Method and system for active battery pack equalization

Abstract

The present disclosure relates to methods and systems for active battery pack equalization. In described examples, a system includes a bus, a primary coil, a first battery terminal, and a second battery terminal. A first circuit is coupled between the bus and the primary coil. A first secondary coil is DC isolated from the primary coil. A second circuit is coupled between the first secondary coil and the first battery terminal. A second secondary coil is DC isolated from the primary coil. A third circuit is coupled between the second secondary coil and the second battery terminal. A controller is configurable to control the second circuit to transfer energy from the first battery terminal through the first secondary coil to the primary coil, and to control the first circuit and the third circuit to transfer energy from the primary coil to the second secondary coil and to provide energy to the second battery terminal.

Description

[0001] Cross-citation of related applications

[0002] This application claims priority to U.S. Provisional Application No. 63 / 727,264, filed on December 3, 2024, entitled “ESSACTIVE PACK BALANCE SYSTEM,” which is hereby incorporated herein by reference in its entirety. Technical Field

[0003] This disclosure generally relates to energy storage systems, and more particularly to methods and systems for active battery pack balancing. Background Technology

[0004] Various energy storage systems (ESS) may contain multiple energy storage cells, such as battery cells, which are connected in series to form a battery pack or module. Energy storage systems containing multiple battery packs can be part of an energy storage infrastructure or a mobile energy storage system (e.g., as part of an electric vehicle). Due to internal factors (e.g., increased battery cell impedance or aging) and external factors (e.g., temperature differences), the capacity or state of charge (SOC) of individual battery packs or modules may differ. These variations can lead to uneven charging and discharging behavior within the series-connected battery stack, resulting in an unbalanced SOC. This SOC imbalance reduces usable energy capacity and can potentially affect system performance and lifespan. Summary of the Invention

[0005] In one example, a system includes a bus, a primary coil, a first battery terminal, and a second battery terminal. A first circuit is coupled between the bus and the primary coil. The first secondary coil is DC isolated from the primary coil. A second circuit is coupled between the first secondary coil and the first battery terminal. The second secondary coil is DC isolated from the primary coil. A third circuit is coupled between the second secondary coil and the second battery terminal. A controller is configurable to control the second circuit to transfer energy from the first battery terminal through the first secondary coil to the primary coil, and to control the first and third circuits to transfer energy from the primary coil to the second secondary coil and to supply energy to the second battery terminal.

[0006] In another example, a system includes a first bidirectional isolated DC-DC converter coupled between a bus and a first battery terminal. A second bidirectional isolated DC-DC converter is coupled between the bus and a second battery terminal. A controller is coupled to the first and second isolated DC-DC converters and is configurable to control the transfer of charge between the first and second battery terminals via the bus.

[0007] In another example, a method includes controlling the transfer of energy from a first battery terminal through a first secondary coil to a primary coil, wherein the first secondary coil is DC isolated from the primary coil. The method also includes controlling the transfer of energy from the primary coil to a second secondary coil to provide energy to a second battery terminal, wherein the second secondary coil is DC isolated from the primary coil. As yet another example, a first bidirectional isolated DC-DC converter includes a primary coil and a first secondary coil, and a second bidirectional isolated DC-DC converter includes a second secondary coil. Attached Figure Description

[0008] Figure 1 This is a schematic diagram illustrating a system for performing Active Battery Pack Balancing (APB) operations based on various examples.

[0009] Figure 2 This is a schematic diagram illustrating examples of bidirectional isolated DC-DC converters that can be implemented to perform active battery pack balancing operations, according to various embodiments.

[0010] Figure 3 Includes illustrations of battery pack usage based on various examples. Figure 2 The circuit charging operation curve.

[0011] Figure 4A and 4B This is a schematic diagram illustrating an ESS containing one or more bidirectional isolated DC-DC converters according to various examples.

[0012] Figure 5 This is a flowchart illustrating methods for performing active battery pack balancing operations based on various instances.

[0013] Figure 6 This is an explanation based on various examples. Figure 5 A schematic diagram of the signal flow for active battery pack equalization operation.

[0014] Figure 7 This is a schematic diagram illustrating battery pack charging and discharging operations as part of active battery pack balancing operations, based on various examples.

[0015] Figure 8 , 9 10 contains graphs illustrating the current and voltage waveforms during the current regulation operation of the active battery pack equalization operation, according to various examples.

[0016] Unless otherwise stated, corresponding reference numerals and symbols in different figures generally refer to corresponding parts. The figures are drawn to clearly illustrate relevant aspects of the preferred embodiments, and the figures are not necessarily drawn to scale. Detailed Implementation

[0017] This disclosure relates to various methods and systems for performing active balancing of energy storage elements (e.g., battery packs) in an energy storage system (ESS).

[0018] As an example, an ESS includes one or more bidirectional isolated DC-DC converters (also known as isolated DC-DC converters). The one or more isolated DC-DC converters are coupled between a bus (e.g., a voltage bus) and a first battery terminal of a corresponding energy storage element (e.g., a battery pack). The battery pack includes multiple battery cells coupled between the first battery terminal and a second battery terminal. The battery cells of the battery pack may be connected in series between the first battery terminal and the second battery terminal.

[0019] As another example, an isolated DC-DC converter includes a primary-side circuit, a secondary-side circuit, and a bidirectional isolation circuit (e.g., a transformer), wherein the primary-side circuit is coupled to the secondary-side circuit via the bidirectional isolation circuit to provide current isolation (or DC isolation) between the primary and secondary-side circuits of the isolated DC-DC converter. The transformer includes a primary coil magnetically coupled to one or more secondary coils. The primary-side circuit is coupled between the primary coil and a bus, and the secondary-side circuit is coupled between the secondary coil and battery terminals. Alternatively, the primary and secondary circuits of the isolated DC-DC converter include corresponding bridge circuits, such as half-bridges or full-bridges, which may depend on the expected current amplitudes through the primary and secondary-side circuits. A controller coupled to one or more isolated DC-DC converters can control each isolated DC-DC converter to transfer energy to or from a voltage bus, and / or to or from a corresponding battery pack, the respective isolated DC-DC converter being coupled to the corresponding battery pack. As described in this article, the direction and amount of energy delivered through each isolated DC-DC converter can vary depending on how the APB is executed.

[0020] For example, the ESS includes at least a first isolated DC-DC converter and a second isolated DC-DC converter. The first isolated DC-DC converter is coupled between a bus (e.g., a voltage bus) and a first battery pack, and the second isolated DC-DC converter is coupled between the voltage bus and a second battery pack. A controller operating in APB mode controls the first and second isolated DC-DC converters to perform APB. In instances where the battery pack voltage of the second battery pack is greater than that of the first battery pack, the controller controls the first isolated DC-DC converter to provide a regulated current signal (e.g., a substantially constant or regulated current) to charge the first battery pack based on the bus voltage. The controller also controls the second isolated DC-DC converter to provide a voltage (e.g., a substantially constant or regulated voltage) to the voltage bus by discharging the second battery pack. Advantageously, when implementing APB, the voltage provided to the voltage bus by the second isolated DC-DC converter can help stabilize the voltage bus, which might otherwise fluctuate in response to the energy used by the first isolated DC-DC converter to charge the first battery pack. The controller can implement APB to charge the first battery pack and discharge the second battery pack until equalization has been achieved (e.g., until the corresponding voltages of the first and second battery packs are approximately the same).

