Ship Power Grid Research Articles

Improved Control of Propeller Ventilation Based on POA-XGBoost and Ship Dynamics/Control Model

Under adverse sea conditions, propeller ventilation caused by in-and-out water can decrease the reliability of the ship power grid and the lifespan of the propulsion shaft system. Predicting the development of propeller ventilation severity while identifying it can contribute to improving propeller ventilation control. In this study, the eXtreme Gradient Boosting (XGBoost) algorithm combined with a ship dynamics/control model is proposed as a propeller ventilation identification and prediction method. Meanwhile, the Pelican optimization algorithm (POA), particle swarm optimization (PSO), and genetic algorithm (GA) are applied to determine the optimal hyperparameters of the XGBoost algorithm. The results indicate that the method can effectively identify the current propeller ventilation state and predict whether a full ventilation state will occur after experiencing a partial propeller ventilation state. The comparison results indicate that the POA has a better optimization effect on the XGBoost algorithm for propeller ventilation identification and prediction. The method proposed in this study provides crucial technical support for the effective switching of propulsion control strategies for ship electric propulsion systems under adverse sea conditions.

Modeling and Simulation of Marine PV Inverter System Based on MPPT Algorithm

Under the influence of the policy of low carbon development, the development of new energy ships is receiving wide attention. Aiming at the fluctuation of the ship power grid caused by the intermittent and random nature of the PV power generation system, this paper builds a set of ship PV power generation microgrid system models based on the Matlab/Simulink simulation platform. Under the conditions of ambient temperature, light intensity, and other factors, the front-stage Boost circuit uses the MPPT conductance increment method to obtain the maximum power point of the PV module. The rear-stage inverter uses SPWM (sinusoidal pulse width modulation) inverter control in the rear stage to observe the output effect under different solar radiance, and the system is also designed to automatically switch the DC load when the light intensity is too low, which reduces the system energy loss and improves the operation efficiency of the marine PV system.

A Convolutional Neural Network-Based Method of Inverter Fault Diagnosis in a Ship’s DC Electrical System

Abstract Multi-energy hybrid ships are compatible with multiple forms of new energy, and have become one of the most important directions for future developments in this field. A propulsion inverter is an important component of a hybrid DC electrical system, and its reliability has great significance in terms of safe navigation of the ship. A fault diagnosis method based on one-dimensional convolutional neural network (CNN) is proposed that considers the mutual influence between an inverter fault and a limited ship power grid. A tiled voltage reduction method is used for one-to-one correspondence between the inverter output voltage and switching combinations, followed by a combination of a global average pooling layer and a fully connected layer to reduce the model overfitting problem. Finally, fault diagnosis is verified by a Softmax layer with good anti-interference performance and accuracy.

Research on the control strategy of grid connection between shore power supply and ship power grid

In order to meet the requirements of smooth connection and gradual load transfer between power supply and ship’s power grid. A control strategy based on an AC/DC/AC converter topology is studied in this paper. Rectification of the grid side by a double closed-loop control model using SVPWM (Space Vector Pulse Width Modulation). The V/f control strategy combined with pre-synchronization control is adopted for grid connection, in order to reduce the shock. A droop control strategy is used after grid connection. Generator gradually exits operation. The output power of the power supply increases gradually. The load is transferred in this way.

Research on Design, Detection and Realization of Monitoring System Based on Ship Power Grid Parameter

The power system of the ship is closely related to the it’s shipping, production and operation, navigation and communication, daily life and other subsystems, and has a very important impact on the operation of the ship. Due to the characteristics of the micro-grid of the ship and the use of a large number of power electronic equipment, the reliability of the power system of the ship is reduced, and the power quality of the power grid continues to decline. This paper studies the power parameter monitoring of the ship’s power grid, and designs a power parameter monitoring system for the ship’s power grid, which can monitor the power parameters of the ship’s power grid in real time. It is helpful to master the operation of the ship power system, and plays a positive role in improving the power quality of the ship power grid, and ensuring the safety and economic operation of the ship power system.

