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China Integrated Electric Propulsion

The Ministry of Industry and Information Technology's Equipment Industry Department announced in 2013 that the 712th Research Institute of China Shipbuilding Industry Corporation had made significant progress in the independent innovation of the integrated power propulsion system for ships. The propulsion system with the core of the system and operation control system had realized the localization of the electric propulsion system for ships with a single-axis propulsion power of less than 20 MW. This means that in the future, Chinese naval vessels are expected to be equipped with domestic electric propulsion systems and have a true "Chinese heart."

As the "heart" of surface ships, traditional power units mainly include steam power, diesel power, gas turbine power, and nuclear power. They are basically mechanical propulsion devices. Since the 1980s, the advantages of electric propulsion technology have become increasingly apparent and have become the focus of research by navies of various countries. In 1986, the United States listed comprehensive electric power propulsion as a new-generation ship's propulsion method in a plan called "The Maritime Revolution." In 1994, the US Navy proposed the concept of "Integrated Electric Propulsion System". The US Navy planned to equip the DD21 destroyer with an all-electric propulsion system.

The integrated electric propulsion system represents the development direction of ship power, and the main feature is the combination of propulsion power and power station power. Unlike the electric propulsion in the earlier sense, the integrated electric propulsion system of modern ships combines propulsion and daily electricity in one electric system. That is, a common generator set generates high-power electricity to meet all the load requirements of the ship-the needs of propulsion systems, daily loads, sensing systems, and shipborne weapons. The system uses a design concept that emphasizes modularization, integration, and systematization. It aims to reduce the total cost and optimize the ship's system and equipment composition. It is embodied in the form of electricity to concentrate the energy required by the entire ship and unify the electricity Provisioning and management. The integrated power system proposed by the US Navy is mainly composed of seven modules: power generation, power distribution, power control, power conversion, platform load, propulsion motor, and energy storage module.

Compared with conventional mechanical propulsion methods, electric propulsion systems mainly have the following advantages:

1. First, it has good economics. Ships equipped with electric propulsion systems have multiple medium-speed diesel engines for power generation. The number of generator generators can be selected according to the power load, so that the unit always runs in a high-efficiency work area to achieve maximum economic efficiency.
2. Second, good maneuverability. After adopting the electric propulsion system, the operation and control are convenient, the starting acceleration is good, the braking is fast, the forward and reverse vehicle speed is switched quickly, the speed of the propellable motor is easy to adjust, and constant torque can be provided under various forward and reverse speeds. The best working characteristics make the ship achieve excellent maneuverability.
3. Third, it has good security. For ships propelled by diesel engines, failure of important parts of the main engine or steering gear and shafting often leads to paralysis of the ship. Electric propulsion uses multiple prime movers, and even if a single unit fails, it does not cause the ship to lose power. Electric propulsion systems usually use more than two sets of spares for each other. The stator of the synchronous motor has two sets of windings independent of each other. One set of faults can still be reduced.
4. Fourth, it can save space. Under normal circumstances, the length of the ship's shafting system using traditional propulsion systems often accounts for about 40% of the ship's length, while ships using electric propulsion systems eliminate the need for transmission shafting and reduction gearboxes, thereby improving the layout of the engine room and enabling power units The arrangement is more reasonable and saves a lot of space.
5. Fifth, the noise is low, which can improve the quietness and concealment of the ship. After using electric propulsion, the engine as the main vibration source is installed on the elastic base and runs at a constant speed. It is also not directly connected to the shaft system and the hull, which greatly reduces vibration and noise, and makes the work area clean and improved. Increased the comfort level of the boat.
6. Sixth, it is beneficial for ships to control environmental pollution and reduce emissions. The use of electric propulsion systems for ships also facilitates computer network management, helps to achieve automatic control of the system, and comprehensively improves the level of ship informationization, intelligence, and automation.

At present, the DDG-21 destroyers and Ford-class aircraft carriers designed and built by the United States have been equipped with integrated electric propulsion systems. The Royal Navy is also at the forefront of the world in the use of electric propulsion: the British Type 45 destroyer and the Queen Elizabeth-class aircraft carrier are equipped with integrated electric propulsion systems.