[0021] Performing APB (Active Pack Balance) in an ESS (Energy Storage System) with a bidirectional isolated DC-DC converter offers various advantages. Specifically, without balancing operations, the battery pack with the lowest SOC (State of Charge) can limit the total capacity of all battery packs, as well as the lifespan and utilization of individual packs, especially when packs are connected in series to increase capacity. Balancing operations improve the SOC balancing of each battery pack. Active pack balancing achieves SOC balancing by moving charge from one battery pack to another, rather than dissipating charge to ground as in passive pack balancing. This avoids the thermal management, weak balancing capabilities, and charge waste associated with passive pack balancing. As described herein, bidirectional isolated DC-DC converters, such as dual-bridge series resonant converters, are provided to perform APB, where the voltage bus can be used to discharge high-voltage battery packs and charge low-voltage battery packs. This arrangement can utilize existing bidirectional isolated DC-DC converters and voltage buses already part of the ESS to perform APB, which can reduce costs. The converter topology described herein can also be used in non-APB operations, such as normal energy storage and discharging operations. Furthermore, phase-shift control can be used to control isolated DC-DC converters, thereby controlling the flow of charge through the voltage bus from one battery pack to another, which simplifies the control of APB operation. All of these improvements enhance the overall performance of the ESS and can be achieved at a reduced cost.

[0022] Figure 1 This is a block diagram illustrating an example of a system 100, such as an energy storage system (ESS). System 100 includes multiple bidirectional isolated DC-DC converters 102, 104, and 106. System 100 may include any number of isolated DC-DC converters 102, 104, and 106. Each of the isolated DC-DC converters 102, 104, and 106 can be implemented according to virtually any isolated converter topology, which may vary depending on the application requirements for a given operating environment. In the example described herein, the isolated DC-DC converters 102, 104, and 106 include isolation structures, such as primary and secondary coils, coupled between respective primary-side and secondary-side circuits, wherein the primary and secondary coils are DC isolated from each other, but signals, including electrical power, can be transmitted between the primary and secondary coils via magnetic coupling between the coils. Furthermore or alternatively, as disclosed herein, each of the isolated DC-DC converters 102, 104, and 106 may include one primary coil and one or more secondary coils. Other types of isolation structures are also possible between the primary-side circuit and the secondary-side circuit.

[0023] exist Figure 1 In this example, each of the isolated DC-DC converters 102, 104, and 106 is coupled between a bus 108 (e.g., a voltage bus) and a corresponding battery pack 110, 112, and 114. Bus 108 provides a bus voltage (denoted as VBUS) to system 100, such as a regulated DC voltage. In some examples, the bus voltage VBUS may be provided by another power source (not shown), which may include one or more other power converters for converting another voltage, which may be AC ​​or DC, to the voltage VBUS. As an example, VBUS may be 24 V. In other examples, VBUS may also be other voltages.

[0024] like Figure 1As shown, battery packs 110, 112, and 114 are connected in series between terminals 116 and 118 of battery rack 120 (or another battery support structure holding multiple battery cells). Each battery pack 110, 112, and 114 contains multiple battery cells connected in series. Each isolated DC-DC converter 102, 104, and 106 is coupled to one or more battery terminals of the respective battery pack 110, 112, and 114. In some exemplary embodiments, the battery cells of one or more battery packs 110, 112, and 114 may be divided into multiple modules (also referred to herein as battery modules), wherein each module of a given battery pack contains a portion (e.g., approximately half) of the battery cells of the given battery pack. Isolated DC-DC converters 102, 104, and 106 coupled to given battery packs 110, 112, and 114 may include individual connections to the battery terminals of the modules for transferring energy (e.g., supplying current) to and from each respective module of the given battery pack (e.g., drawing current). Battery packs 110, 112, and 114 may be divided into multiple modules having designated portions of battery cells.

[0025] System 100 also includes one or more controllers 122 having control outputs coupled to a corresponding control input of each of the isolated DC-DC converters 102, 104, and 106. Each isolated DC-DC converter 102, 104, and 106 may have a dedicated controller 122 to control each isolated DC-DC converter, or in other instances, a given controller may control multiple isolated DC-DC converters. Controller 122 also includes inputs coupled to a corresponding output of each of the battery packs 110, 112, and 114. Controller 122 may also include terminals coupled to a voltage bus 108 to receive a bus voltage VBUS for powering the controller. Voltage measurement circuitry (not shown), which may be implemented internally or externally to the controller, may measure the voltage VBUS at the terminals for use in controlling one or more of the isolated DC-DC converters 102, 104, and 106. The controller 122 may be implemented as a microcontroller (or microcontroller unit) in an integrated circuit (IC) that includes one or more processors, memories, and input / output (I / O) peripherals that cooperate to perform the functions described herein. Alternatively or additionally, the controller 122 may be implemented as or comprise one or more application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or equivalent discrete and / or integrated logic circuit systems.

[0026] In operation, controller 122 can control one or more of the DC-DC converters 102, 104, and 106 to transfer power from bus 108 (which receives power from another power source, such as an AC grid or a DC source) to charge the battery pack and store energy in the battery pack. Controller 122 can also control one or more of the DC-DC converters 102, 104, and 106 to discharge the battery pack to release power to bus 108, which can then transfer the power to a load (which may include an AC grid or another DC power absorber, such as a battery).

[0027] The controller 122 can also operate in APB mode and control one or more of the isolated DC-DC converters 102, 104, and 106 to transfer energy between the respective battery packs 110, 112, and 114 via a voltage bus. For example, the controller 122 receives information about the voltage across each of the battery packs 110, 112, and 114 (e.g., from a voltage sensor) to determine whether APB is required. The controller 122 further identifies which of the battery packs 110, 112, and 114 has the highest battery pack voltage and which has the lowest battery pack voltage. In a first example, the controller determines that battery pack 112 has the highest battery pack voltage and battery pack 110 has the lowest battery pack voltage. The controller may further be pre-programmed to know that isolated DC-DC converter 102 is coupled to battery pack 110 and isolated DC-DC converter 104 is coupled to battery pack 112. The controller 122 can then control the identified pair of isolated DC-DC converters 102 and 104, and isolated DC-DC converter 106, to implement APB. For example, the controller 122 controls isolated DC-DC converter 102 to provide current signals to corresponding terminals to charge the first battery pack 110 based on VBUS, and the controller controls isolated DC-DC converter 104 to provide voltage (e.g., regulated voltage) to the bus 108 by discharging from the second battery pack 112. In this way, the voltage of the highest-voltage battery pack 112 can decrease based on its discharge, while the voltage of the lowest-voltage battery pack 110 can increase based on its charging. Additionally, isolated DC-DC converter 102 can provide voltage to the voltage bus 108 during APB mode to stabilize VBUS, since VBUS tends to decrease in response to the energy utilized by isolated DC-DC converter 102 to charge its battery pack 110. In some instances, the voltage provided by isolated DC-DC converter 102 can supply sufficient energy to allow one or more additional isolated DC-DC converters (e.g., isolated DC-DC converter 106) to also charge the battery pack during APB mode. Controller 122 can control isolated DC-DC converters 102 and 104 to continue in APB mode until battery packs 110 and 112 reach an equalization state (e.g., the voltage difference does not exceed a voltage threshold). More than one pair of isolated DC-DC converters can be controlled to perform APB simultaneously or sequentially.

[0028] Additionally, battery cells (e.g., the cells in battery packs 110, 112, and 114) and battery racks (e.g., battery rack 120) can exhibit variations due to factors such as manufacturing changes, assembly variations, and cell aging. Therefore, each battery pack 110, 112, and 114 in battery rack 120 may operate at different states of charge (SOCs). For example, cell capacity may continuously increase (e.g., from 10 Ah to 280 Ah, to 314 Ah, to 560 Ah, etc.). ESS battery life can reach 10 years or longer. Battery rack 120 may contain a mix of old and new battery packs 110, 112, and 114, which may result in some battery packs having different capacities, potentially causing inconsistent SOCs for each pack. The battery packs 110, 112, and 114 with the lowest SOCs may limit the capacity of battery rack 120, which could affect the utilization and lifespan of battery rack 120. APB can extend the lifespan of battery packs 110, 112, and 114 in battery rack 120. Furthermore, as disclosed herein, by discharging the battery pack exhibiting a higher voltage and charging the battery pack exhibiting a lower voltage, the APB can further advantageously improve the power efficiency of the system 100, which has high balanced energy and low maintenance requirements (e.g., advantageously avoiding manual labor costs), without wasting energy (e.g., this can advantageously improve thermal management) and without reducing the total capacity of the battery rack.

