Vector Control System Research Articles

Optimal Reference Frame Angle Approach for Air-Gap Flux Minimization in Dual Stator Winding Induction Machines

Dual stator winding induction machines (DSWIMs), which have two sets of three-phase windings with unequal pole pairs in their stator and a standard squirrel cage rotor, have overcame the narrow speed operation region and circulating current problems exists in other types of dual winding machines. These advantages are resulted from the independent operation of their winding sets. The independent operation of winding sets will be guaranteed if the flux saturation is avoided. This letter proposes a novel reference frame angle determination technique that not only guarantees the flux saturation avoidance but also results in flux optimization in DSWIMs. Despite pervious methods, the proposed method does not require position or speed sensor and it is easily applicable in various control schemes and in different reference frames. This method is implemented in a flux and torque vector control system for driving a 3.3 kW DSWIM. The experimental results confirm the effectiveness of the proposed method. Moreover, by implementing the proposed method, the torque sharing between the two winding sets is properly done according to the power rating of each of them.

Predictive Direct Control of SPMS Generators Applied to the Machine Side Converter of an OWC Power Plant

A new strategy framed in the field of model predictive direct current control applied to surface permanent magnet synchronous generator (SPMSG) is presented. Compared to conventional space vector control systems, the proposed predictive strategy reduces the number of PI regulators and maintains the advantages of a fixed switching frequency. It also performs a faster response providing a smooth electromagnetic torque and smooth active and reactive power control. The dynamic performance of the proposed control is first analyzed by means of simulations in MATLAB Simulink environment and then compared with two other model predictive controls. Also, the performance of the control is analyzed in simulation using a simple model of an oscillating water column power plant. This application was chosen because it is a difficult case study that demands a fast torque control to handle the power take-off system. Later, the proposed method is tested in a customized SPMSG-based laboratory setup. This article is accompanied by a video.

Studying a voltage stabilization algorithm in the cells of a modular six­level inverter

Multi-level autonomous voltage converters are increasingly used in industry, specifically: in wind and solar energy generation, high-voltage substations, in industrial and traction electric drives. In comparison with two-level inverters, multilevel inverters have a series of significant advantages, specifically, greater output power, greater efficiency value, smaller content of higher harmonics at loading and in a power grid. Reducing the content of higher harmonics in the output current of a multilevel inverter directly decreases additional losses at loading and improves the overall value of efficiency.Our study of a six-level modular inverter has shown that the algorithm of a spatial-vector modulation causes a disbalance in voltage on the capacitors of cells. In this case, voltage in half the cells tends to zero while in the other half of the cells it increases two-fold, which leads to a significant distortion of the output voltage. This paper gives reasons for this instability, as well as presents the improved spatial-vector modulation algorithm of the multilevel converter, which makes it possible to stabilize voltage in cells.We have proposed an algorithm of voltage stabilization on the cells of a modular multilevel inverter. The voltage stabilization is achieved by a hysteresis regulation with an alternating transition of the spatial-vector pulse-width modulation and inverse vector control system under condition that the voltage deviation on the cell is above or below the predefined permissible level.The MATLAB 2017b software was used to conduct simulation of the six-level voltage inverter, which confirmed effectiveness of the proposed modulation algorithm

Design of flux‐weakening space vector control algorithms for permanent magnet brushless DC machines on suitable synchronous reference frames

The design of space vector control (SVC) systems suitable for flux-weakening operation of permanent magnet brushless DC machines (PMBDCMs) is presented in this study. The proposed design approach enables overcoming the critical issues arising from the non-linearities of PMBDCM voltage and torque equations; these issues derive from the trapezoidal shapes of back-emfs and affect PMBDCM constraint management significantly. The SVCs presented in this study have been developed within two different synchronous reference frames, both of which enable distinguishing torque and demagnetising current components clearly. Therefore, reference torque current component is determined in accordance with PMBDCM torque demand, while reference demagnetising current component is computed through a voltage follower PI regulator, which processes the voltage deficit detected on the DC-link. In this regard, a novel synchronous reference frame is proposed in this study, which improves PMBDCM constraint management and results into a wider constant-power speed range, but at the cost of some torque ripple. The enhanced performances achievable by SVC approaches are highlighted by numerical simulations, which regard the comparison among the SVCs and an SVC with no flux-weakening capability, at different operating conditions.

