Design and Simulation of PID Controller for Power Electronics Converter Circuits

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Volume 3, Issue 2, 2016

26 Available online at www.ijiere.com

International Journal of Innovative and Emerging

Research in Engineering

e-ISSN: 2394-3343 p-ISSN: 2394-5494

Design and Simulation of PID Controller for Power

Electronics Converter Circuits

Ms. Kashmira Rathi(Kasat)a

and

Dr.M.S.Ali b

a_{Department of Electronics & Telecommunication Engineering, PRMCEAM, Badnera - Amravati (M.S.) India} b_{Principal, Prof Ram Meghe College of Engineering & Management (PRMCEAM), Badnera– Amravati (M.S.) India}

ABSTRACT:

The use of DC power converters is continuously growing both in power electronics products and systems. In a DC-DC converter application,it is always desired to obtain a regulated output voltage despite changes in input voltage, load current and converter components. To obtain regulated output voltage researchers have used various simple conventional to complex automatic control methods. With the development of semiconductor manufacturing technology, simplicity of design, size of devices, cost and better conversion efficiency have become important design criteria. This paper proposes the design of a simple PID controller that can be applied to any DC-DC converter topology. The designed PID controller is tested with buck and boost converter in MATLAB-Simulink environment. Simulation results show that the controller realizes a better output voltage tracking and improved converter efficiency along with the ease and simplicity in design.

Keywords:DC-DC converter, Boost converter, Buck converter, Proportional-Integral-Derivative controller,

IGBT

I. INTRODUCTION

Power electronics deals with a variety of converters that are used at power level rather than the signal level. A power electronic system system consists of one or more power electronic converters. A power electronic converter is made up of some power semiconductor devices controlled by integrated circuit. The switching characteristics of power semiconductor devices permits a power electronic converter to shape the input power of one form to output power of some other form.

DC-DC converters are some of the simplest power electronic converter circuits. They are widely used in the power supply equipment for most electronic instruments and also in specialised high power applications such as battery charging, plating and welding. The wide variety of circuit topologies ranges from the single transistor buck, boost and buck/boost converters to complex configurations comprising two or four devices and employing some techniques to control the switching losses. The usual requirement of a control system for the converter is to maintain the output voltage constant irrespective of variations in the DC source voltage Vin and the load current. However, load changes affect the output voltage transiently, possibly causing significant deviations from the steady state level. Furthermore,in a practical system circuit losses introduce an output voltage dependency on steady state load current which must be compensated for by the control system[1,2,3].

Recently, with the flourishing of portable devices and development of semiconductor manufacturing technology, conversion efficiency, power consumption and size of devices have become the most important design criteria of switching power converters. It is essential to develop accurate switching power converters, which can reduce more wasted power energy. For small applications it is very important to regulate the output voltage of the converter with high precision and performance. Thus, a tradeoff among cost, efficiency and output transients should be considered.

This paper proposes the design of a simple PID controller for power electronics DC-DC converter topologies. Cost, size, switching speed, efficiency and simplicity are the important points of concern for the design of proposed PID controller.

II. DC-DCCONVERTERCIRCUITS

The DC-DC converter has some functions. These are:

i. Convert a DC input voltage Vs into a DC output voltage Vo. ii. Regulate the DC output voltage against load and line variations.

iii. Reduce the AC voltage ripple on the DC output voltage below the required level. iv. Provide isolation between the input source and the load (if required).

v. Protect the supplied system and the input source from electromagnetic interference

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27 and using switching devices. The widely used switching devices are diodes, thyristors, power MOS, etc.The converter often includes one (or several) transistor(s) in order to control the output voltage, using the control signal (t) . It is desirable that the conversion be made with low losses in the converter. To obtain low losses, resistors are avoided in the converters. Capacitors and inductors are used instead since ideally they have no losses. The electrical components can be combined and connected to each other in different ways, called topologies, each one having different properties. The buck, boost, and buck-boost converters are three basic converter topologies.

