CN109802415B - Battery equalization control method and device and off-grid micro-grid - Google Patents
Battery equalization control method and device and off-grid micro-grid Download PDFInfo
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Abstract
The application discloses a battery balance control method and device and an off-grid micro-grid, so as to realize battery energy balance among energy storage subsystems. The method comprises the following steps: acquiring measured values of balance control variables of energy storage subsystems in an off-grid microgrid; according to eachThe measured values of the balance control variables of the energy storage subsystems are calculated to obtain the weighted average value of the balance control variables of all the energy storage subsystems
Respectively judging the measured value and the weighted average value of the balance control variable of each energy storage subsystem on the premise of keeping at least one energy storage subsystem working in a V/F mode
Whether the deviation between the two exceeds a set range; if not, controlling the energy storage subsystem to work in a V/F mode; and if so, controlling the energy storage subsystem to work in a P/Q mode.
Description
Technical Field
The invention relates to the technical field of battery equalization, in particular to a battery equalization control method and device and an off-grid micro-grid.
Background
The large-capacity energy storage system can be formed by connecting a plurality of small-capacity energy storage subsystems in parallel, as shown in fig. 1, each energy storage subsystem comprises an energy storage battery and an energy storage bidirectional converter, the direct current side of each energy storage bidirectional converter is independently connected with the energy storage battery, and the alternating current side of each energy storage bidirectional converter is connected with an alternating current bus W1 in parallel.
The balance of the battery energy among the energy storage subsystems is crucial, but due to the difference of the battery characteristics (internal resistance, efficiency or capacity and the like) among the energy storage subsystems, after the energy storage subsystems are operated for a long time, the phenomenon of obvious imbalance of the battery energy among the energy storage subsystems can occur, so that a series of operating problems of the energy storage systems are caused, and the overall availability of the energy storage systems is reduced.
Disclosure of Invention
In view of this, the invention provides a battery balance control method and device and an off-grid microgrid, so as to realize battery energy balance among energy storage subsystems.
A battery balance control method is applied to an off-grid micro-grid, and comprises the following steps:
acquiring measured values of balance control variables of each energy storage subsystem;
according to the measured values of the balance control variables of all the energy storage subsystems, calculating to obtain the weighted average value of the balance control variables of all the energy storage subsystems
Respectively judging the measured value and the weighted average value of the balance control variable of each energy storage subsystem on the premise of keeping at least one energy storage subsystem working in a V/F mode
Whether the deviation between the two exceeds a set range;
if not, controlling the energy storage subsystem to work in a V/F mode;
and if so, controlling the energy storage subsystem to work in a P/Q mode.
Optionally, the power setting of the ith energy storage subsystem in the P/Q mode is
Wherein, Pi＞Pmax_chgiWhen is, Pi＝Pmax_chgi，Pmax_chgiThe maximum allowable charging power of the ith energy storage subsystem is obtained; pi＜-Pmax_dischgiWhen is, Pi＝-Pmax_dischgi，Pmax_dischgiThe maximum allowable discharge power of the ith energy storage subsystem; i is 1, 2, … and n, wherein n is the total number of the energy storage subsystems; ciThe battery capacity of the ith energy storage subsystem; x is the number ofiThe measured value of the balance control variable of the ith energy storage subsystem is obtained; pESS＝PPV-PL；PPVIs the generated power, P, of the power generation system in the off-grid type microgridLThe power of an alternating current load in the off-grid type microgrid; λ is an equalization adjustment coefficient.
Optionally, the balance control variable is a battery SOC;
correspondingly, the weighted average
For weighted average SOC, it is recorded as SOCwavgThen, then
In the formula, SOCiThe battery SOC of the ith energy storage subsystem.
Optionally, the balance control variable is a battery voltage;
correspondingly, the weighted average
For weighted average voltage, it is denoted as VwavgThen, then
In the formula, the upper limit of the battery voltage of the energy storage subsystem is assumed to be VmaxLower limit of Vmin；ViThe battery voltage of the ith energy storage subsystem.
