A bidirectional conversion structure and output control method suitable for split-phase power grid

Abstract

The present invention relates to a bidirectional conversion structure suitable for a split-phase power grid, comprising: two DC bus filter capacitors; three output power lines, one end of the three output power lines being respectively connected to a first live line, a second live line and a neutral line of the split-phase power grid; an inverter circuit formed by two bridge arms formed by respectively connecting the output power lines to a switch tube and a filter inductor; when the conversion structure is working, when in a split-phase power grid operation mode, by controlling the on and off of the switch tube, the conversion structure controls the output current and phase difference of each phase when connected to the grid, and controls the voltage and phase difference of the output power line when off-grid; so that the single-phase inverter of the prior art can be simultaneously applicable to the single-phase power grid and the split-phase power grid, and when connected to the split-phase power grid and in an off-grid operation mode, the requirements of different voltage outputs can be met without adding additional transformer split phases.

Description

Technical Field

[0001] The present invention belongs to the technical field of power electronic converters, and in particular, relates to a bidirectional conversion structure and an output control method suitable for a split-phase power grid. Background Art

[0002] An inverter is a system that converts direct current into alternating current. Usually, an inverter includes grid-connected operation and off-grid operation modes. The grid-connected operation mode is to convert the direct current generated by photovoltaic modules such as solar energy into alternating current, and after satisfying the local load consumption, the excess power is transmitted to the grid, which is also the grid-connected mode; while the off-grid operation mode is when the grid is abnormal or stops transmitting power to the grid, the inverter runs off-grid and outputs a fixed voltage, and provides power to the load connected to the off-grid output terminal of the inverter, which is also the off-grid mode.

[0003] The household power supply systems in the world mainly include single-phase power grid systems and split-phase power grid systems. Among them, the household single-phase power grid system is composed of a live wire and a neutral wire in the three-phase power grid system. In this system, the voltage between the live wire and the neutral wire is 220V or 230V. Therefore, the household electrical appliances adapted to the single-phase power grid system area only have a voltage level of 230V. Correspondingly, the split-phase power grid system is composed of two live wires and a neutral wire in the three-phase power grid system. In this system, the voltage between the live wire and the neutral wire is 101V or 120V (120V will be used as an example later), and the live wire to live wire voltage is 202V or 240V (240V will be used as an example later). Therefore, household electrical appliances under the split-phase power grid system also have two levels of 120V and 240V. Generally, electrical appliances with a voltage level of 120V are low-power electrical appliances, and electrical appliances with a voltage level of 240V are high-power electrical appliances.

[0004] However, most of the existing single-phase inverters are configured according to the single-phase power grid system. When the existing single-phase inverter is connected to the single-phase power grid system and is in the grid-connected operation mode, the inverter AC port is connected to the live wire and the neutral wire of the single-phase power grid system. At this time, the current flowing through the live wire and the neutral wire is equal.

[0005] However, if it is necessary to apply the single-phase inverter set according to the single-phase grid system in the prior art to the split-phase grid system, the AC output port of the single-phase inverter is connected to the two live wires in the split-phase grid system, and the neutral wire (i.e., N wire) of the split-phase grid system is left unconnected, or the neutral wire is simply connected to the grid voltage sampling circuit inside the device. In actual use, for example, when a photovoltaic inverter or an energy storage inverter is connected to the grid in the grid-connected operation mode, the inverter output current flows through the two live wires (L1 and L2) of the split-phase grid, and the current flowing through the two live wires should be equal, while the neutral wire N of the split-phase grid connected to the inverter does not flow current. Therefore, since the current flowing through the two live wires is equal at this time, in this mode, the inverter cannot output different powers to the two phases of the grid. Under the prior art, when each phase is required to be independently protected against reverse flow, when the power consumption of the two phases of the grid is inconsistent, the inverter can only output according to the current value of the phase with a smaller current, so that each live wire does not output energy to the grid. It can be imagined that when the photovoltaic energy is sufficient, in order to meet the anti-backflow requirement, the inverter described above will inevitably waste energy by outputting a small current single-phase current value.

[0006] On the other hand, when the power grid is abnormal, the inverter (photovoltaic inverter or energy storage inverter) configured according to the single-phase power grid system is disconnected from the current power grid and operates in off-grid operation mode, and supplies power to the load connected to it. As mentioned above, since the inverter configured according to the single-phase power grid system can only output one voltage level of 120V or 240V, and cannot output two levels of voltage at the same time, that is, it is impossible to supply power to multiple household electrical appliances of different voltage levels at the same time.

[0007] In order to solve the above technical problems, that is, to enable the traditional inverter to output two voltage levels of 120V and 240V at the same time in the off-grid operation mode, a common method in the prior art is to connect the power frequency isolation transformer or autotransformer to the off-grid output port of the inverter for phase separation. In this way, the inverter only outputs one voltage level of 240V in the off-grid operation mode, and the power frequency isolation transformer or autotransformer phases the output voltage so that two voltages of 120V and 240V can be obtained. However, in this common method, due to the use of the power frequency isolation transformer or autotransformer, the volume of the inverter itself increases, and the overall weight of the equipment is heavy, and the energy consumption of the additional transformer itself is also reduced accordingly. The problem on the other hand is that when the inverter in the off-grid operation mode is switched to the power frequency isolation transformer or autotransformer, the transformer excitation requires the inverter to output a large surge current (peak current), and there is a lack of effective means to suppress the surge current, which is easy to damage the semiconductor devices, relays or fuses inside the inverter.

[0008] Of course, in the prior art, an electronic phase splitter can also be used to replace the power frequency isolation transformer or the autotransformer. However, the electronic phase splitter is a loop composed of switching tubes, inductors, capacitors and other energy storage devices. In order to play a phase splitting role, it can be regarded as adding a power conversion circuit to the original system. Since more components are added, additional energy loss is naturally generated in the conversion process, and the equipment cost is further increased, making the system configuration process more cumbersome.

[0009] In view of this, the existing technology should be improved to solve the above-mentioned technical problems existing in the existing technology. Summary of the invention

[0010] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a conversion structure. The inverter using this structure can be applicable to both single-phase power grids and split-phase power grids, and when it is connected to a split-phase power grid, it controls the output current and phase difference of each phase. When in an off-grid operation mode, it can meet the requirements of different voltage outputs without adding additional transformers or electronic phase splitters, which significantly reduces the system cost when the converter is off-grid and requires split-phase voltage, and can also reduce the energy loss in the conversion process.

