Fuzzy logic based soft starting of induction motor with current control

Induction Motors are the most commonly used machines in industries mainly because it is robust, inexpensive and easy to maintain. For an Induction Motor, the starting current is around ten times the rated current and this persists for a few cycles. This may be very much detrimental for the machine and hence there is a need for using starters to limit the starting current. During earlier times, mechanical starters like star delta, direct online and autotransformer starters were used. Thyristorized soft starters are of low cost. Their reliability is on the higher side and they are simple and occupy lesser space, and hence their use is a fruitful solution to the induction motor starting problem. The ac motor starters incorporating power semiconductors are used frequently nowadays for their controlled soft starting ability with reduced starting current. In this study, a closed loop Matlab Simulink model is developed which would reduce the current at the soft starting period. A fuzzy logic based soft start scheme for induction motor drives is used which would give optimal performance. Fuzzy logic has received higher emphasis in the field of power electronics because of its adaptive capability. The three phase stator currents are converted into two phase currents. The magnitude of current is then converted to per unit. Then it is compared with a reference value. The error is passed through a Fuzzy Logic Controller (FLC).The FLC output is used to control the amplitude of the reference sine wave. Hence by controlling the modulation index, the applied voltage to the stator is controlled and hence the starting current is limit

Otimização de reguladores para acionamento controlado de motores de indução alimentados por intermédio de inversor de corrente com comutação natural

The present work has as purpose the study and implementation, in laboratory, the control and drive system for three-phase induction motor fed by a thyristorized current inverter with natural commutation. The current and speed regulators were adjusted according to the symmetrical optimization criterion. In the proposed control and drive system, it has been used a three-phase induction motor fed by a six pulses thyristorized rectifier-inverter group configured as current source inverter. The DC link voltage and current levels are obtained through variation of the rectifier trigger angle, whereas the inverter trigger angle is maintained fixed. At the inverter output, a large capacitor is connected in parallel with the induction motor so that together they require a leading power factor current. The main function of the capacitor is to provide an enough reactive power that is required by inverter bridge thyristors commutation and to ensure that levels and waveforms are compatibles with motor functioning and driving. The capacitor is therefore able to ensure that the induction motor remains magnetized and that it can produce generated voltages, which can assist in the switching of a naturally commuted inverter. The motor drive and control are achieved by using an analogical speed and current control and regulation in closed loop configuration. The control and regulation have been obtained using the symmetrical optimization method and the regulators were calculated (designed) and incorporated in the system by operational amplifiers, according this method. vii In this configuration, where the inverter bridge trigger angle is maintained fixed, the voltage and current values present at the motor terminals are referred to DC link, as an inductive/resistive load. This configuration and the symmetrical optimization method usage make the calculation easy and simplify the use of electromechanical equations involved. In order to verify the system performance and regulation, load disturbances were promoted; the speed and current waveforms were recorded through a memory oscilloscope. It allows that the regulation dynamics could be evaluated and proved. The data and calculations, the parameters and the result relatives to the simulation are presented as well.O presente trabalho tem como objetivo o estudo e implementação, em laboratório, de um sistema de controle e acionamento com motores de indução trifásicos alimentados por intermédio de inversor de corrente tiristorizado, com comutação natural. Os reguladores de corrente e de velocidade foram ajustados de acordo com o critério da otimização simétrica. No sistema de acionamento e controle proposto, foi utilizado um motor de indução trifásico alimentado por um grupo retificador – inversor tiristorizado de seis pulsos, configurado como fonte de corrente. Os valores de tensão e corrente contínua do circuito intermediário (link DC), foram obtidos em função da variação do ângulo de disparo da ponte retificadora CA-CC, ao passo que, na ponte inversora CC-CA, o ângulo de disparo foi mantido fixo. Na saída da ponte inversora e conectados em paralelo com o motor, foram inseridos bancos de capacitores cuja função principal é fornecer potência reativa necessária à comutação dos tiristores da ponte inversora e garantir os níveis e as formas de onda compatíveis ao funcionamento do motor. Para o controle do motor foi utilizado um sistema analógico de regulação de velocidade e de corrente em malha fechada. O controle e regulação foram modelados pelo emprego do método de otimização simétrica, sendo os reguladores dimensionados e empregados conforme esse método. Na configuração utilizada, tendo a ponte inversora um ângulo de disparo fixo, os valores de corrente e tensão nos terminais do motor puderam ser referenciados ao link DC, como uma carga resistiva/indutiva. v O emprego dessa configuração e a utilização do método de otimização simétrica, facilitam os cálculos e simplificam o uso das equações eletromecânicas envolvidas. Para verificação do funcionamento do sistema, foram promovidos distúrbios de carga no motor, registrando-se a velocidade e as formas de onda de corrente através de um osciloscópio de memória o que permitiu avaliar e comprovar toda a dinâmica de regulação. Os cálculos, os parâmetros utilizados e os resultados relativos à simulação, também serão apresentados

Investigations on Direct Torque and Flux Control of Speed Sensorless Induction Motor Drive

