Grid-independent hybrid renewable energy systems (HRESs), being eco-friendly and cost effective, are turning out to be more effective option for the rural areas where grid power availability is poor. This paper presents the techno-economic analysis and optimum design of a HRES, as proposed to meet out the residential and agricultural electric load requirements of an energy poor community of Yamunanagar district in the State of Haryana, India. Three different optimal configurations, viz. wind/battery, PV/battery and wind/PV/battery are compared in respect of net present cost (NPC) and cost of energy (COE) to determine most economically viable option. For economic analysis and optimum sizing, all the necessary modelling and simulation is carried out using HOMER (Hybrid Optimization Model for Electric Renewable) software. From the simulation results, it is established that wind/PV/battery based HRES is the most cost-effective configuration for the specific location this investigation is about and also the optimum sizes of the different components are obtained. Further, for technical analysis, a MATLAB/Simulink model of the optimized system is built and its effectiveness is demonstrated in terms of maintaining active power balance between the different components of HRES as well as keeping DC link voltage (VDC) and output AC voltage constant, irrespective of variations in solar irradiance, wind speed and connected load. The novelty of this work lies in using both HOMER and MATLAB simulation tools sequentially to carry out techno-economic analysis of the proposed HRES and validate the proposition.

Techno-economic analysis of a hybrid renewable energy system for an energy poor rural community

Wind energy is inexhaustible renewable. Unlike conventional fossil fuels, wind energy is clean, abundant energy that will be available for future generations. However, wind speed is a highly stochastic component which can deviate very quickly. Output power of the wind energy conversion system (WECS) is proportional to the cube of wind speed, which causes the output power fluctuation of the wind turbine. The power fluctuation causes frequency fluctuation and voltage flicker inside the power grid. In order to reduce the power fluctuation, various approaches have been proposed in the last decades. This article deals with the review of several power smoothing strategies for the WECS. Power smoothing methods of the WECS are primarily separated into two categories such as energy storage based power smoothing method and without energy storage based power smoothing method. The main objectives of this paper are to introduce operating principles for different power smoothing methods. The energy storage based power smoothing method is effective but installation and maintenance costs of a storage device are very high. According to the literatures review, without energy storage based power smoothing method can reduce the cost of the WECS extensively. Various methods have been proposed to generate a smooth output power of the WECS without energy storage devices. Simulation results are compared among the available methods. From the review of simulation results, the kinetic energy of the inertia control method is the highly efficient power smoothing approach.

A review of output power smoothing methods for wind energy conversion systems

Variable-speed fixed-pitch (VSFP) wind turbines have good prospects in small-to-medium-scale wind power markets due to their simple structure, low cost, and high reliability. One difficulty with VSFP concept wind turbines is to prevent overspeeding and overloading problems at excessive wind velocities, which has rarely been reported in literatures until now. This paper first proposes a sensorless overall power control strategy for a commonly used permanent-magnet-synchronous-generator-based VSFP concept wind power system, with which maximum power point tracking operation, constant speed stalling operation, and constant power soft-stalling operation are all realized. The proposed control scheme has a special advantage of simple structure, i.e., only two regulators are used to realize the three operational modes and also the natural transition between them. An aerodynamic power observer is adopted in the proposed scheme to fasten the MPPT speed. In addition, to enhance system robustness to parameter variations and optimize dynamic and static speed-control performance, an adaptive PI-like fuzzy logic controller is proposed and used as speed regulator in the overall power control scheme. The proposed strategy is verified by simulation and experimental results performed by a 1.2-kW VSFP concept wind turbine prototype.

New Overall Power Control Strategy for Variable-Speed Fixed-Pitch Wind Turbines Within the Whole Wind Velocity Range

Wind energy is becoming more important in recent years due to its contribution to the independence of power generation industry from traditional fossil energy resources and availability of continuous harvest-able potential on earth approximately around 10 6 MW . This paper presents a comprehensive overview of grid interfaced wind power generation systems. This is intended to provide a wide spectrum on the status of wind profile, wind potential estimation, configuration/design of wind energy conversion systems, wind generators, power converter topologies used for grid integration of wind power, energy storage systems for wind power applications, power smoothing methods, HVDC links used for wind integration, international grid codes and maximum power point tracking methods to the researchers, designers, manufacturers, and engineers working on the grid interfaced wind power generation. More than 200 research publications on the topic of grid interfaced wind power generation systems have been critically examined, classified and listed for quick reference. This review is ready-reckoner of essential topics for grid integration of wind energy and available technologies in this field.

Comprehensive overview of grid interfaced wind energy generation systems

A unified power control strategy is proposed for the permanent magnet synchronous generator-based wind energy conversion system (WECS) operating under different grid conditions. In the strategy, the generator-side converter is used to control the dc-link voltage and the grid-side converter is responsible for the control of power flow injected into the grid. The generator-side controller has inherent damping capability of the torsional oscillations caused by drive-train characteristics. The grid-side control is utilized to satisfy the active and reactive current (power) requirements defined in the grid codes, and at the same time mitigates the current distortions even with unsymmetrical grid fault. During grid faults, the generator-side converter automatically reduces the generator current to maintain the dc voltage and the resultant generator acceleration is counteracted by pitch regulation. Compared with the conventional strategy, the dc chopper, which is intended to assist the fault ride through of the WECS, can be eliminated if the proposed scheme is employed. Compared with the variable-structured control scheme, the proposed strategy has quicker and more precise power responses, which is beneficial to the grid recovery. The simulation results verify the effectiveness of the proposed strategy.

Unified Power Control for PMSG-Based WECS Operating Under Different Grid Conditions

Modeling and control of PMSG-based variable-speed wind turbine

Modeling and voltage-control of variable-speed SCAG-based wind farm

This paper presents modeling and control for the emerging IGBT converter-based high-voltage direct-current system (IGBT-HVDC). This paper adds to the representation of the IGBT-HVDC system in the dq-synchronous reference frame and its decoupled control scheme. Additionally, since the IGBT-HVDC is able to actively support the grid due to its capacity to control independently active and reactive power production, a reactive power control scheme is presented in order to regulate/contribute to the voltage at a remote location by taking into account its operational state and limits. The ability of the control scheme is assessed and discussed by means of simulations using ahybrid power system, which consists of a permanent magnetic synchronous-generator (PMSG) based wind turbine, an IGBT-HVDC, and a local load.

Modeling and Control of IGBT Converter-Based High-Voltage Direct Current System

This study performs modelling and simulation of permanent magnetic synchronous generator wind turbine by using Matlab & Simulink. In simulation, change of wind velocity, change of load, and voltage decrease of infinite bus are performed. Through such simulation, different with wiring system that there is only existing load, this study can confirm problems and voltage changing characteristics, which can occur in distributed electric power that load and electric power is mixed and operated, especially, in interconnecting with wind power generation.

Hee-Sang Ko

Papers

Modeling and control of PMSG-based variable-speed wind turbine

Modeling and voltage-control of variable-speed SCAG-based wind farm

Modeling and Control of IGBT Converter-Based High-Voltage Direct Current System

Modeling and Voltage Variation Simulation of a Permanent Magnetic Synchronous Generator Wind Turbine Systems