Bidirectional multi-mode hybrid multi-level inverter circuit and battery energy storage system

Abstract

The application discloses a bidirectional multi-mode hybrid multi-level inverter circuit and a battery energy storage system. The inverter circuit comprises a controller, a power frequency commutation and filtering circuit, a controller and a plurality of corresponding battery and power units connected electrically. The battery and power units are divided into two groups. The power units in each group are connected in cascade to form a unipolar multi-level ladder wave bus. The power frequency commutation and filtering circuit comprises a power frequency commutation circuit and a filtering circuit. The power frequency commutation circuit is composed of a full-bridge topology. The filtering circuit is composed of an AC filtering inductor and an AC filtering capacitor. The controller samples the AC side signal, controls the logical order of each power unit and the switch tube of the power frequency commutation circuit, controls the active balancing of the battery and the bidirectional power conversion of the energy storage system. The application can improve the conversion efficiency, reduce the switching power consumption and volume, and adapt to the global power supply requirements.

Description

Technical Field

[0001] The present invention relates to the field of new energy power electronics technology, and in particular to a bidirectional multi-mode hybrid multi-level inverter circuit and a battery energy storage system. Background Art

[0002] While most countries around the world use single-phase and three-phase power systems, North America and some other countries utilize dual live wires (L1-L2), also known as single-phase systems, single live wires (L1-N and / or L2-N), or dual live wires in parallel (L1 / L2-N). To adapt to the global market, new energy battery energy storage systems need to flexibly switch between these power supply modes and enable bidirectional power conversion.

[0003] Bidirectional multi-mode inverter circuits usually use symmetrical dual half-bridge circuits, such as Figure 1 As shown. This circuit includes two DC filter capacitors Cd1 and Cd2, four power switches Q1 through Q4 and their body diodes, AC filter inductors L1 and L2, and AC filter capacitors Cf1 and Cf2. Power conversion from DC to AC is called inverter discharge (DC / AC), while power conversion from AC to DC is called rectification charging (AC / DC). In inverter discharge mode: In dual-live power supply mode, or a single-phase power system, Cd1, Cd2 and Cf1, Cf2 are connected in series for filtering. Q1 through Q4 form a traditional bidirectional full-bridge circuit. L1 and L2 are connected in series for filtering, providing power to the series-connected AC power sources Va and Vc. Simultaneously, loads RL1 and RL2 are connected in series to receive power from the two live wires, not the neutral wire. In the single-live-wire power supply mode, Cd1, Q1, Q2, L1, and Cf1 form the first bidirectional half-bridge circuit, and Cd2, Q3, Q4, L2, and Cf2 form the second bidirectional half-bridge circuit, thus forming a bidirectional multi-mode inverter circuit. The two circuits provide power to Va, RL1 and Vc, RL2 respectively through the N line.

[0004] The dual-live parallel power supply mode is similar to the single-live mode, still sharing the neutral line. The only difference is that the two live wires are directly connected in parallel, so the amplitude, frequency, and phase of the two sets of single-phase AC voltages must be exactly the same. Conversely, the rectifier charging mode is similar and will not be discussed here. Traditional bidirectional inverter circuits can achieve bidirectional power conversion and offer key advantages such as a simple circuit structure and mature modulation methods.

[0005] Traditional bidirectional multi-mode inverter circuits offer simple control, but require bipolar high-frequency sinusoidal pulse-width modulation (SPWM) for both dual- and single-live-wire modes. All four power switches operate at high frequency, resulting in high switching power consumption, particularly in the reverse recovery power consumption of their body diodes. This results in low conversion efficiency. Furthermore, the output voltage is limited to two levels in different modes, resulting in large output filter inductors and making further efficiency improvements difficult. Bidirectional multi-level multi-mode technology has become a research hotspot in new energy power electronics, reducing switching power consumption, achieving smaller form factors, and enabling flexible switching between inverter and rectifier modes, as well as multiple power supply modes.

[0006] In existing battery energy storage systems, the voltage boost between the battery voltage and the DC bus voltage is relatively large, and the subsequent traditional inverter circuit operates at high-frequency switching and its output voltage is two-level. The main disadvantages are low two-stage conversion efficiency, large inverter size, and high system cost. Summary of the Invention

[0007] The technical problem to be solved by the embodiments of the present invention is to provide a bidirectional multi-mode hybrid multi-level inverter circuit and a battery energy storage system to improve conversion efficiency and reduce switch power consumption and volume.

[0008] To solve the above technical problems, an embodiment of the present invention proposes a bidirectional multi-mode hybrid multi-level inverter circuit, including a controller, a power frequency commutation and filtering circuit, a controller, and a number of corresponding electrically connected batteries and power units. The batteries and power units are divided into two groups, and the outputs of each group of power units are cascaded to form a unipolar multi-level step wave bus; the power frequency commutation and filtering circuit includes a power frequency commutation circuit and a filtering circuit. The power frequency commutation circuit is composed of a full-bridge topology, and the filtering circuit is composed of an AC filter inductor and an AC filter capacitor. The controller samples the AC side signal, controls the logical order of each power unit and the power frequency commutation circuit switch tube, controls the active balancing of the batteries and the bidirectional power conversion of the energy storage system.

[0009] Correspondingly, an embodiment of the present invention further provides a battery energy storage system, comprising the above-mentioned bidirectional multi-mode hybrid multi-level inverter circuit.

[0010] The beneficial effects of the present invention are:

[0011] (1) The batteries of the present invention are not directly connected in series or parallel, and the barrel effect of traditional energy storage solutions does not exist. Each battery of the present invention is independently managed and controlled. On the one hand, the battery discharge time is extended, the battery charging time is shortened, and the battery charging speed is accelerated; on the other hand, the battery thermal management is easier, and the battery thermal runaway is prevented in advance, eliminating the safety risk of battery fire.

