Circuit and control method for voltage measurement and balancing of energy storage monomers

Abstract

The present invention is a circuit and control method for measuring and balancing the voltage of energy storage monomers, and the switch device K i1 With transformer T i The winding 1 is connected in series and then in parallel to the energy storage monomer B i At both ends of the transformer T i One end of winding 2 is connected to node A; transformer T i The other end of winding 2 passes through the switching device K i2 Connected to node B and passing through switch device K i3 Connected to node D; DC power supply V1 and switch device K V1 After being connected in series, they are connected at both ends of node A and node B, wherein the negative pole of DC power supply V1 is connected to node B, and the positive pole of DC power supply V1 is led to node C; DC power supply V2 is connected to switch device K V2 After being connected in series, they are connected in parallel at both ends of node A and node B, where the negative pole of the DC power supply V2 is connected to node B; the voltage conditioning circuit is connected at both ends of node C and node D. This circuit can realize the functions of voltage measurement and voltage balancing circuits, organically combining the two circuits together to improve the reliability and cost of the system.

Description

Technical Field

[0001] The present invention relates to the field of energy storage, and in particular to a circuit and a control method for voltage measurement and balancing of energy storage cells. Background Art

[0002] With the rapid development of energy storage technology and its applications, energy storage monomers represented by lithium-ion batteries and supercapacitors have been increasingly widely used in small portable devices, electric vehicles, energy storage power stations and other systems. Since the voltage of energy storage monomers is generally low, in order to meet the voltage and power level requirements of the load, energy storage monomers with lower voltage levels are usually connected in series to form a string (hereinafter referred to as a series energy storage string) to increase the voltage level.

[0003] When energy storage cells are repeatedly charged or discharged, the voltage between the series energy storage cells will gradually become unbalanced due to differences in capacity, internal resistance, self-discharge rate, etc., causing the cells with lower capacity in the system to repeatedly experience a vicious cycle of overcharge / overdischarge. The overcharge / overdischarge of some energy storage cells in the system not only affects the life of these cells, reducing the available capacity of the entire system, but in worse cases, it can also cause dangerous accidents such as fire or explosion.

[0004] Based on the above reasons, energy storage systems usually need to be equipped with energy storage cell voltage measurement circuits and energy storage cell balancing circuits. Figure 1 As shown, the energy storage monomer B is connected in series 1 -B n Through the bidirectional converter charging and discharging, the energy storage monomer B is connected in series 1 -B n Connect voltage measurement circuit and equalization circuit.

[0005] The resistor voltage divider method and the operational amplifier differential amplification method are the two most commonly used voltage measurement methods. The resistor voltage divider method has a relatively complex configuration and poor scalability, while the operational amplifier differential amplification method requires the use of an isolated operational amplifier, which increases the cost of the system. Equalization technology is divided into two types: passive balancing technology and active balancing technology. Compared with passive balancing circuits, active balancing circuits have the advantages of fast balancing speed and high balancing efficiency. Typical active balancing technologies include balancing solutions based on bidirectional DC / DC converters, capacitors, inductors or transformers, etc. The existing bidirectional DC / DC converter method requires an additional isolated voltage measurement circuit, and the existing transformer balancing solution mostly adopts balancing based on multi-winding transformers. This method has multiple windings and strict requirements on parameter matching between windings, which brings difficulties to the design and reduces scalability. Summary of the invention

[0006] In view of the deficiencies of the prior art, the technical problem to be solved by the present invention is to provide a circuit for voltage measurement and equalization of energy storage cells and a control method thereof, which can realize the functions of voltage measurement and voltage equalization circuits, organically combine the two circuits, and do not require the introduction of additional isolation circuits, thereby improving the reliability and cost of the system. The control method can measure the voltage of energy storage cells and balance energy storage between energy storage cells in the three working states of the energy storage system, namely, charging, discharging and static states, and can implement balancing in multiple working states.

[0007] The technical solution adopted by the present invention to solve the technical problem is:

[0008] In the first aspect, the present invention provides a circuit for measuring and balancing the voltage of energy storage cells, characterized in that a single energy storage cell is used for B i Indicates, i = 1 ~ n, the switch device K i1 With transformer T i The winding 1 is connected in series and then in parallel to the energy storage monomer B i At both ends of the transformer T i One end of winding 2 is connected to node A, where transformer T i The terminal of winding 2 connected to node A is connected to the winding 1 of transformer Ti and the energy storage monomer B i The terminals connected to the positive poles are opposite terminals; transformer T i The other end of winding 2 passes through the switching device K i2 Connected to node B and passing through switch device K i3 Connected to node D, where transformer T i Winding 2 and switching device K i2 and switch device K i3 The terminals connected to the winding 1 of the transformer Ti are the same as the energy storage monomer B i The terminals connected to the positive poles are the same-name terminals; the DC power supply V 1 With the switch device K V1 After being connected in series, they are connected at both ends of node A and node B, where the DC power supply V 1 The negative pole is connected to node B, and the DC power supply V 1 The positive electrode leads to node C; DC power supply V 2 With the switch device K V2 After being connected in series, they are connected in parallel at both ends of node A and node B, where the DC power supply V 2 The negative electrode is connected to the node B; the voltage conditioning circuit is connected to both ends of the node C and the node D;

[0009] The above connection method is repeated n times, that is, from i=1 to i=n, ​​n is the number of energy storage monomers connected in series, and the nodes A and B connected by the n energy storage monomers are the same connection point.

[0010] In a second aspect, the present invention further provides a control method for the circuit for measuring and balancing the voltage of energy storage monomers, wherein the switch device K il is a diode, the switching device K i2 A diode is connected in parallel or no diode is set; the process of this control method is:

[0011] 1) Measure voltage. The energy storage system must measure the voltage of the energy storage monomer when it is in the charging and discharging working state. It is not necessary to measure the voltage of the energy storage monomer when it is at rest. If it is necessary to implement balancing at rest, voltage measurement must be performed;

[0012] 1-1) K V2 Disconnect, K i3 Closed, K V1 Under closed conditions, closed K i2 , the initial value of i is 1;

[0013] 1-2) After a given time t 2 After shutting off K i2 , control t 2 The value is less than or equal to V Bmin / f s (V 1 +V Bmin ), where V Bmin is the discharge cut-off voltage of the energy storage unit;

[0014] 1-3) In K i2 After shutdown, the voltage conditioning circuit samples and processes the voltage across CD, and obtains B by detecting the knee voltage. i Voltage;

[0015] 1-4) Repeat the above steps n times, i.e., from i=1 to i=n, ​​to achieve voltage measurement of n series-connected energy storage cells;

[0016] 2) Implementation balance

[0017] 2-1) According to the measured values ​​of the voltages of each energy storage cell, when the balancing requirements are not met, balancing is performed to determine the target cell that needs to be charged and discharged during balancing: balancing is performed by selecting a cell with the lowest voltage for charging;

[0018] The process of charging and controlling the energy storage monomer with the lowest voltage is:

[0019] Select the energy storage cell with the lowest voltage as the target cell through V 2 To charge, if B i The voltage is the lowest, then switch K V2 Closed, K i3 Shutdown, K V1 Shutdown, K i2Closed, K i2 During the closing period, i Charging; time t E2 Shutdown K i2 , control t E2 The value of the time period is less than or equal to V Bmin / f s (V 2 +V Bmin ), thereby ensuring the core reset;

[0020] 2-2) Selection of balanced implementation plan

[0021] The energy storage system has three working states, namely, charging state, discharging state and static state. There are seven schemes for implementing balancing: (1) balancing in the charging state; (2) balancing in the discharging state; (3) balancing in the static state; (4) balancing in the charging state and balancing in the discharging state; (5) balancing in the charging state and balancing in the static state; (6) balancing in the discharging state and balancing in the static state; (7) balancing in the charging state, balancing in the discharging state and balancing in the static state.

