Reduction of the ripple in the current of a three-phase PV
inverter connected to the grid by using PR controller
Ahmed Althobaiti, Matthew Armstrong and Basher Zahawi
Department of Electrical and Electronic Engineering, Newcastle University
Newcastle upon Tyne, U.K
Ahmed.althobaiti@ncl.ac.uk
The fast dispersion of using renewable energy source and DG system has been boosted power
photovoltaic converter to the distribution network. The photovoltaic three phase inverter (PV) and
its control system are the main parts of the grid connected VSCs. In addition, one of the most
common issues in the PV grid connected inverter is harmonic distortion. This leads the
implementers to imply the standard requirement such as IEEE Standard 519 and 1547 which
requires a maximum of 5% from total harmonic distortion (THD )[1, 2]. Recently, many control
technique of PV grid inverters have been proposed in the literature.
The most common controller used in grid connected inverter is the conventional proportional and
integral (PI) controller with grid voltage feed-forward [3] [4]. This method is based on d-q
rotating reference frame by using Park transformation. As a result, this concept converts the threephase sinusoidal signals to d.c constant values. Therefore, PI controller is implemented to
eradicate the error between the measured and actual values. PI controller has many advantages
such as being easy to implement in the control system. Moreover, controlling and filtering can be
obtained. However, PI futures have some weaknesses as :


PI regulator may not track a sinusoidal reference devoid of steady state error.
d-q coordinates has cross-coupling between the d and q currents and this needs to be
decoupled and this makes it complicated to design the system.
To overcome with the drawback of PI controller, an alternative solution has been used a
proportional Resonance controller (PR) in the stationary reference frame current control method
[5]. PR controller has many advantages such as:

No need to implement the phase angle of the grid voltage as well as phase voltage to the
reference current waveform.

Currents in α-β coordinates are not necessary to be decoupled.
References:
[1]
"IEEE Standard for Interconnecting Distributed Resources With Electric Power Systems," IEEE Std 1547-2003, pp.
0_1-16, 2003.
[2]
"Draft Application Guide for IEEE Standard 1547, Interconnecting Distributed Resources with Electric Power
Systems," IEEE Unapproved Draft Std P1547.2/D10, Mar 2008, 2008.
[3]
R. K. M. Kazmierkowski, F.Blaabjerg, Control in Power Electronics. Selected Problems: ISBN 0-12- 402772-5., 2002.
[4]
C. Cecati, A. Dell'Aquila, M. Liserre, and V. G. Monopoli, "Design of H-bridge multilevel active rectifier for traction
systems," Industry Applications, IEEE Transactions on, vol. 39, pp. 1541-1550, 2003.
[5]
R. Teodorescu, F. Blaabjerg, U. Borup, and M. Liserre, "A new control structure for grid-connected LCL PV inverters
with zero steady-state error and selective harmonic compensation," in Applied Power Electronics Conference and Exposition,
2004. APEC '04. Nineteenth Annual IEEE, 2004, pp. 580-586 Vol.1.