Hybrid inverter

Abstract

The invention discloses a hybrid inverter, and relates to the technical field of power electronics. And the energy storage loop and the bridge arm main switch tube branch are connected in parallel, two ends of the energy storage loop and the bridge arm main switch tube branch are connected with a power supply, and the energy storage loop and the bridge arm main switch tube branch are used for providing stable direct-current bus voltage and absorbing voltage ripples through charging and discharging to stabilize the direct-current bus voltage at a target value so as to provide stable direct-current energy input. And the input end of the bridge arm auxiliary switch tube branch is grounded and is connected with a middle reference point of the energy storage loop. And the half-BUS bus voltage in split-phase or two-phase power grid types can be realized conveniently. The output end of the bridge arm main switch tube branch and the output end of the bridge arm auxiliary switch tube branch are connected with the two ends of the follow current loop. In this way, a loop is formed through the middle reference point of the energy storage loop and the middle reference point of the load in the split-phase or two-phase power grid type. The hybrid inverter can adapt to the flexibility requirement in a multi-standard power grid or hybrid load scene, equipment resources are fully utilized, and the equipment cost is saved.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, and in particular to a hybrid inverter. Background Technology

[0002] The inverter only supports one of the following grid types: single-phase, two-phase, or split-phase. If the load type changes, it cannot be adapted through software upgrades or simple hardware adjustments. The entire inverter must be replaced, resulting in a waste of equipment resources. It has poor flexibility and limited use in multi-system grids or mixed load scenarios.

[0003] Therefore, how to improve the grid type adaptability of inverters while saving inverter costs is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0004] The purpose of this application is to provide a hybrid inverter to solve the problems of low adaptability, limited use, and wasted equipment resources caused by inverters supporting only one type of power grid in conventional solutions.

[0005] To solve the above-mentioned technical problems, this application provides a hybrid inverter, including an energy storage circuit, a freewheeling circuit, a bridge arm main switch branch, and a bridge arm auxiliary switch branch connected in parallel at both ends of the bridge arm main switch branch;

[0006] The energy storage circuit and the main switch branch of the bridge arm are connected in parallel, and both ends are connected to the power supply; the input end of the auxiliary switch branch of the bridge arm is grounded and connected to the intermediate reference point of the energy storage circuit; the output ends of the main switch branch of the bridge arm and the output ends of the auxiliary switch branch of the bridge arm are both connected to the two ends of the freewheeling circuit; the other two ends of the freewheeling circuit are connected to the load, and the intermediate reference point of the load is grounded.

[0007] Specifically, in the case of a split-phase or two-phase power grid, the switching transistors of the main switch branch and the auxiliary switch branch of the bridge arm are controlled to turn on and off, and the freewheeling device of the freewheeling circuit is used to output the corresponding voltage; in the case of a single-phase power grid, the switching transistors of the main switch branch of the bridge arm are controlled to turn on and off, and the freewheeling device of the freewheeling circuit is used to output the corresponding voltage.

[0008] On one hand, the energy storage circuit includes a first capacitor and a second capacitor, and each of the main switch branch and the auxiliary switch branch of the bridge arm is connected in parallel with a diode; the main switch branch of the bridge arm includes a first switch, a second switch, a third switch, and a fourth switch; the auxiliary switch branch of the bridge arm includes a fifth switch, a sixth switch, a seventh switch, and an eighth switch; the freewheeling device of the freewheeling circuit includes a first inductor and a second inductor;

[0009] The first terminal of the first capacitor is connected to the positive terminal of the power supply and is connected to the collector of the first switching transistor and the collector of the second switching transistor; the second terminal of the first capacitor is connected to the first terminal of the second capacitor and is connected to the collector of the fifth switching transistor and the collector of the seventh switching transistor, and is grounded; wherein, there is an intermediate reference point between the first capacitor and the second capacitor, and it is grounded.

[0010] The emitter of the fifth switch is connected to the emitter of the sixth switch, and the emitter of the seventh switch is connected to the emitter of the eighth switch.

[0011] The emitter of the first switch, the collector of the sixth switch, the collector of the third switch, and the first terminal of the first inductor are connected; the emitter of the third switch is connected to the second terminal of the second capacitor; the emitter of the second switch, the collector of the eighth switch, the collector of the fourth switch, and the first terminal of the second inductor are connected; the emitter of the fourth switch is connected to the second terminal of the second capacitor.

[0012] The second end of the first inductor is connected to the first end of the first resistor; the second end of the first resistor is connected to the first end of the second resistor; the second end of the second resistor is connected to the second end of the second inductor; wherein, there is an intermediate reference point between the first resistor and the second resistor, and it is grounded.

[0013] On the other hand, when the grid type is split phase or two phase, a control mode combining half BUS bus and hybrid inverter port phase voltage is adopted to control the switching tubes of the main switch tube branch of the bridge arm and the auxiliary switch tube branch of the bridge arm to turn on and off, and combine the freewheeling device of the freewheeling circuit to output the corresponding voltage.

[0014] When the grid is a single-phase grid, a control mode combining the full BUS bus and the hybrid inverter port line voltage is adopted to control the switching transistors of the main switching transistor branch of the bridge arm to turn on and off, and to output the corresponding voltage in conjunction with the freewheeling device of the freewheeling circuit.

[0015] On the other hand, in the case of split-phase or two-phase power grids, a control mode combining the half-bus and hybrid inverter port phase voltage is adopted to control the switching transistors of the main switch branch and the auxiliary switch branch of the bridge arm to turn on and off, and to output the corresponding voltage in conjunction with the freewheeling device of the freewheeling circuit, including:

[0016] During the positive half-cycle of phase A, the first switch is turned on, and the other switches are turned off, allowing current to flow from the first capacitor through the first switch and the first inductor to the power grid; the first switch is turned off, and the fifth switch is turned on, allowing the first inductor to freewheel, and the current returns to the first inductor through the diodes corresponding to the fifth and sixth switches, thus completing the voltage output of phase A;

[0017] During the negative half-cycle of phase A, the third switch is turned on, and all other switches are turned off, allowing current to flow from the second capacitor through the first inductor and the third switch to the power grid; the third switch is turned off, and the sixth switch is turned on, allowing the first inductor to freewheel, and the current returns to the first inductor through the diodes corresponding to the sixth and fifth switches, thus completing the voltage output of phase A.

[0018] During the positive half-cycle of phase B, the second switch is turned on, and all other switches are turned off, allowing current to flow from the first capacitor through the second switch and the second inductor to the power grid; the second switch is turned off, and the seventh switch is turned on, allowing the second inductor to freewheel. The current returns to the second inductor through the diodes corresponding to the seventh and eighth switches, completing the voltage output of phase B.

[0019] During the negative half-cycle of phase B, the fourth switch is turned on, and all other switches are turned off, allowing current to flow from the second capacitor through the second inductor and the fourth switch to the power grid; the fourth switch is turned off, and the eighth switch is turned on, allowing the second inductor to freewheel, and the current returns to the second inductor through the diodes corresponding to the eighth and seventh switches, thus completing the voltage output of phase B.

[0020] In the case of a split-phase power grid, the phase angle interval between phase A and phase B is 180°, and in the case of a two-phase power grid, the phase angle interval between phase A and phase B is 120°.

[0021] On the other hand, in the case of a single-phase power grid, a control mode combining the full BUS bus and the hybrid inverter port line voltage is adopted to control the switching transistors of the main switching transistor branch of the bridge arm to turn on and off, and to output the corresponding voltage in conjunction with the freewheeling device of the freewheeling circuit, including:

[0022] During the positive half-cycle, the first and fourth switches are turned on, while the other switches are turned off, allowing current to flow from the first and second capacitors in series, through the first switch, the first inductor, the second inductor, and the fourth switch to the power grid. The first and fourth switches are turned off, and the fifth and eighth switches are turned on, allowing the first and second inductors to freewheel. The current then flows back to the first and second inductors through the diodes corresponding to the fifth and sixth switches, the first inductor, the second inductor, the eighth switch, and the diodes corresponding to the seventh switch, completing the single-phase voltage output.

