Voltage Regulation of Active Distribution Networks

Abstract

The amount of non-centralized generation connected to distribution networks nowadays is still increasing. The structure and control methods of existing distribution networks are planned and operated assuming unidirectional power flows. Distributed generation (DG) affects power flows in the distribution networks and its effect on their operation can be positive or negative depending on the size, location and time variation of the generator. Anyways, DGs force the operational and planning principles of distribution networks to be changed radically. The voltage rise is usually the factor that limits the hosting capacity of the networks for DG. At the meantime, this rise is often handled by passive means such as increasing the conductor size or connecting the generator to a specially constructed feeder. These passive means keep the traditional principles of the operation of networks but leads to high connection costs of DGs and do not sufficiently increase their hosting capacity. Modern means referred as active voltage control methods change the network operational principles radically but leads to significantly smaller total costs of the distribution network and higher hosting capacity for DG than the passive approach. These methods can utilize active resources such as DGs in their control in addition to the existing voltage control equipment such as the main transformer tap changer. However, the implementations of active control approach in real distribution networks are still very low and the distribution network operators (DNOs) do not consider that approach as a real option in planning. Hence, much work is still required to enable the widespread utilization of active voltage control.