Abstract：Aiming at the problem that the ripple content of current and voltage in cycloconverter speed control

system is large and the ripple period is time-varying，the real-time sampling value is not suited for feeding back to

the speed control system directly，a variable period mean sampling algorithm was proposed. Firstly，the algorithm

took the interval time of trigger pulse of cycloconverter power device as the mean period to calculate the meanvalue

of actual current and voltage. Secondly，the phase lag angle caused by the mean period was calculated according to

the real-time frequency and mean period of current and voltage. Finally，the lag compensation and interpolation

operation were carried out according to the phase lag angle. More ideal voltage and current feedback values were

obtained for speed control system. Compared with the average sampling method，this algorithm is more suitable for the time-varying ripple period of cycloconverter conversion，and it eliminate the sampling lag and improve the

performance and stability of the speed control system.

      Key words：variable period mean sampling；lag compensation；interpolation operation；cycloconverter