EP3011654A1

EP3011654A1 - Power system

Info

Publication number: EP3011654A1
Application number: EP14733983.2A
Authority: EP
Inventors: Leif Aggerholm NIELSEN
Original assignee: DEIF AS
Current assignee: DEIF AS
Priority date: 2013-06-17
Filing date: 2014-06-17
Publication date: 2016-04-27
Also published as: WO2014202087A1

Abstract

The present invention relates to an electric power system and method for power control of a main generator driven by a main engine of a ship, which power system com- prises a second auxiliary generator, which generators are controlled by an electronic control system to adjust the fuel index of the auxiliary generator while running parallel with the shaft generator. It is the object of the invention to achieve long period of parallel operation of a shaft generators and an auxiliary generator connected directly to a common grid. A further object of the invention is fuel saving during by parallel operation. The object can be if the electronic control system is adapted to perform supervision and control of heavy consumer on the vessel to mitigate load jumps, which heavy consumers are adapted to transmit a request for power consumption to the electronic control system, which electronic control system is adapted to adjust the fuel specific index for change of power demand, which electronic system is adapted to transmit an acknowledge to the heavy consumers, which heavy consumers are adapted to connect to the grid by receiving acknowledge from the electronic control system.

Description

POWER SYSTEM

Field of the Invention

The present invention relates to an electric power system and method for power con- trol, which power system comprises at least one first main shaft generator, which first main generator is driven by a main engine of a ship, which power system comprises at least one second auxiliary generator, which generators are electrically connected by switching means to a common or more phased grid, which generators are controlled by one or more electronic control systems, which electronic control system is adapted to measure the actual frequency of the generators, which electronic control system is adapted to measure the generated power of the generators, which electronic control system is adapted to perform adjustment of a speed reference for the auxiliary generator, which electronic control system is adapted to adjust the fuel index of the auxiliary generator while running parallel with the shaft generator. Background of the Invention

DieselFacts 1/2012 by MAN Diesel and Turbo ( page 4) discloses a regulation principle for a shaft generator where the load distribution is controlled by direct fuel index control of the auxiliary engine. However, to be utilized commercially, the new control strategy must be implemented in the Power Management System and the auxiliary- engine governor software must be adjusted to facilitate this type of control.

Since the shaft generator is mechanically connected to the main propulsion propeller, the frequency of the shaft generator cannot be held steady like the auxiliary generator. Inevitable there will a fluctuating load when sharing with the shaft generator. Object of the Invention

It is the object of the invention to achieve a long period of parallel operation of one or more shaft generators and one or more auxiliary generators connected directly to a common grid. A further object of the invention is fuel saving during parallel operation. Description of the Invention

An object can be fulfilled by a system as disclosed in the preamble to claim 1 if the electronic control system is adapted to perform supervision and control of heavy consumer on the vessel to anticipate load jumps, which heavy consumers are adapted to transmit a request for power consumption to the electronic control system, which electronic control system is adapted to adjust the fuel specific index for change of power demand, which electronic system is adapted to transmit an acknowledge to the heavy consumers, which heavy consumers are adapted to connect to the grid by receiving acknowledge from the electronic control system.

An object can achieved by a power system as disclosed in the preamble, where the electronic control system is adapted to perform supervision and control of at least one heavy consumer on the vessel to accommodate load jumps, and which electric control system is adapted to retrieve from at least one heavy consumer a transmitted request for power consumption, and which electronic control system is adapted to adjust the specific fuel index for change of power demand, which electronic control system is adapted to transmit an acknowledgement to at least one heavy consumer, to connect to the grid by receiving an acknowledgement from the electronic power system. Hereby it can be achieved that parallel operation of the shaft generator and an auxiliary generator is possible even in situations when heavy consumers are switched on and off to the common grid. As soon as the system reaches a request, the system is able to change the fuel index, and in this way to reach a new fuel index for the auxiliary generator before the heavy consumer changes its power consumption. In that way it can be avoided that voltage or maybe frequency is slightly changed in situations where heavy consumers are switched on and off. Heavy consumers on ships are probably switching in and out of thrusters, which thrusters are only in use in short periods of time when the ship reaches harbour. During normal operation of a ship where it sails day after day, it is highly efficient that the shaft generator is connected in parallel to the same grid together with one or more auxiliary generators. Adjusting the auxiliary generators to a frequency slightly higher than the frequency of the shaft generator ensures that the auxiliary generator delivers all its power to the grid and the power delivered is simply controlled by the fuel index. This is the case even in situations where waves around the ship cause the main engine to change frequency together with the shaft generator, depending on the position of the propeller in the water so that slight change in frequency of the grid occurs.