Optionally, after controlling the energy storage subsystem to operate in the P/Q mode, the battery balancing control method further includes:
judgment of PPV-PLWhether the maximum allowable charging power of the energy storage system is larger than or not, if so, taking a power limiting measure on the power generation system, wherein the value of the power limiting measure is
A battery equalization control device is applied to an off-grid micro-grid, and comprises:
the acquisition unit is used for acquiring measured values of the balance control variables of the energy storage subsystems;
the mean value calculating unit is used for calculating and obtaining the weighted mean value of the balance control variables of all the energy storage subsystems according to the measured values of the balance control variables of all the energy storage subsystems
A mode switching unit for respectively judging the measured value and the weighted average value of the balance control variable of each energy storage subsystem on the premise of keeping at least one energy storage subsystem working in the V/F mode
Whether the deviation between the two exceeds a set range; if not, controlling the energy storage subsystem to work in a V/F mode; and if so, controlling the energy storage subsystem to work in a P/Q mode.
Optionally, the power setting of the ith energy storage subsystem in the P/Q mode is
Wherein, Pi＞Pmax_chgiWhen is, Pi＝Pmax_chgi，Pmax_chgiThe maximum allowable charging power of the ith energy storage subsystem is obtained; pi＜-Pmax_dischgiWhen is, Pi＝-Pmax_dischgi，Pmax_dischgiThe maximum allowable discharge power of the ith energy storage subsystem; i is 1, 2, … and n, wherein n is the total number of the energy storage subsystems; ciThe battery capacity of the ith energy storage subsystem; x is the number ofiThe measured value of the balance control variable of the ith energy storage subsystem is obtained; pESS＝PPV-PL；PPVIs the generated power, P, of the power generation system in the off-grid type microgridLThe power of an alternating current load in the off-grid type microgrid; λ is an equalization adjustment coefficient.
Optionally, the balance control variable is a battery SOC;
correspondingly, the mean value calculating unit is specifically configured to calculate a weighted average SOC of all energy storage subsystems according to the battery SOC of each energy storage subsystem, and record the weighted average SOC as the SOCwavgThen, then
In the formula, SOCiThe battery SOC of the ith energy storage subsystem.
Optionally, the balance control variable is a battery voltage;
correspondingly, the mean value calculating unit is specifically configured to calculate a weighted average voltage of all energy storage subsystems according to the battery voltages of the energy storage subsystems, and mark the weighted average voltage as VwavgThen, then
In the formula, the upper limit of the battery voltage of the energy storage subsystem is assumed to be VmaxLower limit of Vmin；ViThe battery voltage of the ith energy storage subsystem.
An off-grid microgrid comprises an energy storage system, a power generation system and an alternating current load which are connected in parallel on the same alternating current bus, wherein the energy storage system is formed by connecting a plurality of energy storage subsystems in parallel;
the off-grid microgrid also comprises any battery balance control device disclosed above, and the battery balance control device is in communication connection with the power generation system, the alternating current load and each energy storage subsystem.
According to the technical scheme, the x of the ith energy storage subsystem isiAnd
when the deviation is overlarge, the energy storage subsystem is controlled to be switched from a V/F mode to a P/Q mode, and the whole off-grid type is accurately respondedThe system power scheduling of the micro-grid realizes the battery energy balance among the energy storage subsystems; meanwhile, the off-grid micro-grid is supported by an energy storage system in a networking mode, so that at least one energy storage bidirectional inverter is ensured to work in a V/F mode in the balancing process.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic structural diagram of an energy storage system disclosed in the prior art;
fig. 2 is a schematic diagram of an off-grid microgrid structure according to an embodiment of the present invention;
fig. 3 is a flowchart of a battery equalization control method according to an embodiment of the present invention;
fig. 4 is a schematic structural diagram of a battery equalization control apparatus according to an embodiment of the present invention;
fig. 5 is a schematic structural diagram of another battery balancing control apparatus according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The embodiment of the invention discloses a battery balance control method, which is used for realizing battery energy balance among energy storage subsystems in an off-grid micro-grid.
