Pulse width modulation interleaving

A pulse width modulation (PWM) interleaving system, comprising:

• an input line by which upstream current is carried from a grid;
• an output line by which downstream current is carried toward a load;
• active harmonic filters (AHFs) disposed in parallel with each other and with the load;
• the AHFs being electrically coupled to a common coupling point that is electrically interposed between the input and output lines;
• and
• the AHFs being configured to affect, by PWM, a characteristic of the downstream current;
• and
• a controller operably coupled to the AHFs and configured to synchronize the PWMs of the AHFs to thereby cancel ripple currents propagating towards the grid in the upstream current;
• wherein:
• the AHFs comprise an even total number of two or more first and two or more second parallel AHFs, each of the two or more first AHFs having a corresponding one of the two or more second AHFs,
• the controller comprises a master-slave micro controller unit (MCU) disposed in each corresponding pair of the first and second AHFs,
• the controller synchronizes the PWMs of corresponding ones of the first and second AHFs to exhibit a 180° phase shift,
• the grid comprises an electrical grid and the load comprises a rectifier front end type variable frequency drive in a high tier chiller, and
• controller moderates synchronization of the PWMs of the first and second AHFs to exhibit a controllable phase shift.

A pulse width modulation (PWM) interleaving method for use with a system in which active harmonic filters (AHFs) are disposed in parallel with each other and with a load, the AHFs being electrically coupled to a common coupling point that is electrically interposed between a grid and the load, the PWM interleaving method comprising:

• executing PWM of each of the AHFs to affect a characteristic of current flowing between the grid and the load;
• synchronizing, by a controller, the executing of the PWM of each of the AHFs to cancel ripple currents propagating towards the grid;
• measuring, by the controller, remaining ripple currents propagating towards the grid from the AHFs;
• and
• moderating, by the controller, synchronization of the PWMs of the AHFs to exhibit a controllable phase shift based on results of the measuring;
• wherein:
• the AHFs comprise an even total number of two or more first and two or more second parallel AHFs, each of the two or more first AHFs having a corresponding one of the two or more second AHFs,
• the controller comprises a master-slave micro controller unit (MCU) disposed in each corresponding pair of the first and second AHFs,
• the controller synchronizes the PWMs of corresponding ones of the first and second AHFs to exhibit a 180° phase shift, and
• the grid comprises an electrical grid and the load comprises a rectifier front end type variable frequency drive in a high tier chiller.