Synchronous reference frame interface for geographically distributed real-time simulations

The increasing complexity of power systems has warranted the development of geographically distributed real-time simulations (GD-RTS). However, the wide scale adoption of GD-RTS remains a challenge owing to the (i) limitations of state-ofthe- A rt interfaces in reproducing faster dynamics and transients, (ii) lack of an approach to ensure a successful implementation within geographically separated research infrastructures (RIs) and (iii) lack of established evidence of its appropriateness for smart grid applications. To address the limitations in reproduction of faster dynamics and transients, this study presents a synchronous reference frame interface for GD-RTS. By means of a comprehensive performance characterisation, the superior performance of the proposed interface in terms of accuracy (reduced error on average by 60% and faster settling times) and computational complexity has been established. This study further derives the transfer function models for GD-RTS with interface characteristics for analytical stability analysis that ensure stable implementations avoiding the risks associated with multiple RI implementations. Finally, to establish confidence in the proposed interface and to investigate GD-RTS applicability for real-world applications, a GD-RTS implementation between two RIs at the University of Strathclyde is realised to demonstrate inertial support within transmission network model of the Great Britain power system

Enhanced virtual synchronous machine (VSM) control algorithm for hybrid grid forming converters

There has been considerable interest in convertor solutions which to a greater or lesser extent mimic the behaviour of synchronous machines, thus overcoming many of the disadvantages of the existing technology which are potentially destabilizing at high penetration. These solutions are frequently referred to as Grid Forming Convertors (GFC). For offshore installations, where some equipment is on shore, locating equipment offshore is more expensive and carries greater commercial risks, requiring extensive testing and confidence building prior to deployment in real applications. This is time consuming and particularly significant for GB and where there are significant quantities of offshore generation. Onshore solutions to stability are therefore desirable for Off-Shore Transmission Owners (OFTOs) and might also be applied by retrofitting to existing conventional converter plant. This paper presents and discusses findings of the second stage of the research focusing on the enhanced control algorithm for Hybrid Grid Forming Convertors for Offshore Wind Applications and its performance, while the previous paper [3] presents the initial findings comparing various hybrid solutions for offshore networks where the STATCOM onshore is replaced by synchronous compensator and GFC or Virtual Synchronous Machines (VSM) converter of similar rating with the aim to achieve levels of Grid-Forming capability

Experimental assessment and validation of inertial behaviour of virtual synchronous machines

Increasing integration of converter-interfaced renewable generation has led to significant operational challenges for power systems. Such challenges are mainly caused by the different capabilities and dynamic responses of the converters compared with synchronous machines, for example, converters do not naturally provide inertia to the system. Virtual Synchronous Machine (VSM) is considered as a promising solution to address the challenges associated with reduced system inertia via the provision of emulated inertial response to support the operation of converter-dominated power systems. However, it has been observed that the dynamic behaviour of the VSM could differ significantly from that of a Synchronous Condenser (SC) and a Synchronous Generator (SG) in terms of inertial response provision, even when the VSM is configured with the same inertia constant. Furthermore, effective practical methods for evaluating the damping performance of VSMs are not presently available. To gain a better understanding and achieve a more accurate assessment of the dynamic inertial and damping performance of VSMs, this paper presents an experimental methodology for systematic evaluation of the dynamic response of the VSM in the frequency domain using the Network Frequency Perturbation (NFP) method. Experimental design and implementation of the NFP method are presented to assess VSM system's equivalent inertia and damping constants, where the VSM system under test can be treated as a black box without any knowledge of internal settings and control design. Case studies are conducted, where the proposed experimental design has been applied for testing and assessing the inertial and damping constants of a physical 246 kVA VSM prototype driven by a Battery Energy Storage System with comparison of the SC and SG with equivalent inertia constant. Power-Hardware-in-the-Loop (PHiL) testing is also conducted to demonstrate the VSM's inertia performance. The studies demonstrate that the developed experimental approach based on NFP method provides a valuable tool for network operators and manufacturers for evaluating the inertial and damping performance

