WO2019165750A1

WO2019165750A1 - Protection apparatus, protection control method and modularized multi-level converter

Info

Publication number: WO2019165750A1
Application number: PCT/CN2018/096319
Authority: WO
Inventors: 符松格
Original assignee: 北京天诚同创电气有限公司
Priority date: 2018-02-28
Filing date: 2018-07-19
Publication date: 2019-09-06
Also published as: CN108448537B; CN108448537A

Abstract

A protection apparatus, a protection control method and a modularized multi-level converter. The protection apparatus comprises a plurality of protection devices (11) and a controller (12). Each protection device (11) comprises N capacitors (101), N direct-current short-circuit control units (102), and N+1 fast-acting fuses (103). The fast-acting fuses (103) are connected between a direct-current bus (104, 105) and a direct-current bus bar (204, 205, 206). The controller (12) is separately connected to the direct-current short-circuit control units (102) in each protection device (11), and is used for controlling the direct-current short-circuit control units (102) to be conducted.

Description

Protection device, protection control method and modular multilevel converter

Cross-reference to related applications

The present application claims priority to Chinese Patent Application No. 201 810 167 168 </ RTI> filed on February 28, 2018, entitled "Protection Equipment, Protection Control Method, and Modular Multi-Level Converter", the entire contents of which are incorporated by reference. Incorporated herein.

Technical field

The present application relates to the field of circuit electronics, and in particular, to a protection device, a protection control method, and a modular multi-level converter.

Background technique

A converter is an electrical device that changes the voltage, frequency, number of phases, and other electrical quantities or characteristics of a power system. In order to solve the problem of high current sharing in the converter, the converter is generally connected in parallel to meet the high current requirements of the converter.

The parallel mode of the converter is mainly as follows: the DC busbars of the converter are connected in parallel, and the AC output terminals are also connected in parallel, and each converter is controlled by a synchronous pulse control method.

When a converter in a parallel converter has a short-circuit fault, it is necessary to quickly remove the faulty converter to prevent the fault from expanding and affect the operation of other converters.

In order to protect the converter, a fast fuse is usually added on the DC side of the parallel branch, and the fast fuse is connected in series and operates. FIG. 1 is a topological schematic diagram of a converter with a DC fast fuse in the prior art. Among them, S1 to S6 in Fig. 1 are power semiconductor devices, 1 and 2 are fast fuses, DC+ is a positive DC bus, and DC- is a negative DC bus. When a short-circuit fault of the converter occurs, the heat of the short-circuit current on the DC side is accumulated to fuse the

fuses

1 and 2, while ensuring that the heat accumulation of the fuse does not malfunction during normal operation.

In the above manner, the fast-acting

fuses

1 and 2 are always connected in series and operate in the circuit. The fast-fuse continues to pass current and generates losses. When the working environment temperature is high, an additional cooling design of the quick-blow fuse is required, and the fuse is quickly blown. The selection of the device is more difficult.

In addition, when a short-circuit fault occurs in one power semiconductor device S1 in the converter, the short-circuit on the DC side is not caused, and the fast-blow fuse cannot be blown, and the protection effect is poor. At this time, the fault needs to be enlarged, and the power semiconductor device S2 connected in series with S1 is broken, so that the two power semiconductor devices connected in series are simultaneously short-circuited, so that the fast fuse can be blown. If the fault is enlarged, there will be a safety hazard and a safety accident will occur.

Summary of the invention

Embodiments of the present application provide a protection device, a protection control method, and a modular multilevel converter.

In one aspect, the embodiment of the present application provides a protection device for a modular multi-level converter, where the protection device includes: multiple protection devices and controllers;

Each protection device comprises: N capacitors, N DC short circuit control units and N+1 fast fuses, N being a positive integer not less than 1;

N capacitors are connected in series between the positive DC bus and the negative DC bus;

Each of the N capacitors is connected in parallel with one of the N DC short-circuit control units;

The positive DC bus is connected to the positive DC bus by the first quick fuse of the N+1 fast fuses;

The negative DC bus is connected to the negative DC bus bar through the N+1th fast fuse in the N+1 fast fuses;

The node in which the ith capacitor and the i+1th capacitor are connected in series is connected to the ith DC bus bus through the i+1th fast fuse in the N+1 fast fuses, 1≤i≤N-1;

The controller is respectively connected to the DC short-circuit control unit in each protection device for controlling the DC short-circuit control unit in the protection device connected to the multi-level converter module in which the short-circuit fault occurs.

