Improved control of an electrically heatable expander thermostat in the thermal coolant circuit of fuel cell systems

摘要

A control algorithm for a bypass valve in a thermal subsystem of a fuel cell system, wherein the bypass valve comprises an expansion element which is heated by a heating element. A stack energy loss is applied to a PDT1 controller, which associates the loss with a dynamic PDT function. The difference between the setpoint temperature of the stack and the actual temperature of the stack is applied to a PI controller which provides an error value of the difference. The actual temperature of the stack is applied to a look-up table which provides a value based on how close the actual temperature is to the opening temperature of the expansion element. The values from the PDT1 controller, the PI controller and the look-up table are added to provide an output signal to control the current applied to the heater element and thus the heat applied to the expansion element.