Showing papers on "Synchronous frame published in 2018"

Dynamic Performance Improvement of Five-Phase Permanent-Magnet Motor With Short-Circuit Fault

Abstract: Multiphase permanent-magnet (PM) brushless motors are popularly adopted for their high efficiency and high power density. However, short-circuit phase fault results in serious problems, such as increased torque fluctuations and deteriorated dynamic performance. This paper proposes a new vectorial approach to minimize pulsating torque and improve dynamic performance in a five-phase PM motor with short-circuit fault. The novelty of the proposed strategy is voltage feedforward compensation based on the relation of the short-circuit current and its fault-phase back electromotive force. First, the compensatory voltages are used to eliminate the impact of the short-circuit current. Then, its combination with the orthogonal reduced-order transformation matrices derived from fault-tolerant current references can improve the dynamic performance of the faulty PM motor. The effect of the short-circuit phase fault on the PM motor model under rotating synchronous frame is also discussed. This control strategy allows minimal reconfiguration of the control structure from healthy operation to fault-tolerant one and exhibits the improved dynamic performance. The simulated and experimental results are presented as validation for the proposed strategy.

Active and reactive power control of single phase inverter with seamless transfer between grid-connected and islanded mode

Abstract: In this paper, a seamless transfer control strategy or algorithm for single phase grid-tied inverter is proposed using synchronous frame PLL. The inverter is controlled using the Direct-Quadrature synchronous reference frame transformation for active and reactive power control in the grid connected mode and output voltage control in the islanded mode of operation. The breaker status is responsible for the switching between the two control modes and the breaker status is decided by the proposed algorithm. The seamless transfer algorithm observes the PCC voltage on the grid side and the frequency of the grid and decides an action based on the whether the two parameters are within a particular limit. The SF-PLL is responsible for the synchronization process, it takes the reference from the grid or from a constant d-q component of the voltage depending on the output setting of the algorithm. The output of the SF-PLL will determine the frequency and phase angle of the inverter. Simulations verify the operation of this algorithm and the control modes used on the single phase inverter.

Methodology for Analysis and Design of DiscreteTime Current Controllers for Three-Phase PWM Converters

Abstract: In this work, a methodology for the analysis and design of robust, high bandwidth current controllers for three phase converters is presented. The overall goal is to demonstrate how the proposed model based control structure and the design methodology lead to an optimized digital current controller that exhibits fast and smooth dynamics as well as an excellent disturbance rejection ability. First, accurate discrete time models are derived and used to review classical current control from the perspective of the synchronous and stationary reference frame. Then, implementation options for the synchronous frame proportional integral (SFPI) regulator and the proportional resonant (PR) regulator are discussed and systematically compared in the stationary frame leading to the formulation of a general controller framework based on space vector resonators. It embodies multiple complex resonators and can represent the SFPI regulator, the PR regulator and beyond that any higher order regulator structure. For this framework, a step by step design procedure based on the complex root locus is proposed that allows an insightful optimization of its feedback gains. Finally, the performance of the presented control design techniques is evaluated experimentally.

A Modified Active Power Control Scheme for Enhanced Operation of PMSG-Based WGs

Abstract: This paper emphasizes the development of a simplified active power control scheme for enhanced operation of grid integrated permanent magnet synchronous generator based wind-driven generators (WGs). An active power reference generation scheme is proposed for the machine side converter (MSC) to inject active power into the grid even under grid disturbances, without violating system components rating. In this scheme, the controller employed for MSC adjusts the active power captured proportionate to the drop in the grid voltage upon considering wind speed and rotor speed. Furthermore, unlike dual vector control scheme, the grid side converter controller is implemented in a positive synchronous frame with the proposed current oscillation cancellation scheme to suppress the oscillations in dc-link voltage, active and reactive power of the grid and to obtain symmetrical sinusoidal grid current. Extensive analytical simulation has been carried out in PSCAD/ EMTDC to validate the superiority of proposed control scheme over the conventional schemes when WG is subjected to various grid disturbances. The reduced percentage of oscillation in the system parameters such as dc-link voltage and grid active power confirms the efficacy of the proposed method when compared with the conventional control techniques.

