International Journal of Modern Research in Engineering & Management (IJMREM) ||Volume|| 2 ||Issue|| 4 ||Pages|| 07-12 || April 2019 || ISSN: 2581-4540
PID Controller for DC-DC Boost Converter for Photovoltaic Power Generation Zoya Hanif1 , Prof. Dr. Syed Asif Ali Shah2 1,
Student M.E. (Electrical Power) IICT, Mehran UET Jamshoro; 2, Professor, Electrical Engg. Mehran UET, Jamshoro
----------------------------------------------------------ABSTRACT-----------------------------------------------The output voltage of solar energy systems or rectifier converter is basically unregulated DC voltage. DC-DC Boost converter is used to provide stable output DC voltage. In this research work, PI controller proposed for Boost converter having solar pv as input. DC-DC Boost converter has switching transients resulting in harmonics generation and switching losses. Proposed system is simulated using MATLAB SIMULINK to observe its performance. Simulation results shows that system has low overshoot and settling time for initial transient supply and load variations. INDEX TERMS: Photovoltaic Generation, DC-DC Boost Converter, PID Controller -------------------------------------------------------------------------------------------------------------------------------------- Date of Submission: Date, 02 January 2019 Date of publication: 15. April 2019 ----------------------------------------------------------------------------------------------------------------------------- ----------
I.
INTRODUCTION
Energy is important in improving living standard of nation. Economic growth of a country is also dependent on its energy status. Renewable energy resources are available naturally in abundance to fulfil energy demand of the country [1]. Renewable energy is produced and continually replenished from earth’s natural process. Renewable energy is sustainable & inexhaustible; it is available in infinite supply & can’t be depleted. Solar Photovoltaic (PV) cells are considered as most commonly used renewable energy source. It offers simple installation and low cost for small power applications [2]. PV power generation is dependent upon weather condition and solar irradiance therefore nonlinear PV output needs to be controlled to be supplied to loads. Solar PV cell output is dependent on temperature and solar irradiance hence its output varies with operating conditions [3]. DC-DC converters are connected with solar power generation to obtain a fixed SC voltage. DC-DC converters are used to step-up, step-down and regulate the output voltage. In this research work DC-DC Boost Converter is employed to get regulated output voltage. Boost converter is basically a switch mode power regulator which steps up the input voltage to get the higher output voltage in DC [4]. The frequent use of boost converter is due to its high efficiency, compact size as well as low cost. Any boost converter consists of the same components which includes two switches, metal oxide semiconductor field effect transistor (MOSFET) and di electrode (Diode), inductor and capacitor [5]. In this proposed system PI Controller is added to the Boost converter which has values of kp and ki as 0.25 and 6.25 respectively. Where subsystem block “Boost” has equation model of boost converter in it. The reference voltage is compared by the output voltage that generates an error signal which is then controlled by the PI controller which in turn is compared with repeating sequence signal having the frequency of 100 kHz by relational operator to generate Pulse width modulation (PWM) signal to provide gate pulses to the gate of MOSFET to control output voltage [6]. In this research work, PI controller is proposed for boost converter having solar PV as input and interfaced the output by comparing and controlling the errors during operation to get regulated voltage at the end. Proposed system is simple and easy with reduced size and cost.
II. SYSTEM DESCRIPTION Proposed system consists of DC-DC Boost Converter. Block diagram of the system is shown in Fig. 1. PV array is connected as an input to the DC-DC Boost converter with the output voltage of 12 volts and output current of 6 Amps. DC-DC Boost converter is having output of 24 volts. Outputs of the generation resources are regulated through DC-DC boost converters and connected to a load of 100V. P controller is added with the values of Kp and Ki as 0.25 and 625 respectively which compares it with the repeating sequence signal and eliminating the error.
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PID Controller for DC-DC Boost Converter for Photovoltaic‌
Fig.1 Block diagram of DC-DC Boost converter with PI controller is shown
III. RESEARCH METHODOLOGY Proposed system is developed in MATLAB/SIMULINK@ 2016(a) as shown in Fig: 2. Simulation of PV array and DC-DC Boost converter is interfaced to analyze performance of the proposed model. PV model was developed in MATLAB/SIMULINK while developing different sub systems. Input parameters of PV are temperature and irradiance and model generates output voltage and output current of PV module according to these input parameters. As the output of PV is variable in terms of voltage and current hence DC-DC Boost converter is used at the output terminals of PV to increase its voltage to 100V. Boost converter performs function of voltage regulator. Also, voltage is increased to desired level for utilization of heavy loads and better transfer of power over distribution line reducing its voltage drop and power losses. DC-DC converters are controlled though PI controllers. Block diagram for the control scheme implementation for Boost converter is shown in Fig. 3. The error signal between output voltage and reference voltage is proceed through PI controller so to control PWM pulse is generated. By eliminating settling and overshoot time of the voltage with load and line variations such as when load voltage varies from 12 to 15 volts and load varies from 6 to 10 ohms. Provides basic results by comparing and eliminating the errors to the output voltage. Suitable results are shown in the figures below.
Fig 2. Simulation model of the system
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PID Controller for DC-DC Boost Converter for Photovoltaic…
Fig 3. Boost converter with proposed PI controller
IV.
RESULTS AND DISCUSSIONS
In this paper performance of PI controller with DC-DC Boost converter system under normal steady state operation is analyzed. Proposed system with its individual controller is simulated using MATLAB/SIMULINK. Fig. 4 shows waveform for PV voltage at start, Boost voltage and Boost output voltage steady state ripples. Fig 5 shows boost inductor current and its steady state ripples at start. Fig 6 shows voltage and Inductor current when input voltage changes from 12V to 9V. Fig 7 shows voltage and Inductor current when input voltage changes from 12V to 15V. Fig 8 shows Voltage and Inductor Current Response to load i.e; 8 to 6 Ω) and fig 9 shows Voltage and Inductor Current Response to load i.e; 8 to 10 Ω). The overshoot and settling time is decreased as load varies.