The development of China's electric propulsion system is relatively slow. For a long time, the core equipment of electric propulsion ships built has been dependent on imports. Since the 1980s, China has begun to study its own electric propulsion system and install imported electric propulsion systems for some civilian ships, which has accumulated experience for China to develop comprehensive electric propulsion systems.

China has an industrial foundation in key technologies such as prime movers, generators, power distribution, and variable frequency speed regulation; China has more mature technologies in the production of megawatt-class diesel engines, generators, and medium and high-voltage power distribution boards. Through international exchanges, some ship design and manufacturing units in China have also accumulated a lot of experience in designing and building comprehensive all-electric propulsion ships.

In the field of civil ships in China, the application of electric propulsion has taken many forms. The all-electric propulsion ship "Shengli 232" engineering ship of Shengli Oilfield, which adopts "cross-straight" electric propulsion, with a motor power of 3,000 horsepower and Megawatt pod-type thruster.

In July 2013, China finally realized the "zero breakthrough" in the independent development of core equipment for marine electric propulsion-China Shipbuilding Industry Corporation 712 Research Institute announced that China's first medium-voltage 3 MW electric propulsion system and core with independent intellectual property rights. The equipment (medium voltage propulsion inverter, propulsion motor, etc.) was successfully developed and passed China Classification Society certification. The main technical indicators of the system reached the international advanced level, marking that China has the ability to design and manufacture large-capacity medium-voltage electric propulsion systems for ships, and has become one of the few countries in the world that have mastered this technology. This is of great strategic significance to China's comprehensive breakthrough in the application of core equipment for electric power propulsion and independent research and development on high-tech ships, to enhance the national offshore engineering equipment design and manufacturing capabilities, and to promote China's transition from a large shipbuilding power to a strong power.

The ship's electric propulsion system is divided into two types of low voltage and medium voltage, which are used for small and medium power propulsion and main propulsion of medium and large ships, respectively. With the increasing power demand of ship propulsion systems, low-voltage propulsion equipment is gradually eliminated due to limited capacity, and medium-voltage systems have become the development trend of electric propulsion. China Water Transport News reports that the medium-voltage 3 MW electric propulsion system developed in China can be appropriately customized according to customer requirements.

Although China ’s medium-voltage 3 MW electric propulsion system still has a gap compared with the power of European and American electric propulsion systems, the system is capable of meeting the needs of civilian ships and some special ships. For example, in order to precisely control its own position at sea, special ships such as sea monitoring ships, offshore oil production platforms, and marine survey ships need to adopt electric propulsion systems.

In May 2013, in the bidding for the comprehensive electric propulsion system of four 6,000-horsepower (about 5.4 MW) deepwater platform supply vessels of CNOOC, the 712 Research Institute and ABB, GE and other well-known foreign companies tendered at the same time. This contract became the first domestic integrator for this type of ship. This is the first time that China's marine engineering equipment field has selected a domestic ship electric propulsion system integrator.

In addition to the 712 Research Institute, other domestic companies are also developing integrated electric propulsion systems. In March 2013, the 704th Research Institute of China Shipbuilding Industry Corporation successfully signed the "1500-ton marine surveillance rights enforcement law enforcement comprehensive survey ship electric propulsion system" project contract. The 704 will provide all-ship electric propulsion system devices, including generator sets, switchboards, and power station management systems. According to estimates, the power of a 1,500-ton sea surveillance ship may be 4,500 horsepower, which is slightly greater than the level of 3 MW.

In the military field, the requirements for power supply of new-generation ship electronics continue to increase. The demand for new concepts of weapons and equipment, such as laser weapons, electromagnetic catapults, and electromagnetic railguns, has increased geometrically. Therefore, future ship equipment Comprehensive electric propulsion devices have become inevitable. In addition, for anti-submarine warfare requirements, electric propulsion systems are conducive to reducing ship noise and increasing mission success rates.

In order to enhance anti-submarine performance and improve quietness, the 054B missile frigate will use an integrated electric propulsion system. The predecessor of Type 054B frigate-Type 054A frigate currently uses 4 diesel engines. If electric propulsion is used, an electric propulsion system of about 10 MW will be required.

According to the official website of the 712 Research Institute, the institute has successively completed the system integration work of several electric propulsion ships, and can provide overall system integration solutions and related key equipment for various types of ships using electric propulsion systems and other industrial electric drive systems. It can produce a variety of electric propulsion systems covering power levels below 10 MW. Such an electric propulsion system already has the ability to provide support for the 054B frigate.

