Showing papers on "Synchronous frame published in 2013"

Dynamic Modeling and Control for SPMSMs With Internal Turn Short Fault

Abstract: A dynamic model for a faulted surface-mount permanent magnet synchronous motor (SPMSM) is derived using a deformed flux model. In reflecting the internal turn short into the dynamics, the variations in inductance and back EMF term were considered. Then, the faulted model was transformed into the two synchronous dq-models: one for the positive sequence and the other for the negative sequence. Also, a torque equation, which shows the relation between the ripple and the negative sequence current, is derived. The negative sequence current should be suppressed to eliminate the torque ripple. The dual current controller is utilized for this purpose: in the dual controller, the positive and negative sequences are controlled separately in their own synchronous frames. Notch filters are utilized in each synchronous frame to extract positive or negative sequence component. Experiments were performed with an SPMSM specially designed to make an internal turn short artificially. The experimental results coincide well with the corresponding simulation results, and exhibit a strength of the dual current controller in suppressing the negative sequence current.

Wireless Paralleled Control Strategy of Three-phase Inverter Modules for Islanding Distributed Generation Systems

Abstract: This paper presents a control strategy for distributed systems, which can be used in islanded microgrids. The control strategy is based on the droop method, which uses locally measured feedback to achieve load current sharing. Instead of the traditional droop method, an improved one is implemented. A virtual inductor in the synchronous frame for three-phase inverters is proposed to deal with the coupling of the frequency and the amplitude related to the active and reactive power. Compared with the traditional virtual inductor, the proposed virtual inductor is not affected by high frequency noises because it avoids differential calculations. A model is given for the distributed generation system, which is beneficial for the design of the droop coefficients and the value of the virtual inductor. The effectiveness of the proposed control strategy is verified by simulation and experiment results.

A novel IMC controller based on bacterial foraging optimization algorithm applied to a high speed range PMSM drive

Abstract: This paper is a proposal of a modified internal model control based on an intelligent technique. The indirect field oriented control strategy (IFOC) is used as a permanent magnet synchronous motor (PMSM) drive platform. Neural network controller and estimator are respectively added to replace the conventional speed regulator and the speed encoder in the global drive scheme. A wide speed working range is considered and high speed mode is incorporated in the study testes. In the IFOC inner control loops, the commonly used synchronous frame conventional proportional plus integral (PI) controllers are replaced by two modified internal model control (IMC) regulators. Therefore, a method based on the bacterial foraging optimization (BFO) algorithm is performed to optimize and adjust the IMC low pass filter parameters. The robustness of the proposed PMSM sensorless drive scheme is confirmed by simulation tests in the MATLAB/SIMULINK. Moreover, a comparative evaluation results are illustrated to prove the effectiveness of the proposed control algorithm according to different controllers combinations.

Harmonic state space modelling of voltage source converters

Abstract: The thesis describes the development of a model of the three-phase Voltage Source Converter (VSC) in the Harmonic State Space (HSS) domain, a Linear Time Periodic (LTP) extension to the Linear Time Invariant (LTI) state space. The HSS model of the VSC directly captures harmonic coupling effects using harmonic domain modelling concepts, generalised to dynamically varying signals. Constructing the model using a reduced-order three-phase harmonic signal representation achieves conceptual simplification, reduced computational load, and direct integration with a synchronous frame vector control scheme. The numerical switching model of the VSC is linearised to gain a small-signal controlled model, which is validated against time-domain PSCAD/EMTDC simulations. The controlled model is evaluated as a STATCOM-type system, exercising closed-loop control over the reactive power flow and dc-side capacitor voltage using a simple linear control scheme. The resulting statespace model is analysed using conventional LTI techniques, giving pole-zero and root-locus analyses which predict the dynamic behaviour of the converter system. Through the ability to independently vary the highest simulated harmonic order, the dependence on the closed-loop response to dynamic harmonic coupling is demonstrated, distinguishing the HSS model from fundamental-only Dynamic Phasor models by its ability to accurately model these dynamics.

An accurate torque control of permanent magnet brushless motor using low-resolution hall-effect sensors for light electric vehicle applications

Abstract: In this paper, a microprocessor-based PMSM drive with three hall-effect sensors for detecting rotor position is studied. First, three PMSM control methods, namely 120° six-step with current limit, 180° six-step with current control, synchronous frame vector control, are compared based on some key performance indexes, such as vibration, acoustic noise and efficiency. According to the analysis, a PMSM drive which is combined with 180° six-step current control in lower speed and synchronous frame vector control in middle to high speed range is proposed. Therefore, high torque in low speed and less vibration and acoustic noise in high speed can be obtained. Furthermore, overall system efficiency is improved. Further enhancement of the torque control, a rotor position observer based on average rotor speed and considered loading effect is added to track the interpolated signals from hall-effect sensors. Hence a high resolution rotor position signal is yielded for improving vector control. All the control schemes are implemented by software. Some measured results are provided to show its successful operation and effectiveness on the torque control for PMSM in light electric vehicle applications.

