A genset output switching control system and method

Abstract

The present application relates to generator set output control technology, disclose a kind of generator set output switching control system and method.System can include multiple inverter units, switching execution unit, mode input unit, main controller, state detection unit and output interface.Main controller adjusts the voltage, frequency and phase of inverter unit according to target mode, and controls target branch to close after confirming original connection to be disconnected.Three inverter units can be in phase parallel in single-phase mode, and output respectively according to 120 ° phase difference in three-phase mode;Two mutually isolated inverter units can output first voltage by parallel, and output second voltage by series or 180 ° split phase;Combined system can form single-phase first voltage, single-phase second voltage, three-phase first voltage and three-phase second voltage mode.The present application reduces large-current universal switch and complex wiring harness, improves power utilization and switching safety.

Description

Technical Field

[0001] This invention relates to the field of power conversion and generator set output control technology, specifically to a control system and method capable of selectively generating single-phase output, three-phase output, first voltage output, and second voltage output. More particularly, it relates to an AC output control technology that achieves different phase systems and voltage levels by adjusting the voltage, frequency, and phase of multiple inverter output branches and reconstructing the electrical connections between each inverter output branch and the output port. This invention can be applied to variable frequency generator sets, fuel-fired generator sets, gas-fired generator sets, energy storage inverters, mobile power supplies, backup power supplies, and uninterruptible power supplies (UPS). Background Technology

[0002] Variable frequency generator sets typically first rectify the electrical energy generated by the prime mover-driven generator, and then use an inverter to convert the direct current (DC) into alternating current (AC) with relatively stable frequency and voltage. As the application scenarios for generator sets increase, different electrical devices have different requirements for power supply phase system, voltage level, and output power. For example, some loads require single-phase AC, while some industrial loads require three-phase AC; different countries, regions, or types of electrical devices may also use different rated voltages. Therefore, variable frequency generator sets capable of handling single-phase output, three-phase output, low-voltage output, and high-voltage output have gradually emerged in the market.

[0003] Existing generator sets capable of switching between single-phase and three-phase output typically have multiple inverter output branches, and the connection relationship between each inverter output branch and the output terminals is changed through a universal transfer switch (also known as a multi-turn switch), a rotary combination switch, or other multi-contact mechanical switches. In three-phase output mode, each inverter output branch forms a corresponding phase line output; in single-phase output mode, the corresponding output branches need to be recombined so that multiple inverter output branches participate in single-phase power supply. To simultaneously complete the switching between phase lines, neutral lines, and multiple output terminals, the universal transfer switches used typically have a large number of layers, a large number of contacts, and a high current-carrying capacity.

[0004] The aforementioned mechanical switching structure requires connecting multiple high-current wires to the universal transfer switch, which not only increases the switch's size and occupies significant installation space on the generator set control panel, but also results in a large number of wiring harnesses, complex wiring, and cumbersome assembly procedures. When the number of output terminals or output modes increases, the number of contact layers and terminals of the universal transfer switch also needs to increase accordingly, easily leading to problems such as incorrect wiring connections, loose terminals, and difficulties in maintenance. Simultaneously, the main output current needs to pass through the mechanical switch contacts on the control panel; the contact resistance, temperature rise, insulation performance, and long-term mechanical wear of the switch contacts directly affect output reliability. In cases of load switching or asynchronous contact operation, arcing, transient inrush currents, or short-term abnormal connections at the output terminals may also occur.

[0005] For variable frequency generator sets that require two different rated voltages, existing technologies typically create different voltages by changing the series, parallel, or branch connections between the inverter output windings, inverter modules, or output terminals. Some solutions that can fully utilize the unit's power under different voltage modes require multi-wire output, isolated sampling circuits, or multiple voltage detection and control circuits, resulting in complex hardware structures and insulation designs, and higher manufacturing costs. Other cost-effective solutions may employ non-isolated sampling, power-sharing output, or separate control programs for different voltages, but these can easily lead to only some inverter branches operating under specific voltage modes, limiting the unit's actual usable power. Multiple control programs also increase the complexity of software adaptation, production configuration, and after-sales maintenance.

[0006] Furthermore, existing single-phase and three-phase switching structures and dual-voltage switching structures are typically designed separately, lacking unified coordination in output topology, sampling circuits, control programs, mechanical switches, and terminal configurations. When the same unit needs to simultaneously provide single-phase, three-phase, single-voltage, and dual-voltage output capabilities, multiple transfer switches or complex combined wiring structures are often required, further increasing control panel area, wiring harness quantity, assembly costs, and potential failure points. Some solutions also struggle to ensure the optimal utilization of each inverter output branch after switching between different output modes, thus failing to balance output power, switching safety, and operational reliability under different output modes.

[0007] Therefore, it is necessary to provide a new AC output control scheme that coordinates and controls the connection relationship between multiple inverter output branches and each AC output port without relying on large-volume, multi-layer, high-current universal transfer switches. This allows the same power supply equipment to form single-phase output, three-phase output, first voltage output, or second voltage output as needed, while taking into account power utilization, switching interlocking, operational reliability, wiring harness simplification, and control panel space utilization under different output modes. Summary of the Invention

[0008] The purpose of this invention is to provide a generator set output control scheme with clear structural boundaries and safe switching capability, so as to reduce the large volume, multi-layer high-current universal transfer switches and complex main circuit harnesses, and improve the power utilization rate under different output modes.

[0009] A first aspect of the present invention provides a single-phase and three-phase output switching control system. The system includes three inverter units, a single-phase output terminal L, a neutral line output terminal N, a first-phase output terminal U, a second-phase output terminal V, a third-phase output terminal W, three switching devices, a mode input unit, and a main controller. The first AC output terminals of the three inverter units are selectively connected to the single-phase output terminal L or the corresponding phase output terminals U, V, and W via corresponding switching devices. The second AC output terminals of the three inverter units are connected to the neutral line output terminal N. In single-phase output mode, the three inverter units are connected in parallel with the same frequency, amplitude, and phase; in three-phase output mode, the three inverter units have the same frequency and are sequentially 120° out of phase.

[0010] Preferably, the three inverter units have the same rated output power. Total permissible output power refers to the rated active power or rated apparent power that the system is allowed to continuously output under the same ambient temperature, the same continuous operating time, and a specified power factor. The total permissible output power is the same for single-phase output mode and three-phase output mode, or the difference between the two is no more than 10% of the smaller one.

[0011] A second aspect of the present invention provides a dual-voltage output switching control system. A first inverter unit has output terminals A1 and A2, and a second inverter unit has output terminals B1 and B2. The AC output sides of the two inverter units are electrically isolated from each other and there are no unintended conductive paths. The first voltage output port is composed of a low-voltage phase line terminal L and a neutral line terminal N, and the second voltage output port is composed of a first high-voltage terminal H1 and a second high-voltage terminal H2. In parallel connection, A1 and B1 are connected to L, and A2 and B2 are connected to N. The two inverter units output the first voltage with the same frequency, amplitude, and phase. In series connection, A2 and B1 are connected to form a series intermediate point M, A1 is connected to H1, and B2 is connected to H2. The two inverter units output the second voltage according to the polarity and phase relationship of the voltage vector addition.

