The present invention relates to systems including fuel cells, and more particularly to an air control system for a system including a fuel cell.
Systems such as vehicles and stationary power plants use fuel cell systems to generate power. In many fuel cell systems, several different components may require a controlled airflow. An air delivery device such as a compressor typically supplies air to a manifold. Flow controllers (FCs) are coupled to outputs of the manifold. The air delivery device maintains a desired manifold pressure, which is used to supply the fuel cell components. A flow controllers (FCs) control airflow to the fuel cell components. A system controller calculates a manifold pressure setpoint, which is used to control the air delivery device. Conventional fuel cell systems typically control the air delivery device by controlling to a desired airflow.
An air control system and method according to the present invention for a fuel cell system includes a manifold, a air delivery device that supplies air to the manifold, and a plurality of fuel cell components. A plurality of flow controllers (FCs) control airflow from the manifold to the fuel cell components. A controller communicates with the FCs and the air delivery device and generates a manifold pressure setpoint based on a first factor that is related to fuel cell system stability and a second factor that is a based on minimum and maximum pressures of the air delivery device for a predetermined airflow.
In other features, the controller generates the manifold pressure setpoint based on a third factor that is related to fuel cell system efficiency. When the controller calculates the first factor, the controller uses a first mass flow signal of a first FC of a first component to look up a first delta pressure minimum in a first table, adds the first delta pressure minimum to a first pressure of air delivered to the first component, and generates a first pressure minimum.
In still other features, when the controller calculates the first factor, the controller uses a second mass flow signal of a second FC of a second component to look up a second delta pressure minimum in a second table, adds the second delta pressure minimum to a second pressure of air delivered to the second component, and generates a second pressure minimum.
In yet other features, a first maximum selecting circuit selects a first maximum value of inputs thereto. The first and second pressure minimums are input to the first maximum selecting circuit. A summing circuit sums inputs thereto. The first and second mass flow signals are input to the summing circuit.
In still other features, an upper limit table generates a high pressure limit for the air delivery device based on the summed mass flow signals. A first minimum selecting circuit selects a first minimum value of the first maximum value and the upper pressure limit. A lower limit table generates a low pressure limit for the air delivery device based on the summed mass flow signals. A second maximum selecting circuit selects a second maximum value of inputs thereto. The lower pressure limit and the first minimum value are input to the second maximum selecting circuit.
In still other features, an efficiency table provides an efficiency pressure valve based on the summed mass flow signals. A third maximum selecting circuit selects a third maximum value based on the efficiency pressure valve and the second maximum value.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.