In August 2013, China's single-axis propulsion power of ships below 20 MW was fully domesticated. This helps to significantly increase the speed of ships equipped with electric propulsion systems. The British Navy uses a fully electric propulsion Type 45 destroyer with a displacement of 7,300 tons. The ship uses dual-axis propulsion with 20 MW of power per shaft and a speed of more than 29 knots (this is public data from the Royal Navy, which should actually exceed 30 knots). The Queen Elizabeth-class aircraft carrier with the same power as the Type 45 destroyer has a displacement of 45,000 tons, and its four diesel engines can provide approximately 40 megawatts of power at a speed of 26 knots.

Judging from the current situation of the Chinese Navy's ship displacement not exceeding 8000 tons, if the 052C and 052D destroyers use all-electric propulsion, it can achieve high-speed cruising of more than 30 knots. However, limited by the CODOG power mode (that is, diesel and gas turbines are used alternately), these ships have limited high-speed cruising time and speed. In addition, on the aircraft carrier power system, in the future, like the Queen Elizabeth class aircraft carrier, electric propulsion will be adopted, and if the 4-shaft power system is used, a regular aircraft carrier with a speed of more than 30 knots can be completely constructed.

However, there is still a gap between China's power propulsion system and other countries. The integrated electric propulsion system power of the British Type 45 destroyer can reach 50 MW, and the electric propulsion system power of the United States new concept warship DDG-1000 can reach 78 MW. In addition, although China's domestic all-electric propulsion system has been introduced, before the world's most advanced all-electric propulsion can be achieved, another important power problem needs to be solved, that is, having a reliable and long-lasting gas turbine.

The Chinese Navy destroyers uses CODOG. Generally, it uses a diesel engine for cruising, and switches to a gas turbine when it needs acceleration. That is to say, the Chinese Navy does not have a gas turbine that can be used for long cruises like the US-made LM02500 gas turbine. However, the use of China's good and reliable diesel engine can not drive a single-shaft 20 MW electric propulsion at all. The Chinese navy still needs to overcome the difficulties of the ship's gas turbines in order to achieve greater breakthroughs in the field of integrated electric propulsion systems.

China’s state papers have praised a military scientist whose contributions could reportedly make the People’s Liberation Army’s next-generation warships “realize full electric propulsion”. In July 2018 Prof. Xiao Fei, head of a research institution at PLA’s Naval University of Engineering in Wuhan, received a first-class merit citation in an honor list signed by President Xi Jinping, who also heads the Central Military Commission. Xiao’s research concentrates on reconfiguring future warships’ powertrains in order to supply more power to shipborne weapons systems.

“A first-class merit citation is very rare in peacetime, which means Xiao’s contributions to China’s naval development are extraordinary and remarkable,” Wang Yunfei, a naval expert and retired PLA Navy admiral, told the People’s Daily. The PLA Daily reported that Xiao, 41, led a team that drove research and innovation that helped the Chinese Navy to surmount vital technical hurdles during the modernizing of its nuclear submarine fleet. It also helped develop highly efficient steam turbines for the nation’s first homemade aircraft carrier.

But it was Xiao’s original research into an electric powertrain, namely, a medium-voltage direct current (MVDC) integrated power system that earned him a mention from President Xi. The MVCD was devised for a prototype of the nation’s shipborne full electric propulsion system. The benefits of integrated electric propulsion are mainly the ability to place the electric motors closer to the propeller to shorten the shaftline and reduce space lost to funnels. This obviates the need for a gearbox or controllable pitch propellers, as well as giving designers the freedom to run all propulsion and ship services from a single prime mover for much of the ship’s life, thus dramatically reducing engine running hours and emissions.

Technologies developed by Xiao’s team will be used on the Type 052E destroyer, an improved version of the Type 052D, and might possibly be employed in the nation’s future nuclear-powered carriers. The Global Times additionally revealed that Xiao’s MVDC power system is also the foundation of an electromagnetic gun system which, China claims , is the first operation-ready railgun to feature on a warship. The Type 055, China’s 10,000-ton class destroyer, is very likely to see an improved powertrain with electric propulsion in the near future.