Huiyu Zhu

Average modeling of three-phase and nine-phase diode rectifiers with improved AC current and DC voltage dynamics

This paper presents a new average modeling approach for three-phase and nine-phase diode rectifiers with improved AC and DC dynamics. The key assumption taken in this paper is to model the DC load current using its first-order Taylor series expansion throughout the entire averaging timespan, i.e., commutation and conduction periods. The resultant average models present an excellent steady-state and transient behavior, matching their respective detailed switching models with less than 1 % measured error. Moreover, the analytic nature of these models makes them suitable for simulation and stability studies of variable frequency power systems. The paper presents an in-depth description of the modeling approach, together with a thorough static and transient validation of the proposed models. The model is validated through comparison of average model in MATLAB, switching model in Saber and the experimental results

Evaluation of average models for nine-phase diode rectifiers with improved AC and DC dynamics

This paper presents an in-depth comparison and evaluation of average models for nine-phase diode rectifiers, proposing a new model featuring improved static and dynamic characteristics exceeding by far those of previously existent models. The key to the proposed model is the representation of the dc load current by means of its Taylor series expansion. The analysis revealed a 10% and 3% average error reduction of the proposed model in steady state and transient conditions respectively, as well as an accurate calculation of the converter output impedance to less than 10deg and 1 dB phase and magnitude error. The paper shows too that average models of diode rectifiers and line-commutated converters are also subject to the sampling theorem limitations, i.e., their frequency response is limited to half of the averaging period. Finally, key steady state, transient and frequency response results are validated using a 2kW experimental prototype showing the high accuracy achieved by the proposed average model

Modeling and Prediction of DC-Bus Harmonic Resonance for AC-to-AC Motor Drive Systems

This paper presents a modeling and analysis methodology to study the harmonic resonance on the dc-bus filter of ac-to-ac motor drives. Specifically, a system comprised of a synchronous generator, a multi-pulse diode rectifier, a dc-bus filter and a PWM motor drive is considered. The proposed method employs Thevenin and Norton equivalent circuits to model the generator-rectifier and motor drive on the dc-bus, thus resulting in a fully linear system when combined with the dc-bus filter components. Transfer functions of interest describing possible resonance conditions are then readily derived and used to assess and predict harmonic resonance on the system. Detailed simulations with Synopsys Saber are used to validate the proposed methodology, showing its effectiveness for the study of harmonic resonance on this type of application.

Analysis of new 18-pulse direct symmetric autotransformer rectifiers with dual AC-voltage feeding capability

Ever increasing power quality requirements have impelled the development and usage of new front end AC-to-DC converters. Multi-pulse direct symmetric autotransformer rectifiers (DSAR) have arisen as a most advantageous passive solution, featuring high reliability and simplicity of operation, minimum kVA ratings, solid multi-pulse operation insensitive to impedance path mismatch or voltage distortion, reduced common-mode voltage, and reduced size and weight-hence the interest for transport applications. This paper proposes three new DSAR topologies with the capability to operate from 0.5 pu and 1 pu voltage sources while generating 1 pu output DC voltage, thus significantly enhancing their operational flexibility. The paper presents a complete evaluation using simulated (Synopsys Saber) and experimental results in order to fully assess the thermo-electromagnetic capabilities of these new topologies, focusing on losses and efficiency, size and weight, and the overall power quality of these converters. Specifically, it analyzes efficiency, input current distortion, common-mode voltage and DC voltage ripple, all of this while operating from ideal and low power quality AC voltage networks rated at 0.5 pu and 1 pu. From these results specific design guidelines and criteria for selection are derived and presented.

Optimization of driving amplifiers for smart actuators using genetic algorithm

A high-efficiency low-profile driving amplifier for smart actuators is essential for portable actuator devices. In this paper, an optimized design of a half-bridge switching circuit to drive smart actuators is described. A genetic algorithm, which is well suited for solving the discrete optimization problem, is applied to the traditional circuit design to make it smaller and more efficient. The calculation of the power dissipation of the MOSFET is a prerequisite for obtaining realistic designs. The results of the optimization procedure are summarized.

Energy optimization of driving amplifiers for smart actuators

A high-efficiency driving amplifier with small profile for smart actuators is essential for portable actuator devices. In this paper, a detailed optimized design of half-bridge switching circuit to drive smart actuators is described. The mathematical optimization procedure is applied to the traditional circuit design to make the circuit smaller and more efficient. The objecitve function presented in this paper is to minimize the total weight of the circuit, including heat sink, inductor and bus capacitor. The calculation of the power dissipation of MOSFET is adopted as a critical step to get the suitable heat sink. The optimization results are presented to demonstrate the effectiveness of this method.

INTERTIALLY STABILIZED RIFLE USING RECURVE ACTUATORS

This paper describes an INertially STabilized Rifle where a Recurve actuator, constructed from piezoelectric material, is used to internially stabilize the barrel assembly of a tactical rifle to compensate for the small user-induced disturbances. The requirements of this system are discussed and the actuator requirements are derived. A prototype Recurve actuator is described and the test results reported. Similarly, the power electronics needed for INSTAR are discussed. Test results for an prototype circuit are given.Copyright

Nonlinear compensation of quadratic behavior in a magnetostrictor material

The constitutive behavior of magnetostrictive materials exhibits many nonlinearities. One of the dominate nonlinearities is the quadratic dependence between the drive current and the transducer displacement. While the transducer can be operated at low drive levels with little distortion, at high drive levels the square law distortion is evident. In this paper we propose a nonlinear feedback loop for the drive amplifier such that the amplifier provides a compensation for this transducer nonlinearity. Thus the combination of the amplifier and the magnetostrictive transducer presents a linear input output relationship to the user. The effectiveness of this nonlinear control is demonstrated in simulation.

Combined Design of Recurve Actuators and Drive Electronics for Maximum Energy Efficiency

Smart structures typically consist of many interacting components, which result in a closed loop formed by an actuator, structure, sensors, controller, and drive circuit components. Despite the recognition of component interactions, much of the traditional design approach for such systems is highly compartmentalized and sequential. The primary objective of the present work is to develop a basic understanding of the energy flow and dynamic interaction between the electrical and mechanical subsystems of smart actuators. When operating from portable power sources, a crucial factor in determining the performance of such a smart system is the battery capacity required for the actuator to operate through a given time span along with its life time. The real and reactive power in such a system will determine the battery life and size separately. While the real power is dissipated only in the drive circuit, the reactive power of the circuit and the actuator cannot be calculated individually, where the interaction arises. Multi-objective function optimization problem, which combines the real and reactive power by different weights, will result in a better balanced solution than optimizing either one of them separately. Genetic algorithm is applied for discrete component selection to generate more realistic designs. The optimization result is illustrated in the paper, as well as their relationship with multi-objective functions.