[0029] Figure 2 This describes an example of an ESS 200 that can be implemented to perform APB functionality relative to a battery pack 202. The ESS 200 includes a bidirectional isolated DC-DC converter 203 (referred to as an isolated DC-DC converter). The isolated DC-DC converter 203 is a method that can be used to implement... Figure 1 An example converter of the isolated DC-DC converters 102, 104, and 106 of system 100. Therefore, Figure 2 The description can be found here. Figure 1 In some aspects.

[0030] like Figure 2 As shown, the isolated DC-DC converter 201 includes a primary-side circuit 204, a secondary-side circuit 206, and a bidirectional isolation structure 208, wherein the primary-side circuit is coupled to the secondary-side circuit through the isolation structure. Figure 2In one example, isolation structure 208 is a transformer comprising a primary coil 210 (e.g., a winding) and a secondary coil 212 (e.g., a winding) that are DC isolated from each other. In other examples, the isolation structure may comprise more than one secondary coil. Primary-side circuitry 204 includes one or more I / O terminals 214 and 216, and secondary-side circuitry 206 includes one or more I / O terminals 218 and 220. I / O terminal 214 is coupled to a terminal 222 of a bus (e.g., a voltage bus with a bus voltage VBUS), and I / O terminal 216 is coupled to another terminal 224 of the bus, which is coupled to a first ground, such as ground, signal ground, or chassis ground. The voltage potential across terminals 222 and 224 defines the bus voltage VBUS of system 200. Capacitor C1 may be coupled between bus terminals 222 and 224 to help ensure a stable DC voltage at I / O terminals 214 and 216. The primary-side circuit 204 also includes a bridge circuit, shown as a half-bridge circuit, which includes switches, shown as transistors Q1 and Q2. In other instances, depending on the expected current requirements, the primary-side circuit 204 may include a full-bridge circuit or be implemented according to another bridge circuit topology.

[0031] In this example, each of transistors Q1 and Q2 is a field-effect transistor (FET), such as an n-channel or p-channel FET. Transistor Q1 (e.g., an n-channel FET) includes a first current terminal (e.g., drain), a second current terminal (e.g., source), and a control terminal (e.g., gate), wherein the first current terminal is coupled to terminal 214, and the second current terminal is coupled to a terminal of the primary coil 210 via a resonant inductor LR. Transistor Q2 (e.g., an n-channel FET) includes a first current terminal (e.g., drain), a second current terminal (e.g., source), and a control terminal (e.g., gate), wherein the first current terminal is coupled to the second current terminal (e.g., source) of Q1, and the second current terminal is coupled to terminal 216. Terminal 216 of the primary-side circuit 204 is also coupled to another terminal of the primary coil 210 via capacitor C2. LR and C2 may form a resonant tank circuit. A first gate driver 226 is coupled to the control terminal of transistor Q1, and a second gate driver 228 is coupled to the control terminal of transistor Q2.

[0032] In the secondary-side circuit 206, I / O terminal 218 is coupled to a first terminal 230 of the battery pack 232, and I / O terminal 220 is coupled to a second terminal 234 of the battery pack. I / O terminal 220 is also coupled to a second ground (e.g., ground, signal ground, or chassis ground), which is different from and isolated from the ground of the primary-side circuit 204 to which terminal 224 is coupled.

[0033] Secondary-side circuit 206 also includes a bridge circuit, shown as a half-bridge. In other instances, depending on the expected current requirements, a full-bridge circuit may be implemented in secondary-side circuit 206. Alternatively, isolated DC-DC converter 203 may include multiple secondary-side circuits. Figure 2 In this example, the half-bridge of the secondary-side circuit 206 includes switches, shown as transistors Q3 and Q4 (e.g., FETs). For example, transistor Q3 (e.g., FET) includes a first current terminal (e.g., drain), a second current terminal (e.g., source), and a control terminal (e.g., gate), wherein the first current terminal is coupled to terminal 218, and the second current terminal is coupled to a terminal of the secondary coil 212. Transistor Q4 (e.g., FET) includes a first current terminal (e.g., drain), a second current terminal (e.g., source), and a control terminal (e.g., gate), wherein the first current terminal is coupled to the second current terminal (e.g., source) of Q3. The second current terminal of Q4 is coupled to terminal 220, which is also coupled to another terminal of the secondary coil 212. Gate drivers 236 and 238 are coupled to the control terminals of transistors Q3 and Q4, respectively. Although Q3, Q4, Q5, and Q6 are shown as FETs, in other instances, different types of transistors can be used to implement such transistors, such as bipolar junction transistors (BJTs), insulated gate bipolar transistors (IGBTs), laterally diffused metal-oxide-semiconductor (LDMOS) transistors, etc. One or more of the gate drivers 226, 228, 236, and 238 can be implemented in the IC chip of the controller via traces on a printed circuit board or through other connections.

[0034] Controller (e.g., Figure 1The controller 122 provides control signals (e.g., modulated signals, such as pulse width modulation or frequency modulation signals) to the inputs of each of the gate drivers 226, 228, 236, and 238, shown as CONTROL1, CONTROL2, CONTROL3, and CONTROL4. The gate drivers 226, 228, 236, and 238 can control the operation of Q1, Q2, Q3, and Q4 of the isolated DC-DC converter 203, for example, to charge the battery pack 232 using power from the primary side or to discharge the battery pack 232 to supply power to the primary side. In one example, the controller provides control signals CONTROL1, CONTROL2, CONTROL3, and CONTROL4 to control the isolated DC-DC converter 203 to charge the battery pack 232 from the primary side, to support, for example, APB or non-APB operation (e.g., normal charging / discharging of the battery pack from / to the voltage bus). In another example, the controller provides control signals CONTROL1, CONTROL2, CONTROL3, and CONTROL4 to control the isolated DC-DC converter 203 to discharge the battery pack 232 to support APB or non-APB operation.

[0035] Reference Figure 3 The signal timing diagram 300 describes the operation of the isolated DC-DC converter 203, as part of the APB, charging the battery pack 232 using the current I_CHARGE. The signal timing diagram includes graphs of control signals CONTROL1, CONTROL2, CONTROL3, and CONTROL4, shown as signal pulses (e.g., square waves) 302, 304, 306, and 308, respectively. Control signals CONTROL1 and CONTROL2 are shown as complementary signal pulses 302 and 304 to implement the mutually exclusive switching operation of Q1 and Q2. Similarly, control signals CONTROL3 and CONTROL2 are shown as complementary signal pulses 306 and 308 to implement the mutually exclusive switching operation of Q3 and Q4. Furthermore, relative to control signals 302 and 304 (CONTROL1 and CONTROL2), control signals 306 and 308 (CONTROL3 and CONTROL4) have a phase transition interval (e.g., provided by the controller), shown as Φ.

[0036] Based on control signals 302 and 304 (CONTROL1 and CONTROL2), a current ILR flowing through the inductor LR is provided via the primary coil 210, such as... Figure 3 As shown in 310. (As...) Figure 3As shown, when control signal 302 (CONTROL1) is high and control signal 304 (CONTROL2) is low, the current ILR increases because the resonant circuit (e.g., LR, primary coil 210, and C2) is charged by the voltage VBUS provided by Q1 when Q2 is turned off. When control signal 304 (CONTROL2) is high and control signal 302 (CONTROL1) is low, the current ILR decreases because the resonant circuit (e.g., LR, primary coil 210, and C2) is discharged by Q2 when Q1 is turned off. The current ILR experiences a higher rate of change (e.g., slope) during the phase transition interval Φ.

