Multi-output power electronic transformer topological structure for intelligent power grid

Abstract

The utility model discloses a multi-output power electronic transformer topological structure for an intelligent power grid, which comprises a high-frequency multi-output transformer, and the input end of the high-frequency multi-output transformer is connected with a high-frequency high-voltage square wave which is obtained by rectifying and converting alternating current through an AC / DC rectifier and a DC / AC converter. The output end of the high-frequency multi-path output transformer is divided into three paths of output; one path is converted into direct current through the first AC / DC converter and then connected with the DC / DC converter to output low-voltage direct current, one path is converted into direct current through the second AC / DC converter and then connected with the first DC / AC inverter to output intermediate-frequency low-voltage single-phase alternating current, and one path is converted into direct current through the third AC / DC converter and then connected with the second DC / AC inverter to output power-frequency low-voltage three-phase alternating current. The transformer topological structure provides multi-path output, so that the number of equipment in a power grid system can be reduced, the complexity of the system is reduced, meanwhile, various voltage levels and frequencies are supported, different load requirements are met, electric energy can be distributed more accurately, and the energy efficiency of the whole system of the intelligent power grid is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of power electronic transformers, in particular to a topological structure of a multi-channel output power electronic transformer for a smart grid. Background Art

[0002] In smart grids, power electronic transformers (PET) provide higher energy conversion efficiency than traditional transformers by using high-frequency switching circuits, can effectively isolate grid faults, protect sensitive loads from grid problems, and can seamlessly access distributed energy resources such as solar energy and wind energy, helping to integrate the above renewable distributed energy resources into smart grids. Since power electronic transformers support bidirectional energy flow, they are particularly important for the development of smart grids with source, grid, load and storage.

[0003] However, the power electronic transformer in the prior art has the disadvantages of weak regulation ability on the DC side, a large number of switching devices and filter capacitors, and is not suitable for AC / DC mixed power supply scenarios. Therefore, it is necessary to design a power electronic transformer with a multi-stage conversion structure for medium and high voltage levels, which has both AC and DC load power supply interfaces to adapt to different load requirements. Utility Model Content

[0004] The technical problem to be solved by the utility model is to provide a power electronic transformer topology structure supporting multiple voltage levels and frequency outputs, so as to be suitable for different load requirements.

[0005] In order to solve the above technical problems, the utility model provides the following technical solutions.

[0006] A multi-channel output power electronic transformer topology for a smart grid comprises a high-frequency multi-channel output transformer, wherein the input end of the high-frequency multi-channel output transformer is connected to a high-frequency high-voltage square wave obtained by rectifying and converting alternating current through an AC / DC rectifier and a DC / AC converter, and the output end of the high-frequency multi-channel output transformer is divided into three paths and connected to different current conversion components to output a target electric energy signal; wherein one path converts alternating current into direct current through a first AC / DC converter and then is connected to a DC / DC converter to output low-voltage direct current, one path converts alternating current into direct current through a second AC / DC converter and then is connected to a first DC / AC inverter to output medium-frequency low-voltage single-phase alternating current, and one path converts alternating current into direct current through a third AC / DC converter and then is connected to a second DC / AC inverter to output industrial-frequency low-voltage three-phase alternating current.

[0007] Furthermore, a number of capacitors are provided between the AC / DC rectifier and the DC / AC converter, between the first AC / DC converter and the DC / DC converter, between the second AC / DC converter and the first DC / AC inverter, and between the third AC / DC converter and the second DC / AC inverter.

[0008] Furthermore, a number of capacitors and inductors are provided between the DC / AC converter and the high-frequency multi-channel output transformer, in the internal circuit of the DC / DC converter, in the internal circuit of the first DC / AC inverter, and in the internal circuit of the second DC / AC inverter.

[0009] Furthermore, the AC / DC rectifier includes three mid-point clamped rectifiers, each of which includes four insulated gate bipolar transistors IGBTs, a diode anti-parallel to each insulated gate bipolar transistor IGBT, and two clamping diodes.

[0010] Furthermore, the DC / AC converter performs open-loop control on the rectified DC voltage, converts the DC into a high-frequency square wave with a duty cycle of 50%, and outputs a high-frequency and high-voltage square wave signal.

[0011] Furthermore, the DC / AC converter, the high-frequency multi-channel output transformer, the first AC / DC converter, the second AC / DC converter, and the third AC / DC converter form a dual active bridge DC converter.

