A battery energy storage system using modular multilevel converter(MMC)as the interfacing converter could have several inherent advantages when compared with battery energy storage systems based on two-level inverter ...A battery energy storage system using modular multilevel converter(MMC)as the interfacing converter could have several inherent advantages when compared with battery energy storage systems based on two-level inverter or cascaded H-bridge converter.It can manage the state-of-charges(SOCs)of all batteries to be equal to avoid the overcharge or over discharge of single battery.The inherent power exchange characteristics using circulating currents could increase the control flexibility and consequently improve the output quality and the internal regulation capability.This paper investigates the operational principle and control strategy of MMC battery energy storage system under unbalanced grid voltage condition,where key issues of system model and corresponding control methods are very different from those under the normal grid voltage condition.The injected de current control,SOC balancing control and circulating current control methods are fully discussed in this paper.Finally,the theoretical findings were verified through Matlab simulation and a scaled down experimental prototype.展开更多
Asymmetrical voltage swells during recovery of a short-circuit fault lead to fluctuations in the dc-link voltage of a renewable energy conversion system(RECS),and may induce reversed power flow and even trip the RECS....Asymmetrical voltage swells during recovery of a short-circuit fault lead to fluctuations in the dc-link voltage of a renewable energy conversion system(RECS),and may induce reversed power flow and even trip the RECS. This paper studies characteristics of both typical causes resulting in the practical asymmetrical voltage swell and the voltage at the point of common coupling(PCC)during the fault recovery. As analyzed, the fault recovery process can be divided into two continuous periods in which different control strategies have to be applied. Also protective measures are necessary in the transient period of the process. Additionally, the asymmetrical high-voltage ride-through capability and the controllability criteria of the RECS are analyzed based on eliminating the fluctuations. Furthermore, an asymmetrical control scheme is proposed to maintain the controllability of the RECS and ride through the entire recovery process. As verified by the simulation, the scheme can promise the RECS to deal with the practical fault recovery period and mitigate the dc-link voltage fluctuations, which improves the reliability of the RECS and the power system.展开更多
文摘A battery energy storage system using modular multilevel converter(MMC)as the interfacing converter could have several inherent advantages when compared with battery energy storage systems based on two-level inverter or cascaded H-bridge converter.It can manage the state-of-charges(SOCs)of all batteries to be equal to avoid the overcharge or over discharge of single battery.The inherent power exchange characteristics using circulating currents could increase the control flexibility and consequently improve the output quality and the internal regulation capability.This paper investigates the operational principle and control strategy of MMC battery energy storage system under unbalanced grid voltage condition,where key issues of system model and corresponding control methods are very different from those under the normal grid voltage condition.The injected de current control,SOC balancing control and circulating current control methods are fully discussed in this paper.Finally,the theoretical findings were verified through Matlab simulation and a scaled down experimental prototype.
基金supported by National Natural Science Foundation of China(NSFC)(No.U1510208,No.61273045,No.51361135705)National High Technology Research and Development Program of China(No.2012AA050217)Grants from Beijing Higher Education Young Elite Teacher Project
文摘Asymmetrical voltage swells during recovery of a short-circuit fault lead to fluctuations in the dc-link voltage of a renewable energy conversion system(RECS),and may induce reversed power flow and even trip the RECS. This paper studies characteristics of both typical causes resulting in the practical asymmetrical voltage swell and the voltage at the point of common coupling(PCC)during the fault recovery. As analyzed, the fault recovery process can be divided into two continuous periods in which different control strategies have to be applied. Also protective measures are necessary in the transient period of the process. Additionally, the asymmetrical high-voltage ride-through capability and the controllability criteria of the RECS are analyzed based on eliminating the fluctuations. Furthermore, an asymmetrical control scheme is proposed to maintain the controllability of the RECS and ride through the entire recovery process. As verified by the simulation, the scheme can promise the RECS to deal with the practical fault recovery period and mitigate the dc-link voltage fluctuations, which improves the reliability of the RECS and the power system.
