DSP Control Improves Inverter Performance and Density

Focus:

Because 16-bit, fixed point DSPs integrate numerous functions such as PWM channels, ADCs, CAN interfaces, memory, serial ports, event timers, and encoder interfaces, they can be used to implement low-cost inverter designs than traditional designs based on analog control. The DSP-based designs can also achieve smaller size, higher efficiency, and lower total harmonic distortion (THD) than competing solutions, especially when required to drive highly nonlinear loads. A design proposed here reduces the size of the inverter's output LC filter (the greatest influence on inverter size) without moving to a high switching frequency (which would increase power losses). The key to the design is using the DSP rather than the LC filter to suppress lower-order harmonics. The DSP implements a series of resonant controllers that act as narrow band-stop filters to suppress odd-order harmonics up to the 29th. As a result, the output LC filter only has to suppress the high-frequency harmonics. The operation of this inverter design is explained, and experimental results are presented for a 15-kVA IGBT-based inverter prototype. The results verify that the inverter rejects the distortion produced by nonlinear loads.

What you’ll learn:

• How to improve inverter performance and shrink its size by using DSP-based control

Notes:

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Author & Publication:

Liviu Mihalache, and Mihai Chis, Power Conversion Technologies Inc., Harmony, Pa., Power Electronics Technology, Feb 01 2003

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