Yingwei Huang

Improved Fault-Tolerant Control for Brushless Permanent Magnet Motor Drives With Defective Hall Sensors

Brushless permanent magnet motor drives based on Hall sensors have received significant attention in recent years. In this area, the faults of Hall sensors become a new concern and several fault-tolerant control (FTC) methods have been proposed. However, most of the state-of-the-art FTC methods require some time to reconstruct the correct Hall sensor signals, which results in significant transient currents and speed dip during fault diagnostic process (FDP). In this paper, a new and improved FTC scheme based on FDP and vector-tracking observer is proposed. A method to identify the duration of FDP is proposed based on the analysis of acceleration estimation and the fault diagnosis results. During FDP, the method defaults to an open-loop observer control, which removes the undesirable current/torque transient. After that, the close-loop observer is re-enabled and the motor operation is restored. The proposed FTC is demonstrated in detailed simulations and experimentally on 120° brushless dc motor drives and sinusoidal PM motor drives. For both types of drives, a significant improvement is achieved in steady state and transient operation with faults of up to two Hall sensors, which has not been possible with available alternative FTC approaches (unless a sensorless control is used).

Fault Diagnosis and Signal Reconstruction of Hall Sensors in Brushless Permanent Magnet Motor Drives

Brushless permanent magnet (BLPM) motor drives based on Hall sensors have received extensive attention in the literature and are widely used in many applications. However, most of the available and published controllers assume that the Hall signals are always available, which is not true if any of the sensors are faulted. In this paper, several fault-tolerant control schemes for BLPM motor drives are proposed. The methodology is based on fault diagnosis and its classification, and subsequent signal reconstruction. Simulation and experimental results demonstrate the effectiveness and advantages of the proposed fault-tolerant schemes in restoring the motor operation when failures occur in up to two Hall sensors. The proposed fault-tolerant schemes can be easily and flexibly realized for conventional drive systems, either by adding the code in the existing driver or by adding a simple auxiliary circuit between the Hall sensors and the driver.

A Constant-Parameter Voltage-Behind-Reactance Synchronous Machine Model Based on Shifted-Frequency Analysis

Recently, the concepts of dynamic phasors and shifted-frequency analysis (SFA) have received renewed attention as a possible solution framework for the modeling of power system components and transients, as opposed to using instantaneous time-domain variables or conventional phasors. In this paper, a new voltage-behind-reactance (VBR) synchronous machine model based on SFA is presented. Using dynamic phasors, the proposed model permits the use of a much larger range of step sizes to efficiently simulate electromagnetic and electromechanical transients. Moreover, the proposed model has a constant-parameter (CP) stator interface, which is simple to implement and numerically more efficient compared with the prior state-of-the-art models with rotor-position-dependent stator inductance matrices. Rigorous transient case studies demonstrate that the new model requires significantly fewer time steps than the conventional time-domain models, and is more efficient than the previously established variable-parameter SFA model.

Using LED lighting drivers for harmonic current cancellation in intelligent distribution power systems

Harmonic currents injected from low-cost rectifier loads can cause adverse impacts in electrical distribution systems. This paper presents a harmonic cancellation approach using the light-emitting-diode (LED) lighting systems, which are becoming widely considered in commercial, office, and residential buildings and homes. The proposed approach is based on redesigning the existing LED converter controller to absorb/cancel a specific harmonic current injected by other devices. This can be further exploited in conjunction with the energy management system (EMS) and advanced control network, where a smart meter can inform the LED converters of the harmonic currents to be canceled. A maximum capability of injecting individual harmonics by the LED converter is estimated for the 3rd, 5th, and 7th significant harmonics currents. Simulation results are demonstrated to verify the effectiveness of the proposed approach.

State-space voltage-behind-reactance modeling of induction machines based on shifted-frequency analysis

Modeling and simulation of power systems for general-purpose transient studies has been receiving significant attention in the literature. Among recently proposed methods, the so-called shifted-frequency analysis (SFA) approach has been shown to facilitate accurate and numerically efficient simulation of electromagnetic and electromechanical transients with the use of dynamic phasors. This paper proposes a SFA-based voltage-behind-reactance (VBR) model of induction machines (IMs), which is shown to permit the use of a large range of step sizes to effectively simulate various types of transients. The proposed VBR-SFA IM model is developed in state-space formulation, which is simple to implement and can be solved with built-in variable-step solvers in MATLAB/Simulink and other programs. Computer studies demonstrate that the proposed VBR-SFA IM model requires significantly fewer time steps and is more efficient than the conventional/existing time-domain models.