Improved voltage unbalance and harmonics compensation control strategy for an isolated microgrid

Abstract: This paper suggests an enhanced control scheme for a four-leg battery energy storage systems (BESS) under unbalanced and nonlinear load conditions operating in the isolated microgrid. Simplicity, tiny steady-state error, fast transient response, and low total harmonic distortion (THD) are the main advantages of the method. Firstly, a new decoupled per-phase model for the three-phase four-leg inverter is presented. It can eliminate the effect of power stage coupling on control design; thus, the three-phase four-leg power inverter can be viewed as three single input single output (SISO) control systems. Then, using an improved orthogonal signal generation method, the per-phase model of the four-leg inverter in the stationary and synchronous frame is derived. As the second step, a per-phase multi-loop control scheme for the four-leg inverter under unbalanced load conditions is suggested. The proposed control strategy has the ability to provide balanced output voltages under unbalanced load conditions by avoiding the need to deal with the symmetrical components. Finally, a multi-resonant harmonic compensator is used to actively prevent low-order harmonic currents to distort the output voltages of the three-phase four-leg grid-forming power converter. Simulations results are also presented to verify the performance of the suggested control strategy.

Unified approach to redshift in cosmological/black hole spacetimes and synchronous frame

Abstract: Usually, interpretation of redshift in static spacetimes (for example, near black holes) is opposed to that in cosmology. In this methodological note we show that both explanations are unified in a natural picture. This is achieved if considering the static spacetime one (i) makes a transition to a synchronous frame, (ii) returns to the original frame by means of local Lorentz boost. To reach our goal, we consider a rather general class of spherically symmetric spacetimes. In doing so, we construct frames that generalize the well-known Lemaitre and Painleve--Gullstand ones and elucidate the relation between them. This helps to understanding in an unifying approach, how gravitation reveals itself in different branches of general relativity. This can be useful for general relativity university courses.

Modeling, Control and Experimental Investigation of a Cascaded Hybrid Modular Inverter for Grid Interface Application

Abstract: Research on modeling of cascaded hybrid modular inverters has concentrated on conventional H-bridge topologies. In addition, research on hybrid H-bridge that gives a five-level output voltage is well documented, but a detailed analysis on how this model can be cascaded has not been researched on. This paper presents a detailed modeling analysis of a cascaded hybrid modular inverter topology. First a PWM control law is derived and used in developing a novel switching model. Derived state space equations are used in a developing generalized N-cascaded hybrid model. Simplified average models both in abc to dqo are proposed and described. Finally, small signal model computed in dq synchronous frame is developed. Feedback controller design is presented with main focus on grid voltage regulation and overall system capacitor voltage balance. A modular balance circuit is proposed for individual cell capacitor voltage. Both the MATLAB simulation and laboratory results show good performance of the proposed PWM control scheme and the accuracy of the hybrid model.

Model Predictive Control of Three-phase Grid-connected Voltage Source Inverter with LCL Filter

Abstract: This paper presents a discrete model predictive control (DMPC) to realize the direct current control of three-phase grid -connected Voltage Source Inverter (VSI) with LCL filter. The DMPC is designed in rotational synchronous frame, thus a long horizon can be adopted to guarantee the stability of the system. Laguerre functions are used to model the control sequence in order to reduce computation burden. The proposed control method can obtain good performance in steady and dynamic states even with distorted grid voltage, as well as robustness to parameter mismatch and grid voltage sags.

Frequency Adaptive Digital Filter Implementation of Proportional-Resonant Controller for Inverter Applications

Abstract: The Proportional-Resonant control is used in control schemes that directly act on AC variables avoiding synchronous frame transformation. In this paper, the PR controller is realized using an IIR digital filter and implemented using direct form II transposed structure. It has a simpler discrete time implementation, however, the disadvantage of being difficult to make them frequency adaptive, i.e. change the filter's resonant frequency. Simple closed loop expressions are derived for the coefficients in terms of resonant frequency, sampling time and damping factor. Based on this, a frequency adaptive proportional-resonant controller is proposed. It is shown that by modifying a single coefficient in the IIR realization, the controller adapts its resonant frequency to grid frequency fluctuation resulting in a simple and efficient frequency-adaptive proportional-resonant controller.

