CN111987711A - Ship direct-current micro-grid system - Google Patents

Abstract

The invention discloses a marine DC micro-grid system, which comprises a main DC bus, a backup DC bus, a plurality of power generation units and a plurality of load units. According to the status of the two DC buses, each power generation unit and load unit are preferentially connected to the main DC bus, and are connected to the backup DC bus when the main DC bus fails. The invention adopts the micro-grid technology to provide a flexible and efficient platform for the integration and utilization of clean energy such as solar energy and wind energy, effectively solves the fluctuation and uncontrollable problems of intermittent energy, and applies the micro-grid technology to the ship power system. According to the characteristics of the ship's power system, a DC microgrid is used to replace the traditional AC microgrid, and the power supply reliability is improved through a redundant busbar structure. The invention can be widely used in marine ships, and the DC micro-grid technology is applied to the ship power system, and has the characteristics of environmental friendliness, reliable power supply, full energy utilization, low operation cost and the like.

Description

A ship DC microgrid system

technical field

The invention relates to the field of electric power technology, in particular to a ship direct current micro-grid system.

Background technique

With the rapid development of global trade, shipping has always been one of the most important ways of world trade transportation due to its comprehensive advantages of low transportation cost and large transportation volume. The marine ship power generation system is mainly fueled by fossil energy, and its combustion products include: C02, NOX, SOX and carbon particles. For a ship with a deadweight of 20,000 tons and a speed of 15 knots, the daily fuel consumption will be as high as 65 tons, and the corresponding C02 emissions will be as high as 202 tons.

The increasing number of marine ships has also caused serious environmental pollution. The consumption of non-renewable energy sources such as diesel fuels the earth's resources and increases the cost of electricity generation. The production of greenhouse gases increases the temperature of the earth and affects the ecological balance.

In some existing technologies, the use of microgrid as the power system of the ship can partially improve the above problems. Microgrid is a small power generation and distribution system that organically combines distributed power sources, energy storage devices, electrical loads, and power electronic devices. Through the application of technologies such as microgrid operation control and energy management, the output of distributed power sources can be maximized to improve power quality and power supply reliability. In the terrestrial power grid, the main purpose of adopting the microgrid is to solve the problem of high penetration of distributed power generation into the power grid on a large scale, thereby weakening the impact of distributed power generation on the power grid. The proposal of microgrid technology provides a flexible and efficient platform for the integration and utilization of clean energy such as solar energy and wind energy.

However, the large-scale access of existing distributed power sources to the power grid has the problem of high penetration, which has a strong impact on the power grid. The intermittent, fluctuating and uncontrollable nature of clean energy such as solar power generation and wind power generation restricts the new energy power generation technology. Application on ships.

Traditional microgrids are mostly AC systems, but AC systems have problems of reactive power balance and stability, and the reliability of power supply is not high. Most electrical appliances use direct current, and alternating current can only be used after being rectified and filtered. The direct current can be used directly without rectification and filtering equipment.

The traditional microgrid is built near the user side as a supplement to the main grid, but the marine microgrid is different from the traditional microgrid because it is a compact and complete integrated power generation, transmission, transformation, distribution and consumption. The power system, which makes the distributed power source in the ship power system have a wide variety of types, various operating states and different control methods, has become a multi-dimensional complex system with many variables, complex operation and strong uncertainty.

In addition, traditional microgrids are mostly single-bus structure. The single-bus structure power system has poor power supply reliability and is suitable for small civil ships with a single voltage level of electrical equipment and only the third type of load, which is not suitable for widespread use. The structure of the single-bus ship DC microgrid is shown in Figure 1.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a kind of ship direct current micro-grid system according to the deficiencies of the above-mentioned prior art,

The realization of the object of the present invention is accomplished by the following technical solutions:

A marine DC micro-grid system, comprising a main DC bus, a backup DC bus, a plurality of power generation units, and a plurality of load units;

When the main DC bus is normal, each of the power generation units and each of the load units are connected to the main DC bus; when the main DC bus is faulty, each of the power generation units and each of the load units are connected to the main DC bus. Standby DC bus;

The power generation unit includes a photovoltaic power generation unit, a wind power generation unit, a fuel cell unit, a gas turbine and a battery energy storage system; the photovoltaic power generation unit is connected to the DC bus through a one-way DC/DC converter, and the wind power generation unit is connected to the DC bus through a one-way DC/DC converter. The AC/DC converter is connected to the DC bus, the fuel cell unit is connected to the DC bus through a one-way DC/DC converter, the gas turbine is connected to the DC bus through a one-way AC/DC converter, and the battery energy storage system Access the DC bus through a bidirectional DC/DC converter;

The load unit includes a DC load unit and an AC load unit; the DC load unit is connected to the DC bus through a unidirectional DC/DC converter; the AC load unit is connected to the DC bus through a unidirectional DC/AC converter.

