To meet the augmented load power demand, the doubly-fed induction generator (DFIG) based wind electrical power conversion system (WECS) is a better alternative. Further, to enhance the power flow capability and raise security margin in the power system, the STATCOM type FACTS devices can be adopted as an external reactive power source. In this paper, a three-level STATCOM coordinates the system with its dc terminal voltage is connected to the common back-to-back converters. Hence, a lookup table-based control scheme in the outer control loops is adopted in the Rotor Side Converter (RSC) and the grid side converter (GSC) of DFIG to improve power flow transfer and better dynamic as well as transient stability. Moreover, the DC capacitor bank of the STATCOM and DFIG converters connected to a common dc point. The main objectives of the work are to improve voltage mitigation, operation of DFIG during symmetrical and asymmetrical faults, and limit surge currents. The DFIG parameters like winding currents, torque, rotor speed are examined at 50%, 80% and 100% comparing with earlier works. Further, we studied the DFIG system performance at 30%, 60%, and 80% symmetrical voltage dip. Zero-voltage fault ride through is investigated with proposed technique under symmetrical and asymmetrical LG fault for super-synchronous (1.2 p.u.) speed and sub-synchronous (0.8 p.u.) rotor speed. Finally, the DFIG system performance is studied with different phases to ground faults with and without a three-level STATCOM. INDEX TERMSDoubly-fed induction generator (DFIG), field oriented control (FOC), common-capacitor based STATCOM, voltage compensation, balanced and unbalanced faults, zero-voltage fault ride through.

This paper discussed the topology development of a single-stage microinverter in grid-connected PV system. In general, the microinverter topologies can be categorized into four type of topologies:          1) Flyback inverter, 2) Double-boost inverter, 3) Derived zeta-cuk configuration and 4) Buck-boost inverter. Flyback configuration is widely used for single-stage microinverter which offers protection between solar panel and utility grid. However due to the bulkiness of the transformer, new arrangement circuit employ the Half-Bridge topology with film capacitor and microcontroller provide a good room for research and future developments to obtain greater efficiency and compact design of single-stage microinverter grid-connected PV system. Plus, there are several characteristics need to be taken care for future development of the microinverter technology.

<span>The development of active power filter (APF) using rectifier boost technique has been identified to compensate for the pulsating nature of the distorted supply current waveform of non-linear load. In this work, investigation is carried out on the operation of rectifier without any filters function. This is then extended to operate the rectifier converter with an active power filter function. APF function is implemented by enabling the closed-loop control using standard proportional integral control to rectify the distorted supply current to become continuous, sinusoidal and in-phase with the supply voltage waveform. Consequently, the total harmonic distortion (THD) level was reduced to meet the acceptable limit defined in the standard of IEEE-519 1992. The selected simulation results obtained from MATLAB/Simulink are presented to justify the proposed filter structure.</span>

This paper presents a novel single-stage Microinverter topology using only two-power switches. The number of components count are directly proportional to the power losses, weight, cost and complexity of the design. Nowadays, conventional Microinverter without transformer having minimum of six power switches, while only three power switches involved in a Microinverter structure with the presence of a transformer. Thus, this paper proposed a novel Microinverter topology with only two-power switches to convert DC-voltage from Photovoltaic (PV) module to an AC-output. Modes of operation and current flow during each cycle are being explained. Variation of modulation index, irradiance and temperature of the PV module, the switching frequency and harmonic content of the proposed Microinverter are being analysed. A simulated model of Microinverter topology, employed only two power switches with a standard Unipolar Sinusoidal Pulse Width Modulation (SPWM) having 0.85% harmonic percentage; able to inject current to the load; have been successfully built and demonstrated through simulation based on MATLAB/Simulink, thus provide theoretical validation for further research.

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