CN111987925B - Open-circuit fault ride-through method and system based on MMC - Google Patents

Open-circuit fault ride-through method and system based on MMC Download PDF

Info

Publication number
CN111987925B
CN111987925B CN202010700882.8A CN202010700882A CN111987925B CN 111987925 B CN111987925 B CN 111987925B CN 202010700882 A CN202010700882 A CN 202010700882A CN 111987925 B CN111987925 B CN 111987925B
Authority
CN
China
Prior art keywords
submodule
sub
module
group
fault
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active
Application number
CN202010700882.8A
Other languages
Chinese (zh)
Other versions
CN111987925A (en
Inventor
彭力
王臻
肖云涛
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Huazhong University of Science and Technology
Original Assignee
Huazhong University of Science and Technology
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Huazhong University of Science and Technology filed Critical Huazhong University of Science and Technology
Priority to CN202010700882.8A priority Critical patent/CN111987925B/en
Publication of CN111987925A publication Critical patent/CN111987925A/en
Application granted granted Critical
Publication of CN111987925B publication Critical patent/CN111987925B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/483—Converters with outputs that each can have more than two voltages levels
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/10—Measuring sum, difference or ratio
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/165—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values
    • G01R19/16566—Circuits and arrangements for comparing voltage or current with one or several thresholds and for indicating the result not covered by subgroups G01R19/16504, G01R19/16528, G01R19/16533
    • G01R19/16576—Circuits and arrangements for comparing voltage or current with one or several thresholds and for indicating the result not covered by subgroups G01R19/16504, G01R19/16528, G01R19/16533 comparing DC or AC voltage with one threshold
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
    • G01R31/54—Testing for continuity
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
    • H02M7/5387—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
    • H02M7/53871—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or current
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • H02M1/325—Means for protecting converters other than automatic disconnection with means for allowing continuous operation despite a fault, i.e. fault tolerant converters

Abstract

The invention discloses an open-circuit fault ride-through method and system based on MMC, belonging to the field of fault diagnosis of modular multilevel converters, wherein the method comprises the following steps: grouping a plurality of serially connected submodules on each bridge arm in the MMC into a plurality of submodule groups, and collecting output voltage measured values of the submodule groups; updating the capacitor voltage and the switch state of each submodule group according to the control period to obtain the output voltage estimation value of each submodule group; comparing the output voltage measured value and the output voltage estimated value corresponding to each submodule group to obtain a voltage difference value corresponding to each submodule group; and acquiring an open-circuit fault condition and a corresponding fault ride-through strategy according to the voltage difference value corresponding to each sub-module group. The method and the system provided by the invention can reduce the hardware burden and the maintenance cost of the MMC sub-module caused by a large number of voltage sensors, and simultaneously improve the fault detection efficiency of the MMC sub-module, thereby realizing open-circuit fault ride-through of the MMC and enhancing the operation stability of the MMC.

