WO2021259091A1

WO2021259091A1 - Multi-level soft-switching inversion driving system and voltage window switching method therefor

Info

Publication number: WO2021259091A1
Application number: PCT/CN2021/100102
Authority: WO
Inventors: 周衍
Original assignee: 周衍
Priority date: 2020-06-22
Filing date: 2021-06-15
Publication date: 2021-12-30
Also published as: DE102021115784B4; CN111697861A; CN111697861B; DE102021115784A1

Abstract

Disclosed are a multi-level soft-switching inversion driving system and a voltage window switching method therefor. The system comprises a multi-phase inversion drive circuit. Each phase inversion drive circuit comprises n DC power supply input ends, an AC output end, a voltage window switching circuit, a soft-switching inversion drive module, a control module, an inductor, and an output end capacitor. In operation, the control module is used for measuring and comparing the magnitude of a voltage on the AC output end with the magnitude of a voltage on each DC power supply output end in real time, determining a voltage window where the voltage on the AC output end is located, and outputting a control signal to the voltage window switching circuit. The voltage window switching circuit is used for allocating DC input levels of the DC power supply input ends to a plurality of voltage windows which mutually overlap. The soft-switching inversion drive module is used for converting the DC voltage output by the voltage window switching circuit into an AC for outputting. The present invention enables the whole system to achieve extremely low switching loss, and improves the energy utilization efficiency.

Description

Multi-level soft switch inverter drive system and voltage window switching method thereof

Technical field

The invention relates to the field of inverter drive circuits, in particular to a multi-level soft switch inverter drive system and a voltage window switching method thereof.

Background technique

In the existing multi-level soft-switching inverter drive system, the soft-switching structure itself has extremely low switching loss, but unipolar switching devices such as MOSFET or GaN-FET are used. However, due to the limitations of materials, the voltage resistance and current-carrying capacity per unit area of such devices are not high. It is difficult to obtain both high voltage and high current-carrying capacity at the same time, and the cost is high, which limits its practical application. The bipolar device has strong current-carrying capacity and high withstand voltage, but its switching loss cannot be avoided, making its energy utilization efficiency low.

Summary of the invention

In view of the problems in the background art, the purpose of the present invention is to provide a multi-level soft-switching inverter drive system and a voltage window switching method thereof.

In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows:

A multi-level soft-switching inverter drive system, including multi-phase mutually independent inverter drive circuits with the same structure;

Each phase of the inverter drive circuit includes n DC power input terminals, an AC output terminal, a voltage window switching circuit, a soft-switching inverter drive module, a control module, an inductor L and an output capacitor. The input terminal of the voltage window switching circuit is correspondingly connected to the n DC power input terminals, and the output terminal of the voltage window switching circuit is correspondingly connected to the input terminal of the soft-switching inverter drive module. The soft-switching inverter The output end of the drive module is connected to the AC output end through the inductor L, one end of the output end capacitor is connected to a DC power input end, and the other end is connected to the AC output end; the control module corresponds to the voltage window The switching circuit, the AC output terminal and the n DC power input terminals are connected;

The control module is used for real-time measurement and comparison of the voltage at the AC output terminal and the input terminal voltage of each DC power supply in the corresponding phase inverter drive circuit, to determine the voltage window where the AC output terminal voltage is located, and to combine the required AC output terminal The voltage change trend output control signal to the voltage window switching circuit;

Voltage window switching circuit for distributing the DC input level of each DC power input terminal into multiple overlapping and continuous voltage windows;

Soft switch inverter drive module, used to convert the DC voltage output by the voltage window switching circuit into AC output;

Wherein, n≥4, and n is an integer.

In some embodiments, the voltages of the n DC power input terminals included in the inverter drive circuit of each phase take the midpoint potential between the highest-level DC power input terminal and the lowest-level DC power input terminal as the potential reference point, The input voltage of each DC power input terminal and the output voltage of each phase AC output terminal are the voltages from each terminal to this potential reference point.

In some embodiments, the voltage window switching circuit is a voltage window switching circuit with a number of input terminals that matches the number of the n DC power supply input terminals;

The soft-switching inverter drive module is a soft-switching inverter drive circuit with a number of input terminals that matches the number of output terminals included in the voltage window switching circuit;

Each input terminal included in the voltage window switching circuit is correspondingly connected to one of the DC power input terminals;

Each input terminal included in the soft switch inverter drive module is correspondingly connected to an output terminal of the voltage window switching circuit.

In some embodiments, the voltage window switching circuit is a voltage window switching circuit with four input terminals and two output terminals;

The soft-switching inverter drive module is a half-bridge circuit or a floating capacitor bridge circuit with a positive DC input terminal +Uzk, a negative DC input terminal -Uzk, and an output terminal;

The four input terminals included in the voltage window switching circuit are correspondingly connected to four DC power supply input terminals with different potential values, and the voltages of the four DC power supply input terminals with different potential values are UinDC1, UinDC2, UinDC3, and UinDC3 from high to low. UinDC4;

The two output terminals included in the voltage window switching circuit are correspondingly connected to the two input terminals of the soft switch inverter drive module;

The voltage window switching circuit includes four switching devices S1, S2, S3, and S4; of which two switching devices S1, S2 are connected in series between two DC power input terminals with voltages UinDC1 and UinDC2; the other two switching devices S3 and S4 are connected in series between the two DC power input terminals with voltages UinDC3 and UinDC4;

The positive DC input terminal +Uzk of the half-bridge circuit or floating capacitor bridge circuit corresponds to the common terminal of the two switching devices S1 and S2 connected in series between the two DC power input terminals with voltages UinDC1 and UinDC2 respectively, and the negative DC input The terminal -Uzk is connected to the common terminal of the other two switching devices S3 and S4 connected in series between the two DC power input terminals with voltages UinDC3 and UinDC4 respectively, and the output terminal is correspondingly connected to the inductor L.

