CN102005957B - Single-supply cascaded multilevel converter - Google Patents

Abstract

The invention belongs to a multilevel power conversion technology, and particularly relates to a topological structure of a cascade multilevel inverter, which reduces the number of used direct current power supplies under the condition of outputting the same number of levels as that of a traditional cascade inverter. The realization method is to use a capacitor to replace a direct current voltage source in the traditional topology and maintain the voltage of the capacitor by discontinuously charging the capacitor. The invention is mainly used in high-voltage and high-power occasions, and omits a multi-secondary-side transformer of the original cascade circuit. Under the condition that the harmonic wave of the traditional multi-level converter is kept small and each power transistor only bears the single power supply voltage, the sine wave output of three times of the power supply voltage amplitude can be obtained, and the large-capacity and energy bidirectional flow is easy to realize.

Description

Single-supply cascaded multilevel converter

Technical field:

The invention relates to a multi-level power inverter technology, which adopts a bootstrap method to realize the topological structure of a cascaded multi-level converter of a single power supply.

Background technique:

In recent years, the idea of multilevel converter has become a research hotspot in the field of high voltage and high power frequency conversion. The multilevel converter outputs a voltage step wave, so that the output voltage waveform can have smaller harmonics and lower du/dt. As the number of output levels increases, the harmonics of the output voltage will decrease. In addition, the multi-level inverter technology has excellent performance in reducing the switching loss and conduction loss of the system, reducing the withstand voltage of the tube and the EMI of the system.

Multilevel converters can be divided into three structural topologies: diode clamped, capacitor clamped, and cascaded. Diode clamped converters have different switching devices and clamps as the number of levels increases. The number of bit diodes will increase a lot, so it is usually only suitable for multilevel topologies below five levels. However, the capacitor-clamped converter has the problem of balancing the charging and discharging voltage of the capacitor, and when the number of levels increases, more clamping capacitors are required, so there are also certain weaknesses. Cascaded multilevel inverters use several low-voltage PWM power units in series to achieve direct high-voltage output, which has less harmonic pollution to the power grid, lower current harmonic content, and higher input power factor, and does not need to use input harmonics. Wave filter and power factor correction are widely used in the field of high voltage and high power.

However, for cascaded multilevel converters, when multiple levels are required, more DC power supplies are required, which can be rectified separately by multi-secondary transformers, or multiple independent power supplies are used. The working frequency of the multi-side transformer is industrial frequency, which is bulky, complicated to connect, and expensive; while using multiple independent power sources, if the animal battery is used as the independent power source, the total capacity is limited, and the voltage of the animal battery is not high. It is not easy to achieve large capacity. If multiple independent rectifying power supplies are used, the volume will be even larger and the price will be more expensive. This makes this topology restricted in application.

The traditional cascaded multi-level cannot realize the back-to-back connection in the AC-DC-AC power converter, so the application of the cascaded multi-level in the inverter is also limited.

Invention content:

In order to overcome the above-mentioned problems existing in the prior art, the present invention proposes a single power supply cascaded multilevel converter with relatively simple topology and control strategy. This topology realizes seven-level cascaded multi-level converters that only need a single DC power input. This topology increases the output AC sine wave voltage amplitude to three times when all switching tubes only bear a single power supply voltage. at the DC supply voltage. This topology realizes the back-to-back connection of cascaded multilevel converters.

The technical scheme that the present invention solves its technical problem adopts is:

The phase cascading part of three inverter bridges adopts twelve switch tubes to connect into three inverter bridge structures. The DC side of the first inverter bridge and the DC side of the third inverter bridge are respectively connected to a capacitor, and the second The DC side of each inverter bridge is connected to a DC voltage source. The positive pole or negative pole of the DC power supply is respectively connected to the positive pole or negative pole of the capacitor on the DC side of the first and third inverter bridges through an auxiliary switch tube or a one-way switch tube.

