A method for operating parallel working units of a system with advanced process control, comprising: developing a model for advanced process control, the model comprising: a model identification phase; and a model combination phase; and wherein: the model identification phase comprises obtaining models of each working unit of a plurality of parallel working units of a system by performing an identification experiment for each unit of the plurality of parallel working units, where each unit is individually enabled while the other working units are disabled and obtaining a model of a remaining system which has no working unit of the plurality of parallel working units; and the model combination phase comprises a model of a whole system incorporating the models of the parallel working units and the model of the remaining system; providing the model to a controller of the of the system with advanced process control; and operating the parallel working units with the controller in accordance with the model for advanced process control. developing a model for advanced process control, the model comprising: a model identification phase; and a model combination phase; and wherein: the model identification phase comprises obtaining models of each working unit of a plurality of parallel working units of a system by performing an identification experiment for each unit of the plurality of parallel working units, where each unit is individually enabled while the other working units are disabled and obtaining a model of a remaining system which has no working unit of the plurality of parallel working units; and the model combination phase comprises a model of a whole system incorporating the models of the parallel working units and the model of the remaining system; a model identification phase; and a model combination phase; and wherein: the model identification phase comprises obtaining models of each working unit of a plurality of parallel working units of a system by performing an identification experiment for each unit of the plurality of parallel working units, where each unit is individually enabled while the other working units are disabled and obtaining a model of a remaining system which has no working unit of the plurality of parallel working units; and the model combination phase comprises a model of a whole system incorporating the models of the parallel working units and the model of the remaining system; the model identification phase comprises obtaining models of each working unit of a plurality of parallel working units of a system by performing an identification experiment for each unit of the plurality of parallel working units, where each unit is individually enabled while the other working units are disabled and obtaining a model of a remaining system which has no working unit of the plurality of parallel working units; and the model combination phase comprises a model of a whole system incorporating the models of the parallel working units and the model of the remaining system; providing the model to a controller of the of the system with advanced process control; and operating the parallel working units with the controller in accordance with the model for advanced process control.