A single-stage five-level boost inverter

Abstract

The application discloses a single-stage five-level boost inverter, comprising a parallel switch capacitor converter, a first group of power electronic switches and a second group of power electronic switches, wherein the switch capacitor converter is composed of four power electronic switches and a bridge capacitor; the first group of power electronic switches and the second group of power electronic switches each comprise two series-connected power electronic switches; the switch capacitor converter comprises a first power electronic switch S1, a second power electronic switch S2, a third power electronic switch S3 and a fourth power electronic switch S4 connected in series, the collector of S1 is connected to the collector of S2, the emitter of S2 is connected to the collector of S3, the emitter of S3 is connected to the collector of S4; and the bridge capacitor has one end connected to the collector of S2 and the other end connected to the collector of S4. The application reduces the implementation cost and improves the power density, increases the number of output voltage levels, reduces the size of the filter, realizes the function of voltage boosting and can be applied in the scene of low DC input voltage, and reduces the switching loss.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, and in particular to a single-stage five-level boost inverter. Background Technology

[0002] Distributed generation systems have become an important part of the new energy industry due to their advantages such as flexible application scenarios, wide application range, and rational utilization of land space resources. In distributed systems, most new energy power generation devices (such as photovoltaic power generation devices and wind power generation devices) output DC voltage, which needs to be connected to the grid through a grid-connected inverter. Therefore, the performance requirements for grid-connected inverters are constantly increasing, namely higher energy conversion efficiency, smaller size, and lower cost. Currently, the most widely used grid-connected inverter topology is the H-bridge inverter. The simple circuit structure is the main advantage of this type of inverter. However, this type of inverter can only be used in scenarios with high DC input voltage, that is, the DC input voltage must be higher than the peak value of the AC output voltage. In order to expand the application scenarios with low DC input voltage, traditional grid-connected inverter systems adopt a two-stage structure of a boost converter and an H-bridge inverter. This two-stage configuration will reduce the overall conversion efficiency and lead to an increase in cost and circuit complexity.

[0003] Currently, single-stage boost inverters are widely developed and used in photovoltaic applications. The dual-boost inverter topology uses two boost converters to achieve boosting of the AC power supply during the positive and negative half-cycles, respectively. This topology allows the output voltage to be higher than the input voltage. However, all power electronic switching devices operate under high frequency and high voltage stress, leading to significant switching losses. Another similar inverter is the dual-Buck structure Buck-Boost inverter. Based on the Buck-Boost principle, it operates symmetrically, eliminating shoot-through issues for the positive and negative half-cycles of the output AC voltage. However, the use of six inductors in this topology results in high implementation cost and low power density. Furthermore, there is a Buck-Boost inverter that includes a DC-AC conversion circuit. However, the high voltage stress of the Buck-Boost circuit reduces conversion efficiency. Therefore, due to considerations of conversion efficiency and voltage stress, the power capacity of this topology inverter is limited.

[0004] Currently, for boost inverters, to achieve single-stage DC-AC conversion, there are solutions that integrate switched capacitor topologies into a single-stage inverter to improve voltage gain. One such inverter topology employs a flying capacitor and a boost converter with a midpoint clamping configuration. This topology possesses both high-frequency common-mode buck and boost capabilities. However, the seven power electronic switching devices in this topology operate at high frequencies, resulting in high switching losses. Summary of the Invention

[0005] The objective of this invention is achieved through the following technical solutions.

[0006] The present invention provides a single-stage five-level boost inverter, comprising a parallel switched capacitor converter, a first group of power electronic switches, and a second group of power electronic switches, wherein the switched capacitor converter consists of four power electronic switches and a bridge capacitor.

[0007] Furthermore, the first group of power electronic switches and the second group of power electronic switches each include two power electronic switches connected in series.

[0008] Furthermore, the switched capacitor converter includes a first power electronic switch S1, a second power electronic switch S2, a third power electronic switch S3, and a fourth power electronic switch S4 connected in series. The collector of S1 is connected to the collector of S2, the emitter of S2 is connected to the collector of S3, and the emitter of S3 is connected to the collector of S4. One end of the bridge capacitor is connected to the collector of S2, and the other end is connected to the collector of S4.

