CN108322072B - Capacity reduction operation method and device of modular multilevel converter - Google Patents

Capacity reduction operation method and device of modular multilevel converter Download PDF

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Publication number
CN108322072B
CN108322072B CN201810051387.1A CN201810051387A CN108322072B CN 108322072 B CN108322072 B CN 108322072B CN 201810051387 A CN201810051387 A CN 201810051387A CN 108322072 B CN108322072 B CN 108322072B
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bridge arm
sub
modular multilevel
multilevel converter
upper bridge
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CN108322072A (en
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闻福岳
张帆
李帅
赵成勇
陈光焰
许建中
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State Grid Corp of China SGCC
North China Electric Power University
State Grid Fujian Electric Power Co Ltd
NARI Group Corp
China EPRI Electric Power Engineering Co Ltd
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State Grid Corp of China SGCC
North China Electric Power University
State Grid Fujian Electric Power Co Ltd
NARI Group Corp
China EPRI Electric Power Engineering Co Ltd
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    • 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
    • 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
    • H02M7/4835—Converters with outputs that each can have more than two voltages levels comprising two or more cells, each including a switchable capacitor, the capacitors having a nominal charge voltage which corresponds to a given fraction of the input voltage, and the capacitors being selectively connected in series to determine the instantaneous output voltage
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]

Abstract

The invention provides a capacity reducing operation method and device of a modular multilevel converter, which are characterized in that the number of sub-modules put into upper bridge arms of the modular multilevel converter is firstly obtained, then the number of the sub-modules put into the upper bridge arms of the modular multilevel converter is respectively judged to be in an increasing stage or a decreasing stage under the condition that the number of the sub-modules put into the upper bridge arms of the modular multilevel converter is smaller than N/2 and larger than N/2, and switching control of corresponding bridge arm reactors is carried out, so that the capacity reducing operation of the modular multilevel converter is realized, and the capacity reducing effect is obvious; the method has the advantages of simple process, no need of complex operation, lower requirement on the controller of the modular multilevel converter, low investment cost and only need of adding a few thyristors; compared with CCSC, the fundamental frequency and the double frequency component of the voltage waveform of the capacitor of the submodule can be reduced to a greater extent, so that the voltage fluctuation of the capacitor of the submodule can be further reduced, and the method has certain significance for further reducing the weight of the submodule of the converter.

Description

Capacity reduction operation method and device of modular multilevel converter
Technical Field
The invention relates to the technical field of direct current transmission, in particular to a capacity reduction operation method and device of a modular multilevel converter.
Background
The high-voltage direct-current transmission technology based on the voltage source converter, particularly the modular multilevel converter, is called as flexible direct-current transmission in China, and due to various advantages, more and more attention is paid to the high-voltage and extra-high-voltage direct-current transmission technology. The advantages of the inverter are due to the low inertia of the power electronics. The direct-current side voltage of the converter is supported by the capacitance voltage of the input sub-modules through controlling the corresponding power electronic devices, the volume of the converter station is determined by the number of the sub-modules and the volume of each sub-module, and the capacitance of the sub-modules for storing energy accounts for 80% of the volume of the sub-modules. With the increasing transmission voltage level and transmission capacity, in addition to considering some common problems such as stability of the MMC converter station, the problem of increasing the occupied area of the converter station becomes very prominent due to the increase of the volume of the sub-module capacitor capacity. And the manufacturing cost of the capacitor is not a small proportion for the sub-modules. In order to keep the ripple of the capacitor within a certain range, that is, to reduce the capacitance value of the capacitor, the capacitance reduction operation method of the modular multilevel converter in the prior art mainly suppresses the negative-sequence circulating current component of the bridge arm through the control strategy of the secondary system, so as to reduce the ripple amplitude of the capacitor voltage of the sub-module, and further achieve the purpose of reducing the capacitance value of the capacitor. However, the method needs a very complex control algorithm to achieve the purpose of circulation suppression, and the proportion of the negative sequence circulation component is small, so that the capacity reduction effect of the method is poor.
Disclosure of Invention
In order to overcome the defect of poor capacity reduction effect in the prior art, the invention provides a capacity reduction operation method and a capacity reduction operation device of a modular multilevel converter, which are used for acquiring the number of sub-modules input by an upper bridge arm of the modular multilevel converter, then respectively judging that the number of the sub-modules input by the upper bridge arm is in an increase stage or a decrease stage under the two conditions that the number of the sub-modules input by the upper bridge arm of the modular multilevel converter is smaller than N/2 and the number of the sub-modules input by the upper bridge arm of the modular multilevel converter is larger than N/2, and carrying out switching control on corresponding bridge arm reactors, so that the capacity reduction operation of the modular multilevel converter is realized, and the capacity reduction effect is obvious.
