A battery power equalization circuit, method, and energy storage system

Abstract

A battery power equalization circuit, method and energy storage system, comprising: a controller, N battery control switches, a filter capacitor control unit, an equalization unit and a sampling circuit; the equalization unit charges and discharges the target battery, the sampling unit detects the voltage of the target battery; the filter capacitor control unit performs filtering processing; the controller is connected with the battery control switch of the target battery, obtains the voltage value of the target battery detected by the sampling unit; or, the controller controls the equalization unit to charge and discharge the target battery. The sampling unit and the equalization unit in the application multiplex N battery control switches, which realizes the active equalization function and the battery sampling function, thereby reducing the complexity of the power equalization circuit under the traditional scheme, in addition, the power supply is not directly connected to the battery, but indirectly charges through the equalization unit, and the feedback energy is fed back through the indirect feedback method, which can solve the problem that the battery is continuously charged when it is full.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a battery electric energy equalization circuit, method and energy storage system. BACKGROUND

[0002] With the wide use of lithium battery energy storage systems, the requirement for cell equalization is also getting higher and higher. The current cell equalization method has gradually transitioned from the previous passive equalization to active equalization, and the requirement for energy utilization efficiency is also getting higher and higher when performing cell equalization.

[0003] The passive equalization scheme refers to the way of connecting a resistor in series with the cell with a higher voltage to consume the cell energy through the resistor to achieve cell voltage equalization when the voltage is too high. The active equalization scheme refers to transferring energy from the cell with a higher voltage to the cell with a lower voltage. Compared with the active equalization, the passive equalization circuit has the advantages of simple structure, low cost and easy implementation, but its disadvantages are also obvious, i.e., the use of resistors consumes energy and makes the energy utilization rate low. The active equalization can transfer energy and avoid the invalid consumption of energy, but it is relatively complex to implement and uses more devices, which is high in cost. The current active equalization schemes include the capacitor energy transfer type, the inductor energy transfer type and the transformer isolation type. In the capacitor energy transfer type, the capacitor acts as an energy storage element to absorb the energy of the high-voltage battery and transfer it to the low-voltage battery. In the inductor energy transfer type, the inductor acts as an energy storage element to realize the transfer of energy from the high-voltage cell to the low-voltage cell. The transformer isolation type uses an isolation transformer to realize the bidirectional conversion of energy. When the cell voltage is low, the energy flows from the bus to the low-voltage cell through the transformer. When the cell voltage is high, the energy flows from the cell to the bus through the transformer.

[0004] The above-mentioned active cell equalization topology circuits are not compatible with cell sampling functions, and the overall circuit structure of the battery management system (BMS) is complex. In addition, the energy fed back by the existing scheme is directly fed back to the battery, which causes the problem that the battery is continuously charged due to the storage of energy in the transformer when the cell is full. Therefore, a new equalization circuit topology structure needs to be proposed to realize efficient energy utilization while reducing the complexity and cost of the circuit. SUMMARY

[0005] The present application provides a battery electric energy equalization circuit, method and energy storage system for realizing efficient energy utilization while reducing the complexity and cost of the circuit.

[0006] In a first aspect, the application provides a battery power equalization circuit applied to a series battery group composed of N batteries in series, comprising: a controller, N battery control switches, a filter capacitor control unit, an equalization unit, and a sampling unit; each battery in the N batteries is connected to the first end of each battery control switch in the N battery control switches in a one-to-one correspondence, the second end of each battery control switch in the N battery control switches is connected to the filter capacitor control unit; the filter capacitor control unit is connected to the equalization unit and the sampling unit; the equalization unit is connected to a power supply, and the power supply is used to supply power to the equalization unit; the equalization unit is used to charge and discharge a target battery, and the target battery is any one of the N batteries; the sampling unit is used to detect the voltage of the target battery; the filter capacitor control unit is used to filter the current input to the target battery by the equalization unit; the controller is used to control the battery control switch connected to the target battery to be closed, obtain the voltage value of the target battery detected by the sampling unit, or control the equalization unit to charge and discharge the target battery.

[0007] The sampling unit and the equalization unit in the battery power equalization circuit of the application multiplex the N battery control switches, realize the active equalization function and the battery sampling function, and do not affect each other, thereby reducing the complexity of using the BMS in the traditional scheme, and in addition, the power supply of the application is not directly connected to the battery, but indirectly charges through the transformer of the equalization unit, thereby feeding back the energy through the indirect feedback method, and solving the problem that the battery is continuously charged when it is full.

[0008] As a possible implementation, the battery power equalization circuit further comprises a first bus and a second bus, the N batteries comprise a plurality of first batteries and a plurality of second batteries; the equalization unit comprises a primary winding, a first secondary winding, a second secondary winding, and a first control switch; the sampling unit comprises an analog-to-digital converter (ADC) and a sampling circuit; the second end of the battery control switch connected to the first battery is connected to the first bus, and the second end of the battery control switch connected to the second battery is connected to the second bus; the first bus is connected to the first end of the filter capacitor control unit, and the second bus is connected to the second end of the filter capacitor control unit; the first bus is connected to the first secondary winding, and the second bus is connected to the second secondary winding; the primary winding is connected to the power supply, and the primary winding is grounded through the first control switch; the first bus is connected to the first input end of the sampling circuit, the second bus is connected to the second input end of the sampling circuit, the output end of the sampling circuit is connected to the ADC, and the output end of the ADC is connected to the controller.

[0009] The battery power equalization circuit of the application adopts the design of primary single winding and secondary double winding, and adopts multi-switch control between the battery control switch and the winding of the equalization unit, wherein only two paths are high-frequency switch driving, thereby reducing the number of high-frequency switch driving, making the driving circuit in the controller more easily realized and reducing the cost of high-frequency driving. In addition, the battery control switch of the application adopts the top-MOS structure, thereby realizing bidirectional conduction, and through the controllable filter capacitor access, the voltage sampling circuit and the equalization unit can better multiplex the effect of N battery control switches, realizing both active equalization function and battery sampling function, and reducing the complexity of using BMS under the traditional scheme.

