A single-input buck-boost type non-electrolytic capacitor single-phase inverter

Abstract

The present invention provides a novel single-input buck-boost type electrolytic capacitor-free single-phase inverter, which belongs to the field of power electronic power conversion, and comprises a direct current power supply and an inverter circuit. The inverter circuit comprises a first switch tube S1, a second switch tube S2, a third switch tube S3, a fourth switch tube S4, a first diode D1, a second diode D2, a first capacitor C1, a second capacitor C2, a filter capacitor C3, a first inductor L1, a second inductor L2, a filter inductor L3 and a load R, wherein the third switch tube S3 and the fourth switch tube S4 are switch tubes without anti-parallel diodes; one end of the first capacitor C1 is connected to the emitter of the first switch tube S1 and the first inductor L1, and the other end is connected to the cathode of the first diode D1; one end of the second capacitor C2 is connected to the emitter of the second switch tube S2 and the second inductor L2, and the other end is connected to the anode of the first diode D2. The circuit structure of the present invention is simple, the capacitors are all electrolytic capacitors, there are many working modes, and the voltage can be adjusted in a large range.

Description

Technical Field

[0001] The invention relates to the field of power electronic electric energy conversion, and in particular to a novel single-input buck-boost type non-electrolytic capacitor single-phase inverter. Background Art

[0002] With the rapid development of productivity and science and technology, the use of clean renewable energy has become a hot topic in various fields. New energy sources such as solar energy and wind energy have the advantages of no geographical restrictions, easy mining and transportation, and no need for storage and delivery. For photovoltaic power generation systems, inverters are an indispensable part of converting the direct current generated by the array into alternating current.

[0003] In order to achieve a wide range of output, traditional inverters often adopt a non-isolated structure and use large electrolytic capacitors to achieve voltage stabilization. This type of inverter not only increases circuit components, but also occupies a large area and is more troublesome to maintain. In order to improve the existing technology and achieve the goals of wide gain, simple structure, small size, high efficiency, etc., the present invention proposes a new type of non-isolated buck-boost type non-electrolytic capacitor single-phase inverter. Summary of the invention

[0004] In order to solve and make up for the deficiencies of the prior art, the present invention provides a novel non-electrolytic capacitor single-phase inverter, which has a wide range of voltage output and does not require a large electrolytic capacitor inside the circuit.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A novel non-electrolytic capacitor single-phase inverter, comprising a DC power supply and a novel inverter circuit;

[0007] The novel inverter circuit specifically includes: a first switch tube S1, a second switch tube S2, a third switch tube S3 (without an anti-parallel diode), a fourth switch tube S4 (without an anti-parallel diode), a first diode D1, a second diode D2, a first capacitor C1, a second capacitor C2, a filter capacitor C3, a first inductor L1, a second inductor L2, a filter inductor L3 and a load R.

[0008] The collector of the first switch tube S1 is connected to the positive electrode of the DC power supply, the first inductor L1 is connected to the emitter of the first switch tube S1, one end of the second inductor L2 is connected to the positive electrode of the DC power supply, and one end is connected to the collector of the second switch tube S2, and the emitter of the second switch tube S2 is connected to the first inductor L1. One end of the first capacitor C1 is connected to the emitter of the first switch tube S1, and the other end is connected to the cathode of the first diode D1. The anode of the first diode D1 is connected to the cathode of the second diode D2 and is connected to the emitter of the second switch tube S2. One end of the second capacitor C2 is connected to the collector of the second switch tube S2, and one end is connected to the anode of the second diode D2. The filter capacitor C3 is connected in parallel with the load R and in series with the filter inductor L3, and one end of the filter capacitor C3 is connected to the anode of the first diode D1, and the other end is connected to the emitter of the third switch tube S3. The collector of the third switch tube S3 is connected to the cathode of the first diode D1, and the emitter of the third switch tube S3 is connected to the collector of the fourth switch tube S4. The fourth switch tube S4 is connected to the anode of the second diode D2.

[0009] When the AC load or AC output voltage is in the first half cycle, the states of the first switch tube S1 and the second switch tube S2 are alternately turned on and off, and the first switch tube S1 and the second switch tube S2 are turned on at the same time but not turned off at the same time. When the second switch tube S2 is turned off, the first switch tube S1 may be in the on state, and when the second switch tube S2 is in the on state, the first switch tube S1 is also in the on state, but the second switch tube S2 is in the on state for a very short time and can be ignored. At this time, the third switch tube S3 is in the on state, and the fourth switch tube S4 is in the off state.

