Low cost inverter
By integrating energy storage devices on the bus and simplifying the control method, the high cost problem caused by high bus capacitance was solved, realizing the design of a low-cost inverter and improving system stability and operating efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HUNAN UNIV
- Filing Date
- 2023-11-29
- Publication Date
- 2026-06-02
Smart Images
Figure CN117639541B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of inverter technology, and more specifically to a low-cost inverter. Background Technology
[0002] With increasing environmental awareness, various clean energy sources have been widely adopted, with photovoltaics, a rapidly developing sector, showing great promise. However, photovoltaic cells exhibit random and intermittent operation. Therefore, to improve the reliability and stability of photovoltaic power generation systems, energy storage devices of a certain capacity can be introduced to improve the system structure. These storage devices can absorb the extra electricity generated by photovoltaic cells during periods of abundant sunlight, while providing energy supply to the system during nighttime and periods of low sunlight. This maintains system power balance and buffers fluctuations in photovoltaic cell output power, significantly improving system performance and operational stability.
[0003] Currently, photovoltaic (PV) power generation system structures are generally improved using PV-storage inverters. A typical two-stage high-gain PV-storage inverter topology is as follows: Figure 1 As shown, a Boost circuit is used to control the maximum power output of the photovoltaic cells and connect them to the DC bus. A Buck-Boost converter controls the power absorption and output of the photovoltaic cells and transmits the electrical energy to the DC bus. Finally, the DC bus is connected to the grid via a single-phase full-bridge inverter. The advantages of this topology are its simple and clear working principle and control method, the decoupling of the maximum power point tracking (MPPT) section and the power inverter section, and the different control objectives of the two parts, allowing for the design of corresponding control algorithms.
[0004] However, the bus capacitor voltage of a typical two-stage high-gain photovoltaic-storage inverter topology is high, resulting in higher cost. Summary of the Invention
[0005] (a) Technical problems to be solved
[0006] To address the shortcomings of existing technologies, this invention provides a low-cost inverter that solves the technical problems of high bus capacitor voltage and high cost in typical two-stage high-gain photovoltaic-storage inverter topologies.
[0007] (II) Technical Solution
[0008] To achieve the above objectives, the present invention provides the following technical solution:
[0009] This invention provides a low-cost inverter, wherein the input terminal of the low-cost inverter is connected to a DC source and the output terminal is connected to a load or the power grid, and the low-cost inverter includes a front-end circuit, a back-end circuit and an energy storage device.
[0010] The front-end circuit includes a first inductor, a second inductor, a bus capacitor, an energy storage side capacitor, and a four-terminal selection module. The four-terminal selection module is connected to several control terminals to control the conduction or disconnection between the first terminal and the second terminal, the second terminal and the third terminal, and the third terminal and the fourth terminal in the four-terminal selection module.
[0011] The subsequent circuit includes an H-bridge module and a filter module;
[0012] The first end of the first inductor is connected to the positive terminal of the DC source, and the second end is connected to the second end of the four-terminal gating module;
[0013] The first end of the second inductor is connected to the third end of the four-terminal selection module, and the second end is connected to the common terminal of the bus capacitor and the energy storage side capacitor.
[0014] The first terminal of the bus capacitor is connected to the first terminal of the four-terminal selection module, the second terminal of the energy storage side capacitor is connected to the fourth terminal of the four-terminal selection module, and the common terminal of the energy storage side capacitor and the four-terminal selection module is connected to the negative terminal of the DC source.
[0015] The common terminal of the bus capacitor and the four-terminal gating module is connected to the first terminal of the H-bridge module;
[0016] The common terminal of the energy storage side capacitor and the four-terminal gating module is connected to the third terminal of the H-bridge module;
[0017] The second and fourth ends of the H-bridge module are connected to the load or power grid via a filter module.
[0018] The positive terminal of the energy storage device is connected to the first terminal of the energy storage side capacitor, and the negative terminal is connected to the second terminal of the energy storage side capacitor.
[0019] Preferably, a first switching transistor is connected between the first and second ends of the four-terminal selection module.
