Active power coefficient control for grid-tied photovoltaic system under voltage distortions

ABSTRACT

Grid-integrated solar photovoltaic (GSPV) system requires a simpler and computationally less intensive control algorithm for continuous maneuver of real power inoculation and power quality enhancement underneath diverse operating conditions. In order to reduce the computational burden, this article presents an active power coefficient (APC)-based control strategy for extracting the fundamental weight factor. The proposed structure utilizes only three mathematical operators for weight extraction, and thereby reduces the computational burden. Therefore, only 35 µs sampling time is required to implement the proposed control through low-cost ARM cortex M4-based microcontroller. As a result, the proposed control provides following advantages: 1) faster response 2) lesser current distortions, 3) lesser DC-link oscillations, and 4) lower implementation cost. Moreover, the improved linear time invariant-enhanced phase look loop (LTI-EPLL) structure is also proposed for synchronization of GSPV system. This structure accurately trails the phase angle and frequency of voltage signals despite the presence of DC component and harmonics. Besides, the amplitude estimation loop removes the dependency of supply magnitude from unit template. Further, the proposed APC algorithm and synchronizing control is designed in waijung environment of MATLAB/Simulink for testing various operating conditions. Finally, the total harmonic distortion of source current is remarkably decreased to 1.67%, which is well within the limits of IEEE 519 standard.

KEYWORDS:

• – Solar photovoltaic system
• power conditioning
• active power coefficient
• LTI-EPLL
• microcontroller
• waijung environment

Nomenclature

GSPV	=	Grid-integrated solar photovoltaic
SPV	=	Solar Photovoltaic
VSC	=	Voltage source converter
APC	=	Active power coefficient
PQ	=	Power quality
UPF	=	Unity Power Factor
PLL	=	Phase locked loop
LTI-EPLL	=	Linear time invariant-enhanced phase locked loop
PL-EPLL	=	Pseudo linear-enhanced phase locked loop
SRF	=	Synchronous reference frame
LPF	=	Low pass filter
SOGI	=	Second order generalized integrator
IGBT	=	Integrated bipolar junction transistor
PCC	=	Point of common coupling
ADC	=	Analog to digital controllers
MPPT	=	Maximum power point tracking
THD	=	Total harmonic distortion
$K,G_a$	=	Conductance coefficient and equivalent conductance of phase ‘a’
$v_{Sa},v_{Sb},v_{Sc}$	=	Phase voltages of three-phase system
$i_{Sa},i_{Sb},i_{Sc}$	=	Source currents of three-phase system
$i_{La},i_{Lb},i_{Lc}$	=	Load currents of three-phase system
$i_a,i_b,i_c$	=	Three phase inverter currents
$u_{pa},u_{pb},u_{pc}$	=	In-phase unit vector templates for utility voltage
$L_S,L_f$	=	Source side conductance and interfacing inductor
$V_{DC},V_{D{C}_r},V_{DC}^{\ast }$	=	DC-link voltage, generated DC-link voltage error and reference DC-link
$I_{PV},V_{PV},P_{PV},G$	=	PV current, PV voltage, PV power and solar irradiance
$i_{Sa}^{\ast },i_{Sb}^{\ast },i_{Sc}^{\ast }$	=	Three-phase reference currents
$V_{sw},I_{sw}$	=	Voltage and current ratings of semiconductor switches
$V_{ab},V_{bc},V_{ca}$	=	Line voltages of three-phase system
$V_S$	=	Magnitude of PCC voltage
$K_{ploss},K_{iloss}$	=	Gain parameters of PI controller
$w_{DC},w_{sp},w_{pv}$	=	Loss component, average active weight component, and PV array weight component
$w_{pa},w_{pb},w_{pc}$	=	Active Weight components of three-phase system
$P_S,Q_S,P_{MPP}$	=	Source active power, source reactive power, and maximum PV power
$PF$	=	Power factor

Additional information

Notes on contributors

Ajay Kumar

Ajay Kumar was born in Bhiwani, India, 1989. He received the B.Tech. degree in electrical and electronics engineering in 2012 from Kurukshetra University, Kurukshetra, India, and the M.Tech. degree in power systems in 2016 from the Malaviya National Institute of Technology Jaipur, Jaipur, India, where he is currently working toward the Ph.D. degree with the Department of Electrical Engineering. His areas of interest include power quality, custom power devices, renewable integration, and application of power electronics in the power system. He is a Student Member of IEEE.

Nirav Patel

Nirav Patel acquired his B.E. degree in Electrical Engineering from Parul Institute of Engineering and Technology (Presently Parul University), Vadodara, India, in 2014. He holds M.Tech degree in Electrical Power Systems from Institute of Technology, Nirma University, Ahmedabad, India, in 2016. Since 2017, he has been working toward his Ph.D. degree in the Department of Electrical Engineering, Malaviya National Institute of Technology Jaipur, India. His research interests are in the areas of Distributed Generation, Integration of Renewable Energy Sources, Power Quality Assessment and Improvement, and related fields. More specifically, his research spans theory and control structures of an electronically interfaced multifunctional photovoltaic (PV) system, with applications to science and technology. One line of his recent work emphasizes the theme of renewable energy integration (control structure development, hardware testing, and result analysis). In general, he spends his time developing new controllers for acquiring the efficient operation of the grid-integrated PV system. He is a Student Member of IEEE and Life Member of ISTE.

Nitin Gupta

Nitin Gupta received the graduate degree in electrical engineering from Government Engineering College, Kota, India, in 2000, the M.E. degree in power electronics from the College of Technology and Engineering, Udaipur, India, and the Ph.D. degree in electrical engineering from the Indian Institute of Technology Roorkee, Roorkee, India, as a full-time research scholar under MHRD in 2012. He is currently an Assistant Professor with the Department of Electrical Engineering, Malaviya National Institute of Technology Jaipur, Rajasthan, India. He has guided four Ph.D. theses and eight M.Tech dissertations. He is a reviewer of several international journals and international conferences. His areas of interest include power electronics and drives, power quality, renewable energy grid integration, APFs, and multilevel inverters. He is a Member of IEEE.

Vikas Gupta

Vikas Gupta (M’ 15)received his B.E. (electrical) from University of Jodhpur in 1979; his M.S. in electrical engineering from University of Saskatoon, Canada, in 1984; and his Ph.D. in 1992 from University of Rajasthan, India. In 1985, he joined the Department of Electrical Engineering, Malaviya Regional Engineering College, Jaipur (presently MNIT, Jaipur), as a lecturer. Presently he is a professor in the Department of Electrical Engineering, MNIT, Jaipur, India. His research interests include power system dynamics, electrical machines, drives and non-conventional energy sources.

B. Chitti Babu

B. Chitti Babu received the Ph.D. in Electrical Engineering from National Institute of Technology Rourkela, India in 2012. He had been with National Institute of Technology Rourkela, India as an Assistant Professor in the Electrical Engineering Department from 2007 to 2013. Subsequently, he had two post-doc research appointments with Wroclaw University of Science & Technology, Poland from Dec 2013- June 2014 and VSB-Technical University of Ostrava, Czech Republic from Sep 2014 to Sep 2015 and both the appointments have been sponsored by European Commission, the U.K. In September 2016, he was appointed as an Assistant Professor in the department of electrical & electronics engineering, The University of Nottingham Malaysia Campus, Malaysia. His research interests include power electronics applications in smart distribution grid containing renewable energy sources and low-power electronics design, including photovoltaic energy systems.