Robust H∞ control for stability assessment in grid‐connected offshore wind and marine current hybrid system

Abstract

The geographic suitability brings the offshore wind farm (OWF) and marine current farm (MCF) together with their aggregated power fed to grid simultaneously in most relevant energy harnessing infrastructures. However, stability assessment of the integrated system is a major concern due to the integration of stochastic and intermittent sources with parametric uncertainty. Bridge-type fault current limiter (BFCL) has consolidated their application for a suitable enhancement of stability margin for most modern supply systems. In this article, a detailed modelling of the integrated system is carried out in the presence of BFCL along with consideration of uncertainty as well. A robust H∞ controller design strategy for stability assessment of grid-connected OWF and MCF in the presence of parametric uncertainties is presented in this article. Linear matrix inequality (LMI) conditions are derived in the context of evaluating the robust controller gain with respect to desired robust stability margin. The efficacy of the controller design is compared with that of H∞ loop shaping and conventional P-I control through different case studies with simulation followed by real-time digital simulator (RTDS) validation. Nomenclature ω bw , ω bmr angular velocity of the wind turbine and marine current turbine ρ w , ρ m density of wind and marine current, respectively λ dq0s , λ dq0r ′ flux linkage of stator and rotor, respectively J mct moment of inertia of the marine current turbine T m0 , T e0 mechanical and electrical output torque of generator C pw (λ w , β w) power coefficient of offshore wind turbine C p_mct (λ mr , β mr) power coefficient of marine current turbine R rw , R mct radius of wind and marine current turbine ω ref , ω r reference and rotor angular speed of DFIG i dq0s , i dq0r ′ stator and rotor current of SCIG in d-q frame of reference, respectively i s , i r stator and rotor current of DFIG r s , r r stator and rotor resistance of DFIG v s , v r stator and rotor voltage of DFIG ψ s , ψ r stator and rotor linkage flux of DFIG V dq0s terminal voltage of SCIG in d-q frame of reference V w , V m velocity of wind and marine current

Impact of resources distribution on high‐frequency behaviour of photovoltaic systems

“…Up to now, the effect of different factors including filter and controller parameters, controller types, and also increasing the number of resources on their interaction dynamics with the grid have been discussed and elaborated in the literature [14][15][16][17][18][19]. While, in this study, for the first time, it has been shown that, besides the mentioned factors, different arrangements of CCIs can also play a key role in determining the system stability.…”

“…Regarding the constant total power of 25 kW, the centralised CCI is segmented into four distributed arrangements in which the n values are 2, 5, 25, and 100. Consequently, according to (15), the power of each CCI in distributed arrangements are 12.5, 5, 1, and 0.25 kW, respectively. The distributed arrangement states are described in Table 1.…”

“…So far, the interaction of CCIs with the power grid has been the topic of plenty of studies [11][12][13][14][15][16]. In these studies, the interaction in an individual grid-connected CCI and also in grid-connected paralleled CCIs have been thoroughly addressed.…”

“…To improve the stability of the alluded microgrid, a virtual-harmonic-resistance-based active damping method incorporated into the conventional deadbeat control scheme is introduced. In [15], a type of H-infinity controller is utilised to guarantee the stability and robustness of a hybrid integrated system including CCIs. Moreover, it is found in [16] that by modelling the output admittance of the peak-current controlled flyback microinverters, harmonic interactions with a distorted grid can be effectively forecasted; hence, the harmonic quasi-resonance problem has been tackled.…”

A Review of Technology Development and Numerical Model Equation for Ocean Current Energy

“…Numerical equations used to complete research consist of various mathematical and physical approaches. From paper [26] describe mechanical power P m_mct captured by turbine is written as follows:…”