In some embodiments, the voltage window switching circuit is a voltage window switching circuit with four input terminals and three output terminals;

The soft switch inverter drive module is a T-type inverter circuit with a positive DC input terminal +Uzk, a negative DC input terminal -Uzk, an intermediate DC input terminal Uzkm, and an output terminal;

The three output terminals included in the voltage window switching circuit are correspondingly connected to the three input terminals of the soft switch inverter drive module;

The voltage window switching circuit contains six switching devices S1, S2, S3, S4, S5, and S6; the six switching devices S1, S2, S3, S4, S5, and S6 are connected in series with the potential values respectively. Between the four DC power input terminals of UinDC1, UinDC2, UinDC3 and UinDC4;

The positive DC input terminal +Uzk of the T-type inverter circuit corresponds to the common terminal of the two switching devices S1 and S2 connected in series between the two DC power input terminals with voltage values UinDC1 and UinDC2 respectively, and the middle DC input terminal Uzkm Corresponding to the common terminals of the two switching devices S3 and S4 connected in series between the two DC power input terminals with voltage values UinDC2 and UinDC3 respectively, the negative DC input terminal -Uzk corresponds to the series connected with the voltage values UinDC3 and UinDC4 respectively The common ends of the two switching devices S5 and S6 between the two DC power input ends of the DC power supply are connected, and the output ends are correspondingly connected to the inductor L.

In some embodiments, the voltage window switching circuit is a voltage window switching circuit with five input terminals and two output terminals;

The five input terminals included in the voltage window switching circuit 1 are correspondingly connected to five DC power supply input terminals with different potential values, and the voltages of the five DC power supply input terminals with different potential values are UinDC1, UinDC2, UinDC3 from high to low. , UinDC4 and UinDC5;

The voltage window switching circuit contains eight switching devices S1, S2, S3, S4, S5, S6, S7, and S8; three of the switching devices S1, S2, S3 are connected in series with DC power inputs with voltage values UinDC1 and UinDC3, respectively Between the terminals, three switching devices S4, S5, S6 are connected in series between the DC power supply input terminals with voltage values UinDC3 and UinDC5; and the DC power supply input terminal with voltage value UinDC2 passes through a switching device S7 and two switching devices The common ends of S1 and S2 are connected, and the DC power input end with a voltage value of UinDC4 is connected to the common ends of two switching devices S5 and S6 through a switching device S8;

The positive DC input terminal +Uzk of the half-bridge circuit or floating capacitor bridge circuit is correspondingly connected to the common terminal of the two switching devices S2 and S3, and the negative DC input terminal -Uzk is correspondingly connected to the common terminal of the two switching devices S4 and S5, and the output The terminal is correspondingly connected to the inductor L.

In some embodiments, the switching device used is an IGBT device or a GTO device.

In some embodiments, three phases are mutually independent and inverter drive circuits with the same structure are included.

Another aspect of the present invention provides a voltage window switching method of the above-mentioned multi-level soft-switching inverter drive system:

When the AC output terminal voltage UoutAC is in the overlapping part of two adjacent voltage windows, the voltage window switching circuit switches the input terminal of the soft-switching inverter drive module to the next required adjacent voltage window at the same time; or

When the AC output terminal voltage UoutAC is in the overlapping part of two adjacent voltage windows, the voltage window switching circuit switches the input terminal of the soft-switching inverter drive module to the next required adjacent voltage window in two steps; Step, the voltage window switching circuit first switches the input terminal of the soft-switch inverter drive module to the overlapping part of the current voltage window and the next required adjacent voltage window, and maintains it for a period of time; in the second step, the soft-switch is reversed. The input terminal of the variable drive module is switched to the next required adjacent voltage window.

In some embodiments, the method specifically includes:

Set a window downward switching threshold voltage and a window upward switching threshold voltage within the overlap voltage range of every two adjacent voltage windows; when switching to a lower voltage window is required, the control module compares the AC output voltage in real time UoutAC and the window downward switching threshold voltage, when the AC output voltage UoutAC is lower than the window downward switching threshold voltage, the voltage window switching circuit is triggered to simultaneously switch the input terminal of the soft-switch inverter drive module to the next required adjacent When switching to a higher voltage window, the control module compares the AC output terminal voltage UoutAC with the window upward switching threshold voltage in real time. When the AC output terminal voltage is higher than the window upward switching threshold voltage, the voltage window is triggered The switching circuit switches the input terminal of the soft switch inverter drive module to the next required adjacent voltage window at the same time; or

