阅读说明：本技术 一种混合t型多电平逆变装置及其控制方法 (Hybrid T-type multi-level inverter and control method thereof ) 是由 王要强 库若含 梁军 王明东 董亮辉 陈根永 袁艺森 王昌龙 于 2019-08-14 设计创作，主要内容包括：本发明提供了一种混合T型多电平逆变装置及其控制方法,所述逆变装置中：电容组串与直流电压源V<Sub>dc</Sub>并联连接；电容组串的中心点与反串桥臂Ⅰ的一端相连,反串桥臂Ⅰ的另一端分别与中间桥臂的第一连接端、反串桥臂Ⅱ的一端以及反串桥臂Ⅲ的一端相连,构成T型桥臂；反串桥臂Ⅰ、反串桥臂Ⅱ、反串桥臂Ⅲ、中间桥臂和分压电容构成开关电容单元；正串桥臂与分压电容并联连接；正串桥臂的中心点和电容组串的中心点,作为该混合T型多电平逆变装置的交流电压输出端。本发明有效解决了开关电容多电平逆变器中输出电压增高导致的开关管承受电压应力过大的技术问题,使得本发明适用于高压大功率场合,扩展了逆变器的应用范围。(the invention provides a mixed T-type multi-level inverter and a control method thereof, wherein the inverter comprises the following components: capacitor series and DC voltage source V dc Are connected in parallel; the center point of the capacitor bank string is connected with one end of a reverse-string bridge arm I, and the other end of the reverse-string bridge arm I is connected with a first connecting end of a middle bridge arm, one end of a reverse-string bridge arm II and one end of a reverse-string bridge arm III respectively to form a T-shaped bridge arm; the anti-series bridge arm I, the anti-series bridge arm II, the anti-series bridge arm III, the middle bridge arm and the voltage-dividing capacitor form a switched capacitor unit; the positive series bridge arm is connected with the voltage-dividing capacitor in parallel; and the central point of the positive series bridge arm and the central point of the capacitor group string are used as alternating current voltage output ends of the hybrid T-shaped multi-level inverter. The invention effectively solves the technical problem that the output voltage in the switched capacitor multi-level inverter is increased to cause overlarge voltage stress of the switch tube, so that the invention is suitable for high-voltage and high-power occasions and expands the application range of the inverter.)

1. a mixed T-type multi-level inverter is arranged at a DC voltage source V_dcAnd a load, characterized in thatIn the following steps: the bridge comprises a capacitor bank string, a reverse-string bridge arm I, a reverse-string bridge arm II, a reverse-string bridge arm III, a middle bridge arm, a voltage-dividing capacitor and a positive-string bridge arm;

The capacitor string and the DC voltage source V_dcAre connected in parallel;

The center point of the capacitor bank string is connected with one end of the reverse-string bridge arm I, and the other end of the reverse-string bridge arm I is connected with the first connecting end of the middle bridge arm, one end of the reverse-string bridge arm II and one end of the reverse-string bridge arm III respectively to form a T-shaped bridge arm;

The anti-series bridge arm I, the anti-series bridge arm II, the anti-series bridge arm III, the middle bridge arm and the voltage-dividing capacitor form a switched capacitor unit;

The second connecting end of the middle bridge arm is connected with one end of the capacitor group string, and the third connecting end of the middle bridge arm is respectively connected with one end of the voltage-dividing capacitor and one end of the positive string bridge arm; the other end of the reverse-series bridge arm II is connected with the other end of the capacitor bank string, and the other end of the reverse-series bridge arm III is respectively connected with the other end of the voltage-dividing capacitor and the other end of the positive-series bridge arm;

The positive series bridge arm is connected with the voltage-dividing capacitor in parallel;

And the central point of the positive string bridge arm and the central point of the capacitor group string are used as alternating current voltage output ends of the hybrid T-shaped multi-level inverter.

2. The hybrid T-type multilevel inverter device according to claim 1, wherein: the capacitor group string comprises equivalent capacitors C connected in series in the forward direction₁Sum equivalent capacitance C₂said equivalent capacitance C₁Anode of (2) is connected to the DC voltage source V_dcThe positive electrode of (1), the equivalent capacitance C₂Is connected with the DC voltage source V_dcThe negative pole of (1), the equivalent capacitance C₁And said equivalent capacitance C₂The anodes of which are respectively connected with one end of the load;

the positive serial bridge arm comprises a switch tube S connected in series in the same direction₁₀And a switching tube S₁₁Said switch tube S₁₀And the switching tube S₁₁Respectively connected to the other end of the load.

