Efficient multiple-reference-frame controller for harmonic suppression in custom power devices

Comprehensive control for unified power quality conditioners

“…Therefore, w i has been selected larger in the shunt compensator than in the series compensator. Coordination between series and shunt compensators was not addressed in the partial problems discussed in [19] and [20].…”

“…Fourthly, voltage and current unbalance and harmonics are compensated for by using the multiple synchronous reference frame (SRF)-based controller proposed in [19] for series devices and in [20] for shunt devices. This approach avoids the use of resonant controllers (RCs) like those in [14] but it is proved in [19,20] that the resulting controller is mathematically equivalent to use of RCs in a stationary reference frame.…”

“…This approach avoids the use of resonant controllers (RCs) like those in [14] but it is proved in [19,20] that the resulting controller is mathematically equivalent to use of RCs in a stationary reference frame. This harmonic controller ensures zero-error tracking of the harmonic components and gives the UPQC a seamless frequency-adaptation capability during grid frequency variations.…”

“…This last feature was never addressed before in the literature related to UPQCs. The implementation proposed in [19,20] is very efficient because only two trigonometric functions are calculated and the results are provided by a phase locked loop (PLL) which synchronises the converters with the grid.…”

“…Clearly, the application of a multiple SRF-based controller here is a consequence of the good results found in [19,20] but the coordination of the series and shunt compensation was not included in those references and will be detailed in this paper. The LQG approach for the design of the inner (or main) controller was not used in those references, either, where arbitrary pole placement was used.…”