In order to achieve the purpose of the invention, the invention adopts the following technical scheme:
in one aspect, the present invention provides a capacity reduction operation method for a modular multilevel converter, including:
acquiring the number of sub-modules input by an upper bridge arm of the modular multilevel converter;
when the number of the sub-modules input into the upper bridge arm of the modular multilevel converter is smaller than N/2, judging that the number of the sub-modules input into the upper bridge arm is in an increasing stage or a decreasing stage, if the number of the sub-modules input into the upper bridge arm is in the increasing stage, cutting off the bridge arm reactors in the lower bridge arm and inputting the bridge arm reactors in the upper bridge arm when the number change rate of the sub-modules input into the upper bridge arm is equal to a first change rate set value; if the bridge arm reactor is in the reduction stage, cutting off the bridge arm reactor in the upper bridge arm and putting the bridge arm reactor in the lower bridge arm;
when the number of the sub-modules input into the upper bridge arm of the modular multilevel converter is larger than N/2, judging that the number of the sub-modules input into the upper bridge arm is in an increasing stage or a decreasing stage, if the number is in the increasing stage, cutting off a bridge arm reactor in a lower bridge arm and inputting the bridge arm reactor in the upper bridge arm; if the number of the input sub-modules of the upper bridge arm is equal to a second change rate set value, cutting off bridge arm reactors in the upper bridge arm and inputting bridge arm reactors in the lower bridge arm;
and N represents the number of sub-modules in the upper bridge arm.
The modular multilevel converter comprises three upper bridge arms and three lower bridge arms, wherein the upper bridge arms and the lower bridge arms respectively comprise a capacity reduction circuit and a plurality of sub-modules;
and after being connected in series, the sub-modules are connected in series with the capacitance reducing circuit.
The capacity reducing circuit comprises a bridge arm reactor L1, a bridge arm reactor L2 and a switching circuit which are connected in series;
the switching circuit is connected with the bridge arm reactor L1 in parallel and comprises a first branch and a second branch which are connected in anti-parallel.
The step of judging whether the number of the submodules input by the upper bridge arm is in an increasing stage or a decreasing stage comprises the following steps:
if it is
Figure BDA0001552440140000021
The number of the sub-modules put into the upper bridge arm is in an increasing stage;
if it is
Figure BDA0001552440140000022
The number of the sub-modules put into the upper bridge arm is in a reduction stage;
wherein, the first and the second end of the pipe are connected with each other,
Figure BDA0001552440140000023
and representing the change rate of the number of the input sub-modules of the upper bridge arm.
When the modular multilevel converter is in an inversion running state, the cutting off the bridge arm reactors in the lower bridge arm and putting the bridge arm reactors in the upper bridge arm comprises the following steps:
and triggering all thyristors in the first branch of the lower bridge arm to cut off the bridge arm reactor in the lower bridge arm, and locking all thyristors in the first branch of the upper bridge arm to realize the input of the bridge arm reactor in the upper bridge arm.
When the modular multilevel converter is in a rectifying operation state, the cutting off the bridge arm reactors in the lower bridge arm and putting the bridge arm reactors in the upper bridge arm comprises the following steps:
and triggering all thyristors in the second branch of the lower bridge arm to cut off the bridge arm reactors in the lower bridge arm, and locking all thyristors in the second branch of the upper bridge arm to realize the input of the bridge arm reactors in the upper bridge arm.
When the modular multilevel converter is in an inversion running state, the cutting off the bridge arm reactors in the upper bridge arm and putting the bridge arm reactors in the lower bridge arm comprises the following steps:
and triggering all thyristors in the first branch of the upper bridge arm to cut off the bridge arm reactor in the upper bridge arm, and locking all thyristors in the first branch of the lower bridge arm to realize the input of the bridge arm reactor in the lower bridge arm.
When the modular multilevel converter is in a rectifying operation state, the cutting off the bridge arm reactors in the upper bridge arm and putting the bridge arm reactors in the lower bridge arm comprises the following steps:
and triggering all thyristors in the second branch of the upper bridge arm to cut off the bridge arm reactors in the upper bridge arm, locking all thyristors in the second branch of the lower bridge arm and inputting the bridge arm reactors in the lower bridge arm.
