CN114513030A

CN114513030A - Battery system, balance control method of battery system and power generation system

Info

Publication number: CN114513030A
Application number: CN202210138964.7A
Authority: CN
Inventors: 赵云飞; 李青; 邵俊伟
Original assignee: Sungrow Energy Storage Technology Co Ltd
Current assignee: Sungrow Energy Storage Technology Co Ltd
Priority date: 2022-02-15
Filing date: 2022-02-15
Publication date: 2022-05-17

Abstract

The application provides a battery system, a balance control method of the battery system and a power generation system, and relates to the technical field of batteries and the technical field of photovoltaic power generation. The battery system includes a controller and a plurality of battery clusters. Each battery cluster comprises a plurality of battery modules connected in series, and each battery module comprises a plurality of battery cells; each battery core is provided with a path of equalizing circuit. When the controller determines that the battery system meets the execution condition of first equalization control according to the first parameter of each battery cell, the controller controls each equalization circuit to perform first equalization control on the battery system; when the battery system does not meet the execution condition of the first balance control and the battery system meets the execution condition of the second balance control according to the second parameter of each battery cell, controlling each balance circuit to perform the second balance control on the battery system; the first parameter includes voltage and capacity and the second parameter includes voltage. By using the scheme, the balanced starting opportunity and the balanced effect are improved.

Description

Battery system, balance control method of battery system and power generation system

Technical Field

The present disclosure relates to the field of battery technologies, and in particular, to a battery system, a balancing method for the battery system, and a power generation system.

Background

With the aggravation of the problems of energy shortage and environmental pollution in the modern society, the photovoltaic power generation is gradually applied at present, but the characteristics of volatility and intermittency of the photovoltaic power generation are increasingly prominent, and the influence on the safe and stable operation of a power grid system is more serious. The battery system has the characteristics of high flexibility, charge and discharge controllability, high energy density and the like, and in order to overcome the above problems of photovoltaic power generation, the photovoltaic power generation system which stores energy by using the battery system is gradually applied.

The battery system generally includes a plurality of battery cells, and the plurality of battery cells are connected in series and in parallel to increase the capacity and output power of the battery system. However, due to the influence of the inconsistency among the cells, the endurance time of the battery system is shortened, a part of the cells may be damaged when overcharging or overdischarging occurs, and a fire or explosion risk exists in a serious case. At present, the electric cores in the battery system are mainly controlled through an electric quantity balancing strategy, that is, the electric quantity of each electric core is detected in real time, and the electric core with high electric quantity is discharged through a balancing resistor, so that the electric quantity of each electric core is balanced.

However, since it is difficult to accurately acquire the charge of each cell, the above method uses an estimated value of the cell charge, resulting in a small chance of starting equalization.

Disclosure of Invention

In order to solve the technical problem, the application provides a battery system, a balancing method of the battery system and a power generation system, so that the balancing starting opportunity is improved, and the balancing effect is further improved.

In a first aspect, the present application provides a battery system for a photovoltaic power generation system, the battery system comprising a controller and a plurality of battery clusters. Every battery cluster in a plurality of battery clusters includes a plurality of battery modules of series connection, and every battery module in a plurality of battery modules includes a plurality of electric cores, and every electric core in a plurality of electric cores sets up equalizer circuit all the way. When the controller determines that the battery system meets the execution condition of first balance control according to the first parameter of each battery cell, the controller controls each balance circuit to perform first balance control on the battery system; and when the battery system does not meet the execution condition of the first balance control and the battery system meets the execution condition of the second balance control according to the second parameter of each battery cell, performing the second balance control on the battery system by controlling each balance circuit.

The first parameter includes voltage and capacity, that is, the first equalization control is electric quantity equalization, and the second parameter includes voltage, that is, the second equalization control is differential pressure equalization. The scheme provided by the application adopts two equalization control modes to equalize the battery system, judges whether the first equalization control can be carried out or not, checks whether the second equalization control condition is met or not after the battery system does not meet the execution condition of the capacity first equalization control, and executes the second equalization control when the second equalization control condition is met so as to increase the equalization starting opportunity, thereby improving the equalization precision and the equalization effect.

In a possible implementation manner, each cell is connected in parallel with one path of equalization circuit.

In one possible implementation, the execution condition of the first equalization control includes: and the electric quantity difference value between the electric cores is greater than or equal to the threshold value of the starting electric quantity difference. And when the difference value between the maximum electric quantity and the minimum electric quantity in the electric quantities of the electric cells is greater than or equal to the threshold value of the difference of the starting electric quantities, the battery system is determined to meet the execution condition of the first balance control.

In a possible implementation manner, the controller specifically determines the state of charge of each battery cell by using an open-circuit voltage method, that is, determines the state of charge of each battery cell by using a pre-calibrated correspondence between the open-circuit voltage and the state of charge and the voltage of each battery cell, and determines the electric quantity of each battery cell by using the state of charge of each battery cell and the capacity of each battery cell. The electric quantity of the battery cell is equal to the product of the charge state of the battery cell and the capacity of the battery cell.

In one possible implementation manner, the first parameter further includes a temperature, and the execution condition of the first equalization control further includes: the temperature of each cell is within a starting temperature range, and the voltage of each cell is within a starting voltage range. This way, the accuracy of the first equalization control can be improved.

In a possible implementation manner, the controller is specifically configured to determine, according to a difference between the electric quantity of each electric core and the minimum electric quantity, the electric quantity that each electric core needs to be released through the balancing circuit; and determining the balance time corresponding to each battery cell according to the electric quantity required to be released by each battery cell through the balance circuit and the balance current of the balance circuit corresponding to each battery cell. The equalization time is equal to the electric quantity consumed by the battery cell divided by the equalization current of the equalization circuit corresponding to the battery cell.

And releasing the electric quantity of each high-electric-quantity battery cell by performing first balance control so as to enable the electric quantity of each battery cell to be equal to the minimum electric quantity.

In one possible implementation manner, the controller is further configured to stop performing the first equalization control on the battery system after the equalization time is ended or when it is determined that the battery system does not satisfy the execution condition of the first equalization control within the equalization time.

In one possible implementation, the execution condition of the second equalization control includes: and the voltage difference value between the battery cells is greater than or equal to the threshold value of the starting voltage difference.

