Capacitor Steps Research Articles

Certain investigations in enhancing power yield from wind farms

India has moved up to the fourth position globally, following Germany, Spain, and USA with an installed capacity of 11 806.69 MW at the end of March 2010. India has some special requirements. The penalty for low power factor is severe, but European designs do not have provision for compensation to this level. In Tamil Nadu, the Tamil Nadu Electricity Board has introduced the penalty only in the late 1990s. Since most of the wind turbine generators are being imported from European countries and as the principals have failed to understand the problem and provide solution, most of the Indian subsidiaries have approached third parties. A wide range of reactive power compensation schemes are available today. The cheapest and easiest solution preferred was to add more contactors and more capacitor steps. This will reduce the reactive power consumption but results in other problems. There is no systematic study to evaluate losses and scope for improving productivity. This article is an attempt to make realistic evaluation of wind farms provided with different systems in Tamil Nadu, India. To enhance the power yield from the wind farms, several methodologies are proposed.

Control Algorithm for Coordinated Reactive Power Compensation in a Wind Park

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> The penetration level of wind energy is continuously growing, and it is especially relevant in European countries such as Denmark, Germany, and Spain. For this reason, grid codes in different countries have been recently revised, or are now under revision in order to integrate this energy in the network taking into account the security of supply. This paper is related to reactive compensation, which is one aspect usually included in these codes. On the other hand, a great number of installed wind parks are formed by fixed speed wind turbines equipped with induction generators. The typical scheme for reactive compensation in this kind of wind parks is based on capacitor banks locally controlled in each machine. This configuration makes very difficult to follow the requirements of the new grid codes. To overcome this problem, a configuration with a central controller that coordinates the actuation over all the capacitor steps in the wind park is proposed in this paper. A central controller algorithm that is based on a dynamic programming is presented and evaluated by means of simulation. At this time, the proposed scheme has been installed at the Sotavento Experimental Wind Park (Spain) and it is currently being tested. </para>

Capacitor failure analysis

This article investigates capacitor failures and fuse operations in an automatically switched capacitor bank in an industrial facility. The fuses that cleared were protecting individual capacitor steps in the bank. It was initially believed that harmonics were the source of the problem. The investigation determined that the failures were occurring due to capacitor energization transients from an unexpected source. Capacitor analysis reveals that capacitors must be built to tolerate voltages and currents in excess of their ratings according to IEEE standards

Comparative study on the performance of a commercially designed induction generator with induction motors operating as self excited induction generators

The paper presents the performance characteristics of different induction machines of various ratings operating as a capacitor self-excited induction generator. Their computed performance is compared with commercially designed line excited induction generators operating as self excited induction generators. An algorithm, using the Newton-Raphson method and steady state equivalent circuit for the machine, is developed to compute the excitation requirement for maintaining a constant terminal voltage at different loads. This technique is also used to compute the number of capacitor steps required to load the machine, from no load to full load, while maintaining terminal voltage within specified limits. The optimum output power of the machine is computed without exceeding the rated stator current for its rated speed. The voltage range within which the machine is expected to operate at or above its rated capacity in stand alone mode, but without being overloaded, is also obtained. The effect of speed on excitation requirements is studied.

A Single-Phase Self-Excited Induction Generator for Lighting Loads in Remote Areas

For a self-excited single-phase cage induction generator, the possibility of few discrete capacitor steps to keep the terminal voltage within specified tolerance at different loads, is evolved for implementing a simple regulating scheme. The capacitance/reactive VARs requirements for the generator are also obtained to maintain constant terminal voltage at various loads.

Extending the Use of Shunt Capacitors by Means of Automatic Switching

It generally is recognized that the kilowatt loading on distribution circuits or plant feeders may be increased substantially by using capacitors to supply the kilovar load and relieve the current-carrying system of this burden. The use of capacitors to boost voltage or actually to regulate voltage has increased during recent years. Automatic switching of capacitors makes it possible to obtain the benefits of adding capacitors to take care of the full load kilovars without the objection of excess capacitor kilovars at light loads. It also makes it possible not only to apply capacitors in the most effective manner from the standpoint of meeting power-factor limits established by the utility, but also to regulate voltage in the plant or on the system. Capacitors may be switched automatically by the same switching means controlling the load, or they may be switched in response to changes in circuit conditions such as voltage, current flowing, or the reactive kilovars drawn by the load. The advantages of the various types of control and the choice of the number and size of capacitor steps to be switched are discussed fully.