CN103219907B - Five-level inverter - Google Patents

Abstract

The present invention provides a five-level inverter, wherein: the first and second capacitors are connected in series, the connecting point of the first and second capacitors is the middle point of the capacitor; the first and second switching tubes, the seventh and eighth switching tubes They are respectively connected in parallel between the first and second capacitors in turn; the first and second switching tubes are connected to the third node, the seventh and eighth switching tubes are connected to the fourth node; the third and fourth switching tubes are connected in series, and the fifth and sixth switching tubes After being connected in series and then in parallel, the parallel branch is connected between the third node and the midpoint of the capacitor, wherein the third and fifth switching tubes are connected to the first node, and the fourth and sixth switching tubes are connected to the second node; the first node Connected to the midpoint of the capacitor, the second node is connected to the third node; the other end of the third node is connected to one end of the filter, the other end of the filter is connected to the fourth node, and the first to eighth diodes correspond to the corresponding parallel connections in the first to both ends of the eighth switch tube. The invention can obviously improve the loss of the commonly used five-level circuit and improve the efficiency of the inverter.

Description

Five Level Inverter

technical field

The present invention relates to the technical field of power electronics, in particular to an inverter, especially a five-level inverter.

Background technique

With the continuous development of wind power generation, photovoltaic power generation, and UPS (uninterruptible power supply) technology, the requirements for inverter efficiency have been paid more and more attention, so five-level inverters have emerged as the times require.

For example, the traditional five-level inverter shown in Figure 1, which can output five levels, has lower loss compared with two-level and three-level circuits, and can reduce the harmonics of the output current, reducing Output filter size. However, when the circuit outputs Vdc, Vdc/2, 0, -Vdc/2, -Vdc, no matter whether the current is positive or negative, as shown by the solid line and dotted line arrows in Figure 2-4, the current needs to pass through three power devices, with higher conduction losses.

Contents of the invention

Aiming at the defects in the prior art, the purpose of the present invention is to provide a five-level inverter, which can reduce the conduction loss and improve the efficiency of the inverter.

To achieve the above object, the present invention provides a five-level inverter, comprising: a first capacitor, a second capacitor, a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, and a fifth switch tube tube, the sixth switch tube, the seventh switch tube, the eighth switch tube, the first diode, the second diode, the third diode, the fourth diode, the fifth diode, the sixth two pole tube, the seventh diode, the eighth diode and the inductance, wherein:

The first capacitor and the second capacitor are connected in series, and the connection point between the two is the midpoint of the capacitor;

The first switch tube and the second switch tube are sequentially connected in parallel between the first capacitor and the second capacitor; the first switch tube and the first capacitor are connected to a fifth node, and the The second switch tube and the second capacitor are connected to the sixth node; the first switch tube and the second switch tube are connected to the third node;

The seventh switch tube is connected in series with the eighth switch tube; the seventh switch tube is connected to the fifth node, and the eighth switch tube is connected to the sixth node; the seventh switch tube Connecting the eighth switch tube to the fourth node;

The third switching tube is connected in series with the fourth switching tube, the fifth switching tube is connected in series with the sixth switching tube, and the two series branches are connected in parallel, and the parallel branch is connected between the third node and the Between the capacitor midpoints, wherein the third switch tube and the fifth switch tube are connected to the first node, the fourth switch tube and the sixth switch tube are connected to the second node; the first node Connected to the midpoint of the capacitor, the second node is connected to the third node; the other end of the third node is connected to one end of the inductor;

The other end of the inductor is connected in series with the load and then connected to the fourth node;

The first diode, the second diode, the third diode, the fourth diode, the fifth diode, the sixth diode, the seventh diode and the eighth diode are respectively Corresponding to the first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube, the sixth switch tube, the seventh switch tube and the eighth switch tube, and correspondingly connected in parallel to each switch tube both ends.

Preferably, the anode of the first diode is connected to the third node, the cathode of the first diode is connected to the first capacitor; the cathode of the second diode is connected to the third node, the The anode of the second diode is connected to the second capacitor; the anode of the third diode is connected to the first node, and the cathode of the third diode is connected to the fourth switch tube and the The cathode of the fourth diode, the anode of the fourth diode is connected to the second node; the anode of the fifth diode is connected to the sixth switch tube and the sixth diode anode, the The cathode of the fifth diode is connected to the first node, the cathode of the sixth diode is connected to the second node; the anode of the seventh diode is connected to the fourth node, the first The cathode of the seven diodes is connected to the fifth node; the cathode of the eighth diode is connected to the fourth node, and the anode of the eighth diode is connected to the sixth node.