[0011] In order to solve the above technical problems, the present invention adopts a bidirectional conversion structure suitable for a phase-splitting power grid, and the bidirectional conversion structure suitable for a phase-splitting power grid includes: two DC bus filter capacitors, defined as a first filter capacitor and a second filter capacitor; three output power lines, one end of each of the three output power lines is connected to between the first filter capacitor and the second filter capacitor, and the other end of the three output power lines is respectively connected to the first live wire, the second live wire and the neutral wire of the phase-splitting power grid, then the three output power lines are respectively defined as a first live wire output power line, a second live wire output power line and a neutral wire output power line; the first live wire output power line and the second live wire output power line are respectively connected to An inverter circuit formed by two bridge arms composed of a switch tube and a filter inductor; an auxiliary switch element, which enables the conversion structure to switch between a single-phase grid operation mode and a split-phase grid operation mode, wherein when the conversion structure is working, the on and off of the auxiliary switch element is controlled by a control unit, so that the conversion structure is in a single-phase grid operation mode or a split-phase grid operation mode, and when the conversion structure is in the split-phase grid operation mode, the on and off of the switch tube is controlled so that the conversion structure controls the output current and phase difference of each phase when connected to the grid, and the conversion structure controls the voltage and phase difference of the output power line when off the grid.

[0012] Further preferably, the bridge arm formed by the first live wire output power line is defined as the first bridge arm, and the bridge arm formed by the second live wire output power line is defined as the second bridge arm, wherein the first bridge arm includes a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, and a first filter inductor; the second bridge arm includes a fifth switch tube, a sixth switch tube, a seventh switch tube, an eighth switch tube, and a second filter inductor.

[0013] Still further preferably, on the first bridge arm, the drain of the first switch tube is connected to the first filter capacitor, the source of the first switch tube is connected to the source of the third switch tube, and the drain of the third switch tube is connected to the drain of the second switch tube; on the second bridge arm, the drain of the sixth switch tube is connected to the drain of the seventh switch tube, the source of the seventh switch tube is connected to the drain of the eighth switch tube, and the source of the eighth switch tube is connected to the second filter capacitor, wherein the source of the second switch tube and the source of the sixth switch tube are both connected to the midpoint between the first filter capacitor and the second filter capacitor, and the drain of the fourth switch tube is connected to the source of the first switch tube, and its source is connected between the source of the eighth switch tube and the second filter capacitor, the drain of the fifth switch tube is connected to the drain of the first switch tube, and the source of the fifth switch tube is connected to the drain of the eighth switch tube.

[0014] Further preferably, the auxiliary switch element includes a first switch element and a second switch element, wherein one end of the first switch element is connected between the second switch tube and the third switch tube, and the other end of the first switch element is connected between the sixth switch tube and the seventh switch tube, and the second switch element is arranged on the neutral line output power line. Then, when the conversion structure is in the single-phase grid operation mode, the first switch element is closed and the second switch element is disconnected; when the conversion structure is in the split-phase grid operation mode, the first switch element is disconnected and the second switch element is closed.

[0015] Still further preferably, the control unit is at least one independent digital controller, and when the conversion structure is in a split-phase grid operation mode, the control unit independently controls the energy flow on the first bridge arm and the second bridge arm, wherein the control unit sends a drive signal to each of the switching tubes to control the conduction and cutoff of the switching tubes.

[0016] Still further preferably, when the conversion structure is in the split-phase grid operation mode, the control unit controls the first switch tube and the second switch tube, the third switch tube and the fourth switch tube, the fifth switch tube and the sixth switch tube, and the seventh switch tube and the eighth switch tube to selectively turn on.

[0017] Correspondingly, the present invention also provides a split-phase power grid output control method based on the aforementioned split-phase power grid bidirectional control device, and the output control method includes the following steps: step A1 of configuring three output power lines to be connected to the first live wire, the second live wire and the neutral wire of the split-phase power grid respectively; step A2 of configuring the auxiliary switch element for switching the conversion structure operation mode, configuring the switch tube and the filter inductor; step A3 of configuring the control unit to control the switching timing of the switch tube; step A4 of configuring the phase difference between the first live wire, the second live wire and the neutral wire and the voltage between the first live wire, the second live wire and the neutral wire, and when in the grid-connected operation mode, respectively configuring the current value of the first live wire and the second live wire.

[0018] Further preferably, the auxiliary switch element includes a first switch element and a second switch element, wherein, in the step A2, the two ends of the first switch element are respectively connected to the first live wire output power line and the second live wire power output line, and the second switch element is arranged on the output power line connected to the neutral line, so that when connected to a single-phase power grid, the first switch element is controlled to be closed and the second switch element is disconnected; when connected to a split-phase power grid, the first switch element is controlled to be disconnected and the second switch element is closed.

[0019] Further preferably, the bridge arm formed by the first live wire output power line is defined as the first bridge arm, and the bridge arm formed by the second live wire output power line is defined as the second bridge arm, wherein in the step A4, when the conversion structure is working, sampling is used to determine whether the access is a single-phase grid or a split-phase grid, and the control unit controls the on and off of the auxiliary switch, so that the conversion structure is in a single-phase grid operation mode or a split-phase grid operation mode

[0020] When the conversion structure is in the phase-splitting grid operation mode, by controlling the on and off of the switch tube, the conversion structure controls the output current and phase difference of each phase when connected to the grid, and controls the voltage and phase difference of the output power line when off the grid.

[0021] Preferably, when in the off-grid operation mode, the step of configuring the phase difference between the first live wire, the second live wire and the neutral wire is to control the output voltage between the first live wire and the second live wire by adjusting the phase difference between the first live wire and the neutral wire and the phase difference between the second live wire and the neutral wire within a preset range.

[0022] Due to the adoption of the above technical solution, the present invention has the following beneficial technical effects compared with the prior art:

[0023] 1. Three output power lines are configured, one end of each of the three output power lines is connected between the first filter capacitor and the second filter capacitor, and the other ends of the three output power lines are respectively connected to the first live line, the second live line and the neutral line of the split-phase power grid, so that in the conversion structure, the output power line is connected to the neutral line of the split-phase power grid, and the conversion structure provides a current loop for the neutral line so that the neutral line of the split-phase power grid can not only be used for sampling by the sampling circuit, but also has current passing through it at the same time, which solves the technical problem that when the inverter is connected to the split-phase power grid under the prior art, when the inverter is grid-connected, different currents cannot be output to the two phases of the split-phase power grid, and when it is off-grid, the voltage and phase of the first live line to the neutral line and the second live line to the neutral line cannot be controlled respectively;