Scalable real-time controller hardware-in-the-loop testing for multiple interconnected converters

This project is aiming to make the first steps in investigating and pushing the boundaries of real-time simulation. To that end it will focus on real-time representation of converter devices on different platforms, enabling the future coupling of prototyping controllers to power system simulation tools. The small time-step, high fidelity representation of the converter devices and the large time-step model of the grid will be carried out on RTDS Technologies, RTDS and perhaps expanding the attempt, on OPAL-RT Technologies, OPAL-RT Simulator in the future. The controller prototyping, including the converter switching strategy will be implemented on ADI's rtXand the use of other rapid controller prototyping systems will also be evaluated. This will effectively allow the exploration of the scalability and limits of such schemes. Namely, how many converters can be simulated on real-time simulation devices? How many controllers can be implemented on a prototyping platform using modern microprocessors

Distributed ReStart: Non-Conventional Black-Start Resources : RTDS Based Network Energization from Grid Forming Converters: Part 1

Following the past two studies submitted as part of Distributed ReStart project tasks between SPEN and Iberdrola Innovation Middle East, this report summarizes preliminary results achieved as part of the third work package of the project, undertaken in experimental collaboration with the state-of-the-art smart grid laboratories at the University of Strathclyde, namely the Dynamic Power Systems Laboratory (DPSL) and the Power Networks Demonstration Center (PNDC). The aim of this report is to shed light on the real-time modeling of grid forming converters for black-start applications, starting from a similar simplified network reported in work package 2 study for proof of concept, and then expanding into Chaplecross electrical network in Scotland to simulate the black-start energization of a smaller segment from this network as a preliminary step to extended planned tests that take into account further scenarios. Throughout this report, the GFC control used is illustrated in Figure 1, including soft energization, voltage support and grid synchronization capabilities. The modified grid-synchronization control requires access to high-precision voltage measurements from the synchronizing point

Validating grid-forming capabilities of hybrid power park technologies in future OFTO networks

In recent years there has been considerable interest in convertor based generating solutions which to a greater or lesser extent mimic the behaviour of synchronous machines, thus overcoming many of the disadvantages of the existing technologies which are potentially destabilising at high penetration. Such solutions are frequently referred to as Grid Forming Convertors (GFC). This paper focuses the application of GFC technologies in offshore windfarms, where installation, maintenance and/or modification of any offshore equipment is very expensive and carries greater commercial risks, requiring extensive testing and confidence building prior to deployment in real applications. This is time consuming and particularly significant for GB and where there are large quantities of offshore generation. Onshore solutions to stability are therefore desirable for Off-Shore Transmission Owners (OFTOs), especially, if they could be applied by retrofitting to existing conventional converter plant. Consequently, this paper proposes and investigates the performance of hybrid solutions for offshore networks where the conventional STATCOM onshore unit is replaced by alternative options such as synchronous compensator and VSM converter of similar (or appropriate) rating with the aim of achieving Grid-Forming capability. A laboratory scale implementation of the proposed control algorithm is also presented with selected validation test results

Performance of hybrid power park technologies in future OFTO networks with the aim to achieve grid-forming capability

There has been considerable interest in convertor solutions which to a greater or lesser extent mimic the behaviour of synchronous machines, thus overcoming many of the disadvantages of the existing technology which are potentially destabilizing at high penetration. These solutions are frequently referred to as Grid Forming Convertors (GFC). For offshore installations, where some equipment is on shore, locating equipment offshore is more expensive and carries greater commercial risks, requiring extensive testing and confidence building prior to deployment in real applications. This is time consuming and particularly significant for GB and where there are significant quantities of offshore generation. Onshore solutions to stability are therefore desirable for Off-Shore Transmission Owners (OFTOs) and might also be applied by retrofitting to existing conventional converter plant. Consequently, NG ESO and UoS embarked on a project to investigate hybrid solutions for offshore networks where the STATCOM onshore is replaced by alternative options such as synchronous compensator and VSM converter of similar or appropriate rating with the aim of achieving Grid-Forming capability