A New Voltage Control Strategy for Power Systems with Massive Distributed Generation

The presented paper highlights the importance of voltage regulation at the distribution level in the presence of massive generation from renewable, intermittent sources such as wind and photovoltaic. Until a few decades ago, traditional power stations were connected mainly to transmission systems. Power flows were unidirectional, that is to say, they passed from very high-voltage systems toward medium and low voltage systems. The recent development of generation plants from renewable sources, such as wind and photovoltaic, are becoming more and more often responsible of important, inverse power flows on the grids. In addition, the electrical energy produced from distributed generation (DG) usually is intermittent and often has a unitary power factor. This means that also important DG power plants do not produce reactive power and consequently do not participate to the system voltage control. In these conditions, the problems associated to the control of the whole system have increased in number and complexity. On the other hand, electrical installations range from very high voltage (HHV) to low voltage and are widely dispersed in the territory. This paper shows how the spread of generation systems from renewable sources, which can be connected to either low, medium or high voltage, can be used as an new chance to improve procedures towards an effective voltage control. In order to demonstrate the validity of the proposed strategy for voltage regulation, a number of field tests were performed whose results are properly reported and commented.