Description

Open-circuit fault ride-through method and system based on MMC
Technical Field
The invention belongs to the field of fault diagnosis of modular multilevel converters, and particularly relates to an open-circuit fault ride-through method and system based on an MMC (modular multilevel converter).
Background
Currently, Modular Multilevel Converters (MMC) are gaining wide attention in medium and high voltage application fields, which derives from its outstanding advantages: high efficiency, modularization, flexible expansibility, high output waveform quality and the like. Meanwhile, the MMC sub-modules are all provided with a voltage sensor to measure the capacitance voltage of the MMC, so that a large burden is brought to a hardware measuring system.
A large amount of research to MMC submodule piece open circuit trouble is based on MMC tradition structure, and its fault diagnosis time probably needs tens of milliseconds, leads to output current serious distortion, and trouble submodule piece capacitance voltage obviously exceeds the tolerance value, and MMC reliability is difficult to guarantee.
Disclosure of Invention
Aiming at the defects or improvement requirements of the prior art, the invention provides an MMC-based open-circuit fault ride-through method and system, aiming at reducing the hardware burden and maintenance cost of an MMC sub-module caused by a large number of voltage sensors and improving the fault detection efficiency of the MMC sub-module, thereby realizing the MMC open-circuit fault ride-through and enhancing the operation stability of the MMC, and further solving the technical problem of low fault detection efficiency of the MMC sub-module.
To achieve the above objects, according to one aspect of the present invention, an MMC-based open fault ride-through method and system are provided.
An open-circuit fault ride-through method based on MMC comprises the following steps:
grouping a plurality of serially connected submodules on each bridge arm in the MMC into a plurality of submodule groups, and collecting output voltage measured values of the submodule groups;
updating the capacitance voltage and the switch state of each submodule group according to the control period to obtain the output voltage estimation value of each submodule group;
comparing the output voltage measured value and the output voltage estimated value corresponding to each submodule group to obtain a voltage difference value corresponding to each submodule group;
and acquiring an open-circuit fault condition and a corresponding fault ride-through strategy according to the voltage difference value corresponding to each sub-module group.
In one embodiment, the obtaining the open-circuit fault condition and the corresponding fault ride-through policy according to the voltage difference value corresponding to each sub-module group includes:
if the voltage difference value d corresponding to the first sub-module group1Between (-k)1-e)Uc1～(-k1+e)Uc1Within the range, and if the current direction of the bridge arm where the first submodule group is located is negative, it is determined that k exists in the first submodule group1An open-circuit fault of a switch on a submodule, wherein e is an error threshold of the output voltage measurement value, Uc1For the first sub-module groupA capacitance voltage reference value for each sub-module;
obtaining N in a throw-in state at fault time1Individual suspicion submodule, in the next N1Within one control period, the N1The suspicion submodules are used by-pass in turn; if one of the suspect submodules is bypassed, d1Between (-k)1-e+1)Uc1～(-k1+e+1)Uc1If the current sub-module is in the range, the suspect sub-module is judged to be a fault sub-module, and the switch S1 on the suspect sub-module has an open-circuit fault;
investing N in the next control periodin1Submodule, Nin1And inputting the instruction value of the number of the sub-modules to the bridge arm where the first sub-module group is located.
In one embodiment, the obtaining the open-circuit fault condition and the corresponding fault ride-through policy according to the voltage difference value corresponding to each sub-module group includes:
if the voltage difference value d corresponding to the second sub-module group2Between (k)2-e)Uc2～(k2+e)Uc2Within the range, and if the current direction of the bridge arm where the second submodule group is located is positive, the fact that k exists in the second submodule group is judged2Sub-module lower switch S2 open circuit fault, Uc2E is a capacitance voltage reference value of each submodule of the second submodule group, and e is an error threshold value of the output voltage measured value;
obtaining N in bypass state at fault moment2Individual suspicion submodule, in the next N2Within one control period, the N2The suspicion submodules are put into use in turn; if one of the suspect submodules is put into use, d2Between (k)2-e-1)Uc2～(k2+e-1)Uc2If the current sub-module is in the range, the suspect sub-module is judged to be a fault sub-module, and the switch S2 is subjected to open-circuit fault;
investing in (N) the next said control periodin2-k2) Submodule, Nin2Is said secondAnd inputting the instruction value of the number of the sub-modules on the bridge arm where the sub-module group is located.
In one embodiment, the method further comprises:
if the current direction of the bridge arm where the fault submodule is located is positive in the period from the completion of fault positioning to the completion of isolation, the instruction value of the number of the input submodules on the bridge arm where the fault submodule is located is as follows:
Figure BDA0002592994360000031
wherein, U* armFor the output voltage command value of the bridge arm,
Figure BDA0002592994360000032
for the ith faulty submodule capacitor voltage within the group,
Figure BDA0002592994360000033
and the average value of the capacitance and the voltage of the normal submodule in the second submodule group is obtained.
In one embodiment, the obtaining the open-circuit fault condition and the corresponding fault ride-through policy according to the voltage difference value corresponding to each sub-module group includes:
if the voltage difference value d corresponding to the third sub-module group3Between- (1+ e) Uc3～-(1-e)Uc3Within the range, judging that one submodule in the third submodule group is isolated by a bypass, and Uc3The capacitance voltage reference value of each submodule in the third submodule group is obtained;
the number of throw-in sub-modules is increased in the next said control cycle to compensate for the level variations due to faulty sub-modules resulting from the natural throw-in to the isolation bypass.
In one embodiment, the obtaining the open-circuit fault condition and the corresponding fault ride-through policy according to the voltage difference value corresponding to each sub-module group includes:
if the voltage difference value d corresponding to the safety sub-module group0Between-e x Uc0～e*Uc0Within the range, judging that each switch in the safety submodule group has no fault, and not needing to carry out fault processing operation on each submodule group;
wherein e is an error threshold of the output voltage measurement value, Uc0And the reference value of the capacitance voltage of each submodule in the safety submodule group is obtained.
In one embodiment, the collecting the output voltage measurement value of each submodule group comprises: and measuring the output voltage measured value corresponding to each sub-module group by using the voltage sensor configured for each sub-module group.
An MMC-based open circuit fault ride-through system, comprising:
the acquisition module is used for grouping a plurality of serially connected submodules on each bridge arm in the MMC into a plurality of submodule groups and acquiring output voltage measurement values of the submodule groups;
the acquisition module is used for updating the capacitance voltage and the switch state of each submodule group according to the control period so as to acquire the output voltage estimation value of each submodule group;
the comparison module is used for comparing the output voltage measured value and the output voltage estimated value corresponding to each submodule group to obtain a voltage difference value corresponding to each submodule group;
and the processing module is used for acquiring an open-circuit fault condition and a corresponding fault ride-through strategy according to the voltage difference value corresponding to each submodule group.
Generally speaking, compared with the prior art, the technical scheme of the invention has the advantages that a plurality of serially connected submodules on each bridge arm in the MMC are grouped into a plurality of submodule groups, and the output voltage measured value of each submodule group is collected; updating the capacitance voltage and the switch state of each submodule group according to the control period to obtain the output voltage estimation value of each submodule group; comparing the output voltage measured value and the output voltage estimated value corresponding to each submodule group to obtain a voltage difference value corresponding to each submodule group; according to the voltage difference value corresponding to each submodule group, the open-circuit fault condition and the corresponding fault ride-through strategy are obtained, and the following beneficial effects can be achieved:
(1) the open-circuit fault can be rapidly and accurately detected and processed, fault positioning can be completed in a plurality of control cycles, output current distortion caused by open-circuit faults of the sub-modules is almost eliminated, and overvoltage of capacitors of the faulty sub-modules is remarkably suppressed;
(2) the detection of the fault isolation time is added, the seamless fault ride-through is realized, the reliability of the MMC is improved, and the power grid disturbance caused by the sub-module fault is avoided;
(3) the voltage sensors are used for replacing a large number of sub-module voltage sensors to collect the output voltage measured values of each sub-module group, so that the hardware cost and the maintenance cost can be obviously reduced.
Drawings
FIG. 1 is a schematic diagram of a MMC main circuit topology and sensor configuration of the present invention;
FIG. 2 is a flow chart of an MMC-based open circuit fault ride-through method in an embodiment of the present invention;
fig. 3 is a flowchart of steps of obtaining an open-circuit fault condition and a corresponding fault ride-through policy according to a voltage difference value corresponding to each submodule group in an embodiment of the present invention;
fig. 4 is a flowchart of steps of obtaining an open-circuit fault condition and a corresponding fault ride-through policy according to a voltage difference value corresponding to each submodule group in another embodiment of the present invention;
fig. 5 is a flow chart of a method for handling upper switch faults and lower switch faults in an embodiment of the invention.
The same reference numbers will be used throughout the drawings to refer to the same or like elements or structures, wherein,
an upper switch S1 and a lower switch S2.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
FIG. 1 is a schematic diagram of a MMC main circuit topology and a sensor configuration according to the present invention. Each bridge arm comprises N sub-modules { SM1，SM2，......，SMNIs divided into G sub-module groups (u)1，u2，......，uGAnd the number of submodules in each submodule group may be the same (as shown in fig. 1) or different, which is not limited herein. Each submodule group is only provided with one voltage sensor to measure the voltage of the output end of the submodule group. In addition, in order to isolate timely the faulty submodule within the submodule group, each submodule includes in addition to: on the basis of the complementary semiconductor switch S1 (upper switch), S2 (lower switch) and the capacitor C, a mechanical bypass switch is added on the output side for bypass processing when the sub-module fails. Compared with a semiconductor switch, the conduction loss of the mechanical switch is lower, but the response time is longer, and is generally 5-10 ms.
