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In an islanded microgrid, harmonic current is controlled (or shared) by modifying the effective impedance in the path of harmonic current. This effective impedance includes line impedance and the internal impedance of the generation unit. Reported works consider the aforementioned impedances as separate entities and their combined effect in harmonic current flow has not been discussed so far. This...
This paper presents a simplified modeling approach for power flow equations considering on-load tap-changers (OLTCs). The modeling approach consists of only four active and reactive nodal power injections and line power flows equations, and treats the elements of Ybus admittance matrix as constant parameters. The transformer tap ratios are only included in the simplified four equations as control...
This paper provides a comparative study of coordinated voltage control (CVC) strategies for on-load tap-changers (OLTCs) and voltage regulator (VRs) under active and passive network management schemes (ANM and PNM). In PNM scheme, OLTC and VR are restricted to only regulate the secondary bus voltages at fixed set-points, while in ANM scheme, control of the secondary bus voltages within the statutory...
This paper proposes an adaptive power management strategy for Distributed Generation (DG) inverters in a standalone microgrid. The existing droop control technique ensures load sharing among the DG inverters. However, the intermittency in power generation of renewable energy based DG pose many challenges to the standalone operation of a microgrid. Of which, the ineffective VA utilization is addressed...
This paper proposes a control strategy for harmonic power sharing in an islanded microgrid, without affecting the voltage quality at the load bus. The harmonic power distribution in islanded microgrid depends on the line impedance. The proposed control strategy employs negative virtual harmonic impedance to compensate the effect of line impedance on harmonic power delivery. The influence of mismatched...
The distribution network planning under active network management (ANM) schemes is becoming of interest due to substantial benefits in facilitating the increasing integration of renewable energy sources. This paper presents various potential ANM schemes based on the photovoltaic inverter control (PVIC) considering enhanced utilization of the inverter reactive power capability. Depending on the active...
Harmonic power sharing is important in islanded microgrid due to the presence of excessive nonlinear loads in distribution network. The lack of effective harmonic power sharing techniques may lead to overloading of certain distributed generation (DG) units. The concept of variable negative virtual harmonic impedance to share non-linear load in an islanded microgrid has been proposed recently. This...
Electric spring (ES) has been reported recently as an alternative device for achieving the grid voltage stability in distribution system using demand side management. ES comprises of six switches in total and injects the voltage in quadrature with the non-critical load current for regulating the PCC voltage to a predefined value. The voltage across the non-critical load decreases/increases as a result...
This paper presents a characteristic comparison among reduced semiconductor equivalents of dual back-to-back converter. Being widely reported, the nine-switch and ten-switch based converters are considered for the comparative analysis. Conduction losses of both these converters are compared to identify the merits and drawbacks as they are used in dc-ac, ac-dc, dc-dc or ac-ac energy conversion systems...
Primarily this paper investigates the key functions that should be carried out by a master distributed generator (DG) that adopts the master-slave control approach within a microgrid. Grid-connected operation, islanding detection, islanded operation, load shedding, phase locking and grid re-synchronization are key functions of the master DG that need to be executed in a logical and sequential manner...
This paper deals with the issues related to the interconnection between the microgrid and main network. The Dynamic Voltage Restorer (DVR) is proposed as an interface between the main network and microgrid in order to improve reliability and limit fault currents. The performance of DVR is demonstrated during fault conditions in two different locations, firstly in the main grid and then within the...
This paper proposes a novel control strategy for harmonic current filtering in an inverter-based-islanded microgrid, to minimize harmonic propagation in the distribution network. In most of the reported works, the nonlinear load is shared among the distributed generation units by altering either the effective line impedance or the inverter output impedance. In the proposed control scheme, the DG,...
Planning distribution systems without considering the operation status of multiple Distributed Generation (DG) units could result in constraining the network, lowering the utilization of its assets and minimizing the total DG capacity that can be accommodated. In this paper, the impact of multiple DG configurations on the potential of Active Network Management (ANM) schemes is firstly investigated...
A novel fault tolerant configuration of doubly fed induction generator (DFIG) for wind energy conversion systems (WECS) is proposed in this paper for the seamless operation during all kinds of grid faults. The proposed configuration is developed by replacing traditional six-switch grid side converter (GSC) of DFIG with a nine-switch converter. With the additional three switches, the nine-switch converter...
This work deals with single-stage three-phase grid-connected Photovoltaic (PV) systems with a focus on developing an efficient Maximum Power Point Tracking (MPPT) technique under partial shading conditions. As partially shaded PV arrays exhibit a multi-modal behavior on their Power-Voltage (P-V) characteristics with a number of possible patterns, the MPPT strategy under such conditions is a complex...
Adaptive linear neuron (ADALINE) is a powerful estimation technique that has been used in power system applications, such as fault detection and classification, and shunt active power filter (APF). In this paper, an ADALINE based approach for control of three-phase three-wire unified power quality conditioner (UPQC) is presented. Two ADALINEs are used in the UPQC control strategy, one for load current...
Droop control techniques of Inverter Based Distributed Generation (IBDG) are generally the most common approach for controlling micro-grids especially in the islanded mode of operation. An improved transient response as well as better load sharing can be achieved using higher droop gains. However, large droop gains drive the system into the unstable region. In this paper, a new control topology is...
This paper proposes an adaptive control for grid connected photovoltaic (PV) system that allows for the active power injection (API) and active power filtering (APF) functionality while allowing the maximum utilization of the PV inverter. This PV system operates in three modes: (i) API only, (ii) API and APF with the full utilization of PV inverter VA capacity, and (iii) API and APF with specific...
This paper presents a comprehensive design and implementation of a DFIG (Doubly Fed Induction Generator) for a micro-level WECS (Wind Energy Conversion System). The design is carried out for a 3.7 kW doubly fed induction machine with the reduced power conditioning circuit requirements. The control algorithm is implemented using a DSP (Digital Signal Processor). The GSC (Grid-Side Converter) is controlled...
The concept of “electric spring” is recently proposed to enhance the stability of smart grid with intermittent renewable energy sources. Electric springs can be integrated into the non-critical electrical loads to form smart loads. The smart load has the characteristics of (i) following intermittent power generation by changing its load demand dynamically and (ii) regulating the voltage at the point...
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