Open-phase Fault Condition Research Articles

Analysis of a nuclear power plant’s responses to the open-phase fault of preferred power supply

This paper explores the phenomenon of open-phase fault of nuclear power plants for preferred power supply, focusing on three distinct scenarios, normal operation, start, and overhaul. For each scenario, the paper discusses the responses of existing relay protection devices, which are crucial for detecting and mitigating open-phase faults. These responses vary depending on the impedance at the fault location and the load rate of the plant. This paper highlights that open-phase faults can lead to three-phase imbalances in the power system, but their impact on voltage levels is not always straightforward due to the transformer and motor compensation effects. Additionally, the paper identifies blind zones in open-phase fault detection, where existing relays may fail to respond effectively, leading the plant to enter a station blackout state. In conclusion, the research underscores the importance of open-phase fault detection and protection in nuclear power plants. It reveals potential vulnerabilities in existing relay configurations and emphasizes the need for enhanced monitoring and safety measures to prevent extended plant operation under open-phase fault conditions.

Wide-Speed Range Sensorless Control of Five-Phase PMSM Drive under Healthy and Open Phase Fault Conditions for Aerospace Applications

This paper presents a speed sensorless control of a five-phase PMSM in healthy operation and under the Open-Phase Fault on any phase of the machine. The solution is recommended for mission-critical applications requiring high reliability capacities, such as Aerospace applications. An adapted Active Fault Tolerant Control is proposed with the aim of obtaining electromechanical torque as close as possible to that normally developed by a machine working in healthy condition. In instances of a loss of power to one phase of the machine, a reconfiguration of the control law is performed to ensure the continuity of service and to maintain acceptable control performances without requiring a hardware rearrangement of the power architecture. The motor rotation speed and position, required for the Field Oriented Control (FOC) of the stator currents, are estimated using a Back-Electromotive Forces (Back-EMF) observer based on a mathematical model of the motor and implemented in the stator diphase reference frame. Different electrical models that describe the behavior of the five-phase machine in the normal and degraded operations are given. Experimental results on a 1.25 kW synchronous PM machine are shown to confirm the effectiveness of the motor control.

A Phase-Domain Model of Dual Three-Phase Segmented Powered Linear PMSM for Hardware-Assisted Real-Time Simulation

In this article, a hardware-assisted real-time simulation phase-domain (PD) model of a dual three-phase segmented powered linear permanent magnet synchronous machine (SP-LPMSM) used in electromagnetic drive is established. The model is able to consider the end-effect, saturation effect, coupling effect, and open-phase fault conditions, which are specially occurs in the segmented structure in SP-LPMSM. The unbalanced inductances and saturation effect caused by the segmented structure are investigated and a simplified look-up table for inductances is introduced. Additionally, to accurately evaluate the coupling effect, the permanent magnet (PM) flux linkage is decoupled into the product of unit PM flux linkage and coupling coefficient. In order to avoid the numerical impulse caused by the derivative in the progress of calculating back-EMF, sigmoid function is adopted to express the coupling coefficient. Meanwhile, to make the PD-model compatible with the open-circuit fault conditions, incidence matrices and current constraint matrices are introduced to unify the PD-models with different winding connection types and open circuit faults into one general form. The PD-model realized in field-programmable gate arrays (FPGA) based hardware is validated in comparison with finite-element analysis results.

Open-Phase Faulty Five-Phase Permanent Magnet Assisted Synchronous Reluctance Motor Model With Stepped Skew

Commonly, healthy five-phase permanent magnet assisted synchronous reluctance machines (PMaSynRMs) are modeled in harmonic fixed rotating ( dq1dq ) reference frames. Such approaches feature several levels of detail, namely, constant parameters or saturation in four axes, i.e., 4-D saturation or cross-saturation effects in conjunction with space harmonics in 5-D models. In this article, a 6-D model is proposed that comprises all aforementioned nonlinearities not just in faultless but also in open-phase fault conditions. Moreover, magnetic axial asymmetry introduced by discrete skew is taken into account and included in the investigated modeling. The proposed 6-D model is based on flux maps obtained from static Finite-Element program posteriori modified to comprise the skewing effect. Very close to finite-element precision is guaranteed and experimental validations have been performed to confirm the authenticity and contrast the effectiveness of the open-phase model with skew.

