Showing papers on "Synchronous frame published in 2012"

Low-THD, Fast-Transient, and Cost-Effective Synchronous-Frame Repetitive Controller for Three-Phase UPS Inverters

Abstract: This paper presents a novel synchronous-frame repetitive controller for three-phase UPS inverters. Distinguished from conventional repetitive control techniques, the proposed synchronous-frame approach minimizes the repetitive control time delay to one-sixth of the fundamental period such that the dynamic response is significantly improved. In order to overcome the harmonic distortions under severe load conditions (e.g., unbalanced and nonlinear), in this paper, three synchronous rotating frames are deliberately selected, in each of which the repetitive controller is incorporated. Resultantly, the (6n ±1)th harmonics as well as the triplen harmonics are compensated. Moreover, a high-performance fourth-order linear phase infinite-impulse-response filter is applied to further enhance the accuracy of steady-state tracking. The proposed controller is programmed on the 16-bit fixed-point digital signal processor (TI TMS320LF2407) and eliminates high-resolution current sensors for cost effectiveness. Simulations and experimental tests have been carried out based on an 18-kW three-phase UPS system. Low total harmonic distortion (<;0025;) has been achieved under heavily distorted nonlinear load and unbalanced load. Fast dynamic response has been demonstrated during step load transients.

A Predictive Current Control Scheme for Permanent Magnet Synchronous Motors

Abstract: This paper presented a discrete predictive current control scheme for permanent magnet synchronous motors(PMSM) based on the dead-beat algorithm in the synchronous frame to improve the performance of the current loop.Based on the mathematical model of PMSM,the current controller directly calculated the expected voltage vector according to the current reference and feedback values;then transformed the voltage vector into switch signals with space vector pulse width modulation model.The robust predictive current control was introduced to decrease the sensitivity of system stability caused by the model parameters error.Simulation and experiment results showed that the PMSM current predictive control scheme efficiently improved both the dynamic performance and the steady-state precision of the current loop.

Implementation of high-performance sensorless interior permanent-magnet synchronous motor control systems using a high-frequency injection technique

Abstract: This study proposes a high-performance sensorless interior permanent-magnet synchronous motor control system using a high-frequency injection technique. A new estimation method that uses both the high-frequency d-axis current and q-axis current to estimate the rotor position is investigated. By using the proposed method, the hypothesis-synchronisation signal used in the conventional high-frequency injection method can be eliminated. A 1.25 kHz, 15 V, sinusoidal waveform voltage is injected into the d-axis synchronous frame of the motor and then the high-frequency d-axis and q-axis currents can be measured to determine the rotor position of the motor. In addition, a new compensation method is developed to reduce the estimation position error because of the mutual inductance and saturation effect of the motor. By using this new method, the estimated rotor-position error is within ±2 electrical degrees. A digital signal processor, TMS-320-F2812, is used as the estimating and control centre. The experimental results show that the proposed method can be applied in both a sensorless speed control system and a sensorless position control system. The sensorless speed control system has fast response, good load disturbance response and good tracking response.

Predictive current control for Permanent Magnet Synchronous Motor based on deadbeat control

Abstract: This paper presents a discrete predictive current control of PMSM (Permanent Magnet Synchronous Motor) based on dead-beat algorithm, in the synchronous frame, to improve the performance of current loop. Based on the mathematical model of PMSM the current controller directly calculated the expected voltage vector according to the current reference and feedback values, then transforms the voltage vector into switch signals with SVPWM model. The robust predictive current control is introduced to decrease the sensitivity of system stability with the model parameters error. Simulation and experiment results show that the PMSM current predictive control scheme improves both the dynamic performance and steady-state precision of the current loop efficiently.

A Novel Double Closed Loops Control of the Three-phase Voltage-sourced PWM Rectifier

Abstract: The double closed loop control strategy, which is composed of inner current loop and outer voltage loop in the d-q synchronous frame, is a relatively common control strategy of the three-phase voltage-sourced PWM rectifier. This strategy is suitable for the digital control system with the digital signal processor (DSP), because of its simple structure. The decoupling part is often ignored without the exact value of the boost inductance. And the nonlinear outer voltage loop is also the limit to improve the control performance. This paper proposed a novel double closed loop control strategy, which consists of decoupling current controller without exact value of the boost inductance in d-q synchronous frame, and the outer voltage linear control strategy with the control amount of the square of the voltage. Both the simulation analysis and experimental results demonstrate the validity of the proposed method and the feasibility of the control strategy.