[0009] Furthermore, the single-stage five-level boost inverter further includes a DC power supply, the positive terminal of which is connected to the collector of S3, and the negative terminal of which is connected to the emitter of S4.

[0010] Furthermore, the single-stage five-level boost inverter further includes a diode, the anode of which is connected to the emitter of S4, and the cathode of which is connected to the emitter of S1.

[0011] Furthermore, the first group of power electronic switches includes power electronic switch S A , Where S A emitter connection The collector, S A The collector is connected to the emitter of S1. The emitter of S4 is connected to the emitter of S4.

[0012] Furthermore, the second group of power electronic switches includes power electronic switch S B , Where S B emitter connection The collector, S B The collector is connected to the emitter of S1. The emitter of S4 is connected to the emitter of S4.

[0013] Furthermore, the single-stage five-level boost inverter further includes a first inductor, one end of which is connected to S. A One end is the emitter, and the other end is connected to one end of the load.

[0014] Furthermore, the single-stage five-level boost inverter further includes a second inductor, one end of which is connected to S. B The emitter is connected to the other end of the load.

[0015] Furthermore, the single-stage five-level boost inverter further includes a second capacitor connected across the load.

[0016] The advantages of this invention are:

[0017] A single-stage DC-AC conversion was achieved, reducing implementation costs and increasing power density. The number of output voltage levels was increased, reducing filter size. A boost function was implemented, enabling applications with low DC input voltages. Power electronic switching devices do not operate entirely at high frequencies, but mostly at low frequencies, reducing switching losses. Attached Figure Description

[0018] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0019] Figure 1 A schematic diagram of a novel single-stage five-level boost inverter topology according to an embodiment of the present invention is shown.

[0020] Figure 2 A circuit diagram of switch state V1 according to an embodiment of the present invention is shown.

[0021] Figure 3 A circuit diagram of switch state V2 according to an embodiment of the present invention is shown.

[0022] Figure 4 A circuit diagram of switch state V3 according to an embodiment of the present invention is shown.

[0023] Figure 5 A circuit diagram of switch state V4 according to an embodiment of the present invention is shown.

[0024] Figure 6 A circuit diagram of switch state V5 according to an embodiment of the present invention is shown. Detailed Implementation

[0025] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0026] Boost converter circuit: The boost converter circuit is one of the six basic chopper circuits. It is a switching DC boost circuit that uses the ratio of the turn-on and turn-off time of the switching transistor to maintain a stable output. It can make the output voltage higher than the input voltage and the output voltage and input voltage have the same polarity.

[0027] Buck step-down circuit: The Buck step-down circuit is one of the six basic chopper circuits. It is a type of switching DC step-down circuit that uses the ratio of the turn-on and turn-off time of the switching transistor to maintain a stable output. It can make the output voltage lower than the input voltage and the output voltage have the same polarity as the input voltage.

[0028] Buck-Boost Circuit: The Buck-Boost circuit is one of the six basic chopper circuits. It is a type of DC switching circuit that uses the ratio of the turn-on and turn-off time of the switching transistor to maintain a stable output. It can make the output voltage lower or higher than the input voltage, and the output voltage has the opposite polarity to the input voltage.

[0029] Switched Capacitor Converter: A switched capacitor converter uses only capacitors and switching transistors to achieve voltage transformation. Its switching sequence is typically switching on, doubling or halving the input power supply voltage. Energy transfer and storage are provided by external capacitors.

[0030] This invention combines a switched-capacitor converter and a DC-AC converter to propose a novel single-stage five-level boost inverter. Its detailed circuit diagram is shown below. Figure 1 As shown.

[0031] The present invention provides a single-stage five-level boost inverter, comprising a parallel switched capacitor converter, a first group of power electronic switches, and a second group of power electronic switches, wherein the switched capacitor converter consists of four power electronic switches and a bridge capacitor.

[0032] Furthermore, the first group of power electronic switches and the second group of power electronic switches each include two power electronic switches connected in series.