[0020] Preferably, a second switching transistor is connected between the second and third terminals of the four-terminal selection module.
[0021] Preferably, a third switch is connected between the third and fourth terminals of the four-terminal selection module.
[0022] Preferably, when the output terminal is connected to a load, the filter circuit includes a filter inductor and a filter capacitor, wherein the first end of the filter inductor is connected to the second end of the H-bridge module, the second end of the filter inductor is connected to the fourth end of the H-bridge module via the filter capacitor, and the load is connected in parallel across the two ends of the filter capacitor.
[0023] Preferably, when the output terminal is connected to the power grid, the filter circuit includes a first filter inductor and a second filter inductor, wherein the first end of the first filter inductor is connected to the second end of the H-bridge module, and the second end of the first filter inductor is connected to the fourth end of the H-bridge module via the power grid and the second filter inductor.
[0024] Preferably, the DC source includes a photovoltaic cell.
[0025] Preferably, the front-end of the low-cost inverter has five operating modes, specifically:
[0026] Operating state 1: In the four-terminal selection module, the first terminal is connected to the second terminal, the second terminal is connected to the third terminal, and the third terminal is disconnected from the fourth terminal. When the output terminal is connected to the power grid, the power grid provides power to charge the energy storage device.
[0027] Operating state 2: In the four-terminal selection module, the first terminal is disconnected from the second terminal, the second terminal is connected to the third terminal, and the third terminal is connected to the fourth terminal. The DC source and energy storage are operating in Boost mode, and the first inductor and the second inductor are charging.
[0028] Operating state 3: In the four-terminal selection module, the first terminal is disconnected from the second terminal, the second terminal is disconnected from the third terminal, and the third terminal is connected to the fourth terminal. The DC source and energy storage are operating in Boost mode, the first inductor is discharging, and the second inductor is charging.
[0029] Operating state 4: In the four-terminal selection module, the first terminal is disconnected from the second terminal, the second terminal is connected to the third terminal, the third terminal is disconnected from the fourth terminal, the DC source works in Buck mode, and energy storage and charging are performed.
[0030] Operating state 5: In the four-terminal selection module, the first terminal is disconnected from the second terminal, the second terminal is disconnected from the third terminal, and the third terminal is disconnected from the fourth terminal. The front end of the low-cost inverter is in freewheeling state.
[0031] When the DC source voltage V DC When the voltage is less than 360V, the preamplifier circuit operates in Boost mode, including operating states 2, 3, and 5; when the DC source voltage V... DC When the voltage is ≥360V, the preamplifier circuit operates in Buck mode, including operating states 4 and 5; when the output is connected to the power grid and the power grid charges the energy storage device, it includes operating states 1 and 5.
[0032] Preferably, the bridge arm output voltage value of the H-bridge module is V. Cbus +V Cbt Or -(V) Cbus +V Cbt ), where, where, V Cbus V is the voltage across the bus capacitor. Cbt This is the voltage across the energy storage capacitor.
[0033] Preferably, when the output terminal is only connected to the load, a diode is connected between the first and second terminals of the four-terminal gating module, with the anode of the diode connected to the second terminal and the cathode connected to the first terminal.