[0024] 2. Based on the above reasons, since the three output power lines are respectively connected to the first live line, the second live line and the neutral line of the split-phase grid, this conversion structure provides a power circuit for the neutral line of the split-phase grid, so that when connected to the grid, the inverter can output different powers to the two phases of the split-phase grid, that is, it can control the output of each phase, so that each phase can be prevented from reverse flow separately;

[0025] 3. When the inverter is in off-grid operation, the voltage between the first live wire, the second live wire and the neutral wire of the split-phase grid is controlled to be 120V, and the phase difference between the first live wire and the neutral wire and the second live wire and the neutral wire is 180 degrees. In this way, the voltage between the first live wire and the second live wire can be 240V, thereby achieving the simultaneous output of 120V and 240V voltage levels, solving the technical problem that the inverter designed based on the single-phase grid cannot simultaneously output different levels of voltage when connected to the split-phase grid under the existing technology;

[0026] 4. Since it replaces the existing technology of adding transformer phase separation or external electronic sharer to achieve different levels of voltage output, the overall complexity of the system is reduced, the use of system components is reduced, and the workload of system configuration and installation and system operating costs are significantly reduced;

[0027] 5. Based on the above advantages, the inverter designed based on the single-phase power grid in the prior art can be applied to both the single-phase power grid and the split-phase power grid, and by introducing the auxiliary first switch element and the second switch element, the switching of the inverter conversion structure operation mode is completed by controlling the opening and closing of the switch element, thereby reducing the energy loss of the system during the conversion process;

[0028] 6. By controlling the multiple switch tubes in the two bridge arms respectively through multiple independent controllers, or by configuring the switching timing for each switch tube through an independent controller, the energy flow of each bridge arm in the entire conversion process of the inverter can be controlled, which provides a basis for controlling the output current of each phase when connected to the grid and controlling the voltage and phase of each phase when off the grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a schematic diagram showing a bidirectional conversion structure applicable to a phase-separated power grid according to a preferred embodiment of the present invention;

[0030] Figure 2 A schematic diagram showing Figure 1 The structure of connecting the bidirectional conversion structure applicable to the split-phase power grid and the single-phase power grid as described in the preferred embodiment shown;

[0031] Figure 3 A schematic diagram showing Figure 1 The structure of the bidirectional conversion structure applicable to the split-phase power grid and the connection with the split-phase power grid described in the preferred embodiment shown;

[0032] Figure 4 A schematic diagram showing Figure 3 The driving signals of the first to fourth switching tubes in the bidirectional conversion structure applicable to the split-phase power grid described in the preferred embodiment shown;

[0033] Figure 5 A schematic diagram showing Figure 3 The driving signals of the fifth to eighth switching tubes in the bidirectional conversion structure applicable to the split-phase power grid described in the preferred embodiment shown;

[0034] Figure 6 A schematic diagram showing Figure 3 The bidirectional conversion structure applicable to the split-phase grid described in the preferred embodiment shown, when the split-phase grid voltage is in the positive half cycle when connected to the grid or the output L1-L2 voltage is in the positive half cycle when off-grid, the control unit controls the equivalent circuit structure when the bidirectional conversion structure is in state 1;

[0035] Figure 7 A schematic diagram showing Figure 3 The bidirectional conversion structure applicable to the split-phase grid described in the preferred embodiment shown, when the split-phase grid voltage is in the positive half cycle when connected to the grid or the output L1-L2 voltage is in the positive half cycle when off-grid, the control unit controls the equivalent circuit structure when the bidirectional conversion structure is in state 2;

[0036] Figure 8 A schematic diagram showing Figure 3 The bidirectional conversion structure applicable to the split-phase grid described in the preferred embodiment shown, when the split-phase grid voltage is in the positive half cycle when connected to the grid or the output L1-L2 voltage is in the positive half cycle when off-grid, the control unit controls the bidirectional conversion structure to be in state 3 when the equivalent circuit structure;

[0037] Fig. 9 A schematic diagram showing Figure 3The bidirectional conversion structure applicable to the split-phase grid described in the preferred embodiment shown, when the split-phase grid voltage is in the positive half cycle when connected to the grid or the output L1-L2 voltage is in the positive half cycle when off-grid, the control unit controls the bidirectional conversion structure to be in state 4 when the equivalent circuit structure;

[0038] Fig.10 A schematic diagram showing Figure 3 The bidirectional conversion structure applicable to the split-phase grid described in the preferred embodiment shown, when the split-phase grid voltage is in the negative half cycle when connected to the grid or the output L1-L2 voltage is in the negative half cycle when off-grid, the control unit controls the bidirectional conversion structure to be in state 5;

[0039] Fig.11 A schematic diagram showing Figure 3 The bidirectional conversion structure applicable to the split-phase grid described in the preferred embodiment shown, when the split-phase grid voltage is in the negative half cycle when connected to the grid or the output L1-L2 voltage is in the negative half cycle when off-grid, the control unit controls the bidirectional conversion structure to be in state 6;

[0040] Fig.12 A schematic diagram showing Figure 3 The bidirectional conversion structure applicable to the split-phase grid is connected to the grid in the preferred embodiment shown. When the split-phase grid voltage is connected to the grid or the output L1-L2 voltage is in the negative half cycle when off-grid, the control unit controls the equivalent circuit structure when the bidirectional conversion structure is in state 7;

[0041] Fig.13 A schematic diagram showing Figure 3 The bidirectional conversion structure applicable to the split-phase grid described in the preferred embodiment shown, when the split-phase grid voltage is in the negative half cycle when connected to the grid or the output L1-L2 voltage is in the negative half cycle when off-grid, the control unit controls the bidirectional conversion structure to be in state 8;

[0042] Fig.14 FIG. 4 is a flow chart showing the process of the phase-splitting grid output control method described in another preferred embodiment of the present invention. DETAILED DESCRIPTION

[0043] The following will describe an embodiment of a bidirectional conversion structure and output control method applicable to a phase-separated power grid according to the present invention with reference to the accompanying drawings. It will be appreciated by those skilled in the art that the described embodiments may be modified in various ways without departing from the spirit and scope of the present invention. Therefore, the drawings and descriptions are illustrative in nature and are not intended to limit the scope of protection of the claims. In addition, in this specification, the drawings are not drawn to scale and the same reference numerals represent the same parts.

[0044] It should be noted that the expressions “first” and “second” used in the embodiments of the present invention are intended to distinguish two non-identical entities with the same name or non-identical parameters. It can be seen that “first” and “second” are only for the convenience of expression and should not be understood as limitations on the embodiments of the invention. The subsequent embodiments will not explain this one by one.

