Simulation of Distance Relay Operation on Fault Condition in MATLAB Software/Simulink

In this paper a distance relay is simulated in theproposed transmission line protection which is combinationof overhead line and significant part of underground cable.Transmission line is modeled as distributed parameter insteadof lumped parameter to have more accurate analysis compareto conventional analysis. Voltage and current are sampled atrelay point. But, high charging current of cable affects distancerelay operation. Using appropriate filtering can reduce chargingcurrent effect on distance relay. Simulated impedance will becompared with positive sequence impedance of power system inorder to evaluate simulated relay. The relay shows a good resultfor faults in zone 1, but high resistance faults force distance relayto mis-operation

An improved synchronous reference frame current control strategy for a photovoltaic grid-connected inverter under unbalanced and nonlinear load conditions - Fig 6

<p>System DG unit currents and NLL current waveforms with THD without any compensation: (a) system currents; (b) PV currents; (c) MT currents; (d) FC currents; (e) NLL 1 currents; (f) NLL 2 currents.</p

Current and THD results.

<p>Current and THD results.</p

Power Line Parameters.

<p>Power Line Parameters.</p

PLL structure of the three phase.

<p>PLL structure of the three phase.</p

Load/DG Parameters.

<p>Load/DG Parameters.</p

Block diagram of the power electronic interface configuration.

<p>Block diagram of the power electronic interface configuration.</p

Block diagram of the control system for the APF.

<p>Block diagram of the control system for the APF.</p

Block diagram of the control active and reactive powers.

<p>Block diagram of the control active and reactive powers.</p

An improved synchronous reference frame current control strategy for a photovoltaic grid-connected inverter under unbalanced and nonlinear load conditions

<div><p>In recent years, renewable energy sources have been considered the most encouraging resources for grid and off-grid power generation. This paper presents an improved current control strategy for a three-phase photovoltaic grid-connected inverter (GCI) under unbalanced and nonlinear load conditions. It is challenging to suppress the harmonic content in the output current below a pre-set value in the GCI. It is also difficult to compensate for unbalanced loads even when the grid is under disruption due to total harmonic distortion (THD) and unbalanced loads. The primary advantage and objective of this method is to effectively compensate for the harmonic current content of the grid current and microgrid without the use of any compensation devices, such as active and passive filters. This method leads to a very low THD in both the GCI currents and the current exchanged with the grid. The control approach is designed to control the active and reactive power and harmonic current compensation, and it also corrects the system unbalance. The proposed control method features the synchronous reference frame (SRF) method. Simulation results are presented to demonstrate the effective performance of the proposed method.</p></div