CN103490419A - Flexible alternating-current direct-current hybrid power supply system of power distribution network - Google Patents

Abstract

The invention provides a flexible AC-DC hybrid power supply system for a distribution network. The system includes a high-voltage level unit, an isolation level unit, a low-voltage level unit, and a DC power supply unit; the high-voltage level unit, isolation level unit, and low-voltage level unit are connected in sequence , the high-voltage level unit and the isolation level unit, and the isolation level unit and the low-voltage level unit are all connected through a DC bus. The DC power supply unit is connected in parallel with the DC bus between the isolation level unit and the low voltage level unit. The invention provides a flexible AC-DC hybrid power supply system for distribution network, which integrates the functions of traditional distribution transformer and DFACTS controller, completely changes the rigid control structure of traditional transformer, makes the control of distribution network more concise and flexible, and can not only provide High-quality AC power output can also provide high-quality DC power output.

Description

A Flexible AC-DC Hybrid Power Supply System for Distribution Network

technical field

The invention relates to a power supply system, in particular to a flexible AC and DC hybrid power supply system for a distribution network.

Background technique

Since the world's first high-voltage direct current transmission line was completed and put into operation, after more than 60 years of development, high-voltage direct current transmission technology has been widely used in several aspects such as long-distance ultra-high voltage transmission, cross-sea transmission and asynchronous networking. DC transmission has the advantages of less line investment, no system stability problems, fast adjustment, and reliable operation.

At the same time, the demand for DC power consumption and distributed power grid connection and energy storage in the distribution network is becoming increasingly prominent. However, the traditional distribution network is an AC grid that does not have the function of DC power supply. In fact, most electronic loads The required power consumption method is DC power. The current method is to install small power electronic rectifiers on the power load side to convert the AC power provided by the distribution transformer into DC power, so that the DC load can be used normally, as shown in Figure 1.

This distributed rectification method not only increases the cost, is prone to generate harmonics, but also greatly reduces the efficiency. If DC power is directly provided to these DC loads, energy consumption will be greatly reduced. According to the verification of Duke Energy Corporation of the United States, if a Directly supplying DC power to the load of the data center can reduce energy consumption by about 15%.

The current distribution network based on distribution transformers does not have the function of directly providing DC power. Although today's power transformers have reached unprecedented heights in terms of technology and performance, the basic functions, working principles and The structure has not changed. In the context of the new demands of the power system, the power transformer, which is the most basic transformation device of the power system, has a single function that makes its shortcomings more and more obvious. If the most basic component of the power distribution system, the distribution transformer, can be directly used to solve the user's AC and DC hybrid power supply and power quality control problems, the power distribution system will become more efficient, simple and safe.

With the increasing demand for DC loads on the power distribution side and distributed power grid connection, such as electric vehicle charging and discharging, photovoltaic and other distributed power grid connection, etc., and for most loads, it is a form of DC power consumption, and DC power supply Compared with AC power supply, it has the advantages of simple control and low loss. Aiming at the problem that the traditional iron-core distribution transformer can only transmit AC power, it cannot effectively meet the user's needs for DC power consumption.

Contents of the invention

In order to overcome the deficiencies of the prior art above, the present invention provides a flexible AC-DC hybrid power supply system for distribution networks, which integrates the functions of traditional distribution transformers and DFACTS controllers, completely changes the rigid control structure of traditional transformers, and makes power distribution The network control is more concise and flexible, not only can provide high-quality AC power output but also can provide high-quality DC power output.

In order to realize the above-mentioned purpose of the invention, the present invention takes the following technical solutions:

The invention provides a flexible AC-DC hybrid power supply system for a distribution network. The system includes a high-voltage level unit, an isolation level unit, a low-voltage level unit, and a DC power supply unit; the high-voltage level unit, isolation level unit, and low-voltage level unit are connected in sequence , the high-voltage level unit and the isolation level unit, and the isolation level unit and the low-voltage level unit are all connected through a DC bus. The DC power supply unit is connected in parallel with the DC bus between the isolation level unit and the low voltage level unit.