On the other hand, the embodiment of the present application provides a protection control method, which is applied to the protection device provided by the embodiment of the present application. The method includes:

The controller determines that a short circuit fault occurs in the power semiconductor device in the multilevel converter module;

The controller controls the DC short-circuit control unit in the protection device connected to the multi-level converter module in which the short-circuit fault occurs.

In a further aspect, the embodiment of the present application provides a modular multi-level converter, including the protection device provided by the embodiment of the present application.

The protection device, the protection control method and the modular multi-level converter of the embodiment of the present application, the fast fuse is not connected in series in the circuit, only balances the current through a very small power, does not pass the operating current, and does not need a fast fuse The cooling design is carried out; and the fault can be prevented from being enlarged, and the converter that has not failed can be operated normally.

DRAWINGS

The present application can be better understood from the following description of the specific embodiments of the present application, in which:

Other features, objects, and advantages of the present invention will become more apparent from the description of the appended claims.

1 is a topological schematic diagram of a converter with a DC fast fuse in the prior art;

FIG. 2 is a schematic structural diagram of a protection device provided by an embodiment of the present application;

3 is a topological schematic diagram of a modular three-level wind power converter based on a protection device provided by an embodiment of the present application;

FIG. 4 is a schematic topological diagram of a multilevel converter module provided by an embodiment of the present application;

Figure 5 shows a schematic diagram of a process for protecting a modular multilevel converter;

FIG. 6 is a schematic flowchart diagram of a protection control method provided by an embodiment of the present application.

Detailed ways

Features and exemplary embodiments of various aspects of the present application are described in detail below. In the following detailed description, numerous specific details are set forth However, it will be apparent to those skilled in the art that the present disclosure may be practiced without some of the details. The following description of the embodiments is merely provided to provide a better understanding of the present application. In the drawings and the following description, at least some of the known structures and techniques are not shown in order to avoid unnecessary obscuring of the present application; and, for clarity, the dimensions of some of the structures may be exaggerated. The same reference numerals in the drawings denote the same or similar structures, and thus their detailed description will be omitted. Furthermore, the features, structures, or characteristics described hereinafter may be combined in any suitable manner in one or more embodiments.

The embodiment of the present application provides a protection device for a modular multi-level converter, the protection device includes: a plurality of protection devices and a controller;

The controller is respectively connected to the DC short-circuit control unit in each protection device for controlling the DC short-circuit control unit in the protection device connected to the multi-level converter module in which the short-circuit fault occurs to protect the power semiconductor from occurring Multi-level converter module for short-circuit faults in devices.

It should be noted that the ith DC bus bus is not a positive DC bus and is not a negative DC bus.

In the following, the protection device includes two protection devices, each of which includes two capacitors, two DC short-circuit control units, and three quick-blow fuses as an example.

FIG. 2 is a schematic structural diagram of a protection device provided by an embodiment of the present application. The protection device 100 includes two protection devices 11 and a controller 12.

The protection device 11 comprises two capacitors 101, two DC short-circuit control units 102 and three fast-acting fuses 103.

Two capacitors 101 are connected in series between the positive DC bus 104 and the negative DC bus 105.

Each of the capacitors 101 is connected in parallel with a DC short-circuit control unit 102.

The positive DC bus 104 is connected to the positive DC bus bar 204 through the first fast fuse 103.

The negative DC bus 105 is connected to the negative DC bus bar 206 via a third fast fuse 103.

The node in which the first capacitor 101 and the second capacitor 101 are connected in series is connected to the first DC bus bar 205 through the second fast fuse 103.

The controller 12 is respectively connected to the DC short-circuit control unit 102 in the protection device 11 for controlling the DC short-circuit control unit in the protection device connected to the multi-level converter module in which the short-circuit fault occurs to ensure that no power is generated. Multi-level converter module for short-circuit failure of semiconductor devices.

It can be understood that the converter of the embodiment of the present application includes but is not limited to a rectifier, an inverter, an AC drive, and a DC chopper. Based on this, the protection device of the embodiment of the present application can be applied to a wind power generator set, can also be applied to a photovoltaic power generation system, and can also be applied to an energy storage system and the like.

In an embodiment of the present application, the DC short-circuit control unit 102 may include a controllable thyristor.