The pending patent application discloses a system that allows parallel operation of shaft generator and auxiliary generator for several days. With previous systems, power was generated by the shaft generator but power generator by auxiliary generators was mostly isolated so that two different grids existed. Therefore, it has not been possible to produce maximum power at the shaft generator, simply because one of the grids on a ship was supplied by the shaft generator, but because the grid always made changes in demand, a maximum grid connection would not be possible. Instead another part of the ship had to be supplied by the auxiliary generators independently of the shaft generator. Most of the ships had the option of interconnection of the two grids however, it was only possible for short periods of time. Simply because power generated by shaft generator is the most inexpensive power on board a ship, the shaft generator has to generate most of the power for the ship so the shaft generator is operating near its maximum power production most of the time. Therefore, it is possible to reduce the power produced by the auxiliary generators when these are in parallel operation. This can lead to rather large reductions in total fuel consumption on a large ship. In an embodiment of the invention, the electronic control system may be adapted to adjust fuel and speed set to achieve optimized running of the connected generators. Hereby it can be achieved that the fuel index at auxiliary generators has to be adjusted in accordance with the deviation of the frequency that is generated at a shaft generator.

Large frequency deviations from the shaft generator are to be expected. Deviations will under normal droop compensated regulation mode lead to very large power swings because auxiliary generator will try to compensate. When the auxiliary generator is set to a fixed fuel index the power swing will be limited to the power that is used to accelerate or decelerate the auxiliary generator.

There is no doubt that the adjustment of the fuel index at auxiliary generators can be more precise when the shaft generator is operating at a very stable frequency. Depending on weather conditions, the change in the shaft generator frequency will be larger when for example high waves are forcing the propeller of the ship to be outside the water periodically.

In some situations where the weather is severe, it is probably not possible to operate with parallel connections of the auxiliary generators and the shaft generator, but severe weather conditions are anyhow power consuming on the ships.

In an embodiment of the invention, the electronic control system may be adapted to instantly shifting the auxiliary generator from fixed fuel running to droop compen- sated running mode in case of breaker trip. In this way normal speed regulation is activated as soon as any activity at any of the brakes at the grid is detected. Hereby it can be avoided that one or more auxiliary generators are running totally free because part of the grid is interconnected. Thereby, the auxiliary generators will increase the frequency of the grid and this increasing frequency has to be regulated to a fixed max- imum in a traditional way in order to protect the auxiliary power generating system.

In an embodiment of the invention, the electronic control system may be adapted to perform adjustment of the power level of the shaft generator to optimize the power production. Optimized production is achieved if the fuel index of the auxiliary genera- tors is adjusted to a level where the shaft generator is producing most efficiently. In that way the most inexpensive power production at any ship can be obtained.

In an embodiment of the invention, the electronic control system may be adapted to perform supervision and control of heavy consumer on the vessel to anticipate load jumps. By control of the heavy consumers it can be achieved that none of these heavy consumers are connected to the grid before the system has finished a preparation and changed the settings for fuel index control in order to let for example one or more auxiliary generator change their fuel index into a new power level required by the heavy consumer.