[0045] The bidirectional conversion structure described in the present invention can be used to connect with the solar panels of the photovoltaic array or a DC source such as a battery, or it can be connected to another level of DCDC converter, so that the DC voltage generated by the solar panel or output by the DCDC converter is controlled by the control unit to switch the operation mode (including single-phase grid operation mode and split-phase grid operation mode) of the auxiliary switch involved in the conversion structure. When the conversion structure is in the split-phase grid operation mode, by controlling the conduction and cutoff of the switch tube, the conversion structure controls the output current and phase difference of each phase when connected to the grid, and controls the voltage and phase difference of the output power line when off-grid, so that the conversion structure can output different powers on the first and second live wires when connected to the grid; when off-grid, different voltage levels are output, usually taking the split-phase grid in the United States as an example, outputting two voltages of 120V and 240V.

[0046] Specifically, Figure 1 FIG. 1 is a schematic diagram showing a bidirectional conversion structure applicable to a phase-separated power grid according to a preferred embodiment of the present invention. Figure 1 As shown, the DC side is connected to two DC bus filter capacitors, which are defined as the first filter capacitor C1 and the second filter capacitor C2. The theoretical value of the voltage of the first filter capacitor C1 and the second filter capacitor C2 should be equal to half of the DC bus voltage. For the convenience of explanation, in this preferred embodiment, the voltage of the first filter capacitor C1 and the second filter capacitor C2 are defined as positive at the top and negative at the bottom.

[0047] Three output power lines are configured, and the three output power lines correspond to the first live wire L1, the second live wire L2 and the neutral wire N (N line) of the power grid respectively. The three output power lines are defined as the first live wire output power line 10, the second live wire output power line 20 and the neutral wire output power line 30 according to the connection relationship. One ends of the first live wire output power line 10, the second live wire output power line 20 and the neutral wire output power line 30 are all commonly connected to the midpoint position between the first filter capacitor C1 and the second filter capacitor C2.

[0048] The bridge arm formed by the first live output power line 10 is the first bridge arm, and the first bridge arm includes a first switch tube S1, a second switch tube S2, a third switch tube S3 and a first filter inductor La. Figure 1, the drain of the first switch tube S1 is connected to the first filter capacitor C1, and its source is connected to the source of the third switch tube S3, and the drain of the third switch tube S3 is connected to the drain of the second switch tube S2, so that the first switch tube S1, the second switch tube S2, the third switch tube S3 and the first filter capacitor C1 are connected to form a loop, and the second switch tube S2, the third switch tube S3 and the first filter inductor La constitute the first live wire output power line 10, and the first live wire output power line 10 is connected to the first live wire L1 from the midpoint between the first filter capacitor C1 and the second filter capacitor C2. The bridge arm formed by the second live wire output power line 20 is the second bridge arm, and the second bridge arm includes the sixth switch tube S6, the seventh switch tube S7, the eighth switch tube S8 and the second filter inductor Lb. See Figure 1The drain of the sixth switch tube S6 is connected to the drain of the seventh switch tube S7, the source of the seventh switch tube S7 is connected to the drain of the eighth switch tube S8, and the source of the eighth switch tube S8 is connected to the second filter capacitor C2, so that the sixth switch tube S6, the seventh switch tube S7, the eighth switch tube S8 and the second filter capacitor C2 are connected to form a loop, and the sixth switch tube S6, the seventh switch tube S7 and the second filter inductor Lb constitute the second live wire output power line 20, and the second live wire output power line 20 is connected to the second live wire L2 from the midpoint between the first filter capacitor C1 and the second filter capacitor C2. At the same time, the first bridge arm also includes a fourth switch tube S4, and the second bridge arm also includes a fifth switch tube S5. The drain of the fourth switch tube S4 is connected to the source of the first switch tube S1, and the source of the fourth switch tube S4 is connected between the source of the eighth switch tube S8 and the second filter capacitor C2; the drain of the fifth switch tube S5 is connected to the drain of the first switch tube S1, and the source of the fifth switch tube S5 is connected to the drain of the eighth switch tube S8. In this way, the fourth switch tube S4 and the fifth switch tube S5 are switch tubes connected to the first bridge arm and the second bridge arm respectively, so that by controlling the timing of the switch tubes, the flow direction of energy can be controlled, and then the purpose of controlling the output voltage can be achieved. In another preferred embodiment, the second switch tube S2 and the third switch tube S3, the sixth switch tube S6 and the seventh switch tube S7 in the conversion structure can also exchange the drain and source at the same time, that is, the connection mode in the above embodiment is adjusted to that the drain of the first switch tube S1 is connected to the first filter capacitor C1, and its source is connected to the drain of the third switch tube S3, and the source of the third switch tube S3 is connected to the source of the second switch tube S2, so that the first switch tube S1, the second switch tube S2, the third switch tube S3 and the first filter capacitor C1 are connected to form a loop; at the same time, the connection mode of the sixth switch tube S6 and the seventh switch tube S7 is adjusted to that the source of the sixth switch tube S6 is connected to the source of the seventh switch tube S7, the drain of the seventh switch tube S7 is connected to the drain of the eighth switch tube S8, and the source of the eighth switch tube S8 is connected to the second filter capacitor C2, so that the sixth switch tube S6, the seventh switch tube S7, the eighth switch tube S8 and the second filter capacitor C2 are connected to form a loop, which is equivalent to the connection mode in the above embodiment.

[0049] It is worth mentioning that in different embodiments of the present invention, the switch tube can be selected, for example, a gate turn-off thyristor (GTO), a power transistor (GTR), a power field efficiency transistor (VMOSFET), an insulated gate bipolar transistor (IGBT), an integrated gate-commutated thyristor (IGCT) and a symmetrical gate-commutated thyristor (SGCT), etc., but the embodiments of the present invention are not limited to this.

[0050] An auxiliary switch element is configured, including a first switch element T1 and a second switch element T2. One end of the first switch element T1 is connected between the second switch element S2 and the third switch element S3, and the other end is connected between the sixth switch element S6 and the seventh switch element S7. The second switch element T2 is set on the neutral line output power line 30. Figure 2 A schematic diagram showing Figure 1 The preferred embodiment shown in FIG. 1 is a structure in which the bidirectional conversion structure applicable to the split-phase power grid is connected to the single-phase power grid in the grid-connected operation mode, see FIG. Figure 2 In actual use, when connected to an ordinary single-phase power grid, the first switch element T1 is kept closed and the second switch element T2 is disconnected. In this mode, since the second switch element T2 is disconnected, the neutral line is disconnected, and no current flows through the neutral line; since the first switch element T1 is closed, the second switch tube S2 and the sixth switch tube S6 as shown in the figure are bypassed, that is, the conversion structure is switched to the single-phase power grid operation mode. At this time, the first live line output power line of the conversion structure is connected to the L line of the single-phase power grid, and the second live line output power line is connected to the N line of the single-phase power grid.

