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Power systems for undersea observatories combine ideas from
terrestrial power systems and switching power supplies with experience
from undersea cable systems. Basic system tradeoffs for various design
decisions are explored in this paper. First, design questions including
whether the power delivery should be alternating or direct current and a
par...
Contexts in source publication
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... of its size (around 3000 km of cable is planned; see Fig. 1), the proposed NEPTUNE observatory [5] on the Juan de Fuca tectonic plate is required to have more than one power source. Fig. 1 a network. Power infeeds from shore at medium voltage (MV; the IEEE definition is 2.4-72.5 kV) supply a number of junc- tion boxes via a single conductor cable. For cost reasons, the cable will be standard, ...
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... of its size (around 3000 km of cable is planned; see Fig. 1), the proposed NEPTUNE observatory [5] on the Juan de Fuca tectonic plate is required to have more than one power source. Fig. 1 a network. Power infeeds from shore at medium voltage (MV; the IEEE definition is 2.4-72.5 kV) supply a number of junc- tion boxes via a single conductor cable. For cost reasons, the cable will be standard, single-conductor submarine telecommu- nications cable operating with a nominal rating of 10 kV. At each junction box, power is ...
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... simplified solution showing the effect of load power factor can be drawn (Fig. 10). The power on the abscissa is the apparent power, . With a leading power factor load, the total power can exceed the value for a resistive load, because the capacitance compensates for the inductance of the delivery system. Leading power factor loads tend to support voltage, and inductive loads tend to depress ...
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... convergence of the power flow is shown in Fig. 11, where the number of iterations is plotted as a function of power. There is no problem at a load level of 12 or 13 kW. Above this power level, however, the number of iterations required rises rapidly. No solution is found at 14 ...
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... demonstrate the approach, the simple 1-source 3-load system of Fig. 3 was modeled in Pspice. The cable was modeled as 25-km L-sections, with a series inductance of 1 mH/km, a se- ries resistance of 1 /km, and shunt capacitance of 0.2 F/km, and the loads were set at 10 kW (Fig. 12). Because the cable itself is well damped and does not pose any source of instability for the converter, the results and conclusions presented below are not dependent on the precise model or parameters of the ...
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... of these converters were embedded in an arrangement like that shown in Fig. 3 to simulate the entire system. Fig. 13 shows one representative result. First, the source voltage is ap- plied. One hundred milliseconds later, converter 1 load (10 kW) turns on, and 100 ms after that converter 2 load is applied. The transitions from one operating state to another are properly damped. At 600 ms, a 10-kW load is applied to converter 3 with a duration of 200 ...
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... other simulations with this model, the loads were left steady long enough for the system to stabilize, i.e., 1 s. The voltage profile on the line was the same as calculated by steady-state simulations. Users of ready-made dc-dc converters may use the hardware without considering the damping effect of the RC network in the input filter ( and in Fig. 11). This omission could have serious consequences. To demonstrate this, the simulation was run without the damping components present (Fig. ...
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... the line was the same as calculated by steady-state simulations. Users of ready-made dc-dc converters may use the hardware without considering the damping effect of the RC network in the input filter ( and in Fig. 11). This omission could have serious consequences. To demonstrate this, the simulation was run without the damping components present (Fig. ...
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Citations
... In most cases, COOs use a direct current (DC) power supply, which can be either constant current (CC) or constant voltage (CV) [32]. In the CC mode, all nodes are connected in series, whereas in in the CV mode, all nodes are connected in parallel using seawater as a current returning pathway. ...
Cabled ocean observatories (COOs) have enabled real-time in situ ocean observations for decades, thereby facilitating oceanic understanding and exploration. This review discusses typical COOs worldwide in terms of system configurations and state-of-the-art technology, including network structures, power supply modes, and communication capabilities, and provides a comprehensive analysis of their technical routes. The main characteristics of line, ring, star, and grid networks and their applicability in COOs are elucidated, and the advantages and disadvantages of various power supply modes, as well as the opportunities brought by the development of communication technologies, are described. The insights gained from these discussions can inform the implementation of grid structures, optimization of cable routings, expansion of COO scales, application of dual-conductor submarine cables, and upgrading of communication capacity. On this basis, the challenges and future research directions related to COOs are presented.
