TWI646750B - Energy storage system and charging and discharging method - Google Patents

Abstract

An energy storage system and a charging and discharging method thereof for combining different types or states of batteries and solving the problem of overcharging or overdischarging of individual batteries in a conventional battery module. The energy storage system has a plurality of batteries connected in parallel by a plurality of balancing units, and the plurality of balancing units are connected in series, and an arithmetic unit is coupled to each of the balancing units respectively; the charging and discharging method comprises: starting charging Before discharging, the initial state of charge and a state of health of each battery are measured offline to determine the initial charge and discharge ratio of each battery; during the charging and discharging process, the state of the battery is estimated immediately; The charge and discharge power ratio is distributed, and each of the balance units generates an output voltage or generates a charging current.

Description

Energy storage system and charging and discharging method thereof

The invention relates to an energy storage system and a charging and discharging method thereof, in particular to an energy storage system composed of batteries of different states or types, and a charging and discharging method capable of improving charging and discharging efficiency and prolonging battery life.

A plurality of batteries are formed in a series-parallel manner to form a battery module. The battery module can have a high output voltage and a long discharge time, and can also be charged and discharged repeatedly, and is widely used in various types of power devices. The battery module can be combined with a Battery Management System (BMS) or a Smart Battery System (SBS), by measuring and comparing the potential difference between the two terminals of the battery, or by passing current through each of the batteries. The state of charge (SOC) of each of the batteries is converted into time integrals, and the charge and discharge states of the batteries are controlled to balance the state of charge of the plurality of batteries and to improve the charge and discharge efficiency.

A conventional battery management system compares the potential difference between the two terminals of each battery and the potential difference of all the batteries through a balance module, and if it is higher than the average, it discharges more or less, and if it is lower than the average, it discharges less or more. Charging. However, when the battery module is composed of several batteries of different specifications or different state of health (SOH), it may cause one or more battery states to be saturated or continuously charged, or one or more batteries. The state is far lower than the remaining batteries and continues to discharge, which affects the charging and discharging efficiency of the battery module, and shortens the service life of each battery.

Another conventional battery management system is a battery module that is connected in series Each of the batteries is connected in parallel with a balancing resistor so that excess electric energy generated by the charging or discharging process can be converted into thermal energy by each of the balancing resistors. However, this method causes additional energy consumption, and reduces the charging and discharging efficiency of the battery module, and each battery has different states and different optimal charging and discharging currents, and only a single current passes in the series mode, and The optimal charge and discharge state of each of the batteries cannot be achieved.

In view of this, the conventional battery management system does have the need to improve.

In order to solve the above problems, the present invention provides an energy storage system that enables each of the batteries in the energy storage system to operate independently without being affected by other battery states.

An object of the present invention is to provide a charge and discharge method in which power is distributed through an optimization operation to lengthen a discharge time, and at the end of charge and discharge, the state of charge of each of the batteries is balanced.

The energy storage system of the present invention comprises: a battery module, the battery module is composed of a plurality of batteries; a plurality of balancing units, the plurality of balancing units are connected in parallel to the plurality of batteries, and the plurality of balancing units are Connected in series; an arithmetic unit records a working time of each battery charging and discharging, and the computing unit is coupled to each of the balancing units; an output load electrically connected to the first and last ends of the plurality of balancing units in series And a charging power source, the charging power source is electrically connected to the first and second ends of the plurality of balancing units connected in series, and each balancing unit measures the voltage of the two terminals of each battery, and discharge current through each of the batteries And a charging current and an output voltage of each of the balancing units are transmitted to the computing unit, and the computing unit estimates a power state of each of the batteries and an operation optimization power ratio allocation, and the computing unit controls each of the a balancing unit, wherein the battery module generates the output voltage through the balance unit to act on the output load, and each state of the battery is maintained after discharging Value, or the charging power source to generate the charging current through each of the action in each of the cell balancing unit, each of the state of charge of each of the batteries after charging balance.

