A Flexible DSTATCOM Operating in Voltage or Current Control Mode

The topology and control are discussed of a distribution static compensator (DSTATCOM) that can be operated flexibly in the voltage or current control mode. In the voltage control mode, the DSTATCOM can force the voltage of a distribution bus to be balanced sinusoids. In the current control mode, it can cancel distortion caused by the load, such that current drawn by the compensated load is pure balanced sinusoid. Both these objectives are achieved, irrespective of unbalance and harmonic distortions in load currents or source voltages. The chosen DSTATCOM topology includes three single-phase voltage source inverters connected in parallel to a filter-capacitor, which allows the high-frequency component of the current to pass. A switching control scheme is proposed, and its suitability is proved for this problem. The proposed scheme is verified using computer simulation studie

PI-based controller for low-power distributed inverters to maximise reactive current injection while avoiding over voltage during voltage sags

This paper is a postprint of a paper submitted to and accepted for publication in IET Power Electronics and is subject to Institution of Engineering and Technology Copyright. The copy of record is available at the IET Digital Library.In the recently deregulated power system scenario, the growing number of distributed generation sources should be considered as an opportunity to improve stability and power quality along the grid. To make progress in this direction, this work proposes a reactive current injection control scheme for distributed inverters under voltage sags. During the sag, the inverter injects, at least, the minimum amount of reactive current required by the grid code. The flexible reactive power injection ensures that one phase current is maintained at its maximum rated value, providing maximum support to the most faulted phase voltage. In addition, active power curtailment occurs only to satisfy the grid code reactive current requirements. As well as, a voltage control loop is implemented to avoid overvoltage in non-faulty phases, which otherwise would probably occur due to the injection of reactive current into an inductive grid. The controller is proposed for low-power rating distributed inverters where conventional voltage support provided by large power plants is not available. The implementation of the controller provides a low computational burden because conventional PI-based control loops may apply. Selected experimental results are reported in order to validate the effectiveness of the proposed control scheme.Peer ReviewedPostprint (updated version

Neural Network based p-q-r Theory for Harmonic Reduction and Neutral Current Mitigation

The power quality compensator chosen in this paper is a DSTATCOM which integrates a three phase four leg Voltage Source Converter (VSC) with a DC capacitor. The major role of the DSTATCOM is to mitigate the components of harmonic/reactive current present in the line current thereby shapes the grid current to be sinusoidal and improves the power factor nearly unity under varying conditions. In addition DSATATCOM mitigates neutral current (Isn) and balances the load currents under unbalanced conditions in three phase four wire (3P4W) distribution system. The control strategy proposed for the DSTATCOM is a Neural Network (NN) based p-q-r theory with two Artificial Neural Network (ANN) controllers for a 3P4W distribution system. The reference signal for 3P3W Shunt Active Power Filter (SAPF) is calculated by implementing an ANN controller. The alleviation of Isn under unbalanced condition is achieved by another ANN controller which produces reference signal for the 1Φ APF. The performance of the proposed DSTATCOM is analysed for various conditions through simulations in MATLAB SIMULINK and the simulation results justify the effectiveness of the propounded NN based control algorithm for DSTATCOM

An algorithm for optimal sizing of the capacitor banks under non-sinusoidal and unbalanced conditions

In non-sinusoidal and unbalanced systems, optimal sizing of the capacitor banks is not a straightforward task as in sinusoidal and balanced systems. In this paper, by means of qualitative and quantitative analysis, it is interpreted that the classical capacitor selection algorithm widely implemented in Reactive Power Control (RPC) relays does not achieve optimal power factor improvement in non-sinusoidal and unbalanced systems. Accordingly, a computationally efficient algorithm is proposed to find the optimal capacitor bank for smart RPC relays. It is further shown in a simulated test case by using Matlab software that the proposed algorithm provides better power factor improvement when compared with the classical algorithm. It is also figured out from the simulation results that both algorithms cause almost the same harmonic distortion and unbalance deterioration levels in the system

Continuous biodiesel process using ultrasonic in-line reactor for Jatropha Curcas Oil (JCO)

Biodiesel is an alternative fuel for replacing diesel fuel in compression ignition engines. Due to the complexity of the diesel fuel production and exhaust emissions from petroleum-fuelled engines will give negative impact to the environment. In this study, the sodium hydroxide as the catalyst was used to react with methanol for obtaining chemical compound that is called methyl ester which is known as biodiesel. The method used are Ultrasonic. Basically, this method will reduce the reaction time on the conversation of jatropha curcas oil (JCO) into biodiesel. The experiment was to determine the effect of esters contents by reaction time, molar ratio methanol (MeOH) to JCO, the amount of catalyst, frequency and power output of ultrasonic using ultrasonic in-line reactor. The optimum production of biodiesel was achieved at 7 minutes of reaction time, 1%wt of catalyst concentration and molar ratio methanol to oil 12:1, frequency ultrasonic of 20 KHz and ultrasonic output 600 Watt at temperature 65°C. The biodiesel produced by this method has been referred according to ASTM D6751. From the result, the biodiesel produced from this method has satisfied the requirement biodiesel standard. This optimum result in this research can be used to run larger pilot plant designed for industry

Overview of three-phase inverter topologies for distributed generation purposes

The increasing presence of single-phase distributed generators and unbalanced loads in the electric power system may lead to unbalance of the three phase voltages, resulting in increased losses and heating. Distribution network operators are seeking to install larger DG units (viz. $>5$kVA in Belgium) by means of three-phase connections instead of single-phase to reduce voltage unbalance. There are several possible topologies to connect the DG units to the three-phase distribution network. These topologies can be divided into three groups: the three-phase three-wire inverters, the three-phase four-wire inverters and the multilevel inverters. In this paper, an overview of the aforementioned topologies is given

Instantaneous p-q power theory for control of compensators in micro-grids

The main objective of this tutorial is to present the basic concepts on the instantaneous p-q Theory and them show its applicability for controlling switching converters connected in a micro-grid. These converters can be used for connecting renewable energy sources (solar, wind, and others) to the micro-grids or for harmonic, reactive power or unbalance compensation, and even for voltage regulation. The emphasis is given on the compensation characteristics derived from the p-q Theory, and simulation results of test cases are shown. Special attention is put on the oscillating component of the instantaneous real power, as it may produce torque oscillations or frequency variations in weak systems (micro-grids) generators. This oscillating component, as defined in the p-q Theory, gives the amount of oscillating energy between the source and the load, and its compensation through a switching compensator must have an energy storage element to exchange it with the load. With the p-q Theory the energy storage element can be easily calculated as a function of the average component of the instantaneous real power, which depends on the observation period.The authors acknowledge the support from FAPERJ partially for the development of this study and especially for the financial support for the participation in the conference

Compensation of Distribution System Voltage using DVR

A dynamic voltage restorer (DVR) is a power-electronic controller that can protect sensitive loads from disturbances in the supply system. In this paper, it is demonstrated that this device can tightly regulate the voltage at the load terminal against imbalance or harmonic in the source side. The behavior of the device is studied through steady-state analysis, and limits to achievable performance are found. This analysis is extended to the study of transient operation where the generation of the reference voltage of the DVR is discussed. Once the reference signals are generated, they are tracked using a switching band scheme. A suitable structure in which the DVR is realized by voltage-source inverters (VSIs) is also discussed. Particular emphasis to the rating of this device is provided. Extensive simulation results are included to illustrate the operating principles of a DVR