CHINESE JOURNAL OF ELECTRICAL ENGINEERING

: The photovoltaic virtual synchronous generator (PV-VSG) solves the problem of lack of inertia in the PV power-generation system. The existing PV plants without energy storage are required to participate in the power grid’s frequency modulation (FM), but existing PV-VSGs with energy storage have high requirements for coordinated control. Therefore, the active power reserve PV-VSG (APR-PV-VSG) is studied. Based on the different methods to obtain the maximum power point (MPP), the peer-to-peer and master-slave APR-PV-VSG strategies are proposed. The PV inverters are deviated from the MPP to reserve active power, which is used as the virtual inertia and primary FM power. These methods equip the PV power station with FM capability. The effectiveness of the proposed control strategies is verified by simulation results. Abstract : Synchronous reluctance machines (SynRMs) have drawn increasing attention in recent years owing to their advantages such as low cost, simple structure, ease of manufacture, and high robustness. The main obstacle to the promotion of SynRMs is severe parameter nonlinearity, which deteriorates drive performance. Sensorless control methods for SynRMs are critical technologies that can broaden the industrial applications of SynRMs. Various methods of parameter identification and sensorless control strategies are reviewed and discussed, including self-commissioning, which is analyzed in detail. Furthermore, sensorless control strategies that can improve the industrial application of SynRMs are described. Finally, future research trends concerning SynRMs are analyzed and discussed. Abstract : Concentrating solar Abstract : To enhance the control accuracy of permanent magnet synchronous linear motor (PMSLM) servo systems affected by disturbances, such as time-varying parameters and abrupt load changes, an active disturbance rejection control (ADRC) algorithm based on a reduced-order extended state observer (ESO) is adopted to suppress the disturbances on the control system. First, the system’s ability to estimate disturbances is enhanced by linearizing the ESO. Second, the pole placement method is used for the construction of a reduced-order ESO that can reduce the influence of the number of adjustment parameters and the phase lag. The parameters of the reduced-order ADRC are adjusted, the optimal control parameters are selected, and the stability of controller is proved. Finally, practical experiments prove that the proposed method can improve control accuracy under multiple working conditions and features strong anti-interference ability. There is a smaller steady-state error, and no overshoot is observed. Abstract: Two-level voltage source inverters with pulse width modulation (PWM) generate multiple carrier harmonics, thereby exciting high-frequency noise from the motor. Based on a special dual-branch three-phase permanent magnet synchronous motor (PMSM), a method that utilizes a known modified space vector PWM technique is proposed. This method is able to suppress unpleasant high-frequency vibration noise as well as acoustic noise more effectively than other methods. Vibration noise near the twice carrier frequency is eliminated, and PWM vibration noise around the carrier frequency is also reduced. In particular, vibration and acoustic noise at the twice carrier frequency are eliminated using a carrier phase-shift of 0.5 π and the special winding structure of the dual-branch PMSM. The effectiveness of the proposed method is confirmed using detailed experimental results. Abstract : A frequency lock loop (FLL) based steady state linear Kalman filter (SSLKF) for unified power quality conditioner (UPQC) control in three-phase systems is introduced. The SSLKF provides a highly accurate and fast estimation of grid frequency and the fundamental components (FCs) of the input signals. The Kalman filter is designed using an optimized filtering technique and intrinsic adaptive bandwidth architecture, and is easily integrated into a multiple model system. Therefore, the Kalman state estimator is fast and simple. The fundamental positive sequence components (FPSCs) of the grid voltages in a UPQC system are estimated via these SSLKF-FLL based filters. The estimation of reference signals for a UPQC controller is based on these FPSCs. Therefore, both active filters of a UPQC can perform one and more functions towards improving power quality in a distribution network. In addition to the SSLKF-FLL based algorithm, a bat optimization algorithm (based on the echolocation phenomenon of bats) is implemented to estimate the value of the proportional integral (PI) controller gains. The bat algorithm has a tendency to automatically zoom into a region where a promising alternative solution occurs, preventing the solution from becoming trapped in a local minima. The complete three-phase UPQC is simulated in the Matlab/Simulink platform and the hardware is tested under various power quality problems. Abstract : In recent years, voltage stability issues have become a serious concern with regard to the safety of electrical systems, these issues are more evident and have wider consequences in vertical networks with an insufficient reactive power reserve. Pakistan is currently suffering from the worst energy crisis in its history. Owing to an increase in energy demand, the current transmission system is becoming increasingly inadequate. It has thus become necessary to reduce losses and enhance the system voltage profile for more efficient energy utilization. In this study, the main emphasis is on assessing the feasibility of using flexible AC transmission system devices and distributed generation to compensate power failures on the power lines of the Pakistani power transmission system. The load flow and contingency analyses are performed on a 132 kV transmission system that feeds power to the Quetta electric supply company. The region of Baluchistan is studied to evaluate the effectiveness of the proposed method. The system is simulated using NEPLAN, which accurately models the details of all system elements and the optimal power flow. The simulation results indicate that the proposed method helps reduce system losses, voltage deviation, and power flow congestion, with all system constraints within permissible limits. Abstract : A new modified extended state observer (MESO)-based robustness voltage sliding mode control (SMC) strategy is proposed for an AC islanded microgrid under system uncertainties including system parameter and load variation. First, the disturbance effect on the system is regarded as a lumped uncertainty, and a state space model of the uncertain islanded microgrid system is established. Then, a modified extended state observer is designed to estimate external disturbances and internal perturbation. Finally, considering the lumped uncertainty, a sliding mode controller with a multi-power reaching law is proposed to enable the output voltage of the system to track its reference voltage rapidly and accurately, and to enhance the robustness of the system. The simulation results confirm


Active Disturbance Rejection Position Servo Control of PMSLM Based on Reduced-order Extended State Observer
Ming Li, Jiwen Zhao, Yuepeng Hu and Zhen Wang Abstract: To enhance the control accuracy of permanent magnet synchronous linear motor (PMSLM) servo systems affected by disturbances, such as time-varying parameters and abrupt load changes, an active disturbance rejection control (ADRC) algorithm based on a reduced-order extended state observer (ESO) is adopted to suppress the disturbances on the control system. First, the system's ability to estimate disturbances is enhanced by linearizing the ESO. Second, the pole placement method is used for the construction of a reduced-order ESO that can reduce the influence of the number of adjustment parameters and the phase lag. The parameters of the reduced-order ADRC are adjusted, the optimal control parameters are selected, and the stability of controller is proved. Finally, practical experiments prove that the proposed method can improve control accuracy under multiple working conditions and features strong anti-interference ability. There is a smaller steady-state error, and no overshoot is observed.

Reduction of High-frequency Vibration Noise for Dual-branch Threephase Permanent Magnet Synchronous Motors
Wentao Zhang, Yongxiang Xu, Yingliang Huang and Jibin Zou Abstract: Two-level voltage source inverters with pulse width modulation (PWM) generate multiple carrier harmonics, thereby exciting high-frequency noise from the motor. Based on a special dual-branch three-phase permanent magnet synchronous motor (PMSM), a method that utilizes a known modified space vector PWM technique is proposed. This method is able to suppress unpleasant high-frequency vibration noise as well as acoustic noise more effectively than other methods. Vibration noise near the twice carrier frequency is eliminated, and PWM vibration noise around the carrier frequency is also reduced. In particular, vibration and acoustic noise at the twice carrier frequency are eliminated using a carrier phase-shift of 0.5π and the special winding structure of the dual-branch PMSM. The effectiveness of the proposed method is confirmed using detailed experimental results.

Control of UPQC Based on Steady State Linear Kalman Filter for Compensation of Power Quality Problems Sayed Javed Alam and Sabha Raj Arya
Abstract: A frequency lock loop (FLL) based steady state linear Kalman filter (SSLKF) for unified power quality conditioner (UPQC) control in three-phase systems is introduced. The SSLKF provides a highly accurate and fast estimation of grid frequency and the fundamental components (FCs) of the input signals. The Kalman filter is designed using an optimized filtering technique and intrinsic adaptive bandwidth architecture, and is easily integrated into a multiple model system. Therefore, the Kalman state estimator is fast and simple. The fundamental positive sequence components (FPSCs) of the grid voltages in a UPQC system are estimated via these SSLKF-FLL based filters. The estimation of reference signals for a UPQC controller is based on these FPSCs. Therefore, both active filters of a UPQC can perform one and more functions towards improving power quality in a distribution network. In addition to the SSLKF-FLL based algorithm, a bat optimization algorithm (based on the echolocation phenomenon of bats) is implemented to estimate the value of the proportional integral (PI) controller gains. The bat algorithm has a tendency to automatically zoom into a region where a promising alternative solution occurs, preventing the solution from becoming trapped in a local minima. The complete three-phase UPQC is simulated in the Matlab/Simulink platform and the hardware is tested under various power quality problems. Abstract: In recent years, voltage stability issues have become a serious concern with regard to the safety of electrical systems, these issues are more evident and have wider consequences in vertical networks with an insufficient reactive power reserve. Pakistan is currently suffering from the worst energy crisis in its history. Owing to an increase in energy demand, the current transmission system is becoming increasingly inadequate. It has thus become necessary to reduce losses and enhance the system voltage profile for more efficient energy utilization. In this study, the main emphasis is on assessing the feasibility of using flexible AC transmission system devices and distributed generation to compensate power failures on the power lines of the Pakistani power transmission system. The load flow and contingency analyses are performed on a 132 kV transmission system that feeds power to the Quetta electric supply company. The region of Baluchistan is studied to evaluate the effectiveness of the proposed method.
The system is simulated using NEPLAN, which accurately models the details of all system elements and the optimal power flow. The simulation results indicate that the proposed method helps reduce system losses, voltage deviation, and power flow congestion, with all system constraints within permissible limits.

Hao Pan, Qingfang Teng and Dangdang Wu
Abstract: A new modified extended state observer (MESO)-based robustness voltage sliding mode control (SMC) strategy is proposed for an AC islanded microgrid under system uncertainties including system parameter and load variation. First, the disturbance effect on the system is regarded as a lumped uncertainty, and a state space model of the uncertain islanded microgrid system is established. Then, a modified extended state observer is designed to estimate external disturbances and internal perturbation. Finally, considering the lumped uncertainty, a sliding mode controller with a multi-power reaching law is proposed to enable the output voltage of the system to track its reference voltage rapidly and accurately, and to enhance the robustness of the system. The simulation results confirm that the proposed robustness voltage control strategy can perform satisfactory voltage control and demonstrate a strong capability to reject parameter and load variation.