Accordingly, the energy storage system of the present invention allows each of the batteries to pass through each of the balancing units. Charge and discharge, and not affected by the state of charge and health of other batteries, can avoid the saturation of the battery state of each battery or continue to charge, or the state of charge is much lower than the remaining batteries continue to discharge, with improved charging and discharging efficiency and extended each The efficacy of the battery's useful life.

The arithmetic unit allocates each of the balancing units in a discharge power ratio to generate the output voltage, and the sum of the plurality of output voltages satisfies a load requirement of the output load. Thus, it has the effect of stabilizing the discharge amount and prolonging the discharge time.

The computing unit allocates one charging power of the charging power source to each of the balancing units in a charging power ratio, and each of the balancing units generates the charging current to pass through each of the batteries. In this way, it has the same effect of improving the charging efficiency and the state of charge after charging.

Wherein, a cutoff voltage and a cutoff charge state are set in the operation unit. In this way, over-discharge or over-charging of the battery can be avoided, and the charging and discharging efficiency is improved and the battery is protected.

A discharge method is applied to an energy storage system, wherein the energy storage system has a plurality of batteries connected in parallel by a plurality of balance units, and the plurality of balance units are connected in series, and the steps of the method include: before starting discharge Setting a load demand and a cutoff voltage; offline measuring each of the initial state of the battery and a health state to determine the initial discharge ratio of each battery; during the discharge process, measuring and recording each of the battery instants a battery terminal voltage, a discharge current, an output voltage of each of the balancing units, and an operating time; estimating the current state of each of the batteries; calculating an optimized discharge power proportional distribution, and converting the ratio to each of the balancing units Output voltage to meet the load demand, and then return to the measuring step; and during the discharging process, determine whether the battery terminal voltage of each battery is less than or equal to the cutoff voltage, and if not, perform estimation and calculation, redistribution Each of the output voltages, if so, isolates the battery from being discharged, and determines whether the sum of the output voltages can satisfy the load demand, and if not, Stop discharge, if yes, perform calculation and estimation, the output voltage of each of the redistribution.

Among them, the optimal discharge power proportional distribution system is operated to solve an objective function and meets several limit expressions. The objective function is as follows: The several restrictions include: Wherein, X _a is the ratio of the discharge power of each of the batteries, t is the time at which the difference in the state of each of the states of charge is minimized according to each of the discharge power ratios X _a , and T is the time at which the battery is measured for the working time, and n is the battery The number, SOC is the state of each charge, SOH is the health state, Ii is a function of the time u of each discharge current, Q is the rated capacity of each battery, j and k are the numbers of the batteries, and j =1, 2, 3, ..., n and k = 1, 2, 3, ..., n. In this way, it has the effect of finding the optimal power ratio distribution.

The plurality of limiting equations include a voltage characteristic equation of the plurality of batteries, and an unequal restriction formula of each of the discharge current, each of the battery terminal voltages, each of the state of charge states, and a conductivity ratio of each of the balancing units. As such, the discharge method is applicable to batteries of different kinds and different states, and has the effect of finding the optimal power distribution.

A charging method is applied to an energy storage system, wherein the energy storage system has a plurality of batteries connected in parallel by a plurality of balancing units, and the plurality of balancing units are connected in series. The steps of the method include: before starting charging Setting a charging power and a cut-off charging state; offline measuring each of the initial state of the battery and a healthy state to determine the initial charging ratio of each battery; during charging, measuring and recording each of the batteries immediately a battery terminal voltage and a charging current and a working time; estimating the current state of each battery of the battery; computing optimized charging The power ratio distribution is further converted into each charging current of each balance unit to satisfy the charging power, and then returned to the measuring step; and during the charging process, it is determined whether each of the battery states of the battery is greater than or equal to the cutoff The state of charge state, if not, then estimate and calculate, redistribute each of the charge currents, and if so, isolate the battery from charging.