[0022] The specific process of the above sampling and processing is as follows: the voltage across CD is converted to analog after being divided by resistors, a Zener diode is connected between the ADC module and node C to limit the voltage connected to the ADC module to a safe operating range, and the ADC module is delayed for a short time with a value of t c Multiple sampling is performed for the sampling period, where t c <1 / (10f s ), before the knee point, the voltage across CD decreases linearly, with t c The voltage difference between two adjacent samples with an interval is approximately equal. After passing the knee point, the voltage slope at both ends of CD changes, and the voltage difference between the two samples before and after the knee point suddenly increases. The voltage sampling result before the knee point is approximately the knee point voltage.

[0023] In a third aspect, the present invention provides a control method for the circuit for measuring and balancing the voltage of energy storage monomers, wherein the switch device K i1 Including diode D i1 and active switch Q i1 ; diode D i1 Connected in parallel to the active switch, the parallel diode D i1 Can be K i1 The body diode or an external diode, diode D i1 The negative pole of the transformer T is connected i One end of winding 1, diode D i1 The positive electrode is connected to the energy storage monomer B iThe negative electrode of the switching device K i2 Including diode D i2 and active switch Q i2 , diode D i2 The positive terminal is connected to the unidirectional power supply V 1 The cathode of diode D i2 The negative terminal of the i At one end of the winding 2, the active switch is at least one of MOSFET, IGBT, relay, GTO, and triode; the DC power supply V 1 It is a unidirectional power supply, DC power supply V 2 It is a bidirectional power supply. The process of this control method is:

[0024] 1) Measure voltage. The energy storage system must measure the voltage of the energy storage monomer when it is in the charging and discharging working state. It is not necessary to measure the voltage of the energy storage monomer when it is at rest. If it is necessary to implement balancing at rest, voltage measurement must be performed;

[0025] 1-1) In the switching device K V2 Disconnect, active switch Q i1 Disconnect, switch device K i3 Closed, switch device K V1 Under the closed condition, the active switch Q is closed i2 ;The initial value of i is 1;

[0026] 1-2) After a given time t 2 Post-active switch Q i2 , t 2 The value is less than or equal to V Bmin / [f s (V 1 +V Bmin )],

[0027] Where V Bmin is the discharge cut-off voltage of the energy storage unit, V 1 is the DC power supply V 1 The voltage of f s is the switching frequency;

[0028] 1-3) After the dead time, turn on the switch device K i1 ; Active switch Q i1 Closed or open refers to K i1 Close or open, 1-4) control switch device K i1 The on time is equal to the given time t 1 , t 1 The value is less than (t 2 V 1 ) / V Bmax ,

[0029] Where V Bmax is the charging cut-off voltage of the energy storage monomer,

[0030] In t 1 During the time period, the voltage conditioning circuit samples and processes the voltage across CD to obtain B i Voltage;

[0031] 1-5) Repeat the above steps n times, i.e., from i=1 to i=n, ​​to achieve voltage measurement of n series-connected energy storage cells;

[0032] 2) Implementation balance

[0033] 2-1) According to the measured values ​​of the voltage of each energy storage cell, when the balancing requirements are not met, balancing is performed to determine the target cell that needs to be charged and discharged during balancing:

[0034] There are three methods: (1) Select the energy storage unit with the highest voltage as the target unit for discharge in a cycle. A cycle refers to the discharge of B 1 To B n The same operation is performed sequentially; (2) in a cycle, an energy storage monomer with the lowest voltage is selected as the target monomer for charging; (3) method (1) and method (2) are performed alternately, that is, if the energy storage monomer with the highest voltage is selected as the target monomer for discharging in the kth cycle, then the energy storage monomer with the lowest voltage is selected as the target monomer for charging in the k+1th cycle; if the energy storage monomer with the lowest voltage is selected as the target monomer for charging in the kth cycle, then the energy storage monomer with the highest voltage is selected as the target monomer for discharging in the k+1th cycle;

[0035] 2-2) The process of discharging the energy storage unit with the highest voltage is:

[0036] Select the highest voltage series energy storage monomer through V 2 Discharge, if B i The voltage is the highest, then switch K V2 Closed, K i3 Shutdown, K V1 Shutdown, K i1 Closed, K i1 During the closing period, i Discharge, at this time K i2 Disconnect; after time t E1 Shutdown K i1 , control t E1 The value of the time period is less than or equal to V 2 / f s (V 2 +V Bmax );

[0037] 2-3) The process of charging the energy storage monomer with the lowest voltage is:

[0038] Select the lowest voltage series energy storage monomer through V 2 To charge, if B i The voltage is the lowest, then switch K V2 Closed, K i3 Shutdown, K V1 Shutdown, K i2 Closed, K i2 During the closing period, i Charging; time t E2 Shutdown K i2 , control t E2 The value of the time period is less than or equal to V Bmin / f s (V 2 +V Bmin );

[0039] K V2 The entire switching cycle T s Closed, where T s =1 / f s , K V1 The entire switching cycle T s Shutdown, K i3 The entire switching cycle T s Shut down;

[0040] 2-4) Selection of balanced implementation plan

[0041] The energy storage system has three working states, namely, charging state, discharging state and static state. There are seven balancing implementation schemes: (1) balancing in the charging state; (2) balancing in the discharging state; (3) balancing in the static state; (4) balancing in the charging state and balancing in the discharging state; (5) balancing in the charging state and balancing in the static state; (6) balancing in the discharging state and balancing in the static state; (7) balancing in the charging state, balancing in the discharging state and balancing in the static state.

[0042] The sampling and processing process of step 1-4) is as follows: the voltage at both ends of CD is converted into digital-to-analog after being divided by resistors, a Zener diode is connected between the ADC module and node C to limit the voltage connected to the ADC module to a safe range, and the ADC module is switched to the ADC module after a short delay at t c Multiple sampling is performed for the sampling period, where t c <1 / (10f s ), take the average value of the sampling results of the ADC module and get B i voltage.

[0043] The above sampling period t c , switching cycle T s , time t E1 ,t E2 , time t 2 ,t 1 They are all numbers greater than 0, and the specific values ​​can be set according to actual working conditions.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] (1) It can realize the two functions of isolated voltage measurement of energy storage cells and balancing between energy storage cells. For each energy storage cell, the two functional circuits reuse one transformer (the transformer in the present invention is a double-winding transformer with only one primary side and one secondary side, and there is no problem of winding mismatch), reuse two devices with switching functions, reuse connecting wires, simplify the system, improve reliability, and reduce costs.

[0046] (2) The electrical isolation of the energy storage unit and the balancing circuit is achieved, the transformer and connecting wires are reused, and the isolation of the energy storage unit and the measurement circuit is achieved.

[0047] (3) The system can operate in all working states of the energy storage system: charging state, discharging state and static state, and is therefore not limited by the working state of the energy storage system.

[0048] (4) It is possible to select the target energy storage unit according to the working status of the energy storage system and the voltage measurement results, and perform charge balancing or discharge balancing on it, thereby having a fast balancing speed and balancing efficiency, without generating additional heat, and having high efficiency.

