Voltage regulation and reactive power support via photovoltaic inverters as a smart grid application

Date
2011
Authors
Morales, Emiliano
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Abstract

According to the U.S. Department of Energy, there has been a rise in reactive loads in the last 20 years; reactive loads from electronic devices have risen by 40% since 1980, and are anticipated to increase by 60% by 2015. To alleviate some of the burden, the continual increase of interconnected photovoltaic (PV) inverters to grids can beneficially be employed to provide reactive power (VAR) support. Current IEEE standards preclude the active regulation of voltage by PV inverters, eliminating the possibility of providing VAR support. As these standards are anticipated to be amended, the study of VAR support by PV inverters and other renewable resources has become an active area of research.

This Thesis is supported by two years of academic and one year of graduate research. Throughout the research, it was found that a PV inverter can be broken down into two main sections, the DC side (input control) and the AC side (output control). For the output side of the inverter, reactive power control by the use of the Synchronous Reference Frame Control method will be demonstrated, a method introduced first in [18] and employed in multiple papers. This Thesis demonstrates that the control of reactive power can be achieved by this method using the Specification of Smart Inverter Interactions with Electric Grids using International Electrotechnic Commission 61850 report [19]. It was also found that this was possible under response times a little over a 60 Hz cycle.

The second part of this Thesis showcases a demonstration of a converter capable of providing multiple operation modes to the input side control of an inverter, thus eliminating the need of multiple DC-DC converters. It is demonstrated that the proposed converter configuration can provide DC boosting actions, discharging, and charging to integrated battery storage systems. The energy storage system proves to be an essential medium to absorb and inject reactive power actively. Simulation models for both aspects of PV inverters as VAR supporters were conducted using MATLAB's Simulink. Plots that demonstrate the feasibility of this approach were also provided using MATLAB.

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Keywords
Power Electronics, PV Inverters, Reactive Power, VAR
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Department
Electrical and Computer Engineering