer outputs current i oi =0, at which time the battery optimizer is out of operation;
wherein ,R0 For the initial sagging coefficient of the energy storage module, the energy storage module meets the following conditions when selected
Δu omax For sampling the maximum value of allowable deviation of bus output voltage, deltau omin Minimum allowable deviation value of bus output voltage obtained by sampling, i omax Is the maximum value of the output current of the battery optimizer, i omin Is the minimum value of the output current of the battery optimizer, n is the equalizing speed regulating factor of the energy storage module and SOC i For the state of charge of the battery connected to the ith battery optimizer, A SOC For the state of charge of all cellsAverage value, alpha and beta are constants; the value of alpha is required to be the current SOC i alpha|SOC when the value of (a) is large i -A SOC |>The value of 10 beta, beta is required to be beta<1。
S4, making a difference between the reference value of the output voltage of the battery optimizer and the bus output voltage of the battery optimizer, and then obtaining a frequency difference signal through a PI controller and a limiter;
the frequency difference signal Δf is calculated as follows:
wherein ,kp_u Is the proportional control parameter k of the voltage ring PI controller i_u U is the integral control parameter of the voltage ring PI controller o Bus output voltage of battery optimizer obtained by sampling, u' orefi A reference value for the battery optimizer output voltage.
S5, acquiring an actual switching frequency value according to the frequency difference signal and the initial resonant frequency of the CLLC resonant converter, and performing pulse frequency modulation on the actual switching frequency value to acquire a driving signal of the power device of the battery optimizer.
Actual switching frequency value f of driving signal of power device of battery optimizer s The method comprises the following steps:
wherein ,
for the initial resonant frequency of the CLLC resonant converter, Δf is the frequency difference signal.
Pulse frequency modulation is carried out on the actual switching frequency value, and PFM waves under the actual switching frequency value are obtained;
output current i to battery optimizer oi Detecting the state of the battery, and judging that the battery is in a charging or discharging state:
when the battery is excellentOutput current i of the converter oi <When 0, PFM wave driving switch tube S under actual switch frequency value 1 -S 4 When the battery optimizer outputs current i oi >When 0, PFM wave driving switch tube S under actual switch frequency value 5 -S 8 When the battery optimizer outputs current i oi When=0, no driving signal is input to the switching transistor.
The invention provides a distributed energy storage battery optimizer SOC balance control method, which can be implemented according to the following steps.
Step 1: the secondary voltage compensation unit performs secondary voltage compensation on the output voltage of the battery optimizer, so that the bus output voltage is different from the given bus rated voltage, and the secondary voltage compensation quantity is obtained through the PI controller.
Step 2: and superposing the secondary voltage compensation quantity and the bus rated voltage to obtain the bus voltage after the secondary voltage compensation.
Step 3: and the sagging control unit subtracts the product of the dynamic sagging coefficient and the output current of the battery optimizer from the bus voltage after secondary voltage compensation to obtain a reference value of the output voltage of the battery optimizer.
Step 4: the voltage control unit compares the reference value of the output voltage of the battery optimizer with the sampled bus output voltage, and a frequency difference signal is obtained through the PI controller and the limiter to form voltage closed-loop control.
Step 5: adding a frequency modulation ring, and superposing the frequency difference signal and the initial resonant frequency of the CLLC resonant converter to obtain an actual switching frequency value.
And carrying out pulse frequency modulation on the actual switching frequency value to obtain a driving signal of the power device of the battery optimizer.
In the embodiment, an SOC equalization method based on improved droop control is adopted to adjust the output current of the CLLC resonant converters, so that coordination control of a plurality of CLLC resonant converters is realized. Fig. 2 is a schematic diagram of a SOC equalization control method of a distributed energy storage battery optimizer according to an embodiment of the present invention, and steps 1 to 6 are described with reference to fig. 2.
The secondary voltage compensation of the CLLC resonant converter in step 1 may be performed as follows.
The secondary voltage compensation amount δu is represented by the following formula:
wherein ,uoref For a given bus voltage rating, u o For sampling the bus output voltage, k p_b and ki_b And compensating the proportional control parameter and the integral control parameter of the PI controller for the voltage.