In an embodiment of the invention, the electronic control system may be adapted to perform control of the generators based on e.g. actual total power consumption, the reserved power for heavy consumers, direct or indirect measurement or indications of the actual consumption of one or more heavy consumer and parameters for each gen- erator concerning optimal and safe use. Feedback from the power consumption of the heavy consumers can be measured directly as a feedback from the consumer and communicated to the electronic control system. In some situation the feedback can be communicated indirectly to the electronic control system. With a system that has the total control of the power consumption as well as production of a number of generators, but also the power that is in use by consumers, it is possible for this system to predict changes in consumption based on previous situations which can be remembered by the system. A computer algorithm in the control system will be able to predict changes in power consumption of any heavy consumers. Therefore, large power reserves must be available in the power system. Another situation is that the prediction of cooling demand, for example for container ships, if the power control system also has data of for example the number of refrigeration containers on board a ship, the control system can, based on changes in temperature, predict changes in power demand for maybe thousands of containers. With these data the control system is also capable of predicting the total power consumption.

Emergency situations may of course occur on board a ship. Rapid change of the main engine might lead to an isolation of the shaft generator whereby auxiliary generators have to take over. In such a situation it can be important that all large consumers have to send a request before they are connected to the grid. In an emergency situation where for example auxiliary generators are in a start-up procedure and therefore not ready to produce power, large consumers might have to wait for some seconds to be connected to the auxiliary generators until the power production has stabilized. In an embodiment of the invention, the electronic control system may be adapted to perform control of connection or disconnection of one or more loads, which can be disconnected for shorter or longer periods, based on e.g. actual total power consumption, the reserved power for heavy consumers, direct or indirect measurement or indications of the actual consumption of one or more heavy consumer and parameters for each generator concerning optimal and safe use. Some consumers on board a ship can be shut down for shorter or longer periods of time without negative influence. Therefore, a power reserve can exist in some power consumers for shorter or longer periods of time can operate without power. For example, in some situations all refrigeration containers can be shut down for some minutes without causing any detriment to the contents of the containers. The temperature will not change in a way that can be measured if the container control is out of power for example for 10 or 15 minutes. In this way very large power reserves can be achieved. The size of this type of power reserve will of course depend on the actual situation. If the ship sails in tropical areas where the power demand for the refrigeration systems is enormous, it will be quite critical to stop the compressors, even for shorter periods of time. But in situations where temperatures around the ship are rather low, it is possible to stop the compressors for a longer period of time without causing any critical change inside the container. Therefore, the power reserve also depends on the outdoor temperature.

In an embodiment of the invention, the electronic control system may comprise a common controller or at least one control module for each generator, which control modules are communicating by a common fast operating communication bus. Because changes in power consumption can take place quite suddenly, also in situations where heavy consumers are not connected but only small consumers are changing their demand. Therefore, in order to adjust even small changes in the power demand, it is necessary to have a very quick response of an electronic control system. A power control module is therefore connected to these generators and directly connected between the electronic power modules there is one fast communication bus so that data communi- cation between the electronic modules is executed in an extremely fast manner. Even the software that is developed and in operation in the modules, is developed for very for fast reaction. Therefore, the system as described makes it possible to let the system follow adjustment of changes in power demand in a highly efficient manner. In an embodiment of the invention, the electronic control system may comprise parallel power limiter, which parallel power limiter is adapted to be active when an auxiliary generator and a shaft generator is operating in a parallel, which power limiter is active until the electronic control system receives a request for increasing power consumption. The power limiter can be used for performing a more or less automatic cut- off in situations of rapid increase in power demand.