[0012] As an alternative to the series connection, the two inverter units can share the neutral terminal N and form a 180° phase-separated output, creating a first voltage between each phase terminal and the neutral terminal N, and a second voltage between the two phase terminals. When switching from the phase-separated state to the parallel-connected state, the AC output should be stopped first, then the phase should be adjusted and the connection reconfigured.

[0013] A third aspect of the present invention provides a phase control and voltage combination output control system. The system includes three inverter groups and three intra-group switching units corresponding to the three inverter groups. Each inverter group includes two inverter units with their AC output sides isolated from each other. Each intra-group switching unit selects two corresponding inverter units to be connected in parallel or in series in phase to form a first voltage group output terminal or a second voltage group output terminal. The inter-group switching unit selects the corresponding terminals of the three inverter groups to be connected in parallel to a single-phase output port, or connects them to U, V, and W respectively and connects the common terminal to N to form a single-phase connection state or a three-phase connection state. Phase control selection and voltage selection are independent of each other, thereby forming four combination modes: single-phase first voltage, single-phase second voltage, three-phase first voltage, and three-phase second voltage.

[0014] A fourth aspect of the present invention provides an output switching control method. The main controller first reads and verifies the mode selection signal, and disconnects the current connection branch after reducing the output voltage or stopping the pulse width modulation drive. The target connection branch is only closed when it is confirmed that the original connection branch has been disconnected, the residual voltage at the relevant port is below a safety threshold, and the target branch meets the synchronization conditions. After confirming that the target branch is fully closed, an AC output is established according to a preset slope. In the event of contact sticking, abnormal switch status, incorrect connection, output asynchrony, or overcurrent, the system prohibits output and enters a protection state.

[0015] The beneficial effects of this invention are:

[0016] (1) The mode input unit only undertakes mode command input. The AC main output current is carried by the switching execution unit located near the inverter. This can eliminate or reduce the large volume and multi-layer universal transfer switch and increase the usable area of ​​the generator set control panel.

[0017] (2) By changing the connection relationship between the inverter output branch and the output terminal through the electronic control switching device, the length of the high current wire can be shortened, the number of round-trip wires and terminals between the panel and the inverter can be reduced, and the risk of assembly errors and loose terminals can be reduced.

[0018] (3) In single-phase output mode, the three inverter units are connected in parallel with the same frequency and phase. In three-phase output mode, the three inverter units output with a phase difference of 120° respectively, so that all inverter units participate in power supply in both phase control modes, thereby improving the power utilization rate of single-phase output mode.

[0019] (4) By using two inverter units isolated from each other on the AC output side for parallel, series or 180° phase-separated control, two inverter units can be used in both the first voltage mode and the second voltage mode, avoiding the situation where a single inverter unit powers a specific voltage mode.

[0020] (5) By using the disconnect-then-reconnect mechanism, residual voltage detection, synchronous detection, contact status feedback and soft-start control, the risk of short circuit, contact arc, inrush current and parallel circulating current during mode switching can be reduced.

[0021] (6) The control system can adapt to different power levels, different rated voltages and different output formats by changing software parameters, switching the number of devices and the configuration of the output terminals, and has good platformization and expansion capabilities. Attached Figure Description

[0022] Figure 1 This is a flowchart of the output mode safe switching method of the present invention.

[0023] Figure 2 This is a schematic diagram of single-phase and three-phase control principle according to an embodiment of the present invention.

[0024] Figure 3 This is a schematic diagram of a single-pressure and dual-pressure control principle according to an embodiment of the present invention. Detailed Implementation

[0025] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. The following embodiments are used to illustrate the structure, control conditions, and safe switching process of different output topologies. Whether the embodiments can be combined depends on the compatibility of their electrical connection conditions, insulation conditions, and control timing.

[0026] In this embodiment, the first voltage refers to the rated AC output voltage of a single inverter unit or the port voltage of two inverter units connected in parallel in phase; the second voltage refers to the AC voltage formed between the two outer terminals after two inverter units are connected in series or split 180°, with an amplitude greater than the first voltage. Both the first voltage output port and the second voltage output port are ports defined by two conductive terminals, and a single terminal is not used as a complete voltage output port.

[0027] Equal power means that under the same ambient temperature, the same continuous operating time and a specified power factor, the total allowable output power of single-phase output mode and three-phase output mode is the same, or the difference between the two is within a preset range; in this embodiment, the preset range can be set to no more than 10% of the smaller total allowable output power.

[0028] Example 1: System Overall Structure

[0029] This embodiment provides a generator set output switching control system. The system includes a power input unit, a DC bus, an inverter unit group, a switching execution unit, a mode input unit, a main controller, a status detection unit, a protection unit, and an AC output interface. The inverter unit group includes at least two inverter units capable of independently adjusting the output voltage, frequency, and phase; when the system forms a three-phase output, the number of inverter units is no less than three.

[0030] The power input unit is used to provide DC power to the inverter unit group. It may include a generator and rectifier circuit driven by an engine, or a battery pack, energy storage battery, fuel cell, photovoltaic DC power supply, or external DC power supply. Each inverter unit may be connected to the same DC bus or to independent DC power supply or rectifier branch.

[0031] Each inverter unit has a DC input terminal, a first AC output terminal, and a second AC output terminal, and includes a power switching circuit and an inverter control circuit. The power switching circuit can be a full-bridge inverter circuit, a half-bridge inverter circuit, or a multi-level inverter circuit; the power switching devices can be MOSFETs, IGBTs, silicon carbide power devices, or gallium nitride power devices. The specific topology should be matched with the neutral point connection method, DC side connection method, and output series-parallel connection method adopted.

[0032] When multiple inverter units share the same DC bus and their AC output terminals are not isolated, their output terminals may be connected in parallel or form a split-phase output only if the half-bridge, multi-bridge arm or other topology used allows the neutral point to be shared and there is no short circuit or common-mode loop through the DC bus.

[0033] When a second voltage is formed through physical series connection, the AC output sides of the two inverter units within the same series branch should be electrically isolated from each other, and no unintended conductive path should be formed between them through the DC input side, protective ground, sampling circuit, or communication circuit. The required isolation can be achieved using independent rectifier windings, isolated DC / DC converter stages, isolation transformers, or independent DC power supplies.