Fractional Order Proportional-Resonant Controller

Abstract: In this paper, a fractional order synchronous frame controller and its equivalent model, stationary frame control named fractional order proportional resonant controller, have been introduced using fractional order theory. Compared conventional proportional resonant controller, the proposed controller troller not only ensures a zero steady-state error for AC control systems, but also provides more robustness against fluctuations of resonant (center) frequency. Having a wider bandwidth and higher gain in the neighborhood of resonant frequency enhance the capability of this controller to deal with resonant frequency variations and furthermore, improve the time domain transient performance of these systems. Analog and digital implementions of this novel controller have been discussed. In addition, stability of the proposed controller has been investigated. Finally, the proposed fractional order control strategy is successfullyapplied to a grid-connected system as current regulator.

In-depth cross-coupling analysis in high-performance induction motor control

Abstract: High-performance field oriented control (FOC) of induction motors (IMs) relies on the accurate control of their electrical dynamics. In particular, perfect decoupling control of the stator currents should be ideally achieved for a FOC scheme to be efficient. However, the decoupling effectiveness afforded by most stator currents controllers may be influenced not only by the parameters and the operating condition, but also by the specific controller structure and the adopted coordinate system. A measure to assess decoupling effectiveness is non-existent in the IM control literature. To bridge this gap, an in-depth analysis of the cross-coupling inherent characteristics of the electrical subsystem of IMs under different well-known control structures is presented in this paper. Specifically, four control strategies previously studied and experimentally validated in the literature are critically assessed in this work: 1) stationary frame proportional-integral (PI) control, 2) synchronous frame PI control, 3) synchronous frame PI control with decoupling networks, and 4) improved stationary frame diagonal control. The decoupling capabilities of controllers in stationary and synchronous coordinates are examined, with a detailed insight on the role of decoupling methods. The analysis is performed in the frequency domain under the framework of individual channel analysis and design (ICAD). By application of ICAD, the decoupling effectiveness of FOC schemes is clearly exposed and quantified, with an assessment of the effects of parametric uncertainty being carried out for completeness. The effect of the inverter dynamics over cross-coupling is also treated using digital simulations. The results are useful to determine the conditions in which each control strategy has either advantages or disadvantages. Additionally, it is possible to determine the effect of several operating parameters over the stator currents cross-coupling such as nominal flux and torque levels

The equivalent model of controller in synchronous frame to stationary frame

Abstract: The system controlled in synchronous frame is commonly used. However, it is a problem how to transform the controller in synchronous frame to stationary frame. This paper deduces the stationary frame equivalent model of arbitrarily controller in synchronous frame. The equivalent model can reflect the control performance of the input signal at different frequency accurately. The unified frequency-domain model of the overall system can be established using the equivalent model, and the guidance for frequency analysis and stability analysis can be provided. Theoretical derivation and simulation results verify the correctness and generality of the equivalent model.

An MTPA Control Method of a PMSM and a SynRM Based on a DTC in the Stator Flux Linkage Synchronous Frame

Abstract: This paper proposes a method of maximum torque per ampere (MTPA) control for a direct torque control-based (DTC-based) permanent magnet synchronous motor (PMSM) drive system. In the proposed method, the reference flux for MTPA operation is calculated using a mathematical model in a rotating reference frame that is synchronized with the stator flux linkage vector (M-T frame). The mathematical model gives the relationship between the stator flux linkage and the armature current. In this paper, the proposed MTPA control method is applied to three types of motors: an interior PMSM (IPMSM), a surface PMSM (SPMSM), and a synchronous reluctance motor (SynRM). The mathematical models agree with the measured MTPA operating points of the tested motors. Simulation results also demonstrate the validity of the proposed method.

Current Control Strategy of Harmonic Current Injection System for Power Capacitor

Abstract: In order to avoid excessive noise of power capacitors installed in HVDC converter station, it is necessary to test the noise characteristics of the power capacitors before delivery. Simulating the working condition of power capacitor in HVDC converter station effectively is the target of harmonic power supply researching. To ensure the accurate harmonic current injected into the power capacitor, the harmonic current frequency dividing detection and control strategy is proposed. Adapting the harmonic current detection method based on instantaneous reactive power theory and d-q transformation to single-phase harmonic current injection system, the current amplitude can be tracked timely and exactly by using random harmonic current detection method, so that the Proportional Integral (PI) regulator in d-q synchronous frame used directly to achieve zero-error control. The designed phase detection method can accurately detect the initial phase angle of each harmonic, accordingly calculating the compensation angle of the system. Through the accurate detection and control of the injected harmonic current and the more precise noise test result of power capacitor can be obtained. The simulation and experimental results validate the effectiveness of the current detection and control algorithm proposed in this paper.