The beneficial effects of the present invention are: the biggest advantage of this topology is that only a single power supply can be used to obtain a multi-level circuit in which three inverter bridges are cascaded. At the same time, this topology doubles the utilization rate of DC voltage. In the case of single voltage, it outputs a seven-level sine wave voltage that is three times the DC power supply voltage.

advantage:

(1) This design can save the multi-output isolation transformer with only one power supply, so the volume and weight of the whole machine are greatly reduced, and the cost is significantly reduced. The input of the circuit can be directly rectified by the grid without a transformer.

(2) Under the same input voltage, the output voltage is increased, and the DC voltage utilization rate is doubled. Under the condition that each switching tube withstands the power supply voltage, a sine wave output whose amplitude is three times the power supply voltage can be obtained.

(3) The two-way flow of energy can be realized to save electric energy.

(4) Because a bridge circuit is used, it is easy to realize modularization and expansion.

(5) The back-to-back connection of cascaded multi-level can be realized.

(6) The operating frequency of the switching device is low, the loss is small, the efficiency of the circuit is high, and the harmonic content in the output voltage waveform is small. Compared with the clamping circuit, the clamping diode and the clamping capacitor are not required. When the number of output levels is the same, the number of components required is small.

Description of drawings:

Figure 1 The circuit topology in which the auxiliary switch tubes are all connected to the negative pole of the power supply

Figure 2 The circuit topology in which the auxiliary switch tubes are connected to the positive pole of the power supply

Figure 3 The circuit topology of the auxiliary switch tube connected to the positive pole of the power supply and the negative pole of the power supply below

Figure 4 The circuit topology of the auxiliary switching tube connected to the negative pole of the power supply and connected to the positive pole of the power supply

In the above figure, V is the DC input power supply, S11, S12, S13, and S14 are the switches of the first inverter bridge with internal anti-parallel diodes, and S21, S22, S23, and S24 are the second switches with internal anti-parallel diodes. The switching tubes of the first inverter bridge, S31, S32, S33, and S34 are the switching tubes of the third inverter bridge with internal anti-parallel diodes. C1 is the DC side filter capacitor of the first inverter bridge, and C3 is the DC side filter capacitor of the third inverter bridge. Sc1 is an auxiliary switch tube of the capacitor C1, and Sc3 is an auxiliary switch tube of the capacitor C3. Z is the output load. D1 and D2 are diodes combined in parallel with bidirectional switch tubes. D3 and D4 are diodes combined in series with bidirectional switch tubes. D5, D6, D7, and D8 are diodes combined in bridge type of bidirectional switch tubes. T1 and T2 are switch tubes combined in parallel with bidirectional switch tubes. T3 and T4 are switching tubes combined in series with bidirectional switching tubes. T5 is a switching tube of a bridge combination of bidirectional switching tubes.

Detailed ways:

Example 1

In Figure 1, this topology includes an inverter bridge (1), an inverter bridge (2), an inverter bridge (3), an auxiliary switching tube (4) and an auxiliary switching tube (5), where the inverter bridge (1) It is: one end of the capacitor (C1) is connected to the collector of the switching tube (S11) and the collector of the switching tube (S13), the other end is connected to the emitter of the switching tube (S12) and the emitter of the switching tube (S14), and the switching tube The emitter of (S11) connects the collector of the switch tube (S12), and the emitter of the switch tube (S13) connects the collector of the switch tube (S14); the inverter bridge (2) is: the DC voltage source positive pole connects the switch tube ( The collector of S21) and the collector of the switch tube (S23), the negative pole is connected to the emitter of the switch tube (S22) and the emitter of the switch tube (S24), and the emitter of the switch tube (S21) is connected to the switch tube (S22) The collector, the emitter of the switching tube (S23) is connected to the collector of the switching tube (S24); the inverter bridge (3) is: one end of the capacitor (C3) is connected to the collector of the switching tube (S31) and the switching tube (S33) The collector of the switch tube (S32) and the emitter of the switch tube (S34) are connected at the other end, the emitter of the switch tube (S31) is connected to the collector of the switch tube (S32), and the emitter of the switch tube (S33) Connect the current collector of the switch tube (S34); the auxiliary switch tube (4) is: a one-way switch tube or a two-way switch tube; the auxiliary switch tube (5) is: a one-way switch tube or a two-way switch tube; the inverter bridge ( 1) the emitter of the switching tube (S13) and the collector of the switching tube (S14) are connected to the emitter of the switching tube (S21) of the inverter bridge (2) and the collector of the switching tube (S22); the inverter bridge ( 2) the emitter of the switching tube (S23) and the collector of the switching tube (S24) are connected to the emitter of the switching tube (S31) of the inverter bridge (3) and the collector of the switching tube (S32); the inverter bridge ( 1) The emitter of the switching tube (S11) and the collector of the switching tube (S12) are connected to one end of the load (Ro), and the emitter of the switching tube (S33) and the switching tube (S34) of the inverter bridge (3) The collector is connected to the other end of the load; one end of the auxiliary switching tube (4) is connected to the emitter of the switching tube (S12) of the inverter bridge (1) and the emitter of the switching tube (S14), and the other end of the auxiliary switching tube (4) Connect the negative stage of the DC power supply; one end of the auxiliary switching tube (5) is connected to the emitter of the switching tube (S32) of the inverter bridge (3) and the emitter of the switching tube (S34), and the other end of the auxiliary switching tube (5) Connect to the negative stage of the DC power supply;

