Ship Electric Propulsion System Research Articles

Evaluation of a multiphase cascaded H-bridge inverter for induction motor operation

Multi-phase systems are becoming more popular for applications requiring high power and precise motor control, even if single-phase AC power is still frequently utilized in households and some enterprises. While both systems have benefits over single-phase, there are trade-offs associated with each. Because of its balanced operation and effective power transfer, the three-phase (3-Φ) system is the most widely used multi-phase system. Nevertheless, different phase values can be investigated for particular applications where reducing torque ripple and harmonic content is essential. Using odd numbers of phases (such as 5-Φ) that are not multiples of three is one method. This design has the ability to reduce torque ripple by producing a more balanced magnetic field as compared with even-numbered phases. But adding more phases also makes the system design and control circuitry more complex. Systems with five phases (5-Φ) provide a compromise between performance and complexity. Applications such as electric ship propulsion, rocket satellites, and traction systems may benefit from their use. Nevertheless, choosing a multi-phase system necessitates carefully weighing the requirements unique to each application, taking into account elements like cost, power transmission, control complexity, and efficiency. The increasing popularity of electric vehicles and renewable energy technologies has led to the need for inverters in current electric applications. Conventional inverters provide square wave outputs, which cause the drive system to become noisy and cause harmonics. Multi-phase multilevel inverters can be used to enhance inverter functioning and produce an improved sinusoidal output. This study focuses on an induction motor drive powered by a five-phase multilevel cascaded H-Bridge inverter. With less torque and current ripples in the motor rotor, the power conversion harmonics are reduced and the switching components of the inverter are under less stress. However, in comparison to traditional inverters, it does require a greater number of legs. Because the switches needed for the cascaded H-Bridge inverter are less expensive in five-phase systems, they are favoured over higher phase orders. Furthermore, the suggested inverter removes 5th order harmonics, something that is not possible with traditional inverters. A five-phase induction motor appropriate for variable speed driving applications is also suggested by this research. Lastly, utilizing pulse width modulation (PWM) converters and an FPGA controller, an experimental study is carried out to assess the dynamic performance of the suggested induction motor drive. Particular attention is paid to the In-Phase Opposition Disposition (IPD) PWM technique.

High-Resistance Connection Fault Diagnosis in Ship Electric Propulsion System Using Res-CBDNN

The fault detection and diagnosis of a ship’s electric propulsion system is of great significance to the reliability and safety of large modern ships. The traditional fault diagnosis method based on mathematical models and expert knowledge is limited by the difficulty of establishing an accurate model of the complex system, and it is easy to cause false alarms. Data-driven methods, such as deep learning, can automatically learn from the mass of data, extract and analyze fault characteristics, and create a more objective distinction system state. A deep learning fault diagnosis model based on ResNet feature extraction capability and bidirectional long-term memory network timing processing capability is proposed to realize fault diagnosis of high resistance connections in ship electric propulsion systems. The results show that the res-convolutional BiLSTM deep neural network (Res-CBDNN) can fully integrate the advantages of the two networks, efficiently process fault current data, and achieve high-performance fault diagnosis. The accuracy of Res-CBDNN can be kept above 85% in a noisy environment, and it can effectively monitor the high resistance connection fault of ship electric propulsion systems.

Design Principle Considering Structural Mutual Effects of Double-Stator V-Shape-PM Vernier Machines for Electric Ship Propulsion

This paper proposes the design principle considering structural mutual effects of double-stator V-shape permanent-magnet (DS-V-PM) vernier machines for electric ship propulsion (ESP). Due to the flux concentration effect of the V-PM configuration, the double stators can be divided as a major and a minor stator, considering the different torque generation capability. Cooperation mutual effects between the double stators, V-PM arrangement and vernier machine topology are specifically included in the machine design principle exploration. To illustrate the design principle, first, a unified design principle is deduced, fit for general PM vernier machines. Then, a multi-step optimization strategy with auxiliary of sizing equations is presented, focusing on the parameter cooperation with flux modulation effect. Furthermore, through electromagnetic performance comparison, specific mutual effects of the DS configuration, DS angle shift, V-PMs and barrier structure are clearly summarized. Based on the DS machine design, the multi-mode operation for ESP system is introduced and analyzed. The normal/faulty cruise mode and charging mode are included to realize bi-directional operation. Prototype experiments are carried out for verification of the proposed machine design and operating strategy.

