CN106956598A - A kind of electric power electric transformer tractive power supply system for improving power density - Google Patents

Abstract

The invention discloses a traction power supply system for power electronic transformers with improved power density, which includes several groups of power electronic transformers connected to high-voltage AC buses. The DC bus is connected to the traction inverter and the auxiliary power inverter that supply power to the motor. The invention helps to improve the power density and reduce the switching loss. At the same time, it supplies energy in a short time when the pantograph-catenary is offline, absorbs the energy generated by regenerative braking, and reduces the harmonics injected by the power electronic transformer into the traction network.

Description

A power electronic transformer traction power supply system with improved power density

technical field

The invention relates to a power electronic transformer traction power supply system with improved power density.

Background technique

At present, China is the country with the largest scale and fastest development of high-speed railway in the world. According to the statistics of the International Union of Railways (UIC), as of December 2016, CRRC products have been exported to 102 countries and regions on six continents, covering 83% of the countries and regions with railways in the world. The operating mileage of China's high-speed rail has reached 21,000 km, accounting for more than 60% of the total mileage of high-speed rail in the world. The latest "Medium and Long-Term Railway Network Planning" proposes that by 2020, a number of major landmark projects will be completed and put into operation, and the scale of the railway network will reach 150,000 kilometers, including 30,000 kilometers of high-speed railways, covering more than 80% of large cities. Focusing on the implementation of the national "One Belt, One Road" and "Going Global" strategies, China is increasing its efforts in overseas railway projects and promoting the construction of railway interconnection with neighboring countries, with great potential for development.

As shown in Figure 1, the traction transformer is the power source and an important part of the electric locomotive transmission system. When supplying power, a pantograph 3 and a traction transformer 6 are connected between the AC traction network 1 and the rail 2. The traction transformer 6 passes through the main The converter 4 is connected to the traction motor 5 .

The traction transformer 6 has a large volume and weight, occupies a large passenger space, and consumes a large amount of additional energy. The new generation of power electronic traction transformer PETT, due to the use of medium and high frequency transformers, not only has the electrical isolation, two-way power transmission and voltage conversion functions of traditional power frequency traction transformers, but also has the weight and volume reduction of more than 50%, high power factor, harmonic It has many advantages such as low wave content and low pollution, and has been highly valued by theoretical and technical research in the field of international rail transit.

World-renowned locomotive manufacturers have made design plans and test prototypes for PETT one after another. At present, the research on the power density improvement of power electronic transformer traction power supply system mainly focuses on the increase of transformer frequency, and the research and development of high-efficiency and high power density transformer traction power supply. The system has become a strategic high ground for a new generation of international lightweight and high-performance electric locomotives.

Contents of the invention

In order to solve the above problems, the present invention proposes a power electronic transformer traction power supply system with improved power density. The input stage of the traction power supply system provided by the present invention adds an active power decoupling circuit on the basis of the traditional cascaded H-bridge. The active power decoupling module can suppress the secondary power pulsation while rectifying, reduce the filter capacitance, and improve the power density; the intermediate stage DC/DC converter adopts resonant soft switching technology to improve the conversion efficiency and increase the power density at the same time; the low-voltage side DC Parallel output, the DC bus is connected to a composite energy storage system to improve power quality; the traction frequency converter and the auxiliary power inverter are connected to the low-voltage side DC bus.

In order to achieve the above object, the present invention adopts the following technical solutions:

A traction power supply system for power electronic transformers with improved power density, including several groups of power electronic transformers connected to high-voltage AC buses. The low-voltage DC sides output by the above-mentioned power electronic transformers are all connected in parallel to form low-voltage DC buses. Traction inverters and auxiliary power inverters for powering electric motors.

Further, the power electronic transformer is connected behind a pantograph connected to the high-voltage AC busbar.

Further, a resistor for realizing soft start of the power electronic transformer is connected in parallel to the switch on the pantograph.

Further, a filter is connected in series between the pantograph and the power electronic transformer. When the energy of regenerative braking is greater than the set value, the power electronic transformer transmits energy to the traction network, and the filter is used to filter the feed current at this time.

Further, a hybrid energy storage system is connected to the low-voltage DC bus. Such a design, on the one hand, can supply energy in a short time when the pantograph-catenary is offline, on the other hand, it can absorb the energy generated by regenerative braking and reduce the harmonics injected by the power electronic transformer into the traction network.

Preferably, the hybrid energy storage system includes a storage battery and a supercapacitor connected in parallel therewith.

Further, the front-stage rectification link of the power electronic transformer adopts a cascaded H-bridge structure, and each H-bridge structure is equipped with an active power decoupling circuit to reduce the filter capacitance and improve its reliability.

Further, the rectification link adopts SPWM modulation.