The first switch tube, the second switch tube, the seventh switch tube and the eighth switch tube in the present invention are all IGBT tubes (insulated gate bipolar transistors).

The above-mentioned fourth switching tube and the sixth switching tube of the present invention adopt the same type of switching tube; the above-mentioned third switching tube and the fifth switching tube adopt the same type of switching tube; the types and types of the fourth switching tube and the sixth switching tube are Types of the third switch tube and the fifth switch tube may be the same or different.

The third to sixth switch tubes of the present invention can be any one of MOSFET tubes, PowerMosfet tubes (power field effect tubes), Coolmosfet tubes, and IGBT tubes.

Preferably, the first switch tube, the second switch tube, the third switch tube, the fifth switch tube, the seventh switch tube and the eighth switch tube are all IGBT tubes (insulated gate bipolar transistors), wherein: the The emitter of the first switching tube is connected to the third node, and the collector is connected to the first capacitor; the collector of the second switching tube is connected to the third node, and the emitter is connected to the second capacitor; the third switching tube The emitter of the fifth switch tube is connected to the first node, and the collector is connected to the fourth switch tube; the emitter of the fifth switch tube is connected to the sixth switch tube, and the collector is connected to the first node; the emitter of the seventh switch tube The pole is connected to the fourth node, the collector is connected to the fifth node; the collector of the eighth switch tube is connected to the fourth node, and the emitter is connected to the sixth node. The bases of the six IGBT tubes are all connected to the control signal.

Preferably, both the fourth switch tube and the sixth switch tube are Coolmosfet tubes, wherein: the drain of the fourth switch tube is connected to the collector of the third switch tube, and the source of the fourth switch tube is connected to At the second node; the drain of the sixth switch transistor is connected to the second node, and the source of the sixth switch transistor is connected to the emitter of the fifth switch transistor. The gates of the two Coolmosfet tubes are connected to control signals.

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

The five-level inverter of the present invention has all the advantages of the traditional five-level inverter, but it is different from the traditional five-level inverter circuit. When it outputs Vdc, Vdc/2, -Vdc/2, -Vdc, No matter the current is positive or negative, the current only passes through two power devices, which has low conduction loss. Although the current needs to pass through three power devices when the output is 0, the new topology reduces the conduction loss by constructing two parallel circuits; at the same time, it adapts to wind power, photovoltaic and other systems with power fluctuations through the hybrid structure of IGBT and Coolmosfet. The purpose of optimizing system efficiency can be achieved in all occasions of power. In general, it can significantly improve the loss of commonly used five-level circuits and improve the efficiency of inverters, especially for new energy power generation systems such as wind power generation and photovoltaic power generation.

Description of drawings

Other characteristics, objects and advantages of the present invention will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings:

Figure 1 is a circuit diagram of a traditional five-level inverter;

Figures 2 to 4 are current path diagrams of traditional five-level inverters;

5 is a circuit diagram of a five-level inverter according to an embodiment of the present invention;

6-8 are positive half cycle equivalent circuit diagrams of a five-level inverter according to an embodiment of the present invention;

9-11 are equivalent circuit diagrams of the negative half cycle of the five-level inverter according to an embodiment of the present invention.

Detailed ways

The present invention will be described in detail below in conjunction with specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

As shown in FIG. 5 , an embodiment of the present invention provides a five-level inverter, including: a first capacitor C1, a second capacitor C2, a first switching tube T1, a second switching tube T2, a third switching tube T3, The fourth switching tube T4, the fifth switching tube T5, the sixth switching tube T6, the seventh switching tube T7, the eighth switching tube T8, the first diode D1, the second diode D2, the third diode D3, the fourth diode D4, the fifth diode D5, the sixth diode D6, the seventh diode D7, the eighth diode D8, the inductance L and the grid Grid (or other loads), wherein:

The first capacitor C1 and the second capacitor C2 are connected in series, and the connection point between the first capacitor C1 and the second capacitor C2 is the capacitor midpoint O;

The first switching tube T1 and the second switching tube T2 are sequentially connected in series between the first capacitor C1 and the second capacitor C2; the first switching tube T1 and the first capacitor C1 are connected to The fifth node O5, the second switching tube T2 and the second capacitor C2 are connected to the sixth node O6; the first switching tube T1 and the second switching tube T2 are connected to the third node O3;

The seventh switching tube T7 and the eighth switching tube T8 are connected in series, the seventh switching tube T7 is connected to the fifth node O5, and the eighth switching tube T8 is connected to the sixth node O6; The seventh switch tube T7 and the eighth switch tube T8 are connected to the fourth node O4;

The third switching tube T3 is connected in series with the fourth switching tube T4, the fifth switching tube T5 is connected in series with the sixth switching tube T6, and the two series branches are connected in parallel, and the parallel branch is connected to the first Between the three nodes O3 and the capacitor midpoint O, wherein the third switching tube T3 and the fifth switching tube T5 are connected to the first node O1, and the fourth switching tube T4 is connected to the sixth switching tube T6 at the second node O2; the first node O1 is connected to the capacitor midpoint O, and the second node O2 is connected to the third node O3; the other end of the third node O3 is connected to one end of the inductor L;

The other end of the inductance L is connected in series with the grid Grid to the fourth node O4;

The first diode D1, the second diode D2, the third diode D3, the fourth diode D4, the fifth diode D5, the sixth diode D6, and the seventh diode D7 And the eighth diode D8 respectively corresponds to the first switching tube T1, the second switching tube T2, the third switching tube T3, the fourth switching tube T4, the fifth switching tube T5, the sixth switching tube T6, the seventh switching tube The switch tube T7 and the eighth switch tube T8 are correspondingly connected in parallel at both ends of each switch tube;

The anode of the first diode D1 is connected to the third node O3, the cathode of the first diode D1 is connected to the first capacitor C1; the cathode of the second diode D2 is connected to the third node O3 , the anode of the second diode D2 is connected to the second capacitor C2; the anode of the third diode D3 is connected to the first node O1, and the cathode of the third diode D3 is connected to the The fourth switching tube T4 and the cathode of the fourth diode D4, the anode of the fourth diode D4 is connected to the second node O2; the anode of the fifth diode D5 is connected to the first Six switch tubes T6 and the anode of the sixth diode D6, the cathode of the fifth diode D5 is connected to the first node O1, and the cathode of the sixth diode D6 is connected to the second node O2 ; The anode of the seventh diode D7 is connected to the fourth node O4, the cathode of the seventh diode D7 is connected to the fifth node O5; the cathode of the eighth diode D8 is connected to the fourth node O4, the anode of the eighth diode D8 is connected to the sixth node O6.

The first switching tube T1, the second switching tube T2, the third switching tube T3, the fifth switching tube T5, the seventh switching tube T7 and the eighth switching tube T8 are all IGBT tubes (insulated gate bipolar transistors), Wherein: the emitter of the first switching tube T1 is connected to the third node O3, and the collector is connected to the first capacitor C1; the collector of the second switching tube T2 is connected to the third node O3, and the emitter is connected to the first capacitor C1. Two capacitors C2; the emitter of the third switching tube T3 is connected to the first node O1, and the collector is connected to the fourth switching tube T4; the emitter of the fifth switching tube T5 is connected to the sixth switching tube T6, and the collector is connected to the fourth switching tube T4. The electrode is connected to the first node O1; the emitter of the seventh switching tube T7 is connected to the fourth node O4, and the collector is connected to the fifth node O5; the collector of the eighth switching tube T8 is connected to the fourth node O4 , the emitter is connected to the sixth node O6. The bases of the six IGBT tubes are all connected to the control signal.

The fourth switching tube T4 and the sixth switching tube T6 both adopt Coolmosfet tubes, wherein: the drain of the fourth switching tube T4 is connected to the collector of the third switching tube T3, and the source of the fourth switching tube T4 The drain of the sixth switching transistor T6 is connected to the second node O2, and the source of the sixth switching transistor T6 is connected to the emitter of the fifth switching transistor T5. The gates of the two Coolmosfet tubes are connected to control signals.

