CN104426403B - Module unit suitable for high-capacity modularized multi-level voltage source converter - Google Patents

Abstract

The invention discloses a module unit suitable for a large-capacity modular multi-level voltage source converter, which includes a separate converter unit and a fixed DC energy storage unit connected to each other; The plate is movably installed on the bottom plate and can move back and forth on the bottom plate; the separated current conversion unit is installed on the partition plate, and the fixed DC energy storage unit is installed on the bottom plate. This structure can solve the problem that the transmission power is restricted by the device and the maintenance is inconvenient in the current flexible power transmission. The voltage source converter based on this modular unit can increase the power transmission, high equipment efficiency, high reliability of fault protection, and good equipment maintainability. .

Description

A modular unit suitable for large-capacity modular multilevel voltage source converters

technical field

The invention belongs to the field of flexible direct current transmission, and in particular relates to a converter valve module unit suitable for a large-capacity modular multi-level voltage source converter.

Background technique

The core of the flexible DC transmission system is the voltage source converter based on fully controlled devices. Multi-level technology is the optimal solution for realizing high-voltage and large-capacity voltage source converters. Compared with the two-level converter, the multi-level converter can use low-voltage devices to achieve high-voltage level output without direct series connection of switching devices. In recent years, the emergence of Modular Multilevel Converter (MMC) has enabled the successful application of MMC in the field of flexible DC transmission.

The converter valve of the modular multilevel converter adopts a modular design, which is composed of several basic unit sub-modules with the same structure in series. Each sub-module is called a converter valve module unit. By adding The number and current level of the sub-modules in series can increase the voltage and power level of the converter valve. However, due to the development of fully controlled turn-off devices is limited by the development of semiconductor technology, its flow capacity cannot keep up with the development level of large-capacity converter valves, so the transmission power of converter valves is limited to a certain extent.

The modular multilevel converter uses the cascading of modular units to solve the problem of direct series connection of fully controlled devices, but each module requires a large-capacity DC support capacitor to stabilize the voltage. With the continuous improvement of the power level of the converter , The volume, weight and other factors of the DC support capacitor will become the bottleneck of the maintenance and repair of the converter valve.

Contents of the invention

The purpose of the present invention is to provide a modular unit suitable for large-capacity modular multi-level voltage source converters, which can solve the problems of current flexible power transmission being restricted by devices and inconvenient maintenance. Based on this modular unit The advanced voltage source converter can increase the transmission power, has high equipment efficiency, high reliability of fault protection, and good equipment maintainability.

In order to achieve the above object, the solution of the present invention is:

A modular unit suitable for large-capacity modular multi-level voltage source converters, including interconnected separate converter units and fixed DC energy storage units; also includes a bottom plate and a partition, and the partition is movable It is arranged on the base plate and can move back and forth on the base plate; the separated current conversion unit is installed on the partition plate, and the fixed DC energy storage unit is installed on the base plate.

The above-mentioned fixed DC energy storage unit includes a DC energy storage capacitor or at least two DC energy storage capacitors connected in parallel, and the modular unit also includes a first laminated busbar, and all DC energy storage capacitors pass through the first laminated busbar Parallel connection is performed, and the first laminated busbar is fixed on the bottom plate through a frame.

The above separated converter unit includes a bypass switch, 4 power semiconductor switching devices and a secondary control and protection unit, the emitter of the first power semiconductor switching device is connected to the collector of the second power semiconductor switching device, and the third power semiconductor switching device The emitter of the bypass switch is connected to the collector of the fourth power semiconductor switching device, and the collectors of the first and third power semiconductor switching devices are connected, the emitters of the second and fourth power semiconductor switching devices are connected, and one end of the bypass switch is connected to the first Two, the collectors of the four power semiconductor switching devices, and the other end is connected to the emitters of the second and fourth power semiconductor switching devices; the control terminals of the bypass switch and the four power semiconductor switching devices are connected to the secondary control and protection unit;

The module unit also includes a power semiconductor switching device radiator and a second stacked busbar, the power semiconductor switching device radiator is installed on the partition near the fixed DC energy storage unit, and the power semiconductor switching devices are all Installed on the heat sink of the power semiconductor switching device, the second laminated busbar is covered on the power semiconductor switching device; the secondary control and protection unit is set on the lower side of the power semiconductor switching device radiator, and the bypass switch is set on the power The outside of the semiconductor switching device heat sink.

The above-mentioned modular unit also includes at least one water pipe, one end of which is connected to the radiator of the power semiconductor switching device, and the other end is connected to a water source.

The above separated converter unit also includes 4 freewheeling diodes of power semiconductor switching devices and 1 power diode. connected in antiparallel with the second power semiconductor switching device;

The module unit also includes a power diode radiator, and both the power diode and the power diode radiator are arranged on the upper side of the bypass switch.