Since improved droop control compromises the accuracy of poor control and the current sharing effect achieved, a drop in dc bus voltage can result. In order to stabilize the bus voltage within the allowable range, the bus voltage reference value of the battery optimizer is compensated to meet the purpose of stabilizing the bus voltage. And carrying out proportional integral calculation on the deviation of the bus voltage reference value and the bus output voltage, and taking the output result as the compensation quantity of the voltage ring.
The bus voltage after the secondary voltage compensation obtained in step 2 may be implemented as follows.
The bus voltage after the secondary voltage compensation is the result of adding the secondary voltage compensation quantity and the bus rated voltage, and the bus voltage after the secondary voltage compensation is shown in the following formula:
u' oref ＝u oref +δu
the improved sag control in step 3 may be implemented as follows.
Subtracting the product of the dynamic droop coefficient and the output current of the battery optimizer from the bus voltage after secondary voltage compensation to obtain a reference value of the output voltage of the battery optimizer, wherein the reference value is as follows:
u' orefi ＝u' oref -i oi R i
wherein ,u'orefi For the reference value of the output voltage of the battery optimizer, when the system reaches a steady state, the output voltage of the battery optimizer meets u oi ＝u' orefi ，i oi For the output current of the ith battery optimizer, R i Is a dynamic droop coefficient.
Dynamic sag coefficient R i The selection method comprises the following steps:
determining dynamic droop coefficient R based on real-time state-of-charge parameters of each cell i During the charging process, the battery with higher charge state parameters absorbs less electric energy, and the battery with lower charge state parameters absorbs more electric energy; in the discharging process, the battery with higher charge state parameter releases more electric energy, and the battery with lower charge state parameter releases less electric energy.
When the output current i of the battery optimizer oi <0, the battery is in a charged state, and the dynamic sagging coefficient R i The formula of (2) is:
when the output current i of the battery optimizer oi >0, the battery is in a discharge state, and the dynamic sagging coefficient R i The formula of (2) is:
when the output current i of the battery optimizer oi =0, at which point the battery optimizer exits operation.
wherein ,R0 For the initial sagging coefficient of the energy storage module, the energy storage module meets the following conditions when selected
Δu omax and Δuomin Maximum and minimum allowable deviation of bus output voltage obtained by sampling, i omax and iomin Is the maximum value and the minimum value of the output current of the battery optimizer; n is an equilibrium speed adjusting factor of the energy storage module; SOC (State of Charge) i The state of charge of the battery connected to the ith battery optimizer; a is that SOC Is the average value of the states of charge of all the cells; alpha and beta are constants, and the value of alpha is required to be equal to the SOC i alpha|SOC when the value of (a) is large i -A SOC |>The value of 10 beta, beta is required to be beta<1。
As shown in FIG. 3, which is a system structure diagram of the distributed energy storage battery optimizer of the present invention, a main circuit of the battery optimizer is a CLLC resonance bidirectional DC-DC converter, and comprises a high-voltage side capacitor C 1 Primary side resonant capacitor C r1 Primary side resonant inductance L r1 Exciting inductance L m Transformer, secondary side resonance capacitor C r2 Secondary side resonant inductance L r2 Switch tube S 1 To S 8 Low-side capacitance C 2 . One side of the battery optimizer is connected with the battery, and the other side of the battery optimizer is connected with the direct current bus. The battery and the battery optimizer are combined into an energy storage module, and the direct current bus can be connected into any energy storage modules which are mutually connected in parallel; the DC bus is connected with a current source load, and the charging and discharging modes of the converter depend on the requirements of the DC bus, namely the current direction of the current source load.
