A single-phase inverter system based on a battery pack and a bidirectional switch bridge arm

Abstract

The present application relates to power supply circuit device system technical field, especially to a kind of single-phase inverter system based on battery pack and bidirectional switch bridge arm, left half bridge of traditional H bridge inverter is replaced by first battery pack and second battery pack series connection, right half bridge then adopts first bidirectional switch and second bidirectional switch to constitute.Wherein, first battery pack as upper bridge arm, second battery pack as lower bridge arm.In inverter mode, by controlling the access quantity of single battery unit in left half bridge to generate ladder wave to approximate positive half cycle or negative half cycle of sine wave, simultaneously cooperate with the power frequency commutation of right half bridge bidirectional switch, i.e., can be synthesized ac voltage at output end, without complex PWM modulation and filter inductance.In charging mode, by parallelly connecting charging unit to the upper bridge arm of right half bridge, and using battery unit access or bypass control of left half bridge, i.e., the selective charging of any single battery can be realized, so that battery equalization management capability is realized.

Description

Technical Field

[0001] This invention relates to the field of power supply circuit device system technology, and in particular to a single-phase inverter system based on a battery pack and a bidirectional switching bridge arm. Background Technology

[0002] In the field of using battery packs to construct single-phase AC power, a typical system architecture usually includes a battery pack, an inverter, and a charger. The DC power supply from the battery pack needs to be converted into AC power by the inverter to meet the needs of the AC load. Currently, there are three main typical topologies for inverter circuits. In the first topology, one half-bridge consists of two capacitors forming the upper and lower arms, respectively, while the other half-bridge consists of fully controlled power electronic devices forming the upper and lower arms. An independent DC power supply needs to be connected to the DC side. By implementing sinusoidal pulse width modulation (SPWM) control on the half-bridge composed of fully controlled devices and filtering it through an LC filter, a sinusoidal AC voltage is finally output. The second topology uses one half-bridge with two independent DC power supplies forming the upper and lower arms, respectively, and the other half-bridge also consists of fully controlled devices forming the upper and lower arms, but no independent DC power supply is required on the DC side. Based on this, by implementing SPWM modulation control on the half-bridge composed of fully controlled devices and filtering it through an LC filter, a sinusoidal AC voltage can also be output. In the third topology, both the upper and lower arms of the left and right half-bridges use fully controlled devices, and the DC side is connected to an independent DC power supply, thus forming an H-bridge circuit. This H-bridge circuit can apply various control strategies such as unipolar SPWM modulation and bipolar modulation, and outputs a sinusoidal AC voltage after LC filtering.

[0003] All of the aforementioned inverter topologies use a fixed DC power supply as the voltage source. They output an AC voltage source by high-frequency modulation of the bridge arms, which are composed of fully controlled devices, and by using a filter circuit. In practical applications, when lithium iron phosphate batteries are used as the power supply unit and AC voltage output is required, since the nominal voltage of a single lithium iron phosphate battery is approximately 3V, multiple batteries are typically connected in series to form a DC power supply of the required voltage level, and then the AC output is achieved through the aforementioned topologies. However, a common problem with these topologies is that they all require a dedicated inverter circuit to achieve DC-to-AC conversion, resulting in a relatively complex circuit structure. Furthermore, to ensure the safe operation and performance consistency of the series-connected battery pack, an independent equalization control circuit is required to manage the voltage balance of each individual battery. The inverter itself cannot achieve battery pack equalization control, making the equalization function dependent on external circuitry. This increases the overall system cost and hinders widespread application. Summary of the Invention

[0004] The present invention aims to provide a single-phase inverter system based on a battery pack and a bidirectional switching bridge arm to solve the technical problems of existing inverter circuit topologies being relatively complex, unable to achieve balanced control of the battery pack using the inverter itself, and having high system costs.

[0005] To achieve the above objectives, the present invention provides a single-phase inverter system based on a battery pack and a bidirectional switching bridge arm, comprising an H-bridge inverter circuit, a charging unit, and a control unit, wherein: The H-bridge inverter circuit includes a left half-bridge and a right half-bridge. The upper arm of the left half-bridge is a first battery pack composed of several individual battery cells connected in series, and the lower arm of the left half-bridge is a second battery pack composed of several individual battery cells connected in series. The upper arm of the right half-bridge is a first bidirectional switch, and the lower arm of the right half-bridge is a second bidirectional switch. The first bidirectional switch and the charging unit are connected in parallel. The control unit is used to connect the charging unit to the upper arm of the right half bridge after receiving the charging mode instruction, and disconnect the electrical connection between the H-bridge inverter circuit and the external load. In this way, according to the output voltage and output current of the charging unit, the control unit controls the timing of the series connection of several individual battery cells to the circuit and / or bypass, and then charges several individual battery cells. The control unit is used to disconnect the charging unit and the upper arm of the right half-bridge after receiving the inverter mode command, so as to bypass the charging unit and electrically connect the H-bridge inverter circuit to the external load. In this way, according to the current modulation time of the preset AC voltage, the control unit controls the timing of the series connection and / or bypass of several individual battery cells into the circuit, and coordinates with the control of the conduction timing of the first bidirectional switch and the second bidirectional switch to output AC power to the external load.

[0006] The aforementioned single-phase inverter system based on battery packs and bidirectional switch arms replaces the left half-bridge of a traditional H-bridge inverter with a first and second battery pack connected in series, while the right half-bridge uses a first and a second bidirectional switch. The first battery pack serves as the upper arm, the second as the lower arm, and their common terminal directly serves as one of the AC output terminals. The common terminal of the two bidirectional switches on the right half-bridge serves as the other AC output terminal. In inverter mode, by controlling the number of individual battery cells connected in the left half-bridge to generate a stepped wave to approximate the positive or negative half-cycle of a sine wave, and simultaneously coordinating with the power frequency commutation of the bidirectional switches on the right half-bridge, an AC voltage can be synthesized at the output terminal without the need for complex PWM modulation and filtering inductors. In charging mode, by connecting the charging unit in parallel to the upper arm of the right half-bridge and utilizing the battery cell access / bypass control of the left half-bridge, selective charging of any individual battery cell can be achieved, thus realizing battery equalization management capabilities.

[0007] This invention eliminates the complex structure of separating the DC source and inverter bridge arm in traditional inverter circuit topologies, integrating the energy output of the battery pack with the inverter function. Through the timing control of individual battery cells by the control unit, not only is DC-to-AC conversion achieved, but also balanced control of the battery pack is realized by selectively connecting specific individual battery cells to the circuit. This eliminates the need for an additional independent balancing circuit, significantly simplifying the circuit topology, reducing system cost, and improving system integration and reliability.

[0008] Further, the control unit, upon receiving an inverter mode command, disconnects the charging unit from the upper arm of the right half-bridge to bypass the charging unit and electrically connects the two AC output terminals to the external load. This allows the control unit to control the timing of the series connection and / or bypass of several individual battery cells according to the current modulation time of the preset AC voltage, and coordinates with the control of the conduction timing of the first and second bidirectional switches to output AC power to the external load, including: Obtain the voltage amplitude and power frequency period of the preset AC voltage, and obtain the output voltage of a single battery cell; Based on the voltage amplitude, the power frequency period, and the output voltage of a single battery cell, the total number of batteries in the first battery pack and the second battery pack are obtained respectively; based on the voltage amplitude, the power frequency period, and the total number of batteries in the first battery pack and the second battery pack, the AC voltage output value corresponding to each modulation moment is obtained; Determine the current modulation time of the preset AC voltage; When the current modulation time is in the positive half-cycle, based on the current modulation time and the AC voltage output value corresponding to each modulation time, the number of individual battery cells connected in series in the second battery pack is determined, and all individual battery cells in the first battery pack are bypassed, and the first bidirectional switch is turned off and the second bidirectional switch is turned on. When the current modulation time is in the negative half-cycle, based on the current modulation time and the AC voltage output value corresponding to each modulation time, the number of individual battery cells connected in series in the first battery pack is determined, and all individual battery cells in the second battery pack are bypassed, and the first bidirectional switch is turned on and the second bidirectional switch is turned off.

[0009] Preferably, the total number of batteries in the first battery pack and the second battery pack is equal.

[0010] In this implementation, by acquiring the parameters of the preset AC voltage and the output voltage of a single battery cell, the required total number of batteries is accurately calculated. Based on the instantaneous value of the target AC voltage, the number of battery cells connected in series in real time is adjusted. Specifically, during the positive half-cycle of the AC voltage, the upper bridge arm (first battery pack) is completely bypassed, and the lower bridge arm (second battery pack) connects in series with the corresponding number of batteries according to the required voltage. Simultaneously, the second bidirectional switch is turned on, thereby creating a positive current flowing from the positive terminal of the second battery pack through the load to the negative terminal of the second battery pack, resulting in a positive output voltage. During the negative half-cycle of the AC voltage, the lower bridge arm is completely bypassed, and the upper bridge arm connects in series with the corresponding number of batteries according to the required voltage. Simultaneously, the first bidirectional switch is turned on, thereby creating a reverse current flowing from the positive terminal of the first battery pack through the first bidirectional switch, the load, and back to the negative terminal of the first battery pack, resulting in a negative output voltage.