As shown in fig. 2, the off-grid microgrid comprises an energy storage system 100, a power generation system 200 and an ac load 300 which are connected in parallel to the same ac bus W1. The power generation system 200 may be a photovoltaic power generation system, a wind power generation system, or the like, but is not limited to this, and fig. 3 only exemplifies the power generation system 200 as a photovoltaic power generation system, where the photovoltaic power generation system includes a photovoltaic cell panel and a photovoltaic inverter, and a dc side of the photovoltaic inverter is connected to the photovoltaic cell panel, and an ac side of the photovoltaic inverter is connected to the ac bus W1. The energy storage system 100 is formed by connecting a plurality of energy storage subsystems in parallel, each energy storage subsystem comprises an energy storage battery and an energy storage bidirectional converter, the direct current side of each energy storage bidirectional converter is independently connected with the energy storage battery, and the alternating current side of each energy storage bidirectional converter is connected with the alternating current bus in parallel. The energy storage battery in the energy storage subsystem can be a single battery, or can be a battery pack or a battery pack. The energy storage batteries contained in different energy storage subsystems can be different types of energy storage batteries, and also can be energy storage batteries with different powers and different capacities.
The off-grid microgrid carries out unified scheduling management on the power distribution of the whole off-grid microgrid through a battery balance control device to realize balance control, and a corresponding battery balance control method is shown in fig. 3 and comprises the following steps:
step S01: obtaining measured values x of balance control variables of each energy storage subsystem1、x2、…、xn；xiThe measured value of the balance control variable of the ith energy storage subsystem is 1, 2, … and n, and n is the total number of the energy storage subsystems.
Step S02: according to the measured values of the balance control variables of all the energy storage subsystems, calculating to obtain the weighted average value of the balance control variables of all the energy storage subsystems
Specifically, due to the difference in battery characteristics (internal resistance, efficiency or capacity, etc.) between the energy storage subsystems, after long-time operation, an obvious imbalance of battery energy occurs between the energy storage subsystems. The battery energy level of the energy storage subsystem can be intuitively reflected by parameters such as battery voltage, battery SOC (State of Charge) and the like, so when the battery energy among the energy storage subsystems is unbalanced,the battery voltage or the battery SOC of the energy storage subsystem can be used as an equalization control variable, and the measured value and the expected value of the equalization control variable (namely the weighted average value of the equalization control variables of all the energy storage subsystems) can be eliminated or reduced by carrying out certain control
) And the deviation between the energy storage subsystems makes the battery energy tend to be balanced among the energy storage subsystems.
Wherein, when the battery voltage is used as the balance control variable,
is the weighted average SOC of all the energy storage subsystems, and the weighted average SOC is defined as the SOCwavgThen, then
In the formula (1), CiFor battery capacity, SOC, of the ith energy storage subsystemiFor the battery SOC, SOC of the ith energy storage subsystemi＝xi。
When the battery voltage is used as the equalization control variable,
is the weighted average voltage of all energy storage subsystems, and the weighted average voltage is defined as VwavgThen, then
In equation (2), the upper limit of the battery voltage of the energy storage subsystem is assumed to be VmaxLower limit of Vmin；CiThe battery capacity of the ith energy storage subsystem; viFor battery voltage, V, of the ith energy storage subsystemi＝xi。
When the embodiment of the invention is specifically executed, the deviation between the measured value and the expected value of the balance control variable of each energy storage subsystem is within a set range, and the deviation is regarded as the energy balance of the battery between the energy storage subsystems; if the deviation between the actually measured value and the expected value of the equalization control variable of at least one energy storage subsystem is beyond the set range, the embodiment of the invention performs the equalization control through the following steps S03 to S05.
Step S03: respectively judging the measured value x of the balance control variable of each energy storage subsystem on the premise of keeping at least one energy storage subsystem working in a V/F (voltage/frequency) modeiAnd the weighted average
If the deviation is out of the set range, the process proceeds to step S04, otherwise, the process proceeds to step S05.
Step S04: and controlling the energy storage subsystem to work in a P/Q (active/reactive power) mode, and then returning to the step S01.