In this embodiment, two energy storage modules connected in parallel to a dc bus are used as an example for description:
multiple energy storage modules run in parallel on a direct current bus, and the average value A of charge states of all batteries SOC As the charge state of each battery changes, A SOC Is between the state of charge maximum and the state of charge minimum. Assume the state of charge SOC of the battery in the energy storage module 1 1 >A SOC State of charge SOC of a battery in the energy storage module 2 1 <A SOC The output current ratios of the energy storage module 1 and the energy storage module 2 in the charge and discharge modes are respectively as follows:
when the output current i of the battery optimizer oi <0, the battery is in a charged state, and the ratio of the output currents of the energy storage module 1 and the energy storage module 2 is
When the output current i of the battery optimizer oi >0, the battery is in a discharging state, and the ratio of the output currents of the energy storage module 1 and the energy storage module 2 is
Wherein, alpha|SOC i -A SOC |>And (3) 10 beta, neglecting the influence of beta, and simplifying the ratio of the output currents of the energy storage module 1 and the energy storage module 2 in the charge-discharge mode to be:
when the output current i of the battery optimizer oi <0, the battery is in a charged state, and the ratio of the output currents of the energy storage module 1 and the energy storage module 2 is
When the output current i of the battery optimizer oi >0, the battery is in a discharging state, and the ratio of the output currents of the energy storage module 1 and the energy storage module 2 is
The output current ratio of the energy storage module 1 and the energy storage module 2 can be known, and only a constant exists in the output current ratio expression at the moment, so that the output current of each energy storage module is distributed to be a constant value, and the output current distribution of the modules with more energy storage is larger than that of the modules with less energy storage.
The voltage closed-loop control in step 4 is implemented according to the following steps.
The control method of the voltage closed-loop control is as follows:
comparing a reference value of the output voltage of the battery optimizer with the sampled bus output voltage, and obtaining a frequency difference signal through a PI controller and a limiter, wherein the formula of the frequency difference signal is as follows:
wherein ,kp_u Proportional control parameter, k, of voltage loop PI controller i_u Is an integral control parameter of the voltage loop PI controller. The upper limit of the limiter is
The lower limit of the limiter is +.>
f max and fmin Maximum frequency and minimum frequency that the system can withstand, respectively, so Δf satisfies +.>
The addition of the frequency modulation loop in step 5 may be performed as follows.
The control method for adding the frequency modulation ring comprises the following steps: initial resonant frequency of CLLC resonant converter
Subtracting the frequency difference signal delta f to obtain an actual switching frequency value of a driving signal of the power device of the battery optimizer, wherein the actual switching frequency value is expressed as the following formula:
the circuit of the battery optimizer in this embodiment may include the following structure.
The pulse frequency modulation in step 6 may be performed as follows.
And carrying out pulse frequency modulation on the actual switching frequency value to obtain the PFM wave under the actual switching frequency value. The specific process is to input the actual switching frequency value f s The output frequency value is the actual switching frequency value f s The duty ratio is 50%, and two paths of square waves are complementary up and down.
Output current i to battery optimizer oi Detecting the state of the battery, judging that the battery is in a charging or discharging state, and outputting current i when the battery optimizer outputs current i oi <At 0, PFM wave driving switch tube S with actual switch frequency value 1 To S 4, wherein S1 、S 4 Drive signal and S of (2) 2 、S 3 The driving signals of the driving circuit are two complementary square waves; when the battery optimizer outputs current i oi >At 0, the PFM wave at the actual switching frequency value is driven to be turned onClosing tube S 5 To S 8, wherein S5 、S 8 Drive signal and S of (2) 5 、S 6 The driving signals of the driving circuit are two complementary square waves; when the battery optimizer outputs current i oi When=0, no driving signal is input to the switching transistor.
Fig. 4 shows the charging and discharging U/I control characteristics of the dc bus of the present invention. The charging and discharging modes of the converter depend on the requirements of the direct current bus. The specific process is as follows: if the system needs to charge the battery, a current source load injects current into the direct current bus to enable the direct current bus voltage to rise, and when the direct current bus voltage exceeds a charging threshold value, the direct current bus charges an energy storage module connected in parallel on the direct current bus; when the system needs to discharge the battery, the current source load can draw current from the direct current bus, and when the voltage of the direct current bus is lower than a discharge threshold value, the energy storage modules connected in parallel on the direct current bus are discharged to the direct current bus. In order to avoid the converter switching back and forth between charging and discharging, different charging threshold values and discharging threshold values are designed, and the oscillation phenomenon of the CLLC resonant converter switching back and forth is avoided, wherein U is as follows 1 and U2 For discharge threshold and charge threshold, U L and UH Is the bus voltage regulation range.