[0011] The aforementioned control strategy utilizes the stepped voltage of the battery pack to approximate a sine wave, reducing the harmonic content of the output voltage and decreasing the size and loss of the filter. Simultaneously, by symmetrically controlling the number of the first and second battery packs in operation, the symmetry of the output AC power is ensured, enabling bidirectional charging and discharging management of the battery packs and further optimizing the waveform quality of the inverter output.

[0012] Further, the step of determining the number of individual battery cells connected in series in the second battery pack based on the current modulation time and the AC voltage output value corresponding to each modulation time, controlling all individual battery cells in the first battery pack to bypass, and turning off the first bidirectional switch and turning on the second bidirectional switch includes: Obtain the state of charge and temperature parameters of each individual battery cell in the second battery pack; Based on the state of charge and temperature parameters of each individual battery cell in the second battery pack, and the number of individual battery cells connected in series in the second battery pack, several individual battery cells are selected from the second battery pack and connected in series in the second battery pack. The step of determining the number of individual battery cells connected in series in the first battery pack based on the current modulation time and the AC voltage output value corresponding to each modulation time, and controlling all individual battery cells in the second battery pack to bypass, and turning on the first bidirectional switch and turning off the second bidirectional switch, includes: Obtain the state of charge and temperature parameters of each individual battery cell in the first battery pack; Based on the state of charge and temperature parameters of each individual battery cell in the first battery pack, and the number of individual battery cells in the first battery pack that need to be connected in series to the circuit, several individual battery cells in the first battery pack are selected to be connected in series to the circuit.

[0013] In this implementation, after determining the number of individual battery cells to be connected to the circuit, selection is performed based on the state of charge (SOC) and temperature parameters of each individual battery cell. During inverter discharge, the control unit can prioritize connecting individual battery cells with higher SOC or suitable temperatures to the circuit for discharge, while bypassing individual battery cells with lower SOC or abnormal temperatures. Through this dynamic selection mechanism, the system can dynamically balance the depth of discharge and thermal stress of each battery cell during inverter discharge, achieving active balancing and thermal management. This effectively extends the cycle life of the entire battery pack, ensures operational safety, and achieves balanced control of the battery pack state. It solves the technical problem of relying on external balancing circuits in existing technologies, effectively extending the overall lifespan of the battery pack and improving the safety and stability of the system.

[0014] Further, the first bidirectional switch includes a first thyristor and a second thyristor, and the second bidirectional switch includes a third thyristor and a fourth thyristor. The anode of the first thyristor is the positive DC terminal of the first bidirectional switch, and the cathode of the first thyristor is the common terminal of the first bidirectional switch. The second thyristor and the first thyristor are connected in anti-parallel. The cathode of the third thyristor is the negative DC terminal of the second bidirectional switch, and the anode of the third thyristor is the common terminal of the second bidirectional switch. The fourth thyristor and the third thyristor are connected in anti-parallel. The positive terminal of the charging unit is electrically connected to the anode of the first thyristor, and the negative terminal of the charging unit is electrically connected to the cathode of the second thyristor. The control unit, upon receiving a charging mode command, connects the charging unit to the upper arm of the right half-bridge, including: The first thyristor and the third thyristor are controlled to be turned off, and the second thyristor and the fourth thyristor are controlled to be turned on, so that the charging unit is connected to the upper arm of the right half bridge.

[0015] In this implementation, anti-parallel thyristors are used to form a bidirectional switch. Thyristors, as semi-controlled devices, have advantages such as low cost, high voltage withstand capability, and strong current carrying capacity. In charging mode, by turning on the second and fourth thyristors, the charging unit is connected in series into the right half-bridge using the anti-parallel thyristors. At this time, the positive terminal of the charging unit is connected to the common connection point of the left and right half-bridges through the second thyristor, while the negative terminal is directly connected to the negative terminal of the second battery pack, allowing the charging unit to directly charge both the first and second battery packs. In inverter mode, by controlling the conduction of the corresponding thyristors, power frequency commutation can be achieved, bypassing the charging unit and preventing it from affecting the inverter output.

[0016] Further, the step of controlling the timing of the series connection and / or bypass of the plurality of individual battery cells to the circuit based on the output voltage and output current of the charging unit, thereby charging the plurality of individual battery cells, includes: Obtain the state of charge and temperature parameters of each individual battery cell; For any of the individual battery cells, the charging time of the individual battery cell is determined based on the state of charge and temperature parameters of the individual battery cell. Based on the charging time, the individual battery cell is controlled to be connected in series to the circuit for charging, while the remaining individual battery cells are bypassed.

[0017] In this implementation, during charging mode, the time for individual battery cells to be connected in series in the circuit is controlled selectively based on their state of charge (SOC) and temperature parameters. For example, the battery cell with the lowest SOC can be charged first, or a polling method can be used to replenish energy to all battery cells. For individual battery cells with a low SOC, the charging time connected in series in the circuit can be increased; for individual battery cells with a high SOC, the charging time can be reduced. Because individual battery cells can be charged independently and controllably, the system can achieve active balancing during the charging process, avoiding overcharging and ensuring that all battery cells reach the ideal SOC after charging, thus improving charging efficiency and safety, and further enhancing the system's balancing function in charging mode.

[0018] Further, the single-cell battery unit includes a single-cell battery, a series switch, and a bypass switch. The negative terminal of the single-cell battery is the DC negative terminal of the single-cell battery unit. The positive terminal of the single-cell battery is electrically connected to one end of the series switch, and the other end of the series switch serves as the DC positive terminal of the single-cell battery unit. One end of the bypass switch is the DC negative terminal of the single-cell battery unit, and the other end of the bypass switch is the DC positive terminal of the single-cell battery unit. Wherein: When the control unit controls any of the individual battery cells to be connected in series in the circuit, it controls the series switch to be turned on and the bypass switch to be turned off, so that the individual battery cell is connected in series in the circuit. When the control unit controls any of the individual battery cells to bypass, it controls the series switch to turn off and controls the bypass switch to turn on, so that the individual battery cell is bypassed.

[0019] In this implementation, the operating state of a single battery cell is independently controlled through a combination of series switches and bypass switches. When the series switch is on and the bypass switch is off, the single battery cell is connected to the circuit as a power source; when the series switch is off and the bypass switch is on, the single battery cell is short-circuited, without affecting the loop current. That is, the series switch connects the battery to the main circuit, and the bypass switch short-circuits the battery to achieve bypass. Through these series and bypass switches, the state of each battery cell can be flexibly controlled, providing a hardware foundation for stepped-wave inverters and equalization charging, making the battery pack configuration more flexible and adaptable to different voltage levels. Simultaneously, independent switch control provides redundancy for the system. When a single battery cell fails, it can be isolated by the bypass switch, and the system can still operate in degraded mode, improving the system's fault tolerance and reliability.

[0020] Further, the bypass switch includes a first MOSFET and a second MOSFET, the drain of the first MOSFET serves as the negative DC terminal of the single battery cell, the source of the first MOSFET and the source of the second MOSFET are electrically connected, and the drain of the second MOSFET serves as the positive DC terminal of the single battery cell; the series switch includes a third MOSFET and a fourth MOSFET, the drain of the third MOSFET is electrically connected to the positive terminal of the single battery cell, the source of the third MOSFET and the source of the fourth MOSFET are electrically connected, and the drain of the fourth MOSFET serves as the positive DC terminal of the single battery cell; wherein: In the inverter mode, when the control unit controls any single battery cell to switch from a series connection state to a bypass state, for that single battery cell: During the first period of this switching process, the first MOSFET and the second MOSFET are turned off, while the third MOSFET and the fourth MOSFET are turned on. During the second period of this switching process, the fourth MOS transistor is controlled to be turned off; During the third period of this switching process, the first MOS transistor is turned on; During the fourth period of this switching process, the third MOS transistor is turned off. In the fifth period of the switching process, the second MOS transistor is turned on, which ultimately switches the single battery cell from the series connection state to the bypass state.