3. The hybrid T-type multilevel inverter device according to claim 2, wherein: the reverse-series bridge arm I comprises a switch tube S₃And a switching tube S₄the reverse-serial bridge arm II comprises a switch tube S₁And a switching tube S₂The reverse-serial bridge arm III comprises a switch tube S₇And a switching tube S₈The middle bridge arm comprises a switch tube S₅Switch tube S₆And a switching tube S₉The voltage-dividing capacitor is a capacitor C₃；

wherein, the switch tube S₁The positive ends of the capacitors are respectively connected with the equivalent capacitors C of the capacitor bank string₂And said direct voltage source V_dcThe negative pole of (1), the switching tube S₁Is connected with the switching tube S₂A negative terminal of (a); the switch tube S₂The positive ends of the two are respectively connected with the switch tube S₄The positive terminal of the switch tube S₅and the switching tube S₇A positive terminal of; the switch tube S₃The positive ends of the capacitors are respectively connected with the equivalent capacitors C of the capacitor bank string₁Cathode and equivalent capacitance C₂The switching tube S₃is connected with the switching tube S₄A negative terminal of (a); the switch tube S₄The positive ends of the two are respectively connected with the switch tube S₅And the switching tube S₇A positive terminal of; the switch tube S₅The positive ends of the two are respectively connected with the switch tube S₆Negative terminal of (1) and switching tube S₉The negative terminal of the switching tube S₅is connected with the switching tube S₇A positive terminal of; the switch tube S₆The positive ends of the two are respectively connected with the direct-current voltage source V_dcAnd an equivalent capacitance C of the capacitor bank string₁The switching tube S₆Is connected with the switching tube S₉A negative terminal of (a); the switch tube S₇Is connected with the switching tube S₈A negative terminal of (a); the switch tube S₈Are respectively connected with the positive terminalsThe capacitor C₃And a switching tube S of the positive series bridge arm₁₀A negative terminal of (a); the switch tube S₉Are respectively connected with the capacitors C₃And a switching tube S of the positive series bridge arm₁₁The positive terminal of (a).

4. The hybrid T-type multilevel inverter device according to claim 3, wherein: the hybrid T-type multi-level inverter further comprises a plurality of switch capacitor units, and the switch capacitor units are connected to the two ends of the voltage division capacitor and the two ends of the positive series bridge arms in parallel.

5. A control method of a hybrid T-type multi-level inverter device, which is applied to the hybrid T-type multi-level inverter device of claim 3, is characterized in that the control method sets seven working modes: working mode I, working mode II, working mode III, working mode IV, working mode V, working mode VI and working mode VII.

6. The control method according to claim 5, characterized in that:

Working mode I

setting: switch tube S of the switch capacitor unit₁Switch tube S₂Switch tube S₅And a switching tube S₉Conducting, the switching tube S of the positive series bridge arm₁₀Conducting, and turning off the other switching tubes;

Working mode II

Setting: switch tube S of the switch capacitor unit₃Switch tube S₄Switch tube S₅And a switching tube S₉Conducting, the switching tube S of the positive series bridge arm₁₀Conducting, and turning off the other switching tubes;

Mode of operation III

setting: switch tube S of the switch capacitor unit₁Switch tube S₂switch tube S₆Switch tube S₇Switch tube S₈And a switching tube S₉Conducting, the switching tube S of the positive series bridge arm₁₀Conducting the rest switchesThe tube is shut off;

Operating mode IV

Setting: switch tube S of the switch capacitor unit₃switch tube S₄switch tube S₅And a switching tube S₉Conducting, the switching tube S of the positive series bridge arm₁₁Conducting, and turning off the other switching tubes;

Mode of operation V

Setting: switch tube S of the switch capacitor unit₁Switch tube S₂Switch tube S₇And a switching tube S₈Conducting, the switching tube S of the positive series bridge arm₁₁Conducting, and turning off the other switching tubes;

Working mode VI

Setting: switch tube S of the switch capacitor unit₃Switch tube S₄Switch tube S₇And a switching tube S₈Conducting, the switching tube S of the positive series bridge arm₁₁Conducting, and turning off the other switching tubes;

Working mode VII

Setting: switch tube S of the switch capacitor unit₅Switch tube S₆Switch tube S₇And a switching tube S₈Conducting, the switching tube S of the positive series bridge arm₁₁And the other switching tubes are switched on and switched off.

7. The control method according to claim 6, characterized in that: by comparing modulated waves U_refAnd six triangular carriers u_a1~u_a6Obtaining a logic signal u₁~u₆(ii) a Will logic signal u₁~u₆After logical combination, outputting to obtain a driving signal of each switching tube, and driving the corresponding switching tube to act according to the driving signal; the expression of the driving signal of each switching tube is as follows:

Wherein the triangular carrier u_a1~u_a6amplitude of 0 ~ 1, modulation wave U_refthe amplitude of the signal is-1 ~ 1.