Особенности создания трансформаторов судовых систем электродвижения

The necessity of new organizational and technical solutions in shipbuilding to ensure the quality of marine transformer transformers is substantiated. The analysis of the requirements of the Russian Maritime Register of Shipping, the current ISS for dry transformers is carried out, the experience of enterprises of related industries and foreign companies, the design features of power transformers of the ship's electric propulsion system are considered. The results of the analysis of the requirements for power transformers of marine electric propulsion systems, the features of their design and operation are presented. The main parameters of the converters in operating and emergency modes are considered and analyzed. The organizational and technical directions of ensuring increased reliability of marine converter transformers are proposed. Unlike converter transformers for land transport, there are no regulatory documents for power converter transformers in shipbuilding. The regulatory documents in force in shipbuilding do not fully take into account the specifics of marine conversion transformers. The existing main features of marine converter transformers are noted. High economic losses in the event of an accident of marine converter transformers determine higher requirements for their electrodynamic stability compared with converter transformers for land transport. In shipbuilding, there are no requirements for determining the partial short-circuit voltage and the splitting short-circuit voltage during testing of transformers necessary for the analysis of their characteristics and modes. When creating marine converter transformers, it is necessary to justify the characteristic modes of marine transformers using computer modeling, develop methods for measuring and calculating the parameters of selected modes and perform process calculations for the most likely accidents in the transformer – rectifier system. With the increase in the power of shipboard electric propulsion systems, the development of state regulatory documentation to ensure the quality of development and operation of converter transformers is becoming increasingly relevant.

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.

Numerical analysis of 40 MW HTS motor electromagnetic characteristics for ship electric propulsion

In recent years, with the development of ship electric propulsion system, High Temperature Superconducting (HTS) motors have gained attention as a promising potential resolution due to their high-power density and the progression of cryogenic refrigeration technology. We present an electromagnetic characteristics numerical analysis of 40 MW, 120 rpm, HTS synchronous motor which is a semi-superconducting motor: in fact, it has a superconducting rotor composed of YBCO material and a conventional stator. Combining electric resistivity variation of rotor copper shielding sleeve in low temperature environment and YBCO coil critical current, the electromagnetic behavior of the 40 MW HTS synchronous motor is analyzed with non-ferromagnetic stator support structure. To assess the effects of varying stator winding currents and thickness on eddy current losses of the copper shielding sleeve, calculations were done, and a preliminary discussion was initiated. This study has certain reference significance for electromagnetic design and optimization of multi-ten MW HTS motors, especially used in ship electric propulsion system.

Heat Integration of Liquid Hydrogen-Fueled Hybrid Electric Ship Propulsion System

This study introduced the methodology for integrating ethylene glycol/water mixture (GW) systems which supply heat energy to the liquid hydrogen (LH2) fuel gas supply system (FGSS), and manage the temperature conditions of the battery system. All systems were designed and simulated based on the power demand of a 2 MW class platform supply vessel assumed as the target ship. The LH2 FGSS model is based on Aspen HYSYS V11 and the cell model that makes up the battery system is implemented based on a Thevenin model with four parameters. Through three different simulation cases, the integrated GW system significantly reduced electric power consumption for the GW heater during ship operations, achieving reductions of 1.38% (Case 1), 16.29% (Case 2), and 27.52% (Case 3). The energy-saving ratio showed decreases of 1.86% (Case 1), 21.01% (Case 2), and 33.80% (Case 3) in overall energy usage within the GW system. Furthermore, an examination of the battery system’s thermal management in the integrated GW system demonstrated stable cell temperature control within ±3 K of the target temperature, making this integration a viable solution for maintaining normal operating temperatures, despite relatively higher fluctuations compared to an independent GW system.

