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Photovoltaic (PV) systems can be connected to the utility grid to ensure the reliability and continuity of the electrical energy supply. Although the output of the PV modules and many electrical loads are direct current (DC), most grid connected PV systems use alternating current (AC) grid through the inverter. This study presents an analysis of DC microgrid PV system connected to PLN utility grid using controlled rectifier. The controlled rectifier circuit uses a thyristor which can be controlled at its ignition angle to regulate the output voltage and current supplied from utility. The proposed PV system configuration simulations are performed using PSIM software. The system supplies resistive loads in the form of DC lights. Simulations are carried out with variations in load resistance and the thytistor ignition angle. The simulation results show the rectifier circuit has a voltage ripple of 1.57 V (6.47%). While the efficiency of the system under various loading conditions and ignition angle varies between 95.08%–97.72%. The highest system efficiency is obtained under high thyristor ignition conditions.

A power loss analysis of multilevel current-source inverter (MCSI) circuits developed from two basic configurations of three-level current-source inverters, i.e. H-bridge and common-emitter inverter configurations is presented and discussed. The first circuit topology of the MCSI is developed by using DC current modules connected to the primary three-level H-bridge inverter. The second MCSI circuit is created by connecting the current-modules to a three-level common-emitter inverter. The DC current modules work generating the intermediate level waveform of the inverter circuits. Power loss analysis of the both topologies was carried out to explore the efficiency performance of the inverter circuits. The results showed that for the H-bridge and common-emitter MCSI using DC current modules, the amount of conduction losses in the inverter circuits could be diminished when the level number of AC output current increase. The measurement test results have also proved that using these MCSI topologies, the power conversion efficiency will also increase.

Research and development on power converters are getting more interesting in recent years. It is also buttressed by rapid development in related fields, such as power semiconductor, digital advanced control, magnetic material and use of power converters in many sectors. In addition to the power quality matter, simplicity of inverter circuits is another notable aspect that should be considered toward economical feature. Adding the quantity of power switches will increase complexity of overall inverter circuits. This paper discusses a circuit configuration of three-level modified sine wave neutral point shorted power inverter which work converting dc power into ac power with less number of power switches. To improve the performance and feature of inverter circuits, the inverter was equipped with online temperature monitoring, and overheat protection based on internet of things. Adding online temperature monitoring system makes easier in monitoring of circuits to prevent the excessive faults of inverter. Some computer-based test data are shown and discussed. Furthermore, experiment results of the inverter prototype, and its online monitoring system are presented. Test outputs demonstrated that the proposed system worked properly generating a three-level modified sine wave voltage, with online temperature monitoring system.

Photovoltaic (PV) system is an alternative solution to provide electricity at rural area. A common implementation problem at rural area is the PV power plant cannot be monitored continuously. This research proposes wireless node for PV power plant monitoring based on Internet of Things (IoT). Wireless node is aimed for monitoring electrical parameter from the PV and environmental parameter (temperature and solar radiation). Measured parameters are sent to the cloud database to be accessible via the internet. The device consist of a sensor module, signal processing module and wireless transceiver module. Wireless transceiver module is an ESP8266 for connection to the IoT gateway and to the internet. Unidirectional ACS758 is used for current sensing, which give a reading error of 0.091 Ampere. For voltage sensing, a voltage divider is used. It has a reading error of 0.063 Volt. DHT22 is used for temperature sensing. Its reading error is 0.0097 °C. The radiation sensor has a reading error of 0.3 W/m2. Proposed design has been tested at Laboratorium of Energy Convertion, Electrical Engineering Department, UNSOED, on 300Wp PV system. This device provides reliable monitoring data transmission with average and deviation in delivery time consecutively 57 seconds and 2 seconds.

Renewable power generation using photovoltaic is very interesting to be developed to deal with the problems of conventional energy sources and environmental issues. The photovoltaic power generation can operate both in stand-alone and grid-connected operations. This paper presents an application of the five-level common-emitter current-source inverter (CE-CSI) for grid connected photovoltaic system without batteries as energy storage system. In the proposed system, the five-level CE-CSI works generating a sinusoidal output current from photovoltaic system to be injected into the power grid. The transformer is used in the system to step-down the grid voltage to meet the voltage level of the photovoltaic system, and also works as a galvanic insulation between the power grid and the inverter system. Two conditions of the power grid voltage, i.e. a pure sinusoidal and a distorted power grid, are tested through computer simulation using PSIM software. Furthermore, experimental test result of the five-level inverter is also presented. The test results show that the five-level CE-CSI works well injecting a sinusoidal current into the power grid with low harmonic contents, and with unity power factor operation. The results also show that the distorted grid voltage affects the harmonic contents of the current injected by the inverter. DOI: http://dx.doi.org/10.11591/ijpeds.v4i4.6464