The system is a three-phase four-wire AC-DC hybrid power supply system.

The high-voltage stage unit includes a first AC/DC converter, and the first AC/DC converter includes a three-phase full-bridge rectifier active front end, a controller and auxiliary equipment; the controller generates a modulation signal to the three-phase full-bridge rectifier The main circuit of the power electronic device of the active front end is controlled; the auxiliary equipment receives the modulation signal of the controller and generates a driving signal, which drives the on-off of the power electronic device of the three-phase full-bridge rectification active front-end, and controls the three-phase full-bridge The over-temperature, over-voltage and over-current of the active front end of the rectification are protected, and the variable detection and feedback control of the active front end of the three-phase full-bridge rectification are realized, so that the active front-end of the three-phase full-bridge rectification can start, stop and dissipate heat safely; The AC side of the first AC/DC converter is connected to the distribution network line, and the DC side is connected to the DC side of the first DC/AC converter of the isolation level unit through a DC bus.

The isolation level unit includes a first DC/AC converter, an isolation transformer and a second AC/DC converter.

The first DC/AC converter includes a single-phase H-bridge high-frequency resonant inverter, a controller and auxiliary equipment; the controller generates a modulation signal for the main circuit of the power electronic device of the single-phase H-bridge high-frequency resonant inverter Control, to realize the input of DC to high frequency AC square wave; the auxiliary equipment receives the modulation signal of the controller and generates a driving signal to drive the power electronic device of the single-phase H-bridge high-frequency resonant inverter on and off, and to control the single-phase The over-temperature, over-voltage and over-current of the H-bridge high-frequency resonant inverter are protected, so that the single-phase H-bridge high-frequency resonant inverter can be started, stopped and dissipated safely; the DC side of the first DC/AC converter It is connected in parallel with the high-voltage DC busbar, and the AC side outputs high-frequency AC square waves and is connected to the primary side of the isolation-level medium/high-frequency transformer.

The isolation stage transformer is an isolation transformer with 1 input on the primary side and 3 outputs on the secondary side; the primary side is connected in parallel with the high frequency square wave AC side of the first DC/AC converter of the isolation stage, and the secondary side has 3 interfaces They are respectively connected in parallel with the high-frequency square-wave AC sides of the three single-phase H-bridge high-frequency resonant rectifiers of the second AC/DC converter of the isolation stage.

The isolation transformer is an intermediate frequency isolation transformer or a high frequency isolation transformer.

The second AC/DC converter includes 3 single-phase H-bridge high-frequency resonant rectifiers, a controller and auxiliary equipment; the controller generates a modulation signal to the main circuit of the power electronic device of the 3 single-phase H-bridge high-frequency resonant rectifiers Control, to realize the input high-frequency square wave AC to DC conversion; the auxiliary equipment receives the modulation signal of the controller and generates a driving signal, which drives the power electronic device of the single-phase H-bridge high-frequency resonant rectifier on and off, and controls the single-phase H bridge The over-temperature, over-voltage and over-current of the bridge high-frequency resonant rectifier are protected, so that the single-phase H-bridge high-frequency resonant rectifier can be started, stopped and dissipated safely; the second AC/DC converter has three single-phase H-bridges on the AC side The high-frequency resonant rectifiers are respectively connected in parallel with the 3 outputs on the secondary side of the isolation transformer, and the 3 DC sides are respectively connected to the DC sides of the 3 single-phase H-bridge inverters of the second DC/AC converter of the low-voltage stage through the DC bus. connected in parallel and respectively connected in parallel with the high-voltage sides of the three half-bridge choppers of the DC/DC converter of the DC power supply unit.

