Chem Nayar

An optimum dispatch strategy using set points for a photovoltaic (PV)-diesel-battery hybrid power system

Abstract This paper presents dispatch strategies for the operation of a solar photovoltaic (PV)–diesel–battery hybrid power system using ‘set points’. This includes determination of the optimum values of set points for the starting and stopping of the diesel generator to minimise the overall system costs. A computer program for a typical dispatch strategy has been developed to predict the long-term energy performance and the lifecycle cost of the system.

Novel wind/diesel/battery hybrid energy system

In most of the remote areas of Australia and in many other parts of the world, diesel generators are used to provide electrical power. Such systems are often characterised by either poor efficiency and high maintenance costs because of prolonged operation at low load levels, or intermittent power because the unit is only run during period of significant load. The addition of a battery bank and a power conditioner to produce a diesel-battery-inverter hybrid system has been identified as produccing a number of benefits. Such systems can be broadly classified according to their configuration as series, switched, or parallel hybrid systems. A new parallel hybrid energy system developed in Western Australia is described in this article. The heart of the system is a high quality sinewave inverter which can also be operated in reverse as a battery charger. The system can cope with loads ranging from zero (inverter only operation) to approximately three times the generator capacity (inverter and diesel operating in parallel) with excellent efficiency. The system is fully automatic, provides continuous power, and can readily incorporate input from wind or photovoltaic systems. This article also includes a description of a 5 kW wind generator charging a battery bank as part of the hybrid system, and an economic analysis indicates a favourable result for this hybrid system with payback period estimated to be the order of three years.

Control and Interfacing of a Grid-Connected Small-Scale Wind Turbine Generator

An ac/dc/ac power converter is an important component to extract power from a variable speed permanent magnet wind generator and feed into the grid. This paper describes such a converter incorporating maximum power point tracking based on power fed to the grid at different wind speeds. Using the permanent magnet generator voltage, the grid current and the grid voltage samples, the proposed system achieves an enhanced dynamic behavior. This feature effectively prevents the grid from “boost” charging the dc side of the H bridge inverter at the beginning of operation. Since small wind turbines normally do not have expensive pitch control mechanisms, a thyristor based “dump-load circuit” is employed to protect the turbine from high wind speed operation when disconnected from the grid. The thyristor controller also protects the inverter from high dc voltage input from the wind generator at high wind speed. Preliminary results are included based on a laboratory 2kW prototype converter.

Wind/PV/diesel micro grid system implemented in remote islands in the Republic of Maldives

This paper presents an innovative wind/PV/diesel hybrid system implemented in three remote islands in the Republic of Maldives. The design methodology and preliminary results are presented. It is expected that the newly developed and installed system will provide very good opportunities to showcase high penetration of renewable energies using state of the art wind turbines, photovoltaic modules and advanced power electronics and control technology and the future possibilities of distributed generation in remote locations.

Conceptual model for marketing solar based technology to developing countries

Developing countries are faced with large shortfalls of electric-power generation, shortages of usable indigenous fuels, and transportation bottlenecks for those fuels. The loss of revenue that is forced upon the industry due to power cuts and frequent interruptions of power supply is substantial. Renewable sources of energy have an important role to play in providing much needed power in the context of growing global concern about sustainable energy supplies and protecting the environment from the adverse effects of fossil fuel utilization. The purpose of the study is to identify the factors that influence the adoption of solar-based technology. An examination of the literature in the area of diffusion of technology has led to the identification of different variables. The possible relationships that may exist between these variables is depicted in the conceptual framework. This paper attempts to clarify the relationships between the variables that have been identified and the decision to adopt.

Modelling, simulation and testing of grid connected small scale wind systems

This paper will show the theory, simulation and application of maximum power point tracking for small scale wind turbines. The theoretical section of this paper will cover modelling of the wind turbine, the and the power electronic converters (the full-bridge DC/DC converter and the grid connected current controlled voltage source inverter (CCVSI)). It is shown that by controlling the duty ratio of the DC/DC converter, the wind turbine generator is operated at the maximum power point. This is achieved without measuring the wind speed using a look up table where the power output vs the shaft speed is recorded. In order to keep the output current waveform sinusoidal at varying wind speeds, the DC link voltage of the CCVSI is kept constant. This system meets the utility requirements such as galvanic isolation, anti-islanding protection and protection of the wind turbine at high wind speeds.

Investigation of capacitor-excited induction generators and permanent magnet alternators for small scale wind power generation

This paper examines two electric generator options for use in autonomous wind systems producing asynchronous electric power. The first makes use of a capacitor-excited squirrel-cage induction generator feeding a battery bank and an induction motor driven centrifugal pump. The second uses a permanent magnet alternator. Results obtained from field tests and laboratory experiments are included. A model to calculate the wind energy captured by a commercial 5 kW wind turbine, used in the field tests, is presented. This information is then used in a cost benefit analysis based on the present value method.

Solar/wind/diesel hybrid energy systems for remote areas

The economics associated with the major system components for remote-area power supplies is discussed, and a detailed description of the various system configurations is given. The discussion covers diesel generators, battery storage, inverters, photovoltaic and wind-powered generators. Series, switched and parallel hybrid systems are considered. Results and conclusions based on tests carried out at Murdoch University Energy Research Institute are included.<<ETX>>

A new modular hybrid power system

This paper presents a new modular hybrid power system incorporating photovoltaic and small scale wind generators connected to an AC bus. The system is based on voltage source inverters using both current control and voltage control. Preliminary experimental and simulation results are included.

A combined voltage controlled and current controlled "dual converter" for a weak grid connected photovoltaic system with battery energy storage

In this paper, a novel power converter capable of extracting maximum power from solar photovoltaic panels is described. It employs a combination of a voltage controlled voltage source inverter and a current controlled voltage source inverter, connected in series on the DC side and in parallel on the AC side. This dual converter is able to provide uninterruptible power supply feature, load voltage stabilisation, unity power factor operation, maximum power point tracking as well as reactive power support. The overall efficiency of the proposed converter is higher than the conventional system with a DC-DC converter between the PV panels and the battery.