Granulated load-side control of power systems with electric spring aggregators

To achieve expected active power balancing in the transmission network and regulate frequency in a practical way, aggregate controllable loads would be useful. Such a scheme would need to be granulated down to sub-transmission networks in which active power flows affect both frequency and bus voltage, and hence a new control method should be adopted. A control scheme is proposed for sub-transmission networks by coordinating electric spring (ES) aggregators which consist of ESs and controllable loads to implement frequency and voltage control simultaneously by adopting d-q transformation. On one hand, decentralized PI control is adopted for voltage regulation by adjusting the q component of the ES voltage. On the other hand, the d component of the ES voltage is adjusted to guarantee expected active power consumption of the ES aggregator. Simulation results show that the proposed control method can achieve expected active power compensation accurately and meanwhile maintain bus voltages within the acceptable range.