CN117293888A - Weak current network low voltage treatment method based on back-to-back modularized multi-level converter - Google Patents
Weak current network low voltage treatment method based on back-to-back modularized multi-level converter Download PDFInfo
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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
- 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
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- 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 belongs to the technical field of flexible direct current power distribution, and discloses a weak current network low voltage treatment method based on back-to-back modularized multi-level converters. In a weak grid distribution system, the distribution line distance is long, resulting in a large line impedance. The user voltage drops significantly when its user uses electricity. In the invention, a weak grid ac bus delivers ac to MMCs on the distribution grid side. At this time, the MMC works in a rectifying mode, and the direct-current voltage at the output end is higher than the original alternating-current voltage. The MMC distributes direct current to the MMC at the user end on the original alternating current line. The MMC works in an inversion mode, and converts direct current of a direct current bus into alternating current to be transmitted to a user. Finally, the voltage on the distribution line of the weak current network is improved through back-to-back MMC, and the problem of low voltage of the user of the weak current network is solved.
Description
Technical Field
The invention relates to the application field of flexible direct current distribution technology, in particular to a weak current network low voltage treatment method based on back-to-back modularized multi-level converters.
Background
Aiming at a long-distance low-voltage multi-user centralized power supply scene, the characteristics of large power supply radius of a station area, long power transmission line, low power consumption reliability, poor electric energy quality and the like are generally existed. The problem of serious loss of active power and reactive power can occur in the power supply process due to the influence of the power supply distance, so that when power is distributed to long-distance users, serious voltage drop is generated at the user side, the power supply reliability is severe, and the power supply load voltage is always lower than the minimum voltage requirement of 200V.
The flexible direct current transmission technology is used as a new generation direct current transmission technology, and has the outstanding advantages of active and reactive independent control, rapid and flexible response, strong expansibility and the like. Conventional power transmission techniques may generate high losses for long distances, resulting in significant voltage drops. The traditional two-level converter has high switching frequency, large loss, strong electromagnetic noise, high output voltage harmonic content and expensive high-voltage capacitor sets installed on the side of a direct current bus, and the problems limit the application of the two-level converter in voltage occasions. Modular multilevel converter, english: modular multilevel converter, abbreviated as: MMC. The MMC adopts a low-voltage capacitor, and has the characteristics of low switching frequency, small loss, strong expansibility, high conversion efficiency, simple structure and easy maintenance of the submodule.
Disclosure of Invention
Aiming at the problem that high loss is generated in long-distance power distribution so as to cause serious voltage drop at a user side, the invention utilizes the back-to-back modularized multi-level converter to realize the flexible direct current power distribution technology under long distance, improves the stability of a power grid side and a user side as much as possible on the premise of meeting voltage requirements, and realizes the maximization of economic benefits.
A weak current network low voltage treatment method based on back-to-back modularized multi-level converter. The method comprises the following steps:
step 1: the low voltage cause of the weak current network user side is defined;
step 2: based on the principle of a flexible direct current transmission technology, designing a back-to-back MMC power distribution network model;
step 3: designing a control algorithm and a circulation suppression algorithm by utilizing the working principle of the MMC, modulating a submodule input by the MMC by adopting a latest level approximation modulation technology, and determining the working state of a capacitor by sequencing capacitor voltages of the submodule to generate a PWM signal;
step 4: the MMC at the power distribution side works in a rectification mode, and the rectification voltage is ensured to be stable by adopting double closed-loop control;
step 5: the MMC at the user side works in an inversion mode and adopts a V/f control mode;
further, the step 1 specifically includes: the step 1 specifically includes: the voltage balance relation of the power distribution network is as follows:
U grid =U line +U load ＝IZ line +IZ load …………(1)
wherein U is load For the load voltage, U line For the voltage on the distribution line, U grid Is the voltage of the power grid, I is the current, Z line For line impedance, Z load Is the load impedance. In the power distribution network, when the line is longer, Z line Larger. When U is grid At a fixed value, Z line The larger U line The larger, thereby resulting in U load And (3) reducing.
Further, the step 2 specifically includes: and converting 220V alternating-current phase voltage of the power distribution network into 1000V direct-current voltage by using two working modes of MMC rectification and inversion. Because the voltage of the distribution network is increased from 220V to 1000V, when the distribution power is constant, the higher the voltage, the smaller the current on the line, and the smaller the power lost on the line. And finally converting the 1000V direct current voltage of the direct current bus into 220V alternating current phase voltage and directly transmitting the 220V alternating current phase voltage to a user terminal, so that the user voltage is ensured to be stable at 220V.