The anode of the capacitor connected in parallel with the DC short-circuit control unit is connected to the anode of the controllable thyristor; the cathode of the capacitor connected in parallel with the DC short-circuit control unit is connected to the cathode of the controllable thyristor; and the control pole of the controllable thyristor is connected to the controller.

In an embodiment of the present application, the DC short-circuit control unit 102 may include: a controllable thyristor and a reactor.

The controllable thyristor and the reactor are connected in series; the control pole of the controllable thyristor is connected to the controller.

If one end of the reactor is connected to the anode of the controllable thyristor, the other end of the reactor is connected to the anode of the capacitor connected in parallel with the DC short-circuit control unit, and the cathode of the controllable thyristor is connected to the cathode of the capacitor connected in parallel with the DC short-circuit control unit.

If one end of the reactor is connected to the cathode of the controllable thyristor, the other end of the reactor is connected to the cathode of the capacitor connected in parallel with the DC short-circuit control unit, and the anode of the controllable thyristor is connected to the anode of the capacitor connected in parallel with the DC short-circuit control unit.

In one embodiment of the present application, the reactor may be an air core reactor, and the air core reactor can limit the short circuit current.

The following is an example in which a protection device is applied to a modular three-level wind power converter.

FIG. 3 shows a schematic topology diagram of a modular three-level wind power converter based on a protection device provided by an embodiment of the present application.

In Figure 3, M is a permanent magnet synchronous motor; 201, 202 and 203 are frame circuit breakers respectively; 204 is a positive DC bus bar, 205 is a neutral point NP DC bus bar (ie, the first DC bus bar), 206 is negative DC bus bars; 211, 212, 213, ..., 21N are multi-level converter modules, respectively, each multi-level converter module including a rectifier 21 and an inverter 22 and a protection device 100 A protection device 11. Q11, Q12, Q21, Q22, Q31, Q32, ..., QN1 and QN2 are contactors, respectively.

The multi-level converter module 211, the multi-level converter module 212, the multi-level converter module 213, ..., the motor side of the multi-level converter module 21N pass through the contactor Q11, respectively. The contactor Q21, the contactor Q31, ..., the contactor QN1 are connected to the motor side AC bus.

The motor side AC bus bar is connected to the permanent magnet synchronous motor M through the frame breaker 201 and the frame breaker 202.

The grid side of the multilevel converter module 211, the multilevel converter module 212, the multilevel converter module 213, ..., the multilevel converter module 21N passes through the contactor Q12, respectively. The contactor Q22, the contactor Q32, ..., the contactor QN2 are connected to the grid AC bus bar.

The grid AC busbar is connected to the grid via a frame breaker 203.

For the sake of clarity, the controller 12 included in the protection device 100 and its connection to the DC short-circuit control unit 102 in the protection device 11 are not shown in FIG.

The topology of the rectifier 21 and/or the inverter 22 of the embodiment of the present application may be a diode clamp type, a flying capacitor type, or a cascade type. The embodiment of the present application does not limit the topology of the multilevel converter module. Any possible manner can be applied to the embodiments of the present application.

FIG. 4 shows a topological schematic diagram of a multilevel converter module of an embodiment of the present application. The multilevel converter module includes a rectifier 21, an inverter 22, a protection device 11 of the protection device 100, and a braking unit 23.

The rectifier 21 includes 12 insulated gate bipolar transistor IGBT modules, which are an IGBT module T1 to an IGBT module T12, respectively.

The collectors of T1, T2 and T3 are respectively connected to the positive DC bus.

The emitter of T1 is electrically connected to the collector of T4, the collector of T7, and the L1 of the input three-phase power, respectively;

The emitter of T2 is electrically connected to the collector of T5, the collector of T9, and the L2 phase of the input three-phase power, respectively;

The emitter of T3 is electrically connected to the collector of T6, the collector of T11, and the L3 of the input three-phase power, respectively;

The emitters of T4, T5 and T6 are respectively connected to the negative DC bus.

The emitters of T7, T9 and T11 are connected to the emitters of T8, T10 and T12, respectively.

The collectors of T8, T10 and T12 are each connected to the junction point (i.e., neutral point NP) of the two capacitors C1 and C2 in the protection device 11.

The inverter 22 includes 12 IGBT modules, which are an IGBT module T15 to an IGBT module T26, respectively.

The collectors of T15, T16 and T17 are respectively connected to the positive DC bus.