An object may be achieved by a method, which method involves operating an electric power system as disclosed and where at least one heavy consumer is connected to a common grid and adapted to transmit a request for change of power consumption to the electronic control system, which method comprises at least: a. the act of letting the electronic control system perform supervision of power and frequency of at least one shaft generator , b. the act of letting the electronic control system perform supervision of power and frequency of at least one auxiliary generator, c. the act of letting the electronic control system control the specific fuel index of one or more auxiliary generators(DGl)(8,9) for long period parallel operation with the shaft generator, d. the act of letting the electronic control system perform supervision and control of at least one heavy consumer, e. the act of letting the electronic control system adjust the specific fuel index for change in power demand from the heavy consumers, f. the act of letting the electronic control system transmit an acknowledgement to the heavy consumers, g. the act of letting the electronic control system control connection or disconnection of the heavy consumers, h. the act of letting the electric control system return to specific fuel index control of one or more auxiliary generator, and i. the electric control system optimizes power distribution on connected gen-sets based on heavy consumer actual consumption, heavy consumer reserved power and actual demand on other load groups.

The pending patent application further discloses a method, which method comprises at least the following sequence of steps: a. let the electronic control system perform supervision of power and frequency of at least one shaft generator (SGI), b. let the electronic control system perform supervision of power and frequency of at least one auxiliary generator (DG1), c. let the electronic control system control the fuel index of one or more auxiliary generators (DG1) for a long period parallel operation with the shaft generator (SGI), d. let the electronic control system perform supervision and control of heavy consumer, e. heavy consumers connected to the common grid are adapted to transmit a request for change of power consumption to the electronic control system, f. the electronic control system adjusts the fuel index for change in power demand from the heavy consumers, g. the electronic control system transmits an acknowledge to the heavy consumers, and h. the electronic control system performs connection of the heavy consumers, By the disclosed method it should be possible for a shaft generator to operate in parallel with an auxiliary generator for a very long period of time. The system is highly efficient and is able to reduce the fuel consumption of a ship because most of the power in this way can be delivered from the shaft generator which is absolutely the most inexpensive way of generating power on a ship. However, the shaft generator is often dimensioned so that it is not able to fully support the power demand on a ship. Therefore, one or more auxiliary generators are in place and can be connected if necessary. In many situations this system will allow the shaft generator to produce up to 90 percent of the power required and the auxiliary generators are then reduced to producing only maybe 10 percent of the power consumed on the ship. Therefore, an in- vention of this type can lead to reduction of pollution because most of the electric power is produced by means of a main engine.

Description of the Drawing

Fig. 1 discloses a schematic view of a power system.

Fig. 2 shows a flowchart indicating a power limiter routine.

Detailed Description of the Invention

Fig. 1 shows an electric power system 2 which power system comprises at least one shaft generator 4 which by a shaft is connected to an optional gear system 5 which gear system further by a shaft is connected to an engine 6 which engine further drives a propeller 3. The power system 2 further comprises a first auxiliary engine 7 which drives an auxiliary generator 8. Further an engine 11 is indicated which drives a second auxiliary generator 9. Via a switch 10A the shaft generator 4 is connected to a power grid 12A where the auxiliary generator 8 is connected to the grid 12A by switch 10B. Further, by a switch IOC, the auxiliary generator 9 is connected to the power grid 12B. The power grid 12A and the power grid 12B can be connected by the switch 13. The engine 6 is controlled by an electronic control system 14A through a control line 15 A. Further the auxiliary engine 7 is controlled by an electronic control system 14B connected by the line 15B. Further the auxiliary engine 11 is connected with an electronic control system 14C by a line 15C.

Over a switch 24 A a heavy consumer 16 is connected to the power grid 12 A. Further, a heavy consumer 16B is connected to the power grid 12B via a switch 24B.

By a line l lA the electronic control system 14A controls the switch 10A. Further, the electronic control system 14B controls the switch 10B through line 1 IB.

Further, the electronic control system 14C controls the switch IOC by line 11C.

The three electronic control systems 14A, 14B, 14C are interconnected by a common data bus 20.

In operation the electronic control system 14 A can control the fuel index of the main engine 6 through the communication line 15 A. By controlling the fuel index, the main engine 6 is operating mostly at constant speed keeping the revolutions per minute (rpm) more or less constant. Because the shaft is driving the propeller 3, this propeller might have different loads depending on the position of the blades in water. Therefore, inside the specific fuel index, the rpm of the main engine will change slightly. By line 15B the electronic control system 14B further controls the fuel index of the auxiliary engine 7. By efficient control of the fuel index it is possible to let the auxiliary generator 8 work in parallel with the shaft generator 4. Further, if the power demand on board a ship is increasing, the second auxiliary engine 1 1 can be started and generate power by means of the auxiliary generator 9.