Set a window downward switching threshold voltage and a window upward switching threshold voltage within the overlap voltage range of every two adjacent voltage windows, and the window downward switching threshold voltage is higher than the window upward switching threshold in the overlapping part of each voltage window Voltage; when it is necessary to switch to a lower voltage window, the control module compares the AC output terminal voltage UoutAC with the window downward switching threshold voltage in real time. When the AC output terminal voltage UoutAC is lower than the window downward switching threshold voltage, the trigger voltage The window switching circuit switches the input terminal of the soft-switching inverter drive module to the overlapping part of the current voltage window and the next required adjacent voltage window. When the AC output terminal voltage UoutAC is lower than the window upward switching threshold voltage, the voltage window is triggered The switching circuit switches the input terminal of the soft-switching inverter drive module to the next required adjacent voltage window; when it is necessary to switch to a voltage window with a higher level, the control module compares the AC output terminal voltage UoutAC with the window upward in real time Switching threshold voltage. When the AC output terminal voltage UoutAC is higher than the window upward switching threshold voltage, the voltage window switching circuit is triggered to switch the input terminal of the soft switch inverter drive module to the current voltage window and the next required adjacent voltage window. In the overlapping part, when the AC output terminal voltage UoutAC is higher than the window down switching threshold voltage, the voltage window switching circuit is triggered to switch the input terminal of the soft-switching inverter drive module to the next required adjacent voltage window.

Compared with the prior art, the present invention proposes a multi-level soft-switching inverter drive system and its voltage window switching method, which combines a voltage window switching circuit, a soft-switching inverter drive module and a control module, and can achieve better performance. Low voltage is applied to the soft switching circuit, and since the switching frequency of the voltage window switching circuit is the same as the frequency of the AC output terminal, the resulting switching loss can be ignored, and it can be implemented in the voltage window switching circuit if the synchronous switch is controlled. With Zero Current Switching (ZCS), no obvious switching loss is generated at this time, so that the entire multi-level soft-switching inverter drive system achieves extremely low switching loss and improves energy efficiency.

Description of the drawings

Through the following description of the present invention with reference to the accompanying drawings, other objects and advantages of the present invention will be apparent and can help a comprehensive understanding of the present invention.

Fig. 1 is a schematic diagram of the principle of a multi-level soft-switching inverter drive system provided by the present invention;

2 to 6 are schematic diagrams of each phase inverter drive circuit in the first embodiment to the fifth embodiment;

7 and 8 are schematic diagrams of switching between the output terminal voltage and the voltage window corresponding to the first embodiment and the second embodiment;

9 is a schematic diagram of switching between the output terminal voltage and the voltage window corresponding to the third embodiment;

10 and 11 are schematic diagrams of switching between the output terminal voltage and the voltage window corresponding to the fourth embodiment and the fifth embodiment;

Description of reference signs:

1. Voltage window switching circuit; 2. Soft switch inverter drive module; 3. Control module.

detailed description

In order to make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the described embodiments of the present invention, all other embodiments obtained by a person of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.

Unless otherwise defined, the technical terms or scientific terms used in the present invention shall have the usual meanings understood by those with ordinary skills in the field to which the present invention belongs.

1, the present invention provides a multi-level soft-switching inverter drive system, which includes multi-phase independent inverter drive circuits with the same structure; each phase of the inverter drive circuit includes n DC power input terminals, one AC output terminal, a voltage window switching circuit 1, a soft-switching inverter drive module 2, a control module 3, an inductor L and output terminal capacitance, the output terminal capacitance can include two capacitors C1, C2, voltage window switching circuit 1 The input terminal of is connected to the input terminals of the n DC power supply, n≥4, and n is an integer; the output terminal of the voltage window switching circuit 1 is connected to the input terminal of the soft-switching inverter drive module 2, and the soft-switching inverter drive The output terminal of module 2 is connected to the AC output terminal through the inductor L. Two capacitors C1 and C2 are connected in series between the highest level DC power input terminal and the lowest level DC power input terminal of the n DC power input terminals, and two The capacitors C1 and C2 are also correspondingly connected to the AC output terminal; the control module 3 is correspondingly connected to the voltage window switching circuit 1, the AC output terminal and n DC power input terminals.

Control module 3. It is used to measure and compare the voltage of the AC output terminal and the voltage of each DC power supply input terminal in the corresponding phase inverter drive circuit in real time, to determine the voltage window where the AC output terminal voltage is located, and to combine the required AC output Terminal voltage change trend output control signal to voltage window switching circuit 1. Voltage window switching circuit 1, used to distribute the DC input level of each DC power input terminal into multiple overlapping and continuous voltage windows; soft switching inverter drive module 2. It is used to convert the DC voltage output by the voltage window switching circuit 1 into AC output.

Further, the voltages of the n DC power supply input terminals included in each phase inverter drive circuit take the potential of the midpoint between the highest level DC power supply input terminal and the lowest level DC power supply input terminal as the potential reference point, and each DC power supply input The input voltage of the terminal and the output voltage of each phase AC output terminal are the voltages from each terminal to this potential reference point.