[0012] (2) The present invention deeply integrates batteries and their management and active balancing with power electronics technology, adopts hierarchical round-robin carrier stacking modulation and its improved method, and the batteries and power units can be switched to bypass state, thereby increasing the redundancy of battery operation and further improving the reliability of the energy storage system.

[0013] (3) The present invention can use multiple types of batteries, such as lithium batteries, sodium batteries or solid-state batteries, or mix different types of batteries or mix new and old batteries of the same type. It is suitable for battery management at the battery pack level, cell level, and battery cluster level, and realizes active balancing of battery SoC / SoH, expands the effective capacity of the battery and prolongs the battery life.

[0014] (4) The present invention works in a dual-live-wire, i.e., single-phase power system, a single-live-wire, a single-live-wire series, and a dual-live-wire parallel power supply mode, and can flexibly switch between these power supply modes to meet global power supply and utilization requirements.

[0015] (5) The present invention can realize bidirectional power conversion between the battery and AC power supply or grid: rectifier charging or inverter discharging, without the need for a separate charger or inverter.

[0016] (6) The power factor of the present invention is adjustable and can operate in active power and reactive power modes, meeting the requirements of power load and grid dispatch diversity;

[0017] (7) The bus voltage of the present invention is a unipolar multi-level step wave, and its output equivalent frequency is several times the switching frequency, which improves the conversion efficiency, reduces the output harmonics and electromagnetic interference, reduces the AC filter inductance and the volume of the energy storage device, and reduces the system cost.

[0018] (8) The power switch tube inside the power unit of the present invention is of low voltage level. In the dual-live-wire power supply mode, only one power switch tube inside the power unit works at high frequency switching at the same time. In the single-live-wire or dual-live-wire parallel power supply mode, only two power switch tubes inside the power unit work at high frequency switching at the same time. In addition, there is no high-frequency switching loss in the power frequency commutation and filtering circuit, thereby further improving the conversion efficiency.

[0019] (9) The control method of the present invention simplifies the controller design, makes it easy to develop new control strategies, and facilitates the expansion of the energy storage system capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a traditional bidirectional inverter circuit diagram.

[0021] Figure 2 1 is a schematic structural diagram of a bidirectional multi-mode hybrid multi-level inverter circuit according to an embodiment of the present invention.

[0022] Figure 3 This is an output control flow chart of an embodiment of the present invention.

[0023] Figure 4 is the battery active equalization control flowchart of the embodiment of the present application.

[0024] Figure 5 is the circuit diagram of the bidirectional multi-mode hybrid multi-level inverter circuit of the embodiment of the present application.

[0025] Figure 6 In the figure, (a) is the main working waveform diagram of the double-live-line power supply mode (i.e. single-phase electric system Vac) of the embodiment of the present application, (b) is the main working waveform diagram of the single-live-line or double-live-line parallel power supply mode Va, Vc of the embodiment of the present application.

[0026] Figure 7 is the DC boost and half-bridge cascade circuit diagram of the embodiment 1 of the present application.

[0027] Figure 8 is the negative-end inductance DC boost and half-bridge cascade circuit diagram of the embodiment 2 of the present application.

[0028] Figure 9 is the four-tube DC boost and half-bridge cascade circuit diagram of the embodiment 3 of the present application.

[0029] Figure 10 is the negative-end inductance four-tube DC boost and half-bridge cascade circuit diagram of the embodiment 4 of the present application.

[0030] Figure 11 is the DC resonance boost and half-bridge cascade circuit diagram of the embodiment 5 of the present application.

[0031] Figure 12 In the figure, (a) is the circuit diagram of the battery positive end internally provided with a protection switch of the embodiment 6 of the present application, (b) is the circuit diagram of the battery positive end externally provided with a protection switch of the embodiment 6 of the present application, (c) is the circuit diagram of the battery negative end internally provided with a protection switch of the embodiment 6 of the present application, (d) is the circuit diagram of the battery negative end externally provided with a protection switch of the embodiment 6 of the present application.

[0032] Figure 13 In the figure, (a) is the circuit diagram of the battery positive end internally provided with a protection switch of the embodiment 7 of the present application, (b) is the circuit diagram of the battery positive end externally provided with a protection switch of the embodiment 7 of the present application, (c) is the circuit diagram of the battery negative end internally provided with a protection switch of the embodiment 7 of the present application, (d) is the circuit diagram of the battery negative end externally provided with a protection switch of the embodiment 7 of the present application.

[0033] Figure 14 is the battery boost and positive-end half-bridge cascade circuit diagram of the embodiment 8 of the present application.

[0034] Figure 15 is another form of bidirectional multi-mode hybrid multi-level inverter circuit diagram of the embodiment 9 of the present application. DETAILED DESCRIPTION

[0035] It should be noted that, unless there is a conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The present invention is further described in detail below with reference to the drawings and specific embodiments.

[0036] In the embodiments of the present invention, if there are directional indications (such as up, down, left, right, front, back, etc.), they are only used to explain the relative position relationship and movement status of the various components under a specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0037] In addition, the terms "first," "second," and so on, used in this disclosure are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features being referred to. Therefore, features specified as "first" or "second" may explicitly or implicitly include at least one of these features.

[0038] Please refer to Figures 2-6 The bidirectional, multi-mode, hybrid multi-level inverter circuit of this embodiment includes a controller, a power-frequency commutation and filtering circuit, a controller, and several correspondingly electrically connected batteries and power units. The preferred circuit connection relationship is: battery ↔ power unit ↔ filtering circuit ↔ power-frequency commutation circuit (Sync & Gate Drive) ↔ power grid (L1 / L2 / L3 / N).

