Axis Current Research Articles

Analysis of a Three-Phase Grid-Connected PV Power System Using a Modified Dual-Stage Inverter

This paper presents a grid-connected PV system in a centralized configuration constructed through a three-phase dual-stage inverter. For the DC-DC stage the three-phase series resonant converter is chosen thanks to the advantages that it exhibits. However, it is inadequate for the accomplishment of MPPT, due to its efficiency strongly depending on the implemented deadtime and switching frequency. Then, this paper proposes a conceptual modification, that is, a modified dual-stage inverter in which the inverter stage is responsible for both the MPPT and the grid-current control. In addition, the DC-DC converter operates with constant duty cycle and frequency. Such configuration requires a new concept, introduced as Behavior Matching. It serves as a fundamental feature for the DC-DC converter to reproduce the PV array I–V characteristic when they are connected, without control action. The maximum power operating point is found by maximizing the direct axis current, obtained by Park's transformation from the inverter, through the perturbation and observation algorithm. Any specific measurement to realize the MPPT is needed. The galvanic isolation is achieved by using a high-frequency transformer. The structure is appropriate for high power applications, above 10 kW.

Speed Control for PMSM Servo System Using Predictive Functional Control and Extended State Observer

The speed regulation problem for permanent magnet synchronous motor (PMSM) servo system is studied in this paper. In order to optimize the control performance of the PMSM servo system, the predictive functional control (PFC) method is introduced in the control design of speed loop. The PFC-based speed control design consists of two steps. A simplified model is employed to predict the future q -axis current of PMSM. Then, an optimal control law is obtained by minimizing a quadratic performance index. However, it is noted that the standard PFC method does not achieve a satisfying effect in the presence of strong disturbances. To this end, an improved PFC method, called the PFC+ESO method, is developed. It introduces extended state observer (ESO) to estimate the lumped disturbances and adds a feedforward compensation item based on the estimated disturbances to the PFC speed controller. Simulation and experiment comparisons are made for these PFC methods and proportional-integral method with antiwindup control method to verify the effectiveness of the proposed methods.

A Novel Speed-Sensorless Suspension Decoupling Control Strategy for Bearingless Motor Based on Linear Extended State Observer

In this paper, a novel speed-sensorless suspension decoupling control strategy for bearingless motor was proposed based on linear Extended State Observer (ESO). In the proposed control strategy, a second-order and a third-order linear-ESO algorithm were added respectively into torque d-q axis current-loop and suspension system x-y direction displacement-loop. A product of electrical angular speed and torque system d-q axis current and a product of torque q axis flux and suspension system d-q axis current were defined as disturbances in order to use the linear-ESO algorithm to estimate the defined disturbances. By obtaining speed information and compensation for disturbance force, the motor can work on speed-sensorless condition and traditional decoupling algorithm can be simplified. The simulation results show that the proposed control strategy can realize accurate speed estimation and guarantee stable suspension under the rated speed.

Solar Vehicle을 위한 IPMSM 드라이브의 새로운 MPPT 제어

The solar vehicle is in the spotlight in the eco-friendly aspect of photovoltaic system using unlimited solar energy. The solar vehicle uses energy of photovoltaic and battery. The solar vehicle uses stored energy in battery when photovoltaic power is lower than consumption power by solar vehicle and if photovoltaic power is higher than consumption power by solar vehicle then photovoltaic power is stored to battery. To improve use efficiency of photovoltaic, the researches about MPPT method to operate maximum power point and interior permanent magnet synchronous motor(IPMSM)drive system using photovoltaic is necessary. This paper proposes MPPT control algorithm for solar vehicle using new fuzzy control(NFC). In this paper, to reduce switching loss, the DC-DC converter is omitted. The NFC controller can be use instead of PO. The NFC controller is performed MPPT control using solar cell voltage and q -axis current of IPMSM. The output of NFC is command q -axis current of IPMSM and this current is operated IPMSM. The response characteristics of algorithm proposed in this paper is compared response characteristics of conventional PO method by PSIM program and validity of this paper prove using this result.

Simple Online Fault Detecting Scheme for Short-Circuited Turn in a PMSM Through Current Harmonic Monitoring

To detect a stator winding fault caused by a short-circuited turn in a permanent magnet synchronous motor, a simple online fault detecting scheme is presented. The proposed scheme is based on the monitoring of the second-order harmonic components in the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> -axis current through harmonic analysis. To verify the effectiveness of the proposed scheme, a test motor which allows an interturn short in the stator winding has been built, and the entire control system has been implemented using the DSP TMS320F28335.