Further, the voltage window switching circuit 1 is a voltage window switching circuit with the number of input terminals matching the number of n DC power supply input terminals; the soft-switching inverter drive module 2 is a circuit containing the number of input terminals and the voltage window switching circuit 1 contains a soft-switching inverter drive circuit with a matching number of output terminals; each input terminal included in the voltage window switching circuit 1 is connected to a DC power input terminal; each input terminal included in the soft-switching inverter drive module 2 corresponds to One output terminal of the voltage window switching circuit 1 is connected.

In addition, under the control of the control module 3, the voltage window switching circuit 1 has the following two voltage window switching methods:

Method 1: When the AC output terminal voltage UoutAC is in the overlapping part of two adjacent voltage windows, the voltage window switching circuit 1 switches the DC input terminal of the soft-switching inverter drive module 2 to the next required adjacent voltage window at the same time . Specifically, one window downward switching threshold voltage and one window upward switching threshold voltage are set within the overlap voltage range of every two adjacent voltage windows; when it is necessary to switch to a voltage window with a lower level, the control module 3 compares in real time The AC output terminal voltage UoutAC and the window downward switching threshold voltage. When the AC output terminal voltage is lower than the window downward switching threshold voltage, the voltage window switching circuit 1 is triggered to simultaneously switch the DC input terminal of the soft-switch inverter drive module 2 to the downward A required adjacent voltage window; when switching to a higher level voltage window, the control module compares the AC output terminal voltage UoutAC with the window upward switching threshold voltage in real time, when the AC output terminal voltage is higher than the window upward switching threshold When the voltage is applied, the voltage window switching circuit 1 is triggered to simultaneously switch the DC input terminal of the soft-switching inverter drive module 2 to the next required adjacent voltage window.

Method 2: When the AC output terminal voltage UoutAC is in the overlapping part of two adjacent voltage windows, the voltage window switching circuit 1 switches the DC input terminal of the soft-switching inverter drive module 2 to the next required adjacent in two steps In the first step, the voltage window switching circuit 1 switches the DC input terminal of the soft-switching inverter drive module 2 to the overlapping part of the current voltage window and the next required adjacent voltage window, and keeps it for a period of time; In the second step, the DC input terminal of the soft-switching inverter drive module 2 is switched to the next required adjacent voltage window. Specifically, one window downward switching threshold voltage and one window upward switching threshold voltage are set within the overlapping voltage range of every two adjacent voltage windows, and the window downward switching threshold voltage is higher than the window in the overlapping portion of each voltage window Switch up the threshold voltage; when it is necessary to switch to a lower voltage window, the control module 3 compares the AC output terminal voltage UoutAC with the window downward switching threshold voltage in real time. When the AC output terminal voltage UoutAC is lower than the window downward switching threshold voltage When the voltage window switching circuit 1 is triggered, the DC input terminal of the soft switch inverter drive module 2 is switched to the overlapping part of the current voltage window and the next required adjacent voltage window. When the AC output terminal voltage UoutAC is lower than the window, it switches upwards When the threshold voltage is reached, the voltage window switching circuit 1 is triggered to switch the DC input terminal of the soft-switching inverter drive module 2 to the next required adjacent voltage window; when it is necessary to switch to a voltage window with a higher level, the control module 3 Compare the AC output terminal voltage UoutAC with the window upward switching threshold voltage in real time. When the AC output terminal voltage UoutAC is higher than the window upward switching threshold voltage, the voltage window switching circuit 1 is triggered to switch the DC input terminal of the soft switch inverter drive module 2 to The overlapping part of the current voltage window and the next required adjacent voltage window. When the AC output terminal voltage UoutAC is higher than the window downward switching threshold voltage, the voltage window switching circuit 1 is triggered to soft switch the DC input of the inverter drive module 2 Switch to the next required adjacent voltage window.

Further referring to FIG. 2, in the first embodiment, the voltage window switching circuit 1 has four input terminals, and the four input terminals are respectively connected to four DC power supplies with different potential values. UinDC2, UinDC3 and UinDC4; voltage window switching circuit 1 is used to divide the level of DC power input into two voltage windows: the voltage range of the first voltage window is from UinDC1 to UinDC3, and the voltage range of the second voltage window is from UinDC1 to UinDC3. UinDC2 to UinDC4; the control module 3 is used to measure and compare the voltage of the AC output terminal and the voltage of each DC power input terminal in real time. According to the comparison result, the control module 3 controls the voltage window switching circuit 1 to switch the input to the input terminal of the soft switch inverter drive module 2. Voltage window.

In addition, the voltage window switching circuit 1 includes four switching devices S1, S2, S3, and S4; the switching devices S1, S2 are connected in series between the DC power supplies UinDC1 and UinDC2; the positive DC input terminal +Uzk of the soft-switching inverter drive module 2 and The common ends of the switching devices S1 and S2 are connected; the switching devices S3 and S4 are connected in series between the DC power supplies UinDC3 and UinDC4; the negative DC input terminal-Uzk of the soft switching inverter drive module 2 is connected to the common ends of the switching devices S3 and S4; The soft-switching inverter drive module 2 adopts a half-bridge circuit with two-level input.

3, in the second embodiment, the only difference from the first embodiment is that the soft-switching inverter drive module 2 adopts a dual-level input floating capacitor bridge circuit.