[0012] Furthermore, the DC / DC converter is configured as a BUCK circuit.

[0013] Furthermore, each phase of the first DC / AC inverter and the second DC / AC inverter includes two insulated gate bipolar transistors IGBTs and a diode anti-parallel to each insulated gate bipolar transistor IGBT.

[0014] Furthermore, the first DC / AC inverter is a single-phase bridge inverter circuit, and the second DC / AC inverter is a three-phase bridge inverter.

[0015] Beneficial effects of the utility model:

[0016] The embodiment of the utility model provides a multi-output power electronic transformer topology structure. Through rectification, inversion, transformation and other links, the output end can obtain low-voltage DC power, low-voltage medium-frequency single-phase AC power and low-voltage industrial frequency three-phase AC power. Providing multiple outputs through a transformer can reduce the number of devices in the smart grid system and reduce the complexity of the system. At the same time, it supports multiple voltage levels and frequencies, which is suitable for different load needs. It can also distribute power more accurately, reduce energy waste, and improve the energy efficiency of the overall smart grid system. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic diagram of the basic structure of a power electronic transformer provided by an embodiment of the utility model;

[0018] Figure 2(a) shows Figure 1 Schematic diagram of the topological structure corresponding to the input circuit of the medium and high frequency multi-channel output transformer.

[0019] Figure 2(b) shows Figure 1 Schematic diagram of the topological structure corresponding to the output circuit of the medium and high frequency multi-channel output transformer.

[0020] Description of the main figures:

[0021] 1-AC / DC rectifier; 2-DC / AC converter; 3-high frequency multi-channel output transformer; 4-first AC / DC converter; 5-second AC / DC converter; 6-third AC / DC converter; 7-DC / DC converter; 8-first DC / AC inverter; 9-second DC / AC inverter. DETAILED DESCRIPTION

[0022] In order to clearly illustrate the purpose, technical solution and advantages of the utility model, the technical solution of the utility model will be clearly and completely described through the implementation method with reference to the drawings in the embodiments of the utility model. Obviously, the described embodiments are part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0023] See also Figure 1 The embodiment of the utility model provides a multi-channel output power electronic transformer topology structure for smart grid, and the multi-channel output power electronic transformer includes a high-frequency multi-channel output transformer 3 for transforming current and isolating input and output. The input end of the high-frequency multi-channel output transformer 3 is connected to the high-frequency high-voltage square wave after the AC / DC rectifier 1 and the DC / AC converter 2 rectify and convert the industrial frequency high-voltage three-phase AC power, and the output end of the high-frequency multi-channel output transformer 3 is divided into three paths connected to different current conversion components. They are: one path converts AC to DC through the first AC / DC converter 4 and then connects to the DC / DC converter 7 to output low-voltage DC power, one path converts AC to DC through the second AC / DC converter 5 and then connects to the first DC / AC inverter 8 to output medium-frequency low-voltage single-phase AC power, and one path converts AC to DC through the third AC / DC converter 6 and then connects to the second DC / AC inverter 9 to output industrial frequency low-voltage three-phase AC power.

[0024] Referring to FIG. 2( a ) and FIG. 2( b ), the topological structure of the multi-output power electronic transformer for the smart grid is specifically as follows:

[0025] AC / DC rectifier 1 is connected to industrial frequency high voltage three-phase alternating current, and rectifies the alternating current, and the output voltage is stabilized at a given value and is continuously adjustable within a certain range. AC / DC rectifier 1 includes three neutral point clamped (NPC) rectifiers, each of which includes four IGBTs (Insulated Gate Bipolar Transistor, insulated gate bipolar transistors), a diode anti-parallel to each IGBT, and two clamping diodes. For example, the composition structure of one of the neutral point clamped rectifiers includes four insulated gate bipolar transistors SA1, SA2, SA1', SA2', diodes anti-parallel to the SA1, SA2, SA1', SA2', respectively, and clamping diodes D1, D2.

[0026] The DC / AC converter 2 performs open-loop control on the rectified DC voltage, converts the DC into a high-frequency square wave with a duty cycle of 50% and outputs a high-frequency and high-voltage square wave signal.