Fig. 2 is a flowchart of an MMC-based open circuit fault ride-through method in an embodiment of the present invention, and as shown in fig. 2, an MMC-based open circuit fault ride-through method includes: step 201 to step 204.
Step 201, grouping a plurality of serially connected submodules on each bridge arm in an MMC into a plurality of submodule groups, and collecting output voltage measured values of the submodule groups;
step 202, updating the capacitor voltage and the switch state of each submodule group according to a control period to obtain an output voltage estimation value of each submodule group;
step 203, comparing the output voltage measured value and the output voltage estimated value corresponding to each submodule group to obtain a voltage difference value corresponding to each submodule group;
and 204, acquiring an open-circuit fault condition and a corresponding fault ride-through strategy according to the voltage difference value corresponding to each submodule group.
Specifically, taking any submodule group of any bridge arm of the MMC as an example, it is assumed that the submodule group includes M submodules, and capacitance output voltage estimated values of the M submodules are respectively defined as u1，u2，…，uMThe corresponding sub-module switch states are respectively s1，s2，…，sM. The submodule has 2 switch states in normal mode: s1 is conducted, S2 is turned off, and the switch state is 1; s1 turns off S2 turns on, and the switch state is 0. Neglecting the conduction voltage drop of the switch tube, the estimated value u of the output voltage of the submodule groupeCan be expressed as: u. ofe＝s1*u1+s2*u2+…+sM*uM. The output voltage estimated value u of the submodule groupeOutput voltage measured value u measured by voltage sensor in the submodule groupmComparing to obtain deviation value d, d is equal to um-ue. And judging whether an open-circuit fault exists in the submodules in the submodule group or not according to the value interval of d. And if the open-circuit fault exists, acquiring the fault type, and positioning and fault ride-through processing the fault. It should be added that the open faults of the submodules include a fault of the upper switch S1, a fault of the lower switch S2, and a fault of both the upper switch S1 and the lower switch S2. As the upper switch S1 and the lower switch S2 are simultaneously opened, the current loop only flows through one of the upper switch S1 and the lower switch S2 at the same time, so the actual influence of the fault on the MMC is equivalent to the fault of S1 or S2, and the fault diagnosis and processing mode can be classified into the first two faults.
In the embodiment, the voltage sensors are used for collecting the output voltage measurement values of each submodule group instead of the submodule voltage sensors with huge number, so that the hardware cost and the maintenance cost can be obviously reduced. Meanwhile, fault detection and fault location are carried out through voltage difference values corresponding to the submodules, open-circuit faults can be processed quickly and efficiently, and accordingly stability of the MMC is improved.
In one embodiment, the plurality of sub-module groups includes at least one first sub-module group, and as shown in fig. 3, the step of obtaining the open-circuit fault condition and the corresponding fault-ride through policy according to the voltage difference value corresponding to each sub-module group may include: step 301 to step 303.
Step 301, if the voltage difference d corresponding to the first sub-module group1Between (-k)1-e)Uc1～(-k1+e)Uc1Within the range, and the current direction of the bridge arm where the first submodule group is located is negative, the situation that k exists in the first submodule group is judged1Open-circuit fault of switch on submodule, where e is error threshold of output voltage measured value, Uc1The capacitance voltage reference value of each submodule in the first submodule group is set;
step 302, obtaining N in a throw-in state at fault time1Individual suspicion submodule, in the next N1Within one control period, N is added1The suspicion submodules are used by-pass in turn; if one of the suspect submodules is bypassed, d1Between (-k)1-e+1)Uc1～(-k1+e+1)Uc1Within the range, one suspect submodule is judged to be a fault submodule and the switch S1 on the suspect submodule is subjected to open-circuit fault;
step 303, inputting N in the next control periodin1Submodule, Nin1And inputting the instruction value of the number of the sub-modules for the bridge arm where the first sub-module group is located.
Specifically, if there is a voltage difference d corresponding to at least one first sub-module group in the plurality of sub-module groups1Between (-k)1-e)Uc1～(-k1+e)Uc1Within the range, if the bridge arm current direction is negative (positive in the same direction as the current direction in fig. 1, and negative in the opposite direction to the current direction in fig. 1), it indicates that k is in the first submodule group1The upper switch S1 of the sub-module has an open fault. And assuming that the capacitance voltage reference values of all the submodules in the first submodule group are the same, marking as Uc1. e is set according to the error of the voltage sensor corresponding to the first sub-module group, and e is more than or equal to 0.1<0.5. If the error of the voltage sensor is small enough, 0.1 can be obtained, and in order to ensure that the fault misdiagnosis is avoided, the value is smaller than the critical value of 0.5. Preferably, e is 0.4, and the practical application of the method is that the e is 0.4In the case of various voltage sensor accuracies. Suppose that there is N in the submodule group at the moment of failure detection1When the sub-module is in the input state, the N is set1The sub-module is regarded as N1Individual suspicion submodule. At the next N1Within one control period, N is added1The suspicion submodules are used by-pass in turn; if a suspect submodule is bypassed, d1Between (-k)1+(1-e))Uc1～(-k1+(1+e))Uc1Within the range, the upper switch S1 of the suspect submodule is judged to have open-circuit fault. In addition, during the next MMC operation, k is added1Each fault sub-module is set to be in a natural bypass state, and in order to ensure that the bridge arm voltage still follows the instruction value, the number of sub-modules which are input by the bridge arm control is still Nin1And (4) respectively. As shown in fig. 5, fault detection, fault location, and reconstruction after fault are realized based on the above steps.