The emitter of T15 is electrically connected to the collector of T18, the collector of T22, and the U phase of the three-phase power of the output;

The emitter of T16 is electrically connected to the collector of T19, the collector of T24, and the V phase of the three-phase power of the output;

The emitter of T17 is electrically connected to the collector of T20, the collector of T26, and the W phase of the three-phase power of the output;

The emitters of T18, T19 and T20 are respectively connected to the negative DC bus.

The emitters of T22, T24 and T26 are connected to the emitters of T21, T23 and T25, respectively.

The collectors of T21, T23 and T25 are all connected to the neutral point NP.

The brake unit 23 includes a braking resistor R and two IGBT modules, and the two IGBT modules are: IGBT module T13 to IGBT module T14.

The collector of T13 is connected to the positive DC bus. The emitter of T13 is connected to the collector of T14. The emitter of T14 is connected to the negative DC bus. The braking resistor R is connected in parallel with T14.

The three quick fuses in the protection device 11 are respectively 303, 304 and 305, wherein 303 is connected between the positive DC bus and the positive DC bus bar 204; 304 is connected to the neutral point NP and the neutral point NP DC bus bar. Between 205; 305 is connected between the negative DC bus and the negative DC bus 206.

The protection device 11 includes a DC short-circuit control unit 102 including a series controllable thyristor 301 and an air core reactor 306; the other DC short-circuit control unit 102 includes a series controllable thyristor 302 and an air core reactor 307.

For each converter module, three fast-fuse fuses are connected to the positive DC bus, the NP DC bus, and the negative DC bus. The positive DC bus, the NP DC bus, and the negative DC bus dynamically balance the DC bus voltage of each converter and maintain consistency. The three fast-blow fuses of each protection device are not connected in series in the circuit, only through a very small power balance current, and do not pass the operating current, so you can choose a small current fast fuse, which reduces the difficulty of fast fuse selection. In addition, the low-current fast-acting fuses are lower in price, which in turn saves costs. And because the fast fuse is not connected in series, the loss of the fast fuse during normal operation is reduced.

In an embodiment of the present application, the controller 12 may include: a detection module and a control module.

The detection module determines that a short circuit fault has occurred in the power semiconductor device in the rectifier 21 and the inverter 22.

The control module controls the DC short-circuit control unit in the protection device connected to the rectifier 21 and/or the inverter 22 in which the short-circuit fault occurs to be turned on to fuse the protection device connected to the rectifier 21 and/or the inverter 22 in which the short-circuit fault has occurred. The fast fuse in the protection of the multi-level converter module that does not cause a short circuit fault of the power semiconductor device.

In one embodiment of the present application, the control module can determine the location of the power semiconductor device where the short-circuit fault occurs, and the protection device that controls the connection of the modular multi-level converter that has a short-circuit fault with the power semiconductor device. The DC short-circuit control unit corresponding to the determined position is turned on.

Illustratively, when the power semiconductor device in which the short-circuit fault occurs is at least one of the IGBT modules T1, T2, T3, T15, T16, and T17 in FIG. 4, it is determined that the IGBT module in which the short-circuit fault occurs is located in the upper arm, The controllable thyristor 301 is closed to form a short circuit between the positive DC bus and the neutral point NP, and the fast fuses 303 and 304 are blown.

When the power semiconductor device in which the short-circuit fault occurs is at least one of the IGBT modules T4, T5, T6, T18, T19, and T20 in FIG. 3, it is determined that the IGBT module in which the short-circuit fault occurs is located at the lower arm, and the control is controllable The thyristor 302 is closed, forming a short circuit between the negative DC bus and the neutral point NP, and the fast fuses 305 and 304 are blown.

When the power semiconductor device in which the short-circuit fault occurs is at least one of the IGBT modules T13, T14, T7, T8, T9, T10, T11, T12, T21, T22, T23, T24, T25, and T26 in FIG. 4, it is determined When the IGBT module in which the short-circuit fault occurs is located at the zero-level bridge arm or the brake unit, the

controllable thyristors

301 and 302 are simultaneously closed, so that between the positive DC bus and the neutral point NP, between the negative DC bus and the neutral point NP All constitute a short circuit, and the

fuses

303, 304 and 305 are blown.

When the short circuit fault occurs simultaneously in the IGBT modules of the upper arm and the lower arm, the

controllable thyristors

301 and 302 are simultaneously closed, so that the positive DC bus and the neutral point NP, the negative DC bus and the neutral point NP Each of them constitutes a short circuit, and the

fuses

303, 304 and 305 are blown.