The idle start strategy is as follows: the voltage of the direct current bus is lower than the discharge threshold during no-load starting, so that the energy storage module discharges to the direct current bus. The soft start strategy is adopted during starting, and the output initial value of the voltage loop PI controller in the fifth step is set
Actual switching frequency value f of driving signal for power device of battery optimizer s At the starting time is the frequency maximum f s_max Then gradually decreasing to the initial resonance frequency +.>
When the DC bus voltage is equal to the discharge threshold, the battery optimizer exits operation, maintains the DC bus voltage near the discharge threshold, and waits until the DC bus voltage stabilizes before being incorporated into the load.
The control system of the distributed energy storage battery optimizer SOC balance control method provided by the invention, as shown in fig. 5, comprises:
the secondary voltage compensation quantity acquisition module is used for making a difference between the bus output voltage of the battery optimizer and the bus rated voltage of the battery optimizer and then obtaining the secondary voltage compensation quantity of the battery optimizer through the PI controller;
the secondary voltage compensated bus voltage acquisition module is used for acquiring the secondary voltage compensated bus voltage according to the secondary voltage compensation quantity of the battery optimizer and the bus rated voltage of the battery optimizer;
the reference value acquisition module of the output voltage of the battery optimizer is used for acquiring the reference value of the output voltage of the battery optimizer according to the bus voltage after secondary voltage compensation, the dynamic sagging coefficient and the output current of the battery optimizer;
the frequency difference signal acquisition module is used for making a difference between a reference value of the output voltage of the battery optimizer and the bus output voltage of the battery optimizer, and then passing through the PI controller and the limiter to obtain a frequency difference signal;
the driving signal acquisition module is used for acquiring an actual switching frequency value according to the frequency difference signal and the initial resonant frequency of the CLLC resonant converter, and carrying out pulse frequency modulation on the actual switching frequency value to obtain a driving signal of the power device of the battery optimizer.
An embodiment of the present invention provides a terminal device, where the terminal device includes: a processor, a memory, and a computer program stored in the memory and executable on the processor. The steps of the various method embodiments described above are implemented when the processor executes the computer program. Alternatively, the processor may implement the functions of the modules/units in the above-described device embodiments when executing the computer program.
The computer program may be divided into one or more modules/units, which are stored in the memory and executed by the processor to accomplish the present invention.
The terminal equipment can be computing equipment such as a desktop computer, a notebook computer, a palm computer, a cloud server and the like. The terminal device may include, but is not limited to, a processor, a memory.
The processor may be a central processing unit (Central Processing Unit, CPU), but may also be other general purpose processors, digital signal processors (Digital Signal Processor, DSP), application specific integrated circuits (Application Specific Integrated Circuit, ASIC), off-the-shelf programmable gate arrays (Field-Programmable Gate Array, FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, or the like.
The memory may be used to store the computer program and/or module, and the processor may implement various functions of the terminal device by running or executing the computer program and/or module stored in the memory and invoking data stored in the memory.
The modules/units integrated in the terminal device may be stored in a computer readable storage medium if implemented in the form of software functional units and sold or used as separate products. Based on such understanding, the present invention may implement all or part of the flow of the method of the above embodiment, or may be implemented by a computer program to instruct related hardware, where the computer program may be stored in a computer readable storage medium, and when the computer program is executed by a processor, the computer program may implement the steps of each of the method embodiments described above. Wherein the computer program comprises computer program code which may be in source code form, object code form, executable file or some intermediate form etc. The computer readable medium may include: any entity or device capable of carrying the computer program code, a recording medium, a U disk, a removable hard disk, a magnetic disk, an optical disk, a computer Memory, a Read-Only Memory (ROM), a random access Memory (RAM, random Access Memory), an electrical carrier signal, a telecommunications signal, a software distribution medium, and so forth. It should be noted that the computer readable medium contains content that can be appropriately scaled according to the requirements of jurisdictions in which such content is subject to legislation and patent practice, such as in certain jurisdictions in which such content is subject to legislation and patent practice, the computer readable medium does not include electrical carrier signals and telecommunication signals.
