The doubly-excited machine can be used as a variablespeed
generator or as a variable-speed-drive motor. In
this thesis the focus is on the aspects associated with
generating electric power (real and reactive) from erratic
energy resources such as water or wind. In such cases,
the power input to the prime...
An important task of a Variable Speed Generation (VSG)
system is the capability to maintain and control the terminal
voltage at some desired value as determined by the
reactive power dispatch strategy.The main objective is to
design a sub-optimal fixed-parameter controller in the
sense that constraints with respect to practical...
An EMCON-D distributed process controller is evaluated
for control and monitoring of an experimental doubly-fed
machine system. A closed-loop control circuit is
implemented to operate the doubly-fed machine with
constant rotor current. A standard PID algorithm as well
as an algorithm tailored to the doubly-fed machine are
evaluated.
With the introduction of high speed semiconductor power devices and the
increased application of adjustable speed drives (ASDs) for efficient speed control of ac
motors, there has been a growing number of costly motor-drive related process failures. It
has been found that the high dv/dt and high switching frequency have...
With the development of high performance power electronic and semiconductor technologies, Adjustable Speed Drive (ASD) systems are increasingly applied in residential, commercial and industrial applications. Due to the advantages at higher power ratings, the three-level Neutral-Point-Clamped (NPC) Voltage Source Inverter (VSI) is being employed in industrial and traction applications, static...
The continuing desire of industry to further improve process efficiency,
through tighter control and energy conservation, has prompted users to pay closer
attention to Adjustable Speed Drives (ASDs). The conventional ASDs consist of
induction or synchronous motors controlled by power electronic controllers through
the adjustment of supply frequency and line...
The awareness of electric power quality has increased over the past decade as electronic equipment
has become more susceptible to power disturbances. The most disruptive power disturbances are voltage
sags and momentary interruptions and their effect on adjustable speed drives (ASDs) is studied in this
thesis.
Several solutions have been...
Use of conventional induction machines (IM) in adjustable
speed drives (ASD) has increased in recent years. Electronic
power processing has facilitated this increased use. The IM
is an inexpensive and robust machine, but when used as part of
an ASD, the cost of the system increases due to the inclusion...
A new and improved stabilizer was developed for the variable speed generation (VSG) system. The VSG system exhibits periodic oscillations which sometimes leads to a loss of synchronism. After careful study, a simple but effective strategy to stabilize the system was implemented with real time digital feedback control. The VSG...
This thesis presents both an analysis and simulations of a passively controlled variable-speed generator system, which can be applied for renewable energy sources such as wind turbines. Parallel connected passive/external resistors and inductors are connected to the slip rings of a wound rotor induction machine to provide an acceptable speed...
Generation of electricity from the wind is becoming increasing popular as an
environmentally responsible resource. Current methods for generating electricity from
the wind involve the use of fixed-speed generators. However, the use of variable-speed
generators increases the amount of energy that can be extracted from the wind.
Most variable-speed technologies...
With the increased attention on high efficiency and controllability of industrial processes, as well as reduced weight, volume and cost of consumer products, the applications of nonlinear power electronic converters such as adjustable speed drives (ASDs) are showing a rapid rise. Power Quality (PQ) is becoming an increasing concern with...
Recent opportunities for new hydropower generation in the United States have often been in non-powered dams and run-of-river type flows occurring in low-impact natural areas and unregulated conduits. At the same time, a changing water resource paradigm is challenging some existing generation in drought stricken areas where supply reservoirs behind...
Modern variable speed machine drive (VSMD) systems are used for a variety of purposes including generation, propulsion, pumps and compressors. They employ high switching frequency power electronics to drive the electric machine. The machine is subject to large voltage overshoot if long power cables, are used, called Reflected Wave Phenomena...