The fusing process of the quick-

blowers

303, 304, and 305 will be described below with reference to the case where the first multi-level converter module in FIG. 3 fails, taking the structure of FIG. Considering that the multi-level converter module is a single modular cabinet in industrial applications, in the following, the term "module cabinet" means a multi-level converter module.

The first state: the controllable thyristor 301 is turned on.

When the short-circuit fault of the upper arm T1, T2, T3, T15, T16, T17 is detected, the controllable thyristor 301 can be separately turned on to form a short circuit of the positive DC bus DC+ to NP. At the same time, the

frame breakers

201, 202 and 203 are issued a breaking command to maintain Q11 to QN1, and Q12 to QN2 are in a closed state. At this point, the DC capacitor bank of all module cabinets will first be discharged through the short-circuit path formed by the fast fuse and 301. When the DC bus voltage of DC+ to the negative DC bus DC- is lower than the uncontrolled rectified DC voltage, the three-phase AC current of the machine side and the net side flows into the DC bus through the freewheeling diode of the IGBT, and then passes through the short circuit path of 301 and NP to The DC-capacitor constitutes a short circuit. The upper half of the module fuses 303 and 304 in which the IGBT short-circuit failure occurs are responsible for N-1 times the discharge current of a single module cabinet (only DC+ to NP capacitor discharge), and the module cabinet without IGBT short-circuit failure The body is responsible for 1 times the discharge current of the single module cabinet. According to the I ² t melting law of the fast fuse (N-1 times the square of the discharge current, much larger than the square of the discharge current), the IGBT short circuit occurs. The failed module cabinet will first blow. When either of the 303 and 304 fast-acting fuses are blown (when either of the two fuses on the DC loop to DC+ is blown), the DC side of the module cabinet in which the IGBT failure has occurred is disconnected from the DC busbar. After the

frame breakers

201, 202 and 203 disconnect the AC short-circuit current, the controller controls the AC contactors Q11 and Q12 of the failed module cabinet to be disconnected, and the entire failed module cabinet is completely separated from the other module cabinets from the electrical circuit. . Then, the main controller controls the

frame breakers

201, 202 and 203 to reclose, and the other module cabinets resume work, completing the work of the entire automatic bypass fault module cabinet.

The second state: the controllable thyristor 302 is turned on.

When the short-circuit fault occurs in the lower half of the bridge arms T4, T5, T6, T18, T19, T20, the conduction can be controlled to form a short circuit of NP to DC-. At the same time, the

frame breakers

201, 202 and 203 are issued a breaking command to maintain Q11 to QN1, and Q12 to QN2 are in a closed state. At this point, the DC capacitor banks of all module cabinets are first discharged through the short-circuit path formed by the fast fuses and 302. When the DC bus voltage of DC+ to DC- is lower than the uncontrolled rectified DC voltage, the three-phase AC current of the machine side and the net side flows into the DC bus through the freewheeling diode of the IGBT, and then passes through the short circuit of 302 and the capacitance of DC+ to NP. Form a short circuit. The lower half of the module cabinets with IGBT short-circuit failures, the fast-blowers 304 and 305, are responsible for N-1 times the discharge current of a single module cabinet (only NP to DC-capacitor discharge), and modules without IGBT short-circuit failure The cabinet is responsible for 1 times the discharge current of a single module cabinet. According to the I ² t melting law of the fast-acting fuse (the square of the discharge current of N-1 times, which is much larger than the square of the discharge current of 1 time), the module cabinet in which the IGBT short-circuit fails will first be blown. When either of the 304 and 305 fast-acting fuses is blown (when either of the two fuses on the NP to DC-DC circuit is blown), the DC side of the module cabinet in which the IGBT failure has occurred is disconnected from the DC busbar. After the

frame breakers

201, 202 and 203 disconnect the AC short-circuit current, the controller controls the AC contactors Q11 and Q12 of the failed module cabinet to be disconnected, and the entire failed module cabinet is completely separated from the other module cabinets from the electrical circuit. open. Then, the main controller controls the

frame breakers

The third state: the

controllable thyristors

301 and 302 are simultaneously turned on.

