Abstract:
A drive system for a compressor of a chiller system includes a variable speed drive. The variable speed drive receives an input AC power at a fixed input AC voltage and a fixed input frequency, and provides an output AC power at a variable voltage and variable frequency. The variable speed drive includes a converter connected to an AC power source. The converter is arranged to convert the input AC voltage to a DC voltage. A DC link is connected to the converter and configured to filter and store the DC voltage from the converter. An inverter is connected to the DC link. A motor is connectable to the compressor for powering the compressor. A controller is arranged to control switching in the converter and the inverter. The controller is arranged to apply randomized pulse width modulation to vary the switching frequency of transistors in the converter and the inverter at each switching cycle. The motor may be a permanent magnet synchronous motor.
Abstract:
A drive system for a compressor of a chiller system includes a variable speed drive. The variable speed drive is arranged to receive an input AC power at a fixed AC input voltage and fixed input frequency and provide an output AC power at a variable voltage and variable frequency. The variable speed drive includes a converter connected to an AC power source providing the input AC voltage. The converter is arranged to convert the input AC voltage to a DC voltage. A DC link is connected to the converter. The DC link is arranged to filter and store the DC voltage from the converter. A first inverter and a second inverter are each connected to the DC link. A motor includes stator windings connected between the first inverter and the second inverter to power the motor by the output AC power from the first inverter and the second inverter. The motor is connectable to a compressor of the chiller system to power the compressor. The motor may be a permanent magnet synchronous motor.
Abstract:
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.