CN105634257A - Virtual impedance based DC-side fault current suppression method of modular multilevel converter (MMC) - Google Patents
Virtual impedance based DC-side fault current suppression method of modular multilevel converter (MMC) Download PDFInfo
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Abstract
The invention relates to a virtual impedance based DC-side fault current suppression method of a modular multilevel converter (MMC), belonging to the technical field of power transmission. A DC-side fault of the MMC can cause overcurrent of a switching device; and based on a traditional control strategy, a virtual impedance parallel circuit in a primary system is mapped to a controller by a feedback function, DC bus impedance is equivalently risen, thus, instantaneous rising speed of a fault current when a fault occurs in a DC side of the MMC is effectively prevented without increasing the fault current rising speed of other types of faults. In the core scheme, firstly, the DC bus voltage and current of a MMC system and the active power of a PCC point of an AC side are measured in real time; secondly, if the virtual impedance circuit is connected in series to a DC bus, the DC voltage deviation and the active power deviation are calculated when the DC current passes through the virtual circuit; and finally, the associated deviation correction quantity is additionally added to a measurement value of an active power type control quantity of a DQ decoupling controller for correction.
Description
Technical field
The invention belongs to power transmission and distribution technical field, particularly relate to a kind of MMC DC side fault current suppressing method based on virtual impedance.
Background technology
Modularization multi-level converter (ModularMultilevelConverter, MMC) there is higher power transmission capacity, bear that voltage change ratio is low without a large amount of IGBT crimping series connection, device and the advantage such as harmonic characterisitic is better, be increasingly becoming the development trend of flexible DC power transmission.
The DC side fault of MMC can cause sending end and the significantly charge and discharge of receiving end inverter submodule, and then causes switching device to cross stream. Compared with AC fault, the Evolution Rates after the DC side fault generation of MMC is exceedingly fast, and the properly functioning of the alternating current-direct current side of the MMC that very easily all the other is connected produces impact, and causes switching device to cross stream within the extremely short time. The transient current size flowing through device under fault condition before switching device locking directly affects choosing of switching device parameter. The suppression of fault current when being realized MMC generation DC side fault by control mode, existing research does not almost relate to.
Summary of the invention
The fault current of DC side fault is occurred to suppress problem for above-mentioned background technology is mentioned MMC, the present invention adopts virtual impedance control strategy, based on existing DQ decoupling control policy, by increasing the feedback element of real power control amount at D axle, ssystem transfer function is modified, feedback control is mapped in primary system and forms virtual impedance parallel circuit, equivalence increases dc bus impedance such that it is able to the instantaneous rate of climb of DC current and bridge arm current when effectively suppressing MMC DC side to break down.
The present invention is the mapping in primary system of the control system, and the steady state operating condition of system will not be produced impact by itself; And during other faults such as system generation AC fault, the additional control designed by the present invention will not accelerate the rate of climb of its fault current. The feature of technical scheme comprises the following steps:
Step 1: utilize current sensor to measure MMC system dc bus current in real time, utilizes voltage sensor to measure MMC system dc busbar voltage in real time, utilizes power-measuring device to measure MMC system PCC point place active power.
Step 2: according to the resistance value in MMC circuit system parameter setting virtual impedance circuit and reactance value, it is connect into dc bus place after parallel connection that virtual resistance links system form with virtual reactance; DC current is carried out DC voltage deviation calculating through virtual impedance parallel circuit, carries out active power deviation calculating according to DC voltage deviation.
Step 3: according to the difference of the meritorious class controlled quentity controlled variable of MMC controller, relevant drift correction amount is attached to DQ decoupling controller meritorious class controlled quentity controlled variable measured value on be modified, thus realizing the monitoring in real time to direct fault current and suppressing.
The present invention passes through three above step, it is possible to realize realizing the rate of climb of direct fault current (DC current, bridge arm current) when MMC system generation DC side fault effectively suppressing.
Accompanying drawing explanation
Fig. 1 is the virtual impedance circuit diagram being attached to dc bus; Fig. 2 is DC voltage deviation and active power deviation computing block diagram; Fig. 3 is the DQ decoupling controller of additional meritorious class controlled quentity controlled variable deviation.
Detailed description of the invention
A kind of MMC DC side fault current suppressing method based on virtual impedance that the present invention relates to will be elaborated below. It is emphasized that the description below is merely exemplary, rather than in order to limit the scope of the present invention and application thereof.
