Sharad W. Mohod

A STATCOM-Control Scheme for Grid Connected Wind Energy System for Power Quality Improvement

Injection of the wind power into an electric grid affects the power quality. The performance of the wind turbine and thereby power quality are determined on the basis of measurements and the norms followed according to the guideline specified in International Electro-technical Commission standard, IEC-61400. The influence of the wind turbine in the grid system concerning the power quality measurements are-the active power, reactive power, variation of voltage, flicker, harmonics, and electrical behavior of switching operation and these are measured according to national/international guidelines. The paper study demonstrates the power quality problem due to installation of wind turbine with the grid. In this proposed scheme STATic COMpensator (STATCOM) is connected at a point of common coupling with a battery energy storage system (BESS) to mitigate the power quality issues. The battery energy storage is integrated to sustain the real power source under fluctuating wind power. The STATCOM control scheme for the grid connected wind energy generation system for power quality improvement is simulated using MATLAB/SIMULINK in power system block set. The effectiveness of the proposed scheme relives the main supply source from the reactive power demand of the load and the induction generator. The development of the grid co-ordination rule and the scheme for improvement in power quality norms as per IEC-standard on the grid has been presented.

Micro Wind Power Generator With Battery Energy Storage for Critical Load

In the micro-grid network, it is especially difficult to support the critical load without uninterrupted power supply. The proposed micro-wind energy conversion system with battery energy storage is used to exchange the controllable real and reactive power in the grid and to maintain the power quality norms as per International Electro-Technical Commission IEC-61400-21 at the point of common coupling. The generated micro-wind power can be extracted under varying wind speed and can be stored in the batteries at low power demand hours. In this scheme, inverter control is executed with hysteresis current control mode to achieve the faster dynamic switchover for the support of critical load. The combination of battery storage with micro-wind energy generation system (μ WEGS), which will synthesize the output waveform by injecting or absorbing reactive power and enable the real power flow required by the load. The system reduces the burden on the conventional source and utilizes μ WEGS and battery storage power under critical load constraints. The system provides rapid response to support the critical loads. The scheme can also be operated as a stand-alone system in case of grid failure like a uninterrupted power supply. The system is simulated in MATLAB/SIMULINK and results are presented.

Power quality issues &it’s mitigation technique in wind energy generation

Awareness of power quality is highly increased in a sensitive industry, where the standardization and performance is an important aspect. The connection of wind turbine to the grid affectpsilas the electric grid power supply quality. Therefore it is necessary to maintain the power quality norm at the interface of the grid from the disruptive effect caused by wind turbine such as voltage fluctuation, switching operation, voltage dips, and reactive power & harmonics distortion on the grid. These disruptive effected can be minimized by adopting suitable control technique. The paper proposed the control scheme for voltage source inverter (VSI) in a current control mode to inject the compensating current into the power system at point of common coupling. A hysteresis current controller has been implemented to generate the inverter switching signals using the reference from source voltage. This ensures that wind turbine system will inject current through inverter to maintain unity power factor. The wind turbine shall provide active and reactive power support to the load. Thus the power system will operate with stipulated power quality norm at point of common connection. The typical system is simulated in Matlab/Simulink for practical condition in power system and simulated results under varying operating condition are presented.

Energy storage to strengthen the wind generator in integrated power system

The wind energy generation, utilization and its grid penetration in electrical grid is increasing world wide. The wind generated power is always fluctuating due to its time varying nature and causing stability problem. This weak interconnection of wind generating source in the electrical network affect the power quality and reliability. The localized energy storages shall compensate the fluctuating power and support to strengthen the wind generator in the power system. In this paper, it is proposed to control the voltage source inverter (VSI) in current control mode with energy storage, that is, batteries across the dc bus. The generated wind power can be extracted under varying wind speed and stored in the batteries. This energy storage maintains the stiff voltage across the dc bus of the voltage source inverter. The propose scheme enhances the stability and reliability and maintain unity power factor as well as operated in stand alone mode in the power system. The power exchange across the wind generation and the load under dynamic situation is feasible while maintaining the power quality norms at the common point of coupling, strengthen the weak grid in the power system. This control strategy is evaluated on the test system under dynamic condition by using simulation.

Energy Storage to Stabilize the Weak Wind Generating Grid

The wind energy generation, utilization and its grid penetration in electrical grid is increasing world wide. The wind generated power is always fluctuating due to its time varying nature and causing stability problem. This weak interconnection of wind generating source in the electrical network affect the power quality and reliability. The localized energy storages shall compensate the fluctuating power and support to stabilize the weak grid. In this paper, it is proposed to control the voltage source inverter (VSI) in current control mode with energy storage, that is, batteries across the DC bus. The DC bus voltage control is obtained by using bi-directional DC/DC converter. The generated wind power can be extracted under varying wind speed and stored in the batteries. This energy storage maintains the stiff voltage across the DC bus of the voltage source inverter. The propose scheme enhances the stability and reliability of the power system. The power exchange across the wind generation and the load under dynamic situation is feasible while maintaining the power quality norms at the common point of coupling. This control strategy is evaluated on the test system under dynamic condition by using simulation.