[0021] This implementation provides a specific timing sequence for the switch to switch from series to bypass in inverter mode. Two MOSFETs are connected back-to-back in series to form a bypass switch and / or a series switch, which can block current in both directions and provide a freewheeling path through their body diodes when necessary. Specifically, by dividing the switching process into five time periods, a soft switching process is implemented, ensuring that the voltage across the battery cell does not change abruptly during switching, and that the main circuit current always has a continuous path. This avoids overvoltage caused by current interruption, achieves arc-free switching, and avoids the risk of instantaneous open-circuit voltage spikes or short circuits caused by inconsistent switching actions. This significantly reduces switching losses and electromagnetic interference, improving system reliability and efficiency. Furthermore, in high-frequency modulation applications, this timing control can effectively suppress electromagnetic interference caused by voltage surges, protect power devices from impact damage, and ensure the smoothness of the inverter output voltage waveform.

[0022] Furthermore, in the inverter mode, when the control unit controls any single battery cell to switch from a bypass state to a series connection state, for that single battery cell: During the first period of this switching process, the first MOSFET and the second MOSFET are turned on, while the third MOSFET and the fourth MOSFET are turned off; During the second period of this switching process, the second MOSFET is controlled to be turned off; During the third period of this switching process, the third MOS transistor is turned on; During the fourth period of this switching process, the first MOSFET is turned off. In the fifth period of the switching process, the fourth MOS transistor is turned on, which ultimately switches the single battery cell from the bypass state to the series connection state.

[0023] In this implementation, a five-stage switching logic is designed for the process of switching a single battery cell from the bypass state to the series connection state. Following the safety principle of "turn on first, then turn off", the transient current path is constructed during the switching process by utilizing the source connection relationship of the MOSFET. This achieves soft switching of the battery cell at the moment of connection, effectively limiting the inrush current at the moment of connection, preventing the battery voltage from dropping instantly or the switching transistor from overheating, and improving the stability and safety of the system during dynamic adjustment.

[0024] Furthermore, in the charging mode, when the control unit controls any one of the individual battery cells to switch from a series connection state to a bypass state, for that individual battery cell: During the first period of this switching process, the first MOSFET and the second MOSFET are turned off, while the third MOSFET and the fourth MOSFET are turned on. During the second period of this switching process, the third MOS transistor is controlled to be turned off; During the third period of this switching process, the second MOSFET is turned on. During the fourth period of this switching process, the fourth MOS transistor is turned off. In the fifth period of the switching process, the first MOS transistor is turned on, which ultimately switches the single battery cell from the series connection state to the bypass state.

[0025] In this implementation, a specific five-stage switching logic is designed for the current characteristics in charging mode. Since the current direction differs between charging and inverter modes, the switching sequence must adapt to the change in current flow. By controlling the operating sequence of the first to fourth MOSFETs, the charging current is ensured to remain continuous during the transfer from the series branch to the bypass branch. This prevents damage to the battery or switching transistors caused by the back electromotive force generated by the inductive components, ensuring a smooth charging process, preventing charging interruptions or voltage fluctuations due to switching, and ensuring balanced charging control.

[0026] Furthermore, in the charging mode, when the control unit controls any one of the individual battery cells to switch from a bypass state to a series connection state, for that individual battery cell: During the first period of this switching process, the first MOSFET and the second MOSFET are turned on, while the third MOSFET and the fourth MOSFET are turned off; During the second period of this switching process, the first MOSFET is controlled to be turned off. During the third period of this switching process, the fourth MOS transistor is turned on; During the fourth period of this switching process, the second MOSFET is turned off. In the fifth period of the switching process, the third MOS transistor is turned on, which ultimately switches the single battery cell from the bypass state to the series connection state.

[0027] In this implementation, a five-stage switching logic is designed for the process of a single battery cell switching from bypass to connection during charging mode. This logic ensures that the charging current can be smoothly established the instant the single battery cell is connected to the charging circuit, avoiding current surges caused by hard switching operations. By controlling the MOSFETs in stages, switching losses and heat accumulation are effectively reduced, ensuring the reliability of the system when frequently switching battery cells during charging mode.

[0028] The single-phase inverter system based on a battery pack and a bidirectional switching arm provided by the present invention has at least the following advantages compared with the prior art: First, by incorporating the battery pack itself as part of the inverter and using a bidirectional switch to form the other half of the H-bridge, the complex PWM modulation circuit and filter inductor in traditional inverters are eliminated, greatly simplifying the circuit structure and reducing hardware costs.

[0029] Secondly, the system achieves independent control and energy management of each battery cell by dynamically accessing / bypassing individual battery units, enabling the balancing of the series battery pack without the need for any external balancing circuits. This reduces system cost and complexity, and improves the overall lifespan and safety of the battery pack.

[0030] Third, the inverter process employs a fundamental frequency stepped wave synthesis method, with the switching devices operating at the power frequency, resulting in extremely low switching losses. Simultaneously, a refined five-segment commutation timing sequence is used during battery cell state switching, achieving soft switching and further reducing losses and electromagnetic interference.

[0031] Fourth, the system can adjust the output voltage by controlling the number of batteries connected in series, making it suitable for AC output requirements of different voltage levels. At the same time, the intelligent screening strategy based on SOC and temperature can dynamically balance the depth of discharge and thermal stress of each battery cell, achieving active balancing and thermal management, thereby effectively extending the cycle life of the entire battery pack and ensuring operational safety.

[0032] In summary, this invention utilizes a battery pack inverter to generate AC output voltage and optimizes battery utilization efficiency; it achieves optimal charging performance through a combination of the charging power supply and the built-in switches of the battery cells. Its ingenuity and advantages lie in the following: each individual battery cell achieves balanced control through reasonable logic control during inverter operation; the switches within each individual battery cell switch twice per power frequency cycle, resulting in a very low switching frequency; the use of thyristors to form a bridge arm results in low loss, low cost, and speed that meets inverter requirements. Optimal charging performance is achieved by fully utilizing the series switches and bypass switches of each individual battery cell in conjunction with the charging power supply. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of a single-phase inverter system based on a battery pack and a bidirectional switch arm provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of another single-phase inverter system based on a battery pack and a bidirectional switch arm provided in an embodiment of the present invention; Figure 3 This is a schematic flowchart illustrating the control process of a single-phase inverter system with a battery pack and a bidirectional switching arm, provided by an embodiment of the present invention. Figure 4 This is a schematic diagram of the structure of a single battery cell provided in an embodiment of the present invention; Figure 5This is a control timing diagram provided by an embodiment of the present invention, showing how the control unit controls any of the individual battery cells to switch from a series connection state to a bypass state under the inverter mode. Figure 6 This is a control timing diagram provided by an embodiment of the present invention, showing the control unit controlling any single battery cell to switch from a bypass state to a series connection state in an inverter mode. Figure 7 This is a timing diagram of the control unit controlling any single battery cell to switch from a series connection state to a bypass state in a charging mode provided by an embodiment of the present invention; Figure 8 This is a timing diagram of the control unit controlling any single battery cell to switch from a bypass state to a series connection state in a charging mode provided by an embodiment of the present invention. Detailed Implementation

[0034] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that the following detailed descriptions are exemplary and intended to provide further detailed explanation of the invention. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein in the specification is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms "comprising" and "having," and any variations thereof, in the specification, claims, and foregoing drawings, are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the specification, claims, or foregoing drawings are used to distinguish different objects, not to describe a particular order.

[0035] It should be noted that a single-phase AC power supply using a battery pack generally includes the battery pack, an inverter, and a charger. A DC power source consisting of a battery pack needs to be connected to an inverter to output AC power. There are currently three main inverter circuit topologies.

[0036] In the first topology, one half-bridge uses two capacitors to form the upper and lower bridge arms respectively, and the other half-bridge uses fully controlled devices to form the upper and lower bridge arms. The DC side is then connected to a separate DC power supply. After the half-bridge composed of fully controlled devices is controlled by SPWM modulation, it is then filtered by LC to output an AC sinusoidal voltage.

[0037] In the second topology, one half-bridge consists of two DC power supplies forming the upper and lower arms respectively, while the other half-bridge uses fully controlled devices to form the upper and lower arms. The DC side is no longer connected to a separate DC power supply. After the half-bridge composed of fully controlled devices is controlled by SPWM modulation, it is then filtered by LC to output an AC sinusoidal voltage.

[0038] In the third topology, the upper and lower arms of the left and right half-bridges use fully controlled devices, and the DC side is connected to a separate DC power supply. The H-bridge circuit composed of fully controlled devices can be controlled by unipolar SPWM modulation, bipolar modulation and other control methods, and then output AC sinusoidal voltage after LC filtering.

[0039] All of these methods use a fixed DC power supply as the voltage source, and output an AC voltage source by high-frequency modulation and filtering of the bridge arm composed of fully controlled devices.

[0040] When using lithium iron phosphate batteries for power and requiring AC output via inverter, since a single battery has a voltage of around 3V, a DC power supply consisting of multiple batteries connected in series is needed, followed by AC output through the aforementioned topology. Common problems with these topologies include: the need for a dedicated inverter circuit; the requirement for a separate equalization control circuit for the battery pack; the inability to achieve equalization control using the inverter; and high cost.

