An enhanced semi-quasi-Z-source inverter

Abstract

The invention discloses an enhanced semi-quasi-Z source inverter, which belongs to the technical field of electric energy conversion and includes: inductors L1, L2, L3, capacitors C1, C2, diodes D1, D2, D3, D4, D5, D6, D7, D8, a DC power supply and a three-phase inverter bridge. The positive electrode of the DC power supply is connected to one end of the inductor L1, the other end of the inductor L1 is connected to the anodes of the diodes D1 and D2, the cathode of the diode D2 is connected to the anodes of the diodes D3 and D6, the positive electrode of the capacitor C1 and one end of the inductor L2, the cathode of the diode D3 is connected to the cathode of the diode D4 and one end of the inductor L3, the anode of the diode D4 is connected to the anode of the diode D5 and the other end of the inductor L2, the cathode of the diode D5 is connected to the cathode of the diode D1, the other end of the inductor L3 and the positive electrode of the three-phase inverter bridge DC bus, the cathode of the diode D7 is connected to the negative electrode of the capacitor C1, the anode of the diode D8, the anode of the diode D7 is connected to the cathode of the diode D6 and the positive electrode of the capacitor C2, and the cathode of the diode D8 is connected to the negative electrode of the capacitor C2 and the negative electrode of the DC power supply. The present invention has higher voltage gain and lower current harmonics than the traditional Z-source inverter.

Description

Technical Field

[0001] The invention belongs to the field of power electronic electric energy conversion, and in particular relates to an enhanced semi-quasi-Z-source inverter. Background Art

[0002] The Z-source inverter has the advantages of single-stage control, adjustable voltage and no dead time, and has a wide range of application prospects in new energy power generation and electric vehicle driving. However, the conventional Z-source inverter has insufficient boost capability, so a larger through-duty cycle is required to increase the output voltage. When the through-duty cycle increases, the instantaneous peak value of the DC bus voltage of the three-phase inverter bridge will increase, resulting in increased device voltage stress and increased inverter cost. In addition, when the DC power supply is provided by an uncontrolled rectifier, the input current harmonics on the rectifier side of the conventional Z-source inverter are large. To this end, the present invention proposes an enhanced semi-quasi-Z-source inverter, which improves the voltage gain and reduces the current harmonics without adding active devices, so that the inverter has both low cost and high characteristics. Summary of the invention

[0003] In view of the defects or shortcomings described in the background technology, the present invention provides an enhanced semi-quasi-Z-source inverter, and the system has the characteristics of low cost, high voltage gain and low current harmonics.

[0004] An enhanced semi-quasi-Z-source inverter includes an inductor L1, diodes D1 and D2, module one, module two, a DC power supply and a three-phase inverter bridge. Module one includes capacitors C1 and C2, diodes D6, D7 and D8. Module two includes inductors L2 and L3, diodes D3, D4 and D5. The three-phase inverter bridge includes active devices K1, K2, K3, K4, K5 and K6. In module one, the cathode of diode D7 is connected to the negative electrode of capacitor C1 and the anode of diode D8, the anode of diode D7 is connected to the cathode of diode D6 and the positive electrode of capacitor C2, the cathode of diode D8 is connected to the negative electrode of capacitor C2, and the anode of diode D6 is connected to the positive electrode of capacitor C1. The anode of the diode D3 in the module 2 is connected to one end of the inductor L2, the cathode of the diode D3 is connected to the cathode of the diode D4 and one end of the inductor L3, the anode of the diode D4 is connected to the anode of the diode D5 and the other end of the inductor L2, and the cathode of the diode D5 is connected to the other end of the inductor L3. The collectors of K1, K2, and K3 in the three-phase inverter bridge are connected to the positive pole of the DC bus of the three-phase inverter bridge, the emitters of K4, K5, and K6 in the three-phase inverter bridge are connected to the negative pole of the DC bus of the three-phase inverter bridge, the emitter of K1 is connected to the collector of K4, the emitter of K2 is connected to the collector of K5, and the emitter of K3 is connected to the collector of K6. The positive electrode of the DC power supply is connected to one end of the inductor L1, the other end of the inductor L1 is connected to the anodes of the diodes D1 and D2, the cathode of the diode D2 is connected to the anodes of the diodes D3 and D6, the cathode of the diode D1 is connected to the cathode of the diode D5 and the collector of the active device K1, and the cathode of the diode D8 is connected to the negative electrode of the DC power supply and the emitter of the active device K4.

[0005] In the through state of the module 1, the diodes D6 and D8 are turned off, the diode D7 is turned on, and the capacitors C1 and C2 are connected in series to charge the inductors L2 and L3. At this time, the diode D1 is turned on and D2 is turned off.

