Transport refrigeration system and method of operating

A method of operating a transport refrigeration system comprising:

• electrically powering a first plurality of components of a first refrigeration unit including a first compression device and a second plurality of components of a second refrigeration unit including a second compression device, wherein electrically powering comprises operating a prime mover and an electric generation device;
• monitoring a plurality of operating parameters of the first refrigeration unit;
• monitoring a plurality of operating parameters of the second refrigeration unit;
• calculating a combined power load of the first refrigeration unit and the second refrigeration unit;
• and
• comparing the combined power load to a maximum available power of the prime mover;
• further comprising taking a corrective action in response to the combined power load exceeding the maximum available power;
• wherein the corrective action comprises:
• determining whether the first refrigeration unit or the second refrigeration unit is to be unloaded;
• and
• unloading one of the first refrigeration unit and the second refrigeration unit;
• wherein determining whether the first or second refrigeration unit is to be unloaded comprises:
• calculating a control error of the first refrigeration unit;
• calculating a control error of the second refrigeration unit, wherein the control error for each refrigeration unit is defined by the difference between a control temperature and a control set point;
• and
• comparing the control error of the first refrigeration unit to the control error of the second refrigeration unit, wherein the refrigeration unit to be unloaded is the refrigeration unit with the lower control error;
• wherein the maximum available power of the prime mover is calculated from atmospheric air temperature and an operating speed of the prime mover.