For the first embodiment and the second embodiment, the voltage window switching circuit 1 is the same, so the switching methods of the two are also the same, and both of the foregoing two switching methods can be used.

The first switching method: As shown in Figure 7, the overlap range of the first voltage window and the second voltage window is UinDC2 to UinDC3. When the AC output terminal voltage UoutAC is in the overlap portion, the voltage window switching circuit 1 will soften The DC input terminals +Uzk and -Uzk of the switching inverter drive module 2 are simultaneously switched to the next required adjacent voltage window, and at this time, the window downward switching threshold voltage and the window upward switching threshold voltage are both 0V.

The specific switching process is shown in Table 1:

Table 1 The voltage of the AC output terminal and the voltage of the DC input terminal of the soft-switching inverter drive module during the switching of the voltage window

The switching state of each switching device during the switching process is shown in Table 2 (0 means off, 1 means on):

Table 2 The switching state of each switching device during the switching process of the voltage window

The second switching method: As shown in Figure 8, when the AC output terminal voltage UoutAC is in the overlapping part of the voltage window, the voltage window switching is clear. 1 The DC input terminal +Uzk and -Uzk of the soft switch inverter drive module 2 are divided into two Step switch to the next required adjacent voltage window; the first step, first switch the DC input terminals +Uzk and -Uzk of the soft-switch inverter drive module 2 to the current voltage window and the next required adjacent voltage The overlapping part of the window is maintained for a period of time; in the second step, the DC input terminals +Uzk and -Uzk of the soft-switching inverter drive module 2 are switched to the next required adjacent voltage window. In addition, the window downward switching threshold voltage is greater than 0V and less than Uzk2; the window upward switching threshold voltage is less than 0V and greater than UinDC3. The specific switching process is shown in Table 3:

Table 3 The voltage of the AC output terminal and the voltage of the DC input terminal of the soft-switching inverter drive module during the switching of the voltage window

The switching state of each switching device during the switching process is shown in Table 4:

Table 4 Switching status of each switching device during the switching process of the voltage window

Further, as shown in FIG. 4, in the third embodiment, the voltage window switching circuit 1 also has an intermediate output terminal, which is correspondingly connected to the intermediate DC input terminal Uzkm of the soft-switching inverter drive module 2; at this time, the voltage window The switching circuit 1 includes six switching devices S1, S2, S3, S4, S5 and S6; the switching devices S1, S2 are connected in series between the DC power supplies UinDC1 and UinDC2; the positive DC input +Uzk of the soft-switching inverter drive module 2 and The common ends of the switching devices S1 and S2 are connected; the switching devices S3 and S4 are connected in series between the DC power supplies UinDC2 and UinDC3; the intermediate DC input terminal Uzkm of the soft switching inverter drive module 2 is connected to the common ends of the switching devices S3 and S4; switch The devices S5 and S6 are connected in series between the DC power supplies UinDC3 and UinDC4; the negative DC input terminal-Uzk of the soft-switching inverter drive module 2 is connected to the common terminals of the switching devices S5 and S6; the soft-switching inverter drive module 2 adopts three-level Input T-type inverter circuit. In this embodiment, the intermediate DC input terminal of the soft-switching inverter drive module 2 is added, which can further optimize the working state of the soft-switching inverter drive module 2.

The voltage window switching method of this embodiment is shown in FIG. 9. At this time, the overlap range of the first voltage window and the second voltage window is UinDC2 to UinDC3. When the AC output terminal voltage UoutAC is in the overlap portion, the voltage window switching circuit 1 Switch the DC input terminals +Uzk, Uzkm, and -Uzk of the soft-switching inverter drive module 2 to the next required adjacent voltage window at the same time, and at this time, the window downward switching threshold voltage and the window upward switching threshold voltage are both 0V . The specific switching process is shown in Table 5:

Table 5 The voltage of the AC output terminal and the voltage of the DC input terminal of the soft-switching inverter drive module during the switching of the voltage window

The switching state of each switching device during the switching process is shown in Table 6:

Table 6 Switching status of each switching device during the switching process of the voltage window

Further, as shown in FIG. 5, in the fourth embodiment, the voltage window switching circuit 1 has five input terminals, and the five input terminals are respectively connected to five DC power supplies with different potential values, the voltages of which are from high to low. They are UinDC1, UinDC2, UinDC3, UinDC4 and UinDC5 in order; voltage window switching circuit 1 is used to distribute the level of DC power input into three voltage windows: the voltage range of the first voltage window is from UinDC1 to UinDC3, and the second voltage The voltage range of the window is from UinDC2 to UinDC4, and the voltage range of the third voltage window is from UinDC3 to UinDC5; the control module 3 is used to measure and compare the voltage of the AC output terminal and the voltage of each DC power input terminal in real time. According to the comparison result, the control module 3 The control voltage window switching circuit 1 switches the voltage window input to the input terminal of the soft switch inverter drive module 2.

