Four-quadrant AC Drive System Energy Forming And Nonlinear Control

The four-quadrant AC drive system is widely used in motor speed control system, electric energy conversion and power system and other fields, which has many advantages, such as bidirectional energy flow, flexible power control and small output harmonic content, etc. However, the control system is formed by back-to-back PWM converter and IM. which has time-varying parameters, close coupling, multiple variables and high-order. The problems, such as parameters’ change in real time, independent control between grid-side and motor-side and uncertain load, can not be solved completely by the traditional control strategies. Besides, the stability of AC drive system is needed urgently to improve.For those disadvantages in the four-quadrant AC drive system, the research of nonlinear control strategy has been intensified. Some experts" attentions are attraceted by the control strategy based on the energy shaping and port-controlled hamilton (PCH). In the paper, the desired equilibrium points and controllers are designed based on the mothods of energy shaping, interconnection configuration and damping injection. The control object of system is achieved.First, background and significance of the research are introduced. The development trends of four-quadrant AC drive system are analyzed. And the development trends of main circuit, control circuit and control strategy are included.Second, the working principle and port-controlled hamiltonian dissipative (PCHD) model are researched. The relationship between system running state and power flow are analyzed based on the working principle of system. The structures of control system are analyzed. The models of AC drive system are established under the three-phase static coordinate system and two-phase rotating coordinate system. And the mathematical models and PCHD models of grid-side and motor-side are included.Third, the state error PCH control strategy of four-quadrant AC drive system is studied. The state error PCH control strategy based on energy shaping is put forward and proved. The desired equilibrium point and controller are designed based on the control object of system. The analysis and proof of the system stability are included.Fourth, state error PCH control strategy is simulated in Matlab/Simulink environment, which is based on the comprehensive coordination control strategy and SVPWM and compared with vector control strategy. The simulation results prove that the state error PCH control strategy is better in the static and dynamic performance.