[0037] The time-varying current ILR 310 flowing through the primary coil 210 induces a voltage at the secondary coil 212 (e.g., through magnetic or inductive coupling of the transformer 208), which is used to supply a current I_CHARGE to the battery pack 232, such as... Figure 3 As shown in 312. (As...) Figure 3 As shown, the current I_CHARGE 312 increases in amplitude in response to a high level for control signal 306 (CONTROL3) and a low level for control signal 308 (CONTROL4). The current I_CHARGE 312 decreases in amplitude in response to a high level for control signal 308 (CONTROL4) and a low level for control signal 306 (CONTROL3). The voltage across the battery pack can increase based on the current I_CHARGE provided during APB. The current I_CHARGE 312 defines a substantially constant current because it varies only between about 5.05 A and about 4.95 A (e.g., a variation of about 1%). In other instances, variations in the current I_CHARGE 312 may occur (e.g., variations greater than or less than 1%, such as ±5%) to provide a substantially constant current.

[0038] To improve power efficiency, APB may involve discharging another battery pack to supply at least a portion of the energy used to charge battery pack 232. APB may continue until the voltages of the respective battery packs are substantially equalized (e.g., the voltage difference does not exceed a threshold voltage difference). As another example, another instance of the isolated DC-DC converter 203 (referred to as the second isolated DC-DC converter) is coupled between a voltage bus (e.g., terminals 222 and 224) and another battery pack (referred to as the second battery pack), for example... Figure 1As shown. In this example of APB, the controller has determined that the voltage of the second battery pack is greater than that of the battery pack 232 to be charged. The controller (e.g., controller 122) controls the second isolated DC-DC converter (e.g., by providing control signals to its primary and secondary bridge circuits) to generate current in the secondary-side circuit by discharging the second battery pack. The current in the secondary-side circuit of the second isolated DC-DC converter induces a voltage on the primary coil of the primary-side circuit, which is used by the primary-side circuit to provide a second voltage (e.g., a regulated DC voltage) to terminal 222 of the voltage bus. In this way, the first and second isolated DC-DC converters performing APB cooperate to transfer energy from the second battery pack to the first battery pack. Advantageously, the second isolated DC-DC converter provides voltage to the voltage bus by discharging its associated battery pack, thereby further reducing VBUS fluctuations (e.g., stabilizing VBUS) caused by the current ILR generated by the primary-side circuit 204 of the isolated DC-DC converter 203 for charging the battery pack 232.

[0039] Figure 4A and 4B This describes another example of an ESS 400 that includes one or more bidirectional isolated DC-DC converters 402 (also known as isolated DC-DC converters). Figure 4A and 4B In the example ESS 400, one or more isolated DC-DC converters 402 are each coupled between a voltage bus 404 and a corresponding battery pack 406. ESS 400 also includes a controller 408 coupled to each isolated DC-DC converter 402 and battery pack 406 to perform APB. Figure 4A and 4B The document illustrates a configuration of an isolated DC-DC converter 402, and each other isolated DC-DC converter 402 in the ESS 400 can be implemented as another instance thereof or in other ways disclosed herein. The isolated DC-DC converter 402 provides a configuration suitable for implementation. Figure 1 The converter instance in System 100. Additional features of ESS also apply. Figure 2 The ESS 200. Therefore, Figure 4A and 4B The description can be found here. Figure 1 , 2 And certain aspects of 3.

[0040] As an example, the isolated DC-DC converter 402 includes a primary-side circuit 410 and one or more secondary-side circuits. Figure 4A and 4BThe diagram shows a primary side circuit 412 and a secondary side circuit 414. The primary side circuit 410 is coupled to each of the secondary side circuits 412 and 414 via a bidirectional isolation structure 416. For example, the bidirectional isolation structure 416 is implemented as a transformer comprising a primary coil 418 and one or more secondary coils 420 and 422, wherein the primary coil is DC isolated from each of the one or more secondary coils. Each of the primary coil 418 and the secondary coils has a plurality of windings (or turns), shown as N1, N2, and N3 respectively, and the voltage ratio between the coils is proportional to the turns ratio of the respective coils. The primary side circuit 410 is coupled to the primary coil 418. The secondary side circuit 412 is coupled to the secondary coil 420, and the secondary side circuit 414 is coupled to the secondary coil 422.

[0041] like Figure 4B As shown, the primary-side circuit 410 includes one or more I / O terminals 424 and 426, which are coupled to one or more corresponding terminals 428 and 430 of the voltage bus 404. For example, terminal 424 has a first voltage (e.g., a positive voltage, such as about 24 V) and terminal 426 has a lower second voltage, such as ground (e.g., ground or chassis ground), and the voltages across terminals 424 and 426 define the bus voltage VBUS of system 400.

[0042] exist Figure 4BIn one example, the primary-side circuit 410 includes a full-bridge circuit with a switching arrangement shown as transistors Q1, Q2, Q3, and Q4, such as FETs. Other types of transistors may also be used as disclosed herein. Q1 and Q2 may define the first half of the bridge circuit, and Q3 and Q4 may define the other half. For example, transistor Q1 (e.g., FET) includes a first current terminal (e.g., drain), a second current terminal (e.g., source), and a control terminal (e.g., gate), wherein the first current terminal is coupled to I / O terminal 424, and the second current terminal is coupled to a terminal of the primary coil 418. Transistor Q2 (e.g., FET) includes a first current terminal (e.g., drain), a second current terminal (e.g., source), and a control terminal (e.g., gate), wherein the first current terminal is coupled to the second current terminal (e.g., source) of Q1, and the second current terminal is coupled to I / O terminal 426. Additionally, transistor Q3 (e.g., FET) includes a first current terminal (e.g., drain), a second current terminal (e.g., source), and a control terminal (e.g., gate), wherein the first current terminal is coupled to I / O terminal 424, and the second current terminal is coupled to another terminal of primary coil 418 via one or more switches shown as one or more transistors Q13 (e.g., one or more FETs). Transistor Q4 (e.g., FET) includes a first current terminal (e.g., drain), a second current terminal (e.g., source), and a control terminal (e.g., gate), wherein the first current terminal is coupled to the second current terminal (e.g., source) of Q3, and the second current terminal is coupled to I / O terminal 426.

[0043] Driver circuit 432 has one or more inputs and outputs, wherein one or more inputs are coupled to one or more outputs of controller 408, and the outputs of driver circuit are coupled to the corresponding control inputs of Q1, Q2, Q3, Q4, and Q13. Driver circuit 432 controls transistors Q1, Q2, Q3, Q4, and Q13 based on one or more control signals received from controller 408 to control the flow of energy to and from bus 404, as described herein. In one example, controller 408 controls primary-side circuit 410 to transfer energy from bus 404 through bidirectional isolation structure 416 to one or both of secondary-side circuits 412 and 414. In another example, controller 408 controls primary-side circuit 410 to transfer energy received via primary coil 418 from one or both of secondary-side circuits 412 and 414 through bidirectional isolation structure 416 to bus 404.

