Bandwidth oriented approach for the design of a PI controller for a three phase two-stage grid-connected PV system

ABSTRACT

The two-stage power converter is currently the most widespread topology for three-phase grid-connected photovoltaic (PV) systems. The PV power is injected to the grid through the regulation of the dc-link voltage. This method is commonly called the voltage control method, whereby the current is controlled indirectly. This paper focuses on the modelling of power converters and the parameter design of proportional-integral (PI) controllers, based on the bandwidth of the inner current loop and the outer voltage loop. It is assumed that the inner loop has a bandwidth that is ten-fold bigger than that of the outer loop, in order to fully decouple the dual loops. The PI parameters are thus determined through this relationship, and two sets of simulations are run to validate the methodology used. Results show that the controllers give highly satisfactory performance even in the presence of transients introduced by rapidly varying irradiance model.

KEYWORDS:

• Current loop
• voltage loop
• Park and Clark transformations
• pulse-width modulation
• voltage regulation

Abbreviations

FO-PI	=	fractional order proportional – integral
FRIT	=	fictitious reference iterative tuning
INC	=	incremental conductance
MPPT	=	maximum power point tracking
PCC	=	point of common coupling
PCU	=	power conditioning unit
PI	=	proportional−integral
P&O	=	perturb and observe
PSO	=	particle swarm optimisation
PV	=	photovoltaic
PWM	=	pulse-width modulation

Disclosure statement

No potential conflict of interest was reported by the authors.