Deep Reinforcement Learning-Based Energy Management for Liquid Hydrogen-Fueled Hybrid Electric Ship Propulsion System

This study proposed a deep reinforcement learning-based energy management strategy (DRL-EMS) that can be applied to a hybrid electric ship propulsion system (HSPS) integrating liquid hydrogen (LH2) fuel gas supply system (FGSS), proton-exchange membrane fuel cell (PEMFC) and lithium-ion battery systems. This study analyzed the optimized performance of the DRL-EMS and the operational strategy of the LH2-HSPS. To train the proposed DRL-EMS, a reward function was defined based on fuel consumption and degradation of power sources during operation. Fuel consumption for ship propulsion was estimated with the power for balance of plant (BOP) of the LH2 FGSS and PEMFC system. DRL-EMS demonstrated superior global and real-time optimality compared to benchmark algorithms, namely dynamic programming (DP) and sequential quadratic programming (SQP)-based EMS. For various operation cases not used in training, DRL-EMS resulted in 0.7% to 9.2% higher operating expenditure compared to DP-EMS. Additionally, DRL-EMS was trained to operate 60% of the total operation time in the maximum efficiency range of the PEMFC system. Different hydrogen fuel costs did not affect the optimized operational strategy although the operating expenditure (OPEX) was dependent on the hydrogen fuel cost. Different capacities of the battery system did not considerably change the OPEX.

Speed control of marine main thruster motor based on super-twisting sliding mode variable structure

In order to solve the problem of torque-ripple in the control system of ship main propulsion motor controlled by direct torque control, this paper proposes a super-twisting sliding mode calculation method based on the traditional sliding mode controller, and designs the corresponding controller according to this method. The method is verified by Matlab/Simulink simulation tool. In the simulation waveform, the estimated speed of the super-twisting sliding mode control is almost consistent with the actual speed of the main propulsion motor, and the estimated rotor position is almost consistent with the actual rotor position of the motor, with small error. It is proved that this method has good practicability and effective feasibility in ship electric propulsion system, and provides theoretical reference for the design of ship electric propulsion system.

Distributed Input Multiport MMC Based Power Converter for AC and DC Loads

A distributed input multi-port topology is proposed in this work based on the use of a Modular Multilevel Converter (MMC). The Distributed Input Modular Multilevel Converter (DIMMC) is based on the application of an MMC to multi- phases systems, such as multiport generators or multiport transformers. The proposed converter is devised for high voltage and high-power applications with distributed inputs such as ship electric propulsion systems or industrial application available for both ac or dc loads. The main claims of the DIMMC are integration, modularity, scalability and fault tolerance. This work analyzes the steady state behavior of the converter, fault tolerance and the advantages/disadvantage of its application.

System-Level Consideration and Multiphysics Design of Propulsion Motor for Fully Electrified Battery Powered Car Ferry Propulsion System

The Korean government is facing growing concern over the increasing levels of fine dust. A significant contribution to this problem comes from coastal vessels. To mitigate this, an electric ship propulsion system has been proposed as a solution to reduce air pollution. The application of a fully electric propulsion system in a ship is challenging due to size, capacity limitations, and the cost investment of the battery system. To address the challenges of battery limitation and initial investment costs, the development and supply of removable battery supply systems (RBSSs) for fully electrified battery powered (F-EBP) car ferries are studied. A permanent magnet synchronous motor (PMSM) for the F-EBP car ferry using a roll-on/roll-off-type RBSS is developed in this work. Firstly, the concept of the F-EBP car ferry is discussed, and the specifications of the electric car ferry propulsion system are provided. Secondly, motor design and electromagnetic analysis are performed using finite-element analysis (FEA), where the heat sources including copper loss, core loss, and PM loss are calculated. Mechanical loss is also considered. Finally, a thermal network of the motor is built considering the lumped-parameter model. The results of the thermal analysis indicate that the motor operates within the safe region and can perform well in rated working conditions.