[0023] During the negative half-cycle, the fifth and eighth switches are turned off, while the second and third switches are turned on, allowing current to flow from the first and second capacitors in series, through the second switch, the second inductor, the first inductor, and the third switch to the power grid. The second and third switches are turned off, while the sixth and seventh switches are turned on, allowing the first and second inductors to freewheel. The current then flows back to the first and second inductors through the diodes corresponding to the seventh and eighth switches, the second inductor, the first inductor, the sixth switch, and the diode corresponding to the fifth switch, completing the single-phase voltage output.

[0024] On the other hand, the hybrid inverter also includes a voltage detection circuit;

[0025] The first end of the voltage detection circuit is connected to the freewheeling circuit, and the second end is connected to the load.

[0026] The voltage detection circuit is used to identify split-phase and single-phase power grid types.

[0027] On the other hand, the voltage detection circuit includes a first diode and a third resistor;

[0028] The anode of the first diode is connected to the second terminal of the first inductor and the first terminal of the first resistor; the cathode of the first diode is connected to the first terminal of the third resistor; the second terminal of the third resistor is connected to the second terminal of the first resistor and the first terminal of the second resistor.

[0029] Alternatively, the first end of the third resistor is connected to the second end of the first resistor and the first end of the second resistor; the second end of the third resistor is connected to the cathode of the first diode; and the anode of the first diode is connected to the second end of the second resistor and the second end of the second inductor.

[0030] On the other hand, the process for identifying split-phase and single-phase power grid types includes:

[0031] The voltage at the first end of the first resistor, the voltage between the first resistor and the second resistor, and the voltage at the second end of the second resistor are respectively taken as the first voltage, the second voltage, and the third voltage;

[0032] Detect whether the voltage waveforms of the first voltage and the third voltage are symmetrical; if the waveforms are symmetrical, then it is determined to be a split-phase power grid type.

[0033] If the waveform is asymmetrical, it is determined to be a single-phase power grid type.

[0034] On the other hand, the hybrid inverter also includes a filter circuit, which includes a third capacitor and a fourth capacitor;

[0035] The first terminal of the third capacitor is connected to the second terminal of the first inductor and the first terminal of the first resistor; the second terminal of the third capacitor, the second terminal of the first resistor, the first terminal of the second resistor, and the first terminal of the fourth capacitor are interconnected and grounded;

[0036] The second terminal of the fourth capacitor is connected to the second terminal of the second inductor and the second terminal of the second resistor.

[0037] On the other hand, in the case of a split-phase or two-phase power grid, the triggering process for the switching on and off of the main switch branch and the auxiliary switch branch of the bridge arm includes:

[0038] Collect the fundamental frequency of the grid voltage and the carrier wave obtained from the switching frequency;

[0039] During the positive half-cycle, and when the carrier amplitude is less than the fundamental frequency, the first switch is turned on and the other switches are turned off; when the carrier amplitude is greater than the fundamental frequency, the first switch is turned off and the fifth switch is turned on.

[0040] During the negative half-cycle, and when the carrier amplitude is less than the fundamental frequency, the third switch is turned on and the other switches are turned off; when the carrier amplitude is greater than the fundamental frequency, the third switch is turned off and the sixth switch is turned on.

[0041] On the other hand, in the case of a single-phase power grid, the triggering process for controlling the on / off switching of the main switch branch of the bridge arm includes:

[0042] Collect the fundamental frequency of the grid voltage and the carrier wave obtained from the switching frequency;

[0043] During the positive half-cycle, and when the carrier amplitude is less than the fundamental frequency, the first and fourth switches are turned on, and the remaining switches are turned off except for the first and fourth switches; when the carrier amplitude is greater than the fundamental frequency, the first and fourth switches are turned off, and the fifth and eighth switches are turned on.

[0044] During the negative half-cycle, and when the carrier amplitude is less than the fundamental frequency, the fifth and eighth switches are turned off, and the second and third switches are turned on; when the carrier amplitude is greater than the fundamental frequency, the second and third switches are turned off, and the sixth and seventh switches are turned on.

[0045] This application provides a hybrid inverter. First, the inverter circuit includes a bridge arm main switch branch and a bridge arm auxiliary switch branch connected in parallel across the bridge arm main switch branch. The bridge arm main switch branch is arranged in a vertical series configuration, and through alternating on and off, it inverts the DC bus voltage into AC voltage pulses. The bridge arm auxiliary switch branch is arranged in a horizontal parallel configuration, and works with the freewheeling device in the freewheeling circuit to achieve rapid freewheeling and suppress voltage spikes when the switch is turned off. Second, the energy storage circuit is connected in parallel with the bridge arm main switch branch, and both ends are connected to a power supply to provide a stable DC bus voltage. By absorbing voltage ripple through charging and discharging, the DC bus voltage is stabilized at the target value, thus providing a smooth DC energy input. The input terminal of the bridge arm auxiliary switch branch is grounded and connected to the intermediate reference point of the energy storage circuit. This facilitates the implementation of a half-bus voltage in split-phase or two-phase grid types, using the intermediate reference point as a common DC reference point to provide the energy source. Similarly, it does not affect the energy source provided by the full BUS bus voltage in single-phase grid types, achieving compatibility with different grid types. The output terminals of both the main switch branch and the auxiliary switch branch of the bridge arm are connected to both ends of the freewheeling circuit. Here, the freewheeling circuit provides a freewheeling path for the current, and the magnetic energy stored in the freewheeling device is released through the freewheeling circuit, suppressing voltage spikes and preventing the switch from being damaged by overvoltage breakdown. The remaining two ends of the freewheeling circuit are connected to the load, and the intermediate reference point of the load is grounded. Thus, in split-phase or two-phase grid types, a loop is formed between the intermediate reference point of the energy storage circuit and the intermediate reference point of the load, achieving voltage waveform output for split-phase or two-phase grid types. Finally, in split-phase or two-phase grid types, the switches of the main switch branch and the auxiliary switch branch of the bridge arm are controlled to turn on and off, and the freewheeling device in the freewheeling circuit is used to output the corresponding voltage; in single-phase grid types, the switches of the main switch branch of the bridge arm are controlled to turn on and off, and the freewheeling device in the freewheeling circuit is used to output the corresponding voltage. By controlling the switching transistors of the hybrid inverter, modulation methods for different power grid types can be achieved to adapt to multiple power grid types. Using a single hybrid inverter can meet the flexibility requirements of multi-system power grids or mixed load scenarios, making full use of equipment resources and saving equipment costs. Attached Figure Description

[0046] To more clearly illustrate the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0047] Figure 1 This is a schematic diagram of the structure of a hybrid inverter provided in an embodiment of this application;

[0048] Figure 2 A schematic diagram of the positive half-cycle energy storage current flow in a split-phase or two-phase power grid type provided in this application embodiment;

[0049] Figure 3 A schematic diagram of the positive half-cycle freewheeling current flow direction in a split-phase or two-phase power grid type is provided for embodiments of this application;

[0050] Figure 4 A schematic diagram of the negative half-cycle energy storage current flow in a split-phase or two-phase power grid type is provided for an embodiment of this application;

[0051] Figure 5 A schematic diagram of the flow direction of the negative half-cycle freewheeling current in a split-phase or two-phase power grid type is provided for embodiments of this application;

[0052] Figure 6 A schematic diagram of control logic for split-phase or two-phase power grids provided in this application embodiment;

[0053] Figure 7 This application provides a positive half-cycle control timing diagram for split-phase or two-phase power grid types.

[0054] Figure 8 This application provides a negative half-cycle control timing diagram for split-phase or two-phase power grid types.

[0055] Figure 9 This application provides a schematic diagram of the positive half-cycle energy storage current flow direction for a single-phase power grid type.

[0056] Figure 10 This application provides a schematic diagram of the positive half-cycle freewheeling current flow direction for a single-phase power grid type.