[0049] (5) It has good scalability and is not limited by the number of energy storage units, so it can be used in various energy storage systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 Schematic diagram of the energy storage system.

[0051] Figure 2 Schematic diagram of the structure of the circuit used for energy storage cell voltage measurement and balancing.

[0052] Figure 3A Schematic diagram of the voltage measurement and equalization circuit for hardware configuration type 1.

[0053] Figure 3B Schematic diagram of the voltage measurement and equalization circuit for hardware configuration type 2.

[0054] Figure 4(a) shows the voltage measurement process of K in hardware configuration type 1. V2 Disconnect, K i1 Disconnect, K i3 Closed, KV1 Closed, K i2 Schematic diagram of the closing process.

[0055] Figure 4(b) shows the voltage measurement process of K in hardware configuration type 1. V2 Disconnect, K i1 Disconnect, K i3 Closed, K V1 Closed, K i2 Schematic diagram of the disconnection process.

[0056] Figure 4(c) shows the voltage measurement process of K in hardware configuration type 1. V2 Disconnect, K i1 Closed, K i3 Closed, K V1 Closed, K i2 Schematic diagram of the disconnection process.

[0057] Figure 4(d) shows the voltage measurement process of K in hardware configuration type 1. V2 Disconnect, K i1 Disconnect, K i3 Closed, K V1 Closed, K i2 Schematic diagram of the disconnection process.

[0058] Figure 5 Schematic diagram of the voltage waveform across CD.

[0059] Figure 6(a) shows the voltage measurement process of K in hardware configuration type 2. V2 Disconnect, K i3 Closed, K V1 Closed, K i2 Schematic diagram of the closing process.

[0060] Figure 6(b) shows the voltage measurement process of K in hardware configuration type 2. V2 Disconnect, K i3 Closed, K V1 Closed, K i2 Schematic diagram of the disconnection process.

[0061] Fig. 7A Schematic diagram of equalization of Example 1.

[0062] Figure 7B Schematic diagram of equalization of Example 2.

[0063] Figure 7C Schematic diagram of equalization of Example 3.

[0064] Fig.7D Schematic diagram of equalization of Example 4.

[0065] Fig. 7E Schematic diagram of equalization of Example 5.

[0066] Figure 7F Schematic diagram of equalization of Example 6.

[0067] Figure 8 The switch device K of a certain energy storage unit in hardware configuration type 1 i1 , K i2 Schematic diagram of the connection circuit.

[0068] Fig. 9 K is the switching device V2 , Switching device K V1 , Switching device K i3 Schematic diagram of the connection circuit when MOSFET is used.

[0069] Fig.10 K is the switching device V2 , Switching device K V1 , Switching device K i3 Schematic diagram of the connection circuit when IGBT is used.

[0070] Fig.11 K is the switching device V2 , Switching device K V1 , Switching device K i3 Schematic diagram of the connection circuit when relays are used.

[0071] Fig.12 The switch device K of a certain energy storage unit in hardware configuration type 2 i1 , K i2 Schematic diagram of the connection circuit. DETAILED DESCRIPTION

[0072] The present invention is further explained below in conjunction with the embodiments and drawings, but this is not intended to limit the scope of protection of the present application.

[0073] The circuit connection of the present invention for measuring and balancing the voltage of energy storage monomers is as follows Figure 2 As shown: Figure 2 Middle, B i (i=1,2,……n) represents the energy storage monomer, n is the number of energy storage monomers connected in series, which can be batteries or supercapacitors, and can be a single monomer or a combination of multiple monomers in series and parallel. Hereinafter referred to as energy storage monomer, B i The voltage is V Bi Indicates; each B i The energy storage string is connected in series, which is referred to as the series energy storage string below. The external power supply can charge the energy storage string through the transformer, and the energy storage string can also discharge the external load through the transformer. i The inductance of winding 1 is L i1 , transformer T iThe inductance of winding 2 is L i2 , the transformation ratio of winding 1 to winding 2 is N, winding 1 and winding 2 represent the primary side or the secondary side; K i1 , K i2 is a device with switching function, where K il It can be a MOSFET, other active switches in parallel with a diode, or a diode; K i2 It can be a MOSFET, other active switching devices, or other active switching devices in parallel with a diode; K i3 , K V1 , K V2 A device with a switching function, which can be a MOSFET, a relay, or other active switches (transistor, thyristor high electron mobility transistor (HEMT) and IGBT, etc.). Switching device K i2 , K il Relays cannot be used alone. If relays are used, they need to be connected in parallel with diodes so that the current in the windings naturally returns to zero, thereby resetting the magnetic core. If only relays are used, it is impossible to ensure that the current naturally returns to zero without current measuring elements. 1 、V 2 Represents a DC power supply, where V 1 Is a unidirectional power supply, V 2 It can be a unidirectional power supply or a bidirectional power supply. The side of the transformer connected to the energy storage monomer (battery) is winding 1, and the connection method is as follows: Figure 2 As shown. C and D are connected to a voltage conditioning circuit, which may be a microcontroller unit (MCU) with an analog-to-digital conversion (ADC) function or other voltage sensors. Figure 3A The balancing circuit in the circuit can both charge and discharge the monomer. Figure 3B The equalization circuit in the i1 It is a diode with unidirectional conductivity, so only single cells can be charged.

[0074] The specific circuit connection is: having multiple energy storage monomers B connected in series i , switching device K i1 (The initial value of i is 1) and the transformer T i The winding 1 is connected in series and then in parallel to the energy storage monomer B i At both ends of the transformer T i One end of winding 2 is connected to node A, where transformer T i The terminal of winding 2 connected to node A is connected to the winding 1 of transformer Ti and the energy storage monomer B i The terminals connected to the positive poles are opposite terminals. i The other end of winding 2 passes through the switching device K i2Connected to node B and passing through switch device K i3 Connected to node D, where transformer T i Winding 2 and switching device K i2 and K i3 The terminals connected to the winding 1 of the transformer Ti are the same as the energy storage monomer B i The terminals connected to the positive poles are the same-name terminals. 1 With the switch device K V1 After being connected in series, they are connected in parallel at both ends of node A and node B, where the DC power supply V 1 The negative pole is connected to node B, and the DC power supply V 1 The positive electrode leads to node C; DC power supply V 2 With the switch device K V2 After being connected in series, they are connected at both ends of node A and node B, where the DC power supply V 2 The negative electrode is connected to node B. The voltage conditioning circuit is connected to both ends of node C and node D. The above connection method is repeated n times, that is, from i=1 to i=n, ​​nodes A and B on n energy storage units are the same connection point, which is the connection method applied to n series energy storage monomers of the present invention.

[0075] The control method of the circuit for measuring and balancing the voltage of energy storage monomers of the present invention can measure the voltage of energy storage monomers and balance between energy storage monomers in three working states of the energy storage system, namely, charging, discharging and static states, and the implementation of balancing can be carried out in one, two or three working states;

[0076] When the present invention is working: (1) the switch device K is closed. V1 , close the switch device K i3 (The initial value of i is 1), turn off the switch device K V2 , through the switch device K i2 With K i1 Energy storage monomer B can be obtained at both ends of the voltage conditioning circuit i (2) Repeat step (1) n times, that is, i=1 to i=n, ​​to obtain the voltage of the n energy storage cells in the series energy storage string. (3) Use the measured values ​​of the voltage of the n energy storage cells to select the energy storage cell B that needs to be charged or discharged. i , turn off the switch device K V1 , disconnect the switch device K i3 , close the switch device K V2 If necessary, the energy storage unit B i Charging, then control the switch device K i2 The conduction time of energy storage monomer B i If the amount of electricity increases, the energy storage unit B i Discharge, then control the switch device Ki1 The conduction time of energy storage monomer B i (4) Repeat step (1), step (2), and step (3) continuously to achieve the goal of voltage measurement of energy storage cells and balance between energy storage cells.