8. The control method according to claim 5, characterized in that: setting m (m =1,2, … …) switched capacitor units, wherein the control method correspondingly sets 4n-5 (n =3,4, … …) working modes;

wherein n-m = 2.

Technical Field

The invention relates to the field of electric energy conversion, new energy power generation, distributed grid-connected power generation and high-voltage large working condition, in particular to a hybrid T-shaped multi-level inverter and a control method thereof.

Background

With the increasing serious environmental pollution, the application of clean and renewable energy sources is receiving much attention, the research in the fields of photovoltaic power generation, wind power generation, electric vehicles and the like is gradually increased, and the inverter as the core of the research is also the key point of the research. The multilevel inverter technology overcomes the defects of high output harmonic content and large voltage stress of the traditional inverter, and is widely applied in production and life. The conventional multilevel inverter mainly has a diode clamp type, a flying capacitor type and a cascade type. The diode-clamped multi-level inverter and the flying capacitor multi-level inverter are clamped through a diode and a capacitor respectively to achieve multi-level output; however, the number of diodes and capacitors is too large, the structure is complex, and the control difficulty is high.

The cascade inverter outputs more levels through a series H-bridge structure, but has the problems of excessive switching devices and input sources and high application cost; with the increase of the output level, the voltage stress borne by the bridge arm of the H-bridge structure is gradually increased; that is, to achieve multi-level output, the bridge arms are subjected to excessive voltage stress.

The T-type multi-level inverter has the advantages of few switching devices and simple structure, and is a research direction of multi-level inverters in recent years. However, the number of output levels of the T-type multi-level inverter is not high, and the harmonic content of the output voltage is high. The switch capacitor structure utilizes the combination of the switch device and the capacitor, can improve the gain and the level number of output voltage under the condition of single input power supply, and has the advantages of high efficiency, small volume, wide voltage stabilizing range and the like.

At present, in the switched capacitor multi-level inverter in the prior art, the maximum voltage stress borne by the switching device increases with the increase of the output voltage gain, and the application range of the switched capacitor multi-level inverter is limited to a certain extent. Therefore, how to achieve low input, high output, multi-level number and low voltage stress is critical in the selection and design process of the inverter topology.

In order to solve the above problems, people are always seeking an ideal technical solution.

Disclosure of Invention

The invention aims to overcome the defects of the prior art, and provides a hybrid T-type multi-level inverter and a control method thereof.

In order to achieve the purpose, the invention adopts the technical scheme that:

The invention provides a hybrid T-type multi-level inverter device which is arranged on a direct-current voltage source V_dcAnd the load, its characterized in that: the bridge comprises a capacitor bank string, a reverse-string bridge arm I, a reverse-string bridge arm II, a reverse-string bridge arm III, a middle bridge arm, a voltage-dividing capacitor and a positive-string bridge arm;

The capacitor string and the DC voltage source V_dcAre connected in parallel;

The center point of the capacitor bank string is connected with one end of the reverse-string bridge arm I, and the other end of the reverse-string bridge arm I is connected with the first connecting end of the middle bridge arm, one end of the reverse-string bridge arm II and one end of the reverse-string bridge arm III respectively to form a T-shaped bridge arm;

The anti-series bridge arm I, the anti-series bridge arm II, the anti-series bridge arm III, the middle bridge arm and the voltage-dividing capacitor form a switched capacitor unit;

The second connecting end of the middle bridge arm is connected with one end of the capacitor group string, and the third connecting end of the middle bridge arm is respectively connected with one end of the voltage-dividing capacitor and one end of the positive string bridge arm; the other end of the reverse-series bridge arm II is connected with the other end of the capacitor bank string, and the other end of the reverse-series bridge arm III is respectively connected with the other end of the voltage-dividing capacitor and the other end of the positive-series bridge arm;

The positive series bridge arm is connected with the voltage-dividing capacitor in parallel;

And the central point of the positive string bridge arm and the central point of the capacitor group string are used as alternating current voltage output ends of the hybrid T-shaped multi-level inverter.

The second aspect of the present invention provides a control method for a hybrid T-type multi-level inverter, which is applied to the hybrid T-type multi-level inverter, and the control method sets seven working modes: working mode I, working mode II, working mode III, working mode IV, working mode V, working mode VI and working mode VII.