Further, the specific process of the step 3 is as follows:
(1) According to the control principle of the MMC, the control targets of the MMC are divided into three layers, and the outermost layer is integrally controlled, including active power control, reactive power control and direct current voltage control; the middle layer is MMC internal energy balance control, including overall energy balance control, interphase energy balance control, inter-bridge arm energy balance control and submodule energy balance control; the innermost layer is current control including loop current suppression, dc current control, and ac current control.
(1.1) for the outermost layer, the object to be controlled is an active or inactive amount; when the MMC works in a rectification mode, double closed-loop control is adopted to ensure the stability of rectification voltage; when the MMC works in the inversion mode, the overall control strategy is V/f control, and the voltage V and the frequency f of the user are ensured to reach the standard.
(1.2) for the middle layer, the balance of internal energy is ensured by balancing the capacitance voltage of the sub-modules, and PWM signals of the MMC are obtained by comparing and calculating the sampled voltages and currents of the upper and lower bridge arms and the number of the reference sub-modules of the upper and lower bridge arms, so that the stable operation of the MMC is controlled.
(1.3) regarding the innermost layer, taking into account the harmonic component of MMC, the upper arm voltage u u And lower bridge arm voltage u l And (3) after summation and finishing, obtaining:
wherein,t is time, U C For the capacitance voltage of the submodules, N is Shan Qiaobei submodules, M is the modulation ratio of MMC, and DeltaU C,1 And DeltaU C,2 The fluctuation amplitude of the capacitor voltage of fundamental frequency and double frequency respectively, w is the angular frequency of the output alternating voltage,/and%>Is the phase lag angle; because of circulation components in the MMC, the capacitor voltage of the submodule fluctuates and serious shadow is generated by circulation and reciprocationBecause of the electric energy quality, a loop current suppression algorithm is provided, and a loop current calculation formula is as follows:
wherein i is circ_j Is the circulation of j phase, i uj And i lj Is the bridge arm current of the upper and lower bridge arms. The a, b, c three-phase circulation is converted by dq to obtain the values of the circulation on d axis and q axis, and the values are compared with the given reference current values of the d axis and the q axis to obtain the residual errors of the d axis and the q axis, and then PIR adjustment is carried out on the residual errors to obtain the j-phase reference voltage under the circulation inhibitionThe transfer function of PIR is:
wherein s is complex frequency domain independent variable, K p And K is equal to i Respectively is a proportion and an integral coefficient, K r2 And K is equal to r4 Gain, w of the frequency doubling and quadrupling resonant controller respectively c Is the bandwidth.
(2) The MMC modulation technology is the key of efficient and stable operation of the converter, the implementation process of the recent level approximation modulation is simple, and the effect obtained by the recent level approximation modulation is that a step U is used C The step wave of the upper bridge arm and the lower bridge arm of the j phase can be obtained by combining the reference voltage with the reference voltage of loop current inhibitionAnd (3) with
Wherein,for the voltage reference value of the j phase of MMC through closed loop control, < >>For the voltage reference value of j phase obtained by the loop current suppressor, U dc As dc side voltage, round is a downward rounding function.
Further, the specific process of the step 4 is as follows:
when the MMC works in the rectification mode, double closed-loop control is adopted to ensure stable rectification voltage, the controlled active quantity of the outer ring is given direct-current voltage of the direct-current bus, the controlled inactive quantity is reactive power, and d-axis instructions are respectively obtained through PI regulationAnd q-axis instruction>Sampling the voltage and current of the alternating current side and obtaining a corresponding current instruction i through dq conversion d0 And i q0 The method comprises the steps of carrying out a first treatment on the surface of the Ask for->And->Is the difference between (1); the obtained difference is subjected to PI regulation to obtain a voltage reference value of j phases>
Further, the specific process of the step 5 is as follows:
when the MMC works in the inversion mode, the overall control strategy is V/f control, the controlled active quantity of the outer ring is frequency, the controlled inactive quantity is alternating voltage, and d-axis instructions are respectively obtained through PI regulationAnd q-axis instruction>Sampling the voltage and current of MMC output side and obtaining corresponding current instruction i through dq conversion d1 And i q1 The method comprises the steps of carrying out a first treatment on the surface of the Ask for->And->Is the difference between (1); the obtained difference is subjected to PI regulation to obtain a voltage reference value of j phases>
The invention relates to a weak current network low-voltage treatment method based on back-to-back modularized multi-level converter, which is characterized in that a weak current network alternating current bus is used for conveying alternating current to MMC at the side of a power distribution network. At this time, the MMC works in a rectifying mode, and the MMC distributes direct current to the MMC at the user side through the original alternating current line. The MMC works in an inversion mode, converts direct current of a direct current bus into alternating current and transmits the alternating current to a user, and ensures the stability of a power grid side and the user side while meeting the conditions.