Dynamic Phasor Modeling of Line-Commutated Rectifiers With Harmonics Using Analytical and Parametric Approaches

Line-commutated rectifiers (LCRs) are widely used in various industrial applications, wherein they are also known to be a significant source of harmonics. The dynamic phasor (DP) modeling approaches have been well studied in the literature to simulate the dynamics of power systems and their components including harmonics. In this paper, the state-of-the-art analytical DP (ADP) models of LCRs, which relate the ac and dc subsystems through complicated switch functions, are first investigated. Then, a new parametric DP (PDP) model of LCRs is proposed, wherein the DP dynamics of rectifier/dc-link are represented using a set of explicit algebraic functions that are numerically established. Rigorous computer studies demonstrate that the proposed PDP methodology is capable of accurately predicting the steady-state and transient responses of LCR systems under a wide range of loading conditions, while providing significant computational advantages over the conventional detailed model and the established ADP models.

Interfacing SFA- and GAM-type dynamic phasors for modeling of integrated AC-DC power systems

This paper focuses on the modeling of integrated ac-dc backup and generation power systems, which has received increasing attention due to the emergence of microgrids and distributed generations. The conventional shifted-frequency analysis (SFA) type dynamic phasors (DPs) assume a bandpass spectrum of power system signals, and thus are only suitable to model system components wherein the 60Hz fundamental frequency is dominant. To account for high-order harmonics of interest in ac-dc systems, this paper considers another type of DPs based on the generalized averaging method (GAM), and proposes a possible interface between the SFA- and GAM-type DP models. Computer studies demonstrate that the proposed DP interface allows for accurate simulations of both fundamental frequency components and high-order harmonics in integrated ac-dc power systems, while providing significant numerical advantages over the conventional time-domain detailed models.

Efficient simulation of wind farms using switching reduced models of converters and VBR formulation of six-phase PM synchronous generators

Wind generation systems with variable frequency generators commonly utilize several power electronics converters. Using numerically efficient models for converters and electrical machines can decrease simulation time of wind farms. In this paper, a voltage-behind-reactance model is developed for a six-phase permanent magnet synchronous generator. Then, a multiresolution simulation methodology is presented which utilizes different combinations of detailed and average-value models of twelve-pulse rectifier and three-phase inverter systems in conjunction with different six-phase machine models. The presented models are verified through simulations to provide superior performance in terms of speed and numerical efficiency.

A parametric dynamic phasor model of line-commutated rectifier systems

Recently, the generalized averaging method (GAM) has received significant attention to effectively model and simulate dynamics of ac-dc power systems using dynamic phasors (DPs). The conventional analytical DP (ADP) models of line-commutated rectifiers (LCRs) have been derived based on switch functions, which are only valid for certain operating mode. In this paper, a new parametric DP (PDP) model of LCRs is presented, which relates the ac-dc subsystems through a set of parametric algebraic functions that account for various loading conditions. Simulation results validate the advantageous accuracy of the proposed PDP model of LCRs, and demonstrate its superior numerical efficiency over the time-domain detailed model and the prior ADP model.

Generalized Parametric Average-Value Model of Line-Commutated Rectifiers Considering AC Harmonics With Variable Frequency Operation

Line-commutated rectifiers are often utilized in machine-converter systems and many energy conversion applications. Simulation of such power systems using detailed switching models of rectifiers is computationally expensive, and as an alternative for system-level studies, the so-called average-value modeling (AVM) techniques have become indispensable. The parametric AVM (PAVM) uses a computerized approach for establishing the key relationships between the averaged ac and dc variables. In this paper, a generalized PAVM (GPAVM) is proposed, which extends several previously proposed models. The new GPAVM includes the ac harmonics in thyristor-controlled rectifier models considering their nonlinear dependency on the line frequency. The new model is verified using detailed simulations and experimental results and is demonstrated to have better accuracy in a wider range of operating conditions and speeds/frequencies.