In a possible implementation manner, the second parameter further includes a temperature, and the execution condition of the second equalization control further includes: the temperature of each cell is within the turn-on temperature range and the voltage of each cell is within the turn-on voltage range. This way, the accuracy of the second equalization control can be improved.

In a possible implementation manner, the controller is further configured to determine a starting voltage difference threshold corresponding to a voltage interval in which the voltage of each battery cell is located, where a corresponding relationship between the voltage interval and the starting voltage difference threshold is preset.

In one possible implementation, the controller is further configured to stop performing the second equalization control on the battery system when it is determined that the battery system does not satisfy the execution condition of the second equalization control.

In a second aspect, the present application also provides an equalization method of a battery system, which may be applied to the battery system provided in the above implementation manner, the method including the steps of,

when the battery system is determined to meet the execution condition of first balance control according to the first parameters of each battery cell, each balance circuit is controlled to carry out first balance control on the battery system, and the first parameters comprise voltage and capacity;

and when the battery system does not meet the execution condition of the first balance control and the battery system meets the execution condition of the second balance control according to the second parameter of each battery cell, controlling each balance circuit to perform the second balance control on the battery system, wherein the second parameter comprises voltage.

By using the method, the battery system is balanced by adopting two balancing control modes, whether the first balancing control can be carried out or not is judged firstly, whether the second balancing control condition is met or not is checked after the battery system does not meet the execution condition of the capacity first balancing control, and the second balancing control is executed when the second balancing control condition is met so as to increase the balancing starting opportunity, so that the balancing precision and the balancing effect are improved.

In one possible implementation, the execution condition of the first equalization control includes: the maximum electric quantity difference value among the electric cores is larger than or equal to the threshold value of the starting electric quantity difference;

when it is determined that the battery system meets the execution condition of the first balance control according to the first parameter of each battery cell, controlling each balance circuit to perform the first balance control on the battery system, specifically including:

determining the electric quantity of each battery cell by using the voltage and the capacity of each battery cell;

when the difference value between the maximum electric quantity and the minimum electric quantity in the electric quantities of the electric cores is larger than or equal to the starting electric quantity difference threshold value, determining that the battery system meets the execution condition of first balance control;

and performing first balance control on the battery system by controlling each balance circuit.

In a possible implementation manner, determining the electric quantity of each battery cell by using the voltage and the capacity of each battery cell specifically includes:

determining the charge state of each battery cell by using the corresponding relation between the open-circuit voltage and the charge state calibrated in advance and the voltage of each battery cell;

and determining the electric quantity of each battery cell by using the charge state of each battery cell and the capacity of each battery cell.

In one possible implementation manner, the first parameter further includes a temperature, and the execution condition of the first equalization control further includes: the temperature of each cell is within the opening temperature range.

In a possible implementation manner, controlling each balancing circuit to perform first balancing control on the battery system specifically includes:

determining the electric quantity which needs to be released by each electric core through the equalizing circuit according to the difference value between the electric quantity of each electric core and the minimum electric quantity;

and determining the balance time corresponding to each battery cell according to the electric quantity required to be released by each battery cell through the balance circuit and the balance current of the balance circuit corresponding to each battery cell.

In one possible implementation, the method further includes:

and stopping the first equalization control on the battery system after the equalization time is over or when the battery system is determined not to meet the execution condition of the first equalization control within the equalization time.

In a possible implementation manner, the second parameter further includes a temperature, and the execution condition of the second equalization control further includes: the temperature of each cell is within the turn-on temperature range and the voltage of each cell is within the turn-on voltage range.

In a possible implementation manner, before determining that the battery system satisfies the execution condition of the second balancing control according to the second parameter of each battery cell, the method further includes:

and determining a starting voltage difference threshold corresponding to a voltage interval where the voltage of each battery cell is located, wherein the corresponding relation between the voltage interval and the starting voltage difference threshold is preset.

In one possible implementation, the method further includes:

and stopping performing the second equalization control on the battery system when it is determined that the battery system does not satisfy the execution condition of the second equalization control.

In a third aspect, the present application further provides a power generation system, where the power generation system includes the battery system provided in the foregoing implementation manner, and further includes a power generation end. The power generation end is connected with the battery system, and the power generation system is used for charging the battery system.

The battery system of the power generation system adopts different equalization control modes for equalization, namely the battery system judges whether first equalization control can be carried out or not at first, checks whether a second equalization control condition is met or not after the battery system does not meet the execution condition of capacity first equalization control, and executes the second equalization control when the second equalization control condition is met so as to increase the equalization starting opportunity, thereby improving the equalization precision and the equalization effect.

In one possible implementation, the power generation system is a photovoltaic power generation system.

Drawings

FIG. 1 is a schematic diagram of a photovoltaic power generation system;

fig. 2 is a schematic diagram illustrating a principle of passive equalization of electric quantity of a cell;

fig. 3 is a schematic diagram of a battery system according to an embodiment of the present disclosure;

fig. 4 is a schematic diagram of another battery system provided in an embodiment of the present application;

fig. 5 is a schematic diagram of a starting voltage range of a lithium iron phosphate battery according to an embodiment of the present disclosure;

fig. 6 is a flowchart of an equalizing method of a battery system according to an embodiment of the present disclosure;

fig. 7 is a flowchart illustrating a first equalization control according to an embodiment of the present application;

fig. 8 is a flowchart illustrating a second equalization control according to an embodiment of the present application;

fig. 9 is a schematic view of a photovoltaic power generation system according to an embodiment of the present application.

Detailed Description

In order to make the technical solution more clearly understood by those skilled in the art, an application scenario of the technical solution of the present application is first described below.

Referring to fig. 1, a schematic diagram of a photovoltaic power generation system is shown.

The illustrated photovoltaic power generation system includes a battery system 10, a photovoltaic power generation terminal 20, and a direct current bus.

The direct current bus comprises a positive direct current bus and a negative direct current bus. The output end of the photovoltaic power generation end 20 is connected with a direct current bus, and the direct current bus is also connected with the battery system 10.