Compared with the prior art, the invention has the following technical advantages:
aiming at the long-distance multi-user centralized power distribution scene of a weak power grid, the problems of large power distribution radius, ageing of a line, small wire diameter and the like exist, and the problems of serious line power loss, low voltage of a user side and the like exist in the power distribution process. By applying the method of the invention, the voltage of the distribution line is high, the power loss is small, and the voltage of the user terminal is stable and has no low voltage problem.
Drawings
Fig. 1 is a schematic diagram of the low voltage compensation of the power distribution network of the present invention.
Fig. 2 is a circuit topology of an MMC in the present invention.
FIG. 3 is a flow chart of the MMC submodule capacitor voltage balancing method and corresponding PWM signal generation.
Fig. 4 is a diagram of a low voltage example of a conventional weak grid customer premises.
FIG. 5 is a graph of an example of the side voltage of the distribution network and the rectified side voltage of the MMC for low voltage compensation according to the present invention.
Fig. 6 is a diagram of an example of a power distribution network with low voltage compensation at a customer end after implementation of the present invention.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The embodiment of the invention provides a weak current network low-voltage treatment method based on back-to-back modularized multi-level converter, which comprises the following steps:
step 1: analyzing the low voltage cause, the high impedance of the line can cause serious active power and reactive power loss due to long-distance transmission, thereby causing serious voltage drop of the user side.
As shown in fig. 4, the output voltage at the distribution network side and the port voltage at the user side in the conventional distribution mode are shown, the voltage of one of the three phases is 220V, and the port voltage at the user side is 169V only.
Step 2: based on analysis of low voltage reasons, according to a power distribution network model shown in fig. 1, 220V alternating-current phase voltage of a power distribution network is converted into 1000V direct-current voltage by utilizing two working modes of MMC rectification and inversion, and finally the 1000V direct-current voltage of a direct-current bus is converted into 220V alternating-current phase voltage to be directly transmitted to a weak power network user side. The invention ensures that the voltage of the user reaches the standard after a while, and also avoids reactive current loss on the traditional alternating current distribution network line.
Step 3: based on the analysis of MMC control principle, a circulation suppression algorithm is provided, the MMC is modulated by adopting a nearest level approximation modulation technology, the energy balance in the MMC is ensured by balancing the capacitance voltage of the sub-module, and the working state of the capacitor is determined by sequencing the capacitance voltage of the sub-module to generate PWM signals.
According to MMC topology (shown in FIG. 2) control flow (shown in FIG. 3) and equation (5), n * And a reference value representing the number of upper (lower) bridge arm input sub-modules. Taking the bridge arm as an example for illustration, the capacitor voltage and the bridge arm current of the sub-module are sampled, the capacitor voltage of the sub-module is sequenced from small to large by an bubbling sequencing method,the reference value of the number of the upper bridge arm input sub-modules obtained through the nearest level approximation is set to be 0 if the reference value is smaller than or equal to 0 or larger than 6 (the number of the single bridge arm sub-modules is 6 in the design); in contrast, if the reference value is between 0 and 6, the PWM signal is further set by the positive and negative of the bridge arm current. If the bridge arm current is positive, +.>The corresponding voltage measurement will be set to 1, indicating an output PWM signal; if the bridge arm current is negative, then the remainder +.>The corresponding voltage measurement is set to 1, indicating that the PWM signal is output. The generation method of the PWM signals of the lower bridge arm is consistent with the generation method of the PWM signals of the upper bridge arm, and the reference value of the number of the sub-modules input into the lower bridge arm is +.>Also from the recent level approximations.
Step 4: the control algorithm of the modularized multi-level rectifier is provided, and d-axis instructions are respectively obtained through PI adjustment by using given direct-current voltage and reactive powerAnd q-axis instruction>Sampling the voltage and current of the alternating current side and obtaining a corresponding current instruction i through dq conversion d0 And i q0 . Ask for->And->Is the difference between (1); the obtained difference is subjected to PI regulation to obtain a voltage reference value of j phases>And finally, returning to the step 3 to obtain a corresponding PWM signal sequence.
As shown in fig. 5, the output phase voltage on the power distribution network side is stabilized at 220V, and at 0.4s, the dc voltage on the dc bus is substantially stabilized at a given value of 1000V.