[0010] As a possible implementation, the filter capacitor control unit specifically includes a filter capacitor and a second control switch connected in series with the filter capacitor; and the controller is specifically configured to: control the battery control switch connected with the target battery to close and control the second control switch to open, and acquire the voltage value of the target battery detected by the sampling unit; or control the battery control switch connected with the target battery to close and control the second control switch to close, and control the equalization unit to perform charge-discharge processing on the target battery.

[0011] As a possible implementation, the controller is specifically configured to: when detecting that the voltage difference between the first target battery and the second target battery is greater than a set voltage threshold, the first target battery and the second target battery are any two batteries in a series battery pack composed of N batteries in series, and the voltage value of the first target battery is less than the voltage value of the second target battery; control the battery control switch connected with the first target battery to close and use the equalization unit to charge the first target battery; and control the battery control switch connected with the second target battery to close and use the equalization unit to discharge the second target battery. The controller can judge the voltage between each battery, and if it is judged that the voltage of the battery is greater than the set voltage threshold than the voltage of other batteries, it is determined that the battery has under-voltage or over-voltage. If the battery has under-voltage, the equalization unit charges the battery; if the battery has over-voltage, the equalization unit charges the battery.

[0012] As a possible implementation, the battery power equalization circuit can further include a current detection circuit and a temperature detection circuit, the current detection circuit is configured to detect the current value of each battery in the N batteries, and the temperature detection circuit is configured to detect the temperature value of each battery in the N batteries.

[0013] As a possible implementation, the equalization unit further comprises: a first power switch tube, a second power switch tube, a third power switch tube and a fourth power switch tube; a first end of the first power switch tube is connected with a same name end of the first secondary winding, a second end of the first power switch tube is connected with the first bus, a first end of the second power switch tube is connected with a different name end of the first secondary winding, a second end of the second power switch tube is connected with the second bus, a first end of the third power switch tube is connected with a different name end of the second secondary winding, a second end of the third power switch tube is connected with the first bus, a first end of the fourth power switch tube is connected with a same name end of the second secondary winding, a second end of the fourth power switch tube is connected with the second bus; the power supply is connected with a same name end of the primary winding, a different name end of the primary winding is grounded through the first control switch. Specifically, in the above embodiment, the transformer in the equalization unit adopts the design of a primary single winding and a secondary double winding, and the four-switch control is adopted between the bus switch network bus and the transformer winding. Among them, two switches are low-frequency signal switch drives, and two are high-frequency signal switch drives, thereby reducing the number of high-frequency switch drives, making the drive circuit in the controller easy to implement, and also reducing the cost of high-frequency signal drive.

[0014] As a possible implementation, the controller is specifically used for, when charging the battery, if the voltage of the first bus is greater than the voltage of the second bus, controlling the first power switch tube and the second power switch tube to be open, the third power switch tube to be closed, and the fourth power switch tube to be set to a rectification state, controlling the first control switch to be open, and releasing the electrical energy stored in the excitation inductance on the primary winding to the battery through the second secondary winding. By selecting and controlling the battery control switch corresponding to the battery voltage in the N battery control switches to be closed, when the battery voltage is low, the battery is charged by the flyback converter through the pre-stored electrical energy or the power supply, thereby realizing the charging equalization of the low-voltage battery, and the electrical energy stored in the excitation inductance is released to the battery with lower voltage through the second secondary winding.

[0015] As a possible implementation, the controller is specifically used for, when charging the battery, if the voltage of the first bus is greater than the voltage of the second bus, controlling the first power switch tube and the second power switch tube to be open, the third power switch tube to be closed, and the fourth power switch tube to be set to a rectification state, controlling the first control switch to be open, and releasing the electrical energy stored in the excitation inductance on the primary winding to the battery through the second secondary winding.

[0016] As a possible implementation, the controller is specifically configured to: when discharging the battery, if the voltage of the first bus is greater than the voltage of the second bus, control the third power switch and the fourth power switch to be open, the second power switch to be closed, the first control switch to be set to a rectification state, control the first power switch to be closed, and store the electric energy into the excitation inductor on the primary winding.

[0017] As a possible implementation, the controller is specifically configured to: when discharging the battery, if the voltage of the first bus is less than the voltage of the second bus, control the first power switch and the second power switch to be open, the third power switch to be closed, the first control switch to be set to a rectification state, and control the fourth power switch to be closed, so as to store the electric energy into the excitation inductor on the primary winding.

[0018] As a possible implementation, each of the N battery control switches is a cascode MOS tube, and the cascode MOS tube comprises: a first switch tube and a second switch tube; the source of the first switch tube is connected with the source of the second switch tube, the gates of the first switch tube and the second switch tube are connected with the controller, the drain of the first switch tube is connected with the battery, and the drain of the second switch tube is connected with the corresponding first bus or second bus. The battery control switch of the application adopts the cascode MOS structure, so that bidirectional conduction can be realized.

[0019] In a second aspect, the application provides a battery electric energy equalization method, which comprises: controlling the battery control switch connected with the target battery to be closed, and obtaining the voltage value of the target battery detected by the sampling unit; or controlling the equalization unit to perform charging and discharging processing on the target battery.

[0020] As a possible implementation, the method further comprises: controlling the battery control switch connected with the target battery to be closed and controlling the second control switch to be open, and obtaining the voltage value of the target battery detected by the sampling unit; or controlling the battery control switch connected with the target battery to be closed and controlling the second control switch to be closed, and controlling the equalization unit to perform charging and discharging processing on the target battery.

[0021] As a possible implementation, when the balancing treatment needs to be performed on each of the N batteries, the second control switch is controlled to be closed, and each of the N batteries is charged and discharged by the balancing unit through controlling the closing of the N battery control switches, including: when the voltage difference between the first target battery and the second target battery is greater than the set voltage threshold, the first target battery and the second target battery are any two batteries in the series battery group composed of the N batteries in series, and the voltage value of the first target battery is less than that of the second target battery; the battery control switch connected with the first target battery is controlled to be closed, and the first target battery is charged by the balancing unit; the battery control switch connected with the second target battery is controlled to be closed, and the second target battery is discharged by the balancing unit.

