WO2018129975A1

WO2018129975A1 - Grid-connection inverter and inverter system

Info

Publication number: WO2018129975A1
Application number: PCT/CN2017/106928
Authority: WO
Inventors: 刘龙
Original assignee: 珠海格力电器股份有限公司
Priority date: 2017-01-12
Filing date: 2017-10-19
Publication date: 2018-07-19
Also published as: CN107508480A; CN107070280A

Abstract

A grid-connection inverter and an inverter system. The grid-connection inverter comprises: an auxiliary circuit configured to provide a first freewheel path and a second freewheel path. The auxiliary circuit comprises: a first transistor (S6) provided with a first body diode (D6), the source electrode being connected with a first port (21) of the grid-connection inverter, and the gate electrode being a control end; a first diode (7), the anode being connected with the drain electrode of the first transistor; a second transistor (S5) provided with a second body diode (D5), the drain electrode being connected with the cathode of the first diode, the source electrode being connected with a second port (22) of the grid-connection inverter, and the gate electrode being a control end; and a second diode (8), the anode being connected with the drain electrode of the second transistor, and the cathode being connected with the drain electrode of the first transistor. The first transistor, the first diode and the second transistor form the first freewheel path; the first transistor, the second diode and the second transistor form the second freewheel path; and the first port and the second port are connected with a power grid. The grid-connection inverter and the inverter system comprising the grid-connection inverter solve the technical problem of low working efficiency of the inverter.

Description

Grid-connected inverter and inverter system

Technical field

The present invention relates to the field of electric power, and in particular to a grid-connected inverter and an inverter system.

Background technique

The grid-connected inverter is divided into an isolated grid-connected inverter and a non-isolated grid-connected inverter. The isolated grid-connected inverter is divided into power frequency isolation and high-frequency isolation. Power frequency isolated grid-connected inverters are bulky, cumbersome and inefficient; high-frequency isolated grid-connected inverters are less efficient than non-isolated grid-connected inverters, and control comparison of high-frequency isolated grid-connected inverters complex.

Among them, single-phase non-isolated grid-connected inverters now generally use full-bridge inverter circuits, as shown in Figure 1. Non-isolated grid-connected inverters have bipolar modulation and unipolar modulation modes of operation:

1. Bipolar modulation working mode: As shown in Fig. 1, when the grid is in the positive half cycle, S1 and S4 are simultaneously turned on, and S2 and S3 are turned off. The current path is: Vdc+→S1→L1→Grid→L2→S4→Vdc-; when S1 and S4 are simultaneously cut off, S2 and S3 are simultaneously turned on. The current path is: Grid→L2→D2→C→D3→L1. When the grid is negative for half a week, it is symmetrical with the positive half of the grid, and will not be described here. S1, S4, S2, and S3 all work at high frequencies, and the switching loss of the bipolar modulation transistor is large, and the efficiency of the inverter is low.

2. Single-Phase Modulation Mode: Four transistors in a full-bridge single-phase inverter topology with unipolar modulation, two of which operate at the power frequency and the other two operate at high frequencies. As shown in Fig. 1, when the grid is in the positive half cycle, S1 and S4 are simultaneously turned on, S2 and S3 are cut off, and the current path is: Vdc+→S1→L1→Grid→L2→S4→Vdc-; when S1 is disconnected, S4 still leads Pass, and S2, S3 remain at this time, the current path is: Grid → L2 → S4 → D3 → L1. The negative half cycle of the grid is symmetrical with the positive half of the grid.

Further, when unipolar modulation is used, the high-frequency on-off of the transistor in the inverter generates a high-frequency time-varying voltage acting on the parasitic capacitance, generating a large common-mode leakage current, reducing the efficiency of the inverter, and also affecting the EMC. performance. Among them, the parasitic capacitance is that the solar panel has parasitic capacitance to the earth. The high-frequency on-off of the transistor in the inverter generates a high-frequency time-varying voltage on the parasitic capacitance, which results in a large common-mode leakage current, which reduces the efficiency of the inverter and also affects EMC (Electro Magnetic Compatibility). , ie electromagnetic compatibility) performance. If the single-phase non-isolated grid-connected inverter works with bipolar modulation, the transistor switching loss is large and the inverter efficiency is low. If unipolar modulation is used, the efficiency of the inverter will also be reduced due to the large common mode leakage current, and it will also affect the EMC performance.

