Asynchronized machines as a means of counter-emergency control and frequency regulation in a power system

Abstract

The possibility of using asynchronized machines, operating with a variable rotor rotation frequency, as counter-emergency control and high-speed regulation of the active power, is shown. The problems involved in using asynchronized machines to increase the active power and frequency regulation quality, and also to improve the dynamic characteristic of power systems, are considered.The use in power plants of units operating with an adjustable rotation frequency, based on asynchronized generators, proposed by the power systems of the USSR [1], has been widely used during the past few years by a number of foreign companies and power-supply enterprises [2,3].The main effect of the use of such units is an increase in the efficiency as a result of operating at an adjustable rotation frequency with a variable pressure. Moreover, the vibration is reduced and the units themselves can be employed for high-speed regulation of the active power, which enables the quality of the frequency regulation in the power system to be increased, as is confirmed by successful experience in using an asynchronized compensator with a flywheel on the shaft in Japan [4].The property of an asynchronized machine of rapidly adjusting the distributed or consumed active power is an urgent one for Russian power systems in both hydroelectric and thermal power plants. In this paper we investigate the possibilities of asynchronized machines for counter-emergency control and frequency regulation in a power system.Asynchronized electrical machines differ from synchronous machines in the fact that they have a two-phase or three-phase excitation winding (Fig. 1). A multiphase excitation winding enables "vector" control of the excitation current by an asynchronized method to be achieved, i.e., one can control the reactive and active powers separately. In this way, not only is the control quality increased, but it also becomes possible to regulate the active power of the machine as rapidly as the reactive power.In an asynchronized machine with a symmetrical winding on the loaded rotor it is possible to regulate the rotation frequency. The excitation system then supplies the rotor winding with an adjustable current. The power of the excitation system is proportional to the maximum slippage of the rotor.In a synchronous generator, the active power delivered to the network can only be adjusted by regulating the turbine power. For a synchronous hydrogenerator the rate of adjustment of the electric active power is determined by the rate of control of the adjusting apparatus of the turbine.In an asynchronized machine, due to the particular features of the construction, the asynchronized-machine principle for controlling and exciting the adjustable current provides the possibility of controlling the electric active power independently of the turbine power, and independently of the mechanical power on the shaft. The active power delivered to the circuit or consumed from the circuit is regulated practically instantaneously. A change in the electromagnetic power of t...