[0057] Figure 11 This application provides a schematic diagram of the negative half-cycle energy storage current flow direction for a single-phase power grid type.

[0058] Figure 12 This application provides a schematic diagram of the flow direction of the negative half-cycle freewheeling current in a single-phase power grid type.

[0059] Figure 13 A schematic diagram of control logic for a single-phase power grid type is provided in an embodiment of this application;

[0060] Figure 14 A positive half-cycle control timing diagram for a single-phase power grid type is provided as an embodiment of this application;

[0061] Figure 15 A negative half-cycle control timing diagram for a single-phase power grid type is provided as an embodiment of this application;

[0062] Figure 16 A schematic diagram of voltage waveforms under single-phase and split-phase power grid types is provided for embodiments of this application;

[0063] Figure 17 A waveform diagram of a split-phase power grid provided in an embodiment of this application;

[0064] Figure 18 A waveform diagram with an interval range of 2 under a single-phase power grid provided as an embodiment of this application;

[0065] Figure 19 This is a waveform diagram with an interval range of 0.25 under a single-phase power grid, provided as an embodiment of this application. Detailed Implementation

[0066] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of this application.

[0067] The core of this application is to provide a hybrid inverter to solve the problems of low adaptability, limited use, and wasted equipment resources caused by inverters only supporting one type of power grid in conventional solutions.

[0068] To enable those skilled in the art to better understand the present application, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0069] Conventional single-grid inverters only support one of the following: single-phase, two-phase, or split-phase. This results in incompatibility with geographical regions and grid systems, limited scenario adaptability, and complete failure when faced with loads of mixed voltage and phase. This necessitates either abandoning some load requirements or adding additional transformers and converters, increasing system complexity. The hybrid inverter provided in this application solves these technical problems.

[0070] Figure 1 This is a schematic diagram of the structure of a hybrid inverter provided in an embodiment of this application, as shown below. Figure 1 As shown, it includes an energy storage circuit 1, a freewheeling circuit 2, a bridge arm main switch tube branch 3, and a bridge arm auxiliary switch tube branch 4 connected in parallel at both ends of the bridge arm main switch tube branch 3.

[0071] Energy storage circuit 1 and bridge arm main switch branch 3 are connected in parallel, and both ends are connected to the power supply; the input end of bridge arm auxiliary switch branch 4 is grounded and connected to the intermediate reference point of energy storage circuit 1; the output ends of bridge arm main switch branch 3 and bridge arm auxiliary switch branch 4 are both connected to the two ends of freewheeling circuit 2; the other two ends of freewheeling circuit 2 are connected to the load, and the intermediate reference point of the load is grounded.

[0072] Specifically, in the case of a split-phase or two-phase power grid, the switching transistors of the main switch branch 3 and the auxiliary switch branch 4 of the control arm are turned on and off, and the freewheeling device of the freewheeling circuit 2 is used to output the corresponding voltage; in the case of a single-phase power grid, the switching transistors of the main switch branch 3 of the control arm are turned on and off, and the freewheeling device of the freewheeling circuit 2 is used to output the corresponding voltage.

[0073] Specifically, the energy storage circuit is used for DC-side voltage regulation and filtering, providing a stable, low-ripple DC bus voltage for the subsequent inverter bridge. It is a key intermediate circuit connecting the preceding DC source and the subsequent inverter stage. The energy storage circuit can consist solely of a bus (BUS) capacitor, such as an electrolytic or film capacitor, or it can be an LC filter circuit or an energy storage-enhanced filter circuit. The BUS capacitor in the capacitor filter circuit has a simple structure and is suitable for small to medium power inverters; its core function is to filter out high-frequency ripple. The inductor-capacitor (LC) filter circuit uses a BUS capacitor and a DC filter inductor, resulting in a stronger filtering effect, simultaneously suppressing voltage and current ripple, making it suitable for medium to high power applications. The energy storage-enhanced filter circuit uses a BUS capacitor plus a supercapacitor / small energy storage battery, strengthening energy buffering capabilities and suitable for inverters with large load fluctuations or weak power grids.

[0074] The freewheeling circuit acts as an energy transfer station in the circuit: when the switch is on, the inductor absorbs and stores energy from the DC bus; when the switch is off, the inductor releases energy through the freewheeling circuit, thereby achieving controllable energy transfer (e.g., current shaping when driving an inverter bridge, voltage rise and fall during DC-DC conversion). It cannot work independently and must form a topology with a switch and a freewheeling diode to function. Its goal is to stabilize the current waveform during power conversion, suppress current ripple caused by switching actions, and control the energy transfer rate to ensure stable power output to the downstream load or the power grid.

[0075] The freewheeling device in a freewheeling circuit can be an inductor. Without an inductor, the sudden current change at the moment the switch is turned off would cause a voltage spike, exceeding the switch's withstand voltage and directly damaging the device. The inductor's characteristic of not allowing sudden current changes maintains current flow through the freewheeling circuit when the switch is turned off, preventing the impact of current interruption.

[0076] The main switch branches of the bridge arm are arranged in a vertical series configuration, undertaking the main power conversion of the inverter. They achieve DC-AC power conversion through the alternating conduction of the upper and lower switches. The auxiliary switch branches of the bridge arm are arranged in a horizontal parallel configuration in the topology diagram. Through parallel connection with the main switch branches, they achieve current shunting, power expansion, or auxiliary freewheeling. When the current-carrying capacity of a single vertical switch is insufficient, parallel horizontal switches achieve current sharing, increasing the total output current of the bridge arm. Auxiliary freewheeling: In some topologies, the auxiliary switch branches of the bridge arm can work with inductors to achieve rapid freewheeling, suppressing voltage spikes when the switches are turned off. The switching sequence of the auxiliary switch branches of the bridge arm is usually synchronized with the corresponding main switch branches of the bridge arm to enhance power.

[0077] The energy storage circuit and the main switch branch of the bridge arm are connected in parallel, with both ends connected to the power supply. Voltage fluctuations exist at the DC input of the inverter. The charging and discharging of the capacitors in the energy storage circuit absorbs these voltage ripples, stabilizing the DC bus voltage at the target value (e.g., 300V), providing a stable DC energy input for the subsequent inverter bridge switches. When the load power increases, the energy storage circuit discharges to replenish energy; when the load power decreases, the energy storage circuit charges to store excess energy, preventing sudden voltage spikes or drops in the DC power supply due to power fluctuations.

[0078] The input terminal of the auxiliary switch branch of the bridge arm is grounded and connected to the intermediate reference point of the energy storage circuit. It should be noted that the intermediate reference point of the energy storage circuit is used to realize the bus voltage for split-phase, two-phase, or single-phase grid types for the inverter. If there is no intermediate reference point, it is the full bus voltage on the DC side; if an intermediate reference point exists, it is the half bus voltage on the DC side, thus realizing various grid types such as single-phase, split-phase, or two-phase.

[0079] The output terminals of both the main and auxiliary switching transistor branches of the bridge arm are connected to the two ends of the freewheeling circuit. The remaining two ends of the freewheeling circuit are connected to the load, and the intermediate reference point of the load is grounded. This provides a freewheeling path for the current, allowing the magnetic energy stored in the inductor to be released through the freewheeling circuit, suppressing voltage spikes and preventing the switching transistors from being damaged by overvoltage. After the common terminal of the main and auxiliary switching transistor branches of the bridge arm is connected to the freewheeling circuit, the freewheeling current can be shared by both branches (current sharing effect), preventing individual switching transistors from overheating and being damaged due to excessive current. This indirectly improves the total power carrying capacity of the bridge arm, allowing the inverter to adapt to larger power loads.

[0080] In the circuit structure described above, the switching transistors of the main switching transistor branch and the auxiliary switching transistor branch of the control arm are turned on and off, and the freewheeling device in the freewheeling circuit is used to output the corresponding voltage to achieve a split-phase or two-phase power grid type. Alternatively, the switching transistors of the main switching transistor branch of the control arm are turned on and off, and the freewheeling device in the freewheeling circuit is used to output the corresponding voltage to achieve a single-phase power grid type.