The photovoltaic power generation end 20 comprises a plurality of photovoltaic modules, and the photovoltaic modules can be connected in series to form a photovoltaic array; alternatively, a plurality of photovoltaic modules may be connected in series to form a plurality of photovoltaic strings, which are then connected in parallel to form a photovoltaic array. The photovoltaic module is used for converting light energy into direct current and transmitting the direct current to the direct current bus.

The battery system 10 is used for storing electric energy output by the photovoltaic power generation end 20 during the electricity consumption valley period, or converting alternating current provided by a power grid into direct current and then storing the direct current; and discharging at the peak time of electricity usage or when the amount of electricity generated by the photovoltaic power generation terminal 20 is low.

The battery system generally includes a plurality of battery clusters connected in parallel, and each battery cluster may include a plurality of battery modules connected in series, each battery module including a plurality of battery cells. The electric cores in the battery module are connected in series or in series-parallel.

Ideally, all the cell states in the battery system 10 should be consistent, but the production process and the use process may cause inconsistency of the battery pack, and specifically, the production process mainly causes inconsistency of internal resistance and initial capacity state between the cells due to inconsistency of raw materials, and influence of the production process and the production environment; in actual use, the inconsistency of the battery pack is continuously increased due to the difference of the working temperature and the discharge depth of each battery cell.

When the phenomenon of inconsistency exists in the battery pack, the endurance time of a battery system can be shortened, partial electric cores can be overcharged or over-discharged possibly, further damage occurs, the service life of the electric cores is shortened, and even the risk of fire or explosion exists.

Referring to fig. 2, the diagram is a schematic diagram of a principle of passive cell electric quantity equalization.

At present, the electric cores in the battery system are mainly controlled through an electric quantity balancing strategy, each electric core 101 in the battery system is connected in parallel with one path of balancing circuit, and the balancing circuit comprises a resistor R and a controllable switch S. The controller of the battery system controls the controllable switch S to be closed, so that the equalization circuit is switched on, the resistor R discharges electricity to the corresponding battery cell 101, and the balance of the electric quantity of each battery cell is further realized.

Since it is difficult to accurately acquire the remaining capacity of each cell in the actual control process, the above method uses the estimated value of the remaining capacity of the cell, resulting in less chance of starting equalization.

In order to solve the above problems, embodiments of the present application provide a battery system, a balancing method for a battery system, and a photovoltaic power generation system, where two balancing control methods are used to balance a battery system, and first, it is determined whether a first balancing control is possible or not, after the battery system does not satisfy an execution condition of the first balancing control, it is checked whether a second balancing control is satisfied or not, and when the second balancing control is satisfied, the second balancing control is executed to increase a balancing start opportunity, so that a balancing precision and a balancing effect are improved. The first equalization control is electric quantity equalization, and the second equalization control is differential pressure equalization.

In order to make the technical solutions more clearly understood by those skilled in the art, the technical solutions in the embodiments of the present application will be described below with reference to the drawings in the embodiments of the present application.

The terms "first", "second", and the like in the description of the present application are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implying any number of technical features indicated

In the present application, unless expressly stated or limited otherwise, the term "coupled" is to be construed broadly, e.g., "coupled" may be a fixed connection, a removable connection, or an integral part; may be directly connected or indirectly connected through an intermediate.

The embodiment of the present application provides a battery system, which is described in detail below with reference to the accompanying drawings.

The battery system provided by the embodiment of the present application may include one or more battery clusters, and the embodiment of the present application does not limit the specific number of the battery clusters, and only one battery cluster is taken as an example to describe below, and the specific implementation manner of other battery clusters in the battery system is similar.

Referring to fig. 3, the figure is a schematic diagram of a battery system according to an embodiment of the present disclosure.

The illustrated battery system includes a battery cluster 11 and a controller 12.

The battery cluster 11 includes a plurality of battery modules 110 connected in series, and each battery module of the plurality of battery modules 110 includes a plurality of battery cells 101.

Each of the plurality of battery cells 101 is connected in parallel to one of the equalizing circuits 102.

When it is determined that the battery system satisfies the execution condition of the first equalization control according to the first parameter of each battery cell 101, the controller 12 performs the first equalization control on the battery system by controlling each equalization circuit 102.

The first parameter includes voltage and capacity, the voltage is also the real-time output voltage of the battery core, and the capacity refers to the maximum electric quantity that can be stored by the battery.

In some embodiments, the first balance control is electric quantity balance, that is, the electric quantities of the battery cells are controlled to be the same. The electric quantity of the battery cell refers to the electric quantity currently stored by the battery cell, the electric quantity of the battery cell reflects the amount of the electric energy currently stored by the battery cell, and when the battery cell is fully charged, the electric quantity is equal to the capacity of the battery cell. The electric core of high electric quantity discharges during the balanced mode that adopts in this application embodiment to make the electric quantity of the electric core of original high electric quantity, descend to the electric quantity that equals the electric core of low electric quantity, and then make the electric quantity of each electric core the same. After the electric quantity of each electric core is controlled to be the same through electric quantity balance, the discharging synchronism of each electric core is improved, the probability that the discharging of the battery with low electric quantity is finished firstly and other batteries with higher electric quantity are discharged is reduced, when the situation occurs, the battery with low electric quantity is possibly overdischarged, and the damage risk exists, so that the safety of a battery system can be improved by avoiding the occurrence of the situation; and the probability that the situation that the charging of the battery with high electric quantity is finished first and other batteries with lower electric quantity are charged is reduced, when the situation occurs, the battery with high electric quantity is possibly overcharged, and the risk of damage is caused, so that the occurrence of the situation is avoided, and the safety of a battery system can be improved.

When the battery system does not satisfy the execution condition of the first equalization control and it is determined that the battery system satisfies the execution condition of the second equalization control according to the second parameter of each battery cell 101, the controller 12 controls each equalization circuit 102 to perform the second equalization control on the battery system.

The second parameter includes voltage, that is, real-time output voltage of the battery cell. In some embodiments, the second balancing control is voltage difference balancing, that is, the maximum voltage and the minimum voltage of the voltages corresponding to the battery cells are controlled to be within a preset voltage difference threshold.

The scheme provided by the embodiment of the application adopts two equalization control modes to equalize the battery system, firstly judges whether the first equalization control can be carried out or not, checks whether the second equalization control condition is met or not after the battery system does not meet the execution condition of the capacity first equalization control, and executes the second equalization control when the second equalization control condition is met so as to increase the equalization starting opportunity, thereby improving the equalization precision and the equalization effect.

