Modification of the PDF controller
After another week of modification of the model, I find that the problem is not fix on the ASHP but the controller itself. The system can`t be stable if the controlled parameters' value change. So I finally decides use a constant value of both Kp and Ki.
Faced with the critical damping situation, the relation between "g" and "p" can be obtained, then the value of Kp and Ki could be calculated as well.
The simulation results show that a better temperature tracking is obtained. The improvement is mainly focus on the oscillation, on the tracking plots is perfect smooth. However, for the period of the 2 hours, the room temperature can`t reach the target value as SAP required. The reason may due to the slow response and time constant of ASHP heating system.
In order to solve the problem, or at least to reduce the error range. One possible solution is to adding a optimum starter for the heating system. The optimum start algorithm will calculate a pre-start time based on the SAP requirement, so the heat pump will begin to operating before the SAP time point, in order to achieve the required temperature in advance or on time.
The simplest way is to operate the heat pump 3 times of time constant in advance. As for my project, I have modified a previous algorithm codes and its performance will be better than the plots shown above.
