<p>To solve the energy consumption demand of the world and environmental problems in the future the distributed generation is considered an alternative approach. In this paper a new passive islanding detection technique was proposed for the Hybrid distributed generation (HDG) system based on changes in negative sequence voltage (NSV) and currents during an unintentional islanding. Islanding is caused in the distributed generation system due to failures in the power grid. As per distribution energy resources interconnection standards, it should be detected within 2 sec with the equipments connected to it. It is difficult to detect islanding during zero power imbalance condition. Sequence analyzer will separate the positive, negative and zero sequence components of voltages and currents from the voltages and currents obtained at the point of common coupling (PCC). During a wide range of power imbalance conditions the change in negative sequence voltage and currents are examined for islanding detection. The simulation shows that this method is free from Non detection zone, even at zero power imbalances between load and distribution generation. The computer simulations made in Matlab/ Simulink laboratory show the effectiveness of this method</p>
High power demands are usually met by advanced power electronics converters in several large utility and electric drives applications. Applications from high power drives commonly uses solution based multi pulse and multilevel converters. A common DC link with atleast one voltage source converter (VSC) working with almost fundamental switching frequency are used in converters of multipulse type, and each output module is connected with the multipulse transformer in series. When compared to that of solution with single-VSC, Several VSCs generating different triggering pulses are adjused in order to achieve current injected with low specified total harmonic distortion (THD) with losses of abridged switching. Huge structure in complexity and expensive cost expenditure of the multipulse transformer is the major limitation of this scheme. DC link split capacitors in addition are eliminated by modifying the topology of the circuit. Thus, the independent voltages of the DC capacitor are controlled and decreased in number and the flow of third harmonic current component in the transformer is eliminated. The scheme of the designed controller is depending on the derived mathematical system model. Simulaion observation is used to check the scheme performance and efficiency in a detailed way with drive control technique.
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