Also, over line 15C, the control system 14C is able to control the auxiliary engine 11 by a specific fuel index. The heavy consumers 16A and 16B have to request that the electronic control systems 14 A, 14B, 14C are allowed to connect by switches 24 A or 24B. The heavy consumers cannot start operation until acknowledgment. With the system a short waiting time can occur as the fuel index of one or more of the engines 6,7, 11 has to be adjusted to overcome an increasing electric power demand.

A flowchart 122 which has a first block 124 is meant as an activation block for the diesel generator and the shaft generator power limiter. Line 126 leads to block 128 which receives a request from one of the large consumers on board a ship. This request can be acknowledged by line 130 or not acknowledged by line 132. Line 132 leads to a block 124 which controls the shaft generator on a fixed set point. From here a line 144 leads back to the line 126, and the process continues. If block 128 leads to a YES decision, line 130 leads to block 134 which block analyses if the power gener- ated at the shaft generator is lower than what is requested. If NO, this means that there is no room for large consumer at this moment because the shaft generator has no extra power for the large consumer.

Therefore, line 138 now leads towards line 142 where the shaft generator is set at a fixed point of operation. Therefore, once again through line 144, the signal is sent back to line 126 from where the process is repeated. If block 134 can accept by YES, then, by line 136, the block 137 is accepting that the heavy consumer is connected. Therefore, by line 140, this line leads to the box 142 from where line 144 leads back to line 126. By this flowchart it is possible that the control of heavy consumers is effected in such a way that these cannot be interconnected in a way where these pull down the power from a shaft generator. The heavy consumer has to wait until the power level of the shaft generator and the shaft engine is set to a fixed set point for the shaft generator. In other situations, in parallel to the shaft generator, the system can also command auxiliary generators to start operation.

Claims

1. Electric power system (2), which power system (2) comprises at least one first main shaft generator (SG1)(4), which first main shaft generator (4) is driven by a main en- gine (6) of a vessel, which power system (2) comprises at least one second auxiliary generator (8)(DG1), which generators (SGI, DG1)(4,8) are electrically connected by switching means (lOa-c) to a common one or more phased grid (12a,b), which generators (SG1,DG1)(4,8) are controlled by one or more electronic control systems (14a-c), which electronic control system (14a-c) are adapted to measure at least the actual fre- quency of the generators (SG1,DG1)(4,8,9), which electronic control system (14a-c) is adapted to measure the generated power of the generators (SG1,DG1,DG2)(4,8,9), which electronic control system (14a-c) is adapted to perform adjustment of a speed reference for the auxiliary generators (DG1,DG2)(8,9), which electronic control system (14a-c) is adapted to adjust a specific fuel index of at least one auxiliary generator (DG1,DG2)(8,9) while operating in parallel with the main shaft generator (SG1)(4) characterized in, that the electronic control system (14a-c) is adapted to perform supervision and control of at least one heavy consumer (16a,b) on the vessel to accommodate load jumps, and which electric control system (14a-c) is adapted to retrieve from at least one heavy consumer (16a,b) a transmitted request for power consump- tion and which electronic control system (14a-c) is adapted to adjust the specific fuel index for change of power demand, which electronic control system (14a-c) is adapted to transmit an acknowledgement to at least one heavy consumer (16a,b), to connect to the grid (12a,b) by receiving an acknowledgement from the electronic power system (2).

2. Electric power system (2) according to claim 1, characterized in that the electronic control system (14a-c) is adapted to adjust fuel index and speed set to achieve optimized running of the connected generators (SG1,DG1,DG2)(6,8,9).

