Operation Zone Analysis of the Voltage Source Converter Based on the Influence of Different Grid Strengths

With the increasing penetration of renewable energy into the power system, the voltage source converter (VSC) for integrating renewable energy has become the most common device in the electric network. However, the operating stability of the VSC is strongly dependent on its operating control strategy, which is also highly related to the strength of the AC system. Choosing the control strategy of VSC for different strengths of AC systems becomes an essential issue for maintaining the symmetry between high proportion of renewable energy integration and stable operation of AC system. In order to obtain the operation zones of the control strategies of the VSC under different strengths of AC system, in this paper, the two common VSC control strategies, vector current control (VCC) and power synchronization control (PSC), are compared. Firstly, the principle of VCC and PSC are introduced. Then, based on the short circuit ratio (SCR) and the power limit calculation under steady-state conditions of the VSC, the operation zones of the vector current control and power synchronization control are proposed. Finally, a medium voltage modular multilevel converter (MMC) system was built in PSCAD/EMTDC and the proposed operation zones of the VCC and PSC were tested by changing the SCR of the modified IEEE 33 bus system and analyzed via the critical short circuit ratio (CSCR) analysis, the small-signal stability analysis, and transient stability analysis. The results indicate that, as the SCR decreases, the VSC based on VCC is gradually worked into unstable conditions, while the stability of VSC based on PSC gradually increases. The analysis results provide a criterion for the converter operation strategy change that could significantly improve the operating stability of the VSC in the power system and realize the symmetry of the stability of the converter and the change of the strength of the AC system.

Exponential synchronization control of delayed memristive neural network based on canonical Bessel-Legendre inequality

<abstract><p>In this paper, we study the exponential synchronization problem of a class of delayed memristive neural networks(MNNs). Firstly, a intermittent control scheme is designed to solve the parameter mismatch problem of MNNs. A discontinuous controller with two tunable scalars is designed, and the upper limit of control gain can be adjusted flexibly. Secondly, an augmented Lyaponov-Krasovskii functional(LKF) is proposed, and vector information of N-order canonical Bessel-Legendre(B-L) inequalities is introduced. LKF method is used to obtain the stability criterion to ensure exponential synchronization of the system. The conservatism of the result decreases with the increase of the order of the B-L inequality. Finally, the effectiveness of the main results is verified by two simulation examples.</p></abstract>

Control of vibrational field in an elastic vibration unit with DC motors and time-varying observer

In the paper the problem of feedback control of vibrational fields in a vibration unit is analyzed taking into account the influence of the elasticity of cardan shafts, the drive dynamics, saturation for control torques. In addition, the synthesized rotor synchronization control algorithm uses the estimates of a non-stationary observer, which makes it possible to implement it practically on a two-rotor vibration unit SV-2. The performance of the closed loop mechatronic systems is examined by simulation for the model of the two-rotor vibration unit SV-2.

Leader-following Synchronization Control of Multiple Electrohydraulic Actuators Under Switching Network Topologies

A leader-following quasi-synchronization control is proposed in multiple electrohydraulic actuators (MEHAs) under different switching network topologies to guarantee the follower electrohydraulic actuators (EHAs) tracking the leader motion. Firstly, each electro-hydraulic actuator (EHA) has a 3-order nonlinear dynamics with unknown external load. Then by using Lie derivative technique, the MEHAs nonlinear models with $n+1$ nodes are feedback linearized for convenient control design. Furthermore, the leader node is constructed as a virtual simulation model to be stabilized by PI controller. Meanwhile, a quasi-synchronized controller together with a disturbance observer is designed by LMI and Lyapunov techniques to guarantee that the synchronization errors between the n follower nodes and the leader node 0 are uniformly ultimate boundaries. Finally, the effectiveness of the leader-following quasi-synchronized controller is verified by a MEHAs experimental bench with 3 EHAs under switching network topologies.