R. D. Patidar

Harmonics estimation and modeling of residential and commercial loads

The distortion in the voltage and current waveforms deteriorates the performance of the equipment/devices connected in the distribution systems. The analysis of the harmonics is essential to determine the performance and designing of these equipment and optimal location of the harmonic mitigation devices. In this paper a preliminary survey has been carried out in the domestic and commercial areas to identify the existing level of current and voltage harmonic and their characteristics for different type of residential and commercial loads. The voltage and current waveforms of some of the commonly used loads and their harmonics have been recorded using power analyzer and digital storage oscilloscope. The total harmonic distortion is used as a harmonic index to identify the effects of different nonlinear loads. The detail mathematical modeling of the personal computer type load is established to estimate the harmonic contents of such loads. To verify their characteristics whether the nonlinear loads behave like current-type or voltage-type harmonic source, some nonlinear loads are simulated and validated experimentally.

Single-phase single-stage grid-interactive photovoltaic system with active filter functions

This paper deals with modeling, control and co-simulation of a single-phase single-stage Grid-interactive photovoltaic (PV) system with active filter functions. Single-phase PV systems are the most prevalent in roof-top configurations. In this paper, the modeling of a PV array with maximum power point tracking is performed in MATLAB/Simulink. The developed PV array model may be directly connected to dc-side of the voltage source inverter used for grid PV interaction in order to evaluate its performance. This paper also deals with the development of a controller which either controls PV power or works as an active power filter or performs both the functions simultaneously. The injected active and reactive powers are regulated by changing the phase and amplitude, respectively, of the inverter output voltage. The simulation model of the overall system is developed in MATLAB/Simulink environment and then co-simulated (real-time) in digital signal processor TMS320F2812 through processor in loop (PIL) under rapidly changing atmospheric and load conditions to confirm its effectiveness as well as robustness.

Grid interconnection of distributed generation system with power quality improvement features

This paper presents the modelling and control of grid interfaced Distributed Generation (DG) system with embedded active filter function. The output of the DG is given to the DC side of the Voltage Source Inverter for interfacing to the Grid. In the presented work, the features of Active Power Filter have been incorporated in the control circuit of the current controlled-voltage source inverter interfacing the DG to the grid. Thus the same inverter is utilised to inject power generated from DG source to the Grid and also to act as Shunt Active Power Filter to compensate for load current harmonics and reactive power demand. Thus, after compensation, the Grid current is sinusoidal and in-phase with Grid voltage. The entire system is modelled in MATLAB/Simulink environment and simulations carried out to verify the operation and the control principle. Various simulation results are presented for the proposed Grid interfaced DG system.

Non-linear load compensation in Fuel Cell grid interfaced system using active power filter

The increasing global warming concerns and diminishing fossil fuels have made us necessary to look for alternative sources of energy. Fuel Cell technology holds promise towards sustainable power generation, it being pollution free and using readily available fuels. This paper presents the modeling, control and design analysis of a three-phase Grid-interactive Fuel Cell system with active filter functions. The main focus of this paper is to control the active power supplied by the Fuel Cell Distributed Generation system while compensating harmonics and reactive currents caused by the nonlinear loads using shunt active power filter. The developed Fuel Cell model is connected to the DC-side of the voltage source inverter for interfacing with the grid. Thus the same inverter is utilized as power converter to inject the power generated from the Fuel Cell to the grid and to act as active power filter to compensate load current harmonics and load reactive power demand. The designed controller either regulates the power flow between the Fuel Cell and the Grid or works as an active power filter or performs both the functions simultaneously. The simulation model of the overall system is developed in MATLAB/Simulink environment using SimPower Systems blocksets and then PIL simulated using TMS320F2812 DSP. The results are obtained for different operating conditions with varying load demands to prove the effectiveness of the entire system.

