Rotor Position Synchronization in Central-Converter Multi-Motor Electric Actuation Systems

The aerospace industry is increasingly transitioning from hydraulic and pneumatic drives to power-electronic based drive systems for reduced weight and maintenance. Electromechanical thrust reverse actuation systems (EM-TRAS) are currently being considered as a replacement for mechanical based TRAS for future aircraft. An EM-TRAS consists of one or more power-electronic drives, electrical motors, and gear-trains that extend/retract mechanical members to produce a drag force that decelerates the aircraft upon landing. The use of a single (“central”) power electronic converter to simultaneously control a set of parallel induction machines is a potentially inexpensive and robust method for implementing EM-TRAS. However, because the electrical motors may experience different shaft torques—arising from differences in wind forces and a flexible nacelle—a method to implement rotor position synchronization in central-converter multi-motor (CCMM) architectures is needed. This paper introduces a novel method for achieving position synchronization within CCMM architecture by using closed-loop feedback of variable stator resistances in parallel induction machines. The feasibility of the method is demonstrated in several case studies using electromagnetic transient simulation on a set of parallel induction machines experiencing different load torque conditions, with the central converter implementing both voltage-based and current-based primary control strategies. The key result of the paper is that the CCMM architecture with proposed feedback control strategy is shown in these case studies to dynamically drive the position synchronization error to zero. The initial findings indicate that the CCMM architecture with induction motors may be a viable option for implementing EM-TRAS in future aircraft.

Simulation study on power system short circuit fault based on EMTP

Electromagnetic transient simulation program EMTP is a common simulation commercial software in power system. It can effectively analyze and study power system. In this paper, EMTP is used to build the power system simulation model, and a variety of short-circuit faults in the power system are simulated and analyzed. The results show that the results accord with the actual theory, and the waveform can accurately and intuitively investigate the dynamic characteristics of power system faults. In addition, through the simulation comparison and analysis between different faults, it can be seen that the three-phase short-circuit fault is the most serious fault in the power system, which should be avoided in the actual production and life. This shows that EMTP is a powerful tool for power system simulation research, and provides a reference for the actual equipment selection requirements of the project.

Transient Performance Analysis of Reactive Power Compensators at LCC-HVDC Station Feeding Weak AC System

This paper focuses on analyzing the dynamic performance of various reactive power compensators at weak LCC-HVDC terminals. Four scenarios based on combination of active and passive reactive power compensation schemes are presented. The comparative performance analysis of various compensators in different types of AC and DC system faults are evaluated using electromagnetic transient simulation program PSCAD/EMTDC. The analysis shows that fixed capacitor has poor performance and results in reducing effective short circuit ratio of system, while STATCOM on the other hand, increases AC system strength and has significant performance in areas like immunity to commutation failure, suppression of temporary overvoltage, AC bus voltage regulation and fault recovery time.

Influence of Synchronous Condensers on Operation Characteristics of Double-Infeed LCC-HVDCs

Considering the advantages that dynamic reactive power (var) equipment (such as synchronous condensers (SCs), which can control var independently and improve voltage stability), SCs are widely used in AC/DC hybrid power grid to provide emergency var and voltage support. In order to evaluate the dynamic var reserve capacity of SCs and analyze the influence of SCs on the operation characteristics of power system, a model with double-infeed line-commutated converter-based high-voltage direct currents (LCC-HVDCs) and SCs is established. Through theoretical derivation and PSCAD/EMTDC simulation, the effects of SCs on the operation characteristics of double-infeed LCC-HVDCs networks are studied. Then, the non-smooth voltage waveform of electromagnetic transient simulation is approximately transformed into smooth waveform by data fitting method. Finally, the processed voltage waveform is searched step by step to explore the boundary of voltage safety region to determine the dynamic var reserve capacity of SCs. The numerical results show that SCs can enlarge the voltage security region of the direct current (DC) subsystem, thus effectively improving the steady-state and transient security level of the double-infeed LCC-HVDCs networks.