Fig1: Block diagram of a DC-DC converter

By using pulse-width modulation (PWM) control, regulation of output voltage is achieved by varying the duty cycle of the switch. Duty cycle refers to ratio of the period where power semiconductor is kept ON to the cycle period. Pulse width modulation (PWM) is a powerful technique for controlling analog circuits. PWM is employed in a wide variety of applications, ranging from measurement and communications to power control and conversion. Control of PWM is usually effected by an IC , necessary for regulating the output[3,11]. The transistor switch is the most important thing of the switched supply and controls the power supplied to the load. It is also stated that Power MOSFET’s are more suitable than BJT at power output of the order of 50 W. Choosing of transistor also must consider its fast switching times and able to withstand the voltage spikes produced by the inductor.

The proposed converter uses IGBT as the switching device. Use of IGBTs allow to build cheaper and better converters. They have three attractive advantages: higher switching frequency, easy and simple gate control and no need for snubber circuits. IGBTs are continuously controllable during turn on and turn off. This makes overcurrent limitation much easier and allows dV/dt control to reduce the and dV/dt stresses[3].

Many aspects must be considered in the case where a converter is to be designed. One such aspect is keeping the output voltage in the specified voltage interval. Here are some examples of changes that can decrease the variation of the output voltage[6-10]:

 Change the properties of some of the components in the converter, e.g. increase the capacitance of the capacitor.

 Change the converter topology.  Change to a more advanced controller.

 Increase the number of signals that are measured and used by the controller. Each one of these changes has one or several disadvantages such as:

 Higher cost.

 Increased weight and volume.  Lower reliability.

 Lower efficiency.

Therefore, the change or changes that are most suitable depend to a large extent on the converter specification at hand. Converters can be improved as better components are developed and more knowledge becomes available. This motivates research in the areas of components, converter topologies and controllers for example. To obtain high performance control of a system, a good model of the system is needed[6-10].

III.PIDCONTROLLER

Proportional-Integral-Derivative (PID) controller has been used for several decades in industries for process control applications. PID involves three separate parameter, the proportional, the integral and derivatives. By tuning the three constants in PID controller algorithm, the controller can provide control action designed for specific process requirement.

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28 There are various methods available for the tuning of PID controller. But for convenience purpose trial and error method is generally used[5,8,9].

First the PID controller works in a closed-loop system shown in Figure2. The variable (e) represents the tracking error, the difference between the desired input value (R) and the actual output. This error signal (e) will be sent to the PID controller, and the controller computes both the derivative and the integral of this error signal. The signal (u) just past the controller is now equal to the proportional gain (Kp) times the magnitude of the error plus the integral gain (Ki) times the integral of the error plus the derivative gain (Kd) times the derivative of the error where, this signal (u) will be sent to the plant, and the new output will be obtained. This new output will be sent back to the sensor again to find the new error signal (e). The controller takes this new error signal and computes its derivative and its integral again. This process goes on and on, this signal (u) is obtained as follows

IV.DC-DCBUCK CONVERTER CIRCUIT

The operation of basic buck converter for mathematical modeling and analysis is represented in figure below[1,4],

Fig3: Basic Buck Converter circuit (open loop)

Fig4: Buck Converter circuit with PWM

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29

V. DC-DCBOOST CONVERTER CIRCUIT

The operation of basic boost converter for mathematical modeling and analysis is represented in the figures 6,7 and 8 below[1,4].

Fig6: Basic Boost converter circuit (open

loop)

Fig7: Boost converter circuit with PWM

Fig8: Boost converter with PID controller(closed loop)

Two topologies of DC-DC converter namely ,buck and boost converters have been designed and analysed. Figures 3, 4, 5 show buck converter in open loop and closed loop. The PID controller controls the duty cycle of PWM signal applied to semiconductor switch IGBT as per the output requirement. For buck converter the output DC voltage is less than the input DC voltage. The same PID controller is applied to boost converter shown in figures 6,7,8. The design and simulation is carried out in MATLAB-Simulink environment.