[0010] When the AC load or AC output voltage is in the second half cycle, the states of the first switch tube S1 and the second switch tube S2 are alternately turned on and off, and the first switch tube S1 and the second switch tube S2 are turned on at the same time but not turned off at the same time. When the first switch tube S1 is turned off, the second switch tube S2 may be in the on state, and when the first switch tube S1 is in the on state, the second switch tube S2 is also in the on state, but the first switch tube S1 is in the on state for a very short time and can be ignored. At this time, the fourth switch tube S4 is in the on state, and the third switch tube S3 is in the off state.

[0011] Optionally, the novel non-electrolytic capacitor single-phase inverter circuit further includes:

[0012] Filter circuit;

[0013] The filter circuit is composed of a filter capacitor C3 and a filter inductor L3. One end of the filter circuit is connected to the anode of the first diode D1 and the cathode of the second diode D2, and the other end is connected to the emitter of the third switch tube S3 and the collector of the fourth switch tube S4. The load R is connected in parallel with the filter capacitor C3.

[0014] Optionally, the first capacitor C1, the second capacitor C2 and the filter capacitor C3 are all non-electrolytic capacitors.

[0015] The converter described in the present invention has four switching states and six working states in one working cycle. Switching state 1 is that the first switch tube S1 and the third switch tube S3 are turned on, and the second switch tube S2 and the fourth switch tube S4 are turned off. At this time, there are two working states. In the first working state, the DC power supply charges the first inductor L1 and charges the first capacitor C1 through the first diode D1 while supplying power to the load. The second working state is when the first capacitor C1 reaches charging saturation, at this time, the potential of the anode of the first diode D1 is lower than the potential of the cathode connected to the first capacitor C1, and the first diode D1 is no longer turned on. At this time, the DC power supply no longer supplies power to the first capacitor C1, and the first capacitor C1 starts to supply power to the load. The two working states are alternately performed with the charging and discharging process of the first capacitor C1. At the same time, in the two working states, the DC power supply continuously charges the second inductor L2 and the second capacitor C2.

[0016] Switching state 2 is that the third switch tube S3 is turned on, and the first switch tube S1, the second switch tube S2, and the fourth switch tube S4 are turned off. This is the third working state, the first inductor L1 charges the first capacitor C1 through the first diode D1, and the load side is freewheeling by the filter inductor L3 through the first diode D1. The DC power supply continuously charges the second inductor L2 and the second capacitor C2.

[0017] Switch state 3 is that the second switch tube S2 and the fourth switch tube S4 are turned on, and the first switch tube S1 and the third switch tube S3 are turned off. Similar to switch state 1, there are two working states. In the fourth working state, the DC power supply and the second capacitor C2 supply power to the load at the same time. At this time, the cathode potential of the second diode D2 is higher than the anode potential and is not turned on. No current passes through the first inductor L1, the first capacitor C1, and the first diode D1. When the potential of the second capacitor C2 decreases so that the cathode potential of the second diode D2 is lower than the anode potential, the fifth working state is entered, and the DC power supply charges the second inductor L2 and the second capacitor C2. The load side is continuously energized by the filter inductor L3 through the second diode D2.

[0018] Switching state 4 is that the fourth switch tube S4 is turned on, and the first switch tube S1, the second switch tube S2, and the third switch tube S3 are turned off. In the sixth working state, the DC power supply charges the second inductor L2 and the second capacitor C2. The load side is freewheeled by the filter inductor L3 through the second diode D2.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) The present invention is a circuit topology with a wide output voltage range, which is suitable for occasions with large voltage fluctuations and has the superior performance of both Cuk circuit and Zeta circuit;

[0021] (2) The circuit structure of the present invention is very simple, using only two diodes and four switch tubes, but it realizes multiple working states to avoid dead time;

[0022] (3) In the circuit of the present invention, under the same switching state, the potential difference of the diode is positive or negative due to the charging result of the capacitor, thus generating two different working states, resulting in different working states of the charging capacitor even if the structure is symmetrical;

[0023] (4) The high-frequency working switch in the present invention has no danger of direct power supply, basically no common conduction time, no need to consider dead zone, and relies on the intermediate capacitor to transfer energy. The capacitor voltage has the characteristic of not being able to change suddenly. The value of the intermediate capacitor is also relatively flexible, and the intermediate capacitor can also suppress the disturbance of the input voltage.

