Introduction Industry Overview Incentives for Renewables Utility Perspective References Wind Power Wind in the World The U.S.A. Europe India Mexico Ongoing Research and Development References Photovoltaic Power Present Status Building Integrated pv Systems pv Cell Technologies pv Energy Maps References Wind Speed and Energy Distributions Speed and Power Relations Power Extracted from the Wind Rotor Swept Area Air Density Global Wind Patterns Wind Speed Distribution Wind Speed Prediction Wind Resource Maps References Wind Power System System Components Turbine Rating Electrical Load Matching Variable-Speed Operation System Design Features Maximum Power Operation System Control Requirements Environmental Aspects References Electrical Generator Electromechanical Energy Conversion Induction Generator References Generator Drives Speed Control Regions Generator Drives Drive Selection Cut-Out Speed Selection References Solar Photovoltaic Power System The pv Cell Module and Array Equivalent Electrical Circuit Open Circuit Voltage and Short Circuit Current i-v and p-v Curves Array Design Peak Power Point Operation pv System Components References Solar Thermal System Energy Collection Solar II Power Plant Synchronous Generator Commercial Power Plants References Energy Storage Battery Types of Batteries Equivalent Electrical Circuit Performance Characteristics More on Lead-Acid Battery Battery Design Battery Charging Charge Regulators Battery Management Flywheel Compressed Air Superconducting Coil References Power Electronics Basic Switching Devices AC to DC Rectifier DC to AC Inverter Grid Interface Controls Battery Charge/Discharge Converters Power Shunts References Stand-Alone System pv Stand-Alone Electric Vehicle Wind Stand-Alone Hybrid System System Sizing Wind Farm Sizing References Grid-Connected System Interface Requirements Synchronizing with Grid Operating Limit Energy Storage and Load Scheduling Utility Resource Planning Tool References Electrical Performance Voltage Current and Power Relations Component Design for Maximum Efficiency Electrical System Model Static Bus Impedance and Voltage Regulation Dynamic Bus Impedance and Ripple Harmonics Quality of Power Renewable Capacity Limit Lightning Protection National Electrical Code on Renewable Power Systems References Plant Economy Energy Delivery Factor Initial Capital Cost Availability and Maintenance Energy Cost Estimates Sensitivity Analysis Profitability Index Hybrid Economics References The Future World Electricity Demand to 2015 Wind Future pv Future Declining Production Costs Market Penetration Effect of Utility Restructuring References Further Reading Appendix 1 Appendix 2 Acronyms Conversion of Units Index

Wind and Solar Power Systems

Hybrid renewable energy systems (HRES) are becoming popular for remote area power generation applications due to advances in renewable energy technologies and subsequent rise in prices of petroleum products. Economic aspects of these technologies are sufficiently promising to include them in developing power generation capacity for developing countries. Research and development efforts in solar, wind, and other renewable energy technologies are required to continue for, improving their performance, establishing techniques for accurately predicting their output and reliably integrating them with other conventional generating sources. The paper describes methodologies to model HRES components, HRES designs and their evaluation. The trends in HRES design show that the hybrid PV/wind energy systems are becoming gaining popular. The issues related to penetration of these energy systems in the present distribution network are highlighted.

Modeling of hybrid renewable energy systems

The neutral wire in most power flow software is usually merged into phase wires using Kron's reduction. Since the neutral wire and the ground are not explicitly represented, neutral wire and ground currents and voltages remain unknown. In some applications, like power quality and safety analyses, loss analysis, etc., knowing the neutral wire and ground currents and voltages could be of special interest. In this paper, a general power flow algorithm for three-phase four-wire radial distribution networks, considering neutral grounding, based on backward-forward technique, is proposed. In this novel use of the technique, both the neutral wire and ground are explicitly represented. A problem of three-phase distribution system with earth return, as a special case of a four-wire network, is also elucidated. Results obtained from several case studies using medium- and low-voltage test feeders with unbalanced load, are presented and discussed.

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Power flow in four-wire distribution networks-general approach

The theory, design, and implementation of a constant-frequency hysteresis current control for grid-connected voltage source inverter (VSI) is presented. The proposed control technique retains the benefit of the hysteresis control having fast dynamic response and tackles the drawback of the standard hysteresis control having variable switching frequency. The concept is based on predicting the current reference, system dynamic behavior, and past time to formulate the switching function for dictating the switching times of the switches in the inverter within a predefined switching period. Of particular importance, no hysteresis bandwidth (a challenge in the practical implementation) is needed in the entire control method. The operating principles of the proposed technique and mathematical derivation of the switching functions will be given. The proposed method is successfully applied to a 300 W, 110 V, 60 Hz grid-connected VSI prototype with the controller implemented by a simple analog circuit. The steady-state and large-signal dynamic response of the VSI are studied. Experimental results show that the inverter can reach the steady state in two switching actions after the inverter is subject to large-signal input and output disturbances.

Constant-Frequency Hysteresis Current Control of Grid-Connected VSI Without Bandwidth Control

Experimental assessment of the waveform distortion in grid-connected photovoltaic installations

Neutral currents flow in four-wire distribution systems due to linear load unbalances and triplen harmonics associated with mainly the magnetizing currents of (distribution) transformers. It is known that high levels of neutral currents can lead to overloaded/burned neutral conductors, common-mode noise problems, derating of transformers and/or excessive voltage distortion. The proliferation of nonlinear loads which inject harmonic currents into the distribution system has brought more attention upon the levels of neutral currents and voltages found in distribution systems. To this end, this paper evaluates measurements taken on the neutral conductors of a distribution feeder at two different sites. The analysis of the measurements focuses on the magnitudes of the triplen-harmonic currents and voltages relative to their corresponding phase RMS values in order to separate the impact on the neutral conductors of nonlinear loads and linear load unbalances.

Measurements of neutral currents and voltages on a distribution feeder

It is envisaged that the use of photovoltaic (PV) dispersed generation will become more widespread in the near future due to advances in PV technology which will lead to cost reductions In order to gain an understanding of the effects that PV dispersed generation may have upon the quality of electric power, this paper presents a power quality study performed on a PV generator The study includes measured waveforms, trends, a statistical analysis of the measurements and the results of a connection/disconnection test

D.W. McNabb

Papers

Measurements of neutral currents and voltages on a distribution feeder

Power-quality monitoring of a PV generator