CN112865505A - Double-frequency circulating current injection method for inhibiting MMC bridge arm power fluctuation under fault - Google Patents
Double-frequency circulating current injection method for inhibiting MMC bridge arm power fluctuation under fault Download PDFInfo
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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
- H02M1/00—Details of apparatus for conversion
- H02M1/32—Means for protecting converters other than automatic disconnection
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/001—Methods to deal with contingencies, e.g. abnormalities, faults or failures
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
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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
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
- H02J2003/365—Reducing harmonics or oscillations in HVDC
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- 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]
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Abstract
The invention discloses a double-frequency circulating current injection method for inhibiting MMC bridge arm power fluctuation under a fault, which comprises the following steps: establishing an optimized objective function by taking the fundamental frequency and the double-frequency fluctuation component of the instantaneous power of the bridge arm when the alternating-current single-phase fault occurs as an inhibition target; performing global optimization by taking the objective function minimization as an objective to obtain the optimal amplitude and phase of the double frequency circulation injection; and generating a reference signal according to the amplitude and the phase of the optimal double frequency circulation injection, and combining a modulation algorithm to realize the injection of the double frequency circulation. The method can effectively reduce the fluctuation of the sub-module capacitor voltage during the fault period, and reduce the maximum voltage born by the MMC sub-module during the fault period.
Description
Technical Field
The invention relates to the technical field of flexible direct current power transmission, in particular to a double-frequency circulating current injection method for inhibiting the power fluctuation of an MMC bridge arm under a fault.
Background
Flexible direct current transmission (VSC-HVDC) is a new generation of direct current transmission technology following alternating current transmission, conventional direct current transmission. The flexible direct current transmission technology has the characteristics of independent active and reactive power adjustment, strong weak power grid access and low voltage ride through capability, low alternating current filtering, reactive power compensation requirements and the like. The Modular Multilevel Converter (MMC) has the characteristics of flexible control, module expansibility, low switching frequency, low harmonic content and the like. At present, MMC structures are adopted in Shanghai south-Virginia flexible direct current engineering, Nanao three-terminal flexible direct current engineering, Zhoushan five-terminal flexible direct current engineering, Xiamen +/-320 kV flexible direct current demonstration engineering and Zhang Bei direct current power grid engineering which are built in China.
Ac single-phase earth faults are the most common and frequent type of fault occurring in electrical power systems. When the alternating-current single-phase earth fault occurs, the dynamic characteristic of the MMC can be greatly changed, the fluctuation of the sub-module capacitor voltage can be inevitably increased, and the overvoltage of a device can be possibly generated, so that the power electronic device is damaged. And the voltage fluctuation of the capacitor of the submodule is positively correlated with the power fluctuation of the bridge arm. Therefore, a method for restraining the power fluctuation of the bridge arm of the MMC under the alternating-current single-phase earth fault is explored, the reliability of the MMC is improved, and the method has important engineering significance.
Disclosure of Invention
The invention aims to provide a double-frequency circulating current injection method for inhibiting the power fluctuation of an MMC bridge arm under a fault, which can effectively inhibit the power fluctuation of the bridge arm of a converter valve, further reduce the capacitor voltage fluctuation of a submodule during the fault and reduce the maximum voltage borne by the MMC submodule during the fault.
The purpose of the invention is realized by the following technical scheme:
a double-frequency circulating current injection method for inhibiting MMC bridge arm power fluctuation under a fault is characterized by comprising the following steps:
establishing an optimized objective function by taking the fundamental frequency and the double-frequency fluctuation component of the instantaneous power of the bridge arm when the alternating-current single-phase fault occurs as an inhibition target;
performing global optimization by taking the objective function minimization as an objective to obtain the optimal amplitude and phase of the double frequency circulation injection;
and generating a reference signal according to the amplitude and the phase of the optimal double frequency circulation injection, and combining a modulation algorithm to realize the injection of the double frequency circulation.
It can be seen from the above technical solutions that the fundamental frequency and the double frequency fluctuation component of the instantaneous power are used as the suppression target, the amplitude and the phase of the injected double frequency circulating current are optimally designed, and finally the calculated double frequency circulating current is injected into the three phases by changing the modulation wave signal. The method can effectively inhibit the fluctuation of the bridge arm power of the converter valve, further reduce the fluctuation of the sub-module capacitance voltage during the fault period and reduce the maximum voltage born by the MMC sub-module during the fault period.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.