As shown in Figure 6-8, in the positive half cycle, the circuit can output 0, Vdc/2 and Vdc, when the first and eighth switching tubes T1 and T8 are turned on and the other switching tubes are turned off, the circuit outputs Vdc. At this time, if the direction of the current is positive, as shown by the solid arrow in FIG. 6 , the current flows to the load through the first switching transistor T1 and the eighth switching transistor T8 . When the current direction is negative as shown by another arrow, the current returns to the positive bus through the eighth diode D8 and the first diode D1.

When the switch tubes T3, T4, T5, T6, T8 are turned on and other switch tubes are turned off, the circuit outputs Vdc/2. At this time, if the current direction is positive, as shown by the solid arrow in Figure 7, the current flows to the load through the third diode D3, the fourth switching tube T4, and the eighth switching tube, and at the same time, the current flows through the fifth switching tube T5 and the sixth diode D6 are connected in parallel, and flow to the load side through the eighth switch tube T8. When the current direction is negative as shown by another arrow, the current passes through the eighth diode, the fourth diode D4 and the third switching tube T3, and the eighth diode, the sixth switching tube T6 and the fifth switching tube T6. The diode D5 is connected in parallel to return to the midpoint O of the capacitor.

And when the second switching tube T2 and the eighth switching tube T8 are turned on, the circuit outputs 0. When the current is positive, the current flows through D2, the load, and T8 to form a loop; when the current is negative, the current flows through D8, the load, and T2 to form a loop. As shown in Figure 8.

As shown in Figure 9-11, the negative half cycle can be analyzed in the same way. In the negative half cycle, the circuit can output 0, -Vdc/2 and -Vdc. When the second and seventh switching tubes T2 and T7 are turned on, other switches are turned off. When the tube is in use, the circuit outputs -Vdc. At this time, if the current direction is positive, as shown by the solid arrow in FIG. 9 , the current returns to the positive bus through the seventh diode D7 and the second diode D2. If the current direction is negative, the current passes through the seventh switching tube T7, the load, and the second switching tube T2 to the negative bus.

When the third switching tube T3, the fourth switching tube T4, the fifth switching tube T5, the sixth switching tube T6 and the eighth switching tube T8 are turned on and other switching tubes are turned off, the circuit outputs Vdc/2. At this time, if the current direction is positive, as shown by the solid arrow in FIG. 10 , the current passes through the third diode D3 and the fourth switching transistor T4 , the load and the eighth switching transistor T8 to form a loop. At the same time, the current passes through the fifth switch tube T5, the sixth diode D6, the load and the eighth switch tube T8 to form a parallel circuit. When the current direction is negative as shown by another arrow, the current passes through the eighth diode D8, the fourth diode D4 and the third switching tube T3, and the eighth diode D8, the sixth switching tube T6 and The fifth diode D5 is connected in parallel to return to the midpoint O of the capacitor.

And when the first switching tube T1 and the seventh switching tube T7 are turned on, the circuit outputs 0. When the current is positive, the current flows through the first switching tube T1, the load, and the seventh diode D7 to form a loop; when the current is negative, the current flows through the seventh switching tube T7, the load, and the first diode D1 to form a loop, such as Figure 11 shows.

It should be understood that there are multiple options for each switch tube in the structure of the above embodiment, and the following three types are listed: the intermediate switch tubes T3, T4, T5, and T6 all adopt CoolMosfet, or all adopt IGBT, or all adopt the form of MOSFET. The same switch tubes T1 , T2 , T7 , T8 can also be in the form of MOSFET or Coolmosfet, etc., which are not listed here one by one, and their implementation principles are the same or similar to those of the above-mentioned preferred embodiment.

Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims (7)

1. A five-level inverter, characterized in that it comprises: a first capacitor, a second capacitor, a first switching tube, a second switching tube, a third switching tube, a fourth switching tube, a fifth switching tube, a first switching tube Six switching tubes, seventh switching tube, eighth switching tube, first diode, second diode, third diode, fourth diode, fifth diode, sixth diode, seventh diode, eighth diode and inductor, where: The first capacitor and the second capacitor are connected in series, and the connection point between the two is the midpoint of the capacitor; The first switch tube and the second switch tube are connected in series, and the series branch formed is connected in parallel with the series branch formed by the first capacitor and the second capacitor; the first switch tube and the first capacitor connected to the fifth node, the second switch tube and the second capacitor connected to the sixth node; the first switch tube and the second switch tube connected to the third node; The seventh switch tube is connected in series with the eighth switch tube; the seventh switch tube is connected to the fifth node, and the eighth switch tube is connected to the sixth node; the seventh switch tube Connecting the eighth switch tube to the fourth node; The third switching tube is connected in series with the fourth switching tube, the fifth switching tube is connected in series with the sixth switching tube, and the two series branches are connected in parallel, and the parallel branch is connected between the third node and the Between the capacitor midpoints, wherein the third switch tube and the fifth switch tube are connected to the first node, the fourth switch tube and the sixth switch tube are connected to the second node; the first node Connected to the midpoint of the capacitor, the second node is connected to the third node; the third node is connected to one end of the inductor; The other end of the inductor is connected in series with the load and then connected to the fourth node; The first diode, the second diode, the third diode, the fourth diode, the fifth diode, the sixth diode, the seventh diode and the eighth diode are respectively Corresponding to the first switching tube, the second switching tube, the third switching tube, the fourth switching tube, the fifth switching tube, the sixth switching tube, the seventh switching tube and the eighth switching tube, and correspondingly connected in parallel to each switch both ends of the tube. 2. The five-level inverter according to claim 1, wherein the anode of the first diode is connected to the third node, and the cathode of the first diode is connected to the first capacitor; The cathode of the second diode is connected to the third node, the anode of the second diode is connected to the second capacitor; the anode of the third diode is connected to the first node, and the anode of the second diode is connected to the first node. The cathodes of the three diodes are connected to the fourth switching tube and the cathodes of the fourth diodes, and the anodes of the fourth diodes are connected to the second node; the anodes of the fifth diodes are connected to In the sixth switch tube and the anode of the sixth diode, the cathode of the fifth diode is connected to the first node, and the cathode of the sixth diode is connected to the second node; The anode of the seventh diode is connected to the fourth node, the cathode of the seventh diode is connected to the fifth node; the cathode of the eighth diode is connected to the fourth node, and the eighth diode The anode of the tube is connected to the sixth node. 3. The five-level inverter according to claim 1, wherein the first switch tube, the second switch tube, the seventh switch tube, and the eighth switch tube are all IGBT tubes. 4. The five-level inverter according to any one of claims 1-3, wherein the fourth switch tube and the sixth switch tube use the same type of switch tube; the third switch tube, The fifth switch tube adopts the same type of switch tube; the types of the fourth switch tube and the sixth switch tube are the same or different from those of the third switch tube and the fifth switch tube. 5 . The five-level inverter according to claim 4 , wherein the third to sixth switch tubes are any one of MOSFET, PowerMosfet, Coolmosfet and IGBT. 6. The five-level inverter according to claim 5, wherein the first switch tube, the second switch tube, the third switch tube, the fifth switch tube, the seventh switch tube and the eighth switch tube The tubes are all IGBT tubes, wherein: the emitter of the first switching tube is connected to the third node, and the collector is connected to the first capacitor; the collector of the second switching tube is connected to the third node, and the emitter is connected to the The second capacitor; the emitter of the third switching tube is connected to the first node, and the collector is connected to the fourth switching tube; the emitter of the fifth switching tube is connected to the sixth switching tube, and the collector is connected to the first node; the emitter of the seventh switching tube is connected to the fourth node, and the collector is connected to the fifth node; the collector of the eighth switching tube is connected to the fourth node, and the emitter is connected to the sixth node. The bases of each IGBT tube are connected to the control signal. 7. The five-level inverter according to claim 5, wherein the fourth switch tube and the sixth switch tube both use Coolmosfet tubes, wherein: the drain of the fourth switch tube is connected to the first The collector of the three switching transistors, the source of the fourth switching transistor is connected to the second node; the drain of the sixth switching transistor is connected to the second node, and the source of the sixth switching transistor is connected to the fifth The emitter of the switch tube; the gates of the two Coolmosfet tubes are connected to the control signal.