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A Static Synchronous Series Compensator incorporating energy storage device (SSSC-ES) at the DC bus enables the exchange of true power with the system in addition to line reactance compensation. This facilitates improved control of real and reactive power in a transmission system. However, the fourquadrant operation of SSSC presents additional problems for the accurate operation of conventional transmission line protection. In this paper, an in-depth analysis of the effect of emulated reactance and resistance by SSSC-ES installed at the center of a hybrid series compensated line on the performance of distance relay is carried out. An investigation is performed with all possible operating modes and control strategies of SSSC-ES, and the possibility of mal-operation of distance protection are explored. A novel adaptive setting based on constant reactance and constant resistance emulation control strategy of SSSC is proposed for quadrilateral distance relay to prevent the mal-operation. MATLAB / SIMULINK is used for the simulation study.

Static Synchronous series compensator without energy storage device can exchange only reactive power with the network and can operate in limited operating range in two quadrants only. When energy storage device is connected at the DC bus of SSSC (SSSC -ES), it can also exchange real power with the network. Operating range of SSSC will be much broader and it covers all the four quadrants. However, emulated reactance and resistance by SSSC -ES is likely to affect the performance of a distance protection system. This paper presents a detailed model of an SMIB system with SSSC -ES. Injected voltage by SSSC -ES in all the four quadrants of operation is presented. Impact of operation of SSSC -ES in different quadrants and various control strategies for SSSC -ES on impedance emulated by SSSC -ES during steady state condition and transient system disturbance is discussed.

Large numbers of non-dissipative equalizers have been proposed for solving the inconsistency problem of lithium battery strings. However, these equalizers face problems such as slow speed or using excessively large numbers of energy storage elements. This paper improved a multiple switch-inductors equalizer (MSIE), and proposed a novel inductor-based non-dissipative equalizer (NIBNDE). A simulation is built to compare the NIBNDE with two other equalizers, which indicated that the NIBNDE can reduce the number of energy storage elements while remaining at a good equalization speed. Experimental results validate the analysis of the simulation and the feasibility of the NIBNDE.

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