Georgios Adamidis

Shunt active power filter control using fuzzy logic controllers

This paper presents a shunt active filter which eliminates current harmonics and compensates the reactive power of the load. The majority of shunt active power filter control methods which have been presented require a complex and sophisticated mathematical model, especially for the tuning of the PI controllers. To simplify and improve the shunt active filter control system, fuzzy logic theory is applied. In this paper, by the way of controlling the capacitor voltage of the dc bus a fuzzy logic algorithm is implemented. One such algorithm is also implemented to control the output current of the inverter. The performance of the capacitor voltage fuzzy logic control system was investigated, and the improvement of the dynamic response of the fuzzy controller compared to the conventional PI controller became evident. For the reduction of the grid current THDi index, a fuzzy logic hysteresis current controller is investigated. In order to improve the performance of shunt active filter under non ideal grid voltages, a modified version of the p-q theory is proposed. The simulation results are presented and discussed showing the advantages of fuzzy logic theory in the dc bus voltage control and current control.

A three-level space vector modulated grid connected inverter with control scheme based on instantaneous power theory

In this paper the control scheme of a three-level three-phase inverter for grid integration of distributed generation (DG) units is investigated. Furthermore, the inverter compensates the reactive power of the load. The presented control scheme is based on instantaneous power theory in order to generate the appropriate inverter reference currents. In the outer DC bus voltage control loop and in the inner current control loop, the fuzzy logic (FL) control and the Proportional-Resonant (PR) control is applied respectively. The switching pattern generation is achieved using Space Vector Pulse Width Modulation technique. The steady state and dynamic response of the proposed electric power system has been evaluated under various operating conditions. Simulation results verify the effectiveness of the proposed control system.

Direct torque control using space vector modulation and dynamic performance of the drive, via a fuzzy logic controller for speed regulation

This paper presents a method of controlling the Torque of an asynchronous motor that is fed by a PWM-Inverter. The control method that is used is a modified direct torque control (DTC) scheme with constant switching frequency, using space vector modulation (SVM). In this scheme a closed loop of torque control is applied. Small and rapid changes on motors torque are achieved by applying an appropriate voltage vector, which is responsible for the jerky movement of the stators flux vector. The voltage vector can be of any magnitude and angle and is produced using Space Vector Pulse Width Modulation. The modified method of DTC using SVM improves the electrical magnitudes of asynchronous machine, such as reduction of current and flux ripple and also fading out the edges of torque ripple which are occurred during the sector changes of stator flux vector. Another point of this paper is the presentation of speed control in dynamic situations. The production of the reference torque value is achieved by using a fuzzy logic speed controller. The response of the fuzzy PI is compared to the response of a classic PI speed controller. Results, shows that the fuzzy PI speed controller has a better response in a wide range area of motor speed. Combining the characteristics of DTC-SVM scheme and the fuzzy logic speed controller we can have a high performance vector controlled asynchronous motor drive.

Photovoltaic system MPPTracker investigation and implementation using DSP engine and buck - boost DC-DC converter

In this paper, solar radiation simulation using clearness index kt, hour of day omegas and day of year n is studied. Daily distributions of solar radiation are presented for various clearness indexes kt. Additionally, taking into account the studies about solar radiation, a photovoltaic array system and a DC/DC buck - boost converter are studied. Simulation of the whole system is presented focusing on DC/DC converterpsilas control strategy so that the system operates in maximum power point (MPP) and converterpsilas output voltage remains constant. Incremental conductance algorithm is used for maximum power point tracker (MPPT) implementation. A simplest method for controlling duty cycle D and photovoltaic arraypsilas voltage by using a new variable (d = D/1-D) is proposed. Simulation results are shown and analyzed. For the implementation of this system, the dsPIC30F2010 Microchippsilas microcontroller was programmed to provide pulses to the semiconductor element of the DC-DC converter in order to track the Maximum Power Point (MPP) of the photovoltaic array.