[0034] In this embodiment, "electrical isolation between the AC output sides" means that, with all switching contacts used to form a series connection open and both inverter units stopped outputting, there is no direct metallic conductive connection between any AC output terminal of the first inverter unit and any AC output terminal of the second inverter unit for continuously transmitting load current. The two AC output circuits can be powered by independent rectifier windings, isolated DC / DC converter stages, isolation transformers, or independent DC power supplies. The drive power supply, status sampling, and communication connections associated with the two AC output circuits can be electrically isolated using isolated power supplies, isolation amplifiers, optocouplers, digital isolators, or isolated communication transceivers. Protective ground can be connected to the chassis, shielding layer, or surge protection device according to electrical safety requirements, but this protective ground connection must not create a connection between the working conductors of the two AC output circuits that can bypass a predetermined series path and continuously transmit load current.

[0035] In this embodiment, "unintended conductive path" refers to a low-impedance current path formed through a shared DC bus, rectifier winding, protective ground, non-isolated sampling circuit, non-isolated drive power supply, communication ground, or other conductors, excluding the series intermediate point, parallel node, or other predetermined connection established by the switching execution unit according to the target output mode. This current path may bypass the predetermined series branch, clamp the AC output terminal potential, cause a short circuit, or generate a circulating current between the two inverter units that cannot be limited by the main controller. The minute leakage current or transient coupling formed by safety capacitors, surge protectors, insulation monitoring circuits, and high-impedance sampling networks under normal insulation conditions does not belong to the aforementioned unintended conductive path, but its leakage current should be lower than the preset insulation judgment threshold and should not affect the voltage vector superposition, output regulation, and fault protection of the two inverter units.

[0036] Electrical isolation conditions can be confirmed through at least one of circuit structure review and electrical testing. As a testing method, after the switching execution unit is fully disconnected, each inverter unit is de-energized, and the energy storage element has been released, a preset insulation test voltage is applied between the AC output circuit of the first inverter unit and the AC output circuit of the second inverter unit, and the insulation resistance, leakage current, or withstand voltage is detected. If the insulation resistance is not less than a preset insulation resistance threshold, the test leakage current is not greater than a preset leakage current threshold, and no breakdown or flashover occurs within the preset withstand voltage and duration, the two AC output circuits are deemed to meet the electrical isolation conditions. The preset insulation resistance threshold, preset leakage current threshold, preset withstand voltage, and duration are determined based on the rated operating voltage, insulation category, pollution level, and applicable electrical safety requirements; for example, the preset insulation resistance threshold can be set to 1 MΩ or higher, but this value is only an optional example.

[0037] When the inverter structure does not meet the physical series connection condition, the two AC outputs are not directly connected in series. Instead, a 180° phase-separated control with a shared neutral point or an additional isolation conversion stage is used. This avoids short circuits between different implementations due to incompatibility of DC-side reference points or common-mode paths.

[0038] The main controller is connected to the inverter unit group, mode input unit, switching execution unit, status detection unit and protection unit respectively. It is used to determine the target output mode according to the mode input signal, control the output voltage, output frequency, output phase and output current of each inverter unit, and control the switching execution unit to change the electrical connection relationship between each inverter unit and the AC output interface.

[0039] The mode input unit is used to receive output mode selection commands from users or higher-level control devices. The mode input unit can be a two- or multi-position rocker switch, rotary switch, button, touchscreen, DIP switch, or a communication module that receives control commands via CAN, LIN, RS485, Ethernet, wireless communication interface, or other communication interfaces. The mode input unit is only used to transmit low-current control signals and does not handle the AC main output current.

[0040] The status detection unit includes one or more of the following: voltage detection circuit, current detection circuit, frequency detection circuit, phase detection circuit, temperature detection circuit, and switch status detection circuit. The current detection circuit can use a current transformer, Hall sensor, shunt resistor, or fluxgate sensor; the voltage detection circuit can use an isolation transformer, optocoupler isolation sampling, isolation amplifier, resistor voltage divider sampling, or a combination thereof.

[0041] The protection unit is used to perform one or more of the following protection functions: overvoltage protection, undervoltage protection, overcurrent protection, short circuit protection, overtemperature protection, phase loss protection, phase sequence error protection, frequency anomaly protection, inverter unit asynchrony protection, relay contact sticking protection, and mode conflict protection. When a fault is detected, the main controller stops the drive signal of at least one inverter unit and puts the switching execution unit into a disconnected state or a preset safe state.

[0042] Example 2: Single-phase and three-phase equal power switching

[0043] In this embodiment, the second output terminals of the three inverter units are connected to the neutral line output terminal N. The first output terminals of the three inverter units are respectively connected to the common terminal of the first switching device, the second switching device, and the third switching device. Each switching device includes three-phase side contacts and single-phase side contacts.

[0044] The three-phase contacts of the first switching device are connected to the first phase output terminal U, the three-phase contacts of the second switching device are connected to the second phase output terminal V, and the three-phase contacts of the third switching device are connected to the third phase output terminal W. The single-phase contacts of the three switching devices are interconnected and connected together to the single-phase output terminal L.

[0045] In three-phase output mode, the main controller controls three switching devices to connect their corresponding three-phase side contacts, connecting the first inverter unit to the first-phase output terminal U, the second inverter unit to the second-phase output terminal V, and the third inverter unit to the third-phase output terminal W. The main controller controls the three inverter units to output AC voltages with the same frequency and amplitude, or AC voltages with phases differing by 120° according to a preset ratio, thereby forming a three-phase AC output between the U, V, and W output terminals.

[0046] When the effective value of the phase voltage of each inverter unit is V0, the effective value of the line voltage V_LL between any two phase output terminals can be determined according to the following formula:

[0047] VLL=√3×V0

[0048] With the loads of each phase basically balanced, all three inverter units participate in power supply, and the total allowable output power Ptotal of the system can reach or approach the sum of the rated output power of the three inverter units:

[0049] Ptotal = 3 × P0

[0050] In single-phase output mode, the main controller controls three switching devices to disconnect the corresponding three-phase side contacts and connect the corresponding single-phase side contacts, so that the first output terminals of the three inverter units are connected to the single-phase output terminal L, and the second output terminals of the three inverter units are connected to the neutral line output terminal N. The main controller controls the three inverter units to output with the same frequency and amplitude and to remain in phase, so that the three inverter units form a parallel output.

[0051] To suppress circulating current between parallel inverter units, the main controller also performs current sharing control. Current sharing control can employ master-slave current sharing, average current sharing, droop control, virtual impedance control, or power distribution control based on a communication bus. For example, if the output currents of the three inverter units are denoted as I1, I2, and I3 respectively, the average output current I_avg is determined according to the following formula:

[0052] Iavg = (I1 + I2 + I3) / 3

[0053] The main controller adjusts the modulation signal of each inverter unit according to the difference between I1, I2 and I3 and I_avg, so that the difference between the output current of each inverter unit and the average output current is kept within the allowable range.