Step S05: and controlling the energy storage subsystem to work in the V/F mode, and then returning to the step S01.
Specifically, the energy storage system 100 is a voltage source and is responsible for providing networking support for the entire off-grid microgrid (i.e., maintaining the voltage and frequency on the ac bus stable) and for balancing the power of the entire off-grid microgrid. Power P of energy storage system 100ESS＝PPV-PL，PPVFor the real-time power generation of the power generation system 200, PLReal-time power for load 300; when the power P of the energy storage system 100ESSWhen > 0, the energy storage system 100 charges, when P isESS< 0, the energy storage system 100 discharges, when PESSWhen 0, the energy storage system 100 is at rest.
When the energy storage subsystem works in a V/F mode (namely an energy storage bidirectional converter in the energy storage subsystem works in the V/F mode), the energy storage subsystem is a voltage source, and the charging and discharging power of the energy storage subsystem is uncontrollable. When the energy storage subsystem works in a P/Q mode (namely an energy storage bidirectional converter in the energy storage subsystem works in the P/Q mode), the charging and discharging power of the energy storage subsystem is controllable, and can be set according to a set valueAnd outputting, so that the system power scheduling of the whole off-grid micro-grid can be accurately responded according to the balance requirement. To this end, the embodiment of the present invention lets xiAnd
the energy storage subsystems with the deviation exceeding the set range are switched from the V/F mode to the P/Q mode according to the set power PiOutputting; let xiAnd
the energy storage subsystems with the deviation not exceeding the set range continuously work in a V/F mode, and power is automatically distributed; x of energy storage subsystem working in P/Q modeiAnd
and when the deviation does not exceed the set range, the mode is switched back to the V/F mode in time to ensure the networking robustness of the energy storage system 100.
Wherein, the power P of the ith energy storage subsystem in the P/Q modeiCan be set as
In the formula (3), Pi＞Pmax_chgiWhen is, Pi＝Pmax_chgi，Pmax_chgiThe maximum allowable charging power of the ith energy storage subsystem is obtained; pi＜-Pmax_dischgiWhen is, Pi＝-Pmax_dischgi，Pmax_dischgiThe maximum allowable discharge power of the ith energy storage subsystem; ciThe battery capacity of the ith energy storage subsystem; λ is an equalization adjustment coefficient.
P set in formula (3)iThe power is not distributed to each energy storage subsystem according to the battery capacity of each energy storage subsystem, and the real-time battery energy level of each energy storage subsystem is combined, so that less energy is distributed to the energy storage subsystems with more battery energy, and the peak clipping and valley filling are performedAnd finally, the balance of the battery energy among the energy storage subsystems is realized.
Wherein, in accordance with xiAnd
if the deviation between the energy storage subsystems exceeds a set range, the set range can be expressed as a range [ -a, a [ -a [, a [ ]]The value of a is not suitable to be set too small or too large, the too small value can cause the energy storage subsystem to be frequently switched from the V/F mode to the P/Q mode, and the too large value can cause the energy storage subsystem to work in the P/Q mode for too long time. When the battery voltage is used as the balance control variable, the set range may be the range [ -SOCoffset，SOCoffset]，SOCoffsetGenerally, the content is 1-10%.
As can be seen from the above description, embodiments of the present invention are described in the ith tank subsystem xiAnd
when the deviation is overlarge, the energy storage subsystems are controlled to be switched to a P/Q mode from a V/F mode, system power scheduling of the whole off-grid micro-grid is accurately responded, and battery energy balance among the energy storage subsystems is achieved; meanwhile, the off-grid microgrid is supported by the energy storage system 100 in a networking mode, so that at least one energy storage bidirectional inverter is ensured to work in a V/F mode in the balancing process.