Step 5: providing a control algorithm of a modularized multi-level inverter, and respectively obtaining d-axis instructions by PI regulation through given frequency and alternating voltageAnd q-axis instruction>Sampling the voltage and current of the output side of the modularized multi-level converter and obtaining a corresponding current instruction i through dq conversion d1 And i q1 . Ask for->And->Is the difference between (1); the obtained difference is subjected to PI regulation to obtain a voltage reference value of j phases>And finally, returning to the step 3 to obtain a corresponding PWM signal sequence.
As shown in fig. 6, the port voltage and current at the user side enter a steady state before 0.1s, and the port voltage at the user side is always stabilized at 220V in the whole process. At 0.3s the load is added at the user side, the phase voltage stabilizes at 220V, the current increases and stabilizes after 0.02s, the added load is cut off at 0.6s, the current decreases and stabilizes to the original magnitude after 0.02 s.
The foregoing is merely illustrative embodiments of the present invention, and the present invention is not limited thereto, and any changes or substitutions that may be easily contemplated by those skilled in the art within the scope of the present invention should be included in the scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.
Claims (6)
1. A weak current network low voltage treatment method based on back-to-back modularized multi-level converter is characterized by comprising the following steps:
step 1: the low voltage cause of the weak current network user side is defined;
step 2: aiming at the low-voltage reason of a weak power grid, based on the principle of a flexible direct current transmission technology, a back-to-back MMC power distribution network model is provided;
step 3: a control algorithm and a circulation suppression algorithm are provided by utilizing the working principle of the MMC, a submodule input by the MMC is modulated by adopting a nearest level approximation modulation technology, and the working state of a capacitor is determined by sequencing the capacitor voltage of the submodule to generate a PWM signal;
step 4: the MMC at the power distribution side works in a rectification mode, and the rectification voltage is ensured to be stable by adopting double closed-loop control;
step 5: the MMC at the user side works in an inversion mode and adopts a V/f control mode.
2. The weak grid low voltage management method based on back-to-back modular multilevel converter according to claim 1, wherein: the step 1 specifically includes: the voltage balance relation of the power distribution network is as follows:
U grid ＝U line +U load =IZ line +IZ load
wherein U is load For the load voltage, U line For the voltage on the distribution line, U grid Is the voltage of the power grid, I is the current, Z line For line impedance, Z load Is the load impedance; in the power distribution network, when the line is longer, Z line Larger; when U is grid At a fixed value, Z line The larger U line The larger, thereby resulting in U load And (3) reducing.
3. The weak grid low voltage management method based on back-to-back modular multilevel converter according to claim 1, wherein: the step 2 specifically includes: converting 220V alternating-current phase voltage of a power distribution network into 1000V direct-current voltage by using two working modes of MMC rectification and inversion, wherein the power distribution network voltage is increased from 220V to 1000V, when the power distribution is constant, the higher the voltage is, the smaller the current on a line is, and the smaller the electric power loss on the line is; and finally converting the 1000V direct current voltage of the direct current bus into 220V alternating current phase voltage and directly transmitting the 220V alternating current phase voltage to a user terminal, so that the user voltage is ensured to be stable at 220V.
4. The weak grid low voltage management method based on back-to-back modular multilevel converter according to claim 1, wherein: the step 3 specifically includes:
(1) According to the control principle of the MMC, the control targets of the MMC are divided into three layers, and the outermost layer is integrally controlled, including active power control, reactive power control and direct current voltage control; the middle layer is MMC internal energy balance control, including overall energy balance control, interphase energy balance control, inter-bridge arm energy balance control and submodule energy balance control; the innermost layer is current control including circulation suppression, direct current control and alternating current control;
(1.1) for the outermost layer, the object to be controlled is an active or inactive amount; when the MMC works in a rectification mode, double closed-loop control is adopted to ensure the stability of rectification voltage; when the MMC works in the inversion mode, the overall control strategy is V/f control, so that the voltage V and the frequency f of the user are ensured to reach the standard;
(1.2) for the middle layer, the balance of internal energy is ensured by balancing the capacitance voltage of the sub-modules, and PWM signals of the MMC are obtained by comparing and calculating the sampled voltages and currents of the upper and lower bridge arms and the number of the reference sub-modules of the upper and lower bridge arms, so that the stable operation of the MMC is controlled;