[0054] Before implementing parallel connection, the effective voltage difference between each inverter unit can be controlled within 5% of the rated voltage, the frequency difference within 0.1Hz, and the phase difference within 5°. These values ​​are optional examples and can be adjusted according to inverter capacity, parallel control accuracy, and load type.

[0055] In single-phase output mode, all three inverter units supply power to the single-phase load between the L and N terminals. Therefore, the total allowable single-phase output power of the system can reach or approach 3×P0. The rated currents of the single-phase output terminal L, the neutral output terminal N, the connecting busbar, the wiring harness, and the protection devices should be selected according to the combined output current of the three inverter units.

[0056] In an alternative configuration, the second outputs of the three inverter units are not directly fixedly connected, but are instead connected to the neutral line via bipolar relays or bipolar contactors. This configuration allows for switching the neutral line while switching the phase lines, making it suitable for applications requiring complete output isolation, floating ground output, or different neutral point connection methods for different modes.

[0057] In another alternative structure, the first to third switching devices can be replaced by a three-pole double-throw contactor or a set of contactors with mechanical interlocking relationships. As long as the three inverter units can be connected to the U, V, and W terminals respectively in the three-phase output state, and connected in parallel with the L terminal in the same phase in the single-phase output state, the technical effect of this embodiment can be achieved.

[0058] like Figure 2As shown, this embodiment provides a single-phase output and three-phase output switching control structure. This structure includes three controllers, a control system, transfer switches 1, 2, and 3 located within the inverter, and neutral output terminal N, single-phase output terminal L, first-phase output terminal U, second-phase output terminal V, third-phase output terminal W, and transfer switches located outside the inverter. The three controllers are connected to the control system via control connection lines labeled 1, 2, and 3, respectively, forming AC output terminals L1 and N1, L2 and N2, and L3 and N3, respectively. The three AC output terminals N1, N2, and N3 are all connected to the neutral output terminal N, and the three AC output terminals L1, L2, and L3 are connected to the common contact 2 of transfer switches 1, 2, and 3, respectively. Contact 1 of changeover switch 1 is connected to the single-phase output terminal L, and contact 3 is connected to the first-phase output terminal U; contact 1 of changeover switch 2 is connected to the single-phase output terminal L, and contact 3 is connected to the second-phase output terminal V; contact 1 of changeover switch 3 is connected to the single-phase output terminal L, and contact 3 is connected to the third-phase output terminal W. Changeover switches 1, 2, and 3 are connected to the control system via switching control circuits marked 4, 5, and 6, respectively, so that the control system can control the common contact 2 of each changeover switch to selectively connect with contact 1 or contact 3. The switching switch includes single-phase program contacts, three-phase program contacts, and a GND common terminal, and is connected to the control system via mode signal lines marked 7 and 8. When the switching switch selects the single-phase program, the control system controls the three controllers to output AC voltages with the same frequency, amplitude, and phase, and controls the common contact 2 of the three switching switches to conduct with the corresponding contact 1, so that the AC output terminals L1, L2, and L3 are connected to the single-phase output terminal L, and the AC output terminals N1, N2, and N3 are connected to the neutral output terminal N, thus forming a parallel single-phase output of the three controllers. When the switching switch selects the three-phase program, the control system controls the three controllers to output AC voltages with the same frequency and phases differing by 120°, and controls the common contact 2 of the three switching switches to conduct with the corresponding contact 3, so that the AC output terminals L1, L2, and L3 are connected to the first phase output terminal U, the second phase output terminal V, and the third phase output terminal W, respectively, and the AC output terminals N1, N2, and N3 are still connected to the neutral output terminal N, thus forming a three-phase four-wire AC output. During mode switching, the control system first controls the three controllers to reduce the output voltage or stop the AC output, and then controls the transfer switches 1, 2 and 3 to disconnect the current connection and switch to the target connection position. After confirming that each transfer switch has acted in place, the control system sets the output voltage, output frequency and output phase of the three controllers according to the target output mode, and gradually restores the AC output to reduce the risk of contact arcing, inrush current, output short circuit and parallel circulating current.

[0059] This embodiment does not limit the number of inverter units to three. When the number of inverter units is n, different inverter units can form multiple output branches with a preset phase difference in multi-phase output mode, and all or some inverter units can be connected in parallel in the same phase in single-phase output mode. For a three-phase system, each phase can also be composed of two or more inverter units connected in parallel.

[0060] Example 3: Dual-voltage series-parallel output

[0061] This embodiment uses two inverter units, each with a rated output voltage of V0 and a rated output power of P0, as an example. The first inverter unit has output terminals A1 and A2, and the second inverter unit has output terminals B1 and B2. The AC output sides of the two inverter units are electrically isolated from each other, and there are no unintended conductive paths between them formed through the DC input side, protective ground, sampling circuit, or communication circuit.

[0062] The switching execution unit includes multiple electrically and / or mechanically interlocked switching contacts, and has both parallel and series connection states. In the parallel connection state, output terminals A1 and B1 are connected to form the low-voltage phase line terminal L, and output terminals A2 and B2 are connected to form the neutral line terminal N. The main controller controls the two inverter units to operate at the same frequency, amplitude, and phase, and uses current sharing control to ensure that the two inverter units share the load. At this time, the first voltage output port formed by terminals L and N outputs V0, and the system allows the output power to reach or approach 2×P0.

[0063] In series connection mode, the switching execution unit connects output terminal A2 and output terminal B1 to form a series intermediate point M, connects output terminal A1 to the first high voltage terminal H1, and connects output terminal B2 to the second high voltage terminal H2. The main controller controls the two inverter units to operate according to the polarity and phase relationship of voltage vector addition, so that the second voltage output port formed by terminals H1 and H2 outputs approximately 2×V0, and the system allows the output power to still reach or approach 2×P0.

[0064] The series neutral point M can serve as an internal connection point or as the external neutral terminal. For example, with V0 equal to 120V, approximately 120V can be provided between H1 and M, and between M and H2, while approximately 240V can be provided between H1 and H2. For other applications, V0 can also be 110V, 115V, 220V, 230V, or other rated voltages.

[0065] When the series intermediate point M is used as the neutral terminal for output, the main controller can detect the load current of the H1 to M branch and the M to H2 branch respectively. When the load imbalance of the two low-voltage branches exceeds the preset value, the main controller can reduce the total output power, issue a load adjustment prompt, or disconnect the branch with the larger load to prevent overload of a single inverter unit.

[0066] In this embodiment, the load imbalance degree is used to characterize the difference in load borne by the first branch between the first high-voltage terminal H1 and the series midpoint M, and the second branch between the series midpoint M and the second high-voltage terminal H2. The main controller obtains the effective current value I1 of the first branch and the effective current value I2 of the second branch within the same sampling period, and can calculate the current imbalance rate according to DI = |I1 - I2| / max(I1, I2) × 100%. When both I1 and I2 are less than the preset minimum load current Imin, DI can be set to zero or the imbalance protection can be temporarily suspended to avoid misjudgment caused by light-load sampling noise. Alternatively, the main controller can also calculate the power imbalance rate according to DP = |P1 - P2| / max(P1, P2) × 100% based on the active power P1 and P2 of the two branches. The term "load imbalance degree" as used herein includes the current imbalance rate, power imbalance rate, or a parameter that can equivalently reflect the load difference between the two branches.