Wherein, the optimized charging power proportional distribution system is operated to solve an objective function and conforms to a plurality of limiting formulas, and the objective function is as follows: The several restrictions include: Where X _b is the ratio of the charging power of each of the batteries, t is the time at which the difference in the state of each state of charge is minimized according to each of the charging power ratios X _b , and T is the time at which the battery is measured for the working time, and n is the battery The number, SOC is the state of each charge, SOH is each of the health states, SOC _{set is} the off charge state, Ic is a function of each charge current time u, Q is the rated capacity of each battery, j is each The number of the battery, and j = 1, 2, 3, ..., n. In this way, it has the effect of finding the best power distribution.

The plurality of limiting equations include a voltage characteristic equation of the plurality of batteries, and an unequal restriction formula of each of the charging current, each of the state of charge, each of the battery terminal voltages, and a conduction ratio of each of the balancing units. As such, the charging method is applicable to batteries of different kinds and different states, and has the effect of finding the optimal power distribution.

According to this, in the charge and discharge method of the present invention, the power is distributed by the optimization operation, and the discharge time can be lengthened, and when the charge and discharge are completed, the state of charge of each of the batteries is balanced and improved. Charge and discharge efficiency and the effect of extending the life of each battery.

1‧‧‧ battery module

11‧‧‧Battery

2‧‧‧Balance unit

3‧‧‧ arithmetic unit

4‧‧‧Output load

5‧‧‧Charging power supply

SOC‧‧‧Charge status

SOH‧‧‧Health status

Vi‧‧‧ battery terminal voltage

Ii‧‧‧discharge current

Vo‧‧‧ output voltage

Ic‧‧‧Charging current

T‧‧‧ working hours

V _off ‧‧‧ cutoff voltage

SOC _set ‧‧‧OFF charge status

L‧‧‧load demand

Pc‧‧‧Charging power

Figure 1 is a diagram of an energy storage system in accordance with a preferred embodiment of the present invention.

Figure 2 is a block diagram showing the steps of a discharge method in accordance with a preferred embodiment of the present invention.

Figure 3 is a block diagram showing the steps of a charging method in accordance with a preferred embodiment of the present invention.

The above and other objects, features, and advantages of the present invention will become more apparent from the aspects of the appended claims. An embodiment of the energy storage system of the present invention comprises a battery module 1, a plurality of balancing units 2, an arithmetic unit 3, an output load 4, and a charging power source 5, wherein the plurality of balancing units 2 are respectively electrically The battery module 1 is connected, and the plurality of balancing units 2 are respectively coupled to the computing unit 3, and the plurality of balancing units 2 are connected in series. The first and second ends of the plurality of balancing units 2 are electrically connected to each other. The load 4 and the charging power source 5 are output.

The battery module 1 includes a plurality of batteries 11, each of which can have different state of charge SOC and different health states SOH.

The plurality of balancing units 2 are connected in parallel to the plurality of batteries 11 , and each of the balancing units 2 can have a sensor for measuring the voltage of the battery terminals Vi of each of the batteries 11 and passing through the batteries 11 . a discharge current Ii, a charging current Ic, and a value of the output voltage Vo of each of the balancing units 2, and converting the values of the battery terminal voltage Vi, the respective discharging currents Ii, the charging currents Ic, and the respective output voltages Vo For the signal mode. Each of the balancing units 2 may be a power optimizer or a DC-DC converter having a voltage and current measuring function, and the output voltage Vo or the charging current Ic may be controlled.

The computing unit 3 is coupled to each of the balancing units 2, and the computing unit 3 can receive each of the battery terminal voltages Vi, each of the discharging currents Ii, each of the charging currents Ic and each of the measuring units 2 in a signal mode. The operation unit 3 records a working time T of each of the batteries 11 for charging and discharging, so that the computing unit 3 is configured to estimate each of the battery states SOC of the battery 11, wherein each of the battery terminals The voltage Vi, each of the discharge currents Ii, each of the charging currents Ic, and each of the output voltages Vo and the respective state of charge SOC change with the operating time T. The calculating unit 3 to calculate the optimum ratio of charge-discharge power distribution, each of the balance unit and the second command; the calculating unit 3 can also set a cut-off voltage V _off, and a state of charge off charge SOC _set. The arithmetic unit 3 can be a computer or a microprocessor.

