Md. Imran Azim

Droop Control for islanded microgrids with compensating approach

This paper proposes a droop control algorithm to distribute load changes automatically between two inverter-sourced generators in an islanded microgrid. A compensating approach is added to the conventional droop control scheme in order to add a power offset to the active power so that the output powers of the inverters remain balanced if the output of renewable energy varies. The droop control parameters are chosen based on eigenvalue analysis obtained from linear modal analysis. In this paper, it is shown that the proposed control method ensures effective power sharing and provides good performance under diverse operating conditions without the need for communication.

Design of a general droop controller for islanded microgrids

This paper proposes an automatic load distributing algorithm called a general droop control for an inverter-interfaced islanded microgrid under different loading conditions and transmission line parameters. In this control scheme, both resistive and inductive nature of the transmission lines are considered. A linear model-based power sharing approach with the general droop controller is also described in this paper. The performance of the proposed controller is tested by simulating a simple two-source and one load-based microgrid test system and the simulation results show that the proposed method is useful to manage the load variation of an islanded microgrid accurately and efficiently.

Primary voltage control of a single-phase inverter using linear quadratic regulator with integrator

This paper proposes a linear quadratic regulator with integral action, ensuring fast dynamic response and resisting capability of voltage deviation from instantaneous reference grid voltage, to control the inverter voltage that can also be used in a microgrid. The proposed control strategy is based on a linear quadratic regulator, minimizing the cost function of the system, with integral action used to impede voltage degradation from a reference voltage for outside disturbances of the system, such as abrupt load change. The combined integral term assists to recover the voltage difference between grid and reference grid voltage. The validity of the proposed controller has been tested with linear and non-linear loads under various conditions. In both cases, the effectiveness of the controller has been proved. The result of the proposed controller is good to track the instantaneous reference grid voltage.

Proportional reactive power sharing for islanded microgrids

In this paper, droop-based automatic control schemes are presented to control parallel inverter-interfaced distributed generators (DG) in a way that proportional reactive power sharing is possible in islanded microgrids under different structures. This paper modifies the conventional reactive power-voltage (Q-V) droop control strategy used in inductive (L-type) islanded microgrids by implementing voltage control law in overall control operation such that reactive power becomes inversely proportional to the reactive droop gain if the initial values of inverter-interfaced voltage-sources are the same. Reactive power sharing approach for resistive (R-type) islanded microgrids is also included in this paper; in which it is shared depending on rate-of-angle of voltage-sources, i.e., reactive power-frequency (Q-f) droop. The proposed control methods utilize linear modal analysis to design both types of droop-based controllers. A 5-bus microgrid with 4-parallel inverter-connected DG units is considered for simulations under load changing phenomenon where results show the excellency of the designed control schemes.

Utilization of single phase inverters in Photovoltaic system

This paper presents a Photovoltaic (PV) system, in which solar energy is taken into consideration as a renewable energy source. Furthermore, the variation in the output responses of PV system because of the effect of various factors, including solar irradiation, temperature, ideality factor and saturation current are shown here in great details. However, it has been noticed that these factors cause reduction in the systems performance. Therefore, in order to improve PV systems efficiency, it is recommended to use a solar panel which follows an ideal solar panel. Finally, with a view to supplying this derived solar energy to the consumers end, the implementation of inverter is required. For this reason, this paper deals with both half bridge and full bridge single phase inverters with an LC low pass filter appended at their output terminals. It has been found that full bridge inverter gives two times more output than half bridge inverter and this has certainly the advantage of using less valued step up transformer.

Voltage stability management with the help of optimization techniques

This paper deals with the injection of reactive power, which is vitally important in case of too much load variations, by means of Static VAr Compensator (SVC) so that both, the voltage profile and voltage stability of the power system can be improved. The reactive power management is formulated as an optimization problem that can be solved by the evolutionary advanced optimization algorithms. Two well known algorithms, namely linear algorithm and genetic algorithm are applied in this case and it has been found that the genetic algorithm gives more efficient outputs compared to the linear algorithm as it is based on the biological metaphor, in which best individuals are selected among parents and offspring generation. As far as this paper is concerned, 0.2 MVAR reactive power would be enough for voltage compensation and maintaining stability throughout the system.