[0041] Please refer to Figure 1 To address the aforementioned problems, this invention provides a single-phase inverter system based on a battery pack and a bidirectional switching bridge arm, comprising an H-bridge inverter circuit, a charging unit 100, and a control unit 200, wherein: The H-bridge inverter circuit includes a left half-bridge and a right half-bridge. The upper arm of the left half-bridge is a first battery pack T1 composed of several individual battery cells connected in series, and the lower arm of the left half-bridge is a second battery pack T2 composed of several individual battery cells connected in series. The common terminal of the first battery pack T1 and the second battery pack T2 serves as one AC output terminal of the H-bridge inverter circuit. The upper arm of the right half-bridge is a first bidirectional switch K1, and the lower arm of the right half-bridge is a second bidirectional switch K2. The common terminal of the first bidirectional switch K1 and the second bidirectional switch K2 serves as another AC output terminal of the H-bridge inverter circuit. The first battery pack T1 and the positive DC terminal of the first bidirectional switch K1 are electrically connected, and the second battery pack T2 and the negative DC terminal of the second bidirectional switch K2 are electrically connected. The first bidirectional switch K1 and the charging unit 100 are connected in parallel. The control unit 200 is used to connect the charging unit 100 to the upper arm of the right half bridge after receiving the charging mode instruction, and disconnect the electrical connection between the two AC output terminals and the external load, thereby controlling the timing of the series connection of several individual battery cells to the circuit and / or bypass according to the output voltage and output current of the charging unit 100, and then charging several individual battery cells. The control unit 200, upon receiving an instruction for inverter mode, disconnects the charging unit 100 from the upper arm of the right half-bridge to bypass the charging unit 100 and electrically connects the two AC output terminals to the external load. Based on the current modulation time of the preset AC voltage, it controls the timing of the series connection and / or bypass of several individual battery cells into the circuit, and coordinates with the control of the conduction timing of the first bidirectional switch K1 and the second bidirectional switch K2 to output AC power to the external load.

[0042] In such Figure 1 In one possible embodiment, the first battery pack T1 comprises N individual battery cells connected in series, including cell 1-1, cell 1-2, ..., cell 1-N. The second battery pack T2 comprises N individual battery cells connected in series, including cell 2-1, cell 2-2, ..., cell 2-N. The common terminal of the first battery pack T1 and the second battery pack T2 is electrically connected to the positive AC terminal of the load via an AC output switch, outputting a current io.

[0043] The aforementioned single-phase inverter system based on battery packs and bidirectional switch arms replaces the left half-bridge of a traditional H-bridge inverter with a first battery pack T1 and a second battery pack T2 connected in series, while the right half-bridge uses a first bidirectional switch K1 and a second bidirectional switch K2. The first battery pack T1 serves as the upper bridge arm, and the second battery pack T2 as the lower bridge arm, with their common terminal directly serving as one of the AC output terminals. The common terminal of the two bidirectional switches on the right half-bridge serves as the other AC output terminal. In inverter mode, by controlling the number of individual battery cells connected in the left half-bridge to generate a stepped wave to approximate the positive or negative half-cycle of a sine wave, and simultaneously coordinating with the power frequency commutation of the bidirectional switches on the right half-bridge, an AC voltage can be synthesized at the output terminal without the need for complex PWM modulation and filtering inductors. In charging mode, by connecting the charging unit 100 in parallel to the upper bridge arm of the right half-bridge and utilizing the battery cell access / bypass control of the left half-bridge, selective charging of any individual battery cell can be achieved, thus realizing battery equalization management capabilities.

[0044] This invention eliminates the complex structure of separating the DC source and inverter bridge arm in traditional inverter circuit topologies, integrating the energy output of the battery pack with the inverter function. Through the timing control of individual battery cells by the control unit 200, not only is DC-to-AC conversion achieved, but also balanced control of the battery pack is realized by selectively connecting specific individual battery cells to the circuit. This eliminates the need for an additional independent balancing circuit, significantly simplifying the circuit topology, reducing system cost, and improving system integration and reliability.

[0045] Further, the control unit 200, upon receiving an inverter mode command, disconnects the charging unit 100 from the upper arm of the right half-bridge to bypass the charging unit 100 and electrically connects the two AC output terminals to the external load. This allows the control unit 200 to control the timing of the series connection and / or bypass of several individual battery cells according to the current modulation time of the preset AC voltage, and coordinates with the control of the conduction timing of the first bidirectional switch K1 and the second bidirectional switch K2 to output AC power to the external load, including: Obtain the voltage amplitude and power frequency period of the preset AC voltage, and obtain the output voltage of a single battery cell; The total number of batteries in the first battery pack T1 and the second battery pack T2 are obtained based on the voltage amplitude, the power frequency period, and the output voltage of a single battery cell; wherein the total number of batteries in the first battery pack T1 and the second battery pack T2 are equal. Based on the voltage amplitude, the power frequency period, and the total number of batteries in the first battery pack T1 and the second battery pack T2, the AC voltage output value corresponding to each modulation moment is obtained; Determine the current modulation time of the preset AC voltage; When the current modulation time is in the positive half-cycle, based on the current modulation time and the AC voltage output value corresponding to each modulation time, the number of individual battery cells connected in series in the second battery pack T2 is determined, and all individual battery cells in the first battery pack T1 are bypassed, and the first bidirectional switch K1 is turned off and the second bidirectional switch K2 is turned on. When the current modulation time is in the negative half-cycle, based on the current modulation time and the AC voltage output value corresponding to each modulation time, the number of individual battery cells connected in series in the first battery pack T1 is determined, and all individual battery cells in the second battery pack T2 are bypassed, and the first bidirectional switch K1 is turned on and the second bidirectional switch K2 is turned off.

[0046] In this implementation, by acquiring the parameters of the preset AC voltage and the output voltage of a single battery cell, the required total number of batteries is accurately calculated. Based on the instantaneous value of the target AC voltage, the number of battery cells connected in series in real time is adjusted. Specifically, during the positive half-cycle of the AC voltage, the upper bridge arm (first battery pack T1) is completely bypassed, and the lower bridge arm (second battery pack T2) is connected in series with the corresponding number of batteries according to the required voltage. Simultaneously, the second bidirectional switch K2 is turned on, thereby creating a positive current flowing from the positive terminal of the second battery pack T2 through the load to the negative terminal of the second battery pack T2, resulting in a positive output voltage. During the negative half-cycle of the AC voltage, the lower bridge arm is completely bypassed, and the upper bridge arm is connected in series with the corresponding number of batteries according to the required voltage. Simultaneously, the first bidirectional switch K1 is turned on, thereby creating a reverse current flowing from the positive terminal of the first battery pack T1 through the first bidirectional switch K1, the load, and back to the negative terminal of the first battery pack T1, resulting in a negative output voltage.

[0047] The aforementioned control strategy utilizes the stepped voltage of the battery pack to approximate a sine wave, reducing the harmonic content of the output voltage and decreasing the size and loss of the filter. Simultaneously, by symmetrically controlling the number of battery packs T1 and T2 in operation, the symmetry of the output AC power is ensured, enabling bidirectional charging and discharging management of the battery packs and further optimizing the waveform quality of the inverter output.

[0048] In one specific embodiment, when operating in inverter mode, the output AC voltage is set to... As shown in Equation 1 below: (Equation 1) in, The desired output voltage amplitude, For AC output voltage frequency, For the modulation period, This is the starting time.

[0049] Based on the desired output voltage amplitude Based on the individual cell voltage, the total number N of individual cell units that need to be connected in series in a battery pack can be determined, i.e., the desired output voltage amplitude. It equals the sum of the voltage amplitudes of the individual battery cells in a battery pack. AC output voltage frequency. Typically, 50Hz is chosen, corresponding to a power frequency period T=20ms. k represents the modulation time.

[0050] Specifically, modulation period This is related to the number N of batteries connected in series. Since the single battery unit includes a single battery cell, a series switch, and a bypass switch, the negative terminal of the single battery cell is the DC negative terminal of the single battery unit, the positive terminal of the single battery cell is electrically connected to one end of the series switch, and the other end of the series switch serves as the DC positive terminal of the single battery unit. One end of the bypass switch is the DC negative terminal of the single battery unit, and the other end is the DC positive terminal of the single battery unit. Generally, in each half-modulation cycle, all switches connected in series with the single battery cell, including the bypass switch and the series switch, operate at most twice. Therefore, we get... The values ​​are shown in Equation 2 below: (Equation 2) in, Given that the power frequency period of the output AC power is T = 20ms, by combining equations 1 and 2, the output voltage value that can be taken for each modulation cycle in each power frequency period can be obtained. Total number of modulation times The relationship with N is shown in Equation 3 below: (Equation 3) Based on equations 1 to 3 above, the number of individual battery cells that need to be connected in series and the current output AC voltage can be calculated at each modulation time k during one cycle of the output AC power. .

