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Emerging smart grid concept compels microgrids to adopt decentralized methods. Centralized methods of operation are more susceptible to failure due to single point of failure held by the single controller. Decentralized microgrid control architecture is proposed, improving system reliability and avoiding control command transmission over the network. Delays in communications are unpredictable, uncertainty...
The asymmetry of the inherent distributed capacitances causes the rise of neutral-to-ground voltage in ungrounded system or high resistance grounded system. Overvoltage may occur in resonant grounded system if Petersen coil is resonant with the distributed capacitances. Thus, the restraint of neutral-to-ground voltage is critical for the safety of distribution networks. An active grounding system...
This paper presents a novel digital deadbeat + repetitive control (DBRC) strategy for output voltage regulation of pulsed power resonant converters used in high energy physics applications. The proposed converter contains three individual series resonant parallel loaded (SRPL) converter arms, which effectively mitigate the influence of resonant tank unbalances on the converter operation. The deadbeat...
Hydraulic wind power transfer systems deliver the captured energy by the blades to the generators through an intermediate medium i.e. hydraulic fluid. This paper develops a control system for an experimental setup of hydraulic wind power transfer systems. To maintain a fixed frequency electrical voltage by the system, the generator should remain at a constant rotational speed regardless of the wind...
In power electronics based power systems like wind farms, the interactions between the inner control systems of the power converters and the passive components may lead to high frequency oscillations, which can be called harmonic instability. In this paper, a simple methodology is presented to identify harmonic instability problems in wind farms, where many wind turbines, cables, transformers, capacitor...
Ancillary services offered by renewable energy sources frequently requires the capability of bidirectional power flow and power reserve, so an energy storage system (ESS) is a solution for this requirement. A large variety of ESS solutions are in the market, and frequently are mixed to optimize the global performance. This paper presents the integration of supercapacitors (SC) and electrochemical...
Multiple unit of PFC converters can be utilized for better power quality in the residential applications. It is important to set proper amount of reactive power contribution from each unit of PFC converter to reduce power loss and increase stability. To set the referenced amount of reactive power contribution for each PFC converter, a dynamic supervisory controller is necessary. In this paper, a wireless...
Droop-controlled inverters are widely employed as power sources in three-phase AC power electronics system, such as distributed generation, while the interaction between the source and the load may lead overall system to be unstable. Terminal-characteristics based stability criteria are very attractive for analyzing the stability of three-phase AC power electronics system. However, the systems, composed...
Output-inductor-less full-bridge converter for a High-Voltage Direct-Current power distribution system has been proposed. This proposed circuit topology suppresses the surge voltage due to the secondary-side diode's recovery, and miniaturizes the converter because the number of circuit components is reduced. On the other hand, some problems occur, such as the increasing switching-loss of primary switches...
In this paper, a controller capable of simultaneously providing both peak-load shaving and capacity firming required by renewable energy sources is proposed. This controller is designed to combine power/energy from multiple energy storage systems, including unidirectional systems such as fuel cells. Quick response energy storage systems such as ultracapacitors meet the requirements of initial fluctuations...
The benefits of modular multilevel converters come at a price: Their high level of complexity demands for an intricate design methodology and a sophisticated control structure. This is especially true for converters that need to be able to recover from short-circuits, grid faults, communication faults or module faults. In order to build a reliable system, it is thus important to understand the effect...
Advances in switching power electronic converter technology have brought about a resurgence of interest in the use of DC power distribution systems for a variety of applications. However, the notional power electronic based DC distribution system is a complex and extensively interconnected system consisting of multiple power converters. A number of system-level challenges related to stability arise...
The use of series connected capacitors for high voltage applications has been proven to be beneficial for voltage stress reduction across power semiconductors. In a 3-phase grid any asymmetry in the value of the series capacitance may lead to significant variations in the voltage seen across the low voltage converter. This paper investigates the effects of an unbalanced set of series connected capacitors...
The design of a smart EV charging system that provides maximum power delivery from renewable energy (PV) sources is described, through the application of control strategies which ensure that system power converters are operated in regions of high efficiency. Using the proposed approach, system level models predict power efficiency improvements of up to 6% for a 6.5 kW PV installation with four EV...
This work proposes the usage of a repetitive-based control to dynamically restore the voltage applied to sensitive and critical loads of power systems. Besides, sag and voltage swells, the proposed control can intrinsically mitigate harmonic distortions. Furthermore, the filter is able to work out on sinusoid references and, thus, avoids the need of employing the dq transform. A recursive least-squares...
This paper proposes a nonlinear control system based on a nonlinear observer to manage the active and reactive power within a single-phase-frequency-modulated Dual-Active-Bridge DC/DC converter directly. It is accomplished by employing a nonlinear controller to regulate the direct and quadrature current, id(t) and iq (t), as they are directly proportional to two power components, respectively. A nonlinear...
In this paper, the open-loop control for permanent magnet synchronous motor (PMSM) driven by a square-wave voltage is proposed. The proposed control is able to transit from the PWM region to the square-wave voltage region via the over modulation region seamlessly. When the PMSM is driven by the square-wave voltage using the proposed control, the low-frequency torque vibration except 6th or 12th order...
In this paper a novel unified modelling and control procedure for Back-to-Back converters is introduced. The proposed procedure captures in a single state-space model detailed converter dynamics of both LCL filters and DC-capacitor. A linear multivariable approach has been identified as the most suitable control strategy for taking full advantage of the unified model. A state-feedback controller has...
This paper presents an optimized energy management system (OEMS) to control the microgrid of a remote temporary military base featuring the diesel generators, the battery energy storage system (BESS) and photovoltaic panels (PV). The information of the expected electric demand is suitably used to improve the sizing and management of the BESS. The OEMS includes power electronics to charge the batteries...
In this paper, a new configuration of a multi-functional grid-connected inverter is proposed to improve both voltage-based and current-based power quality issue. By implementing bidirectional switches using semiconductor devices, a multi-functional grid-connected inverter can be connected in series or parallel to the grid and provides three modes of operation. This paper presents the control scheme...
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