Control loop of a digital control device of a rotary electrical machine with excitation for a motor vehicle

Control loop (10) of a digital control device (2) of a rotary electrical machine with excitation (1) for a motor vehicle of the type which can function as a generator supplying an output voltage (Ub+) adjusted by an excitation current (Ie), said digital control device (2) comprising means (11) for controlling said excitation current (Ie) and said control loop (10) comprising, as input, means (31) for measurement by sampling of said output voltage (Ub+) generating a measurement signal (Um), means (13) for error calculation generating an error signal (e) equal to a difference between said measurement signal (Um) and a set value (U0), means (14) for processing of said error signal (e) comprising an amplifier (14) and generating a control signal (Ysat), and, as output, means (35) for generation of a control signal (PWM) which controls said control means (11) according to said control signal (Ysat), wherein said processing means (14, 24) additionally comprise a phase advance filter (24), said phase advance filter (24) having a transfer function at Z which has the form:

• FT
• ⁡
• (
• z
• )
• =
• 1
• -
• (
• 1
• -
• 1
• /
• a
• )
• ·
• Z
• -
• 1
• 1
• -
• (
• 1
• -
• 1
• /
• b
• )
• ·
• Z
• -
• 1
• where a is a first predetermined coefficient and b is a second predetermined coefficient such that a>b, and said phase advance filter (24) comprises means for implementation of a recurrence equation, said recurrence equation having the form:
• Yn+1=YnZ−1−YnZ−11/b+Xn−XnZ−1+XnZ−11/a
• where X and Y are respectively a digital input and a digital output of said phase advance filter (24), and a and b are respectively said first and second predetermined coefficients.