[0051] Figure 3 A schematic diagram showing Figure 1 The structure of the bidirectional conversion structure applicable to the split-phase grid and the split-phase grid connection described in the preferred embodiment shown. As described above, when the conversion structure is applied to the inverter sampling the split-phase grid, the first switch T1 is kept in the open state, and the second switch T2 is kept in the closed state, so as to work in the split-phase grid mode, provide a power loop for the neutral line, and the grid connection can control each phase current (power) separately, and the grid-connected can control the voltage and phase of each phase. In this preferred embodiment, two independent SPWM controllers send driving signals to the first to eighth switch tubes respectively, that is, one SPWM controller controls the conduction and cutoff of the first to fourth switch tubes (S1~S4), and the other SPWM controller controls the conduction and cutoff of the fifth to eighth switch tubes (S5~S8), so that each controller corresponds to a phase bridge arm and controls the energy flow direction on the bridge arm. Of course, in other embodiments of the present invention, a separate controller can also be used to control the on and off of all switch tubes, but it is better to be able to achieve independent control of the bridge arm.

[0052] Figure 4 A schematic diagram showing Figure 3 The preferred embodiment shown is a driving signal for the first to fourth switching tubes in a bidirectional conversion structure suitable for a split-phase power grid. Figure 5 A schematic diagram showing Figure 3 The driving signals of the fifth to eighth switching tubes in the bidirectional conversion structure suitable for the split-phase power grid described in the preferred embodiment shown in FIG. Figure 4 and Figure 5, the driving signal sent by the SPWM controller corresponds to the first to eighth switch tubes (S1-S8), which are PWM1-PWM8 respectively, then PWM1 and PWM2 are complementary turned on, PWM3 and PWM4 are complementary turned on, PWM5 and PWM6 are complementary turned on, and PWM7 and PWM8 are complementary turned on. That is, the SPWM controller controls the first switch tube and the second switch tube, the third switch tube and the fourth switch tube, the fifth switch tube and the sixth switch tube, and the seventh switch tube and the eighth switch tube to select one to be turned on.

[0053] Based on the above conversion structure, in actual application, no matter it is working in the grid-connected operation state or in the off-grid operation state, the AC power outputted from the output side is a sine wave including positive and negative half cycles. Since one of the complementary switch tubes is controlled to be turned on, there are 8 possible working states. The following is a description of the 8 inverter working process states when the output voltage of the conversion structure is in the positive half cycle and the negative half cycle in combination with the accompanying drawings.

[0054] Figure 6 A schematic diagram showing Figure 3 The bidirectional conversion structure suitable for split-phase power grid described in the preferred embodiment shown, when the split-phase power grid voltage is in the positive half cycle when connected to the grid or the output L1-L2 voltage is in the positive half cycle when off-grid, the control unit controls the equivalent circuit structure of the bidirectional conversion structure when it is in state 1. In state 1, the drive signals of the SPWM controller are PWM1 high, PWM2 low, PWM3 high, PWM4 low, PWM5 low, PWM6 high, PWM7 low, PWM8 high, and the corresponding switches are the first switch S1 turned on, the second switch S2 turned off, the third switch S3 turned on, the fourth switch S4 turned off, the fifth switch S5 turned off, the sixth switch S6 turned on, the seventh switch S7 turned off, and the eighth switch S8 turned on. See Figure 6 The solid arrow in the accompanying drawing shows the direction of energy flowing through the first inductor La, and the hollow arrow shows the direction of energy flowing through the second inductor Lb. As shown in the figure, when the conversion architecture is in this state, the energy of the first bridge arm starts from the positive electrode of the first filter capacitor C1, flows through S1→La→L1→N→T2 and returns to the negative electrode of the first filter capacitor C1; at the same time, the energy of the second bridge arm starts from the positive electrode of the second filter capacitor C2, flows through N→L2→Lb→S8 and returns to the negative electrode of the second filter capacitor C2.

[0055] Figure 7 A schematic diagram showing Figure 3The bidirectional conversion structure suitable for split-phase power grid described in the preferred embodiment shown, when the split-phase power grid voltage is in the positive half cycle when connected to the grid or the output L1-L2 voltage is in the positive half cycle when off-grid, the control unit controls the equivalent circuit structure of the bidirectional conversion structure when it is in state 2. In state 2, the drive signals of the SPWM controller are PWM1 high, PWM2 low, PWM3 high, PWM4 low, PWM5 low, PWM6 high, PWM7 high, PWM8 low, and the corresponding switches are the first switch S1 turned on, the second switch S2 turned off, the third switch S3 turned on, the fourth switch S4 turned off, the fifth switch S5 turned off, the sixth switch S6 turned on, the seventh switch S7 turned on, and the eighth switch S8 turned off. See Figure 7 , the solid arrow in the accompanying drawing shows the direction of energy flowing through the first inductor La, and the hollow arrow shows the direction of energy flowing through the second inductor Lb. As shown in the figure, when the conversion architecture is in this state, the energy of the first bridge arm starts from the positive electrode of the first filter capacitor C1, flows through S1→La→L1→N→T2 and returns to the negative electrode of the first filter capacitor C1; at the same time, the energy of the second bridge arm starts from the left end of the second filter inductor Lb, flows through S7→S6→the second filter capacitor→T2→N→L2 and returns to the right end of the second filter inductor Lb.

[0056] Figure 8 A schematic diagram showing Figure 3 The bidirectional conversion structure suitable for split-phase power grid described in the preferred embodiment shown, when the split-phase power grid voltage is in the positive half cycle when connected to the grid or the output L1-L2 voltage is in the positive half cycle when off-grid, the control unit controls the equivalent circuit structure of the bidirectional conversion structure in state 3; in state 3, the driving signals of the SPWM controller are PWM1 is low, PWM2 is high, PWM3 is high, PWM4 is low, PWM5 is low, PWM6 is high, PWM7 is low, and PWM8 is high, and the corresponding switches are the first switch S1 turned off, the second switch S2 turned on, the third switch S3 turned on, the fourth switch S4 turned off, the fifth switch S5 turned off, the sixth switch S6 turned on, the seventh switch S7 turned off, and the eighth switch S8 turned on. See Figure 8 , the solid arrow in the accompanying drawing shows the direction of energy flowing through the first inductor La, and the hollow arrow shows the direction of energy flowing through the second inductor Lb. As shown in the figure, when the conversion architecture is in this state, the energy of the first bridge arm starts from the right end of the first filter inductor La, flows through L1→N→T2→S2→S3 and returns to the left end of the first filter inductor La; at the same time, the energy of the second bridge arm starts from the left end of the second filter inductor Lb, flows through S7→S6→C2→T2→N→L2 and returns to the right end of the second filter inductor Lb.

