Dual Vector Control Strategy for a Three-Stage Hybrid Cascaded Multilevel Inverter

Abstract

This paper presents a voltage control algorithm for a hybrid multilevel inverter based on a staged-perception of the inverter voltage vector diagram. The algorithm is applied to control a three-stage eighteen-level hybrid inverter, which has been designed with a maximum number of symmetrical levels. The inverter has a two-level main stage built using a conventional six-switch inverter and medium-and low-voltage three-level stages constructed using cascaded H-bridge cells. The distinctive feature of the proposed algorithm is its ability to avoid the undesirable high switching frequency for high-and medium-voltage stages despite the fact that the inverter's dc sources voltages are selected to maximize the number of levels by state redundancy elimination. The high-and medium-voltage stages switching algorithms have been developed to assure fundamental switching frequency operation of the high voltage stage and not more than few times this frequency for the medium voltage stage. The low voltage stage is controlled using a SVPWM to achieve the reference voltage vector exactly and to set the order of the dominant harmonics. The inverter has been constructed and the control algorithm has been implemented. Test results show that the proposed algorithm achieves the desired features and all of the major hypotheses have been verified.

Robust hybrid anti-islanding method for inverter-based distributed generation

“…DG technologies include photovoltaics, wind turbines, fuel cells, small-scale gas turbines, Stirling-engines, and internal combustion engines. Depending on the conversion technology and nature of the energy source, the distributed generator can be directly connected to the grid, through a rotating generator, or indirectly through a DC-AC or AC-AC converter as given in [4][5][6][7]. Many issues rise when the DG connected to electric power networks.…”

Three-phase multilevel inverter with high value of resolution per switch employing a space vector modulation control scheme

“…Hence, the maximum length of the reference vector is given by Eq. (17). Figure 2 shows the switching vectors for a three-level inverter and the reference vector position of the equivalent phase switches are fixed by Eq.…”

“…This ratio is very useful to design high number of levels generation and therefore it shows a small voltage distortion [16,17]. Research shows that the conventional high frequency PWM control technique is not enough for this ratio of three dc source configuration, since the high voltage stage faces high switching loss for high switching frequency [18][19][20].…”

Cascaded half-full-bridge PWM multilevel inverter configuration

“…The field applications include use in industrial medium-voltage motor drives [7], utility interface for renewable energy systems [8], flexible AC transmission systems (FACTS), and traction drive systems [9,10]. Subsequently, several multilevel inverter configurations have been developed [11][12][13][14][15][16] in addition to the fundamental topologies:…”