[0024] (5) The capacitors of the present invention are non-electrolytic capacitors and are of non-isolated structure, which greatly reduces device loss and maintenance costs, and has a small footprint and high efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A circuit topology diagram of the present invention;

[0026] Figure 2 It is a schematic diagram of the switch tube control signal of the present invention;

[0027] Figure 3 is a schematic diagram of the working mode 1 of the present invention;

[0028] Figure 4 is a schematic diagram of working mode 2 of the present invention;

[0029] Figure 5 is a schematic diagram of working mode 3 of the present invention;

[0030] Figure 6 is a schematic diagram of the working mode 4 of the present invention;

[0031] Figure 7 is a schematic diagram of the working mode 5 of the present invention;

[0032] Figure 8 is a schematic diagram of the working mode 6 of the present invention;

[0033] Fig. 9 It is a schematic diagram of the voltage of the first capacitor under boost inversion in the present invention;

[0034] Fig.10 It is a schematic diagram of the voltage of the first capacitor under step-down inversion in the present invention;

[0035] Fig.11 It is a schematic diagram of the voltage of the second capacitor under boost inversion in the present invention;

[0036] Fig.12 It is a schematic diagram of the voltage of the second capacitor under step-down inversion in the present invention;

[0037] Fig.13 It is a schematic diagram of the first inductor current under boost inversion in the present invention;

[0038] Fig.14 It is a schematic diagram of the first inductor current under buck inversion in the present invention;

[0039] Fig.15 A schematic diagram of the second inductor current under boost inversion in the present invention;

[0040] Fig.16 A schematic diagram of the second inductor current under buck inversion in the present invention;

[0041] Fig.17 The waveform diagram of the DC input voltage and the output AC voltage under boost inversion in the present invention;

[0042] Fig.18 The waveform diagram of the DC input voltage and the output AC voltage under step-down inversion in the present invention;

[0043] Fig.19 This is a structural diagram of the control circuit in the present invention. DETAILED DESCRIPTION

[0044] The exemplary embodiments, features and aspects of the present invention will be described in detail below with reference to the accompanying drawings. The same reference numerals in the drawings represent elements with the same or similar functions. Although various aspects of the embodiments are shown in the drawings, the drawings need not be drawn to scale unless otherwise specified. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0045] The object of the present invention is to provide a novel non-electrolytic capacitor single-phase inverter having the capability of stepping up and down voltage.

[0046] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0047] Figure 1 : is a structural diagram of a novel non-electrolytic capacitor single-phase inverter in an embodiment of the present invention, such as Figure 1 As shown, the single-phase inverter includes: a DC power supply and an inverter circuit, and the inverter circuit specifically includes: a first switch tube S1, a second switch tube S2, a third switch tube S3 (without an anti-parallel diode), a fourth switch tube S4 (without an anti-parallel diode), a first diode D1, a second diode D2, a first capacitor C1, a second capacitor C2, a first inductor L1, a second inductor L2 and a filter circuit.

[0048] The positive electrode of the DC power supply is respectively connected to the collector of the first switch tube S1 and one end of the second inductor L2, and the first inductor L1 is connected to the emitter of the first switch tube S1. One end of the second inductor L2 is connected to the collector of the second switch tube S2, and the emitter of the second switch tube S2 is connected to the first inductor L1. One end of the first capacitor C1 is connected to the emitter of the first switch tube S1, and the other end is connected to the cathode of the first diode D1. The anode of the first diode D1 is connected to the cathode of the second diode D2 and is connected to the emitter of the second switch tube S2, and the anode of the second diode D2 is connected to the second capacitor C2. The collector of the third switch tube S3 is connected to the cathode of the first diode D1, and the emitter of the third switch tube S3 is connected to the collector of the fourth switch tube S4, and the fourth switch tube S4 is connected to the anode of the second diode D2.

[0049] The filter circuit is composed of a filter capacitor C3 and a filter inductor L3. One end of the filter circuit is connected to the anode of the first diode D1 and the cathode of the second diode D2, and the other end is connected to the emitter of the third switch tube S3 and the collector of the fourth switch tube S4. The load R is connected in parallel with the filter capacitor C3.

[0050] The inverter has the working characteristics of both Cuk and Zeta circuits, so the analysis of the inverter can rely on the analysis of Cuk and Zeta circuits.

[0051] The following assumptions are made: (1) all components in the circuit are ideal devices; (2) the inverter in the present invention operates in a stable state.

[0052] like Figure 2 The six operating modes generated are shown in Table 1.

[0053]

[0054] Working state 1, such as Figure 3 As shown, the DC power supply charges the first inductor L1 and charges the first capacitor C1 through the first diode D1 while supplying power to the load.

[0055] Working state 2, such as Figure 4 As shown, the first capacitor C1 starts to supply power to the load, and the DC power supply continuously charges the second inductor L2 and the second capacitor C2.

[0056] Working state 3, such as Figure 5 As shown, the first inductor L1 charges the first capacitor C1 through the first diode D1, and the load side is freewheeled by the filter inductor L3 through the first diode D1. The DC power supply continuously charges the second inductor L2 and the second capacitor C2.

[0057] Working state 4, such as Figure 6 As shown, the DC power supply and the second capacitor C2 supply power to the load at the same time, at which time the cathode potential of the second diode D2 is higher than the anode potential and is not conducting. No current flows through the first inductor L1, the first capacitor C1, and the first diode D1.

