Voltage control of critical and non-critical loads in distribution networks with electric spring

The electric spring (ES) is a novel voltage compensator which is series with a noncritical load to regulate the critical load voltage. The voltage fluctuation is caused by wind speed fluctuation, load fluctuation, and generator tripping. In busbar voltage drop situation, the electric spring decreases the voltage of non-critical load in order to support the critical load (busbar) voltage. All the non-critical loads couldn’t work under any voltage (for example 0.5pu). In this paper, a control strategy founded on active and reactive power compensations has been proposed for voltage control of critical loads on a reference value while it controls the voltage of non-critical loads between an acceptable boundary. The proposed controller has two voltage control loops which adjusts active and reactive power of the electric spring. The experimental results from the case study show that the ES with the proposed control strategy can effectively mitigate double voltage control of both critical and non-critical loads while dynamically managing the demand response of the system at the same time.