CN201584899U - Topological structure of power electronic transformer - Google Patents

Abstract

The utility model relates to a topological structure of a power electronic transformer, which comprises three stages, i.e., an input stage, an isolation stage and an output stage, wherein the structures of three phases of circuits are same, and the input ends of power converter groups of the input stage and the output stage of each single phase are connected in a star shape; the power converter adopts a bridge type topological structure, and the isolation stage comprises a high-frequency transformer of each single phase; the input end of a basic power unit of a single phase structure is connected with a capacitor in parallel, and in the basic power unit, the output end of a first power converter (1) is connected with the primary side of the high-frequency transformer (3), and the secondary side of the high-frequency transformer (3) is connected with the input end of a second power converter (2); and the output end of the basic power unit is connected with the input end of a filter (4); the output end of the filter (4) is connected with three phases of supply networks. The device can automatically adjust line output voltage, stabilize output voltage, and suppress the dropping, rising and flickering of the line voltage, over-voltage, under voltage and other voltage quality problems.

Description

A topology of a power electronic transformer

technical field

The utility model relates to a power electronic transformer used in a power distribution network, which belongs to the technical field of application of power electronics in power systems.

Background technique

Since the power transformer was invented in the 19th century, it has become the basic component equipment of the power transmission and distribution system, and the quantity is huge. At present, the traditional power transformer usually adopts iron core oil-immersed type, which has the advantages of simple manufacturing process and high reliability, but the disadvantages are also very obvious, including: large volume and weight, high no-load loss, and the threat of transformer oil to the environment. Its main function is voltage transformation and isolation, and its function is relatively single. When the iron core is saturated, harmonics will be generated, and it will also cause a large excitation inrush current when it is put into the power grid. The shortcomings and single functions of traditional power transformers are difficult to meet the needs and goals of future power grid construction.

For this reason, the concept of power electronic transformer (PET-Power electronic transformer) was proposed in the 1970s. PET uses power electronic commutation technology to realize voltage conversion and energy transfer. Its outstanding feature is the continuous controllable adjustment of the amplitude and phase of the primary and secondary AC side voltage and current through a voltage source converter (VSC). Therefore, PET can not only overcome the defects of traditional transformers, but also solve the problems faced by the power system, such as electromagnetic ring network, power quality, reactive power dynamic compensation, and improving the stability limit of the system.

Therefore, with the development of power electronic devices and high-frequency transformer materials, power electronic transformers will replace traditional transformers and be widely used in power systems.

Contents of the invention

Technical problem: The purpose of this utility model is to propose a topological structure of a power electronic transformer, which not only realizes voltage conversion, electrical isolation, and energy transfer, but also automatically adjusts the voltage of the distribution network line, and can be flexibly applied to different input voltages. Level distribution network lines. Compared with traditional power transformers, the size of the transformer is greatly reduced, the loss is reduced, the overall conversion efficiency is improved, and the output voltage can be stabilized, and the drop, rise, flicker, overvoltage and undervoltage of the line voltage can be suppressed. Quality issues.

Technical solution: The utility model discloses a topological structure of a power electronic transformer. The device adopts a three-stage structure, that is, an input stage, an isolation stage, and an output stage; the three-phase circuits have the same structure, and each single-phase input stage and output stage The input ends of the power converter group are connected in star form, and the power converter adopts a bridge topology; the isolation stage includes high-frequency transformers for each single phase; a capacitor is connected in parallel to the input end of the basic power unit of the single-phase structure, and in the basic power unit, The output terminal of the first power converter is connected to the primary side of the high-frequency transformer, and the secondary side of the high-frequency transformer is connected to the input terminal of the second power converter; the output terminal of the basic power unit is connected to the input terminal of the filter, and the output terminal of the filter connected to the three-phase power supply network.