In view of the low efficiency of the above inverters, no effective solution has been proposed yet.

The content of the present invention

The embodiments of the present invention provide a grid-connected inverter and an inverter system to solve at least the technical problem that the operating efficiency of the inverter is low.

According to an aspect of an embodiment of the present invention, a grid-connected inverter includes: an auxiliary circuit for providing a first freewheeling path and a second freewheeling path, wherein the auxiliary circuit includes: a first transistor of the body diode, the source is connected to the first port of the grid-connected inverter, the gate is a control terminal; the first diode is connected to the drain of the first transistor; and the second body diode is a second transistor having a drain connected to a negative terminal of the first diode, a source connected to a second port of the grid-connected inverter, and a gate being a control terminal; a second diode, a positive electrode and the first a drain of the two transistors connected to the drain of the first transistor, wherein the first transistor with the first body diode, the first diode, and the second diode The second transistor constitutes a first freewheeling path, and the first transistor with the first body diode, the second diode, and the second transistor with the second body diode form a second freewheeling path, wherein Said first port and said second port Network connection.

Further, the auxiliary circuit further includes: a first body diode, a positive electrode connected to a source of the first transistor, a negative electrode connected to a drain of the first transistor; a second body diode, a positive electrode and the second body The source of the transistor is connected, and the negative electrode is connected to the drain of the second transistor.

Further, the first port is connected to the power grid by a first inductance, and the second port is connected to the power grid by a second inductance.

Further, the grid-connected inverter further includes: a third switch tube, the drain is connected to the input end of the grid-connected inverter, the source is connected to the drain of the second transistor, and the gate is the control end; a four-switching transistor, the drain is connected to the input end of the grid-connected inverter, the source is connected to the drain of the first transistor, the gate is the control terminal, and the fifth switching transistor, the drain and the source of the second transistor The pole is connected, the source is connected to the negative pole of the DC power source, the gate is the control terminal, the sixth switch transistor is connected to the source of the first transistor, the source is connected to the cathode of the DC power source, and the gate is the control terminal. .

Further, the grid-connected inverter further includes: a fifth diode, a cathode connected to a drain of the third switch tube, a positive pole connected to a source of the third switch tube; and a sixth diode a cathode connected to a drain of the fourth switch transistor, a positive electrode connected to a source of the fourth switch transistor, a seventh diode connected to a drain of the fifth switch transistor, and a positive electrode and the The source of the fifth switch is connected; the eighth diode is connected to the drain of the sixth switch, and the positive electrode is connected to the source of the sixth switch.

Further, in the inverter phase where the grid voltage is positive half cycle, the third switch transistor, the sixth switch transistor, and the second transistor are turned on, and the fourth switch transistor, the fifth switch transistor, and the first transistor are turned off, and the third switch transistor is turned off. The second transistor, the second inductor, the grid Grid, the first inductor, and the sixth switch tube constitute an inverter loop; in the inductor freewheeling phase in which the grid voltage is positive half cycle, the third switch transistor and the sixth switch transistor are disconnected, The second transistor remains conductive, and the fourth switch, the fifth switch, and the first transistor remain off, and the grid Grid, the first inductor, the first body diode, the first diode, the second transistor, and the second inductor remain Forming an inductive freewheeling circuit; in the inverter phase where the grid voltage is negative half cycle, the fourth switching transistor, the fifth switching transistor, and the first transistor are turned on, and the third switching transistor, the sixth switching transistor, and the second transistor are turned off, The four switch tubes, the first transistor, the first inductor, the grid Grid, the second inductor, and the fifth switch tube constitute an inverter loop; in the inductor freewheeling phase where the grid voltage is a negative half cycle, the fourth switch transistor and the fifth switch Disconnected, the first transistor remains conductive, and the third switch, the sixth switch, and the second transistor remain off, and the grid Grid, the second inductor, the second body diode, the second diode, and the first transistor remain The first inductor constitutes an inductive freewheeling circuit.