The low-voltage stage unit includes a second DC/AC converter including 3 single-phase H-bridge inverters, a controller, 3 LC filters and auxiliary equipment; the controller generates modulation The signal controls the main circuits of the power electronic devices of the three single-phase H-bridge inverters to realize the conversion of input DC to power frequency AC; the auxiliary equipment receives the modulation signal of the controller and generates a driving signal, which is used for the single-phase H-bridge inverter Drive the on-off of the power electronic devices, and protect the over-temperature, over-voltage and over-current of the single-phase H-bridge inverter, realize the variable detection and feedback control of the single-phase H-bridge inverter, and make the single-phase H-bridge inverter The bridge inverter starts, stops and dissipates heat safely; the DC sides of the three single-phase H-bridge inverters are respectively connected in parallel with the three DC buses of the isolation stage, and the AC sides are respectively connected in parallel with three LC filters to eliminate voltage harmonics Wave, to achieve the role of filtering, the output is connected by YN to form a three-phase four-wire output, to achieve a power frequency AC output with constant three-phase voltage, sinusoidal waveform, and a phase difference of 120°.

The DC power supply unit includes a DC/DC converter, and the DC/DC converter includes 3 half-bridge choppers, 3 LCL filters, a controller and auxiliary equipment; the controller generates a modulation signal to the 3 half-bridges The main circuit of the power electronic device of the chopper is controlled to realize the DC conversion from the input DC to the required voltage level; the auxiliary equipment receives the modulation signal of the controller and generates a driving signal to switch on and off the power electronic device of the half-bridge chopper Drive, and protect the over-temperature, over-voltage and over-current of the half-bridge chopper, realize the variable detection and feedback control of the single-phase H-bridge inverter, and make the half-bridge chopper safe to start and stop to dissipate heat; The high-voltage sides of the three half-bridge choppers of the DC/DC converter are connected in parallel with the three DC buses of the isolation stage, and the low-voltage sides are respectively connected with three LCL filters to output DC power with high power quality.

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

(1) Integrating the functions of traditional distribution transformers and DFACTS controllers, it completely changes the rigid control structure of traditional transformers, making distribution network control more concise and flexible, and can not only provide high-quality AC power output but also provide high-quality DC power output;

(2) Propose the main technical scheme and main circuit topology of three-phase four-wire AC power supply and simultaneous DC power supply;

(3) A control strategy for multi-pole controlled AC-DC hybrid power supply and power quality control is proposed.

Description of drawings

Fig. 1 is a structural diagram of a traditional power supply mode in the prior art;

Figure 2 is a structural block diagram of a flexible AC-DC hybrid power supply system in a distribution network;

Fig. 3 is a topological structure diagram of the main circuit of AC and DC hybrid power supply and power quality control;

Fig. 4 is a flow chart of the control of the high-voltage stage unit;

Fig. 5 is a control flow chart of the low-voltage stage unit;

Fig. 6 is a control flow chart of the DC power supply unit.

Detailed ways

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

Flexible power distribution technology (Distribution FACTS, DFACTS), that is, Custom Power technology (CP), focuses on strengthening the controllability of power supply, improving power quality and solving the problem of distributed power grid connection. Applying DFACTS technology to the design of distribution transformers completely changes the rigid system structure of traditional distribution transformers and realizes fully flexible control, so that the distribution network not only has the functions of AC power transmission, voltage transformation and isolation, but also has DC power supply And the function of power quality control, completely changing the rigid control structure of the current power distribution system machinery, electromechanical and so on.

As shown in Figure 2, the present invention provides a flexible AC-DC hybrid power supply system for a distribution network. The system includes a high-voltage level unit, an isolation level unit, a low-voltage level unit, and a DC power supply unit; The level units are connected in sequence, and the high-voltage level unit and the isolation level unit, and the isolation level unit and the low-voltage level unit are all connected through a DC bus. The DC power supply unit is connected in parallel with the DC bus between the isolation level unit and the low voltage level unit.

The system is a three-phase four-wire AC-DC hybrid power supply system.

As shown in Figure 3 and Figure 4, the high-voltage stage unit includes a first AC/DC converter, and the first AC/DC converter includes a three-phase full-bridge rectifier active front end, a controller and auxiliary equipment; the controller generates a modulation signal Control the main circuit of the power electronic device of the active front end of the three-phase full-bridge rectification; the auxiliary equipment receives the modulation signal of the controller and generates a driving signal to drive the on-off of the power electronic device of the active front-end of the three-phase full-bridge rectification, It also protects the over-temperature, over-voltage and over-current of the active front end of the three-phase full-bridge rectification, realizes the variable detection and feedback control of the active front-end of the three-phase full-bridge rectification, and enables the active front-end of the three-phase full-bridge rectification to start safely, Shutdown and heat dissipation: the AC side of the first AC/DC converter is connected to the distribution network line, and the DC side is connected to the DC side of the first DC/AC converter of the isolation level unit through a DC bus.

