Pakistan is faced with energy crises from the last two decades. Generation cannot balance the load demands of the electricity consumers. Power delivery systems are generally old-fashioned and overloaded. They are unable to provide consistent and uninterrupted supply to commercial, industrial, and domestic loads. Generally speaking, the Power Systems consist of loads that are inductive and resistive in nature. Heavy machinery, induction motors, and arc furnaces are heavily inductive in nature. Inductive loads when operated in a weak power system results in lagging VARs (Volt Ampere Reactive) and poor voltage regulation, which must be balanced by the same number of leading VARs in order to ensure unity power factor and thus helps in improving the voltage profile. At times the reactive VARs injected may not be sufficient to balance the VARs requires by the system, but still the power factor is improved up to some extent. In hot and humid climatic conditions, air-cooling system and chillers greatly burdens the grids. Such loads require excessive reactive VARs, and if not offered with ample reactive power, causes severe voltage drops in distribution system. To manage low voltages and power-factor, household users use automatic voltage regulators while industries connect capacitor banks. Voltage regulators control output voltage within the required limits at the expense of excessive line current from transformer, which may overburden it. Moreover, with each operation of tap changer, current rises which further intensifies line losses. Static capacitors provide stable voltage but repeated variations in load demands reliable and vigorous voltage regulation. This investigation aims to come up with a power quality improvement scheme which would deliver instantaneous control of power (reactive) with SVC (Static VAR Compensator) thus overcoming the shortcomings of step-wise banks of capacitors and or voltage regulators. Simulation work is carried out in MATLAB/SIMULINK and the results are compliance with IEEE Standards for SVCs. The device can offer steady state as well as dynamic VAR compensation under changing load conditions. Result showed considerable improvement both in terms of response time and power factor. Switching time has been improved to less than 1/10th fraction of a second which in previous simulations was 0.7 seconds approximately. Initial power factor without disturbance and without compensation was recorded to be 0.6 lagging, which after compensation was improved to 0.95 lagging. Similarly, in presence of disturbance without compensation the power factor fluctuated between 0.55 and 0.9 lagging, which after compensation was improved to 0.95 lagging and above throughout the course of operation.
A review on different control techniques using DSTATCOM for distribution system studies