Power fluctuation control strategy of ship power system based on hybrid energy storage system

Objective Aiming at the problems of the power quality degradation of the power grid and the power distribution of energy storage devices when the load power of a ship power system fluctuates sharply, a power fluctuation control strategy based on the hybrid energy storage of batteries and supercapacitors is proposed. Methods First, based on the low-pass filtering algorithm, the power fluctuation of the ship's power system is initially allocated to the corresponding energy storage unit according to its fluctuation frequency. Then, based on the droop control strategy, the output current of each energy storage unit is adjusted according to the allocated power. Finally, based on the state of charge of each energy storage unit, the charge and discharge control of the hybrid energy storage system is conducted to smooth out the power fluctuations. Results The simulation results show that this power distribution strategy realizes the reasonable distribution of power between energy storage units and the charge and discharge power control of the energy storage system, which can effectively smooth out the load power fluctuations of the ship's power system. Conclusion The results of this study can provide valuable references for the optimal power quality design of a ship's power grid.

Automatic Test Method for Dynamic Load of Ship Shaft-belt Power Generation System

Zheng, H., 2020. Automatic test method for dynamic load of ship shaft-belt power generation system. In: Bai, X. and Zhou, H. (eds.), Advances in Water Resources, Environmental Protection, and Sustainable Development. Journal of Coastal Research, Special Issue No. 115, pp. 110-112. Coconut Creek (Florida), ISSN 0749-0208.Ship shaft generator is a power supply device widely deployed on large ships, which is driven by ship main shaft. Some automatic testing methods for power dynamic load of ship shaft-belt power generation systems have the problems of low testing accuracy and long testing time. Some large ship loads account for a large proportion of the ship's total load capacity. When this part of the load starts or stops, it will have a great impact on the ship's power grid. The traditional shaft generator system has many disadvantages, such as large loss, noise pollution, inconvenience in maintenance and inability to be coupled with the entire marine power grid. For the ship, the dynamic load test is the basis of the planning and control of the shaft power generation system. The accuracy of the test directly affects the stability of the shaft power generation system and the economy of the ship navigation. This paper analyzes the automatic test method of the power dynamic load of the marine shaft generator system, in order to meet the control demand of the marine power grid for the generator and realize the independent and stable operation of the marine diesel generator set.

Multi-objective optimization design of passive filter based on particle swarm optimization

Using particle swarm optimization algorithm, aiming at the investment cost, filtering effect and reactive power compensation ability of passive filter, the weight of each objective function is determined according to the dispersion order method, and the passive filter is designed by multi-objective optimization. In addition, the actual calculation is carried out by taking the power grid parameters of the self-elevating and self-propelled petroleum engineering ship of “Feng Long 01” as an example. Further, a ship power grid simulation model is built under the Matlab/Simulink environment to verify the practicality of the optimized passive filter design.

Effect of U-shape trench etching process on electrical properties of GaN vertical trench metal-oxide-semiconductor field-effect transistor

