Speed Control of DC Series Motor Using Continuous Input Output Power Buck Converter

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1 Speed Control of DC Series Motor Using Continuous Input Output Power Buck Converter 1. E. Maheswari, Associate Professor/EEE, Sri Sairam Institute of Technology, Chennai 2. Dr. V.Balaji, Associate Professor/EEE, Bahirdar University, Ethiopia. 1.ABSTRACT This paper presents the speed control of DC series motor using continuous input output power Buck Converter using voltage mode control. The input and output current is continuous for low values of duty ratio in this proposed converter compared to normal buck converter. The speed can be controlled for armature voltage control method to very low values of speed using this converter. In voltage mode control the ramp signal compared with control signal to generate the PWM pulse given to the converter. The control signal can be generated using the PI controller. The reference speed can be achieved by varying the slope of the ramp signal. 2.INTRODUCTION DC-TO-DC converters with continuous input current are used extensively in systems for the maximum utilization of solar, marine, wind energy, fuel cells, and batteries. Also, dc-to-dc converters are a basic building block for ac input, unity power factor single and three-phase ac-to-dc converters, termed active front end converters [1]. The buck converter can be considered a basic buck converter with a second order LC input filter, hence the low input ripple current. The buck converterhas the best current regulation compared to the boost converter having the poorest current regulation at low current. That is, in open loop, the buck converter is best for accurately tracking the current transfer ratio. The converters consists of the two inductors are effectively in series with the output or input tend to have a lower ripple current. [1] The buck boost converter fed DC series motors possess a good operation performance with a minimum ripple in the output of the motor current and voltage. In open loop the steady-state and transient operating conditions were investigated and in the closed loop system, a positive step change in the load were investigated [2]. The sensor less generalized proportional integral (GPI) observer-based ADR controller used for the control of a buck-boost-converter feeding a dc motor.the GPI observer simultaneously estimates the angular velocity [3]. The single-transistor converters have more conversion efficiency compared to two stage converters. The two stage converters were used for high frequency applications with large range of conversion ratios[4,5]. The continuous input output power converters give less voltage and current ripple compared to the two stages or cascaded dc to dc converters [6, 7&8]. 3.CONTINUOUS INPUT OUTPUT POWER BUCK CONVERTER 321 Fig 1 Continuous input output power Buck Converter

2 This converter can give continuous input and output current for low values of duty ratio compared to normal buck converter.the current ripple also minimum compared to normal buck converter.this converter can be used for controlling the speed of DC series motor using volatge control method for speed lesser than rated speed. This coneverter can also be act as preregulator for power factor correction applications. The input inductor can be tuned to get the unity power factor with low harmonic distortion. The output voltage of the converter is given by V in δ similar to the normal buck converter. The circuit diagram of continuous input output power buck converter as shown in figure1. MODE 1 OPERATION : Fig 2 Circuit Diagram for Mode 1 operation In mode 1 operation the switch is closed and the current flows through inductor L1. The input inductor and output capacitor get charged during mode 1. The capacitor C1 and inductor L2 get discharged to the load. The circuit diagram of the mode 1 operation as shown in figure 2 with the flow of current direction. MODE 2 OPEARTION: Fig 3 Circuit Diagram for Mode 2 operation In mode 2 operation the switch is opened and diode is in ON condition.during this mode the capacitor C1 and inductor L2 get charging by the voltage delivered by inductor L1. The capacitor C2 discharges energy to the load side. The circuit diagram of the mode 2 operation as shown in figure 3. 4.DESIGN PARAMETERS The converter designed for 5W with switching frequency of 40kHz. The input current ripple and volatge ripple taken as 5% for designing the inductor and capacitor. In the voltage mode control the input given the converter is 12V. This converter implemented for speed control of DC series motor with the input voltage of 100V. 322