According to another aspect of the embodiments of the present invention, an inverter system is further provided, the inverter system comprising: the grid-connected inverter described above.

Further, the inverter system further includes: a DC power source, a positive pole of the DC power source is connected to an anode of an input end of the grid-connected inverter, and a cathode of the DC power source and an input of the grid-connected inverter The negative terminal of the terminal is connected.

Further, the inverter system further includes: a filter capacitor, one end is connected to the anode of the DC power source, and the other end is connected to the cathode of the DC power source.

Further, the DC power source includes: a photovoltaic power source, a wind power source, and a power device power source.

Further, the inverter system further includes: a first inductor, the first end is connected to the first port of the grid-connected inverter, the second end is connected to the power grid; and the second inductor is connected to the first end The second port of the grid-connected inverter is connected, and the second end is connected to the power grid.

In the embodiment of the present invention, the grid-connected inverter adds an auxiliary circuit for providing the first freewheeling path and the second freewheeling path, wherein the auxiliary circuit includes: the first transistor with the first body diode The source is connected to the first port of the grid-connected inverter, the gate is the control end; the first diode is connected to the drain of the first transistor; the second transistor with the second body diode, the drain and the a diode is connected to the negative pole, the source is connected to the second port of the grid-connected inverter, the gate is the control terminal, the second diode is connected to the drain of the second transistor, and the drain of the cathode and the first transistor a first connection, wherein the first transistor, the first diode, and the second transistor form a first freewheeling path, and the first transistor, the second diode, and the second transistor form a second freewheeling path, wherein the first port And the second port is connected to the grid. In the above embodiment, by adding a new crystal of the body diode The tube and the diode make the freewheeling path different from the freewheeling path during the bipolar modulation operation and the freewheeling path during the unipolar modulation operation, and also make the freewheeling path smaller during the inverter operation, thereby avoiding The bipolar modulation transistor has a large switching loss problem, and also suppresses the common mode leakage current, improves the inverter efficiency and the EMC performance, and further solves the technical problem of low efficiency of the inverter.

DRAWINGS

The drawings described herein are intended to provide a further understanding of the invention, and are intended to be a part of the invention. In the drawing:

1 is a schematic diagram of a full bridge inverter circuit according to the prior art;

2 is a new freewheeling path of a grid-tied inverter according to an embodiment of the invention;

3 is a schematic diagram of a grid-connected inverter according to an embodiment of the invention;

4 is a schematic diagram of a transistor driving signal in a circuit in accordance with an embodiment of the present invention;

5 is a schematic diagram of a current path during a positive half cycle inversion phase of a grid voltage, in accordance with an embodiment of the present invention;

6 is a schematic diagram of a current path in a freewheeling phase of a positive half cycle of a grid voltage, in accordance with an embodiment of the present invention;

7 is a schematic diagram of a current path during a negative half cycle inverter phase of a grid voltage according to an embodiment of the invention;

8 is a schematic diagram of a current path during a freewheeling phase of a negative half cycle of a grid voltage, in accordance with an embodiment of the present invention.

detailed description

The technical solutions in the embodiments of the present invention are clearly and completely described in the following with reference to the accompanying drawings in the embodiments of the present invention. It is an embodiment of the invention, but not all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of the present invention.

It is to be understood that the terms "first", "second" and the like in the specification and claims of the present invention are used to distinguish similar objects, and are not necessarily used to describe a particular order or order. It is to be understood that the data so used may be interchanged where appropriate, so that the embodiments of the invention described herein can be implemented in a sequence other than those illustrated or described herein. In addition, the terms "comprises" and "comprising" and "the" and "the" are intended to cover a non-exclusive inclusion, for example, a process, system, product, or device that comprises a series of units is not necessarily limited to those that are clearly listed. Yes can include not clearly listed or for these Other units inherent to the process, product, or equipment.