[0081] This application provides a hybrid inverter. First, the inverter circuit includes a bridge arm main switch branch and a bridge arm auxiliary switch branch connected in parallel across the bridge arm main switch branch. The bridge arm main switch branch is arranged in a vertical series configuration, and through alternating on and off, it inverts the DC bus voltage into AC voltage pulses. The bridge arm auxiliary switch branch is arranged in a horizontal parallel configuration, and works with the freewheeling device in the freewheeling circuit to achieve rapid freewheeling and suppress voltage spikes when the switch is turned off. Second, the energy storage circuit is connected in parallel with the bridge arm main switch branch, and both ends are connected to a power supply to provide a stable DC bus voltage. By absorbing voltage ripple through charging and discharging, the DC bus voltage is stabilized at the target value, thus providing a smooth DC energy input. The input terminal of the bridge arm auxiliary switch branch is grounded and connected to the intermediate reference point of the energy storage circuit. This facilitates the implementation of a half-bus voltage in split-phase or two-phase grid types, using the intermediate reference point as a common DC reference point to provide the energy source. Similarly, it does not affect the energy source provided by the full BUS bus voltage in single-phase grid types, achieving compatibility with different grid types. The output terminals of both the main switch branch and the auxiliary switch branch of the bridge arm are connected to both ends of the freewheeling circuit. Here, the freewheeling circuit provides a freewheeling path for the current, and the magnetic energy stored in the freewheeling device is released through the freewheeling circuit, suppressing voltage spikes and preventing the switch from being damaged by overvoltage breakdown. The remaining two ends of the freewheeling circuit are connected to the load, and the intermediate reference point of the load is grounded. Thus, in split-phase or two-phase grid types, a loop is formed between the intermediate reference point of the energy storage circuit and the intermediate reference point of the load, achieving voltage waveform output for split-phase or two-phase grid types. Finally, in split-phase or two-phase grid types, the switches of the main switch branch and the auxiliary switch branch of the bridge arm are controlled to turn on and off, and the freewheeling device in the freewheeling circuit is used to output the corresponding voltage; in single-phase grid types, the switches of the main switch branch of the bridge arm are controlled to turn on and off, and the freewheeling device in the freewheeling circuit is used to output the corresponding voltage. By controlling the switching transistors of the hybrid inverter, modulation methods for different power grid types can be achieved to adapt to multiple power grid types. Using a single hybrid inverter can meet the flexibility requirements of multi-system power grids or mixed load scenarios, making full use of equipment resources and saving equipment costs.

[0082] In some embodiments, such as Figure 1As shown, the energy storage circuit 1 includes a first capacitor C1 and a second capacitor C2. Each of the main switch branch 3 and the auxiliary switch branch 4 of the bridge arm has a diode connected in parallel. The main switch branch 3 includes a first switch Q1, a second switch Q2, a third switch Q3, and a fourth switch Q4. The auxiliary switch branch 4 includes a fifth switch Q5, a sixth switch Q6, a seventh switch Q7, and an eighth switch Q8. The freewheeling circuit 2 includes a first inductor L1 and a second inductor L2.

[0083] The first terminal of the first capacitor C1 is connected to the positive terminal of the power supply and is connected to the collector of the first switch Q1 and the collector of the second switch Q2; the second terminal of the first capacitor C1 is connected to the first terminal of the second capacitor C2 and is connected to the collector of the fifth switch Q5 and the collector of the seventh switch Q7, and is grounded; wherein, there is an intermediate reference point between the first capacitor C1 and the second capacitor C2, and it is grounded.

[0084] The emitter of the fifth switch Q5 is connected to the emitter of the sixth switch Q6, and the emitter of the seventh switch Q7 is connected to the emitter of the eighth switch Q8.

[0085] The emitter of the first switch Q1, the collector of the sixth switch Q6, the collector of the third switch Q3, and the first terminal of the first inductor L1 are connected; the emitter of the third switch Q3 is connected to the second terminal of the second capacitor C2; the emitter of the second switch Q2, the collector of the eighth switch Q8, the collector of the fourth switch Q4, and the first terminal of the second inductor L2 are connected; the emitter of the fourth switch Q4 is connected to the second terminal of the second capacitor C2.

[0086] The second end of the first inductor L1 is connected to the first end of the first resistor R1; the second end of the first resistor R1 is connected to the first end of the second resistor R2; the second end of the second resistor R2 is connected to the second end of the second inductor L2; wherein, there is an intermediate reference point between the first resistor R1 and the second resistor R2, and it is grounded.

[0087] Specifically, the energy storage circuit uses a first capacitor and a second capacitor, with an intermediate reference point between them, which is grounded. This conforms to the split-phase or two-phase power grid type. The DC side of the split-phase inverter uses two equal capacitors connected in series to divide the full BUS bus voltage into two half-BUS voltages (e.g., full BUS = 400V → half BUS = 200V + 200V). The midpoint of the capacitor serves as the DC reference point for the common neutral line.

[0088] Each of the main and auxiliary switching transistors in the bridge arm is connected in parallel with a diode. This diode can be either the body diode of the transistor or an external freewheeling diode. Its function is to provide a freewheeling path, protect the transistor, and maintain continuous current. At the moment the transistor turns off, the inductor at the output terminal (freewheeling circuit) will generate a reverse electromotive force due to the inability of the current to change abruptly. Without a freewheeling diode, the reverse current would force the transistor to withstand extremely high voltage spikes. The freewheeling diode guides the reverse current to the DC bus / load circuit, clamping the voltage across the transistor and preventing overvoltage damage. During high-frequency switching of the transistor, the current in the load / inductor cannot be interrupted instantaneously. The freewheeling diode provides a continuous current path: after the transistor turns off, the magnetic energy stored in the inductor is released through the freewheeling diode, maintaining continuous load current. Combined with the freewheeling devices in the subsequent freewheeling circuit, the pulse current is smoothed into a sinusoidal AC current, ensuring the quality of the output power.

[0089] The type of switching transistor can be a transistor or other types; there are no restrictions here, and it can be set according to the actual situation.

[0090] Regarding the connection relationship between the switches in the main switch branch and the auxiliary switch branch of the bridge arm, the first and third switches are connected in series perpendicularly, and the second and fourth switches are connected in series perpendicularly. These two series-connected branches are then connected in parallel to form a dual-arm bridge. The midpoint of the series connection is the AC output voltage VA and VB. Through the alternating switching of "upper switch on, lower switch off" and "lower switch on, upper switch off", the DC bus voltage is inverted into AC voltage pulses (achieving DC to AC power conversion).

[0091] The fifth and sixth switching transistors are connected in parallel with the first switching transistor, and the seventh and eighth switching transistors are connected in parallel with the fourth switching transistor. Since the current carrying capacity of a single switching transistor is limited, current shunting is achieved by connecting multiple transistors in parallel.

[0092] After adding a freewheeling circuit, the switching transistors were protected, the output waveform was optimized, and the power redundancy of the bridge arm was enhanced.

[0093] The specific connection relationships of the hybrid inverter provided in this embodiment can realize multiple grid types such as split-phase, two-phase and single-phase in one inverter, thereby improving the applicability and versatility of the hybrid inverter.

[0094] In some embodiments, when the grid is split-phase or two-phase, a control mode combining the phase voltage of the hybrid inverter port with the half-bus is adopted to control the switching transistors of the main switch branch and the auxiliary switch branch of the bridge arm to turn on and off, and to output the corresponding voltage in combination with the freewheeling device of the freewheeling circuit.

[0095] When the grid is single-phase, a control mode combining the full BUS bus and the hybrid inverter port line voltage is adopted to control the switching transistors of the main switching transistor branch of the bridge arm to turn on and off, and to output the corresponding voltage in combination with the freewheeling device of the freewheeling circuit.