[0057] Fig. 9A schematic diagram showing Figure 3 The bidirectional conversion structure suitable for split-phase power grid described in the preferred embodiment shown, when the split-phase power grid voltage is in the positive half cycle when connected to the grid or the output L1-L2 voltage is in the positive half cycle when off-grid, the control unit controls the equivalent circuit structure when the bidirectional conversion structure is in state 4. In state 4, the drive signals of the SPWM controller are PWM1 is low, PWM2 is high, PWM3 is high, PWM4 is low, PWM5 is low, PWM6 is high, PWM7 is high, and PWM8 is low. The corresponding switches are the first switch S1 turned off, the second switch S2 turned on, the third switch S3 turned on, the fourth switch S4 turned off, the fifth switch S5 turned off, the sixth switch S6 turned on, the seventh switch S7 turned on, and the eighth switch S8 turned off. See Fig. 9 , the solid arrow in the accompanying drawing shows the direction of energy flowing through the first inductor La, and the hollow arrow shows the direction of energy flowing through the second inductor Lb. As shown in the figure, when the conversion architecture is in this state, the energy of the first bridge arm starts from the right end of the first filter inductor La, flows through L1→N→T2→S2→S3 and returns to the left end of the first filter inductor La; at the same time, the energy of the second bridge arm starts from the left end of the second filter inductor Lb, flows through S7→S6→C2→T2→N→L2 to the right end of the second filter inductor Lb.

[0058] Fig.10 A schematic diagram showing Figure 3 The bidirectional conversion structure suitable for split-phase power grid described in the preferred embodiment shown, when the split-phase power grid voltage is in the negative half cycle when connected to the grid or the output L1-L2 voltage is in the negative half cycle when off-grid, the control unit controls the equivalent circuit structure when the bidirectional conversion structure is in state 5. In state 5, the drive signals of the SPWM controller are PWM1 is low, PWM2 is high, PWM3 is low, PWM4 is high, PWM5 is high, PWM6 is low, PWM7 is high, and PWM8 is low. The corresponding switches are the first switch S1 turned off, the second switch S2 turned on, the third switch S3 turned off, the fourth switch S4 turned on, the fifth switch S5 turned on, the sixth switch S6 turned off, the seventh switch S7 turned on, and the eighth switch S8 turned off. See Fig.10 , the solid arrow in the accompanying drawing shows the direction of energy flow through the first inductor La, and the hollow arrow shows the direction of energy flow through the second inductor Lb. As shown in the figure, when the conversion architecture is in this state, the energy of the first bridge arm starts from the positive electrode of the second filter capacitor C2, flows through T2→N→L1→La→S4 and returns to the negative electrode of the second filter capacitor C2; at the same time, the energy of the second bridge arm starts from the positive electrode of the first filter capacitor C1, flows through S5→Lb→L2→N→T2 and returns to the negative electrode of the first filter capacitor C1.

[0059] Fig.11 A schematic diagram showing Figure 3 The bidirectional conversion structure suitable for split-phase power grid described in the preferred embodiment shown, when the split-phase power grid voltage is in the negative half cycle when connected to the grid or the output L1-L2 voltage is in the negative half cycle when off-grid, the control unit controls the equivalent circuit structure when the bidirectional conversion structure is in state 6. In state 6, the drive signals of the SPWM controller are PWM1 is low, PWM2 is high, PWM3 is low, PWM4 is high, PWM5 is low, PWM6 is high, PWM7 is high, and PWM8 is low. The corresponding switches are the first switch S1 turned off, the second switch S2 turned on, the third switch S3 turned off, the fourth switch S4 turned on, the fifth switch S5 turned off, the sixth switch S6 turned on, the seventh switch S7 turned on, and the eighth switch S8 turned off. See Fig.11 , the solid arrow in the accompanying drawing shows the direction of energy flowing through the first inductor La, and the hollow arrow shows the direction of energy flowing through the second inductor Lb. As shown in the figure, when the conversion architecture is in this state, the energy of the first bridge arm starts from the positive electrode of the second filter capacitor C2, flows through T2→N→L1→La→S4 and returns to the negative electrode of the second filter capacitor C2; at the same time, the energy of the second bridge arm starts from the right end of the second filter inductor Lb, flows through L2→N→T2→S6→S7 and returns to the left end of the second filter inductor Lb.

[0060] Fig.12 A schematic diagram showing Figure 3 The bidirectional conversion structure suitable for split-phase power grid described in the preferred embodiment shown, when the split-phase power grid voltage is in the negative half cycle when connected to the grid or the output L1-L2 voltage is in the negative half cycle when off-grid, the control unit controls the equivalent circuit structure when the bidirectional conversion structure is in state 7. In state 7, the drive signals of the SPWM controller are PWM1 is low, PWM2 is high, PWM3 is high, PWM4 is low, PWM5 is high, PWM6 is low, PWM7 is high, and PWM8 is low. The corresponding switches are the first switch S1 turned off, the second switch S2 turned on, the third switch S3 turned on, the fourth switch S4 turned off, the fifth switch S5 turned on, the sixth switch S6 turned off, the seventh switch S7 turned on, and the eighth switch S8 turned off. See Fig.12 , the solid arrow in the accompanying drawing shows the direction of energy flowing through the first inductor La, and the hollow arrow shows the direction of energy flowing through the second inductor Lb. As shown in the figure, when the conversion architecture is in this state, the energy of the first bridge arm starts from the left end of the first filter inductor La, flows through S3→S2→T2→N→L1 and returns to the right end of the first filter inductor La; at the same time, the energy of the second bridge arm starts from the positive electrode of the first filter capacitor C1, flows through S5→Lb→L2→N→T2 and returns to the negative electrode of the first filter capacitor C1.

