This paper proposes a new topology for bidirectional multiinput direct dc-ac converter for clean-power-generation system, therefore, at the input port, a boost converter is used to meet the requirement of many distributed generation systems, such as photovoltaic, and fuel cell systems. The boost converter can increase the dc input voltage. This point results in a turn ratio reduction of high-frequency isolating link transformer. Furthermore, the boost inductor reduces the input current ripple, therefore, the saturation of the transformer can be avoided for higher output currents. The count of used devices has been reduced in the proposed converter. As a result, the cost, size, and the volume of the converter can be reduced. The reduced conversion steps increase the efficiency of the converter. The converter is analyzed step by step to show the principles of the operation in providing energy management based on duty-cycle variations. The system capability in different operation conditions has been simulated, and the simulation results have been compared with measurement results.
Dynamic analysis and control design of the bidirectional dc-ac converter is presented based on nonlinear control by input-output feedback linearization.Index Terms-Clean power generation (CPG), dc-ac converter, distributed generation (DG) interface, high-frequency isolating link (HFIL), input-output feedback linearization (IOL), multiinput converter, steady-state analysis.
DC Electrified railways play an important role for metropolitan public transportation because of high efficiency, heavy ridership and fast transportation. However, the electrified railways cause great problems for the power quality of the distribution system feeding the traction system such as injecting harmonics, reactive power compensation and low power factor issue. These problems can be solved by using a hybrid filter in the traction substations. In this paper, a modified PQ control system has been applied for the control of shunt active filter, while the passive filters are used for reducing most of the severe harmonics. The simulation is done with PSCAD/EMTDC proving the efficiency of the proposed hybrid filter structure for reducing the current harmonics, voltage and current balancing, reactive power compensation and power factor improvement.
In this paper a new inverter unit is proposed. It is a compact switched-capacitor-based inverter, which is combined of four switches, two diodes and four capacitors. Since this inverter unit is a mid-point-clamped inverter, it can mitigate the capacitive leakage current in many applications. One of the main applications of the proposed inverter is in grid-tied photovoltaic (PV) systems, where the commonmode current brings many challenges. Other than the mentioned feature, the proposed inverter includes the following advantages: i) spontaneous balancing of the voltage across the capacitors without needing any control system or auxiliary circuits, ii) capability of full reactive power transfer, iii) low voltage stress on the capacitors compared to common three-level inverter topologies (NPC, T-type-NPC, FC and etc.), and iv) symmetric switching sequence, which causes a continuous input current. The feasibility and versatility of the proposed inverter unit is validated by experimental tests, which are conducted by using a lab-scale prototype.
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