In another aspect, the present invention further provides a capacity reduction operation apparatus for a modular multilevel converter, including:
the acquisition module is used for acquiring the number of sub-modules input by an upper bridge arm of the modular multilevel converter;
the control module is used for judging that the number of the sub-modules put into the upper bridge arm of the modular multilevel converter is in an increasing stage or a decreasing stage when the number of the sub-modules put into the upper bridge arm of the modular multilevel converter is smaller than N/2, and cutting off a bridge arm reactor in a lower bridge arm and putting the bridge arm reactor in the upper bridge arm when the number change rate of the sub-modules put into the upper bridge arm is equal to a first change rate set value if the number of the sub-modules put into the upper bridge arm is in the increasing stage; if the bridge arm reactor is in the reduction stage, cutting off the bridge arm reactor in the upper bridge arm and putting the bridge arm reactor in the lower bridge arm;
when the number of the sub-modules input into the upper bridge arm of the modular multilevel converter is larger than N/2, judging that the number of the sub-modules input into the upper bridge arm is in an increasing stage or a decreasing stage, if the number is in the increasing stage, cutting off a bridge arm reactor in a lower bridge arm and inputting the bridge arm reactor in the upper bridge arm; if the number of the input sub-modules of the upper bridge arm is equal to a second change rate set value, cutting off bridge arm reactors in the upper bridge arm and inputting bridge arm reactors in the lower bridge arm;
and N represents the number of sub-modules in the bridge arm.
The modular multilevel converter comprises three upper bridge arms and three lower bridge arms, wherein the upper bridge arms and the lower bridge arms respectively comprise a capacity reduction circuit and a plurality of sub-modules;
and after being connected in series, the plurality of sub-modules are connected in series with the capacitance reducing circuit.
The capacity reducing circuit comprises a bridge arm reactor L1, a bridge arm reactor L2 and a switching circuit which are connected in series;
the switching circuit is connected with the bridge arm reactor L1 in parallel and comprises a first branch and a second branch which are connected in anti-parallel.
The first branch circuit comprises n thyristors T connected in series 11 、……、T 1n The second branch circuit comprises m thyristors T connected in series 21 、……、T 2m And thyristor T 1n The cathode of the reactor is connected with a bridge arm reactor L2 and a thyristor T 2 m Is connected to a bridge arm reactor L2.
The control module comprises a judging unit, and the judging unit judges whether the number of the submodules input by the upper bridge arm is in an increasing stage or a decreasing stage according to the following process:
if it is
Figure BDA0001552440140000031
The number of the sub-modules put into the upper bridge arm is in an increasing stage;
if it is
Figure BDA0001552440140000032
The number of the sub-modules put into the upper bridge arm is in a reduction stage;
wherein the content of the first and second substances,
Figure BDA0001552440140000033
and representing the change rate of the number of the input sub-modules of the upper bridge arm.
The control module includes:
the first control unit is used for cutting off the bridge arm reactors in the lower bridge arm and inputting the bridge arm reactors in the upper bridge arm according to the following process when the modular multilevel converter is in an inversion running state:
and triggering all thyristors in the first branch of the lower bridge arm to cut off the bridge arm reactors in the lower bridge arm, locking all thyristors in the first branch of the upper bridge arm and inputting the bridge arm reactors in the upper bridge arm.
The control module includes:
the second control unit is used for cutting off the bridge arm reactors in the lower bridge arm and inputting the bridge arm reactors in the upper bridge arm according to the following process when the modular multilevel converter is in a rectification operation state, and comprises the following steps:
and triggering all thyristors in the second branch of the lower bridge arm to cut off the bridge arm reactors in the lower bridge arm, and locking all thyristors in the second branch of the upper bridge arm to realize the input of the bridge arm reactors in the upper bridge arm.
The control module includes:
and the third control unit is used for cutting off the bridge arm reactors in the upper bridge arm and inputting the bridge arm reactors in the lower bridge arm according to the following process when the modular multilevel converter is in an inversion running state:
and triggering all thyristors in the first branch of the upper bridge arm to cut off the bridge arm reactor in the upper bridge arm, and locking all thyristors in the first branch of the lower bridge arm to realize the input of the bridge arm reactor in the lower bridge arm.
The control module includes:
the fourth control unit is used for cutting off the bridge arm reactors in the upper bridge arm and inputting the bridge arm reactors in the lower bridge arm according to the following process when the modular multilevel converter is in a rectification operation state:
and triggering all thyristors in the second branch of the upper bridge arm to cut off the bridge arm reactors in the upper bridge arm, and locking all thyristors in the second branch of the lower bridge arm to realize the input of the bridge arm reactors in the lower bridge arm.
