The reactive power control of the power system load node at the voltage instability of the power supply

The mathematical model of the power system load node is proposed. The main elements of the model are synchronous and asynchronous motors, a power transformer, power transmission lines and capacitor banks. The voltage instability of the electrical grid and the starting transients of the asynchronous motors are considered in the proposed model, in contrast to the counterparts. On the basis of this model the automatic reactive power control system (ARPCS) of the power system load node is developed; it is the open-loop reactive power system including the closed-loop excitation current controller and the synchronous motor closed-loop reactive power controller that produce the signals as a function of active and reactive powers of the asynchronous motors. The assessment of the influence of the voltage instability in the electrical grid on the reactive power deviation is given. The proposed ARPCS of the power system load node is shown to enhance the quality of the control.