A further improvement of the present invention is that it also includes a shore power access unit; the shore power access unit is connected to the DC bus through a one-way AC/DC converter.

The advantages of the invention are: the micro-grid technology provides a flexible and efficient platform for the integration and utilization of clean energy such as solar energy and wind energy, which effectively solves the fluctuation and uncontrollable problems of intermittent energy, and applies the micro-grid technology to ship power system. According to the characteristics of the ship's power system, the DC microgrid is used to replace the traditional AC microgrid, and the power supply reliability is improved by using the standby DC bus as a redundant bus structure. The invention can be widely used in marine ships, and the DC micro-grid technology is applied to the ship power system, and has the characteristics of environment-friendly, reliable power supply, full energy utilization and low operating cost.

Description of drawings

Fig. 1 is a schematic diagram of an existing ship DC microgrid;

Fig. 2 is a schematic diagram of the marine DC microgrid of the present invention.

Detailed ways

Below in conjunction with the accompanying drawings, the features of the present invention and other related features will be described in further detail by embodiments, so as to facilitate the understanding of those skilled in the same industry:

Embodiment: As shown in FIG. 2 , an embodiment of the present invention includes a marine DC micro-grid system, which includes a main DC bus, a backup DC bus, multiple power generation units, and multiple load units;

When the main DC bus is normal, each of the power generation units and each of the load units are connected to the main DC bus; when the main DC bus is faulty, each of the power generation units and each of the load units are connected to the main DC bus. Backup DC bus.

The power generation unit includes a photovoltaic power generation unit, a wind power generation unit, a fuel cell unit, a gas turbine and a battery energy storage system. Most power generation units only generate energy and do not consume energy, and the power transmission is unidirectional. The photovoltaic power generation unit is connected to the DC bus through a one-way DC/DC converter, the wind power generation unit is connected to the DC bus through a one-way AC/DC converter, and the fuel cell unit is connected to the DC bus through a one-way DC/DC converter. The gas turbine is connected to the DC bus through a unidirectional AC/DC converter, and the battery energy storage system is connected to the DC bus through a bidirectional DC/DC converter.

In this embodiment, the battery energy storage system is very important in the ship's DC microgrid. It can generate energy and consume energy. The power transmission is bidirectional. When the output power of the system is greater than the consumption power, the internal battery energy storage Energy; when the output power of the system is less than the consumed power, the battery releases energy to achieve peak power consumption, which improves the stability and reliability of the microgrid.

The load unit includes a DC load unit and an AC load unit; the DC load unit is connected to the DC bus through a unidirectional DC/DC converter; the AC load unit is connected to the DC bus through a unidirectional DC/AC converter.

The ship DC microgrid system of this embodiment further includes a shore power access unit; the shore power access unit is connected to the DC bus through a one-way AC/DC converter.

In this embodiment, distributed power generation technologies such as photovoltaic power generation, wind power generation, fuel cells, and energy storage are applied in the ship microgrid, the connection form of the distributed power generation and the DC bus is simpler, and it is easy to realize the coordination among the distributed power sources. control, and the bus voltage is the only indicator to measure the active power balance in the ship's DC microgrid system, there is no problem of reactive power balance and stability in the ship's AC microgrid, and the reliability of power supply is improved.

The ship DC microgrid in this embodiment is a split energy supply formed by a group of offshore renewable new energy power generation and traditional fossil fuel power generation as a cluster, combined with the ship's operating characteristics and the power quality management of some important loads of the ship's DC microgrid network.

The marine DC microgrid in this embodiment is an independent small power system. Ships operate at sea most of the time, and the ship’s DC microgrid does not enter the island state when the main grid fails or operates abnormally, but is in the state of island operation most of the time. The microgrid itself is regarded as the main grid of the ship’s power system. .

Ships are limited in size. The DC microgrid uses power electronic converters with higher power density instead of bulky and heavy transformers to realize voltage conversion, which can save the space area of ships. Because the generator prime mover speed is decoupled from the electrical system frequency, fuel consumption is reduced, allowing it to run at optimum speed. This feature is especially useful for ships with variable load heights. Greater cargo space and a more capable vessel are achieved due to the reduced electrical equipment footprint. Save up to 30% in electrical space requirements and weight. These significant savings come primarily from reductions in switchboard size and ratings, the use of smaller high-speed generators, and the elimination of large low-frequency thrust transformers. At the same time, due to the short line, the influence of network loss on system economy and stability can usually be ignored.