Fuzzy logic based dynamic performance enhancement of five phase induction motor under arbitrary open phase fault for electric vehicle

Abstract The multiphase induction motor can be a highly preferable choice for the EV application, where the reliability and safety of passengers are one of the major concerns. The main objective of this article is to design high performance fault tolerant control of five phase induction motor (FPIM) drive to enhance the dynamic performance under healthy, faulty and fault tolerant modes of operation under arbitrary open phase fault condition. First, a simple method of modeling open phase fault in any phase of the FPIM drive is proposed. The most frequently occurring open phase faults due to the power electronics switch failure in the inverters are considered for the analysis. A generalized method of modeling arbitrary open phase fault in FPIM drive using back EMF calculations in faulty phase is suggested. The developed method utilizes the same transformation matrix for any open phase fault such that the minimum modification in control strategy is required under fault condition. Thereafter, the control technique is detailed. The rotor field oriented control (RFOC) of FPIM with fuzzy logic speed controller is developed to generate optimal torque reference. The design of FLC is detailed with fine-tuned scaling factor, rule base and membership function to obtain robust performance of the drive under healthy and fault tolerant modes of operation. The complete RFOC scheme for 2 HP FPIM drive is built in MATLAB/SIMULINK incorporating fuzzy logic based controller to verify its performance. The comparison of transient and steady state response and robustness (to the load disturbance as well as fault) obtained using developed fuzzy logic based controller with those using conventional PI controller is presented to prove the efficiency of the suggested controller under various speed torque profiles. The effectiveness of the proposed fuzzy based fault tolerant controller for FPIM drive is validated using OP4510 controller based real time HIL simulator.

Comparative Study of Hysteresis Controller, Resonant Controller and Direct Torque Control of Five-Phase IM under Open-Phase Fault Operation

The need for regulating the operation of unhealthy motor drives has motivated the researchers to modify the control techniques in order to be valid for the new drive state. The use of a fault-tolerant facility is an attractive feature of multiphase machines; therefore, the applicability of different controllers has been established for the operation under open-phase fault conditions. The considered control algorithms were utilized to analyze the operation of the unhealthy system and evaluating the capability of the control to regulate the speed and torque under the fault condition. However, the majority of these studies considered only one control algorithm to be tested with the faulty system without comparing its performance with other techniques. The performance comparison is a vital way to visualize the features and characteristics of each algorithm. For this purpose, this paper deals with the performance comparison of the hysteresis controller, RFOC based on resonant controller and direct torque control (DTC) control under open-circuit fault conditions. A detailed comparison between the three control techniques is presented to outline the main differences between the three control procedures and identify the most appropriate technique in between.

Torque Ripple Suppression Under Open-Phase Fault Conditions in a Five-Phase Induction Motor With Harmonic Injection

This article has made a study of the torque ripple suppression and torque capability maximization of a five-phase induction motor under open-phase fault conditions. The torque ripples are caused by the couplings between spatial harmonic fields after an open-phase fault in the motor. In order to assess the degree of coupling, multiple space vectors are introduced, which can be mapped onto different spatial harmonic planes. The current space vector components that cause torque ripples are eliminated for the goal of torque ripple suppression in the proposed strategies. Meanwhile, both the torque capability and the torque ripple after an open-phase fault need to be considered. When the phase current is limited to the rated value, the motor cannot simultaneously produce the maximum output torque and the minimum torque ripple. Hence, several postfault control strategies for different levels of torque capability and torque ripple have been proposed to meet the application requirements. Furthermore, postfault current space vectors have been optimized in the case of single- and two-phase faults. Finally, tests have been conducted on a five-phase prototype induction motor to verify the strategies proposed in this article.

Improved Mathematical Modeling of Six Phase Induction Machines Based on Fractional Calculus

Multiphase induction machine modelling represents a crucial research topic for both machine control and performance evaluation purposes. Generally, multiphase induction machines are preferably modelled using the vector space decomposition technique with some assumptions to simplify the mathematical model. However, different sources of non-linearities, including low order harmonics mapped to secondary subspaces, cross-coupling saturation and iron losses result in a notable deviation from the experimentally measured waveforms. Furthermore, considering full symmetry amongst motors phases seems to be a rather idealistic assumption. Fractional order modelling has recently emerged as a promising mathematical technique to model highly nonlinear electrical and mechanical systems. This paper proposes an improved vector space decomposition (VSD)-based fractional order model of an asymmetrical six-phase induction machine under both healthy and open phase fault conditions with different neutral arrangements. The appropriate differentiation orders have been obtained by optimizing the error function between simulated and experimental waveforms. The results are compared with the conventional integral order-based model. Experimental validation has been carried out using a 1.5Hp prototype induction machine.