[0034] (III) Beneficial Effects
[0035] This invention provides a low-cost inverter. Compared with the prior art, it has the following advantages:
[0036] This invention provides a low-cost inverter, wherein the input terminal of the inverter is connected to a DC source, and the output terminal is connected to a load or the power grid, and includes a front-end circuit, a back-end circuit, and an energy storage device; wherein, the front-end circuit includes a first inductor, a second inductor, a bus capacitor, an energy storage side capacitor, and a four-terminal gating module; the four-terminal gating module is connected to several control terminals for controlling the conduction or disconnection between the first terminal and the second terminal, the second terminal and the third terminal, and the third terminal and the fourth terminal in the four-terminal gating module; the back-end circuit includes an H-bridge module and a filter module; the first terminal of the first inductor is connected to the positive terminal of the DC source, and the second terminal is connected to the second terminal of the four-terminal gating module; the first terminal of the second inductor is connected to the four-terminal gating module. On the third end of the module, the second end is connected to the common terminal of the bus capacitor and the energy storage side capacitor; the first end of the bus capacitor is connected to the first end of the four-terminal selection module, the second end of the energy storage side capacitor is connected to the fourth end of the four-terminal selection module, and the common terminal of the energy storage side capacitor and the four-terminal selection module is connected to the negative terminal of the DC source; the common terminal of the bus capacitor and the four-terminal selection module is connected to the first end of the H-bridge module; the common terminal of the energy storage side capacitor and the four-terminal selection module is connected to the third end of the H-bridge module; the second and fourth ends of the H-bridge module are connected to the load or the power grid via a filter module; the positive terminal of the energy storage device is connected to the first end of the energy storage side capacitor, and the negative terminal is connected to the second end of the energy storage side capacitor. Compared with the typical two-stage photovoltaic-energy storage inverter topology, the inverter of this invention integrates the energy storage device on the bus, effectively reducing the bus capacitor and lowering the cost. Attached Figure Description
[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0038] Figure 1 This is a circuit diagram of a typical two-stage high-gain photovoltaic-storage inverter in the existing technology.
[0039] Figure 2 This is a block diagram of a low-cost inverter according to an embodiment of the present invention;
[0040] Figure 3 This is a circuit diagram of a low-cost inverter according to an embodiment of the present invention;
[0041] Figure 4 This is a schematic diagram of the front-end operating state 1 of the low-cost inverter in an embodiment of the present invention;
[0042] Figure 5 This is a schematic diagram of the front-end operating state 2 of the low-cost inverter in an embodiment of the present invention;
[0043] Figure 6 This is a schematic diagram of the front-end operating state 3 of the low-cost inverter in an embodiment of the present invention;
[0044] Figure 7 This is a schematic diagram of the front-end operating state 4 of the low-cost inverter in an embodiment of the present invention;
[0045] Figure 8 This is a schematic diagram of the front-end operating state 5 of the low-cost inverter in an embodiment of the present invention;
[0046] Figure 9 This is the modulation strategy of the front-end of the low-cost inverter in this embodiment of the invention;
[0047] Figure 10 This is a schematic diagram of the downstream operating state 1 of the low-cost inverter in an embodiment of the present invention;
[0048] Figure 11 This is a schematic diagram of the downstream operating state 2 of the low-cost inverter in an embodiment of the present invention;
[0049] Figure 12 This is the modulation strategy for the downstream stage of the low-cost inverter in this embodiment of the invention;
[0050] Figure 13 Circuit diagram of a low-cost inverter for connecting to the power grid;
[0051] Figure 14 This is a circuit diagram showing the connection of the first and second terminals of the four-terminal gating module to the load for the output connection of a low-cost inverter, using diodes. Detailed Implementation
[0052] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0053] This application provides a low-cost inverter that solves the technical problems of high bus capacitor voltage and high cost in typical two-stage high-gain photovoltaic-storage inverter topologies, thereby reducing bus capacitor voltage and lowering costs.
[0054] The technical solution in this application is to solve the above-mentioned technical problems, and the general idea is as follows:
[0055] like Figure 1 The typical two-stage high-gain photovoltaic-storage inverter topology shown has a high bus capacitor voltage and high cost. Furthermore, the presence of two energy conversion sections results in a large number of required semiconductor devices, further increasing costs, and the complex system structure leads to reduced efficiency due to the multi-stage conversion. To address these issues, this invention proposes a low-cost inverter that integrates the energy storage device on the bus, effectively reducing the bus capacitor and lowering costs. Simultaneously, this inverter reduces the use of semiconductor devices, further reducing costs.
[0056] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.