According to an aspect of an embodiment of the present invention, a grid-connected inverter includes: an auxiliary circuit for providing a first freewheeling path and a second freewheeling path, wherein the auxiliary circuit includes: a first body diode a first transistor, a source connected to a first port of the grid-connected inverter, a gate being a control terminal; a first diode having a positive electrode connected to a drain of the first transistor; and a second transistor having a second body diode The drain is connected to the cathode of the first diode, the source is connected to the second port of the grid-connected inverter, the gate is the control terminal, the second diode is connected to the drain of the second transistor, and the cathode and the cathode a drain connection of a transistor, wherein the first transistor with the first body diode, the first diode, and the second transistor with the second body diode constitute a first freewheeling path, the first transistor with the first body diode The second diode and the second transistor with the second body diode form a second freewheeling path, wherein the first port and the second port are connected to the grid.

2 is a schematic diagram of a new freewheeling path of a grid-tied inverter according to an embodiment of the present invention. As shown in FIG. 2, the freewheeling path includes: an auxiliary circuit for providing a first freewheeling path and a The second freewheeling path, wherein the auxiliary circuit comprises: a first transistor S6 with a first body diode D6, a source connected to the first port 21 of the grid-connected inverter, a gate being a control terminal; and a first diode D7, The positive electrode is connected to the drain of the first transistor; the second transistor S5 with the second body diode D5 has a drain connected to the negative terminal of the first diode, and the source is connected to the second port 22 of the grid-connected inverter. The second diode D8, the positive electrode is connected to the drain of the second transistor, and the negative electrode is connected to the drain of the first transistor, wherein the first transistor S6 with the first body diode D6 and the first diode D7 and second transistor S5 with second body diode D5 constitute a first freewheeling path, first transistor S6 with first body diode D6, second diode D8 and second transistor S5 with second body diode D5 Forming a second freewheeling path, wherein the first port 21 is connected to the first inductor L2 The second port 22 is connected to one end of the second inductor L1, and the other end of the first inductor L2 and the second inductor L1 are connected to the grid Grid.

With the above embodiment, the grid-connected inverter adds an auxiliary circuit for providing a first freewheeling path and a second freewheeling path, wherein the auxiliary circuit comprises: a first transistor with a first body diode, a source and a The first port of the network inverter is connected, the gate is a control end; the first diode has a positive pole connected to the drain of the first transistor; the second transistor with the second body diode, the drain and the first diode a cathode is connected, a source is connected to a second port of the grid-connected inverter, a gate is a control terminal, a second diode is connected to a drain of the second transistor, and a cathode is connected to a drain of the first transistor, wherein a first transistor with a first body diode, a first diode, and a second transistor with a second body diode constitute a first freewheeling path, a first transistor with a first body diode, a second diode, and a band The second transistor of the two-body diode forms a second freewheeling path, wherein the first port is connected to one end of the first inductor, the other end of the first inductor is connected to the power grid, the second port is connected to one end of the second inductor, and the other end of the second inductor Connected to the grid. In the above embodiment, the freewheeling path is provided by the newly added auxiliary circuit, and the auxiliary circuit includes a transistor and a diode with a body diode, and the freewheeling path does not pass through the DC power supply side, so that the freewheeling path becomes smaller during the inverter operation. And avoiding bipolar modulation transistors, reducing switching losses and solving the prior art The technical problem of low efficiency of the inverter.

Further, by adding a new transistor and diode with a body diode, the freewheeling path during inverter operation is different from the freewheeling path during bipolar modulation operation and the freewheeling path during unipolar modulation operation, and also makes the inverter The freewheeling path becomes smaller during operation, thereby avoiding the problem of large switching loss of the bipolar modulation transistor, and also suppressing the common mode leakage current, improving the efficiency of the inverter and the EMC performance, thereby solving the problem of the inverter. Technical problems with low work efficiency.

As shown in FIG. 2, the first body diode has a positive electrode connected to a source of the first transistor, a negative electrode connected to a drain of the first transistor, and a second body diode connected to a source of the second transistor, a negative electrode and a second body. The drain of the transistor is connected.

Specifically, the first body diode D6, the positive electrode is connected to the source of the first transistor S6 of the first switch transistor, the negative electrode is connected to the drain of the first transistor S6 of the first switch transistor; the second body diode D5, the positive electrode and the second switch The source of the second transistor S5 is connected, and the cathode is connected to the drain of the second transistor S5 of the second switching transistor.