[0022] In a third aspect, the present application provides a kind of energy storage system, comprising: at least one energy storage unit and at least one conversion unit corresponding to at least one energy storage unit one by one, each of at least one conversion unit is connected to power grid;Each of at least one energy storage unit includes: the series battery group of N batteries in series and the battery energy equalization circuit of the first aspect;Each of at least one energy storage unit, for: to the corresponding conversion unit output direct current, or receive the direct current input by the corresponding conversion unit, charge the series battery group of N batteries in series;Each of at least one conversion unit, for: the direct current input by the corresponding energy storage unit is converted into alternating current and output to power grid, or receive the alternating current input by power grid, alternating current is converted into direct current and output to the corresponding energy storage unit.

[0023] These aspects or other aspects of the present application will be more apparent in the following description of embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 It is a structural schematic diagram of a kind of energy storage system;

[0025] Figure 2 It is a structural schematic diagram of a kind of battery energy equalization circuit Figure 1 ;

[0026] Figure 3 It is a structural schematic diagram of a kind of battery energy equalization circuit Figure 2 ;

[0027] Figure 4 It is a structural schematic diagram of a kind of sampling circuit;

[0028] Figure 5 It is a structural schematic diagram of a kind of top MOS tube;

[0029] Figure 6 It is a structural schematic diagram of a kind of balancing unit. DETAILED DESCRIPTION

[0030] In order to make the purposes, technical solutions and advantages of the present application clearer, the following further describes the present application with reference to the accompanying drawings. The example embodiments can be implemented in various forms and should not be construed as being limited to the embodiments set forth herein; on the contrary, these embodiments are provided so that the present application is more comprehensive and complete and the concept of the example embodiments is fully conveyed to those skilled in the art. The same reference signs in the drawings represent the same or similar structures, and thus repeated descriptions thereof will be omitted. The expressions of position and direction described in the present application are described with reference to the drawings, but can be changed as needed, and the changes are included in the protection scope of the present application. The drawings of the present application are only used to show the relative positional relationship and do not represent the actual proportions.

[0031] In order to make the purposes, technical solutions and advantages of the present application clearer, the following further describes the present application with reference to the accompanying drawings. The specific operation methods in the method embodiments can also be applied to the device embodiments or system embodiments. It should be noted that "at least one" in the description of the present application means one or more, and the plurality means two or more than two. In view of this, "plurality" in the embodiments of the present application can also be understood as "at least two". In addition, it should be understood that "first", "second" and the like in the description of the present application are only used for the purpose of distinguishing the description and cannot be understood as indicating or implying relative importance or indicating or implying order.

[0032] It should be noted that "connection" in the embodiments of the present application means electrical connection, and the connection between two electrical elements can be direct or indirect connection between the two electrical elements. For example, A and B are connected, which can be direct connection between A and B, or indirect connection between A and B through one or more other electrical elements, for example, A and B are connected, which can be direct connection between A and C, direct connection between C and B, and connection between A and B through C.

[0033] It should be noted that "same name end" and "different name end" in the present application are used to judge the phase relationship of the internal electromotive force of the primary winding and the secondary winding in the transformer when the transformer is working. Under the action of the same magnetic flux, the end heads with the same potential polarity in the two (or more than two) windings at any time are "same name end" to each other. Under the action of the same magnetic flux, the end heads with opposite potential polarity in the two (or more than two) windings at any time are "different name end" to each other.

[0034] Even if the batteries connected in series in an energy storage system have identical performance parameters initially, performance differences will inevitably emerge between them over a long period, making it difficult to achieve battery balancing. A balancing circuit includes a bidirectional flyback converter composed of multiple power switches and a selection switch. When a battery voltage is too low, energy from the storage system's batteries or an external power source can be transferred to the low-voltage battery via a transformer; conversely, when a battery voltage is too high, energy from the high-voltage battery can be transferred to the storage system's batteries via a transformer.

[0035] The above structure is not compatible with the sampling function, and the overall circuit structure of the BMS used for sampling is complex. In addition, the energy fed back in the existing solution is directly fed back to the battery. There is a problem that when the battery is fully charged, the battery is still being charged because the transformer still stores energy. Furthermore, multiple power switches require high-frequency signals to drive them. Therefore, the driving circuit is also relatively complex, and multiple driving circuits need to be isolated and powered, resulting in high circuit complexity and cost.

[0036] In view of this, this application provides a battery power balancing circuit that can reduce circuit complexity and cost while achieving efficient energy utilization. To facilitate understanding of the embodiments of this application, the following is combined with... Figure 1 Describe the application scenarios of this application. Figure 1 This is a structural diagram illustrating an application scenario applicable to the embodiments of this application. For example... Figure 1 As shown, the energy storage system 100 can be used to store electrical energy. The energy storage system 100 can be powered by the power grid 101, an external DC source, or an external AC source. Figure 1 (Not shown in the image) The energy storage system 100 can charge the device and also generate alternating current (AC) to supply power to the grid 101. The energy storage system 100 may include an energy storage module 102, a combiner unit 103, and a conversion unit 104. The energy storage module 102 may include multiple energy storage units, and the conversion unit 104 may include multiple inverters. The energy storage module 102 stores energy and outputs current to or receives current from the combiner unit 103. The combiner unit 103 integrates the current provided by the energy storage module 102 or the current provided by the grid 101. The conversion unit 104 converts the DC current provided by the energy storage module 102 into AC current for input to the grid 101, or converts the AC current provided by the grid 101 into DC current to charge the energy storage module 102. Figure 1 The energy storage system 100 described herein is merely for illustrating the application scenario of the embodiments of this application and is not intended to limit the scope of this application. Furthermore, it should be understood that the embodiments of this application do not limit the circuit connection relationships; in practical applications, Figure 1Other devices can also be connected between each component in the above-mentioned energy storage system 100, for example, the output end of the conversion unit 104 can be directly connected to the power grid or connected to the power grid through a transformer, and the present application does not limit this. The battery power equalization circuit provided in the present application can be included in each energy storage unit of the above-mentioned energy storage system 100. It should be noted that the above-mentioned conversion unit 104 includes but is not limited to a direct current to direct current (DCDC) or a power conversion system (PCS), and the above-mentioned conversion unit 104 can be isolated or non-isolated.