The embodiment can quickly and accurately detect and process the open circuit fault, can complete fault positioning in a plurality of control cycles, almost eliminates output current distortion caused by open circuit faults of the sub-modules, and obviously inhibits the overvoltage of capacitors of the faulty sub-modules.
In one embodiment, the plurality of sub-module groups includes at least one second sub-module group, as shown in fig. 4, the step of obtaining the open-circuit fault condition and the corresponding fault-ride through policy according to the voltage difference value corresponding to each sub-module group may include: step 401 to step 403.
Step 401, if the voltage difference d corresponding to the second sub-module group2Between (k)2-e)Uc2～(k2+e)Uc2Within the range, and the current direction of the bridge arm where the second submodule group is located is positive, the fact that k exists in the second submodule group is judged2Sub-module lower switch S2 open circuit fault, Uc2The reference value of the capacitance voltage of each submodule of the second submodule group is set, and e is the error threshold value of the output voltage measured value;
step 402, obtaining N in bypass state at fault time2Individual suspicion submodule, in the next N2Within one control period, N is added2Alternative investment of suspicion submodulesThe use is carried out; if one of the suspect submodules is put into use, d2Between (k)2-e-1)Uc2～(k2+e-1)Uc2Within the range, one suspect submodule is judged to be a fault submodule, and the switch S2 under the suspect submodule has an open-circuit fault;
step 403, invest in the next control period (N)in2-k2) Submodule, Nin2And inputting the instruction value of the number of the sub-modules for the bridge arm where the second sub-module group is located.
Specifically, assuming that e is 0.4, if there is at least one voltage difference d corresponding to a second submodule group in the plurality of submodule groups2Between (k)2-0.4)Uc2～(k2+0.4)Uc2In the range (k)2Is a positive integer), and the direction of the bridge arm current is positive, it indicates that k is in the second submodule group2The sub-module lower switch S2 has an open fault. The capacitance voltage reference values of all the submodules of the second submodule group are the same and are marked as Uc2. Assume that there is N in the group at the time of failure detection2The sub-module is in bypass state, then in the next N2Within one control period, the N2The suspicion submodules are put into use in turn, and when a certain suspicion submodule is put into use, the voltage difference value d2Between (k-1.4) Uc2～(k-0.6)Uc2Within range, it indicates that the sub-module' S2 has an open fault. Furthermore, since k is2The fault sub-modules are in a natural input state, and in order to ensure that the bridge arm voltage still follows the instruction value, the number of the sub-modules which are input by the bridge arm control is (N)in2-k2). As shown in fig. 5, fault detection, fault localization, and operation with fault are achieved based on the above steps. In addition, fault isolation detection and reconstruction after fault can be carried out.
The embodiment can quickly and accurately detect and process the open circuit fault, can complete fault positioning in a plurality of control cycles, almost eliminates output current distortion caused by open circuit faults of the sub-modules, and obviously inhibits the overvoltage of capacitors of the faulty sub-modules.
In one embodiment, the method further comprises: if the current direction of the bridge arm where the fault submodule is located is positive in the period from the completion of fault positioning to the completion of isolation, the instruction value of the number of the input submodules on the bridge arm where the fault submodule is located is as follows:
Figure BDA0002592994360000091
wherein, U* armFor the output voltage command value of the bridge arm,
Figure BDA0002592994360000092
for the ith faulty submodule capacitor voltage within the group,
Figure BDA0002592994360000093
and the average value of the capacitance and the voltage of the normal submodule in the second submodule group is obtained.
In one embodiment, the step of obtaining the open-circuit fault condition and the corresponding fault ride-through policy according to the voltage difference value corresponding to each submodule group may further include: if the plurality of sub-module groups comprise at least one third sub-module group, the voltage difference value d corresponding to the third sub-module group3Between- (1+ e) Uc3～-(1-e)Uc3Within the range, judging that one submodule in the third submodule group is isolated by a bypass, and recording the capacitance voltage reference value of each submodule in the third submodule group as Uc3(ii) a The number of input sub-modules is increased in the next control cycle to compensate for the level variation due to the faulty sub-module resulting from the natural input to the isolation bypass. The detection of the fault isolation time is added in the embodiment, the seamless fault ride-through is realized, the reliability of the MMC is improved, and the power grid disturbance caused by sub-module faults is avoided.