In an alternative embodiment, the first port is connected to the grid via a first inductance and the second port is connected to the grid via a second inductor.

Specifically, the first port 21 is connected to the grid Grid through the first inductor L2, and the second port 22 is connected to the grid Grid through the second inductor L1.

In an optional embodiment, the grid-connected inverter further includes: a third switch tube, the drain is connected to the input end of the grid-connected inverter, the source is connected to the drain of the second transistor, and the gate is controlled a fourth switch, the drain is connected to the input end of the grid-connected inverter, the source is connected to the drain of the first transistor, the gate is the control end, and the fifth switch, the drain and the source of the second transistor Connected, the source is connected to the negative pole of the DC power supply, the gate is the control terminal; the sixth switching transistor has a drain connected to the source of the first transistor, the source is connected to the negative pole of the DC power supply, and the gate is the control terminal.

3 is a schematic diagram of a grid-connected inverter according to an embodiment of the present invention. As shown in FIG. 3, the drain of the third switch S1 is connected to the input end of the grid-connected inverter, that is, the third switch tube. The drain of S1 is connected to the input terminal of the grid-connected inverter, the source is connected to the drain of the second transistor S5, the gate is the control terminal, and the drain of the fourth switch transistor S2 is connected to the input terminal of the grid-connected inverter. Connected, that is, the drain of the fourth switch S2 is connected to the input terminal of the grid-connected inverter, the source is connected to the drain of the first transistor S6, the gate is the control terminal, and the drain of the fifth switch S3 is The source of the second transistor S5 is connected, the source is connected to the cathode of the DC power source, and the gate is the control terminal; the drain of the sixth switch S4 is connected to the source of the first transistor S6, and the source is connected to the cathode of the DC power source. The gate is the control terminal.

The control terminal in the above embodiment is used to receive a driving signal of the controller.

Optionally, the grid-connected inverter further includes: a fifth diode, and the cathode is connected to the drain of the third switch tube, and the anode Connected to the source of the third switch tube; the sixth diode, the negative pole is connected to the drain of the fourth switch tube, the positive pole is connected to the source of the fourth switch tube; the seventh diode, the negative pole and the fifth switch tube The drain is connected, the positive pole is connected to the source of the fifth switch tube; the eighth diode is connected to the drain of the sixth switch tube, and the positive pole is connected to the source of the sixth switch tube.

Specifically, as shown in FIG. 3, the fifth diode D1, the negative electrode is connected to the drain of the third switching transistor S1, the positive electrode is connected to the source of the third switching transistor S1, and the sixth diode D2, the negative electrode and the first The drain of the four switch S2 is connected, the positive pole is connected to the source of the fourth switch S2, the seventh diode D3, the negative electrode is connected to the drain of the fifth switch S3, and the source of the positive and fifth switch S3 Connected; the eighth diode D4, the negative electrode is connected to the drain of the sixth switch tube S4, and the positive electrode is connected to the source of the sixth switch tube S4. Among them, the diode is a device having two electrodes in the electronic component, and only allows current to flow in a single direction.

Next, in conjunction with FIG. 4, FIG. 5 and FIG. 6, the working principle of the grid-connected inverter when the grid voltage is positive half cycle is explained. In the inverter phase where the grid voltage is positive half cycle, the third switch transistor, the sixth switch transistor, and the second transistor are turned on, and the fourth switch transistor, the fifth switch transistor, and the first transistor are turned off, and the third switch transistor and the second transistor are turned off. The transistor, the second inductor, the grid Grid, the first inductor, and the sixth switch form an inverter loop. As shown in FIG. 5, when the third switch tube S1, the sixth switch tube S4, and the second transistor S5 are turned on, the fourth switch tube S2, the fifth switch tube S3, and the first transistor S6 are turned off, and the current path is: Vdc+→ S1→S5→L1→Grid→L2→S4→Vdc-, this is the inverter phase, and the schematic diagram of the current path is shown in Figure 5. This constitutes the inverter circuit to deliver current to the grid. At this time, the transistor drive signal in the circuit As shown in Figure 4.