[0037] Embodiments of the present application Figure 2 A structural schematic diagram of a battery power equalization circuit 200 is shown, which is applied to a series battery group 201 composed of N batteries in series, and the circuit includes a controller 202, N battery control switches 203, a filter capacitor control unit 204, an equalization unit 205, and a sampling unit 206. Wherein each battery in the N batteries is connected one-to-one with the first end of each battery control switch in the N battery control switches 203, and the second end of each battery control switch in the N battery control switches 203 is connected with the filter capacitor control unit 204; the filter capacitor control unit 204 is connected with the equalization unit 205 and the sampling unit 206; the equalization unit 205 is connected with a power supply 207, which is used to supply power to the equalization unit 205; the equalization unit 205 is used to charge and discharge the target battery, which is any one of the N batteries; the sampling unit 206 is used to detect the voltage of the target battery; the filter capacitor control unit 204 is used to filter the current input to the target battery by the equalization unit 205. The controller 202 is used to control the battery control switch 203 connected with the target battery to be closed, to obtain the voltage value of the target battery detected by the sampling unit 206; or to control the equalization unit 205 to charge and discharge the target battery. Optionally, the power supply 207 can be an external direct current source or an external alternating current source, or an energy storage battery, which is not specifically limited here.

[0038] The controller 202 in the embodiments of the present application can be a central processing unit (CPU), a general processor, a digital signal processing (DSP), an application specific integrated circuits (ASIC), a field programmable gate array (FPGA) or other programmable logic devices, transistor logic devices, hardware components or any combination thereof. The controller 202 can implement or execute various exemplary logical blocks, modules and circuits described in combination with the disclosure of the present application. The processor can also be a combination of computing functions, such as one or more microprocessor combinations, combinations of DSP and microprocessor, etc. The controller 202 can be independent of the battery equalization circuit 200 or integrated in other units, which is not specifically limited here.

[0039] In addition, the controller 202 can also include a battery management system (BMS). The BMS is used to detect the battery parameters of the series battery pack 201 composed of N batteries in series, so as to prevent the series battery pack 201 composed of N batteries in series from overcharging or overdischarging, etc., thereby prolonging the service life of each battery in the series battery pack 201 composed of N batteries in series. For example, there are multiple electrical connection points between the BMS and each battery in the series battery pack 201 composed of N batteries in series. The BMS detects whether an arc fault occurs at each electrical connection point and takes corresponding protective measures.

[0040] The equalization unit 205 in the embodiments of the present application can be a direct current converter. The controller 202 can control the equalization unit 205 based on a preset battery equalization algorithm to perform equalization control on the battery that needs to be equalized. Alternatively, the controller 202 controls the equalization unit to charge and discharge each battery in the series battery pack 201 to achieve SOC equalization. The corresponding charging and discharging current can be transmitted through the positive and negative equalization buses added in the equalization unit 205.

[0041] The sampling unit 206 in the embodiment of the present application can collect the battery parameter of each battery in the series battery, the battery parameter at least including the voltage parameter, and send the voltage parameter of each battery to the controller 202, and the controller 202 judges whether each battery in the N batteries is abnormal according to the voltage parameter of each battery. The voltage of each battery in the N batteries is collected by the sampling unit 206, so that the voltage of each battery in the battery pack is detected. In addition, the battery parameter can also include temperature and current. Therefore, as a possible implementation, the battery energy equalization circuit 200 can also include a current detection circuit and a temperature detection circuit, the current detection circuit is used for detecting the current value of each battery in the N batteries, and the temperature detection circuit is used for detecting the temperature value of each battery in the N batteries. The sampling unit 206 in the present application can continuously sample each battery in the series battery group composed of N batteries for multiple times, when the sampling values of continuous multiple sampling are basically the same, the sampling value is taken again, which reduces the error and improves the sampling voltage accuracy of the battery.

[0042] The filter capacitor control unit 204 in the embodiment of the present application can include a filter capacitor, so as to filter the current input to the target battery by the equalization unit 205, and filter out the pulsation brought by the power supply 207, so as to achieve the effect of smoothing the current. In order to avoid that the too large filter capacitor C0 causes sampling delay to the sampling unit 206, the filter capacitor control unit 204 can also include a control switch, and whether the filter capacitor C0 is connected to the circuit is controlled by the off of the control switch, so as to prevent that the too large filter capacitor C0 affects the sampling of the sampling unit 206.

[0043] As a possible implementation, referring to Figure 3 The battery energy equalization circuit 200 also includes a first bus 208 and a second bus 209, and the N batteries include a plurality of first batteries and a plurality of second batteries. The equalization unit 205 includes a primary winding 2051, a first secondary winding 2052, a second secondary winding 2053 and a first control switch 2054. The sampling unit 206 includes an analog-to-digital converter ADC 2061 and a sampling circuit 2062.

[0044] The second end of the battery control switch 203 connected with the first battery is connected with the first bus 208, and the second end of the battery control switch 203 connected with the second battery is connected with the second bus 209; the first bus 208 is connected with the first end of the filter capacitor control unit 204, the second bus 209 is connected with the second end of the filter capacitor control unit 204, the first bus 208 is connected with the first secondary winding 2052, and the second bus 209 is connected with the second secondary winding 2053; the primary winding 2051 is connected with the power supply 207, and the primary winding 2051 is grounded through the first control switch 2054; the first bus 208 is connected with the first input end of the sampling circuit 2062, the second bus 209 is connected with the second input end of the sampling circuit 2062, the output end of the sampling circuit 2062 is connected with the ADC 2061, and the output end of the ADC 2061 is connected with the controller 202.

[0045] The controller 202 in the embodiment of the application controls the battery control switch 203 connected with the target battery to be closed when detecting the voltage value of the target battery, and obtains the voltage value of the target battery detected by the ADC 2061, and the target battery is any one of the N batteries; when the target battery is balanced, the controller controls the equalization unit 205 to charge and discharge the target battery. The battery control switch 203 is connected with the first bus 208 and the second bus 209 together, and when the battery control switch is closed in turn (only one battery control switch is allowed to be closed at the same time), the voltage of the positive electrode of the corresponding battery to the reference ground of the battery pack will be added to the voltage dividing resistor of the sampling circuit 2062, and after being attenuated by the voltage dividing resistor, it is sent to the analog to digital converter (ADC) for A / D conversion, so that the voltage value of the corresponding battery can be obtained.