[0044] like Figure 4AAs shown, the secondary-side circuit 412 includes a switching arrangement of transistors Q5, Q6, Q7, and Q8 (e.g., FETs) configured as a full-bridge circuit, where Q5 and Q6 define the first half of the bridge, and Q7 and Q8 define the other half. For example, transistor Q5 (e.g., FET) includes a first current terminal (e.g., drain), a second current terminal (e.g., source), and a control terminal (e.g., gate), wherein the first current terminal is coupled to I / O terminal 434 of the secondary-side circuit 412, and the second current terminal is coupled to a first terminal of the secondary coil 420 via inductor LR1. Transistor Q6 (e.g., FET) includes a first current terminal (e.g., drain), a second current terminal (e.g., source), and a control terminal (e.g., gate), wherein the first current terminal is coupled to the second current terminal (e.g., source) of Q5, and the second current terminal is coupled to another I / O terminal 436 of the secondary-side circuit. Additionally, transistor Q7 (e.g., FET) includes a first current terminal (e.g., drain), a second current terminal (e.g., source), and a control terminal (e.g., gate), wherein the first current terminal is coupled to I / O terminal 434, and the second current terminal is coupled to the second terminal of secondary coil 420. Transistor Q8 (e.g., FET) includes a first current terminal (e.g., drain), a second current terminal (e.g., source), and a control terminal (e.g., gate), wherein the first current terminal is coupled to the second current terminal (e.g., source) of Q7, and the second current terminal is coupled to I / O terminal 436. I / O terminals 434 and 436 of secondary-side circuit 412 are coupled to battery terminals 438 and 440 of battery pack 406, respectively. Driver circuit 442 has one or more inputs and outputs, wherein one or more inputs are coupled to one or more outputs of controller 408, and the output of driver circuit is coupled to the corresponding control inputs of transistors Q5, Q6, Q7, and Q8. The driver circuit 442 controls transistors Q5, Q6, Q7 and Q8 based on one or more control signals received from the controller 408 to control the flow of energy (shown as current I_CHARGE1) to and from the battery terminal 438, as described herein.

[0045] Another secondary-side circuit 414 includes a switching arrangement of transistors Q9, Q10, Q11, and Q12 (e.g., FETs) shown as a full-bridge circuit, wherein Q9 and Q10 define the first half of the bridge, and Q11 and Q12 define the other half. For example, transistor Q9 (e.g., FET) includes a first current terminal (e.g., drain), a second current terminal (e.g., source), and a control terminal (e.g., gate), wherein the first current terminal is coupled to I / O terminal 444 of the secondary-side circuit 414, and the second current terminal is coupled to a first terminal of the secondary coil 422 via inductor LR2. Transistor Q10 (e.g., FET) includes a first current terminal (e.g., drain), a second current terminal (e.g., source), and a control terminal (e.g., gate). The first current terminal is coupled to a second current terminal (e.g., source) of Q9, and the second current terminal is coupled to another I / O terminal 446 of the secondary-side circuit 414, which is also coupled to ground (e.g., ground plane or chassis ground). The ground coupled to I / O terminal 446 is different from and electrically isolated from the ground coupled to terminal 430 on the primary side. Additionally, transistor Q11 (e.g., FET) includes a first current terminal (e.g., drain), a second current terminal (e.g., source), and a control terminal (e.g., gate). The first current terminal is coupled to I / O terminal 444, and the second current terminal is coupled to another terminal of the secondary coil 422. Transistor Q12 (e.g., FET) includes a first current terminal (e.g., drain), a second current terminal (e.g., source), and a control terminal (e.g., gate), wherein the first current terminal is coupled to the second current terminal (e.g., source) of Q11, and the second current terminal is coupled to I / O terminal 446. I / O terminals 444 and 446 of secondary-side circuitry 414 are coupled to battery terminals 448 and 450 of battery pack 406, respectively. Driver circuitry 452 has one or more inputs and outputs, wherein one or more inputs are coupled to one or more outputs of controller 408, and the outputs of driver circuitry are coupled to the respective control inputs of transistors Q9, Q10, Q11, and Q12. Driver circuitry 452 controls transistors Q9, Q10, Q11, and Q12 based on one or more control signals received from controller 408 to control the flow of energy (shown as current I_CHARGE2) to and from battery terminal 448, as described herein.

[0046] Additionally, battery pack 406 includes multiple battery cells between battery terminals 438 and 450 (e.g., these battery cells are coupled in series, parallel, or a combination of both). In the example of Figure 4, there are 104 battery cells, numbered cell 1 to cell 104. In other examples, battery pack 406 may contain other numbers of battery cells. Furthermore, in Figure 4AIn one example, battery cells 1 to 52 coupled between battery terminals 438 and 440 may be part of module 454 of battery pack 406, and battery cells 53 to 104 coupled between battery terminals 448 and 450 may be part of another module 456 of the battery pack. In other examples, battery pack 406 may contain more than two modules, or the battery pack may define a single module (or contain no modules). As described herein, controller 408 controls one or more of the isolated DC-DC converters 402 in ESS 400 to perform APB operation. Controller 408 may also control the isolated DC-DC converters 402 to perform non-APB operations, such as the battery pack charging / discharging from / to the voltage bus.

[0047] In some instances, the battery pack 406 includes one or more voltage measurement circuits 460, such as one or more analog or digital voltmeters. For example, each voltage measurement circuit 460 includes an input coupled across a corresponding plurality of battery cells (e.g., cells 1 to 104) and an output coupled to a controller 408. Each voltage measurement circuit 460 measures the voltage across the corresponding battery cell and provides an output signal to the controller 408 representing the measured voltage. Figure 4A As shown, each voltage measurement circuit 460 is coupled across the battery cell of the corresponding module 454 or 456. For example, one voltage measurement circuit has inputs coupled to terminals 438 and 440, and another voltage measurement circuit has inputs coupled to terminals 448 and 450. In another example, the corresponding voltage measurement circuit 460 has inputs coupled to terminals 438 and 450 to enable sensing of the battery pack voltage (e.g., within the range of PACK+ and PACK-).

[0048] The battery pack 406 also includes one or more current monitoring circuits 462. For example, the current monitoring circuit 462 has an input coupled across a sensing resistor RS, which is connected in series with the current path of the battery cells through terminals 438 and 450. The current monitoring circuit 462 has an output coupled to a corresponding input of the controller 408 for providing a current sensing signal representing the sensed current. As described herein, the controller 408 controls one or more of the isolated DC-DC converters 402 in the ESS 400 to perform APB (e.g., by controlling the current charging or discharging of the cells relative to the battery pack).

[0049] As another example, each voltage measurement circuit 460 and current monitoring circuit 462 may include an amplifier with an input coupled to a battery terminal, the amplifier providing an amplified voltage measurement signal. An analog-to-digital converter converts the amplified voltage or current measurement signal into a digital signal. Each of the voltage measurement circuit 460 and current measurement circuit 462 may further include digital signal processing (e.g., filtering, windowing, compensation, etc.) to transform the digital signal into a form desired for evaluation and / or analysis by the controller 408. The controller 408 determines the current flowing through the battery pack for controlling the charging or discharging of the current during APB. The controller 408 also determines the voltage of each corresponding battery pack 406 (and / or modules 454 and 456) based on the sensed voltage signal, for example, for controlling APB.

[0050] In some instances, another voltage measurement circuit ( Figure 4A and 4B (Not shown) can be coupled to voltage bus 404 to measure voltage VBUS, which can be provided to controller 408 via, for example, a feedback data path (e.g., an optical link, capacitor, transformer, etc.). Alternatively, voltage measurement circuitry can be included as part of controller 408.

[0051] Figure 5 This is a flowchart illustrating instance method 500 for executing APB. Method 500 can be... Figure 1 , 2 The system implementation of 4. For example, machine-readable instructions may be stored in the memory of a controller (e.g., controller 122, 408), which, when executed by one or more processors of the controller, cause one or more processors to execute method 500. Therefore, Figure 5 The description can be found here. Figure 1 , 2 Certain aspects of points 3 and 4. (See reference) Figure 6 and 7 Method 500 is described further.