Complex state variable- and disturbance observer-based current controllers for AC drives: an experimental comparison

Abstract: In vector-controlled AC drives, the design of current controller is usually based on a machine model defined in synchronous frame coordinate, where the drive performance may be degraded by both the variation of the machine parameters and the cross-coupling between the d- and q-axes components of the stator current. In order to improve the current control performance an alternative current control strategy was proposed previously aiming to avoid the undesired cross- coupling and non-linearities between the state variables. These effects are assumed as disturbances arisen in the closed-loop path, extracted by a disturbance observer and then injected into the current controller. In this study, a revised version of a disturbance observer-based controller and a well known complex variable model-based design with a single set of complex pole are compared in terms of design aspects and performance evaluation by simulation and by experiment for two different sampling rates. Several comparative results that verify the promising performance of the proposed control scheme are presented. The advantages of the proposed controller are an easy implementation and offering a unique solution for the variation of the parameter and the cross-coupling effect. Moreover, it provides a better performance, smooth and low noisy operation with respect to the complex variable controller.

Fuzzy positive feedback for islanding mode detection in distributed generation

Abstract: This paper proposes a fuzzy voltage and frequency positive feedback (PF) for islanding detection in distributed generation system (DG). The proposed method is based on positive feedback in dq synchronous frame and the design methodology of the fuzzy detection is based on fuzzy inference rules. The main idea is to reduce the injection of disturbances at the point of common coupling (PCC) during the grid-connected operation. A comparison between the fuzzy algorithm and the classical methods are done. The simulation results demonstrate the effectiveness of the proposed approach.

Modeling and design of matrix converter based unified power flow controller with implementation of complex vector synchronous frame PI current regulators

Abstract: As one of the most influential members of Flexible AC Transmission Systems (FACTS), UPFC is capable of both managing power flow and maintaining the stable performance of power systems. This paper firstly demonstrates the topology of a matrix converter based UPFC (MC-UPFC), which outweighs traditional UPFC in power losses, weight, and cost, for MC-UPDC possesses no capacitors in the DC link. Control strategies incorporating decoupling control and space vector modulation (SVM) are applied to control the nine bidirectional switches. However, transient performance in response to the power flow changes is limited due to the dependence of traditional PI current regulators on the synchronous frequency. In this paper, an alternative complex vector synchronous frame PI current regulator is analyzed and implemented in MC-UPFC. Furthermore, the system fault ride-through ability of this complex vector PI regulator-based control scheme is also investigated. This control strategy is validated by the simulation studies on Matlab/Simulink, thereby demonstrating an improved performance of power flow control in both transient and steady states.

Sliding mode observer for voltage sensorless current control of grid-connected converters

Abstract: This paper proposes a sliding mode observer for voltage sensorless grid-connected converter. The grid angular position required to the synchronous frame transformations is obtained through the estimated line voltage derived from a sliding mode grid current observer combined with a positive sequence separator. Simulations and experimental results demonstrated the simplicity and good performance of the proposed voltage sensorless approach.

Honeycomb cardboard crosscutting mechanism

Abstract: The utility model relates to a cardboard crosscutting mechanism of a honeycomb cardboard production line, and the mechanism comprises a main frame, a synchronous system and a crosscutting system; the synchronous system comprises a synchronous frame, a synchronous lead screw, a synchronous driving connecting piece and a servo motor; the synchronous frame is longitudinally and slidably matched on the main frame; the servo motor is connected with the synchronous lead screw; the synchronous lead screw can be rotationally arranged on the main frame; the synchronous driving connecting piece is fixedly arranged on the synchronous frame, and is rotationally matched with the synchronous lead screw; the crosscutting system comprises a crosscutting trolley, a crosscutting driving component and a crosscutting driving connecting piece; the crosscutting trolley is slidably matched on the synchronous frame; a cutting motor and a cutting blade are arranged on the crosscutting trolley; and the crosscutting driving component is arranged on the synchronous frame, and is connected with the crosscutting trolley through the crosscutting driving connecting piece According to the honeycomb cardboard crosscutting mechanism, a honeycomb cardboard is synchronously tracked by the synchronous system, so that the cutting blade is always kept static with the cardboard when cutting the cardboard, and the cutting precision is improved

An improved current regulation scheme used in indirect rotor field oriented control for AC traction applications

Abstract: The influence of cross coupling effect on the performance of the indirect rotor field oriented control (IFOC) for high power AC traction drives cannot be neglected due to the wide operation range, low switching frequency and so on. In this paper, the cross coupling problem between d and q axis current component in the IFOC scheme is discussed. An improved current regulation scheme is proposed based on the analysis and comparisons of the existing decoupling schemes including classical synchronous frame PI controller, feed-forward controller and dynamic decoupling controller. The proposed scheme combines the advantages of feed forward controller and dynamic decoupling controller. Experimental results show that the proposed method can effectively improve the dynamic performance of IFOC for high power AC traction drives.