The isolation level unit includes a first DC/AC converter, an isolation transformer and a second AC/DC converter.

The first DC/AC converter includes a single-phase H-bridge high-frequency resonant inverter, a controller and auxiliary equipment; the controller generates a modulation signal for the main circuit of the power electronic device of the single-phase H-bridge high-frequency resonant inverter Control, to realize the input of DC to high frequency AC square wave; the auxiliary equipment receives the modulation signal of the controller and generates a driving signal to drive the power electronic device of the single-phase H-bridge high-frequency resonant inverter on and off, and to control the single-phase The over-temperature, over-voltage and over-current of the H-bridge high-frequency resonant inverter are protected, so that the single-phase H-bridge high-frequency resonant inverter can be started, stopped and dissipated safely; the DC side of the first DC/AC converter is connected to the The high-voltage DC buses are connected in parallel, and the AC side outputs high-frequency AC square waves and is connected to the primary side of the isolation-level medium/high-frequency transformer.

The isolation stage transformer is an isolation transformer with 1 input on the primary side and 3 outputs on the secondary side; the primary side is connected in parallel with the high frequency square wave AC side of the first DC/AC converter of the isolation stage, and the secondary side has 3 interfaces They are respectively connected in parallel with the high-frequency square-wave AC sides of the three single-phase H-bridge high-frequency resonant rectifiers of the second AC/DC converter of the isolation stage.

The isolation transformer is an intermediate frequency isolation transformer or a high frequency isolation transformer.

The second AC/DC converter includes 3 single-phase H-bridge high-frequency resonant rectifiers, a controller and auxiliary equipment; the controller generates a modulation signal to the main circuit of the power electronic device of the 3 single-phase H-bridge high-frequency resonant rectifiers Control, to realize the input high-frequency square wave AC to DC conversion; the auxiliary equipment receives the modulation signal of the controller and generates a driving signal, which drives the power electronic device of the single-phase H-bridge high-frequency resonant rectifier on and off, and controls the single-phase H bridge The over-temperature, over-voltage and over-current of the bridge high-frequency resonant rectifier are protected, so that the single-phase H-bridge high-frequency resonant rectifier can be safely started, stopped and dissipated; the second AC/DC converter has three single-phase H-bridges on the AC side The high-frequency resonant rectifiers are respectively connected in parallel with the 3-way output of the secondary side of the isolation transformer, and the 3-way DC sides are respectively connected to the DC side of the 3 single-phase H-bridge inverters of the second DC/AC converter of the low-voltage stage through the DC bus. connected in parallel and respectively connected in parallel with the high-voltage sides of the three half-bridge choppers of the DC/DC converter of the DC power supply unit.

As shown in Figure 3 and Figure 5, the low-voltage level unit includes a second DC/AC converter, and the second DC/AC converter includes 3 single-phase H-bridge inverters, a controller, 3 LC filters and Auxiliary equipment; the controller generates a modulation signal to control the main circuit of the power electronic device of the three single-phase H-bridge inverters, and realizes the conversion of input DC to power frequency AC; the auxiliary equipment receives the modulation signal of the controller and generates a drive signal to The power electronic devices of the single-phase H-bridge inverter are driven on and off, and the over-temperature, over-voltage and over-current of the single-phase H-bridge inverter are protected to realize the variable detection and monitoring of the single-phase H-bridge inverter. Feedback control enables the single-phase H-bridge inverter to start, stop and dissipate heat safely; the DC sides of the three single-phase H-bridge inverters are respectively connected in parallel with the three DC buses of the isolation stage, and the AC sides are respectively connected to three LC filters The phases are connected in parallel to eliminate voltage harmonics and achieve the function of filtering. The output is connected by YN to form a three-phase four-wire output to achieve a power frequency AC output with constant three-phase voltage, sinusoidal waveform, and a phase difference of 120°.