The controller in the above embodiments of the present application may be an Application Specific Integrated Circuit (ASIC), a Programmable Logic Device (PLD), a Digital Signal Processor (DSP), or a combination thereof. The PLD may be a Complex Programmable Logic Device (CPLD), a Field-Programmable Gate Array (FPGA), a General Array Logic (GAL), or any combination thereof, and the embodiments of the present invention are not limited in particular.

Further, the controller in the present application may be a one-stage controller, or may be a multi-stage controller. When the controller is a multi-stage controller, a higher-level controller in the multi-stage controller may perform data communication with a lower-level controller, and the higher-level controller and the lower-level controller may be located at different physical locations, respectively.

In some embodiments, when the controller is a multi-level controller, the controller may include a Container Monitoring Unit (CMU) and a Battery Monitoring Unit (BMU). Each BMU may detect a working State of a corresponding battery module, for example, a State of Charge (SOC), electric quantity information, temperature information, voltage information, and the like of each battery in the corresponding battery module, and send a detection result to the CMU, and the CMU determines whether the battery system needs to satisfy an execution condition of the equalization control according to the acquired information of each battery cell.

The following description is made with reference to specific implementations.

When the battery system provided by the embodiment of the application executes the equalization strategy, whether the condition of electric quantity equalization is met or not is checked firstly, if the condition of starting the electric quantity equalization is met, the electric quantity equalization is executed, if the condition of the electric quantity equalization is not met, whether the condition of starting the pressure difference equalization is met or not is checked continuously, if the condition of starting the pressure difference equalization is met, the pressure difference equalization is executed, and if the condition of starting the electric quantity equalization is not met or the condition of starting the pressure difference equalization is not met, the equalization control is not performed.

Referring to fig. 4, a schematic diagram of another battery system provided in the embodiments of the present application is shown.

For specific description of the battery system, reference is made to the above embodiments, which are not repeated herein, and the equalizing circuit 102 in the embodiment of the present application includes a resistor and a controllable switch connected in series.

The controllable switch in the equalizer circuit may be an Insulated Gate Bipolar Transistor (IGBT), a Metal Oxide Semiconductor Field Effect Transistor (MOSFET), a Silicon Carbide field Effect Transistor (SiC MOSFET), or the like. The controller sends a level signal to the controllable switch to control the controllable switch to be switched on or switched off.

The reason for carrying out the electric quantity equalization is judged firstly in the technical scheme of the application as follows: for a chemical battery used in a battery system, the plateau region where the voltage exists may reduce the chance of triggering voltage equalization. For example, for a lithium iron phosphate battery, when voltage equalization is actually performed, when the electric quantity of the battery is at two ends (that is, when the electric quantity of the battery is higher or lower), the voltage equalization may be triggered more easily, and the electric quantity of the battery is in a middle platform area, so that the voltage equalization is not easily started; however, after the time required for balancing is determined by the power balancing, the power balancing can be performed in the platform area and in the low power or high power, so that the determination of the power balancing is performed first.

First, the principle of the controller controlling the battery system to perform the electric quantity equalization control will be described.

The controller firstly acquires information such as SOC, electric quantity and temperature of each battery cell in the battery system, and then judges whether the current battery system meets the condition for balancing the electric quantity, wherein the condition comprises the following steps: whether the electric quantity difference value between the battery cells is larger than or equal to the starting electric quantity difference threshold value, whether the battery cell temperature is in the starting temperature range and whether the battery cell voltage is in the starting voltage range. The following description will be made separately.

First, an implementation manner of determining whether the electric quantity difference between the battery cells is greater than or equal to the threshold of the starting electric quantity difference by the controller is described below.

The controller acquires the SOC of each battery cell, and the acquisition method may be an Open Circuit Voltage method, an Open Circuit Voltage (OCV), that is, a terminal Voltage of the battery cell in an Open Circuit state, generally having a certain monotonic relationship with the SOC of the battery cell. The data of the open-circuit voltage under different SOCs are tested in advance through experiments, and a relation curve between the open-circuit voltage and the SOC is fitted, so that the SOC corresponding to the battery cell can be estimated according to the measured voltage.

Wherein, the SOC represents the ratio of the current capacity of the battery cell to the fully charged capacity thereof, and is usually expressed in percentage. The value ranges from 0 to 1, and indicates that the cell is completely discharged when the SOC is 0, and indicates that the cell is completely filled when the SOC is 1.

And the controller determines to acquire the residual electric quantity of each battery cell according to the capacity of each battery cell and the corresponding SOC. The product of the capacity of the battery cell and the SOC is the remaining capacity of the battery cell. After the controller obtains the residual electric quantity between the battery cores, the maximum electric quantity and the minimum electric quantity in the residual electric quantity are determined, then the difference value between the maximum electric quantity and the minimum electric quantity is the maximum electric quantity difference value between the battery cores, and the condition is met when the maximum electric quantity difference value is larger than or equal to a starting electric quantity difference threshold value.

In practical application, aiming at the problem that the range of a platform area of a lithium iron phosphate battery core is wide, the SOC is limited to be obtained in a non-platform area when the judgment is carried out by adopting an open-circuit voltage method.

The controller then compares the maximum power difference between the cells to a preset threshold for the on-power difference.

The following describes an implementation manner in which the controller determines whether the cell temperature is within the start temperature range.

In the process of equalizing the electric quantity, the temperature of the battery cell should be within a specified temperature range, otherwise, the voltage sampling precision cannot be guaranteed, and the specific temperature range is determined according to the battery cell and the hardware platform. In some embodiments, the core temperature may be detected by using a temperature sensor, and the temperature sensor may be implemented based on a thermistor, which is a relatively mature prior art and is not repeated herein in the embodiments of the present application.

The controller still needs to judge whether electric core voltage is in opening the voltage range, and when the voltage of electric core was lower, the electric quantity of electric core was lower this moment in the sign, if carry out the electric quantity when electric core electric quantity is lower balanced, the balanced accuracy of electric quantity reduces on the one hand, and on the other hand still makes electric core appear putting excessively easily. Therefore, the equalization control is not started when the electric quantity of the battery cell is low. The starting voltage range is not particularly limited in the embodiments of the present application, and the starting voltage range is related to the type of the battery cell.

