An efficient pulse width modulation scheme for Cascaded H-Bridge inverter (CHBI) is proposed in this paper. The proposed modulation scheme is a low switching frequency modulation scheme termed as modified Nearest Level Modulation (mNLM) scheme. Compared to the conventional nearest level modulation (NLM) scheme, the proposed modulation scheme reduces the total harmonic distortion (THD) at the ac output of the inverter. The mNLM follows an algorithm presented in the paper in order to arrive at a set of switching angles for MLI which offers reduced THD. Simulation is carried out using MATLAB/Simulink 2015b software and hardware is presented which validates the simulation results. Results show that there is a notable reduction in the THD content with the use of proposed modulation scheme. Because of the improved THD content, improvement in the other inverter parameters such as rms voltage, rms current and increased output power is also observed.

Modular Multilevel Converters (MMC) are gaining importance because of their flexible structure, re-configurable property, and simplicity of operation. The operation of MMC at a low-switching frequency (LSF) helps in enhancing the performance of the converter. This paper proposes an improved harmonics mitigation scheme for a Multilevel DC-Link Inverter (MLDCLI), which is a variant of MMC. The proposed scheme is a modified version of the conventional Nearest Level Modulation (NLM) scheme, termed as modified Nearest Level Modulation (mNLM) Scheme. The proposed scheme is effective compared to NLM because of the choice of the switching angles obtained by the use of the algorithm proposed. The MLDCLI topology is operated for twelve different configurations, and mNLM is implemented on all the configurations. Using MATLAB software, the simulation results are validated, and the same is extended to a hardware prototype. The simulation and experimental results of NLM and mNLM schemes are compared. The effectiveness of the proposed scheme is evident by the reduced voltage THD, increased rms voltage, increased rms current, and increased output power.INDEX TERMS Modular multilevel converters, DC-AC power converters, pulse width modulation converters, power conversion harmonics, nearest level modulation, total harmonics distortion.

A high number of research work is being carried out in the field of DC-DC converters to improve the performance of microgrid operation. The DC microgrid has a high level of acceptance because of the integration of renewable energy sources. In DC Microgrid, there is a need for improved DC-DC converter topologies which offer high gain, small size, enhanced efficiency, reduced voltage stress and reduced component count etc. A new Triple-Mode Active-Passive Parallel Intermediate Links (TM-A2P-IL) converter is proposed in the paper. The A2P-IL is designed by a combination of an inductor, capacitor, diode, and control switch. The proposed converter is derived by inserting A2P-IL in conventional boost converter. The proposed TM-A2P-IL converter operates in three modes and provides a high voltage gain without using a transformer, voltage multiplier stages, coupled inductor, switched inductor/capacitor circuitry. The other benefits of the proposed TM-A2P-IL converters are flexibility in the selection of duty cycles, reduced voltage stress of devices, small reactive components, single-stage power conversion. The proposed converter circuit, operating principle, steady-state analysis is studied for both CCM and DCM, discussed. The comparison between available similar type converters and the proposed converter is provided. The operation and performance of the proposed A2P-IL converter are validated through simulation and experimental work.

The solar photovoltaic (PV) system is emerging energetically in meeting the present energy demands. A rise in PV module temperature reduces the electrical efficiency, which fails to meet the expected energy demand. The main objective of this research was to study the nature of OM29, which is an organic phase change material (PCM) used for PV module cooling during the summer season. A heat transfer network was developed to minimize the experimental difficulties and represent the working model as an electrical resistance circuit. Most existing PV module temperature (TPV) reduction technology fails to achieve the effective heat transfer from the PV module to PCM because there is an intermediate layer between the PV module and PCM. In this proposed method, liquid PCM is filled directly on the back surface of the PV module to overcome the conduction barrier and PCM attains the thermal energy directly from the PV module. Further, the rear side of the PCM is enclosed by tin combined with aluminium to avoid any leakages during phase change. Experimental results show that the PV module temperature decreased by a maximum of 1.2 °C using OM29 until 08:30. However, after 09:00, the OM29 PCM was unable to lower the TPV because OM29 is not capable of maintaining the latent heat property for a longer time and total amount of the PCM experimented in this study was not sufficient to store the PV module generated thermal energy for an entire day. The inability of the presented PCM to lower the temperature of the PV panel was attributed to the lower melting point of OM29. PCM back sheet was incapable of dissipating the stored PCM’s thermal energy to the ambient, and this makes the experimented PCM unsuitable for the selected location during summer.

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