Study on technical solutions for shore power supply of motor yacht

The report presents an analysis of modern technical solutions for shore power supply of a specific class of passenger ships - luxury yachts for charter trips. The design data of a motor yacht in its different operating modes are considered, as well as the energy mix related to the fuel consumption at shore supply of the yacht during its stay at the port. The use of modern technical systems for shore supply includes the application of specific frequency converters, through which compatibility between the different voltage standards and the frequency for different shore power supply systems is realized. The costs of onshore power, compared to those of marine fuel, can be calculated from the current prices of onshore electricity and the energy produced from its own generators. The analysis of the basic design data of the motor yacht and the assessment of the energy costs on board, fuel economy and emission reductions will provide a clear answer to the advantages of the power supply from the shore of the vessel.

DESIGN OF UNIVERSAL CONTROL SYSTEM FOR H-BRIDGE MULTILEVEL CONVERTER

The medium voltage frequency converters mostly utilize the low-voltage multi-cell topology. However, available PWM techniques have some drawbacks, such as time delayed operation, which limits current loop response time, need reinitialization of the PWM carriers in case of cell failure, or have unequal distribution of losses. To solve the set of these problems the PWM strategy, which utilize PWM in a single cell with sequential cell switching, was introduced. This PWM strategy can operate in case of partial inverter failures, provides maximum available voltage to the load and has low response time due to operation at high PWM frequency of a single cell, while the average switching frequency is limited. The proposed PWM technique was examined using a model, where the switching losses distribution and high quality of the output voltage were confirmed.

Estimation of Phase Noise Transfer Function

Quantifying frequency converters’ residual phase noise is essential in various applications, including radar systems, high-speed digital communication, or particle accelerators. Multi-input signal source analyzers can perform such measurements out of the box, but the high cost limits their accessibility. Based on an analysis of phase noise transmission theory and the capabilities of popular instrumentation, we propose a technique extending the functionality of single-input devices. The method supplements absolute noise measurements with estimates of the phase noise transfer function (also called the jitter transfer function), allowing the calculation of residual noise. The details of the hardware setup used for the method verification are presented. The injection of single-tone and pseudo-random modulations to the test signal is examined. Optional employment of a spectrum analyzer can reduce the time and number of data needed for characterization. A wideband synthesizer with an integrated voltage-controlled oscillator was investigated using the method. The estimated transfer function matches a white-box model based on synthesizer’s structure and values of loop components. The first results confirm the validity of the proposed technique.

Inactive capacity compensation device in frequency converters in the composition of electric power systems of marine vehicles

Управление режимами работы гребного электрического двигателя осуществляется полупроводниковыми преобразователями частоты, применение которых значительно ухудшает качество электроэнергии на общих шинах судовых электроэнергетических систем. Основными причинами являются уменьшение коэффициента мощности и появление высших гармоник в потребляемом токе. В результате этого снижается надежность работы потребителей, и увеличиваются потери электроэнергии. Поэтому уменьшение указанных негативных последствий является актуальной задачей. В связи с этим, большое внимание уделяется вопросам, связанным с изучением и разработкой различных методов и устройств обеспечения качества электроэнергии, увеличения коэффициента мощности и фильтрации высших гармоник. В настоящее время, перспективным методов улучшения качества электроэнергии, является применение устройств управления реактивной мощностью и активной фильтрации, т.е. компенсаторов неактивной мощности. Подобные системы можно применять не только для надводных судов, но и в автономных подводных транспортных средствах, в качестве энергетической установки которых выступает батарея топливных элементов. The control of the operating modes of the propulsion electric motor is carried out by semiconductor frequency converters, the use of which significantly degrades the quality of electricity on the common buses of the ship power systems. The main reasons are a decrease in the power factor and the appearance of higher harmonics in the current consumption. As a result, the reliability of the consumers is reduced, and the losses of electricity increase. Therefore, the reduction of these negative consequences is an urgent task. In this regard, much attention is paid to issues related to the study and development of various methods and devices for ensuring the quality of electricity, increasing the power factor and filtering higher harmonics. Currently, a promising method for improving the quality of electricity is the use of reactive power control devices and active filtering, i.e. compensators of inactive power. Such systems can be used not only for surface crafts, but also in autonomous underwater vehicles, the power plant of which is a fuel-cell stack.