The distributed energy storage battery optimizer SOC balance control method and system provided by the invention have the following advantages: 1) The invention carries out secondary voltage compensation on the busbar voltage drop caused by sagging control, solves the problem that the busbar voltage deviates from a given value to a certain extent due to sagging control, and reduces the fluctuation range of the busbar voltage. 2) In the prior art, a main circuit of the battery optimizer adopts a non-isolated bidirectional DC/DC converter topology, cannot be suitable for occasions with high voltage levels, and works in a hard switching state. The invention adopts the CLLC resonant converter as the topology of the bidirectional DC/DC converter, has higher voltage gain and natural soft switching characteristic, has the advantages of high power density and high efficiency, can realize the electrical isolation of the input end and the output end, and improves the safety performance of the converter. 3) The invention provides a combined no-load starting strategy to reduce the overshoot of the resonance current in the starting process; setting a discharge threshold and a charge threshold, and avoiding oscillation phenomenon of the converter during back and forth switching. 4) In the prior art, the sagging coefficient does not have the capability of adjusting the sagging coefficient in real time according to the charge state of the battery, the battery pack with high SOC may be overcharged due to a single charging speed, the battery pack with low SOC is overdischarged due to a single discharging speed, and the electric quantity of the other battery pack cannot be fully utilized. The invention adopts a control strategy, and the output power of the energy storage modules can be adjusted in real time according to the state of charge parameters of the batteries according to the dynamic sagging coefficient determined by the state of charge parameters of each battery, so that the bus power is reasonably distributed among the energy storage modules, and the state of charge balance speed of each energy storage module is improved. And when the output power of the plurality of battery optimizers is controlled simultaneously, the coordination control of the plurality of battery optimizers can be realized.
The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. The SOC balance control method for the distributed energy storage battery optimizer is characterized by comprising the following steps of:
the bus output voltage of the battery optimizer is differed from the bus rated voltage of the battery optimizer, and then the secondary voltage compensation quantity of the battery optimizer is obtained through the PI controller;
obtaining bus voltage after secondary voltage compensation according to the secondary voltage compensation quantity of the battery optimizer and the bus rated voltage of the battery optimizer;
obtaining a reference value of the output voltage of the battery optimizer according to the bus voltage after secondary voltage compensation, the dynamic sagging coefficient and the output current of the battery optimizer;
the reference value of the output voltage of the battery optimizer is differed from the bus output voltage of the battery optimizer, and then a frequency difference signal is obtained through a PI controller and a limiter;
and acquiring an actual switching frequency value according to the frequency difference signal and the initial resonant frequency of the CLLC resonant converter, and performing pulse frequency modulation on the actual switching frequency value to acquire a driving signal of the power device of the battery optimizer.
2. The SOC equalization control method of a distributed energy storage battery optimizer as set forth in claim 1, wherein the secondary voltage compensation amount δu of the battery optimizer is calculated as follows:
wherein ,uoref U for the bus voltage rating of a given battery optimizer o Bus output voltage, k, of battery optimizer for sampling p_b For compensating proportional control parameters, k, of a PI controller for voltage i_b The integral control parameters of the PI controller are compensated for the voltage.
3. The distributed energy storage battery optimizer SOC balance control method of claim 1, wherein the secondary voltage compensated bus voltage u' oref The calculation method of (2) is as follows:
u' oref ＝u oref +δu
wherein ,uoref For a given bus voltage rating of the battery optimizer, δu is the amount of secondary voltage compensation of the battery optimizer.
4. The method for SOC equalization control of a distributed energy storage battery optimizer as recited in claim 1, wherein the reference value u 'of the battery optimizer output voltage' orefi The following are provided:
u′ orefi ＝u′ oref -i oi R i
wherein when the system reaches a steady state, the output voltage of the battery optimizer satisfies u oi ＝u' orefi ，i oi For the output current of the ith battery optimizer, R i Is a dynamic sag factor;
dynamic sag coefficient R determined from state of charge parameters of each cell i In the charging process, the battery with higher charge state parameters absorbs less electric energy, and the battery with lower charge state parameters absorbs more electric energy; in the discharging process, the battery with higher charge state parameter releases more electric energy, and the battery with lower charge state parameter releases less electric energy.