Interturn Fault Diagnosis for Model-Predictive-Controlled-PMSM Based on Cost Function and Wavelet Transform

Interturn fault (ITF) is a common fault for permanent magnet synchronous machine (PMSM). If the ITF is not detected in time, its propagation may result in the secondary damage, even the damage to the whole electrical machine. Recently, model predictive control (MPC) has been widely studied for the PMSM drive system because of its simple structure and excellent dynamic performance. However, the previous ITF diagnosis methods are mainly focused on vector control and direct toque control systems, and few research works are specifically focused on ITF diagnosis for the model-predictive-controlled-PMSM. Hence, to fill this gap and improve the reliability of the model-predictive-controlled-PMSM, this article first proposes an ITF diagnosis method for the model-predictive-controlled-PMSM, taking into account the characteristics of the MPC system. In this method, wavelet transform is applied to extract the fault feature from the cost function existing in the MPC system, and the ITF is diagnosed by monitoring the normalized energy-related feature vector calculated from the wavelet transform coefficients. Additionally, to further show the performance of the proposed method, the popular diagnosis methods based on the stator current and zero sequence voltage component are studied for the comparative analysis. Both the simulation and experimental results verify the effectiveness of the proposed fault diagnosis method.

Human Resources for Health challenges during health emergencies—low number of workers in El Salvador

Abstract El Salvador is one of the 57 countries considered to be in Human Resources for Health (HRH) crisis according to the World Health Organization (WHO). El Salvador’s healthcare worker density is 1.95 health professionals per 1,000 population, with even lower numbers in certain departments of the country. There have been improvements in the distribution of healthcare workers since 2010; however, on average it has remained “in crisis” based on the 2006 World Report definition. The increase in vector borne diseases in the region, has resulted in an overwhelmed vector control system and public health sector in many Central American countries. This study aims to analyze whether the healthcare workers identify the numbers of HRH as a factor that affects the health system response during health emergencies. Through an extensive review of scientific literature, country reports, 16 meetings and 34 in depth semi-structured interviews with key stakeholders; this paper explores the challenges healthcare workers faced and how they were influenced by the numbers of available HRH during recent arboviral epidemics in El Salvador, using the recent Zika epidemic as a point of comparison. The study findings suggest that some of the barriers that the health workforce identified during health emergencies include factors related to the low availability of HRH such as feelings of tiredness, being overwhelmed, as well as a need to rely on doctors in their social year in some areas of the country. Despite this, they also recognize that the recent intersectoral work done by the government and the Ministry of Health, has helped to overcome the obstacles of a low healthcare workforce by involving other sectors of society into the emergency response. Therefore, there is not a clear consensus on how the low number of HRH affect the health emergency response. Key messages The study findings suggest that some of the barriers that the health workforce identified during health emergencies include factors related to the low availability of HRH. They also recognize that the recent intersectoral work done by the government and the Ministry of Health, has helped to overcome the obstacles of a low healthcare workforce.

An operation algorithm for the combined thrust vector control system of a rocket engine

The new combined rocket engine (RE) control system consists of combining various control systems - mechanical thrust vector control system (MTVCS) and gas-dynamic one (GDTVCS) within one bifunctional system that performs the functions of controlling and stabilizing the rocket stage flight. Previously it was shown that the MTVCS speed has limit, since with its speed increase the sensitivity to high-frequency random disturbances rises, which increases random errors. In addition, the system performance rise leads to an increase in the mass and dimensions of the steering drive of the engine swing. As part of the combined system, GDTVCS supplies any given speed requirements, and MTVCS provides maximum control efforts with minimum drive power and maximum element simplicity of the thrust vector control system as a whole. However, there is a problem of rational function distribution between subsystems and coordination of their functioning. For automatic control of the RE thrust vector, the input data are angle deviations in a certain plane, which characterize the direction violations of the installation.The purpose of the work is to study the input signal characteristics of the thrust vector system of steering engines applied to the combined RE control system and the design of an optimal algorithm for its operation.There were analyzed possible determining methods for the trend existence of the input signal on the characteristic RE operation intervals and method was proposed for selected trend using. This made it possible to develop an algorithm for the functioning of the combined (mechanical and gas-dynamic) thrust vector control system of the rocket engine. The created algorithm provides the processing of the TVCS input signal with the selection of the deterministic (static) component (trend) and high-frequency signal oscillations (deviations from the trend). The trend type of the deviation angle perturbation of the RE thrust vector is also taken into account. The typical dependence of the output control actions for the steering RE on the input signals at different operation time intervals is investigated.The developed algorithm allows optimal separating (in terms of energy consumption for creating control efforts) the subsystem functions of the combined RE thrust vector control system, to improve the quality and reliability of the flight control system of the rocket stage.

