Optimal load-side control for frequency regulation in smart grids

Abstract

Frequency control rebalances supply and demand while maintaining the network state within operational margins.It is implemented using fast ramping reserves that are expensive and wasteful, and which are expected to grow with the increasing penetration of renewables. The most promising solution to this problem is the use of demand response, i.e. load participation in frequency control. Yet it is still unclear how to efficiently integrate load participation without introducing instabilities and violating operational constraints.In this paper we present a comprehensive load-side frequency control mechanism that can maintain the grid within operational constraints. In particular, our controllers can rebalance supply and demand after disturbances, restore the frequency to its nominal value and preserve inter-area power flows. Furthermore, our controllers are distributed (unlike the currently implemented frequency control), can allocate load updates optimally, and can maintain line flows within thermal limits. We prove that such a distributed load-side control is globally asymptotically stable and robust to unknown load parameters. We illustrate its effectiveness through simulations.

Optimal decentralized primary frequency control in power networks

“…Recovery to nominal frequency needs secondary frequency control [1]- [3], which is traditionally centralized within a control area; see [26], [31], [32], [34] for recent work on distributed secondary frequency control.…”

“…As renewable generation introduces larger and faster fluctuations in real power and frequency, recent studies integrate functions traditionally realized by slower-timescale control, e.g, economic dispatch, with faster-timescale control, e.g., primary frequency control. Examples of these studies range from primary and/or secondary frequency control on the generator side [23]- [28], or the load side [29]- [32], to microgrids where inverters have similar dynamic behavior to generators [33], [34]. The control schemes in all these recent studies are decentralized or distributed, and hence are scalable to networks with a large number of controllable endpoints and suitable for deployment in future power grids.…”

Distributed Optimal Frequency Control for Integrated Energy Systems with Electricity and Heat

“…To prove the algorithm is robust to inaccurate damping coefficient Di, following changes are made: Under assumptions in Theorem 2, since 0 H  , adopting an invariance principle can we prove the robustness for the inaccurate coefficient i D , which is very similar to that in [12]. V. CASE STUDIES Case studies research the necessity of considering electricheat coupling in IES frequency control and the robustness under inaccurate coefficients, which demonstrate the effectiveness of the proposed algorithm.…”

“…where i  is the virtual phase angle [12] to eliminate the measurement of real phase angle i III. THE DISTRIBUTED OPTIMAL FREQUENCY CONTROL ALGORITHM In this section, a fully-distributed algorithm is proposed to solve the OLFC problem (6) based on the reverse engineering [11]- [13].…”

Steady-State Optimal Frequency Control for Lossy Power Grids with Distributed Communication

“…In previous publications dealing with real-time dynamic pricing for frequency control of power grids, the controllers were always designed under the assumption that line conductances are all zero [7]- [12]. However, this is an inadmissible assumption especially for distribution grids, see.…”