[0058] Working state 5, such as Figure 7 As shown, the DC power supply charges the second inductor L2 and the second capacitor C2. The load side is freewheeled by the filter inductor L3 through the second diode D2.

[0059] Working state 6, such as Figure 8 As shown, the flow path is the same as that in working state 5, but the switch state is different. The DC power supply charges the second inductor L2 and the second capacitor C2. The load side is freewheeled by the filter inductor L3 through the second diode D2.

[0060] from Figure 9-12 It can be obtained that, whether in the buck inverter or the boost inverter, the voltage of the first capacitor is approximately half of the voltage of the second capacitor. Such a numerical relationship greatly increases the flexibility of device selection. At the same time, the first capacitor and the second capacitor are symmetrical in circuit structure, ensuring the stability of the output AC voltage.

[0061] In order to realize the above working principle, the control circuit in the embodiment of the present invention adopts a voltage-current double closed-loop structure. At the same time, the control circuit is added with inner loop load current feedforward and outer loop inverter given voltage feedforward to obtain stable dynamic performance.

Claims

1. A single-input buck-boost type non-electrolytic capacitor single-phase inverter, characterized in that: The invention comprises a DC power supply and an inverter circuit, wherein the inverter circuit comprises a first switch tube S1, a second switch tube S2, a third switch tube S3, a fourth switch tube S4, a first diode D1, a second diode D2, a first capacitor C1, a second capacitor C2, a filter capacitor C3, a first inductor L1, a second inductor L2, a filter inductor L3 and a load R, wherein the third switch tube S3 and the fourth switch tube S4 are switch tubes without anti-parallel diodes, and the first capacitor C1, the second capacitor C2 and the filter capacitor C3 are all non-electrolytic capacitors; The collector of the first switch tube S1 is connected to the positive electrode of the DC power supply, the first inductor L1 is connected to the emitter of the first switch tube S1, one end of the second inductor L2 is connected to the positive electrode of the DC power supply, and one end is connected to the collector of the second switch tube S2, and the emitter of the second switch tube S2 is connected to the first inductor L1; one end of the first capacitor C1 is connected to the emitter of the first switch tube S1, and the other end is connected to the cathode of the first diode D1, the anode of the first diode D1 is connected to the cathode of the second diode D2 and the emitter of the second switch tube S2, and the anode of the second diode D2 is connected to the second capacitor C2; the filter capacitor C3 is connected in parallel with the load R and then connected in series with the filter inductor L3, and one end is connected to the anode of the first diode D1, and the other end is connected to the emitter of the third switch tube S3, the collector of the third switch tube S3 is connected to the cathode of the first diode D1, the emitter of the third switch tube S3 is connected to the collector of the fourth switch tube S4, and the fourth switch tube S4 is connected to the anode of the second diode D2; It also includes a filter circuit, which consists of a filter capacitor C3 and a filter inductor L3. One end of the filter circuit is connected to the anode of the first diode D1 and the cathode of the second diode D2, and the other end is connected to the emitter of the third switch tube S3 and the collector of the fourth switch tube S4. The load R is connected in parallel with the filter capacitor C3.

2. A single-input buck-boost type non-electrolytic capacitor single-phase inverter according to claim 1, characterized in that: When the AC output voltage is in the first half cycle, the states of the first switch tube S1 and the second switch tube S2 are alternately turned on and off, and the first switch tube S1 and the second switch tube S2 are turned on at the same time but not turned off at the same time. When the second switch tube S2 is turned off, the first switch tube S1 may be in the on state, and when the second switch tube S2 is in the on state, the first switch tube S1 is also in the on state, but the second switch tube S2 is in the on state for a very short time and can be ignored. At this time, the third switch tube S3 is in the on state, and the fourth switch tube S4 is in the off state.

3. The single-input buck-boost type non-electrolytic capacitor single-phase inverter according to claim 1, characterized in that: When the AC output voltage is in the second half cycle, the states of the first switch tube S1 and the second switch tube S2 are alternately turned on and off, and the first switch tube S1 and the second switch tube S2 are turned on at the same time but not turned off at the same time. When the first switch tube S1 is turned off, the second switch tube S2 may be in the on state, and when the first switch tube S1 is in the on state, the second switch tube S2 is also in the on state. However, the first switch tube S1 is in the on state for a very short time and can be ignored. At this time, the fourth switch tube S4 is in the on state, and the third switch tube S3 is in the off state.

4. The single-input buck-boost type non-electrolytic capacitor single-phase inverter according to claim 1, characterized in that: The first capacitor C1, the second capacitor C2 and the filter capacitor C3 are all non-electrolytic capacitors with consistent parameters. The symmetrically positioned first capacitor C1 and the second capacitor C2 work together to stabilize the output voltage while presenting different working states.

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