Since the reactor is connected to the three-phase AC input side and the three-phase AC output side of the converter, and the DC bus of each converter is connected with a capacitor bank, when the

controllable thyristors

301 and 302 of the single module cabinet are connected In all time, the DC capacitor bank of all module cabinets will first be discharged through the short-circuit path formed by the fast fuse and 301, 302. When the DC bus voltage is lower than the uncontrolled rectified DC voltage, the three-phase AC current of the machine side and the grid side flows into the DC bus through the freewheeling diode of the IGBT, and then forms a short circuit through the short circuit of 301 and 302.

At this time, the

quick fuses

303 and 305 of the module cabinet in which the IGBT short-circuit fails are responsible for the discharge current of the N-1 times of the single module cabinet, and the module cabinet that does not have the IGBT short-circuit failure bears 1 times of the single module cabinet. The discharge current of the body is firstly fused according to the I ² t melting law of the fast-acting fuse (the square of the discharge current of N-1 times, which is much larger than the square of the discharge current of 1 time). The fast fuse 304 passes the short-circuit current in the opposite direction, and the magnitude of the current substantially cancels (when either of the fast-acting

fuses

303 and 305 is blown, 304 passes through the one-way short-circuit current and a fuse action occurs). When the 303 fast-blow fuse is blown, the 304 and 305 fast-acting fuses continue to bear N-1 times the discharge current of a single module cabinet. When either the 304 and 305 fast-blow fuses are blown (at this time, the three on the DC loop) The fuses blow at least two), and the DC side of the module cabinet in which the IGBT short-circuit failure occurs is disconnected from the DC bus. After the

frame breakers

In one embodiment of the present application, the power semiconductor device includes any of the following items:

Insulated gate bipolar transistor IGBT, integrated gate commutated thyristor IGCT, electron injection enhanced gate transistor IEGT, electrostatic induction thyristor SITH, power field effect transistor Power MOSFET.

Specifically, the detecting module detects that the power semiconductor device in the rectifier 21 and the inverter 22 enters the desaturation working area, that is, the short circuit fault of the power semiconductor device is detected, and the controller 12 approaches the frame breaker 201 and the frame breaker 202. And the frame breaker 203 sends a disconnection command; meanwhile, the DC short-circuit control unit 102 in the protection device 11 connected to the multi-level converter module that has a short-circuit fault of the power semiconductor device is turned on to constitute a DC short-circuit path. The multi-level converter module in the protection device that is connected to the rectifier 21 and/or the inverter 22 in which the short-circuit fault has occurred is blown to protect the multi-level converter module in which the short-circuit failure of the power semiconductor device does not occur.

A reactor is connected to both the three-phase AC input side of the rectifier 21 and the three-phase AC output side of the inverter 22. And the DC bus of each converter is connected with a capacitor bank. When the DC short-circuit control unit 102 in the protection device 11 in a single modular cabinet is turned on, the DC capacitor banks of all the modular cabinets will pass through the fast. The short circuit formed by the fuse and the DC short-circuit control unit 102 is discharged.

At this time, the fast fuse in the modular cabinet in which the power semiconductor device is short-circuited is responsible for the N-1 times the discharge current of the modular cabinet, and the rapid fuse in the modular cabinet without the short-circuit fault of the power semiconductor device The device is responsible for 1 times the discharge current of the modular cabinet. According to the fuse of the fast fuse, the quick fuse in the modular cabinet where the short circuit of the power semiconductor device occurs will be first blown.

When the three fast-acting fuses 103 are all blown or only one of the three fast-acting fuses 103 is not blown, the DC side of the modular cabinet in which the power semiconductor device is short-circuited is disconnected from the DC-current busbar to protect the power from occurring. Modular multilevel converter for short circuit faults in semiconductor devices.

In an embodiment of the present application, the detecting module can also detect the three-phase current on the output side of the converter in real time, when detecting that the output three-phase current exceeds the preset current threshold, and detecting the rectifier 21 and the inverter 22 The power semiconductor device is short-circuited, at which time the controller 12 sends a disconnection command to the frame breaker 201, the frame breaker 202, and the frame breaker 203; at the same time, controls the modular multi-level change of the short-circuit fault with the power semiconductor device. The DC short-circuit control unit 102 in the protection device 11 connected to the flow device is turned on to constitute a DC short-circuit path. The multi-level converter module in the protection device that is connected to the rectifier 21 and/or the inverter 22 in which the short-circuit fault has occurred is blown to protect the multi-level converter module in which the short-circuit failure of the power semiconductor device does not occur.