At this time, the voltage window switching circuit 1 includes eight switching devices S1, S2, S3, S4, S5, S6, S7, and S8; the switching devices S1, S2, S3 are connected in series between the DC power supplies UinDC1 and UinDC3; soft switching inverter The positive DC input terminal +Uzk of the drive module 2 is connected to the common terminal of the switching devices S2 and S3; the DC power supply UinDC2 is connected to the common terminal of the switching devices S1 and S2 through the switching device S7; the switching devices S4, S5, and S6 are connected in series to the DC power supply Between UinDC3 and UinDC5; the negative DC input terminal Uzk of the soft switching inverter drive module 2 is connected to the common terminal of the switching devices S4 and S5; the DC power supply UinDC4 is connected to the common terminal of the switching devices S5 and S6 through the switching device S8; The switching inverter drive module 2 adopts a two-level input half-bridge circuit.

6, in the fifth embodiment, the only difference from the fourth embodiment is that the soft-switching inverter drive module 2 adopts a floating capacitor bridge circuit with dual-level input.

For the fourth embodiment and the fifth embodiment, the voltage window switching circuit 1 is the same, so the switching methods of the two are also the same, and both of the foregoing two switching methods can be used.

The first switching method: As shown in Figure 10, the overlap range of the first voltage window and the second voltage window is UinDC2 to UinDC3, and the overlap range of the second voltage window and the third voltage window is UinDC3 to UinDC4; The window downward switching threshold voltage between the voltage window and the second voltage window is the same as the window upward switching threshold voltage, both greater than UinDC3 and less than UinDC2; the window downward switching threshold voltage between the second voltage window and the third voltage window is the same as the window upward switching threshold voltage. The window upward switching threshold voltage is the same, which is greater than UinDC4 and less than UinDC3. When the AC output terminal voltage UoutAC is in the overlapping part of two adjacent voltage windows, the voltage window switching circuit 1 switches the DC input terminals +Uzk and -Uzk of the soft-switching inverter drive module 2 to the next required adjacent at the same time. Voltage window. The specific switching process is shown in Table 7:

Table 7 The voltage of the AC output terminal and the voltage of the DC input terminal of the soft-switching inverter drive module during the switching of the voltage window

The switching states of each switching device during the switching process are shown in Table 8:

Table 8 Switching status of each switching device during the switching process of the voltage window

The second switching method: As shown in Figure 11, when the AC output terminal voltage UoutAC is in the overlapping part of two adjacent voltage windows, the voltage window switching circuit 1 soft-switches the DC input terminal +Uzk of the inverter drive module 2 and -Uzk switches to the next required adjacent voltage window in two steps; the first step is to switch the DC input terminals +Uzk and -Uzk of the soft switch inverter drive module 2 to the current voltage window and the next required voltage window. In the second step, the DC input terminals +Uzk and -Uzk of the soft-switching inverter drive module 2 are switched to the next required adjacent voltage window. Moreover, the window downward switching threshold voltage and the window upward switching threshold voltage between the first voltage window and the second voltage window are both greater than UinDC3 and less than UinDC2, and the window downward switching threshold voltage is greater than the window upward switching threshold voltage; the second voltage The window downward switching threshold voltage and the window upward switching threshold voltage between the window and the third voltage window are both greater than UinDC4 and less than UinDC3, and the window downward switching threshold voltage is greater than the window upward switching threshold voltage. The specific switching process is shown in Table 9:

Table 9 The voltage of the AC output terminal and the voltage of the DC input terminal of the soft-switching inverter drive module during the switching of the voltage window

The switching state of each switching device during the switching process is shown in Table 10:

Table 10 Switching status of each switching device during the switching process of the voltage window

Preferably, as shown in FIGS. 2-6, in each embodiment, the switching devices used are all bipolar devices, such as IGBT devices or GTO devices, preferably IGBT devices.

Preferably, the multi-level soft-switching inverter drive system includes three-phase mutually independent inverter drive circuits with the same structure.

In summary, a multi-level soft-switching inverter drive system proposed by the present invention combines a voltage window switching circuit, a soft-switching inverter drive module and a control module, and forms a voltage window by using bipolar devices (such as IGBT, GTO) The switching circuit applies a lower voltage to the soft switching circuit. At the same time, since the switching frequency of the voltage window switching circuit is the same as the frequency of the AC output terminal, the switching loss generated by it can be ignored, and if the synchronous switching control method is used to achieve zero current switching (Zero Current Switching, ZCS) in the voltage window switching circuit At this time, no obvious switching loss is generated, so that the entire multi-level soft-switching inverter drive circuit achieves extremely low switching loss and improves energy efficiency.

The specific embodiments described above further describe the purpose, technical solutions and beneficial effects of the present invention in further detail. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the present invention. Within the spirit and principle of the present invention, any modification, equivalent replacement, improvement, etc., shall be included in the protection scope of the present invention.