The basic power unit is based on the AC-AC power electronic transformer, and the first power converter in the input stage of each phase adopts the first power switch unit, the second power switch unit, the third power switch unit, and the fourth power switch unit to form a bridge topology Structure, the first power switch unit and the second power switch unit are connected to the positive terminal of the primary side of the high-frequency transformer after complementary conduction, and the third power switch unit and the fourth power switch unit are connected to the negative terminal of the primary side of the high-frequency transformer after complementary conduction. Each power switch unit is composed of two IGBTs and a reversely connected diode connected in parallel; the second power converter in the output stage of each phase adopts the fifth power switch unit, the sixth power switch unit, the seventh power switch unit, The eighth power switch unit forms a bridge topology, the positive terminals of the fifth power switch unit and the seventh power switch unit are connected to the positive terminal of the secondary side of the high-frequency transformer, and the negative terminals of the sixth power switch unit and the eighth power switch unit are connected to the high The negative terminal of the secondary side of the frequency transformer, the fifth power switch unit and the sixth power switch unit are connected to the input terminal of the filter after complementary conduction, and the seventh power switch unit and the eighth power switch unit are connected to the input terminal of the filter after complementary conduction , each power switching unit is composed of two IGBTs and a reversely connected diode connected in parallel.

The first power converters in each single-phase input stage are connected in series; the output stage adopts a bridge-type power converter parallel structure, and the filter is composed of an output filter inductor 1 and an output filter capacitor, and the negative pole of the output filter inductor 1 is connected to the fifth power switch unit, The output terminal of the sixth power switch unit, the negative terminal of the output filter capacitor is connected to the output terminals of the seventh power switch unit and the eighth power switch unit, and the positive terminal of the output filter capacitor is connected to the positive pole of the output filter inductor; or the output stage adopts a bridge type power converter stage The filter is composed of an output filter capacitor and connected to the output filter inductor 1 and the output filter inductor 2 with the same name. The negative pole of the output filter inductor 1 is connected to the fifth power switch unit and the sixth power switch unit in the first basic power unit. The output terminal of the output filter inductor is connected to the output terminals of the seventh power switch unit and the eighth power switch unit in the third basic power unit.

S2和

每个功率开关单元由两个IGBT及其反并联二极管连接组成，可以实现电流双向流动；子隔离级为高频变压器，可以减小装置体积，提高整体效率，实现电压变换及能量传递的功能；子输出级由功率变换器构成，和输入级一样，功率变换器也采用桥式拓扑结构，包括第五功率开关单元、第六功率开关单元、第七功率开关单元、第八功率开关单元，每个功率开关单元由两个IGBT及其反并联二极管连接组成，可以实现电流双向流动，输出级还连接滤波器，以提高电压电流波形质量。图3为该装置的输出级采用功率变换器并联的单相结构图，单相的输入级由基本功率单元的子输入级功率变换器串联而成，并在每个基本功率单元的输入端并联相同的电容器，以实现将输入电压平均分配到每个基本功率单元的作用；隔离级由各个基本功率单元的子隔离级高频变压器构成；输出级由基本功率单元的子输出级功率变换器并联而成。图4为该装置的第二种单相拓扑结构，单相的输入级由基本功率单元的子输入级功率变换器串联而成，并在每个基本功率单元的输入端并联相同的电容器，以实现均压作用；隔离级由各个基本功率单元的子隔离级高频变压器构成；输出级由基本功率单元的子输出级功率变换器级联而成，输出级还连接滤波器，以提高电压电流波形质量。图5和图6分别是采用功率变换器并联的单相结构和采用功率变换器级联的单相结构的该装置的三相结构拓扑图，由三个单相结构组合而成，输入级由各单相的输入级功率变换器组按照星型连接组成，隔离级由各单相的隔离级高频变压器组组成，输出级由各单相的输出级功率变换器组按照星型连接，以适应三相四线制线路的应用。The three-phase structure in the power electronic transformer is the same, and each phase structure is composed of basic power units. Figure 1 is a structural model diagram of the basic power unit of the power electronic transformer. Its working principle is: the primary side converts the power frequency signal into a high frequency signal through a power electronic converter, that is, up-converting, and then couples it to the secondary side through an intermediate high frequency isolation transformer, and then uses the power electronic converter to restore it into a power frequency signal. That is, frequency reduction. By adopting an appropriate control scheme to control the work of power electronic devices, the electrical energy of one frequency, voltage, and waveform can be transformed into electrical energy of another frequency, voltage, and waveform. Figure 2 is a topology diagram of the basic power unit of the device. The basic power unit is composed of three stages, namely, sub-input stage, sub-isolation stage, and sub-output stage; the sub-input stage is composed of a power converter, and the power converter adopts a bridge topology, including power switch unit S1,

