Control of A Single-Phase Induction Generator - Report Example

Control of a single-phase induction generator Student Name: Student Number: Submission Date: Supervisor: Acknowledgements I would like to send my sincere appreciation first to my instructor (insert title and name) for his unwavering and continued guidance. I also extend my gratitude to my classmates, who often listened to my consultative questions, positively criticized me and encouraged me to continue up to the utmost end. Feel appreciated and almighty God bless you abundantly Executive Summary This research document presents an elaborate report on development of a control system for a single phase induction motor by means of frequency and voltage regulation. The system uses a PIC18f4550 microcontroller to achieve both active and reactive power management which in turn makes it possible to establish and measure inverter output voltage as well as the rotor frequency. The major underlying operation principle hence subsequent development of this motor control system is to provide a more simple way of adjusting the control signal using a microcontroller to display the inverter output voltage and the frequency values. The system will also use a high level programing language (C), widely used nowadays due to its simplicity than the assembly language in microprocessor and its much cheaper .in addition, designing a control system of a single-phase inverter using PSIM program in order to test the reliability of the control system performance. Contents 1.0. Introduction 5 1.1.Project global overview 5 2. Technical Work. 6 2.1. Selection of main components 6 2.1.1. Voltage source inverter 6 2.1.2. Microcontroller 6 2.1.3. Optocoupler (isolator): 7 2.1.4. PICkit 3: 7 2.2. Test framework 7 2.3. Hardware design 8 2.4. Software design 8 3.0. Project Timeline 9 3.1. Progress against Methodology steps and timeline 9 4.0. Problems/issues identified, and mitigation or changes made 10 5.0. Results and Discussion 10 5.1. Results 10 5.2. Discussion 13 6.0. Conclusions and Future work. 16 6.1. Conclusion 16 6.2. Future work 17 7.0. References 18 1.0. Introduction 1.1. Project global overview One major application of control systems in power generation by the use of three-phase magnetic flux controlled variable reactor .The variable reactor controls induction generator’s voltage to the extent of attaining a value similar to that of previous three-phase designs. The voltage control has previously been implemented using external source of power only where grid power is not present .Additionally, self-sufficient designs have been proposed such that the power needed for voltage control is obtained from the generated power while switching power supply has provided reduction of the control power to about 25% of that needed for previous designs. The proposed research involves development of a control system for a single-phase induction generator that involves frequency and voltage regulation. In addition, active and reactive management of power to achieve reliable measurement of both the inverter output voltage and the frequency values via PIC18f4550 microcontroller. The system includes a preferable way of adjusting the control signal using a microcontroller to display the inverter output voltage and the frequency values. It will also use a high level programing language (C), widely used in microprocessor due to its simplicity. It will also incorporate designing a control system of a single-phase inverter using PSIM program to test the reliability of the control system. This project aims at offering contribution in the field of control system of electrical mechanics such as motors and generators. This is because it supports implementation of technologies that allow creating new strategies at minimized development costs and cost effective technology. 2. Technical Work. 2.1. Selection of main components 2.1.1. Voltage source inverter The system design incorporates within its circuit, a voltage source inverter with four-switch single-phase inverter source. The four induction motor circuit switches are labeled S1, S2, S3, and S4 with split capacity C and Cdc. Rectifier switches are used to synchronize the single-phase AC input signal with fixed frequency. The power circuit single-phase four-switch inverter is further made up of two phases, one phase connected to the legs of the inverter and the other phase connected directly to the center point of the DC link capacitors. The VSI and the DL are used in the circuit to provide balance operation and parameters regulation for autonomous three-phase IG during single-phase supply. The circuit has a capacitor bank, an isolator and microcontroller. The isolator acts as a connector between the inverter and the microcontroller without direct conduction. 2.1.2. Microcontroller The project used a PIC18F4550 microcontroller. This is because besides being cheap, it is both compact and light compared to computers. Furthermore, the microcontroller has a simple application and easier to implement than microprocessor in a system with least failure chances. Microcontroller applications also run much faster compared to similar applications in a computer. The microcontroller will subsequently be loaded with instruction in C programing language. C is a high level language (C) often widely used nowadays because it is much simpler than the assembly language in microprocessor. 2.1.3. Optocoupler (isolator): The FOD3120 was chosen for use in this experiment. The optocoupler has an output gate drive current of 2.5A. It is subsequently capable of driving a a 1200V/20A IGBTs as well as MOSFETs. Another feature of the FOD3120 optocoupler is that it can achieve the industry’s highest CMR rating even in the noisiest industrial environment. It also has a number of advantages. For instance, it offers support between power circuit and PIC microcontroller so as to enhance signals feedback. Besides, the device also offers tight pulse width distortion (100ns), hence smaller filters which lead to improved power efficiency. 