[0052] Method 500 begins at 502, where the voltages of one or more battery packs are evaluated. For example, the evaluation at 502 is based on voltages measured across terminals of one or more battery packs (e.g., voltages measured across terminals 230 and 234 or terminals 438 and 450, said voltages being based on, for example, the output of voltage measurement circuit 460) (e.g., by controllers 122, 408). At 504, the evaluation at 504 determines whether an APB (Automatic Packing Buffer) is required. For example, controllers 122, 408 analyze the voltages of various battery packs to determine whether the voltage difference between two or more battery packs exceeds a specified threshold, and / or whether the voltage deviations of one or more battery packs from a target voltage reach at least the same or different specified thresholds. In response to a negative determination (“No”) at 504, indicating that the battery pack voltage difference between the battery packs is below a voltage threshold, the method returns to 502 to continue monitoring and evaluating the voltages of the respective battery packs (e.g., according to measurement intervals). In response to a positive ("Yes") determination at 504, indicating that the voltage difference between battery packs exceeds a voltage threshold, the method proceeds to 508 (e.g., entering APB operation mode) to select one or more pairs of battery packs for performing APB. As an example, (at 508) a pair of battery packs can be selected to include the battery pack with the highest battery pack voltage and the battery pack with the lowest battery pack voltage. In other examples, more than two battery packs can be selected at 508, allowing APB to be performed simultaneously with respect to two or more battery packs (e.g., three, four, five, or more battery packs). For simplicity, Figure 5 The remaining description describes the APB method 500 for selecting two battery packs at 508.

[0053] At 510, an isolated DC-DC converter coupled to (at 508) a battery pack selected to have the highest battery pack voltage is controlled in a constant voltage (CV) loop to provide voltage to the voltage bus by discharging the highest voltage battery pack. For example, controller 408 can implement the constant voltage loop by changing the pulse width or frequency of the transistors in the primary-side circuitry based on sensed bus voltage and / or current feedback. Additionally, at 512, another isolated DC-DC converter coupled to (at 508) a battery pack selected to have the lowest battery pack voltage is controlled in a constant current (CC) loop to provide current to charge the lowest voltage battery pack based on the voltage of the voltage bus. Controller 408 can implement the constant current loop by changing the pulse width or frequency of the transistors in the secondary-side circuitry based on sensed battery pack current and / or sensed voltage feedback. As another example, constant voltage and constant current loops for transferring charge between corresponding battery packs while simultaneously sensing the bus voltage and current to the battery pack with the lowest voltage (e.g., via current monitoring circuit 462) can be implemented using proportional-integral (PI) control functions implemented by the ESS controller (e.g., controller 122 or 408). In other examples, the controller may implement the constant voltage and constant current loops according to other types of control methods (e.g., proportional-integral-derivative (PID) control or machine learning methods, such as fuzzy logic control and neural network control).

[0054] At 514, the method includes determining whether battery pack equalization has been achieved for the battery pack selected at 510 and 512. In response to a positive determination (“Yes”) at 514, indicating that the selected battery pack is substantially equalized (e.g., the voltage difference does not exceed a threshold voltage difference, such as a percentage or voltage value), the method proceeds to 516 and APB ends. From 516, method 500 may return to 502 to continue evaluating the battery pack voltage to control whether APB will be performed on the battery pack. In response to a negative determination (“No”) at 514, indicating that equalization has not yet been achieved, the method returns to 510 to continue the equalization operation by actively charging and discharging the selected battery pack. Method 500 may cycle between 508 and 514 until battery pack equalization has been achieved.

[0055] As another example, Figure 6 It is shown in Figure 1 Implemented in the context of ESS 100 Figure 5 The block diagram of the APB method 500. (See attached diagram.) Figure 6As shown, each of battery packs 110, 112, and 114 has a corresponding battery pack voltage, shown as V1, V2, and V3. Controller 1200 receives signals representing the battery pack voltages V1, V2, and V3 as measured by a voltage measurement circuit (e.g., voltage measurement circuit 460). Controller 122 also receives signals I1, I2, and I3 representing the currents flowing through battery packs 110, 112, and 114, as measured by a current monitoring circuit (e.g., current monitoring circuit 460). For example, before performing APB, it is assumed that the target battery pack voltage is approximately 48 V, V1 = 40 V, V2 = 48 V, and V3 = 58 V. Therefore, controller 122 (at 508) selects battery pack 114 with the highest voltage V3 and selects battery pack 110 with the lowest voltage V1. Controller 122 (e.g., in a constant voltage loop) controls isolated DC-DC converter 106 to draw current IDISCHARGE from battery pack 114 and supply a regulated (e.g., substantially constant) voltage to voltage bus 108, as shown by dashed line 602. Controller 122 can control DC-DC converter 106 in a constant voltage loop based on, for example, adjusting pulse width (e.g., in a PWM scheme) or frequency (in a frequency modulation scheme). Additionally, controller 122 (e.g., in a constant current loop, by controlling the phase angle between the primary-side and secondary-side switches) controls isolated DC-DC converter 102 to supply (e.g., substantially constant) current ICHARGE to battery pack 110 based on the voltage VBUS of voltage bus 108, as shown by dashed line 604. Controller 122 controls isolated DC-DC converters 110 and 114 to provide charging and discharging currents based on (e.g., by current monitoring circuit 462) current signals I1 and I3 measured for the respective battery packs. The voltage supplied to the bus by the isolated DC-DC converter 106 is reduced to reduce fluctuations, so that the isolated DC-DC converter 102 can operate in constant current mode.

[0056] Specifically, during charging, the voltage VBUS may rise, and during discharging, the voltage VBUS may fall. By regulating the voltage VBUS to a constant value (e.g., through the CV loop), the impact of voltage VBUS fluctuations on the charging / discharging of the battery pack can be mitigated. Furthermore, by regulating the voltage VBUS and the charging current, it can be ensured that the power of the discharging module (the power obtained from discharging from the high-voltage battery pack) is equal to or exceeds the power of the charging module (the power delivered to the low-voltage battery pack via charging). All of these facilitate APB operation. Controller 122 continues to control isolated DC-DC converters 102 and 106 until (at 514) it has been determined that battery pack balancing has been achieved.

[0057] As another example, return to the reference. Figure 4A and 4BThe controller 408 controls the isolated DC-DC converter 402 of the ESS 400 to perform APB by transferring charge to or from battery pack 406, for example, to transfer energy from one battery pack of the ESS to another. In a first instance of implementing APB to transfer energy from the bus to battery pack 406, the controller 408 controls the bridge circuit (e.g., Q1, Q2, Q3, and Q4) and switch Q13 of the primary-side circuit 410 to provide AC current to the primary coil 418 based on the bus voltage VBUS. The AC current flowing through the primary coil 418 induces voltages at the secondary coils 420 and 422 (e.g., through magnetic or inductive coupling). Based on the voltage induced at the secondary coil 420, the controller 408 further controls the bridge circuit (e.g., Q5, Q6, Q7, and Q8) of the secondary-side circuit 412 to provide a current I_CHARGE1 (e.g., a substantially constant current) to the battery terminal 438 for charging battery pack 406. Alternatively, based on the voltage induced at the secondary coil 422, the controller 408 controls the bridge circuit (e.g., Q9, Q10, Q11, and Q12) of the secondary side circuit 414 to supply a current I_CHARGE2 (e.g., a substantially constant current) to the battery terminal 448.

[0058] In a second example of implementing APB to transfer energy from battery pack 406 to bus 404, controller 408 controls the bridge circuit of secondary-side circuit 412 (e.g., Q5, Q6, Q7, and Q8) to provide an AC current (ILR1) flowing through LR1 and secondary coil 420 by allowing current I_CHARGE1 to flow from terminal 438 of battery pack 406. When energy in battery pack 406 is released by providing current to secondary coil 420, the voltage of the battery pack decreases accordingly. Alternatively, controller 408 controls the bridge circuit of secondary-side circuit 414 (e.g., Q9, Q10, Q11, and Q12) to provide an AC current (ILR2) flowing through LR2 and secondary coil 420 by allowing current I_CHARGE2 to flow from terminal 448 of battery pack 406. Continuing with the second example, controller 408 controls the bridge circuit (e.g., Q1, Q2, Q3, and Q4) and switch Q13 of the primary-side circuit 410 to provide a substantially constant (e.g., regulated) voltage to the bus 404 (e.g., across bus terminals 428 and 430) based on the voltage induced at the primary coil 418 by the current flowing through the secondary coils 420 and / or 422 via the isolation structure 416. Controller 408 controls the primary-side circuit 410 based on closed-loop feedback (e.g., a measurement of VBUS) to keep the bus voltage VBUS substantially constant during APB.

