ADVANCED INVERTER CONTROL FOR UNINTERRUPTIBLE POWER
SUPPLIES AND GRID-CONNECTED RENEWABLE ENERGY
APPLICATIONS
By
Shuai Jiang
A DISSERTATION
Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of
Electrical Engineering – Doctor of Philosophy
2013
ABSTRACT
ADVANCED INVERTER CONTROL FOR UNINTERRUPTIBLE POWER SUPPLIES
AND GRID-CONNECTED RENEWABLE ENERGY APPLICATIONS
By
Shuai Jiang
The advancement of digital signal processors (DSPs) and programmable logic devices in
modern power electronics systems offer great control flexibility and capability, providing
attractive features particularly for applications in which complex control tasks are involved. This
dissertation investigates some DSP based advanced control algorithms for pulse-width
modulation (PWM) inverter applications, in particular, voltage regulated inverters connected
with AC loads and current regulated inverters connected with utility grids.
Uninterruptible power supply (UPS) is a typical example of voltage regulated inverter
applications. It is widely used to supply high quality, continuous and disturbance-free AC power
to critical loads such as medical equipments, computers and communication systems. A good
UPS system requires not only excellent steady state performances in terms of voltage regulation
and total harmonic distortions (THD) regardless of unknown load disturbances but also a fast
transient response during load step change.
In this dissertation, a three-phase four-wire AC-DC-AC double conversion UPS system is first
studied. Multi-loop control strategies are designed to regulate the system input currents, DC
voltages, and output voltages. Next, study will deep dive into a DC-AC three-phase UPS
inverter. A high performance repetitive controller (RC) for the voltage regulated three-phase
inverter is proposed. The proposed control algorithm can eliminate all the periodic distortions
and guarantees a high quality sinusoidal output voltage under unknown and severely distorted
loads. A novel 4th-order linear phase infinite-impulse-response (IIR) filter is first used in the RC
such that harmonic distortions up to the 19th order are rejected. In order to achieve fast response
during step load transient while still maintaining the low THD feature, a modified synchronousframe
approach with significantly reduced delay is later proposed and investigated.
Grid-connected inverters utilizing renewable energy sources (e.g., photovoltaic, wind, fuel
cell, etc.) are growing rapidly in recent years along with the constantly growing global demand
for electricity. A grid-connected inverter injects a synchronously regulated sinusoidal current to
the utility grid with required low THD and high power factor. Using an LCL filter in such a
system has been recognized as a small size low cost solution due to its -60dB/dec high frequency
attenuation. In this dissertation, a high-resonance-frequency LCL filter with minimal size and
cost requirement is designed. A proportional plus repetitive control hybrid strategy is then
proposed to achieve very low THD current regulation and high power factor.
FULL THESIS LINK:
http://etd.lib.msu.edu/islandora/object/etd%3A2193/datastream/OBJ/view