[0046] The first bus 208 and the second bus 209 can jointly constitute the odd-even bus. Specifically, in each battery of the series battery pack 201 composed of N batteries in series, the positive electrodes of all the odd-numbered batteries are connected to each other and connected to the first bus 208, the positive electrodes of all the even-numbered batteries are connected to each other and connected to the second bus 209, and the positive electrodes of all the even-numbered batteries are connected to the negative electrode of the first battery in the series battery pack 201 composed of N batteries in series.

[0047] Fuses can be arranged on the first bus 208 and the second bus 209 to prevent the current on the above bus from being too large, so as to further improve the safety of the battery energy equalization circuit 200, which will not be described in detail here.

[0048] Optionally, the filter capacitor control unit 204 in the embodiment of the present application can specifically include: a filter capacitor C0 and a second control switch connected in series with the filter capacitor; and the controller 202 is specifically configured to: control the battery control switch connected with the target battery to be closed and the second control switch to be opened, and acquire the voltage value of the target battery detected by the sampling unit 206; or control the battery control switch connected with the target battery to be closed and the second control switch to be closed, and control the equalization unit 205 to perform charging and discharging processing on the target battery. The connection between the filter capacitor and the sampling unit 206 is disconnected through the second control switch, so as to prevent the filter capacitor C0 from affecting the sampling precision of the sampling unit 206.

[0049] The ADC 2061 in the sampling unit 206 is configured to convert the analog quantity input by the sampling circuit 2062 into a digital quantity. The sampling circuit 2062 in the embodiment of the present application can include a voltage dividing resistor, which is configured to perform voltage dividing processing on the voltage of the battery. As a possible implementation, refer to FIG. 4. Figure 4 As shown in FIG. 4, the sampling circuit 2062 can include a first voltage dividing resistor 401, a second voltage dividing resistor 402, a third voltage dividing resistor 403 and a fourth voltage dividing resistor 404. The voltage output by the first bus 208 and the second bus 209 is sent to the ADC 2061 for sampling after being divided by the first voltage dividing resistor 401, the second voltage dividing resistor 402, the third voltage dividing resistor 403 and the fourth voltage dividing resistor 404.

[0050] Each of the N battery control switches 203 in the embodiment of the present application is a top opposite MOS tube structure. Refer to FIG. 5. Figure 5 As shown in FIG. 5, Figure 5 which is a schematic diagram of the top opposite MOS tube structure, and the top opposite MOS tube structure includes a first switch tube 501 and a second switch tube 502. The first switch tube 501 and the second switch tube 502 can be one or more of a metal oxide semiconductor field effect transistor (MOSFET), a bipolar junction transistor (BJT), an insulated gate bipolar transistor (IGBT), a field effect transistor (FET), a silicon carbide (SiC) or gallium nitride (GaN) power tube, etc. The embodiment of the present application does not enumerate all of them. The switch tube can include a first electrode (source), a second electrode (drain) and a control electrode (gate), wherein the controller 202 controls the conduction or disconnection of the switch device through the control electrode.

[0051] For example, in the embodiment of the present application, in order to realize the isolation function of the battery control switch, the MOS tube in the embodiment of the present application is a negative channel-metal-oxide-semiconductor (NMOS). In order to supply power to the battery control switch, the controller 202 can further include an auxiliary driving power supply and the like.

[0052] The source of the first switch tube 501 is connected with the source of the second switch tube 502, the gate of the first switch tube 501 and the gate of the second switch tube 502 are connected with the controller 202, the drain of the first switch tube 501 is connected with the battery, and the drain of the second switch tube 502 is connected with the corresponding first bus 208 or the second bus 209.

[0053] The ADC 2061 can collect the battery parameters of each battery in the N series batteries, the battery parameters at least including voltage parameters, and send the voltage parameters of each battery to the controller 202, and the controller 202 judges whether each battery in the N batteries is abnormal according to the voltage parameters of each battery. By collecting the voltage of each battery in the N batteries through the sampling circuit 2062, the voltage of each battery in the battery pack is detected. In addition, the battery parameters can also include temperature and current. Therefore, as a possible implementation manner, the battery energy equalization circuit 200 can further include a current detection circuit and a temperature detection circuit, the current detection circuit is used for detecting the current value of each battery in the N batteries, and the temperature detection circuit is used for detecting the temperature value of each battery in the N batteries.

[0054] Therefore, as a possible implementation manner, the battery energy equalization circuit 200 can further include a current detection circuit and a temperature detection circuit, the current detection circuit is used for detecting the current value of each battery in the N batteries, and the temperature detection circuit is used for detecting the temperature value of each battery in the N batteries.

[0055] The current detection circuit can include a current transformer (CT) for example. The current transformer is an instrument for measuring the primary side large current by converting it into a secondary side small current according to the principle of electromagnetic induction. The current transformer is composed of a closed iron core and a winding. The current transformer is sleeved on the first bus 208 or the second bus 209 in the line where the current needs to be measured. By controlling the closing of the N battery control switches 203, the current on the first bus 208 or the second bus 209 is detected by using the principle of electromagnetic induction, so as to determine the current parameter of the battery. Specifically, a magnetic field is generated around the measured bus. After the current transformer is sleeved on the measured cable, the coil on the current transformer will generate an induced current due to the magnetic field of the measured cable. After amplifying the induced current, the current of the measured cable can be obtained.

[0056] The above circuit can be used to detect the current and temperature of each of the N batteries. When the controller 202 determines that the N batteries are abnormal, the battery pack is stopped from charging or discharging in time, thereby protecting the series battery pack 201 composed of the N batteries in series and prolonging the service life. When the battery in the battery pack has overvoltage or undervoltage, the equalization unit 205 discharges or charges the battery, thereby improving the performance of the battery and the safety of the series battery pack 201 and prolonging the service life of the battery pack.