Compared with the closest prior art, the technical scheme provided by the invention has the following beneficial effects:
according to the capacity reducing operation method of the modular multilevel converter, the number of the sub-modules put into the upper bridge arm of the modular multilevel converter is firstly obtained, then under the condition that the number of the sub-modules put into the upper bridge arm of the modular multilevel converter is smaller than N/2 and the number of the sub-modules put into the upper bridge arm of the modular multilevel converter is larger than N/2, the number of the sub-modules put into the upper bridge arm is respectively judged to be in an increasing stage or a decreasing stage, switching control of corresponding bridge arm reactors is carried out, capacity reducing operation of the modular multilevel converter is achieved, and the capacity reducing effect is obvious;
the capacity reducing operation device of the modular multilevel converter comprises an acquisition module and a control module, wherein the acquisition module is used for acquiring the number of sub-modules input by an upper bridge arm of the modular multilevel converter, and the control module respectively judges whether the number of the sub-modules input by the upper bridge arm is in an increasing stage or a decreasing stage under the two conditions that the number of the sub-modules input by the upper bridge arm of the modular multilevel converter is less than N/2 and the number of the sub-modules input by the upper bridge arm of the modular multilevel converter is greater than N/2, and performs switching control on corresponding bridge arm reactors, so that the capacity reducing operation of the modular multilevel converter is realized, and the capacity reducing effect is obvious;
the technical scheme provided by the invention has the advantages of simple process, no need of complex operation, lower requirement on the controller of the modular multilevel converter, low investment cost and only need of adding a few thyristors;
compared with CCSC, the technical scheme provided by the invention can reduce the fundamental frequency and the double frequency component of the voltage waveform of the capacitor of the submodule to a greater extent, thereby further reducing the fluctuation of the voltage of the capacitor of the submodule and having certain significance for further reducing the weight of the submodule of the converter.
Drawings
Fig. 1 is a flow chart of a method for operating a modular multilevel converter with reduced capacitance according to an embodiment of the present invention;
fig. 2 is a block diagram of a modular multilevel converter in an embodiment of the invention;
fig. 3 is a structure diagram of a capacitance reducing circuit according to an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings.
The embodiment of the invention provides a capacity reduction operation method of a modular multilevel converter, a specific flow chart is shown in figure 1, and the specific process comprises the following steps:
s101: acquiring the number of sub-modules input by an upper bridge arm of the modular multilevel converter;
s102: the capacity reduction operation of the modular multilevel converter is realized under the following two conditions:
1. when the number of the sub-modules input into the upper bridge arm of the modular multilevel converter is smaller than N/2, judging that the number of the sub-modules input into the upper bridge arm is in an increasing stage or a decreasing stage, if the number of the sub-modules input into the upper bridge arm is in the increasing stage, cutting off a bridge arm reactor in a lower bridge arm and inputting the bridge arm reactor in the upper bridge arm when the number change rate of the sub-modules input into the upper bridge arm is equal to a first change rate set value (the first change rate set value is the change rate of the number of the sub-modules input into the upper bridge arm when the number of the sub-modules input into the upper bridge arm is increased to N/2); if the bridge arm reactor is in the reduction stage, cutting off the bridge arm reactor in the upper bridge arm and putting the bridge arm reactor in the lower bridge arm;
2. when the number of the sub-modules put into the upper bridge arm of the modular multilevel converter is larger than N/2, judging that the number of the sub-modules put into the upper bridge arm is in an increasing stage or a decreasing stage, if the number of the sub-modules put into the upper bridge arm is in the increasing stage, cutting off a bridge arm reactor in a lower bridge arm and putting into the bridge arm reactor in the upper bridge arm; if the number of the input sub-modules of the upper bridge arm is in the reduction stage, cutting off the bridge arm reactors in the upper bridge arm and inputting the bridge arm reactors in the lower bridge arm when the change rate of the number of the input sub-modules of the upper bridge arm is equal to a second change rate set value (the second change rate set value is the change rate of the number of the input sub-modules of the upper bridge arm when the number of the input sub-modules of the upper bridge arm is reduced to N/2);
and N represents the number of the neutron modules of the upper bridge arm, and the number of the neutron modules of the upper bridge arm is equal to that of the neutron modules of the lower bridge arm.
The structure diagram of the modular multilevel converter is shown in fig. 2, wherein SM in fig. 2 represents a sub-module, LSM represents a capacitance reduction circuit, the modular multilevel converter comprises three upper bridge arms and three lower bridge arms, and the upper bridge arms and the lower bridge arms both comprise the capacitance reduction circuit and a plurality of sub-modules; and after being connected in series, the plurality of sub-modules are connected in series with the capacitance reducing circuit.
The structure diagram of the capacity reducing circuit is shown in fig. 3, and the capacity reducing circuit comprises a bridge arm reactor L1, a bridge arm reactor L2 and a switching circuit which are connected in series;
the switching circuit is connected with the bridge arm reactor L1 in parallel and comprises a first branch and a second branch which are connected in anti-parallel.
The first branch comprises n thyristors T connected in series 11 、……、T 1n The second branch circuit comprises m thyristors T connected in series 21 、……、 T 2m And thyristor T 1n The cathode of the reactor is connected with a bridge arm reactor L2 and a thyristor T 2 m The anode of the reactor is connected with a bridge arm reactor L2; n = m or n ≠ m.