[0059] As another example, Figure 7This is a schematic diagram illustrating the APB of the ESS 700, which includes bidirectional isolated DC-DC converters 702a and 702b coupled between a bus 703 (e.g., a voltage bus with a bus voltage VBUS) and corresponding battery packs 704a and 704b. Figure 7 In this document, each of the isolated DC-DC converters 702a and 702b has the same configuration. Other converter configurations are also possible. The isolated DC-DC converter 702a includes a primary-side circuit 706a and multiple secondary-side circuits 708a and 710a magnetically coupled to each other via corresponding coils of a transformer 712a. Each secondary-side circuit 708a and 710a may include inductors L2a and L3a, respectively. The isolated DC-DC converter 702b also includes a primary-side circuit 706b and multiple secondary-side circuits 708b and 710b magnetically coupled to each other via corresponding coils of a transformer 712b. The isolated DC-DC converters 702a and 702b may be implemented according to any of the examples disclosed herein. For example, each of the primary-side circuits 706a and 706b and the secondary-side circuits 708a, 710a, 708b and 710b may include a bridge circuit (e.g., a half-bridge or a full-bridge) configured according to the expected current requirements of the respective circuit.

[0060] like Figure 7 As shown, isolated DC-DC converters 702a and 702b transfer energy from one battery pack 704b to another battery pack 704a to perform APB between the respective battery packs. For example, arrow 714 illustrates the energy flow from the bus to battery pack 704a in response to controlling the primary-side circuitry 706a and the secondary-side circuitry 708a and 710a to charge battery pack 704a (e.g., with a substantially constant current), as disclosed herein. Additionally, another arrow 716 illustrates the energy flow from battery pack 704b to bus 703 in response to controlling the primary-side circuitry 706b and the secondary-side circuitry 708b and 710b to discharge battery pack 704b and provide voltage to bus 703, as disclosed herein. Advantageously, fluctuations on bus 703 and other voltage and current demands on the bus caused by the energy transfer 714 from battery pack 704b to battery pack 704a can be mitigated based on the energy transfer 716 from battery pack 704b to bus.

[0061] Figure 8 , 9 Figures 1 and 10 are graphs illustrating examples of the waveforms of an ESS performing an APB. For ease of explanation, regarding... Figure 6 The ESS 100 shown is used to describe Figure 8 , 9 And 10. About Figure 6The APB concept described herein applies to other example embodiments disclosed herein. For example, Figure 8 This is a graph 800 showing an example of the discharge current 802 (IDISCHARGE) from the higher voltage battery pack 114, which is based on the operation of an isolated DC-DC converter 106 in a constant voltage (CV) loop to transfer energy to its primary-side circuitry and provide an output voltage to stabilize VBUS, as described herein. In the CV loop, the controller 122 controls the discharge current based on the battery pack voltage. Figure 8 As shown, the amplitude of the discharge current 802 from the battery pack increases until time T1, at which time, based on the CV loop of the isolated DC-DC converter 106, the discharge current is approximately 3.5 A. Figure 9 Graph 900 shows an example of the charging current (ICHARGE) provided to the lower voltage battery pack 110, which is based on the operation of the isolated DC-DC converter 102 in a constant current (CC) loop to transfer energy to its secondary side circuitry and provide ICHARGE. Figure 9 As shown, the isolated DC-DC converter 102 provides approximately 5 A of current ICHARGE starting from time T0 to charge the battery pack 110. Furthermore, Figure 8 and 9 The comparison shows that during APB, the discharge current 802 can be lower than the charging current 902. Figure 10 Graph 1000 shows the voltage 1002 of bus 108 during APB, which has been shown to be stable during APB. Bus voltage 1002 initially exceeds the target voltage, as shown in 1004, and then stabilizes at a target voltage of approximately 24 V based on the operation of isolated DC-DC converter 106. Advantageously, based on the operation of isolated DC-DC converter 106 in the CV loop, the approximately 24 V DC bus voltage is resistant to fluctuations, including responses to the current drawn by isolated DC-DC converter 102.

[0062] It should be understood that the various aspects described herein can be combined in combinations different from those specifically presented in the specification and figures. It should also be understood that, depending on the instance, certain actions or events of any process or method described herein may be performed in a different order, and may be added, combined, or omitted entirely (e.g., performing these techniques may not require all the described actions or events). Furthermore, although some aspects of this specification are described as being performed by a single module or unit for clarity, it should be understood that the techniques of this specification can be performed by a combination of units or modules.

[0063] In one or more instances, the described techniques can be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functionality can be stored as one or more instructions or code on a computer-readable medium and executed by a hardware-based processing unit. The computer-readable medium may comprise non-transitory computer-readable media, corresponding to tangible media such as data storage media (e.g., RAM, ROM, EEPROM, flash memory, or any other media available for storing the desired program code in the form of instructions or data structures and accessible by a processor). For example, the instructions can be executed by one or more processors, such as one or more digital signal processors (DSPs), general-purpose microprocessors, application-specific integrated circuits (ASICs), field-programmable arrays (FPGAs), or other equivalent integrated or discrete logic circuit systems. Therefore, the term "processor" as used herein can refer to any of the foregoing structures or any other physical structure suitable for implementing the described techniques. Furthermore, the techniques can be entirely implemented in one or more circuit or logic elements.

[0064] In this specification, the numerical labels "first", "second", etc., are not necessarily the same as the same labels in the technical solutions herein, and these numerical labels are only used to distinguish one component from another.

[0065] Additionally, the term "coupling" may encompass connection, communication, or signaling paths that enable functional relationships to be consistent with this specification. For example, if device A generates a signal to control device B to perform an action, then: (a) in a first instance, device A is coupled to device B via a direct connection; or (b) in a second instance, device A is coupled to device B via an intermediate component C, provided that the intermediate component C does not alter the functional relationship between device A and device B, such that device B is controlled by device A via control signals generated by device A.

[0066] As used herein, the term "circuit" may include a collection of active and / or passive components that perform circuit functions (e.g., analog or digital circuits). Alternatively, for example, the term "circuit" may include an IC in which all or part of the circuit elements are fabricated on a common substrate (e.g., a semiconductor substrate, such as a die or chip), as disclosed herein.

[0067] In this specification, a device "configured to" or "configurable to" perform a task or function may be configured (e.g., programmed and / or hardwired) to perform the function during manufacturing by the manufacturer, and / or may be configured (or reconfigured) by the user after manufacturing to perform the function and / or other additional or alternative functions. Configuration may be achieved through firmware and / or software programming of the device, through the construction and / or layout of the device's hardware components and interconnects, or a combination thereof. Furthermore, circuits or devices described herein as containing specific components may actually be configured to couple to those components to form the circuit system or device described herein. For example, a structure described herein as containing one or more semiconductor elements (e.g., transistors), one or more passive elements (e.g., resistors, capacitors, and / or inductors), and / or one or more sources (e.g., voltage sources and / or current sources) may actually contain only semiconductor elements within a single physical device (e.g., semiconductor dies and / or integrated circuit (IC) packages) and may be configured to couple to at least some passive elements and / or sources to form the structure during manufacturing or after manufacturing, for example, by an end user and / or a third party.