Claims

A multi-level soft-switching inverter drive system, which is characterized in that it comprises a multi-phase independent inverter drive circuit with the same structure;

The inverter drive circuit of each phase includes n DC power input terminals, an AC output terminal, a voltage window switching circuit (1), a soft switch inverter drive module (2), a control module (3), and a Inductance L and output terminal capacitance, the input terminal of the voltage window switching circuit (1) is correspondingly connected to the n DC power input terminals, and the output terminal of the voltage window switching circuit (1) is corresponding to the soft switch The input terminal of the inverter drive module (2) is connected, the output terminal of the soft switch inverter drive module (2) is connected to the AC output terminal through the inductor L, and one end of the output terminal capacitor is connected to a DC power supply input The control module (3) is connected to the voltage window switching circuit (1), the AC output terminal and n DC power input terminals;

The control module (3) is used for real-time measurement and comparison of the voltage at the AC output terminal and the voltage at the input terminal of each DC power supply in the corresponding phase inverter drive circuit, to determine the voltage window where the AC output terminal voltage is located, and combine it with the required The voltage change trend of the AC output terminal outputs a control signal to the voltage window switching circuit (1);

Voltage window switching circuit (1) for distributing the DC input level of each DC power supply input terminal into a plurality of overlapping and continuous voltage windows;

The soft-switching inverter drive module (2) is used to convert the DC voltage output by the voltage window switching circuit (1) into AC output;

Wherein, n≥4, and n is an integer.
The multi-level soft-switching inverter drive system according to claim 1, wherein the voltage of the n DC power input terminals included in the inverter drive circuit of each phase is determined by the highest level DC power input terminal and the lowest voltage The intermediate point potential between the input terminals of the flat DC power supply is the potential reference point, and the input voltage of each DC power supply input terminal and the output voltage of each phase AC output terminal are the voltages from each terminal to this potential reference point.
The multi-level soft-switching inverter drive system according to claim 2, characterized in that the voltage window switching circuit (1) has a number of input terminals that matches the number of input terminals of the n direct current power supplies. Voltage window switching circuit;

The soft-switching inverter drive module (2) is a soft-switching inverter drive circuit with a number of input terminals matching the number of output terminals of the voltage window switching circuit (1);

Each input terminal included in the voltage window switching circuit (1) is correspondingly connected to one of the DC power input terminals;

Each input terminal included in the soft switch inverter drive module (2) is correspondingly connected with an output terminal of the voltage window switching circuit (1).
The multi-level soft-switching inverter drive system according to claim 3, wherein the voltage window switching circuit (1) is a voltage window switching circuit with four input terminals and two output terminals;

The soft-switching inverter drive module (2) is a half-bridge circuit or a floating capacitor bridge circuit with a positive DC input terminal +Uzk, a negative DC input terminal -Uzk, and an output terminal;

The four input terminals included in the voltage window switching circuit (1) are correspondingly connected to four DC power supply input terminals with different potential values, and the voltages of the four DC power supply input terminals with different potential values are UinDC1 and UinDC2 from high to low. , UinDC3 and UinDC4;

The two output terminals included in the voltage window switching circuit (1) are correspondingly connected to the two input terminals of the soft switch inverter drive module (2);

The voltage window switching circuit (1) contains four switching devices (S1, S2, S3, and S4); two of the switching devices (S1, S2) are connected in series to one of the two DC power input terminals with voltages UinDC1 and UinDC2. The other two switching devices (S3, S4) are connected in series between the two DC power input terminals with voltages UinDC3 and UinDC4;

The positive DC input terminal +Uzk of the half-bridge circuit or floating capacitor bridge circuit corresponds to the common terminal of the two switching devices (S1, S2) connected in series between the two DC power input terminals with voltages UinDC1 and UinDC2 respectively, and the negative The DC input terminal -Uzk is connected to the common terminal of the other two switching devices (S3, S4) connected in series between the two DC power input terminals with voltages UinDC3 and UinDC4 respectively, and the output terminal is correspondingly connected to the inductor L.
The multi-level soft-switching inverter drive system according to claim 3, wherein the voltage window switching circuit (1) is a voltage window switching circuit with four input terminals and three output terminals;

The soft switching inverter drive module (2) is a T-type inverter circuit with a positive DC input terminal +Uzk, a negative DC input terminal -Uzk, an intermediate DC input terminal Uzkm, and an output terminal;

The four input terminals included in the voltage window switching circuit (1) are correspondingly connected to four DC power supply input terminals with different potential values, and the voltages of the four DC power supply input terminals with different potential values are UinDC1 and UinDC2 from high to low. , UinDC3 and UinDC4;

The three output terminals included in the voltage window switching circuit (1) are correspondingly connected to the three input terminals of the soft switch inverter drive module (2);

The voltage window switching circuit (1) contains six switching devices (S1, S2, S3, S4, S5, S6); the six switching devices (S1, S2, S3, S4, S5, S6) are paired Connected in series between the four DC power input terminals with voltage values UinDC1, UinDC2, UinDC3 and UinDC4 respectively;

The positive DC input terminal +Uzk of the T-type inverter circuit corresponds to the common terminal of the two switching devices (S1, S2) connected in series between the two DC power input terminals with voltage values UinDC1 and UinDC2 respectively, and the middle DC input The terminal Uzkm corresponds to the common terminal of the two switching devices (S3, S4) connected in series between the two DC power input terminals with voltage values UinDC2 and UinDC3 respectively, and the negative DC input terminal -Uzk corresponds to the voltage value in series. The common ends of the two switching devices (S5, S6) between the two DC power input ends of UinDC3 and UinDC4 are connected, and the output ends are correspondingly connected to the inductor L.
The multi-level soft-switching inverter drive system according to claim 3, wherein the voltage window switching circuit (1) is a voltage window switching circuit with five input terminals and two output terminals;

