Apparent power and reactive power are two critical quantities in energy flow studies in electrical power systems. Existing definitions for these terms work well when both voltages and currents are sinusoidal with respect to time. However, both apparent and reactive power have no physical meaning. When these physically unclarified quantities are applied to non-sinusoidal systems, the following questions related to power flow remain not fully answered to date. What do these quantities really mean? Is it fair to bill customers based on the measurement of physically not meaningful quantities? What is the efficient way, both economical and technical, to compensate non-active power in power networks?;To answer the above mentioned questions, this thesis analyzes energy flow in nonlinear circuits, clarifies and proposes new power quantities with physical interpretations that are practical and effective when voltages and/or currents are non-sinusoidal. The suggested definitions are measurable quantities based on time-domain approach, and are useful in evaluating the power quality and efficiency in electrical systems. The measurement method and compensation with active filters are also discussed.
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