[0096] Specifically, in split-phase or two-phase power grid types, the full BUS bus is connected in series with two equal voltage divider resistors (first / second resistors) and a capacitor to form a half-BUS bus (e.g., 400V→200V+200V), with the midpoint of the resistors serving as the common reference point (neutral). Control logic: Based on the half-BUS voltage, the two bridge arms (main / auxiliary switch branches) are controlled using a phase-separated voltage control mode: by controlling the on / off sequence of the main / auxiliary switch transistors of the bridge arms, the two phase voltage amplitudes are made equal, with a phase difference of 180° (split-phase) or 120° (two-phase); the current is maintained continuously through a freewheeling circuit (freewheeling diode / inductor) to ensure a smooth phase voltage waveform.

[0097] In single-phase power grids, the midpoint connection of the voltage divider resistor is disconnected, and the entire BUS bus is used directly (without voltage division). Based on the full BUS voltage, a hybrid inverter port line voltage control mode is adopted, controlling only the on / off state of one set of bridge arm main switch branches: when the upper switch of the bridge arm is on, the positive half-cycle voltage is output, and when the lower switch is on, the negative half-cycle voltage is output; the freewheeling circuit, in conjunction with filtering, smooths the Pulse Width Modulation (PWM) pulses into a single-phase sinusoidal voltage.

[0098] This embodiment provides compatibility across different power grid types without requiring hardware replacement. Adaptation to different power grid types can be achieved simply by switching the control mode under the topology, thereby improving scenario coverage.

[0099] In some embodiments, when the grid type is split-phase or two-phase, a control mode combining the half-bus and hybrid inverter port phase voltage is adopted to control the switching transistors of the main switch branch and the auxiliary switch branch of the bridge arm to turn on and off, and to output the corresponding voltage in conjunction with the freewheeling device of the freewheeling circuit, including:

[0100] During the positive half-cycle of phase A, the first switch is turned on and the other switches are turned off, allowing current to flow from the first capacitor through the first switch and the first inductor to the power grid; the first switch is turned off and the fifth switch is turned on, allowing the first inductor to freewheel, and the current returns to the first inductor through the diodes corresponding to the fifth and sixth switches, thus completing the voltage output of phase A.

[0101] During the negative half-cycle of phase A, the third switch is turned on, and the other switches are turned off, allowing current to flow from the second capacitor through the first inductor and the third switch to the power grid; the third switch is turned off, and the sixth switch is turned on, allowing the first inductor to freewheel. The current returns to the first inductor through the diodes corresponding to the sixth and fifth switches, completing the voltage output of phase A.

[0102] During the positive half-cycle of phase B, the second switch is turned on and the other switches are turned off, allowing current to flow from the first capacitor through the second switch and the second inductor to the power grid; the second switch is turned off and the seventh switch is turned on, allowing the second inductor to freewheel, and the current returns to the second inductor through the diodes corresponding to the seventh and eighth switches, completing the voltage output of phase B.

[0103] During the negative half-cycle of phase B, the fourth switch is turned on, and the other switches are turned off, allowing current to flow from the second capacitor through the second inductor and the fourth switch to the power grid; the fourth switch is turned off, and the eighth switch is turned on, allowing the second inductor to freewheel. The current returns to the second inductor through the diodes corresponding to the eighth and seventh switches, completing the voltage output of phase B.

[0104] In the case of a split-phase power grid, the phase angle interval between phase A and phase B is 180°, and in the case of a two-phase power grid, the phase angle interval between phase A and phase B is 120°.

[0105] Specifically, taking the L1N phase (A phase) as an example, Figure 2 A schematic diagram illustrating the positive half-cycle energy storage current flow direction in a split-phase or two-phase power grid type, as provided in this application embodiment, is shown below. Figure 2 As shown, during the positive half-cycle, the first switch is turned on, and the other switches are turned off, so that the current flows from the first capacitor through the first switch and the first inductor to the power grid. Figure 3 A schematic diagram illustrating the flow direction of the positive half-cycle freewheeling current in a split-phase or two-phase power grid, as provided in this application embodiment, is shown below. Figure 3 As shown, the first switch is turned off and the fifth switch is turned on, allowing the first inductor to freewheel. The current returns to the first inductor through the diodes corresponding to the fifth and sixth switches, thus completing the voltage output of phase A.

[0106] Figure 4 A schematic diagram illustrating the flow direction of energy storage current during the negative half-cycle in a split-phase or two-phase power grid, as provided in this application embodiment, is shown below. Figure 4 As shown, during the negative half-cycle of phase A, the third switch is turned on, and the other switches are turned off, so that the current flows from the second capacitor through the first inductor and the third switch to the power grid. Figure 5A schematic diagram illustrating the flow direction of the negative half-cycle freewheeling current in a split-phase or two-phase power grid, as provided in this application embodiment, is shown below. Figure 5 As shown, the third switch is turned off and the sixth switch is turned on, allowing the first inductor to freewheel. The current returns to the first inductor through the diodes corresponding to the sixth and fifth switches, thus completing the voltage output of phase A.

[0107] Similarly, L2N also has energy storage and follow current during both positive and negative half-cycles.

[0108] This embodiment provides a control mode under split-phase or two-phase power grid types to achieve energy storage and freewheeling during the positive and negative half cycles, ensuring the realization of the functions of split-phase or two-phase power grid types.

[0109] In some embodiments, when the power grid is split-phase or two-phase, the triggering process for the switching of the main switch branch and the auxiliary switch branch of the bridge arm includes:

[0110] Collect the fundamental frequency of the grid voltage and the carrier wave obtained from the switching frequency;

[0111] During the positive half-cycle, and when the carrier amplitude is less than the fundamental frequency, the first switch is turned on and the other switches are turned off; when the carrier amplitude is greater than the fundamental frequency, the first switch is turned off and the fifth switch is turned on.

[0112] During the negative half-cycle, and when the carrier amplitude is less than the fundamental frequency, the third switch is turned on and the other switches are turned off; when the carrier amplitude is greater than the fundamental frequency, the third switch is turned off and the sixth switch is turned on.

[0113] It should be noted that the timing of the above control logic is determined by timing control. Figure 6 This application provides a schematic diagram of control logic for split-phase or two-phase power grids, as shown in the embodiments. Figure 6 As shown, the voltage is compared with the fundamental voltage waveform of the power grid (VA voltage waveform) during the positive and negative half-cycle carrier waves, respectively, to drive the first, fifth, sixth, and third switching transistors, thereby achieving control of the positive and negative half-cycles. Figure 6 In the first diagram from top to bottom, there are three waveforms: the top and bottom waveforms represent VC1 and VC2 respectively, and the middle one, which is a sine wave, is the A-phase voltage waveform. Figure 7 This application provides an embodiment of a positive half-cycle control timing diagram for split-phase or two-phase power grid types, such as... Figure 7As shown, during the positive half-cycle, VL1 is the carrier wave, and VC2 and VC1 are the fundamental waves. When the carrier wave amplitude is less than the fundamental wave of the same frequency, the first switch is turned on and the other switches are turned off. When the carrier wave amplitude is greater than the fundamental wave of the same frequency, the first switch is turned off and the fifth switch is turned on.

[0114] Figure 8 A negative half-cycle control timing diagram for split-phase or two-phase power grid types is provided in the embodiments of this application, such as... Figure 8 As shown, during the negative half-cycle, and when the carrier amplitude is less than the fundamental frequency, the third switch is turned on and the other switches are turned off; when the carrier amplitude is greater than the fundamental frequency, the third switch is turned off and the sixth switch is turned on.

[0115] This embodiment provides PWM control (typically sinusoidal pulse width modulation (SPWM)) that compares the carrier amplitude with the fundamental frequency to trigger the switching transistors. This enables energy storage and freewheeling during the positive and negative half-cycles of a split-phase / two-phase power grid. The fundamental frequency amplitude changes with the grid cycle (alternating between positive and negative half-cycles). The PWM control dynamically adjusts the duty cycle of the switching transistors: the upper transistor has a higher conduction ratio during the positive half-cycle, and the lower transistor has a higher conduction ratio during the negative half-cycle. The energy stored in the inductor and the freewheeling current are matched with the fundamental frequency amplitude, avoiding energy waste and improving the inverter's conversion efficiency. In addition, by matching the specific carrier frequency with the fundamental frequency phase, the voltage spike when the switching transistor is turned off is suppressed, the reverse recovery loss of the freewheeling diode is reduced, the device lifespan is extended, and the cost of the heat dissipation system is reduced.