Optionally, the energy storage subsystem is controlled to work in a P/Q (active/reactive power) mode, and the power P of the energy storage subsystem is setiThen, if P is judged to be obtainedESSIf the maximum allowable charging power of the energy storage system is higher than the maximum allowable charging power of the energy storage system, it is necessary to take power limiting measures on the power generation system 200 to ensure the networking robustness of the energy storage system 100 and protect the energy storage battery, and the power limiting value of the power generation system 200 is as follows
Corresponding to the method embodiment, the embodiment of the invention also discloses a battery balance control device, which is used for realizing the battery energy balance among the energy storage subsystems in the off-grid micro-grid. The off-grid micro-grid comprises an energy storage system, a power generation system and an alternating current load which are connected in parallel on the same alternating current bus, wherein the energy storage system is formed by connecting a plurality of energy storage subsystems in parallel. As shown in fig. 4, the battery equalization control apparatus includes:
an obtaining unit 100, configured to obtain measured values of the balance control variables of the energy storage subsystems;
a mean value calculating unit 200, configured to calculate a weighted mean value of the equalization control variables of all energy storage subsystems according to the measured values of the equalization control variables of all energy storage subsystems
A mode switching unit 300, configured to respectively determine the measured value and the weighted average value of the equalization control variable of each energy storage subsystem on the premise of maintaining at least one energy storage subsystem operating in the V/F mode
Whether the deviation between the two exceeds a set range; if not, controlling the energy storage subsystem to work in a V/F mode; and if so, controlling the energy storage subsystem to work in a P/Q mode.
Optionally, the power setting of the ith energy storage subsystem in the P/Q mode is
Wherein, Pi＞Pmax_chgiWhen is, Pi＝Pmax_chgi，Pmax_chgiThe maximum allowable charging power of the ith energy storage subsystem is obtained; pi＜-Pmax_dischgiWhen is, Pi＝-Pmax_dischgi，Pmax_dischgiThe maximum allowable discharge power of the ith energy storage subsystem; i is 1, 2, … and n, wherein n is the total number of the energy storage subsystems; ciIs the ith storageBattery capacity of the subsystem; x is the number ofiThe measured value of the balance control variable of the ith energy storage subsystem is obtained; pESS＝PPV-PL；PPVIs the generated power, P, of the power generation system in the off-grid type microgridLThe power of an alternating current load in the off-grid type microgrid; λ is an equalization adjustment coefficient.
Optionally, the balance control variable is a battery SOC;
correspondingly, the mean value calculating unit 200 is specifically configured to calculate a weighted average SOC of all energy storage subsystems according to the battery SOC of each energy storage subsystem, and record the weighted average SOC as the SOCwavgThen, then
In the formula, SOCiThe battery SOC of the ith energy storage subsystem.
Or, the balance control variable is a battery voltage;
correspondingly, the mean value calculating unit 200 is specifically configured to calculate a weighted average voltage of all energy storage subsystems according to the battery voltages of the energy storage subsystems, and mark the weighted average voltage as VwavgThen, then
In the formula, the upper limit of the battery voltage of the energy storage subsystem is assumed to be VmaxLower limit of Vmin；ViThe battery voltage of the ith energy storage subsystem.
Optionally, as shown in fig. 5, the battery balancing control apparatus further includes a power limiting unit 400, configured to determine PPV-PLWhether the maximum allowable charging power of the energy storage system is larger than or not, if so, taking a power limiting measure on the power generation system, wherein the value of the power limiting measure is
The embodiment of the invention also discloses an off-grid micro-grid, which comprises an energy storage system, a power generation system and an alternating current load which are connected in parallel on the same alternating current bus, wherein the energy storage system is formed by connecting a plurality of energy storage subsystems in parallel; the off-grid microgrid also comprises any battery balance control device disclosed above, and the battery balance control device is in communication connection with the power generation system, the alternating current load and each energy storage subsystem.
Optionally, the power generation system is a photovoltaic power generation system or a wind power generation system.
In summary, the present invention is applied to x of the ith energy storage subsystemiAnd
when the deviation is overlarge, the energy storage subsystems are controlled to be switched to a P/Q mode from a V/F mode, system power scheduling of the whole off-grid micro-grid is accurately responded, and battery energy balance among the energy storage subsystems is achieved; meanwhile, the off-grid micro-grid is supported by an energy storage system in a networking mode, so that at least one energy storage bidirectional inverter is ensured to work in a V/F mode in the balancing process. The invention can realize the battery energy balance of each energy storage subsystem to the maximum extent on the premise of meeting the requirements of maximum power generation of the power generation system as far as possible and stable operation of the off-grid type micro-grid.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. The device disclosed by the embodiment corresponds to the method disclosed by the embodiment, so that the description is simple, and the relevant points can be referred to the method part for description.
