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This paper studies a seamless power supply strategy for a ship-controlled inverter system, which is installed on the ship and includes rectifiers, inverters, the storage battery. Based on the V/f control and the P/Q control, an improved software phase-locked method is proposed by combining the working characteristics when the operating mode is switching to guaranteed the continuity and stability of grid voltage phase under all kinds of switching conditions, which can lay a solid foundation for seamless switching of different operation modes and optimize controls’ parameters. Finally, a platform of simulation experiment for switching operation modes between ship generator and rectifier (power storage)-inverter is established. The results of simulation and experiment prove the efficiency and superiority of the seamless power supply strategies for the ship-controlled inverter system.

The wavelet PWM (WPWM) technique has been applied in two-level inverters successfully, but directly applying the WPWM technique to three-level inverters is impossible. This paper proposes a WPWM technique suitable for a single-phase three-level inverter. The work analyzes the control strategy with the WPWM and obtains the design of its parameters. Compared with the SPWM technique for a single-phase three-level inverter under the same conditions, the WPWM can obtain high magnitudes of the output fundamental frequency component, low total harmonic distortion, and simpler digital implementation. The feasibility experiment is given to verify of the proposed WPWM technique.

This paper introduced the development of marine on-shore power supply system in China and abroad, and described the different control strategy of shore power based on uninterruptable power on-shore connection, as well as instance of variable frequency power supply between the port and ship for controlling harmonicdistortion, based on the Matlab simulation software to establish the simulation model of active power filter system,so as to provide the guarantee for achieving reliable paralleling between shore power and marine electrical system with effective harmonic elimination.

The dissertation demonstrated movable equipment to realize uninterruptable power supply on-shore connection, i.e. the movable switchgear and mobile synchronizing cabinet, which can unchanging structure of ship power station rather than hugely increase the investment of shore power transformation, and also achieve continuous electricity power supply for domestic vessels berthing on the ports with shore power interface connecting on-shore power, so as to realize environmental protection in port and expenditure savings for the ship. Ship controlling shore power connection system, by means of the movable switchgear and mobile synchronizing cabinet, can achieve paralleling operation between 400 V/ 50 Hz shore power and marine power generator correspondingly, and also transferring the load and paralleling off marine generators, as well as, paralleling accordingly marine generator with the shore power, corresponding transferring load and cut off shore power. Movable equipment for realizing seamless power supply between the port and ship is simple, reliable, convenient, economical and efficient. The dissertation proves that the device is simple, reliable, convenient, economical and efficient.

The dissertation discussed marine generator synchronous technology, as well as, intelligent on-shore controlling circulation current by means of using reactor to limit circulation current, both of which may realize seamless connection between ship electrical system and shore power; and also demonstrated intelligent FCL all-controlling power electronic device GTO (Gate Turn-off Thyristor) blocking and conducting, that can ensure the rapidity of connecting and disconnecting reactor and notable current limit effect. The dissertation proves the effect of seamless power supply between the port and ship, as a result of simulation model of intelligent FCL on-shore controlling circulation current. And intelligently dealing with electricity bills processing, as well as seamless power supply, which realize marine energy conservation and low-carbon emissions reduction in the port, can ensure to realize uninterruptable power on-shore connection, and at the same time promote the development of intelligent port.

The estimation of the frequency of a complex exponential sinusoid that is corrupted by random noise is fundamental in the domain of signal processing, as it has a variety of application in many areas. In this study, we presented a frequency estimator in the frequency domain of a complex signal. The estimator is composed of two steps: a standard maximum bin coarse search and a fine search. The fine search aims at searching for the frequency offset and is implemented by adopting a sliding iterative scheme, where the frequency offset is estimated based on three spectral points that are dynamically determined in the iterative procedure. Our approach requires only one calculation of Fourier coefficient in each iteration. The simulation results show the superiority of our algorithm, especially in the aspect of time complexity. It can serve as a promising alternative to other methods in the case of real-time application.