[0116] In some embodiments, when the grid type is single-phase, a control mode combining the full BUS bus and the hybrid inverter port line voltage is adopted to control the switching transistors of the main switching transistor branch of the bridge arm to turn on and off, and to combine the freewheeling device of the freewheeling circuit to output the corresponding voltage, including:

[0117] During the positive half-cycle, the first and fourth switches are turned on, while the other switches are turned off. This allows current to flow from the first and second capacitors in series, through the first switch, the first inductor, the second inductor, and the fourth switch to the power grid. The first and fourth switches are turned off, while the fifth and eighth switches are turned on. This allows the first and second inductors to freewheel. The current then flows back to the first and second inductors through the diodes corresponding to the fifth and sixth switches, the first inductor, the second inductor, the eighth switch, and the diodes corresponding to the seventh switch, thus completing the single-phase voltage output.

[0118] During the negative half-cycle, the fifth and eighth switches are turned off, while the second and third switches are turned on, allowing current to flow from the first and second capacitors in series, through the second switch, the second inductor, the first inductor, and the third switch to the power grid. The second and third switches are turned off, while the sixth and seventh switches are turned on, allowing the first and second inductors to freewheel. The current then flows back to the first and second inductors through the diodes corresponding to the seventh and eighth switches, the second inductor, the first inductor, the sixth switch, and the diode corresponding to the fifth switch, completing the single-phase voltage output.

[0119] Specifically, Figure 9 This application provides a schematic diagram of the positive half-cycle energy storage current flow direction for a single-phase power grid type, as shown in the embodiment. Figure 9 As shown, during the positive half-cycle, the first and fourth switching transistors are turned on, while the other switching transistors are turned off, allowing current to flow from the first and second capacitors in series, through the first switching transistor, the first inductor, the second inductor, and the fourth switching transistor to the power grid. Figure 10 This application provides a schematic diagram of the positive half-cycle freewheeling current flow direction for a single-phase power grid type, as shown in the embodiment. Figure 10 As shown, the first and fourth switches are turned off, while the fifth and eighth switches are turned on, allowing the first and second inductors to freewheel. The current flows through the diodes corresponding to the fifth and sixth switches, the first inductor, the second inductor, the diodes corresponding to the eighth and seventh switches, and back to the first and second inductors, thus completing the single-phase voltage output.

[0120] Figure 11 This application provides a schematic diagram of the negative half-cycle energy storage current flow in a single-phase power grid type, as shown in the embodiment. Figure 11 As shown, during the negative half-cycle, the fifth and eighth switches are turned off, while the second and third switches are turned on, so that the current is output from the first and second capacitors in series, and flows to the power grid through the second switch, the second inductor, the first inductor, and the third switch. Figure 12 This application provides a schematic diagram of the negative half-cycle freewheeling current flow direction for a single-phase power grid type, as shown in the embodiment. Figure 12 As shown, the second and third switches are turned off, and the sixth and seventh switches are turned on, allowing the first and second inductors to freewheel. The current returns to the first and second inductors through the diodes corresponding to the seventh and eighth switches, the second inductor, the first inductor, the sixth switch, and the diodes corresponding to the fifth switch, thus completing the single-phase voltage output.

[0121] This embodiment provides a control mode under a single-phase power grid type to achieve energy storage and freewheeling during both positive and negative half-cycles, ensuring the realization of the functions of the single-phase power grid type.

[0122] In some embodiments, when the power grid is a single-phase type, the triggering process for controlling the on / off switching of the main switch branch of the control arm includes:

[0123] Collect the fundamental frequency of the grid voltage and the carrier wave obtained from the switching frequency;

[0124] During the positive half-cycle, and when the carrier amplitude is less than the fundamental frequency, the first and fourth switches are turned on, and the other switches are turned off; when the carrier amplitude is greater than the fundamental frequency, the first and fourth switches are turned off, and the fifth and eighth switches are turned on.

[0125] During the negative half-cycle, and when the carrier amplitude is less than the fundamental frequency, the fifth and eighth switches are turned off, and the second and third switches are turned on; when the carrier amplitude is greater than the fundamental frequency, the second and third switches are turned off, and the sixth and seventh switches are turned on.

[0126] It should be noted that the timing of the above control logic is determined by timing control. Figure 13 A control logic diagram for a single-phase power grid type is provided as an embodiment of this application, such as... Figure 13 As shown, during the positive and negative half-cycle carrier waves, the waveform is compared with the fundamental voltage of a single-phase power grid (VAB voltage waveform). Regarding the fundamental voltage of the single-phase power grid... Figure 13 The first image from top to bottom shows a sine wave waveform. This waveform drives the first, fourth, fifth, eighth, sixth, seventh, third, and second switches to achieve control of the positive and negative half-cycles. Figure 14 A positive half-cycle control timing diagram for a single-phase power grid type is provided as an embodiment of this application, such as... Figure 14 As shown, during the positive half-cycle, and when the carrier amplitude is less than the fundamental frequency, the first and fourth switches are turned on, and the other switches are turned off; when the carrier amplitude is greater than the fundamental frequency, the first and fourth switches are turned off, and the fifth and eighth switches are turned on.

[0127] Figure 15 A negative half-cycle control timing diagram for a single-phase power grid type is provided as an embodiment of this application, such as... Figure 15 As shown, during the negative half-cycle, and when the carrier amplitude is less than the fundamental frequency, the fifth and eighth switches are turned off, and the second and third switches are turned on; when the carrier amplitude is greater than the fundamental frequency, the second and third switches are turned off, and the sixth and seventh switches are turned on.

[0128] This embodiment uses SPWM control, which compares the carrier wave (high-frequency triangular wave) with the fundamental wave (single-phase sine wave), to trigger the switching transistors. This achieves energy storage and freewheeling during the positive and negative half-cycles of the single-phase power grid. The amplitude, frequency, and phase of the output voltage are highly matched with the single-phase power grid, ensuring stable power supply to the load and meeting the power quality requirements of grid connection. During the positive half-cycle, the fundamental wave amplitude is positive, and the conduction ratio of the upper transistor dynamically changes with the fundamental wave amplitude (the conduction ratio is highest at the peak). During the negative half-cycle, the fundamental wave amplitude is negative, and the conduction ratio of the lower transistor changes synchronously. The inductor's energy storage / freewheeling energy is precisely matched with the fundamental wave demand, reducing redundant energy losses and improving the inverter's conversion efficiency.

[0129] In some embodiments, the hybrid inverter further includes a voltage detection circuit;

[0130] The first terminal of the voltage detection circuit is connected to the freewheeling circuit, and the second terminal is connected to the load.

[0131] Voltage detection circuits are used to identify split-phase and single-phase power grid types.

[0132] Figure 16 A voltage waveform diagram for single-phase and split-phase power grid types is provided for embodiments of this application, as shown below. Figure 16 As shown, the voltage waveforms (VA and VB waveforms) are completely identical under both single-phase and split-phase power grid types, making identification impossible. Considering the 180° phase difference between LAN and LBN in a split-phase power grid, the phase difference between LAN and LBN is also 180° when LA and LB are connected in a single-phase power grid, preventing the software from correctly identifying the power grid type. Therefore, a voltage detection circuit needs to be added. Figure 1 As shown, the first end of the voltage detection circuit 5 is connected to the freewheeling circuit 2, and the second end is connected to the load.

[0133] The voltage detection circuit provided in this embodiment can identify split-phase and single-phase power grids without the need for manual mode switching. The voltage detection circuit can identify the current power grid type in real time, avoiding hardware damage caused by incorrect power grid connection, enhancing safety protection, and improving the accuracy of power grid type identification.