[0039] The battery energy storage system of an embodiment of the present invention includes a bidirectional, multi-mode, hybrid, multi-level inverter circuit. The present invention can be widely applied to various bidirectional or unidirectional charging or inverter circuits, such as new energy wind and photovoltaic power generation and energy storage systems using lithium, sodium, and solid-state batteries, battery capacity conversion systems, battery charging and discharging systems in power tools and construction machinery, and motor controllers for electric and off-road vehicles.

[0040] The multiple batteries and their power cells can be divided into two groups. The first group is A1 to An, and the second group is B1 to Bn, where n is the number of batteries or power cells within each group. The power cells consist of a half-bridge cascade circuit. All batteries are connected to their corresponding power cells. The AC side includes the loads RLa and RLc, as well as the AC power sources Va and Vc, and AC. The power frequency commutation and filtering circuitry consists of a full-bridge topology with power frequency modulation, four switching transistors, and AC filter inductors and capacitors.

[0041] Each battery positive and negative pole is connected to the corresponding power unit first port and second port respectively. The first group of bottom power unit A1 fourth port is connected to the power frequency commutation and filter circuit tenth port, which is the single polarity multi-level ladder wave bus negative pole, its third port is connected to the adjacent upper layer another power unit A2 fourth port, and its third port is connected to the adjacent upper layer another power unit fourth port, and so on, after cascading through multiple power units, the top power unit An third port is connected to the power frequency commutation and filter circuit midpoint seventh port, which is the single polarity multi-level ladder wave bus midpoint. The second group of bottom power unit B1 fourth port is also connected to the power frequency commutation and filter circuit midpoint seventh port, its third port is connected to the adjacent upper layer another power unit B2 fourth port, and its third port is connected to the adjacent upper layer another power unit fourth port, and so on, after cascading through multiple power units, the top power unit Bn third port is connected to the power frequency commutation and filter circuit ninth port, which is the single polarity multi-level ladder wave bus positive pole. The controller is connected to the power unit fifth port, and the power frequency commutation and filter circuit eighth port. The power frequency commutation and filter circuit seventh port is connected to the neutral line N, the sixth port is connected to the first live wire L1, and the fifth port is connected to the second live wire L2. The voltage difference between L1 and N is the alternating current source Va, the voltage difference between N and L2 is the alternating current source Vc, and Va and Vc are equivalent to the alternating current source AC in series.

[0042] The controller can be a single controller, including sampling, conditioning and feedback circuits, and switch tube driving circuits, etc. Alternatively, it is divided into master controller and slave controller, and the master and slave controllers are wired or wireless communication. The master controller samples the alternating current side signal, controls the logical order of each power unit and the switch tube of the power frequency commutation circuit, and at the same time realizes external communication; the slave controller detects voltage, current, power and temperature, etc. Battery side electrical parameters, calculates the state of charge / health (SOC / SOH), which is equivalent to completing the battery management function, reports the battery parameters such as SOC / SOH to the master controller, and receives and executes the instructions and data issued by the master controller, such as rectification charging / inversion discharging and battery active balancing control, power unit logical order arrangement, ladder wave output voltage and battery number information, etc., and controls the work of each switch tube inside the power unit. Alternatively, the slave controller is placed inside the corresponding power unit. It works in double live wire, that is, single-phase power supply system, single live wire, single live wire in series and double live wire in parallel power supply mode, and can flexibly switch between these three power supply modes.

[0043] The bidirectional DC / AC circuit can flexibly operate in off-grid inverter discharge, grid-connected inverter discharge, and rectifier charging modes, depending on actual application needs. The power flow (inverter discharge) from the battery to the AC power source follows the following path: In a dual-live or single-live series power supply mode, or a single-phase system with a grid voltage or AC output of 220V / 230V / 240V, all batteries and power units A1-An and B1-Bn form a single inverter circuit. A unipolar multi-level step-wave busbar is formed between the ninth and tenth ports of the power frequency commutation and filtering circuit. A symmetrical step-wave busbar with a power frequency cycle is generated between the midpoints of the two bridge arms of the full-bridge topology. After filtering by the AC inductor and capacitor, a sinusoidal AC voltage is generated, supplying power to the series-connected AC power sources Va and Vc (Vac) or the grid. Simultaneously, the loads RLa and RLc receive power from the two live wires L1 and L2, not the neutral line, in a dual-live series power supply mode. Therefore, the dual-live power supply mode is essentially a single-phase system. In single-live-wire power supply mode, when the grid voltage or AC output is 100V / 110V / 120V, the first battery group and the first power unit A1-An form the first inverter circuit; the second battery group and the second power unit B1-Bn form the second inverter circuit. These two groups form two unipolar multi-level step-wave buses between the ninth and eighth ports, and between the eighth and tenth ports, of the power-frequency commutation and filtering circuit, respectively. Similarly, two symmetrical positive and negative step-waves are generated between the midpoints of the two bridge arms of the full-bridge topology. After filtering by the AC inductor and AC capacitor, two AC sinusoidal voltages are generated. These voltages are then supplied to Va, RLa, Vc, RLc, or the grid via the neutral line from the two live wires L1 and L2, respectively. In single-live-wire power supply mode, the two AC output powers can be different, thus accommodating different types of loads.

