Jason Wells

Modulation-Based Harmonic Elimination

A modulation-based method for generating pulse waveforms with selective harmonic elimination is proposed. Harmonic elimination, traditionally digital, is shown to be achievable by comparison of a sine wave with modified triangle carrier. The method can be used to calculate easily and quickly the desired waveform without solution of coupled transcendental equations

Selective harmonic control: a general problem formulation and selected solutions

Selective harmonic elimination/control has been a widely researched alternative to traditional pulse-width modulation techniques. Previous and current work has made fundamental assumptions that enforce output waveform quarter-wave symmetry, presumably in order to reduce the complexity of the resulting equations. However, the quarter-wave symmetric assumption is not strictly necessary. It restricts the solution space, which can result in sub-optimal solutions with regards to the uncontrolled harmonic distribution. A more general formulation is proposed, removing the quarter-wave symmetry constraint for two classes of the m-level, n-harmonic harmonic control problem. The special cases of two- and three-level harmonic elimination are presented in detail along with representative solutions for each harmonic control problem. New solutions previously unattainable based on quarter-wave symmetric techniques are identified.

INVENT Modeling, Simulation, Analysis and Optimization

In this paper, a new subsystem-based approach to solve aerospace vehicle energy management issues is described. The goal of this approach is to create an “Energy Optimized Aircraft” that will maximize energy utilization for broad capabilities while minimizing complexity. To support this goal, an advanced modeling and simulation ICD process is established. This process addresses several of the current challenges facing modeling and simulation of large integrated systems.

Optimal harmonic elimination control

Harmonic elimination and control has been a widely researched alternative to traditional PWM techniques. The equations that govern harmonic elimination have multiple solutions based on different switching angles. Each solution will result in the uncontrolled harmonic content having a unique distribution of energy. To determine which solution is optimal, a cost function must be developed for a given specific application. Typical cost functions will require evaluation significantly beyond the last controlled harmonic. This paper develops a cost function and provides experimental results for a single-phase inverter and a three-phase induction motor drive system. Ultimately, it is shown that there exists an optimal harmonic control solution for a given application , which minimizes some cost function; in this case, system power loss.

Dead-Time Distortion in Generalized Selective Harmonic Control

The selective harmonic control (SHC) method of pulsewidth modulation is meant to place switching edges to eliminate or set precisely given harmonics. This manuscript discusses the practical impact of edge placement sensitivity due to dead time that occurs in generalized SHC. It further provides experimental validation to theoretical work presented in a previous publication.

Harmonic elimination switching through modulation

Harmonic elimination methods create discrete-valued switching control waveforms with explicit harmonic content. A major drawback is that these methods do not allow dynamic adjustment as frequencies and amplitudes change continuously. Harmonic elimination is constructed in a general manner here, leading to infinite numbers of solutions. A modified carrier approach that closely approximates the performance of harmonic elimination is introduced. The modified approach can produce even lower weighted total harmonic distortion than conventional harmonic elimination, and supports dynamic PWM with low harmonics.

Generalization of Selective Harmonic Control/Elimination

Previous work on selective harmonic elimination/control has made fundamental assumptions that enforce output waveform quarter- or half-wave symmetry, presumably in order to reduce the complexity of the resulting equations. However, the quarter- or half-wave symmetric assumption is not required and it restricts the solution space, which can result in sub-optimal solutions with regard to the uncontrolled harmonic distribution. More general formulations can be proposed which have varying degrees of additional complexity. In order to understand how these more general formulations can be obtained, a qualitative description of the waveform construction process for the two-level waveform case is discussed followed by presentation of the resulting system of equations. This two-level case is then generalized to the m-level, n-harmonic control problem. Finally, this generalization is used to analyze three-level waveforms. All solutions presented in this paper are unattainable utilizing previous techniques

Applications of ripple correlation control of electric machinery

Ripple correlation control can be applied to electric drive systems in order to optimize some cost function independent of parameters. This involves correlating the perturbations in the cost function with the perturbations in the independent variable to obtain a command for the independent variable. The perturbations are normally due to ripple that is naturally present in electric drive systems. In the steady state, the fast-average value of the independent variable converges asymptotically to a point no more than the magnitude or the ripple away from the optimum set point. In certain applications, cost function observers must be created to obtain the correct correlation information. In this paper, ripple correlation control is developed and demonstrated for DC, induction, and brushless DC drives.

Low-cost single-phase powered induction machine drive for residential applications

In conjunction with the 2003 future energy challenge (FEC), a low-cost integrated machine end drive system is considered for residential applications between 50 and 500 W. The objective is to remain cost competitive with traditional single phase induction machine solutions while improving system performance. The basic architecture includes a power factor correction boost rectifier, a hex-bridge inverter, control circuitry implementing selective harmonic elimination, auxiliary power supplies, and a three phase induction machine designed for inverter operation. This paper discusses system design, performance, cost, and lifetime.

Fundamental aspects of ripple correlation control of electric machinery

Ripple correlation control (RCC) has been established as a cost function minimization strategy for problems ranging from source impedance matching to static VAR compensators and more recently to electric machinery. The dynamics of machines often makes direct application of RCC not possible or not practical. This paper addresses the fundamental challenges associated with implementation of RCC optimization in electric machinery. Specifically, the paper presents a steady state error analysis of several practical RCC control laws, develops a systematic approach to observer design to cast the optimization of a dynamic process into a static framework, and presents the benefits of an alternative RCC control law for use in electric machinery controllers.