Loren H. Walker

10 MW GTO converter for battery peaking service

The description is given of a bidirectional 18-pulse voltage source converter utilizing gate turn-off thyristors (GTOs). The converter, which is rated at 10 MVA, has been placed in service to connect an energy storage battery to a utility grid. The converter is rated and controlled to operate in all four quadrants (discharge, charge, leading VArs, or lagging VArs) at the full 10 MVA rating. It is capable of independent, rapid control of real and reactive power with a transient response of 16 ms to changes in commanded value of real or reactive power. Thus it is usable as a reactive power controller (static VAr control), voltage control, frequency control, power system stabilizer, or as a real power peaking station. The author describes the design, construction, control, and application of the converter, and gives performance data taken at the installation.<<ETX>>

Symmetrical GTO current source inverter for wide speed range control of 2300 to 4160 volt, 350 to 7000 hp, induction motors

A line of variable-speed 2300-4160 V, 350-7000 hp induction-motor drives for either fan or constant torque load applications is described. The drives are current-sourced, consisting of one or two six-pulse thyristor phase-controlled source converters in series, a DC link reactor, a six-pulse, symmetric-GTO (gate-turn-off), load inverter, a three-phase load capacitor in parallel with the induction motor. The drive features a wide speed range of operation, high inverter efficiency, and good motor current and voltage waveshape over the speed range.<<ETX>>

Force-Commutated Reactive-Power Compensator

A reactive-power compensator (RPC) is a type of static var compensator (SVC) that is used to dynamically correct power factor to prevent voltage variation (flicker) in ac power sources due to large dynamic loads. It also minimizes total source current. Thus the application of an RPC or SVC to a load may allow addition of substantial new load to existing feeders or substations. A reactive-power compensator suited to industrial ratings (1.0-25 MVA) is described. It utilizes a force-commutated current-source bridge to provide both leading and lagging reactive power. The ability to operate both leading and lagging can reduce by 2:1 the ratings of the RPC itself and the capacitors and magnetics associated with it. The characteristics of the power circuit, the means used to control it, and the resulting dynamic performance is described. Speed of response compares favorably to the thyristor-controlled reactors now in common use as SVCs at higher MVA ratings. This RPC is suited to compensate any balanced three-phase dynamic load.

A High-Performance Controlled-Current Inverter Drive

A production variable-frequency drive is described which uses an induction motor and a controlled-current inverter. The control loops of the drive have been arranged so that the performance of the drive is extended to zero speed and to the theoretical upper limit speed. Operating modes include torque smoothing by programmed dc link current, pulsewidth modulated (PWM) current shaping, and flux-controlled constant horsepower operation.

Design and Control Techniques for Extending High Frequency Operation of a CSI Induction Motor Drive

An investigation of the maximum speed capability of a current source inverter (CSI) drive in both a three-and a six-phase connection is presented. It is shown that a six-phase configuration has distinct advantages over a three-phase connection in high speed capability for the same peak motor spike voltages. In addition, with proper control of the firing pulses fed to the inverters supplying the six-phase machine, the speed range can be substantially extended beyond the maximum limit predicted using conventional control. Predicted analytical results are correlated with results obtained by a detailed hybrid computer simulation.

Application Factors Affecting the Weight of Aerospace Static Inverters

The purpose of this paper is to reconcile the wide range of weights quoted for aerospace static inverters of the same VA rating. The inverters discussed are of conventional input and output: 15 to 500 vdc input and 400 cps sine wave output. Specification and application factors affecting inverter weight are tabulated. Graphical relationships are given for the effects of some factors for which relationships can be defined. Trends are indicated for the weight effect of factors for which graphical relationships are not given. The data presented should be useful to systems designers, in avoiding undue inverter weight, by proper specification and application of static inverters.