Improving the power quality performance for distributed power generation

The main aim of this paper is to analysis and improve the power quality (voltage sag, swell and harmonics) performance of smart grid connected inverter used in distributed generation. The structure of the designed controller consists of outer power with harmonic control loop, middle voltage control loop and inner current control loop for real and reactive power control in dq reference frame. The operation of the controller is investigated for varying power demands with linear and nonlinear loads from the customer side and for varying smart grid impedance along with varying distributed generation source voltage. An increase in reactive power demand at PCC would affect the system power factor at PCC. The conventional type PI controller for such change in customer load and variation of smart grid impedance do not exhibit a satisfactory dynamic behaviour. Alternatively, the proposed controller simultaneously computes current dynamics and harmonics of the parameters for generating the control reference values to meet the current additional reactive power requirement with reduced total harmonic distortion and is used as new reactive power reference value for power controller. The state space model of the proposed controller is developed. The simulation results clearly indicates that the developed controller is able to maintain constant voltage at the point of common coupling (PCC) and exhibits good dynamic response for varying smart grid impedance and dynamic load changes besides nullifying the effect of voltage swell, sag and harmonics at PCC. The comparisons have been made with the conventional SVPWM based PI controller employed for the same hybrid scheme with the proposed controller. The results clearly bring out suppleness of the proposed scheme.