الفهرس 
ON-LINE STATIC UPS SYSTEMSOnly 14 pages are availabe for public view
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Abstract
The thesis is concerned with applying a convenient simulation technique for
studying the performance of an on-line static UPS system under different steady
state and transient conditions. The PSPICE simulation package is found to be a
convenient tool for simulating and analyzing on-line static UPS systems.
Each part of the UPS system is modeled and simulated as an individual
element. These submodels are then integrated to give the complete model of
the system. The modeling covers semiconductor power switches (Thyristors
and MOSFETS), power transformers, filters, batteries and sinusoidal pulse
width modulation (SPWM) generators. Feedback and feedforward controllers
are considered to regulate the output voltage and suppress the undesired low
order harmonics.
The steady state and transient performance of an on-line static UPS system
feeding a resistive load are analyzed. This includes the steady state
performance for normal as well as for standby operations. The transient
behaviour is determined for different cases; namely, transients from normal to
standby condition and vice-versa, the application of a sudden pulse spike
appearing in the normal supply, the application of a sudden short circuit in some
battery cells, and the application of a sudden load or short circuiting the load.
A computer load is also considered. The main requirements for a UPS
system feeding a computer load are discussed, and the reflection of the
computer load on the UPS performance is studied. By the help of simulation,
the effect of different UPS output waveforms on the crest factor and efficiency
is investigated. Different steady state and transient simulations are performed
to identify the behaviour and critical conditions that may encounter the
computer system fed from a UPS system under severe supply interruption
conditions and UPS transients.
The PSPICE simulation package is proved to be a very effective tool in
studying the steady state and transient behaviour of on-line static UPS systems
under different control strategies, with feedforward and feedback controllers,
and when feeding different types of loads. The simulation package provides the
time response as well as the frequency spectrum of the different system variables. It helps in investigating many features of UPS systems, such as total
harmonic distortion, voltage stabilization and regulation, and efficiency.