Abdelaziz Talha

Linear Feedback Control of Multi DC Bus Link Voltages of Multilevel NPC VSI Cascade

Voltage source multilevel inverters have become very attractive for power industries in power electronics applications during last years. The main purposes that have led to the development of the studies about multilevel inverters are the generation of output voltage signals with low harmonic distortion; the reduction of switching frequency. A serious constraint in a multilevel inverter is the capacitor voltage-balancing problem. The stability problem of the input DC voltages in a three-level neutral point clamping (NPC) voltage source inverter (VSI) is recalled and illustrated in this paper. Power structure is proposed. It consists in using one CV rectifiers but the instability of intermediary DC voltages is observed. To solve this problem the power structure is modified by adding clamping bridges across capacitors in order to limit their deviations. The obtained results are full of promise to be used to stabilise the input DC voltages of this converter.

Modeling and Control of a Power Electronic Cascade for the Multi DC Bus Supply of a Seven-Level NPC Voltage Source Inverter

The stability problem of the input DC voltages in a seven-level Neutral Point Clamping (NPC) Voltage Source Inverter (VSI) is recalled and illustrated. A first solution involving six controlled-voltage (CV) rectifiers is presented. A knowledge model of this converter using switching functions and a PWM strategy is detailed. For an economic point of view, a second power structure is proposed. It consists in using only 3 CV rectifiers but the instability of intermediary DC voltages is observed. To solve this problem the power structure is modified by adding clamping bridges across capacitors in order to limit their deviations. Additional control functions are then introduced. The obtained results are full of promise to be used to stabilise the input DC voltages of these converters.

Novel algebraic PWM strategy of a multilevel Voltage Source Inverter

In this paper, the authorpsilas present one algorithm of algebraic PWM strategy for seven-level neutral point clamping (NPC) voltage source inverter (VSI) is presented. This algorithm uses a control model of the inverter developed previously by the authors. In the first part, we develop a working model of this inverter, without presumption on its control, by using the connection functions of this converter. In the second part the control models of this converter by using respectively instantaneous and generating connection functions are reviewed. In the last part, one algebraic PWM control strategy of the inverter is proposed. The obtained results are full of promise to use this digital strategy to control seven-level NPC VSI used in high voltage, high power applications as electrical traction.

Control and energy management of grid-connected pv system with battery-supercapacitor hybrid energy storage

An optimized energy management technique to reduce the cost and increase the effectiveness of a photovoltaic (PV) system is proposed in this paper. It is based on the optimum sizing of the energy storage system, to meet the needs of the system in normal conditions, while in the critical cases, the AC residential load will be supplied by the grid itself. In addition, the surplus of the PV power will be injected to the grid. However, to extend the battery life and reduce its size, a supercapacitor has been combined with the batteries, to quickly respond to the short-time peak current demand, while the battery will deliver a smooth current. Furthermore, the proposed algorithm will supervise the battery state of charge (SOC) and satisfy the highest priority load demand under different situation. A simulation work is carried out to evaluate the control of the whole PV system and determine the performance of proposed algorithm. Finally, the obtained results show the effectiveness of the proposed management algorithm, including the control techniques of different components of the whole system.

An efficient asymmetric cascaded H-bridge inverter for photovoltaic systems

This paper presents a single-phase seven levels cascaded and asymmetric-bridge inverter for grid-connected photovoltaic system with non-linear power load. The asymmetric cascaded H-bridge inverter appears to be the perfect candidate for photovoltaic applications; thanks to its modularity, scalability and distributed maximum power point tracking possibility. However the power mismatch from cascaded individual photovoltaic inverters can bring dc-link voltage drift, involving loss of the maximum power point tracking and reducing the effectiveness of the system. This paper, address this issue. The operations and performances of the suggested control strategy are verified by simulation, using Matlab/Simulink software. The tests results confirm the feasibility and reliability of the developed control scheme.

Grid-connected hybrid renewable energy system using DFIG and multilevel inverter

The objective of this work is to study the performances of hybrid system comprising wind and photovoltaic sources with battery storage. The grid integration of the PV system is carried out via a three phase three level neutral point clamped (NPC) inverter. The interface of connection to the electrical supply network consisted of a continuous bus, filters RL, the regulation of the powers and the management of the system will be described. This interface will make it possible to function in network connected with an automatic commutation The control strategies of the sources are based on power, voltage and current control with Maximum Power Point Tracking (MPPT). This control will enable us to inject the power activates desired and to regulate the voltage at the point of connection with grid, and to impose the voltage and the frequency in separate network. The proposed energy management strategy has been simulated. Numerical results are presented and discussed, showing the effectiveness of the proposed hybrid system.

Advanced control for wind energy conversion systems with flywheel storage dedicated to improving the quality of energy

In this article, we present two techniques of commands DTC (direct torque control) and DPC (direct power control), applied to in the system for converting wind energy with storage. The use of the wind generator is based on a double fed induction Generator (DFIG) where the stator is connected directly to the network and the rotor is connected to the network through the power converter. The Flywheel Energy Storage System (FESS) based on a flywheel, an induction machine (IM) and an electronic power converter is associated with the wind generator via the DC bus. The two converters side DFIG and the (FESS) are controlled by the DTC. The three-level converter side electricity grid which ensures constant DC bus voltage is controlled by the DPC. In the literature, this control strategy has been frequently used for the two levels converter. The direct control of these systems has purpose to eliminate the block of pulse width modulation and loops of regulations internal controlled variables. The use of switching table makes the system more efficient from the technical and economic view.

Fuzzy logic control for a speed of a flywheel energy storage system associated the wind generator

The type of distributed generation unit that is the subject of this article relates to renewable energy sources, especially wind power. The wind generator used is based on a double fed induction Generator (DFIG). The stator of the DFIG is connected directly to the network and the rotor is connected to the network through the power converter. The objective of this work is to study the association a Flywheel Energy Storage System (FESS) in wind generator. This system is used to improve the quality of electricity provided by wind generator. It is composed of a flywheel; an asynchronous machine has cage and a power electronic converter. The control of FESS proposed in this paper and velocity using a fuzzy logic controller is validated by simulations is compared with results obtained PI. The results are presented and discussed.