[0006] When the module 1 is in the non-through state, the diodes D6 and D8 are turned on, and the diode D7 is turned off. At this time, the diode D1 is turned off, and D2 is turned on, and the DC power supply charges the capacitors C1 and C2.

[0007] In the through state of the module 2, the diodes D3 and D5 are turned on, and the diode D4 is turned off. In the non-through state, the diodes D3 and D5 are turned off, and the diode D4 is turned on.

[0008] The inductor L1 is charged by a DC power supply in a through state, and is discharged through a diode D2 in a non-through state. At this time, the diode D1 is turned off and D2 is turned on.

[0009] The benefits of the present invention compared with the prior art are:

[0010] (1) The present invention forms module 1 through capacitors C1, C2, diodes D6, D7, D8, and module 2 through inductors L2, L3, diodes D3, D4, D5, and no active devices are added to module 1 and module 2. When charging, C1 and C2 are charged separately, and when discharging, C1 and C2 are connected in series and then discharged, thereby improving the voltage gain, thereby reducing the device voltage stress of the three-phase inverter bridge and reducing the cost.

[0011] (2) When the DC power supply is provided by an uncontrolled rectifier, the input current harmonics of the rectifier can be controlled by the enhanced semi-quasi-Z-source inverter. In the direct-through state, the DC power supply only charges the inductor L1, and the capacitors C1 and C2 are connected in series to charge the inductors L2 and L3. In the non-direct-through state, the DC power supply and the inductors L1, L2, and L3 supply power to the load together. This provides feasibility for suppressing the input current harmonics of the rectifier. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 A schematic diagram of the topological structure of an enhanced semi-quasi-Z-source inverter provided for an example of the present invention.

[0013] Figure 2 The equivalent circuit of the enhanced semi-quasi-Z-source inverter in the direct-on state provided by the example of the present invention.

[0014] Figure 3 The equivalent circuit of the enhanced semi-quasi-Z-source inverter in the non-through state provided by the example of the present invention. DETAILED DESCRIPTION

[0015] In order to describe the present invention more specifically, the present invention is further described below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0016] like Figure 1As shown, an enhanced semi-quasi-Z-source inverter includes an inductor L1, diodes D1 and D2, module one, module two, a DC power supply and a three-phase inverter bridge. Module one includes capacitors C1 and C2, diodes D6, D7 and D8. Module two includes inductors L2 and L3, diodes D3, D4 and D5. The three-phase inverter bridge includes active devices K1, K2, K3, K4, K5 and K6. In module one, the cathode of diode D7 is connected to the negative electrode of capacitor C1 and the anode of diode D8, the anode of diode D7 is connected to the cathode of diode D6 and the positive electrode of capacitor C2, the cathode of diode D8 is connected to the negative electrode of capacitor C2, and the anode of diode D6 is connected to the positive electrode of capacitor C1. In module 2, the anode of diode D3 is connected to one end of inductor L2, the cathode of diode D3 is connected to the cathode of diode D4 and one end of inductor L3, the anode of diode D4 is connected to the anode of diode D5 and the other end of inductor L2, and the cathode of diode D5 is connected to the other end of inductor L3. The collectors of K1, K2, and K3 in the three-phase inverter bridge are connected to the positive pole of the DC bus of the three-phase inverter bridge, the emitters of K4, K5, and K6 in the three-phase inverter bridge are connected to the negative pole of the DC bus of the three-phase inverter bridge, the emitter of K1 is connected to the collector of K4, the emitter of K2 is connected to the collector of K5, and the emitter of K3 is connected to the collector of K6. The positive electrode of the DC power supply is connected to one end of the inductor L1, the other end of the inductor L1 is connected to the anodes of the diodes D1 and D2, the cathode of the diode D2 is connected to the anodes of the diodes D3 and D6, the cathode of the diode D1 is connected to the cathode of the diode D5 and the collector of the active device K1, and the cathode of the diode D8 is connected to the negative electrode of the DC power supply and the emitter of the active device K4.

[0017] When module 1 is in the direct-on state, diodes D6 and D8 are turned off, diode D7 is turned on, capacitors C1 and C2 are connected in series to charge inductors L2 and L3. At this time, diode D1 is turned on and D2 is turned off.

[0018] When module 1 is in the non-through state, diodes D6 and D8 are turned on, and diode D7 is turned off. At this time, diode D1 is turned off, and D2 is turned on, and the DC power supply charges capacitors C1 and C2.

[0019] When module 2 is in the direct-through state, diodes D3 and D5 are turned on, and diode D4 is turned off. When module 2 is in the non-direct-through state, diodes D3 and D5 are turned off, and diode D4 is turned on.

