Search

This manuscript presents a novel control architecture for the E-STATCOM (STATCOM integrated with Energy Storage System (ESS)) that is common for both the Stand-Alone (SA) as well as the Grid-Connected (GC) modes of operation of a microgrid operating under unbalanced conditions. The proposed control architecture fulfils the aim of regulating the E-STATCOM in such a manner so as to smoothen the power fluctuations of a nearby renewable energy source (solar, wind, etc) and also to maintain the voltage and frequency at the Point of Common Coupling (PCC) within the normal range of operation. Hence, the resultant real power injected by the renewable energy source along with the E-STATCOM is constant in magnitude, irrespective of whether the microgrid is in the GC or the SA mode of operation. Dynamically varying limits are introduced to provide inherent VSC over-current protection. In order to illustrate the performance of these control architectures, a model of the IEEE 34 node power distribution network that is being supplied by a solar Photo-Voltaic (PV) Distributed Generation (DG) unit, a wind DG unit and two identical E-STATCOMs (for compensating the power fluctuations from the PV and wind DG units) has been considered for study in PSCAD/EMTDC. [ABSTRACT FROM AUTHOR]

This manuscript develops a unified control structure for Distributed Generation (DG) units based on Voltage Source Converters considering unbalanced and non-linear operating conditions. This control structure works for both the Islanded and the Grid-connected modes of operation of the Micro-Grid (MG). The objective of this control scheme is to regulate the line currents of the DG unit in such a manner that the voltage at the Point of Common Coupling (PCC) remains balanced despite the line currents of the DG unit being unbalanced and distorted. Multiple adaptive P-R controllers have been proposed for the current control loop of the Voltage Source Converter (VSC). These controllers have been implemented with resettable integrators so as to limit the DC components in the post fault current of the VSC. The Battery Energy Storage System (BESS) is interfaced to the DC link of the VSC through bi-directional dc-dc converters. An improved control structure for the bi-directional dc-dc converter has been developed. The effectiveness of these control structures have been presented and tested in PSCAD/EMTDC in an IEEE 34 node distribution system model being fed by two identical DG units. [ABSTRACT FROM AUTHOR]

Network operators and utilities are challenged with increasing extreme weather conditions, resulting in interrupted power supply to critical loads. Resiliency metrics, which can capture the level of preparedness to resist adverse impact of extreme conditions on a distribution system, can be leveraged in multiple ways to provide better operation of the network and design of the future systems. In this paper, a methodology to quantify resiliency and maintain power supply to critical loads (CLs) during extreme contingencies has been proposed. Resiliency evaluation of power distribution system has been defined as a multi-criteria decision making problem and quantified using graph theoretic approach and Choquet integral. The algorithm proposed in this paper to calculate the resiliency for all feasible network configurations supplying CLs in a network is useful in planning as well as operation of the distribution network. The application of the proposed algorithm is demonstrated through several case studies using two proximal CERTS microgrids and IEEE 123 node distribution system. Simulation studies are also provided for planning of resilient network, by placing additional switches in the considered distribution systems with microgrid. [ABSTRACT FROM AUTHOR]

This paper presents the positive-sequence, negative-sequence, and zero-sequence voltage and current control schemes in the dq frame for the voltage-source converter (VSC)-based distributed generation (DG) units in order to compensate for voltage unbalance in a microgrid. The objective of these schemes is to control the positive-, negative-, and zero-sequence components (separately and independently) of the voltage at the point of common coupling and the VSC currents to their respective reference commands. Dynamically varying limits have been proposed for the positive- and negative-sequence references for the current control schemes in order to protect the VSC from overloading (under unbalanced conditions) and unsymmetrical faults. The active power control, frequency control, and the reactive power–voltage droop control schemes decide the references of the positive-sequence voltage control scheme in order to fulfill the objective of using the same control schemes for the grid-connected and the islanded modes of operation of the microgrid, thereby eliminating the need for islanding detection. The performance of the various control schemes employed for controlling the VSC-based DG unit has been tested on two identical VSC-based DG units feeding power to the IEEE 34 node distribution network implemented in PSCAD/EMTDC. [ABSTRACT FROM PUBLISHER]

Multiple microgrids (MMGs) may be interconnected through voltage source converters (VSC) for controlled power sharing among themselves. VSCs in large interconnected micro- grids may use non-communication based droop control to share total power demand in the ratio of their droop coefficients. However, a constant droop ratio restricts the power delivery capability of the VSCs although surplus power may be available in their respective sources. In this paper, along with a unified power management strategy for intra and inter microgrid power sharing in a hybrid AC-DC MMG system, a novel adaptive droop control algorithm is presented that dynamically changes droop coefficients of the VSCs to ensure maximum utilization of available resources in each microgrid under different operating modes. Stability analysis of the proposed control method is performed and comparison of the system performance with fixed and adaptive droop ratio is illustrated by simulating the MMG in MATLAB SIMULINK using real solar irradiance field data. It is validated from simulation results that the adaptive droop control method increases utilization of renewable energy sources within microgrids and reduces energy import from utility grid. [ABSTRACT FROM AUTHOR]