This special issue brings together a group of internationally renowned experts in the fields of electrical systems and automatic control to present their recent research developments. The selected topics are focused on both classical and emerging issues concerning optimisation and control of electrical systems, which include smart power grid control, renewable energy system control, inverter control and electrical drive control. The contributing authors to this special issue consist of professors and researchers who are the leaders in electrical drives and power converters as well as those whose expertise is in the systems and control, applying optimisation and control theory to solve emerging problems in electrical systems.
The first three papers of the special issue deal with the investigation of smart grid control as an emerging research area that has become more and more attractive to systems and control engineers. Professors Aldeen and Evans and their colleagues (University of Melbourne, Australia) present a quantitative framework for assessment of voltage stability in smart power networks. In their work, new stability indices similar to gain and phase margins in linear time-invariant control systems are established for power grid stability analysis. From a different angle, Dr Kefayati and Professor Baldicky (University of Texas, USA) tackle the problem of smart power grid control through optimal decision making in the presence of a flexible load subject to rate constraints. In their paper, under arbitrarily distributed and correlated Markovian energy and ancillary services prices, optimal policies for minimising expected total cost are derived. Another aspect of smart grid control is investigated by Professor Bittanti and his colleagues (Politecnico di Milano, Italy), through automatic control of a grid connected energy storage system. Their investigation is based on a plant that consists of a photovoltaic generator, an energy storage system, a DC bus and an inverter where the control strategy in a hierarchical manner maximises the self-consumption of the local load unit, managing the power exchange variability at the plant with the grid.
Electrical drive control is a classical topic in electrical systems. How to control electrical drives to make them more energy efficient and better performance is an ongoing research topic. The next three papers in the special issue are to present optimisation and predictive control of electrical drives. Professor Kennel and his colleagues (TUM, Germany) propose an effective model predictive current control scheme for induction machines driven by a three-level neutral point clamped inverter. Their strategy, verified by experiments, is to enable effective variable switching point at the inverter in order to reduce current ripples and computational complexity. Professor Kennel (TUM, Germany) and Professor Rodrıguez (Universidad Andres Bello, Chile) and their colleagues present a model predictive torque control of electrical drives where the best voltage vector is selected by minimising the value of a cost function, which aims to achieve a low torque ripple. From the perspective of a systems engineer, Dr Nicholas and Professor Boyd (Stanford, USA) investigate optimal current waveforms for brushless permanent magnet motors via convex optimisation. Their paper shows how to use the alternating direction method of multipliers to find the optimal current in milliseconds or hundreds of microseconds, depending on the processor used, which allows the possibility of generating optimal waveforms in real time.
The final two papers in the special issue discuss the issues associated with inverter control, which is one of the key components in electrical drives and renewable energy systems. Dr Mirzaeva and Professor Goodwin (University of Newcastle, Australia) proposed a new approach to delay compensation and harmonic suppression in inverter voltage using a variable horizon nonlinear predictive control. Professor Zhong and his colleagues (University of Sheffield, UK) present stability analysis and fail-safe operation of inverters when they are operated in parallel.
In conclusion, this special issue has presented recent developments of optimisation and control of electrical systems. We hope, as guest editors for this special issue, that the papers are interesting to researchers, students and engineers in the electrical and control engineering community.