[0057] As a possible implementation, the controller 202 is specifically configured to: when it is detected that the difference between the voltages of a first target battery and a second target battery is greater than a set voltage threshold, the first target battery and the second target battery being any two batteries in the series battery pack composed of the N batteries in series, the voltage value of the first target battery being less than the voltage value of the second target battery; control the battery control switch connected with the first target battery to be closed, and charge the first target battery by using the equalization unit 205; and control the battery control switch connected with the second target battery to be closed, and discharge the second target battery by using the equalization unit 205.

[0058] The controller 202 performs equalization control on the battery that needs to be equalized according to the preset battery equalization algorithm based on the voltage values of the batteries collected by the ADC 2061. Specifically, the controller can judge the voltage of each battery. If it is judged that the difference between the voltages of a first target battery and a second target battery is greater than a set voltage threshold, the voltage value of the first target battery being less than the voltage value of the second target battery, then the first target battery has undervoltage, and the equalization unit 205 charges the battery; and the second target battery has overvoltage, and the equalization unit 205 discharges the battery.

[0059] It should be noted that when there are multiple first target batteries or multiple second target batteries, the batteries can be sorted based on the magnitude of the voltage of the batteries, and the batteries can be balanced based on the sorted order. The specific sorting method is not limited. For example, the battery with the lowest voltage among the multiple batteries can be selected for charging, and the battery with the highest voltage among the multiple batteries can be selected for discharging.

[0060] In addition, when the battery parameters can also include current parameters, the controller 202 can also determine the current of each battery in the N batteries. If the current of the battery is greater than the rated current value, the battery has an overcurrent phenomenon, and charging or discharging of the battery or the battery pack in which the battery is located is stopped. When the battery parameters can also include temperature parameters, the controller 202 can determine the temperature of each battery in the N batteries or the temperature of the entire battery pack. If the temperature of at least one battery in the N batteries or the temperature of the entire battery pack is greater than a predetermined temperature value, it is determined that the battery or the battery pack has an over-temperature phenomenon, and charging or discharging of the battery or the battery pack in which the battery is located is stopped. If the battery parameters include at least two of voltage, current, and temperature, the battery can be comprehensively determined to be abnormal based on the battery parameters of each battery.

[0061] Taking the determination of the voltage of each battery by the controller 202 as an example, if it is determined that the voltage of the battery is less than a set voltage value, the battery with the maximum voltage in the series battery pack in which the battery is located can be obtained first, and a loop is established between the battery with the voltage less than the set voltage value and the battery with the maximum voltage. The battery with the maximum voltage charges the battery with the voltage less than the set voltage value through the loop until the voltage of the battery with the voltage less than the set voltage value reaches the set voltage value.

[0062] In order to reduce the number of high-frequency switching tubes, so that the drive circuit in the controller 202 is easy to implement, as a possible implementation, referring to Figure 6 As shown in FIG. 6, the balancing unit 205 further includes a first power switching tube 601, a second power switching tube 602, a third power switching tube 603, and a fourth power switching tube 604.

[0063] The first end of the first power switch tube 601 is connected with the same end of the first secondary winding 2052, the second end of the first power switch tube 601 is connected with the first bus 208, the first end of the second power switch tube 602 is connected with the different end of the first secondary winding 2052, the second end of the second power switch tube 602 is connected with the second bus 209, the first end of the third power switch tube 603 is connected with the different end of the second secondary winding 2053, the second end of the third power switch tube 603 is connected with the first bus 208, the first end of the fourth power switch tube 604 is connected with the same end of the second secondary winding 2053, and the second end of the fourth power switch tube 604 is connected with the second bus 209. The power supply is connected with the same end of the primary winding 2051, and the different end of the primary winding 2051 is grounded through the first control switch 2054. It should be noted that the first control switch 2054 can also be a top MOS tube, and the first power switch tube 601, the second power switch tube 602, the third power switch tube 603 and the fourth power switch tube 604 can be any one of the switch types described in the above embodiment.

[0064] Specifically, in the above embodiment, the transformer in the balancing unit 205 adopts the design of a primary single winding and a secondary double winding, and four switches are used for controlling the bus switch network bus and the transformer winding. Among them, two switches are low-frequency signal switch drives, and two are high-frequency signal switch drives, thereby reducing the number of high-frequency switch drives, making the drive circuit in the controller 202 easy to implement, and also reducing the cost of high-frequency signal drive.

[0065] The following describes specific ways in which the several controllers 202 provided by the embodiments of the present application actively balance the battery by controlling the turn-off of the first power switch tube 601, the second power switch tube 602, the third power switch tube 603, the fourth power switch tube 604 and the first control switch 2054.

[0066] Mode one: when charging the battery, if the voltage of the first bus is greater than the voltage of the second bus, the first power switch tube and the second power switch tube are controlled to be open, the third power switch tube is controlled to be closed, the fourth power switch tube is controlled to be in a rectification state, the first control switch is controlled to be open, and the excitation inductance on the primary winding releases the stored electrical energy to the battery through the second secondary winding. Specifically, by selecting and controlling the battery control switch corresponding to the battery voltage in the N battery control switches 203 to be closed, when the battery voltage is low, the battery is charged by the power supply or the pre-stored electrical energy through the flyback converter, so as to realize the charging balance of the low-voltage battery, and the electrical energy stored in the excitation inductance is released to the battery with low voltage through the second secondary winding.

[0067] Mode two: when charging the battery, if the voltage of the first bus is less than the voltage of the second bus, the third power switch tube and the fourth power switch tube are controlled to be open, the second power switch tube is controlled to be closed, the first power switch tube is controlled to be in a rectification state, and the first control switch is controlled to be open, so that the excitation inductance on the primary winding releases the stored electrical energy to the battery through the first secondary winding.

[0068] Mode three: when discharging the battery, if the voltage of the first bus is greater than the voltage of the second bus, the third power switch tube and the fourth power switch tube are controlled to be open, the second power switch tube is controlled to be closed, the first control switch is controlled to be in a rectification state, and the first power switch tube is controlled to be closed, so that the electrical energy is stored in the excitation inductance on the primary winding. Specifically, by selecting and controlling the battery control switch corresponding to the battery voltage in the N battery control switches 203 to be closed, when the battery voltage is high, the electrical energy of the high-voltage battery is released through the flyback converter, so as to balance the high-voltage battery, and the electrical energy stored in the excitation inductance is released to the battery with low voltage through the second secondary winding.

