Mohammad Moradi Ghahderijani

Frequency-Modulation Control of a DC/DC Current-Source Parallel-Resonant Converter

This paper proposes a frequency-modulation control scheme for a dc/dc current-source parallel-resonant converter with two possible configurations. The basic configuration comprises an external voltage loop, an internal current loop, and a frequency modulator: the voltage loop is responsible for regulating the output voltage, the current loop makes the system controllable and limits the input current, and the modulator provides robustness against variations in resonant component values. The enhanced configuration introduces the output inductor current as a feed-forward term and clearly improves the transient response to fast load changes. The theoretical design of these control schemes is performed systematically by first deriving their small-signal models and second using Bode diagram analysis. The actual performance of the proposed control schemes is experimentally validated by testing on a laboratory prototype.

Transient analysis of PV-based industrial microgrids between grid-connected and islanded modes

This paper presents a networked control scheme for a photovoltaic-based industrial microgrid to adaptably operate in both grid-connected and islanded modes, and even to transfer smoothly between these two modes. The control scheme is mainly based on the droop method for active and reactive power sharing by means of voltage and frequency regulation. In addition, to get a smooth transfer between islanded and grid-connected modes, a phase-locked loop is also used in the control system. This loop is only activated during islanded mode to eliminate the phase deviation between the voltages in both sides of the point of common coupling switch. The output of this loop is send to all power units following a one-to-all communication scheme with low bandwidth. Finally, selected simulation results are reported in order to prove the effectiveness of the control scheme.

Design and control of a small-scale industrial microgrid in islanding mode

Microgrid increases the reliability and quality of supply of industrial and commercial buildings. The operation in islanding mode is a challenging issue due to the limited energy available and the lack of a main grid for synchronizing purposes. This paper presents both the design of a small-scale industrial microgrid and a hierarchical control strategy for islanding mode operation. The control scheme consists of primary and secondary layers to provide good power sharing among generators and elimination of voltage and frequency deviations in steady state, respectively. In addition, the control strategy mitigates undesired circulating currents and reduces power losses. Selected simulation results are included to verify the system performance.

Multi-objective optimized daily schedule for an efficient solar-based industrial microgrid

In this paper, an optimal daily management for a solar-based industrial microgrid is proposed by analyzing two different load profiles. For each profile, the first step is to find the optimum size of the battery bank in order to identify the best daily configuration. The second step is to solve a multi-objective optimization problem, which takes into account economic evaluation indices (such as the initial investment, replacement, maintenance cost and the cost related to selling or purchasing energy to or from the grid) as well as the loss of power-supply probability index for evaluating system reliability. To solve the multi-objective optimization problem, first the weighted-sum method is used to convert it into a single objective optimization problem. Second, the new formulation is solved using an enhanced version of the bacterial foraging algorithm.

Voltage sag mitigation in a PV-based industrial microgrid during grid faults

The growing interests in industrial microgrid and its high power rating, have made it as a good candidate for voltage support purposes. The aim of this paper is to present a reactive current injection control strategy for a photovoltaic-based industrial microgrid during voltage sags. During the sag, depending on the grid code requirements, the maximum rated reactive current should be injected by the local inverters. The current can be injected through the positive and negative sequences depending on the sag characteristics and power rating of the local inverters. Moreover, to prevent over voltage, the higher phase voltage should be raised to a predefined maximum boundary. Finally, some selected simulation results are presented in order to show the features of the control scheme.