S2 and

Each power switch unit is composed of two IGBTs and their anti-parallel diode connections, which can realize bidirectional current flow; the sub-isolation stage is a high-frequency transformer, which can reduce the size of the device, improve the overall efficiency, and realize the functions of voltage conversion and energy transfer; The sub-output stage is composed of a power converter. Like the input stage, the power converter also adopts a bridge topology, including the fifth power switch unit, the sixth power switch unit, the seventh power switch unit, and the eighth power switch unit. A power switch unit is composed of two IGBTs and their anti-parallel diode connections, which can realize bidirectional current flow, and the output stage is also connected with a filter to improve the voltage and current waveform quality. Figure 3 is a single-phase structure diagram in which the output stage of the device is connected in parallel with power converters. The single-phase input stage is composed of sub-input stage power converters of the basic power unit in series, and connected in parallel at the input end of each basic power unit The same capacitor is used to evenly distribute the input voltage to each basic power unit; the isolation stage is composed of sub-isolation high-frequency transformers of each basic power unit; the output stage is connected in parallel by the sub-output stage power converters of the basic power unit made. Figure 4 shows the second single-phase topology of the device. The single-phase input stage is composed of the sub-input stage power converters of the basic power unit in series, and the same capacitor is connected in parallel at the input end of each basic power unit to To achieve voltage equalization; the isolation stage is composed of sub-isolation high-frequency transformers of each basic power unit; the output stage is composed of sub-output stage power converters of the basic power unit cascaded, and the output stage is also connected to a filter to increase the voltage and current Waveform quality. Figure 5 and Figure 6 are the three-phase structure topological diagrams of the device using a single-phase structure in parallel with power converters and a single-phase structure in cascaded power converters, respectively. It is composed of three single-phase structures, and the input stage consists of Each single-phase input-stage power converter group is composed of a star-shaped connection, the isolation stage is composed of each single-phase isolation-level high-frequency transformer group, and the output stage is composed of each single-phase output-stage power converter group according to a star connection. Adapt to the application of three-phase four-wire circuit.

The single-phase input stage of the power electronic transformer is connected in series by the sub-input stage power converters of the basic power unit, which can directly input high voltage without using transformer coupling, and the output stage has two topologies: the first one is a bridge-type power converter Parallel structure, the second is to use bridge power converter cascade structure to meet the needs of high voltage and high power occasions. Each phase structure of the whole device is composed of basic power units, which can be flexibly applied to distribution lines of different voltage levels. The power electronic transformer used in the distribution network can not only replace the traditional power transformer, realize the functions of voltage conversion, energy transfer, and electrical isolation, but also stabilize the output voltage through the corresponding control strategy, realize the function of voltage regulator, and suppress the power of the line. Voltage quality problems such as voltage drop, rise, flicker, overvoltage and undervoltage.

Beneficial effects: In addition to the advantages of traditional power transformers, the power electronic transformer of the utility model also has the following advantages:

1. Since the high-frequency transformer is used for voltage transformation, the volume of the whole device is greatly reduced and the efficiency of the whole device is improved.

2. It is composed of basic power unit combination, which is convenient for flexible application to distribution network lines of various voltage levels. The single-phase input stage is connected in series by the input-stage power converter of the basic power unit, which can directly input high voltage without using transformer coupling, and the output stage adopts a bridge-type power converter parallel structure or cascaded structure to meet the needs of high-voltage and high-power occasions .

3. Realize the interference isolation between the load and the power supply system, suppress harmonics, and improve the electrical environment of the power grid. With the corresponding control strategy, the function of automatic voltage regulation can be realized, and the drop, rise, flicker, overvoltage and undervoltage of the line voltage can be suppressed.

4. The high-power power electronic devices used in this power electronic transformer can be turned off instantaneously (us level), so the power electronic transformer adopts a control method to realize the function of fault current limitation.

5. This power electronic transformer uses full digital technology to realize online monitoring, which is convenient for the implementation of digital substations. At the same time, it can save the old-fashioned relay protection device through its own protection and monitoring.

Description of drawings

Fig. 1: is the block diagram of the basic power unit structure model of the present utility model.