DC Injection Suppression for Three-phase PV Grid-connected Inverter

Abstract: For three-phase photovoltaic(PV) systems,DC components may be induced by any phase direct current(DC) injection,which is in contrast with single-phase PV systemsIn order to solve the problem,the virtual capacitor based synchronous frame control strategy is discussedBased on the further theoretical analysis,a new decoupling virtual capacitor based synchronous frame control strategy is proposed to achieve the DC injection suppressionIn order to simplify the control structure,a frame control strategy is presented for easy implementation and DC injection elimination Finally,time-domain simulation and experimental tests are carried out to verify the effectiveness of the proposed solution

DFIG Operation Control Strategy Under Distorted Grid Conditions Based on VPI Current Regulators

Abstract: Based on the mathematical model of doubly-fed induction generators(DFIG) under harmonic distorted grid voltage conditions,harmonic current control strategy is proposed with the control target being no pulsation of the electromagnetic torque and stator reactive power.The vector proportional integral(VPI) current regulator is introduced to regulate the rotor current in the synchronous frame,and its excellent current tracking ability is well proved by analyzing and comparing the amplitude frequency and phase frequency curves with PIR current regulators.The DFIG harmonic control strategy is well validated by the experiment result based on DFIG experimental systems.

Feedback Linearization Control of a Shunt Active Power Filter Using a Fuzzy Controller

Abstract: In this paper, a novel feedback linearization based sliding mode controlled parallel active power filter using a fuzzy controller is presented in a three-phase three-wire grid. A feedback linearization control with fuzzy parameter self-tuning is used to implement the DC side voltage regulation while a novel integral sliding mode controller is applied to reduce the total harmonic distortion of the supply current. Since traditional unit synchronous sinusoidal signal calculation methods are not applicable when the supply voltage contains harmonics, a novel unit synchronous sinusoidal signal computing method based on synchronous frame transforming theory is presented to overcome this disadvantage. The simulation results verify that the DC side voltage is very stable for the given value and responds quickly to the external disturbance. A comparison is also made to show the advantages of the novel unit sinusoidal signal calculating method and the super harmonic treatment property of the designed active power filter.

3D four-wheel localizer verification device and synchronous dragging frame device thereof

Abstract: The invention discloses a 3D four-wheel localizer verification device and a synchronous dragging frame device thereof. The synchronous dragging frame device comprises a synchronous dragging frame and a synchronous frame limiting device, wherein the synchronous dragging frame comprises a cross rod, longitudinal rods and sensor jacket devices. The 3D four-wheel localizer verification device comprises a toe-in zero test frame, a front rack test portion, a rear rack test portion and the synchronous dragging frame, wherein the front rack test portion and the rear rack test portion are arranged on the toe-in zero test frame, and the synchronous dragging frame is respectively connected with a transverse shaft in the front rack test portion and a transverse shaft of the rear rack test portion in a locking mode through the four sensor jacket devices. Simultaneous rotation of four sensors is achieved, the actual work process that a 3D four-wheel localizer verifies the angle of wheels of an automobile is completely simulated, and 3D four-wheel localizer verification is achieved.

A novel single loop control structure for standalone inverter with multi loop harmonic compensation

Abstract: In this paper, a new control structure for standalone inverter with multi loop harmonic compensation capability is presented. In this method, voltage harmonics are eliminated with a single loop and only one control variable. The proposed method has several advantages such as lack of Park transformation and tuning of several control parameters. It can also be implemented with lower computational burden, less complexity and easier tuning. Simulation results indicate results within standard limits with reduced computation burden compared to conventional multi loop synchronous frame PI harmonic controller.

Assessment of synchronous-frame PI current control dynamics by means of multivariable analysis with time-delays consideration

Abstract: Current control performance is key in some ac power conversion applications, such as renewable energies and motor drives. This paper presents a method for accurate assessment of dq-PI current controllers dynamics. The proposed methodology is based on linear control for multivariable systems. First, the plant and controller matrices are modeled including time-delays and cross-coupling effects. Subsequently, the closed-loop characteristic polynomial is obtained from the sensitivity matrices. Then, a computer-aided process to calculate the system closed-loop poles (eigenvalues of the characteristic polynomial as a function of the control gains) is applied. From some specific constraints (e.g., desired time responses), the optimum tuning is available by inspection of the closed-loop root-loci. Different tests have been performed in a 6 kVA lab-prototype. The experimental results prove the validity and accuracy of the analysis.