[0077] Example 1

[0078] The circuit connection of the embodiment 1 of the present invention is as follows Figure 3A The following is a schematic diagram of the voltage measurement and equalization circuit of hardware configuration type 1: B i (i=1,2,……n) represents the energy storage monomer, n is the number of energy storage monomers connected in series, which can be batteries or supercapacitors, and can be a single monomer or a combination of multiple monomers in series and parallel. Hereinafter referred to as energy storage monomer, B i The voltage is V Bi Indicates; each B i The energy storage string is connected in series, which is referred to as the series energy storage string below. The external power supply can charge the energy storage string through the transformer, and the energy storage string can also discharge the external load through the transformer. i The inductance of winding 1 is L i1 , transformer T i The inductance of winding 2 is L i2 , the transformation ratio of winding 1 to winding 2 is N; K i1 , K i2 For a device with a switching function, K i3 , K V1 , K V2 A device with a switching function, which can be a MOSFET, a relay, or other active switches such as an IGBT; V 1 、V 2 Represents a DC power supply, where V 1 Is a unidirectional power supply, V 2 It is a bidirectional power supply; the side of the transformer connected to the battery is winding 1. The two ends of C and D are connected to a voltage conditioning circuit, which can be a microcontroller unit (MCU) with analog-to-digital conversion (ADC) function or other voltage sensors.

[0079] The switch device K in this embodiment i1 Including diode D i1 and active switch Q i1 ; diode D i1 Connected in parallel to the active switch, the parallel diode D i1 Can be K i1 The body diode or an external diode, diode D i1 The negative pole of the transformer T is connected i One end of winding 1, diode D i1 The positive electrode is connected to the energy storage monomer Bi The negative electrode of the switching device K i2 Including diode D i2 and active switch Q i2 , diode D i2 The positive terminal is connected to the unidirectional power supply V 1 The cathode of diode D i2 The negative terminal of the i At one end of the winding 2, the active switch may be a MOSFET, an IGBT, a relay, a GTO, a triode, etc.

[0080] The control method of the above circuit is:

[0081] 1) Measure voltage. The energy storage system must measure the voltage of the energy storage monomer when it is in the charging and discharging working state. It is not necessary to measure the voltage of the energy storage monomer when it is at rest. If it is necessary to implement balancing at rest, voltage measurement must be performed;

[0082] 1-1) In the switching device K V2 Disconnect, active switch Q i1 Disconnect (the initial value of i is 1), switch device K i3 Closed, switch device K V1 Under the closed condition, the active switch Q is closed i2 ;

[0083] 1-2) After a given time t 2 Post-active switch Q i2 , t 2 The value is less than or equal to V Bmin / [f s (V 1 +V Bmin )],

[0084] Where V Bmin is the discharge cut-off voltage of the energy storage unit, V 1 is the DC power supply V 1 The voltage of f s is the switching frequency. In this embodiment, K i2 Controllable, all switching devices have the same switching frequency, active switch Q i2 Closed or open refers to K i2 Close or open;

[0085] 1-3) After the dead time (about tens of nanoseconds), the switch device K is turned on. i1 ; Active switch Q i1 Closed or open refers to K i1 Close or open,

[0086] 1-4) Control switch device K i1 The on time is equal to the given time t1 , t 1 The value is less than (t 2 V 1 ) / V Bmax ,

[0087] Where V Bmax is the charging cut-off voltage of the energy storage monomer,

[0088] In t 1 During the time period, the voltage conditioning circuit samples and processes the voltage across CD to obtain B i Voltage;

[0089] The specific sampling and processing process is as follows: the voltage across CD is divided by resistors and then converted to digital-to-analog (ADC). A Zener diode is connected between the ADC module and node C to limit the voltage connected to the ADC module to a safe range. After a short delay, the ADC module is set to t c Multiple sampling is performed for the sampling period, where t c <1 / (10f s ), take the average value of the sampling results of the ADC module and get B i Voltage;

[0090] 1-5) Repeat the above steps n times, that is, from i=1 to i=n, ​​to achieve voltage measurement of n series-connected energy storage cells.

[0091] The above process is as follows Figure 4(a)-Figure 4(d) Figure 4(a): K V2 Disconnect, K i1 Disconnect, K i3 Closed, K V1 Closed, K i2 Closed, this state lasts for a period of time t 2 , transformer T i There is no current flowing through winding 1, and the transformer T i Current flows in winding 2;

[0092] Figure 4(b): K during the dead time V2 Disconnect, K i1 Disconnect, K i3 Closed, K V1 Closed, K i2 Disconnect, transformer T i There is current flowing through winding 1, T i There is no current flowing in winding 2, and the current flows through diode D i1 ;

[0093] Figure 4(c): K V2 Disconnect, K i1 Closed, K i3 Closed, KV1 Closed, K i2 Disconnected, this state lasts for a period of time t 1 , T i There is current flowing through winding 1, T i There is no current flowing in winding 2, and the current flows through K i1 ;

[0094] Figure 4(d): K V2 Disconnect, K i1 Disconnect, K i3 Closed, K V1 Closed, K i2 Disconnect, T i There is current flowing through winding 1, T i There is no current flowing in winding 2, and the current flows through D i1 When there is current in winding 1 and no current in winding 2, the voltage across winding 2 is V Bi / N, then the correct voltage measurement result can be obtained.

[0095] 2) Implementation balance

[0096] 2-1) According to the measured values ​​of the voltage of each energy storage cell, when the balancing requirements are not met, balancing is performed to determine the target cell that needs to be charged and discharged during balancing:

[0097] There are three methods: (1) Select the energy storage unit with the highest voltage as the target unit for discharge in a cycle. A cycle refers to the discharge of B 1 To B n The same operations are performed in sequence; (2) in a cycle, an energy storage monomer with the lowest voltage is selected as the target monomer for charging; (3) when at rest (it is optimal to select the alternating method when at rest, and the alternating method can also be used for balancing in other states; it can also be alternating in the charging state, but the system efficiency is relatively low during balancing), method (1) and method (2) are performed alternately, that is, if the energy storage monomer with the highest voltage is selected as the target monomer for discharge in the kth cycle, then the energy storage monomer with the lowest voltage is selected as the target monomer for charging in the k+1th cycle; if the energy storage monomer with the lowest voltage is selected as the target monomer for charging in the kth cycle, then the energy storage monomer with the highest voltage is selected as the target monomer for discharge in the k+1th cycle;

[0098] 2-2) The process of discharging the energy storage unit with the highest voltage is:

[0099] Select the highest voltage series energy storage monomer through V 2 Discharge, if B i The voltage is the highest, then switch K V2 Closed, K i3Shutdown, K V1 Shutdown, K i1 Closed, K i1 During the closing period, i Discharge (at this time K i2 disconnect); after time t E1 Shutdown K i1 , control t E1 The value of the time period is less than or equal to V 2 / f s (V 2 +V Bmax ).