In one embodiment, the obtaining of the open-circuit fault condition and the corresponding fault ride-through policy according to the voltage difference value corresponding to each submodule group includes: if the voltage difference value d corresponding to the safety sub-module group0Between-e x Uc0～e*Uc0Within the range, each switch in the safety submodule group is judged to have no faultThe fault processing operation is not required to be carried out on each of the plurality of sub-module groups; wherein e is the error threshold of the output voltage measurement value, and e is more than or equal to 0.1<0.5. The capacitance voltage reference values of all the submodules in the safety submodule group are the same and are marked as Uc0。
In one embodiment, collecting the output voltage measurement value of each submodule group comprises: and measuring the output voltage measured value corresponding to each submodule group by using the voltage sensor configured for each submodule group.
In one embodiment, since the output side of each sub-module is provided with a mechanical bypass switch, after fault location is implemented, the open-circuit fault ride-through method based on the MMC may further include:
and if the sub-module has the fault of the upper switch S1, sending a bypass signal to the mechanical bypass switch corresponding to the sub-module with the fault S1, wherein the switch function of the corresponding sub-module is constantly 0.
If the submodule has a fault of a lower switch S2, sending a bypass signal to a mechanical bypass switch corresponding to the submodule with the fault of S2, and when the current direction of a bridge arm is positive, taking 1 as a switch function of the corresponding submodule; and when the current direction of the bridge arm is negative, the switching function of the corresponding sub-module is 0.
If sub-modules S1 and S2 simultaneously have faults, the corresponding mechanical bypass switch sends out a bypass signal, and when the current direction of the bridge arm is positive, the switch function of the corresponding sub-module takes 1; and when the current direction of the bridge arm is negative, the switching function of the corresponding sub-module is 0.
An embodiment of the present application further provides an open circuit fault ride-through system based on an MMC, including: the device comprises an acquisition module, a comparison module and a processing module. The acquisition module is used for grouping a plurality of serially connected submodules on each bridge arm in the MMC into a plurality of submodule groups and acquiring output voltage measurement values of the submodule groups; the acquisition module is used for updating the capacitance voltage and the switch state of each submodule group according to the control period so as to acquire the output voltage estimation value of each submodule group; the comparison module is used for comparing the output voltage measured value and the output voltage estimated value corresponding to each submodule group to obtain a voltage difference value corresponding to each submodule group; and the processing module is used for acquiring an open-circuit fault condition and a corresponding fault ride-through strategy according to the voltage difference value corresponding to each submodule group.
In one embodiment, the processing module is configured to determine the voltage difference d corresponding to the first sub-module group1Between (-k)1-e)Uc1～(-k1+e)Uc1Within the range, and the current direction of the bridge arm where the first submodule group is located is negative, the situation that k exists in the first submodule group is judged1Open-circuit fault of switch on submodule, where e is error threshold of output voltage measured value, Uc1The capacitance voltage reference value of each submodule in the first submodule group is set; obtaining N in a throw-in state at fault time1Individual suspicion submodule, in the next N1Within one control period, N is added1The suspicion submodules are used by-pass in turn; if one of the suspect submodules is bypassed, d1Between (-k)1-e+1)Uc1～(-k1+e+1)Uc1Within the range, one suspect submodule is judged to be a fault submodule and the switch S1 on the suspect submodule is subjected to open-circuit fault; throwing N in the next control periodin1Submodule, Nin1And inputting the instruction value of the number of the sub-modules for the bridge arm where the first sub-module group is located.
In one embodiment, the processing module is further configured to determine a voltage difference d corresponding to the second sub-module group2Between (k)2-e)Uc2～(k2+e)Uc2Within the range, and the current direction of the bridge arm where the second submodule group is located is positive, the fact that k exists in the second submodule group is judged2Sub-module lower switch S2 open circuit fault, Uc2The reference value of the capacitance voltage of each submodule of the second submodule group is set, and e is the error threshold value of the output voltage measured value; obtaining N in bypass state at fault moment2Individual suspicion submodule, in the next N2Within one control period, N is added2The suspicion submodules are put into use in turn; if one of the suspect submodules is put into use, d2Between (k)2-e-1)Uc2～(k2+e-1)Uc2Within the range, one of them is determinedThe suspect submodule is a fault submodule and the switch S2 under the suspect submodule has an open-circuit fault; put into the next control cycle (N)in2-k2) Submodule, Nin2And inputting the instruction value of the number of the sub-modules for the bridge arm where the second sub-module group is located.
In one embodiment, the processing module is further configured to determine a voltage difference d corresponding to the third sub-module group3Between- (1+ e) Uc3～-(1-e)Uc3Within the range, judging that one submodule in the third submodule group is isolated by a bypass, and Uc3The capacitance voltage reference value of each submodule in the third submodule group; the number of input sub-modules is increased in the next control cycle to compensate for the level variation due to the faulty sub-module resulting from the natural input to the isolation bypass.
It will be understood by those skilled in the art that the foregoing is merely a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included within the scope of the present invention.