Динамические характеристики комбинированной системы управления вектором тяги ракетного двигателя

Динамические характеристики комбинированной системы управления вектором тяги ракетного двигателя

Enhanced Complex Space Vector Modeling and Control System Design of Multiphase Magnetically Levitated Rotary–Linear Machines

Rotary–linear electric machines can perform coupled rotary and linear motion. In addition, they can have magnetic bearings (MBs) integrated and magnetically coupled with the rotary, linear, or rotary–linear machine operation. Since rotary–linear machines with MBs have not been thoroughly analyzed in the literature, the models that provide understanding of their operation and give basis for the control system implementation are not entirely covered. Hence, in this article, an enhanced complex space vector-based model of the rotary–linear machine with MBs is derived and expressions for the torque, thrust force, and MB force are given. The rotary–linear machine complex space vector of the voltage, current, or flux linkage is defined using the proposed transformation with two complex frames: one related to the rotation and MBs and another to the linear motion. This results in complex space vectors with two complex units; however, the techniques used for a conventional complex space vector calculation can also be applied to the proposed complex space vector description. This is also experimentally validated on a hardware prototype of a magnetically levitated linear tubular actuator (MALTA), whose position control system is designed and implemented based on the enhanced space vector modeling approach, with the dynamic operation of the MALTA, including linear motor operation with an axial stroke of 10mm and a mechanical frequency of 17Hz.

Synthesis of vector control systems by localization method

The paper presents a method for synthesis of a speed control system of induction motor drive and synthesis of output voltage control system for permanent magnet synchronous generator fed by three phase inverter with active rectifier. The mathematical model of a wind mill connected to the permanent magnet synchronous generator unit with output voltage control is considered. A structural and parametric synthesis of vector control systems can be implemented using a special localization method, which makes it possible to purposefully organize loops of slow and fast motions by establishing deep feedbacks. The developed localization method of control systems synthesis provides robust and stable operation of objects under study. The paper also examines difficulties in the differentiating filter designing. The approach of multimovement closed loops design is used to decompose the synthesis task. Deep feedbacks allow engineers to design control systems insensitive to disturbances and to compensate signal and parametric disturbances of control object. The proposed approach could be used for synthesis of wide range of nonlinear and unstable systems. The operability and robustness of proposed approach is discussed in this paper.

Reusable Launchers: Development of a Coupled Flight Mechanics, Guidance, and Control Benchmark

This paper studies the mechanics of reusable retropropelled flight of slender low lift-to-drag bodies via integrated guidance and control simulations. To do this, a simulation benchmark focused on the coupling between flight mechanics, guidance, and control must be developed, as opposed to mission-optimization-oriented ones that simplify (or directly ignore) these couplings. The developed simulator covers vertical takeoff and landing of a first-stage booster for return to launch site and downrange landing missions. To steer it toward a controlled entry, followed by descent and precision landing, the vehicle is configured with a deep throttling thrust vector control system, fins, and cold gas thrusters. Comparative performance results are derived in terms of aerodynamic loads and heat fluxes for both recovery scenarios, as well as through a detailed closed-loop controllability analysis. The latter demonstrates that the configuration has sufficient authority and resolution to perform stable flight and adequate wind gust rejection. The developed benchmark (because of the coupled flight mechanics, guidance, and control) allows to provide a first assessment of operational limits, as well as mission and GNC specifications. This in turn paves the way for the synthesis and assessment of more sophisticated reusable launcher guidance and control algorithms.

