Operation of transport refrigeration systems to prevent engine stall and overload

A method for controlling the performance of a transport refrigeration system having a transport refrigeration unit powered by an engine, comprising matching a capacity output of the transport refrigeration unit to an available shaft power of the engine;

• the method further comprising:
• monitoring an operating engine load of the engine;
• monitoring an operating engine speed of the engine;
• operating the transport refrigeration system at the capacity output necessary to meet a current refrigeration demand load so as long as both the operating engine load of the engine is not at or above a predetermined maximum value and the operating engine speed of the engine is not below a predetermined engine operating speed;
• and
• reducing the cooling capacity output of the refrigeration unit to a non-zero cooling capacity by adjusting a flow of refrigerant to a compressor when the operating engine load of the engine is at or above the predetermined maximum value and an operating engine speed of the engine is less than the predetermined engine operating speed.