[0051] Therefore, when In the positive half-cycle, the number of individual battery cells to be connected in series in the second battery pack T2 of the lower left bridge arm can be determined based on the current modulation time k. According to the performance of each individual battery cell, the control unit 200 selects suitable individual batteries to be connected in series, making the output voltage value closest to the desired value. This forms a circuit with the continuously triggered and conducting second bidirectional switch K2 of the lower right bridge arm, outputting the positive half-cycle of the AC voltage. Each increment of k... Update: Control unit 200 recalculates the number of individual battery cells that need to be connected in series and selects which individual battery cells to prioritize for series connection.

[0052] Further, the step of determining the number of individual battery cells connected in series in the second battery pack T2 based on the current modulation time and the AC voltage output value corresponding to each modulation time, controlling all individual battery cells in the first battery pack T1 to bypass, and turning off the first bidirectional switch K1 and turning on the second bidirectional switch K2 includes: Obtain the state of charge and temperature parameters of each individual battery cell in the second battery pack T2; Based on the state of charge and temperature parameters of each individual battery cell in the second battery pack T2, and the number of individual battery cells in the second battery pack T2 that need to be connected in series to the circuit, several individual battery cells in the second battery pack T2 are selected to be connected in series to the circuit, and the remaining individual battery cells are bypassed. The step of determining the number of individual battery cells connected in series in the first battery pack T1 based on the current modulation time and the AC voltage output value corresponding to each modulation time, and controlling all individual battery cells in the second battery pack T2 to bypass, and turning on the first bidirectional switch K1 and turning off the second bidirectional switch K2, includes: Obtain the state of charge and temperature parameters of each individual battery cell in the first battery pack T1; Based on the state of charge and temperature parameters of each individual battery cell in the first battery pack T1, and the number of individual battery cells in the first battery pack T1 that need to be connected in series to the circuit, several individual battery cells in the first battery pack T1 are selected to be connected in series to the circuit, and the remaining individual battery cells are bypassed.

[0053] In this implementation, after determining the number of individual battery cells to be connected to the circuit, selection is performed based on the state of charge (SOC) and temperature parameters of each individual battery cell. During inverter discharge, the control unit 200 can prioritize connecting individual battery cells with higher SOC or suitable temperatures to the circuit for discharge, while bypassing individual battery cells with lower SOC or abnormal temperatures. Through this dynamic selection mechanism, the system can dynamically balance the depth of discharge and thermal stress of each battery cell during inverter discharge, achieving active balancing and thermal management. This effectively extends the cycle life of the entire battery pack, ensures operational safety, and achieves balanced control of the battery pack state. It solves the technical problem of relying on external balancing circuits in existing technologies, effectively extends the overall service life of the battery pack, and improves the safety and stability of the system.

[0054] Please refer to Figure 2Furthermore, the first bidirectional switch K1 includes a first thyristor K11 and a second thyristor K12, and the second bidirectional switch K2 includes a third thyristor K23 and a fourth thyristor K24. The anode of the first thyristor K11 is the positive DC terminal of the first bidirectional switch K1, and the cathode of the first thyristor K11 is the common terminal of the first bidirectional switch K1. The second thyristor K12 and the first thyristor K11 are connected in reverse parallel. The cathode of the third thyristor K23 is the negative DC terminal of the second bidirectional switch K2, and the anode of the third thyristor K23 is the common terminal of the second bidirectional switch K2. The fourth thyristor K24 and the third thyristor K23 are connected in reverse parallel. The positive terminal of the charging unit 100 is electrically connected to the anode of the first thyristor K11, and the negative terminal of the charging unit 100 is electrically connected to the cathode of the second thyristor K12.

[0055] The control unit 200 is configured to connect the charging unit 100 to the upper arm of the right half-bridge after receiving a charging mode command, including: The first thyristor K11 and the third thyristor K23 are controlled to be turned off, and the second thyristor K12 and the fourth thyristor K24 are controlled to be turned on, so that the charging unit 100 is connected to the upper arm of the right half bridge.

[0056] In this implementation, anti-parallel thyristors are used to form a bidirectional switch. Thyristors, as semi-controlled devices, have advantages such as low cost, high voltage withstand capability, and strong current carrying capacity. In charging mode, by turning on the second and fourth thyristors K24, the charging unit 100 is connected in series with the right half-bridge using the anti-parallel thyristors. At this time, the positive terminal of the charging unit 100 is connected to the common connection point of the left and right half-bridges through the second thyristor K12, while the negative terminal is directly connected to the negative terminal of the second battery pack T2, allowing the charging unit 100 to directly charge the first battery pack T1 and the second battery pack T2. In inverter mode, by controlling the conduction of the corresponding thyristors, power frequency commutation can be achieved, bypassing the charging unit 100 and preventing it from affecting the inverter output.

[0057] Further, the step of controlling the timing of the series connection and / or bypass of the plurality of individual battery cells to the circuit based on the output voltage and output current of the charging unit 100, thereby charging the plurality of individual battery cells, includes: Obtain the state of charge and temperature parameters of each individual battery cell; For any of the individual battery cells, the charging time of the individual battery cell is determined based on the state of charge and temperature parameters of the individual battery cell. Based on the charging time, the individual battery cell is controlled to be connected in series to the circuit for charging, while the remaining individual battery cells are bypassed.

[0058] In this implementation, during charging mode, the time for individual battery cells to be connected in series in the circuit is controlled selectively based on their state of charge (SOC) and temperature parameters. For example, the battery cell with the lowest SOC can be charged first, or a polling method can be used to replenish energy to all battery cells. For individual battery cells with a low SOC, the charging time connected in series in the circuit can be increased; for individual battery cells with a high SOC, the charging time can be reduced. Because individual battery cells can be charged independently and controllably, the system can achieve active balancing during the charging process, avoiding overcharging and ensuring that all battery cells reach the ideal SOC after charging, thus improving charging efficiency and safety, and further enhancing the system's balancing function in charging mode.

[0059] Please refer to Figure 2 In one specific embodiment, the single battery unit includes a single battery, a series switch, and a bypass switch. The negative terminal of the single battery is the DC negative terminal of the single battery unit. The positive terminal of the single battery is electrically connected to one end of the series switch, and the other end of the series switch serves as the DC positive terminal of the single battery unit. One end of the bypass switch is the DC negative terminal of the single battery unit, and the other end of the bypass switch is the DC positive terminal of the single battery unit.

[0060] Among them, single battery unit 1-1 includes single battery B1-1, series switch T1-1C and bypass switch T1-1. Single battery unit 1-2 includes single battery B1-2, series switch T1-2C and bypass switch T1-2. Single battery unit 1-N includes single battery B1-N, series switch T1-NC and bypass switch T1-N.

[0061] Single battery unit 2-1 includes single battery B2-1, series switch T2-1C, and bypass switch T2-1. Single battery unit 2-2 includes single battery B2-2, series switch T2-2C, and bypass switch T2-2. Single battery unit 2-N includes single battery B2-N, series switch T2-NC, and bypass switch T2-N.

[0062] The charging unit 100 includes a charging power supply. The negative terminal of the charging power supply is electrically connected to the cathode of the second thyristor K12, and the positive terminal of the charging power supply is electrically connected to the anode of the first thyristor K11, thereby generating a charging current ic when connected to the circuit.

[0063] In inverter mode, when the current modulation time is in the positive half-cycle, the first thyristor K11, the second thyristor K12 and the fourth thyristor K24 are turned off, and the third thyristor K23 is turned on.

[0064] When the current modulation time is in the negative half-cycle, the first thyristor K11 is turned on, and the second thyristor K12, the third thyristor K23 and the fourth thyristor K24 are turned off.

[0065] In such Figure 1 In one possible embodiment, the first battery pack T1 comprises N individual battery cells connected in series, including cell 1-1, cell 1-2, ..., cell 1-N. The second battery pack T2 comprises N individual battery cells connected in series, including cell 2-1, cell 2-2, ..., cell 2-N. The common terminal of the first battery pack T1 and the second battery pack T2 is electrically connected to the positive AC terminal of the load via an AC output switch, outputting a current io.

[0066] Please refer to Figure 2 and Figure 3 In such Figure 3 In one possible embodiment, when the system operates in inverter mode, the AC output switch is closed and the second thyristor K12 is open. Based on the set AC voltage amplitude and frequency, the instantaneous voltage value at the current moment, along with the corresponding current modulation time k and the number of individual battery cells to be connected in series, is calculated. When the instantaneous voltage value is in the positive half-cycle, the third thyristor K23 is first triggered to conduct, keeping the first bidirectional switch K1 off. Then, based on the battery performance evaluation results, the individual battery cells of the second battery pack T2 are controlled to be connected in series or bypassed, so that the total output voltage is close to the instantaneous AC voltage value, while ensuring that each battery cell operates at its optimal performance.