In the inductor freewheeling phase where the grid voltage is positive half cycle, the third switching transistor and the sixth switching transistor are disconnected, the second transistor remains conductive, and the fourth switching transistor, the fifth switching transistor, and the first transistor remain off. The grid Grid, the first inductor, the first body diode, the first diode, the second transistor, and the second inductor form an inductive freewheeling circuit. When the third switch S1 and the sixth switch S4 are disconnected, the second transistor S5 remains turned on, and the fourth switch S2, the fifth switch S3, and the first transistor S6 remain off due to the second inductance L1 and The current of the first inductor L2 cannot be abrupt, so the current path is: Grid→L2→D6→D7→S5→L1. At this time, the inductor is in the freewheeling phase. The current path diagram is shown in Figure 6, which can constitute the inductor freewheeling loop. The grid delivers current, and the transistor drive signal in the circuit is shown in Figure 4.

The operation principle of the grid-connected inverter when the grid voltage is negative half cycle is explained below with reference to FIG. 4, FIG. 7 and FIG. In the inverter phase where the grid voltage is negative half cycle, the fourth switch transistor, the fifth switch transistor, and the first transistor are turned on, and the third switch transistor, the sixth switch transistor, and the second transistor are turned off, and the fourth switch transistor is first. The transistor, the first inductor, the grid Grid, the second inductor, and the fifth switch form an inverter loop. As shown in FIG. 7, the fourth switch tube S2, the fifth switch tube S3, and the first switch tube first transistor S6 are turned on, and the third switch tube S1, the sixth switch tube S4, and the second switch tube second transistor S5 are turned off. At this time, the current path is: Vdc+→S2→S6→L2→Grid → L1 → S3 → Vdc-, at this time in the inverter phase, the current path diagram shown in Figure 7, can constitute the inverter loop to deliver current to the grid, at this time the transistor drive signal in the circuit is shown in Figure 4.

In the inductor freewheeling phase where the grid voltage is negative half cycle, the fourth switching transistor and the fifth switching transistor are disconnected, the first transistor remains conductive, and the third switching transistor, the sixth switching transistor, and the second transistor remain off. The grid Grid, the second inductor, the second body diode, the second diode, the first transistor, and the first inductor form an inductive freewheeling circuit. When the fourth switch S2 and the fifth switch S3 are disconnected, the first transistor S6 remains turned on, and the third switch S1, the sixth switch S4, and the second transistor S5 remain turned off because the second inductor L1 and The current of the first inductor L2 cannot be abrupt, so the current path is: Grid→L1→D5→D8→S6→L2. At this time, the inductor is in the freewheeling phase, and the current path diagram is shown in Fig. 8. The inductor freewheeling loop can be constructed to the grid. The current is delivered, and the transistor drive signal in the circuit is shown in Figure 4.

When the grid voltage is positive half cycle, the third switch tube S1 and the sixth switch tube S4 are sinusoidal pulse width modulation high frequency turn-on and turn-off with the same driving signal, and the second transistor S5 is turned on and off at the same low frequency as the grid frequency. . When the grid voltage is negative for half a cycle, the fourth switch tube S2 and the fifth switch tube S3 are sinusoidal pulse width modulation high frequency turn-on and turn-off with the same drive signal. S6 is turned on and off at the same low frequency as the grid frequency.

In the embodiment of the present invention, by newly adding the transistors S5 and S6 with the body diodes and the diodes D7 and D8, a new freewheeling path and freewheeling are provided when the second inductor L1 and the first inductor L2 continue to flow in the positive and negative half cycle of the grid voltage. The path becomes smaller, there is no problem of large loss like bipolar modulation transistor switching, and the common mode leakage current is also suppressed, thereby improving inverter efficiency and EMC performance.

As shown in FIG. 3, the inverter system includes: the grid-connected inverter described above.

In an optional embodiment, the inverter system further includes: a DC power source, the anode of the DC power source is connected to the anode of the input end of the grid-connected inverter, and the cathode of the DC power source is connected to the cathode of the input end of the grid-connected inverter. .

As an optional embodiment, the inverter system further includes: a filter capacitor, one end is connected to the anode of the DC power source, and the other end is connected to the cathode of the DC power source.