The output load 4 has a load demand L, and the operation unit 3 can set the load demand L. The operation unit 3 causes each of the balance units 2 to adjust each of the output voltages Vo such that the sum of the plurality of output voltages Vo satisfies the Load demand L, which may be load voltage or load power.

The charging power source 5 has a charging power Pc, and the computing unit 3 can set the charging power Pc, and the charging unit Pc is distributed by the computing unit 3, so that each balancing unit 2 controls each charging current Ic passing through each of the batteries 11. .

According to the foregoing structure, the battery module 1 discharges the output load 4 through the plurality of balancing units 2, or the charging power source 5 charges the battery module 1 through the plurality of balancing units 2; the battery terminal voltage Vi is less than or equal to the cut-off voltage V _off, the balancing unit parallel sum by the corresponding 2 isolated from the battery 11, to avoid the battery 11 over discharge; when the state of charge of each of the cells 11 of the SOC is greater than or equal to the cut-off When the charge state SOC _set is charged, the battery 11 is isolated by the balance unit 2 corresponding to the parallel connection, and the battery 11 is prevented from being overcharged.

Referring to Figure 2, a block diagram of the steps of the method of its discharging system of the present invention, before the start of discharge, and sets the load demand of the L off voltage V _off, and off-line measurement of each of the cells 11 of each of the initial state of charge SOC And each of the health states SOH to determine an initial discharge ratio of each of the batteries 11; during the discharge process, measuring and recording each of the battery terminal voltages Vi, each of the discharge currents Ii, and the working time T of the battery 11 The current state of charge SOC can be estimated again, and the optimization operation of the discharge power proportional distribution can be performed according to the above information, and then converted into each of the output voltages Vo of each of the balancing units 2 to satisfy the load demand L; further, the discharge process, it is determined that each of the batteries of the battery terminal voltage Vi 11 is less than or equal to the cut-off voltage V _off, if not, be estimated and the operation of each of the redistribution Vo of the output voltage, if yes, the isolated The battery 11 is no longer discharged, and it is judged whether the sum of the output voltages Vo can satisfy the load demand L. If not, the battery module 1 stops discharging, and if so, the estimation and calculation are performed, and each of the batteries is re-allocated. Voltage Vo of; measuring step back.

The optimization operation of the discharge power proportional distribution solves an objective function and conforms to several limit functions. The objective function is as follows: The several restrictions include: Wherein, X _a is the ratio of the discharge power of each of the batteries 11 , t is the time at which the difference in the state of charge SOC is minimized according to each of the discharge power ratios X _a , and T is the time at which the battery 11 is measured for the working time. n is the number of batteries 11, SOC is the state of each charge, SOH is each of these health states, Ii is a function of time u of each discharge current, Q is the rated capacity of each battery 11, and j and k are each The number of the battery 11 and j = 1, 2, 3, ..., n and k = 1, 2, 3, ..., n.

The plurality of limiting formulas may be the voltage characteristic equations of the plurality of batteries 11 , and the corresponding equations may be replaced according to different types of batteries; the plurality of limiting equations may also be the respective discharging currents Ii and the battery terminal voltages Vi. And each of the state of charge SOC and the unequal limit of the conductivity of each of the balancing units 2 .

Thus, each of the batteries 11 is based on the calculated optimal discharge power ratio. Each of the balance units 2 supplies the respective output voltages Vo, so that the difference between the states of charge SOC of each of the batteries 11 after the discharge is reduced, and the time during which the battery 11 having a low state of charge SOC is isolated is delayed. Extend the discharge time.

