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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 the actual power system three-phase voltages are distorted and asymmetric and contain a large number of negative sequence components. Traditional ip-iq method which detect harmonic currents based on instantaneous reactive power theory will be inaccurate, so the positive sequence voltage component of A-phase need be extracted. Improved instantaneous symmetrical components structured a rotary phases...
In this paper is presented the structure and working principle of the cascaded H-bridge multilevel converter with PWM rectifier and phase-shift transformer. Using the leak inductance as the filter reactor of the PWM rectifier can reducing the volume and cost of the converter; the phase-shift secondary side of the transformer can eliminate the current harmonics caused by the single power unit, restraining...
The use of some electrical equipment attached to typical power systems creates voltage quality concerns. There is an increasing awareness that some equipment is not designed to withstand the surges, faults, distortion, and reclosing duty present on typical utility distribution systems. Traditional concerns about steady-state voltage levels and light flicker due to voltage fluctuation also remain....
This paper presents and compares the performance of two controllers namely Fuzzy Logic and Proportional Integral applied to a voltage source inverter/converter operating as an active power filter. The active power filter is operated to compensate harmonics and reactive power generated by the non-linear load and power factor correction simultaneously. This work is performed in order to make an accurate...
A three-phase four-wire DSTATCOM (distribution static compensator) based on three-leg VSC (voltage source converter) isolated with a star/hexagon transformer is demonstrated for power quality enhancement in a three-phase four-wire distribution system. The DSTATCOM is controlled to compensate the reactive power, eliminate harmonic currents, balances the load and also to mitigate the neutral current...
This paper presents the implementations of a new control algorithm for a three-phase shunt active power filter to regulate load terminal voltage, eliminate harmonics, and improve the power factor in systems with an uncontrolled rectifier and an AC controller as the non-linear loads. Different methods are used to control the active power filters. The reference current to be detected from the load current...
This paper deals with a novel configuration of single-phase hybrid active power filter. One of the advantages of the proposed hybrid filter is its adjustable capability to determine voltage rating and current rating of active power stage by selecting appropriate values for its passive filter parameters. Equivalent circuit of proposed hybrid filter has been presented and its filtering characteristic...
Power converter is the key element of the photovoltaic generation system. In order to improve the energy conversion efficiency and achieve an economic solution, hybrid cascade inverter (HCI) is employed and implemented to realize DC-AC conversion in this paper. HCI has a similar topology with conventional H-bridge cascade inverter, while the voltages of its DC buses are in a geometric sequence. In...
Thyristor based, phase angle controlled, speed regulators are widely used for energy efficient control of single-phase induction motors. This leads to power saving but adversely affects the life of insulation in the motors due to non-sinusoidal voltage and current waveforms. The accelerated insulation ageing is due to increased voltage peaks, voltage transients, sharp dV/dt and increased thermal stress...
There are many consumers and equipments in distributed generation (DG) systems and distributed networks which have rapid changes in the reactive power consumption. These changes can result in large variations in the load-side voltage that may affect the operation of other power consumers which are fed from Point of Common Coupling (PCC). In this paper a current control strategy for inverters, based...
This paper presents a control algorithm for improving the performance of a three-phase, four-wired (3P4W) active power filter (APF) under unbalanced and distorted supply voltages. A low pass filter (LPF) is designed to filter the nonsinusoidal supply voltages. The minimal optimal values of active power filter source reference currents are estimated in natural a-b-c reference frame. The proposed method...
This paper presents a new digital signal processor (DSP)-based control method for shunt active power filter (SAF) for three-phase power distribution systems. Compared to conventional analog-based methods, the DSP-based solution provides a flexible and cheaper method to control the SAF. The proposed technique requires fewer current sensors than other solutions which require both the source current...
Through analyzing the typical systempsilas characteristic and Ultra-High Voltage(UHV) ac transmission linepsilas characteristic, the strategy by controllable shunt reactor is presented to improve transmission quality in electric networks in this paper. By using MATLAB PSB, simulation model of UHV ac transmission line from Jindongnan to Jingmen was built to study control effects on frequency over voltage,...
In this paper, two control strategies for three-phase series-parallel uninterruptible power supplies are compared. A series-parallel UPS consists of a parallel and a series converter. In this topology, most power required by load is supplied directly from AC line during standby mode. Therefore the overall efficiency is higher than that of a conventional UPS. Traditionally, the control strategy of...
A high performance modular three-phase utility-interactive converter is designed and implemented in this paper. This converter has three operation modes: grid-connection inverter mode, stand-alone inverter mode and rectifier mode. Control principles and modes of every mode are analyzed in detail and the modular design method is adopted. A simple but valid control strategy is proposed. Finally a 10...
The multiple overlap mode of the overlap carrier wave phase shift PWM (SVPWM) inverter is one of the development directions of the super-high capacity inverter, this paper reasons the relation between carrier wave phase shift SVPWM circuit output voltage and phase shift angle, put forward the best phase shift angle formula, proposed two kinds of control schemes and compares them. Through the experiment...
For the sake of energy saving, harmonic current suppression and drive performance improvement, inverter-fed air-conditioner drive systems are used more and more extensively, and the selected motors include ASM,BLDCM and PMSM. Generally, the front stage AC/DC converter of inverter aircon is complete active power factor corrector (PFC), which can bring about better correction effects. Whereas the traditional...
This paper proposes rating lowering of inverter module by using power factor correction (PFC). Most application of PFC is found frequently in AC-DC converters but seldom in inverters. It has been considered that the use of PFC in inverter modules is not effective because of additional circuit of PFC and its costs. However, this paper shows that the ratings of an inverter can be lowered down by using...
This paper proposes a four-multiple pulse width modulation (PWM) converter for grid interface, which is apply to the variable-speed constant-frequency direct-drive wind turbine systems. The paper introduces the principle of PWM converter, in order to improve DC voltage utilization, space vector pulse width modulation (SVPWM) technology is adopted. Then the advantages of the multiple based on carrier...
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