Mass flow interpolation systems and methods of dynamic compressors

A controller for a dynamic compressor without a mass flow sensor, the dynamic compressor including an impeller, a motor operably connected to the impeller, a variable frequency drive (VFD) coupled to the motor, and a variable inlet guide vane (VIGV), the controller comprising:

• a processor;
• and
• a memory, the memory storing:
• a map of a plurality of predetermined operating points of the dynamic compressor, each predetermined operating point including a mass flow of the dynamic compressor at that predetermined operating point;
• and
• instructions that program the processor to:
• operate the dynamic compressor to compress the working fluid by controlling a position of the VIGV and controlling a speed of the motor driving the impeller using the VFD;
• determine, while operating the dynamic compressor, a current operating point of the compressor;
• calculate a mass flow for the current operating point from the map of the plurality of predetermined operating points;
• and
• continue to operate the dynamic compressor to compress the working fluid based at least in part on the calculated mass flow for the current operating point by inputting the calculated mass flow into a control algorithm that calculates an operating point value based at least in part on the calculated mass flow and controlling an unloading device of the dynamic compressor based on the operating point value and a margin.

A method of determining a mass flow of a dynamic compressor that is compressing a working fluid and does not include a mass flow sensor, the dynamic compressor including an impeller, a motor operably connected to the impeller, a variable frequency drive (VFD) coupled to the motor, and a variable inlet guide vane (VIGV), the method comprising:

• operating the dynamic compressor to compress the working fluid by controlling a position of the VIGV and controlling a speed of the motor driving the impeller using the VFD;
• determining, while operating the dynamic compressor, a current operating point of the compressor;
• calculating the mass flow for the current operating point from a map of a plurality of predetermined operating points, each predetermined operating point including a mass flow of the dynamic compressor at that predetermined operating point;
• and
• continuing to operate the dynamic compressor to compress the working fluid based at least in part on the calculated mass flow for the current operating point by inputting the calculated mass flow into a control algorithm that calculates an operating point value based at least in part on the calculated mass flow and controlling an unloading device of the dynamic compressor based on the operating point value and a margin.