2.1.4. PICkit 3: The PG164130 - PICkit 3 is an in-Circuit Debugger. The circuit allows debugging and programming of PIC(R) and dsPIC(R) Flash microcontrollers using the powerful graphical user interface of the MPLAB Integrated Development Environment (IDE). Microchip’s PICkit 3 In-Circuit Debugger/Programmer uses in-circuit debugging logic incorporated into each chip with Flash memory to provide a low-cost hardware debugger and programmer. In-circuit debugging offers such benefits as being cheap in cost requires minimum additional hardware for debugging and does not necessarily need expensive sockets or adopters. The PICkit 3 can also reprogram any PIC microcontroller with a simple push of a button. 2.2. Test framework This refers to the object-oriented approach to project execution environment, often done with automated tests. It is defined as the set of assumptions, concepts, and practices that constitute a work platform or support for automated testing. Test frameworks help in organizing their test suites and in turn improving the efficiency of testing. 2.3. Hardware design The hardware design was done using the set up and configured as presented in the figure below. The circuit contains a 50v DC input signal fed into a system of MOSFET channels with Gate Drive Optocoupler to give out a corresponding 50v AC signal as an output. 2.4. Software design The software design consists of a mounted microcontroller, loaded with instructions in C language and whose output s obtained via an LCD display unit as shown in the set up figure bellow. 3.0. Project Timeline 3.1. Progress against Methodology steps and timeline Title of Activity Timelines First Semester Final Semester 1. Research/proposal/ideas 2. Project/Research/ideas final draft 3. Writing research introduction and literature review and designing the circuit 4. Identification of system configuration, designing circuit, and control system VSI 5. Coding using C programming language 6. Configuring the microcontroller and Programming the it using the c source code 7. Configuring the microcontroller and Programming the it using the c source code 8. Delivery to client 4.0. Problems/issues identified, and mitigation or changes made Software simulation was the most difficult part of the project. Creating the right program files for the microcontroller was an involving a tedious task. For instance, on several occasions, an error “Time step too small” frequently opened up on the display screen. However, with continuous and persistent corrections, the error was finally cleared. Using a power supply unit as the power source also gave error reports. This was subsequently solved by using a signal voltage as the power source. Problems were also encountered during the design of a triggering circuit. Initially, the board had been designed in an eagle 6 demo version which corrupted most of the program files, a move that prompted eventual use of a printed circuit body as a remedy. 5.0. Results and Discussion 5.1. Results For a H-bridge inverter, either A+ or A- is closed but never at the same time. In the same case, either B+ or B- is closed, but never at the same time. Same time closing would cause a short circuit from Vdc to ground (shoot-through).To avoid shoot-through when using real switches (i.e. there are turn-on and turn-off delays) a dead-time or blanking time is implemented Operational states considered 1) A+ closed and B– ,closed, Vab = Vdc 2) A+ closed and B+ ,closed, Vab = 0 3) B+ closed and A– ,closed, Vab = -Vdc 4) B- closed and A– ,closed, Vab = 0 The freewheeling diodes are incorporated to allow current to flow when all switches are open. They also allow lagging currents to flow in all loads. Keeping V/f ratio constant for different values of voltage and frequency, the subsequent frequency and voltage Matlab simulations are obtained. Hardware Circuit diagram the inverter dc/ac Hardware and PC schematic 5.2. Discussion The power circuit is a full bridge inverter circuit. In the circuit for this project, four MOSFET are connected in series at each leg of H-Bridge. Four MOSFETs are used to increase the current rating of circuit. A total of 16 n channel MOSFETs are used in our project. As microcontroller output is in maximum 5V which is direct to MOSFET gate but MOSFET is not active until 12V that why we need MOSFET driver for our circuit. For driving the high side MOSFET we used TLP250 and a capacitor of 50V, 100μfarad in output of TLP250, this capacitor is called boost strip capacitor. The capacitor in the output of TLP is used for protection. For the low side of inverter we used totem pole configuration, where totem pole passes 12V to MOSFET gate .There should be a resistance between nMOSFET gate and source as gate resistance to drive the MOSFET otherwise MOSFET can’t be on. There are used many protection diode in every stage of connection so that reverse current can’t hamper to other circuit component such as TLP250, BJT, microcontroller. As MOSFET is very heat sensitive so for cooling purpose we used four heat sinks at four lags of H-bridge inverter. The drain of the MOSFET is mounted to heat sink. The output of the inverter is then passed to the transformer. The output is taken from the two lower MOSFETs drain as upper MOSFET source is connected to the drain of lower MOSFET. Simulation of SPWM PWM is widely used in power electronics to “digitalize” the power so that a sequence of voltage pulses can be generated by the on and off of the power transistors. The fundamental component has variable magnitude and variable frequency. The PWM Output pulses and its frequency spectrum is shown in figure bellow. T1 and T4 are off while T3 and T2 are on Sinusoidal triangle PWM (SPWM) is the mostly used method. Triangle wave is used as carrier and reference signal is sinusoidal wave, whose frequency is the desired frequency and amplitude is determined by desired voltage amplitude, DC voltage and carrier amplitude. The fundamental component is what we want to drive the motor. Because the equivalent circuit of the motor is composed of resistors and inductors, the motor is like inductive impedance so that the effect high frequency components can be neglected. The frequency was varied by changing the frequency of the modulating signal i.e. sinusoidal signal. We can vary voltage at output by the varying value of MODULATING INDEX (m). Where; m=vm/vc Vm= Reference sinusoidal signal. Vc=Carrier signal The magnitude of modulation index is limited below one (i.e., 0 Read More

