System operating for mCCHP system is off-grid type. In this case the Stirling engine is in electricity-driven operating mode. The principle applied in the control strategy consists in using the voltage of the electrical energy accumulator and the temperature of the heat accumulation tank, as values sensitive to the misbalance between the produced power and the consumed one. In the case of both accumulations, if the power produced is less than the consumed one, then the electrical/ thermal potential decreases and vice versa. The control system must maintain at constant (nominal) values the capacities through which the electrical/thermal potential (voltage and temperature) are evaluated, by adjusting the produced power.
Thus, the equilibrium between production and consumption is achieved. It has to be mentioned the fact that the Stirling engine is driven by the control loop of battery voltage and the fact that the back-up boiler is driven by the control loop of temperature tank. Two types of control methods could be adopted:
(a) using a PI continuous controller with PWM control. It ensures a smooth variation of the system variables;
(b) control on/off that has the advantage of simplicity in implementation.
Further the first control solution has been taken into consideration in both operating regimes (winter and summer).