Referring to fig. 5, the diagram is a schematic diagram of a starting voltage range of a lithium iron phosphate battery provided in an embodiment of the present application.

The voltage of the lithium iron phosphate battery has a platform area, the voltage difference equalization can be triggered at two ends of the battery power more easily during actual execution, the middle platform area is difficult to execute the voltage difference equalization judgment and start, but after the power equalization judges the required equalization time, the power equalization can be executed in the platform area and at the time of low power or high power, so that the power equalization judgment is performed first, and after the power equalization is not performed, the voltage difference equalization is determined to be performed or not so as to improve the probability of starting the equalization.

The starting voltage range of the lithium iron phosphate battery is between the lower limit voltage BAL _ VOLOFF and the fully charged voltage FULLCAP _ VOL in the figure.

The sequence of the three determinations performed by the controller in the embodiment of the present application is not particularly limited, and may be determined according to actual conditions. In other embodiments, only two conditions may be set as the judgment basis, for example, whether the maximum power difference between the battery cells is greater than or equal to the threshold of the turn-on power difference and whether the battery cell voltage is within the turn-on voltage range, which is not described herein again.

And the controller determines the required equalization time of each battery cell when the three conditions are met. In some embodiments, the equalization time is equal to the amount of power to be discharged divided by the equalization current, which can be detected in real time.

Then, electric quantity equalization is performed on the electric cells needing electric quantity equalization, and for the realization principle of the electric quantity equalization, reference may be made to the description corresponding to fig. 2, that is, the electric cells are discharged by using the resistors in the equalization circuit, so that the electric cells with higher electric quantity consume part of the electric quantity, and further, the maximum electric quantity difference between the electric cells of the battery system is smaller than the threshold of the opening electric quantity difference.

And the controller stops the electric quantity equalization when the equalization time is over, or the cell temperature exceeds the starting temperature range, or the cell voltage is lower than the starting voltage range. The equalization time ending comprises the normal ending of the equalization time and the zero clearing of the equalization time caused by the equalization overtime.

The principle of the controller controlling the battery system to perform the pressure difference equalization is explained below.

The controller firstly acquires information such as voltage and temperature of each electric core in the battery system, and then judges whether the current battery system meets the condition for balancing electric quantity, wherein the condition comprises the following steps: whether the maximum voltage difference between the cells is greater than or equal to the threshold of the starting voltage difference, whether the cell temperature is within the starting temperature range, and whether the cell voltage is within the starting voltage range. The following description will be made separately.

First, an implementation manner of determining whether the voltage difference between the battery cells is greater than or equal to the threshold of the turn-on difference value by the controller is described below.

The controller obtains voltage values of each battery cell in the battery system, then determines the maximum voltage value and the minimum voltage value in the voltage values, then takes the difference value between the maximum voltage value and the minimum voltage value as the maximum voltage difference, compares the maximum voltage difference with a preset threshold value of a starting voltage difference, and meets the condition when the maximum voltage difference is greater than or equal to the threshold value of the starting voltage difference.

The embodiment of the application does not specifically limit the opening voltage difference threshold, and the specific value of the opening voltage difference threshold can be determined by the battery characteristics and the sampling precision.

In some embodiments, the threshold of the turn-on voltage difference may also be dynamically adjusted according to the current cell voltage range, for example, when the cell voltage is faster to change, the corresponding threshold of the turn-on voltage difference is the first voltage difference; when the cell voltage changes slowly, the corresponding threshold of the starting voltage difference is a second voltage difference, the first voltage difference is greater than the second voltage difference, that is, when the cell voltage changes rapidly, the maximum voltage difference between the cells meets the condition of voltage difference balance when the maximum voltage difference between the cells is greater; when the cell voltage changes slowly, the maximum voltage difference between the cells can meet the condition of voltage difference balance when the maximum voltage difference is small.

The specific arrangement needs to incorporate the dynamic characteristics of the cell. Taking the lithium iron phosphate battery in fig. 5 as an example, in the discharging process of the battery cell, a platform region and a region with obvious voltage change exist in a dynamic voltage characteristic curve, and a voltage interval of the battery cell is divided into five continuous intervals, such as [ BAL _ VOLOFF, CAPBAL _ judgedev 1], [ CAPBAL _ judgedev 1, CAPBAL _ judgedev 2], [ CAPBAL _ judgedev 2, CAPBAL _ judgedev 3], [ CAPBAL _ judgedev 3, CAPBAL _ judgeve 4], [ CAPBAL _ judgevev 4, and FULLCAP _ VOL ], where each interval may be set with a threshold of a starting voltage difference correspondingly, and when determining whether to perform voltage difference equalization, the controller determines a corresponding threshold of the starting voltage difference based on the current interval to perform judgment.

The controller still needs to judge whether electric core voltage is in opening voltage range, and when the voltage of electric core was lower, the electric quantity of electric core was lower this moment in the sign, if carry out the pressure differential equilibrium when electric core electric quantity is lower, the balanced accuracy of pressure differential reduces on the one hand, and on the other hand still makes electric core appear overdischarging easily. Therefore, the equalization control is not started when the electric quantity of the battery cell is low. The starting voltage range is not particularly limited in the embodiments of the present application, and the starting voltage range is related to the type of the battery cell.

Continuing with the example of the lithium iron phosphate battery shown in fig. 5, the starting voltage range is between the lower limit voltage BAL _ VOLOFF and the fully charged voltage FULLCAP _ VOL in the figure.

The sequence of the three determinations performed by the controller in the embodiment of the present application is not particularly limited, and may be determined according to actual conditions.

And the controller judges that when the three conditions are met, the pressure difference equalization is executed on the battery cell needing the pressure difference equalization.

The principle of implementing the voltage difference equalization may be as described in fig. 2, that is, the resistance in the equalization circuit is used to discharge the electric core, so that the electric core with higher voltage consumes part of the electric quantity, and the voltage of the electric core is reduced by consuming part of the electric quantity, thereby making the maximum voltage difference between the electric cores of the battery system smaller than the threshold of the opening voltage difference.

