A review on power quality problems and solutions

Introduction SOLID-STATE control of ac power using thyristors and other semiconductor switches is widely employed in do-mestic and industrial loads. Examples of such application such as adjustable speed drives (ASD’s), furnaces, diode and thyristor rectifiers, uninterruptible power supplies (UPSs), computers and their peripherals, consumer electron-ics appliances (TV sets for example), among others. Com-puter power supplies as well in , etc. Such controllers are also used in HV dc systems and renewable electrical power generation. As nonlinear loads, these solid-state converters draw harmonic and reactive power components of current from ac mains. In three-phase systems, they could also cause unbalance and draw excessive neutral currents. The injected harmonics, reactive power burden, unbalance, and excessive neutral currents cause low sys-tem efficiency and poor power factor. They also cause disturbance to other consumers and interference in nearby communication networks. Extensive surveys [1]–[7] have been carried out to quantify the problems associated with electric power networks having nonlinear loads. Conven-tionally passive L–C filters were used to reduce harmon-ics and capacitors were employed to improve the power factor of the ac loads. However, passive filters have the demerits of fixed compensation, large size, and resonance. The increased severity of harmonic pollution in power networks has attracted the attention of power electronics and power system engineers to develop dynamic and ad-justable solutions to the power quality problems. Such equipment, generally known as active filters (AF’s) The basic principle of active power filtering is to synthesize and apply a certain current or voltage waveform at a specified point of a distribution network. Active filters are fundamentally static power converters designed to synthe-size a current or voltage source; alternatively, they can be made to emulate specified impedances, both in magnitude and phase. Advantages of active filters over conventional means (passive filters, special transformer connections and special transformers) are mainly: flexibility in defin-ing and implementing the functions of the filter, a very fast control response, and no additional problems caused by possible resonant frequencies or network configura-tion. This paper aims at presenting a comprehensive survey on the on power quality problems and solutions by various types of AF’s. Impact of Power Pollution Unexplained computer network failures, premature motor burnouts, humming in telecommunication lines, and transformer overheating are only a few of the damages that quality problems may bring into home and industrial in-stallations. What may seem like minor quality problems may bring whole factories to a standstill. Studies by the Canadian Electrical Association indicate that power qual-ity problems, including voltage sags and surges, tran-sients, and harmonics, are estimated to cost Canada about $1.2 billion annually in loss production. Most of the cost of harmonics is not incurred in the power system itself but rather within the customer’s facility [8]. While system solutions are being searched and even power quality mar-kets are being formulated in the present deregulated envi-ronments, the solution starts at the individual industrial and commercial facilities. With the risks and costs of pol-lution in mind, researchers and equipment manufacturers are looking for alternatives for protection, while industry and businesses are increasingly investing in sophisticated and innovative devices to improve power quality. An overview of power quality pro-lems, their causes and effects: Electrical systems are subject to a wide variety of power quality problems which can interrupt production proc-esses, affect sensitive equipment, and cause downtime, scrap, and capacity losses [1]–[7]. Power Quality Solution We have seen number of power quality problems, nowadays there are number of power Quality problems solu-tions