In the above S102, the specific process of determining that the number of the submodules put into the upper bridge arm is in the increasing stage or the decreasing stage is as follows:
1) If it is
Figure BDA0001552440140000061
The number of the sub-modules put into the upper bridge arm is in an increasing stage;
2) If it is
Figure BDA0001552440140000062
The number of the sub-modules put into the upper bridge arm is in a reduction stage;
wherein, the first and the second end of the pipe are connected with each other,
Figure BDA0001552440140000063
and the change rate of the number of input submodules of the upper bridge arm is represented, numup represents the number of the input submodules of the upper bridge arm, and Numup = N-Numdown is satisfied, wherein Numdown is the number of the input submodules of the lower bridge arm.
Because the modular multilevel converter can be in an inversion operation state and also can be in a rectification operation state, the capacity reduction operation process of the modular multilevel converter is explained in the following two cases:
1. the modularized multi-level converter is in an inversion operation state:
1) When the modular multilevel converter is in an inversion running state, the specific process of cutting off the bridge arm reactors in the lower bridge arm and putting the bridge arm reactors in the upper bridge arm is as follows:
and triggering all thyristors in the first branch of the lower bridge arm to cut off the bridge arm reactor in the lower bridge arm, and locking all thyristors in the first branch of the upper bridge arm to realize the input of the bridge arm reactor in the upper bridge arm.
2) When the modular multilevel converter is in an inversion running state, the specific process of cutting off the bridge arm reactors in the upper bridge arm and putting the bridge arm reactors in the lower bridge arm is as follows:
and triggering all thyristors in the first branch of the upper bridge arm to cut off the bridge arm reactor in the upper bridge arm, and locking all thyristors in the first branch of the lower bridge arm to realize the input of the bridge arm reactor in the lower bridge arm.
2. The modularized multi-level converter is in a rectification operation state:
1) When the modular multilevel converter is in a rectification running state, the specific process of cutting off the bridge arm reactors in the lower bridge arm and putting the bridge arm reactors in the upper bridge arm is as follows:
and triggering all thyristors in the second branch of the lower bridge arm to cut off the bridge arm reactors in the lower bridge arm, and locking all thyristors in the second branch of the upper bridge arm to realize the input of the bridge arm reactors in the upper bridge arm.
2) When the modular multilevel converter is in a rectification running state, the specific process of cutting off the bridge arm reactors in the upper bridge arm and putting the bridge arm reactors in the lower bridge arm is as follows:
and triggering all thyristors in the second branch of the upper bridge arm to cut off the bridge arm reactors in the upper bridge arm, and locking all thyristors in the second branch of the lower bridge arm to realize the input of the bridge arm reactors in the lower bridge arm.
Based on the same concept, an embodiment of the present invention further provides a capacity reduction operation apparatus for a modular multilevel converter, which includes an obtaining module and a control module, and the specific functions of the two modules are respectively described below:
the acquisition module is used for acquiring the number of sub-modules input by an upper bridge arm of the modular multilevel converter;
the control module is used for judging that the number of the sub-modules put into the upper bridge arm of the modular multilevel converter is in an increasing stage or a decreasing stage when the number of the sub-modules put into the upper bridge arm of the modular multilevel converter is smaller than N/2, cutting off a bridge arm reactor in a lower bridge arm and putting the bridge arm reactor in the upper bridge arm when the number change rate of the sub-modules put into the upper bridge arm is equal to a first change rate set value (the first change rate set value is the number change rate of the sub-modules put into the upper bridge arm when the number of the sub-modules put into the upper bridge arm is increased to N/2) if the number of the sub-modules put into the upper bridge arm is in the increasing stage, and cutting off the bridge arm reactor in the upper bridge arm and putting the bridge arm reactor in the lower bridge arm if the number of the sub-modules put into the upper bridge arm is in the decreasing stage;
when the number of the sub-modules put into the upper bridge arm of the modular multilevel converter is larger than N/2, judging that the number of the sub-modules put into the upper bridge arm is in an increasing stage or a decreasing stage, if the number of the sub-modules put into the upper bridge arm is in the increasing stage, cutting off a bridge arm reactor in a lower bridge arm and putting into the bridge arm reactor in the upper bridge arm; if the number of the input sub-modules of the upper bridge arm is in the reduction stage, cutting off the bridge arm reactors in the upper bridge arm and inputting the bridge arm reactors in the lower bridge arm when the change rate of the number of the input sub-modules of the upper bridge arm is equal to a second change rate set value (the second change rate set value is the change rate of the number of the input sub-modules of the upper bridge arm when the number of the input sub-modules of the upper bridge arm is reduced to N/2);
and N represents the number of the sub-modules in the upper bridge arm, numup represents the number of the sub-modules put into the upper bridge arm, numup = N-Numdown is satisfied, and Numdown is the number of the sub-modules put into the lower bridge arm.