Specifically, the inverter system further includes: a filter capacitor C, one end of which is connected to the anode of the DC power source Vdc, and the other end of which is connected to the cathode of the DC power source Vdc.

In another optional embodiment, the DC power source includes: a photovoltaic power source, a wind power source, and a power device power source.

Among them, the positive and negative poles of the DC power supply Vdc belong to the input of the grid-connected inverter, that is, the grid-connected inverter The input of the device is the DC power supply Vdc, the output is the junction of the second inductor L1, the first inductor L2 and the grid Grid, and the input of the grid-connected inverter (ie, the DC power source Vdc) passes through the second inductor L1 and the first inductor L2. When it is connected to the grid Grid, it is sent to the grid Grid.

Specifically, the grid-connected inverter can be generally divided into a photovoltaic power generation grid-connected inverter, a wind power grid-connected inverter, a power equipment grid-connected inverter, and other power generation equipment to generate a grid-connected inverter. The main function of the inverter is to convert direct current into alternating current. Optionally, the DC power source includes: a photovoltaic power source, a wind power source, and a power device power source.

In addition, in an optional embodiment, the inverter system further includes: a first inductor, the first end is connected to the first port of the grid-connected inverter, the second end is connected to the power grid; and the second inductor is first The end is connected to the second port of the grid-connected inverter, and the second end is connected to the grid.

Specifically, the inverter system further includes: the first end of the first inductor L2 is connected to the first port of the grid-connected inverter, the second end is connected to the grid; the second inductor L1, the first end is connected to the grid-connected inverter The second port is connected and the second end is connected to the grid.

Among them, the inductor (inductor coil) is an electromagnetic induction component wound by an insulated wire (for example, an enameled wire or a yarn wrapped wire), and is also one of the commonly used components in an electronic circuit. Or: a set of series coaxial coils wound on an insulating skeleton or a magnetic core or a core with an enameled wire, a yarn wrapped wire or a plasticized wire, which is represented by a letter "L" in the circuit, and the main function is Is to isolate the AC signal, filter or form a resonant circuit with capacitors, resistors, etc. It is also a property of a closed loop. When the coil passes the current, after the coil, a magnetic field induction is formed in the coil, and the induced magnetic field generates an induced current to resist the current flowing through the coil. It is also a physical quantity used to measure the ability of a coil to generate electromagnetic induction.

The serial numbers of the embodiments of the present invention are merely for the description, and do not represent the advantages and disadvantages of the embodiments.

In the above-mentioned embodiments of the present invention, the descriptions of the various embodiments are different, and the parts that are not detailed in a certain embodiment can be referred to the related descriptions of other embodiments.

In the several embodiments provided by the present application, it should be understood that the disclosed technical contents may be implemented in other manners. The device embodiments described above are only schematic. For example, the division of the unit may be a logical function division. In actual implementation, there may be another division manner, for example, multiple units or components may be combined or may be Integrate into another system, or some features can be ignored or not executed. In addition, the mutual coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection through some interface, unit or module, and may be electrical or otherwise.

The units described as separate components may or may not be physically separated, and the components displayed as the unit may or may not be physical units, that is, may be located in one place, or may be distributed to multiple On the unit. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of the embodiment.

In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above integrated unit can be implemented in the form of hardware or in the form of a software functional unit.

The above description is only a preferred embodiment of the present invention, and it should be noted that those skilled in the art can also make several improvements and retouchings without departing from the principles of the present invention. It should be considered as the scope of protection of the present invention.

Claims

A grid-connected inverter, wherein:

An auxiliary circuit for providing a first freewheeling path and a second freewheeling path, wherein the auxiliary circuit comprises:

a first transistor with a first body diode, a source connected to a first port of the grid-connected inverter, and a gate being a control terminal;

a first diode having a positive electrode connected to a drain of the first transistor;

a second transistor with a second body diode having a drain connected to a negative terminal of the first diode, a source connected to a second port of the grid-connected inverter, and a gate being a control end;

a second diode having a positive electrode connected to a drain of the second transistor and a negative electrode connected to a drain of the first transistor;

Wherein the first transistor with the first body diode, the first diode and the second transistor with the second body diode constitute a first freewheeling path, the first with the first body diode The transistor, the second diode, and the second transistor with the second body diode form a second freewheeling path;