[0067] When the instantaneous voltage value is in the negative half-cycle, the first thyristor K11 is triggered to conduct; the second bidirectional switch K2 remains off. Based on the battery performance evaluation results, the individual battery cells of the first battery pack T1 are controlled to be connected in series or bypassed, so that the total output voltage is close to the instantaneous AC voltage value, while ensuring that each battery cell operates at its optimal performance.

[0068] When the system is operating in charging mode, the AC output switch is open; the second thyristor K12 is closed; the first bidirectional switch K1 remains on, and the first thyristor K11 is off. Based on the voltage and current output by the charging power supply, and according to the state of charge and performance of each individual battery cell, the system controls the series connection or bypass of each individual battery cell and the duration of series connection, so that all individual battery cells achieve optimal performance.

[0069] Please refer to Figure 4Furthermore, the single-cell battery unit includes a single-cell battery, a series switch, and a bypass switch. The negative terminal of the single-cell battery is the DC negative terminal of the single-cell battery unit. The positive terminal of the single-cell battery is electrically connected to one end of the series switch, and the other end of the series switch serves as the DC positive terminal of the single-cell battery unit. One end of the bypass switch is the DC negative terminal of the single-cell battery unit, and the other end of the bypass switch is the DC positive terminal of the single-cell battery unit. Wherein: When the control unit 200 controls any of the individual battery cells to be connected in series in the circuit, it controls the series switch to be turned on and controls the bypass switch to be turned off, so that the individual battery cell is connected in series in the circuit. When the control unit 200 controls any of the individual battery cells to bypass, it controls the series switch to turn off and controls the bypass switch to turn on, so that the individual battery cell is bypassed.

[0070] In this implementation, the operating state of a single battery cell is independently controlled through a combination of series switches and bypass switches. When the series switch is on and the bypass switch is off, the single battery cell is connected to the circuit as a power source; when the series switch is off and the bypass switch is on, the single battery cell is short-circuited, without affecting the loop current. That is, the series switch connects the battery to the main circuit, and the bypass switch short-circuits the battery to achieve bypass. Through these series and bypass switches, the state of each battery cell can be flexibly controlled, providing a hardware foundation for stepped-wave inverters and equalization charging, making the battery pack configuration more flexible and adaptable to different voltage levels. Simultaneously, independent switch control provides redundancy for the system. When a single battery cell fails, it can be isolated by the bypass switch, and the system can still operate in degraded mode, improving the system's fault tolerance and reliability.

[0071] In one specific embodiment, the control unit 200 collects the voltage and temperature parameters of each individual battery cell. When the battery is discharging in inverter mode, the current of the individual batteries in the upper arm of the left half-bridge and the lower arm of the left half-bridge can be obtained by collecting the AC output current; when the battery is charging, the charging current of the battery can be obtained by collecting the output current of the charging power supply. By combining the aforementioned voltage, temperature, and current data of each individual battery cell, the state of charge and state of health of each individual battery cell are calculated.

[0072] Please refer to Figure 4Furthermore, the bypass switch includes a first MOSFET Tp and a second MOSFET Tn. The drain of the first MOSFET Tp serves as the negative DC terminal of the single battery cell. The source of the first MOSFET Tp is electrically connected to the source of the second MOSFET Tn, and the drain of the second MOSFET Tn serves as the positive DC terminal of the single battery cell. The series switch includes a third MOSFET Tpc and a fourth MOSFET Tnc. The drain of the third MOSFET Tpc is electrically connected to the positive terminal of the single battery cell. The source of the third MOSFET is electrically connected to the source of the fourth MOSFET Tnc, and the drain of the fourth MOSFET Tnc serves as the positive DC terminal of the single battery cell.

[0073] Specifically, each individual battery cell consists of one individual battery cell and two switches, namely, a series switch and a parallel switch. Each switch is a bidirectional switch, and each bidirectional switch consists of two MOSFET switching transistors connected in reverse series.

[0074] The two MOSFET switches are connected in reverse series and designed with a common source. The direction of the battery discharge current is assumed to be positive.

[0075] Two switching transistors are connected at one end to form the positive output terminal of a single battery cell. The other end of one of the switching transistors is connected to the positive terminal of the single battery cell, which can be called a series switch; the other end of the other switching transistor is connected to the negative terminal of the single battery cell, which can be called a bypass switch.

[0076] Theoretically, the two switching transistors in a single battery cell should conduct complementaryly. However, since the turn-on and turn-off processes require a certain amount of time, when switching between the series branch and the bypass branch is needed, if the switching command is issued simultaneously, the overlapping turn-off and turn-on durations will cause a short circuit in the battery, potentially damaging it. Conversely, if one branch switch is turned off first and then the other is turned on, the entire series bridge arm will be open-circuited, causing a power outage to the load. Therefore, a dedicated switching control logic needs to be designed to prevent both short circuits in the battery and power outages to the load.

[0077] When the series switch and bypass switch in each individual battery cell need to be switched, to ensure that the battery is not short-circuited and the load is not open-circuited during the switching process, it is divided into 4 states according to the switching direction and current direction. Each switching process is further divided into 5 time periods, namely t1, t2, t3, t4, and t5. Based on this, the 4 MOSFET switches are controlled according to the set timing sequence to achieve smooth switching and ensure that the battery is not short-circuited and the load is not open-circuited.

[0078] Please refer to Figure 5 In the inverter mode, when the control unit 200 controls any single battery cell to switch from a series connection state to a bypass state, for that single battery cell: During the first period of this switching process, the first MOSFET and the second MOSFET Tn are turned off, while the third MOSFET Tpc and the fourth MOSFET Tnc are turned on. During the second period of this switching process, the fourth MOSFET Tnc is controlled to be turned off; During the third period of this switching process, the first MOSFET Tp is turned on; During the fourth period of this switching process, the third MOS transistor Tpc is turned off. In the fifth period of the switching process, the second MOSFET Tn is turned on, which ultimately switches the single battery cell from the series connection state to the bypass state.

[0079] like Figure 5 The diagram shows the control timing diagram of the control unit 200 controlling any of the individual battery cells to switch from a series connection state to a bypass state. This switching process is state 1. A high level indicates conduction, and a low level indicates cutoff. During time period t1, the series switch is on, meaning the third MOSFET Tpc and the fourth MOSFET Tnc are on. When time period t1 ends and time period t2 begins, the fourth MOSFET Tnc is turned off. Because it is discharging, the battery discharge path is maintained by the diodes inside the third MOSFET Tpc and the fourth MOSFET Tnc. When time period t2 ends and time period t3 begins, the first MOSFET Tp is turned on. Because it is discharging, there is no battery short-circuit loop. When time period t3 ends and time period t4 begins, the third MOSFET Tpc is turned off. Because the first MOSFET Tp is already on, the output current is transferred from the series switch to the bypass switch, and the discharge loop is not interrupted. When time period t4 ends and time period t5 begins, the second MOSFET Tn is turned on. At this time, the bidirectional switch successfully achieves switching.

[0080] This implementation provides a specific timing sequence for the switch to switch from series to bypass in inverter mode. Two MOSFETs are connected back-to-back in series to form a bypass switch and / or a series switch, which can block current in both directions and provide a freewheeling path through their body diodes when necessary. Specifically, by dividing the switching process into five time periods, a soft switching process is implemented, ensuring that the voltage across the battery cell does not change abruptly during switching, and that the main circuit current always has a continuous path. This avoids overvoltage caused by current interruption, achieves arc-free switching, and avoids the risk of instantaneous open-circuit voltage spikes or short circuits caused by inconsistent switching actions. This significantly reduces switching losses and electromagnetic interference, improving system reliability and efficiency. Furthermore, in high-frequency modulation applications, this timing control can effectively suppress electromagnetic interference caused by voltage surges, protect power devices from impact damage, and ensure the smoothness of the inverter output voltage waveform.

[0081] Furthermore, in the inverter mode, when the control unit 200 controls any single battery cell to switch from a bypass state to a series connection state, for that single battery cell: During the first period of this switching process, the first MOSFET Tp and the second MOSFET Tn are turned on, while the third MOSFET Tpc and the fourth MOSFET Tnc are turned off. During the second period of this switching process, the second MOSFET Tn is turned off. During the third period of this switching process, the third MOS transistor Tpc is turned on. During the fourth period of this switching process, the first MOSFET Tp is turned off. In the fifth period of the switching process, the fourth MOS transistor Tnc is turned on, which ultimately switches the single battery cell from the bypass state to the series connection state.

