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The impact of Dstatcom size and location on the voltage regulation of a distribution system is investigated in this research work. Possibility of coordination between Dstatcom units at different locations in the system is investigated. Dstatcom model available in Matlab Simulink is adopted for the study. The dynamic behavior of the Dstatcom due to switching on a large industrial load, line outage...
In highly microgrid (MG) integrated distribution systems, problems such as a sudden cut out of the MGs due to grid faults may lead to adverse effects to the grid. As a consequence, ancillary services provided by MGs are preferred since it can make the MG a contributor to ride through the faults. In this paper, a voltage support strategy based on negative sequence droop control, which regulate the...
This work proposes the usage of a repetitive-based control to dynamically restore the voltage applied to grid sensitive loads. The control is able to wipe off harmonic distortion and relies on simple transfer function. As a consequence, there is no need to apply harmonic selective filters. Moreover, the filter is able to work on sinusoid references and avoids employment of the dq transform. The design...
This paper describes the situation of a modern electric drive (induction machine supplied from indirect frequency converter with voltage source inverter) in industry (paper mills, etc.), where a voltage sag can bring significant problems with long-time interruption of the production process. One method of operation is a direct increase of voltage in the DC-link of a frequency converter with a step-up...
This paper investigates the low-voltage ride-through (LVRT) characteristics of microgrid with DSTATCOMs and microgrid capability to support the utility grid during external faults. Two approaches are taken in order to investigate the LVRT behaviour of a grid connected microgrid as a single entity. A distribution static synchronous compensator (DSTATCOM) is installed at different locations of the microgrid,...
The interconnection of Type-4 wind farms into weak distribution feeders may result in voltage rise and flicker concerns. This paper investigates a wind farm control scheme employing a slow-acting reactive power controller to regulate the steady-state voltage at the point of common coupling (PCC) and a fast-acting active power controller, streaming from an embedded energy storage system (ESS) to mitigate...
In this paper, application of a cascaded H-bridge (CHB) converter to connect strings of solar panels to a single-phase medium voltage AC grid is discussed. With solar insolation levels differing from one string to another, it is challenging to control a CHB converter in order to minimize the variations in the dc link voltages of each of the converter modules and hence the device voltage stress levels...
Alternate arm converter (AAC) is a recently proposed promising modular multilevel converter. This paper presents a module-capacitor voltage fluctuation suppression strategy based on optimized zero-sequence voltage injection for the AAC. A mathematical analysis for the module-capacitor voltage fluctuation is presented first. Meanwhile, a set of control procedures is designed to synthesize the control...
This paper investigates the impact of grid disturbances on the electric vehicle (EV) batteries in the grid-to-vehicle (G2V)/vehicle-to-grid (V2G) mode and the vehicle-to-home (V2H) mode. An 8 kW bi-directional EV charger system is designed and simulated. Based on the developed EV charger system, the different practical cases of voltage sag, voltage unbalance and local load variation are tested and...
Sags are the foremost power quality problem encountered by industrial consumers since they frequently causes the interruption of manufacturing processes that can result in significant economic loss. To resolve such problems, a voltage sag compensator is often installed by industrial consumers within critical industrial applications. However, the operation of the compensator takes a few milliseconds...
Three-phase voltage-source converters (VSC) are commonly used as a power flow interface in AC/DC hybrid power systems. The system may suffer from unpredictable transient disturbance from DC-side or grid-side faults. The nonlinear characteristics of VSCs have already been identified as exhibiting catastrophic bifurcation when there is a DC-side disturbance. In this paper, the transient response of...
Custom power park is an industrial/commercial park that integrates state-of-the-art power quality devices. The power quality devices can be classified into two catalogues: voltage quality enhancement devices and current quality enhancement devices. In order to meet the requirement of large capacity, high reliability, high flexibility in both the voltage and current compensation, several operation...
The future custom power park will realize the hierarchical power supply of different voltage quality grade, meanwhile and present the grid-friendly characteristics including low pollution for grid, organic combination with distributed generation (DG) and energy storage (ES). In order to gradually achieve the goals, the function reuse and integration in the equipment level should be solved firstly...
In general, residential solar inverters can operate in either island or grid-tied mode. In grid-tied mode, the inverter can be operated based on either voltage control or current control. In this paper, a grid-connected current controlled inverter is presented. A stationary frame nonideal proportional resonant (PR) controller, in lieu of a conventional PI based controller, is applied to the outer...
Modern wind turbines operate with variable speed and most of them are based on doubly fed induction generators (DFIG), with a back-to-back power converter. During voltage dips, the stator terminals can cause overcurrents in the rotor windings, which could threaten the converter integrity. The use of crowbar systems is the most common technique to avoid this situation. The crowbar activation disables...
Starting of large induction motors may produce voltage dip in a weak microgrid because of high current and reactive power demand in transient period. This paper develops a solution for black start issue of an Induction Motor (IM) using Voltage-Sourced Converter (VSC) interfaced source in an autonomous microgrid. This paper provides procedures and techniques for controlling the VSC. First, a dynamic...
The deployment of modern DFIG or full converter turbine technologies on a large scale into distribution networks is raising issues for electric utilities with regard to voltage rise and flicker amongst other power quality issues. This paper proposes an real-time reactive power coordination scheme employed with the voltage control technique, the concurrent means for achieving both voltage regulation...
Solar photovoltaic systems continue to expand across the United States due to cost competitiveness, Federal and state incentives, and Renewable Portfolio Standards (RPSs). Transmission Planners and Operators must ensure high levels of grid reliability as increasing penetration levels further affect system variability and generation intermittency. A Time Step Simulation (TSS) is developed to study...
Increased penetration levels of Distributed Generation (DG) can cause steady state and transient voltage issues and possible overloading conditions. This paper aims to verify the overvoltage and overloading issues caused by DG at high penetration levels. A typical utility distribution feeder was selected using cluster analysis for simulations. DG at various penetration levels was interconnected at...
Dc microgrids including grid-tied inverter, energy storage system, and distributed generations have the advantage of high efficiency as compared to the ac system. Droop control has been realized to suppress the current mismatching among distributed sources. However, the conventional droop control involves distribution loss due to the line impedance. In this paper, a novel droop control is proposed...
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