In this document, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, the use of the verb "comprise a" to define an element does not exclude the presence of another, identical element in a process, method, article, or apparatus that comprises the element.
For the system embodiment, since it basically corresponds to the method embodiment, the description is relatively simple, and for the relevant points, reference may be made to the partial description of the method embodiment. The above-described embodiments of the apparatus are merely illustrative, and the units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. One of ordinary skill in the art can understand and implement it without inventive effort.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the embodiments. Thus, the present embodiments are not intended to be limited to the embodiments shown herein but are to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. A battery balance control method is characterized by being applied to an off-grid type micro-grid, wherein the off-grid type micro-grid comprises an energy storage system, a power generation system and an alternating current load which are connected in parallel on the same alternating current bus; the energy storage system is formed by connecting a plurality of energy storage subsystems in parallel, each energy storage subsystem comprises an energy storage battery and an energy storage bidirectional converter, the direct current side of each energy storage bidirectional converter is independently connected with the energy storage battery, and the alternating current side of each energy storage bidirectional converter is connected with the alternating current bus in parallel;
the battery balance control method comprises the following steps:
acquiring measured values of balance control variables of each energy storage subsystem;
according to the measured values of the balance control variables of all the energy storage subsystems, calculating to obtain the weighted average value of the balance control variables of all the energy storage subsystems
Respectively judging the measured value and the weighted average value of the balance control variable of each energy storage subsystem on the premise of keeping at least one energy storage subsystem working in a V/F mode
Whether the deviation between the two exceeds a set range;
if not, controlling the energy storage subsystem to work in a V/F mode;
if yes, controlling the energy storage subsystem to work in a P/Q mode;
when the energy storage subsystem works in a P/Q mode, the charging and discharging power of the energy storage subsystem is controllable, and is output according to a set value, and the method specifically comprises the following steps: according to the battery capacity of each energy storage subsystem, and by combining the real-time battery energy level of each energy storage subsystem, less energy is distributed to the energy storage subsystems with more battery energy, and the peak clipping and valley filling are performed, so that the battery energy among the energy storage subsystems is balanced.
2. The battery equalization control method of claim 1, wherein the power setting of the ith energy storage subsystem in P/Q mode is set to
Wherein, Pi＞Pmax_chgiWhen is, Pi＝Pmax_chgi，Pmax_chgiThe maximum allowable charging power of the ith energy storage subsystem is obtained; pi＜-Pmax_dischgiWhen is, Pi＝-Pmax_dischgi，Pmax_dischgiThe maximum allowable discharge power of the ith energy storage subsystem; i is 1, 2, … and n, wherein n is the total number of the energy storage subsystems; ciThe battery capacity of the ith energy storage subsystem; x is the number ofiThe measured value of the balance control variable of the ith energy storage subsystem is obtained; pESS＝PPV-PL；PPVIs the generated power, P, of the power generation system in the off-grid type microgridLThe power of an alternating current load in the off-grid type microgrid; λ is an equalization adjustment coefficient.
3. The battery equalization control method according to claim 1 or 2, wherein the equalization control variable is a battery SOC;
correspondingly, the weighted average
For weighted average SOC, it is recorded as SOCwavgThen, then
In the formula, SOCiThe battery SOC of the ith energy storage subsystem.
4. The battery equalization control method according to claim 1 or 2, wherein the equalization control variable is a battery voltage;
correspondingly, the weighted average
To weightAverage voltage, denoted as VwavgThen, then
In the formula, the upper limit of the battery voltage of the energy storage subsystem is assumed to be VmaxLower limit of Vmin；ViThe battery voltage of the ith energy storage subsystem.