The technical problem to be solved adopts virtual impedance control strategy, based on existing DQ decoupling control policy, by increasing the feedback element of real power control amount at D axle, ssystem transfer function is modified, feedback control is mapped in primary system and forms virtual impedance parallel circuit, equivalence increases dc bus impedance such that it is able to the instantaneous rate of climb of DC current and bridge arm current when effectively suppressing MMC DC side to break down. The present invention adopts the following technical scheme that realization:
Step 1: utilize current sensor to measure MMC system dc bus current in real time, be designated asI dc, utilize voltage sensor to measure MMC system dc busbar voltage in real time and be designated asU dc, utilize power-measuring device to measure MMC system PCC point place active power, be designated asP s��
Step 2: according to the resistance value in MMC circuit system parameter setting virtual impedance circuitR virAnd reactance valueL vir,R virWithL virLinking system form is connect into dc bus place after parallel connection, as shown in Figure 1;
To DC currentI dcCarry out DC voltage deviation calculating through virtual impedance parallel circuit, have:
Carry out active power deviation calculating according to DC voltage deviation, have:
��
Controller realizes block diagram as shown in Figure 2.
Step 3: according to the difference of the meritorious class controlled quentity controlled variable of MMC controller, relevant drift correction amount is attached to DQ decoupling controller meritorious class controlled quentity controlled variable measured value on be modified, thus realizing the in real time monitoring to direct fault current and suppressing: if current conversion station is constant DC voltage control station, then use step 2 calculate DC voltage deviation value to dc voltage measurementsU dcBeing modified, controller outer loop feedback value is modified to:
;
If current conversion station is for determine active power controller station, then use step 2 calculate active power deviation value to wattful power messurement valueP sBeing modified, controller outer loop feedback value is modified to:
��
Controller implements block diagram as shown in Figure 3.
It should be noted that step 1,2 and 3 entirety are as summary of the invention, and three steps are organic indivisible entirety.
The above; being only the present invention preferably detailed description of the invention, but protection scope of the present invention is not limited thereto, any those familiar with the art is in the technical scope that the invention discloses; the change that can readily occur in or replacement, all should be encompassed within protection scope of the present invention. Therefore, protection scope of the present invention should be as the criterion with scope of the claims.
Claims (2)
1. the MMC DC side fault current suppressing method based on virtual impedance, it is characterized in that introducing the virtual impedance parallel circuit at dc bus place, comprise the following steps: step 1: measure MMC system dc busbar voltage, electric current and AC PCC point active power in real time; Step 2: assume that virtual impedance circuit connected in series enters dc bus place, passes through this virtual circuit and carries out DC voltage deviation and the calculating of active power deviation DC current; Step 3: relevant drift correction amount is attached to DQ decoupling controller meritorious class controlled quentity controlled variable measured value on be modified.
2. based on a kind of MMC DC side fault current suppressing method based on virtual impedance described in claim 1, it is characterized in that step 1,2 and 3 entirety are as summary of the invention, enabling realize realizing the rate of climb of direct fault current (DC current, bridge arm current) when MMC system generation DC side fault effectively suppressing; And the fault current rate of climb of other types fault will not be accelerated, three steps are organic indivisible entirety.
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| CN106451634A (en) * | 2016-10-26 | 2017-02-22 | 徐州工业职业技术学院 | Distributed equalization charge and discharge method for storage battery and distributed microgrid structure |
| CN107154641A (en) * | 2017-06-05 | 2017-09-12 | 湖南大学 | The stable control method of VSC HVDC transmission systems |
| CN107528495A (en) * | 2017-09-25 | 2017-12-29 | 中国电力科学研究院 | A kind of control method and system for improving PWM inverter impact resistance |
| CN107895965A (en) * | 2017-10-18 | 2018-04-10 | 广东电网有限责任公司电力调度控制中心 | A kind of analysis method of grid-connected MMC ac input power characteristic |
| CN108258891A (en) * | 2016-12-28 | 2018-07-06 | 中国电力科学研究院 | The method and apparatus of resonance between a kind of end-to-end MMC-HVDC DC sides station of inhibition |