The Induction motors (IM) are used worldwide as the workhorse in most of the industrial applications due to their simplicity, high performance, robustness and capability of operating in hazardous as well as extreme environmental conditions. However, the speed control of IM is complex as compared to the DC motor due to the presence of coupling between torque and flux producing components. The speed of the IM can be controlled using scalar control and vector control techniques. The most commonly used technique for speed control of IM is scalar control method. In this method, only the magnitude and frequency of the stator voltage or current is regulated. This method is easy to implement, but suffers from the poor dynamic response. Therefore, the vector control or field oriented control (FOC) is used for IM drives to achieve improved dynamic performance. In this method, the IM is operated like a fully compensated and separately excited DC motor. However, it requires more coordinate transformations, current controllers and modulation schemes. In order to get quick dynamic performance, direct torque and flux controlled (DTFC) IM drive is used. The DTFC is achieved by direct and independent control of flux linkages and electromagnetic torque through the selection of optimal inverter switching which gives fast torque and flux response without the use of current controllers, more coordinate transformations and modulation schemes. Many industries have marked various forms of IM drives using DTFC since 1980. The linear fixed-gain proportional-integral (PI) based speed controller is used in DTFC of an IM drive (IMD) under various operating modes. However, The PI controller (PIC) requires proper and accurate gain values to get high performance. The PIC gain values are tuned for a specific operating point and which may not be able to perform satisfactorily when the load torque and operating point changes. Therefore, the PIC is replaced by Type-1 fuzzy logic controller (T1FLC) to improve the dynamic performance over a wide speed range and also load torque disturbance rejections. The T1FLC is simple, easy to implement and effectively deals with the nonlinear control system without requiring complex mathematical equations using simple logical rules, which are decided by the expert. In order to further improve the controller performance, the T1FLC is replaced by Type-2 fuzzy logic controller (T2FLC). The T2FLC effectively handles the large footprint of uncertainties compared to the T1FLC due to the availability of three-dimensional control with type-reduction technique (i.e. Type-2 fuzzy sets and Type-2 reducer set) in the defuzzification process, whereas the T1FLC consists only a Type-1 fuzzy sets and single membership function. The training data for T1FLC and T2FLC is selected based on the PIC scheme

Sensorless drives for aerospace applications

This Engineering Doctorate thesis investigates the different implementations and theories allowing drives to control motors using sensorless techniques that could be used in an aerospace environment. A range of converter topologies and their control will be examined to evaluate the possible techniques that will allow a robust and reliable drive algorithm to be implemented. The focus of the research is around sensorless drives for fuel pump applications, with the potential to replace an existing analogue implementation that is embedded in a fuel pump, contained within the fuel tank. The motor choice (Brushless DC) reflects the requirement for endurance and tight speed control over the life of the aircraft. The study of currently understood sensorless control will allow a critical analysis over the best and most robust sensorless control technique for a controller of this nature, where reliability is a fundamental requirement.EThOS - Electronic Theses Online ServiceEaton AerospaceTitchfieldGBUnited Kingdo

Rotorflussorientierte Ansteuerverfahren für Asynchronmotoren am Drehstromsteller

In der vorliegenden Arbeit werden zwei neue Verfahren zur Ansteuerung von Drehstromstellern vorgestellt, die die auftretenden Verlustenergien im Drehstromsteller und Asynchronmotor reduzieren. Es wird sowohl der Start- als auch der Bremsbetrieb betrachtet. Zunächst wird dazu ein Ansatz präsentiert mit dem Zündentscheidungen auf Basis einer Prädiktion getroffen werden. Dieser Ansatz wird so ergänzt, dass ein rampenförmiger Hochlauf möglich ist, wie Anwender ihn von heutigen Industrieprodukten kennen. Außerdem werden erste Validierungsmessungen präsentiert. Im Folgenden wird das „Softstarter Torque and Flux Control”-Verfahren (STFC-Verfahren) vorgestellt, das das Verhalten des prädiktiven Verfahrens nachbildet. Die Nachbildung geschieht mit deutlich verringertem Rechenaufwand und erfordert kaum noch Kenntnis der Parameter des angeschlossenen Motors. Anschließend wird das STFC-Verfahren so umgebaut, dass zusätzlich auf die Verwendung eines Drehgebers verzichtet werden kann. Abschließend wird die Eignung der klassischen Phasenanschnittsteuerung, des prädiktiven Verfahrens, des STFC-Verfahrens und des geberlosen STFC-Verfahrens für verschiedene Applikationen ausführlich diskutiert. Außerdem werden Stärken und Schwächen der Verfahren diskutiert

Application of Reactive Energy to UK Low Voltage Networks and Embedded Generation Effects on Networks Performance

The objective of this thesis is to study thoroughly a specific low-voltage network by determining its performance in different scenarios, in order to define voltages and currents in the various nodes with different operating conditions of the network, for a given maximum load provided by historical measures. The operating conditions cited include the reactive compensation using different methods and distributed generation with reactive compensatio

Fuzzy Logic based Soft Starting of Three Phase Induction Motor

ABSTRACT: This paper presents the current control of three phase induction motor using Fuzzy logic. A thyristorized AC voltage Inverter is utilized as the starting equipment while the motor current regulation is carried out using an optimally tuned Proportional-Integral (PI) controller. AC voltage Inverter fed starting of induction motor is a non-linear process. The complete drive system including AC voltage inverter fed induction motor in conjunction with PI controller is optimized using Fuzzy logic. The successful implementation with a low cost microcontroller demonstrates the feasibility of the new approach. The simulation is carried out by Matlab/Simulink

Fuzzy Control of a Three Phase Thyristorized Induction Motor

Abstract — Nowadays the control of stator voltage at a constant frequency is one of the traditional and low expense methods in order to control the speed of induction motors near its nominal speed. The torque of induction motor is a nonlinear function of the firing angle, phase angle and speed. In this paper the speed control of induction motor regarding various load torque and under different conditions will be investigated based on a fuzzy controller with inverse training