2.1.2. Microcontroller The project used a PIC18F4550 microcontroller. This is because besides being cheap, it is both compact and light compared to computers. Furthermore, the microcontroller has a simple application and easier to implement than microprocessor in a system with least failure chances. Microcontroller applications also run much faster compared to similar applications in a computer. The microcontroller will subsequently be loaded with instruction in C programing language. C is a high level language (C) often widely used nowadays because it is much simpler than the assembly language in microprocessor. 2.1.3. Optocoupler (isolator): The FOD3120 was chosen for use in this experiment.

The optocoupler has an output gate drive current of 2.5A. It is subsequently capable of driving a a 1200V/20A IGBTs as well as MOSFETs. Another feature of the FOD3120 optocoupler is that it can achieve the industry’s highest CMR rating even in the noisiest industrial environment. It also has a number of advantages. For instance, it offers support between power circuit and PIC microcontroller so as to enhance signals feedback. Besides, the device also offers tight pulse width distortion (100ns), hence smaller filters which lead to improved power efficiency. 2.1.4. PICkit 3: The PG164130 - PICkit 3 is an in-Circuit Debugger.

The circuit allows debugging and programming of PIC(R) and dsPIC(R) Flash microcontrollers using the powerful graphical user interface of the MPLAB Integrated Development Environment (IDE). Microchip’s PICkit 3 In-Circuit Debugger/Programmer uses in-circuit debugging logic incorporated into each chip with Flash memory to provide a low-cost hardware debugger and programmer. In-circuit debugging offers such benefits as being cheap in cost requires minimum additional hardware for debugging and does not necessarily need expensive sockets or adopters.

The PICkit 3 can also reprogram any PIC microcontroller with a simple push of a button. 2.2. Test framework This refers to the object-oriented approach to project execution environment, often done with automated tests. It is defined as the set of assumptions, concepts, and practices that constitute a work platform or support for automated testing. Test frameworks help in organizing their test suites and in turn improving the efficiency of testing. 2.3. Hardware design The hardware design was done using the set up and configured as presented in the figure below.

The circuit contains a 50v DC input signal fed into a system of MOSFET channels with Gate Drive Optocoupler to give out a corresponding 50v AC signal as an output. 2.4. Software design The software design consists of a mounted microcontroller, loaded with instructions in C language and whose output s obtained via an LCD display unit as shown in the set up figure bellow. 3.0. Project Timeline 3.1. Progress against Methodology steps and timeline Title of Activity Timelines First Semester Final Semester 1.

Research/proposal/ideas 2. Project/Research/ideas final draft 3. Writing research introduction and literature review and designing the circuit 4. Identification of system configuration, designing circuit, and control system VSI 5. Coding using C programming language 6. Configuring the microcontroller and Programming the it using the c source code 7. Configuring the microcontroller and Programming the it using the c source code 8. Delivery to client 4.0. Problems/issues identified, and mitigation or changes made Software simulation was the most difficult part of the project.

Creating the right program files for the microcontroller was an involving a tedious task. For instance, on several occasions, an error “Time step too small” frequently opened up on the display screen. However, with continuous and persistent corrections, the error was finally cleared. Using a power supply unit as the power source also gave error reports. This was subsequently solved by using a signal voltage as the power source.

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