Modular multilevel converter (MMC) has been a promising candidate in high voltage direct current (HVDC) transmission system. Due to the features of simple structure, low cost and low power losses, half-bridge (HB) is usually adopted as the submodule circuit in traditional MMC. However, HB submodule circuit based MMC (HB-MMC) does not have capability of blocking DC short-circuit fault, which obstructs the development of low cost HVDC system with overhead lines. In order to solve this problem, a MMC with active clamped T-type submodule (ACTSM) to own DC fault blocking capability is proposed in this paper. Compared with other submodule circuits, the proposed ACTSM has many features, such as symmetrical blocking capability, low power losses, low voltage stress and less amount of independent drive signals. The topology, operation principle, DC fault blocking capability and power losses distribution of ACTSM are presented in this paper. The effectiveness of ACTSM based MMC is validated by both simulations and experiments.

A brushless doubly-fed generator (BDFG) for wind power applications with double-rotor structure is presented. Firstly, field modulation ring and its application in the proposed BDFG are introduced. The geometric constraints of the field modulation ring are analyzed. Then, the operation principle of variable-speed constant- frequency BDFG system is presented. The design of the BDFG is discussed and finite element analysis (FEA) for the BDFG is carried out to obtain the performance of the machine. Finally, a small-size prototype machine is designed and manufactured to verify the theoretical analysis. The proposed BDFG has some advantages, such as high efficiency and high reliability. It has good potential on the applications of future large-scale wind power generation systems.

The brushless doubly fed machine (BDFM) has been one of the key topics in the research of wind power generation. To improve the performances of the BDFM, a new permanent magnet (PM) brushless doubly fed generator (BDFG) with complementary structure is proposed in this paper. Compared with the traditional BDFM, there is an additional PM rotor providing excitation magnetic field for power and control windings. Benefiting from the absence of the exciting current and the excitation loss, the efficiency, and the power density may be increased. In order to solve a series of problems due to the introduction of PM rotor and the field modulation ring, the segmented structure is adopted. The improvement schemes are introduced in detail. Finally, the performances of the proposed BDFG are analyzed by the finite-element analysis and the results verify the effectiveness of the proposed methods.

In this paper, a new brushless doubly fed generator (BDFG) with double stator is proposed. Compared with the traditional BDFG, the winding configurations of the proposed double-stator BDFG are in great flexibility as the power winding and control winding are separately put on the two stators. The double-stator BDFG also has the advantages of increased slot filling factor and improved power density. The asymmetry of the structure and electromotive force in this BDFG is investigated. An improvement is put forward for the double-stator BDFG with segmented structure and this could solve the asymmetry problems effectively. The simulation model is built in finite-element analysis, and the simulation results verify the effectiveness of the improvement very well.

This paper presents a novel interior permanent magnet brushless doubly fed generator (IPM-BDFG) for wind power applications, which is based on the magnetic field modulation theory. The basic structure and working principle of the IPM-BDFG are put forward first. As the rotor structure has a great influence on the performance of the IPM-BDFG, the merits of the IPM rotor are discussed by comparing with the surface-mounted rotor. In order to solve the asymmetry phenomena and reduce the harmonics caused by the introduction of field modulation ring, a three-segmented structure for the outer rotor is adopted. Finally, the performances of the proposed IPM-BDFG are validated by using finite-element analysis (FEA). The FEA results show that the IPM-BDFG with segmented outer rotor has excellent performances and owns good potential in the applications of future large-scale wind power generation systems.

The insulated-gate bipolar transistor (IGBT) module that is sensitive to high temperature has been identified as one of the most fragile parts in electric vehicles. In this article, a new adaptive electrothermal model that is independent of solder aging is proposed to acquire junction temperature in real time for the health management of IGBTs. Compared with the traditional adaptive electrothermal model, the proposed model can update the parameters of thermal resistance and thermal capacitance simultaneously to adapt to the solder aging conditions. Besides, the update process just relies on the measured case temperatures, which is cost-effective and is not affected by the degradation of bond wires and gate oxide. Simulation and experimental results are provided to verify the effectiveness of the proposed method. Under the test conditions, the estimated errors of the junction temperature by the proposed model are reduced by about 60% compared with the traditional model.