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Medium/High power converters usually employ low switching frequency to reduce power loss, resulting in large system delay in their control system. The multi-sampling technique is an effective method to reduce the system delay while this will make the system a Linear Periodic Time Varying (LPTV) system. Modeling this kind of system by using LTI modeling method, such as Laplace transform, Z-transform,...
The electricity system has to balance demand and supply every second, a task that is becoming evermore challenging due to the increased penetration of renewable energy sources and subsequent inertial levels. In the UK, a number of grid frequency support services are available, which are developed to provide a real-time response to changes in the grid frequency. The National Grid Electricity Transmission...
The increased integration of wind generation via high power converters imposses numerous gauntlet to the management and control of modern power systems. One of them is caused by the decoupling effect between the power sources from the AC grid. It negatively impacts the system frequency response of modern power systems. This paper proposes a controller to enable the primary frequency regulation on...
Various models have been proposed to analyze the impact of synthetic inertia on frequency response. On one hand, the models that are detailed and realistic in terms power system impact normally overlook detailed representation of inertia emulation, which prevents the analysis of the impact of different control/optimization synthetic inertia policies on power systems. On the other hand, systematic...
This paper proposes a method to modulate the power output of converter interfaced generators (CIGs) according to frequency variations. With the proposed approach, CIGs can successfully engage in the primary frequency regulation of a power system. The approach is a variation on the traditional droop-like proportional controller where the feedback signal is a global frequency measurement instead of...
System frequency response can be negatively impacted by significant penetration of wind generation. This paper studies the effects of integrating Type-4 full converter wind turbine generators (WTG) on the frequency response of a test system. A controller that enables frequency response in a Type-4 WTG is then proposed to restore and improve the frequency regulation of the system. The design and performance...
In this paper, the design of a data driven controller using a small-gain theorem approach for improving the positioning accuracy of a piezoelectric tube scanner (PTS) is demonstrated. Open-loop frequency responses of both the X-PTS and Y-PTS are measured using a band-limited sweep sine signal and are used as primary data for this control design. The frequency response of the controllers is synthesized...
Air conditioning loads have the potential to participate in frequency response when the power shortage accident occurs. In this paper, a decentralized frequency response control strategy is proposed to take advantage of the potential of air condition loads. Firstly, we analyze the existing decentralized control strategy, which adjusts the setting temperature of air conditioners according to the frequency...
In the last 7 years, the UK has seen an unexpectedly large increase in embedded power electronic connected generation connecting to both the transmission and distribution network. This is problematic to system inertia, since there is no inherent rotational mass within Power electronic connected generation to provide kinetic energy to the grid as required. National Grid must secure the system to protect...
This paper presents some results concerning the cancellation of a periodic disturbance acting on a time-invariant linear stable, possibly non-minimum phase, plant. In particular it shows that a fractional-order repetitive controller can be designed under the hypothesis that the frequency response of the plant, in the range starting from the fundamental frequency of the disturbance signal to infinity,...
Balancing the grid at 50 Hz requires managing many distributed generation sources against a varying load, which is becoming an increasingly challenging task due to the increased penetration of renewable energy sources such as wind and solar and loss of traditional generation which provide inertia to the system. In the UK, various frequency support services are available, which are developed to provide...
The current and massive deployment of non-synchronous generation is degrading the inertial response in power systems. The addition of an extra control loop, the so-called synthetic inertia, can contribute in the improvement of the frequency response, through an additional power injection. In this paper, the active damping method is used to enhance both, the closed-loop current control and the synthetic...
This paper proposes a methodology for assessment to measure the impact of the inertial frequency response provided by battery energy storage systems (BESS) considering power system uncertainties. The proposed methodology is used to assess the impact of the BESS equipped with sensible frequency controller on the frequency behaviour of the system after a system frequency disturbance considering the...
The main objective of this paper is to comparatively assess alternative control schemes for high voltage dc (HVDC) links based on voltage source converters (VSCs), adapted for island systems with mixed ac and dc interconnectors operating in parallel. A suitable study-case system is selected, which corresponds to the planning for the future interconnection of Crete island to the Greek mainland system,...
This paper presents some experiences concerning the testing of generating units response to frequency transient. The tests have been performed both for modeling and monitoring the compliance of the settings of the generating units with the operational requirements. A test methodology, based on mathematical modeling, is developed and proposed. The approach is intended to interfere (or disturb) less...
A control method of reducing transient-glitch voltage in variable frequency (VF) DC-DC converters is proposed in this paper. By modulating the period between two hopping frequencies to a calculated time length, the proposed control method keeps the average of the inductor current undisturbed and leads to less transient effects. Simulation results show the improvements on the transient-glitch voltage,...
Power networks have to withstand a variety of disturbances that affect system frequency, and the problem is compounded with the increasing integration of intermittent renewable generation. Following a large-signal generation or load disturbance, system frequency is arrested leveraging primary frequency control provided by governor action in synchronous generators. In this work, we propose a framework...
The advent of microgrids paved the way for energy decentralization and self-sufficiency among consumers. Reciprocating engine driven synchronous generators (also known as gensets) are one of the most commonly found distributed energy resources (DERs) installed in a microgrid. A key concern in microgrid operation is the frequency regulation, especially when it is islanded from the main grid. In recent...
A method for formulating system frequency response (SFR) model-derived frequency indexes into optimum framework of sizing energy storage systems (ESSs) that participate in frequency control in power systems is presented. A novel simplified SFR model, approximating frequency and governor responses with quadratic and linear functions respectively, is first developed, leading to a fast and accurate computation...
A rapid increase in wind power installed capacities in many countries can potentially have an effect on their power grid dynamics, in particularly, on the system frequency stability. This is due to the fact that some basic wind turbine generator technologies such as doubly fed induction generator (DFIG), which is most commonly and widely used at present time, do not originally contribute to frequency...
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