Fig. 2: It is a block diagram of the topology structure of the basic power unit of the present invention.

Figure 3: Single-phase block diagram using power converters connected in parallel for the output stage.

Figure 4: Single-phase block diagram using a power converter cascade for the output stage.

Figure 5: Three-phase structure diagram using parallel connection of power converters for the output stage.

Figure 6: Three-phase block diagram using cascaded power converters for the output stage.

Among them are: power converter 1, power converter 2, high frequency transformer 3, filter 4.

第三功率开关单元S2、第四功率开关单元

第五功率开关单元S3、第六功率开关单元

第七功率开关单元S4、第八功率开关单元

The first power switch unit S1, the second power switch unit

The third power switch unit S2, the fourth power switch unit

The fifth power switch unit S3, the sixth power switch unit

The seventh power switch unit S4, the eighth power switch unit

Vin: single-phase device input voltage,

Vo: single-phase line output voltage,

La1: Output filter inductor 1,

La2: Output filter inductor 2,

C1, C2, Cn: equalizing capacitors,

Ca1: output filter capacitor.

UA, UB, UC: three-phase power electronic transformer input voltage terminals,

Ua, Ub, Uc, N: Three-phase power electronic transformer output voltage terminals.

Detailed ways

Below is the specific embodiment of the utility model to further describe:

The utility model relates to a topological structure of a power electronic transformer. The device adopts a three-stage structure, that is, an input stage, an isolation stage, and an output stage; The terminals are connected in star form, and the power converter adopts a bridge topology; the isolation stage includes each single-phase high-frequency transformer group; the single-phase structure includes a capacitor connected in parallel to the input end of the basic power unit, wherein the first power converter The output terminal of 1 is connected to the primary side of the high-frequency transformer 3, and the secondary side of the high-frequency transformer 3 is connected to the input terminal of the second power converter 2; the output terminal of the basic power unit is connected to the input terminal of the filter 4, and the output terminal of the filter 4 Terminate the three-phase power supply network.

第三功率开关单元S2、第四功率开关单元组成，第一功率开关单元S1、第二功率开关单元互补导通后接高频变压器3原边正端，第三功率开关单元S2、第四功率开关单元

互补导通后接高频变压器3原边负端，所述每个功率开关单元由两个IGBT和一个反并联二极管并联组成；各相输出级中第二功率变换器2采用桥式拓扑结构由第五功率开关单元S3、第六功率开关单元

第七功率开关单元S4、第八功率开关单元

组成，第五功率开关单元S3、第七功率开关单元S4的正端接高频变压器3副边正端，第六功率开关单元第八功率开关单元

的负端接高频变压器3副边负端，第五功率开关单元S3、第六功率开关单元

互补导通后接滤波器4的输入端，第七功率开关单元S4、第八功率开关单元

互补导通后接滤波器4的输入端，所述每个功率开关单元由两个IGBT和一个反并联二极管并联组成。In the power electronic transformer used in the distribution network, the basic power unit is based on the AC-AC type power electronic transformer, and the first power converter 1 in the input stage of each phase adopts a bridge topology and consists of the first power switch unit S1, the second power switching unit

The third power switch unit S2, the fourth power switch unit Composition, the first power switch unit S1, the second power switch unit After complementary conduction, it is connected to the positive terminal of the primary side of the high-frequency transformer 3, the third power switch unit S2, and the fourth power switch unit

After the complementary conduction, the negative terminal of the primary side of the high-frequency transformer 3 is connected, and each power switch unit is composed of two IGBTs and an anti-parallel diode connected in parallel; the second power converter 2 in the output stage of each phase adopts a bridge topology and consists of The fifth power switch unit S3, the sixth power switch unit

The seventh power switch unit S4, the eighth power switch unit

The positive terminals of the fifth power switch unit S3 and the seventh power switch unit S4 are connected to the positive terminal of the secondary side of the high-frequency transformer 3, and the sixth power switch unit Eighth power switch unit

The negative terminal of the high-frequency transformer 3 is connected to the negative terminal of the secondary side of the high-frequency transformer, the fifth power switch unit S3, and the sixth power switch unit

After the complementary conduction, it is connected to the input end of the filter 4, the seventh power switch unit S4, and the eighth power switch unit

The input end of the filter 4 is connected after the complementary conduction, and each power switch unit is composed of two IGBTs and an antiparallel diode connected in parallel.