[0100] 2-3) The process of charging the energy storage monomer with the lowest voltage is:

[0101] Select the lowest voltage series energy storage monomer through V 2 To charge, if B i The voltage is the lowest, then switch K V2 Closed, K i3 Shutdown, K V1 Shutdown, K i2 Closed, K i2 During the closing period, i Charging; time t E2 Shutdown K i2 , control t E2 The value of the time period is less than or equal to V Bmin / f s (V 2 +V Bmin ).

[0102] K V2 The entire switching cycle T s Closed, where T s =1 / f s , K V1 The entire switching cycle T s Shutdown, K i3 The entire switching cycle T s Shut down.

[0103] 2-4) Selection of balanced implementation plan

[0104] The energy storage system has three working states, namely, charging state, discharging state and static state. You can choose one, two or all three of them to implement the balancing. There are 7 balancing implementation plans: (1) balancing in the charging state; (2) balancing in the discharging state; (3) balancing in the static state; (4) balancing in the charging state and balancing in the discharging state; (5) balancing in the charging state and balancing in the static state; (6) balancing in the discharging state and balancing in the static state; (7) balancing in the charging state, balancing in the discharging state and balancing in the static state. Combined with the three target monomers selected for each balancing, 21 feasible balancing implementation plans can be implemented under the circuit conditions of this embodiment.

[0105] In the prior art, balancing takes time. The present invention can implement balancing in the entire operating state, reduce costs, and meet the different selection requirements of users. 2 When it is a unidirectional power supply, balancing can only be implemented by selecting an energy storage cell with the lowest voltage as the target cell for charging in a cycle.

[0106] Fig. 7A A schematic diagram of the equilibrium process is given, B i B is the energy storage unit with the lowest voltage. j It is the energy storage monomer with the highest voltage.

[0107] Switch device K of a certain energy storage unit in hardware configuration type 1 i1 , K i2 See the connection circuit diagram for Figure 8 , in hardware configuration type 1, the switch device K i1 The end connected to the negative electrode of the energy storage unit is marked as point a, and the end connected to the negative electrode of the transformer T i1 The end of winding 1 is marked as point b, and the switch device K i2 With unidirectional power supply V 1 The negative terminal of the transformer is connected to point d. i1 One end of winding 2 is connected as point c.

[0108] When the switching device K i1 and switch device K i2 When only transistors and diodes are used, the cathode of the diode is connected to the collector of the transistor, and the anode of the diode is connected to the emitter of the transistor. At this time, the transistor is an active switch, point b is connected to the collector of the transistor, and point a is connected to the emitter of the transistor. i2 When using a transistor, point c is connected to the collector of the transistor, and point d is connected to the emitter of the transistor.

[0109] When the switching device Ki2 When using GTO, point c is connected to the anode of GTO, and point d is connected to the cathode of GTO.

[0110] When the switching device K i1 When using GTO and an additional diode, point b is connected to the anode of GTO, and point a is connected to the cathode of GTO. When a positive voltage is applied to the anode of GTO, a positive trigger current is applied to the gate of GTO, and GTO is turned on. When the GTO gate is turned on, a sufficiently large reverse trigger pulse current is applied to the gate of GTO, and GTO switches from on to off. i1 With K i2 When using GTO, since there is no body diode in GTO, when it is applied in hardware configuration type 1, an additional diode needs to be connected in parallel. The cathode of the diode is connected to the anode of GTO, and the positive electrode of the diode is connected to the cathode of GTO. At this time, GTO is an active switch.

[0111] When the switching device K i1 It can be realized by using only IGBT, point b is connected to the collector of IGBT, point a is connected to the emitter of IGBT. Generally, IGBT has a body diode inside, the cathode of the body diode is connected to the collector of IGBT, and the anode of the body diode is connected to the emitter of IGBT. i2 When using IGBT, point c is connected to the collector of the IGBT, and point d is connected to the emitter of the IGBT. i1 With K i2 It can also be realized by combining an IGBT and an additional diode.

[0112] When the switching device K i1 When using MOSFET, point b is connected to the drain in the MOSFET and point a is connected to the source in the MOSFET. i2 When using MOSFET, point c is connected to the drain in the MOSFET, and point d is connected to the source in the MOSFET. Switching device K i1 With K i2 It can also be realized by combining a MOSFET and an additional diode.

[0113] When the switching device K i1 With K i2When using a relay and an additional diode, the relay is a bidirectional switch tube with symmetry at both ends. Point b is connected to the A end of the relay, point a is connected to the B end of the relay, point c is connected to the A end of the relay, and point d is connected to the B end of the relay. Since there is no body diode in the relay, when it is applied in hardware configuration type 1, an additional diode needs to be connected in parallel. The end of the relay connected to the positive end of the diode is recorded as the B end, and the end of the relay connected to the negative end of the diode is recorded as the A end. When K V2 , K V1 , K i3 When it is a relay, the polarity of the relay is not distinguished and no additional parallel diode is required, such as Fig.11 shown.

[0114] Fig. 9 K is the switching device V2 , Switching device K V1 , Switching device K i3 Schematic diagram of the connection circuit when MOSFET is used. When the switch device K V2 When using MOSFET, the drain of MOSFET is connected to the DC power supply V 2 The positive electrode of the MOSFET is connected to the positive electrode of the MOSFET; the source of the MOSFET is connected to the node A. V1 When using MOSFET, the source of MOSFET is connected to the DC power supply V 1 The positive electrode of the MOSFET is connected to the positive electrode; the drain of the MOSFET is connected to the node A. i3 When using MOSFET, the sources of the two MOSFETs need to be connected, and the drains of the two MOSFETs are connected to nodes E and D respectively. Node E is the transformer T. i Winding 2 and switch device K i2 The connection points between.

[0115] Fig.10 K is the switching device V2 , Switching device K V1 , Switching device K i3 The connection circuit diagram when all IGBTs are used, when the switch device K V2 When using IGBT, the collector of IGBT is connected to the DC power supply V 2 The positive electrode of the IGBT is connected to the positive electrode of the IGBT; the emitter of the IGBT is connected to the node A. V1 When using IGBT, the emitter of IGBT is connected to the DC power supply V 1 The positive electrode of the MOSFET is connected to the positive electrode; the collector of the MOSFET is connected to the node A. When the switching device K i3 When using IGBT, the emitters of the two IGBTs need to be connected together, and the collectors of the two IGBTs need to be connected to node E and node D respectively.

[0116] Example 2

[0117] The circuit connection of the second embodiment of the present invention is as follows Figure 3A As shown:

[0118] The control method selects the implementation scheme of equalization in the charging state in Example 1, that is, equalization is only performed when the energy storage system is charged, and equalization is not performed in other states. When the series energy storage string is charged, the energy storage monomer with the lowest voltage is selected to be charged, such as Figure 7B As shown in Figure B i The voltage is the lowest, which is the target monomer.

[0119] The voltage measurement process is the same as the voltage measurement process in Example 1, and can determine the voltage of each energy storage cell in the series energy storage string.

[0120] For the energy storage unit B with the lowest voltage i Charging control method: Select the energy storage monomer with the lowest voltage as the target monomer, and 2 To charge, if B i The voltage is the lowest, then switch K V2 Closed, K i3 Shutdown, K V1 Shutdown, K i2 Closed, K i2 During the closing period, i Charging; time t E2 Shutdown K i2 , control t E2 The value of the time period is less than or equal to V Bmin / f s (V 2 +V Bmin ).