[0033] Furthermore, the switched capacitor converter includes a first power electronic switch S1, a second power electronic switch S2, a third power electronic switch S3, and a fourth power electronic switch S4 connected in series. The collector of S1 is connected to the collector of S2, the emitter of S2 is connected to the collector of S3, and the emitter of S3 is connected to the collector of S4. One end of the bridge capacitor is connected to the collector of S2, and the other end is connected to the collector of S4.

[0034] Furthermore, the single-stage five-level boost inverter further includes a DC power supply, the positive terminal of which is connected to the collector of S3, and the negative terminal of which is connected to the emitter of S4.

[0035] Furthermore, the single-stage five-level boost inverter further includes a diode D1, the anode of which is connected to the emitter of S4, and the cathode of which is connected to the emitter of S1.

[0036] Furthermore, the first group of power electronic switches includes power electronic switch S A , Where S A emitter connection The collector, S A The collector is connected to the emitter of S1. The emitter of S4 is connected to the emitter of S4.

[0037] Furthermore, the second group of power electronic switches includes power electronic switch S B , Where S B emitter connection The collector, S B The collector is connected to the emitter of S1. The emitter of S4 is connected to the emitter of S4.

[0038] Furthermore, the single-stage five-level boost inverter further includes a first inductor L1, one end of which is connected to S. A One end is the emitter, and the other end is connected to one end of the load.

[0039] Furthermore, the single-stage five-level boost inverter further includes a second inductor L2, one end of which is connected to S. B The emitter is connected to the other end of the load.

[0040] Furthermore, the single-stage five-level boost inverter further includes a second capacitor C2, which is connected across the two ends of the load.

[0041] The switched-capacitor converter section consists of four power electronic switches and one bridge capacitor. It can convert the DC input voltage V... inConverted into three different positive voltage levels: 0, V in V in +V C This invention achieves input voltage boosting and limits the maximum voltage gain to twice the input voltage. The positive three-level boost voltage output from the switched-capacitor converter is extended into a five-level boost voltage containing both positive and negative voltages by a DC-AC converter consisting of four power electronic switches operating at low switching frequencies and two output inductors. Compared to conventional DC-AC inverters, in the novel single-stage five-level boost inverter topology proposed in this invention, the four power electronic switches in the DC-AC converter section only switch at the zero-crossing point of the AC output, thus their switching losses are negligible. Furthermore, through single-stage power conversion, this inverter can transfer DC power to the AC output.

[0042] Among them, switch S A , S B and The inverter operates at low frequency. Switch S1 only operates at high frequency when the AC output voltage is lower than the DC input voltage. During this time, switches S2 and S4 are continuously on, and switch S3 is continuously off. Once the AC output voltage reaches the DC input voltage, switch S1 begins to continuously switch on and off, and switches S2 and S4 begin to operate at high frequency. The drive signal for switch S3 is complementary to that of switches S2 and S4 and has a short dead time. Based on the above operating states, it can be seen that switches S1, S2, S3, and S4 do not operate entirely at high frequency during one output AC cycle. When the AC output voltage is lower than the DC input voltage, switches S2 and S4 have no switching losses, and switch S3 has neither switching nor conduction losses. When the AC output voltage is higher than the DC input voltage, switch S1 has no switching losses. Therefore, the novel single-stage five-level boost inverter proposed in this invention reduces the overall switching losses of the power electronic devices.

[0043] Assume the DC input voltage is V in The AC output voltage is V out Then the maximum voltage that each of the power electronic switches S1, S2, S3, and S4 can withstand should be V. in Power electronic switch S A , S B and The maximum withstand voltage for each should be V. out The peak value.

[0044] Based on the novel single-stage five-level boost inverter topology proposed above, five different voltage levels can be obtained, due to the power electronic switch S... A and SB and They operate in a complementary manner, and Table 1 only lists switches S1, S2, S3, S4, and S6. A S B The operating mode and its corresponding output voltage.

[0045] Example:

[0046] Table 1: Operating Status of the New Single-Stage Five-Level Boost Inverter

[0047]

[0048]

[0049] In ensuring the power electronic switch S A and S B and Under the premise that they all operate in a complementary manner, the novel single-stage five-level boost inverter topology proposed in this invention can obtain five different voltage levels and has five different switching states.