[0044] In the dual-live-wire parallel power supply mode, when the grid voltage or AC output is 100V / 110V / 120V, the system operates similarly to the single-live-wire power supply mode, still forming two inverter circuits. The only difference is that the two live wires, L1 and L2, are directly connected in parallel. The full-bridge topology switches in the power-frequency commutation and filtering circuits are appropriately adjusted in their switching mode: the two upper transistors are turned on and off simultaneously, and the two lower transistors are turned on and off simultaneously. The two AC voltages, Va and Vc, have identical amplitudes, frequencies, and phases, allowing them to operate in parallel. Conversely, the power flow from the AC power source to the battery (rectification and charging) occurs as follows: the input and output terminals of the power-frequency commutation and filtering circuits are interchanged, with the input terminals being ports 6 and 7, and the output terminals being ports 9 and 10. Port 8 is the neutral line. The input and output terminals of the power unit are also interchanged, with the positive and negative input terminals being ports 3 and 4, and the positive and negative output terminals being ports 1 and 2. The AC power supply provides a sinusoidal voltage, which is filtered by the AC inductor and capacitor in the power-frequency commutation and filtering circuits before entering the full-bridge topology for power-frequency rectification. The full-bridge topology can also operate in synchronous rectification mode, where the switching transistors operate at power frequency instead of conducting their body diodes, thereby reducing power losses in the full-bridge topology. The cascaded input power cells form a unipolar multi-level ladder-wave bus, charging each battery individually with a constant current or constant voltage. The operating principle is similar to that of the inverter discharge mode and will not be further explained here. It should be noted that in these modes, the power cells, power-frequency commutation, and filtering circuits are all bidirectional conversion circuits.

[0045] The master controller issues instructions to the slave controller based on the SOC / SOH information of each battery to control the logical order of the corresponding power units. During inverter discharge / rectifier charging, the controller switches the battery with the highest / lowest SOC and its power unit to the bottom layer of the unipolar multi-level step wave bus for low-frequency square wave modulation (NLM), and switches the battery with the lowest SOC and its power unit to the top layer for high-frequency sinusoidal pulse width modulation (SPWM). During inverter discharge or rectifier charging, this mixed modulation method of high-frequency SPWM and low-frequency NLM is called carrier stacking modulation, which is mainly used for multi-level conversion switch modulation, and is further combined with battery management and active balancing, deeply integrating batteries and their management and active balancing with power electronics technology, thereby forming hierarchical round-robin carrier stacking modulation. The control method flow chart is shown below. Figure 3 、 4 shown.

[0046] For a single power-frequency sine wave cycle, the bottom layer of the unipolar multi-level ladder bus represents more charge and discharge energy, while the top layer represents less. The remaining batteries and their power units are arranged in this order, resulting in high-capacity batteries discharging more energy and charging less energy, while low-capacity batteries discharging less energy and charging more energy. This enables battery management and active SOC / SOH balancing. This control method allows the use of multiple battery types, allowing for a mix of different battery types or a mix of old and new batteries of the same type. In dual-live power supply mode, only one top-level power unit operates with high-frequency SPWM switching, while one bottom-level power unit operates with low-frequency NLM switching. The switching operation of the remaining power units is between SPWM and NLM. In single-live or dual-live parallel power supply modes, only two top-level power units operate with high-frequency SPWM switching, and two bottom-level power units operate with low-frequency NLM switching. The switching operation of the remaining power units is between SPWM and NLM. The full-bridge topology in the power-frequency commutation circuit also operates with power-frequency switching. Each power unit is independently controlled by its own controller, eliminating the need for direct series and parallel connections between batteries. The "barrel effect" of traditional solutions is eliminated, and each battery in the energy storage system is independently managed and controlled. This not only extends battery discharge time, shortens battery charging time, and accelerates battery charging speed, but also facilitates battery thermal management, preventing battery thermal runaway in advance and eliminating the safety risk of battery fire. Optionally, the hierarchical round-robin carrier stack modulation method can be further improved. When inverter discharge or rectifier charging does not affect normal operation, the battery with the lowest SOC and its power unit can be switched to bypass mode. This means that the main circuit in the half-bridge cascade circuit that requires bypass is continuously turned on. This allows prematurely failing or faulty batteries and their power units to be disconnected online, thereby increasing battery operational redundancy and further improving the reliability of the energy storage system.

[0047] In dual-live-wire power supply mode, also known as a single-phase power system, the two groups of cells and their power units operate together as a whole. The number of unipolar multilevel step wave busbar levels is (2n+1), and the equivalent output level of the positive and negative symmetrical step wave or sine wave output over the power frequency cycle is (4n+1). In single-live-wire or dual-live-wire parallel power supply mode, the two groups of cells and their power units operate independently. The number of unipolar multilevel step wave busbar levels is (n+1), and the equivalent output level of the positive and negative symmetrical step wave or sine wave output over the power frequency cycle is (2n+1). It should be noted that in single-live-wire series power supply mode, the multilevel modulation method is changed, and the number of levels is different from that in dual-live-wire power supply mode, also known as a single-phase power system. The number of unipolar multilevel step wave busbar levels, formed by the superposition of two voltages, is (n+1), and the equivalent output level of the positive and negative symmetrical step wave or sine wave output over the power frequency cycle is (2n+1). Optionally, the number of batteries or power units within the two groups of cells or within each power module can be different without affecting normal circuit operation. Furthermore, the power unit can be applied at the pack, cell, or cluster level. Optionally, in dual-live power supply mode, i.e., a single-phase power system, one of the two AC filter inductors in the power frequency commutation and filtering circuit can be removed; a single AC filter inductor does not affect normal circuit operation. Optionally, the AC filter inductor and capacitor in the filtering circuit can be located between the unipolar multi-level ladder bus and the full-bridge topology. By sampling the AC and DC voltage and current signals, the controller identifies the input and output power flow direction, determines and controls the operation of the power switches based on actual operating conditions, and provides real-time closed-loop feedback on the operating status to stabilize the output voltage or current. Adaptive control allows operation in either inverter discharge or rectifier charge mode, achieving bidirectional power conversion for the energy storage system. The controller can flexibly change the phase of the AC voltage and current to achieve adjustable power factor. It can operate in both active and reactive power modes to meet the diverse requirements of power loads and grid scheduling. The control method simplifies controller design, makes it easy to develop new control strategies, and facilitates the expansion of energy storage system capacity.