[0057] This invention provides a low-cost inverter, wherein the input terminal of the inverter is connected to a DC power source, and the output terminal is connected to a load or the power grid, such as... Figure 2 As shown ( Figure 2 Taking the output terminal connected to the load as an example, it includes the front-end circuit, the back-end circuit and the energy storage device;
[0058] The front-end circuit includes a first inductor L1, a second inductor L2, and a bus capacitor C. bus Energy storage side capacitor C bt And a four-terminal selection module; the four-terminal selection module is connected to several control terminals, which are used to control the conduction or disconnection between the first terminal and the second terminal, the second terminal and the third terminal, and the third terminal and the fourth terminal in the four-terminal selection module;
[0059] The subsequent circuit includes an H-bridge module and a filter module;
[0060] The first end of the first inductor L1 is connected to the positive terminal of the DC source, and the second end is connected to the second end of the four-terminal gating module;
[0061] The first terminal of the second inductor L2 is connected to the third terminal of the four-terminal selection module, and the second terminal is connected to the bus capacitor C. bus and energy storage side capacitor C bt On public platforms;
[0062] The first terminal of the bus capacitor is connected to the first terminal of the four-terminal selection module, and the energy storage side capacitor C bt The second terminal is connected to the fourth terminal of the four-terminal selection module, and the energy storage side capacitor Cbt Connect the common terminal of the four-terminal gating module to the negative terminal of the DC power source;
[0063] The bus capacitor C bus The common terminal of the four-terminal gating module is connected to the first terminal of the H-bridge module;
[0064] The energy storage side capacitor C bt Connect the common terminal of the four-terminal gating module to the third terminal of the H-bridge module;
[0065] The second and fourth ends of the H-bridge module are connected to the load or power grid via a filter module.
[0066] The positive terminal of the energy storage device BT is connected to the energy storage side capacitor C. bt At the first terminal, the negative terminal is connected to the energy storage side capacitor C. bt On the second end.
[0067] In practical implementation, the four connection terminals in the four-terminal selection module can be connected via switching transistors or other devices with disconnect and conduction functions. In this embodiment, the four connection terminals are connected via MOS switching transistors. Simultaneously, to ensure the normal operation of each switching device, a freewheeling diode needs to be connected in parallel with each switching device. The parallel direction of the freewheeling diode is related to the type of switching device, and technicians can set it according to the type of switching device; it is not limited here. Unless otherwise specified, the switching device implicitly includes a freewheeling diode; special cases will be indicated in this embodiment. The switching transistors in the H-bridge module can be IGBTs or MOSFETs. In this embodiment, IGBTs are selected.
[0068] like Figure 3 As shown, the four-terminal gating module includes three switching transistors T1, T2, and T3; the H-bridge module includes T4, T5, T6, and T7; and the filtering module includes a filter inductor L. o Filter capacitor C o The output is connected to a load, and the DC source is a photovoltaic cell.
[0069] Figure 3 The five operating modes of the front-end of the low-cost inverter are shown in Table 1, and the states of the switching devices in each operating mode are shown in Table 1.
[0070] Table 1 Switching Status Table of Front-End Switching Transistors for Low-Cost Inverters
[0071]
[0072] Working status 1: such as Figure 4 As shown, switching transistors T1 and T2 are turned on, and T3 is turned off. When the inverter output is connected to the grid, the grid side can provide power to charge the energy storage device.
[0073] Working status 2: such as Figure 5 As shown, switch T1 is off, T2 and T3 are on, the photovoltaic cell and energy storage operate in Boost mode, and inductors L1 and L2 are charged.
[0074] Working status 3: such as Figure 6 As shown, switches T1 and T2 are off, T3 is on, the photovoltaic cell and energy storage operate in Boost mode, inductor L1 discharges, and L2 charges.
[0075] Working status 4: such as Figure 7 As shown, when switches T1 and T3 are off and T2 is on, the photovoltaic cell operates in Buck mode for energy storage and charging.
[0076] Working status 5: such as Figure 8 As shown, switching transistors T1, T2, and T3 are all turned off, and the front end of the low-cost inverter is in freewheeling mode.