As reported by several market analysts, GaN-based power devices show great potential applications in the low and medium voltage range ( < 900 V). For high voltage ( > 1200 V), including ship transportation and power grid, the future applications of GaN highly depend on the development of vertical devices based on GaN substrates. Several vertical devices have been reported, such as current aperture vertical electron transistors (CAVETs), U-shape trench metal-oxide-semiconductor field-effect transistors (UMOSFETs), and fin power transistors. And the UMOSFETs show potential advantages due to greater simplicity in material epitaxy and fabrication process. In the fabrication of UMOSFETs, the U-shape trench dry etching is the most critical process. The GaN sidewalls after dry etching directly affect the interface state characteristics in the MOS structure and the channel electron transport. In this work, etching optimization including etching radio-frequency (RF) power and etching mask is investigated and process-dependent electrical characteristics of GaN UMOSFETs are also studied. The appropriate decrease of RF power ensuring the steep sidewalls can effectively improve the channel electron mobility from 35.7 cm<sup>2</sup>/(V·s) to 48.1 cm<sup>2</sup>/(V·s) and consequently increase the ON-state current and reduce the ON-state resistance. Larger etching damage to the p-GaN sidewall caused by higher RF power leads the scattering effects to increase and the mobility of the channel carriers to decrease. The interface state density at the channel can be extracted by the subthreshold swing. The interface state density decreases to 1.90 × 10<sup>12</sup> cm<sup>–</sup><sup>2</sup>·eV<sup>–1</sup> when the RF power is regulated to 50 W, which is only half of the interface state density when RF power is 135 W. Similar breakdown voltages (350－380 V) are measured for these devices with varying RF power, which are governed by gate early breakdown. Positive valence band offset is formed in the SiO<sub>2</sub>/GaN MOS structure and the early breakdown occurs due to the holes accumulating at the SiO<sub>2</sub>/GaN interface. The etching uniformity at the bottom of U-shape trench can be improved by using the SiO<sub>2</sub> hard masks instead of photoresist masks. Sub-trenches at both ends of the trench bottom are observed in the device with photoresist masks, leading the carrier scattering to increase and ON-state current to decrease. Besides, the interface state density decreases from 3.42 × 10<sup>12</sup> cm<sup>–2</sup>·eV<sup>–1</sup> to 2.46 × 10<sup>12</sup> cm<sup>–2</sup>·eV<sup>–1</sup> with a SiO<sub>2</sub> hard mask layer used. Compared with 1.6 μm photoresist mask, the thinner SiO<sub>2</sub> mask with a thickness of 500 nm has a small sidewall area, which weakens the high-energy ion reflection in the inductively coupled plasma system. Consequently, the over-etching at the bottom ends of the trench is improved significantly and therefore the fabricated GaN UMOSFET has higher channel mobility and a lower interface state density.

The Application of Solar Photovoltaic Power Generation System in Ships

Chen, L.; Li, X., and Xu, C.-X., 2019. The application of solar photovoltaic power generation system in ships. In: Gong, D.; Zhu, H., and Liu, R. (eds.), Selected Topics in Coastal Research: Engineering, Industry, Economy, and Sustainable Development. Journal of Coastal Research, Special Issue No. 94, pp. 525–529. Coconut Creek (Florida), ISSN 0749-0208.Nowadays, we are in the era of information technology explosion. Science and technology are various and changing with each passing day. All of these are responding positively to the continuously deepening innovative ideas throughout the country. It has become one of the most concerned green technologies on ships to use solar energy and other new energy power generation technology and electric propulsion technology to form integrated electric propulsion technology. Aiming at the application of solar photovoltaic system in ships, based on the introduction of the principle and mode of use of solar photovoltaic system, the application characteristics of solar photovoltaic system and its components in ships are analyzed, and the important characteristics of ship power grid based on solar photovoltaic system are discussed and summarized, which provides a basis for future system design and application. The results showed that the pollutants CO, NOX and HC showed a downward trend. With the further development of solar photovoltaic technology, the utilization of solar energy will be one of the key measures to realize green navigation for ships in the future.

Techno-economic analysis of PV systems integrated into ship power grid: A case study

The integration of a photovoltaic (PV) system into a ship power grid has recently become an important strategy of saving energy and reducing emissions from ships. Since the close relationship between the energy derived from the PV system and the navigation plans of ships including location, navigation routes and times, the techno-economic evaluation of the PV systems integrated into ship power grid is very important to ensure their proper application in ships. In this study, a ship-PV grid-connected power system incorporating in the COSCO TENGFEI pure car and truck carrier is selected as a case to conduct a comprehensive techno-economic analysis and an environmental performance assessment based on single and multi-criteria evaluation methods. Taking into account the uncertainty of navigation plan, the techno-economic efficiency of the power system along six main navigation routes are evaluated separately. The evaluation results show that the hybrid power system has high financial feasibility and environmental performance. Furthermore, the Asia-Malacca-Gibraltar-Europe navigation route has the best feasibility while the Asia-Bering-Europe navigation route has the worst feasible among the six main navigation routes. This case study provides a reliable reference for investment of hybrid power system.