As shown in Fig. 3 and Fig. 6, the DC power supply unit includes a DC/DC converter, and the DC/DC converter includes 3 half-bridge choppers, 3 LCL filters, a controller and auxiliary equipment; the controller generates The modulation signal controls the main circuits of the power electronic devices of the three half-bridge choppers to realize the DC conversion from the input DC to the required voltage level; the auxiliary equipment receives the modulation signal of the controller and generates a driving signal, which is used for the half-bridge chopper Drive the on-off of the power electronic devices, and protect the over-temperature, over-voltage and over-current of the half-bridge chopper, realize the variable detection and feedback control of the single-phase H-bridge inverter, and make the half-bridge chopper Safe start, stop and heat dissipation; the high-voltage sides of the three half-bridge choppers of the DC/DC converter are respectively connected in parallel with the three DC buses of the isolation stage, and the low-voltage sides are respectively connected with three LCL filters to output high power quality DC electricity.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: the present invention can still be Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention shall be covered by the scope of the claims of the present invention.

Claims (10)

1. a power distribution network flexible AC direct current mixed power supply system, it is characterized in that: described system comprises hiigh pressure stage unit, isolation level unit, low-pressure stage unit and DC power supply unit; Described hiigh pressure stage unit, isolation level unit and low-pressure stage unit are connected successively, between described hiigh pressure stage unit and isolation level unit, all be connected by DC bus between isolation level unit and low-pressure stage unit; Described DC power supply unit is in parallel with the DC bus between isolation level unit and low-pressure stage unit.

2. power distribution network flexible AC direct current mixed power supply system according to claim 1, is characterized in that: the AC/DC mixed power supply system that described system is three-phase four-wire system.

3. power distribution network flexible AC direct current mixed power supply system according to claim 1, it is characterized in that: described hiigh pressure stage unit comprises an AC/DC converter, and a described AC/DC converter comprises three phase full bridge rectification Active Front End, controller and auxiliary equipment; Controller produces modulation signal the power electronic device main circuit of three phase full bridge rectification Active Front End is controlled; Auxiliary equipment receives the modulation signal of controller and produces and drives signal, break-make to the power electronic device of three phase full bridge rectification Active Front End is driven, and excess temperature, overvoltage and the overcurrent of three phase full bridge rectification Active Front End are protected, the variable of realizing three phase full bridge rectification Active Front End detects and FEEDBACK CONTROL, makes the clean boot of three phase full bridge rectification Active Front End, shutdown and heat radiation; A described AC/DC converter AC access distribution network line, DC side is connected with a DC/AC converter DC side of isolation level unit by DC bus.

4. power distribution network flexible AC direct current mixed power supply system according to claim 1, it is characterized in that: described isolation level unit comprises a DC/AC converter, isolating transformer and the 2nd AC/DC converter.

5. power distribution network flexible AC direct current mixed power supply system according to claim 4, it is characterized in that: a described DC/AC converter comprises single-phase H bridge high-frequency resonant inverter, controller and auxiliary equipment; Controller produces modulation signal the power electronic device main circuit of single-phase H bridge high-frequency resonant inverter is controlled, and realizes that input direct-current is to the high-frequency ac square wave; Auxiliary equipment receives the modulation signal of controller and produces and drives signal, break-make to the power electronic device of single-phase H bridge high-frequency resonant inverter is driven, and excess temperature, overvoltage and the overcurrent of single-phase H bridge high-frequency resonant inverter are protected, make the clean boot of single-phase H bridge high-frequency resonant inverter, shutdown and heat radiation; A described DC/AC converter DC side is with hiigh pressure stage DC bus phase and connect, and AC output high-frequency ac square wave is connected with the medium/high frequency power transformer primary side of isolation level.