[0069] Mode four: when discharging the battery, if the voltage of the first bus is less than the voltage of the second bus, the first power switch tube and the second power switch tube are controlled to be open, the third power switch tube is controlled to be closed, the first control switch is controlled to be in a rectification state, and the fourth power switch tube is controlled to be closed, so that the electrical energy is stored in the excitation inductance on the primary winding. The controller 202 can control the equalization unit 205 to realize the equalization discharge of the high-voltage battery and the equalization charge of the low-voltage battery through the principle of the flyback converter.

[0070] The battery power equalization circuit of the application adopts a primary single winding and secondary double winding design, and a plurality of switches are used to control the connection between the battery control switch and the winding of the equalization unit, wherein two paths are high-frequency switch driving, thereby reducing the number of high-frequency switch driving, making the driving circuit in the controller easier to realize and reducing the cost of high-frequency driving. In addition, the battery control switch of the application adopts a top MOS structure, thereby realizing bidirectional conduction, and through the controllable filter capacitor access, the voltage sampling circuit and the equalization unit can better reuse the effect of N battery control switches, both active equalization function and battery sampling function are realized, and they do not affect each other, reducing the complexity of using BMS under the traditional scheme. In addition, the power supply of the application is not directly connected to the battery, but indirectly charged through the transformer of the equalization unit, thereby feeding back the energy through the indirect feedback method, solving the problem that the battery is continuously charged when it is full.

[0071] In addition, the application also provides a battery power equalization method, applied to the battery power equalization circuit 200, the method comprises: controlling the battery control switch connected with the target battery to be closed, and acquiring the voltage value of the target battery detected by the sampling unit; or controlling the equalization unit to charge and discharge the target battery.

[0072] As a possible implementation, the method further comprises: controlling the battery control switch connected with the target battery to be closed and controlling the second control switch to be opened, and acquiring the voltage value of the target battery detected by the sampling unit; or controlling the battery control switch connected with the target battery to be closed and controlling the second control switch to be closed, and controlling the equalization unit to charge and discharge the target battery.

[0073] As a possible implementation, the method further comprises: controlling the battery control switch connected with the target battery to be closed and controlling the second control switch to be opened, and acquiring the voltage value of the target battery detected by the sampling unit; or controlling the battery control switch connected with the target battery to be closed and controlling the second control switch to be closed, and controlling the equalization unit to charge and discharge the target battery.

[0074] Those skilled in the art will appreciate that embodiments of the present application can be readily used as software, hardware, or a combination of software and hardware. In one

[0075] The present application is described in reference to the flow diagrams and / or block diagrams of the methods, apparatus (systems) and computer program products according to this application. It will be understood that each block of the flow diagrams and / or block diagrams, and combinations of blocks in the flow diagrams and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flow diagrams and / or block diagrams block or blocks. Figure 1 The flow diagrams and / or block diagrams in the present application can also be implemented as computer program instructions on a computer readable storage medium, which can be executed by a computer or other programmable apparatus. Figure 1 The flow diagrams and / or block diagrams in the present application can also be implemented as computer program instructions on a computer readable storage medium, which can be executed by a computer or other programmable apparatus.

[0076] These computer program instructions can also be loaded onto a computer or other programmable apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flow diagrams and / or block diagrams block or blocks. Figure 1 The flow diagrams and / or block diagrams in the present application can also be implemented as computer program instructions on a computer readable storage medium, which can be executed by a computer or other programmable apparatus. Figure 1 The flow diagrams and / or block diagrams in the present application can also be implemented as computer program instructions on a computer readable storage medium, which can be executed by a computer or other programmable apparatus.

[0077] These computer program instructions can also be loaded onto a computer or other programmable apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flow diagrams and / or block diagrams block or blocks. Figure 1 The flow diagrams and / or block diagrams in the present application can also be implemented as computer program instructions on a computer readable storage medium, which can be executed by a computer or other programmable apparatus. Figure 1 The flow diagrams and / or block diagrams in the present application can also be implemented as computer program instructions on a computer readable storage medium, which can be executed by a computer or other programmable apparatus.

[0078] Obviously, numerous modifications and variations of the present application are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims and their legal equivalents, the application can be practiced otherwise than as specifically described.

Claims

1. A battery energy balancing circuit, applied to a series battery pack consisting of N batteries connected in series, characterized in that, The circuit includes: a controller, N battery control switches, a filter capacitor control unit, an equalization unit, and a sampling unit. The filter capacitor control unit includes a filter capacitor and a filter capacitor control switch. Each of the N batteries is connected to the first terminal of each of the N battery control switches in a one-to-one correspondence; the second terminal of each of the N battery control switches is connected to the filter capacitor control unit; the filter capacitor control unit is connected to the equalization unit and the sampling unit; the equalization unit is connected to the power supply, and the power supply is used to supply power to the equalization unit. The equalization unit is used to: perform charge and discharge processing on the target battery, wherein the target battery is any one of the N batteries; The sampling unit is used to: detect the voltage of the target battery; The filter capacitor control unit is used to: filter the current input to the target battery from the equalization unit; and when the sampling unit detects the voltage of the target battery, the filter capacitor control switch controls the filter capacitor to disconnect from the sampling unit. The controller is configured to: control the battery control switch connected to the target battery to close, and acquire the voltage value of the target battery detected by the sampling unit; or, control the equalization unit to perform charging and discharging processing on the target battery.

2. The equalization circuit according to claim 1, characterized in that, The battery power balancing circuit further includes: a first bus and a second bus, and the N batteries include multiple first batteries and multiple second batteries; The equalization unit includes: a primary winding, a first secondary winding, a second secondary winding, and a first control switch; The sampling unit includes: an analog-to-digital converter (ADC) and a sampling circuit; The second end of the battery control switch connected to the first battery is connected to the first bus, and the second end of the battery control switch connected to the second battery is connected to the second bus. The first busbar is connected to the first terminal of the filter capacitor control unit, and the second busbar is connected to the second terminal of the filter capacitor control unit; The first busbar is connected to the first secondary winding, and the second busbar is connected to the second secondary winding; The primary winding is connected to the power supply, and the primary winding is grounded through the first control switch; The first bus is connected to the first input terminal of the sampling circuit, the second bus is connected to the second input terminal of the sampling circuit, the output terminal of the sampling circuit is connected to the ADC, and the output terminal of the ADC is connected to the controller.