A Novel, PWM-Inverter Scheme for Grid Connected WEGS for Power Quality Measure

Injection of the wind power into an electric grid affects the power quality. The performance of the wind turbine and their power quality are determined on the basis of measurements, and according to the guideline specified in International Electro-technical Commission , IEC 61400-21.The influence of the wind turbine in the grid system concerning the power quality measurements are-the active power, reactive power, variation of voltage, flicker, harmonics, and electrical behavior of switching operation and these are measured according to national / international guidelines. The paper study demonstrates the power quality problem due to installation of wind turbine with the grid. The pulse width modulation (PWM) inverter scheme for the grid connected wind energy generation system for power quality improvement is simulated using MATLAB/SIMULINK in power system block set. Due to improvement in technologies, the wind turbine is expected to support the grid and therefore the wind turbine has to control the reactive power over a wide range, and also to deliver the reactive power, in case of voltage drop and can remain connected during short-term voltage drop. Hence to ensure its fulfillments, the power quality measure is specified in IEC 61400- 21.The development in the grid co-ordination rule and the scheme for improvement in power quality has been presented in the paper. Keywords-component; International Electro-technical Commission (IEC), power quality, Wind Generating System (WES) I. INTRODUCTION The power quality is an essential customer-focused measure and is greatly affected by the operation of a distribution and transmission network. The issue of power quality is of great importance to the wind turbine. The individual units can be of large capacity, up to 2 MW, feeding into distribution network with high source impedance, particularly with customers connected in close proximity (1). In case of fixed-speed wind turbine operation, all the fluctuation in the wind speed are transmitted as fluctuations in the mechanical torque , electrical power on the grid and leads to large voltage fluctuations. Thus the network needs to manage, the excessive voltage transients which are to be avoided. Today in the variable-speed wind turbine designs, the uses of power electronic converters are mostly used. During the normal operation, wind turbine produces a continuous variable output power. These power variations are mainly caused by the effect of turbulence, wind shear, and tower-shadow and of control system in the power system. Thus the power quality issues can be viewed with respect to the wind generation, transmission and distribution network can cause the variation in voltage to which the wind turbine is connected, such as voltage sag, swells, etc. However the wind generator introduces disturbances into the distribution network. Today the PWM inverter control technology has been developed and it can technically manage to control the power level associates with the commercial wind turbines. The wind turbine and their quality are assessed according to the national and international guidelines, and so it is important to evaluate the grid connection with wind generating system.

Wind energy conversion system simulator using variable speed induction motor

The conventional synchronous generator in wind energy conversion system are now getting replaced by variable speed induction generator to extract maximum power with wide range of wind speed limit. The design and performance of such system are required a simplified digital simulator, especially for development of optimal control solutions. The proposed work is to make a prototype of an variable speed wind conversion system simulator, to get a required operational condition under variable wind speed. In this paper variable speed induction motor drive using scalar control is interfaced in wind energy conversion system as an alternative to make the real time wind simulator for wind energy researchers. The basic power curve from wind generator is carried out through d-SPACE and interface of induction motor through an inverter control system. The induction motor is operated in wide speed range using Volt /Hertz speed control scheme. The laboratory prototype consists of 3 kW, 415 Volt, 50Hz induction motor controlled by voltage source inverter for various wind speed. The basic control strategy is implemented through hardware system. The result verifies that the wind turbine simulator can reproduce the steady state characteristics of a given wind turbine at various wind condition.

Analysis and design of a grid connected wind generating system with VSC

This paper describes the analysis and design of a grid connected wind generating system with voltage source converter (VSC). When wind generating system (WGS) is connected to grid create a problem of power quality such as poor power factor, voltage distortion, and harmonic distortion on the grid. The grid connection is realized by a controlled PWM voltage source inverter. The VSC is operated in hysteresis current control mode. The WGS and the electrical grid are de-coupled by means of DC link capacitor, which act as a buffer between the systems. The proposed digital control scheme can achieve the unity power factor and reduces the current harmonic distortion on the utility side. Thus with proper design and control of VSC in grid system, is the solution for reducing the magnitude of current harmonics injected in to grid and to maintain power quality norm on the grid. The proposed system is simulated in MATLAB/SIMULINK and result is presented in the paper.

Wind Energy Generation Interfaced System with Power Quality and Grid Support

The integration of the wind generator into the grid connected system becomes a challenge. The major problem is to have a dynamic reactive power support along with the controlled real power support from the source. In this paper a control algorithm is proposed to maintain the unity power factor of the source supply with no reactive power support from the source. The static compensator ( STATCOM ) is connected at a point of common coupling (PCC) with a battery energy storage system (BESS).The STATCOM and energy storage is interfaced with wind generating system, supporting the real and reactive power and also maintain the stable voltage at PCC and support the grid. The effectiveness of the proposed scheme relieves the main supply source from the reactive power demand of the load and the induction generator. The reactive power compensation by STATCOM with bang-bang controller with hysteresis based technique maintains the dynamic stability of the grid and matches the operating behavior of grid system. This scheme is simulated with a MATLAB/SIMULINK in power system block set, having interface of induction generator and non-linear load at PCC and performance is evaluated.

Power Quality and Grid Code Issues in Wind Energy Conversion System

The aim of the electric power system is to produce and deliver to the consumer’s electric energy of defined parameters, where the main quantities describing the electric energy are the voltage and frequency. During normal operation of system the frequency varies as a result of the variation of the real power generated and consumed. At the same time, because of voltage drops in the transmission lines and transformers it is impossible to keep the voltage at the nominal level in all the nodes of the power system. It is also impossible to keep an ideal sinusoidal shape of the voltage or current waveform due to the nonlinearities in many devices use for electric energy generation, transmission and at end users. That is why the electric power system require to keep the quantities near the nominal value[1]-[5].