Claims (6)

1. An open-circuit fault ride-through method based on MMC is characterized by comprising the following steps:
s1: grouping a plurality of serially connected submodules on each bridge arm in the MMC into a plurality of submodule groups, wherein each submodule group comprises: an upper switch S1, a lower switch S2, a capacitor C and a mechanical bypass switch; collecting output voltage measured values of each submodule group;
s2: updating the capacitance voltage and the switch state of each submodule group according to the control period to obtain the output voltage estimation value of each submodule group;
s3: comparing the output voltage measured value and the output voltage estimated value corresponding to each submodule group to obtain a voltage difference value corresponding to each submodule group;
s4: acquiring an open-circuit fault condition and a corresponding fault ride-through strategy according to the voltage difference value corresponding to each sub-module group;
the S4 includes:
the plurality of sub-module groups comprise at least one first sub-module group, and if the voltage difference value d corresponding to the first sub-module group1Between (-k)1-e)Uc1～(-k1+e)Uc1Within the range, and if the current direction of the bridge arm where the first submodule group is located is negative, it is determined that k exists in the first submodule group1Open-circuit failure of a switch on a submodule, e is an error threshold of the output voltage measurement value, Uc1The capacitance voltage reference value of each submodule in the first submodule group is obtained; obtaining N in a throw-in state at fault time1Individual suspicion submodule, in the next N1Within one control period, the N1The suspicion submodules are used by-pass in turn; if one of the suspect submodules is bypassed, d1Between (-k)1-e+1)Uc1～(-k1+e+1)Uc1If the current sub-module is in the range, the suspect sub-module is judged to be a fault sub-module, and the switch S1 on the suspect sub-module has an open-circuit fault; investing N in the next control periodin1Submodule, Nin1Inputting the instruction value of the number of the sub-modules for the bridge arm where the first sub-module group is located;
the plurality of sub-module groups comprise at least one second sub-module group, and if the voltage difference value d corresponding to the second sub-module group2Between (k)2-e)Uc2～(k2+e)Uc2Within the range, and if the current direction of the bridge arm where the second submodule group is located is positive, the fact that k exists in the second submodule group is judged2Sub-module lower switch S2 open circuit fault, Uc2E is a capacitance voltage reference value of each submodule of the second submodule group, and e is an error threshold value of the output voltage measured value; obtaining N in bypass state at fault moment2Individual suspicion submodule, in the next N2Within one control period, the N2The suspicion submodules are put into use in turn; if one of the suspect submodules is put into use, d2Between (k)2-e-1)Uc2～(k2+e-1)Uc2Within the range, the suspect submodule is judged to be a fault submodule and the switch is turned onS2 open circuit fault; investing in (N) the next said control periodin2-k2) Submodule, Nin2And inputting the instruction value of the number of the sub-modules to the bridge arm where the second sub-module group is located.
2. The MMC-based open circuit fault ride-through method of claim 1, further comprising:
if the current direction of the bridge arm where the fault submodule is located is positive in the period from the completion of fault positioning to the completion of isolation, the instruction value of the number of the input submodules on the bridge arm where the fault submodule is located is as follows:
Figure FDA0003325780850000021
wherein, U* armFor the output voltage command value of the bridge arm,
Figure FDA0003325780850000022
for the ith faulty submodule capacitor voltage within the group,
Figure FDA0003325780850000023
and the average value of the capacitance and the voltage of the normal submodule in the second submodule group is obtained.
3. The MMC-based open circuit fault ride-through method of claim 1, wherein the plurality of sub-module groups comprises at least one third sub-module group, and the obtaining of the open circuit fault condition and the corresponding fault ride-through strategy according to the voltage difference value corresponding to each of the sub-module groups comprises:
if the voltage difference value d corresponding to the third sub-module group3Between- (1+ e) Uc3～-(1-e)Uc3Within the range, judging that one submodule in the third submodule group is isolated by a bypass, and Uc3The capacitance voltage reference value of each submodule in the third submodule group is obtained;
the number of throw-in sub-modules is increased in the next said control cycle to compensate for the level variations due to faulty sub-modules resulting from the natural throw-in to the isolation bypass.
4. The MMC-based open circuit fault ride-through method according to any of claims 1-3, wherein the plurality of submodule groups includes at least one safety submodule group, and the obtaining the open circuit fault condition and the corresponding fault ride-through strategy according to the voltage difference value corresponding to each submodule group comprises:
if the voltage difference value d corresponding to the safety sub-module group0Between-e x Uc0～e*Uc0Within the range, judging that each switch in the safety submodule group has no fault, and not needing to carry out fault processing operation on each submodule group;
wherein e is an error threshold of the output voltage measurement value, Uc0And the reference value of the capacitance voltage of each submodule in the safety submodule group is obtained.
5. The MMC-based open circuit fault ride-through method of any of claims 1-3, wherein the collecting output voltage measurements for each of the sub-module groups comprises:
and measuring the output voltage measured value corresponding to each sub-module group by using the voltage sensor configured for each sub-module group.
6. An MMC-based open circuit fault ride-through system, comprising:
the acquisition module is used for grouping a plurality of serially connected submodules on each bridge arm in the MMC into a plurality of submodule groups and acquiring output voltage measurement values of the submodule groups;
the acquisition module is used for updating the capacitance voltage and the switch state of each submodule group according to the control period so as to acquire the output voltage estimation value of each submodule group;
the comparison module is used for comparing the output voltage measured value and the output voltage estimated value corresponding to each submodule group to obtain a voltage difference value corresponding to each submodule group;
the processing module is used for acquiring an open-circuit fault condition and a corresponding fault ride-through strategy according to the voltage difference value corresponding to each submodule group;
the processing module is further configured to,
the plurality of sub-module groups comprise at least one first sub-module group, and if the voltage difference value d corresponding to the first sub-module group1Between (-k)1-e)Uc1～(-k1+e)Uc1Within the range, and if the current direction of the bridge arm where the first submodule group is located is negative, it is determined that k exists in the first submodule group1An open-circuit fault of a switch on a submodule, wherein e is an error threshold of the output voltage measurement value, Uc1The capacitance voltage reference value of each submodule in the first submodule group is obtained; obtaining N in a throw-in state at fault time1Individual suspicion submodule, in the next N1Within one control period, the N1The suspicion submodules are used by-pass in turn; if one of the suspect submodules is bypassed, d1Between (-k)1-e+1)Uc1～(-k1+e+1)Uc1If the current sub-module is in the range, the suspect sub-module is judged to be a fault sub-module, and the switch S1 on the suspect sub-module has an open-circuit fault; investing N in the next control periodin1Submodule, Nin1Inputting the instruction value of the number of the sub-modules for the bridge arm where the first sub-module group is located;
the plurality of sub-module groups comprise at least one second sub-module group, and if the voltage difference value d corresponding to the second sub-module group2Between (k)2-e)Uc2～(k2+e)Uc2Within the range, and if the current direction of the bridge arm where the second submodule group is located is positive, the fact that k exists in the second submodule group is judged2Sub-module lower switch S2 open circuit fault, Uc2E is a capacitance voltage reference value of each submodule of the second submodule group, and e is an error threshold value of the output voltage measured value; obtaining N in bypass state at fault moment2The suspicion submodule is connected withFrom N2Within one control period, the N2The suspicion submodules are put into use in turn; if one of the suspect submodules is put into use, d2Between (k)2-e-1)Uc2～(k2+e-1)Uc2If the current sub-module is in the range, the suspect sub-module is judged to be a fault sub-module, and the switch S2 is subjected to open-circuit fault; investing in (N) the next said control periodin2-k2) Submodule, Nin2And inputting the instruction value of the number of the sub-modules to the bridge arm where the second sub-module group is located.
CN202010700882.8A 2020-07-20 2020-07-20 Open-circuit fault ride-through method and system based on MMC Active CN111987925B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202010700882.8A CN111987925B (en) 2020-07-20 2020-07-20 Open-circuit fault ride-through method and system based on MMC