[0067] The preset value for the load imbalance degree can be set according to the rated current, allowable temperature rise, and continuous operating capability of a single inverter unit, for example, it can be set to 10% to 30%. To avoid malfunctions caused by the instantaneous connection of the load or the start-up impact, the main controller can perform sliding averaging, low-pass filtering, or duration determination on I1, I2, P1, and P2, and take protective measures only after the load imbalance degree continuously exceeds the preset value for a preset determination time. The branch with a larger load refers to the branch with a larger effective value of current or active power within the preset determination time; reducing the total output power can be achieved by reducing the common power limit of the two inverter units, and cutting off the branch with a larger load can be achieved by controlling the corresponding branch switch to disconnect or stop the AC output of the inverter unit supplying power to the corresponding branch.

[0068] In an alternative implementation, instead of forming a second voltage through physical series connection, the two inverter units share a neutral point, and the phase outputs of the two inverter units are controlled to be 180° out of phase. The voltages of both phase terminals relative to the neutral point are both V0, and the voltage between the two phase terminals is approximately 2 × V0, thereby forming a split-phase dual-voltage output.

[0069] In the first voltage full-power output mode, the two inverter units are first stopped from outputting, then they are adjusted to be in phase, and the corresponding terminals of the same polarity are connected in parallel to the first voltage output port through the switching execution unit. Thus, both inverter units can participate in power supply in both the first and second voltage modes, avoiding the reduction in output power caused by using only one inverter unit in the first voltage mode.

[0070] For structures where the AC output side is not isolated or where there is a common DC bus conductive path between the two inverter branches, the above direct series scheme is not adopted. In this case, a high-frequency isolation transformer, a power frequency isolation transformer, an independent DC power supply, or an isolated DC / DC converter stage can be added, or a 180° phase-separated control method with a shared neutral point can be used to form a second voltage.

[0071] like Figure 3As shown, this embodiment provides a dual-voltage output switching control structure. This structure is located inside the inverter and includes a controller 1, a controller 2, a control system, a transfer switch, and a switching switch. It is externally connected to sockets 1, 2, and 3. Controller 1 has AC output terminals L and N, and controller 2 has AC output terminals L1 and N1. Controller 1 and controller 2 are connected to the control system via control connection lines marked 1 and 2, respectively, so that the control system coordinates the output voltage, output frequency, and output phase of the two controllers. The transfer switch is located on the AC output lines between controller 1, controller 2, and each socket, and is connected to the control system via a switching control line marked 3. The control system changes the electrical connection between the AC output terminals L1 and N1 of controller 2, the AC output terminals L and N of controller 1, and each socket by controlling contacts 1, 2, and 3 of the transfer switch. In single-voltage output mode, the control system controls controllers 1 and 2 to output AC voltages of the same frequency, amplitude, and phase, and sets the changeover switch to the corresponding parallel connection position, so that the two controllers jointly provide a single-phase first voltage to the corresponding socket. In dual-voltage output mode, the control system adjusts the output phase relationship of controllers 1 and 2, and sets the changeover switch to the corresponding dual-voltage connection position, so that the output terminals of the two controllers form a phase-separated or voltage vector superposition connection relationship, so that some sockets are provided with the first voltage, and a second voltage higher than the first voltage is formed between the corresponding terminals of socket 1. The changeover switch includes a single-voltage program contact, a dual-voltage program contact, and a GND common terminal, and is connected to the control system through signal lines marked 4 and 5. When the changeover switch selects a single-voltage program or a dual-voltage program, the control system recognizes the corresponding mode selection signal and controls the two controllers and the changeover switch to operate according to the preset switching sequence. During mode switching, the control system first reduces or stops the AC output of controller 1 and controller 2, controls the changeover switch to disconnect the current connection, and switches to the target connection after confirming that the contacts have been disconnected. Then, the voltage, frequency and phase parameters of the two controllers are set according to the target mode, and the AC output is gradually restored to reduce the risk of short circuit, inrush current, contact arc or parallel circulating current during the switching process.

[0072] Example 4: Single-phase, three-phase and dual-voltage combined output

[0073] This embodiment provides a system capable of utilizing the power of all inverter units in four combined output modes. The system includes a first inverter group 301, a second inverter group 302, and a third inverter group 303. Each inverter group includes two inverter units with a rated output voltage of V0 and a rated output power of P0, and their AC output sides are isolated from each other, for a total of six inverter units. The system's output interfaces include a single-phase first voltage output port consisting of a single-phase phase line terminal L and a neutral line output terminal N; a single-phase second voltage output port consisting of a first high voltage terminal H1 and a second high voltage terminal H2; a first phase output terminal U; a second phase output terminal V; a third phase output terminal W; and a neutral line output terminal N.

[0074] Two inverter units in the same inverter group can be connected in parallel or in series under the control of the intra-group switching unit; three inverter groups can form three-phase output or single-phase parallel output under the control of the inter-group switching unit.

[0075] In the single-phase first voltage mode, the two inverter units in each inverter group are connected in parallel in phase. The first set of output terminals of the three inverter groups are connected in parallel to the single-phase phase line terminal L, and the second set of output terminals of the three inverter groups are connected in parallel to the neutral line output terminal N. The single-phase first voltage output port composed of the L terminal and the N terminal outputs voltage V0. All six inverter units participate in the output, and the total allowable output power of the system can reach or approach 6×P0.

[0076] In single-phase second voltage mode, two inverter units in each inverter group are connected in series to form a second voltage group output port with an output voltage of approximately 2×V0. The three inverter groups maintain the same frequency and phase. The first set of output terminals of the three second voltage group output ports are connected in parallel to the first high voltage terminal H1, and the second set of output terminals of the three second voltage group output ports are connected in parallel to the second high voltage terminal H2. The single-phase second voltage output port formed by terminals H1 and H2 outputs approximately 2×V0. All six inverter units participate in the output, and the total allowable output power of the system can reach or approach 6×P0.

[0077] In the three-phase first voltage mode, the two inverter units in each inverter group are connected in parallel with the same phase. The first set of output terminals of the three inverter groups are connected to the first phase output terminal U, the second phase output terminal V, and the third phase output terminal W, respectively. The second set of output terminals of the three inverter groups are connected to the neutral line output terminal N. The output phases of the three inverter groups are 120° apart. Each phase is shared by two inverter units, and the total allowable output power of the system can reach or approach 6×P0.