The resistive ground fault of PWM voltage inverter in the EV charging station

During the direct touch of the inverter output voltage or with the ungrounded shield of the cable connecting the inverter to the motor or other type of load, the nonsinusoidal ground currents with a basic harmonic frequency between 1.5 and 16 kHz, flow via a human’s body. Here was proved that Residual Current Device (RCD) ($$I_{\triangle n}$$ I ▵ n = 30 mA) does not switch off the power supply when a ground current with a value of about some hundred milliamps occurs. Because RCDs do not disconnect the power supply, the touch on the inverter’s voltage is dangerous to health and life. For the authors, the RCD usage in the Voltage Frequency Converters (VFCs) is not a good engineer practice when high-frequency common-mode distortion currents flow through it. The paper presents tests of RCD operation in the event of a resistance ground fault (via human body) during EV battery charging where the PWM voltage inverter is connected to the external rectifier to provide DC charging battery voltage. Finally, the authors propose a method of eliminating common-mode (CM) current from short protection system by using a separate circuit in which the parasitic leakage current omits an RCD.

Frequency Converter as a Node for Edge Computing of Big Data, Related to Drive Efficiency, in Industrial Internet of Things

The article presents a method of generating key performance indicators related to electric motor energy efficiency on the basis of Big Data gathered and processed in a frequency converter. The authors proved that using the proposed solution, it is possible to specify the relation between the control mode of an electric drive and the control quality-energy consumption ratio in the start-up phase as well as in the steady operation with various mechanical loads. The tests were carried out on a stand equipped with two electric motors (one driving, the other used to apply the load by adjusting the parameters of the built-in brake). The measurements were made in two load cases, for motor control modes available in industrially applied frequency converters (scalar V/f, vector Voltage flux control without encoder, vector voltage flux control with encoder, vector current flux control, and vector current flux control with torque control). During the experiments, values of the current intensities (active and output), the actual frequency value, IxT utilization factor, relative torque, and the current rotational speed were measured and processed. Based on the data, the level of energy efficiency was determined for various control modes.

Combined control of fans of gas cooling units electric drives

The problem of the temperature control at the outlet of gas cooling units of compressor stations of main gas pipelines is discussed. To solve the problemt, a discrete or frequency control of electric motors of fans of gas air cooling devices is used. The problems of electromagnetic compatibility that arise in typical power supply systems of gas cooling installations when connecting electric motors of fans through frequency converters are noted. A combined fan motor control system is considered, in which the electric motors are divided into two groups. The electric motors of the first group are connected to the network directly, the second through frequency converters. By reducing the number of electric motors connected to the network through frequency converters, the negative impact of frequency-controlled drives on the quality of electricity is reduced and the costs of modernization projects are reduced in comparison with the option of the variant using a frequency converter for each electric motor. The energy characteristics of the combined control system are analyzed. The relations that establish the relationship between the temperature difference at the cooling unit and the power of the fan motors for various control methods are obtained. The optimal control algorithm according to the criterion of maximum power saving is proposed, which provides for the interconnected control of the number of discrete-controlled motors and the speed of frequency-controlled drives. The variants of the implementation of the optimal control algorithm are discussed. Analytical expressions for power saving on the fan motor shaft in a combined system compared with a discrete one and a method for estimating energy savings are considered. The obtained results are recommended to be used to assess the technical and economic efficiency of projects for the modernization of electrical complexes of gas cooling units.

A Comprehensive Weight-Based Severity Evaluation Method of Voltage Sag in Distribution Networks

With the increasing use of sensitive loads in frequency converters and in relays in distribution networks, voltage sag has become a major power quality issue that urgently needs to be solved. For the purpose of improving the understanding of voltage sag severity in distribution networks, a comprehensive weight-based severity evaluation method of voltage sag is presented in this paper. First, a multi-side index system that takes into account the combined influence of the source, network, and the load is established. A comprehensive weight method, which combines the improved analytic hierarchy process (IAHP) and the entropy method, is then adopted to determine the index weight. The weight of each index and the degree of superiority are linearly weighted to obtain the severity of voltage sag at different observation points. Finally, the effectiveness of the proposed method is verified using a distribution network model established in DIgSILENT PowerFactory (15.1.7, Gomaringen, Germany).