[0134] In some embodiments, the voltage detection circuit includes a first diode and a third resistor;

[0135] The anode of the first diode is connected to the second terminal of the first inductor and the first terminal of the first resistor; the cathode of the first diode is connected to the first terminal of the third resistor; the second terminal of the third resistor is connected to the second terminal of the first resistor and the first terminal of the second resistor.

[0136] Alternatively, the first end of the third resistor is connected to the second end of the first resistor and the first end of the second resistor; the second end of the third resistor is connected to the cathode of the first diode; and the anode of the first diode is connected to the second end of the second resistor and the second end of the second inductor.

[0137] Specifically, such as Figure 1 As shown, the voltage detection circuit 5 includes a first diode D1 and a third resistor R3, which can be connected in parallel across the first resistor R1 or across the second resistor R2; no limitation is made here. Its core principle is to utilize the difference between the two-phase voltage difference of a split-phase power grid and the single-phase voltage characteristics of a single-phase power grid to achieve identification. Using only a diode and resistor circuit, without complex sensors or chips, it can distinguish between split-phase and single-phase power grids: In a split-phase power grid, VA and VN are one phase voltage, while the voltages of the other phase, VB and VN, are out of phase with VA. The diode will exhibit specific current characteristics due to the alternating conduction of the two-phase voltages. In a single-phase power grid, only VA and VN have voltage, and the diode conducts only in one direction. The voltage phase difference between VA, VB, and VN in a split-phase power grid is 180°. The diode conducts during the positive half-cycle of VA, and VB also conducts during the positive half-cycle due to the out-of-phase voltage; while in a single-phase power grid, only VA conducts in one direction.

[0138] This embodiment provides a voltage detection circuit composed of diodes and resistors to identify split-phase and single-phase power grid types, achieving power grid identification with extremely low hardware costs and reducing the overall product cost. By utilizing the difference in diode conduction timing, split-phase (bidirectional conduction characteristics) and single-phase (unidirectional conduction characteristics) can be accurately distinguished, avoiding misjudgment.

[0139] In some embodiments, the process for identifying split-phase and single-phase power grid types includes:

[0140] The voltage at the first end of the first resistor, the voltage between the first resistor and the second resistor, and the voltage at the second end of the second resistor are respectively taken as the first voltage, the second voltage, and the third voltage;

[0141] Detect whether the voltage waveforms of the first voltage and the third voltage are symmetrical;

[0142] If the waveform is symmetrical, it is determined to be a split-phase power grid type;

[0143] If the waveform is asymmetrical, it is determined to be a single-phase power grid type.

[0144] Specifically, Figure 17 A waveform diagram of a split-phase power grid provided in an embodiment of this application is shown below. Figure 17 As shown, the waveform of the split-phase power supply network is the same as before. Since it is connected to a strong power grid, it will force the N line of the inverter to be pulled to the midpoint. Figure 18 A waveform diagram with an interval range of 2 under a single-phase power grid is provided as an embodiment of this application, as shown below. Figure 18 As shown, when connected to a single-phase power grid, because the inverter's N line is left floating, there will be a DC bias in VA and VB. In other words, after adding the voltage detection circuit, when connected to a single-phase power grid, the N line is left floating, which is marked with a box in the figure, and there will be a DC bias voltage.

[0145] Figure 19 The following is a waveform diagram with an interval range of 0.25 under a single-phase power grid, provided as an embodiment of this application. Figure 19 As shown, it can still be seen that when connected to a single-phase power grid, the N line is left floating, and there will be a DC bias voltage.

[0146] Therefore, the voltage waveforms of the first and third voltages are checked for symmetry. If the waveforms are symmetrical, there is no DC bias, indicating a split-phase power grid. If the waveforms are asymmetrical, there is DC bias, indicating a single-phase power grid.

[0147] The voltage detection circuit provided in this embodiment identifies the voltage waveforms of VA and VB, simplifying the detection process, improving detection efficiency, and increasing accuracy.

[0148] In some embodiments, the hybrid inverter further includes a filter circuit, which includes a third capacitor and a fourth capacitor;

[0149] The first terminal of the third capacitor is connected to the second terminal of the first inductor and the first terminal of the first resistor; the second terminal of the third capacitor, the second terminal of the first resistor, the first terminal of the second resistor and the first terminal of the fourth capacitor are connected to each other and grounded;

[0150] The second terminal of the fourth capacitor is connected to the second terminal of the second inductor and the second terminal of the second resistor.

[0151] Specifically, such as Figure 1 As shown, the third and fourth capacitors in the filter circuit are connected in parallel. The two ends of the third and fourth capacitors are short-circuited and connected in parallel to the parallel branch of the load. The principle of parallel capacitor connection is capacitance superposition and voltage equalization / current sharing. A single capacitor has limited filtering and energy storage capacity; after parallel connection, the total capacity doubles, which can better filter out voltage ripple on the DC bus or provide more stable temporary energy support for the load. The charging and discharging current is shared by the third and fourth capacitors, halving the current load of a single capacitor; at the same time, the voltage is evenly distributed, preventing damage to a single capacitor due to overvoltage / overcurrent and extending the capacitor's lifespan.

[0152] The parallel connection of the third and fourth capacitors provided in this embodiment better filters out voltage ripple on the DC bus or provides more stable temporary energy support for the load. It also prevents single capacitors from being damaged by overvoltage / overcurrent, extending the capacitor's lifespan.

[0153] The hybrid filter provided in this application has been described in detail above. The various embodiments in the specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to in the method section. It should be noted that those skilled in the art can make several improvements and modifications to this application without departing from the principles of this application, and these improvements and modifications also fall within the protection scope of this application.

[0154] It should also be noted that, in this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

Claims

1. A hybrid inverter, characterized in that, It includes an energy storage circuit, a freewheeling circuit, a bridge arm main switch branch, and a bridge arm auxiliary switch branch connected in parallel at both ends of the bridge arm main switch branch; The energy storage circuit and the main switch branch of the bridge arm are connected in parallel, and both ends are connected to the power supply; the input end of the auxiliary switch branch of the bridge arm is grounded and connected to the intermediate reference point of the energy storage circuit; the output ends of the main switch branch of the bridge arm and the output ends of the auxiliary switch branch of the bridge arm are both connected to the two ends of the freewheeling circuit; the other two ends of the freewheeling circuit are connected to the load, and the intermediate reference point of the load is grounded. Specifically, in the case of a split-phase or two-phase power grid, the switching transistors of the main switch branch and the auxiliary switch branch of the bridge arm are controlled to turn on and off, and the freewheeling device of the freewheeling circuit is used to output the corresponding voltage; in the case of a single-phase power grid, the switching transistors of the main switch branch of the bridge arm are controlled to turn on and off, and the freewheeling device of the freewheeling circuit is used to output the corresponding voltage.

2. The hybrid inverter according to claim 1, characterized in that, The energy storage circuit includes a first capacitor and a second capacitor. Each of the main switch branch and the auxiliary switch branch of the bridge arm is connected in parallel with a diode. The main switch branch of the bridge arm includes a first switch, a second switch, a third switch, and a fourth switch. The auxiliary switch branch of the bridge arm includes a fifth switch, a sixth switch, a seventh switch, and an eighth switch. The freewheeling device of the freewheeling circuit includes a first inductor and a second inductor. The first terminal of the first capacitor is connected to the positive terminal of the power supply and is connected to the collector of the first switching transistor and the collector of the second switching transistor; the second terminal of the first capacitor is connected to the first terminal of the second capacitor and is connected to the collector of the fifth switching transistor and the collector of the seventh switching transistor, and is grounded; wherein, there is an intermediate reference point between the first capacitor and the second capacitor, and it is grounded. The emitter of the fifth switch is connected to the emitter of the sixth switch, and the emitter of the seventh switch is connected to the emitter of the eighth switch. The emitter of the first switch, the collector of the sixth switch, the collector of the third switch, and the first terminal of the first inductor are connected; the emitter of the third switch is connected to the second terminal of the second capacitor; the emitter of the second switch, the collector of the eighth switch, the collector of the fourth switch, and the first terminal of the second inductor are connected; the emitter of the fourth switch is connected to the second terminal of the second capacitor. The second end of the first inductor is connected to the first end of the first resistor; the second end of the first resistor is connected to the first end of the second resistor; the second end of the second resistor is connected to the second end of the second inductor; wherein, there is an intermediate reference point between the first resistor and the second resistor, and it is grounded.

