Direct Power Control of Series Converter of Unified Power-Flow Controller With Three-Level Neutral Point Clamped Converter

Abstract-

A unified power-flow controller (UPFC) can enforce unnatural power flows in a transmission grid, to maximize the power flow while maintaining stability. Theoretically, active and reactive power flow can be controlled without overshoot or cross coupling. This paper develops direct power control, based on instantaneous power theory, to apply the full potential of the power converter. Simulation and experimental results of a full three-phase model with nonideal transformers, series multilevel converter, and load confirm minimal control delay, no overshoot nor cross coupling. A comparison with other controllers demonstrates better response under balanced and unbalanced conditions. Direct power control is a valuable control technique for a UPFC, and the presented controller can be used with any topology of voltage-source converters. In this paper, the direct power control is demonstrated in detail for a third-level neutral point clamped converter.

Integration of Distributed Generating Units into Distribution Networks

Abstract- 

This paper discusses the technical aspects of distributed generation (DG) unit’s integration into distribution systems. The paper objectives are: selection of the site and size of DG unit/s to be investigated to the system and to check the system performance as follows: reduce the power losses, increase the stability limit as well as improve the protection devices settings. A matlab simulink model of the system is done at different operating conditions to check the feasibility of DG units'
implementation into distribution systems. Simulation results based on one real power distributor system of Egyptian network of voltage level 11 kV are efficiently presented.

Predictive current control implementation in the sensorless induction motor drive

Abstract-

A speed sensorless control system for an induction motor with predictive current controller is presented. The whole control does not require measurements of the motor speed and motor flux. A closed loop observer system with robustness against parameters variation is used for the control approach. The proposed observer computes the required state variables correctly in wide frequency range. In the system predictive current controller based on the computation of back electromagnetic force by the observer is implemented. In case of motor choke use, the choke parameters are added to predictive current controller algorithm. It is shown that the choke inductance has to be taken into account in predictive controller. The whole proposed control idea makes the system practically insensitive to the changes of motor parameters, even at very low frequency. It is proved that the drive system is applicable to the high dynamic performance and wide range of rotor speed. The description of test bench is included. The obtained simulation and experimental results confirm the good properties of the proposed speed sensorless induction motor drive.

A single sensor based PFC Zeta converter Fed BLDC motor drive for fan applications

Abstract-

A novel PFC (Power Factor Corrected) Converter using Zeta DC-DC converter feeding a BLDC (Brush Less DC) motor drive using a single voltage sensor is proposed for fan applications. A single phase supply followed by an uncontrolled bridge rectifier and a Zeta DC-DC converter is used to control the voltage of a DC link capacitor which is lying between the Zeta converter and a VSI (Voltage Source Inverter). Voltage of a DC link capacitor of Zeta converter is controlled to achieve the speed control of BLDC motor. The Zeta converter is working as a front end converter operating in DICM (Discontinuous Inductor Current Mode) and thus using a voltage follower approach. The DC link capacitor of the Zeta converter is followed by a VSI which is feeding a BLDC motor. A sensorless control of BLDC motor is used to eliminate the requirement of Hall Effect position sensors. A MATLAB/Simulink environment is used to simulate the developed model to achieve a wide range of speed control with high PF (power Factor) and improved PQ (Power Quality) at the supply.

Power-Management Strategies for a Grid-Connected PV-FC Hybrid System

Abstract—

This paper presents a method to operate a grid connected hybrid system. The hybrid system composed of a Photovoltaic (PV) array and a Proton exchange membrane fuel cell (PEMFC) is considered. The PV array normally uses a maximum power point tracking (MPPT) technique to continuously deliver the highest power to the load when variations in irradiation and temperature occur, which make it become an uncontrollable source. In coordination with PEMFC, the hybrid system output power becomes controllable. Two operation modes, the unit-power control (UPC) mode and the feeder-flow control (FFC) mode, can be applied to the hybrid system. The coordination of two control modes, the coordination of the PV array and the PEMFC in the hybrid system, and the determination of reference parameters are presented. The proposed operating strategy with a flexible operation mode change always operates the PV array at maximum output power and the PEMFC in its high efficiency performance band, thus improving the performance of system operation, enhancing system stability, and decreasing the number of operating mode changes.

A combined protection and control strategy to enhance the LVRT capability of a wind turbine driven by DFIG

Abstract—

 In order to enhance the low voltage ride-through (LVRT) capability of a wind turbine driven doubly
fed induction generator (DFIG)， this paper proposes a combined protection and control strategy including the Active Crowbar and Battery Energy Storage System. The conventional crowbar is activated to protect the rotor side converter during the fault interval, premature removal the crowbar will not achieve good purpose of protection for the converter, too late removal will make the motor absorption the reactive power too much from the grid. This problem can be improved by using a control scheme which is auto-switching the crowbar according to the size of rotor current .Furthermore, under fault condition the voltage will ripple in the DC link side, a battery energy storage system (BESS) connected to the DC bus is proposed which is controlled to attenuate the DC voltage ripple via absorbing the redundant power stored in the DC link capacitor. Simulation results show the effectiveness of this combined protection and control strategy.

Application of UPFC Based on Improved Double-loop Decoupling PI Control in Photovoltaic Systems

Abstract—

The mutation of solar irradiance can cause the output power of photovoltaic power plant to mutate, and it takes great changes to active power and reactive power which feed into the power grid. When the system security constraint is exceeded, the photovoltaic power plant will stop running. In this paper, the structure and the mathematical model of large grid-connected photovoltaic power plant are introduced; then an improved double loop PI decoupling control system is proposed based on the d-q model of UPFC parallel converter. On the basis of traditional PI control, DC load current is directly used as feed-forward control in the control system of capacitor voltage. It is not only easy to get feedback, but also conducive to design and operate the series controller and the parallel controller independently. Finally, this paper sets up a Simulink model of UPFC in the environment of Matlab/Simulink after analyzing its principle. And then, this model was applied into a three-phase system to observe its influences to power quality. The simulation results show that this control system based on the UPFC can effectively control the voltage and the power flow, maintain bus voltage and reduce reactive exchange. It can also improve the active photovoltaic power transmission, as well as maintaining the stability of the system.