[0068] The phrase “based on” means at least partially based on. Therefore, if X is based on Y, then X can depend on Y and any number of other factors. Furthermore, as used herein, the term “includes” means includes but is not limited to, and the term “including” means includes but is not limited to.

[0069] In this specification, unless otherwise stated, “about,” “approximately,” or “substantially” preceding a parameter means within + / -10% of the parameter, or, if the parameter is zero, within a reasonable range of values ​​approximately zero.

[0070] Within the scope of the claims, modifications may be made to the described embodiments, and other embodiments are possible.

Claims

1. A system comprising: bus; Primary coil; A first circuit is coupled between the bus and the primary coil; The first-stage coil is DC isolated from the primary coil. First battery terminal; Second battery terminal; A second circuit is coupled between the primary coil and the first battery terminal; A second-stage coil, wherein the second-stage coil is DC isolated from the primary coil; A third circuit is coupled between the second stage coil and the second battery terminal; as well as A controller configured to control the second circuit to transfer energy from the first battery terminal through the first stage coil to the primary coil, and to control the first circuit and the third circuit to transfer energy from the primary coil to the second stage coil and provide energy to the second battery terminal.

2. The system according to claim 1, further comprising: A first bidirectional isolated DC-DC converter includes the first circuit, the primary coil, the secondary coil, and the third circuit, wherein the primary coil is a first primary coil; as well as The second bidirectional isolated DC-DC converter includes the second circuit, the first primary coil, the second primary coil, and the fourth circuit, wherein the fourth circuit is coupled between the bus and the second primary coil, and the first primary coil is DC isolated from the second primary coil.

3. The system of claim 2, wherein the controller is configurable to control the second circuit and the fourth circuit to transfer energy from the first battery terminal through the first primary coil to the second primary coil and to supply energy to the bus, and to control the first circuit and the third circuit to transfer energy from the bus through the first primary coil to the second primary coil and to supply energy to the second battery terminal.

4. The system of claim 2, wherein the first bidirectional isolated DC-DC converter further comprises: Third stage coil; Third battery terminal; as well as A fifth circuit is coupled between the third stage coil and the third battery terminal, wherein the second stage coil and the third stage coil are magnetically coupled to the first primary coil.

5. The system according to claim 4, further comprising: A plurality of first battery cells connected in series between the second battery terminals; as well as A second plurality of battery cells connected in series between the third battery terminals.

6. The system according to claim 5, further comprising: A battery pack comprising the first plurality of battery cells and the second plurality of battery cells.

7. The system of claim 6, wherein the battery pack is a first battery pack, and the system further comprises: A second battery pack coupled to the first battery terminal, wherein the controller is configurable to control the second circuit and the fourth circuit to transfer energy from the second battery pack through the first primary coil to the second primary coil and to supply energy to the bus, and to control the first circuit and at least one of the third and fifth circuits to transfer energy from the bus through the first primary coil to at least one of the second or third primary coil and to supply energy to the first battery pack.

8. The system of claim 1, further comprising a plurality of battery cells connected in series between the second battery terminals.

9. The system of claim 1, wherein the first circuit includes a first bridge circuit, the second circuit includes a second bridge circuit, and the third circuit includes a third bridge circuit.

10. A system comprising: A first bidirectional isolated DC-DC converter is coupled between a bus and a first battery terminal; A second bidirectional isolated DC-DC converter is coupled between the bus and the second battery terminal; as well as A controller coupled to the first isolated DC-DC converter and the second isolated DC-DC converter, and configured to control the first isolated DC-DC converter and the second isolated DC-DC converter to transfer charge between the first battery terminal and the second battery terminal via the bus.

11. The system according to claim 10, The first isolated DC-DC converter includes: First primary coil; A first circuit is coupled between the bus and the first primary coil; The first primary coil is magnetically coupled to the first primary coil; as well as A second circuit is coupled between the primary coil and the first battery terminal; The second isolated DC-DC converter includes: Second primary coil; A third circuit is coupled between the bus and the second primary coil; The second-stage coil, which is magnetically coupled to the second primary coil; and A fourth circuit is coupled between the second stage coil and the second battery terminal.

12. The system of claim 11, wherein the controller is coupled to the first circuit, the second circuit, the third circuit, and the fourth circuit, and is configured to control the first circuit and the second circuit to transfer energy between the first battery terminal and the bus, and to control the third circuit and the fourth circuit to transfer energy between the second battery terminal and the bus.

13. The system of claim 11, further comprising: A plurality of battery cells connected in series between the first battery terminals; as well as A second plurality of battery cells connected in series between the second battery terminals.

14. The system of claim 13, further comprising: A first battery pack, which includes the first plurality of battery cells; as well as The second battery pack contains the second plurality of battery cells. The controller is configured to control the first and second circuits to transfer energy from the first battery pack through the first primary coil to the first primary coil and to supply energy to the bus, and to control the third and fourth circuits to transfer energy from the bus through the second primary coil to the second secondary coil and to supply energy to the second battery pack.

15. The system of claim 13, wherein the controller is configurable to control the first circuit to provide a substantially constant voltage to the bus based on energy transferred from the first primary coil to the first primary coil, and to control the fourth circuit to provide a substantially constant current to the second plurality of battery cells based on energy transferred from the second primary coil to the second secondary coil.

16. The system according to claim 11, The first isolated DC-DC converter includes: The third-stage coil is magnetically coupled to the first-stage coil; as well as The fifth circuit is coupled between the third-stage coil and the first battery terminal. The second isolated DC-DC converter includes: The fourth secondary coil is magnetically coupled to the second primary coil; as well as A sixth circuit, coupled between the third-stage coil and the first battery terminal, and The controller is coupled to the fifth and sixth circuits and is configured to control at least one of the first, second, and fourth circuits to transfer energy between the first battery terminal and the bus, and to control at least one of the third, fourth, and sixth circuits to transfer energy between the second battery terminal and the bus.

17. The system of claim 11, wherein the first circuit includes a first bridge circuit, the second circuit includes a second bridge circuit, the third circuit includes a third bridge circuit, and the fourth circuit includes a fourth bridge circuit.

18. A method comprising: Controlling the transfer of energy from the first battery terminal through the first secondary coil to the primary coil, wherein the first secondary coil is DC isolated from the primary coil; as well as The transfer of energy from the primary coil to the secondary coil is controlled to provide energy to the second battery terminal, wherein the secondary coil is DC isolated from the primary coil.

19. The method according to claim 18, The first bidirectional isolated DC-DC converter includes a primary coil, a first circuit, the first primary coil, and a second circuit. The primary coil is a first primary coil. The first circuit is coupled between the first primary coil and the bus, and the second circuit is coupled between the first primary coil and the first battery terminal. The second bidirectional isolated DC-DC converter includes a second stage coil, a second primary coil, a third circuit, and a fourth circuit. The third circuit is coupled between the bus and the second primary coil, and the fourth circuit is coupled between the second stage coil and the second battery terminal. The method further includes: The first and second circuits are controlled to transfer energy from the first battery terminal to the bus; as well as The third and fourth control circuits transfer energy from the bus to the second battery terminal.

20. The method according to claim 19, The control of the first and second circuits includes controlling the first circuit to provide a substantially constant voltage to the bus based on the energy transferred from the first primary coil to the first secondary coil by controlling the discharge of the first plurality of battery cells coupled to the first battery terminal by the second circuit, and The control of the third and fourth circuits includes controlling the third circuit via voltage control of the bus, and controlling the fourth circuit to provide a substantially constant current based on the energy delivered to the second stage coil to charge a second plurality of battery cells coupled to the second battery terminal.

21. The method of claim 19, wherein the first circuit includes a first bridge circuit, the second circuit includes a second bridge circuit, the third circuit includes a third bridge circuit, and the fourth circuit includes a bridge circuit.

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