Frequency-based demand side response considering the discontinuity of the ToU tariff

Abstract

Demand side response (DSR) according to the time-of-use (ToU) tariff can bring a number of benefits to consumers and networks. However, for microgrids with high penetrations of renewable energy and flexible load, the sudden and drastic variations of loads triggered by the discontinuity of the ToU tariff could be fatal to the frequency stability of this low inertia system. This paper proposes a new frequency-based DSR (FB-DSR) strategy through a two-stage model with the frequency dynamics expressed analytically as the exchange power. The first stage optimizes the day-ahead DSR strategy based on the ToU tariff and equipment degradation cost. At the second stage, frequency response is constrained through the whole process of inertia support, frequency nadir and quasi-steady-state by integrating time-domain optimization and frequency-domain control. Numerical results demonstrate that the proposed strategy can effectively reduce the volatility of flexible load when responding to the ToU tariff, and thus significantly lowering the cost of maintaining the system frequency stability. At the same time, the negative impact of this strategy on the economic benefits of DSR is negligible. The overall operating cost of the test system is reduced by 7.34% even considering the increased degradation cost.