[0048] In both inverter discharge and rectifier charge modes, the bus voltage is a unipolar, multi-level step waveform. The voltage change rate (dv / dt) across the AC filter inductor is low, resulting in a smaller AC filter inductor value in the filter circuit. The low output voltage, current, and power of the power unit allows for a reduced rated voltage level for the internal power switches. In dual-live power supply mode, only one power unit's internal power switch operates simultaneously at high frequency. In single-live or dual-live parallel power supply mode, only two power units' internal power switches operate simultaneously at high frequency. Furthermore, there are no high-frequency switching losses in the power frequency commutation and filter circuits, resulting in an output equivalent frequency several times the switching frequency. This improves conversion efficiency, reduces output harmonics and electromagnetic interference, and reduces the size of the energy storage device, thereby lowering system cost. The proposed technical solution is primarily targeted at energy storage systems, with batteries used on the DC side of the bidirectional circuit. Optionally, a DC power supply can be used on the DC side, further expanding the scope of bidirectional DC / AC applications.

[0049] Optionally, to accommodate varying power levels and battery capacities, the power unit includes a high-frequency pulse-width modulated (PWM) direct-to-direct-current (DC / DC) circuit. The DC / DC input is connected to the battery, and its output is routed through a half-bridge cascade circuit before being connected to the mains frequency commutation and filtering circuits. The DC / DC circuit utilizes non-isolated or isolated topologies, including but not limited to non-isolated topologies such as Buck, Boost, Buck-Boost, Cuk, SEPIC, and Zeta, as well as isolated topologies such as half-bridge, full-bridge, push-pull, flyback, forward, and forward-flyback, or a combination of LLC, LCC, LCLC, CLCL, or basic series-parallel resonant circuits. The DC / DC circuit utilizes high-frequency PWM modulation, with each battery and its switching unit ranked according to a state-of-charge (SOC) algorithm. The half-bridge or full-bridge cascade circuit utilizes hierarchical round-robin stack modulation or its improved variant, and the mains frequency commutation circuit utilizes mains frequency modulation. The battery and its power unit outputs are cascaded to form a unipolar multi-level ladder bus.

[0050] The DC / DC circuits, half-bridge cascade circuits, and power-frequency commutation circuits in the power unit can utilize interleaved parallel or series technology, as well as various multi-level circuits, to achieve higher power levels or higher voltage levels. It should be noted that the DC / DC circuits and half-bridge cascade circuits can utilize voltage-mode control, as well as average current mode, peak current mode, quasi-resonant control, single-cycle control, and other control modes. They can also employ different operating modes, such as continuous conduction mode (CCM), discontinuous current mode (DCM), or critical conduction mode (CRM).

[0051] The power switches in the power unit use fully controlled devices, such as metal oxide field-effect transistors (MOSFETs) and insulated gate bipolar transistors (IGBTs). Third-generation wide bandgap (WBG) power devices, such as silicon carbide (SiC) and gallium nitride (GaN) MOSFETs, can also be used. A mixture of these fully controlled power switches is also acceptable. The power switches in the power frequency commutation circuit can use either fully controlled or partially controlled devices, such as silicon controlled rectifiers (SCRs) and thyristors (TRIACs). A mixture of fully and partially controlled devices is also acceptable.

[0052] The controller can be built using discrete electronic components or designed and implemented using application-specific integrated circuits, such as analog control chips, software-programmable microcontrollers (MCUs), digital signal processors (DSPs), or programmable logic devices (FPGAs / CPLDs). These components can be implemented using discrete or integrated components, or integrated into the controller to form a large-scale hybrid integrated circuit. This highly integrated controller design can further reduce the size of the energy storage device.

[0053] The present invention is implemented as follows Figure 5As shown, four batteries and their power cells are used. They can be divided into two groups, namely two battery groups and their power cells. The power cells comprise a half-bridge cascade circuit. The first battery group includes batteries A1 and A2, and the second battery group includes batteries B1 and B2. The first power cell A1 of the first power cell group includes a DC filter capacitor C11 and MOSFET switches Q11 and Q12, while the second power cell A2 includes a DC filter capacitor C12 and MOSFET switches Q13 and Q14. The first power cell B1 of the second power cell group includes a DC filter capacitor C21 and MOSFET switches Q21 and Q22, while the second power cell B2 includes a DC filter capacitor C22 and MOSFET switches Q23 and Q24. All batteries are connected to their respective power cells. The AC side includes loads RLa and RLc, and AC power sources Va and Vc. The power frequency commutation and filtering circuitry includes four IGBT switches Q5-Q8 forming a full-bridge topology, AC filter inductors Lf1 and Lf2, and AC filter capacitors Cf1 and Cf2. Two power switches connected in series form a bridge arm. For example, Q11 and Q12, Q5 and Q6, and so on, each form a separate bridge arm. To facilitate illustration of the basic principle, the internal or external diodes of the power switches are not shown in the diagram, but this does not affect their actual function and performance. The DC side of power units A1-B2 is connected to their respective batteries A1-B2. The midpoint of each power unit's internal half-bridge cascade circuit arm is connected to the negative terminal of the half-bridge cascade circuit of another adjacent power unit, forming an output cascade. A unipolar multi-level ladder busbar is formed between the midpoints of the Q23 and Q24 arms and the midpoints of the Q11 and Q12 arms. The midpoints of the switching tubes Q7 and Q8 are connected to one end of Lf1, the midpoints of the switching tubes Q5 and Q6 are connected to one end of Lf2, the other ends of Lf1 and Lf2 are connected to one end of Cf1 and Cf2, RLa and RLc, and the two live wires L1 and L2 of the AC voltage Vac, respectively. The other ends of Cf1, Cf2, RLa and RLc are connected to the connection point of the two cascaded modules, Q13 and Q22, and the neutral line N. Furthermore, a positive and negative symmetrical step wave with a power frequency cycle is formed between the midpoints of the Q5 and Q6 arms and the midpoints of the Q7 and Q8 arms.