[0121] Example 3

[0122] The circuit connection of the second embodiment of the present invention is as follows Figure 3A As shown: the control method selects the implementation scheme of equalization in the discharge state in Example 1, and equalization is only implemented when the energy storage system is discharged, and no equalization is implemented in other states. When the series energy storage string is discharged, the energy storage monomer with the highest voltage is discharged, such as Figure 7C As shown in this case B i It is the target monomer with the highest voltage.

[0123] For the energy storage unit B with the highest voltage i Discharge: Select the series energy storage monomer with the highest voltage through V 2 Discharge, if B i The voltage is the highest, then switch K V2 Closed, K i3 Shutdown, K V1 Shutdown, Ki1 Closed, K i1 During the closing period, i Discharge; after time t E1 Shutdown K i1 , control t E1 The value of the time period is less than or equal to V 2 / f s (V 2 +V Bmax ).

[0124] Example 4

[0125] The circuit connection of the embodiment of the present invention is as follows Figure 3B The following is a schematic diagram of the voltage measurement and equalization circuit of hardware configuration type 2: B i (i=1,2,……n) represents the energy storage monomer, n is the number of energy storage monomers connected in series, which can be batteries or supercapacitors, and can be a single monomer or a combination of multiple monomers in series and parallel. Hereinafter referred to as energy storage monomer, B i The voltage is V Bi Indicates; each B i The energy storage string is connected in series, which is referred to as the series energy storage string below. The external power supply can charge the energy storage string through the transformer, and the energy storage string can also discharge the external load through the transformer. i The inductance of winding 1 is L i1 , transformer T i The inductance of winding 2 is L i2 , the transformation ratio of winding 1 to winding 2 is N; the switching device K i1 At this time, the diode D il , diode D il The positive electrode of the diode D is connected to the negative electrode of the energy storage monomer. il The negative pole of the transformer T is connected i One end of winding 1; K i2 A device with a switching function, which can be a MOSFET or other active switching devices; K i3 , K V1 , K V2 A device with a switching function, which can be a MOSFET, a relay, or other active switches such as an IGBT. Components such as MOSFET and IGBT usually contain a body diode. The current in the winding naturally returns to zero through the body diode, thereby resetting the magnetic core. The parallel diodes of MOSFET and IGBT can reduce losses and protect the device. For bidirectional switches such as relays, it is difficult to determine whether the current in the winding is naturally zero without a current detection device, so a parallel diode is required. After the relay is turned off, the current in the winding flows through the parallel diode to reset the magnetic core. The circuits in Examples 4, 5, and 6 have Kil It is only a diode, so the balancing current can only flow from the DC source into the battery. It is only necessary to ensure that the current in winding 1 naturally returns to zero to reset the magnetic core. Therefore, at this time, the switch device K i2 A diode can be connected in parallel or not. 1 、V 2 Represents DC power supply, V 1 、V 2 It can be a unidirectional power supply or a bidirectional power supply, and the side of the transformer connected to the energy storage unit is winding 1. The voltage conditioning circuit is connected to both ends of C and D, which can be a micro control unit (MCU) with analog-to-digital conversion (ADC) function or other voltage sensors.

[0126] The control method of the above circuit is:

[0127] 1) Measure voltage. The energy storage system must measure the voltage of the energy storage monomer when it is in the charging and discharging working state. It is not necessary to measure the voltage of the energy storage monomer when it is at rest. If it is necessary to implement balancing at rest, voltage measurement must be performed;

[0128] 1-1) K V2 Disconnect, K i3 Closed, K V1 Under closed conditions, closed K i2 (The initial value of i is 1);

[0129] 1-2) After a given time t 2 After shutting off K i2 , control t 2 The value is less than or equal to V Bmin / f s (V 1 +V Bmin ), where V Bmin is the discharge cut-off voltage of the energy storage unit;

[0130] 1-3) In K i2 After shutdown, the voltage conditioning circuit samples and processes the voltage across CD. By detecting the knee voltage, B can be obtained. i The voltage, such as Figure 5 As shown in the figure, t c is the voltage sampling time interval, V K represents the knee voltage;

[0131] The specific process of sampling and processing is as follows: the voltage across CD is divided by resistors and then converted to digital-to-analog (ADC). A Zener diode is connected between the ADC module and node C to limit the voltage connected to the ADC module to a safe operating range. After a short delay, the ADC module generates a signal with a value of t c Multiple sampling is performed for the sampling period, where t c <1 / (10fs ), before the knee point, the voltage across CD decreases linearly, with t c The voltage difference between two adjacent samples with an interval is approximately equal. After passing the knee point, the voltage slope at both ends of CD changes, and the voltage difference between the two samples before and after the knee point suddenly increases. The voltage sampling result before the knee point is approximately the knee point voltage.

[0132] 1-4) Repeat the above steps n times, that is, from i=1 to i=n, ​​to achieve voltage measurement of n series-connected energy storage cells.

[0133] The above process is as follows Figure 6(a)-Figure 6(b) Figure 6(a): K V2 Disconnect, K i3 Closed, K V1 Closed, K i2 Closed, this state lasts for a period of time t 2 , T i There is no current flowing through winding 1, T i Current flows in winding 2;

[0134] Figure 6(b): K V2 Disconnect, K i3 Closed, K V1 Closed, K i2 Disconnect, T i There is current flowing through winding 1, T i There is no current flowing in winding 2, and the current flows through diode D i1 .

[0135] 2) Implementation balance

[0136] 2-1) According to the measured values ​​of the voltages of the energy storage cells, when the balancing requirements are not met, balancing is performed to determine the target cell that needs to be charged and discharged during balancing: balancing is performed by selecting a cell with the lowest voltage for charging.

[0137] The schematic diagram of the balance of Example 4 is as follows: Fig.7D As shown, at this time B i For the target cell with the lowest voltage, the charging control process for the energy storage cell with the lowest voltage is:

[0138] Select the energy storage cell with the lowest voltage as the target cell through V 2 To charge, if B i The voltage is the lowest, then switch K V2 Closed, K i3 Shutdown, K V1 Shutdown, K i2 Closed, K i2 During the closing period, i Charging; time t E2Shutdown K i2 , control t E2 The value of the time period is less than or equal to V Bmin / f s (V 2 +V Bmin ), which can improve the control accuracy of the balance.

[0139] 2-2) Selection of balanced implementation plan

[0140] The energy storage system has three working states, namely, charging state, discharging state and static state. There are seven methods for implementing balancing: (1) balancing in the charging state; (2) balancing in the discharging state; (3) balancing in the static state; (4) balancing in the charging state and balancing in the discharging state; (5) balancing in the charging state and balancing in the static state; (6) balancing in the discharging state and balancing in the static state; (7) balancing in the charging state, balancing in the discharging state, and balancing in the static state.

[0141] Since in this case balancing can only be implemented by charging control of the energy storage unit with the lowest voltage, combined with the balancing implementation plans given due to different working conditions, there are a total of 7 feasible solutions.

[0142] Embodiment 1 and embodiment 4 proposed by the present invention may include 28 feasible balancing solutions in total.

