High power converters and ac drives bin wu pdf
High-Power Converters and AC Drives, 2nd Edition | WileyVFDs are used in applications ranging from small appliances to large compressors. Systems using VFDs can be more efficient than those using throttling control of fluid flow, such as in systems with pumps or fans. However, the global market penetration for all applications of VFDs is relatively small. Over the last four decades, power electronics technology has reduced VFD cost and size and has improved performance through advances in semiconductor switching devices, drive topologies, simulation and control techniques, and control hardware and software. Some types of single-phase motors or synchronous motors can be advantageous in some situations, but generally three-phase induction motors are preferred as the most economical.
High Voltage, High Power DC DC Converters, Applications & Topologies
High-Power Converters and AC Drives (2nd ed.)
To eliminate the even-order harmonics produced by the SVM, making the dc current continuous over almost the full operation range. Each of the switches in the inverter turns on and off once per sampling period. The discontin- uous current operation normally does not occur in the series-type higy since the dc load sees the leakage inductances of the secondary windings in series, a modified modulation scheme is presented. It is com- posed of a phase-shifting transformer and two identical bij SCR rectifiers.Finally, the operation of four- and five-level diode-clamped inverters with carrier-based modulation techniques is introduced. This is understandable since the harmonic content should not alter when a secondary current is referred to the primary side? The details of the line current distortion are discussed in the following sections. The line inductance Ls is assumed to be zero, and the total leakage inductance Llk is 0.
Traction drives for locomotives, light-track trains. Sommer, et al. Thus, and the efficiency of the drive is improved if the drive is frequently required to brake the motor. Some drives have a noise smoothing feature that can be turned on to introduce a random variation to the switching frequency.
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A sim- plified circuit diagram for a two-level voltage source inverter for high-power medi- um-voltage applications is shown in Fig. Asad ABbas marked it as to-read Feb 07, V ref can be approximated by two adjacent active vectors and one zero vector. Under this assumption, The causes of the dynamic voltage unbalance can be divided into two groups: a unbalance due to the difference in device switching behavior and b unbalance caused by the difference in gate signal delays between the system controller and the switches.
Therefore, the modulation index of 0. This is partially due to the conservative design of the insulation sys- tem for low-voltage motors. This book also provides adequate technical background for most of its topics such that it can be adopted as a textbook for a graduate-level course in power electronics and ac drives. The zero state convedters sig- nifies that switches S1 and S4 in inverter phase leg A conduct simultaneously and the other four switches in the inverter are off.
Therefore, suc. The basic drive controller can be configured to selectively include such optional power components and accessories as follows:. Carrier-based and space-vector modula- tion schemes for the multilevel inverters are elaborated. The configuration of the pulse SCR rectifier can be easily derived and thus is not shown.
As expected, the pulse rectifier has better line current THD profile than the pulse SCR rectifier while the pulse rectifier is superior to the pulse rectifier. The inverter is loaded with a su inductive load with a power factor of 0. The pulse rectifiers have a better harmonic profile, pdr the pulse rectifiers provide excellent harmonic performance. The torsional vibrations may be excited when the natural frequency of the mechanical system is coincident with the frequency of torque pulsations caused by distorted motor currents!The negative current is produced by the utility voltage when the SCR is used in a rectifier or by the load voltage in a load commutated inverter. In doing so, the SVM algorithm for hibh NPC inverter is simplified and can be performed in the same manner as for the two-level inverter. Views Read Edit View history. The power flow in the SCR rectifier is, there.
Design requirement a is satisfied. Due to the presence of the line inductance L s, the commutation process cannot nad instantly. By comparing the waveform of vAB with that in Fig? The principle of harmonic current cancellation by the phase-shifting transformers is also demon- strated.