5. The method for SOC equalization control of a distributed energy storage battery optimizer as defined in claim 4, wherein the battery optimizer output current i is sampled oi Judging the battery state;
dynamic sag factor R in charge or discharge state i The calculation method of (2) is as follows:
when the battery optimizer outputs current i oi <0, the battery is in a charged state, and the dynamic sagging coefficient R i The formula of (2) is:
when the battery optimizer outputs current i oi >0, the battery is in a discharge state, and the dynamic sagging coefficient R i The formula of (2) is:
/>
when the battery optimizer outputs current i oi =0, at which time the battery optimizer is out of operation;
wherein ,R0 For the initial sagging coefficient of the energy storage module, the energy storage module meets the following conditions when selected
Δu omax For sampling the maximum value of allowable deviation of bus output voltage, deltau omin Minimum allowable deviation value of bus output voltage obtained by sampling, i omax Is the maximum value of the output current of the battery optimizer, i omin Is the minimum value of the output current of the battery optimizer, n is the equalizing speed regulating factor of the energy storage module and SOC i For the state of charge of the battery connected to the ith battery optimizer, A SOC The average value of the charge states of all batteries is that alpha and beta are constants; the value of alpha is required to be the current SOC i alpha|SOC when the value of (a) is large i -A SOC |>The value of 10 beta, beta is required to be beta<1。
6. The SOC equalization control method of a distributed energy storage battery optimizer as recited in claim 1, wherein the frequency difference signal Δf is calculated as follows:
wherein ,kp_u Is of voltageProportional control parameter, k, of loop PI controller i_u U is the integral control parameter of the voltage ring PI controller o Bus output voltage of battery optimizer obtained by sampling, u' orefi Outputting a reference value of voltage for the battery optimizer;
actual switching frequency value f of driving signal of power device of battery optimizer s The method comprises the following steps:
wherein ,
for the initial resonant frequency of the CLLC resonant converter, Δf is the frequency difference signal.
7. The SOC equalization control method of a distributed energy storage battery optimizer as claimed in claim 6, wherein pulse frequency modulation is performed on an actual switching frequency value to obtain a PFM wave at the actual switching frequency value;
output current i to battery optimizer oi Detecting the state of the battery, and judging that the battery is in a charging or discharging state:
when the battery optimizer outputs current i oi <When 0, PFM wave driving switch tube S under actual switch frequency value 1 -S 4 When the battery optimizer outputs current i oi >When 0, PFM wave driving switch tube S under actual switch frequency value 5 -S 8 When the battery optimizer outputs current i oi When=0, no driving signal is input to the switching transistor.
8. A distributed energy storage battery optimizer SOC equalization control system, comprising:
the secondary voltage compensation quantity acquisition module is used for making a difference between the bus output voltage of the battery optimizer and the bus rated voltage of the battery optimizer and then obtaining the secondary voltage compensation quantity of the battery optimizer through the PI controller;
the secondary voltage compensated bus voltage acquisition module is used for acquiring the secondary voltage compensated bus voltage according to the secondary voltage compensation quantity of the battery optimizer and the bus rated voltage of the battery optimizer;
the reference value acquisition module of the output voltage of the battery optimizer is used for acquiring the reference value of the output voltage of the battery optimizer according to the bus voltage after secondary voltage compensation, the dynamic sagging coefficient and the output current of the battery optimizer;
the frequency difference signal acquisition module is used for making a difference between a reference value of the output voltage of the battery optimizer and the bus output voltage of the battery optimizer, and then passing through the PI controller and the limiter to obtain a frequency difference signal;
the driving signal acquisition module is used for acquiring an actual switching frequency value according to the frequency difference signal and the initial resonant frequency of the CLLC resonant converter, and carrying out pulse frequency modulation on the actual switching frequency value to obtain a driving signal of the power device of the battery optimizer.
9. A computer device comprising a memory and a processor, the memory storing a computer program, characterized in that the processor, when executing the computer program, implements the steps of the distributed energy storage battery optimizer SOC balancing control method of any of claims 1 to 7.
10. A computer-readable storage medium storing a computer program, characterized in that the computer program when executed by a processor implements the steps of the distributed energy storage battery optimizer SOC equalization control method of any of claims 1 to 7.
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| CN117200566A (en) * | 2023-08-23 | 2023-12-08 | 深圳市正浩创新科技股份有限公司 | Method and related device for starting isolated bidirectional DC converter |
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| US20230040992A1 (en) * | 2019-12-24 | 2023-02-09 | Wolfspeed, Inc. | Circuits and methods for controlling bidirectional cllc converters |
| CN117200566A (en) * | 2023-08-23 | 2023-12-08 | 深圳市正浩创新科技股份有限公司 | Method and related device for starting isolated bidirectional DC converter |
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