[0027] The high-frequency multi-channel output transformer 3 transforms the high-frequency high-voltage square wave signal, isolates the input and output, and outputs multiple low-voltage high-frequency voltages. In this embodiment, it is designed according to the requirements of different AC and DC loads in the smart grid, and outputs three different electric energies, namely low-voltage DC power, low-voltage medium-frequency single-phase AC power, and low-voltage industrial frequency three-phase AC power. Note: The letter T in Figure 2 (a) and Figure 2 (b) represents the high-frequency multi-channel output transformer 3.

[0028] The first AC / DC converter 4, the second AC / DC converter 5 and the third AC / DC converter 6 are used to convert the alternating current stepped down by the high-frequency multi-channel output transformer 3 into direct current, and different AC / DC converters convert different direct currents.

[0029] Among them, the DC / AC converter 2, the high-frequency multi-channel output transformer 3 and the first AC / DC converter 4, the second AC / DC converter 5, and the third AC / DC converter 6 are composed of a dual active bridge DC converter (DAB), which can realize electrical isolation of input and output, has bidirectional power processing capability, has the advantages of high power density and easy soft switching, and is used to improve power transmission efficiency. Among them, the DC / AC converter 2, the high-frequency multi-channel output transformer 3 and the first AC / DC converter 4, the second AC / DC converter 5, and the third AC / DC converter 6 together constitute a DC-DC isolation transformer circuit.

[0030] The DC / DC converter 7 is composed of a BUCK circuit. The BUCK circuit is a common switching regulator topology, which uses periodic switching elements to reduce the input voltage to the required output voltage level on average over time. Specifically, the DC / DC converter 7 uses S z1 and S z2 The action of turning on and off in turn adjusts the voltage output and achieves the function of stabilizing the voltage output.

[0031] Each phase of the first DC / AC inverter 8 and the second DC / AC inverter 9 includes 2 IGBTs and a diode connected in reverse parallel to each IGBT. The first DC / AC inverter 8 is a single-phase bridge inverter circuit, which is used to invert the DC voltage output by the second AC / DC converter 5 into a low-voltage single-phase AC power required by the connected network; the first DC / AC inverter 8 includes 4 IGBTs (Sh, Sl, S1', Sh') and a diode connected in reverse parallel to each IGBT. By changing the switching frequency of Sh, S1' and Sl, Sh', the frequency of the output AC power can be changed. The second DC / AC inverter 9 is a three-phase bridge inverter, which is used to invert the DC voltage output by the third AC / DC converter 6 into a low-voltage three-phase AC power required by the connected network; the second DC / AC inverter 9 includes 6 IGBTs (Sa, Sa', Sb, Sb', Sc, Sc') and a diode connected in reverse parallel to each IGBT.

[0032] In the circuit, a number of capacitors are also provided between the AC / DC rectifier 1 and the DC / AC converter 2, between the first AC / DC converter 4 and the DC / DC converter 7, between the second AC / DC converter 5 and the first DC / AC inverter 8, and between the third AC / DC converter 6 and the second DC / AC inverter 9.

[0033] Several capacitors and inductors are also provided between the DC / AC converter 2 and the high-frequency multi-channel output transformer 3, in the internal circuit of the DC / DC converter 7, in the internal circuit of the first DC / AC inverter 8, and in the internal circuit of the second DC / AC inverter 9.

[0034] The capacitor C is used to reduce the ripple of the output voltage of the frequency conversion circuit and improve the stability and efficiency of the circuit; the inductor L is used to stabilize the output voltage, prevent capacitor oscillation, and improve the quality and stability of the output voltage.

[0035] A specific example of voltage conversion output by the multi-output power electronic transformer topology structure provided by this embodiment is:

[0036] The power grid input voltage is 10kV, 50Hz industrial frequency high-voltage three-phase AC power, which outputs 15kV DC voltage after passing through the AC / DC rectifier 1 with a switching frequency of 10kHz, and outputs 8kV high-frequency square waves with a duty cycle of 50% after passing through the DC / AC converter 2 with a switching frequency of 1kHz, and outputs three high-frequency square waves with a duty cycle of 50% and voltages of 300V, 450V, and 550V respectively after passing through the high-frequency multi-channel output transformer 3;

[0037] The 300V high-frequency square wave outputs a 540V DC voltage after passing through the first AC / DC converter 4 with a switching frequency of 1kHz; the 540V DC voltage outputs a 48V low-voltage DC power through the DC / DC converter 7 to supply industrial robots, PLC controllers and other equipment;

[0038] The 450V high-frequency square wave outputs 800V DC voltage after passing through the second AC / DC converter 5 with a switching frequency of 1kHz; the 800V DC voltage outputs 120V, 400Hz medium-frequency low-voltage single-phase AC power through the first DC / AC inverter 8 with a switching frequency of 5kHz for electronic equipment in the fields of aviation, ships, railways, etc.