输出端，输出滤波电容Ca1负端接第七功率开关单元S4、第八功率开关单元

输出端，输出滤波电容Ca1正端接输出滤波电感一La1正极。The first power converter 1 in each single-phase input stage is connected in series; the output stage adopts a bridge-type power converter parallel structure, and the filter 4 is composed of an output filter inductor La1 and an output filter capacitor Ca1, and the negative pole of the output filter inductor La1 is connected to the first Fifth power switch unit S3, sixth power switch unit

The output terminal, the negative terminal of the output filter capacitor Ca1 is connected to the seventh power switch unit S4 and the eighth power switch unit

At the output terminal, the positive terminal of the output filter capacitor Ca1 is connected to the positive terminal of the output filter inductor La1.

的输出端，输出滤波电感二La2负极接第3个基本功率单元中第七功率开关单元S4、第八功率开关单元的输出端。The output stage can also adopt the cascade structure of bridge power converters. The filter 4 is composed of the output filter capacitor Ca1 and connected to the end of the same name of the output filter inductor La1 and the output filter inductor La2. The negative pole of the output filter inductor La1 is connected to the first The fifth power switch unit S3 and the sixth power switch unit in a basic power unit

The output terminal of the output filter inductor 2 La2 is connected to the seventh power switch unit S4 and the eighth power switch unit in the third basic power unit output terminal.

The input stage is composed of power converters with a bridge topology in series to meet the needs of different input voltage levels; the isolation stage uses multiple high-frequency transformers for isolation, voltage transformation and energy transfer; the output stage has two Two topological structures: The first one is composed of parallel connection of power converters using bridge topology. As shown in Figure 5, the output stage adopts parallel structure of bridge power converters to meet the needs of low voltage and high current. The second is the cascaded structure of power converters using bridge topology and connecting LC filters at the same time. As shown in Figure 6, the output stage adopts the cascaded structure of bridge power converters to meet the needs of high voltage and high power to increase the voltage Current waveform quality. The whole device is composed of basic power units, which can be flexibly applied to distribution network lines of different voltage levels

第三功率开关单元S2、第四功率开关单元

每个功率开关单元由两个IGBT及其反并联二极管连接组成，可以实现电流双向流动；子隔离级为高频变压器3，可以减小装置体积，提高整体效率，实现电压变换及能量传递的功能；子输出级由功率变换器2构成，和输入级一样，功率变换器采用桥式拓扑结构，包括功率第五功率开关单元S3、第六功率开关单元

第七功率开关单元S4、第八功率开关单元

每个功率开关单元由两个IGBT及其反并联二极管连接组成，可以实现电流双向流动，输出级还连接滤波器4，以提高电压电流波形质量。The three-phase structure in the device is the same, which is composed of single-phase structures, and each single-phase structure is composed of basic power units. The working principle of the basic power unit is: the original side converts the power frequency voltage signal through the power converter 1 It is a high-frequency signal (600Hz to 1.2kHz), that is, up-converted, and then coupled to the secondary side through the intermediate high-frequency isolation transformer 3, and then restored to a power frequency voltage signal by the power converter 2, that is, down-frequency. Through corresponding control, the amplitude of the fundamental wave of the output voltage can be changed. The basic power unit is composed of three stages, namely, sub-input stage, sub-isolation stage, and sub-output stage; the sub-input stage is composed of a power converter 1, and the power converter adopts a bridge topology, including the first power switch unit S1, the second power switching unit

The third power switch unit S2, the fourth power switch unit

Each power switch unit is composed of two IGBTs and their anti-parallel diode connections, which can realize bidirectional current flow; the sub-isolation stage is a high-frequency transformer 3, which can reduce the size of the device, improve the overall efficiency, and realize the functions of voltage conversion and energy transfer ; The sub-output stage is composed of a power converter 2, the same as the input stage, the power converter adopts a bridge topology, including the fifth power switch unit S3 and the sixth power switch unit

The seventh power switch unit S4, the eighth power switch unit

Each power switching unit is composed of two IGBTs and their antiparallel diode connections, which can realize bidirectional current flow, and the output stage is also connected with a filter 4 to improve the voltage and current waveform quality.

