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Nowadays, most of the electrical railway tractions, especially the high-speed tractions are using AC-DC-AC power driving system. The best choice for the AC-DC link is four-quadrant PWM rectifier, which can provide controllable DC link voltage and better power factor for the grid. In high power drive applications, the switch frequency of the power semiconductor device cannot be very high, usually less...
In this paper, the Line-Modulated Fixed Off-Time method is used as the current control strategy for a Power Factor Corrector (PFC) pre-regulator. A zero voltage switching PWM (ZVS-PWM) auxiliary circuit is configured to perform ZVS in the switches. Soft commutation of the main switch is achieved without additional current stress. A significant reduction in the total conduction loss is achieved, since...
This paper proposes a fixed frequency modulation scheme for a three-phase PWM rectifier operating at unity power factor. It provides a constant and reduced switching frequency for all the switches of the rectifier by controlling the occurrence and duration of the zero vector states indirectly. The two legs of the converter are operated in hysteresis current tracking mode and the third leg is controlled...
This paper focuses on a three-level pulse width modulation (PWM) rectifier with direct power control (DPC) strategy based on switching table. The influences of power control coupling on system performances are analyzed and an optimized three-level DPC strategy is developed. The proposed three-level DPC changes the selection of control vectors dynamically according to the location of grid voltage vector...
Voltage-source multilevel inverters have become very attractive for power industries in power electronics applications during last years. The main purposes that have led to the development of the studies about multilevel inverters are the generation of output voltage signals with low harmonic distortion; the reduction of switching frequency. A serious constraint in a multilevel inverter is the capacitor...
The mathematical model of the three-level PWM rectifiers is set up in this paper. By comparing it with the model of DC motors, some similarities are established. Based on the state feedback decoupling, the dual-loop close control scheme of DC motors is implemented to three-level PWM rectifiers. As a result, the three-level rectifier has favorable dynamic and steady state performance, sinusoidal input...
Improvements in the efficiency and size of DC-DC converters have resulted from advances in components, primarily semiconductors, and improved topologies. One topology, which has shown very high potential in limited applications, is the partial power processing boost technique, wherein a small DC-DC converter output is connected in series with the input bus to provide an output voltage equal to or...
It is talked, the rule of voltage converter control, which is used to introducing of added voltage, in this article. It is given procedure of switching converter rectifiers to hold received voltage comes from controller how most approximate to set voltage.
This paper proposes a new circuit topology for a multilevel PWM rectifier. The proposed circuit combines a diode clamp type topology with a flying capacitor type topology. As a result, the proposed circuit uses only 12 switches, despite the use of a five-level three-phase PWM rectifier. Further, the proposed circuit can obtain good performance as same as to a conventional multilevel circuit. This...
Three-phase ac-dc-ac voltage stiff systems consisting of a front-end rectifier, a dc link with a capacitor, and an inverter are widely used in on-line UPS, motor drive, and distributed generation systems. A PWM controlled front-end rectifier is desirable in three-phase ac-dc-ac systems. With the conventional PWM rectifier control technique, the input current tends to be unbalanced under unbalanced...
This paper proposes a direct power control (DPC) strategy employed for the neutral-point-clamped (NPC) three-level PWM rectifier. Mathematic model of NPC three-level rectifier is conducted firstly as a theoretical base. This topology generates a higher number of output voltage levels, increasing the flexibility for selecting an appropriate voltage vector. The direct instantaneous power control technique...
To draw a sinusoidal line current and to achieve high power factor and low voltage stress of power switches, Some single-phase three-level switching mode unidirectional rectifiers with power diodes have been presented. But there is an inherited disadvantage of imbalance of the DC-link voltage, which is difficult to be solved only by control method. A novel three-level rectifier with asymmetrical legs...
The proposed auxiliary converter system operates as a shunt active filter compensating for harmonic current of the diode rectifier and provides re-generation capability. However, the combination of the auxiliary converter and diode rectifier causes circulating current, which results in increased operational losses and noise. Circulating current is a zero-sequence component resulted from the pulse...
A soft switching converter with parallel-connected full-wave rectifiers is presented. In the proposed converter, the primary windings of two transformers are connected in series. Two full-wave rectifiers with ripple current cancellation are connected in parallel at the output side to reduce the current stress of the secondary winding of transformer. The clamp circuit based on an auxiliary switch and...
This paper proposes novel high input power factor single-stage single-phase AC/AC converter to give high input power factor and low current distortion on the rectifier side and provide clean and stable AC voltage on the inverter side. The proposed AC/AC converter can not only provide regulation of the output AC voltage magnitude but provide variable output AC voltage frequency. A significant reduction...
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