An internal power angle control strategy for high-speed sensorless brushless DC motors

High-speed Brushless DC Motors(BLDCMs)usually adopt a sensorless control strategy and operate in three-phase six-state drive mode.However,the sampling errors of the rotor position and the driving method increase the Internal Power Angle(IPA),resulting in a decrease in the efficiency of the system.Conventional IPA reduction strategies are either sensitive to motor parameters,or ignore diode freewheeling during the commutation process,or require additional current sensors.In this paper,a new strategy to reduce the IPA is proposed.Firstly,a Zero-Crossing Point(ZCP)detection method for the back-EMF without filter is proposed to reduce the sampling errors of the rotor position.Secondly,the relationship between the non-energized terminal voltage and the ZCP of the corresponding back-EMF is analyzed.The non-energized terminal voltage that has completed the diode freewheeling is divided into two triangles by half of the bus voltage.When the IPA is suppressed,the areas of the two triangles are equal.Thirdly,an advanced angle for reducing the IPA is obtained through a PI regulator which can eliminate the deviation between the two areas.Finally,both a simulation model and an experimental circuit are built to verify the proposed control strategy.

Impact of interconnections and renewable energy integration on the Philippine-Sabah Power Grid systems

This study presents a comprehensive impact analysis of the rotor angle stability of a proposed international connection between the Philippines and Sabah,Malaysia,as part of the Association of Southeast Asian Nations(ASEAN)Power Grid.This study focuses on modeling and evaluating the dynamic performance of the interconnected system,considering the high penetration of renewable sources.Power flow,small signal stability,and transient stability analyses were conducted to assess the ability of the proposed linked power system models to withstand small and large disturbances,utilizing the Power Systems Analysis Toolbox(PSAT)software in MATLAB.All components used in the model are documented in the PSAT library.Currently,there is a lack of publicly available studies regarding the implementation of this specific system.Additionally,the study investigates the behavior of a system with a high penetration of renewable energy sources.Based on the findings,this study concludes that a system is generally stable when interconnection is realized,given its appropriate location and dynamic component parameters.Furthermore,the critical eigenvalues of the system also exhibited improvement as the renewable energy sources were augmented.

Influences of Resistor-Type Superconducting Fault Current Limiter on Power System Transient Stability with Asymmetrical Short-Circuit Faults

The transient stability of a single machine to infinite-busbar power system with resistortype superconducting fault current limiters （SFCL） is analyzed under asymmetrical short-circuit fault conditions. The SFCL is considered to introduce a resistance into the three-phase circuits when faults occur. Based on the power-angle curves for different short-circuit conditions of the single-line to ground, double-line to ground and line to line short-circuit faults, the influences of the SFCLs on transient stability are analyzed in detail. The time-domain simulation of transient stability is carried out to verify the analytical results.

Effect of blade pitch angle on aerodynamic performance of straight-bladed vertical axis wind turbine

Wind energy is one of the most promising renewable energy sources, straight-bladed vertical axis wind turbine(S-VAWT) appears to be particularly promising for the shortage of fossil fuel reserves owing to its distinct advantages, but suffers from poor self-starting and low power coefficient. Variable-pitch method was recognized as an attractive solution to performance improvement, thus majority efforts had been devoted into blade pitch angle effect on aerodynamic performance. Taken into account the local flow field of S-VAWT, mathematical model was built to analyze the relationship between power outputs and pitch angle. Numerical simulations on static and dynamic performances of blade were carried out and optimized pitch angle along the rotor were presented. Comparative analyses of fixed pitch and variable-pitch S-VAWT were conducted, and a considerable improvement of the performance was obtained by the optimized blade pitch angle, in particular, a relative increase of the power coefficient by more than 19.3%. It is further demonstrated that the self-starting is greatly improved with the optimized blade pitch angle.

Research on Influence of Motor Parameters on the Negative-Salient Permanent Magnet Synchronous Motor

The d-axis inductance(Ld)of the negative-salient permanent magnet synchronous motor(NSPMSM)is larger than the q-axis inductance(Lq).Compared with the traditional motor,the NSPMSM has the characteristics of a high overload capacity,wide speed range,and preventing permanent magnet demagnetization.Positive d-axis current(id)is applied to control positive reluctance torque when running at base speed.When the motor is running at high speed,a relatively small id can achieve speed expansion and effectively expand the motor flux-weakening range.The use of a magnetic bridge to increase the Ld and a W-type permanent magnet to reduce the Lq is proposed in this article as a novel NSPMSM rotor structure.Firstly,the working principle of the NSPMSM was determined according to the equivalent magnetic circuit.Secondly,using the finite element method,the influence of motor structure on torque and speed performance of NSPMSM was analyzed,and the motor structure was optimized.Thirdly,the effect of the internal power factor angle on the performance of the two motors is analyzed.Finally,the short circuit simulation and analysis verified that the NSPMSM has a stronger short circuit current suppression ability without sacrificing overload ability.

Remote monitoring system for real time detection and classification of transmission line faults in a power grid using PMU measurements

Remote monitoring of transmission lines of a power system is significant for improved reliability and stability during fault conditions and protection system breakdowns.This paper proposes a smart backup monitoring system for detecting and classifying the type of transmission line fault occurred in a power grid.In contradiction to conventional methods,transmission line fault occurred at any locality within power grid can be identified and classified using measurements from phasor measurement unit(PMU)at one of the generator buses.This minimal requirement makes the proposed methodology ideal for providing backup protection.Spectral analysis of equivalent power factor angle(EPFA)variation has been adopted for detecting the occurrence of fault that occurred anywhere in the grid.Classification of the type of fault occurred is achieved from the spectral coefficients with the aid of artificial intelligence.The proposed system can considerably assist system protection center(SPC)in fault localization and to restore the line at the earliest.Effectiveness of proposed system has been validated using case studies conducted on standard power system networks.