The structure diagram of the modular multilevel converter is shown in fig. 2, SM in fig. 2 represents a sub-module, LSM represents a capacitance reduction circuit, the modular multilevel converter comprises three upper bridge arms and three lower bridge arms, and the upper bridge arms and the lower bridge arms both comprise the capacitance reduction circuit and a plurality of sub-modules; after being connected in series, the sub-modules are connected in series with the capacitance reducing circuit.
The capacity reducing circuit comprises a bridge arm reactor L1, a bridge arm reactor L2 and a switching circuit which are connected in series;
the switching circuit is connected with the bridge arm reactor L1 in parallel and comprises a first branch and a second branch which are connected in anti-parallel.
The first branch comprises n thyristors T connected in series 11 、……、T 1n The second branch circuit comprises m thyristors T connected in series 21 、……、 T 2m And thyristor T 1n Is connected with a bridge arm reactor L2 and a thyristorPipe T 2 m The anode of the reactor is connected with a bridge arm reactor L2; the number of thyristors in the first branch and the number of thyristors in the second branch may be equal or unequal, i.e., n = m or n ≠ m.
The control module comprises a judging unit, and the judging unit judges whether the number of the submodules input by the upper bridge arm is in an increasing stage or a decreasing stage according to the following process:
1) If it is
Figure BDA0001552440140000071
The number of the sub-modules input by the upper bridge arm is in an increasing stage;
2) If it is
Figure BDA0001552440140000081
The number of the sub-modules put into the upper bridge arm is in a reduction stage;
wherein, the first and the second end of the pipe are connected with each other,
Figure BDA0001552440140000082
and representing the change rate of the number of the input sub-modules of the upper bridge arm.
The control module further comprises:
the first control unit is used for cutting off the bridge arm reactors in the lower bridge arm and inputting the bridge arm reactors in the upper bridge arm according to the following process when the modular multilevel converter is in an inversion running state:
and triggering all thyristors in the first branch of the lower bridge arm to cut off the bridge arm reactor in the lower bridge arm, and locking all thyristors in the first branch of the upper bridge arm to realize the input of the bridge arm reactor in the upper bridge arm.
The control module further comprises:
the second control unit is used for cutting off the bridge arm reactors in the lower bridge arm and inputting the bridge arm reactors in the upper bridge arm according to the following process when the modular multilevel converter is in a rectification operation state, and comprises the following steps:
and triggering all thyristors in the second branch of the lower bridge arm to cut off the bridge arm reactors in the lower bridge arm, and locking all thyristors in the second branch of the upper bridge arm to realize the input of the bridge arm reactors in the upper bridge arm.
The control module further comprises:
and the third control unit is used for cutting off the bridge arm reactors in the upper bridge arm and inputting the bridge arm reactors in the lower bridge arm according to the following process when the modular multilevel converter is in an inversion running state:
and triggering all thyristors in the first branch of the upper bridge arm to cut off the bridge arm reactor in the upper bridge arm, and locking all thyristors in the first branch of the lower bridge arm to realize the input of the bridge arm reactor in the lower bridge arm.
The control module further comprises:
the fourth control unit is used for cutting off the bridge arm reactors in the upper bridge arm and inputting the bridge arm reactors in the lower bridge arm according to the following processes when the modular multilevel converter is in a rectification running state:
and triggering all thyristors in the second branch of the upper bridge arm to cut off the bridge arm reactors in the upper bridge arm, and locking all thyristors in the second branch of the lower bridge arm to realize the input of the bridge arm reactors in the lower bridge arm.
For convenience of description, each part of the above-described apparatus is separately described as being functionally divided into various modules or units. Of course, the functionality of the various modules or units may be implemented in the same one or more pieces of software or hardware when implementing the present application.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and so forth) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
Finally, it should be noted that: the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the same, and those skilled in the art can make modifications or equivalent substitutions to the specific embodiments of the present invention with reference to the above embodiments, and any modifications or equivalent substitutions which do not depart from the spirit and scope of the present invention are within the scope of the claims of the present invention as filed in the application.