[0061] Fig.13 A schematic diagram showing Figure 3 The bidirectional conversion structure suitable for the split-phase power grid described in the preferred embodiment shown, when the split-phase power grid voltage is in the negative half cycle when connected to the grid or the output L1-L2 voltage is in the negative half cycle when off the grid, the control unit controls the equivalent circuit structure when the bidirectional conversion structure is in state 8. In state 8, the drive signals of the SPWM controller are PWM1 is low, PWM2 is high, PWM3 is high, PWM4 is low, PWM5 is low, PWM6 is high, PWM7 is high, and PWM8 is low. The corresponding switches are the first switch S1 turned off, the second switch S2 turned on, the third switch S3 turned on, the fourth switch S4 turned off, the fifth switch S5 turned off, the sixth switch S6 turned on, the seventh switch S7 turned on, and the eighth switch S8 turned off. See Fig.13 , the solid arrow in the accompanying drawing shows the direction of energy flowing through the first inductor La, and the hollow arrow shows the direction of energy flowing through the second inductor Lb. As shown in the figure, when the conversion architecture is in this state, the energy of the first bridge arm starts from the left end of the first filter inductor La, flows through S2→S2→T2→N→L1 and returns to the right end of the first filter inductor La; at the same time, the energy of the second bridge arm starts from the right end of the second filter inductor Lb, flows through L2→N→T2→S6→S7 and returns to the left end of the second filter inductor Lb.

[0062] When the inverter is off-grid, the voltage and phase of each live wire to the neutral wire can be controlled so that the voltage of the first live wire L1 and the second live wire L2 to the neutral wire N is 120V. At the same time, the phase of the voltage of the first live wire L1 to the neutral wire N is configured to be different from the phase of the voltage of the second live wire L2 to the neutral wire N, so as to control the output voltage of the first live wire L1 to the second live wire L2. For example, if the phase of the voltage of the first live wire L1 to the neutral wire N and the phase difference of the voltage of the second live wire L2 to the neutral wire N are configured to be 180°, the output voltage of the first live wire L1 to the second live wire L2 is 240V. However, in the actual power grid, due to the deviation between the power grid frequency and phase and the theoretical value, the effective voltage value between the first live wire L1 and the neutral wire N and the second live wire L2 and the neutral wire N are both 120V, and the phase difference between the first live wire L1 and the neutral wire N and the phase difference between the second live wire L2 and the neutral wire N may be 179° or 181°. Therefore, in this case, the effective voltage value between the first live wire L1 and the second live wire L2 is less than 240V. Based on the above situation in the actual power grid, the output voltage between the first live wire L1 and the second live wire L2 can be controlled by adjusting the phase difference between the first live wire L1 and the neutral wire N and the second live wire L2 and the neutral wire. For example, if the phase difference between the first live wire L1 and the neutral wire N and the second live wire L2 and the neutral wire N is adjusted to 0°, the effective voltage value between the first live wire L1 and the second live wire L2 is 0V. In this way, if the phase difference between the first live wire L1 and the neutral wire N and the second live wire L2 and the neutral wire N is dynamically adjusted, the effective voltage value between the first live wire and the second live wire can be adjusted to change within the range of 0V to 240V. Therefore, when the inverter including the power architecture described in the preferred embodiment of the present invention is in an off-grid operation state, by controlling the output voltage, 120V and 240V voltages can be output simultaneously, thereby solving the problem that the traditional inverter cannot supply power to 120V loads and 240V loads at the same time when off-grid.

[0063] Correspondingly, the present invention also provides an output control method based on various preferred embodiments of the present invention including the above-mentioned control state. Fig.14 FIG. 1 is a flow chart showing the process of the phase-separated power grid output control method described in a preferred embodiment of the present invention. Fig.14 In this preferred embodiment of the present invention, the method for controlling the output of a phase-splitting power grid includes the following steps: step A1 of configuring three output power lines to be connected to the first live line, the second live line and the neutral line of the phase-splitting power grid respectively; step A2 of configuring an auxiliary switch for switching the operation mode of the conversion structure, and configuring a switch tube and a filter inductor; step A3 of configuring a control unit to control the switching timing of the switch tube, and step A4 of configuring the phase difference between the first live line, the second live line and the neutral line when in the off-grid operation mode.

[0064] Due to the adoption of the above technical solution, the present invention has the following beneficial technical effects compared with the prior art:

[0065] 1. Three output power lines are configured, one end of each of the three output power lines is connected between the first filter capacitor and the second filter capacitor, and the other ends of the three output power lines are respectively connected to the first live line, the second live line and the neutral line of the split-phase power grid, so that in the conversion structure, the output power line is connected to the neutral line of the split-phase power grid, and the conversion structure provides a current loop for the neutral line so that the neutral line of the split-phase power grid can not only be used for sampling by the sampling circuit, but also has current passing through it at the same time, which solves the technical problem that when the inverter is connected to the split-phase power grid under the prior art, when the inverter is grid-connected, different currents cannot be output to the two phases of the split-phase power grid, and when it is off-grid, the voltage and phase of the first live line to the neutral line and the second live line to the neutral line cannot be controlled respectively;

[0066] 2. Based on the above reasons, since the three output power lines are respectively connected to the first live line, the second live line and the neutral line of the split-phase grid, this conversion structure provides a power circuit for the neutral line of the split-phase grid, so that when connected to the grid, the inverter can output different powers to the two phases of the split-phase grid, that is, it can control the output of each phase, so that each phase can be prevented from reverse flow separately;

[0067] 3. When the inverter is in off-grid operation, the voltage between the first live wire, the second live wire and the neutral wire of the split-phase grid is controlled to be 120V, and the phase difference between the first live wire and the neutral wire and the second live wire and the neutral wire is 180 degrees. In this way, the voltage between the first live wire and the second live wire can be 240V, thereby achieving the simultaneous output of 120V and 240V voltage levels, solving the technical problem that the inverter designed based on the single-phase grid cannot simultaneously output different levels of voltage when connected to the split-phase grid under the existing technology;

[0068] 4. Since it replaces the existing technology of adding transformer phase separation or external electronic sharer to achieve different levels of voltage output, the overall complexity of the system is reduced, the use of system components is reduced, and the workload of system configuration and installation and system operating costs are significantly reduced;

[0069] 5. Based on the above advantages, the inverter designed based on the single-phase power grid in the prior art can be applied to both the single-phase power grid and the split-phase power grid, and by introducing the auxiliary first switch element and the second switch element, the switching of the inverter conversion structure operation mode is completed by controlling the opening and closing of the switch element, thereby reducing the energy loss of the system during the conversion process;

[0070] 6. By controlling the multiple switch tubes in the two bridge arms respectively through multiple independent controllers, or by configuring the switching timing for each switch tube through an independent controller, the energy flow of each bridge arm in the entire conversion process of the inverter can be controlled, which provides a basis for controlling the output current of each phase when connected to the grid and controlling the voltage and phase of each phase when off the grid.