Current Optimization-Based Fault-Tolerant Control of Standard Three-Phase PMSM Drives

A standard three-phase motor drive means a typical two-level voltage source inverter fed three-phase motor drive without any auxiliary circuits. Without fault-tolerant control, common open-circuit faults will cause the breakdown of the standard three-phase motor drives. Although the torque pulsation is theoretically inevitable under the open-circuit faults of standard three-phase motor drives, it's still meaningful to improve the fault-tolerant capability of standard three-phase drives to prolong the reliable operation. In this article, a current optimization based fault-tolerant control is proposed to minimize the proportion of torque loss for standard three-phase permanent-magnet synchronous motor (PMSM) drives under open-phase fault and open-switch fault conditions. Firstly, a two-mode current control is designed to minimize the proportion of torque loss without changing the mathematical model of the faulty motor. Secondly, a three-mode current control is proposed and combined with adjustment of pulse width to tolerate the open-switch faults. Instead of removing the faulty inverter leg directly, the remaining healthy switch in the faulty inverter leg is still utilized. In this way, the damage from torque pulsation can be relieved in the aspect of both frequency and intensity. Finally, the validity of the proposed fault-tolerant control is verified by experiments.

IRFOC of Induction Motor Drives Under Open-Phase Fault Using Balanced and Unbalanced Transformation Matrices

In this article, a vector control strategy based on indirect rotor field-oriented control (IRFOC) for star-connected three-phase induction motor (SCTPIM) drives under open-phase fault (OPF) using balanced and unbalanced transformation matrices (TMs) is proposed. Most of the current works studying SCTPIM drives under this type of fault are based on using two unbalanced TMs and ignore the leakage inductance in the FOC equations. This article studies a novel control strategy, considering the leakage inductance in the FOC equations of an SCTPIM drive under OPF. It is shown that using an unbalanced TM for stator current components and the conventional balanced TM for stator voltage components, it is possible to control an SCTPIM under OPF using a modified IRFOC system. The proposed vector control scheme is simulated and implemented using MATLAB/M-File software and DSP/TMS320F28335 controller board for a 0.75 kW SCTPIM drive system. Results show that the introduced IRFOC technique can satisfactorily control the SCTPIM under OPF condition.

An Improved Open-Phase Fault-Tolerant DTC Technique for Five-Phase Induction Motor Drive Based on Virtual Vectors Assessment

The multiphase machine (MM) drives are best suitable for safety-critical applications due to its inherent fault-tolerant capability. The fault-tolerant operation of MM drives is challenging and necessary for applications such as off-shore ship propulsion, highway electric vehicles, and more electric aircraft. A two-level voltage source inverter fed five-phase induction motor (FPIM) drive has been considered for the postfault performance assessment. In this article, an improved fault-tolerant direct torque control (DTC) technique is proposed for the FPIM drive based on virtual vector (VV)s assessment under the open-phase fault condition. The theoretical analysis is carried out to investigate the impact of VVs on the change in torque as well as flux response at different speeds and loading conditions. Based on this analysis, a modified lookup table, flux, and torque hysteresis bands are designed to improve the functioning of the fault-tolerant DTC of FPIM drive. The FPIM drive performance is analyzed and tested experimentally with an open-phase fault. Studies have confirmed the reliability and superiority of the proposed DTC controller over existing postfault solutions. In addition, the robustness of the FPIM drive at steady-state and dynamic operating conditions is evaluated from the given results, including the transition from pre-to-post fault operation.