[0082] like Figure 6 The diagram shows the timing of the control unit 200 controlling any of the individual battery cells to switch from a bypass state to a series connection state. This switching process is state 2. Specifically, when the battery is discharging and the bypass switch switches to the series switch: During time period t1, the bypass switch is on, meaning the second MOSFET Tn and the first MOSFET Tp are on; when time period t1 ends and time period t2 begins, the second MOSFET Tn is off. Because it is discharging, the diodes inside the first MOSFET Tp and the second MOSFET Tn maintain the battery discharge path; when time period t2 ends and time period t3 begins, the third MOSFET Tpc is on. Because it is discharging, there is no battery short-circuit loop; when time period t3 ends and time period t4 begins, the first MOSFET Tp is off. Because the third MOSFET Tpc is on, the output current is transferred from the bypass switch to the series switch, and the discharge loop is not interrupted; when time period t4 ends and time period t5 begins, the fourth MOSFET Tnc is on. At this time, the bidirectional switch successfully switches.

[0083] In this implementation, a five-stage switching logic is designed for the process of switching a single battery cell from the bypass state to the series connection state. Following the safety principle of "turn on first, then turn off", the transient current path is constructed during the switching process by utilizing the source connection relationship of the MOSFET. This achieves soft switching of the battery cell at the moment of connection, effectively limiting the inrush current at the moment of connection, preventing the battery voltage from dropping instantly or the switching transistor from overheating, and improving the stability and safety of the system during dynamic adjustment.

[0084] Furthermore, in the charging mode, when the control unit 200 controls any of the individual battery cells to switch from a series connection state to a bypass state, for that individual battery cell: During the first period of this switching process, the first MOSFET Tp and the second MOSFET Tn are turned off, while the third MOSFET and the fourth MOSFET Tnc are turned on. During the second period of this switching process, the third MOSFET Tpc is controlled to be turned off; During the third period of this switching process, the second MOSFET Tn is turned on; During the fourth period of this switching process, the fourth MOS transistor Tnc is turned off. In the fifth period of the switching process, the first MOSFET Tp is turned on, which ultimately switches the single battery cell from the series connection state to the bypass state.

[0085] like Figure 7 The diagram shows the timing of the control unit 200 controlling any of the individual battery cells to switch from a series connection state to a bypass state. This switching process is state 3. When the battery is charging and the connection is switched from the series switch to the bypass switch: During time period t1, the series switch is on, meaning the fourth MOSFET Tnc and the third MOSFET Tpc are on. When time period t1 ends and time period t2 begins, the third MOSFET Tpc is turned off. Because charging is in progress, the battery charging path is maintained by the diodes inside the fourth MOSFET Tnc and the third MOSFET Tpc. When time period t2 ends and time period t3 begins, the second MOSFET Tn is turned on. Because charging is in progress, there is no battery short-circuit loop. When time period t3 ends and time period t4 begins, the fourth MOSFET Tnc is turned off. Because the second MOSFET Tn is already on, the output current is transferred from the series switch to the bypass switch, and the charging loop remains unbroken. When time period t4 ends and time period t5 begins, the first MOSFET Tp is turned on. At this time, the bidirectional switch successfully switches.

[0086] In this implementation, a specific five-stage switching logic is designed for the current characteristics in charging mode. Since the current direction differs between charging and inverter modes, the switching sequence must adapt to the change in current flow. By controlling the operating sequence of the first to fourth MOSFETs (Tnc), the charging current is ensured to remain continuous during the transfer from the series branch to the bypass branch. This prevents damage to the battery or switching transistors caused by the back electromotive force generated by the inductive components, ensuring a smooth charging process, preventing charging interruptions or voltage fluctuations due to switching, and ensuring balanced charging control.

[0087] Furthermore, in the charging mode, when the control unit 200 controls any one of the individual battery cells to switch from a bypass state to a series connection state, for that individual battery cell: During the first period of this switching process, the first MOSFET Tp and the second MOSFET Tn are turned on, while the third MOSFET Tpc and the fourth MOSFET Tnc are turned off. During the second period of this switching process, the first MOSFET Tp is turned off. During the third period of this switching process, the fourth MOS transistor Tnc is turned on. During the fourth period of this switching process, the second MOSFET Tn is turned off. In the fifth period of the switching process, the third MOSFET Tpc is turned on, which ultimately switches the single battery cell from the bypass state to the series connection state.

[0088] like Figure 8 The diagram shows the timing of the control unit 200 controlling any of the individual battery cells to switch from a bypass state to a series connection state. This switching process is state 4. When the battery is charging and the bypass switch switches to the series switch: During time period t1, the bypass switch is on, meaning the second MOSFET Tn and the first MOSFET Tp are on; when time period t1 ends and time period t2 begins, the first MOSFET Tp is turned off. Because it is charging, the battery charging path is maintained by the diodes inside the second MOSFET Tn and the first MOSFET Tp; when time period t2 ends and time period t3 begins, the fourth MOSFET Tnc is turned on. Because it is charging, there is no battery short-circuit loop; when time period t3 ends and time period t4 begins, the second MOSFET Tn is turned off. Because the fourth MOSFET Tnc is already on, the output current is transferred from the bypass switch to the series switch, and the charging loop is not interrupted; when time period t4 ends and time period t5 begins, the third MOSFET Tpc is turned on. At this time, the bidirectional switch successfully switches.

[0089] In this implementation, a five-stage switching logic is designed for the process of a single battery cell switching from bypass to connection during charging mode. This logic ensures that the charging current can be smoothly established the instant the single battery cell is connected to the charging circuit, avoiding current surges caused by hard switching operations. By controlling the MOSFETs in stages, switching losses and heat accumulation are effectively reduced, ensuring the reliability of the system when frequently switching battery cells during charging mode.

[0090] The single-phase inverter system based on a battery pack and a bidirectional switching arm provided by the present invention has at least the following advantages compared with the prior art: First, by incorporating the battery pack itself as part of the inverter and using a bidirectional switch to form the other half of the H-bridge, the complex PWM modulation circuit and filter inductor in traditional inverters are eliminated, greatly simplifying the circuit structure and reducing hardware costs.

[0091] Secondly, the system achieves independent control and energy management of each battery cell by dynamically accessing / bypassing individual battery units, enabling the balancing of the series battery pack without the need for any external balancing circuits. This reduces system cost and complexity, and improves the overall lifespan and safety of the battery pack.

[0092] Third, the inverter process employs a fundamental frequency stepped wave synthesis method, with the switching devices operating at the power frequency, resulting in extremely low switching losses. Simultaneously, a refined five-segment commutation timing sequence is used during battery cell state switching, achieving soft switching and further reducing losses and electromagnetic interference.

[0093] Fourth, the system can adjust the output voltage by controlling the number of batteries connected in series, making it suitable for AC output requirements of different voltage levels. At the same time, the intelligent screening strategy based on SOC and temperature can dynamically balance the depth of discharge and thermal stress of each battery cell, achieving active balancing and thermal management, thereby effectively extending the cycle life of the entire battery pack and ensuring operational safety.

[0094] In summary, this invention utilizes a battery pack inverter to generate AC output voltage and optimizes battery utilization efficiency; it achieves optimal charging performance through a combination of the charging power supply and the built-in switches of the battery cells. Its ingenuity and advantages lie in the following: each individual battery cell achieves balanced control through reasonable logic control during inverter operation; the switches within each individual battery cell switch twice per power frequency cycle, resulting in a very low switching frequency; the use of thyristors to form a bridge arm results in low loss, low cost, and speed that meets inverter requirements. Optimal charging performance is achieved by fully utilizing the series switches and bypass switches of each individual battery cell in conjunction with the charging power supply.

[0095] The term "embodiment" as used herein means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described; however, any combination of these technical features that does not contradict each other should be considered within the scope of this specification.

[0096] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various improvements and substitutions without departing from the concept of this application, and these improvements and substitutions should also be considered within the scope of protection of this invention. Therefore, the scope of protection of this application should be determined by the appended claims.

Claims

1. A single-phase inverter system based on a battery pack and a bidirectional switching arm, characterized in that, It includes an H-bridge inverter circuit, a charging unit, and a control unit, wherein: The H-bridge inverter circuit includes a left half-bridge and a right half-bridge. The upper arm of the left half-bridge is a first battery pack composed of several individual battery cells connected in series, and the lower arm of the left half-bridge is a second battery pack composed of several individual battery cells connected in series. The upper arm of the right half-bridge is a first bidirectional switch, and the lower arm of the right half-bridge is a second bidirectional switch. The first bidirectional switch and the charging unit are connected in parallel. The control unit is used to connect the charging unit to the upper arm of the right half bridge after receiving the charging mode instruction, and disconnect the electrical connection between the H-bridge inverter circuit and the external load. In this way, according to the output voltage and output current of the charging unit, the control unit controls the timing of the series connection of several individual battery cells to the circuit and / or bypass, and then charges several individual battery cells. The control unit is used to disconnect the charging unit and the upper arm of the right half-bridge after receiving the inverter mode command, so as to bypass the charging unit and electrically connect the H-bridge inverter circuit to the external load. In this way, according to the current modulation time of the preset AC voltage, the control unit controls the timing of the series connection and / or bypass of several individual battery cells into the circuit, and coordinates with the control of the conduction timing of the first bidirectional switch and the second bidirectional switch to output AC power to the external load.

