A heat pump includes a compressor, a first heat exchanger, a main expansion mechanism and a second heat exchanger arranged in a refrigeration path, the compressor having a suction port, a compression port and an injection port; a gas injection valve connected on a first side to the refrigeration path between the first heat exchanger and the main expansion mechanism and on a second side to the injection port of the compressor; a liquid injection valve connected on a first side to the refrigeration path between the first heat exchanger and the main expansion mechanism and on a second side between the second heat exchanger and the suction port of the compressor; and a controller configured to operate the gas injection valve to inject partly gaseous refrigerant into the compressor, and operate the liquid injection valve to inject liquid refrigerant into the compressor through the suction port of the compressor.

Certain example embodiments provide a vapor compression refrigeration system, comprising: a compressor configured to suction refrigerant at a low pressure and temperature from a suction return, compress the refrigerant, and output refrigerant at a higher pressure and temperature; a condenser configured to cool refrigerant received from the compressor as the refrigerant passes though coils in the condenser; an expansion device configured to reduce the pressure of the refrigerant received from the condenser; and an evaporator configured to allow the refrigerant received from the expansion device to absorb heat surrounding the evaporator. The system may include a plurality of sensors configured to measure temperature of the system and a controller configured to control, based on the signals from one or more sensors, operation of the compressor and/or an evaporator fan motor configured to allow the refrigerant received from the expansion device to absorb heat surrounding the evaporator.

An air conditioning control system including a motor and a controller is provided. The controller is configured to: filter a received signal using a filter function Q(Z), where the received signal is a difference between a feedback value of an electrical angular velocity of the motor and a given value of the electrical angular velocity of the motor; perform phase compensation on the filtered signal using a phase compensation function S(Z); determine a motor speed control signal, using a speed regulation function Gpi(Z), based on the phase-compensated signal; and discretize the motor speed control signal using a discrete transfer function Gp(Z), and control a speed of the motor based on the discretized motor speed control signal. Poles of a transfer function of the controller constructed based on the functions Q(Z), S(Z), Gpi(Z), and Gp(Z) are located within a unit circle.

Computerised methods of controlling a vapour compression cycle system. In a first aspect, the method comprises determining a cooling or heating power demand value based on the prevailing temperature and comparing (730) it with a required set point temperature. The power demand value is converted to a speed demand value according to a model or map (720) and according to evaporating and condensing pressure/temperature, which is sent to the compressor motor speed controller (70). In another aspect, the power demand value for hysteresis control to maintain the temperature is dynamically chosen (710) from a plurality of possible power demand values according to evaporating and condensing pressure/temperature and according to a measure of efficiency calculated for each candidate power demand value. In another aspect, a compressor capacity value is selected (930) by looking up a compressor capacity in a look up table according to evaporating and condensing pressure/temperature.

A recreational vehicle air conditioning system supports multiple recreational vehicle air conditioning units having closed air conditioning circuits and a controller that is electronically coupled to each of the recreational vehicle air conditioning units to control each of the closed air conditioning circuits to regulate an overall power consumption of the multiple recreational vehicle air conditioning units. A recreational vehicle air conditioning system may also support multiple recreational vehicle air conditioning units where a refrigerant line set is coupled between the recreational vehicle air conditioning units such that a compressor in one of the recreational vehicle air conditioning units is capable of supplying refrigerant to the evaporators of the multiple recreational vehicle air conditioning units, and such that valves coupled in series with each of the evaporators may be regulated to control cooling by each recreational vehicle air conditioning unit.

An AC/DC converter includes: a charge accumulation unit including first and second capacitors connected in series; a switching unit including a switch unit; a control unit; a switch drive unit; and first current and second current detection units. The switch unit includes first and second switching elements connected in series. The switching unit switches between charging and non-charging of each of the first and second capacitors. The switch drive unit causes the first and second switching elements to perform an ON/OFF operation exclusively to each other. A current detector of the first current detection unit is disposed between a rectifier circuit and the switch unit. The control unit detects a current flowing through the switch unit on the basis of based on a difference value between a detection value of a first current detected by the first current detection unit and a detection value of a second current detected by the second current detection unit.

An electric motor drive device includes: a three-phase diode bridge which rectifies and converts a three-phase AC voltage into a DC voltage; an electrolytic capacitor which smooths a DC voltage; a DC reactor provided between the three-phase diode bridge and the electrolytic capacitor; an inverter which converts a DC voltage smoothed by the electrolytic capacitor into an AC voltage and outputs the AC voltage to a motor; a voltage detecting unit which detects a DC voltage output from the three-phase diode bridge; and an inverter control unit which detects an imbalanced state of the three-phase AC voltage on the basis of a DC voltage value which is a detection value of the DC voltage obtained by the voltage detecting unit, and controls the inverter on the basis of a detection result of the imbalanced state.

A compressor and a refrigeration device are provided. The compressor has a crankshaft, a connecting structure, and an avoidance part arranged on the connecting structure and/or the crankshaft. The avoidance part is located at a position where the connecting structure is matched with the crankshaft. The avoidance part is configured to be suitable for avoiding at least one of the connecting structure and the crankshaft. A gap between the crankshaft and the connecting structure is increased through the arrangement of the avoidance part, so that the avoidance part can avoid the crankshaft when the crankshaft is obliquely deformed.

A control method includes determining an actual capacity requirement and a target evaporation temperature of each indoor unit of a multi-split air conditioning system, calculating a total capacity requirement of an outdoor unit of the multi-split air conditioning system according to the actual capacity requirements of the indoor units, and determining an initial frequency of a compressor of the outdoor unit according to the total capacity requirement, and adjusting a frequency of the compressor based on the initial frequency, and according to temperature characteristic values of evaporator coils of all the plurality of indoor units and a reference evaporation temperature if all the indoor units operate in an air blowing mode or according to the temperature characteristic values and a preset evaporation temperature threshold if not all the indoor units operate in the air blowing mode.

A discharge device includes a capacitor, first and second discharge circuits each connected in parallel to the capacitor, and a comparator. The first discharge circuit includes a first discharge resistor. The second discharge circuit includes: a second discharge resistor smaller in resistance value than the first discharge resistor; and a switch connected in series to the second discharge resistor. The comparator turns off the switch when a voltage (VH) between power lines is equal to or higher than a prescribed voltage, and turns on the switch when the voltage becomes lower than the prescribed voltage. The comparator is configured to turn off the switch after an elapse of a prescribed time period since turning on of the switch.