[0143] Fig.12 The switch device K of a certain energy storage unit in hardware configuration type 2 i1 , K i2 Schematic diagram of the connection circuit, the switch device K i1 It is a diode, the positive electrode is connected to the negative electrode of the energy storage monomer, and the switching device K i2 Connect transformer T i One end of winding 2 is marked as point c, connected to a DC power supply V 1 The negative end of the switch device K is marked as point d. i2 When using a transistor, point c is connected to the collector of the transistor, and point d is connected to the emitter of the transistor. i2 When using GTO, point c is connected to the anode of GTO, and point d is connected to the cathode of GTO. i2 When using IGBT, point c is connected to the collector of the IGBT, and point d is connected to the emitter of the IGBT. i2 When using MOSFET, point c is connected to the drain in the MOSFET, and point d is connected to the source in the MOSFET. i2When using relays, no polarity distinction is made. In hardware configuration type 2, the switch device K i2 Various implementations may choose not to connect an additional diode in parallel.

[0144] Component K in hardware configuration type 2 V2 , K V1 With K i3 The connection method is the same as in hardware configuration type 1.

[0145] Example 5

[0146] The circuit connection of the embodiment of the present invention is as follows Figure 3B As shown: the control method selects the implementation scheme of equalization in the discharge state in Example 4, that is, equalization is only performed when the energy storage system is discharged, and equalization is not performed in other states. When the series energy storage string is discharged, the energy storage monomer with the lowest voltage is charged (B i The voltage is the lowest, such as Fig. 7E shown).

[0147] The voltage measurement process is the same as that in Example 4.

[0148] For the energy storage unit B with the lowest voltage i Charging control method: Select the energy storage monomer with the lowest voltage in series through V 2 To charge, if B i The voltage is the lowest, then switch K V2 Closed, K i3 Shutdown, K V1 Shutdown, K i2 Closed, K i2 During the closing period, i Charging; time t E2 Shutdown K i2 , control t E2 The value of the time period is less than or equal to V Bmin / f s (V 2 +V Bmin ).

[0149] Example 6

[0150] The circuit connection of the sixth embodiment of the present invention is as follows: Figure 3B As shown: the control method selects the implementation scheme of balancing in the static state in Example 4, and balancing is performed only when the energy storage system is static, and balancing is not performed in other states. When the series energy storage string is static, the energy storage monomer with the lowest voltage is charged (B i The voltage is the lowest, such as Figure 7F shown).

[0151] The voltage measurement process is the same as that in Example 4.

[0152] Balanced implementation: for the energy storage unit B with the lowest voltage i Charging control method: Select the energy storage monomer with the lowest voltage in series through V 2 To charge, if B i The voltage is the lowest, then switch K V2 Closed, K i3 Shutdown, K V1 Shutdown, K i2 Closed, K i2 During the closing period, i Charging; time t E2 Shutdown K i2 , control t E2 The value of the time period is less than or equal to V Bmin / f s (V 2 +V Bmin ).

[0153] Any matters not described in the present invention are applicable to the prior art.

Claims

1. A circuit for measuring and balancing the voltage of energy storage cells, characterized in that: Single energy storage unit uses B i Indicates, i = 1 ~ n, the switch device K i1 With transformer T i The winding 1 is connected in series and then in parallel to the energy storage monomer B i At both ends of the transformer T i One end of winding 2 is connected to node A, where transformer T i The terminal of winding 2 connected to node A is connected to the winding 1 of transformer Ti and the energy storage monomer B i The terminals connected to the positive poles are opposite terminals; transformer T i The other end of winding 2 passes through the switching device K i2 Connected to node B and passing through switch device K i3 Connected to node D, where transformer T i Winding 2 and switching device K i2 and switch device K i3 The terminals connected to the winding 1 of the transformer Ti are the same as the energy storage monomer B i The terminals connected to the positive poles are the same-name terminals; the DC power supply V1 and the switching device K V1 After being connected in series, they are connected at both ends of node A and node B, wherein the negative pole of DC power supply V1 is connected to node B, and the positive pole of DC power supply V1 is led to node C; DC power supply V2 is connected to switch device K V2 After being connected in series, they are connected in parallel at both ends of node A and node B, wherein the negative electrode of the DC power supply V2 is connected to node B; the voltage conditioning circuit is connected at both ends of node C and node D; The above connection method is repeated n times, that is, from i=1 to i=n, ​​n is the number of energy storage monomers connected in series, and the nodes A and B connected by the n energy storage monomers are the same connection point.

2. The circuit for measuring and balancing the voltage of energy storage cells according to claim 1, characterized in that: The energy storage unit is a battery or a supercapacitor, which is a single unit or a combination of multiple units connected in series and parallel. i3 , K V1 , K V2 It is a MOSFET, a relay, an IGBT or a HEMT.

3. The circuit for measuring and balancing the voltage of energy storage cells according to claim 1, characterized in that: Switching device K V2 , Switching device K V1 , Switching device K i3 When MOSFET is used, the switch device K V2 When using MOSFET, the drain of MOSFET is connected to the positive electrode of DC power supply V2; the source of MOSFET is connected to node A; when the switching device K V1 When using MOSFET, the source of MOSFET is connected to the positive electrode of DC power supply V1; the drain of MOSFET is connected to node A; when the switching device K i3 When using MOSFET, the sources of the two MOSFETs need to be connected, and the drains of the two MOSFETs are connected to nodes E and D respectively. Node E is the transformer T i Winding 2 and switch device K i2 The connection points between Switching device K V2 , Switching device K V1 , Switching device K i3 When IGBT is used, when the switch device K V2 When using IGBT, the collector of IGBT is connected to the positive pole of DC power supply V2; the emitter of IGBT is connected to node A; when the switch device K V1 When using IGBT, the emitter of IGBT is connected to the positive pole of DC power supply V1; the collector of MOSFET is connected to node A; when the switching device K i3 When using IGBT, the emitters of the two IGBTs need to be connected together, and the collectors of the two IGBTs need to be connected to node E and node D respectively.

4. The circuit for measuring and balancing the voltage of energy storage cells according to claim 1, characterized in that: The switch device K il is a diode, the switching device K i2 Connect a diode in parallel or do not set a diode.

5. A control method for a circuit for measuring and balancing voltage of an energy storage unit according to claim 4, characterized in that: The process of this control method is: 1) Measure voltage. The energy storage system must measure the voltage of the energy storage monomer when it is in the charging and discharging working state. It is not necessary to measure the voltage of the energy storage monomer when it is at rest. If it is necessary to implement balancing at rest, voltage measurement must be performed; 1-1) K V2 Disconnect, K i3 Closed, K V1 Under closed conditions, closed K i2 , the initial value of i is 1; 1-2) After a given time t2, turn off K i2 , control the value of t2 to be less than or equal to V Bmin / f s (V1+V Bmin ), where V Bmin is the discharge cut-off voltage of the energy storage unit; 1-3) In K i2 After shutdown, the voltage conditioning circuit samples and processes the voltage across CD, and obtains B by detecting the knee voltage. i Voltage; 1-4) Repeat the above steps n times, i.e., from i=1 to i=n, ​​to achieve voltage measurement of n series-connected energy storage cells; 2) Implementation balance 2-1) According to the measured values ​​of the voltages of each energy storage cell, when the balancing requirements are not met, balancing is performed to determine the target cell that needs to be charged and discharged during balancing: balancing is performed by selecting a cell with the lowest voltage for charging; The process of charging and controlling the energy storage monomer with the lowest voltage is: Select the energy storage cell with the lowest voltage as the target cell and charge it through V2. i The voltage is the lowest, then switch K V2 Closed, K i3 Shutdown, K V1 Shutdown, K i2 Closed, K i2 During the closing period, i Charging; time t E2 Shutdown K i2 , control t E2 The value of the time period is less than or equal to V Bmin / f s (V2+V Bmin ), thereby ensuring the core reset; 2-2) Selection of balanced implementation plan The energy storage system has three working states, namely, charging state, discharging state and static state. There are seven schemes for implementing balancing: (1) balancing in the charging state; (2) balancing in the discharging state; (3) balancing in the static state; (4) balancing in the charging state and balancing in the discharging state; (5) balancing in the charging state and balancing in the static state; (6) balancing in the discharging state and balancing in the static state; (7) balancing in the charging state, balancing in the discharging state and balancing in the static state.