AC Voltage Sensorless Method With Bumpless Start for Current-Controlled Converters Connected to Microgrids

Abstract: This paper presents a novel grid synchronization method with bumpless start which requires minimal computational load and can selectively track the positive sequence of the grid voltage in an unbalanced and distorted three-phase weak grid. Only twelve floating-point operations (flops) are required to obtain the in-phase and quadrature components that define a synchronous frame which tracks the positive sequence of the grid voltage. Contrarily to a phase-locked loop (PLL), the presented scheme does not require to measure any ac voltages. Therefore, this sensorless method is particularly suitable in weak-grid conditions in which the voltage at the point of common coupling (PCC) is different from the grid voltage and may contain significant noise. The error in the estimated phase depends on the accuracy of the plant model. If the grid-impedance is assumed to be zero and the LCL filter parameters are known, both the proposal and a PLL-based scheme result in the same steady-state error. Experimental results show the advantages of the proposal compared to a moving average filter (MAF)-based PLL.

Effects of Position Sensing Dynamics on Feedback Current Control of Permanent Magnet Synchronous Machines

Abstract: This paper discusses the effect of dynamics involved in position sensing, including time-delays caused by sensor magnetics, electrical transmission and A/D conversion of sensed signals, on the feedback current control of permanent magnet synchronous motor (PMSM) drives. Position sensing dynamics essentially result in the position measurement errors, which will degrade the steady-state and dynamical tracking performance of the current and torque of the drive system. A detailed analytical model capturing the impact of errors caused by position sensing dynamics as well as back-EMF position offset on the feedback current control system for PMSM drives, along with an effective compensation technique, are presented in this paper. The overall block diagram of the closed-loop current control system in the synchronous frame considering the position sensing related errors is also presented. The analysis is validated through numerous simulation and experimental results for the practical nonsalient-pole and salient-pole PMSMs.

Speed Sensorless Control of IPMSM Using Super-Twisted Sliding Mode Observer Based Integral Backstepping Theory

Abstract: This paper presents a sensorless control of IPMSM using super-twisted sliding mode observer in rotor synchronous frame through integral backstepping. Lyapunov stability theory guaranteed the stability of both an observer and the control system. MATLAB Simulink is used to investigate the system performance under different external load. The result obtained is promising and further study on parameter variation and experimental setup is expected.

Discrete Sliding Mode Control of Induction Motor Torque and Stator Current Components

Abstract: This paper deals with the discrete-time Sliding Mode Control of induction motor. The proposed method allows to control the components of stator current vector expressed in the synchronous frame as well as the rotor flux amplitude and electromagnetic torque indirectly. The control structure ensures the constraints of both stator current and voltage as well ensures stator current vector components are controlled to follow their reference values precisely. Performance of the control structure is validated using wide simulation tests. The influence of the sampling frequency on the control quality is verified as well.

Bus synchronization method and device for EtherCAT-NCUC

Abstract: The invention provides a bus synchronization method and device for EtherCAT-NCUC, and belongs to the technical field of bus control. The method comprises the following steps that a timer controls transmission of an EtherCAT communication frame and a synchronous frame and adjusts a synchronous time difference, so that the synchronous time difference meets a certain condition; data transmission of aperiodic frame and a non-periodic frame of NCUC is dynamically controlled according to the synchronous time difference; and a communication period is dynamically adjusted according to the synchronoustime difference, wherein the adjustment range is one microsecond. The device comprises a time difference adjustment module, a sending time control module and a communication period adjustment module.The scheme can be applied to an EtherCAT-NCUC master station, and bus synchronous control of the EtherCAT-NCUC master station in different stages is realized.

