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-Maximum Power Point Tracking (MPPPT) techniques are employed in PV systems to make full utilization of PV array output power which depends on solar irradiation and temperature. Recently, many MPPT algorithms and control schemes of PV system have been proposed, but different control methods and different PID controller parameters lead to different output efficiency and dynamic response. Therefore, in this paper, a PSCAD/EMTDC user defined module of the solar array is established to easily simulate its inherent characteristics with the basic specification data. Moreover, we also compare the advantages and weakness of the existing MPPT control methods by simulations to give a reference to the Grid-Connected Photovoltaic System (GCPS) designers.

A distribution system was designed and operated by considering unidirectional power flow from a utility source to end-use loads. The large penetrations of distributed generation (DG) into the existing distribution system causes a variety of technical problems, such as frequent tap changing problems of the on-load tap changer (OLTC) transformer, local voltage rise, protection coordination, exceeding short-circuit capacity, and harmonic distortion. In view of voltage regulation, the intermittent fluctuation of the DG output power results in frequent tap changing operations of the OLTC transformer. Thus, many utilities limit the penetration level of DG and are eager to find the reasonable penetration limits of DG in the distribution system. To overcome this technical problem, utilities have developed a new voltage regulation method in the distribution system with a large DG penetration level. In this paper, the impact of DG on the OLTC operations controlled by the line drop compensation (LDC) method is analyzed. In addition, a generalized determination methodology for the DG penetration limits in a distribution substation transformer is proposed. The proposed DG penetration limits could be adopted for a simplified interconnection process in DG interconnection guidelines.

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-The generating systems use Doubly-Fed Induction Generators (DFIGs) to achieve high conversion efficiency and to reduce the installation cost. This paper presents a modeling and Maximum Power Point Tracking (MPPT) control method of DFIG-based variable-speed wind energy conversion system. The generator considered is a wound rotor induction machine whose stator is connected directly to the grid and the rotor is fed through back-to-back Pulse-Width Modulation (PWM) converters. Stator flux-oriented vector control is applied to control the active and reactive current loops independently. The MPPT control method in a Wind Energy Conversion System (WECS) is proposed. The proposed control solution aims at driving the position of the operating point near to optimality. This is a very important aspect to maintain DFIGs efficiently in a variable wind speed. The wind generator is modeled in RSCAD program which is interfaced with the Real Time Digital Simulator (RTDS).

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