Wang H.,Wuhan Naval University of Engineering |
Fu L.,Wuhan Naval University of Engineering |
Jie G.,Wuhan Naval University of Engineering |
Xiao F.,Wuhan Naval University of Engineering |
Wan Z.,No704 Research Institute
Hsi-An Chiao Tung Ta Hsueh/Journal of Xi'an Jiaotong University | Year: 2013
Conventional linear quadratic regulator (LQR) method is regarded as an unsatisfactory solution for voltage source inverter (VSI) systems because it can not ensure reference voltage command tracking. Although linear quadratic tracker (LQT) method can ensure command tracking performance, its control effect may be weakened when the system exhibits non-linear behavior because it can not eliminate steady-state amplitude and phase errors. This paper proposes a new controller based on state-feedback with proportional-resonant (PR) control for three-phase inverter system. Following redefining the LQR problem, this controller improves the capability of optimal tracking, which is placed within a general structure offered by the internal model principle (IMP) of control theory. The method solves these two drawbacks of LQR method in context of command tracking, and eliminates steady-state errors with good tracking performance as LQT. The simulation and experiment verify that the scheme is able to eliminate steady-state amplitude and phase errors and to provide nice dynamic and static characteristics. The total harmonic distortion of output voltage gets lower than 1%, and voltage unbalance factor lower than 1.5% with 30% unbalance load.
Lu Q.,Zhejiang University |
Yao Y.,Zhejiang University |
Ye Y.,Zhejiang University |
Dong J.,No704 Research Institute
2016 11th International Conference on Ecological Vehicles and Renewable Energies, EVER 2016 | Year: 2016
The permanent magnet linear synchronous machine (PMLSM) with long primary is a suitable candidate for ropeless elevator due to high force density and low thrust ripple. For the PMLSM with multi-segment long primary, it is impractical to excite all primary segments. The ordinary method is only energizing the primary segments covered by the secondaries, that is to say, section power supply technology. The switch control technology of primary sections has great influence on system performance because the parameters of PMLSM change with the secondary position. Based on finite element analysis, this paper investigates the characteristics of the PMLSM applied in ropeless elevator, including dand q-axis inductances, PM flux linkage, thrust force, etc. The suitable switching method of primary sections is then proposed to lower the copper loss and thrust force ripple. The fast and steady velocity trajectory tracking is obtained, which is validated by simulation and experiment results. © 2016 IEEE.
Gao Y.-Q.,No704 Research Institute |
Li Y.-X.,No704 Research Institute |
Zhou Z.-D.,No704 Research Institute
Hedongli Gongcheng/Nuclear Power Engineering | Year: 2013
Considering that the power level drops significantly and steam flow separates from the outlet of rotor blades in the last stage of steam turbine at low load conditions, the last stage in whole working conditions was calculated and the height of flow separation in different volume flow was obtained. Different conditions of turbine under the same flow path with nozzle governing and throttle governing were calculated respectively. The results show that the flow separation bubble and separation height increased dramatically when volume flow decreased; the throttle governing at low load conditions increased the steam rate of turbine and the enthalpy drop of pressure stage, while reduced the changes of power distribution under the influence of steam parameters changing; in the same load, the throttle governing increased the volume flow in last stage, and reduced the separation height of rotor blades accordingly; it was propitious to improve the flow of the last stage at low load conditions, and postpone the emergence of zero power conditions.