Further, working mode I

Setting: switch tube S of the switch capacitor unit₁Switch tube S₂Switch tube S₅And a switching tube S₉Conducting, the switching tube S of the positive series bridge arm₁₀Conducting, and turning off the other switching tubes;

Working mode II

Setting: switch tube S of the switch capacitor unit₃Switch tube S₄Switch tube S₅And a switching tube S₉Conducting, the switching tube S of the positive series bridge arm₁₀Conducting, and turning off the other switching tubes;

Mode of operation III

Setting: switch tube S of the switch capacitor unit₁Switch tube S₂Switch tube S₆Switch tube S₇Switch tube S₈And a switching tube S₉conducting, the switching tube S of the positive series bridge arm₁₀Conducting, and turning off the other switching tubes;

Operating mode IV

Setting: switch tube S of the switch capacitor unit₃Switch tube S₄Switch tube S₅And a switching tube S₉Conducting, the switching tube S of the positive series bridge arm₁₁Conducting, and turning off the other switching tubes;

Mode of operation V

Setting: switch tube S of the switch capacitor unit₁Switch tube S₂switch tube S₇And a switching tube S₈Conducting, the switching tube S of the positive series bridge arm₁₁Conducting, and turning off the other switching tubes;

Working mode VI

Setting: switch tube S of the switch capacitor unit₃Switch tube S₄Switch tube S₇And a switching tube S₈conducting, the switching tube S of the positive series bridge arm₁₁conducting, and turning off the other switching tubes;

Working mode VII

Setting: switch tube S of the switch capacitor unit₅Switch tube S₆Switch tube S₇and a switching tube S₈conducting, the switching tube S of the positive series bridge arm₁₁And the other switching tubes are switched on and switched off.

The invention provides a scalable hybrid T-type multi-level inverter device, which further comprises a plurality of switched capacitor units connected in parallel to two ends of the voltage dividing capacitor and the positive series bridge arm.

Compared with the prior art, the invention has prominent substantive characteristics and remarkable progress, particularly:

1) The invention provides a hybrid T-shaped multi-level inverter and a control method thereof, wherein seven working modes are set, and when the inverter is in a working mode I, a working mode II, a working mode VI and a working mode VII, the maximum voltage stress of a switching tube in a topological structure of the hybrid T-shaped multi-level inverter is equal to the input voltage at a direct current side; when the hybrid T-type multi-level inverter is in a working mode IV, the maximum voltage stress of a switching tube in the topological structure of the hybrid T-type multi-level inverter is equal to zero; when the hybrid T-type multi-level inverter is in a working mode III and a working mode V, the maximum voltage stress of a switching tube in the topological structure of the hybrid T-type multi-level inverter is equal to half of the input voltage at the direct current side; under seven working modes, along with the improvement of output voltage, the maximum voltage stress of a switching tube in the topological structure of the hybrid T-shaped multi-level inverter device is not increased along with the increase of voltage gain, and the maximum voltage stress of the switching tube does not exceed the input voltage of a direct current side;

therefore, the technical problem that the output voltage in the switched capacitor multi-level inverter is increased to cause overlarge voltage stress borne by a switching tube is effectively solved, so that the inverter is suitable for high-voltage and high-power occasions, and the application range of the inverter is expanded;

The hybrid T-type multi-level inverter can realize the change of the positive and negative polarities in a topological circuit without an H bridge; the T-shaped structure enables the inverter to have output capacity of more levels, multi-level output is achieved, and harmonic content of output voltage is reduced; the inverter has the advantages of simple structure, easy modulation, low input and high output, more levels and low voltage stress;

2) The invention also provides a scalable hybrid T-type multi-level inverter, which further comprises a plurality of switch capacitor units, wherein the switch capacitor units are connected in parallel between the switch capacitor units and the positive serial bridge arms; with the improvement of voltage gain, the maximum voltage stress of a switching tube in the topological structure of the hybrid T-shaped multi-level inverter device is not increased along with the increase of the voltage gain, and the maximum voltage stress of the switching tube does not exceed the input voltage of a direct current side;

therefore, the switching tube voltage stress is low, the problem of large voltage stress of the switching tube in the switched capacitor multi-level inverter in a high-voltage high-power occasion can be effectively solved, and the method is suitable for new energy power generation, grid-connected control of a distributed power generation system and high-voltage high-power working conditions.

Drawings

FIG. 1 is a block diagram showing the structure of the present invention.

Fig. 2 is a diagram of an inverter topology of the present invention.

Fig. 3 to 9 are circuit schematic diagrams of seven modes of operation of the present invention.

Fig. 10 is a schematic diagram of a modulation method of the inversion topology working mode of the present invention.

Fig. 11 shows simulated waveforms of output voltage and output current of an inverter according to the present invention.

Fig. 12 is a simulated waveform of the capacitor voltage.

Fig. 13 and 14 are graphs of switching tube voltage waveforms.

Fig. 15 is an expanded configuration diagram of the present invention.

Detailed Description

The technical solution of the present invention is further described in detail by the following embodiments.