High-frequency multimegawatt polyphase resonant power conditioning

Abstract

High-frequency multimegawatt polyphase resonant power conditioning techniques have recently been realized as a result of key component developments, cooperative efforts, research and development funding contracts, and newly applied engineering techniques. The first generation 10-MW pulsed converter-modulators, implemented at Los Alamos National Laboratory, Los Alamos, NM, are now utilized for the Oak Ridge National Laboratory, Oak Ridge, TN, Spallation Neutron Source (SNS) accelerator klystron radio frequency amplifier power systems [1]. Three different styles of polyphase resonant converter-modulators were developed for the SNS application. The various systems operate up to 140-kV, or 11-MW pulses, or up to 1.1 MW average power, all from a direct current input of + 1.2 kV. The component improvements realized with the SNS effort coupled with new applied engineering techniques have resulted in dramatic changes in overall power conditioning topology. As an example, the 20-kHz high-voltage transformers are less than 1% the size and weight of equivalent 60-Hz versions. With resonant conversion techniques, load protective networks are not required.A shorted load de-tunes the resonance which results in limited power transfer. This provides for power conditioning systems that are inherently self-protective, with automatic fault "ride-through" capabilities. By altering and iterating the Los Alamos design, higher power and continuous wave power conditioning systems can now be realized with improved performance and flexibility. This paper will examine the SNS engineering data, briefly review the underlying theory of polyphase resonant conversion techniques, and apply this knowledge to future system topologies.

Repetitive Control for High-Performance Resonant Pulsed Power Supply in Radio Frequency Applications

“…Fig. 8 shows the locus curve of S(e jωTs ) with G f (z)=z 4 , Q(z)=0.95, and k RC =0.8 while the frequency varies. All the controller parameters are summarized in Table II.…”

“…The main advantages of soft-switching are low switching stresses and high conversion efficiency, while the high frequency operation ensures smaller volume and lighter weight of passive components. Moreover, low stored energy values and large voltage amplification ratios are also significant added values [4]- [6].…”

Redesign of the SNS modulator H-bridge for utilization of press-pack IGBTs

“…The modulator was originally designed to operate with pulse width modulation (PWM) to achieve a well-regulated output pulse. This has been demonstrated successfully at low pulse repetition rates, but failures have occurred at higher average powers [1].…”

“…There are several configurations of HVCMs at SNS with output voltages in the range of 75-125 kV, peak powers of up to 11 MW, and average powers up to 1 MW. These modulators were developed at Los Alamos National Laboratory and have been configured for application at SLAC and KAERI in addition to SNS [1][2][3].…”

“…A simplified system diagram is shown in Figure 1 and a detailed overview is found in [1]. Unfortunately, there have been an unexpectedly large number of failures of the HVCMs at SNS.…”