Claims (17)

1. A capacity reduction operation method of a modular multilevel converter is characterized by comprising the following steps:
acquiring the number of sub-modules input by an upper bridge arm of the modular multilevel converter;
when the number of the sub-modules input into the upper bridge arm of the modular multilevel converter is smaller than N/2, judging that the number of the sub-modules input into the upper bridge arm is in an increasing stage or a decreasing stage, if the number of the sub-modules input into the upper bridge arm is in the increasing stage, cutting off the bridge arm reactors in the lower bridge arm and inputting the bridge arm reactors in the upper bridge arm when the number change rate of the sub-modules input into the upper bridge arm is equal to a first change rate set value; if the bridge arm reactor is in the reduction stage, cutting off the bridge arm reactor in the upper bridge arm and putting the bridge arm reactor in the lower bridge arm;
when the number of the sub-modules put into the upper bridge arm of the modular multilevel converter is larger than N/2, judging that the number of the sub-modules put into the upper bridge arm is in an increasing stage or a decreasing stage, if the number of the sub-modules put into the upper bridge arm is in the increasing stage, cutting off a bridge arm reactor in a lower bridge arm and putting into the bridge arm reactor in the upper bridge arm; if the number of the input sub-modules of the upper bridge arm is equal to a second change rate set value, cutting off bridge arm reactors in the upper bridge arm and inputting bridge arm reactors in the lower bridge arm;
and N represents the number of sub-modules in the upper bridge arm.
2. The method of claim 1, wherein the modular multilevel converter comprises three upper legs and three lower legs, each of the upper and lower legs comprising a capacitor-reducing circuit and a plurality of sub-modules;
and after being connected in series, the plurality of sub-modules are connected in series with the capacitance reducing circuit.
3. The capacity reduction operation method of the modular multilevel converter according to claim 2, wherein the capacity reduction circuit comprises a bridge arm reactor L1, a bridge arm reactor L2 and a switching circuit which are connected in series;
the switching circuit is connected with the bridge arm reactor L1 in parallel and comprises a first branch and a second branch which are connected in anti-parallel.
4. The capacity reduction operation method of the modular multilevel converter according to claim 1, wherein the step of judging whether the number of the submodules put into the upper bridge arm is in an increasing stage or a decreasing stage comprises the steps of:
if it is
Figure FDA0003796994070000011
The number of the sub-modules input by the upper bridge arm is in an increasing stage;
if it is
Figure FDA0003796994070000012
The number of the sub-modules put into the upper bridge arm is in a reduction stage;
wherein the content of the first and second substances,
Figure FDA0003796994070000013
and representing the change rate of the number of the input sub-modules of the upper bridge arm.
5. The capacity reduction operation method of the modular multilevel converter according to claim 3, wherein the cutting out of the bridge arm reactors in the lower bridge arm and putting the bridge arm reactors in the upper bridge arm when the modular multilevel converter is in an inverter operation state comprises:
and triggering all thyristors in the first branch of the lower bridge arm to cut off the bridge arm reactor in the lower bridge arm, and locking all thyristors in the first branch of the upper bridge arm to realize the input of the bridge arm reactor in the upper bridge arm.
6. The capacity reduction operation method of the modular multilevel converter according to claim 3, wherein the cutting out of the bridge arm reactors in the lower bridge arm and putting the bridge arm reactors in the upper bridge arm when the modular multilevel converter is in a rectification operation state comprises:
and triggering all thyristors in the second branch of the lower bridge arm to cut off the bridge arm reactors in the lower bridge arm, and locking all thyristors in the second branch of the upper bridge arm to realize the input of the bridge arm reactors in the upper bridge arm.
7. The capacity reduction operation method of the modular multilevel converter according to claim 3, wherein the cutting out of the bridge arm reactors in the upper bridge arm and putting the bridge arm reactors in the lower bridge arm when the modular multilevel converter is in an inverter operation state comprises:
and triggering all thyristors in the first branch of the upper bridge arm to cut off the bridge arm reactor in the upper bridge arm, and locking all thyristors in the first branch of the lower bridge arm to realize the input of the bridge arm reactor in the lower bridge arm.
8. The capacity reduction operation method of the modular multilevel converter according to claim 3, wherein the cutting out of the bridge arm reactors in the upper bridge arm and putting the bridge arm reactors in the lower bridge arm when the modular multilevel converter is in a rectification operation state comprises:
and triggering all thyristors in the second branch of the upper bridge arm to cut off the bridge arm reactors in the upper bridge arm, and locking all thyristors in the second branch of the lower bridge arm to realize the input of the bridge arm reactors in the lower bridge arm.