Referring to FIG. 3, it is a block diagram of the charging method of the present invention. Before starting charging, the charging power Pc and the off charging state SOC _{set are set} , and the initial amount of each battery 11 is measured offline. a state SOC and each of the health states SOH to determine an initial charging ratio of each of the batteries 11; during charging, measuring and recording each of the battery terminal voltages Vi, each of the charging currents Ic, and the working time T, the current state of charge SOC can be estimated again, and the optimization operation of the charging power proportional distribution can be performed according to the above information, and then converted into each charging current Ic that each balancing unit 2 charges each of the batteries 11. And satisfying the charging power Pc; and, in the charging process, determining whether each of the state of charge SOC of each of the batteries 11 is greater than or equal to the off-state charge state SOC _set ; if not, performing estimation and calculation, reallocating each The charging current Ic, if yes, isolates the battery 11 from being recharged; and returns to the measuring step; when all of the batteries 11 are isolated, the battery module 1 stops accepting charging.

The optimization operation of the charging power proportional distribution solves an objective function and conforms to several restrictions. The objective function is as follows: The several restrictions include: Where X _b is the charging power ratio of each of the batteries 11 , t is the time at which the difference in the state of charge SOC is minimized according to each of the charging power ratios X _b , and T is the time at which each of the batteries 11 is measured for the working time, n For the number of the batteries 11, the SOC is the state of each of the states of charge, the SOH is for each of the states of health, the SOC _{set is} the state of the off-charge state, Ic is a function of the time u of each of the charging currents, and Q is the rating of each of the batteries 11. The capacity, j is the number of each of the batteries 11, and j = 1, 2, 3, ..., n.

The plurality of limiting formulas may be the voltage characteristic equations of the plurality of batteries 11 , and the corresponding equations may be replaced according to different types of batteries; the plurality of limiting formulas may also be the respective charging currents Ic, the states of the respective states of charge SOC, Each of the battery terminal voltage Vi and the conduction ratio of each of the balancing units 2 are unequal.

In this way, each of the balancing units 2 charges each of the batteries 11 with each of the charging currents Ic according to the calculated optimal charging power ratio, so that the difference between the states of charge SOC of each of the batteries 11 after charging can be reduced. And avoiding excessive charging current Ic causing damage to each of the batteries 11.

The discharge method and the charging method of the present invention are applied to the plurality of batteries, and each of the batteries 11 may be a different type of battery, and each of the state of charge SOC and each of the states of health SOH may be different.

In summary, the energy storage system of the present invention and the charging and discharging method thereof enable each of the batteries to be charged and discharged by each of the balancing units without being affected by the state of charge and health of other batteries, and are distributed through optimization operations. The power can make the discharge time lengthen, and at the end of the charge and discharge, the state of charge of each battery is balanced, and the utility model has the effects of improving the charge and discharge efficiency and prolonging the service life of each battery.

While the invention has been described in connection with the preferred embodiments described above, it is not intended to limit the scope of the invention. The technical scope of the invention is protected, and therefore the scope of the invention is defined by the scope of the appended claims.

Claims (10)