Current control methods for grid-side three-phase PWM voltage-source inverter in distributed generation systems

Abstract: A comparison between two current control methods for grid-side inverter, i.e. PI control and forward predictive control, is made. The PI current control is implemented in d-q synchronous frame, while the forward predictive current control is implemented in abc stationary frame. The paper presents both simulation and experimental results, which were made at a reduced scale (2.2 kW). The constant-power test showed that both methods have good results in respect to existing grid codes.

Synchronous clawing mechanism with multiple manipulators

Abstract: The invention relates to a synchronous clawing mechanism with multiple manipulators, and belongs to the field of automation equipment. The synchronous clawing mechanism with multiple manipulators comprises a synchronous manipulator-clawing platform, a synchronous frame vertical-lifting platform and synchronous frame transverse-moving platforms. The synchronous clawing mechanism with multiple manipulators is characterized in that the synchronous manipulator-clawing platform is fixed on the synchronous frame vertical-lifting platform via a rodless air cylinder slider and linear guide-way sliders, and upper ends and lower ends of linear guide-ways of the synchronous frame vertical-lifting platform are fixed on the synchronous frame vertical-lifting platform. Clawing of the manipulators to targeted objects is realized via the synchronous manipulator-clawing platform. Targeted object grabbing and disposing of the manipulators is realized via the synchronous frame vertical-lifting platform. Transverse moving transfers of the targeted objects by the manipulators are realized by the synchronous frame transverse-moving platforms. The synchronous clawing mechanism with the multiple manipulators has the advantages that machines can be utilized to substitute for manual operation, and a plurality of the targeted objects can be clawed synchronously automatically. Furthermore, the synchronous clawing mechanism with the multiple manipulators is simple in structure, convenient, practical, environment-friendly, energy-saving, high in degree of automation, and reliable in performance.

Clock frequency synchronization method in packet based network

Abstract: The invention relates to a clock frequency synchronization method in a packet based network. The method comprises the steps of: transmitting a synchronous frame by a source node A at a fixed time, wherein the synchronous frame carries information on a frame transmitting moment; receiving the synchronous frame and recording a frame receiving moment value, by a target node B; obtaining a sequence value of synchronous frame transmitting and receiving moments at the node B so as to track and calculate a time delay value of the nodes A and B, and working out a specific value K(n) of a clock cycle between the nodes A and B by using a least square straight line fitting method in two states; and correcting the clock CLKB of the node B in real time by using K(n), wherein the clock CLKA of the source node A can be recovered at the node B, and K(n) can also be directly used for correcting a counter value to eliminate clock skew errors of counters in the nodes A and B. The clock frequency synchronization method disclosed by the invention can be widely applied to clock frequency synchronization and network one-way delay measurement in the packet based network.

Method for realizing encryption synchronization

Abstract: The invention provides a method for realizing encryption synchronization. Original system synchronous codes (SSCs) or sequence number synchronous codes (SNSCs) in a trunking communication system are regarded as synchronous codes to be synchronously encrypted, instead of specially adding synchronous sequence codes to a business data frame for realizing encryption synchronization like in the prior art, so bandwidth resources are saved. In addition, in the scheme provided by the invention, when the SSCs are regarded as the synchronous codes to realize encryption synchronization, a secret key synchronous frame does not need to be used, so the position where the secret key synchronous frame is originally sent can be used for sending the business data frame, and thereby the bandwidth resources are further saved. Moreover, in the prior art, when the secret key synchronous frame is sent, the corresponding business data frame needs to be discarded or deferred, so undoubtedly, the communication quality is reduced; however, after the SSCs are regarded as the synchronous codes to realize encryption synchronization, the secret key synchronous frame does not need to be used, so the communication quality is improved.

Method of Evaluating and Ensuring Stability of AC/DC Power Systems

Abstract: Approximating loci of eigenvalues or characteristic gains of a return ratio matrix of a model of a multi-phase power converter circuit by the loci of the d-d and q-q elements of said synchronous frame of reference applied to said model, allows determination and assessment of stability of the circuit or forbidden operational parameters of the combination of an AC power source and a power converter at an interface thereof by application of a standard Nyquist stability criterion.