[0020] Inductor L1 is charged by a DC power supply in the through state, and is discharged through diode D2 in the non-through state. At this time, diode D1 is turned off and D2 is turned on.

[0021] like Figure 2As shown, in the direct-through state, diodes D2, D4, D6, and D8 are turned off, diodes D1, D3, D5, and D7 are turned on, and the three-phase inverter bridge is equivalent to a short circuit. At this time, the DC power supply charges the inductor L1 alone, and the capacitors C1 and C2 are connected in series to charge the inductors L2 and L3.

[0022] like Figure 3 As shown, in the non-through state, diodes D1, D3, D5, and D7 are turned off, and diodes D2, D4, D6, and D8 are turned on. At this time, the DC power supply charges capacitors C1 and C2, and together with inductors L1, L2, and L3, supplies power to the load.

[0023] The voltages of capacitors C1 and C2 in module 1 are equal, which can be expressed as:

[0024]

[0025] Wherein, VC is the voltage across capacitors C1 and C2 in module 1, d0 is the pass-through duty cycle of the enhanced semi-quasi-Z-source inverter, and Vdc is the DC power supply voltage.

[0026] The peak voltage of the three-phase inverter bridge DC bus can be expressed as:

[0027]

[0028] Wherein, Vpeak is the peak value of the DC bus voltage of the three-phase inverter bridge, d0 is the pass-through duty cycle of the enhanced semi-quasi-Z-source inverter, and Vdc is the DC power supply voltage.

[0029] The above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit them. Those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some of the technical features therein with equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the various embodiments of the present invention.

Claims

1. An enhanced semi-quasi-Z-source inverter, characterized in that: The invention comprises an inductor L1, diodes D1 and D2, a module 1, a module 2, a DC power supply and a three-phase inverter bridge; the module 1 comprises capacitors C1 and C2, diodes D6, D7 and D8; the module 2 comprises inductors L2 and L3, diodes D3, D4 and D5; the three-phase inverter bridge comprises active devices K1, K2, K3, K4, K5 and K6; the cathode of the diode D7 in the module 1 is connected to the negative electrode of the capacitor C1 and the anode of the diode D8, the anode of the diode D7 is connected to the cathode of the diode D6 and the positive electrode of the capacitor C2, the cathode of the diode D8 is connected to the negative electrode of the capacitor C2, and the anode of the diode D6 is connected to the positive electrode of the capacitor C1; the anode of the diode D3 in the module 2 is connected to one end of the inductor L2, the cathode of the diode D3 is connected to the cathode of the diode D4 and one end of the inductor L3, the anode of the diode D4 is connected to the diode The anode of the diode D5 is connected to the other end of the inductor L2, and the cathode of the diode D5 is connected to the other end of the inductor L3; the collectors of K1, K2, and K3 in the three-phase inverter bridge are connected to the positive electrode of the DC bus of the three-phase inverter bridge, the emitters of K4, K5, and K6 in the three-phase inverter bridge are connected to the negative electrode of the DC bus of the three-phase inverter bridge, the emitter of K1 is connected to the collector of K4, the emitter of K2 is connected to the collector of K5, and the emitter of K3 is connected to the collector of K6; the positive electrode of the DC power supply is connected to one end of the inductor L1, the other end of the inductor L1 is connected to the anodes of the diodes D1 and D2, the cathode of the diode D2 is connected to the anodes of the diodes D3 and D6, the cathode of the diode D1 is connected to the cathode of the diode D5 and the collector of the active device K1, and the cathode of the diode D8 is connected to the negative electrode of the DC power supply and the emitter of the active device K4.

2. The enhanced semi-quasi-Z-source inverter according to claim 1, characterized in that: In the through state of the module 1, the diodes D6 and D8 are turned off, the diode D7 is turned on, and the capacitors C1 and C2 are connected in series to charge the inductors L2 and L3. At this time, the diode D1 is turned on and D2 is turned off.

3. The enhanced semi-quasi-Z-source inverter according to claim 1, characterized in that: When the module 1 is in the non-through state, the diodes D6 and D8 are turned on, and the diode D7 is turned off. At this time, the diode D1 is turned off, and D2 is turned on, and the DC power supply charges the capacitors C1 and C2.

4. The enhanced semi-quasi-Z-source inverter according to claim 1, characterized in that: In the through state of the module 2, the diodes D3 and D5 are turned on, and the diode D4 is turned off. In the non-through state, the diodes D3 and D5 are turned off, and the diode D4 is turned on.

5. The enhanced semi-quasi-Z-source inverter according to claim 1, characterized in that: The inductor L1 is charged by a DC power supply in a through state, and is discharged through a diode D2 in a non-through state. At this time, the diode D1 is turned off and D2 is turned on.

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