A Grid-Connected Current Controlled Granular Multilevel Converter

Abstract: This paper proposes a current controlled Granular Modular Multilevel Converter (GMC). The Ramp Current Control (RCC) technique is utilized due its simplicity. Besides controlling the output currents, the proposed control system for the GMC regulates the submodules capacitors voltages at their desired settings. A proper switching state is selected to keep the submodule capacitors voltages based on hysteresis capacitor voltages controllers, the required phase voltage level, and the sign of the output current. The reference phase voltages are determined using the RCC to control the ${d-}$ and $q$-current components of the GMC in the synchronous frame. These current components are set using two Proportional-Integral (PI) controllers to manage the active and reactive powers fed to grid. Simulations results, using EMTDC/PSCAD, are presented to evaluate the dynamic performance of the proposed system under different operating conditions.

DQ Synchronous Frame Nonlinear Controller Design for a Single-Phase Stand-Alone and Grid-Connected Hybrid Wind/Battery System

Abstract: This paper presents a novel DQ synchronous frame nonlinear controller design for a hybrid wind/battery system used in single-phase residential and commercial applications. The system can either be operated in grid-connected mode or standalone mode with no need for switching between two different controllers, contrary to conventional methods. Moreover, the hybrid system provides backup capability to preserve system reliability. It can also support the grid by selling power back to the grid during high wind condition. A single-phase DQ transformation module is used to convert the grid-side converter signals in DQ synchronous frame. The simulation results shows that the system can capture the maximum power available from the wind, as well as perform power management and load voltage control, regardless of the mode of operation.

Two-switch three-phase LLC resonant circuit with power factor correction for microscale wind power generation system

Abstract: In this paper, a novel two-switch three-phase LLC resonant circuit is proposed. The proposed circuit can reduce the input harmonic current of the AC/DC interface of microscale wind turbine generator. Thus, the vibration and noise of the three-phase wind turbine can be decreased and the life span of the wind turbine can be increased. Based on the proposed converter, the primary two switches have zero-voltage switching and the secondary two diodes have zero-current switching. In addition, the three-phase power factor correction can be achieved in both transient and steady states via two-switch LLC resonant circuit without using phase-locked loop and synchronous frame d-q axis control. The maximum power point tracking of wind power system also can be achieved through the voltage control oscillator and hill climbing searching control. Finally, some experimental results are offered to verify the validity of the proposed AC/DC interface of the microscale wind turbine generation system.

Design and Analysis of Discrete Current Regulators for VSIs

Abstract: This paper presents the implementation, analysis, and comparison of discrete synchronous frame current regulators for Voltage Source Inverters (VSIs). Both a two-level inverter and a Modular Multilevel Converter (MMC) were used to emphasize the universality of the studied concepts. This work focuses on direct discrete modeling and in particular coupling effects that are unique to the discrete domain. The well-studied cross-coupling of the currents in the direct quadrature (dq) frame shows different behavior in discrete time. Further, this work studies a coupling of the latched output voltages (Zero Order Hold - ZOH) in the dq-frame in the Z-domain and presents a consequent method for Manipulated Input Decoupling (MID).

Data transmission protocol method

Abstract: The invention discloses a data transmission protocol method. The data transmission protocol method is used for data transmission between a client and a host computer, and comprises: a step S1 of performing bit merging for original data to obtain a combined synchronous frame, wherein the size of the original data is M bytes, each byte has N bits, and the synchronous frame successively comprises a synchronous frame head, the frame number of asynchronous frames, data bits of the plurality of asynchronous frames and a synchronous frame end from beginning to end; a step S2 of transmitting the combined synchronous frame; a step S3 of receiving the combined synchronous frame; and a step S4 of performing bit decomposition for the asynchronous frame data in the combined synchronous frame to recoverthe original data. Through adoption of the data transmission protocol method of the invention, defects that synchronous serial communication is high in efficiency but short in communication distanceand asynchronous serial communication is long in transmission distance but low in efficiency can be avoided, different asynchronous frame bits are selected, a bit stream can be obtained through automatic merging when data is transmitted, and data bytes can be obtained through automatic decomposition when the data is received; therefore, transmission efficiency is improved in the case of ensuring reliable long-distance transmission.

Cascading Sensor Network Clock Synchronization Scheme

Abstract: In this paper, we propose a hybrid clock synchronization architecture for a cascaded sensor network based on GPS time service and synchronous frame protocol. The sensor's upper-level unit is called sensor management unit (SMU) which synchronizes the local clock with the GPS and then use the broadcast sync frame to synchronize the clock of the sensor chain. In this paper, we build a link of 20 cascaded sensors to measure the center frequency and clock stability. The results showed that the center frequency deviation was 0.037 Hz and the stability was 0.045 ppm to 0.066 ppm .The stability of GPS is 0.06ppm, the scheme has achieved the effect similar to installing GPS chip on every sensor.