And when the maximum voltage difference between the battery cells is smaller than the threshold value of the starting voltage difference, or the battery cell temperature exceeds the starting temperature range, or the battery cell voltage is lower than the starting voltage range, the controller stops the electric quantity equalization.

The battery system that this application embodiment provided judges earlier whether can carry out the electric quantity equilibrium, and the balanced actual opportunity of carrying out of electric quantity can be in for the battery system under static, the state of charging or discharging to introduced pressure differential equilibrium, whether the inspection satisfies pressure differential equilibrium after the execution condition that the battery system does not satisfy the electric quantity equilibrium, in order to increase the balanced chance of opening, when carrying out pressure differential equilibrium, support the dynamic control to opening the voltage differential threshold value, improved balanced precision and balanced effect.

In addition, according to the scheme of the application, equalization judgment and equalization execution are decoupled, for example, when the SOC is 20%, the battery system meets an electric quantity equalization starting condition, the battery core and the equalization time which need to be equalized are determined, the battery core and the equalization time are discharged to be below BAL _ VOLOFF, equalization is closed, and equalization can be directly performed after the battery system is charged to be above BAL _ VOLOFF.

In summary, the scheme provided by the embodiment of the application solves the problems that the equalization starting chance is few and the consistency of a battery system is poor in the actual equalization control process at present.

Based on the battery system provided by the above embodiment, the embodiment of the present application further provides a balancing method for the battery system, which is specifically described below with reference to the accompanying drawings.

Referring to fig. 6, which is a flowchart of an equalization method of a battery system according to an embodiment of the present disclosure.

The method provided in the embodiment of the present application is applied to a battery system, and for a specific implementation manner of the battery system, reference may be made to relevant descriptions in the above embodiments, which are not described herein again, and the method includes the following steps:

s601: when the battery system is determined to meet the execution condition of the first balance control according to the first parameters of the battery cells, the first balance control is performed on the battery system by controlling the balance circuits, wherein the first parameters comprise voltage and capacity.

In some embodiments, the first balance control is electric quantity balance, that is, the electric quantities of the battery cells are controlled to be the same.

S602: and when the battery system does not meet the execution condition of the first balance control and the battery system meets the execution condition of the second balance control according to the second parameter of each battery cell, performing second balance control on the battery system by controlling each balance circuit, wherein the second parameter comprises voltage.

In some embodiments, the second balancing control is voltage difference balancing, that is, the maximum voltage and the minimum voltage of the voltages corresponding to the battery cells are controlled to be within a preset voltage difference threshold.

To sum up, the method provided in the embodiment of the present application performs equalization on the battery system by using two equalization control methods, first determines whether the first equalization control can be performed, checks whether the second equalization control condition is satisfied after the battery system does not satisfy the execution condition of the capacity first equalization control, and executes the second equalization control when the second equalization control condition is satisfied, so as to increase the equalization start opportunity, thereby improving the equalization accuracy and the equalization effect.

The following description is made with reference to specific implementations.

Referring to fig. 7, this figure is a flowchart of the first equalization control performed according to the embodiment of the present application.

S701: and acquiring the voltage, capacity and temperature of each battery cell.

S702: and determining the charge state of each battery cell by using the corresponding relation between the open-circuit voltage and the charge state calibrated in advance and the voltage of each battery cell.

With reference to fig. 5, in practical application, for the problem that the range of the platform area of the lithium iron phosphate core is wide, the SOC should be obtained in the non-platform area when the open-circuit voltage method is adopted for judgment.

S703: and determining the electric quantity of each battery cell by using the charge state of each battery cell and the capacity of each battery cell.

S704: and determining whether the maximum electric quantity difference value among the battery cores is larger than or equal to a starting electric quantity difference threshold value.

If yes, go to S705; otherwise, S711 is executed.

S705: and determining whether the voltage between the battery cells is in a starting voltage range.

If yes, go to S706; otherwise, S711 is executed.

When the voltage of electric core is lower, the electric quantity of electric core was lower this moment in the sign, if carry out the electric quantity equilibrium when electric core electric quantity is lower, the accuracy of electric quantity equilibrium reduces on the one hand, on the other hand still makes electric core appear overdischarging easily. Therefore, the equalization control is not started when the electric quantity of the battery cell is low. The starting voltage range is not particularly limited in the embodiments of the present application, and the starting voltage range is related to the type of the battery cell.

S706: and determining whether the temperature between the battery cells is within the opening temperature range.

If yes, executing S707; otherwise, S711 is executed.

In the process of equalizing the electric quantity, the temperature of the battery cell should be within a specified temperature range, otherwise, the voltage sampling precision cannot be guaranteed, and the specific temperature range is determined according to the battery cell and the hardware platform.

S707: and determining the electric quantity which needs to be consumed by each battery cell according to the difference value of the electric quantity of each battery cell and the minimum electric quantity.

The electric quantity that each electric core needs to consume, the electric quantity that each electric core needs to pass through the equalizer circuit release promptly through releasing the electric quantity for the electric quantity of high electric quantity electric core drops to the electric quantity that is equal to low electric quantity electric core.

For example, when the electric quantity of n cells is q1, q2, q3 and … qn in sequence, n is an integer greater than 1. And if q1 is the minimum value, the electric quantity of the first battery cell does not need to be balanced, the electric quantities of the 2 nd to nth battery cells need to be balanced, the electric quantity of the 2 nd battery cell which needs to be released is q2-q1, the electric quantity of the 2 nd battery cell which needs to be released is q3-q1, and so on, the electric quantity of each nth battery cell which needs to be released is qn-q 1.

S708: and determining the balance time corresponding to each battery cell according to the electric quantity required to be consumed by each battery cell and the balance current of the balance circuit corresponding to each battery cell.

In some embodiments, the equalization time is equal to the amount of power to be discharged divided by the equalization current, which can be detected in real time.

S709: and controlling each balancing circuit to perform first balancing control on the battery system.

S710: it is determined whether an end condition of the first equalization control is satisfied.

If yes, go to S711; otherwise, S709 is executed.

Wherein, the ending condition of the first equalization control is as follows: when the equalization time is over, and when it is determined that the battery system does not satisfy the execution condition of the first equalization control within the equalization time.

S711: the first balance control of the battery system is stopped.