The input stage of the single-phase structure of the whole device is composed of the input stage power converter of the basic power unit in series, which can directly input high voltage without using transformer coupling, and connect the same capacitor in parallel at the input end of each basic power unit to realize the The input voltage is evenly distributed to each basic power unit; the isolation stage is composed of isolation-level high-frequency transformers of each basic power unit; the output stage has two topological structures: the first one is connected in parallel by the output stage power converter of the basic power unit The second type is formed by cascading the output stage power converters of the basic power unit.

The input stage of the power electronic transformer is composed of single-phase input-stage power converter groups connected in star form; the isolation stage is composed of single-phase isolation-level high-frequency transformer groups for isolation, voltage transformation, and energy transfer; the output The single-phase output stage power converter group is connected in star form to adapt to the three-phase four-wire line. Using the corresponding control strategy, the function of automatic voltage regulation can be realized, and voltage quality problems such as line voltage drop, rise, flicker, overvoltage and undervoltage can be suppressed.

Claims (3)

1. the topological structure of an electric power electric transformer is characterized in that this device adopts three grades of formations, i.e. input stage, isolation level, output stage; The structure of three-phase circuit is identical, and the input of the power inverter group of each single-phase input stage, output stage is according to star-like connection, and power inverter adopts the bridge type topology structure; Isolation level comprises the high frequency transformer that each is single-phase; The input of phase structure prime power unit electric capacity in parallel, in the prime power unit, the former limit of the output termination high frequency transformer (3) of first power inverter (1), the secondary of high frequency transformer (3) connects the input of second power inverter (2); The output of prime power unit connects the input of filter (4), the output termination three phase supply network of filter (4).

2. the topological structure of a kind of electric power electric transformer as claimed in claim 1, it is characterized in that the prime power unit based on AC-AC type electric power electric transformer, first power inverter (1) adopts first power switch unit (S1), second power switch unit in each phase input stage

The 3rd power switch unit (S2), the 4th power switch unit

Form the bridge type topology structure, first power switch unit (S1), second power switch unit Connect the former limit of high frequency transformer (3) anode, the 3rd power switch unit (S2), the 4th power switch unit after the complementary conducting

Connect the former limit of high frequency transformer (3) negative terminal after the complementary conducting, described each power switch unit is composed in parallel with a diode that oppositely is connected by two IGBT; Second power inverter (2) adopts the 5th power switch unit (S3), the 6th power switch unit in each phase output stage

The 7th power switch unit (S4), the 8th power switch unit

Form the bridge type topology structure, positive termination high frequency transformer (3) the secondary anode of the 5th power switch unit (S3), the 7th power switch unit (S4), the 6th power switch unit

The 8th power switch unit

Negative terminal connect high frequency transformer (3) secondary negative terminal, the 5th power switch unit (S3), the 6th power switch unit

Connect the input of filter (4) after the complementary conducting, the 7th power switch unit (S4), the 8th power switch unit

Connect the input of filter (4) after the complementary conducting, described each power switch unit is composed in parallel with a diode that oppositely is connected by two IGBT.

3. the topological structure of a kind of electric power electric transformer as claimed in claim 1 is characterized in that first power inverter (1) is connected in series in each single-phase input stage; Output stage adopts the bridge power converter parallel-connection structure, and filter (4) is made up of output inductor one (La1) and output filter capacitor (Ca1), and output inductor one (La1) negative pole connects the 5th power switch unit (S3), the 6th power switch unit

Output, output filter capacitor (Ca1) negative terminal connects the 7th power switch unit (S4), the 8th power switch unit

Output, positive termination output inductor one (La1) positive pole of output filter capacitor (Ca1); Perhaps output stage adopts the bridge power converter cascade structure, filter (4) is made up of the end of the same name that output filter capacitor (Ca1) is attempted by output inductor one (La1), output inductor two (La2), and output inductor one (La1) negative pole connects the 5th power switch unit (S3), the 6th power switch unit in first prime power unit

Output, output inductor two (La2) negative pole connects the 7th power switch unit (S4), the 8th power switch unit in the 3rd the prime power unit

Output.

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