Novel Hybrid 12-Pulse Line-Interphase-Transformer Boost-Type Rectifier with Controlled Output Voltage and Sinusoidal Utility Currents

Abstract

Keywords: 12-pulse hybrid rectifier, sinusoidal input current, controlled output voltage, aircraft applications Passive rectifiers are advantageous compared to active rectifiers concerning efficiency, low complexity, EMC, and reliability. Furthermore, for high input frequency applications, such as aircraft and micro gas turbine systems, the magnetic components occupy a smaller volume. On the other hand, hybrid rectifiers can compensate drawbacks of passive rectifiers such as ensuring a controlled output voltage. In this paper, a novel control scheme of the hybrid rectifier is proposed for achieving purely sinusoidal input currents. Furthermore, the control scheme is verified with numerical simulations and experimental results.The main circuit configuration of the hybrid rectifier, which composes a voltage-type 12-pulse passive rectifier and DC-DC converters, is shown in Fig. 1. The output voltage can be controlled by the power transistors T 1 and T 2 . The input current shape depends on only the output voltages of the diode bridges and the turns ratio (w B /w A =0.366) of the line interphase transformers (LIT). The input currents can therefore be controlled by using variable duty cycles of T 1 and T 2 . From space vector equations the optimum voltage modulation in order to achieve purely sinusoidal input currents can be derived aswhere u 1 and u 2 are the local average values of voltages across Fig. 1. Novel hybrid 12-pluse LIT rectifier with controlled output voltage and purely sinusoidal input currents T 1 and T 2 respectively andû is the peak input phase voltage. The waveforms u 1 and u 2 are close to having a trianglar shape that that varies between zero and the output voltage for the angleThe triangular shape can be realized by changing duty cycle of T 1 and T 2 . Fig. 2 shows the experimental input currents of a 10 kW prototype controlled by the conventional constant duty cycle (a) and by triangular modulation (b), which approximates well u 1 and u 2 according to (1). By applying the proposed modulation scheme, sinusoidal input currents are realized. The THD is reduced from 6.1% to 2.0% and the power factor is improved from 0.968 to 0.976. The input inductor L is designed to fulfill the requirements of low-order input current harmonics for aircraft applications. Since low-order input current harmonics can be significantly reduced by the proposed control scheme, the inductance of L can be reduced. However, the flux density through the LIT is increased if the proposed control scheme is applied.In this paper a novel control scheme to achieve purely sinusoidal input currents for a voltage-type hybrid 12-pulse rectifier has been proposed. In further work, the application of the control scheme will be studied for current-type multi-pulse hybrid rectifier systems. MemberA novel injection scheme to improve the input current harmonics of a hybrid 12-pulse line-interphase-transformer rectifier with controlled output voltage by a two-switch boost-type output stage is presented in this paper. A theoretical derivation...

Passive and Hybrid PFC Rectifiers-A Survey and Exploration of New Possibilities-

“…Fig. 1) It is possible to obtain a double-parallel 3-phase-bridge SHC-Inj rectifier without isolation transformer (i.e., with an autotransformer) (35)- (39) . This scheme is included as "A1∼3/B/C1" in Fig.…”

“…1) (35) (36) and "double dc-dc converter" ("A1∼3/B/C1-D" in Fig. 1) scheme (37)- (39) . The "double dc-dc converter" scheme offers dc-voltage control and ideal sinusoidal input current while the "single dc-dc converter" scheme does not offer them.…”

“…A voltage injection can be realized by dc-dc converters on the dc-sides of the bridges as seen in the recent work (39) of the author's group. This effect is applicable for any other schemes with different phase-shifting arrangements, i.e., for the isolation transformer scheme "A," the autotransformer scheme "A1," the semi-isolation scheme "A2" and the semi-direct scheme "A3" although some minor change in the additional circuit is necessary.…”

“…Several arrangements by means of the Ruhr rectifier and PWM dc-dc converters connected on the dc-sides (like that in (39) ) are possible to realize PFC operation. Although the concrete topologies are omitted in this paper due to space limitation, they are expected to offer a high performance and comparable to (or more advantageous than) the PWM rectifier "C2" in some applications mentioned before.…”

“…Further, a simplified MP-PAM rectifier with PWM dc-dc converters on the dc-side for generating the injection current has been proposed very recently (33)- (39) . This Hybrid PFC (i.e., with the MP-PAM as a Passive part and the PWM currentinjector as an Active part) provides a controlled dc voltage and a robust waveshaping capability of the utility linecurrents similarly to the PWM rectifiers.…”