[0077] When the photovoltaic cell voltage V PV When the voltage is <360V, the preamplifier circuit operates in Boost mode, including operating states 2, 3, and 5; when the photovoltaic cell voltage V PV When the voltage is ≥360V, the pre-amplifier circuit operates in Buck mode, including operating states 4 and 5; when the grid-connected power supply charges the energy storage device, it includes operating states 1 and 5. The pre-amplifier modulation strategy is as follows: Figure 9 As shown.
[0078] The H-bridge module in the later stage adopts bipolar modulation, which can suppress leakage current. It has two operating modes, and the state of the switching devices in each operating mode is shown in Appendix Table 2.
[0079] Table 2 Switching Status Table of the Power-End Switching Transistors in Low-Cost Inverters
[0080]
[0081] Working status 1: such as Figure 10 As shown, switches T3 and T6 are turned on, while T4 and T5 are turned off. The bridge arm output voltage is V. Cbus +V Cbt Among them, V Cbus V is the voltage across the bus capacitor. Cbt This is the voltage across the energy storage capacitor.
[0082] Working status 2: such as Figure 11 As shown, switches T4 and T5 are turned on, while T3 and T6 are turned off. The bridge arm output voltage is -(V). Cbus +V Cbt ).
[0083] Post-modulation strategies such as Figure 12 As shown.
[0084] like Figure 13 As shown, the output of the low-cost inverter in this embodiment of the invention can be connected to residential loads, or it can be connected to the grid to provide power to the grid or absorb power from the grid. When the output is connected to the grid, the four-terminal gating module includes three switching transistors T1, T2, and T3; the H-bridge module includes T4, T5, T6, and T7; and the filter circuit includes a filter inductor L. O1 L O2 .
[0085] In practice, the DC input source of the inverter can be, in addition to photovoltaic cells, clean energy sources such as wind power, or an external DC source.
[0086] like Figure 14 As shown, when the output is connected to a residential load, since there is no need for the grid to charge the energy storage device in reverse, the switching transistors on the front end can be replaced with diodes. That is, the four-terminal selection module includes two switching transistors T1 and T2 and a diode D1, which can further reduce costs, and the photovoltaic-energy storage inverter can still work equivalently.
[0087] In summary, compared with existing technologies, it has the following beneficial effects:
[0088] 1. Compared to a typical two-stage photovoltaic-storage inverter topology, the inverter in this embodiment integrates the energy storage device on the bus, effectively reducing bus capacitance and lowering costs. Simultaneously, it reduces the use of one diode or one switching transistor, further reducing costs.
[0089] 2. Compared with the typical two-stage photovoltaic-storage inverter topology, the control method of the low-cost inverter proposed in this embodiment of the invention is simpler.
[0090] 3. The integrated control strategy can realize the charging and discharging of the energy storage device, and can suppress leakage current to a certain extent. While maintaining the power balance of the system, it also buffers the fluctuation of photovoltaic cell output power, thereby improving the system's working performance and operational stability.
[0091] It should be noted that, in this document, 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 said element.
[0092] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims
1. A low-cost inverter, characterized in that, The low-cost inverter has its input terminal connected to a DC source and its output terminal connected to a load or the power grid. The low-cost inverter includes a front-end circuit, a back-end circuit, and an energy storage device. The front-end circuit includes a first inductor, a second inductor, a bus capacitor, an energy storage side capacitor, and a four-terminal selection module. The four-terminal selection module is connected to several control terminals to control the conduction or disconnection between the first terminal and the second terminal, the second terminal and the third terminal, and the third terminal and the fourth terminal in the four-terminal selection module. The subsequent circuit includes an H-bridge module and a filter module; The first end of the first inductor is connected to the positive terminal of the DC source, and the second end is connected to the second end of the four-terminal gating module; The first end of the second inductor is connected to the third end of the four-terminal selection module, and the second end is connected to the common terminal of the bus capacitor and the energy storage side capacitor. The first terminal of the bus capacitor is connected to the first terminal of the four-terminal selection module, the second terminal of the energy storage side capacitor is connected to the fourth terminal of the four-terminal selection module, and the common terminal of the energy storage side capacitor and the four-terminal selection module is connected to the negative terminal of the DC source. The common terminal of the bus capacitor and the four-terminal gating module is connected to the first terminal of the H-bridge module; The common terminal of the energy storage side capacitor and the four-terminal gating module is connected to the third terminal of the H-bridge module; The second and fourth ends of the H-bridge module are connected to the load or power grid via a filter module. The positive terminal of the energy storage device is connected to the first terminal of the energy storage side capacitor, and the negative terminal is connected to the second terminal of the energy storage side capacitor.
