Reverse and forward engineering of frequency control in power networks

IEEE Trans. Control Netw. Syst.

Chen

2016

Self Cite

285

335

Automatic generation control (AGC) regulates mechanical power generation in response to load changes through local measurements. Its main objective is to maintain system frequency and keep energy balanced within each control area so as to maintain the scheduled net interchanges between control areas. The scheduled interchanges as well as some other factors of AGC are determined at a slower time scale by considering a centralized economic dispatch (ED) problem among different generators. However, how to make AGC more economically efficient is less studied. In this paper, we study the connections between AGC and ED by reverse engineering AGC from an optimization view, and then we propose a distributed approach to slightly modify the conventional AGC to improve its economic efficiency by incorporating ED into the AGC automatically and dynamically.

Section: B Proof Of Convergencementioning

confidence: 99%

Connecting Automatic Generation Control and Economic Dispatch From an Optimization View

IEEE Trans. Control Netw. Syst.

Chen

2016

Self Cite

285

335

“…Our work builds on previous optimization-based approaches [17]- [22], [28]. The crux of our solution is the introduction of virtual (line) flows that can be used to implicitly constrain real flows without altering the primaldual interpretation of the network dynamics.…”

Section: Contributions Of This Workmentioning

confidence: 99%

“…This has motivated the recent development of new analytic studies assessing the effect of distributed frequency control in power systems [15]- [22], and microgrids [23]- [27], which can be grouped into three main approaches.…”

Section: Introductionmentioning

confidence: 99%

“…It achieves efficiency but does not manage congestion, i.e., it does not enforce constraints such as thermal limits. The second approach reverse engineers the network dynamics as a primal-dual algorithm of an underlying optimization problem, and then add constraints and modifies the objective function while preserving the primal-dual interpretation of the network dynamics [19]- [22], [28]. It successfully achieves efficiency but it limits the type of operational constraints that can be satisfied.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Optimal Load-Side Control for Frequency Regulation in Smart Grids

Mallada

IEEE Trans. Automat. Contr.

Low

2017

206

244

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.

“…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.…”

Section: Introductionmentioning

confidence: 97%

Optimal decentralized primary frequency control in power networks

53rd IEEE Conference on Decision and Control

Low

2014

We augment existing generator-side primary frequency control with load-side control that are local, ubiquitous, and continuous. The mechanisms on both the generator and the load sides are decentralized in that their control decisions are functions of locally measurable frequency deviations. These local algorithms interact over the network through nonlinear power flows. We design the local frequency feedback control so that any equilibrium point of the closed-loop system is the solution to an optimization problem that minimizes the total generation cost and user disutility subject to power balance across entire network. With Lyapunov method we derive a sufficient condition for any equilibrium point of the closed-loop system to be asymptotically stable. A simulation demonstrates improvement in both the transient and steady-state performance over the traditional control only on generators, even when the total control capacity remains the same.