Method for fault tolerant control of a vapour compression system

A method for controlling a vapour compression system, the vapour compression system comprising at least one compressor, a heat rejecting heat exchanger, at least one expansion device and at least one evaporator, arranged in a refrigerant path, each evaporator being arranged in thermal contact with a refrigerated volume, and each expansion device being arranged to supply refrigerant to an evaporator, the vapour compression system further comprising an ambient temperature sensor arranged to measure an ambient temperature, the method comprising the steps of:

• selecting a time period during which the ambient temperature sensor is unexposed to solar heating,
• during the selected time period, obtaining measurements of the ambient temperature by means of the ambient temperature sensor, and obtaining measurements of at least one further parameter related to the vapour compression system, while operating the vapour compression system,
• deriving model parameters for a model of at least a part of the vapour compression system, based on the obtained measurements, the model providing correlation between the ambient temperature and the at least one further parameter,
• subsequently operating the vapour compression system based on measurements of the at least one further parameter and based on ambient temperatures derived by means of the model including the derived model parameters,
• comparing ambient temperatures derived by means of the model and the derived model parameters to ambient temperatures measured by means of the ambient temperature sensor,
• in the case that the difference between the derived ambient temperatures and the measured ambient temperatures is below a predefined threshold value, operating the vapour compression system based on the measured ambient temperatures, and
• in the case that the difference between the derived ambient temperatures and the measured ambient temperatures is above the predefined threshold value, operating the vapour compression system based on the derived ambient temperatures.