Inertia reduction due to high-level penetration of converter interfaced components may result in frequency stability issues. The paper proposes and analyzes different strategies using synchronous condenser (SC), synthetic inertia (SI) of wind power plant, and their combination to enhance the frequency stability of low inertia systems under various scenarios and wind conditions. Furthermore, one of the SC models includes hardware of AVR for better representation of the reality is implemented. The simplified Western Danish power system simulated in real time digital simulator (RTDS) is used as a test system of low inertia to demonstrate the effectiveness of the strategies. The comparative results show that the combination of SC with AVR hardware-in-the-loop test and SI offers a better improvement not only on frequency stability (rate of change of frequency and frequency deviation) but also on the system synchronism under various operating conditions.

The rapid increase of converter-based generation in the grid causes significant changes in the system dynamic characteristics. These changes require verification and testing of the reliability, optimization, and functionality of power system elements and controllers, which become more important for guaranteeing a secure operation. This paper first introduces a hardware-in-the-loop (HiL) setup of an automatic voltage regulator (AVR) control system and then proposes a softwarein- the-loop (SiL) setup for the parameterization of an IEEE standard AVR/excitation system model and a power oscillation damping (POD) controller of synchronous condenser. The AVR hardware is interfaced with a simulated grid in real-time digital simulator (RTDS) using EMT simulation to evaluate its control functions. Parameter optimization for the POD and the AVR simulation model by SiL simulation is implemented in a closed loop between RTDS and Matlab/Simulink interfaced through OPC to satisfy the optimization objectives. By tests executed on the future Western Danish power system, parameter optimization of the POD and IEEE standard AVR model, and the function of AVR hardware are successfully implemented and verified.

Frequency stability in today’s power systems has become more critical than ever due to the growing contribution of renewable energy sources. This situation has arisen because of the electro-mechanical decoupling between renewable generation sources and the main grid caused by their connection through power electronic converters. This paper designs two synthetic inertia controllers that adhere to the grid code requirements from two different countries and then to utilize them to aid in the integration of high levels of wind power penetration in a test power system. The controllers are designed for a full converter wind turbine generator and are validated in an EMT real-time simulation with isolated testing at different wind speeds and different wind power penetration. The role of synchronous inertia in maintaining frequency stability is also explored through the use of synchronous condensers. Finally, the economic aspect of inertia is discussed, using the real-world example of the Bornholm island power system.

High-level integration of renewable energy sources in power system leads to the displacement of conventional generators and consequently challenges in power system frequency stability are introduced. To mitigate the negative impact of significant wind power penetration in the grid on the frequency stability, this paper proposes supplementary control methods to implement synthetic inertia for doubly-fed induction generator (DFIG) based wind energy system during frequency excursions. Different control strategies and activation schemes are analyzed and implemented on the Western Danish renewable-based system using-real time digital simulator (RTDS) to propose the best one for the synthetic inertia controller. From the comparative simulation results, it can be concluded that the method using a combination of both the frequency deviation and derivative as input signals, and the under-frequency trigger provides the best dynamic response in term of the system frequency stability improvement.

In order to meet the energy demand and at the same time to achieve sustainable development objectives on a global scale, the Danish government has set a long-term strategy of fossil fuel free country by the year 2050. However, the decline of conventional power generation units and a rising amount of converter interfaced components (wind turbine, HVDC, and Photovoltaic) may have negative effects on the stability of the power system. These components do not have enough inertia response to control frequency excursion, so the power grid can depend on few synchronous machines for frequency regulation and reduce the system inertia. Consequently, the frequency stability of the system will be easily jeopardized. To address these issues, the paper studies frequency characteristics of future Western Danish renewable-based system that uses a majority of wind turbine generators. Different scenarios of wind turbine penetration, governor responsibility of synchronous generators, and disturbance are simulated to examine the impact of high-level renewable energy integration on the system frequency characteristics. The effect of synchronous condensers for the frequency stability enhancement is investigated. It can be concluded from the comparative simulation results that synchronous condenser demonstrates a satisfactory performance for improving the system frequency stability.

This paper presents an approach to extend the capabilities of smart grid laboratories through the concept of Power Hardware-in-the-Loop (PHiL) testing by re-purposing existing grid-forming converters. A simple and cost-effective power interface, paired with a remotely located Digital Real-time Simulator (DRTS), facilitates Geographically Distributed Power Hardware Loop (GD-PHiL) in a quasi-static operating regime. In this study, a DRTS simulator was interfaced via the public internet with a grid-forming ship-to-shore converter located in a smart-grid testing laboratory, approximately 40 km away from the simulator. A case study based on the IEEE 13-bus distribution network, an on-load-tap-changer (OLTC) controller and a controllable load in the laboratory demonstrated the feasibility of such a setup. A simple compensation method applicable to this multi-rate setup is proposed and evaluated. Experimental results indicate that this compensation method significantly enhances the voltage response, whereas the conservation of energy at the coupling point still poses a challenge. Findings also show that, due to inherent limitations of the converter’s Modbus interface, a separate measurement setup is preferable. This can help achieve higher measurement fidelity, while simultaneously increasing the loop rate of the PHiL setup.