The above-mentioned modular unit also includes at least one water pipe, one end of the water pipe is connected to the power diode radiator, and the other end is connected to a water source.

After adopting the above scheme, the present invention integrates the fixed DC energy storage unit and the separate converter unit to form the smallest modular unit that constitutes the complete function of the voltage source converter. Through the orderly cascading of the modular units, an applicable For voltage source converters with different voltages and different powers, it has the following beneficial effects:

(1) The separate converter unit is a relatively independent whole, which is fixed on the partition and can move back and forth on the bottom plate. The electrical connection is designed to be detachable, which can be flexibly disassembled on site;

(2) All full-control switching devices are placed in a closed space, and there is no risk of parts splashing when the device fails;

(3) The power diode is used to form overcurrent protection for the freewheeling diode of the power semiconductor switching device connected in parallel, which improves the protection reliability and improves the efficiency of the converter;

(4) The control protection unit includes a full-control switch device driver board, a subunit control board and a power supply, and all electronic circuits are located in the closed area on the back of the full-control switch device and the heat sink of the full-control switch device to ensure the relative independence of electricity .

Description of drawings

Fig. 1 is the front view of the present invention;

Fig. 2 is a top view of the present invention;

Fig. 3 is an electrical schematic diagram of the present invention.

detailed description

The technical solutions of the present invention will be described in detail below in conjunction with the accompanying drawings.

The present invention provides a modular unit suitable for large-capacity modular multi-level voltage source converters, including a fixed DC energy storage unit 3 and a separate converter unit 6. Firstly, as shown in Figure 3, the separate converter unit Unit 6 includes bypass switch K1, 4 power semiconductor switching devices T1, T2, T3, T4, 4 power semiconductor switching devices freewheeling diodes D1, D2, D3, D4, voltage equalizing discharge resistor R1 and secondary control and protection unit KZ1, the fixed DC energy storage unit 3 includes a DC energy storage capacitor or at least two DC energy storage capacitors C1-Cn (n≥2); wherein, T1 and D1 are connected in antiparallel, T2 and D2 are connected in reverse parallel, and T1 The emitter of T3 is connected to the collector of T2, T3 and D3 are connected in antiparallel, T4 and D4 are connected in reverse parallel, and the emitter of T3 is connected to the collector of T4, and the collector of T1 is connected to the collector of T3, T2 and T4 Emitter connection; K1 can use a mechanical holding switch, one end of which is connected to the collectors of T2 and T4, and the other end is connected to the emitters of T2 and T4; one end of R1 is connected to the collectors of T1 and T3, and the other end is connected to The emitters of T2 and T4; the control terminals of the bypass switch K1 and the four power semiconductor switching devices T1-T4 are connected to the secondary control and protection unit KZ1, and the on or off state of each device is controlled by KZ1; The fixed DC energy storage unit 3 is connected in parallel to both ends of the voltage equalizing discharge resistor R1. The foregoing is a common connection structure of existing modular units, and will not be repeated here.

The improvement of the present invention lies in that it further includes a bottom plate 1, a separator 2, a first laminated busbar 4 and a second laminated busbar 5, which will be introduced respectively below.

As shown in Figure 1, the separator 2 is installed on the base plate 1, and can move back and forth on the base plate 1 to realize flexible disassembly on site; the fixed DC energy storage unit 3 is installed on the base plate 1, and the separate inverter The unit 6 is installed on the partition 2, and can move back and forth on the bottom plate 1 with the partition 2; the separated converter unit 6 and the fixed DC energy storage unit 3 are connected by a detachable electrical connection, which is convenient for on-site maintenance It is separated from the heavy fixed DC energy storage unit 3 to facilitate the maintenance and replacement of the module unit.

All the DC energy storage capacitors in the fixed DC energy storage unit 3 are connected in parallel through the first laminated busbar 4, and then the first laminated busbar 4 is fixed on the base plate 1 through the frame.

Separate converter unit 6 includes power semiconductor switching device 13 (ie T1-T4 in Figure 3), power semiconductor switching device radiator 10, bypass switch 7 (ie K1 in Figure 3), secondary control and protection unit 14 (that is, KZ1 in Figure 3), the equalizing discharge resistor and the freewheeling diode of the power semiconductor switching device, the separate converter unit 6 is connected to the fixed DC energy storage unit 3 through the second laminated busbar 5, which can be conveniently installed on site Carry out separation and maintenance work in a timely manner.

In this embodiment, the separated converter unit 6 also includes a power diode D5 (ie, 12 in FIG. 2 ) and a power diode radiator 11. As shown in FIG. 3 , D5 is connected in parallel with D2 and D4 in the same direction, so that The overcurrent protection of D2 and D4 is realized, and the protection reliability is improved. At the same time, since the performance of the power diode D5 is better than that of the power semiconductor switching device freewheeling diode, the loss of the module unit is small, and the efficiency of the entire converter is improved.