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202010700882.8A CN111987925B (en) 2020-07-20 2020-07-20 Open-circuit fault ride-through method and system based on MMC

Publications (2)

Publication Number Publication Date
CN111987925A CN111987925A (en) 2020-11-24
CN111987925B true CN111987925B (en) 2022-03-18

Family

ID=73439467

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202010700882.8A Active CN111987925B (en) 2020-07-20 2020-07-20 Open-circuit fault ride-through method and system based on MMC

Country Status (1)

Country Link
CN (1) CN111987925B (en)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113933752B (en) * 2021-09-09 2022-06-17 华中科技大学 IGBT open-circuit fault detection method and device for cascaded H-bridge converter

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104597370A (en) * 2015-02-16 2015-05-06 哈尔滨工业大学 State observer-based detection method of open-circuit fault of IGBT (insulated gate bipolar transistor) of MMC (modular multilevel converter)

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104597370A (en) * 2015-02-16 2015-05-06 哈尔滨工业大学 State observer-based detection method of open-circuit fault of IGBT (insulated gate bipolar transistor) of MMC (modular multilevel converter)

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
兼具开路故障诊断能力的MMC电容电压测量方法;张正发等;《电力系统自动化》;20170410;第41卷(第7期);第114-119,167页 *

Also Published As

Publication number Publication date
CN111987925A (en) 2020-11-24

Similar Documents

Publication Publication Date Title
CN111562517B (en) NPC three-level inverter switching tube open-circuit fault diagnosis method
KR101331028B1 (en) Fault switch diagnosis apparatus and method of 3 level t type inverter
WO2021184820A1 (en) Two-level three-phase voltage source inverter bridge arm open-circuit fault diagnosis method
CN108828387B (en) MMC submodule open-circuit fault integrated diagnosis method
US20210296713A1 (en) Detection method and detection device for branch states of battery system
CN103344866A (en) Open-circuit fault diagnosis method of current transformer of permanent-magnet direct-drive type wind power generation system
CN111077471A (en) NPC three-level inverter open-circuit fault diagnosis method based on instantaneous frequency
CN111987925B (en) Open-circuit fault ride-through method and system based on MMC
CN109655703B (en) Self-checking method, device and equipment for parallel power modules and storage medium
CN105675957A (en) MMC module voltage measuring and fault locating method based on state monitoring
CN110988742A (en) Open-circuit fault diagnosis method for modular multilevel converter based on quartile
CN110518820A (en) A kind of fault tolerant control method and system of T-type three-level inverter open-circuit fault
CN113281680A (en) Open-circuit fault diagnosis method for single-phase three-level rectifier of high-speed rail traction system
CN112540261A (en) Method and system for rapidly detecting open-circuit fault of MMC sub-module device
CN111679226A (en) Open-circuit fault diagnosis and positioning method for MMC sub-module switching tube
CN104898071A (en) Fault diagnosis method for modularized multi-level inverter based on state observation
CN113281678B (en) Method for positioning open-circuit fault of tubes on half-bridge submodule of modular multilevel converter
CN113358997B (en) MMC submodule IGBT open-circuit fault diagnosis method based on fault model
CN104950201A (en) Fault diagnosis method of modular multilevel inverter based on state observation
CN109444621B (en) Online detection method for power module current of high-power NPC three-level inverter
CN112731193B (en) NPC inverter multi-class fault diagnosis method based on sliding-mode observer
CN114545133B (en) Fault diagnosis method of single-phase cascade H-bridge rectifier based on current detection
CN114994457A (en) MMC switching tube open-circuit fault diagnosis and positioning method based on double sliding-mode observers
CN114865601A (en) Fault judgment method and system based on variable quantity criterion
CN114172401B (en) NPC three-level inverter multi-class fault diagnosis method based on reduced order observer

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant