The frequency stability of a marine power system is determined by the dynamic characteristic of the diesel engine speed regulation system in a marine power station. In order to reduce the effect of load disturbances a...The frequency stability of a marine power system is determined by the dynamic characteristic of the diesel engine speed regulation system in a marine power station. In order to reduce the effect of load disturbances and improve the dynamic precision of a diesel engine speed governor, a controller was designed for a diesel engine speed regulation system using H2 control theory. This transforms the specifications of the system into a standard H2 control problem. Firstly, the mathematical model of a diesel engine speed regulation system using an H2 speed governor is presented. To counter external disturbances and model uncertainty, the design of an H, speed governor rests on the problem of mixed sensitivity. Computer simulation verified that the H2 speed governor improves the dynamic precision of a system and the ability to adapt to load disturbances, thus enhancing the frequency stability of marine power systems.展开更多
Recently,ultrasonic waves had been introduced as the transmission medium in Body Area Networks(BANs) to reduce the incalculable damage caused by radio waves. However,the communications based on ultrasonic waves suffer...Recently,ultrasonic waves had been introduced as the transmission medium in Body Area Networks(BANs) to reduce the incalculable damage caused by radio waves. However,the communications based on ultrasonic waves suffer from poor propagation of signals in air and consume too much energy. To address these limitations,firstly,we make the theoretical analysis to ensure ultrasonic waves could be used in BANs(UBANs). Then,we propose an error control strategy in UBANs to dynamically adjust the error control scheme and the Max-Retries based on the current channel state,which is called UECS. The UECS is based on IEEE 802.15.6 standards and considering the characteristics of ultrasonic waves in BANs. Simulation results show that UECS achieves better performance in terms of packet delivery ratio and energy consumption compared with the traditional strategies.展开更多
In recent years, the increasing application of nonlinear and unbalanced electronic equipment and large single phase loads have made voltage imbalance a serious problem in power distribution systems. A novel approach h...In recent years, the increasing application of nonlinear and unbalanced electronic equipment and large single phase loads have made voltage imbalance a serious problem in power distribution systems. A novel approach has been proposed to eliminate voltage imbalance and disturbances. The main strategy of this scheme is based on series active filter. By improving control circuit toward existing schemes and proposing a new strategy to control the voltage amplitude, simultaneous elimination of voltage imbalance, faults, voltage harmonics and also compensation of voltage drop in transmission lines become possible. Eventually, the voltage on the load side is a perfectly balanced three phase voltage with specific proper amplitude. The proposed scheme has been simulated in a test network and the results show high capability of this scheme for the complete elimination of imbalance without phase shift.展开更多
Multiphase induction machine is normally controlled using rotor field oriented vector control. Under phase（s） loss, the machine currents can be optimally controlled to satisfy certain optimization criteria. In this ...Multiphase induction machine is normally controlled using rotor field oriented vector control. Under phase（s） loss, the machine currents can be optimally controlled to satisfy certain optimization criteria. In this paper, a vector control scheme to a five-phase induction machine is introduced to ensure equal phase currents and minimum torque ripples under a phase open circuit. The controller idea can be extended to any number of phases with any number of open phases. The fundamental dq components of the stator voltage are obtained using only two PI controllers for the fundamental sequence plane, as in conventional vector control of three-phase machines. Based on steady state model, a simple expression is derived to estimate the required dq voltage components of other sequence planes to ensure equal stator phase currents and minimum torque ripple. A five-phase machine is simulated using MATLAB/Simulink to ensure controller validity.展开更多
If the rigidity of a mechanism is stiff enough, the position synchronous error of the two cylinders driving one degree-of-freedom （DOF） of the mechanism may be less than the resolution of position sensors. To handle...If the rigidity of a mechanism is stiff enough, the position synchronous error of the two cylinders driving one degree-of-freedom （DOF） of the mechanism may be less than the resolution of position sensors. To handle this synchronization problem this paper proposes a force/position switching scheme, which partitions the two cylinders into a master cylinder and a slave cylinder. The master cylinder is always position tracking controlled by a second-order sliding mode controller and the slave cylinder is integrated with a force tracking controller which is a first order sliding mode controller. When the position tracking error is less than a given value, the slave cylinder switches to be force controlled. Two synchronization control methods are presented based on the switching scheme： the master - master ＋ force/position switching control and the master - slave ＋ force/position switching control. Simulations show that the formance compared with two given proposed synchronization control position-based control methods. methods can get a better per-展开更多
The indirect vector controlled IM （induction motor） drive involves decoupling of the stator current into torque and flux producing components. This paper proposes the implementation of a fuzzy logic control scheme a...The indirect vector controlled IM （induction motor） drive involves decoupling of the stator current into torque and flux producing components. This paper proposes the implementation of a fuzzy logic control scheme applied to a two d-q current components model of an induction motor. An intelligent based on fuzzy logic controller is developed with the help of knowledge rule base for efficient control. The performance of fuzzy logic controller is compared with that of the proportional integral controller in terms of the settling time and dynamic response to sudden load changes. The harmonic pattern of the output current is evaluated for both fixed gain proportional integral controller and the fuzzy logic based controller. The performance of the IM drive has been analyzed under steady state and transient conditions. Simulation results of both the controllers are presented for comparison.展开更多
This paper proposes a control strategy that can realize seamless microgrid operation mode transition between grid-connected operation and stand-alone operation.The scenario of a microgrid based on master-slave control...This paper proposes a control strategy that can realize seamless microgrid operation mode transition between grid-connected operation and stand-alone operation.The scenario of a microgrid based on master-slave control is considered,where the master distributed generation(DG) unit operates in different control schemes in different microgrid operation modes,while other slave DG units operate with power/current control all the time.The proposed control strategy focuses on the master DG unit,and contains the control state/reference compensation algorithm and separation switch control logic.The proposed method can effectively reduce the impact on the critical loads and DG units caused by microgrid operation mode transitions.展开更多
This paper analyzes the fundamental frequency impedance presents a novel transmission line pilot protection scheme characteristic of a thyristor controlled series capacitor （TCSC） and based on fault component integr...This paper analyzes the fundamental frequency impedance presents a novel transmission line pilot protection scheme characteristic of a thyristor controlled series capacitor （TCSC） and based on fault component integrated impedance （FCII） calculated for a transmission line with TCSC and controllable shunt reactor （CSR）. The FCII is defined as the ratio of the sum of the fault component voltage phasors of a transmission line with TCSC and CSR to the sum of the fault component current phasors where all the phasors are determined at both line＇s terminals. It can be used to distinguish internal faults occurring on the line from external ones. If the fault is an external one the FCII reflects the line＇s capacitive impedance and has large value. If the fault is an internal one on the line the FCII reflects the impedance of the equivalent system and the line and is relatively small. The new pilot protection scheme can be easily set and has the fault phase selection ability and also it is not affected by the capacitive current and the fault transition resistance. It is not sensitive to compensation level and dynamics of TCSC and CSR. The effectiveness of the new scheme is validated against data obtained in ATP simulations and Northwest China 750 kV Project.展开更多
基金Supported by the National Natural Science Foundation of China under Grant No.60774072Heilongjiang Province Natural Science Foundation under Grant No.F01-24Harbin Engineering University Basic Research Foundation under Grant No. HEUFP05014.
文摘The frequency stability of a marine power system is determined by the dynamic characteristic of the diesel engine speed regulation system in a marine power station. In order to reduce the effect of load disturbances and improve the dynamic precision of a diesel engine speed governor, a controller was designed for a diesel engine speed regulation system using H2 control theory. This transforms the specifications of the system into a standard H2 control problem. Firstly, the mathematical model of a diesel engine speed regulation system using an H2 speed governor is presented. To counter external disturbances and model uncertainty, the design of an H, speed governor rests on the problem of mixed sensitivity. Computer simulation verified that the H2 speed governor improves the dynamic precision of a system and the ability to adapt to load disturbances, thus enhancing the frequency stability of marine power systems.
基金partly supported by the National Natural Science Foundation of China(Grant No.61272412)Project 2016194 Supported by Graduate Innovation Fund of Jilin UniversitySpecialized Research Fund for the Doctoral Program of Higher Education under Grant Nos.20120061110044
文摘Recently,ultrasonic waves had been introduced as the transmission medium in Body Area Networks(BANs) to reduce the incalculable damage caused by radio waves. However,the communications based on ultrasonic waves suffer from poor propagation of signals in air and consume too much energy. To address these limitations,firstly,we make the theoretical analysis to ensure ultrasonic waves could be used in BANs(UBANs). Then,we propose an error control strategy in UBANs to dynamically adjust the error control scheme and the Max-Retries based on the current channel state,which is called UECS. The UECS is based on IEEE 802.15.6 standards and considering the characteristics of ultrasonic waves in BANs. Simulation results show that UECS achieves better performance in terms of packet delivery ratio and energy consumption compared with the traditional strategies.