Fig. 1 is a flowchart of a double frequency circulating current injection method for suppressing a power fluctuation of an MMC bridge arm under a fault according to an embodiment of the present invention;
fig. 2 is a block diagram of the overall system control of the double frequency circulating current injection method for suppressing the power fluctuation of the MMC bridge arm in the case of a fault according to the embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention are clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.
The embodiment of the invention provides a double-frequency circulating current injection method for inhibiting MMC bridge arm power fluctuation under a fault, a flow chart and an overall system control block diagram are shown in figures 1-2, and the method mainly comprises the following steps:
1. and establishing an optimized objective function by taking the fundamental frequency and the double-frequency fluctuation component of the instantaneous power of the bridge arm when the alternating-current single-phase fault occurs as an inhibition target.
In the embodiment of the invention, firstly, an expression of bridge arm instantaneous power considering double frequency circulation injection under the condition of single-phase earth fault is calculated, and then an optimized objective function is established.
1) And calculating an expression of the instantaneous power of the bridge arm considering double frequency circulating current injection under the condition of the single-phase earth fault.
When an alternating-current single-phase earth fault occurs (taking a-phase single-phase earth as an example), the three-phase upper bridge arm voltage is as follows:
wherein t is time, and omega is fundamental angular frequency; u shapedcIs a direct current voltage, UmIs the amplitude of the AC voltage, uau_f、 ubu_f、ucu_fRespectively representing the voltages of the upper bridge arms of a, b and c after the fault;
when an alternating-current single-phase ground fault occurs, because a fault phase cannot transmit power, the transmission of 1/3 power is often reduced in consideration of reduced bridge arm current stress, and at the moment, the upper bridge arm currents of three phases are:
wherein, ImIs the amplitude of the alternating current,
is an initial phase angle, I2Showing the magnitude of the double frequency circulating injection,
representing the phase angle of the double frequency circulating current injection, m representing the modulation ratio, and having a value of 2Um/Udc，iau_f、ibu_f、icu_fRespectively representing a, b and c three-phase upper bridges after faultsAn arm current;
to simplify the representation, a frequency doubling circulating injection coefficient k is defined2Comprises the following steps:
when the voltage and the current of a three-phase upper bridge arm are combined when an alternating-current single-phase earth fault occurs, the expression of the instantaneous power of the three-phase upper bridge arm containing double frequency circulating current injection after the fault is obtained as follows: :
wherein, Pau_f、Pbu_f、Pcu_fAnd respectively representing the instantaneous power of the upper bridge arms of the phases a, b and c after the fault.
Those skilled in the art will appreciate that an MMC consists of six arms, phase a up, phase a down, phase b up, phase b down, phase c up, and phase c down. Each bridge arm comprises N sub-modules.
2) And establishing an optimized objective function by taking the fundamental frequency and the double-frequency fluctuation component of the instantaneous power of the bridge arm when the alternating-current single-phase fault occurs as an inhibition target. The main process is as follows:
A. and obtaining the fundamental frequency and double frequency fluctuation of the instantaneous power of the upper bridge arm of the fault phase when the alternating current single-phase fault occurs according to the instantaneous power of the upper bridge arm of the three phases containing double frequency circulation injection after the fault, thereby obtaining the fluctuation amplitude.
If the fault phase is a phase a, the fundamental frequency and the double frequency fluctuation of the instantaneous power of the bridge arm on the phase a are as follows:
wherein, Pau_f1And Pau_f2Fundamental frequency and double frequency fluctuation of instantaneous power of an upper bridge arm of the phase a are respectively;
to Pau_f1And Pau_f2Performing an identity transform to obtain:
the A, B parameters referred to herein for the different subscripts are intermediate parameters.
Obtaining P according to the identity transformation resultau_f1And Pau_f2The fluctuation amplitude is:
B. and obtaining fundamental frequency and double frequency fluctuation of instantaneous power of the non-fault two-phase upper bridge arm by adopting the same mode, and further obtaining the fluctuation amplitude.