A Fast Acting 1/z Controller for Shunt Active Filter Operation for Harmonics and Reactive Power Compensation

This paper focused on the transient behavior of the shunt active power filter during harmonics and reactive power compensation. The transient response of the shunt active power filter (SAPF) is very important while compensating rapidly varying unbalanced and nonlinear loads. The dc-link capacitor voltage of SAPF is the function of load currents. Changes in load currents significantly affect the dc-link voltage of SAPF. The smooth operation of SAPF during change of loads needs variation of the dc-link voltage within prescribed limits. Conventionally, PI controller is used for this purpose which uses the deviation of the dc-link capacitor voltage from its reference value as input. However, the transient response of the conventional dc-link voltage controllers is slow. In this paper, a fast acting 1/z dc-link voltage controller based on the dc-link capacitor energy is proposed. The detailed modeling and simulation verifications are given to prove the capabilities of this fast acting 1/z dc-link voltage controller over conventional dc-link voltage controller. The results at different operating conditions such as application and removal of loads have been demonstrated to show the capabilities of this controller.

An optimal controller for APF for customer harmonics and reactive power compensation

This paper presets an optimal current controller for shunt active power filter to compensate customer generated current harmonics and reactive power. The compensated source current maintains the same level of harmonic distortion as present in the source voltage. The particle swarm optimization technique is employed for minimizing the objective function to get the desired value of controller variables. The proposed controller is simulated in MATLAB/Simulink environment under sinusoidal and distorted supply conditions with varying loads.

Active, Reactive and Harmonic compensation control of grid interfaced fuel cell system

Abstract This paper presents the modelling and control of grid interfaced fuel cell distributed generation system with embedded active filter function. The features of active power filter have been incorporated in the control circuit of the current controlled-voltage source inverter interfacing the fuel cell to the grid. Thus the same inverter is utilised to inject power generated from fuel cell source to the grid and to act as shunt active power filter to compensate for load current harmonics, load reactive power demand and load current imbalance. Thus, after compensation, the grid current is sinusoidal and in-phase with grid voltage. Simulation in MATAB and experimentation using DSP is carried out to verify the operation and the control principle. The results are obtained for different operating conditions with varying load demands to prove the effectiveness of the entire system.

Harmonic, Reactive and Neutral Currents Compensation and Load Balancing in 3P4W Distribution Systems

This paper presents a control algorithm for improving the performance of a three-phase, four-wired (3P4W) active power filter (APF) under unbalanced and distorted supply voltages. A low pass filter (LPF) is designed to filter the nonsinusoidal supply voltages. The minimal optimal values of active power filter source reference currents are estimated in natural a-b-c reference frame. The proposed method is capable for harmonics suppression, reactive and neutral current compensation and load balancing in three-phase four-wire (3P4W) distribution systems. Extensive simulation is carried out under MATLAB Simulink environment. Various simulation results are presented with ideal and distorted mains condition to shows the effectiveness of the algorithm.

Selective harmonic frequency-based non-linear load compensation using hybrid active power filter

This paper presents a hybrid active power filter for harmonics and reactive current compensation while reducing the rating of active power filter. The proposed topology of hybrid active power filter uses the combination of active power filter and a new self-tuned passive filter. The control technique of the proposed system separates the compensation frequency band for active and passive filters. The self-tuned passive filters are tuned to suppress two lower most harmonic components, i.e., fifth and seventh and the active power filter compensates the remaining higher order harmonics. The active power filter control is based on reference current estimation in a-b-c frame. An analytical study of thyristor controlled reactor (TCR)-based self-tuned passive filters is presented to keep the passive filters in the resonant state during deviation of their parameters under the influence of external factors like temperature rise, aging, etc. The firing angle of the TCR is derived as a function of the deviation of passive filter parameters. The proposed hybrid active power filter is also capable to damp out the harmonics propagation due to passive filter resonance. The proposed algorithm is simulated in MATLAB/Simulink environment under various operation conditions to show the effectiveness of the controller.

Design, analysis and implementation of DSP based single-phase shunt active filter controller

A simplified current reference control for single-phase shunt active power filter (APF) to compensate the current harmonics and reactive power required by nonlinear loads is being presented in this paper. The key intention of this method is to represent the APF in parallel with nonlinear load as an equivalent conductance. In the proposed technique, first the distorted voltage signal of PCC is made sinusoidal within the controller, to make the compensated source current sinusoidal and in-phase with the source voltage. A self-charging technique is used to regulate the dc-link capacitor voltage to a desired level. The proposed controller is first realized under MATLAB simulink environment and then experimentally verified using a low cost fixed-point eZdsp to show the effectiveness of the controller.