Further, the filter is an L filter circuit.

Further, the DC side of each H-bridge structure is connected with a DC-DC converter, and the DC-DC converters of multiple sets of force electronic transformers are connected in parallel, and the positive pole lines output by multiple DC-DC converters are connected respectively, and the output The negative pole lines are connected separately and connected in parallel to form a low-voltage DC bus.

Further, the DC-DC converter is a resonant converter, consisting of two H-bridge structures, a resonant capacitor and a high-frequency transformer, and an H-bridge structure is connected to each side of the high-frequency transformer through a resonant capacitor , the resonant converter adopts phase-shift control, and the output terminals of the resonant converter are connected in parallel to form the low-voltage DC output terminal of the power electronic transformer.

Compared with prior art, the beneficial effect of the present invention is:

(1) In the input stage, an active power decoupling circuit is added on the basis of the traditional cascaded H-bridge. The active power decoupling module formed can suppress the secondary power ripple while rectifying, reduce the filter capacitance, and increase the power density.

(2) A resistor is connected in parallel to the switch on the pantograph, which can realize the soft start of the power electronic transformer of the locomotive and reduce the impact on the power electronic transformer when starting.

(3) The high-frequency resonant converter is adopted in the DC-DC link of the power electronic transformer in the present invention, which can not only reduce the volume of the transformer, but also reduce the switching loss.

(4) The hybrid energy storage device is connected to the low-voltage DC bus, which can supply energy in a short time when the pantograph-catenary is offline.

(5) A hybrid energy storage device is connected to the low-voltage DC bus, which can absorb the energy generated by regenerative braking and reduce the harmonics injected by the power electronic transformer into the traction network.

Description of drawings

The accompanying drawings constituting a part of the present application are used to provide further understanding of the present application, and the schematic embodiments and descriptions of the present application are used to explain the present application, and do not constitute improper limitations to the present application.

Figure 1 is a structural diagram of a traditional traction power supply system;

Figure 2 is a structural diagram of a power electronic transformer;

Figure 3 is a structural diagram of the power electronic transformer traction power supply system;

Among them, 1. AC traction network, 2. Rail, 3. Pantograph, 4. Main converter, 5. Traction motor, 6. Traction transformer.

detailed description:

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

It should be pointed out that the following detailed description is exemplary and intended to provide further explanation to the present application. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

It should be noted that the terminology used here is only for describing specific implementations, and is not intended to limit the exemplary implementations according to the present application. As used herein, unless the context clearly dictates otherwise, the singular is intended to include the plural, and it should also be understood that when the terms "comprising" and/or "comprising" are used in this specification, they mean There are features, steps, operations, means, components and/or combinations thereof.

As introduced in the background technology, the traction power supply system in the prior art has a large volume and weight, and there are shortcomings such as a large impact on the traction system due to pantograph-catenary off-line, and large harmonics injected into the power grid during regenerative braking of the locomotive. In order to solve the above technical problems , the present application provides a power electronic transformer traction power supply system with improved power density.

In a typical implementation of the present application, a power electronic transformer traction power supply system with improved power density is provided, including a power electronic transformer connected to a high-voltage AC busbar, and the low-voltage DC side of the power electronic transformer output is connected in parallel to form a low-voltage A DC bus, the low-voltage DC bus is connected to the traction inverter and the auxiliary power inverter for power supply to the electric motor. As shown in Figure 3, the dotted box represents a row of electric locomotives, and the PETT structure is shown in Figure 2. In the present invention, the PETT connected behind the pantograph converts high-voltage alternating current into low-voltage direct current, and then supplies power to each motor from the low-voltage direct-current bus. Multiple traction inverters and auxiliary power supply inverters are connected in parallel on the low-voltage direct-current bus.

In the present invention, a hybrid energy storage system composed of a battery and a supercapacitor is connected to a low-voltage DC bus, and the hybrid energy storage system composed of a battery and a supercapacitor is connected to a low-voltage DC bus. A small amount of energy is fed back into the traction network, and this feedback current contains large harmonic components. The connected hybrid energy storage system can absorb this part of the feedback energy and reduce the harmonic content in the traction network; 2) When the pantograph is caused by When the vibration, excessive and other reasons are offline, the hybrid energy storage device can provide short-term functions for the electric locomotive, and reduce the adverse impact of the pantograph-catenary offline on the power electronic transformer.

In addition, this application connects a resistor in parallel at the switch on the pantograph, which can realize the soft start of the power electronic transformer of the locomotive; a filter is connected in series between the pantograph and the power electronic transformer, and when the energy of regenerative braking is large, the power electronic The transformer transmits energy to the traction network, and the filter is used to filter the feed current at this time. Preferably, the filter is an L filter circuit.