Serial data associated clock extraction method

Abstract: The invention relates to the field of digital communication, in particular to a serial data associated clock extraction method. The method comprises arranging a synchronous frame signal on the transmitting end for transmitting the serial data to enable a frame synchronous searching unit at the receiving end to work effectively; and generating N clocks identical in frequency but different in phases at the receiving end by using a system synchronous clock as the reference clock, thereby completing effective extraction of the associated clock.

Dynamic model of the three-phase single-stage boost inverter for grid-connected applications

Abstract: In this paper, the state-space-averaging method is used to develop the dynamic model of a grid-connected three-phase single-stage boost inverter in a synchronous frame of reference. The case study single-stage inverter has a current source topology, associated with a modified space-vector pulse-width-modulated switching pattern. In the proposed method, the state-space equations of the system in dq-frame of reference are derived and averaged over a switching cycle. Then, the perturbation and linearization technique is applied to derive the small-signal model of the system. The developed model can be used as a tool mainly for the stability and control studies of the grid-connected single-stage boost inverter. The validity of the obtained state-space-averaged model is verified through experiments.

Research on control system of three-level inverter based on indirect field orientation

Abstract: In this paper, the mathematical model of induction motor based on rotor indirect field orientation in synchronous frame is introduced. Based on this, the current controller and the speed controller are designed in the indirect field-oriented space vector control system. The parameter is adjusted using the engineering design method and the three-phase asynchronous motor is controlled using SVPWM control strategy. The control system is simulated by MATLAB. The simulation results show that the proposed scheme is feasible and the space vector control system has a good dynamic respond.

An IPMSM position control system using high frequency injection sensorless technique

Abstract: This paper proposes a high performance sensorless interior permanent magnet synchronous motor control system using a high frequency injection technique. A new estimation method which uses both the high-frequency d-axis current and q-axis current to estimate the rotor position is investigated. By using the proposed method, the hypothesis-synchronization signal used in the conventional high frequency injection method can be eliminated. A 1.25 kHz, 15V, sinusoidal waveform voltage is injected into the d-axis synchronous frame of the motor, and then the high frequency d-axis and q-axis currents can be measured to determine the rotor position of the motor. By using this new method, the estimation rotor position error is within ±2 electrical degrees. A sensorless position control system is implemented by using the high frequency injecting technique. The system can achieve precise position control with satisfactory performance.

Energy efficient control technique for switched reluctance motor drives

Abstract: This paper describes modeling and machine independent method to minimize the energy consumption of a speed controlled Switched Reluctance Motor (SRM). The method for modeling depends on the mathematical models of SRM under an a-b-c stationary frame and a d-q synchronous frame. The control strategy is to vary the dutycycle of the applied current regulator in order to obtain the desired speed quickly. When operating in steady state vary the turn-on angle (θ on ) of the phase-voltage to minimize the energy consumption. The power flow is measured in the DC part and used to control the turn-on angle. Simulations the system on a 6/4 pole SRM justify the algorithm. Measurements on load systems show it is possible to minimize the energy consumption on-line in a speed controlled SRM without loosing the dynamic performance. The algorithm is fully applicable to other SRM at other power levels or with other pole configurations.

Constrained predictive control of three-phase voltage source converters with explicit performance specifications

Abstract: Three-phase voltage source converter is one of the underpinning technologies in a renewable energy system such as wind energy generator and PV arrays. This component is nonlinear and time-varying by nature. However, with the classical synchronous frame transformation, the nonlinear model is linearized to obtain a continuous-time state-space model. Based on the linearized model, in this paper, a continuous-time model predictive control system (Laguerre function based) for a grid connected three-phase voltage source converter is designed and implemented on a laboratory scaled test-bed that was built by the authors. In the proposed design, a method known as closed-loop paradigm is applied to provide a simple tuning parameter to achieve a prescribed degree of stability and damping ratio. Constrained control of the converter is demonstrated using the computationally efficient Hildreth quadratic programming to limit the modulation of switching functions.

Method for controlling a permanent synchronous motor with low resolution rotor position feedback sensors

Abstract: This invention is related to motor control method for a permanent synchronous motor with only three Hall-effect sensors as rotor position feedback sensors. First, the permanent synchronous motor is controlled with 180 DEG six-step current control at start-up and lower speed, and then synchronous frame current control method in middle to high speed range is proposed. Therefore, high torque in low speed and less vibration and noisy in high speed can be obtained. Furthermore, overall system efficiency is improved. Further enhance low speed regulation characteristics, a speed observer with load feedback is added to improve the resolution of the rotor position feedback sensors.

