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AssigneeJohnson Controls Technology Company
InventorsHarold R. SCHNETZKA, Shreesha ADIGA MANOOR
Estimating the term…
Systems and methods for synchronous operation of variable speed drives having active converters include extending the synchronous operation of an active converter to the AC mains voltage during complete line dropout. A phase angle control circuit includes a squaring amplifier, a first phase-lock loop circuit associated and a second phase-lock loop circuit. The squaring amplifier receives the AC power source and outputs a rectangular output signal to a pair of phase lock loop (PLL) circuits. The first PLL circuit with a first lag-lead filter is configured with a high cutoff frequency to provide the converter stage with a phase angle parameter; and the second phase-lock loop circuit including a second lag-lead filter configured to have a low cutoff frequency to provide the lag-lead filter the capability of storing the phase angle of the mains voltage during mains interruption.
A variable speed drive system configured to receive an input AC voltage at a fixed AC input voltage and provide an output AC power at a variable voltage and variable frequency, the variable speed drive comprising:
The position of the each analog switch of the first and second phase lock loop further including a mains voltage detector circuit controlled by sensing a loss of the AC power source input AC voltage.
Each PLL having a phase detector circuit, a VCO and a divide by N circuit, the phase detector circuit having an out-of-lock detector responsive to a phase difference between the squaring amplifier square wave output and a comparison feedback signal generated by the divide by N counter in response to the voltage control oscillator.
Dependencies are inferred from the claim text.