Optimized SVM and Remedial Control Strategy for Cascaded Current-Source-Converters-Based Dual Three-Phase PMSM Drives System

In this article, the switching strategy and the remedial control scheme are studied for the cascaded current-source converters (CSCs) fed dual three-phase permanent-magnet synchronous motor (PMSM) variable-speed drives. An optimized space vector modulation (SVM) strategy is proposed to reduce the DC-link current ripple for the proposed drives system. In particular, this switching strategy can work effectively for motor drives under low speed with low back EMF, where there exists a large voltage difference between peak voltage values on the grid side and the motor side. Apart from that, a hybrid fault-tolerant control scheme is also designed for the open-phase fault in dual three-phase PMSM drives system, aiming at achieving small DC-link current ripple and torque ripple, low copper loss, and machine-friendly waveform quality. With the proposed optimized SVM and the hybrid fault-tolerant control strategy, the DC-link current ripple of the cascaded CSCs system can be effectively reduced and good operational performance can be obtained under both normal operation condition and open-phase fault condition. Experimental results are provided to verify the effectiveness of the proposed methods.

Simplified Modulation Scheme for Open-End Winding PMSM System With Common DC Bus Under Open-Phase Fault Based on Circulating Current Suppression

This letter proposes a simplified modulation strategy for the open-end winding permanent-magnet synchronous motor (OW-PMSM) system with common dc bus under the open-phase fault condition, with the suppression of the circulating current. Based on the analysis of the voltage distribution of the OW-PMSM under the open-phase fault, a phase-shifted stationary coordinate system is proposed and applied to synthesize the reference voltage. In the proposed modulation process, the duration time of the two selected orthogonal voltage vectors is directly obtained and both sector identification and calculation of trigonometric function can be avoided. Furthermore, the arrangement of switching signals is achieved universally according to the switching states of the selected voltage vectors. Thus, the proposed modulation scheme can be greatly simplified, compared with the conventional strategies. Moreover, the current controller with low bandwidth is applied to suppress the circulating current, considering its effect on the currents in the synchronous rotating coordinate system. The performance of the proposed scheme is validated experimentally in an OW-PMSM system with a common dc bus under the open-phase fault.

Effective Model Predictive Control Approach for a Faulty Induction Motor Drive

The paper presents an effective model predictive control (MPC) technique to enhance the performance of the induction motor (IM) drive under open phase fault condition. The mechanism of the proposed MPC approach is based on the stator field oriented control (SFOC) principle in which the stator flux is aligned to the direct axis of the rotating reference frame. In order to apply the proposed MPC approach on the faulty IM drive; the mathematical model of the IM is reconstructed to take the fault effect into account and for this purpose the single phase IM equivalent circuit is utilized. In order to improve the stator flux prediction process, an effective flux estimator is presented as an alternative to that one which uses a low-pass filter (LPF). The finite control set (FCS) principle is used to select the optimal voltages to be applied to the motor directly from the specified eight voltage vectors, which enables the elimination of the pulse width modulation (PWM). To testify the effectiveness of the proposed MPC in enhancing the dynamic performance of the IM drive under the fault condition; the IM drive performance under the proposed MPC is compared with the drive performance when applying the traditional predictive torque control (PTC). The obtained results confirm and emphasize the superiority of the proposed MPC in reducing the accompanied mechanical oscillations in the rotor speed and in eliminating the ripple contents in the controlled variables and enhancing the ability of the IM drive in riding through the fault.

A novel DTC scheme for a sensorless five-phase IM drive under open-phase fault

PurposeThis paper aims to deal with direct torque controller when the five-phase induction motor drive in faulty operation. Precisely, open-phase fault condition is contemplated. Also, the DTC is combined with a speed-adaptive variable-structure observer based on sliding mode observer.Design methodology/approachTwo novel features are presented. First, the concept of the virtual voltage vector is presented, which eliminates low-frequency harmonic currents and simplifies analysis. Second, speed information is introduced into the selection of the inverter states.FindingsDirect torque control (DTC) is largely used in traditional three-phase drives as a backup to rotor-stator flux-oriented methods. The classic DTC strategy was primarily designed on the base of hysteresis controllers to control two independent variables (speed, torque and flux). Due to the additional degrees of freedom offered by multiphase machine, extensive works have been extended on the ensemble five-phase drives in healthy operation. In addition, the ability to continue the operation in faulty conditions is considering one of the main advantages of multiphase machines. One can find in the literature different approaches treating this subject. The applicability of DTC after the appearing of a fault has not been enclosed in the literature.Originality/valueTheoretical development is presented in details followed by simulation results using Matlab/Simulink to analyze the performance of the drive, comparing with the behavior during healthy situation.