6. The control method of the circuit for measuring and balancing the voltage of energy storage cells according to claim 5, characterized in that: The specific process of sampling and processing is as follows: the voltage across CD is converted to analog after being divided by resistors. A Zener diode is connected between the ADC module and node C to limit the voltage connected to the ADC module to a safe operating range. After a short delay, the ADC module is c Multiple sampling is performed for the sampling period, where t c <1 / (10f s ), before the knee point, the voltage across CD decreases linearly, with t c The voltage difference between two adjacent samples with an interval is approximately equal. After passing the knee point, the voltage slope at both ends of CD changes, and the voltage difference between the two samples before and after the knee point suddenly increases. The voltage sampling result before the knee point is approximately the knee point voltage.

7. The circuit for measuring and balancing the voltage of energy storage cells according to claim 1, characterized in that: The switch device K i1 Including diode D i1 and active switch Q i1 ; diode D i1 Connected in parallel to the active switch, the parallel diode D i1 It's K i1 The body diode or an external diode, diode D i1 The negative pole of the transformer T is connected i One end of winding 1, diode D i1 The positive electrode is connected to the energy storage monomer B i The negative electrode of the switching device K i2 Including diode D i2 and active switch Q i2 , diode D i2 The positive pole of the diode D is connected to the negative pole of the unidirectional power supply V1. i2 The negative terminal of the i At one end of the winding 2, the active switch is at least one of a MOSFET, an IGBT, a relay, a GTO, and a triode; the DC power supply V1 is a unidirectional power supply, and the DC power supply V2 is a bidirectional power supply.

8. A control method for a circuit for measuring and balancing voltage of energy storage cells according to claim 7, characterized in that: The process of this control method is: 1) Measure voltage. The energy storage system must measure the voltage of the energy storage monomer when it is in the charging and discharging working state. It is not necessary to measure the voltage of the energy storage monomer when it is at rest. If it is necessary to implement balancing at rest, voltage measurement must be performed; 1-1) In the switching device K V2 Disconnect, active switch Q i1 Disconnect, switch device K i3 Closed, switch device K V1 Under the closed condition, the active switch Q is closed i2 ;The initial value of i is 1; 1-2) After a given time t2, the active switch Q i2 , the value of t2 is less than or equal to V Bmin / [f s (V1+V Bmin )], Where V Bmin is the discharge cut-off voltage of the energy storage unit, V1 is the voltage of the DC power supply V1, where f s is the switching frequency; 1-3) After the dead time, turn on the switch device K i1 ; Active switch Q i1 Closed or open refers to K i1 Close or open, 1-4) Control switch device K i1 The on time is equal to the given time t1, and the value of t1 is less than (t2V1) / V Bmax , Where V Bmax is the charging cut-off voltage of the energy storage monomer, During the t1 period, the voltage conditioning circuit samples and processes the voltage across CD to obtain B i Voltage; 1-5) Repeat the above steps n times, i.e., from i=1 to i=n, ​​to achieve voltage measurement of n series-connected energy storage cells; 2) Implementation balance 2-1) According to the measured values ​​of the voltage of each energy storage cell, when the balancing requirements are not met, balancing is performed to determine the target cell that needs to be charged and discharged during balancing: There are three methods: (1) Select the energy storage unit with the highest voltage as the target unit for discharge in a cycle. A cycle refers to the discharge of B1 to B n The same operation is performed sequentially; (2) in a cycle, an energy storage monomer with the lowest voltage is selected as the target monomer for charging; (3) method (1) and method (2) are performed alternately, that is, if the energy storage monomer with the highest voltage is selected as the target monomer for discharging in the kth cycle, then the energy storage monomer with the lowest voltage is selected as the target monomer for charging in the k+1th cycle; if the energy storage monomer with the lowest voltage is selected as the target monomer for charging in the kth cycle, then the energy storage monomer with the highest voltage is selected as the target monomer for discharging in the k+1th cycle; 2-2) The process of discharging the energy storage unit with the highest voltage is: Select the series energy storage monomer with the highest voltage to discharge through V2. If B i The voltage is the highest, then switch K V2 Closed, K i3 Shutdown, K V1 Shutdown, K i1 Closed, K i1 During the closing period, i Discharge, at this time K i2 Disconnect; after time t E1 Shutdown K i1 , control t E1 The value of the time period is less than or equal to V2 / f s (V2+V Bmax ); 2-3) The process of charging the energy storage monomer with the lowest voltage is: Select the energy storage unit with the lowest voltage in series and charge it through V2. i The voltage is the lowest, then switch K V2 Closed, K i3 Shutdown, K V1 Shutdown, K i2 Closed, K i2 During the closing period, i Charging; time t E2 Shutdown K i2 , control t E2 The value of the time period is less than or equal to V Bmin / f s (V2+V Bmin ); K V2 The entire switching cycle T s Closed, where T s =1 / f s , K V1 The entire switching cycle T s Shutdown, K i3 The entire switching cycle T s Shut down; 2-4) Selection of balanced implementation plan The energy storage system has three working states, namely, charging state, discharging state and static state. There are seven balancing implementation schemes: (1) balancing in the charging state; (2) balancing in the discharging state; (3) balancing in the static state; (4) balancing in the charging state and balancing in the discharging state; (5) balancing in the charging state and balancing in the static state; (6) balancing in the discharging state and balancing in the static state; (7) balancing in the charging state, balancing in the discharging state and balancing in the static state.

9. The control method according to claim 8, characterized in that: The sampling and processing process of step 1-4) is as follows: the voltage at both ends of CD is converted into digital-to-analog after being divided by resistors, a Zener diode is connected between the ADC module and node C to limit the voltage connected to the ADC module to a safe range, and the ADC module is switched to the ADC module after a short delay at t c Multiple sampling is performed for the sampling period, where t c <1 / (10f s ), take the average value of the sampling results of the ADC module and get B i voltage.

10. The circuit for measuring and balancing the voltage of energy storage cells according to any one of claims 1 to 4 or 7, characterized in that: During operation: (1) Close the switch device K V1 , close the switch device K i3 , disconnect the switch device K V2 , through the switch device K i2 With K i1 Energy storage monomer B can be obtained at both ends of the voltage conditioning circuit i Voltage value; (2) Repeat step (1) n times, that is, i=1 to i=n, ​​to obtain the voltages of the n energy storage cells in the series energy storage string; (3) Use the measured values ​​of the voltages of the n energy storage cells to select the energy storage cell B that needs to be charged or discharged. i , turn off the switch device K V1 , disconnect the switch device K i3 , close the switch device K V2 If necessary, the energy storage unit B i Charging, then control the switch device K i2 The conduction time of energy storage monomer B i If the amount of electricity increases, the energy storage unit B i Discharge, then control the switch device K i1 The conduction time of energy storage monomer B i Reduction of power consumption; (4) Step (1), step (2), and step (3) are repeated continuously to achieve the goal of voltage measurement of energy storage cells and balance between energy storage cells.

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