Control Strategy of TPC with A Grid Port

Abstract: An isolated three-port converter (TPC) without DC-link electrolytic capacitor is studied in this paper, which is applicable to vehicle to grid (V2G) and distributed generation (DG) system. The small signal model of the converter is formulated by means of fundamental component approximation. Furthermore, a high bandwidth current controller is employed for DC power source current control which can reduce double grid frequency ripple power on the DC side. A grid-connected current controller in dq synchronous frame for both active and reactive power regulation with virtual damping compensation is presented to eliminate resonance of grid LC filter. Simulation results validate the control strategy, and experiment results will be provided in full paper.

Development of a 10 kVA wind energy conversion system prototype using the DFIG technology

Abstract: This paper presents the development of a prototype of a wind energy conversion system using DFIG (Doubly Fed Induction Generator) technology. This system will be of great importance for conducting studies in relation to the topology of the DFIG, since it is the most used in the world, despite being sensitive to power quality problems of the electrical network. The arrangement of this system uses a back-to-back converter, which has two PWM conversion stages, both operating as voltage sources. Thus, this work presents the implementation of the control of the converter on the side of the grid. The same is done in the synchronous frame of reference, with cascade PI controllers. This methodology allows to approach the control independently, in which the right axis mesh is responsible for the DC link voltage control and the quadrature axis mesh is may be responsible for the control of the reactive power. The purpose of this paper is to validate the method present in the literature, in this way the performance of the controllers was not evaluated. The methodology used and the results obtained will be presented in this article.

Data transmission flow control method based on FC (Fiber Channel)

Abstract: The invention discloses a data transmission flow control method based on a FC (Fiber Channel), which comprises the steps of: designing a synchronous frame transmission module, wherein the module comprises one synchronous frame sending unit and one synchronous frame receiving unit, the synchronous frame sending unit takes charge of configuring and sending a synchronous frame, the synchronous framereceiving unit takes charge of receiving and parsing the synchronous frame, and sending and receiving of the synchronous frame is independent mutually; and designing a flow control module, wherein themodule comprises one FC bus monitoring unit, one FC bus activation unit and one flow counting unit, the FC bus monitoring unit takes charge of monitoring whether a data frame is sent on a FC bus, theFC bus activation unit takes charge of sending an activation instruction to the FC bus, and the flow counting unit takes charge of carrying out initialization, calculation and recovery of flow. The method disclosed by the invention is applicable to both parties of data transmission on the FC bus, is an innovation for a flow control problem in the conventional FC data transmission process, and canimprove efficiency of data transmission of the FC bus.

Signal processing device, method thereof, and program

Abstract: The present technology relates to a signal processing device, a method thereof, and a program capable of inhibiting deterioration in reception sensitivity. According to the present technology, in a case where a frequency band is vacant on the basis of a result of carrier sense, a data frame is transmitted as a wireless signal in the frequency band, and further, a synchronous frame formed of predetermined information different from that of the data frame is transmitted as a wireless signal in the frequency band in a case where the data frame is transmitted predetermined number of times within first time. Also, in the present technology, in a case where the synchronous frame is detected, the data frame is detected from a reception signal of predetermined time before the synchronous frame. The present technology is applicable to, for example, a signal processing device, an information processing device, a signal transmission device, a signal reception device, a signal transmission/reception device, a communication device, an electronic device, a computer, a program, a storage medium, a system and the like.

Universal serial bus controller for automatically generating clock and using method thereof

Abstract: A universal serial bus controller for automatically generating a clock includes an oscillation generator for generating an initial clock, a first phase locked loop for receiving the initial clock andoutputting a controller operating clock having a first frequency, a controller configured to detect at least one universal serial bus device and output an initial frame signal having a second frequency, a second phase locked loop configured to receive the initial frame signal and output a synchronous frame signal having the first frequency, a third phase locked loop configured to receive the synchronous frame signal and output a stable frame signal having the first frequency, and a multiplexer configured to receive the controller operating clock and the stable frame signal and transmit one ofthe controller operating clock and the stable frame signal to the controller.