... Alternating current (AC) transmission requires highly insulated cables that form a large equivalent capacitance with seawater and earth, thereby increasing the reactive power loss; therefore, the power loss of long-distance AC transmission is serious without inductance compensation. Compared with AC transmission, although direct current (DC) transmission also has capacitance to ground, its ripple voltage is small, the voltage is stable in the steady state, and the reactive power loss is small; therefore, DC transmission is more economical and stable (Howe et al., 2002;Yu et al., 2013). ...
Nowadays, nuclear power plays an important role in the energy structure of many countries. However, A bloom of a disaster-causing organism (DCO) in the cold-water intake area of a coastal nuclear power plant can block the water cooling system and seriously affect the operational safety of the nuclear power unit. Currently, the traditional method of protection is to estimate the DCO abundance by regular manual investigation and sampling, but that method cannot give continuous real-time data. Instead, proposed and implemented here is a seafloor in situ integrated monitoring system for DCOs (known as IMSDCO), which is equipped with an optical microscopic imager (OMI) and hydrometric sensors to monitor automatically the DCO abundance and hydrology. All the data are transmitted to a terminal in the shore station through a photoelectric composite cable for real-time display. When the DCO abundance reaches a preset threshold, software automatically raises an alarm. Since placing IMSDCO at the cold-water intake of the Changjiang nuclear power plant, a six-month field trial has been completed, during which large amounts of hydrology data and DCO images were obtained. IMSDCO successfully identified and estimated the abundances of various DCOs (e.g., Phaeocystis globosa, Acetes chinensis, and small fish) and predicted their movements based on hydrology data. Based on the analysis of the experimental data, we discussed the reasons for the error in the abundance estimation of DCO and the methods to reduce the error. The experimental results show that the OMI-based IMSDCO can monitor and give early warning of DCOs in the water intake areas of costal nuclear power plants and is worthy of long-term deployment.
... The normal operation of observation networks relies on the stability of power transmission systems [6] and focuses on analyzing the steady-state characteristics of multinode tree topology power supply system for a regional coastal ocean observation network. Most current studies on the stability of observation networks, such as those on the Hawaii Undersea Geo-Observatory, North-East Pacific Time-series Undersea Networked Experiments (NEPTUNE), Kilo Nalu, and Monterey Accelerated Research System (MARS) [7], have focused on the power boundary of the system or the self-stability of power converters. ...
Subsea observation networks have been increasingly used to explore oceans. However, the stability of the entire system remains a crucial problem. In 2015, flashover discharge occurred in a transmission line during a sea trial in the South China Sea, thereby resulting in node destruction and serious losses. This study investigates flashover discharge in the transmission line and aims to determine its influences on the nodes. We use a damaged submarine cable to conduct a flashover discharge fault experiment and analyze the causes of this voltage change law. A cascade of lumped parameter model is adopted for the transmission line, and the optimal segment length is confirmed through simulation. Step response is applied to the study of flashover discharge, and the results agree well with the PSpice simulation results. Then, simulations and experiments on flashover discharge are conducted on the basis of the cascade of lumped parameter model. Results show that voltage surge is generated in the output side with the occurrence of flashover discharges, especially when they are continuous. An effective method of adding silicon stacks at the converter input and connecting transient voltage suppressor (TVS) in parallel at the output is proposed to suppress this oscillation.
... The operation of connecting devices with the junction boxes is usually achieved by a remotely-operated vehicle (ROV). Some of the early coastal CSOs were designed with an alternating current (AC) power-feeding system [94], which can be readily derived from the local utility and allow the efficiency of high-voltage transmission [95]. However, this kind of power-feeding systems are not suitable for the CSOs that require long-distance power transmission because of the reactive components caused by the parasitic effects of the cables. ...