[0039] The 550V high-frequency square wave outputs a 1kV DC voltage after passing through the third AC / DC converter 6 with a switching frequency of 1kHz; the 1kV DC voltage outputs a 380V, 50Hz industrial frequency low-voltage three-phase AC power through the second DC / AC inverter 9 with a switching frequency of 5kHz for use in motors, lighting equipment, elevators and other equipment.

[0040] The multi-output power electronic transformer topology structure for the smart grid in this embodiment can obtain low-voltage DC power, low-voltage high-frequency single-phase AC power and low-voltage industrial frequency three-phase AC power at the three output ends through rectification, inversion, transformation and other links. It can reduce the number of power electronic transformers in the overall smart grid system and reduce system complexity. It supports multiple voltage levels and frequencies, is suitable for different load needs, and can distribute power more accurately, reduce energy waste, and improve the energy efficiency of the overall smart grid system.

[0041] The above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention is described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A multi-output power electronic transformer topology for smart grid, characterized in that: The invention comprises a high-frequency multi-channel output transformer (3), the input end of which is connected to a high-frequency high-voltage square wave obtained by rectifying and converting alternating current through an AC / DC rectifier (1) and a DC / AC converter (2), and the output end of which is divided into three paths connected to different current conversion components to output target electric energy signals, wherein one path converts alternating current into direct current through a first AC / DC converter (4) and then is connected to a DC / DC converter (7) to output low-voltage direct current, one path converts alternating current into direct current through a second AC / DC converter (5) and then is connected to a first DC / AC inverter (8) to output medium-frequency low-voltage single-phase alternating current, and one path converts alternating current into direct current through a third AC / DC converter (6) and then is connected to a second DC / AC inverter (9) to output industrial-frequency low-voltage three-phase alternating current.

2. The multi-output power electronic transformer topology structure for smart grid according to claim 1 is characterized in that: Several capacitors are also arranged between the AC / DC rectifier and the DC / AC converter, between the first AC / DC converter and the DC / DC converter, between the second AC / DC converter and the first DC / AC inverter, and between the third AC / DC converter and the second DC / AC inverter.

3. The multi-output power electronic transformer topology structure for smart grid according to claim 2 is characterized in that: Several capacitors and inductors are also arranged between the DC / AC converter and the high-frequency multi-channel output transformer, in the internal circuit of the DC / DC converter, in the internal circuit of the first DC / AC inverter, and in the internal circuit of the second DC / AC inverter.

4. The multi-output power electronic transformer topology structure for smart grid according to any one of claims 1 to 3, characterized in that: The AC / DC rectifier includes three mid-point clamped rectifiers, each of which includes four insulated gate bipolar transistors IGBTs, a diode anti-parallel to each insulated gate bipolar transistor IGBT, and two clamping diodes.

5. The multi-output power electronic transformer topology structure for smart grid according to any one of claims 1 to 3, characterized in that: The DC / AC converter performs open-loop control on the rectified DC voltage, converts the DC into a high-frequency square wave with a duty cycle of 50% and outputs a high-frequency and high-voltage square wave signal.

6. The multi-output power electronic transformer topology structure for smart grid according to any one of claims 1 to 3, characterized in that: The DC / AC converter, the high-frequency multi-channel output transformer, the first AC / DC converter, the second AC / DC converter and the third AC / DC converter form a dual active bridge DC converter.

7. The multi-output power electronic transformer topology structure for smart grid according to any one of claims 1 to 3, characterized in that: The DC / DC converter is configured as a BUCK circuit.

8. The multi-output power electronic transformer topology structure for smart grid according to any one of claims 1 to 3, characterized in that: Each phase of the first DC / AC inverter and the second DC / AC inverter includes two insulated gate bipolar transistors IGBTs and a diode connected in anti-parallel to each insulated gate bipolar transistor IGBT.

9. The multi-output power electronic transformer topology structure for smart grid according to claim 8, characterized in that: The first DC / AC inverter is a single-phase bridge inverter circuit, and the second DC / AC inverter is a three-phase bridge inverter.

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