Commelec

Commelec is a framework that provides distributed and real-time control of electrical grids by using explicit setpoints for active/reactive power absorptions/injections.<ref>"EPFL Smart Grid Control - Commelec". École Polytechnique Fédérale de Lausanne.</ref> It is based on the joint-operation of communication and electricity systems. Commelec has been developed by scientists at École Polytechnique Fédérale de Lausanne, a research institute and university in Lausanne, Switzerland. The Commelec project is part of the SNSF’s National Research Programme “Energy Turnaround” (NRP 70).<ref>"Being Able to Give in is a Strength, Even in the Power Grid | National Research Programme Energy". nfp-energie.ch. Retrieved 2020-05-08.</ref><ref>"From the lab to the world – with a good business plan - Profile Swiss National Science Foundation". profile.snsf.ch. Retrieved 2020-05-08.</ref>

Motivation

Due to penetration of a large amount of distributed generation, modern power systems are facing numerous challenges<ref name=":0">Bouman, Niek Johannes; Bernstein, Andrey; Le Boudec, Jean-Yves (2015). Real-Time Control of Microgrids with Explicit Power Setpoints: an API for Resource Agents.</ref><ref name=":1">Bernstein, Andrey; Le Boudec, Jean-Yves; Reyes-Chamorro, Lorenzo; Paolone, Mario (2015). "Real-time control of microgrids with explicit power setpoints: Unintentional islanding". 2015 IEEE Eindhoven PowerTech. Eindhoven, Netherlands: IEEE. pp. 1–6. CiteSeerX 10.1.1.697.3975. doi:10.1109/PTC.2015.7232750. ISBN 978-1-4799-7693-5. S2CID 9250940.</ref> such as the absence of inertia, stochastic power generation, grid stress and stability issues. This could lead to problems related to power balance, power quality, voltage and frequency control, system economics and load dispatch.<ref>Bevrani, Hassan (7 July 2014). Robust Power System Frequency Control. Springer. p. 252. ISBN 978-3-319-07277-7.</ref> The conventional distribution grid was not designed to support the distributed generation of electricity. Therefore Commelec framework is developed in order to guarantee a proper grid operation under these challenges without major grid reinforcements. It can provide both primary frequency control and secondary voltage control, being also capable to operate in islanded mode.<ref name=":1" /><ref name=":3">"New ideas to control power flows in distribution networks (NRP 70) - NFP [Nr.]". www.nfp70.ch. Retrieved 2020-05-08.</ref> In contrast to conventional droop-control,<ref>Kundur, Prabha (22 January 1994). Power system stability and control. McGraw-Hill. pp. 589–594. ISBN 9780070359581.</ref> it keeps the equilibrium point without using the frequency as the main indicator of power imbalance.

Principle of Operation

Commelec is an agent-based framework. The grid agent (GA) is a piece of software that is running on an embedded computer attached somewhere in the grid. It monitors the state of the grid through the measurement system and orchestrates different resources by speaking to resource agents (RAs) that are usually collocated on the inverters of the resources. While GAs are smart and take part in computing decision actions, RAs are simple-minded, merely requested to send information about their internal state in a specified and universal format.<ref name=":0" />

Device-independent Protocol for Message Exchange

Every 100 ms, RA sends a device-independent representation about its internal state to the GA. On receiving this information from RAs through a communication network (e.g. internet), GA solves robust multi-objective optimization problem (taking into account the constraints of the grid), takes local decisions and implements them.<ref name=":2" /> Correction of decisions can be done after receiving new advertisements from RAs. The information that GA receives from RA has pure mathematical abstract description. It consists of:<ref name=":0" /><ref name=":2">Bernstein, Andrey; Bouman, Niek (February 2016). "The Vision of Commelec: Real-Time Control of Electrical Grids By Using Explicit Power Setpoints" (PDF).</ref>

• PQ profile: A convex set <math>\cal A \subseteq \mathbb{R}^2</math> that contains all the possible power setpoints <math>(P,Q)</math> that RA can implement,
• Virtual cost: A continuously differentiable function <math>CF: \cal{A}\rightarrow\mathbb{R}</math> characterized by the preference of the resource to stay in a certain zone of PQ profile,
• Belief function: A set-valued function <math>BF:\cal{A}\rightarrow 2^{\mathbb{R}^2}</math>which captures uncertainty in resource operation due to nature and local inverter control. Requested setpoint <math>(P,Q)</math> for RA to implement and actually implemented setpoint <math>(P',Q')</math>, in general, can be different. By definition, <math>(P',Q')\in BF(P,Q)\subseteq\mathbb{R}^2</math>.

Composability

Power network can be organized in a flat setting where single GA controls the whole grid and leads all the RAs, and in the hierarchical setting in which GA can lead not only RAs, but also the GAs with lower hierarchy level.<ref name=":0" /><ref>Bernstein, Andrey; Reyes-Chamorro, Lorenzo; Le Boudec, Jean-Yves; Paolone, Mario (2015). "A composable method for real-time control of active distribution networks with explicit power setpoints. Part I: Framework". Electric Power Systems Research. 125: 254–264. doi:10.1016/j.epsr.2015.03.023. S2CID 10512369.</ref> Composability property that Commelec provides, enables aggregation of several resources that GA controls to a single entity (i.e. virtual resource) which can be further controlled by a GA with a higher hierarchy level. Such virtual resource uses the same language to advertise internal state to its leading GA which makes the control problem scalable.<ref name=":2" />

Experimental Validation

The performance of Commelec control framework is evaluated through a case study composed of a replica of CIGRÉ’s low-voltage microgrid benchmark TF C6.04.02.<ref>Conseil international des grands réseaux électriques. Comité d'études C6. (2014). Benchmark systems for network integration of renewable and distributed energy resources. CIGRÉ. ISBN 978-2-85873-270-8. OCLC 887524084.{{cite book}}: CS1 maint: numeric names: authors list (link)</ref><ref>Reyes-Chamorro, Lorenzo; Bernstein, Andrey; Le Boudec, Jean-Yves; Paolone, Mario (2015). "A composable method for real-time control of active distribution networks with explicit power setpoints. Part II: Implementation and validation" (PDF). Electric Power Systems Research. 125: 265–280. doi:10.1016/j.epsr.2015.03.022. S2CID 10512369.</ref> This microgrid, built at EPFL, consists of different types of resources such as photovoltaic plants, battery energy storage systems and electric heaters.<ref name=":3" /> For real-time monitoring, phasor measurement units (PMUs) are used.<ref name=":2" />