Space vector pulse width modulation and control technique for single phase three level rectifier in d-q coordinate system

Abstract: In order to reduce the coupling influence between high-speed electric multiple units(EMU) and the voltage of traction power gird,the operation principle of single-phase three-level neutral point clamped(NPC) rectifier in electrical traction converter was analyzed firstly,and the mathematic modeling in d-q reference frame was described.Then an active and reactive current decoupled control scheme in d-q synchronous frame was presented.On the basis of this,a single-phase three-level space voltage pulse width modulation(SVPWM) was proposed.Compared with the traditional sine pulse width modulation(SPWM),the adopted SVPWM method can not only reduce the requirement of insulation grade and voltage jump impulse durability for the traction transformer,but also balance neutral point voltage effectively.Finally,the validity and feasibility of the control and modulation scheme are verified by computer simulation and a low power prototype experiment.

Predictive Control of a Three-Phase Regenerative PWM Converter

Abstract: One of the key components in a renewable energy system such as wind energy generator is a three-phase regenerative PWM converter. This component is nonlinear and time-varying by nature. However, with the classical synchronous frame transformation, the nonlinear model is linearized to obtain a continuous-time state-space model. Based on the linearized model, in this paper, a continuous-time model predictive control system (Laguerre function based) for a three-phase regenerative PWM converter is designed and implemented on a laboratory scaled test-bed that was built by the authors. In particular, a prescribed degree of stability is applied to provide a simple tuning parameter to the closed-loop performance.

Estimation sensorless vector control of induction drive performance with dynamic resistance tuning

Abstract: This paper presents the outcomes of a sensor less indirect stator-flux-oriented control (ISFOC) implementation to an induction motor drive with stator resistance tuning. The estimation of speed and stator resistance is based only on measurement of stator currents. The error of the measured q -axis current from its reference value feeds the proportional plus integral (PI) controller, the output of which provides the estimated slip frequency. Feed forward compensator operates on a Synchronous frame and Owing to its advantages; an IP controller is used for rotor speed regulation. This work focuses on speed estimation techniques for sensor less closed-loop speed Control of an induction machine based on indirect field-oriented control technique. Details of theories behind the algorithms are stated and their performances are verified by the help of simulation.

Electronic signature information processing method and device for realizing different-screen real-time synchronous browsing

Abstract: The invention relates to an electronic signature information processing method and device for realizing different-screen real-time synchronous browsing. The method comprises the following steps: a control end acquires the information input by a user, and sends the information to multiple play ends; the control end calculates the most reasonable frame number as a synchronous frame according to the currently played frame number fed back by each play end, and sends the synchronous frame information to each play end; and the play end corrects the current frame thereof into the synchronous frame to realize electronic signature information processing based on different-screen real-time synchronous browsing. The device comprises a control end, a hub, at least two play ends, a projector, a projection screen, a camera and a handwriting screen, wherein the control end is connected with the play ends through the hub; the play ends are connected with the projector; the projector is connected with the projection screen; and the camera and the handwriting screen are connected with the control end respectively. Compared with the prior art, the method and device provided by the invention have the advantages of flexible configuration, strong synchronization ability and the like, can realize different-screen real-time smooth display, and can thoroughly change the limitation of the traditional browsing.

Communication system and method of communication

Abstract: A master station (100) is provided with an offset time generating unit (101) for generating an offset time, a synchronous frame generating unit (102) for generating a synchronous frame for a plurality of slave stations (120-1, 120-2), and a communication unit (103). A relay station (110) is provided with communication units (111a, 111b, 111c) and a synchronous frame delay time measuring unit (112) for measuring a delay time required for a period from receiving a synchronous frame addressed to each slave station (120-1, 120-2)from the master station (100) to transmitting the synchronous frame to each slave station (120-1, 120-2), and for transmitting the delay time to each slave station (120-1, 120-2). The slave stations (120-1, 120-2) are provided with a communication unit (121), a synchronous counter (123) which is used to synchronize the plurality of slave stations (120-1, 120-2), and a delay correcting unit (124) for calculating a correction time which is calculated by subtracting the delay time from the offset time, and for resetting the synchronous counter (123) after the correction time has passed since the communication unit (121) received the synchronous frame.