[0078] In the three-phase second voltage mode, two inverter units in each inverter group are connected in series, making the phase voltage of each phase approximately 2×V0. The first set of output terminals of the three inverter groups are connected to the first phase output terminal U, the second phase output terminal V, and the third phase output terminal W, respectively. The second set of output terminals of the three inverter groups are connected to the neutral line output terminal N. The output phases of the three inverter groups differ by 120° sequentially. When a star connection is used, the three-phase line voltage VLL can reach approximately 2√3×V0. All six inverter units participate in the output, and the total allowable output power of the system can reach or approach 6×P0.

[0079] Table 1 Connection Status of Different Output Modes

[0080] Target pattern Intra-group connection status Inter-group connection status Output phase and port relationship Single-phase first voltage Two inverter units in each group are connected in parallel with the same phase. The three inverters are connected in parallel with corresponding terminals. The three inverters operate in phase and frequency, outputting to the LN. Single-phase second voltage Two inverter units in each group are connected in series. The three inverters are connected in parallel with corresponding terminals. The three inverters operate in phase and frequency, outputting to H1-H2. Three-phase first voltage Two inverter units in each group are connected in parallel with the same phase. The three inverters are connected to U, V, and W respectively. The three inverter groups are sequentially phased by 120°, and their common terminal is connected to N. Three-phase second voltage Two inverter units in each group are connected in series. The three inverter groups are connected to U, V, and W respectively. The three inverter groups are sequentially phased by 120°, and their common terminal is connected to N.

[0081] The main controller stores the switch state matrix corresponding to Table 1. Hardware electrical interlocks and / or mechanical interlocks are set between parallel contacts and series contacts within the same group, and between single-phase contacts and three-phase contacts. Incompatible contacts must not be closed simultaneously at any time.

[0082] In a simplified structure, the series-parallel switching unit within each inverter group can be omitted. Instead, the inverter units can directly generate AC voltages of different amplitudes by changing the DC bus voltage, pulse width modulation ratio, transformer turns ratio, or multi-level output state. In this case, the switching execution unit is mainly used to change the output topology between single-phase parallel connection and three-phase independent connection.

[0083] In another configuration, there are three inverter units, each with its own low-voltage and high-voltage output terminals, or switchable transformer taps. The main controller achieves single-voltage and dual-voltage switching by selecting different output terminals or transformer taps, and single-phase and three-phase switching by changing the phase relationship of the three inverter units and the connection relationship of their output terminals.

[0084] Example 5: Safe Method for Switching Output Modes

[0085] like Figure 1 As shown, the method of the present invention includes the following process.

[0086] S101, the main controller reads the mode selection signal output by the mode input unit, and performs debouncing and validity confirmation on the mode selection signal by means of duration judgment, repeated sampling or multi-channel signal verification.

[0087] S102, the main controller generates a switching command based on the current output mode and the target output mode, and determines whether the current load current, output power, output voltage, and system temperature meet the switching conditions. When the load current exceeds the allowable load switching threshold, the main controller refuses to switch, issues an unloading prompt, or first controls the main output contactor to disconnect the load.

[0088] S103, the main controller reduces the output voltage of each inverter unit or stops the pulse width modulation drive signal of each inverter unit, so that the AC output current drops below a preset current threshold. Preferably, before switching the execution unit, the residual voltage at the relevant output terminal is reduced to less than 10% of the rated voltage or below a preset safety voltage.

[0089] S104, the main controller controls the switching contact corresponding to the current mode to disconnect and sets a disconnection delay time, so that incompatible connections form a disconnect-then-make switching process. The disconnection delay time can be from 20ms to 1000ms, preferably from 50ms to 500ms, or it can be determined according to the actual release time of the switching device.

[0090] S105: The main controller confirms that the original connection has been broken through auxiliary contacts, voltage detection, or current detection. If contact sticking or abnormal voltage is detected, the target contact is prohibited from being connected, and the system enters fault protection mode.

[0091] S106: With each inverter unit maintaining stopped pulse width modulation drive or safe low voltage output, and the residual voltage at the relevant output terminals lower than the preset safe voltage, the main controller controls the corresponding intra-group switching contacts and inter-group switching contacts to close according to the target output mode, and then checks the actual state of the target contacts again. Hardware electrical interlocks and mechanical interlocks are used to prevent series contacts from closing simultaneously with parallel contacts, single-phase contacts from closing simultaneously with three-phase contacts, or high-voltage contacts from closing simultaneously with low-voltage contacts.

[0092] S107: After confirming that the intra-group switching contacts and inter-group switching contacts corresponding to the target mode are all closed, the main controller sets the target voltage, target frequency, target phase, and current sharing parameters of each inverter unit according to the target output mode. In the first voltage parallel mode, the target phase difference between the two inverter units in the same inverter group is set to zero and the current sharing parameters are enabled; when the second voltage is formed by physical series connection, the voltage vector summation relationship of the two inverter units is set according to the polarity of the series terminals; when the second voltage is formed by phase separation, the target phase difference between the two inverter units is set to 180°; in single-phase mode, the three inverter groups are made to be in phase and at the same frequency; in three-phase mode, the output phases of the three inverter groups are made to be 120° apart sequentially.

[0093] S108: The main controller performs a soft start, gradually increasing the output voltage of each inverter unit or gradually increasing the output power according to a preset slope, and monitoring the output current during the soft start. Parallel circulating current is monitored only when inverter units are connected in parallel in the target mode. If the detection result is normal, the main output contactor is activated or the load is allowed to operate.

[0094] S109 continuously monitors the voltage, current, temperature, frequency, and phase of each inverter unit during system operation. When it detects asynchronous inverter unit outputs, parallel circulating current exceeding a threshold, output phase loss, relay malfunction, or output connection inconsistencies with the target mode, it stops outputting and records the fault information.

[0095] In one implementation that allows for rapid switching, the solid-state switch can be controlled by utilizing the AC voltage zero-crossing point or the current zero-crossing point without completely stopping the inverter unit output. However, live switching is only permitted after the main controller has confirmed that the voltage amplitude, frequency, and phase between the branches to be connected meet the synchronization conditions.

[0096] Example 6: Alternative methods for switching execution units and controllers

[0097] The switching execution unit can be an electromagnetic relay, power relay, magnetic latching relay, AC contactor, mechanical interlocking contactor, solid-state relay, bidirectional thyristor, bidirectional silicon controlled rectifier, reverse series MOSFET, reverse series IGBT, or a hybrid switch formed by combining mechanical contacts and semiconductor switches.

[0098] When using electromagnetic relays or contactors, the rated operating voltage, rated operating current, contact gap, insulation withstand voltage, and electrical life of the relay or contactor should match the maximum output voltage and maximum output current of the generator set. For contacts responsible for mode switching, a break-before-make structure is preferred.