Active Current Harmonic Suppression for Torque Ripple Minimization at Open-Phase Faults in a Five-Phase PMa-SynRM

This paper presents an active phase current harmonic suppression method to smartly and adaptively perform torque ripple minimization (TRM) under open-phase fault conditions in a five-phase permanent-magnet-assisted synchronous reluctance motor (PMa-SynRM). The five-phase machine is gaining increasing attention due to its promising fault-tolerant and wide-speed operation capabilities. However, during the fault-tolerant operation, the torque ripple is substantially increased with dangerous vibrations. Until now, most TRMs have been primarily performed to maintain the constant magnetomotive force while only analyzing its fundamental harmonic. However, large torque variations are also caused by unexpectedly modulated high-order harmonic fluctuations that are challenging to predict. This fluctuation in current harmonics is highly destructive to reluctance machines due to its higher nonlinearity. To address this critical challenge, a real-time active TRM technique has been proposed that will be smartly adaptive to identified harmonic fluctuations. To achieve this, the proposed TRM solution systematically consists of three major steps: first, active harmonic identification; second, harmonic injection; and third, vector rotation of phases. To precisely identify fluctuating harmonics in a real time, a high precision but compact correlation-based monitoring algorithm has been proposed. A detailed theoretical analysis has been carried out through a finite-element analysis. The experimental tests are conducted to validate the proposed theory through a five-phase PMa-SynRM drive controlled by Texas Instruments DSP F28335.

Control of switched reluctance motor by current profiling under normal and open phase operating condition

This study is focused on a new approach of current profile computation to minimise switched reluctance motor (SRM) torque ripple both in healthy and one open phase fault condition. The analysis of static parameters by means of finite element method is carried out and it is verified by measurements. The mathematical model of SRM is described to simulate all transients. The new current profiling method is applied and tested for normal and faulty operation of a real SRM. The torque ripple is measured at a 10 kHz switching frequency. Lower torque ripple is obtained when compared with standard control methods, both under normal and open phase conditions. The simulations of diverse dynamic states are carried out and compared with experimental results.

Production of Circular Stator Current Trajectory in Multi-Phase Induction Drive Under Open Phase Fault Condition

In this paper multi-phase induction drive with a frequency converter is researched under open phase fault condition. Control strategy of stator voltage phase shift is proposed for dealing with over-currents during steady state. Symmetry of stator current trajectory is achieved. Experiments with six-phase induction motor without a neutral wire under one open phase condition were carried out.

Open-Phase Fault-Tolerant Direct Torque Control Technique for Five-Phase Induction Motor Drives

Direct torque control (DTC) has been widely used as an alternative to traditional field-oriented control (FOC) methods for three-phase drives. The conventional DTC scheme has been successfully extended to multiphase drives in recent times, using hysteresis regulators to independently track the desired torque and flux in symmetrical five-phase induction machines (IMs). The fault-tolerant capability of multiphase drives is an interesting intrinsic advantage for safety-critical applications, where recent research has demonstrated the effectiveness of FOC schemes to perform ripple-free postfault operation. In spite of the utility of DTC methods in normal operation of the multiphase machine, no extension to manage the postfault operation of the drive is found in the literature. In this paper, a novel fault-tolerant DTC scheme is presented. The performance of the proposed method is experimentally validated in a five-phase IM drive considering an open-phase fault condition. Provided tests analyze steady and transient states, including the transition from pre- to postfault operation. Obtained results prove the interest of the proposal, which ensures the open-phase fault-tolerant capability of DTC-controlled five-phase IM drives.

Vector control of unbalanced 3-phase IM using forward and backward components

In some industries, continuous operation of 3-phase induction motors (IMs) even under faults until the scheduled maintenance time is essential. Conventional control techniques such as field-oriented control (FOC) cannot be used to control faulty IMs since this will result in significant oscillations in the speed and torque. Consequently, a new control approach must be developed for improving IM performance during fault conditions. This paper presents a method for vector control of 3-phase IMs under open-phase faults. The main advantage of this control scheme is its ability to handle not only one phase but also two phases of open-phase fault conditions. When applying this control technique to a faulty machine, only minor changes to the parameters used in the equations are needed and the conventional FOC algorithm used for healthy 3-phase IMs can still be used. In this paper, simulation and experimental results are presented to study the effectiveness of the proposed technique to control both healthy and faulty 3-phase IMs. The results show that the proposed technique reduces electromagnetic torque pulsations during open-phase fault conditions.