An energy storage system comprising: a battery module, the battery module is composed of a plurality of batteries; a plurality of balancing units, the plurality of balancing units are connected in parallel to the plurality of batteries, and the plurality of balancing units are connected in series An operation unit records a working time of charging and discharging each of the batteries, and the computing unit is coupled to each of the balancing units; an output load electrically connected to the first and second ends of the plurality of balancing units in series And a charging power source, the charging power source is electrically connected to the first and second ends of the plurality of balancing units connected in series, and each balancing unit measures the voltage of the two terminals of the battery, the discharge current through each of the batteries, and Charging current and one of the balance unit output voltages are transmitted to the operation unit, and the operation unit estimates one of the battery state of charge and the operation optimization power ratio distribution, and the operation unit controls each of the balance units And causing the battery module to generate the output voltage through the balance unit to act on the output load, and each state of the battery is balanced after discharging. The charging power source or charging current is generated through the action of each of the units in each of the cell balancing, each of the state of charge of each of the batteries after charging balance. The energy storage system of claim 1, wherein the arithmetic unit allocates each of the balancing units in a discharge power ratio to generate the output voltage, and the sum of the plurality of output voltages satisfies a load requirement of the output load. The energy storage system of claim 1, wherein the computing unit allocates one charging power of the charging power source to each of the balancing units in a charging power ratio, and each of the balancing units generates the charging current through each of the batteries. The energy storage system of claim 1, wherein a cutoff voltage and a cutoff charge state are set in the arithmetic unit. A discharge method is applied to an energy storage system, wherein the energy storage system has a plurality of batteries connected in parallel by a plurality of balance units, and the plurality of balance units are connected in series, and the steps of the method include: before starting discharge Setting a load demand and a cutoff voltage; offline measuring each of the initial state of the battery and a health state to determine the initial discharge ratio of each battery; during the discharge process, measuring and recording each of the battery instants a battery terminal voltage, a discharge current, an output voltage of each of the balancing units, and an operating time; estimating the current state of each of the batteries; calculating an optimized discharge power proportional distribution, and converting the ratio to each of the balancing units Output voltage to meet the load demand, and then return to the measuring step; and during the discharging process, determine whether the battery terminal voltage of each battery is less than or equal to the cutoff voltage, and if not, perform estimation and calculation, redistribution Each of the output voltages, if yes, isolates the battery from being discharged, and determines whether the sum of the output voltages can satisfy the load demand, and if not, stops Discharging, if yes, perform calculation and estimation, the output voltage of each of the redistribution. The discharge method according to claim 5, wherein the optimized discharge power proportional distribution system calculates an objective function and conforms to a plurality of limit functions, and the objective function is as follows: The several restrictions include: Wherein, X _a is the ratio of the discharge power of each of the batteries, t is the time at which the difference in the state of each of the states of charge is minimized according to each of the discharge power ratios X _a , and T is the time at which the battery is measured for the working time, and n is the battery The number, SOC is the state of each charge, SOH is the health state, Ii is a function of the time u of each discharge current, Q is the rated capacity of each battery, j and k are the numbers of the batteries, and j =1, 2, 3, ..., n and k = 1, 2, 3, ..., n. The discharge method of claim 6, wherein the plurality of restrictions include a voltage characteristic equation of the plurality of batteries, and each of the discharge currents, the battery terminal voltages, the states of the respective states, and the balances The unequal limit of the conductivity of the unit. A charging method is applied to an energy storage system, wherein the energy storage system has a plurality of batteries connected in parallel by a plurality of balancing units, and the plurality of balancing units are connected in series. The steps of the method include: before starting charging Setting a charging power and a cut-off charging state; offline measuring each of the initial state of the battery and a healthy state to determine the initial charging ratio of each battery; during charging, measuring and recording each of the batteries immediately a battery terminal voltage and a charging current and a working time; estimating the current state of each battery; calculating an optimized charging power ratio distribution, and converting the charging current to each of the balancing units to satisfy the Charging power, and then returning to the measuring step; and during the charging process, determining whether each of the battery states of the battery is greater than or equal to the off-state charge state, and if not, performing estimation and calculation, and reallocating each of the charging currents If yes, the battery is no longer charged. The charging method according to claim 8, wherein the optimized charging power ratio distribution system calculates an objective function and conforms to a plurality of limit functions, and the objective function is as follows: The several restrictions include: Where X _b is the ratio of the charging power of each of the batteries, t is the time at which the difference in the state of each state of charge is minimized according to each of the charging power ratios X _b , and T is the time at which the battery is measured for the working time, and n is the battery The number, SOC is the state of each charge, SOH is each of the health states, SOC _{set is} the off charge state, Ic is a function of each charge current time u, Q is the rated capacity of each battery, j is each The number of the battery, and j = 1, 2, 3, ..., n. The charging method of claim 9, wherein the plurality of limiting formulas comprise voltage characteristic equations of the plurality of batteries, and each of the charging currents, each of the state of charge states, each of the battery terminal voltages, and each of the balances The unequal limit of the conductivity of the unit.