In recent years, there has been an increased use of power electronic systems and sensitive electronic equipment in power generation, transmission, utilisation of electrical energy and associated systems. Nonlinear impedances predominantly offered by the power converter-based systems draw non-sinusoidal or distorted currents from the power source causing distorted voltage across the transmission line and transformer impedances. This results distortion in power supply waveform and cause distortion voltampere and low power factor in system. Further, asymmetrical distribution of large, single-phase loads results in voltage and current imbalance in the three-phase system. Distorted, unbalanced voltage and/or current waveforms have several adverse effects on both utilities and consumer equipment connected the power supply system. Traditional equipment like heaters and incandescent lamps are least affected by imperfection in sinusoidal waveform of power supply. However modern sensitive electronic items, where its operation depend on supply waveform are more affected by power quality. Thus, in area where extreme accuracy and precision is required, ie., in application involving measurement, instrumentation, communication, signal processing, fault detection, control, automation, robotics etc., are more affected by waveform distortion or power quality. It also increases component heating, higher losses and cause accelerated ageing, necessitating increased frequency of maintenance or even interruption and failure of the system. Thus, incurring huge economic loss.

Having realised the importance of power quality, IEEE and IEC have formulated standards on the topic, more importantly on harmonics. Some countries have imposed economic penalties for violation of its regulations on power quality. Hence, an effective elimination of the harmonics from the supply system is essential for both the utilities and end users. Loads and renewable energy power generation in the system vary randomly and consequently the conventional solution under multiple harmonic frequency using tuned passive filters are ineffective.

Active compensation using voltage source converter is the solution to compensate for voltage or current harmonics, reactive power and imbalance in voltage or current in the system. Generally, current compensation is done using shunt active compensator and voltage compensation by series active compensator and both voltage and current can be controlled at the same time using shunt- series active compensator. Main parts of these compensators are voltage source DC to AC converter which injects required amount of voltage or and current into the system to achieve desired outcome.

Under sinusoidal conditions, shunt compensators control reactive power to improve power factor and series compensators to control reactive power consumed by the transmission line to control active power flow through the line. When voltage is sinusoidal and current is non-sinusoidal, shunt compensator eliminates distortion power in addition to reactive power to achieve unity power factor and distortion free current. However, under non-sinusoidal supply voltage and current conditions, any attempt to achieve unity power factor using shunt compensator, results in a non-sinusoidal current, which increases the total harmonic distortion. On the other hand, attempt at getting harmonic free current may not yield unity power factor because of the harmonics present in the voltage waveform. This tutorial presents an algorithm which optimizes trade-off between power factor and harmonics achieving the best compromise under non-sinusoidal voltage and current conditions. With the technique, an optimal operation of shunt, series and shunt-series compensator is possible. An algorithm developed and validated under various supply and load conditions meeting requirements of IEEE 519 is also covered in the tutorial.