Covering about three quarters of the surface area of the earth, the ocean is a critical source of sustenance, medicine, and commerce. However, such vast expanse in both surface area and depth, presents myriad observing challenges for researchers, such as corrosion, attenuation of electromagnetic waves, and high pressure. Ocean observation technologies are progressing from the conventional single node, static and short-term modalities to multiple nodes, dynamic and long-term modalities, to increase the density of both temporal and spatial samplings. Although people's knowledge of the oceans has been still quite limited, the contributions of many nations cooperating to develop the Global Ocean Observing System (GOOS) have remarkably promoted the development of ocean observing technologies. This paper reviews the typical observing technologies deployed from the sea surface to the seafloor, and discusses the future trend of the ocean observation systems with the docking technology and sustained ocean energy.
... Power plays a key role in such kinds of underwater systems, where two main power solutions are employed including alternative current (AC) and direct current (DC). AC solution dominates the terrestrial power system, however, the DC distribution system, which is further classified into modes of constant current (CC) and constant voltage (CV) [3], is preferred if the cost of underwater deployment is considered [4]. Due to the merit feature of shunt fault tolerance, CC mode observatories are widely adopted at scenarios requiring uninterrupted observation even with fault presence [5]. ...
... For a multi-module converter with the PPMS, however, before and after opening KBi, the power of each BL satisfies Equation (4). No power rebalance process exists between BLs (e.g., assume a twomodule-converter with each module has maximum output power 100 W and the external load is 80 W). ...
A constant current (CC) underwater observatory employing the shunt method to provide constant voltage (CV) power for external loads is favored in occasions where shunt-fault tolerance is required. However, low efficiency of CC to CV conversion with the shunt method limits its application, especially in scenarios of varying loads. In this paper, a highly reliable and stable CC/CV converter with better efficiency is introduced based on the proposed novel active soft bypass (ASB) technology and the proposed novel priority-based power management strategy (PPMS). The ASB technology is a method that employs switches and a special control sequence which greatly depresses the large voltage transient presenting on the input side when trying hard bypass redundant modules, and the PPMS makes the system easy to monitor and ensures the absolute reliability of ASB technology. The theoretical study of this novel reconfigurable CC/CV converter and validation experiments on a prototype are carried out, with results showing great improvement in the performance. In addition, the proposed reconfigurable power converter is applied to a coastal observatory in the East China Sea.
... Large-scale sensor networks and poor working conditions at sea necessitate a system with a convenient and stable power supply [13][14][15]. Most of the exploration instruments on the market adopt a daisy chain structure to transfer high voltage to single nodes. ...
The electric power system plays an important role in sensor networks. In the marine seismic exploration streamer system (MSESS), an underwater power system transmits high-voltage direct current to all nodes in the streamer through a daisy chain structure. As offshore oil exploration develops toward deep water, it is necessary to study long streamers with large-scale sensor networks for deep water exploration. When the length of a streamer is increased to a certain value, the output current of the power supply increases sharply. This results in the activation of the overcurrent protection and the power supply shuts down. This paper puts forward an accurate model for an underwater power system applied to MSESS. Using the Newton iteration algorithm and a reverse algorithm, equations established by the model are solved and laboratory test results are used to verify the accuracy of the model. Based on simulation and analysis of the model, we explain why the power system crashes when the streamer is too long. Software that can quickly calculate the maximum number of nodes (the maximum length with which the system works normally) is developed and it is significant for the design of MSESS. The method of research could also be applied to relevant work such as large-scale sensor networks with daisy-chaining power supply in land seismic exploration.
... Generally, constant current (CC) and constant voltage (CV) direct current (DC) power systems are two types of CSOs [6], as illustrated in Figure 2. The CSOs powered by CV power sources can supply more power and have higher power transmission efficiencies than CC power-feeding CSOs, so that most scientific CSOs use CV power-feeding systems. As the backbone cables have only one conductor, the seawater is used as the current returning path. ...
In scientific cabled seafloor observatories, branching units and optical repeaters are essential backbone devices, in which zener diodes are commonly used in their power supply circuits. However, the low efficiency of zener-diode-based power feeding modules under large currents makes for a significant threat to the long-term reliability of backbone devices. In this paper, a novel full-bridge DC-DC converter with a duty-cycle-overlap control (DCOC) strategy is proposed to achieve high-efficiency current-to-voltage conversion. The circuit design of the converter and the principle of the DCOC strategy are analyzed. A prototype of the converter is implemented to demonstrate the feasibility of the proposed power feeding approach for large-scale cabled seafloor observatories.
