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Date of Award

2017

Document Type

Campus Access Master's Thesis

Degree Name

Master of Science in Electrical Engineering (MS)

Administrative Home Department

Department of Electrical and Computer Engineering

Advisor 1

Seyyedmohsen Azizi

Advisor 2

Saeid V Nooshabadi

Committee Member 1

Sumit Paudyal

Committee Member 2

Mahdi Shahbakhti

Abstract

Distributed generation (DG) systems are getting progressive popularity due to their environmental friendly features, flexible modes of operation, and capability to work in remote areas. Renewable energy sources such as photovoltaic (PV) cells and wind turbines (WT) need power electronic inverters to connect to the utility grid for power transmission. Normally in a local area, multiple DG units from different renewable energy sources connect to the utility grid in the same location, which calls for reliable and robust control algorithms to cooperatively control and balance the power sharing among the DG units. In this thesis, a multi-level hierarchical control algorithm is proposed to regulate the power generation by multiple DG units, while the noises and disturbances including current harmonics (due to nonlinearities) and resonance frequency (due to higher order filters) are attenuated and rejected. Three cascaded (nested) control loops are designed, namely, inner loop, middle loop, and outer loop. The inner loop is the current control loop which includes a proportional-resonant (PR) controller to track the reference current signal by generating the input signal for the pulse width modulation (PWM) module, which actuates the power electronic switches. The middle loop is the power control loop which includes a proportional-integral (PI) controller to track the reference power signal by generating the reference current signal for the inner loop (current control loop). The outer loop is the consensus control loop which includes a consensus algorithm to balance the power sharing among DG units based on their maximum power capacity by generating the reference power signal for the middle loop (power control loop). Simulations are conducted in Matlab/Simulink for the case of single-phase grid- xvii connected DG units. The simulation results confirm the effectiveness of the proposed multi-level hierarchical control algorithm.

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