The Phase Locked Oscillator (PLO) is based on the Phase Vector technique. This technique exploits trigonometric multiplication identities to form an error signal, which speeds up or slows down the PLO in order to match the phase. The output signal q is a ramp synchronized to the Phase A commutating bus L-G voltage.
The block diagram of the PLO used in the 6-Pulse bridge component is shown below:
The output signal is then phase shifted by simply adding a constant angle to the ramp (to account for various Converter Transformer configurations) to generate the firing ramp for valve 1. The ramps for the other valves are generated by adding 60° increments to the valve 1 ramp.
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