Incidentally, since the frame of the circuit breaker breaking operation time is normally 100ms (milliseconds, 10- ³ s) level, and the operation time is generally controlled thyristor 2-10us (microseconds, 10 ^-6 s) level. Therefore, after the frame breaker is first disconnected, the controllable thyristor action is still required to short-circuit the DC bus, thereby blowing the parallel fuse to protect the normal converter module.

In one embodiment of the present application, the detection module can also detect a blown state of the fast fuse in the protection device connected to the modular multilevel converter that has a short circuit fault with the power semiconductor device. When the detecting module detects that all three fast-acting fuses 103 are blown or only one of the three fast-acting fuses 103 is not blown, the control module controls the contactor connected to the modular multi-level converter that has a short-circuit fault of the power semiconductor device. Disconnecting; detecting whether the contactor connected to the modular multilevel converter that has a short circuit fault with the power semiconductor device is disconnected, and if it has been disconnected, reclosing the frame breaker 201, the frame breaker 202, and the frame breaker 203 The entire system is back to operation.

Based on the above description, the process of protecting the modular multilevel converter of the embodiment of the present application is as shown in FIG. 5. Figure 5 shows a schematic diagram of a process for protecting a modular multilevel converter. The general process of protecting a modular multilevel converter is as follows:

Detecting whether the power semiconductor device in the multilevel converter module has a short circuit fault; detecting whether the converter output three-phase current exceeds a preset current threshold.

If a short circuit fault occurs in the power semiconductor device and it is detected that the converter output three-phase current exceeds the preset current threshold, the frame breaker is broken.

The DC short-circuit control unit in the protection device connected to the multi-level converter module that generates a short-circuit fault of the power semiconductor device is turned on to constitute a DC short-circuit path.

The blown state of the fast fuse in the multilevel converter module in which the power semiconductor device is short-circuited is detected. And detecting the breaking state of the frame breaker.

If the quick-blow fuse in the multi-level converter module in which the short-circuit fault of the power semiconductor device is detected is completely blown or only one fast-blow fuse is not blown, and the frame breaker is completely disconnected, the short-circuit fault of the power semiconductor device is broken and generated. The contactor of the multilevel converter module is connected.

A state of a contactor connected to a multi-level converter module in which a short circuit fault of a power semiconductor device occurs is detected.

If it is detected that the contactor connected to the multi-level converter module in which the power semiconductor device is short-circuited is in the disconnected state, the frame breaker is reclosed and the entire system is resumed.

In the protection device of the embodiment of the present application, the fast fuse is not connected in series in the circuit, only balances the current through a very small power, and does not pass the operating current, so a fast fuse with a small current can be selected, and the selection of the fast fuse is reduced. Difficulty; in addition, the low-current fast-acting fuses are less expensive, which in turn saves costs. And because the fast fuse is not connected in series, the loss of the fast fuse during normal operation is reduced. In addition, there is no need to cool the design of the quick-blow fuse; it can prevent the fault from expanding and ensure the normal operation of the un-faulted converter; it can also reduce the occurrence of safety hazards and improve safety.

Based on the above description, the embodiment of the present application further provides a protection control method. It should be noted that the protection control method of the embodiment of the present application is preferably applicable to the protection device provided by the embodiment of the present application.

FIG. 6 is a schematic flowchart diagram of a protection control method provided by an embodiment of the present application. The method can include:

S601: The controller determines that a short circuit fault occurs in the power semiconductor device in the multilevel converter module.

S602: The controller controls the DC short-circuit control unit in the protection device connected to the multi-level converter module in which the short-circuit fault occurs to be turned on to protect the multi-level converter module in which the power semiconductor device short-circuit fault does not occur.

In one embodiment of the present application, the controller controls the DC short-circuit control unit in the protection device connected to the multi-level converter module in which the short-circuit fault of the power semiconductor device is turned on, including:

The controller determines the position of the power semiconductor device in which the short-circuit fault occurs, and controls the DC short-circuit control unit corresponding to the determined position in the protection device connected to the multi-level converter module in which the short-circuit fault of the power semiconductor device is connected .

In an embodiment of the present application, the modular multilevel converter protection method may further include:

The controller detects a blown state of the quick fuse in the protection device connected to the multilevel converter module in which the power semiconductor device is short-circuited;

If it is detected that the quick-blow fuse is in the blown state, the contactor connected to the multi-level converter module that has a short-circuit fault of the power semiconductor device is disconnected.