Energetska optimizacija serijskog hibridnog električnog brodskog porivnog sustava

The electric ship propulsion system due to its economic advantages and, first of all, better mechanical properties than internal combustion engines (influence on ship manoeuvrability) have gained popularity in recent years. This paper presents an investigation of a series hybrid electric propulsion system where two sources of power are used: a permanent magnet synchronous generator and energy storage battery to supply electric propulsion system, which is a permanent magnet synchronous motor. Controlling the power flow from multiple power sources in a series hybrid mechatronic system is important to increase the energy efficiency of the propulsion system. Developing a suitable power flow control method is difficult due to the nonlinear nature of the power sources in the series system. In this paper a method of energy optimization of the system has been verified which allows to improve energy efficiency by reducing reactive power in the system. In this paper, an analytical study of the mechatronic system of a serial hybrid electric ship propulsion system is carried out based on the analysis of the steady-state electromagnetic and energy relations. The proposed control with energy optimization was compared with the commonly used FOC control. The analytical studies have been confirmed by performing simulation studies in Matlab-Simulink program. The proposed optimization method allows its use not only in ship electric drives but also in other autonomous electric drives using the series topology of the hybrid system.

Подхват асинхронного двигателя после потери питания транзисторного электропривода

The solution of the problem of connecting an asynchronous machine with a squirrel-cage rotor to a transistor converter after their disconnection in the absence of a rotor speed sensor is considered. This problem may arise in the drives of pumps, fans, in wind power plants and in other systems, if it is necessary to urgently breaking the mechanism or to ensure its uninterrupted operation. In the article, the problem is solved in relation to the ship's electric propulsion system. When the drive power is lost, the propeller and the rotor of the machine are first slowed down relatively quickly to a speed corresponding to the speed of the vessel. Then braking slows down due to the large inertia of the vessel. The significant duration of the process allows the use of an algorithm for determining the rotor speed, based on testing the machine by feeding the stator of an asynchronous motor from an inverter with low voltages with a frequency that varies within the specified limits. Mathematical and computer models of the system are constructed, numerical experiments are performed confirming the effectiveness of the considered solution.

Multiple Instance Learning With Random Forest for Event Logs Analysis and Predictive Maintenance in Ship Electric Propulsion System

In this article, a novel weakly supervised machine learning approach is proposed for intelligent predictive maintenance (IPdM). It employs balanced random forest and multiple instance learning based on event logs from ships’ electric propulsion systems. The objectives are predicting failure likelihood, time to failure, and explainable predictions to ensure timely crew intervention. The IPdM approach uncovers, then learns, and classifies <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sequences of</i> events that represent early causes or symptoms to forecast imminent failures. In particular, this article contributes effective solutions to irregular, imbalanced, and unlabeled data issues where conventional methods become obsolete. First, the events occur at irregular intervals; they include alarms, warnings, and operational information collected across multiple units and control systems. Second, the datasets exhibit extreme imbalance due to few failures and multiple failure modes; this entails biased predictions. Third, the training datasets are weakly labeled; only the failure timestamp is known without any expert input on prior causes or early symptoms. Temporal random indexing is proposed to transform textual log messages into a numerical lower dimensional space where timeseries analyses are applicable. Balanced random-forest models are developed for unbiased classification and regression. The overall approach learns recursively the ungiven data labels while training the base learners. The IPdM approach is validated through millions of events of multithousand types collected from two years of seagoing vessels. It successfully forecasts actual propulsion failures and performs better when compared with contemporary methods.