Novel voltage limiter for fast torque response of IPMSM in voltage saturation region

AbstractA new voltage limiter for fast torque response of IPMSM in the voltage saturation region is proposed, which we name the “maximum torque response voltage limiter.” In transient condition, the fastest response is vital while voltage saturation occurs. Thus, the problem is to divide the limited voltage into d‐ and q‐axis voltages so as to generate the fastest torque response. The nonlinear relation between the torque and the d‐q axis currents of the IPMSM makes the problem complicated. In our proposed method, both voltage equations and a torque equation of the IPMSM are considered and, based on the Lagrange optimization technique, explicit expressions for the d‐ and q‐axis voltages are derived. Compared with conventional voltage limiters such as the constant phase angle method, the constant back emf method, and the constant d‐axis voltage method, the proposed limiter yields faster torque response in the voltage saturation region, which is confirmed by computer simulation and experimental results. Furthermore, the proposed method uses simple software calculations, and it can be readily implemented without any modification of the hardware system. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 175(4): 57–69, 2011; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21078

The Effect of Direct Axis Current on the Performance of the Synthetic Loading Technique

Synthetic loading is a technique that forces the machine under test to operate at rated speed, torque, and flux without the need for the test machine to be connected to an external load. The technique has been successfully applied to permanent magnet machines but it requires an inverter voltampere (VA) rating that is 1.51 pu of the rated value due to the need for instantaneous phase currents and voltages that are higher than the rated value. In order to reduce the VA rating, it is possible to inject direct axis current. This has important consequences. It reduces the ac perturbation current thereby reducing the peak instantaneous phase current. Also, by reducing the ac perturbation current, the rotor speed variation is reduced, thereby reducing the instantaneous phase voltage requirement. Both these effects reduce the VA rating of the inverter. However, this paper demonstrates through simulation and experiment that such a scheme increases the iron losses in the machine. This is important as it alters the distribution of losses which is not a desired consequence. The effect of direct axis current on the iron loss and the machine efficiency during synthetic loading is assessed and evaluated as is the effect on the minimum dc link voltage and the inverter VA requirements used to conduct the synthetic loading technique. Simulation and experimental results are used to demonstrate the effects and validate the conclusions that while direct axis current injection reduces the inverter VA rating, it reduces the accuracy of the synthetic loading technique.

Compensation of Amplitude Imbalance and Imperfect Quadrature in Resolver Signals for PMSM Drives

This paper proposes a compensation algorithm for reducing the position errors that are due to two nonideal output signals of a resolver in the vector control of a permanent magnet synchronous motor. Practically, a resolver generates periodic position errors because of the amplitude imbalance and imperfect quadrature between the two output signals of the resolver. As a result, the dq-axis currents of the synchronous reference frame have ripple components that are twice the stator fundamental frequency. In this paper, the effects of the position errors are analyzed on the basis of the synchronous dq-axis current equations, including the position errors. The <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> -axis current is directly used as the input signal of the proposed compensator to estimate the position errors by using a simple integral operation according to the rotor position, because the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> -axis current is typically constant or zero. The proposed algorithm additionally considers the bandwidth effect of the closed current control loop to estimate the exact error signals according to the variation of the rotor speed. Therefore, the proposed algorithm does not need any additional hardware and much computation time. Furthermore, this algorithm can be applied to both the steady and transient states. The experimental results verify the effectiveness of the proposed algorithm.

Research and Simulation of PMSM based on Coordination Control Technology

This paper proposed an improved stator current control algorithm of Permanent Magnet Synchronous Motor (PMSM) for efficiency optimization. According to the formula of maximum input power of PMSM, relational expression between d, q axis current is established. Appling multiple input and multiple output system coordinated control theory to current control system; the improved stator current control algorithm is given. The simulation results have proven that the algorithm proposed in this paper can maximization output power in the case of minimum coordination deviation.

High Efficiency Double–Fed Induction Generator Applied to Wind Power Generator Technical Analyses

High efficiency Double-Fed Induction Generator applies new power electronic technology, and utilizes vector control to fix the magnetic direction of the stator to the vertical axis. Adjusting the input current of rotor via an inverter can separately control the cross axis and vertical axis current of real power and reactive power of a generator. Traditionally, rotating speed affects frequency and the output is unstable. This study concentrates on high efficiency Double-Fed Induction Generators and Traditional Generators from mathematic model to derive and control the characteristics simulation and comparison than get an output of high efficiency Double-Fed Industrial Generators. This study utilizes the simulation software MATLAB/Simulink to simulate the response characteristics of vector control of a Double-Fed Industrial Generator. The operating and control functions are better than those of a traditional generator.

A composite speed controller based on a second-order model of permanent magnet synchronous motor system

The speed-regulation problem for a permanent magnet synchronous motor (PMSM) servo system is studied in this paper. In traditional control design for a speed loop, a first-order model is used to approximately describe the relationship between the reference quadrature axis current and the speed output, i.e. the reference quadrature axis current is regarded as the same as the quadrature axis current. This approximation degrades the closed-loop performance of PMSM system when using a vector control scheme. To this end, a second-order model is built to describe the relationship between the reference quadrature axis current and the speed output for a PMSM system. Based on this second-order model, a standard sliding mode controller is designed for the speed loop. Then, to reduce the chattering and improve the performance of the system, a composite controller consisting of a sliding mode feedback part and a disturbance compensation part based on an extended state observer are developed. Simulation and experiment results and comparisons are given to show the effectiveness of the proposed method.