Extended State Observer-Based Predictive Speed Control for Permanent Magnet Linear Synchronous Motor

Combining the feedback of predictive function control and the feedforward of extended state observer, a composite control strategy is proposed for the permanent magnet linear synchronous motor (PMLSM). The mathematical model of the PMLSM vector control system is established based on the basic structure and operation mechanism of PMLSM. Then, a speed regulator based on predictive function control (PFC) is designed to improve the speed tracking performance of the PMLSM drive system. The state and disturbance of the PMLSM system estimated by the extended state observer (ESO) transferred to the PMLSM drive system, and the robustness of the drive system will be improved. Comparative simulation and experiment results show that the proposed method has better speed tracking performance and disturbance rejection property.

Composite Feedforward Compensation for Force Ripple in Permanent Magnet Linear Synchronous Motors

This paper presents a method for compensating the force ripple in permanent magnet linear synchronous motors (PMLSMs) by adopting a composite feedforward compensation scheme. Firstly, the vector control system of PMLSMs is described, and various force disturbances influencing the electromagnetic thrust are analyzed. As a result, the mathematical model of the whole system considering the force ripple is established. Then, a novel composite feedforward compensation scheme is proposed, which consists of a recursive least squares (RLS) parameter identification component and two feedforward compensation loops corresponding to the reference position trajectory and the force ripple, respectively. Finally, the effectiveness and advantages of the proposed composite feedforward compensation are demonstrated by simulation. The main incentive of this paper is the combination with the composite feedforward compensation loop corresponding to the reference position trajectory to improve the compensation effect of force ripple in PMLSMs.

Numerical research on jet tab thrust vector nozzle aerodynamic characteristics

Jet tab thrust vector nozzle is a unique kind of thrust vector device which generates control force by inserting tab into the nozzle exhaust. The influence of tab geometric parameters on the nozzle aerodynamic characteristics is not clear. In order to meet the requirements of control rate modeling and optimization of jet tab thrust vector control system, a computational study was conducted to investigate the effects of tab geometric parameters which include insertion height, width, axial distance, incline angle on nozzle aerodynamic characteristics. The flow structure of nozzle with different tabs are demonstrated, and thrust vector performance is evaluated. Results indicate that the lateral force coefficient and the thrust loss coefficient increased with the increase of the tab insertion height, the thrust vector efficiency decreased as the insertion height increased; increasing tab width increased the thrust vector efficiency, the thrust vector efficiency increased by 24.8% when the tab width increased form 10mm to 18mm; both increasing axial distance and increasing tilt angle decreased the lateral force and efficiency, in practical application, the axial position and incline angle should be minimized.

A new high-response self-balancing sensorless control system of induction motor for weft accumulator

The high-response and self-adaptive yarn delivery system used in weft accumulator is a critical component for improving the efficiency and quality of textile machinery. However, the existing drive system in the weft accumulator has problems such as slow start-up and slow speed-tracking responses, giving difficulties in achieving a high-efficient yarn delivery of the textile machinery. In this paper, a high-response self-balancing sensorless integrated control system of the induction motor for weft accumulator is proposed. Firstly, to enable the motor to start and respond adaptively and quickly to the number of yarn control loops and the speed control of the external equipment, a high-response sensorless vector control system for induction motor based on improved model reference adaptive control(MRAC) is proposed. Secondly, to achieve a high-response adaptive tracking performance of yarn input and output numbers and spool shaft speed, a self-balancing control strategy based on optical electromechanically integrated closed-loop control is proposed. For proving the effectiveness of the proposed scheme, a corresponding test platform was constructed for testing and validation. It can be observed from the results that the system designed in this paper has fast starting speed and better speed tracking performance, satisfying yarn delivery requirements at different speeds with high-response and adaptability.

Vector Control of a Modular Multilevel Matrix Converter Operating Over the Full Output-Frequency Range

The modular multilevel matrix converter (M <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> C) is an ac-to-ac converter topology suitable for the control of high-power variable-speed drives. The control of this converter is complex, particularly when the two ac system frequencies are similar or identical because large voltage oscillations can be produced in the floating capacitors within the M <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> C. This paper proposes a new vector control system based on nested controllers to regulate the M <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> C over the full range of frequencies. The proposed control scheme is especially useful to mitigate or eliminate the oscillations that arise when the frequencies are similar. An extensive discussion of the model and control of the M <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> C is presented in this work. The effectiveness of the proposed vector control system is demonstrated through simulation studies and experimental validation tests conducted with a 27-cell-5kW M <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> C prototype.