[0054] In the dual-live-wire or single-live-wire series power supply mode, that is, a single-phase power system, all batteries A1-B2 and their power units A1-B2, power-frequency phase-commutating switches Q5-Q8, two series-connected filter inductors Lf1 and Lf2, and two series-connected filter capacitors Cf1 and Cf2 form the same inverter circuit, a unipolar multi-level step wave bus, and a power-frequency cycle with positive and negative symmetrical step waves. These provide or obtain power to the series-connected AC power sources Va and Vc (Vac) or the grid. At the same time, the loads RLa and RLc, connected in series, obtain power from the two live wires L1 and L2 without passing through the neutral wire. In single-live-wire power supply mode, all batteries A1-B2 and their power units A1-B2, power-frequency commutation switches Q7 and Q8, filter inductor Lf1, and filter capacitor Cf1 form a first inverter circuit, a first unipolar multi-level step wave bus, and a first power-frequency cycle of positive and negative symmetrical step waves. All batteries A1-B2 and their power units A1-B2, power-frequency commutation switches Q5 and Q6, filter inductor Lf2, and filter capacitor Cf2 form a second inverter circuit, a second unipolar multi-level step wave bus, and a second power-frequency cycle of positive and negative symmetrical step waves, thus forming a multi-mode circuit. This circuit then provides or obtains power from the two live wires L1 and L2 via the N line to Va, RLa, Vc, RLc, or the grid, respectively. The dual-live-wire parallel power supply mode is similar to the single-live-wire power supply mode and still constitutes a multi-mode circuit. The only difference is that the two live wires L1 and L2 are directly connected in parallel. The full-bridge topology switch tubes in the power frequency commutation and filtering circuit appropriately adjust the switching mode: Q5 and Q7 are turned on and off at the same time, and Q6 and Q8 are turned on and off at the same time. The two AC voltages Va and Vc have exactly the same amplitude, frequency and phase, so they can work in parallel.

[0055] When the inverter discharges, the energy is provided by the batteries A1-B2. The bidirectional half-bridge cascaded circuit works in direct current step-down (Buck) mode, at this time MOSFET switch tubes Q11, Q13, Q21, Q23 are main tubes, and MOSFET switch tubes Q12, Q14, Q22, Q24 are synchronous rectifier tubes. The synchronous rectifier tube is turned on slightly later in its internal or external diode in each high-frequency switching cycle, which can achieve zero voltage switching (ZVS). According to different power supply modes and SoC / SoH active balancing requirements, the main controller generates a logical sequence configuration, and the slave controller selects single tube or double tube to work in high-frequency SPWM switching state, and others work in low-frequency NLM switching state. The power frequency commutation and filter inductance Lf1, Lf2 can be used as energy storage inductance. When the main tube of the half-bridge cascaded circuit is turned on, Lf1, Lf2 stores energy and provides energy to the unipolar multi-level ladder wave bus at the same time, and when the inductance stores energy through the synchronous rectifier tube to the unipolar multi-level ladder wave bus. The unipolar multi-level ladder wave bus is then commutated by IGBT switch tubes Q5-Q8 in the power frequency commutation and filter circuit full-bridge topology to form a power frequency period symmetric ladder wave and output a sine wave voltage, which provides energy to the single-phase power Vac or Va, Vc. The main working waveform is shown in Figure 6 (b) is a single or double firewire parallel power supply mode Va, Vc, from top to bottom, respectively, the unipolar ladder wave bus voltage, the power frequency period symmetric ladder wave and the output sine wave voltage.

[0056] During rectification and charging, energy is provided by the AC power source or single-phase grid power (Vac, Va, and Vc). After passing through filter capacitors Cf1 and Cf2, Vac, Va, and Vc enter the full-bridge topology consisting of IGBT switches Q5-Q8 in the power-frequency commutation and filtering circuit for power-frequency rectification. This generates a positive and negative symmetrical staircase waveform within the power-frequency cycle. This waveform then passes through cascaded power units A1-B2 to form a unipolar multi-level staircase waveform bus. Q5-Q8 can also operate in synchronous rectification mode, where the switches conduct at power frequency instead of their body diodes, reducing power losses in the full-bridge topology. The bidirectional half-bridge cascade circuit operates in DC boost mode, with MOSFET switches Q12, Q14, Q22, and Q24 acting as main rectifiers and MOSFET switches Q11, Q13, Q21, and Q23 acting as synchronous rectifiers. During each high-frequency switching cycle, the synchronous rectifiers conduct after their internal or external diodes conduct, achieving zero-voltage switching (ZVS). Based on different power supply modes and the requirements for active balancing in the SoC / SoH, the master controller generates a logical sequence configuration. The slave controller selects one or two transistors to operate simultaneously in the high-frequency SPWM switching state, while the others operate in the low-frequency NLM switching state. The filter inductors Lf1 and Lf2 in the power frequency commutation and filtering circuit can be used as energy storage inductors. When the half-bridge cascade circuit mains are on, Lf1 and Lf2 store energy. When they are off, the stored energy is discharged to batteries A1-B2 through the synchronous rectifiers, thereby charging each battery individually. Rectification and charging can adopt constant current or constant voltage methods. These methods are traditional control measures and will not be explained here.

[0057] In the dual-live power supply mode, i.e., the single-phase power system, the two groups of batteries and their power units form a whole and work together. The single-polarity multi-level step wave bus level number is (5), and the output equivalent level number of the positive and negative symmetrical step wave or sine wave of the power frequency cycle is (9). In the single-live or dual-live parallel power supply mode, the two groups of cells and their power units work independently. The two single-polarity multi-level step wave bus levels are both (3), and the output equivalent level number of the positive and negative symmetrical step wave or sine wave of the power frequency cycle is both (5). It should be noted that in the single-live series power supply mode, the single-polarity multi-level step wave bus level number of the two voltages superimposed is (3), and the output equivalent level number of the positive and negative symmetrical step wave or sine wave of the power frequency cycle is (5).

