Renewable energy resources (RES) are being increasingly connected in distribution systems utilizing power electronic converters. This paper presents a novel control strategy for achieving maximum benefits from these grid-interfacing inverters when installed in 3-phase 4-wire distribution systems. The inverter is controlled to perform as a multi-function device by incorporating active power filter functionality. The inverter can thus be utilized as: 1) power converter to inject power generated from RES to the grid, and 2) shunt APF to compensate current unbalance, load current harmonics, load reactive power demand and load neutral current.
All of these functions may be accomplished either individually or simultaneously. With such a control, the combination of grid-interfacing inverter and the 3-phase 4-wire linear/non-linear unbalanced load at point of common coupling appears as balanced linear load to the grid. This new control concept is demonstrated with extensive MATLAB/Simulink simulation studies and validated through digital signal processor-based laboratory experimental results.Index Terms-Active power filter (APF), distributed generation (DG), distribution system, grid interconnection, power quality (PQ), renewable energy.
This paper presents a study of the performance of distance protection relays when applied to protect shunt Flexible AC Transmission System (FACTS) compensated transmission lines. The objective of this study is to evaluate the performance of distance relays on transmission lines with FACTS devices applied for mid point voltage control. Effect of two types of shunt FACTS devices, Static Var Compensators (SVC) and Static Synchronous Compensators (STATCOM) are studied. The study is conducted in three stages. First the situation is studied analytically, where the errors introduced in the impedance measurement due to the presence of shunt FACTS devices on the line are analyzed. In the second stage, the situation is simulated using transient simulation software, EMTDC. In this method, the response of FACTS devices for different fault conditions and system conditions is also modeled. This method brings out some unique problems that would be experienced by the distance relays due to some specific characteristics of the FACTS devices. Finally, the findings are confirmed by testing a commercial distance relay using a Real Time Digital Simulator (RTDS). The results obtained by testing the commercial relay validate the analytical and simulation studies.Index Terms-Distance protection relay, flexible ac transmission system (FACTS), power system protection, real-time digital simulator (RTDS), shunt compensation, static synchronous compensators (STATCOM), static var compensators (SVC).
The modelling of photovoltaic (PV) solar panels requires electrical parameters which are dependent on the manufacturing materials and their physical properties. Manufacturers typically do not disclose detailed physical properties of the PV module, except for some electrical quantities such as open circuit voltage (V oc), short-circuit current (I sc), maximum power point voltage (V m), maximum power point current (I m) and maximum power (P M). However, to model the PV panels comprehensively, it is necessary to determine other physical parameters, e.g., series resistance of PV cell (R s), shunt resistance of PV cell (R Sh) and diode ideality factor (n). This paper presents a generalised mathematical model of a PV panel utilising only the quantities provided in manufacturer's datasheet. The proposed modelling technique determines all the PV panel parameters without any explicit repetitive iteration. Although the developed model is general and can be implemented on any software platform, its implementation is demonstrated on a commercial electromagnetic transients simulation software electro magnetic transient including direct current power systems computer aided design. The electrical parameters obtained from the proposed PV panel model are validated for six different commercially available PV panels from their datasheet values and also from measurements provided by National Institute of Standards and Technology for solar irradiation and temperature at nonstandard test conditions.
This paper is concerned with the application of damping torque technique to examine the efficacy of various control signals for reactive power modulation of a midpoint located Static Var System (SVS) in enhancing the power transfer capability of long transmission lines. A new auxiliary signal designated Computed Internal Frequency (CIF) is proposed which synthesizes internal voltage frequency of the remote generator from electrical measurements at the SVS bus. It is demonstrated that this signal is far superior than other conventional auxiliary control signals in that it al.lows full utilization of the network transmission capacity. The damping torque results are correlated with those obtained from eigenvalue analysis.
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