Patent ID: 7511459

Claim:
An improved control system for an electrical power generating source comprising a free piston Stirling engine driving a linear alternator having an alternator winding with an inductance L alt , a switching mode rectifier connecting the alternator winding to an output circuit including an electrical energy storage means, and a pulse width modulator for controlling the rectifier switching duty cycle, the control system including a forward loop having an output connected to control the pulse width modulator, wherein the improvement comprises: (a) a sine wave generator in the forward loop for generating a sine wave at an operating frequency Ï‰ for the engine and alternator; and (b) a feedback loop comprising: (i) a current sensor connected in the alternator circuit for sensing a signal that is proportional to alternator current i; (ii) a virtual capacitor summing point in the forward loop and connected to input the sine wave generated by the sine wave generator and output a signal that is the difference between the input sine wave and a second input to the summing point; and (iii) a computing circuit connected to the current sensor for calculating the voltage v across a virtual capacitor and applying a signal representing v to the second input of the virtual capacitor summing point, the computing circuit performing the operation v=L alt Ï‰ 2 âˆ«i(dt).