Modernization of power systems leads to more power electronic interfaced units in the generation, demand, and transmission. Examples are remotely installed renewable energy sources, loads with constant power, or high voltage direct current (HVDC) corridors. These changes significantly affect the frequency stability margins of the system and thus special control techniques should be applied in the converters of the new installed units so as to shoulder the frequency regulation in case of commonly occurred active power imbalances. The response of such units has to be cooperative in order to avoid problems such as insufficient reactions or overshoots. In this chapter, a coordinative tuning approach of the active power gradient control scheme applied to the controllers of modular multilevel converter (MMC)-based HVDC links and proton exchange membrane electrolyzers with the provision of fast frequency support in a multiarea hybrid HVDC-HVAC power system with responsive demand units is proposed. This tuning uses an optimization approach based on mean variance mapping optimization and is able to minimize the frequency excursions in all interconnected areas participating in the frequency regulation even without communication between the system nodes. This technique has shown great results in terms of quality and convergence rate within a short number of fitness evaluations achieving a set of frequency responses within acceptable limits set by operators even in case of the loss of the largest generating unit in the weakest system area. It has also revealed the applicability of such a method in more complex systems and the necessity for sophisticated tuning methods according to the application needs and the system characteristics.

The increasing integration of distributed energy resources such as photovoltaic (PV) systems into distribution networks introduces intermittent and variable power, leading to high voltage fluctuations. High PV integration can also result in increased terminal voltage of the network during periods of high PV generation and low load consumption. These problems can be solved by optimal utilization of the reactive power capability of a smart inverter. However, solving the optimization problem using a detailed mathematical model of the distribution network may be time-consuming. Due to this, the optimization process may not be fast enough to incorporate this rapid fluctuation when implemented in real-time optimization. To address these issues, this paper proposes a co-simulation-based optimization approach for optimal reactive power control in smart inverters. By utilizing co-simulation, the need for detailed mathematical modeling of the power flow equation of the distribution network in the optimization model is eliminated, thereby enabling faster optimization. This paper compares three optimization algorithms (improved harmony search, simplicial homology global optimization, and differential evolution) using models developed in OpenDSS and DigSilent PowerFactory. The results demonstrate the suitability of the proposed co-simulation-based optimization for obtaining optimal setpoints for reactive power control, minimizing total power loss in distribution networks with high PV integration. This research paper contributes to efficient and practical solutions for modeling optimal control problems in future distribution networks.

This paper presents a simple validation of ePHASORSIM's user-defined model of a Virtual Synchronous Machine (VSM) suitable for real-time simulations. The validation consists of a software-to-software comparison of the real-time simulator ePHASORSIM against the offline transient simulation tool PowerFactory. The comparison evaluates the models in the native library and user-defined models imported to ePHASORSIM. These user-defined models are coded in a Modelica environment and imported as a functional mock-up unit (FMU) model-the dynamic model of a voltage source converter operating as a VSM was implemented to test this functionality. A modified version of the IEEE 39-bus New England system was used for testing and validation. The time series from each (software) transient simulation were compared using the percentage error and the mean percentage error (MPE); the results demonstrate the suitability of the proposed approach.

This paper is a step forward in the effort to create an appropriate open-access library of benchmark test systems for offline and real-time simulations. The library will consist of 13 test systems for steady-state and dynamic power system analysis considering different relevant features (topology, control mode and element details). In this scientific paper, the authors selected one of the test systems, the 5-bus test transmission system, in meshed topology. Details of its implementation using several power system analysis platforms for offline and online/real-time simulation. Offline steady-state performance results are presented using PowerWorld, DIgSILENT PowerFactory and IPSA. Plots of the main electromechanical variables of the time-domain response considering a generator outage are presented using offline simulations from PowerFactory and real-time simulation ePHASORSIM. Simulation results show very minimal discrepancies between the results considering different platforms.

Future distribution networks (DN) are subject to rapid load changes and high penetration of variable distributed energy resources (DER). Due to this, the DN operators face several operational challenges, especially voltage violations. Optimal power flow (OPF)-based reactive power control (RPC) from the smart converter (SC) is one of the viable solutions to address such violations. However, sufficient communication and monitoring infrastructures are not available for OPF-based RPC. With the development of the latest information communication technology in SC, cyber-physical co-simulation (CPCS) has been extensively used for real-time monitoring and control. Moreover, deploying OPF-based RPC using CPCS considering the controller design of SC for a realistic DN is still a big challenge. Hence, this paper aims to mitigate voltage violations by using OPF-based RPC in a real-time CPCS framework with multiple SCs in a realistic DN. The OPF-based RPC is achieved by performing the CPCS framework developed in this study. The CIGRE medium-voltage DN is considered as a test system. Real-time optimization and signal processing are achieved by Python-based programs using a model-based toolchain of a real-time DN solver and simulator. Real-time simulation studies showed that the proposed method is capable of handling uncertain voltage violations in real time.

Future carbon-neutral power systems impose many challenges; one is the urgent need for a simulation platform that allows replicating the complex systems’ actual dynamic performance. This paper shows the results of implementing a cyber-physical testbed co-simulation in real-time to analyse the system frequency response considering primary frequency control and emergency frequency control: under-frequency load-shedding (UFLS) protection schemes. The proposed testbed uses a physical layer of two real-time simulators from different vendors in a closed loop, Opal-RT OP4510 and Typhoon HIL 604, being the first simulator for test system modelling and the remainder used to implement the UFLS protection scheme. Two connections of the real-time simulators are considered: physical connection using wires to exchange analogue signals and cybernetic digital communication using ANSI C37.118 communication protocol. The cybernetic layer of the testbed models a test system, controls the real-time simulation, and implements digital communication between the simulators. A modified version of the P.M. Anderson 9-bus systems is used for testing purposes, including phasor measurement units (PMUs). Results of the real-time simulation show the appropriate performance of the proposed testbed.

Electrical power systems are continuously upgrading into networks with a higher degree of automation capable of identifying and reacting to different events that may trigger undesirable situations. In power systems with decreasing inertia and damping levels, poorly damped oscillations with sustained or growing amplitudes following a disturbance may eventually lead to instability and provoke a major event such as a blackout. Additionally, with the increasing and considerable share of renewable power generation, unprecedented operational challenges shall be considered when proposing protection schemes against unstable electro-mechanical (e.g. ringdown) oscillations. In an emergency situation, islanding operations enable splitting a power network into separate smaller networks to prevent a total blackout. Due to such changes, identifying the underlying types of oscillatory coherency and the islanding protocols are necessary for a continuously updating process to be incorporated into the existing power system monitoring and control tasks. This paper examines the existing evaluation methods and the islanding protocols as well as proposes an updated operational guideline based on the latest data-analytic technologies.

The operation schedule of the power generation units in electrical power systems is determined by the optimisation problem known as unit commitment (UC), aiming at minimising the total cost considering the generation constraints. To obtain a feasible solution from the network perspective, the security-constrained UC (SCUC) problem has been defined to embed the network constraints in the optimisation problem as well. Also, the higher penetration of renewable energy sources (RES) has increased the difficulty of UC problem, mainly due to the uncertainty and the high variability of RES. This paper proposed a SCUC with economic dispatch (SCUCED) optimisation developed in two stages. The first one is the solution of a merit-order based zonal day-ahead market (ZDAM) optimisation to define a preliminary generation schedule. In the second stage, the SCUCED is solved based on AC load flow routines and sensitivity factors to embed the full network representation. The approach is applied to a modified version of the IEEE 39-bus test system.