Control Station was the first supplier of
control loop performance monitoring (CLPM) technology to join OSIsoft's Partner EcoSphere, and the company is the only CLPM vendor to capitalize on the PI Asset Framework.
Remind that the aim is to analyze the robust stability of the
control loop that contains feedback controllers (4) and the heating-cooling system (1) with the uncertain parameters (3).
As an actuator in the
control loop, a frequency drive is used.
Figure 5 shows a typical control block of a converter station employing a dual-loop structure: a fast inner current
control loop and a slower outer
control loop.
Let current
control loop, the current loop dynamics were set to 20 times [2] faster than the voltage dynamics with N=20.
In this section, a cascaded
control loop architecture is proposed as a solution to reduce the problem of hunting in building HVAC systems.
A typical current
control loop is based on proportional-integral (PI) controller, highly appreciated in industry due to its simplicity and reliability.
The open current
control loop is described using transfer function:
Due to the potential for interaction between the building pressurization and return fan
control loops, extra care must be taken in selecting the parameters that determine the dynamic response of the digital filters and feedback controllers.
The main controllers are designed via classical SISO synthesis methods (Ziegler Nichols step response method, method of desired model) (1), (7-10) and also via polynomial approach (pole placement method) for SISO
control loop (11-12).