30
Overshoot= 3.15V Boost Output Voltage (V)
25
20
Settling Time= 2 ms 15
10
5
0
0
0.002
0.004
0.006
0.008
0.01
0.012
0.014
0.016
0.018
0.02
Time (s)
Peak to Peak Voltage= 0.3V Boost Output Voltage (V)
24.15
24.1
24.05
24
23.95
23.9
23.85
5.55
5.6
5.65
Time (s)
5.7
5.75
5.8 -3
x 10
Fig 4 a) PV cell output voltage b) Boost voltage at start c) Boost voltage steady state ripples
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PID Controller for DC-DC Boost Converter for Photovoltaic‌ 10 9
Overshoot= 3.2 A Boost Inductor Current (A)
8 7 6 5
Settling Time= 1 ms
4 3 2 1 0
0
0.002
0.004
0.006
0.008
0.01
0.012
0.014
0.016
0.018
0.02
Time (s)
Peak to Peak Current= 1.2 A
Boost Inductor Current (A)
6.06 6.04 6.02 6 5.98 5.96 5.94 5.92 5.9 0.0114
0.0115
0.0115
0.0116
0.0116
0.0117
0.0117
0.0118
0.0118
Time (s)
Fig 5 a) Boost inductor current at start b) Boost inductor current steady state ripples 26
24
Output Voltage 22
Voltage (V)
20
18
16
14
12
Input Voltage 10
8 0.009
0.01
0.011
0.012
0.013
0.014
0.015
0.016
0.017
0.018
0.019
Time (s) 7
6.5
Inductor Current (A)
6
5.5
5
4.5
4
3.5 0.009
0.01
0.011
0.012
0.013
0.014
0.015
0.016
0.017
0.018
0.019
Time (s)
Fig 6 a) Boost output voltage b) inductor current output when input voltage changes from 12-9 26
24
Output Voltage
Voltage (V)
22
20
18
16
Input Voltage
14
12 0.009
0.01
0.011
0.012
0.013
0.014
0.015
0.016
0.017
0.018
0.019
Time (s)
14
Inductor Current (A)
12
10
8
6
4
2
0.009
0.01
0.011
0.012
0.013
0.014
0.015
0.016
0.017
0.018
0.019
Time (s)
Fig 7 a) output voltage b) inductor current output when input changes from 12-15 v
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PID Controller for DC-DC Boost Converter for Photovoltaic‌ 26
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Output Voltage 22
Voltage (V)
20
18
16
14
12
Input Voltage 10
8 0.009
0.01
0.011
0.012
0.013
0.014
0.015
0.016
0.017
0.018
0.019
Time (s)
7
6.5
Inductor Current (A)
6
5.5
5
4.5
4
3.5 0.009
0.01
0.011
0.012
0.013
0.014
0.015
0.016
0.017
0.018
0.019
Time (s)
Fig 8 a) Output voltage b) inductor current when load changes form 8-6 ohms 7
6.5
Inductor Current (A)
6
5.5
5
4.5
4
3.5 0.009
0.01
0.011
0.012
0.013
0.014
0.015
0.016
0.017
0.018
0.019
0.017
0.018
0.019
Time (s) 24.5
24.4
Output Voltage (V)
24.3
24.2
24.1
24
23.9
23.8 0.009
0.01
0.011
0.012
0.013
0.014
0.015
0.016
Time (s)
Fig 9 a) Output voltage b) inductor current load changes from 8-10 ohms V. CONCLUSIONS Boost converter has switching transients and fails to maintain constant output voltage under line and load variations. DC-DC Converters have high efficiency and extensively used in power system. In this paper, PI controller with DC-DC Boost converter is analyzed through simulation using MATLAB/Simulink@ 2016(a). PID controller realizes a better output voltage tracking with minimal overshoot, small steady state error, short settling time and improved converter efficiency. VI. ACKNOWLEDGEMNTS Authors are thankful to Mehran University of Engineering & Technology Jamshoro for providing necessary resources for carrying this research work.
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PID Controller for DC-DC Boost Converter for Photovoltaic… REFERENCES [1]
[2] [3]
[4]
[5]
[6]
Ortiz, G., J. Biela, D. Bortis, and J. W. Kolar. "1 Megawatt, 20 kHz,isolated, bidirectional 12kV to 1.2 kV DC-DC converter for renewable energy applications." In Power Electronics Conference (IPEC), 2010 International, pp. 3212-3219. IEEE, 2010. Muthurkrishan P, Dhanasekaran R, DC-DC Boost Converter for Solar Power Application” Journal of Theoretical and Applied Information Technology, Volume.68, no. 3, pp. 630-636,2014. Ponnian, Armarashid and M.S.A Fatah (2009) “DC-DC Boost Converter design for Solar electric System”. International Conference on Instrumentation, Control and Automation Bandung, Indonesia. Pp 1-10 Guo L, Hung JY, Nelms RM. “PID controller modifications to improve steady state performance of digital controllers for buck and boost converters”, In IEEE Seventeenth Annual IEEE Applied Power Electronics Conference and Exposition, APEC, Dallas, TX, 2002. Vol 1, pp.381-388. Kumar P, Parimi A.M, Rao Uma K. “Performance Analysis of a Two-Diode model of PV cell for PV based generation in MATLAB”, International Conference on Advanced Communication Control and Computing Technologies (ICACCCT), Ramanathapuram 2014 May 8-10, pp. 68-72 Kumar, J. Sai, and Tikeshwar Gajpal. "A Multi Input DC-DC Converter for Renewable Energy Applications." (2016).
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