9. A capacity reduction operation device of a modular multilevel converter is characterized by comprising:
the acquisition module is used for acquiring the number of sub-modules input by an upper bridge arm of the modular multilevel converter;
the control module is used for judging that the number of the sub-modules put into the upper bridge arm of the modular multilevel converter is in an increasing stage or a decreasing stage when the number of the sub-modules put into the upper bridge arm of the modular multilevel converter is smaller than N/2, and cutting off a bridge arm reactor in a lower bridge arm and putting the bridge arm reactor in the upper bridge arm when the number change rate of the sub-modules put into the upper bridge arm is equal to a first change rate set value if the number of the sub-modules put into the upper bridge arm is in the increasing stage; if the bridge arm reactor is in the reduction stage, cutting off the bridge arm reactor in the upper bridge arm and putting the bridge arm reactor in the lower bridge arm;
when the number of the sub-modules put into the upper bridge arm of the modular multilevel converter is larger than N/2, judging that the number of the sub-modules put into the upper bridge arm is in an increasing stage or a decreasing stage, if the number of the sub-modules put into the upper bridge arm is in the increasing stage, cutting off a bridge arm reactor in a lower bridge arm and putting into the bridge arm reactor in the upper bridge arm; if the number of the input sub-modules of the upper bridge arm is equal to a second change rate set value, cutting off bridge arm reactors in the upper bridge arm and inputting bridge arm reactors in the lower bridge arm;
and N represents the number of sub-modules in the upper bridge arm.
10. The apparatus of claim 9, wherein the modular multilevel converter comprises three upper legs and three lower legs, each of which comprises a capacitance reduction circuit and a plurality of sub-modules;
and after being connected in series, the plurality of sub-modules are connected in series with the capacitance reducing circuit.
11. The capacity reduction operation device of the modular multilevel converter according to claim 10, wherein the capacity reduction circuit comprises a bridge arm reactor L1, a bridge arm reactor L2 and a switching circuit which are connected in series;
the switching circuit is connected with the bridge arm reactor L1 in parallel and comprises a first branch and a second branch which are connected in anti-parallel.
12. The apparatus for reduced-capacity operation of a modular multilevel converter according to claim 11, wherein the first branch comprises n thyristors T in series 11 、……、T 1n The second branch circuit comprises m thyristors T connected in series 21 、……、T 2m And thyristor T 1n The cathode of the reactor is connected with a bridge arm reactor L2 and a thyristor T 2m Is connected to a bridge arm reactor L2.
13. The capacity reduction operation device of the modular multilevel converter according to claim 9, wherein the control module comprises a determining unit, and the determining unit determines that the number of the sub-modules put into the upper bridge arm is in an increasing stage or a decreasing stage according to the following process:
if it is
Figure FDA0003796994070000031
The number of the sub-modules put into the upper bridge arm is in an increasing stage;
if it is
Figure FDA0003796994070000032
The number of the sub-modules put into the upper bridge arm is in a reduction stage;
wherein the content of the first and second substances,
Figure FDA0003796994070000033
and representing the change rate of the number of the input sub-modules of the upper bridge arm.
14. The apparatus for reduced-capacity operation of a modular multilevel converter according to claim 11, wherein the control module comprises:
the first control unit is used for cutting off the bridge arm reactors in the lower bridge arm and inputting the bridge arm reactors in the upper bridge arm according to the following process when the modular multilevel converter is in an inversion running state:
and triggering all thyristors in the first branch of the lower bridge arm to cut off the bridge arm reactor in the lower bridge arm, and locking all thyristors in the first branch of the upper bridge arm to realize the input of the bridge arm reactor in the upper bridge arm.
15. The apparatus for reduced-capacity operation of a modular multilevel converter according to claim 11, wherein the control module comprises:
the second control unit is used for cutting off the bridge arm reactors in the lower bridge arm and inputting the bridge arm reactors in the upper bridge arm according to the following process when the modular multilevel converter is in a rectification operation state:
and triggering all thyristors in the second branch of the lower bridge arm to cut off the bridge arm reactors in the lower bridge arm, and locking all thyristors in the second branch of the upper bridge arm to realize the input of the bridge arm reactors in the upper bridge arm.
16. The apparatus for reduced-capacity operation of a modular multilevel converter according to claim 11, wherein the control module comprises:
and the third control unit is used for cutting off the bridge arm reactors in the upper bridge arm and inputting the bridge arm reactors in the lower bridge arm according to the following process when the modular multilevel converter is in an inversion running state:
and triggering all thyristors in the first branch of the upper bridge arm to cut off the bridge arm reactor in the upper bridge arm, and locking all thyristors in the first branch of the lower bridge arm to realize the input of the bridge arm reactor in the lower bridge arm.
17. The apparatus for reduced-capacity operation of a modular multilevel converter according to claim 11, wherein the control module comprises:
the fourth control unit is used for cutting off the bridge arm reactors in the upper bridge arm and inputting the bridge arm reactors in the lower bridge arm according to the following process when the modular multilevel converter is in a rectification operation state:
and triggering all thyristors in the second branch of the upper bridge arm to cut off the bridge arm reactors in the upper bridge arm, and locking all thyristors in the second branch of the lower bridge arm to realize the input of the bridge arm reactors in the lower bridge arm.
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