The switching tubes (S11, S12, S13, S14) of the inverter bridge (1), the switching tubes (S21, S22, S23, S24) of the inverter bridge (2) and the switching tubes ( S31, S32, S33, S34) are switch tubes with anti-parallel diodes in the body or a combination of switch tubes and diodes without diodes in the body; the auxiliary switch tube (4) and the auxiliary switch tube (5) are unidirectional switch tubes or One-way switch combination or two-way switch tube or two-way switch combination.

Example 2

In Fig. 2, the extension includes inverter bridge (1), inverter bridge (2), inverter bridge (3), auxiliary switching tube (4) and auxiliary switching tube (5), wherein the inverter bridge (1) It is: one end of the capacitor (C1) is connected to the collector of the switching tube (S11) and the collector of the switching tube (S13), the other end is connected to the emitter of the switching tube (S12) and the emitter of the switching tube (S14), and the switching tube The emitter of (S11) connects the collector of the switch tube (S12), and the emitter of the switch tube (S13) connects the collector of the switch tube (S14); the inverter bridge (2) is: the DC voltage source positive pole connects the switch tube ( The collector of S21) and the collector of the switch tube (S23), the negative pole is connected to the emitter of the switch tube (S22) and the emitter of the switch tube (S24), and the emitter of the switch tube (S21) is connected to the switch tube (S22) The collector, the emitter of the switching tube (S23) is connected to the collector of the switching tube (S24); the inverter bridge (3) is: one end of the capacitor (C3) is connected to the collector of the switching tube (S31) and the switching tube (S33) The collector of the switch tube (S32) and the emitter of the switch tube (S34) are connected at the other end, the emitter of the switch tube (S31) is connected to the collector of the switch tube (S32), and the emitter of the switch tube (S33) Connect the current collector of the switching tube (S34); the auxiliary switching tube (4) is: the collector of the switching tube (Sc11) is connected to the collector of the switching tube (Sc12); the auxiliary switching tube (5) is: the collector of the switching tube (Sc31) The collector is connected to the collector of the switching tube (Sc32); the emitter of the switching tube (S13) of the inverter bridge (1) and the collector of the switching tube (S14) are connected to the switching tube (S21) of the inverter bridge (2) The emitter and the collector of the switching tube (S22); the emitter of the switching tube (S23) of the inverter bridge (2) and the collector of the switching tube (S24) are connected to the switching tube (S31) of the inverter bridge (3) The emitter and the collector of the switching tube (S32); the emitter of the switching tube (S11) of the inverter bridge (1) and the collector of the switching tube (S12) are connected to one end of the load (Ro), and the inverter bridge (3) The emitter of the switching tube (S33) and the collector of the switching tube (S34) are connected to the other end of the load; one end of the auxiliary switching tube (4) is connected to the collector of the switching tube (S11) of the inverter bridge (1) and the switch The collector of the tube (S13), the other end of the auxiliary switching tube (4) is connected to the positive stage of the DC power supply; one end of the auxiliary switching tube (5) is connected to the collector and switch of the switching tube (S31) of the inverter bridge (3) The collector of the tube (S33), the other end of the auxiliary switching tube (5) is connected to the positive stage of the DC power supply;

