Four-dimensional space vector PWM algorithm for multilevel four-leg converters

Abstract

Four-leg voltage-source converters provide an effective neutral connection in three-phase systems with neutral wire. They can be applied to inverters, rectifiers or active filters to control the neutral current caused by unbalanced or nonlinear loads as well as unbalanced sources. From the modulation point of view, the four-leg converters can be considered as four-phase systems. Hence, the modulation task can be carried out with a generic multiphase modulation algorithm. Recently, a novel space vector PWM technique for multilevel multiphase voltage-source converters has been presented. The four-dimensional space vector PWM algorithm for multilevel four-leg converters presented in this paper is the result of applying such technique to a fourphase converter. Finally, the algorithm is implemented in a lowcost FPGA and it is tested with a prototype by using a five-level cascaded full-bridge inverter.

Performance of solid state transformers under imbalanced loads in distribution systems

“…This shows that SST2 has the slowest start-up and transient response to a step change in load imbalance due to the complex control strategy of the four-leg topology at the inverter stage. In particular the 3-D SVPWM algorithm requires a coordinate transformation for the formulation in the αβγ frame, hence it has higher computational cost [23]. In addition both of the abc to dq0 transforms make use of a phase angle supplied by a PLL which tracks the grid phase as shown in Fig.5 (a) and this PLL introduces a further delay [24] in the response for SST2.…”

Multilevel multiphase space vector PWM algorithm with switching state redundancy applied to three-phase four-leg converters

“…1 is identical to the functional diagram of a multilevel four-phase converter where the neutral leg corresponds to the fourth phase [10]. Hence, the modulation algorithm for four-leg converters can be obtained by making P = 4 in the generic multiphase algorithm that has been summarized in the above section.…”

“…The modulation technique in [7] does not make use of the switching state redundancy available in multilevel converters, which allows to use different switching state combinations with the same phase-to-phase voltages but with different homopolar voltage component. Consequently, the modulation index range available with the SVPWM algorithms in [9] and [10] is not optimal and it can be extended. Such problem is solved by the multilevel multiphase SVPWM technique in [8] that takes advantage of the switching state redundancy.…”

“…The application of the multiphase modulation technique in [7] to multilevel converters with three legs provides the simple modulation algorithm in [9], which is fully equivalent to the previous threedimensional (3D) SVPWM algorithm presented in [12]. If the technique in [7] is applied to multilevel four-leg converters then the result is the novel four-dimensional (4D) SVPWM algorithm presented in [10]. The modulation technique in [7] does not make use of the switching state redundancy available in multilevel converters, which allows to use different switching state combinations with the same phase-to-phase voltages but with different homopolar voltage component.…”

A flying-capacitor-based multilevel shunt active power filter for power quality improvement under severe operating conditions

“…Solutions for harmonic compensation in electrical networks have adopted mostly Active Power Filter (APF) [5][6][7]and Multilevel Active Power Filter (MAPF) [8][9][10][11][12][13] in the last three decades, although extensive research work are still being conducted to optimize the MAPF structures and improve their performance through modern and more adequate control algorithms [14][15][16][17][18][19][20][21].…”