Processamento eletrônico da energia solar fotovoltaica em sistemas conectados à rede elétrica

Este artigo apresenta um sistema fotovoltaico conectado à rede elétrica comercial em configuração centralizada e construído com um inversor trifásico de dois estágios capaz de extrair a máxima potência do arranjo de painéis fotovoltaicos. O algoritmo P&amp;O é adotado como técnica de MPPT. O isolamento é realizado por um transformador de alta frequência. O conversor que compõe o estágio CC-CC dispensa a estrutura de controle, pois funciona com razão cíclica e frequência constantes ao longo de toda a faixa de operação. Isto viabiliza o uso de conversores CC-CC ressonantes, cujo rendimento é elevado em altas frequências, favorecendo a compactação da estrutura de potência. Assim, o conversor trifásico série ressonante é escolhido para compor este estágio. O MPPT é transferido para o estágio CC-CA, que, invariavelmente, possui um controlador para a corrente injetada na rede elétrica. O inversor trifásico PWM alimentado em tensão, que compõe o estágio CC-CA, é controlado e modulado vetorialmente. O controle vetorial impõe a transformação de Park as correntes de linha, de onde resulta a corrente de eixo direto. O MPPT utiliza as mesmas variáveis do controlador de corrente e maximiza a corrente de eixo direto, a qual reflete a potência extraída do arranjo fotovoltaico. Assim, nenhuma medição específica para o MPPT é realizada, resultando em economia de sensores.

On Discrete Soliton and Soliton Lattice at SmCα*-SmC Transition Driven by an Electric Field

Unwinding process of Smectic Cα* phase (SmCα*) to smectic C phase (SmC) in an electric field looks similar to a transition from chiral smectic C phase (SmC*) to SmC which is interpreted as a soliton condensation. As a pitch of the helical structure is quite short in the former, a discrete description is required and the soliton accompanying with should be a discrete type, while in the latter, the soliton is a kink of sine-Gordon equation. Under the condition of constant tilt at SmCα*, it has been elucidated that for the helical pitch larger than four-layer the transition is second order and a wave number versus field relation makes a devil's staircase. Here, a free energy curve for the wave number is proved to be non-differentiable at any rational wave number, monotonous and convex, corresponding to the devil's staircase structure of the wave number. This non-analytic property contrasts with the case of continuous description in SmC*, where the free energy curve is analytic. In the framework of the present model, a change of apparent optical axis and switching current is calculated, which are compared with experimental results reported so far.

Inductance Calculation Method of Synchronous Reluctance Motor Including Iron Loss and Cross Magnetic Saturation

This paper presents the novel method inductance calculation of a synchronous reluctance motor (SynRM). Synchronous inductances (Ld and Lq) are exceedingly important factor of SynRM to drive. Because of self axis current as well as the other axis current, inductances of d-axis and q-axis of SynRM are varied. Using an equivalent circuit model for expressing d-axis and q-axis inductance variation, the authors elicit suitable equation considering iron loss and cross magnetic saturation. Parameters of motor to use calculation are gained by AC signal test.

ANN Based Detection and Location of Severe Three Phase Trip on the Transmission Lines of an Uncontrolled Power System

Severe three phase trips are simulated on four arbitrary locations of an uncontrolled power system transmission lines. The responses of three measurable state variables of the system (rotor speed, stator direct axis current, and stator quadrature - axis current) are recorded, and suitable ANNs are trained to detect and locate the positions of the corresponding trips. The paper proves that this method is quick, active and accurate to diagnose and find the locations of that kind of trips.

Control of IPM Synchronous Generator for Maximum Wind Power Generation Considering Magnetic Saturation

Permanent-magnet synchronous generators (PMSGs) are commonly used for small variable-speed wind turbines to produce high-efficiency, high-reliability, and low-cost wind power generation. This paper proposes a novel control scheme for an interior PMSG (IPMSG) driven by a wind turbine, in which the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> -axis and <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> -axis stator-current components are optimally controlled to achieve the maximum wind power generation and loss minimization of the IPMSG. The effect of magnetic saturation, which causes the highly nonlinear characteristics of the IPMSG, is considered in the control-scheme design. The optimal <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> -axis stator-current command is obtained as a function of the IPMSG rotor speed by solving a constrained nonlinear-optimization problem that minimizes the copper and core losses of the IPMSG. At any wind speed within the operating range, the IPMSG rotor speed is optimally controlled to extract maximum wind power. The optimal <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> -axis stator-current command is then obtained from the optimal IPMSG rotor speed and <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> -axis current. To eliminate the effects of nonlinearity caused by magnetic saturation, an input-output feedback linearization technique is applied to design the high-performance nonlinear current controllers. The proposed control scheme provides the wind generation system with the maximum efficiency and high dynamic performance.

Design of Flux Observer Robust to Interior Permanent-Magnet Synchronous Motor Flux Variation

This paper presents a modified flux observer which is robust to the variation of the permanent-magnet flux linkage of an interior permanent-magnet synchronous motor (IPMSM). The IPMSM is driven by a current-regulated inverter, where the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> - <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> axis currents are controlled by two proportional and integral controllers with feedforward cross-coupling decoupling terms. The integrator outputs of the current regulator reflecting flux errors are used to compensate the flux variation according to the operating temperature and manufacturing tolerance. The proposed flux observer shows satisfactory performance not only in maximum torque per ampere operating region but also in flux weakening region. The experimental results reveal the effectiveness of the proposed observer.

Design and Implementation of a Novel Vector-controlled Drive by Direct Injection of Random Signal

The distribution of harmonics of an inverter output voltage in a PWM inverter can be improved by using a Random Pulse Width Modulation (RPWM) scheme. RPWM dose not affect the fundamental frequency component of voltage, however it can significantly reduce the acoustic noise and mechanical vibrations of an inverter-fed ac motor drive. Up to now, RPWM has been studied in many researches and various RPWM techniques have been introduced, but none of them have actually shown the effects of the behavior of the random signal on the frequency spectrum of the inverter output voltage and performance of the motor drive. In this paper, three different methods of random signals are employed. These different methods and the Probability Density Function (PDF) of the random signal generator will be studied and the performance of the drive is examined. Also a new method in utilizing random signal is proposed. In this method, the random signal is injected to reference value of the quadrature-axis current. It should be noted that the RPWM technique can not be utilized in hysterisis drives. Here, the random signal with different PDF is injected directly to quadrature axis current. The injection of random signal will directly affect the output responses. In this research, comparison between RSPWM technique and direct injection of random signal has been carried out. Different criteria such as total harmonic distortion (THD), torque ripple and frequency spectrum, efficiency and mechanical vibration have been analyzed. The indirect field oriented vector control drive is simulated by using Matlab-Simulink first, and the effects of various methods of employing random signal are compared and the best alternative is introduced. For the validation of the simulation results an experimental set-up is built. The experimental results confirm the simulation outputs. The simulation and experimental result show superiority of Direct Injection of Random Signal (DIRS) method in comparison with randomized Sinusoidal pulse width modulation (RSPWM) technique. Also it is realized that the DIRS method is very simple for implementation and does not need any extra hardware.

A Planar Actuator with a Small Mover Traveling Over Large Yaw and Translational Displacements

We report a three-degree-of-freedom actuator with a small mover that can travel over large displacements on a plane. Such direct drives with multiple degrees of freedom are an emerging technology because of their high performance. Previously, we designed planar actuators capable of generating thrusts anywhere in the movement area and successfully demonstrated the two-dimensional drive of the actuator in the translational direction. However, during translational motion control on the plane, a slight oscillatory yaw motion occurred. Thrusts and torques of the actuator are proportional to the - and -axis currents, which generate flux densities with 90 and 0 phase-leads, respectively, from the flux density generated by the permanent magnets of the mover. Therefore, the thrusts and torques can be generated independently by the - and -axis current control. In our new design, we use a decoupling control on the planar actuator to control both yaw and translational motions on the plane. We describe the experimentally obtained drive characteristics of this actuator. The experimental results indicate that the mover can travel over large yaw and translational displacements independently and simultaneously with relatively precise positioning and response. Thus, we have demonstrated satisfactory performance of a planar actuator with three degrees of freedom.

Novel Voltage Limiter for Fast Torque Response of IPMSM in Voltage Saturation Region

A new voltage limiter for fast torque response of IPMSM in voltage saturation region is proposed, which we name “maximum torque response voltage limiter”. In transient condition, the fastest response is vital while voltage saturation occurs. Then the problem is that how to divide the limitted voltage to d and q axis voltages for generating the fastest torque response. The nonlinear relation between torque and d-q axis currents of IPMSM makes the problem complicated.In our proposed method, both voltage equations and a torque equation of IPMSM are considered and, based on Lagrange optimization technique, the explicit expression of d and q axis voltages are derived. Compared with the conventional voltage limiter such as constant phase angle method, constant back emf. method and constant d-axis voltage method, the proposed limiter yields faster torque response in voltage saturation region, which is confirmed by computer simulation and experimental results. Furthermore, the proposed method uses simple software calculation, and it can be readily implemented without any modification of hardware system.