... For underwater equipment, any failure will induce high maintenance cost. Therefore, reliability is an important indicator for underwater electronic equipment [3]. Since the aim of ocean observatories system is to build underwater observation platform for long-term stable operation, the high-voltage direct current transmission system requires relatively high reliability and redundancy [4]. ...
... Given by datasheet, T j_max and T j_min are the maximum and minimum junction temperature, V CEO_max and V CEO_min are the maximum and minimum collector-to-emitter voltage, K j_max and K j_min are the slopes of maximum and minimum voltage against current, T j is the junction temperature, and i T (t) is the switch current. Conduction loss is the average loss over a grid frequency cycle as in (3). d(i)T(i) is the conducting time of switching frequency and N s is the carrier ratio P con = 1 ...
Underwater long-distance high-voltage direct current transmission system can provide long-term, reliable, and sustainable energy for ocean observatories system which has higher reliability requirement than onshore or conventional underwater equipment. As the main network point for high-voltage direct current transmission system, medium-voltage converter of the primary node is at the top layer of power supply chain and its reliability will directly affect the reliability of high-voltage direct current transmission system. Based on a 2.5 kW medium-voltage converter, this study proposes a method to evaluate the reliability of medium-voltage converter with accuracy using the lifetime model of switch by analysis of component junction temperature providing theoretical foundation and technical guidance for medium-voltage converter design. Owing to the high power density of medium-voltage converter, the heat dissipation space is restricted to pressure vessel. This study proposes a thermal design method to ensure normal operation condition within appropriate temperature for medium-voltage converter and verified using ANSYS finite element analysis software.
... However, it will collapse with any shunt (short to ground) fault in the system, whereas the CC system can continue operation; this may be useful or even essential if the primary purpose of the system is seismic and tsunami early warning (where the high power of a CV system is less important). A new high-voltage power supply was subsequently developed (Howe et al. 2002) and used in MARS (Howe et al. 2006) and NEPTUNE Canada. As these systems evolved, the nodes shrank in mass and volume, simplifying deployment and service. ...
Ocean observatories: An Engineering Challenge
Baggeroer, Howe, Mikhalevsky, Orcutt, Schmidt
Observatories are important components for ocean research in most
developed countries with a coastline. For many decades oceanographic institutions followed what one might term “expeditionary research”: ships went to places to investigate various ocean processes; observations were made and often sensors were deployed to record data for subsequent retrieval. But the observations were sparsely sampled temporally and spatially, leaving many processes not well understood because of the transient and regional nature of the data. As Walter Munk put it, “The key change between the century of the Challenger and the last 50 years is adequate sampling. The key product of the Technology Revolution is sampling” and “the requirement of the sampling theorem” (NRC 2000, p. 49). Ocean observatories will continue to meet the ever increasing requirements for adequate sampling of the oceans.
... The dc distributed power system (DPS) is widely employed in both terrestrial and undersea applications such as data centers, communication systems, renewable energy systems and undersea observatories, thanks to its high efficiency and high power density delivery capability [1][2][3][4][5][6][7][8][9][10][11]. ...
... Most of the research in the literature has focused on constant voltage dc DPS [1][2][3][4][5][6][7][8][9]. For a constant voltage architecture, the modules are parallel connected on a dc voltage bus. ...
... In the design of RF integrated circuits (IC), a resistor in parallel with the input to the IC or in series with the output (as appropriate) is employed as a solution to avoid oscillation caused by the negative resistance [8]. The power loss associated with this technique is acceptable in RF work, but not in a power system. ...
Applications such as undersea power prefer constant current dc distribution in a series trunk cable connection over dc voltage distribution in order to provide robustness against cable impedance and faults. Power converter modules employed in these architectures are connected in series and have a constant current input. In this paper, steady state analysis and a control strategy are presented for series connected resonant converter modules in a constant current dc distributed power system. The control strategy is developed to achieve stable operation of the system with no communications required among modules. Hardware results are provided for a system consisting of two series connected 100 kHz 500 W SRCs with 1 A trunk current and regulated output current.
