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Three-Phase Resonant Link Power Converter
Summary: The client was working on a U.S. Department of Energy research grant, using their existing patent, to improve the efficiency and size of three-phase power converters to be used, at least initially, to connect windmills to the electric power grid. They had the preliminary design completed and had selected the target hardware, but they needed to complete the project with embedded software.
The control system consisted of a fast inner loop running at approximately 50 kHz and a slower outer loop running at approximately 1.2 kHz. The inner and outer loops were updated based on the period of the system waveforms, which were detected by each processor. The workings of the inner loop were based on the theory of a resonant link power converter. An 18-channel logic analyzer was used to evaluate the switching performance of the design.
The demonstration device was designed to run at +/- 15 volts. As such the testing also involved the design of teo three-phase power simulators. One three-phase set was used to simulate the electric power grid at 60 Hz. The other three-phase set was used to simulate a wind generator with variable frequency and amplitude. A PIC 18F452, octal 8-bit DAC and a set of six Apex power amplifiers, along with a Visual Basic GUI were used for the three-phase simulators.
Outer-loop and inner-loop control diagram
Technologies used: Microchip, Inc. dsPIC30F6011 and 18F452, Analog Devices ADSP-2186 DSP
Client: TechEn, Inc.
Related article: "Selecting an inexpensive logic analyzer," Nuts & Volts, July 2004
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