5. The battery equalization control method according to claim 1 or 2, wherein after controlling the energy storage subsystem to operate in the P/Q mode, the battery equalization control method further comprises:
judgment of PPV-PLWhether the maximum allowable charging power of the energy storage system is larger than or not, if so, taking a power limiting measure on the power generation system, wherein the value of the power limiting measure is
6. A battery balance control device is characterized by being applied to an off-grid type micro-grid, wherein the off-grid type micro-grid comprises an energy storage system, a power generation system and an alternating current load which are connected in parallel on the same alternating current bus; the energy storage system is formed by connecting a plurality of energy storage subsystems in parallel, each energy storage subsystem comprises an energy storage battery and an energy storage bidirectional converter, the direct current side of each energy storage bidirectional converter is independently connected with the energy storage battery, and the alternating current side of each energy storage bidirectional converter is connected with the alternating current bus in parallel;
the battery equalization control device includes:
the acquisition unit is used for acquiring measured values of the balance control variables of the energy storage subsystems;
the mean value calculating unit is used for calculating and obtaining the weighted mean value of the balance control variables of all the energy storage subsystems according to the measured values of the balance control variables of all the energy storage subsystems
A mode switching unit for respectively judging the measured value and the weighted average value of the balance control variable of each energy storage subsystem on the premise of keeping at least one energy storage subsystem working in the V/F mode
Whether the deviation between the two exceeds a set range; if not, controlling the energy storage subsystem to work in a V/F mode; if yes, controlling the energy storage subsystem to work in a P/Q mode;
when the energy storage subsystem works in a P/Q mode, the charging and discharging power of the energy storage subsystem is controllable, and is output according to a set value, and the method specifically comprises the following steps: according to the battery capacity of each energy storage subsystem, and by combining the real-time battery energy level of each energy storage subsystem, less energy is distributed to the energy storage subsystems with more battery energy, and the peak clipping and valley filling are performed, so that the battery energy among the energy storage subsystems is balanced.
7. The battery equalization control apparatus of claim 6, wherein the power setting of the ith energy storage subsystem in P/Q mode is set
Wherein, Pi＞Pmax_chgiWhen is, Pi＝Pmax_chgi，Pmax_chgiThe maximum allowable charging power of the ith energy storage subsystem is obtained; pi＜-Pmax_dischgiWhen is, Pi＝-Pmax_dischgi，Pmax_dischgiThe maximum allowable discharge power of the ith energy storage subsystem; i is 1, 2, … and n, wherein n is the total number of the energy storage subsystems; ciThe battery capacity of the ith energy storage subsystem; x is the number ofiThe measured value of the balance control variable of the ith energy storage subsystem is obtained; pESS＝PPV-PL；PPVIs the generated power, P, of the power generation system in the off-grid type microgridLThe power of an alternating current load in the off-grid type microgrid; λ is an equalization adjustment coefficient.
8. The battery equalization control device according to claim 6 or 7, wherein the equalization control variable is a battery SOC;
correspondingly, the mean value calculating unit is specifically configured to calculate a weighted average SOC of all energy storage subsystems according to the battery SOC of each energy storage subsystem, and record the weighted average SOC as the SOCwavgThen, then
In the formula, SOCiThe battery SOC of the ith energy storage subsystem.
9. The battery equalization control device according to claim 6 or 7, wherein the equalization control variable is a battery voltage;
correspondingly, the mean value calculating unit is specifically configured to calculate a weighted average voltage of all energy storage subsystems according to the battery voltages of the energy storage subsystems, and mark the weighted average voltage as VwavgThen, then
In the formula, the upper limit of the battery voltage of the energy storage subsystem is assumed to be VmaxLower limit of Vmin；ViThe battery voltage of the ith energy storage subsystem.
10. An off-grid microgrid is characterized by comprising an energy storage system, a power generation system and an alternating current load which are connected in parallel on the same alternating current bus, wherein the energy storage system is formed by connecting a plurality of energy storage subsystems in parallel;
the off-grid microgrid also comprises a battery balancing control device according to any one of claims 6 to 9, wherein the battery balancing control device is in communication connection with the power generation system, the alternating current load and each energy storage subsystem.
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