Closed Loop Input Current Control of a Hybrid 12-Pulse Rectiﬁer J. Biela, D. Hassler, J. Sch¨ onberger and J. W. Kolar ETH Zurich, Power Electronic Systems Laboratory Physikstrasse 3, CH-8092 Zurich, Switzerland Abstract—This paper presents a novel closed loop cur- rent control strategy for a hybrid 12-pulse rectiﬁer that uses a two-switch boost stage for output voltage regula- tion. Unlike previous attempts to mitigate input current distortion, e.g. by injecting voltages on the rectiﬁer output side in open loop control mode, this new closed loop current control scheme directly controls the input current space vector and/or impresses sinusoidal input currents. In this paper, the control strategy is explained and the modulation functions for each π 3 -wide mains voltage sector are derived. The hardware implementation is described, and experimental results demonstrate that the control strategy ensures a high quality input current for ideal or distorted/unbalanced mains. Index Terms—12-pulse rectiﬁer, current control, space vector modulation I. I NTRODUCTION In aerospace applications, where drive systems are connected to the on-board electrical system, rectiﬁers with a high input current quality are required in order to limit the distortions. There, basically line commutated systems with a high pulse number [1], [2] or active systems, i.e. PWM-rectiﬁers with controlled input cur- rent, can be applied. Due to the high mains frequency of 360Hz to 800Hz, the low cooling effort, and the missing EMI-ﬁlter passive 12-pulse rectiﬁers without galvanic isolation achieve similar power densities than active rectiﬁers systems [3]. Furthermore, passive systems have a high pulse load capability and a low complexity. However, the passive 12-pulse rectiﬁer is not without drawbacks. E.g. no output voltage regulation is provided, and/or the drive system has to be designed for the lowest possible mains voltage, what leads to an oversized motor. Furthermore, the input current contains low order harmonics. One attempt to address the issue of voltage regulation is based on a hybrid 12-pulse rectiﬁer with an LIT and a two-switch interleaved boost output stage [4] as shown in Fig. 1. In the simplest case an approximately constant duty cycle is used for output voltage regulation, while + V DC w A +w B w A w B S 1 S 2 S T R V R V T V S L R L T L S N R S T R’ S’ T’ v R’N S T R Rec1 Rec2 Fig. 1: Two-switch hybrid 12-pulse rectiﬁer with Line Interface Transformer (LIT). the required current carrying capability of the switches is low. In order to achieve sinusoidal input currents besides output voltage control, a modulation of the duty cycles is necessary. There, an output voltage of approximately twice the value given for purely passive operation is required, which is no drawback for drive systems in the higher power region. Consequently, a sinusoidal input current could be achieved without employing a complex 18- or 24-pulse line interface transformer (LIT). Furthermore, the value of the mains side inductors L ν , TABLE I: Speciﬁcation of the 10kW prototype system Input Voltage range 115V± 15% ≈ 98 - 132VRMS Input frequency range 360-800Hz Input Inductor 188μH LIT wA + wB : wA : wB= 29:21:8 Output Power 10kW Nominal V Out 250V (passive) / 520V (closed loop)