Time synchronization control method and control device for wired lan

Abstract: PROBLEM TO BE SOLVED: To provide a simple and relatively low cost time synchronization control method and control device for a wired LAN, capable of avoiding deterioration of time synchronization accuracy caused by the transmission of incorrect timing information.SOLUTION: The time synchronization control device includes: a frame analysis unit 1 for analyzing the header part of a frame to supply to an IFG monitoring unit 2 information on whether or not the frame is a synchronous frame; the IFG monitoring unit 2 for monitoring whether a sufficiently long inter-frame gap (IFG) exists immediately before the frame currently in reception, and when it cannot detect the sufficiently long IFG and receives a synchronous frame detection signal from the frame analysis unit 1, transmitting a frame destruction request signal to a frame destruction unit 3; and the frame destruction unit 3 for processing to add a noise to a currently passing frame signal so that the frame produces an error, on the acquisition of the frame destruction request signal.

Distortion-tolerant method and apparatus for generating phase control signal, and ac/dc converting apparatus thereof

Abstract: The embodiment of the present invention relates to a phase-angle device for generating control signals and a method which strongly distorts the input power source and an alternating current or direct current (AC/DC) conversion device thereof. The embodiment of the present invention provides the generating method including the phase angle control signals for processes in which the difference signals are proportional and the integral control producing the phase angle control signals and device thereof amplifies the clipping processes, the d-q conversion process, a synchronous frame conversion process which converts the d-q stationary coordinate system voltage into the d-q synchronous frame voltage which receives the d-q stationary coordinate system voltage and phase angle control signals, and the d shaft synchronous frame voltage received by the synchronous frame conversion process, a predetermined invalid voltage and the AC/DC conversion device using the d-q stationary coordinate system voltage which converts the limit three-phase voltage producing three-phase voltage which is limited within the predetermined size and amplifies the predetermined size of three phase voltage.

Analysis of grid synchronization techniques for distributed generation system during grid abnormalities

Abstract: This thesis presents a synchronization algorithm aimed to provide an estimation of the angular frequency, and both the positive and negative sequences of the fundamental component of an unbalanced and distorted three-phase reference signal. It does not require transformation of variables into the synchronous frame coordinates as other conventionalphase-locked loop (PLL) schemes. Thus it is not based on the phase angle detection. Instead the angular frequency is detected and used for synchronization purposes. The design of UH-PLL, is based on a complete description of a three-phase signal which involves both positive and negative sequences in stationary coordinates of the fundamental and harmonic components. Also it includes an explicit harmonic compensation mechanism to alleviate the effect of harmonic distortion and unbalances in the supply. Therefore UH-PLL is intended to perform properly under severe unbalanced conditions, subject to distortion caused by low harmonics, and is insensitive against angular frequency variations, and sags and swells in the three-phase reference signal.

Protection relay system and transit time fixing method of protection relay system

Abstract: PROBLEM TO BE SOLVED: To provide a protection relay system capable of fixing a transmission delay time to a synchronous frame at all times and performing highly-accurate sampling synchronization control.SOLUTION: A frame 101 from a client 3(1) is transmitted to a transit time fixing device 2 through a port PHY22(1). Frame type determination means 25a in a control circuit 25 determines a frame type of the frame 101 transmitted from the client 3(1). Destination determination means 25b identifies a frame control circuit 23(n+1) subjected to a delay command by acquiring a destination address from the received frame 101. The frame 101 determined as the synchronous frame is delayed by prescribed time delay means 26a for a prescribed time in the identified frame control circuit 23(n+1).

Asymmetric Voltage Sag Control Strategy for Grid-Connected PV System Based on PIR Controller

Abstract: This paper proposes an improved LVRT control strategy based on PIR controller for grid-connected photovoltaic system under asymmetric voltage sag fault. First, the PIR current controller is designed in the positive synchronous frame without the need to decompose the positive and negative sequence components and the dynamic adjustment method for the current-reference calculation is given in order to gain a constant active power. And then, the principle how control strategies switching between the one in normal state and the other one in fault state is revealed in detail. Finally, simulations and experiment test on a 500kVA grid-connected photovoltaic inverter verify that this control strategy achieves good dynamic performance and it improves the PV inverters’ capacity of riding through asymmetric voltage sag fault effectively.