Power Quality and Stability Analysis of Variable-Speed Drive Systems (VSDS)

Power Quality and Stability Analysis of Variable-Speed Drive Systems (VSDS)

Safwan Mhrez Nadweh (Tishreen University, Syria) and Ola Ahmad Khaddam (Tishreen University, Syria)
Copyright: © 2019 |Pages: 25
DOI: 10.4018/978-1-5225-8030-0.ch017
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This chapter introduces an analysis of power quality of variable-speed drive systems (VSDS). In this chapter, several issues have been discussed as VSDS in terms of cost and effectiveness, VSDS control loops (open loop, closed loop), and power quality in VSDS. Harmonics standards and harmonics in VSDS were discussed in this chapter in addition to highlighting the effects of harmonics on power factor, crest factor, and other power quality specifications. The solutions used to mitigate the harmonics in VSDS were discussed in detail. Finally, simulation of the conventional VSDS model and VSDS with one harmonic mitigation solution in order to clarify the usefulness of using this solution on power quality specifications were discussed.
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Vsds In Terms Of Cost And Effectiveness

There are millions of motors employed in a wide range of applications around the world and the majority of them operate only at 100% speed for short periods of time. This often results in significant energy losses during the operation time, especially after considering the electrical power consumed by motor systems that reach more than 60% of electrical power consumed by industry. Significant energy savings can be achieved when the rotational speed of the motor is decreased to match with the load requirement and that can be achievable by installing VSDs systems. VSDs allow the motor speed to change depending on operating conditions, rather than operating continuously at full speed. Because the power drawn is proportional to the cube of its speed, reducing speed can save a lot of energy

The tendency to automate industrial process, and the persistent need for increased efficiencies from plant and machinery, together with the demand for higher performance at a lower cost, contribute to the rapid growth of VSDs market (ABB, 2009; Davari et al., 2015).

Efficiency of the operation can be increased by allowing motors to be operated at the ideal speed for every load condition through the capability of soft start up and over speed, which reflects on the process precision and improves power factor. Due to speed and torque control, motors endure less wear and tear, which leads to lower maintenance costs and downtime and prolong the life of the motor. VSDs also reduce frictional losses related with mechanical or electromechanical adjustable speed technologies and expensive energy-wasting. Furthermore, Applying VSDs can lead to reduction in the amounts of carbon dioxide emissions by reducing the amount of fuel consumed through the operation.

Some examples of energy saving applications that use VSD systems are:

Key Terms in this Chapter

Power Quality, Involves Voltage, Frequency, and Waveform: Good power quality can be defined as a steady supply voltage that stays within the prescribed range, steady AC without the proper power an electrical device (or load) may malfunction, fail prematurely or not operate at all.

Power Factor (PF or cosf): Is the ratio between the power that can be used in electric circuit (real power, P) and the power from the result of multiplication between the current and voltage circuit (apparent power, S).

Crest Factor: Is a parameter of a waveform, such as alternating current or sound, showing the ratio of peak values to the effective value. In other words, crest factor indicates how extreme the peaks are in a waveform.

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