The fundamental frequency and double frequency fluctuation of the instantaneous power of the bridge arm on the B phase are as follows:
wherein, Pbu_f1And Pbu_f2Fundamental frequency and double frequency fluctuation of instantaneous power of the bridge arm on the B phase are respectively;
to Pbu_f1And Pbu_f2Performing an identity transform to obtain:
obtaining P according to the identity transformation resultbu_f1And Pbu_f2The fluctuation amplitude is:
the fundamental frequency and double frequency fluctuation of the instantaneous power of the bridge arm on the C phase are as follows:
wherein, Pcu_f1And Pcu_f2Fundamental frequency and double frequency fluctuation of the instantaneous power of the C-phase upper bridge arm are respectively;
to Pcu_f1And Pcu_f2Performing an identity transform to obtain:
obtaining P according to the identity transformation resultcu_f1And Pcu_f2The fluctuation amplitude is:
C. establishing a target function according to the obtained fundamental frequency of the instantaneous power of the three-phase bridge arm and the fluctuation amplitude of the double frequency fluctuation
Wherein,
|Pau_f1i and I Pau_f2L isThe fluctuation amplitudes of the fundamental frequency and the double frequency fluctuation of the instantaneous power of the bridge arm on the phase a are respectively; i Pbu_f1I and I Pbu_f2I is the fundamental frequency of the instantaneous power of the bridge arm on the b phase and the fluctuation amplitude of the double frequency fluctuation respectively; i Pcu_f1I and I Pcu_f2And l is the fundamental frequency of the instantaneous power of the bridge arm on the c phase and the fluctuation amplitude of the double frequency fluctuation respectively.
k represents a weight coefficient of the secondary fluctuation of the capacitor voltage. Since the influence of the double frequency voltage fluctuation on the overall voltage fluctuation amplitude is smaller, the k value is set to 0.5 here. It should be noted that the value of k is not fixed, and can be adjusted appropriately according to actual conditions.
2. And performing global optimization by taking the objective function minimization as an objective to obtain the optimal amplitude and phase of the double frequency circulation injection.
In the embodiment of the invention, global optimization is carried out by taking objective function minimization as a target, and k is determined according to different modulation ratios m2、
Optimal values of the two variables. It should be noted that the present invention does not limit the optimization method, and the user can select the optimization method according to the actual situation.
It will be appreciated by those skilled in the art that since the objective function is based on the capacitor voltage fluctuation, its minimized solution can achieve a minimization of the capacitor voltage fluctuation, i.e. if the amplitude and phase of the optimal solution are injected, the objective can be achieved, in particular, by designing the parameter k2，
Can realize suppression of the fluctuation of the capacitor voltage.
3. And generating a reference signal according to the amplitude and the phase of the double frequency circulation injection, and combining a modulation algorithm to realize the injection of the double frequency circulation.
In the embodiment of the invention, the optimal amplitude and phase of double frequency circulating current injection are obtained, namely k is obtained2、
An optimal value, after which a reference signal i can be generated in conjunction with a reference signal generator2fd_refAnd i2fq_ref(ii) a Wherein i2fd_refReference signal, i, for d-axis double frequency circulating injection controller2fq_refInjecting a reference signal of the controller for q-axis double frequency circulation; the reference signal is injected into the controller through the double frequency circulation to obtain a double frequency circulation modulation voltage signal Ucirj_refFinally, the injection of the double frequency circulation is realized by changing the modulation wave of the modulation algorithm.