[0058] Optionally, in order to adapt to different power levels and battery capacities, the power unit includes a high-frequency pulse width modulation (PWM) DC-DC circuit (DC / DC). The DC / DC input is connected to the battery, and its output is connected to the power frequency commutation and filtering circuit through a half-bridge cascade circuit. Optionally, the DC / DC circuit uses a DC boost topology (Boost). Example 1 is as follows Figure 7 As shown in the figure, the power unit consists of a DC boost and a half-bridge cascade circuit. The power frequency commutation and filtering circuit and controller adopt Figures 2-6The similar method and working principle are basically the same, so I will not go into details here.

[0059] Optionally, the DC / DC circuit uses a Boost topology negative terminal inductor form, as shown in Example 2. Figure 8 As shown in the figure, the power unit consists of a negative-end inductor DC boost circuit and a half-bridge cascade circuit. The power frequency commutation and filtering circuit and controller adopt Figures 2-6 The similar method and working principle are basically the same, so I will not go into details here.

[0060] Optionally, the DC / DC circuit uses a four-tube buck-boost topology, as shown in Example 3. Figure 9 As shown, the power unit consists of a four-tube DC buck-boost and half-bridge cascade circuit. When bidirectional power conversion, inverter discharge and rectifier charging are used, two unidirectional DC boost and buck circuits can be realized. The power frequency commutation and filtering circuit and controller adopt Figures 2-6 The similar method and working principle are basically the same, so I will not go into details here.

[0061] Optionally, the DC / DC circuit uses a negative-end inductor four-tube buck-boost topology, as shown in Example 4. Figure 10 As shown in the figure, the power unit consists of a negative-end inductor four-tube DC buck-boost circuit and a half-bridge cascade circuit. The power frequency commutation and filtering circuit and controller adopt Figures 2-6 The similar method and working principle are basically the same, so I will not go into details here.

[0062] Optionally, the DC / DC circuit uses a bidirectional LLC resonant circuit, as in Example 5. Figure 11 As shown, the power unit consists of LLC and half-bridge cascade circuits. The LLC resonant circuit realizes ZVS operation of all power switches, thereby further improving the conversion efficiency. Optionally, the LLC resonant circuit can use multiple types such as half-bridge, full-bridge, push-pull, etc. Optionally, it can be combined with other resonant technologies such as LCC, LCLC, CLCL, basic series-parallel, etc. The power frequency commutation and filtering circuit and controller adopt Figures 2-6 The similar method and working principle are basically the same, so I will not go into details here.

[0063] Optionally, a battery bidirectional protection switch is used inside the power unit, as in Example 6. Figure 12 As shown, that is, in Figure 5A bidirectional protection switch is added, and the power switch tube in the bidirectional protection switch adopts a face-to-back series connection, that is, the two MOSFET drains in the protection switch are connected to each other. Among them, (a) the protection switch is located inside the positive terminal of the battery, (b) the protection switch is located outside the positive terminal of the battery, (c) the protection switch is located inside the negative terminal of the battery, and (c) the protection switch is located outside the negative terminal of the battery. After adding the battery protection switch, the battery connection can be disconnected in time when an abnormality occurs in the battery or system, thereby improving the safety of the system. Optionally, the power switch tube in the bidirectional protection switch adopts a back-to-back series connection, that is, the two MOSFET sources are connected to each other. Optionally, the bidirectional protection switch is composed of a full-bridge rectifier circuit and a power switch tube in series. Optionally, the power unit contains a DC / DC circuit and can use Figures 7-11 The circuit form and working principle are the same as those of the power frequency commutation and filtering circuit and controller. Figures 2-6 The similar method and working principle are basically the same, so I will not go into details here.

[0064] Optionally, a battery bidirectional protection switch is used inside the power unit, as in Example 7. Figure 13 As shown, that is, in Figure 12 The bidirectional protection switch in the battery can remove one power switch tube, and a single power switch tube combined with a half-bridge cascade circuit can also achieve the purpose of battery bidirectional protection. Among them, (a) the protection switch is located inside the positive terminal of the battery, (b) the protection switch is located outside the positive terminal of the battery, (c) the protection switch is located inside the negative terminal of the battery, and (c) the protection switch is located outside the negative terminal of the battery. After adding the battery protection switch, the battery connection can be disconnected in time when an abnormality occurs in the battery or system, thereby improving system safety. Figure 13 Take (a) as an example to illustrate the basic working principle: during inverter discharge, the internal or external diode of the battery protection MOSFET is turned on. This MOSFET can also work in synchronous rectification mode, but uses the upper tube of the half-bridge inverter circuit bridge arm to continuously turn off to achieve battery protection; during rectification charging, the battery protection MOSFET is continuously turned off to achieve battery protection. Therefore, the single-tube structure in the protection switch can also achieve the purpose of bidirectional battery protection. Optionally, there is no need for an external battery bidirectional protection switch, and the purpose of bidirectional battery protection can be achieved by the upper and lower power switch tubes in the half-bridge cascade circuit. Optionally, the power unit contains a DC / DC circuit and can use Figures 7-11 The circuit form and working principle are the same as those of the power frequency commutation and filtering circuit and controller. Figures 2-6 The similar method and working principle are basically the same, so I will not go into details here.