The first port and the second port are connected to a power grid.
The grid-connected inverter according to claim 1, wherein

The first body diode has a positive electrode connected to a source of the first transistor, and a negative electrode connected to a drain of the first transistor;

The second body diode has a positive electrode connected to a source of the second transistor, and a negative electrode connected to a drain of the second transistor.
The grid-tied inverter of claim 1, wherein the first port is connected to the power grid by a first inductance, and the second port is connected to the power grid by a second inductance.
The grid-connected inverter of claim 1 , wherein the grid-connected inverter further comprises:

a third switching transistor, the drain is connected to the input end of the grid-connected inverter, the source is connected to the drain of the second transistor, and the gate is the control end;

a fourth switching transistor, the drain is connected to the input end of the grid-connected inverter, the source is connected to the drain of the first transistor, and the gate is the control end;

a fifth switching transistor, a drain is connected to a source of the second transistor, a source is connected to a cathode of the DC power source, and a gate is a control terminal;

The sixth switching transistor has a drain connected to a source of the first transistor, a source connected to a cathode of the DC power source, and a gate being a control terminal.
The grid-connected inverter of claim 4, wherein the grid-connected inverter further comprises:

a fifth diode, a negative electrode connected to a drain of the third switch tube, and a positive electrode connected to a source of the third switch tube;

a sixth diode, a negative electrode connected to a drain of the fourth switch tube, and a positive electrode connected to a source of the fourth switch tube;

a seventh diode, a cathode connected to a drain of the fifth switch, and a cathode connected to a source of the fifth switch;

The eighth diode has a negative electrode connected to the drain of the sixth switch tube, and a positive electrode connected to the source of the sixth switch tube.
The grid-connected inverter according to claim 5, wherein

In the inverter phase where the grid voltage is positive half cycle, the third switch transistor, the sixth switch transistor, and the second transistor are turned on, and the fourth switch transistor, the fifth switch transistor, and the first transistor are turned off, and the third switch transistor and the second transistor are turned off. The transistor, the second inductor, the grid Grid, the first inductor, and the sixth switch tube constitute an inverter loop;

In the inductor freewheeling phase where the grid voltage is positive half cycle, the third switching transistor and the sixth switching transistor are disconnected, the second transistor remains conductive, and the fourth switching transistor, the fifth switching transistor, and the first transistor remain off. The grid Grid, the first inductor, the first body diode, the first diode, the second transistor, and the second inductor form an inductive freewheeling circuit;

In the inverter phase where the grid voltage is negative half cycle, the fourth switch transistor, the fifth switch transistor, and the first transistor are turned on, and the third switch transistor, the sixth switch transistor, and the second transistor are turned off, and the fourth switch transistor is first. The transistor, the first inductor, the grid Grid, the second inductor, and the fifth switch tube constitute an inverter loop;

In the inductor freewheeling phase where the grid voltage is negative half cycle, the fourth switching transistor and the fifth switching transistor are disconnected, the first transistor remains conductive, and the third switching transistor, the sixth switching transistor, and the second transistor remain off. The grid Grid, the second inductor, the second body diode, the second diode, the first transistor, and the first inductor form an inductive freewheeling circuit.
An inverter system, comprising: the grid-connected inverter of any one of claims 1 to 6.
The inverter system of claim 7, wherein the inverter system further comprises:

a DC power source, wherein a positive pole of the DC power source is connected to an anode of an input end of the grid-connected inverter, and a cathode of the DC power source is connected to a cathode of an input end of the grid-connected inverter.
The inverter system of claim 8, wherein the inverter system further comprises:

The filter capacitor has one end connected to the anode of the DC power source and the other end connected to the cathode of the DC power source.
The inverter system of claim 8, wherein the direct current power source comprises: a photovoltaic power source, a wind power source, and a power device power source.
The inverter system of claim 7, wherein the inverter system further comprises:

a first inductor, the first end is connected to the first port of the grid-connected inverter, and the second end is connected to the power grid;

The second inductor has a first end connected to the second port of the grid-connected inverter and a second end connected to the grid.