The static synchronous series compensator (SSSC) can add a series reactance to the transmission line, and when it is fed using auxiliary signals, it can participate in damping inter-area oscillations by changing the series reactance. In this paper, the effect of the SSSC on small-signal stability is investigated. The design of a controller for damping oscillations is designed and discussed. Moreover, using the firefly and the harmony search algorithms, the optimal parameters controlling SSSC are addressed. The effectiveness of these two algorithms and the rate of SSSC participation in damping inter-area oscillation are also discussed. MATLAB software was used to analyse the models and to perform simulations in the time domain. The simulation results on the sample system, in two areas, indicated the optimal accuracy and precision of the proposed controller.
Many controllers are available in the market for controlling the Permanent Magnet Synchronous Motor (PMSM) drive application, though the most preferably used one is Proportional Integral (PI), controller. However, it is found that the PI and other latest controllers have their own merits and demerits while analyzing their outputs via comparison. Thus it is decided to test the deed of hybrid controllers that can serve a lot better than standalone controllers for precise control applications. In this article, a conventional PI controller has been applied in closed-loop system in combination with recent controllers like Proportional Resonant Controller (PRC), Fractional order Proportional Integral Derivative (FOPID), Hysteresis Current Controller (HCC) and Fuzzy Logic Controller (FLC). The resultant hybrid controllers were (i) PI-FOPID (ii) PI-FLC (iii) FOPID-FLC (iv) HCC-FLC and (v) PRC-FLC. All these hybrid controllers are designed using MATLAB platform and the speed and torque responses are compared to allocate the better performance award to the hybrid controllers. The continuous and intermittent loads are considered while registering time-domain response of PMSM-Pump application. With the aid of time-domain response and THD, the topology to be tested in prototype is chosen and tested for resemblance of the speed response with the simulation output. PI-FLC hybrid controller tends to render optimum performance characteristics among all the other hybrid controllers and the same is validated in real time through hardware results.
This paper proposes an improved hierarchical control strategy consists of a primary and a secondary layer for a three-phase 4-wire microgrid under unbalanced and nonlinear load conditions. The primary layer is comprised of a multi-loop control strategy to provide balanced output voltages, a harmonic compensator to reduce the total harmonic distortion (THD), and a droop-based scheme to achieve an accurate power sharing. At the secondary control layer, a reactive power compensator and a frequency restoration loop are designed to improve the accuracy of reactive power sharing and to restore the frequency deviation, respectively. Simulation studies and practical performance are carried out using the DIgSILENT Power Factory software and laboratory testing, to verify the effectiveness of the control strategy in both islanded and grid-connected mode. Zero reactive power sharing error and zero frequency steady-state error have given this control strategy an edge over the conventional control scheme. Furthermore, the proposed scheme presented outstanding voltage control performance, such as fast transient response and low voltage THD. The superiority of the proposed control strategy over the conventional filter-based control scheme is confirmed by the 2 line cycles decrease in the transient response. Additionally, the voltage THDs in islanded mode are reduced from above 5.1% to lower than 2.7% with the proposed control strategy under nonlinear load conditions. The current THD is also reduced from above 21% to lower than 2.4% in the connection point of the microgrid with the offered control scheme in the grid-connected mode.