The soft-switching inverter drive module (2) is a half-bridge circuit or a floating capacitor bridge circuit with a positive DC input terminal +Uzk, a negative DC input terminal -Uzk, and an output terminal;

The five input terminals included in the voltage window switching circuit (1) are correspondingly connected to five DC power supply input terminals with different potential values, and the voltages of the five DC power supply input terminals with different potential values are UinDC1 and UinDC2 from high to low. , UinDC3, UinDC4 and UinDC5;

The two output terminals included in the voltage window switching circuit (1) are correspondingly connected to the two input terminals of the soft switch inverter drive module (2);

The voltage window switching circuit (1) contains eight switching devices (S1, S2, S3, S4, S5, S6, S7, S8); of which three switching devices (S1, S2, S3) are connected in series with the voltage values respectively Between the DC power input terminals of UinDC1 and UinDC3, three switching devices (S4, S5, S6) are connected in series between the DC power input terminals of UinDC3 and UinDC5 respectively; and the DC power input terminal of UinDC2 passes through A switching device (S7) is connected to the common terminal of two switching devices (S1, S2), and the DC power input terminal with a voltage value of UinDC4 passes through a switching device (S8) and the common terminal of two switching devices (S5, S6) Connected

The positive DC input terminal +Uzk of the half-bridge circuit or floating capacitor bridge circuit corresponds to the common terminal of the two switching devices (S2, S3), and the negative DC input terminal -Uzk corresponds to the common terminal of the two switching devices (S4, S5). The output terminal is connected to the inductor L correspondingly.
The multi-level soft-switching inverter drive system according to any one of claims 4-6, wherein the switching device used is an IGBT or GTO device.
The multi-level soft-switching inverter drive system according to claim 1, characterized in that it comprises three-phase mutually independent inverter drive circuits with the same structure.
A voltage window switching method for a multi-level soft-switching inverter drive system according to claim 1, characterized in that:

When the AC output terminal voltage UoutAC is in the overlapping part of two adjacent voltage windows, the voltage window switching circuit (1) switches the input terminal of the soft-switching inverter drive module (2) to the next required adjacent voltage window at the same time ;or

When the AC output terminal voltage UinDC is in the overlapping part of two adjacent voltage windows, the voltage window switching circuit (1) switches the input terminal of the soft-switching inverter drive module (2) to the next required adjacent in two steps The first step, the voltage window switching circuit (1) first switches the input terminal of the soft-switch inverter drive module (2) to the overlap between the current voltage window and the next required adjacent voltage window, and keep it A period of time; the second step is to switch the input terminal of the soft-switching inverter drive module (2) to the next required adjacent voltage window.
The method according to claim 9, wherein the method specifically comprises:

Set a window downward switching threshold voltage and a window upward switching threshold voltage within the overlapping voltage range of every two adjacent voltage windows; when it is necessary to switch to a lower voltage window, the control module (3) compares the exchange in real time The output terminal voltage UoutAC and the window downward switching threshold voltage, when the AC output terminal voltage UoutAC is lower than the window downward switching threshold voltage, the trigger voltage window switching circuit (1) will soft switch the input terminal of the inverter drive module (2) at the same time Switch to the next required adjacent voltage window; when it is necessary to switch to a higher level voltage window, the control module (3) compares the AC output terminal voltage UoutAC with the window upward switching threshold voltage in real time, when the AC output terminal voltage When the threshold voltage is higher than the window upward switching threshold voltage, the voltage window switching circuit (1) is triggered to switch the input terminal of the soft-switching inverter drive module (2) to the next required adjacent voltage window at the same time; or

Set a window downward switching threshold voltage and a window upward switching threshold voltage within the overlap voltage range of every two adjacent voltage windows, and the window downward switching threshold voltage is higher than the window upward switching threshold in the overlapping part of each voltage window Voltage; when it is necessary to switch to a lower voltage window, the control module (3) compares the AC output terminal voltage UoutAC with the window downward switching threshold voltage in real time, when the AC output terminal voltage UoutAC is lower than the window downward switching threshold voltage , The trigger voltage window switching circuit (1) switches the input terminal of the soft-switch inverter drive module (2) to the overlapping part of the current voltage window and the next required adjacent voltage window, when the AC output terminal voltage UoutAC is lower than the window When the threshold voltage is switched upward, the voltage window switching circuit (1) is triggered to switch the input terminal of the soft-switching inverter drive module (2) to the next required adjacent voltage window; when it is necessary to switch to a higher level voltage window When switching, the control module (3) compares the AC output terminal voltage UoutAC with the window upward switching threshold voltage in real time. When the AC output terminal voltage UoutAC is higher than the window upward switching threshold voltage, the voltage window switching circuit (1) is inverted to invert the soft switch The input terminal of the drive module (2) is switched to the overlapping part of the current voltage window and the next required adjacent voltage window. When the AC output terminal voltage UoutAC is higher than the window downward switching threshold voltage, the voltage window switching circuit (1 ) Switch the input terminal of the soft switch inverter drive module (2) to the next required adjacent voltage window.