Insulated gate bipolar transistor IGBT, integrated gate commutated controllable thyristor IGCT, electronic injection enhanced gate transistor IEGT, electrostatic induction controllable thyristor SITH, power field effect transistor Power MOSFET.

For the details of the parts of the protection method provided by the embodiment of the present application, reference may be made to the description of the protection device of the embodiment of the present application, which is described in FIG. 2 to FIG.

The embodiment of the present application further provides a modular multi-level converter, including the protection device provided by the embodiment of the present application.

The application can be embodied in other specific forms without departing from the spirit and essential characteristics. The present embodiments are to be considered in all respects as illustrative and not restrict All changes in the scope are thus included in the scope of the present application. Also, different technical features that appear in different embodiments can be combined to achieve a beneficial effect. Other variations of the disclosed embodiments can be understood and effected by those skilled in the <RTIgt;

Claims

A protection device for a modular multi-level converter, characterized in that the protection device comprises: a plurality of protection devices and controllers;

Each of the protection devices includes: N capacitors, N DC short circuit control units, and N+1 fast fuses, N being a positive integer not less than one;

The N capacitors are connected in series between the positive DC bus and the negative DC bus;

Each of the N capacitors is respectively connected in parallel with one of the N DC short-circuit control units;

The positive DC bus is connected to the positive DC bus through the first one of the N+1 quick fuses;

The negative DC bus is connected to the negative DC bus through the N+1th fast fuse of the N+1 fast fuses;

The node in which the ith capacitor and the i+1th capacitor are connected in series is connected to the ith DC bus bus through the i+1th fast fuse in the N+1 fast fuses, 1≤i≤N-1 ;

The controller is respectively connected to the DC short-circuit control unit in each protection device for controlling the DC short-circuit control unit in the protection device connected to the multi-level converter module in which the short-circuit fault occurs.
The protection device according to claim 1, wherein the DC short-circuit control unit comprises: a controllable thyristor;

a positive electrode of the capacitor connected in parallel with the DC short-circuit control unit is connected to an anode of the controllable thyristor;

a cathode of the capacitor connected in parallel with the DC short-circuit control unit is connected to a cathode of the controllable thyristor;

The control electrode of the controllable thyristor is connected to the controller.
The protection device according to claim 1, wherein the DC short-circuit control unit comprises: a controllable thyristor and a reactor;

The controllable thyristor and the reactor are connected in series;

The control electrode of the controllable thyristor is connected to the controller.
The protection device of claim 1 wherein said controller comprises:

a detecting module for determining a short circuit fault of the power semiconductor device in the multilevel converter module;

And a control module for controlling conduction of the DC short-circuit control unit in the protection device connected to the multi-level converter module in which the short-circuit fault occurs.
The protection device according to claim 4, wherein the control module is specifically configured to:

The position of the power semiconductor device where the short-circuit fault occurs is determined, and the DC short-circuit control unit corresponding to the position is turned on in the protection device connected to the multi-level converter module in which the short-circuit fault has occurred.
The protection device according to claim 4, wherein the detecting module is further configured to:

Detecting a blown state of the quick fuse in the protection device connected to the multilevel converter module in which the short circuit fault occurs;

The control module is further configured to:

If the fast-blow fuse is in a blown state, the contactor connected to the multi-level converter module in which the short-circuit fault has occurred is controlled to be disconnected.
A protection control method, characterized in that it is applied to the protection device of claim 1, the method comprising:

The controller determines that a short circuit fault occurs in the power semiconductor device in the multilevel converter module;

The controller controls the DC short-circuit control unit in the protection device connected to the multi-level converter module in which the short-circuit fault occurs to be turned on.
The method according to claim 7, wherein the controller controls the DC short-circuit control unit in the protection device connected to the multi-level converter module in which the short-circuit fault occurs, including:

The controller determines a position at which the power semiconductor device in which the short-circuit fault occurs, and controls a DC short-circuit control unit corresponding to the position in the protection device connected to the multi-level converter module in which the short-circuit fault has occurred.
The method of claim 7, wherein the method further comprises:

The controller detects a blown state of the quick fuse in the protection device connected to the multi-level converter module in which the short-circuit fault occurs;

If it is detected that the fast-acting fuse is in a blown state, the contactor connected to the multi-level converter module in which the short-circuit fault has occurred is controlled to be disconnected.
A modular multilevel converter characterized by comprising the protection device according to any one of claims 1 to 6.