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Liu, Muyang
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Liu, Muyang
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Liu, Muyang
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Now showing 1 - 5 of 5
- PublicationPlacement of Virtual Synchronous Generator Controlled Electric Storage combined with Renewable GenerationThe virtual synchronous generator (VSG) control of power converters has been proposed to improve the system inertia. The commonly used VSG requires an energy storage (ESS) to provide the emulated inertia power and the frequency droop power. The placement of the ESS can be either in the DC port of the power electronics generation or co-located with the power electronics generation on the AC side. In the former case, the VSG control makes the total generator behave like a synchronous generator, while in the latter one, the VSG control only regulates the ESS in response to the grid frequency. The different placement of the ESS gives rise to different performance. This paper analyzes this performance firstly by means of simple transfer function analysis and secondly by comparing their effects on the grid frequency at the system level in the IEEE 39 bus test system. The results show that the placement of the ESS has no impact on the system transient stability while it has a significant impact on the frequency dynamics especially in the low inertia situation.
305Scopus© Citations 9 - PublicationModelling, Simulation and Hardware-in-the-Loop Validation of Virtual Synchronous Generator Control in Low Inertia Power System(IEEE, 2018-08-20)
; ; ; ; In recent literature, virtual synchronous generator control (VSG) has been proposed as a means to provide virtual inertia from non-synchronous generation in low inertia power systems. In this work we compare the power system support performance of VSG control to conventional droop when applied to electrical energy storage. A differential-algebraic equations (DAEs) model of VSG control is developed. This model is validated against measurement from a hardware in the loop implementation of the VSG. VSG and droop controlled storage is then incorporated into the IEEE 39 bus system model also incorporating different levels of generation from windfarms. The performance of both controls is compared in terms of their effect on the power system dynamics in the event of a contingency. The results show that VSG control in high wind penetration cases, improves the frequency nadir, reduces oscillations, and provide faster frequency and voltage stabilization.785Scopus© Citations 21 - PublicationSmart Transformer for the Provision of Coordinated Voltage and Frequency Support in the Grid(IEEE, 2018-10-23)
; ; ; ; ; Considering the increase in renewable generation and the consequent reduction in power system inertia, the Virtual Synchronous Machine (VSM) control method has been proposed to control power converters to emulate the inertia and other the characteristics of the synchronous machine. However, to achieve the function of VSM control, an extra energy base, typically storage, is required to connect to the controlled converter. In this work we investigate the application of the VSM control to the distribution system demand through the use of a VSM controlled smart transformer. Through control of the demand in this way, the demand itself can be used to emulate inertia and provide frequency support. This paper presents the details of the flexible demand control applied to a smart transformer supplying a low voltage distribution grid. The operation of the control is validated on scaled hardware using real time simulation with hardware in the loop. Simulations on a 400 kVA, 400 V distribution network are used to quantify the demand flexible. IEEE 39 bus is used to verify the benefit of the proposed control in terms of voltage and frequency in the power system.433Scopus© Citations 15 - PublicationImpact of Current Transients on the Synchronization Stability Assessment of Grid-Feeding ConvertersThe synchronization instability in the presence of a fault is a main issue for the dynamic behavior and control of grid-feeding converters. In the literature, the synchronization stability assessment is carried out considering the dynamics of Phase-Locked Loops (PLL) but the transients of converter currents are neglected. The letter shows that such a simplification leads to inaccuracies and, thus, the current transients cannot be neglected. The letter proposes a model that captures the effect of such current transients on the converter synchronization. This model allows assessing the transient behavior and, hence, the stability, of power electronics converters with high accuracy, comparable, in fact, to EMT models. The fidelity of the proposed model is duly discussed in the case study.
294Scopus© Citations 45 - Publication100% Converter-Interfaced generation using virtual synchronous generator control: A case study based on the irish systemThe increase in the use of Converter-Interfaced Generation (CIG) in the power system will require these generators to not only feed the power but also establish the voltage and maintain the grid stability. Virtual Synchronous Generator (VSG) control of the CIG is proposed to fulfill this requirement since it mimics the dynamics of synchronous generation. This paper takes the all-Island Irish transmission system as an example to investigate the frequency stability of the system as it migrates towards 100% CIG under VSG control and quantifies the minimum conditions for frequency support to sustain the system under 100% CIG. Simulations are carried out considering the worst contingency in the Irish grid which is the loss of largest infeed, namely, the disconnection of the HVDC interconnector to the UK. The results are compared and discussed considering other scenarios that include primary frequency control of conventional power plants.
189Scopus© Citations 27