文摘In recent years, the increasing application of nonlinear and unbalanced electronic equipment and large single phase loads have made voltage imbalance a serious problem in power distribution systems. A novel approach has been proposed to eliminate voltage imbalance and disturbances. The main strategy of this scheme is based on series active filter. By improving control circuit toward existing schemes and proposing a new strategy to control the voltage amplitude, simultaneous elimination of voltage imbalance, faults, voltage harmonics and also compensation of voltage drop in transmission lines become possible. Eventually, the voltage on the load side is a perfectly balanced three phase voltage with specific proper amplitude. The proposed scheme has been simulated in a test network and the results show high capability of this scheme for the complete elimination of imbalance without phase shift.
文摘Multiphase induction machine is normally controlled using rotor field oriented vector control. Under phase（s） loss, the machine currents can be optimally controlled to satisfy certain optimization criteria. In this paper, a vector control scheme to a five-phase induction machine is introduced to ensure equal phase currents and minimum torque ripples under a phase open circuit. The controller idea can be extended to any number of phases with any number of open phases. The fundamental dq components of the stator voltage are obtained using only two PI controllers for the fundamental sequence plane, as in conventional vector control of three-phase machines. Based on steady state model, a simple expression is derived to estimate the required dq voltage components of other sequence planes to ensure equal stator phase currents and minimum torque ripple. A five-phase machine is simulated using MATLAB/Simulink to ensure controller validity.
基金Supported by the Major State Basic Research Development Program of China(No.2006CB5406)Important National Science&Technology Specific Projects(No.2009ZX04002-061,2009ZX04004-102)
文摘If the rigidity of a mechanism is stiff enough, the position synchronous error of the two cylinders driving one degree-of-freedom （DOF） of the mechanism may be less than the resolution of position sensors. To handle this synchronization problem this paper proposes a force/position switching scheme, which partitions the two cylinders into a master cylinder and a slave cylinder. The master cylinder is always position tracking controlled by a second-order sliding mode controller and the slave cylinder is integrated with a force tracking controller which is a first order sliding mode controller. When the position tracking error is less than a given value, the slave cylinder switches to be force controlled. Two synchronization control methods are presented based on the switching scheme： the master - master ＋ force/position switching control and the master - slave ＋ force/position switching control. Simulations show that the formance compared with two given proposed synchronization control position-based control methods. methods can get a better per-
文摘The indirect vector controlled IM （induction motor） drive involves decoupling of the stator current into torque and flux producing components. This paper proposes the implementation of a fuzzy logic control scheme applied to a two d-q current components model of an induction motor. An intelligent based on fuzzy logic controller is developed with the help of knowledge rule base for efficient control. The performance of fuzzy logic controller is compared with that of the proportional integral controller in terms of the settling time and dynamic response to sudden load changes. The harmonic pattern of the output current is evaluated for both fixed gain proportional integral controller and the fuzzy logic based controller. The performance of the IM drive has been analyzed under steady state and transient conditions. Simulation results of both the controllers are presented for comparison.
基金supported by the National Basic Research Program of China ("973" Project) (Grant No. 2009CB219700)the National Natural Science Foundation of China (Grant No. 50837001)
文摘This paper proposes a control strategy that can realize seamless microgrid operation mode transition between grid-connected operation and stand-alone operation.The scenario of a microgrid based on master-slave control is considered,where the master distributed generation(DG) unit operates in different control schemes in different microgrid operation modes,while other slave DG units operate with power/current control all the time.The proposed control strategy focuses on the master DG unit,and contains the control state/reference compensation algorithm and separation switch control logic.The proposed method can effectively reduce the impact on the critical loads and DG units caused by microgrid operation mode transitions.
基金supported by the National Natural Science Foundation of China (Grant Nos.50877061 and 51037005)
文摘This paper analyzes the fundamental frequency impedance presents a novel transmission line pilot protection scheme characteristic of a thyristor controlled series capacitor （TCSC） and based on fault component integrated impedance （FCII） calculated for a transmission line with TCSC and controllable shunt reactor （CSR）. The FCII is defined as the ratio of the sum of the fault component voltage phasors of a transmission line with TCSC and CSR to the sum of the fault component current phasors where all the phasors are determined at both line＇s terminals. It can be used to distinguish internal faults occurring on the line from external ones. If the fault is an external one the FCII reflects the line＇s capacitive impedance and has large value. If the fault is an internal one on the line the FCII reflects the impedance of the equivalent system and the line and is relatively small. The new pilot protection scheme can be easily set and has the fault phase selection ability and also it is not affected by the capacitive current and the fault transition resistance. It is not sensitive to compensation level and dynamics of TCSC and CSR. The effectiveness of the new scheme is validated against data obtained in ATP simulations and Northwest China 750 kV Project.