Research on Application of High-Frequency Pulse Vibration in Ship Electric Propulsion System

Aiming at the problems existing in the method of using sensors to detect the rotor position of marine main propulsion motor at low speed, a sensorless rotor position identification method based on high-frequency pulse vibration signal is proposed. In this method, the low-pass filter is used to separate the high-frequency signal component, and the current component of d-axis to q-axis is demodulated. The control mode of PI action law is used to phase-locked processing of the demodulated signal, in which purpose is to obtain the rotor position signal. The design method is simulated and verified by MATLAB/Simulink software. The error between the estimated position and the actual position of the rotor in the simulation waveform is small, and the accuracy is high. The simulation results show that this method can achieve good results when applied to the ship electric propulsion system without position sensor, which provides a theoretical reference for the design of marine main propulsion motor control system.

Application of composite energy storage device in ship electric propulsion system

Application of composite energy storage device in ship electric propulsion system

Modulation and voltage balancing control of dual five-level ANPC inverter for ship electric propulsion systems

Open-end winding motors are used extensively in ship electric propulsion systems, in which medium-voltage high-power inverters are a critical component. To increase the system voltage and power density, a dual five-level active neutral-point clamped (ANPC) inverter is proposed herein to drive medium-voltage open-end winding motors for ship electric propulsion. Each phase of this inverter comprises two five-level ANPC bridges and all the phases are powered by a common direct-current link. A hybrid modulation method is proposed to control this inverter. The series-connected switches in all the five-level ANPC bridges are operated at the fundamental frequency, and the other switches are controlled with a phase-shifted pulse-width modulation (PWM), which can achieve a natural balance between the neutral-point voltage and flying capacitor voltages in a carrier period. A closed-loop capacitor voltage balancing method based on adjusting the duty ratios of the PWM signals is proposed. The neutral-point voltage and flying capacitor voltages can be controlled independently and balanced without affecting the output phase voltage. Simulation and experimental results are presented to demonstrate the validity of this method.

Operation of propeller motors composed of ship electric propulsion systems with semiconductor converters

The calculations of transient processes in ship electric propulsion systems (EPS) with semiconductor converters (SC) show that when the inverter transistors are locked, overvoltage occurs that may break through the insulation of propeller motors (PM). A feature of this overvoltage is its short duration and large value. Pulsed overvoltage of small duration and the EPS value of dozens or more kilovolts may occur in the circuits of the inverter supplying the PM winding. The main cause of overvoltage is the EPS self-induction resulting from rapid current reduction in circuits with inductances, including in motor windings, when the inverter transistors are locked. The paper presents the results of mathematical modeling of the processes arising when the inverter transistors functioning as part of the frequency converter are locked. The results of the analysis confirmed the possibility of overvoltage on the PM winding, which should be taken into account when designing the EPS and selecting equipment.

Stability Improvement of Electric Ship Propulsion System Using Supercapacitor

Owing to the serious greenhouse gas emissions and inflexible control of traditional ship propulsion system, the electric ship propulsion system has been widely introduced into the ship’s power system. However, the variations of ship propellers will lead to the instability of electric propulsion system so this paper studied the transient characteristics of electric ship propulsion system by performing a series of experiments on a real electric ship propulsion system platform. Based on the experimental results, a detailed model of supercapacitor energy storage system (SCESS) is proposed to improve the voltage and frequency response for the electric ship propulsion system. To enhance the stability and reliability, a double closed-loop control method combined with Pulse-Width Modulation algorithm (PWM) is utilized to control the energy storage system for smoothing the power fluctuations caused by the electric propulsion system. The simulation results demonstrate the high efficiency of supercapacitor to improve the transient stability of the whole power system of the ship.

Research on operating conditions of electric propulsion ships under transformer interturn short circuit

Most ships currently use electric propulsion systems. In this system, the transformer plays a key role in power distribution. The probability of interturn short circuit occurs in the transformer is high, it will cause faults such as three-phase voltage imbalance and endanger the safe operation of the ship. The simulation model of ship electric propulsion system established in this paper includes propellers and transformers, and the influence of the interturn short circuit of a transformer on the sailing conditions is studied. The research results show that the transformer interturn short circuit will generate a huge inrush current and have a huge impact on the torque and speed of the propeller.