In the control block diagram of the whole system shown in fig. 2, the positive sequence and negative sequence double-loop controllers in the upper dotted line frame are the classic control scheme adopted in the current fault; wherein, Tabc/dqThe module is a dq transformation module; i.e. id_refpAnd iq_refpRespectively generating positive sequence differential mode voltage reference values e for positive sequence dq axis current reference values through dq conversionj_refp；id_refnAnd iq_refnRespectively negative sequence dq axis current reference values, and generating a negative sequence differential mode voltage reference value e through dq conversionj_refn；I2And
showing the double frequency circulating current magnitude and phase. The lower dotted line frame shows the working process of the reference signal generator and the double frequency circulation injection controller, wherein the PI module is a proportional integral link; l isarmIs the bridge arm reactance value; t isdq/abcThe module is a dq inverse transformation module; i.e. icira、icirb、icircRespectively measuring the a phase, the b phase and the c phase double frequency circulation; i.e. i2fdAnd i2fqD-axis double frequency circulation current and q-axis double frequency circulation current i2fd_refAnd i2fq_refIs a corresponding reference value; u. ofcird_refAnd ucirq_refD-axis double-frequency circulating current modulation voltage and q-axis double-frequency circulating current modulation voltage are respectively generated into a double-frequency circulating current modulation voltage signal U through dq inverse transformationcirj_ref。
Through the above description of the embodiments, it is clear to those skilled in the art that the above embodiments can be implemented by software, and can also be implemented by software plus a necessary general hardware platform. With this understanding, the technical solutions of the embodiments can be embodied in the form of a software product, which can be stored in a non-volatile storage medium (which can be a CD-ROM, a usb disk, a removable hard disk, etc.), and includes several instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods according to the embodiments of the present invention.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (7)
1. A double-frequency circulating current injection method for inhibiting MMC bridge arm power fluctuation under a fault is characterized by comprising the following steps:
establishing an optimized objective function by taking the fundamental frequency and the double-frequency fluctuation component of the instantaneous power of the bridge arm when the alternating-current single-phase fault occurs as an inhibition target;
performing global optimization by taking the objective function minimization as an objective to obtain the optimal amplitude and phase of the double frequency circulation injection;
and generating a reference signal according to the amplitude and the phase of the optimal double frequency circulation injection, and combining a modulation algorithm to realize the injection of the double frequency circulation.
2. The double-frequency circulating current injection method for inhibiting the MMC bridge arm power fluctuation under the fault according to claim 1, wherein before establishing an optimized objective function, an expression of the bridge arm instantaneous power considering double-frequency circulating current injection under the single-phase ground fault is calculated, and the expression comprises the following steps:
when an alternating-current single-phase earth fault occurs, the three-phase upper bridge arm voltage is as follows:
wherein t is time, and omega is fundamental angular frequency; u shapedcIs a direct current voltage, UmIs the amplitude of the AC voltage, uau_f、ubu_f、ucu_fRespectively representing the voltages of the upper bridge arms of a, b and c after the fault;
when an alternating-current single-phase earth fault occurs, the current of an upper bridge arm of three phases is as follows:
wherein, IdcIs a direct current, ImIs the amplitude of the alternating current,
is an initial phase angle, I2Showing the magnitude of the double frequency circulating injection,
representing the phase angle of the double frequency circulating current injection, m representing the modulation ratio, and having a value of 2Um/Udc，iau_f、ibu_f、icu_fRespectively representing a, b and c three-phase upper bridge arm currents after the fault;
defining a double frequency circulating injection coefficient k2Comprises the following steps:
when the voltage and the current of a three-phase upper bridge arm are combined when an alternating-current single-phase earth fault occurs, the expression of the instantaneous power of the three-phase upper bridge arm containing double frequency circulating current injection after the fault is obtained as follows:
wherein, Pau_f、Pbu_f、Pcu_fAnd respectively representing the instantaneous power of the upper bridge arms of the phases a, b and c after the fault.
3. The double-frequency circulating current injection method for inhibiting MMC bridge arm power fluctuation under the fault according to claim 2, wherein the fundamental frequency and double-frequency fluctuation components of the bridge arm instantaneous power when the alternating-current single-phase fault occurs are used as inhibition targets, and establishing an optimized target function comprises:
obtaining fundamental frequency and double frequency fluctuation of instantaneous power of a fault phase upper bridge arm when an alternating current single-phase fault occurs according to the instantaneous power of the three phase upper bridge arm containing double frequency circulation injection after the fault, and further obtaining a fluctuation amplitude;
obtaining fundamental frequency and double frequency fluctuation of instantaneous power of a non-fault two-phase upper bridge arm by adopting the same mode, and further obtaining a fluctuation amplitude;
establishing a target function according to the obtained fundamental frequency of the instantaneous power of the three-phase bridge arm and the fluctuation amplitude of the double frequency fluctuation
Wherein,
|Pau_f1i and I Pau_f2I is the fundamental frequency of the instantaneous power of the bridge arm on the phase a and the fluctuation amplitude of the double frequency fluctuation respectively; i Pbu_f1I and I Pbu_f2I is the fundamental frequency of the instantaneous power of the bridge arm on the b phase and the fluctuation amplitude of the double frequency fluctuation respectively; i Pcu_f1I and I Pcu_f2And l is the fundamental frequency of the instantaneous power of the bridge arm on the c phase and the fluctuation amplitude of the double frequency fluctuation respectively, and k represents the weight coefficient of the secondary fluctuation of the capacitor voltage.