The ship DC microgrid with redundant busbar structure adopts multiple busbar power supply forms, usually two, one of which is charged and the other is reserved. When the live busbar fails or is repaired, the standby busbar can continue to supply power to ensure uninterrupted power supply to the electrical equipment. The structure of the redundant busbar ship DC microgrid in this embodiment is shown in FIG. 2 .

In this embodiment, in order to reduce the use of non-renewable energy, reduce environmental pollution, and achieve the goal of "green ships", photovoltaic cells, wind power generation, and fuel cells are used to replace diesel units using heavy oil.

In this embodiment, in order to solve the problem of high penetration of distributed power generation into the power grid on a large scale, thereby weakening the impact of distributed power generation on the power grid, the micro-grid technology is adopted.

In this embodiment, in order to overcome the shortcomings of the AC microgrid, a DC microgrid suitable for the characteristics of the ship's power system is selected as the networking mode of the ship's power system.

In this embodiment, in order to improve the reliability and flexibility of power supply and improve the power quality, a redundant busbar ship DC microgrid structure is used.

The ship DC micro-grid system of the present invention actually combines a variety of new energy sources, energy storage devices, energy conversion devices, and loads into a whole, and builds a strong coupling, nonlinearity, and high synergy that can realize self-control, protection and management. autonomous system.

Due to the important position of shipping in the transportation industry and the huge number of ships, traditional ships use diesel to generate electricity. Because of the abundance of new energy at sea, long light hours and strong wind power, it is very suitable to use new energy power generation as the main power generation method of the ship's power system. This greatly reduces pollution and improves the global climate and environment. At the same time, new energy is cheaper than fossil fuels such as diesel, which reduces shipping costs.

The marine DC micro-grid system with redundant busbar structure has flexible wiring methods, reduces power outages caused by line maintenance or faults, has high power supply reliability, and improves power quality.

The invention applies the new energy power generation technology to the marine ships, makes full use of the abundant advantages of marine new energy, reduces the proportion of fossil energy in the power supply of the ship's power system, and introduces clean energy to supplement and gradually replace fossil fuels.

Microgrid technology provides a flexible and efficient platform for the integration and utilization of clean energy such as solar energy and wind energy. It effectively solves the fluctuation and uncontrollable problems of intermittent energy, and applies microgrid technology to ship power systems. According to the characteristics of the ship's power system, a DC microgrid is used to replace the traditional AC microgrid, and the power supply reliability is improved through a redundant busbar structure.

The invention can be widely used in marine ships, and the DC micro-grid technology is applied to the ship power system, and has the characteristics of environment-friendly, reliable power supply, full energy utilization and low operating cost.

The above embodiments of the present invention do not constitute a limitation on the protection scope of the present invention. Any modifications, substitutions and improvements made within the spirit and principle of the present invention should be included within the protection scope of the present invention.

Claims (2)

1. A ship direct-current micro-grid system is characterized by comprising a main direct-current bus, a standby direct-current bus, a plurality of power generation units and a plurality of load units;

when the main direct current bus is normal, each power generation unit and each load unit are connected to the main direct current bus; when the main direct current bus fails, each power generation unit and each load unit are connected to the standby direct current bus;

the power generation unit comprises a photovoltaic power generation unit, a wind power generation unit, a fuel cell unit, a gas turbine and a battery energy storage system; the photovoltaic power generation unit is connected with a direct current bus through a unidirectional DC/DC converter, the wind power generation unit is connected with the direct current bus through a unidirectional AC/DC converter, the fuel cell unit is connected with the direct current bus through the unidirectional DC/DC converter, the gas turbine is connected with the direct current bus through the unidirectional AC/DC converter, and the battery energy storage system is connected with the direct current bus through a bidirectional DC/DC converter;

the load unit comprises a direct current load unit and an alternating current load unit; the direct-current load unit is connected to a direct-current bus through a unidirectional DC/DC converter; the alternating current load unit is connected to the direct current bus through the unidirectional DC/AC converter.

2. The ship direct-current micro-grid system according to claim 1, further comprising a shore power access unit; and the shore power access unit is accessed to the direct current bus through the unidirectional AC/DC converter.

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