| CN110311542A (en) * | 2019-07-09 | 2019-10-08 | 南方电网科学研究院有限责任公司 | Control method and control device for virtual reactance of modular multilevel converter |
| CN111130080A (en) * | 2020-01-17 | 2020-05-08 | 佛山科学技术学院 | Photovoltaic system instantaneous fault overcurrent suppression method based on virtual impedance |
| CN111224409A (en) * | 2020-01-17 | 2020-06-02 | 南方电网科学研究院有限责任公司 | Virtual impedance-based over-current suppression method for direct current access device |
| CN112086995A (en) * | 2019-11-07 | 2020-12-15 | 国网江苏省电力有限公司经济技术研究院 | Control strategy suitable for LCC-MMC hybrid cascade converter station parallel MMC unit |
| CN112152250A (en) * | 2020-09-21 | 2020-12-29 | 四川大学 | Flexible direct-current fault current combined limiting method considering bridge arm current suppression |
| CN112421682A (en) * | 2020-12-11 | 2021-02-26 | 南方电网科学研究院有限责任公司 | Multi-stage voltage correction control method and device for offshore alternating current fault |
| CN113067358A (en) * | 2021-03-25 | 2021-07-02 | 中国矿业大学 | Method for reducing direct current side current-limiting reactor of MMC type direct current network |
| CN113469454A (en) * | 2021-07-20 | 2021-10-01 | 华能陇东能源有限责任公司 | Integrated energy base direct current modulation parameter configuration method and system |
| CN114024294A (en) * | 2021-10-22 | 2022-02-08 | 武汉大学 | Virtual-entity integrated current limiting system and method suitable for half-bridge type MMC |
| CN114362572A (en) * | 2022-01-13 | 2022-04-15 | 国网江苏省电力有限公司 | Method for calculating maximum temporary overvoltage of parallel MMC under AC short-circuit fault |
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| CN106451634B (en) * | 2016-10-26 | 2019-03-22 | 徐州工业职业技术学院 | A kind of distributed storage battery group equalization charging/discharging thereof and distributed micro-grid structure |
| CN106451634A (en) * | 2016-10-26 | 2017-02-22 | 徐州工业职业技术学院 | Distributed equalization charge and discharge method for storage battery and distributed microgrid structure |
| CN108258891B (en) * | 2016-12-28 | 2021-10-01 | 中国电力科学研究院 | Method and device for inhibiting resonance between end-to-end MMC-HVDC direct current side stations |
| CN108258891A (en) * | 2016-12-28 | 2018-07-06 | 中国电力科学研究院 | The method and apparatus of resonance between a kind of end-to-end MMC-HVDC DC sides station of inhibition |
| CN107154641A (en) * | 2017-06-05 | 2017-09-12 | 湖南大学 | The stable control method of VSC HVDC transmission systems |
| CN107528495A (en) * | 2017-09-25 | 2017-12-29 | 中国电力科学研究院 | A kind of control method and system for improving PWM inverter impact resistance |
| CN107895965A (en) * | 2017-10-18 | 2018-04-10 | 广东电网有限责任公司电力调度控制中心 | A kind of analysis method of grid-connected MMC ac input power characteristic |
| CN110311542A (en) * | 2019-07-09 | 2019-10-08 | 南方电网科学研究院有限责任公司 | Control method and control device for virtual reactance of modular multilevel converter |
| US11616369B2 (en) | 2019-11-07 | 2023-03-28 | State Grid Jiangsu Electric Power Co., Ltd. | Control method for a parallel MMC unit of a LCC-MMC hybrid cascade converter station |
| CN112086995A (en) * | 2019-11-07 | 2020-12-15 | 国网江苏省电力有限公司经济技术研究院 | Control strategy suitable for LCC-MMC hybrid cascade converter station parallel MMC unit |
| CN111130080A (en) * | 2020-01-17 | 2020-05-08 | 佛山科学技术学院 | Photovoltaic system instantaneous fault overcurrent suppression method based on virtual impedance |
| CN111224409A (en) * | 2020-01-17 | 2020-06-02 | 南方电网科学研究院有限责任公司 | Virtual impedance-based over-current suppression method for direct current access device |
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| CN112421682A (en) * | 2020-12-11 | 2021-02-26 | 南方电网科学研究院有限责任公司 | Multi-stage voltage correction control method and device for offshore alternating current fault |
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| CN113067358A (en) * | 2021-03-25 | 2021-07-02 | 中国矿业大学 | Method for reducing direct current side current-limiting reactor of MMC type direct current network |
| CN113469454A (en) * | 2021-07-20 | 2021-10-01 | 华能陇东能源有限责任公司 | Integrated energy base direct current modulation parameter configuration method and system |
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| CN114024294A (en) * | 2021-10-22 | 2022-02-08 | 武汉大学 | Virtual-entity integrated current limiting system and method suitable for half-bridge type MMC |
| CN114024294B (en) * | 2021-10-22 | 2023-08-15 | 武汉大学 | Virtual-physical integrated current limiting system and method suitable for half-bridge MMC |
| CN114362572A (en) * | 2022-01-13 | 2022-04-15 | 国网江苏省电力有限公司 | Method for calculating maximum temporary overvoltage of parallel MMC under AC short-circuit fault |
| CN114362572B (en) * | 2022-01-13 | 2024-02-09 | 国网江苏省电力有限公司 | Calculation method for maximum temporary overvoltage of parallel MMC under alternating current short circuit fault |
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