[0099] When using solid-state switches, switching can occur at voltage or current zero-crossing points, reducing arcing and mechanical wear. The heat sink and rated current of the solid-state switch should be determined based on conduction losses and ambient temperature. When using a hybrid structure combining mechanical contacts and solid-state switches, the solid-state switch can handle the current during switching, while the mechanical contacts handle the main current during stable operation.

[0100] The main controller can be a standalone microcontroller, digital signal processor, field-programmable gate array, or programmable logic controller, or it can be integrated into any inverter controller. Multiple inverter units can communicate with each other via a wired communication bus to exchange phase reference and current sharing information, or they can maintain synchronization through a common synchronization signal, phase-locked loop, or local detection.

[0101] When a distributed control structure is adopted, one inverter unit can be set as the master inverter unit, and the remaining inverter units can be set as slave inverter units; alternatively, multiple inverter units can dynamically determine the master inverter unit through priority arbitration. When the master inverter unit fails, the other inverter units can re-determine the master inverter unit or enter a shutdown protection state.

[0102] Example 7: Alternatives to the output interface and protection structure

[0103] AC output interfaces may include single-phase sockets, three-phase sockets, low-voltage sockets, high-voltage sockets, terminals, aviation plugs, or fixed terminal blocks. Single-phase and three-phase interfaces can be provided simultaneously, or they can share some output terminals and be distinguished by a mechanical anti-misplugging structure.

[0104] Different output interfaces can be configured with circuit breakers, fuses, residual current devices, overcurrent protectors, or electronic current limiting circuits. The main controller can automatically adjust the protection thresholds according to the current mode. For example, when three inverter units are connected in parallel to form a single-phase output, the protection threshold of the single-phase total output terminal can be set according to the combined allowable current of the three inverter units; when there is a three-phase output, the protection threshold of each phase can be set according to the rated current of the corresponding inverter unit.

[0105] The neutral conductor can be fixed, switchable, floating, or grounded. Whether the neutral conductor is connected to the protective ground can be determined based on the generator set application scenario and corresponding electrical safety requirements. This invention is not limited to any particular neutral conductor grounding method.

[0106] To prevent incorrect switching due to mode input unit failure, two independent mode signals can be used for consistency verification, or different resistance values ​​can be set in the mode switch, allowing the main controller to identify different gears by detecting analog voltage. For communication control, command check codes, timeout protection, and local priority control can be configured.

[0107] The system will disable output when a relay coil open circuit, contact sticking, output voltage inconsistent with the target mode, or phase sequence error is detected. Fault information can be output to the user or host device via indicator lights, display screen, buzzer, communication interface, or fault codes.

[0108] Example 8: Generalized Alternative Approach

[0109] In the above embodiments, the relay can be replaced by any electronically controlled switching device that can controllably change the AC output connection relationship; the inverter unit can be an independent inverter or multiple power bridge arms or power modules that are independently controlled within the same inverter; the mode switch can be replaced by any local or remote control input.

[0110] The two voltage levels are not limited to 120V and 240V; they can also be 110V and 220V, 115V and 230V, 220V and 380V, 230V and 400V, or other rated voltage combinations. When using a series or 180° phase-splitting configuration, the second voltage is typically approximately twice the first voltage; other predetermined ratios can be achieved when using switchable transformer taps or multi-level conversion structures.

[0111] This invention does not limit the requirement to set all output modes simultaneously. Depending on product requirements, only single-phase to three-phase switching function, only low voltage to high voltage switching function, or any two or more of the following modes can be set simultaneously: single-phase low voltage, single-phase high voltage, three-phase low voltage, and three-phase high voltage.

[0112] The above embodiments are used to illustrate the structure and control process of the present invention. Conventional substitutions for specific device models, rated voltages, rated power, and communication methods should satisfy the electrical isolation, synchronization, interlocking, and disconnect-before-make conditions explicitly stated in this specification; the scope of protection of the present invention is defined by the claims.

Claims

1. A generator set output switching control system, characterized in that, It includes a first inverter unit, a second inverter unit, a third inverter unit, an output interface, a switching execution unit, a mode input unit, and a main controller; The output interface includes a single-phase output terminal L, a neutral line output terminal N, a first-phase output terminal U, a second-phase output terminal V, and a third-phase output terminal W. The switching execution unit includes a first switching device, a second switching device, and a third switching device. Each switching device has a common terminal, a single-phase side contact, and a three-phase side contact. The first AC output terminals of the first inverter unit, the second inverter unit, and the third inverter unit are respectively connected to the common terminal of the corresponding switching device. The three single-phase side contacts are commonly connected to the single-phase output terminal L. The three three-phase side contacts are respectively connected to the first phase output terminal U, the second phase output terminal V, and the third phase output terminal W. The second AC output terminals of the three inverter units are connected to the neutral line output terminal N. The mode input unit is used to receive the phase selection signal of single-phase output mode or three-phase output mode; The main controller is connected to the three inverter units, the switching execution unit, and the mode input unit, respectively. In the single-phase output mode, the main controller controls the three inverter units to output AC voltages with the same frequency, amplitude, and phase, and controls the single-phase side contacts of the three switching devices to close and the three-phase side contacts to open, so that the three inverter units are connected in parallel between the single-phase output terminal L and the neutral line output terminal N. In the three-phase output mode, the main controller controls the three inverter units to output AC voltages with the same frequency and phases that are 120° apart, and controls the single-phase side contacts of the three switching devices to open and the three-phase side contacts to close, so that the three inverter units are connected to the first phase output terminal U, the second phase output terminal V, and the third phase output terminal W, respectively.

2. The generator set output switching control system according to claim 1, characterized in that, The three inverter units have the same rated output power; the total allowable output power refers to the rated active power or rated apparent power that the system is allowed to continuously output under the same ambient temperature, the same continuous operating time and the specified power factor; the total allowable output power in the single-phase output mode is the same as the total allowable output power in the three-phase output mode, or the difference between the two is not greater than 10% of the smaller one.

3. The generator set output switching control system according to claim 1, characterized in that, The main controller is used to perform at least one of master-slave current sharing control, average current sharing control, droop control, virtual impedance control and communication-based power distribution control in the single-phase output mode; the main controller is also used to adjust the output voltage, output frequency and output phase of the three inverter units before they are connected in parallel, so that the voltage difference, frequency difference and phase difference between any two inverter units are less than the corresponding preset synchronization thresholds.

4. The generator set output switching control system according to claim 1, characterized in that, It also includes a status detection unit, which is used to detect at least one of the output voltage, output current, output frequency and output phase of the three inverter units, and to detect the actual switching status of each switching device by means of auxiliary contacts or by means of the voltage and current on both sides of the switching execution unit; the main controller only controls the contacts corresponding to the target mode to close after confirming that the contacts corresponding to the current mode have been opened and the inverter branch to be connected meets the synchronization conditions.