3. The hybrid inverter according to claim 2, characterized in that, When the grid type is split phase or two phase, a control mode combining half bus and hybrid inverter port phase voltage is adopted to control the switching tubes of the main switch tube branch and the auxiliary switch tube branch of the bridge arm to turn on and off, and combine the freewheeling device of the freewheeling circuit to output the corresponding voltage. When the grid is a single-phase grid, a control mode combining the full BUS bus and the hybrid inverter port line voltage is adopted to control the switching transistors of the main switching transistor branch of the bridge arm to turn on and off, and to output the corresponding voltage in conjunction with the freewheeling device of the freewheeling circuit.

4. The hybrid inverter according to claim 3, characterized in that, In the case of split-phase or two-phase power grids, a control mode combining the half-bus and hybrid inverter port phase voltage is adopted to control the switching transistors of the main switch branch and the auxiliary switch branch of the bridge arm to turn on and off, and to output the corresponding voltage in conjunction with the freewheeling device of the freewheeling circuit, including: During the positive half-cycle of phase A, the first switch is turned on, and the other switches are turned off, allowing current to flow from the first capacitor through the first switch and the first inductor to the power grid; the first switch is turned off, and the fifth switch is turned on, allowing the first inductor to freewheel, and the current returns to the first inductor through the diodes corresponding to the fifth and sixth switches, thus completing the voltage output of phase A; During the negative half-cycle of phase A, the third switch is turned on, and all other switches are turned off, allowing current to flow from the second capacitor through the first inductor and the third switch to the power grid; the third switch is turned off, and the sixth switch is turned on, allowing the first inductor to freewheel, and the current returns to the first inductor through the diodes corresponding to the sixth and fifth switches, thus completing the voltage output of phase A. During the positive half-cycle of phase B, the second switch is turned on, and all other switches are turned off, allowing current to flow from the first capacitor through the second switch and the second inductor to the power grid; the second switch is turned off, and the seventh switch is turned on, allowing the second inductor to freewheel. The current returns to the second inductor through the diodes corresponding to the seventh and eighth switches, completing the voltage output of phase B. During the negative half-cycle of phase B, the fourth switch is turned on, and all other switches are turned off, allowing current to flow from the second capacitor through the second inductor and the fourth switch to the power grid; the fourth switch is turned off, and the eighth switch is turned on, allowing the second inductor to freewheel, and the current returns to the second inductor through the diodes corresponding to the eighth and seventh switches, thus completing the voltage output of phase B. In the case of a split-phase power grid, the phase angle interval between phase A and phase B is 180°, and in the case of a two-phase power grid, the phase angle interval between phase A and phase B is 120°.

5. The hybrid inverter according to claim 3, characterized in that, When the grid type is single-phase, a control mode combining the full BUS bus and the hybrid inverter port line voltage is adopted to control the switching transistors of the main switching transistor branch of the bridge arm to turn on and off, and to output the corresponding voltage in conjunction with the freewheeling device of the freewheeling circuit, including: During the positive half-cycle, the first and fourth switches are turned on, while the other switches are turned off, allowing current to flow from the first and second capacitors in series, through the first switch, the first inductor, the second inductor, and the fourth switch to the power grid. The first and fourth switches are turned off, and the fifth and eighth switches are turned on, allowing the first and second inductors to freewheel. The current then flows back to the first and second inductors through the diodes corresponding to the fifth and sixth switches, the first inductor, the second inductor, the eighth switch, and the diodes corresponding to the seventh switch, completing the single-phase voltage output. During the negative half-cycle, the fifth and eighth switches are turned off, while the second and third switches are turned on, allowing current to flow from the first and second capacitors in series, through the second switch, the second inductor, the first inductor, and the third switch to the power grid. The second and third switches are turned off, while the sixth and seventh switches are turned on, allowing the first and second inductors to freewheel. The current then flows back to the first and second inductors through the diodes corresponding to the seventh and eighth switches, the second inductor, the first inductor, the sixth switch, and the diode corresponding to the fifth switch, completing the single-phase voltage output.

6. The hybrid inverter according to claim 2, characterized in that, The hybrid inverter also includes a voltage detection circuit; The first end of the voltage detection circuit is connected to the freewheeling circuit, and the second end is connected to the load. The voltage detection circuit is used to identify split-phase and single-phase power grid types.

7. The hybrid inverter according to claim 6, characterized in that, The voltage detection circuit includes a first diode and a third resistor; The anode of the first diode is connected to the second terminal of the first inductor and the first terminal of the first resistor; the cathode of the first diode is connected to the first terminal of the third resistor; the second terminal of the third resistor is connected to the second terminal of the first resistor and the first terminal of the second resistor. Alternatively, the first end of the third resistor is connected to the second end of the first resistor and the first end of the second resistor; the second end of the third resistor is connected to the cathode of the first diode; and the anode of the first diode is connected to the second end of the second resistor and the second end of the second inductor.

8. The hybrid inverter according to claim 7, characterized in that, The process for identifying split-phase and single-phase power grid types includes: The voltage at the first end of the first resistor, the voltage between the first resistor and the second resistor, and the voltage at the second end of the second resistor are respectively taken as the first voltage, the second voltage, and the third voltage; Detect whether the voltage waveforms of the first voltage and the third voltage are symmetrical; if the waveforms are symmetrical, then it is determined to be a split-phase power grid type. If the waveform is asymmetrical, it is determined to be a single-phase power grid type.

9. The hybrid inverter according to claim 2, characterized in that, The hybrid inverter also includes a filter circuit, which includes a third capacitor and a fourth capacitor. The first terminal of the third capacitor is connected to the second terminal of the first inductor and the first terminal of the first resistor; the second terminal of the third capacitor, the second terminal of the first resistor, the first terminal of the second resistor, and the first terminal of the fourth capacitor are interconnected and grounded; The second terminal of the fourth capacitor is connected to the second terminal of the second inductor and the second terminal of the second resistor.

10. The hybrid inverter according to claim 4, characterized in that, In the case of a split-phase or two-phase power grid, the triggering process for the switching of the main switch branch and the auxiliary switch branch of the bridge arm includes: Collect the fundamental frequency of the grid voltage and the carrier wave obtained from the switching frequency; During the positive half-cycle, and when the carrier amplitude is less than the fundamental frequency, the first switch is turned on and the other switches are turned off; when the carrier amplitude is greater than the fundamental frequency, the first switch is turned off and the fifth switch is turned on. During the negative half-cycle, and when the carrier amplitude is less than the fundamental frequency, the third switch is turned on and the other switches are turned off; when the carrier amplitude is greater than the fundamental frequency, the third switch is turned off and the sixth switch is turned on.

11. The hybrid inverter according to claim 5, characterized in that, In the case of a single-phase power grid, the triggering process for controlling the on / off switching of the main switch branch of the bridge arm includes: Collect the fundamental frequency of the grid voltage and the carrier wave obtained from the switching frequency; During the positive half-cycle, and when the carrier amplitude is less than the fundamental frequency, the first and fourth switches are turned on, and the remaining switches are turned off except for the first and fourth switches; when the carrier amplitude is greater than the fundamental frequency, the first and fourth switches are turned off, and the fifth and eighth switches are turned on. During the negative half-cycle, and when the carrier amplitude is less than the fundamental frequency, the fifth and eighth switches are turned off, and the second and third switches are turned on; when the carrier amplitude is greater than the fundamental frequency, the second and third switches are turned off, and the sixth and seventh switches are turned on.

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