The switching tubes (S11, S12, S13, S14) of the inverter bridge (1), the switching tubes (S21, S22, S23, S24) of the inverter bridge (2) and the switching tubes ( S31, S32, S33, S34) are switch tubes with anti-parallel diodes in the body or a combination of switch tubes and diodes without diodes in the body; the auxiliary switch tube (4) and the auxiliary switch tube (5) are unidirectional switch tubes or One-way switch combination or two-way switch tube or two-way switch combination.

Example 3

In Fig. 3, the extension includes inverter bridge (1), inverter bridge (2), inverter bridge (3), auxiliary switching tube (4) and auxiliary switching tube (5), wherein the inverter bridge (1) It is: one end of the capacitor (C1) is connected to the collector of the switching tube (S11) and the collector of the switching tube (S13), the other end is connected to the emitter of the switching tube (S12) and the emitter of the switching tube (S14), and the switching tube The emitter of (S11) connects the collector of the switch tube (S12), and the emitter of the switch tube (S13) connects the collector of the switch tube (S14); the inverter bridge (2) is: the DC voltage source positive pole connects the switch tube ( The collector of S21) and the collector of the switch tube (S23), the negative pole is connected to the emitter of the switch tube (S22) and the emitter of the switch tube (S24), and the emitter of the switch tube (S21) is connected to the switch tube (S22) The collector, the emitter of the switching tube (S23) is connected to the collector of the switching tube (S24); the inverter bridge (3) is: one end of the capacitor (C3) is connected to the collector of the switching tube (S31) and the switching tube (S33) The collector of the switch tube (S32) and the emitter of the switch tube (S34) are connected at the other end, the emitter of the switch tube (S31) is connected to the collector of the switch tube (S32), and the emitter of the switch tube (S33) Connect the current collector of the switching tube (S34); the auxiliary switching tube (4) is: the collector of the switching tube (Sc11) is connected to the collector of the switching tube (Sc12); the auxiliary switching tube (5) is: the collector of the switching tube (Sc31) The collector is connected to the collector of the switching tube (Sc32); the emitter of the switching tube (S13) of the inverter bridge (1) and the collector of the switching tube (S14) are connected to the switching tube (S21) of the inverter bridge (2) The emitter and the collector of the switching tube (S22); the emitter of the switching tube (S23) of the inverter bridge (2) and the collector of the switching tube (S24) are connected to the switching tube (S31) of the inverter bridge (3) The emitter and the collector of the switching tube (S32); the emitter of the switching tube (S11) of the inverter bridge (1) and the collector of the switching tube (S12) are connected to one end of the load (Ro), and the inverter bridge (3) The emitter of the switching tube (S33) and the collector of the switching tube (S34) are connected to the other end of the load; one end of the auxiliary switching tube (4) is connected to the collector of the switching tube (S11) of the inverter bridge (1) and the switch The collector of the tube (S13), the other end of the auxiliary switching tube (4) is connected to the positive stage of the DC power supply; one end of the auxiliary switching tube (5) is connected to the emitter and switch of the switching tube (S32) of the inverter bridge (3) The emitter of the tube (S34), the other end of the auxiliary switching tube (5) is connected to the negative stage of the DC power supply;

The switching tubes (S11, S12, S13, S14) of the inverter bridge (1), the switching tubes (S21, S22, S23, S24) of the inverter bridge (2) and the switching tubes ( S31, S32, S33, S34) are switch tubes with anti-parallel diodes in the body or a combination of switch tubes and diodes without diodes in the body; the auxiliary switch tube (4) and the auxiliary switch tube (5) are unidirectional switch tubes or One-way switch combination or two-way switch tube or two-way switch combination.