Power-Efficient Control of an Induction Motor: Methods of Increasing Its Dynamics

To improve the efficiency of an electric drive system under low speed conditions, a control strategy optimized for maximal torque per ampere (MTPA) is used in the vector control system of an induction motor. MTPA is a control method of motor excitation that significantly reduces the torsion torque dynamics due to the influence of the rotor time constant. Traditionally, for such a control strategy, steady-state motor conditions are considered, but transient modes are not. MTPA control strategies for an induction motor with and without use of a rotor flux controller are compared. New approaches to improving the dynamics of MTPA control are proposed. The transient modes are described and compared.

LINEARIZATION OF OBJECT MODEL WITH VECTOR CONTROL

Context. A sufficient number of ways to implement vector control algorithms are very complex and in most cases tend to mismatch the vector of the resulting parameters of the control object. Therefore, there is a need to simplify complex non-linear vector control systems and apply linear dynamic models of a non-linear object with vector control for them. Currently, for a complex vector control system, there are no sufficiently accurate equivalent simple models. Development of reliable simple dynamic models will allow to design a vector control system with maximum use of linear methods of synthesis and analysis. Objective. The goal of the paper is development of linear dynamic model of a non-linear object with vector control, which reproduces its dynamics accurately enough for practice. Method. The following methods were used to solve the problems posed: the state space method for describing the operation of control systems; filtering theory, in particular, observers for estimation state vectors, uncertainties, and parameter identification; modal control methods for the synthesis of observers and regulators; numerical simulation method to illustrate the performance of synthesized control systems; vector control of a nonlinear object. Results. For the investigated robust vector control system of the object with a substantial non-linearity of properties and characteristics, simple linear equivalent mathematical models were compiled, rather accurately reproducing the operation of the original system in all modes of operation. Simplification of mathematical models is achieved by considering the dynamics of the entire system in a synchronous basis, robust methods for controlling parameters, and by neglecting really small errors in the work of regulators and observers. The synthesized models, as well as the original nonlinear system, have the property of robustness due to the use of combined control. Conclusions. The simplicity and linearity of the equivalent system allows us to synthesize the control laws of the original nonlinear system by well-developed linear methods with significantly less time spent on modeling. Numerical simulation of the dynamics of the original nonlinear and equivalent linear systems showed a good agreement between transient and stationary processes.

Taking Iron Loss into Account in Control Systems of Synchronous Reluctance Electric Drives

Synchronous reluctance electric drives are being developed due to their advantages of contactlessness, high overload and specific torques, absence of loss in the rotor, and large control range, as well as progress that is being made in the fields of information and power electronics. It is shown that iron loss significantly affects the control algorithms for synchronous reluctance machines. A four-loop vector control system of a synchronous reluctance machine is considered. The main ducts are the current and electromagnetic torque control circuits of the electric machine and the secondary ducts are the stator flux linkage and angular velocity contours. The features of observer synthesis for vector control system taking into account iron losses and magnetic saturation of the system are given. By means of experimental studies, the adequacy of the received observer was shown. The synthesis of algorithms for optimal control of the synchronous reluctance machine, taking into account iron loss, is given. The first algorithm assumes the existence of a table with optimal values of control actions. The second provides for the synthesis of an adaptive torque controller, which will be automatically tuned to the optimal control action. The obtained control algorithms are universal and can be applied in other control systems of synchronous reluctance machines, for example, in direct torque control systems.

Design of band elimination filter for PMSM vector control operable in overmodulation region of inverter

AbstractThis paper proposes a filter design for improving the control performance of the current control system of permanent magnet synchronous motors (PMSMs) using the overmodulation region of an inverter. The control performance of a vector control system for PMSMs using the overmodulation region of an inverter can be improved by suppressing harmonic components that are generated in this region. This paper utilizes band elimination filter (BEF) to eliminate harmonic components; however, unsuitable BEF setting leads to generation of large current oscillation at the resonant frequency of current feedback loop with BEF. In order to deal with these problems, the proposed filter design focuses on gain setting at the cutoff frequency of BEF. The proposed filter design can prevent the generation of current oscillation at the resonant frequency of the system, and can improve current control performance without complex adjustments. Simulations and experiments are carried out to show the effectiveness of the proposed BEF setting.