6. power distribution network flexible AC direct current mixed power supply system according to claim 4, is characterized in that: the isolating transformer that described isolation level transformer is primary side 1 tunnel input, secondary side 3 tunnel outputs; Primary side is with isolation level the one DC/AC converter high frequency square wave AC phase and connect, and 3 interfaces of secondary side are respectively with the high frequency square wave AC phase of 3 single-phase H bridge high-frequency resonant rectifiers of isolation level the 2nd AC/DC converter and connect.

7. power distribution network flexible AC direct current mixed power supply system according to claim 6, it is characterized in that: described isolating transformer is intermediate frequency isolating transformer or high-frequency isolation transformer.

8. power distribution network flexible AC direct current mixed power supply system according to claim 4, it is characterized in that: described the 2nd AC/DC converter comprises 3 single-phase H bridge high-frequency resonant rectifiers, controller and auxiliary equipment; Controller produces modulation signal the power electronic device main circuit of 3 single-phase H bridge high-frequency resonant rectifiers is controlled, and realizes the conversion of input high frequency square wave AC-to DC; Auxiliary equipment receives the modulation signal of controller and produces and drives signal, break-make to the power electronic device of single-phase H bridge high-frequency resonant rectifier is driven, and excess temperature, overvoltage and the overcurrent of single-phase H bridge high-frequency resonant rectifier are protected, make the clean boot of single-phase H bridge high-frequency resonant rectifier, shutdown and heat radiation; 3 single-phase H bridge high-frequency resonant rectifiers of described the 2nd AC/DC converter AC respectively with the secondary side 3 tunnels outputs of isolating transformer mutually and connect, 3 tunnel DC side are 3 single-phase H bridge inverter DC side phases by DC bus and low-pressure stage the 2nd DC/AC converter connect and respectively with the high-pressure side phase of 3 half-bridge choppers of the DC/DC converter of DC power supply unit and connect respectively.

9. power distribution network flexible AC direct current mixed power supply system according to claim 1, it is characterized in that: described low-pressure stage unit comprises the 2nd DC/AC converter, and described the 2nd DC/AC converter comprises 3 single-phase H bridge inverters, controller, 3 LC filters and auxiliary equipment; Controller produces modulation signal the power electronic device main circuit of 3 single-phase H bridge inverters is controlled, and realizes that input direct-current converts to industrial frequency AC; Auxiliary equipment receives the modulation signal of controller and produces and drives signal, break-make to the power electronic device of single-phase H bridge inverter is driven, and excess temperature, overvoltage and the overcurrent of single-phase H bridge inverter are protected, the variable of realizing single-phase H bridge inverter detects and FEEDBACK CONTROL, makes the clean boot of single-phase H bridge inverter, shutdown and heat radiation; 3 single-phase H bridge inverter DC side are respectively with 3 DC bus phases of isolation level and connect, AC is respectively with 3 LC filter phases and connect, eliminate voltage harmonic, reach the effect of filtering, output is pressed YN and is connect, formation three-phase and four-line output, realize that three-phase voltage is constant, waveform is sinusoidal, phase place differs mutually the industrial frequency AC output of 120 °.

10. power distribution network flexible AC direct current mixed power supply system according to claim 1, it is characterized in that: described DC power supply unit comprises the DC/DC converter, and described DC/DC converter comprises 3 half-bridge choppers, 3 LCL filters, controller and auxiliary equipment; Controller produces modulation signal the power electronic device main circuit of 3 half-bridge choppers is controlled, and realizes the DC converting of input direct-current to the required voltage grade; Auxiliary equipment receives the modulation signal of controller and produces and drives signal, break-make to the power electronic device of half-bridge chopper is driven, and excess temperature, overvoltage and the overcurrent of half-bridge chopper are protected, the variable of realizing single-phase H bridge inverter detects and FEEDBACK CONTROL, makes the clean boot of half-bridge chopper, shuts down heat radiation; The high-pressure side of 3 half-bridge choppers of described DC/DC converter is in parallel with 3 DC buss of isolation level respectively, and low-pressure side is connected with 3 LCL filters respectively, exports the direct current electricity consumption of the high quality of power supply.

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