3 S.NO Parameters Specifications 1 Input Voltage 12V 2 Output voltage 5V 3 Switching frequency 40kHz 4 Inductors L1,L2 4mH 5 Capacitor C1 10µF 6 Capacitor C µf 7 Output power 5W Table.1 Design Parameters of Buck Converter 5. VOLTAGE MODE CONTROL Involtage mode control of buck converter the output voltage compared with the reference signal. The error signal given to the PI controller and it gives the control signal Vcon. The ramp generator gives the ramp signal and it is compared with the control signal. The generation of PWM signal depends upon the slope of the ramp signal. The PWM signal generated for the stable output by varying the slope of the ramp signal. Fig 4.Circuit diagram of buck converter for voltage mode control 6. SPEED CONTROL OF DC SERIES MOTOR In speed control the resistive load replaced by DC series motor in voltage mode control of the converter circuit. The main advantage of series motor is high starting torque and it can be uased in traction applications.electrical drives are nowadays used in modern industry, automobile sectors, aircrafts, space crafts, home appliances etc. The rotational speed and torque of the electrical drives are controlled by the power electronic converters with different types of pulse width modulated (PWM) signals. Anyelectrical drive consists of an electric motor, a power converter and feedback controller, and working together with mechanical load. An integral part of the system consists of input power supply and sensors for closed- loop control of the drive. 323

4 Fig. 5 Speed control of DC Series Motor In closed loop speed control of DC series motor, the actual speed of the motor compared with the reference speed. The error signal is given to PI controller and it is converted into control signal. The modulated signal generated by comparing the control signal with ramp signal. When the V con V ramp the switch goes to ON stage and vice versa. The generated PWM signal is given to switch. The duty ratio decided by the slope of the ramp signal. The desired speed can be achived by varying the slope of the ramp signal. The speed of the DC series motor can be controlled for very low values using this continuous input output power buck conveter. 7.SIMULATION RESULTS The buck converter can be designed as per design parameters mentioned in Table.1 The converter has been implemented with voltage mode control using resistive load. The input given to the converter is 12V. The converter has been simulated using MATLAB for open loop as well as closed loop with voltage mode control. The simulation diagrams and waveforms presented as shown in figures 6,7 for open loop and figures 8,9 for closed loop with resistive load. In the speed control the resistive load repalced by DC series motor using voltage mode control. The input given to DC series motor is 100V. The desired speed can be achieved by varying the slope of the ramp signal. The simulation diagram and waveform presented as shown in figures 10,11 and 12. Fig.6.Open Loop simulationcircuit diagram 324

5 Fig 7 Simulation waveform for open loop Fig. 8 Simulation diagram with voltage mode control Fig 9. Simulation Waveform for voltage mode control 325 Fig. 10 Simulation diagram for series motor speed control

6 Fig 11. Simulation waveform for speed, armature current,field current and torque Fig 12. Simulation waveform for Armature Voltage 8.CONCLUSION The continuous input output buck converter was designed for 12V. This converter works under the continuous conduction mode of operation for very low values of duty ratio compared to the normal buck converter. The converter was designed for speed control of DC series motor using voltage mode control with the input voltage as 100V. The speed can be controlled to very low values by varying the slope of the ramp signal. In future it can be implemented with solar energy as the input of the power converter and it will be designed for higher values of input voltage of the DC series motor. The hardware circuit will also be implemented with FPGA controller. REFERENCES [1] DC-to-DC Converters with Continuous Input and Output Power - Barry W.Williams. [2] Buck-Boost converter fed dc series motor - Nabil T. Tweig Academy of Specialist Studies, Workers University, Egypt.Power Systems Conference, MEPCON 2006.Eleventh International Middle East. [3] J. Linares-Flores, J. L. Barahona-Avalos, H. Sira-Ramirez, M. A. Contreras-Ordaz, "Robust Passivity-Based Control of a Buck Boost-Converter/DC-Motor System: An Active Disturbance Rejection Approach", Industry Applications IEEE Transactions on, vol. 48, pp , 2012, ISSN [4] Maksimovic, D. and Cuk, S., General properties and synthesis of PWM DC-to-DC converters, Power Electronics Specialists Conference, PESC, [5] Maksimovic, D. and Cuk, S., Switching converters with wide DC conversion range, Power Electronics, IEEE Transactions on, vol. 6, NO.1, Jan [6] J.A. Morales-Saldana, et al, Modeling of a Cascade Boost Converter with Single Switch, The 32nd Annual Conference of the IEEE Industrial Electronics Society, 2006 [7] H.C. Iu, Experimental Study of Instabilities in Two parallel-connected Boost Converter under Current Mode Control, 11 th European Conference on Power Electronics and Applications [8] N. Vazquez, L. Estrada, C. Hernandez and E. Rodriguez, the Tapped-Inductor Boost Converter, IEEE International Conference on Industrial Electronics (ISIE),