As shown in Figure 2, the front-stage rectification link of the power electronic transformer adopts a cascaded H-bridge structure, and each H-bridge is equipped with an active power decoupling circuit, thereby reducing the size of the filter capacitor and improving power density and system reliability; H The DC side of the bridge circuit is connected to the DC-DC converter, and multiple DC-DC converters are connected in parallel. The positive lines output by the multiple DC-DC converters are connected respectively, and the output negative lines are respectively connected to form a low-voltage DC bus in parallel; The traction inverter is connected to the low-voltage DC bus to supply power to the motor, and the auxiliary power supply inverter is connected to supply power to the auxiliary power supply system; the low-voltage DC bus is connected to the hybrid energy storage system. The DC-DC converter is a resonant converter.

Working principle: This application connects PETT behind the pantograph to convert high-voltage AC power into low-voltage DC power, and then supplies power to each motor from the low-voltage DC bus. Multiple traction inverters are connected in parallel on the low-voltage DC bus. A hybrid energy storage system composed of batteries and supercapacitors. Among them: the power electronic traction transformer is shown in Figure 2, and its rectification link is composed of a cascaded H-bridge with active power decoupling circuit, which adopts SPWM modulation; the DC side of the H-bridge is connected in parallel with a capacitor, followed by a resonant converter , the resonant converter is composed of two H-bridges, two resonant capacitors and a high-frequency transformer. The resonant converter adopts phase-shift control; the output terminals of the resonant converter are connected in parallel to form the low-voltage DC output terminal of the power electronic transformer, and then form a low-voltage DC bus. .

The above descriptions are only preferred embodiments of the present application, and are not intended to limit the present application. For those skilled in the art, there may be various modifications and changes in the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of this application shall be included within the protection scope of this application.

Although the specific implementation of the present invention has been described above in conjunction with the accompanying drawings, it does not limit the protection scope of the present invention. Those skilled in the art should understand that on the basis of the technical solution of the present invention, those skilled in the art do not need to pay creative work Various modifications or variations that can be made are still within the protection scope of the present invention.

Claims (10)

1. A power electronic transformer traction power supply system that improves power density is characterized in that: it includes several groups of power electronic transformers connected on the high-voltage AC busbar, and the low-voltage DC sides output by the above-mentioned power electronic transformers are connected in parallel to form a low-voltage DC busbar. A traction inverter and an auxiliary power inverter connected to the low-voltage direct current bus for powering the electric motor. 2. A power electronic transformer traction power supply system with improved power density according to claim 1, characterized in that: said power electronic transformer is connected behind a pantograph connected to a high-voltage AC busbar. 3. A power electronic transformer traction power supply system with increased power density as claimed in claim 2, characterized in that: a resistor for realizing soft start of the power electronic transformer is connected in parallel to the switch on the pantograph. 4. A power electronic transformer traction power supply system with improved power density as claimed in claim 2, characterized in that: the filter connected in series between the pantograph and the power electronic transformer, when the regenerative braking energy is greater than the set When the value is , the power electronic transformer transmits energy to the traction network, and the filter is used to filter the feed current at this time. 5. A power electronic transformer traction power supply system with improved power density as claimed in claim 1, characterized in that: said low-voltage DC bus is connected to a hybrid energy storage system; Or the hybrid energy storage system includes a storage battery and a supercapacitor connected in parallel therewith. 6. A power electronic transformer traction power supply system with improved power density as claimed in claim 1, characterized in that: the front-stage rectification link of the power electronic transformer adopts a cascaded H-bridge structure, and each H-bridge structure is additionally set Active power decoupling circuitry to reduce filter capacitance and improve its reliability. 7. A power electronic transformer traction power supply system with improved power density as claimed in claim 6, characterized in that: the rectification link adopts SPWM modulation. 8. A power electronic transformer traction power supply system with improved power density as claimed in claim 4, characterized in that: said filter is an L filter circuit. 9. A power electronic transformer traction power supply system with improved power density as claimed in claim 6, characterized in that: the DC side of each H-bridge structure is connected with a DC-DC converter, and the DC-DC converters of multiple groups of force electronic transformers The DC converters are connected in parallel, the positive lines output by the multiple DC-DC converters are connected respectively, and the output negative lines are connected respectively, so as to form a low-voltage direct current bus in parallel. 10. A power electronic transformer traction power supply system with improved power density as claimed in claim 1, characterized in that: said DC-DC converter is a resonant converter consisting of two H-bridge structures, a resonant capacitor and a high The two sides of the high-frequency transformer are connected with an H-bridge structure through a resonant capacitor. The resonant converter adopts phase-shift control, and the output terminals of the resonant converter are connected in parallel to form the low-voltage DC output terminal of the power electronic transformer.