2. The low-cost inverter as described in claim 1, characterized in that, The first terminal of the four-terminal selection module is connected to the second terminal via a first switching transistor.
3. The low-cost inverter as described in claim 1, characterized in that, The second terminal of the four-terminal selection module is connected to the third terminal via a second switching transistor.
4. The low-cost inverter as described in claim 1, characterized in that, A third switch is connected between the third and fourth terminals of the four-terminal selection module.
5. The low-cost inverter as described in claim 1, characterized in that, When the output terminal is connected to a load, the filter circuit includes a filter inductor and a filter capacitor. The first end of the filter inductor is connected to the second end of the H-bridge module, and the second end of the filter inductor is connected to the fourth end of the H-bridge module via the filter capacitor. The load is connected in parallel across the two ends of the filter capacitor.
6. The low-cost inverter as described in claim 1, characterized in that, When the output terminal is connected to the power grid, the filter circuit includes a first filter inductor and a second filter inductor. The first end of the first filter inductor is connected to the second end of the H-bridge module, and the second end of the first filter inductor is connected to the fourth end of the H-bridge module via the power grid and the second filter inductor.
7. The low-cost inverter as described in claim 1, characterized in that, The DC source includes photovoltaic cells.
8. The low-cost inverter as described in any one of claims 1 to 7, characterized in that, The front-end of the low-cost inverter has five operating modes, specifically: Operating state 1: In the four-terminal selection module, the first terminal is connected to the second terminal, the second terminal is connected to the third terminal, and the third terminal is disconnected from the fourth terminal. When the output terminal is connected to the power grid, the power grid provides power to charge the energy storage device. Operating state 2: In the four-terminal selection module, the first terminal is disconnected from the second terminal, the second terminal is connected to the third terminal, and the third terminal is connected to the fourth terminal. The DC source and energy storage are operating in Boost mode, and the first inductor and the second inductor are charging. Operating state 3: In the four-terminal selection module, the first terminal is disconnected from the second terminal, the second terminal is disconnected from the third terminal, and the third terminal is connected to the fourth terminal. The DC source and energy storage are operating in Boost mode, the first inductor is discharging, and the second inductor is charging. Operating state 4: In the four-terminal selection module, the first terminal is disconnected from the second terminal, the second terminal is connected to the third terminal, the third terminal is disconnected from the fourth terminal, the DC source works in Buck mode, and energy storage and charging are performed. Operating state 5: In the four-terminal selection module, the first terminal is disconnected from the second terminal, the second terminal is disconnected from the third terminal, and the third terminal is disconnected from the fourth terminal. The front end of the low-cost inverter is in freewheeling state. When the DC source voltage V DC When the voltage is less than 360V, the preamplifier circuit operates in Boost mode, including operating states 2, 3, and 5; when the DC source voltage V... DC When the voltage is ≥360V, the preamplifier circuit operates in Buck mode, including operating states 4 and 5; when the output is connected to the power grid and the power grid charges the energy storage device, it includes operating states 1 and 5.
9. The low-cost inverter as described in any one of claims 1 to 7, characterized in that, The output voltage value of the bridge arm of the H-bridge module is V. Cbus +V Cbt Or -(V) Cbus +V Cbt ), Among them, V Cbus V is the voltage across the bus capacitor. Cbt This is the voltage across the energy storage capacitor.
10. The low-cost inverter as described in claim 1, characterized in that, When the output terminal is only connected to the load, a diode is connected between the first and second terminals of the four-terminal gating module, with the anode of the diode connected to the second terminal and the cathode connected to the first terminal.