VI.EXPERIMENTALRESULTS

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30 that transient performances can be improved if the P and I gains are big and the D gain is small at the beginning. For both the topologies input voltage is taken as 12V. The operation of the converters can be best verified with step input reference voltage. Simulation has been carried out for various changes in load values and input variations. Results show that the designed PID controller has better output voltage tracking ability, thus improving output voltage regulation. The design is very simple with small size and reduced cost.

Fig9: Output voltage waveform of basic buck converter

Fig10: Output voltage waveform of buck converter with PWM

Fig11: Output voltage waveform of buck converter with PID controller

Fig12: Output voltage waveform of basic boost converter

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31 Fig14: Output voltage waveform of boost converter with PID controller

VII. CONCLUSIONS

The designed buck and boost converter operates effectively when PID controller is used. The controller realizes a better output voltage tracking with minimal overshoot, small steady state error, short settling time and improved converter efficiency. The design is simple and easy with reduced size and cost.

REFERENCES

[1] Hebertt J. Sira-Ramirez & Ramón Silva-Ortigoza, Control Design Techniques in Power Electronics Devices, Springer-Verlog, 2010

[2] Mohan, Undeland and Robbins. Power Electronics: Converters, Applications and Design. – Wiley, 1989. [3] B.K.Bose, Power Electronics and Variable Frequency Drives,IEEE press, 1997

[4] Modelling and Control of DC-DC Converters,Tutorial, Power Engineering Journal, 1998

[5] K.Vijaykaran, Mrs.J.Jeyashanthi,"A Positive Buck Boost DC-DC Converter with Mode Select Circuit using PID Controller",Int. Journal of Innovative Research in Science, Engineering and Technology, Vol.3, March 2014 [6] Siew-Chong Tan, Member, IEEE, Y. M. Lai, Member, IEEE, and Chi K. Tse, Fellow, IEEE, "General Design

Issues Of Sliding Mode Controllers in DC-DC Converters", IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, VOL. 55, NO. 3, MARCH 2008

[7] N. D. Muhamad, M. R -Sahid, A. H. M. Yatim, N. R. N. Idris, and M. S. Ayob," Design of Power Stage and Controller for DC-DC Converter Systems Using PSPICE", IEEE PEDS 2005

[8] Mr.B.Sai Sreenivas, Dr.Ch.Sai Babu, Mr.D. Lenine," Design and Analysis of Predictive control using PI controller for Boost Converter with Active Power Factor Correction",International Journal of Emerging Technology and Advanced Engineering, Volume 2, Issue 6, June 2012

[9] Mitulkumar R. Dave, K.C.Dave,"Analysis of Boost Converter Using PI Control Algorithms", International Journal of Engineering Trends and Technology- Vol3Issue2- 2012

[10]Keyue M. Smedley, Member, IEEE, and Slobodan Cuk, Senior Member, IEEE,"One-Cycle Control of Switching Converters", IEEE Transactions on Power Electronics, Vol. 10, No. 6, Nov 1995

[11]Santosh Raikar.M, Dr.K.S.Aprameya, “Investigations On Various Power Electronic Converters using PWM Technique", Int. Journal of Advanced Research in Electrical, Electronics and Instrumentation Engineering, vol.3 Issue 1, Jan 2014.

[12]Hemant Mehar,"MATLAB Simulation Techniques in Power Electronics",IEEE Technology and Engineering Education, Vol.7 No.4, Dec 2012

Ms. Kashmira Rathi(Kasat) is a Assistant Professor in Electronics and Telecommunication

Department of Prof.Ram Meghe College of Engineering & Management,Badnera-Amravati. She completed her B.E.(Industrial Electronics) and M.E.(Electronics) from Dr.B.A.M.U, Aurangabad in 1999 and 2009 respectively. Her research interests are Power Electronics Systems, Artificial Intelligence and VLSI Design.

Dr. M. S. Ali is a Professor and Principal of Prof RamMeghe College of Engineering &