[0050] Switch state V1: Power electronic switches S2, S4, S A Power electronic switches S1, S3, and S are activated. B Turn off. The specific circuit diagram is as follows: Figure 2 As shown, where i c The direction of current in the bridge capacitor is represented by i. o This indicates the direction of the output current. In this state, the output voltage of the boost inverter is 0.

[0051] Switch state V2: Power electronic switches S1, S2, S4, S A Power on, power electronic switches S3, S B Turn off. The specific circuit diagram is as follows: Figure 3 As shown, where i c The direction of current in the bridge capacitor is represented by i. o This indicates the direction of the output current. In this state, the output voltage of the boost inverter is V. in .

[0052] Switch state V3: Power electronic switches S1, S3, S A Power electronic switches S2, S4, and S are activated. B Turn off. The specific circuit diagram is as follows: Figure 4 As shown, where i c The direction of current in the bridge capacitor is represented by i. o This indicates the direction of the output current. In this state, the output voltage of the boost inverter is V. in +V C .

[0053] Switch state V4: Power electronic switches S1, S2, S4, S B Power on, power electronic switches S3, S A Turn off. The specific circuit diagram is as follows: Figure 5 As shown, where i c The direction of current in the bridge capacitor is represented by i. o This indicates the direction of the output current. In this state, the output voltage of the boost inverter is -V. in .

[0054] Switch state V5: Power electronic switches S1, S3, S B Power electronic switches S2, S4, and S are activated. A Turn off. The specific circuit diagram is as follows: Figure 6 As shown, where i c The direction of current in the bridge capacitor is represented by i. o This indicates the direction of the output current. In this state, the output voltage of the boost inverter is -(V... in +V C ).

[0055] This invention achieves single-stage DC-AC conversion; increases the number of output voltage levels to achieve five-level output; implements boost function, which can be applied in scenarios with low DC input voltage; the power electronic switching devices do not operate entirely at high frequencies, but mostly at low frequencies, reducing switching losses and lowering the voltage stress on the switching transistors.

[0056] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A single-stage five-level boost inverter, characterized in that, It includes a parallel switched capacitor converter, a first group of power electronic switches, and a second group of power electronic switches, wherein the switched capacitor converter consists of four power electronic switches and a bridge capacitor; The switched capacitor converter includes a first power electronic switch connected in series. Second power electronic switch Third power electronic switch Fourth power electronic switch , collector connection The collector, emitter connection The collector, emitter connection The collector of the bridge capacitor; one end of the bridge capacitor is connected to The collector, the other end connected The collector; The single-stage five-level boost inverter includes a diode, the anode of which is connected to... The emitter of the diode is connected to the cathode of the diode. The emitter; The first group of power electronic switches includes power electronic switches , ,in emitter connection The collector, collector connection The emitter, emitter connection The emitter; The second group of power electronic switches includes power electronic switches , ,in emitter connection The collector, collector connection The emitter, emitter connection The emitter; The single-stage five-level boost inverter includes a first inductor, one end of which is connected to... The emitter is connected to one end of the load, and the other end is connected to the other end of the load. The single-stage five-level boost inverter includes a second inductor, one end of which is connected to... One end is the emitter, and the other end is connected to the other end of the load; Among them, switches , , and Operating at low frequency; switching It operates at high frequency only when the AC output voltage is lower than the DC input voltage; at this time, the switch... , In a continuously connected state, the switch It is in a continuously off state; when the AC output voltage reaches the DC input voltage, the switch... Start continuously switching on and off, switch and It begins to operate at a high frequency, while the switch... The drive signal is related to the switch. , Complementary, and has dead time.

2. The single-stage five-level boost inverter according to claim 1, characterized in that, The first group of power electronic switches and the second group of power electronic switches each consist of two power electronic switches connected in series.

3. A single-stage five-level boost inverter according to claim 1, characterized in that, The single-stage five-level boost inverter includes a DC power supply, the positive terminal of which is connected to... The collector of the DC power supply is connected to the negative terminal of the DC power supply. The emitter.

4. A single-stage five-level boost inverter according to claim 1, characterized in that, The single-stage five-level boost inverter includes a second capacitor connected across the load.

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