2. The single-phase inverter system based on a battery pack and a bidirectional switching arm according to claim 1, characterized in that, The step of controlling the timing of connecting several individual battery cells in series to the circuit and / or bypassing according to the current modulation time of the preset AC voltage, and coordinating with the control of the conduction timing of the first bidirectional switch and the second bidirectional switch to output AC power to the external load, includes: Obtain the voltage amplitude and power frequency period of the preset AC voltage, and obtain the output voltage of a single battery cell; The total number of batteries in the first battery pack and the second battery pack are obtained based on the voltage amplitude, power frequency cycle and the output voltage of a single battery cell. Based on the voltage amplitude, power frequency cycle, and the total number of batteries in the first and second battery packs, the AC voltage output value corresponding to each modulation moment is obtained. Determine the current modulation time of the preset AC voltage; When the current modulation time is in the positive half-cycle, based on the current modulation time and the AC voltage output value corresponding to each modulation time, the number of individual battery cells connected in series in the second battery pack is determined, and all individual battery cells in the first battery pack are bypassed, and the first bidirectional switch is turned off and the second bidirectional switch is turned on. When the current modulation time is in the negative half-cycle, based on the current modulation time and the AC voltage output value corresponding to each modulation time, the number of individual battery cells connected in series in the first battery pack is determined, and all individual battery cells in the second battery pack are bypassed, and the first bidirectional switch is turned on and the second bidirectional switch is turned off.

3. A single-phase inverter system based on a battery pack and a bidirectional switching bridge arm according to claim 2, characterized in that, The step of determining the number of individual battery cells connected in series in the second battery pack based on the current modulation time and the AC voltage output value corresponding to each modulation time, and controlling all individual battery cells in the first battery pack to bypass, and turning off the first bidirectional switch and turning on the second bidirectional switch, includes: Obtain the state of charge and temperature parameters of each individual battery cell in the second battery pack; Based on the state of charge and temperature parameters of each individual battery cell in the second battery pack, and the number of individual battery cells connected in series in the second battery pack, several individual battery cells are selected from the second battery pack and connected in series in the second battery pack. The step of determining the number of individual battery cells connected in series in the first battery pack based on the current modulation time and the AC voltage output value corresponding to each modulation time, and controlling all individual battery cells in the second battery pack to bypass, and turning on the first bidirectional switch and turning off the second bidirectional switch, includes: Obtain the state of charge and temperature parameters of each individual battery cell in the first battery pack; Based on the state of charge and temperature parameters of each individual battery cell in the first battery pack, and the number of individual battery cells in the first battery pack that need to be connected in series to the circuit, several individual battery cells in the first battery pack are selected to be connected in series to the circuit.

4. A single-phase inverter system based on a battery pack and a bidirectional switching arm according to claim 1, characterized in that, The first bidirectional switch includes a first thyristor and a second thyristor, and the second bidirectional switch includes a third thyristor and a fourth thyristor. The anode of the first thyristor is the positive DC terminal of the first bidirectional switch, and the cathode of the first thyristor is the common terminal of the first bidirectional switch. The second thyristor and the first thyristor are connected in anti-parallel. The cathode of the third thyristor is the negative DC terminal of the second bidirectional switch, and the anode of the third thyristor is the common terminal of the second bidirectional switch. The fourth thyristor and the third thyristor are connected in anti-parallel. The positive terminal of the charging unit is electrically connected to the anode of the first thyristor, and the negative terminal of the charging unit is electrically connected to the cathode of the second thyristor. The control unit, upon receiving a charging mode command, connects the charging unit to the upper arm of the right half-bridge, including: The first thyristor and the third thyristor are controlled to be turned off, and the second thyristor and the fourth thyristor are controlled to be turned on, so that the charging unit is connected to the upper arm of the right half bridge.

5. A single-phase inverter system based on a battery pack and a bidirectional switching arm according to claim 1, characterized in that, The step of controlling the timing of the series connection and / or bypass of a plurality of individual battery cells to the circuit based on the output voltage and output current of the charging unit, thereby charging the plurality of individual battery cells, includes: Obtain the state of charge and temperature parameters of each individual battery cell; For any of the individual battery cells, the charging time of the individual battery cell is determined based on the state of charge and temperature parameters of the individual battery cell. Based on the charging time, the individual battery cell is controlled to be connected in series to the circuit for charging, while the remaining individual battery cells are bypassed.

6. A single-phase inverter system based on a battery pack and a bidirectional switching arm according to claim 1, characterized in that, The single-cell battery unit includes a single cell, a series switch, and a bypass switch. The negative terminal of the single cell is the DC negative terminal of the single-cell battery unit. The positive terminal of the single cell is electrically connected to one end of the series switch, and the other end of the series switch serves as the DC positive terminal of the single-cell battery unit. One end of the bypass switch is the DC negative terminal of the single-cell battery unit, and the other end of the bypass switch is the DC positive terminal of the single-cell battery unit. Wherein: When the control unit controls any of the individual battery cells to be connected in series in the circuit, it controls the series switch to be turned on and the bypass switch to be turned off, so that the individual battery cell is connected in series in the circuit. When the control unit controls any of the individual battery cells to bypass, it controls the series switch to turn off and controls the bypass switch to turn on, so that the individual battery cell is bypassed.

7. A single-phase inverter system based on a battery pack and a bidirectional switching arm according to claim 6, characterized in that, The bypass switch includes a first MOSFET and a second MOSFET. The drain of the first MOSFET serves as the negative DC terminal of the single battery cell. The sources of the first MOSFET and the second MOSFET are electrically connected. The drain of the second MOSFET serves as the positive DC terminal of the single battery cell. The series switch includes a third MOSFET and a fourth MOSFET. The drain of the third MOSFET is electrically connected to the positive terminal of the single battery cell. The sources of the third MOSFET and the fourth MOSFET are electrically connected. The drain of the fourth MOSFET serves as the positive DC terminal of the single battery cell. Wherein: In the inverter mode, when the control unit controls any single battery cell to switch from a series connection state to a bypass state, for that single battery cell: During the first period of this switching process, the first MOSFET and the second MOSFET are turned off, while the third MOSFET and the fourth MOSFET are turned on. During the second period of this switching process, the fourth MOS transistor is controlled to be turned off; During the third period of this switching process, the first MOS transistor is turned on; During the fourth period of this switching process, the third MOS transistor is turned off. In the fifth period of the switching process, the second MOS transistor is turned on, which ultimately switches the single battery cell from the series connection state to the bypass state.

8. A single-phase inverter system based on a battery pack and a bidirectional switching bridge arm according to claim 7, characterized in that, In the inverter mode, when the control unit controls any single battery cell to switch from bypass state to series connection state, for that single battery cell: During the first period of this switching process, the first MOSFET and the second MOSFET are turned on, while the third MOSFET and the fourth MOSFET are turned off; During the second period of this switching process, the second MOSFET is controlled to be turned off; During the third period of this switching process, the third MOS transistor is turned on; During the fourth period of this switching process, the first MOSFET is turned off. In the fifth period of the switching process, the fourth MOS transistor is turned on, which ultimately switches the single battery cell from the bypass state to the series connection state.

9. A single-phase inverter system based on a battery pack and a bidirectional switching arm according to claim 7, characterized in that, In the charging mode, when the control unit switches any of the individual battery cells from a series connection state to a bypass state, for that individual battery cell: During the first period of this switching process, the first MOSFET and the second MOSFET are turned off, while the third MOSFET and the fourth MOSFET are turned on. During the second period of this switching process, the third MOS transistor is controlled to be turned off; During the third period of this switching process, the second MOSFET is turned on. During the fourth period of this switching process, the fourth MOS transistor is turned off. In the fifth period of the switching process, the first MOS transistor is turned on, which ultimately switches the single battery cell from the series connection state to the bypass state.

10. A single-phase inverter system based on a battery pack and a bidirectional switching arm according to claim 7, characterized in that, In the charging mode, when the control unit controls any one of the individual battery cells to switch from bypass state to series connection state, for that individual battery cell: During the first period of this switching process, the first MOSFET and the second MOSFET are turned on, while the third MOSFET and the fourth MOSFET are turned off; During the second period of this switching process, the first MOSFET is controlled to be turned off. During the third period of this switching process, the fourth MOS transistor is turned on; During the fourth period of this switching process, the second MOSFET is turned off. In the fifth period of the switching process, the third MOS transistor is turned on, which ultimately switches the single battery cell from the bypass state to the series connection state.

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