A Flexible Control Strategy for Shore-to-Ship Power System in Terms of Grid-Connected and Off-Grid Switch

Abstract There are promising application prospects for applying the shore power technology to the ships in the port for the purpose of pollution prevention. However, the grid-connection of the shore power supply to the ship power grid leads to current surges, damages the ship power consumption equipment, and results in the instability of the ship power grid system, which will seriously affect the reliability of the operation of the ship power grid system. In order to address this problem, the mathematical model of virtual synchronous generator is introduced in this paper. Then, a control method for the flexible grid-connection of the shore power supply to the ship power grid based on the virtual synchronous generator is proposed. Next, the output characteristics of the shore power supply are optimized to match the characteristics of the ship generator, which contributes to the flexible grid-connection of the shore power supply to the ship power grid system. The effectiveness and the feasibility of this method are verified by simulation and experiments.

Stability Improvement of DC Power Systems in an All-Electric Ship Using Hybrid SMES/Battery

As the capacity of all-electric ships (AESs) increases dramatically, the sudden changes in the system load may lead to serious problems, such as voltage fluctuations of the ship power grid, increased fuel consumption, and environmental emissions. In order to reduce the effects of system load fluctuations on system efficiency, and to maintain the bus voltage, we propose a hybrid energy storage system (HESS) for use in AESs. The HESS consists of two elements: a battery for high energy density storage and a superconducting magnetic energy storage (SMES) for high power density storage. A dynamic droop control is used to control charge/discharge prioritization. Maneuvering and pulse loads are the main sources of the sudden changes in AESs. There are several types of pulse loads, including electric weapons. These types of loads need large amounts of energy and high electrical power, which makes the HESS a promising power source. Using Simulink/MATLAB, we built a model of the AES power grid integrated with an SMES/battery to show its effectiveness in improving the quality of the power grid.

Study of a Fuzzy Decision Making Based Energy-Saving Controller for Marine Power System

In order to realize energy-saving for marine power system, combining the fuzzy set theory with the traditional PID control technology, the marine power system energy-saving controller was designed, which control ship power grid frequency and voltage collaborative reduction within a certain scope and scale. As several prototypes testing, the application of the energy-saving controller, which control the ship power grid frequency from 60Hz dropping to 57Hz, and the voltage from 450V collaborative falling to 425.5V, and meet the Ship Building Standard, can save 9.85% of electric energy and 9.53% of fuel.

Improved Hilbert-Huang Transform Applied in Power Quality Detection in Ship Power System

In this paper, Hilbert-Huang Transform (HHT) and its improved method is introduced for detection and analysis of power quality in ship power system for the first time. This method is applied in detecting surge current and voltage interruption etc. of the ship power grid. Beginning-ending time, time-frequency, time-amplitude of the disturbance signal can be obtained accurately with HHT method. Mode mixing occurs when using empirical mode decomposition (EMD) to analyze harmonics, and consequently, all single harmonic components cannot be effectively decomposed. The improved HHT method based on Fourier transform is used to solve the problem in this paper. Complicated Harmonic can be decomposed into single harmonic component, and time-amplitude and time -frequency of harmonics can be obtained accurately by the improved method. In MATLAB/Simulink platform, harmonic source model of ship power system is established. Simulation results show that the improved method has better performance in Harmonics analysis than wavelet packet analysis.

Research on simulation of ship electric propulsion system with flywheel energy storage system

Flywheel energy storage has been widely used to improve the ground electric power quality. This paper designed a flywheel energy storage device to improve ship electric propulsion system power grid quality. The practical mathematical models of flywheel energy storage and ship electric propulsion system were established. Simulation research on the effect of ship electric propulsion system power quality, made by flywheel energy storage, was completed by using the software Matlab/simulink. We have done a lot of simulation experiments on sudden load of ship integrated electric propulsion system, one system is with flywheel energy storage, another one is not with. Comparing with these simulation results, we can see that the flywheel energy storage designed in this paper has improved ship electric propulsion system network power quality as well as increases the reliability of the ship power grid. The conclusions can provide a theoretical guidance for the design of flywheel energy storage applied in ship integrated electric propulsion system.