3. Electric power system (2) according to any of claim 1 or 2, characterized in that the electronic control system (14a-c) is adapted to instantly shift the auxiliary generator (DG1)(8,9) from fixed fuel running to droop compensated running mode in case of breaker trip.

4. Electric power system (2) according to any of claims 1-3, characterized in that the electronic control system (14) is adapted to perform adjustment of the power produced by the shaft generator (SG1)(4) to optimize the power production.

5. Electric power system (2) according to any of claims 1-4, characterized in that the electronic control system (14) comprises at least one control module (14a-c, 18a-c) for each generator (SG1,DG1,DG2)(4,8,9), which control modules (14a-c, 18a-c) adapted to communicate by a common operating communication bus (20).

6. Electric power system (2) according to any of claims 1-5, characterized in that the electronic control system (14) comprises a power limiter (22), which power limiter (22) is adapted to be active when at least one auxiliary (8,9) generator and a shaft generator (4) is operating in a parallel, which power limiter (22) is adapted by the elec- tronic control system to changes in power consumption.

7. Electric power system (2) according to any of claims 1-6, characterized in that the electronic control system (14) comprises control means for optimized power distribution on connected gen-sets (SG,DG)(4,8,9) based on heavy consumers (16a,b) actual consumption, heavy consumer (16a,b) reserved power and actual demand on other load groups.

8. Electric power system (2) for power control according to one of the claims 1-7, characterized in that the electronic control system (14) comprises means for connec- tion or disconnection of one or more loads in the system to optimized power distribution on connected gen-sets (SG,DG)(4,8,9) based on heavy consumer (16a,b) actual consumption, heavy consumer (16a,b) reserved power and actual demand on other load groups and on load parameter and/or direct and/or indirect load measurements and/or other indirect measurements related to a load e.g. temperature.

9. Electric power system (2) according to any of claims 1 to 8, where the accommodation is performed by actions based on anticipating load jumps.

10. Electric power system (2) according to claim 9, where anticipating load jumps is performed by predicting changes in consumption based on previous situations.

11. Electric power system (2) according to claim 9 or 10, where anticipating load jumps is performed by predicting changes in power consumption of heavy consumers.

12. Electric power system (2) according to any of claims 9 to 11, where anticipating load jumps is performed by predicting changes in power consumption of heavy consumers based on external conditions such as weather conditions or forecasts of weath- er conditions.

13. Electronic power system (2) according to any of claims 9 to 12, where anticipating load jumps is performed by predicting changes in power consumption of heavy consumers based on tabulated or modelled power consumptions.

14. Method of operating an electric power system (2) as disclosed in any of claims 1-8 and where at least one heavy consumer (16a,b) is connected to the common grid (12) and adapted to transmit a request for change of power consumption to the electronic control system (14a-c), which method comprises at least : a. the act of letting the electronic control system (14a-c) perform supervision of power and frequency of at least one shaft generator (SG1)(4), b. the act of letting the electronic control system (14a-c) perform supervision of power and frequency of at least one auxiliary generator (DG1), c. the act of letting the electronic control system (14a-c) control the specific fuel index of one or more auxiliary generators (DG1)(8,9) for long period parallel operation with the shaft generator (SG1)(4), d. the act of letting the electronic control system (14a-c) perform supervision and control of at least one heavy consumer (16a,b), e. the act of letting the electronic control system adjust the specific fuel index for change in power demand from the heavy consumers (16a,b), f. the act of letting the electronic control system (14a-c) transmit an acknowledgement to the heavy consumers (16a,b), g. the act of letting the electronic control system control connection or disconnection of the heavy consumers, h. the act of letting the electric control system (14a-c) return to specific fuel index control of one or more auxiliary generators (DG1,DG2) (8,9), and i. the electric control system (14a-c) optimizes power distribution on connected gen- sets (SG,DG)(4,8.9) based on heavy consumer (16a,b) actual consumption, heavy consumer (16a,b) reserved power and actual demand on other load groups.