Example 4

In Figure 4, this topology belongs to the topology of cascaded multilevel converters, which includes inverter bridge (1), inverter bridge (2), inverter bridge (3), auxiliary switching tube (4) and auxiliary The switch tube (5), wherein the inverter bridge (1) is: one end of the capacitor (C1) is connected to the collector of the switch tube (S11) and the collector of the switch tube (S13), and the other end is connected to the emitter of the switch tube (S12). pole and the emitter of the switching tube (S14), the emitter of the switching tube (S11) is connected to the collector of the switching tube (S12), and the emitter of the switching tube (S13) is connected to the collector of the switching tube (S14); the inverter bridge (2) is: the positive pole of the DC voltage source is connected to the collector of the switching tube (S21) and the collector of the switching tube (S23), the negative pole is connected to the emitter of the switching tube (S22) and the emitter of the switching tube (S24), and the switching tube The emitter of (S21) is connected to the collector of the switching tube (S22), and the emitter of the switching tube (S23) is connected to the collector of the switching tube (S24); the inverter bridge (3) is: one end of the capacitor (C3) is connected to the switch The collector of the tube (S31) and the collector of the switch tube (S33), the other end is connected to the emitter of the switch tube (S32) and the emitter of the switch tube (S34), and the emitter of the switch tube (S31) is connected to the switch tube (S32) ), the emitter of the switching tube (S33) is connected to the collector of the switching tube (S34); the auxiliary switching tube (4) is: the collector of the switching tube (Sc11) is connected to the collector of the switching tube (Sc12); the auxiliary switching tube (Sc11) is connected to the collector of the switching tube (Sc12); The switch tube (5) is: the collector of the switch tube (Sc31) is connected to the collector of the switch tube (Sc32); the emitter of the switch tube (S13) of the inverter bridge (1) is connected to the collector of the switch tube (S14) The emitter of the switching tube (S21) of the inverter bridge (2) and the collector of the switching tube (S22); the emitter of the switching tube (S23) of the inverter bridge (2) and the collector of the switching tube (S24) are connected The emitter of the switching tube (S31) of the inverter bridge (3) and the collector of the switching tube (S32); the emitter of the switching tube (S11) of the inverter bridge (1) and the collector of the switching tube (S12) are connected One end of the load (Ro), the emitter of the switching tube (S33) of the inverter bridge (3) and the collector of the switching tube (S34) are connected to the other end of the load; one end of the auxiliary switching tube (4) is connected to the inverter bridge ( 1) The emitter of the switching tube (S12) and the emitter of the switching tube (S14), the other end of the auxiliary switching tube (4) is connected to the negative stage of the DC power supply; one end of the auxiliary switching tube (5) is connected to the inverter bridge ( 3) The collector of the switch tube (S31) and the switch tube (S33), and the other end of the auxiliary switch tube (5) is connected to the positive stage of the DC power supply.

The switching tubes (S11, S12, S13, S14) of the inverter bridge (1), the switching tubes (S21, S22, S23, S24) of the inverter bridge (2) and the switching tubes ( S31, S32, S33, S34) are switch tubes with anti-parallel diodes in the body or a combination of switch tubes and diodes without diodes in the body; the auxiliary switch tube (4) and the auxiliary switch tube (5) are unidirectional switch tubes or One-way switch combination or two-way switch tube or two-way switch combination.

Claims (9)

1. single supply cascade connection multi-level current transformer is characterized in that:

This current transformer comprises inverter bridge 1, inverter bridge 2, inverter bridge 3, auxiliary switch 4 and auxiliary switch 5; Inverter bridge 1 is: first utmost point of a termination main switch S11 of capacitor C 1 and first utmost point of main switch S13, second utmost point of another termination main switch S12 and second utmost point of main switch S14, second utmost point of main switch S11 connects first utmost point of main switch S12, and second utmost point of main switch S13 connects first utmost point of main switch S14; Inverter bridge 2 is: dc power anode connects first utmost point of main switch S21 and first utmost point of main switch S23, dc power cathode connects second utmost point of main switch S22 and second utmost point of main switch S24, second utmost point of main switch S21 connects first utmost point of main switch S22, and second utmost point of main switch S23 connects first utmost point of main switch S24; Inverter bridge 3 is: first utmost point of a termination main switch S31 of capacitor C 3 and first utmost point of main switch S33, second utmost point of another termination main switch S32 second utmost point and main switch S34, second utmost point of main switch S31 connects first utmost point of main switch S32, and second utmost point of main switch S33 connects first utmost point of main switch S34; Second utmost point of the main switch S13 of inverter bridge 1 and first utmost point of main switch S14 connect second utmost point of main switch S21 of inverter bridge 2 and first utmost point of main switch S22; Second utmost point of the main switch S23 of inverter bridge 2 and first utmost point of main switch S24 connect second utmost point of main switch S31 of inverter bridge 3 and first utmost point of main switch S32; Second utmost point of the main switch S11 of inverter bridge 1 and first utmost point of main switch S12 connect the end of load Z, and second utmost point of the main switch S33 of inverter bridge 3 and first utmost point of main switch S34 connect the other end of load Z; Auxiliary switch 4 is single-way switch or bidirectional switch, an end of the capacitor C 1 of a termination inverter bridge 1 of auxiliary switch 4, the negative or positive electrode of another termination DC power supply of auxiliary switch 4; Auxiliary switch 5 is single-way switch or bidirectional switch, an end of the capacitor C 3 of a termination inverter bridge 3 of auxiliary switch 5, the negative or positive electrode of another termination DC power supply of auxiliary switch 5.

2. cascade connection multi-level current transformer according to claim 1, it is characterized in that: main switch S11, the S12 of inverter bridge 1, S13, S14, main switch S31, the S32 of main switch S21, the S22 of inverter bridge 2, S23, S24 and inverter bridge 3, S33, S34 are MOSFET.

3. cascade connection multi-level current transformer according to claim 1, it is characterized in that: main switch S11, the S12 of inverter bridge 1, S13, S14, main switch S31, the S32 of main switch S21, the S22 of inverter bridge 2, S23, S24 and inverter bridge 3, S33, S34 are that the interior diodeless switching tube of body and diode combinations form.

4. cascade connection multi-level current transformer according to claim 1 is characterized in that: auxiliary switch 4 and auxiliary switch 5 are by the switching tube and the diodes in parallel that adopt IGBT or GTO, and so latter two described parallel combination body is composed in series again.

5. cascade connection multi-level current transformer according to claim 1 is characterized in that: auxiliary switch 4 and auxiliary switch 5 are connected with diode by the switching tube that adopts IGBT or GTO or MOSFET, and so latter two described tandem compound body composes in parallel again.

6. cascade connection multi-level current transformer according to claim 1 is characterized in that: auxiliary switch 4 and auxiliary switch 5 are composed in series by the switching tube and the diode that adopt IGBT or GTO or MOSFET.

7. cascade connection multi-level current transformer according to claim 1, it is characterized in that: auxiliary switch 4 and auxiliary switch 5 compose in parallel by the IGBT without anti-paralleled diode in GTO or body.

8. cascade connection multi-level current transformer according to claim 1 is characterized in that: auxiliary switch 4 is comprised of diode D5, D6, D7, the D8 full-wave rectification bridge that consists of and the switch transistor T 5 that adopts IGBT or GTO or MOSFET: the emitter/source electrode of described switch transistor T 5 connects the anode of diode D5 and the anode of diode D6; The collector/of switch transistor T 5 connects the negative electrode of diode D7 and the negative electrode of diode D8; The anode of the negative electrode of diode D5 and diode D7 joins as an end of auxiliary switch; The anode of the negative electrode of diode D6 and diode D8 joins as the other end of auxiliary switch.

9. cascade connection multi-level current transformer according to claim 1 is characterized in that: auxiliary switch 5 is comprised of diode D5, D6, D7, the D8 full-wave rectification bridge that consists of and the switch transistor T 5 that adopts IGBT or GTO or MOSFET: the emitter/source electrode of described switch transistor T 5 connects the anode of diode D5 and the anode of diode D6; The collector/of switch transistor T 5 connects the negative electrode of diode D7 and the negative electrode of diode D8; The anode of the negative electrode of diode D5 and diode D7 joins as an end of auxiliary switch; The anode of the negative electrode of diode D6 and diode D8 joins as the other end of auxiliary switch.

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