(1.3) regarding the innermost layer, taking into account the harmonic component of MMC, the upper arm voltage u u And lower bridge arm voltage u l And (3) after summation and finishing, obtaining:
wherein,t is time, U C For the capacitance voltage of the submodules, N is Shan Qiaobei submodules, M is the modulation ratio of MMC, and DeltaU C,1 And DeltaU C,2 The fluctuation amplitude of the capacitor voltage of fundamental frequency and double frequency respectively, w is the angular frequency of the output alternating voltage,/and%>Is DeltaU C,1 And DeltaU C,2 Phase lag angle; the circulation component exists in the MMC, the circulation makes the capacitance voltage of the submodule generate fluctuation, the electric energy quality is seriously influenced, and a circulation suppression algorithm is adopted, and a circulation calculation formula is as follows:
wherein i is circ_j Is the circulation of j phase, i uj And i lj Bridge arm currents of an upper bridge arm and a lower bridge arm respectively; the a, b, c three-phase circulation is converted by dq to obtain the values of the circulation on d axis and q axis, and the values are matched with the parameters of the given d axis and q axisComparing the current values to obtain residual errors, and performing PIR (phase-of-information) adjustment on the residual errors to obtain j-phase reference voltage under loop current inhibitionThe transfer function of PIR is:
wherein s is complex frequency domain independent variable, K p And K is equal to i Respectively is a proportion and an integral coefficient, K r2 And K is equal to r4 Gain, w of the frequency doubling and quadrupling resonant controller respectively c Is the bandwidth; w is the angular frequency of the output alternating voltage;
(2) The MMC modulation technology is the key of efficient and stable operation of the converter, the implementation process of the recent level approximation modulation is simple, and the effect obtained by the recent level approximation modulation is that a step U is used C The step wave of the upper bridge arm and the lower bridge arm of the j phase can be obtained by combining the reference voltage with the reference voltage of loop current inhibitionAnd (3) with
Wherein,for the voltage reference value of the j phase of MMC through closed loop control, < >>Is circulation inhibitionVoltage reference value of j phase obtained by the generator, U dc As the direct-current side voltage, round is a downward rounding function; n is the number of Shan Qiaobei sub-modules.
5. The weak grid low voltage management method based on back-to-back modular multilevel converter according to claim 1, wherein: the step 4 specifically includes: when the MMC works in the rectification mode, double closed-loop control is adopted to ensure stable rectification voltage, the controlled active quantity of the outer ring is given direct-current voltage of the direct-current bus, the controlled inactive quantity is reactive power, and d-axis instructions are respectively obtained through PI regulationAnd q-axis instruction>Sampling the voltage and current of the alternating current side and obtaining a corresponding current instruction i through dq conversion d0 And i q0 The method comprises the steps of carrying out a first treatment on the surface of the Ask for->And->Is the difference between (1); the obtained difference is subjected to PI regulation to obtain a voltage reference value of j phases>
6. The weak grid low voltage management method based on back-to-back modular multilevel converter according to claim 1, wherein: the step 5 specifically includes: when the MMC works in the inversion mode, the overall control strategy is V/f control, the controlled active quantity of the outer ring is frequency, the controlled inactive quantity is alternating voltage, and d-axis instructions are respectively obtained through PI regulationAnd q-axis instructionSampling the voltage and current of MMC output side and obtaining corresponding current instruction i through dq conversion d1 And i q1 The method comprises the steps of carrying out a first treatment on the surface of the Solving forAnd->Is the difference between (1); the obtained difference is subjected to PI regulation to obtain a voltage reference value of j phases>
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| WO2015135352A1 (en) * | 2014-03-13 | 2015-09-17 | 国家电网公司 | Dc fault ride-through control method of hybrid modular multilevel converter |
| CN106602885A (en) * | 2017-03-03 | 2017-04-26 | 哈尔滨工业大学 | Modular multilevel converter (MMC) four-quadrant frequency converter |
| CN113285620A (en) * | 2021-06-25 | 2021-08-20 | 上海交通大学 | Multi-alternating-current port modular multi-level converter and control method thereof |
| CN116581790A (en) * | 2023-07-12 | 2023-08-11 | 广东电网有限责任公司佛山供电局 | Method and system for restraining modularized multi-level converter in unbalanced power grid |
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2023
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2015135352A1 (en) * | 2014-03-13 | 2015-09-17 | 国家电网公司 | Dc fault ride-through control method of hybrid modular multilevel converter |
| CN106602885A (en) * | 2017-03-03 | 2017-04-26 | 哈尔滨工业大学 | Modular multilevel converter (MMC) four-quadrant frequency converter |
| CN113285620A (en) * | 2021-06-25 | 2021-08-20 | 上海交通大学 | Multi-alternating-current port modular multi-level converter and control method thereof |
| CN116581790A (en) * | 2023-07-12 | 2023-08-11 | 广东电网有限责任公司佛山供电局 | Method and system for restraining modularized multi-level converter in unbalanced power grid |
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