As shown in FIG. 2, the power semiconductor switching device radiator 10 is installed on the partition plate 2, and is arranged close to the fixed DC energy storage unit 3, and the power semiconductor switching devices 13 are all installed on the power semiconductor switching device radiator 10 above, and in a relatively closed space, there will be no risk of parts splashing when the device fails; the second stacked busbar 5 covers the power semiconductor switching device 13; the power semiconductor switching device radiator 10 can be set One or more to meet the heat dissipation requirements.

The secondary control protection unit 14 is arranged on the lower side of the power semiconductor switching device radiator 10, and the bypass switch 7 is arranged on the outside of the power semiconductor switching device radiator 10, and the power diode 12 and the power diode radiator 11 are all arranged on the The upper side of the bypass switch 7.

In this embodiment, a water pipe 9 is also provided. As shown in FIG. 1, both the power semiconductor switching device 13 and the power diode 12 adopt a water-cooled heat dissipation method, and the connection mode of the water circuit in the module unit can be connected in series or in parallel, depending on the heat dissipation power. The power semiconductor switching device radiator 10 and the power diode radiator 11 are connected to the external water source through the water pipe 9 .

The secondary control and protection unit 14 includes a drive unit, a main control board and a DC power supply, and the electronic circuit is located in a closed cavity, which effectively reduces the interference of the external electromagnetic environment on the secondary board.

In summary, the present invention is a modular unit suitable for large-capacity modular multi-level voltage source converters. The separate converter unit is designed as a relatively independent whole, and the electrical connection is designed as a detachable type; the fixed Both the DC energy storage unit and the separated converter unit are supported by the bottom plate 1, and can be installed and replaced together, which can solve the problems of current flexible transmission power being restricted by devices and inconvenient maintenance.

The above embodiments are only to illustrate the technical idea of the present invention, and cannot limit the protection scope of the present invention. Those of ordinary skill in the art should understand that any modification or equivalent replacement to the specific implementation of the present invention without departing from the technical idea and scope of the present invention should be covered by the claims of the present invention. among.

Claims (5)

1. A modular unit suitable for large-capacity modular multilevel voltage source converters, comprising interconnected separate converter units and fixed DC energy storage units; characterized in that: it also includes a base plate and a partition, The separator is movably installed on the bottom plate and can move back and forth on the bottom plate; the separated current conversion unit is installed on the separator, and the fixed DC energy storage unit is installed on the bottom plate; The separated converter unit includes a bypass switch, four power semiconductor switching devices and a secondary control and protection unit, the emitter of the first power semiconductor switching device is connected to the collector of the second power semiconductor switching device, and the third power semiconductor switching device The emitter of the device is connected to the collector of the fourth power semiconductor switching device, and the collectors of the first and third power semiconductor switching devices are connected, the emitters of the second and fourth power semiconductor switching devices are connected, and one end of the bypass switch is connected to The collectors of the second and fourth power semiconductor switching devices, and the other ends are connected to the emitters of the second and fourth power semiconductor switching devices; the control terminals of the bypass switch and the four power semiconductor switching devices are all connected to the secondary control and protection unit; The module unit also includes a power semiconductor switching device radiator and a second stacked busbar, the power semiconductor switching device radiator is installed on the partition near the fixed DC energy storage unit, and the power semiconductor switching devices are all Installed on the heat sink of the power semiconductor switching device, the second laminated busbar is covered on the power semiconductor switching device; the secondary control and protection unit is set on the lower side of the power semiconductor switching device radiator, and the bypass switch is set on the power The outside of the semiconductor switching device heat sink. 2. A modular unit suitable for large-capacity modular multilevel voltage source converters as claimed in claim 1, wherein the fixed DC energy storage unit includes a DC energy storage capacitor or at least 2 DC energy storage capacitors connected in parallel, the module unit also includes a first laminated busbar, all DC energy storage capacitors are connected in parallel through the first laminated busbar, and the first laminated busbar is fixed on the frame through the frame bottom plate. 3. A modular unit suitable for large-capacity modular multilevel voltage source converters according to claim 1, characterized in that: said modular unit also includes at least one water pipe, one end of which is connected to The radiator of the power semiconductor switching device, the other end is connected to the water source. 4. A modular unit suitable for large-capacity modular multilevel voltage source converters as claimed in claim 1, characterized in that: said separate converter unit also includes four power semiconductor switching devices for freewheeling a diode and one power diode, the freewheeling diodes of the four power semiconductor switching devices are respectively connected in antiparallel to the four power semiconductor switching devices, and the power diode is connected in antiparallel to the second power semiconductor switching device; The module unit also includes a power diode radiator, and both the power diode and the power diode radiator are arranged on the upper side of the bypass switch. 5. A modular unit suitable for large-capacity modular multilevel voltage source converters as claimed in claim 4, characterized in that: said modular unit also includes at least one water pipe, one end of which is connected to Power diode radiator, the other end is connected to water source.