The offshore wind farm with large capacity and long distance to shore has attracted more and more attention as a promising option in the near future. The large-scale offshore wind farm may be designed with very different configurations, which may cause very different cost, efficiency and reliability. This paper presents different possible configurations for a real offshore wind farm in England and analyzes their efficiencies at different wind speed. The results are compared and the influence of some factors is further discussed. The analysis results are useful both for wind farm layout design and for the evaluation of existing wind farms.

It is important to reduce the impact of the high penetration of wind power into the electricity supply for the purposes of the security and stability of the power grid. As such, the inertia capability of wind farms has become an observation index. The existing control modes cannot guarantee the wind turbine to respond to the frequency variation of the grid, hence, it may lead to frequency instability as the penetration of wind power gets much higher. For the stability of the power grid, a simple and applicable method is to realize inertia response by controlling wind farms based on a high-speed communication network. Thus, with the consideration of the inertia released by a wind turbine at its different operating points, the inertia control mechanism of a doubly-fed wind turbine is analyzed firstly in this paper. The optimal exit point of inertia control is discussed. Then, an active power control strategy for wind farms is proposed to reserve the maximum inertia under a given power output constraint. Furthermore, turbines in a wind farm are grouped depending on their inertia capabilities, and a wind farm inertia control strategy for reasonable extraction of inertia is then presented. Finally, the effectiveness of the proposed control strategy is verified by simulation on the RT-LAB (11.3.3, OPAL-RT TECHNOLOGIES, Montreal, Quebec, Canada) platform with detailed models of the wind farm.

The development of traditional vehicles which consume fossil carbon-based fuels is constrained by environmental pollution and the energy crisis, and it has become a social consensus to develop electric vehicles with new energy resources and low emissions. The drive system of electric vehicles should be able to reliably operate over a long period. When a short-circuit fault occurs in the driving motor, the current in the winding will increase sharply and threaten driving safety. This paper proposed a short-circuit fault-tolerant control strategy for a dual three-phase permanent magnet synchronous traction motor (DT-PMSTM) which can resolve the problem of short-circuit faults. The current in non-short-circuit fault windings has been reconstructed to offset the interference of the short-circuit current and output a stable torque. Based on the principle of constant composited magnetic motive force (MMF), the dimension-reduced orthogonal transformation matrix was derived. The compensation currents were designed according to the interference effect of the short-circuit current to the normal MMF of the motor. Consequently, the lost torque component caused by the lack of the short-circuit winding was compensated, and the torque pulsation was also reduced. The performance of the topologies with neutral point-isolated mode and neutral point-connected mode were both investigated and compared. The validity of the proposed short-circuit fault-tolerant control strategy was proved by the simulation results.

In the control systems with coupled multi-subsystem, the subsystems might be synchronized (i.e. all the subsystems have the same operation states), which results in negative influence to the whole system. For example, in the supermarket refrigeration systems, the synchronized switch of each subsystem will cause low efficiency, inferior control performance and a high wear on the compressor. This paper takes the supermarket refrigeration systems as an example to analyze the synchronization and its coupling strengths of coupled hybrid systems, which may provide a base for further research of control strategies. This paper combines topology and section mapping theories together to show a new way of analyzing hybrid systems.