Comparison between two different methods of calculation of switching time which is used for implementation of SVPWM using DSP

This paper introduces the control of a squirrel cage induction motor which is fed from an inverter. The inverter is driven using the method SVPWM. The central processing unit during the development must be very fast in order to give the pulses in appropriate time into the gates of power semiconductors, compatible in EMI, cheap, with big flash memory. The consumer power electronics, which are used for motor drive, must be reliable and cheap. The central processing unit which is selected in consumer power electronics is cheap with small flash memory in order to reduce the cost of implementation. In this paper is tried to be done a code for a DSP, which can be contained in very small flash memory of a DSP in order to drive an induction motor with very good performance. The new method which is presented in this paper is compared with the classical SVPWM with look up tables. The practical results of these methods are represented and compared.

A multifunction control scheme for current harmonic elimination and voltage sag mitigation using a three phase three level flying capacitor inverter

Abstract This paper presents a novel control scheme for a distribution static compensator (DSTATCOM) aimed at mitigating voltage sag at the Point of Common Coupling (PCC) or eliminating current harmonics of the load. The proposed control scheme uses the d – q reference frame for the decoupling of active and reactive current components. Furthermore a selective algorithm is integrated to the control scheme in order to choose between the voltage support mode or the current harmonics elimination mode. Finally, the DSTATCOM is based on a three phase three level flying capacitor topology. The proposed control scheme outperforms the conventional one due to the ability of the suggested control system to combine multiple functions, allowing DSTATCOM to respond in various power quality issues. The effectiveness of the proposed control scheme to enhance the multifunction ability of the DSTATCOM is verified via Matlab/Simulink© in both steady state and transient response.

A new Space Vector Modulation Strategy for multilevel inverters

In this paper a new Space Vector Pulse Width Modulation method is proposed for multilevel voltage source inverters. This method is based on Space Vector Modulation and is compared to other similar methods. According to the method presented the multiplicity of the switching states of a multilevel inverter is also considered. This means that the new pulse method takes into account the multiplicity of the switching states which means a symmetrical distress of the inverters elements while the number of transitions in a switching time is 7. This method can be applied in a multilevel inverter who feeds a high power three-phase passive load or a high power three-phase motor drive. The new method was used in order to pulse a five-level inverter, which feeds a high power passive load using Matlab-Simulink, and the results are shown in this paper.

Study of a simple control strategy for grid connected VSI using SVPWM and p-q theory

This paper investigates the operation of a Distributed Generation (DG) unit which is connected via a three-phase voltage-source inverter to the distribution grid. The current control method with Space Vector pulse width modulation (SVPWM) is examined and compared to other current control methods. The strategy, which has been developed to control the reactive power and have a better utilization of DG unit, uses the p-q theory to achieve uninterrupted compensation of the reactive power of the system. A PI controller is used to control the active power and regulate the voltage of the capacitor. Finally, the proposed electrical power system is simulated on the computer and the steady-state and dynamic response of the system is evaluated.

Improving the voltage profile of a medium voltage grid using distributed generation units

In this paper the impact of photovoltaic (PV) system connected to the medium voltage distribution grid using three-phase three-level inverter and step-up transformer will be investigated. The PV inverter is capable to control active and reactive power independently. The impact to the grid voltage profile of both active and reactive power regulation of the PV system will be examined. In order to simplify the control scheme and improve the performance of the converters the p-q theory has been chosen due to the ability to compensate the reactive power of the load. The proposed electric power system was investigated via simulation results during steady state and transient response. The analysis will be focused on the grid voltage profile improvement regarding of the of the inverters active and reactive power injection.

Performance Evaluation of PI and Fuzzy Controlled Power Electronic Inverters for Power Quality Improvement

© 2012 Tsengenes and Adamidis, licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Performance Evaluation of PI and Fuzzy Controlled Power Electronic Inverters for Power Quality Improvement