The division of the above steps is only for convenience of description, and does not constitute a limitation to the technical solution of the present application, and a person skilled in the art may adjust the above steps according to actual situations, for example, advance the sequence of steps S705 and S706 to after S701, and further reduce the calculation amount in the process of determining whether the battery system executes the first equalization control when the temperature or the voltage of the battery cell does not satisfy the execution condition of the first equalization control.

Referring to fig. 8, it is a flowchart when performing the second equalization control according to the embodiment of the present application.

S801: when it is determined that the battery system does not satisfy the condition for executing the first equalization control, the voltage of each of the battery cells is acquired.

S802: and determining the threshold of the starting voltage difference corresponding to the voltage interval where the voltage of each battery cell is located.

The corresponding relation between the voltage interval and the threshold of the opening voltage difference is preset.

The threshold of the starting voltage difference can be dynamically adjusted according to the current range of the cell voltage, for example, when the cell voltage is changed rapidly, the corresponding threshold of the starting voltage difference is the first voltage difference; when the cell voltage changes slowly, the corresponding threshold of the starting voltage difference is a second voltage difference, the first voltage difference is greater than the second voltage difference, that is, when the cell voltage changes rapidly, the maximum voltage difference between the cells meets the condition of voltage difference balance when the maximum voltage difference between the cells is greater; when the cell voltage changes slowly, the maximum voltage difference between the cells can meet the condition of voltage difference balance when the maximum voltage difference is small.

S803: and determining whether the maximum voltage difference value between the battery cells is larger than or equal to the threshold of the opening voltage difference.

If yes, go to S804; otherwise, S808 is performed.

S804: and determining whether the voltage between the battery cells is in a starting voltage range.

If yes, go to S805; otherwise, S808 is performed.

S805: and determining whether the temperature between the battery cells is within the opening temperature range.

If yes, executing S806; otherwise, S808 is performed.

S806: and controlling each balancing circuit to perform second balancing control on the battery system.

S807: it is determined whether an end condition of the second equalization control is satisfied.

If yes, go to S808; otherwise, S806 is performed.

S808: and stopping the second balance control on the battery system.

The division of the above steps is only for convenience of explanation and does not limit the technical solution of the present application, and a person skilled in the art can adjust the above steps according to actual situations, for example, the order of steps S and S is changed.

In summary, the scheme provided by the embodiment of the application solves the problems of few equalizing starting opportunities and poor consistency of a battery system in the actual equalizing control process.

Based on the battery system provided by the above embodiment, an embodiment of the present application further provides a power generation system, which includes the battery system described in the above embodiment, and further includes a power generation end. The power generation end is connected with the battery system and used for charging the battery system. In a typical application scenario, the power generation system is a photovoltaic power generation system, which is described in detail below with reference to the accompanying drawings.

Referring to fig. 9, the figure is a schematic view of a photovoltaic power generation system provided in an embodiment of the present application.

The photovoltaic power generation system 900 includes: battery system 10, photovoltaic power generation terminal 20 and dc bus.

The dc bus is used for connecting the battery system 10 and the output terminal of the photovoltaic power generation terminal 20.

For the specific implementation and operation principle of the battery system 10, reference may be made to the description in the above embodiments, and the description of the embodiments of the present application is not repeated here.

The photovoltaic power generation end 20 is used for converting light energy into direct current and transmitting the direct current to a direct current bus. In some embodiments, the photovoltaic power generation end includes a dc combiner box and a plurality of photovoltaic modules. The photovoltaic modules can be connected in series to form a photovoltaic array, or the photovoltaic modules are connected in series to form a plurality of photovoltaic string, and the photovoltaic string is connected in parallel to form the photovoltaic array. The output end of the photovoltaic module is connected with the input end of the Direct Current junction box, and the Direct Current junction box can support the Maximum Power Point Tracking (MPPT) function, namely Direct Current (Direct Current)/Direct Current conversion can be realized. The output end of the dc combiner box is the output end of the photovoltaic power generation end 20, that is, the output end of the dc combiner box is used for connecting a dc bus.

With respect to the specific implementation and operation principle of the battery system 10, reference may be made to the relevant descriptions in the above embodiments, which are not specifically limited in the embodiments of the present application.

In summary, the battery system of the photovoltaic power generation system performs equalization by using two equalization control methods, that is, the battery system first determines whether the first equalization control can be performed, checks whether the second equalization control condition is satisfied after the battery system does not satisfy the execution condition of the capacity first equalization control, and executes the second equalization control when the second equalization control condition is satisfied, so as to increase the equalization start opportunity, thereby improving the equalization precision and equalization effect, and thus improving the safety of the photovoltaic power generation system.

The above description of the power generation system in the embodiment is only one possible implementation manner, and does not constitute a limitation on the power generation system, and the above power generation system may also adopt other implementation manners, such as coupling between the battery system and the power generation end through an ac bus; the power generation system can also be applied to other scenes, such as wind power generation scenes, and the embodiments of the present application are not described herein again.

It should be understood that in the present application, "at least one" means one or more, "a plurality" means two or more. "and/or" for describing an association relationship of associated objects, indicating that there may be three relationships, e.g., "a and/or B" may indicate: only A, only B and both A and B are present, wherein A and B may be singular or plural. The character "/" generally indicates that the former and latter associated objects are in an "or" relationship. "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single item(s) or plural items. For example, at least one (one) of a, b, or c, may represent: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", wherein a, b, c may be single or plural.

The embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. The above-described apparatus embodiments are merely illustrative, and the units and modules described as separate components may or may not be physically separate. In addition, some or all of the units and modules may be selected according to actual needs to achieve the purpose of the solution of the embodiment. One of ordinary skill in the art can understand and implement it without inventive effort.

The foregoing is directed to embodiments of the present application and it is noted that numerous modifications and adaptations may be made by those skilled in the art without departing from the principles of the present application and are intended to be within the scope of the present application.

Claims

1. A battery system, comprising a controller and a plurality of battery clusters;

each battery cluster of the plurality of battery clusters comprises a plurality of battery modules connected in series, and each battery module of the plurality of battery modules comprises a plurality of battery cells;

each of the plurality of battery cells is provided with one path of equalizing circuit;

the controller is configured to perform first equalization control on the battery system by controlling each equalization circuit when it is determined that the battery system satisfies an execution condition of the first equalization control according to the first parameter of each battery cell; when the battery system does not meet the execution condition of the first balance control and the battery system meets the execution condition of the second balance control according to the second parameter of each battery cell, performing the second balance control on the battery system by controlling each balance circuit; the first parameter includes a voltage and a capacity, and the second parameter includes the voltage.

