A method for controlling a refrigeration system having a compressor, heat rejecting heat exchanger, expansion valve and heat absorbing heat exchanger circulating a refrigerant in series flow, the heat absorbing heat exchanger in thermal communication with working fluid, the method includes obtaining an expansion valve position set point; using a feedback control loop to generate a controlled expansion valve position; obtaining a rate of change of an operating parameter of the system; using the rate of change of the operating parameter to generate an adjustment; modifying the controlled expansion valve position using the adjustment; and controlling the expansion valve using the modified controlled expansion valve position.

Disclosed is a method for controlling a refrigerator including a motor driving a compressor. The method for controlling a refrigerator includes: identifying driving revolutions per minute (RPM) for driving of the motor; performing a control of temperature in the refrigerator based on the identified driving RPM; and storing operation information of the motor associated with the performing of the control of temperature, where the identifying of the driving RPM involves identifying stored operation information of the motor associated with a previous motor driving process.

A method of controlling a refrigeration system having a compressor, a condenser, an evaporator, and a variable speed condenser fan is provided. The method includes determining if a change in an ambient temperature or a compressor suction pressure is greater than a predetermined threshold, determining a near-optimal condensing pressure/temperature if the change in the ambient temperature or the compressor suction pressure is above the predetermined threshold, setting a condensing pressure setpoint based on the determined near-optimal condensing pressure/temperature, and setting a speed of the variable speed condenser fan based on the condensing pressure setpoint.

Variable volume ratio compressors may be controlled using a switching parameter based on compressor speed and suction density to improve the matching of compressor volume ratio to desired discharge conditions. Delay periods may be implemented in the determination of when to change volume ratio to control the frequency of changes to the volume ratio. The switching parameter may be a product of the compressor speed and suction density. The volume ratio of the compressor may be controlled by switching valves directing pressure to a piston of a variable volume ratio system of the compressor.

Embodiments of the present invention provide a method for controlling compressor braking, a frequency converter and a variable speed compressor. The method includes steps of: determining to brake a compressor, wherein a brake circuit includes three switching units and the three switching units are respectively electrically connected to three phases of windings of a motor of the compressor; actuating two of the three switching units to short-circuit two phases of windings of the motor. The two phases of windings of the motor are short-circuited by controlling the three switching units to generate braking torque, such that the compressor is braked without introducing a DC voltage, and thus the braking energy consumption is reduced. Besides, by turning on only two switches at a time, the switching abrasion is reduced, and the overall service life of the three switching units is effectively improved.

A method for determining system subcooling in a vapor compression system including a compressor, a condenser, an expansion device and an evaporator operatively connected in a serial relationship in a refrigerant flow circuit, the method including receiving information indicative of a compressor torque or compressor current; and determining a degree of system subcooling in response to the receiving of the information.

Described is a system and method for extracting water from air using a vector drive control system. The water-extraction system may compress ambient air before it comes into contact with an evaporator. The vector drive control system may adjust the speed of one or more motors to increase efficiency and may control a pressure chamber capable of compression and expansion.

A vehicle includes a controller configured to deactivate an inverter driving the rotor. The deactivation being responsive to respective speeds for a rotor derived from respective samples from each of a monitoring core and a current control core over a same temporal window being different by a threshold amount. The cores each generate a different number of the samples due to having different chronometric periods and the temporal window being greater than the chronometric periods.

A controller unit for controlling the speed of a motor for driving an oil injected compressor, the controller unit including: a data connection; and a first module to receive data through the data connection. The controller unit includes a processing unit for determining a minimum working speed of the motor on the basis of the measured working pressure, the ambient temperature and a dew point temperature; and a comparator unit to compare the determined minimum working speed with the retrieved working speed of the motor. The processing unit includes a signal generating unit to send a signal to the motor for increasing the working speed of the motor to at least the determined minimum working speed, if the retrieved working speed is lower than the determined minimum working speed.

The present disclosure relates to the field of air conditioning technology. In particular, it involves a control method and control system based on a variable speed AC compressor.