A review of power electronics equipment for all-electric ship MVDC power systems

Typical radar transmitter signals are frequency-modulated with pulsed constant-amplitude envelopes in order to optimize radio-frequency power amplifier (RFPA) efficiency, which results in spectral broadening and power radiated outside of the radar frequency band. This problem can be alleviated by using an appropriately shaped pulse envelope, provided that high-efficiency operation of the radar transmitter is maintained. This paper introduces a pulse-shaping power supply for RFPAs in radar transmitters which enables high efficiency while reducing the spectral emissions. The pulse-shaping power supply is a simple switched resonant circuit capable of approximating a Gaussian pulse envelope waveform. Operating principles are presented and a state-plane-based design approach is described for the resonant pulse-shaping power supply, which enables improved waveform quality and efficiency. An experimental prototype with efficiency greater than 90% is used to supply a 2.14-GHz GaN RFPA. The RFPA efficiency of up to 76%, overall transmitter efficiency of up to 67%, and output signal having high spectral purity demonstrate feasibility of a high-efficiency, high-performance radar system.

Resonant Pulse-Shaping Power Supply for Radar Transmitters

The final radiofrequency power amplifier (PA) of a radar transmitter module is a large factor in system efficiency. Typical radar transmitter signals are frequency-modulated with constant-amplitude pulse envelopes in order to optimize efficiency, resulting in spectral broadening and power radiated outside of the radar frequency band. This paper demonstrates a PA with a dynamic power supply which enables high efficiency while reducing the spectral emissions. The resonant pulse-shaping power supply generates a raised-cosine pulse envelope waveform with efficiency greater than 90% and peak envelope power around 6 W. Measured results with a 2.14-GHz GaN power amplifier with an efficiency of 76% at peak power demonstrate over 67% transmitter efficiency.

Resonant pulse-shaping power supply for radar transmitters

In a conventional linear-control design of a higher order power-electronic system (PES), the gains of the control laws are typically determined by small-signal analysis of the averaged model of the PES. The closed-loop control of such a PES (driving a pulsating load that periodically shifts the equilibrium) using its small-signal model is often found to be unsatisfactory with regard to the overall stability and performance. To address the challenges in control design for a PES driving such a nonlinear time-varying pulsating load, this paper delineates an optimal switching-sequence-based control (SBC) scheme, which applies stability-bound switching sequence(s) to the PES. A novel method has been formulated to ensure the reachability of the PES dynamics based on its switching sequence in terms of the time horizon of the switching sequence and the allocation of this time among the switching states of the same switching sequence. This is ascertained by modeling the PES and the pulsating load as a nonlinear map and then using this map and multiple Lyapunov functions determined by solving a set of linear-matrix inequalities corresponding to each of the switching states of a given switching sequence. It has been further shown that the knowledge of the stability bounds of a reachable switching sequence helps in reducing the online computation time for optimal SBC associated with solving the optimization problem by reducing the overall search space. Finally, to validate the optimal SBC, an experimental GaN-FET-based 100-kHz  Cuk-PES has been fabricated and tested on a pulsating load. The overall SBC is implemented on a low-cost TMS320F28335 DSP, which also implements an observer to preclude the need for plurality of sensors for the higher order Cuk-PES. The overall performance of the SBC is found to be satisfactory under varied dynamical conditions.

Switching-Sequence Control of a Higher Order Power-Electronic System Driving a Pulsating Load

The operation and circuit analysis of a three-phase inductor converter bridge (ICB) is described. The ICB is used to transfer energy between two superconducting coils and may find application in future tokamak fusion power reactors and large particle accelerators. This circuit provides an efficient, controllable, and reversible means for energy transfer.

Three-Phase Energy Transfer Circuit with Superconducting Energy Storage Coils

There is a growing need for supplying repetitive pulsed power loads of increasing magnitudes up to several hundred megawatts or more in areas of radar, lasers, high-energy physics experiments and thermonuclear fusion. The nature of such loads can be expected to be as diverse as their applications. The pulsed power demands and corresponding reactive volt-amperes requirements are undesirable from the frequency and voltage fluctuation standpoint, even for the large utility power systems. Techniques for supplying large dc-pulsed loads from a relatively small size ac generator by means of inductive storage and the capacitor commutated converters are presented. A theoretical basis is provided for analyzing the converters which serve to minimize the effects of pulsed power and corresponding reactive volt-amperes. Energy transfer between the storage inductor and the pulsed load is permitted with minimal loss, at a readily controllable rate including the reversibility of power in case of inductive loads. Use of a simple control scheme is shown to provide a precise load voltage regulation which may be a requirement for certain applications. The greatest use of these circuits would be in supplying loads with pulse durations of a few milliseconds to many seconds or minutes.

J. Thomas Broach

Papers

Converters for Supplying Pulsed Power Loads