2. The battery system according to claim 1, wherein the execution condition of the first equalization control includes: the electric quantity difference value between the electric cores is greater than or equal to a starting electric quantity difference threshold value;

the controller is specifically configured to determine electric quantities of the battery cells by using the voltages and capacities of the battery cells, and determine that the battery system satisfies the execution condition of the first equalization control when a difference between a maximum electric quantity and a minimum electric quantity in the electric quantities of the battery cells is greater than or equal to the starting electric quantity difference threshold.

3. The battery system according to claim 2, wherein the controller is specifically configured to determine the state of charge of each of the battery cells by using a pre-calibrated correspondence relationship between the open-circuit voltage and the state of charge and the voltage of each of the battery cells, and determine the electric quantity of each of the battery cells by using the state of charge of each of the battery cells and the capacity of each of the battery cells.

4. The battery system according to claim 2, wherein the first parameter further includes temperature, and the execution condition of the first equalization control further includes: the temperature of each of the battery cells is within a starting temperature range, and the voltage of each of the battery cells is within a starting voltage range.

5. The battery system according to claim 2, wherein the controller is specifically configured to determine, according to a difference between the electric quantity of each of the battery cells and the minimum electric quantity, the electric quantity that needs to be released by the balancing circuit for each of the battery cells; and determining the equalization time corresponding to each battery cell according to the electric quantity required to be released by each battery cell through the equalization circuit and the equalization current of the equalization circuit corresponding to each battery cell.

6. The battery system according to claim 5, wherein the controller is further configured to stop performing the first equalization control on the battery system when the equalization time is over or when it is determined that the battery system does not satisfy the execution condition of the first equalization control within the equalization time.

7. The battery system according to any one of claims 1 to 6, wherein the execution condition of the second equalization control includes: and the voltage difference value between the battery cells is greater than or equal to the threshold value of the opening voltage difference.

8. The battery system according to claim 7, wherein the second parameter further includes a temperature, and the execution condition of the second equalization control further includes: the temperature of each of the battery cells is within a turn-on temperature range and the voltage of each of the battery cells is within a turn-on voltage range.

9. The battery system of claim 8, wherein the controller is further configured to determine the threshold of the turn-on voltage difference corresponding to a voltage interval in which the voltage of each of the battery cells is located, and a correspondence relationship between the voltage interval and the threshold of the turn-on voltage difference is preset.

10. The battery system according to claim 9, wherein the controller is further configured to stop performing the second equalization control on the battery system when it is determined that the battery system does not satisfy the execution condition of the second equalization control.

11. The balance control method of the battery system is characterized in that the control method is applied to the battery system, the battery comprises a controller and a plurality of battery clusters, each battery cluster of the plurality of battery clusters comprises a plurality of battery modules connected in series, each battery module of the plurality of battery modules comprises a plurality of battery cells, and each battery cell of the plurality of battery cells is provided with a path of balance circuit, and the method comprises the following steps:

when the battery system is determined to meet the execution condition of first balance control according to the first parameters of the battery cells, controlling the balance circuits to perform the first balance control on the battery system, wherein the first parameters comprise voltage and capacity;

and when the battery system does not meet the execution condition of the first balance control and the battery system meets the execution condition of the second balance control according to the second parameter of each battery core, controlling each balance circuit to perform the second balance control on the battery system, wherein the second parameter comprises the voltage.

12. The balance control method according to claim 11, wherein the execution condition of the first balance control includes: the electric quantity difference value between the electric cores is greater than or equal to a starting electric quantity difference threshold value;

when it is determined that the battery system meets an execution condition of first equalization control according to the first parameter of each battery cell, controlling each equalization circuit to perform the first equalization control on the battery system specifically includes:

when the difference value between the maximum electric quantity and the minimum electric quantity in the electric quantities of the electric cells is greater than or equal to the starting electric quantity difference threshold value, determining that the battery system meets the execution condition of the first balance control;

and performing the first equalization control on the battery system by controlling each of the equalization circuits.

13. The balance control method according to claim 12, wherein the determining the electric quantity of each of the battery cells by using the voltage and the capacity of each of the battery cells specifically comprises:

determining the charge state of each battery cell by using a corresponding relation between the open-circuit voltage and the charge state calibrated in advance and the voltage of each battery cell;

14. The equalization control method according to claim 12, wherein the first parameter further includes temperature, and the execution condition of the first equalization control further includes: the temperature of each of the battery cells is within a starting temperature range, and the voltage of each of the battery cells is within a starting voltage range.

15. The balance control method according to claim 12, wherein the controlling each of the balance circuits to perform the first balance control on the battery system specifically includes:

determining the electric quantity which needs to be released by the equalizing circuit according to the difference value between the electric quantity of each electric core and the minimum electric quantity;

16. The equalization control method of claim 15, further comprising:

and stopping performing the first equalization control on the battery system after the equalization time is over or when the battery system is determined not to meet the execution condition of the first equalization control within the equalization time.

17. The equalization control method according to any one of claims 11 to 16, wherein the execution condition of the second equalization control includes: and the voltage difference value between the battery cells is greater than or equal to the threshold value of the opening voltage difference.

18. The equalization control method according to claim 17, wherein the second parameter further includes temperature, and the execution condition of the second equalization control further includes: the temperature of each of the battery cells is within a turn-on temperature range, and the voltage of each of the battery cells is within a turn-on voltage range.

19. The balance control method according to claim 18, wherein before determining that the battery system satisfies the execution condition of the second balance control according to the second parameter of each of the battery cells, the method further comprises:

and determining the starting voltage difference threshold corresponding to the voltage interval where the voltage of each battery cell is located, wherein the corresponding relation between the voltage interval and the starting voltage difference threshold is preset.

20. The balance control method according to claim 19, further comprising:

21. An electric power generation system comprising the battery system according to any one of claims 1 to 10, and a power generation terminal

The power generation end is connected with the battery system;

the power generation end is used for charging the battery system.