5. A generator set dual-voltage output switching control system, characterized in that, It includes a first inverter unit, a second inverter unit, an output interface, a switching execution unit, and a main controller; The first inverter unit has a first AC output terminal A1 and a second AC output terminal A2, and the second inverter unit has a first AC output terminal B1 and a second AC output terminal B2; the AC output sides of the two inverter units are electrically isolated from each other, and there is no unintended conductive path between them through the DC input side, protective ground, sampling circuit or communication circuit; The output interface includes a first voltage output port consisting of a low-voltage phase line terminal L and a neutral line terminal N, and a second voltage output port consisting of a first high-voltage terminal H1 and a second high-voltage terminal H2. The switching execution unit has a parallel connection state and a series connection state. In the parallel connection state, the first AC output terminal A1 and the first AC output terminal B1 are connected to the low voltage phase line terminal L, and the second AC output terminal A2 and the second AC output terminal B2 are connected to the neutral line terminal N. The main controller controls the two inverter units to operate at the same frequency, amplitude, and phase to output a first voltage at the first voltage output port. In the series connection state, the second AC output terminal A2 and the first AC output terminal B1 are connected to form a series intermediate point M. The first AC output terminal A1 is connected to the first high voltage terminal H1, and the second AC output terminal B2 is connected to the second high voltage terminal H2. The main controller controls the two inverter units to operate according to the polarity and phase relationship of the vector addition of the output voltages to output a second voltage greater than the first voltage at the second voltage output port.

6. The generator set dual-voltage output switching control system according to claim 5, characterized in that, The series intermediate point M is led out as the neutral line terminal. The first voltage is formed between the first high voltage terminal H1 and the series intermediate point M, and between the series intermediate point M and the second high voltage terminal H2. The main controller detects the load current of the two first voltage branches respectively, and reduces the total output power, issues a load adjustment prompt, or cuts off the branch with the larger load when the load imbalance of the two branches exceeds a preset value.

7. The generator set dual-voltage output switching control system according to claim 5, characterized in that, The switching execution unit also has a phase-separated connection state; in the phase-separated connection state, the first AC output terminal A1 is connected to the first high voltage terminal H1, the second AC output terminal B2 is connected to the second high voltage terminal H2, and the second AC output terminal A2 and the first AC output terminal B1 are connected to the neutral line terminal N; the main controller controls the first inverter unit to output the first voltage between the first high voltage terminal H1 and the neutral line terminal N, and controls the second inverter unit to output the first voltage between the second high voltage terminal H2 and the neutral line terminal N, the two first voltages are 180° out of phase, so as to form the second voltage between the first high voltage terminal H1 and the second high voltage terminal H2; when switching from the phase-separated connection state to the parallel connection state, the main controller first stops the AC output of the two inverter units, then adjusts the phase difference between them to zero and connects the corresponding terminals of the same polarity in parallel.

8. A generator set phase control and voltage combined output control system, characterized in that, It includes a first inverter group, a second inverter group, and a third inverter group, three intra-group switching units, an inter-group switching unit, an output interface, a mode input unit, and a main controller, each corresponding to one of the three inverter groups; The output interface includes a single-phase first voltage output port consisting of a single-phase phase line terminal L and a neutral line output terminal N, a single-phase second voltage output port consisting of a first high voltage terminal H1 and a second high voltage terminal H2, a first phase output terminal U, a second phase output terminal V, a third phase output terminal W, and the neutral line output terminal N; each inverter group includes two inverter units with their AC output sides electrically isolated from each other; each group switching unit is used to connect two inverter units in the corresponding inverter group in parallel in the same phase under the first voltage connection state to form a first voltage group output port with a first group output terminal and a second group output terminal, and to connect two inverter units in the corresponding inverter group in series under the second voltage connection state to form a second voltage group output port with a first group output terminal and a second group output terminal. The inter-group switching unit is used to connect the first group output terminals of the three first voltage group output ports in parallel to the single-phase phase line terminal L in single-phase first voltage mode, and connect the second group output terminals of the three first voltage group output ports in parallel to the neutral line output terminal N. In single-phase second voltage mode, the first set of output terminals of the three second voltage group output ports are connected in parallel to the first high voltage terminal H1, and the second set of output terminals of the three second voltage group output ports are connected in parallel to the second high voltage terminal H2; in three-phase connection mode, the first set of output terminals of the three inverter groups are respectively connected to the first phase output terminal U, the second phase output terminal V and the third phase output terminal W, and the second set of output terminals of the three inverter groups are connected together to the neutral line output terminal N; The mode input unit is used to receive independent phase selection signals and voltage selection signals; the main controller selects a single-phase connection state or a three-phase connection state according to the phase selection signal, and selects a first voltage connection state or a second voltage connection state according to the voltage selection signal, thereby forming one of the single-phase first voltage mode, the single-phase second voltage mode, the three-phase first voltage mode, and the three-phase second voltage mode; in the single-phase connection state, the three inverter groups maintain the same frequency and phase, and in the three-phase connection state, the output phases of the three inverter groups differ by 120° sequentially.

9. A generator set output switching control method, applied to a power supply equipment comprising three inverter groups, an intra-group switching unit, an inter-group switching unit, an output interface, and a main controller, wherein each inverter group comprises two inverter units, characterized in that, include: Acquire the phase selection signal and voltage selection signal, and determine the target output mode from the single-phase first voltage mode, single-phase second voltage mode, three-phase first voltage mode and three-phase second voltage mode accordingly; Control each inverter unit to reduce its output voltage or stop its AC output, disconnect the intra-group connection branch and inter-group connection branch corresponding to the current output mode, and confirm that the intra-group connection branch and the inter-group connection branch have been disconnected. When the target output mode is the first voltage mode, the two inverter units in each inverter group are controlled to be connected in parallel with the same phase; when the target output mode is the second voltage mode, the two inverter units in each inverter group are controlled to be connected in series. When the target output mode is a single-phase mode, the three inverter groups are controlled to operate at the same frequency and phase, and their corresponding output terminals are connected in parallel to the single-phase output port; when the target output mode is a three-phase mode, the output phases of the three inverter groups are controlled to be 120° apart and connected to the three phase output terminals respectively. After confirming that both the intra-group switching unit and the inter-group switching unit are in the actual switching state corresponding to the target output mode, each inverter unit is controlled to establish AC output according to a preset rising slope.

10. The generator set output switching control method according to claim 9, characterized in that, Before disconnecting the connection branch corresponding to the current output mode, the output current is detected, and mode switching is prohibited or the main output switch is controlled to disconnect the load when the output current is greater than the preset load switching threshold; disconnect-then-make switching is performed after the residual voltage at the relevant output terminal is lower than the preset safety voltage; AC output is prohibited when contact sticking, abnormal switch status, or actual electrical connection relationship is inconsistent with the target output mode is detected; overcurrent detection is performed when no abnormality is detected, and parallel circulating current detection is performed only when the target output mode includes two or more inverter units connected in parallel.

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