[0071] The present invention has been described in detail above, and the description of the embodiments is only used to help understand the method and core idea of ​​the present invention, and its purpose is to enable people familiar with the technology in this field to understand the content of the present invention and implement it accordingly, and it cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A bidirectional conversion structure suitable for a split-phase power grid, characterized in that: The bidirectional conversion structure applicable to the split-phase power grid includes: Two DC bus filter capacitors, defined as a first filter capacitor and a second filter capacitor, wherein the voltage theoretical values ​​of the first filter capacitor and the second filter capacitor are half of the DC bus voltage; three output power lines, one end of each of the three output power lines is connected between the first filter capacitor and the second filter capacitor, and the other ends of the three output power lines are respectively connected to the first live wire, the second live wire and the neutral wire of the split-phase power grid, then the three output power lines are respectively defined as the first live wire output power line, the second live wire output power line and the neutral wire output power line; An inverter circuit formed by two bridge arms formed by connecting the first live output power line and the second live output power line to a switch tube and a filter inductor respectively; Auxiliary switch element, which enables the conversion structure to switch between a single-phase grid operation mode and a split-phase grid operation mode, wherein: When the conversion structure is working, the control unit controls the on and off of the auxiliary switch component, so that the conversion structure is in a single-phase grid operation mode or a split-phase grid operation mode. When the conversion structure is in the split-phase grid operation mode, the on and off of the switch tube are controlled so that the conversion structure controls the output current and phase difference of each phase when connected to the grid, and controls the voltage and phase difference of the output power line when off the grid.

2. The bidirectional conversion structure applicable to the split-phase power grid according to claim 1 is characterized in that: Define the bridge arm formed by the first live wire output power line as the first bridge arm, and the bridge arm formed by the second live wire output power line as the second bridge arm, wherein, The first bridge arm includes a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, and a first filter inductor; The second bridge arm includes a fifth switch tube, a sixth switch tube, a seventh switch tube, an eighth switch tube, and a second filter inductor, and two ends of the fourth switch tube and the fifth switch tube are connected to the first bridge arm and the second bridge arm respectively.

3. The bidirectional conversion structure applicable to the split-phase power grid according to claim 2 is characterized in that: On the first bridge arm, the drain of the first switch tube is connected to the positive electrode of the first filter capacitor, the source of the first switch tube is connected to the source of the third switch tube, the drain of the third switch tube is connected to the drain of the second switch tube, and on the second bridge arm, the drain of the sixth switch tube is connected to the drain of the seventh switch tube, the source of the seventh switch tube is connected to the drain of the eighth switch tube, and the source of the eighth switch tube is connected to the negative electrode of the second filter capacitor, wherein, The source of the second switch tube and the source of the sixth switch tube are both connected to the midpoint between the first filter capacitor and the second filter capacitor, and the drain of the fourth switch tube is connected to the source of the first switch tube, and its source is connected between the source of the eighth switch tube and the second filter capacitor, the drain of the fifth switch tube is connected to the drain of the first switch tube, and the source of the fifth switch tube is connected to the drain of the eighth switch tube.

4. The bidirectional conversion structure applicable to the split-phase power grid according to claim 3 is characterized in that: The auxiliary switch element includes a first switch element and a second switch element, wherein: One end of the first switch element is connected between the second switch tube and the third switch tube, and the other end of the first switch element is connected between the sixth switch tube and the seventh switch tube. The second switch element is arranged on the neutral line output power line. Then, when the conversion structure is in the single-phase grid operation mode, the first switch element is closed and the second switch element is opened; when the conversion structure is in the split-phase grid operation mode, the first switch element is opened and the second switch element is closed.

5. The bidirectional conversion structure applicable to the split-phase power grid according to claim 4, characterized in that: The control unit is at least one independent digital controller, and when the conversion structure is in the split-phase grid operation mode, the control unit independently controls the energy flow on the first bridge arm and the second bridge arm, wherein: The control unit sends a driving signal to each of the switch tubes to control the on and off of the switch tubes.

6. The bidirectional conversion structure applicable to the split-phase power grid according to claim 5, characterized in that: When the conversion structure is in the split-phase grid operation mode, the control unit controls the first switch tube and the second switch tube, the third switch tube and the fourth switch tube, the fifth switch tube and the sixth switch tube, and the seventh switch tube and the eighth switch tube to selectively turn on.

7. An output control method for a bidirectional conversion structure applicable to a phase-separated power grid based on claims 1-6, characterized in that: The output control method comprises the following steps: Step A1 of configuring three output power lines to be connected to a first live line, a second live line and a neutral line of a split-phase power grid respectively; A step A2 of configuring an auxiliary switch element for switching the operation mode of the conversion structure, configuring a switch tube and a filter inductor; A step A3 of configuring a control unit to control the switching timing of the switch tube, When in the off-grid operation mode, the phase difference between the first live wire, the second live wire and the neutral wire, and the voltage between the first live wire, the second live wire and the neutral wire are configured; when in the grid-connected operation mode, the current value of the first live wire and the second live wire are configured respectively in step A4.

8. The output control method of the bidirectional conversion structure applicable to the split-phase power grid according to claim 7, characterized in that: The auxiliary switch element includes a first switch element and a second switch element, wherein: In step A2, the two ends of the first switch element are respectively connected to the first live wire output power line and the second live wire power output line, and the second switch element is then set on the output power line connected to the neutral line, so that when connected to a single-phase power grid, the first switch element is controlled to be closed and the second switch element is disconnected; when connected to a split-phase power grid, the first switch element is controlled to be disconnected and the second switch element is controlled to be closed.

9. The output control method of the bidirectional conversion structure applicable to the split-phase power grid according to claim 8, characterized in that: Define the bridge arm formed by the first live wire output power line as the first bridge arm, and the bridge arm formed by the second live wire output power line as the second bridge arm, wherein, In step A4, sampling is used to determine whether the connected power grid is a single-phase power grid or a split-phase power grid, and the control unit controls the on and off of the auxiliary switch component so that the conversion structure is in a single-phase power grid operation mode or a split-phase power grid operation mode. When the conversion structure is in the split-phase power grid operation mode, the on and off of the switch tube are controlled so that the conversion structure controls the output current and phase difference of each phase when connected to the grid, and the conversion structure controls the voltage and phase difference of the output power line when off the grid.

10. The output control method of the bidirectional conversion structure applicable to the split-phase power grid according to claim 7, characterized in that: The step of configuring the phase difference between the first live wire, the second live wire and the neutral wire is to control the output voltage between the first live wire and the second live wire by adjusting the phase difference between the first live wire and the neutral wire and the phase difference between the second live wire and the neutral wire within a preset range.

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