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The paper presents distributed generation (DG) system in grid connected mode of operation with asymmetric multi-level inverter (AMLI) topology. Cascaded type DC-DC converter is employed to feed proposed AMLI topology. The DG output voltage (generally low voltage) is stepped up to the required level of voltage using high-gain DC-DC converter. Proposed AMLI topology consists of capacitors at the primary side. The output of high-gain DC-DC converter is fed to split voltage balance single-input multi-output (SIMO) circuit to maintain voltage balance across capacitors of AMLI topology. Cascaded DC-DC converters (both high-gain converter and SIMO circuit) are operated in closed-loop mode. The proposed AMLI feeds active power to grid converting DC type of power generated from DG to AC type to feed the grid. PWM pattern to trigger power switches of AMLI is also presented. The inverting circuit of MLI topology is controlled using simplified Id-Iq control strategy in this paper. With the proposed control theory, the active power fed to grid from DG is controlled and power factor is maintained at unity. The proposed system of DG integration to grid through cascaded DC-DC converters and AMLI structure is validated from fixed active power to grid from DG condition. The proposed system is developed and results are obtained using MATLAB/SIMULINK software.

In this paper, a cascaded based reversing voltage (CBRV) multilevel inverter structure is proposed inorder to compensate the major drawbacks in the conventional multilevel inverters. The proposed topology requires less number of components, less carrier signals and gate drives when compared to existing multilevel inverters particularly at higher levels. Therefore, the complexity and overall cost are greatly reduced particularly for higher output voltage levels. This paper also presents the most relevant control and modulation methods by a triangular based multi carrier pulse width modulation (PWM) scheme for the proposed CBRV inverter topology. This paper presents a comparison between different modulation strategies for CBRV inverter topology based on sinusoidal and space vector references with multi triangular carrier waves. The work strive hard to present the scrutiny that has been made between various PWM control techniques for 1–Ф seven level CBRV inverter structure. The comparison is made in terms of Total Harmonic Distortion (THD) and fundamental RMS voltage. Finally, the simulation results are included to verify the effectiveness of the proposed CBRV inverter topology and validate the proposed theory. A hardware set up was developed for a 1–Ф seven level CBRV inverter topology using FPGA based pulse generation.

Unified Power Quality Conditioner (UPQC) is substantial power conditioner in power system to filter the power system parameters with an objective to improve the quality of power delivered to the customers/utility point. This paper presents a multi-level UPQC to enhance the quality in power distribution system. The series and shunt controllers of UPQC gives out five leveled output which is further filtered to feed compensating signals to improve voltage and current profiles in power distribution system. Series and shunt controllers of UPQC are structured with cascaded H-Bridge (CHB) topology to deliver compensating signals. Two separate control strategies are employed to regulate the power switches of 5-level CHB series and shunt controllers of UPQC. Sag and swell in source voltage and harmonics in source current are strained with UPQC. The proposed system is developed and results are obtained using MATLAB/SIMULINK software.

<table width="0" border="1" cellspacing="0" cellpadding="0"><tbody><tr><td valign="top" width="593"><p>The conventional energy sources available to us are on the verge of depletion. This depletion of conventional energy source leads to concentrate more on alternative energy sources. In this research, the focus is on the role of renewable energy sources (RES) in electrical power generation. Even though, the RES based plants produce power, we cannot directly connect it to the grid or loads. Because, the voltage ratings and nature supply of RES plants would not match with the load. Hence, this is a major issue for connecting RES plants to load or other utility. The power electronic converters are extensively being used as a link between load and supply. As most of the renewable energy power generation is DC in nature, the DC-DC converter is used to increase the voltage level and this DC must be converted to AC for grid connection. Therefore, inverters are used for DC to AC conversion. In this paper, the DC supply of renewable energy is connected to load by using cascade DC-DC converters along with a proposed reversing voltage (RV) multilevel inverter (MLI). The first DC-DC converter is used to enhance the voltage level with high gain and second converter is used to split the DC supply for inverter convenience. In this paper, proposed RV symmetrical and asymmetrical MLI generates 7, 9, 11, 13 and 15 levels with only ten power switches. In-phase level-shifted triangular carrier type sine pulse width modulation (PWM) technique is employed to trigger the commutating switches of proposed RV MLI. Switches of H-Bridge for reverse voltage appearance across the load are triggered by simple pulse generator. The circuits are modeled and simulated in MATLAB/SIMULINK software. Results are presented and discussed.</p></td></tr></tbody></table>

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