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In this paper, we study three stochastic two-species models. We construct the stochastic models corresponding to its deterministic model by introducing stochastic noise into the equations. For the first model, we show that the system has a unique global solution starting from the positive initial value. In addition, we discuss the extinction and the existence of stationary distribution under some conditions. For the second system, we explore the existence and uniqueness of the solution. Then we obtain sufficient conditions for global asymptotic stability of the equilibrium point and the positive recurrence of solution. For the last model, the existence and uniqueness of solution, the sufficient conditions for extinction and asymptotic stability and the positive recurrence of solution and weak persistence are derived. And numerical simulations are performed to support our results. [ABSTRACT FROM AUTHOR]

In this paper, in order to verify the effect of variable DC-bus voltage control, CCS-MPC (Continuous-Control-Set MPC) control is used to research the control of PMSM (Permanent-Magnet Synchronous Machine) in a wide speed range. In order to maximize the speed of PMSM, the MTPA control, the field weakening control and the variable DC-bus voltage control are applied in the different speed range of PMSM. CCS-MPC can eliminate the control delay by controlling the predicted step size. When CCSMPC is applied to the PMSM control with a wide speed range, the advantages of strong adaptability of CCS-MPC can be exerted.

With the development of flywheel technology, the speed and the voltage level of flywheel continue to increase. The Z-type self-balancing modular multilevel converter can have a wide frequency range at medium voltage and is suitable for flywheel driving application. However, the voltage and current characteristics of the flywheel and the variable frequency drive still affect capacitor voltage balance in each phase-leg. The new balance of capacitor voltage can be achieved by controlling the circulating current. This paper proposed a control algorithm of the novel Z-type self-balancing modular multilevel converter for flywheel driving applications. Simulation results are presented to validate the theoretical analysis.