[0065] Optionally, the half-bridge cascade circuit in the power unit adopts a positive end cascade form, as in Example 8. Figure 14 As shown, the positions of output ports ③ and ④ are changed. Optionally, the DC / DC circuit adoptsFigures 7-11 The battery protection switch adopts a form of Figure 12 , 13 The working principle is the same as that of the above, which will not be described here. The power frequency commutation and filter circuit and the controller adopt a similar way, and the working principle is basically similar to that of the above, which will not be described here. Figures 2-6

[0066] Optionally, in the embodiment Figure 4 , the power frequency commutation circuit can be removed, and the half-bridge in the power unit can be replaced with a full-bridge circuit, also known as an H-bridge, as shown in embodiment 9. Optionally, the DC / DC circuit adopts a form of Figure 15 , the battery protection switch adopts a form of Figures 7-11 , Figure 12 , 13 The battery boost and positive end half-bridge cascade circuit adopts a form of Figure 14 The working principle is the same as that of the above, which will not be described here. The power frequency commutation and filter circuit and the controller adopt a similar way, and the working principle is basically similar to that of the above, which will not be described here. Figures 2-6

[0067] The specific experimental data and test results of the embodiments of the present application are shown in Table 1. The test conditions are as follows: 2 groups of batteries: 2 batteries in each group, a total of 4 48V lithium batteries. Electronic component electrical parameters: MOSFET 1mΩ / 40V, IGBT 50A / 650V, filter inductance 20uH, SPWM switching frequency 20kHz, power frequency 50Hz. The 2 groups of 4 batteries only verify the basic principle, and in fact, it can also be extended to multiple batteries. Since the total voltage of the battery corresponding to the power unit is DC 192V, the AC voltage will be lower than that.

[0068] Although the embodiments of the present application have been shown and described, it can be understood by those of ordinary skill in the art that various changes, modifications, replacements and variations can be made to these embodiments without departing from the principles and spirits of the present application, and the scope of the present application is defined by the appended claims and their equivalent ranges.​​

Claims

1. A bidirectional multi-mode hybrid multi-level inverter circuit, comprising a controller, a power frequency commutation and filtering circuit, a controller, and a plurality of corresponding electrically connected batteries and power units, characterized in that: The batteries and power units are divided into two groups, and the outputs of the power units in each group are cascaded to form a unipolar multi-level ladder wave bus. The power frequency commutation and filtering circuit includes a power frequency commutation circuit and a filtering circuit. The power frequency commutation circuit is composed of a full-bridge topology, and the filtering circuit is composed of an AC filter inductor and an AC filter capacitor. The controller samples the AC side signal, controls the logical sequence of each power unit and the power frequency commutation circuit switch tube, controls the active balancing of the batteries and the bidirectional power conversion of the energy storage system. The power unit includes a half-bridge cascade circuit consisting of two power switch tubes or a full-bridge cascade circuit consisting of four power switch tubes; The power unit also includes a PWM modulated DC / DC circuit and uses a non-isolated or isolated topology; The DC / DC circuit uses high-frequency PWM modulation. The controller sorts each battery and its power unit according to the SOC level. During inverter discharge / rectifier charging, the controller switches the battery with the highest / lowest SOC and its power unit to the bottom layer of the unipolar multi-level step wave bus for low-frequency square wave modulation, and switches the battery with the lowest SOC and its power unit to the top layer for high-frequency sinusoidal pulse width modulation, forming a hierarchical round-robin carrier stacked modulation; the power frequency commutation circuit uses power frequency modulation.

2. The bidirectional multi-mode hybrid multi-level inverter circuit according to claim 1, wherein: The controller dynamically obtains the voltage and current values ​​of the battery or AC power supply; then compares the current actual output value obtained with the target value; dynamically confirms the duty cycle and whether the power unit switch tube is working based on the comparison result, and adjusts the instructions based on the confirmation result; controls the power unit switch tube to execute the instructions, and dynamically controls the energy storage / discharge time of the AC filter inductor so that the current actual output value approaches the target value.

3. The bidirectional multi-mode hybrid multi-level inverter circuit according to claim 1, wherein: The controller dynamically obtains the SoC / SoH voltage, current, and temperature values ​​of each battery, and sorts all the actual current power values ​​obtained by highest to lowest; If the battery SoC / SoH is the highest, the power unit corresponding to the battery is placed at the bottom of the step wave bus during inverter discharge, and at the top of the step wave bus during rectifier charging; If the battery SoC / SoH is the lowest, the power unit corresponding to the battery is placed on the top layer of the step wave busbar during inverter discharge, and on the bottom layer of the step wave busbar during rectifier charging; According to the actual power values, the power units corresponding to the batteries with high power are placed at the lower level of the step wave busbar during inverter discharge, and the power units corresponding to the batteries with low power are placed at the upper level of the step wave busbar; during rectifier charging, the power units corresponding to the batteries with high power are placed at the upper level of the step wave busbar, and the power units corresponding to the batteries with low power are placed at the lower level of the step wave.

4. The bidirectional multi-mode hybrid multi-level inverter circuit according to claim 1, wherein: The AC filter inductor and AC filter capacitor are located between the power frequency commutation and filtering circuit and the AC power supply; or The AC filter inductor and the AC filter capacitor are located between the unipolar multi-level step wave bus and the power frequency commutation circuit.

5. The bidirectional multi-mode hybrid multi-level inverter circuit according to claim 1, wherein: The controller is a single controller, including sampling, conditioning and feedback circuits and switch tube drive circuits; or It includes a master controller and a slave controller, and wired and / or wireless communication is adopted between the master controller and the slave controller.

6. The bidirectional multi-mode hybrid multi-level inverter circuit according to claim 5, wherein: The main controller samples the AC side signal, controls the logical order of each power unit and the power frequency commutation circuit switch tube, controls the active balancing of the battery and the bidirectional power conversion of the energy storage system, and realizes external communication at the same time; the slave controller samples the battery side electrical parameters, calculates the SOC and SOH, reports the battery parameters to the main controller, receives and executes its instructions, and controls the operation of each switch tube.

7. A battery energy storage system, characterized in that: The invention comprises the bidirectional multi-mode hybrid multi-level inverter circuit according to any one of claims 1 to 6.

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