A Low Cost Power Quality And Energy Savings Laboratory For Undergraduate Education And Research

This paper describes the design and implementation of a power quality and energy savings laboratory at Merrimack College. Merrimack College is a liberal arts institution north of Boston, MA, which has a small ABET accredited ECE department with 6 faculty and about 90 students. There is strong student interest in learning about power, and local utilities seek graduates with expertise in power. A new course in Power Quality (PQ) has proven popular. A laboratory experience, which includes elements of power quality and energy savings, has been designed and implemented. In addition, the ECE department now requires a sophomore level class in embedded controllers. An extension to the PQ laboratory experience that incorporates embedded controllers has also been designed. The lab set up is based on maximizing student understanding in conjunction with minimizing costs. The students learn causes, impacts, and solutions of PQ problems. They learn how to design a power factor correction capacitor bank and an LC filter to mitigate harmonics. They also conduct simulations of the power system network, and analyze system data. The students are taught methods of calculating energy savings due to the addition of PQ components to the network. One implemented design resulted in savings of over 5 kWh, which based on local rates conservatively gives a yearly savings of $2,600 for the science building alone. The PQ components consist mainly of reactors, capacitors and the monitoring system. A further, complementary laboratory experience incorporating low cost embedded microprocessor designs used to control the PQ system via a remotely accessible, secure TCP/IP Ethernet link has been designed. This additional circuitry allows real time monitoring of the network and modification of the PQ elements based on dynamic loading 24 hours a day. Implementing such a system can yield yet additional energy savings. The embedded processor students, both from ECE and Computer Science, are planned to have remote access to the lab and will be encouraged to help with the development via laboratory assignments. An Introduction to Power Quality and the Power Quality Problems in the Mendel Science Building It is the objective of the electric utility to supply its customers with a sinusoidal voltage of relatively constant magnitude. The generators that produce the electric power generate a very close approximation to a sinusoidal signal. However, there are loads and devices on the system that have linear and nonlinear characteristics and result in voltage sag, voltage spikes, voltage P ge 955.1 Proceedings of the 2004 American Society for Engineering Education Annual Conference and Exposition Copyright © 2004, American Society for Engineering Education transient, voltage surge, low power factor, voltage unbalance, current unbalance, and harmonics distortion of both the voltage and current signals. As more nonlinear loads are introduced within a facility, these waveforms get more distorted. Figure 1 shows both a sinusoidal and nonsinusoidal current waveform. [1] The advancement and wide application of adjustable speed drivers, electronic devices, microprocessors, etc. in many areas have significantly contributed to the voltage and current distortion in distribution systems. This has created the need for better understanding of the impact of harmonic distortion on control and instrumentation in power systems, industrial equipment and even household appliances. Harmonics and Harmonic Filters A harmonic is an integer multiple of the fundamental frequency. For example, the third harmonic in a 60 Hz system is 180 Hz; the fifth harmonic is 300 Hz, and so on. The nonlinear devices needed in a power system, including power converters, arc-furnaces, adjustable-speed motor drives, electronic power supplies, dc motor drives, battery charges, electronic ballasts, gas discharge lighting devices, transformers, personal computers, and monitors cause current and voltage harmonic distortion. A nonlinear load may be defined as a load that, having a sinusoidal voltage applied to it passes a non-sinusoidal current. A nonlinear device is one in which the current is not proportional to the applied voltage. In other words, while the applied voltage is sinusoidal, the resulting current is distorted “garbage”. The increasing use of these nonlinear devices causes the problem of harmonic distortion to grow. Ultimately the harmonic currents will travel to the power source through the power system's wires. The wire’s impedance will cause a voltage distorted waveform from the voltage drop caused by the distorted current. Figure 2 is a good example of current harmonic distortion seen in the Mendel Science Building due to the nonlinear loads.