4. The double-frequency circulating current injection method for inhibiting the MMC bridge arm power fluctuation under the fault according to claim 3, wherein if the fault phase is a phase a, the fundamental frequency and double-frequency fluctuation of the instantaneous power of the bridge arm on the phase a are as follows:
wherein, Pau_f1And Pau_f2Fundamental frequency and double frequency fluctuation of instantaneous power of an upper bridge arm of the phase a are respectively;
to Pau_f1And Pau_f2Performing an identity transform to obtain:
Pau_f1＝Aau_f1 sinωt+Bau_f1 cosωt
Pau_f2＝Aau_f2 sin2ωt+Bau_f2 cos2ωt
obtaining P according to the identity transformation resultau_f1And Pau_f2The fluctuation amplitude is:
5. the double-frequency circulating current injection method for inhibiting the MMC bridge arm power fluctuation under the fault according to claim 3 or 4, wherein if the fault phase is a phase, the fundamental frequency and double-frequency fluctuation of the instantaneous power of the bridge arm on the phase B are as follows:
wherein, Pbu_f1And Pbu_f2Fundamental frequency and double frequency fluctuation of B-phase upper bridge arm instantaneous power respectively
To Pbu_f1And Pbu_f2Performing an identity transform to obtain:
Pbu_f1＝Abu_f1 sinωt+Bbu_f1 cosωt
Pbu_f2＝Abu_f2 sin2ωt+Bbu_f2 cos2ωt
obtaining P according to the identity transformation resultbu_f1And Pbu_f2The fluctuation amplitude is:
6. the double-frequency circulating current injection method for inhibiting the MMC bridge arm power fluctuation under the fault according to claim 3 or 4, wherein if the fault phase is a phase, the fundamental frequency and double-frequency fluctuation of the C-phase upper bridge arm instantaneous power are as follows:
wherein, Pcu_f1And Pcu_f2Fundamental frequency and double frequency fluctuation of the instantaneous power of the C-phase upper bridge arm are respectively;
to Pcu_f1And Pcu_f2Performing an identity transform to obtain:
obtaining P according to the identity transformation resultcu_f1And Pcu_f2The fluctuation amplitude is:
7. the double-frequency circulating current injection method for inhibiting the MMC bridge arm power fluctuation under the fault according to claim 1, wherein the step of generating a reference signal according to the amplitude and the phase of double-frequency circulating current injection and the step of realizing the double-frequency circulating current injection by combining a modulation algorithm comprises the following steps:
generating a reference signal according to the amplitude and the phase of the double frequency circulating current injection and combining a reference signal generator;
the reference signal obtains a double frequency circulation modulation voltage signal through a double frequency circulation injection controller, and finally injection of the double frequency circulation is realized by changing a modulation wave of a modulation algorithm.
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113965057A (en) * | 2021-10-15 | 2022-01-21 | 中国长江三峡集团有限公司 | Coupling harmonic injection method for inhibiting voltage fluctuation of half-bridge MMC capacitor |
| CN113965057B (en) * | 2021-10-15 | 2023-10-13 | 中国长江三峡集团有限公司 | Coupling harmonic injection method for inhibiting voltage fluctuation of half-bridge MMC capacitor |
| CN114204586A (en) * | 2021-12-03 | 2022-03-18 | 华北电力大学 | Second harmonic injection method for inhibiting voltage fluctuation of MMC capacitor and suitable for multiple working conditions |
| CN114826008A (en) * | 2022-05-23 | 2022-07-29 | 南通大学 | Control system and method for reducing bridge arm current peak value of MMC (Modular multilevel converter) |
| CN114826008B (en) * | 2022-05-23 | 2022-12-02 | 南通大学 | Control system and method for reducing bridge arm current peak value of MMC (Modular multilevel converter) |
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