3. The equalization circuit according to claim 1 or 2, characterized in that, The filter capacitor control unit specifically includes: a filter capacitor and a second control switch, wherein the second control switch is connected in series with the filter capacitor; The controller is specifically configured to: control the battery control switch connected to the target battery to close and control the second control switch to open, thereby obtaining the voltage value of the target battery detected by the sampling unit; or, control the battery control switch connected to the target battery to close and control the second control switch to close, thereby controlling the equalization unit to charge and discharge the target battery.

4. The equalization circuit according to claim 1 or 2, characterized in that, The controller is specifically used for: When the voltage difference between the first target battery and the second target battery is detected to be greater than a set voltage threshold, the first target battery and the second target battery are any two batteries in the series battery pack composed of the N batteries connected in series, and the voltage value of the first target battery is less than the voltage value of the second target battery. The battery control switch connected to the first target battery is closed, and the equalization unit is controlled to charge the first target battery. The battery control switch connected to the second target battery is closed, and the equalization unit is controlled to discharge the second target battery.

5. The equalization circuit according to claim 2, characterized in that, The equalization unit further includes: a first power switch, a second power switch, a third power switch, and a fourth power switch; The first end of the first power switch is connected to the same-name end of the first secondary winding, the second end of the first power switch is connected to the first busbar, the first end of the second power switch is connected to the opposite-name end of the first secondary winding, the second end of the second power switch is connected to the second busbar, the first end of the third power switch is connected to the opposite-name end of the second secondary winding, the second end of the third power switch is connected to the first busbar, and the first end of the fourth power switch is connected to the same-name end of the second secondary winding, the second end of the fourth power switch is connected to the second busbar. The power supply is connected to the same-name terminal of the primary winding, and the opposite-name terminal of the primary winding is grounded through the first control switch.

6. The equalization circuit according to claim 5, characterized in that, The controller is specifically used for: When charging the target battery, if the voltage of the first bus is greater than the voltage of the second bus, the first power switch and the second power switch are turned off, the third power switch is turned on, and the fourth power switch is set to rectification state. The first control switch is turned off, and the electrical energy stored in the magnetizing inductor on the primary winding is released to the battery through the second secondary winding.

7. The equalization circuit according to claim 5, characterized in that, The controller is specifically used for: When charging the target battery, if the voltage of the first bus is less than the voltage of the second bus, the third power switch and the fourth power switch are turned off, the second power switch is turned on, the first power switch is set to rectification state, the first control switch is turned off, and the electrical energy stored in the magnetizing inductor on the primary winding is released to the battery through the first secondary winding.

8. The equalization circuit according to claim 5, characterized in that, The controller is specifically used for: When discharging the target battery, if the voltage of the first bus is greater than the voltage of the second bus, the third power switch and the fourth power switch are controlled to open, the second power switch is controlled to close, and the first control switch is set to rectification state, and the first power switch is controlled to close, so that electrical energy is stored in the magnetizing inductor on the primary winding.

9. The equalization circuit according to claim 5, characterized in that, The controller is specifically used for: When discharging the target battery, if the voltage of the first bus is less than the voltage of the second bus, the first power switch and the second power switch are turned off, the third power switch is turned on, the first control switch is set to rectification state, and the fourth power switch is turned on to store electrical energy in the magnetizing inductor on the primary winding.

10. The equalization circuit according to claim 2, characterized in that, Each of the N battery control switches is a top-pair MOSFET, and the top-pair MOSFET includes: a first switch and a second switch. The source of the first switch is connected to the source of the second switch, the gates of the first switch and the second switch are connected to the controller, the drain of the first switch is connected to the battery, and the drain of the second switch is connected to the corresponding first bus or second bus.

11. A battery power balancing method, applied to the battery power balancing circuit as described in any one of claims 1-10, characterized in that, The method includes: The system controls the battery control switch connected to the target battery to close, and obtains the voltage value of the target battery detected by the sampling unit; or, the system controls the equalization unit to charge and discharge the target battery.

12. The method according to claim 11, characterized in that, The filter capacitor control unit specifically includes: a filter capacitor and a second control switch, wherein the second control switch is connected in series with the filter capacitor, and the method further includes: The system controls the battery control switch connected to the target battery to close and the second control switch to open, thereby acquiring the voltage value of the target battery detected by the sampling unit; or, the system controls the battery control switch connected to the target battery to close and the second control switch to close, thereby controlling the equalization unit to charge and discharge the target battery.

13. The method according to claim 11 or 12, characterized in that, Controlling the equalization unit to charge and discharge the target battery includes: When the voltage difference between the first target battery and the second target battery is detected to be greater than a set voltage threshold, the first target battery and the second target battery are any two batteries in the series battery pack composed of the N batteries connected in series, and the voltage value of the first target battery is less than the voltage value of the second target battery. The battery control switch connected to the first target battery is closed, and the equalization unit is controlled to charge the first target battery. The battery control switch connected to the second target battery is closed, and the equalization unit is controlled to discharge the second target battery.

14. An energy storage system, characterized in that, include: At least one energy storage unit and at least one conversion unit corresponding to the at least one energy storage unit, each of the at least one conversion unit being connected to the power grid; Each of the at least one energy storage unit includes: a series battery pack consisting of N batteries connected in series and a battery energy balancing circuit as described in any one of claims 1-10; Each of the at least one energy storage unit is used to: output DC current to the corresponding conversion unit, or receive DC current input from the corresponding conversion unit, to charge the series battery pack composed of the N batteries connected in series. Each of the at least one conversion unit is configured to: convert the DC current input to the corresponding energy storage unit into AC current and output it to the power grid, or receive the AC current input to the power grid and convert the AC current into DC current and output it to the corresponding energy storage unit.

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