ELECTRICAL POWER DISTRIBUTION SYSTEM, METHOD FOR POWERING A CORRESPONDING TASK, PROPULSION SYSTEM AND METHOD FOR A SHIP

Abstract

This electrical energy distribution system comprises assembly of electrical energy generators each driven by a heat engine and supplying a distribution network; means for recovering the heat energy generated during the operation of the heat engines and for vaporizing a working fluid; steam turbine driven by the working fluid and associated with a generator connected to the distribution network for converting the recovered heat energy into electrical energy and at least one frequency converter arranged between the distribution network and an electrical load.

It comprises means for controlling the frequency of the distribution network, where the flow rate of the vaporized working fluid is regulated to a maximum value.

Claims

1. An electrical power distribution system, comprising: an assembly of electrical power generators, each driven by a heat engine and supplying a distribution network; a heat exchanger configured for recovering the heat energy generated during the operation of heat engines and for vaporizing a working fluid; a steam turbine driven by the working fluid and associated with a generator connected to the distribution network for converting the recovered heat energy into electrical energy; at least one frequency converter arranged between the distribution network and an electrical load; and a control device configured for controlling the frequency of the distribution network, where the flow rate of the vaporized working fluid is regulated to a maximum value.

2. A system according to claim 1, wherein the control device comprises a regulator for regulating the frequency of the network between minimum and maximum frequency values.

3. A system according to claim 2, wherein the regulator comprises at least one phase-locked loop associated with proportional integral corrector.

4. A system according to claim 1, wherein the or each frequency converter is a bidirectional converter capable of providing bidirectional power transfer.

5. A system according to claim 4, wherein each converter (11) comprises filter input stage, active rectifier circuit, smoothing circuit and inverter circuit.

6. A system according to claim 5, wherein each converter further comprises output filtering inductor.

7. A method of supply a charge via a system for distributing electrical energy, comprising: driving, by a heat engine, an assembly of electrical energy generators that supply a distribution network; recovering the heat energy generated during the operation of the heat engines and for vaporizing a working fluid; driving, by the working fluid, a steam turbine associated with a generator connected to the distribution network for converting the recovered heat energy into electrical energy and at least one frequency converter arranged between the distribution network and an electrical load; regulating the flow rate of the vaporized working fluid at maximum steam; and controlling the frequency of the distribution network.

8. A method according to claim 7, wherein the regulating of the flow rate of the vaporized working fluid is regulated by opening a valve to the maximum for controlling the flow rate of the vaporized working fluid.

9. A method according to claim 7, wherein the controlling of the frequency of the network is regulated between the minimum and maximum frequency values.

10. Propulsion system for a ship, comprising: a principal heat engine driving a line shafting; an auxiliary electrical motor coupled to the line shafting and supplied by an electrical power distribution network, said distribution network being supplied by auxiliary heat engines associated with electrical energy generators; a heat exchanger configured for recovering the heat energy generated during the operation of the propulsion system and for vaporizing a working fluid; a steam turbine driven by the working fluid and associated with a generator connected to the distribution network for converting the recovered heat energy into electrical energy, and at least one frequency converter arranged between the distribution network and the auxiliary electrical motor, a controller configured for controlling the frequency of the distribution network, where the flow rate of the vaporized working fluid is regulated to a maximum value.

11. A propulsion system according to claim 10, further comprising assembly of electrical power generators, each driven by a heat engine and supplying the distribution network.

12. A propulsion system according to claim 10, further comprising at least one bow thruster comprising an electrical motor capable of being supplied by the electrical power distribution network via the frequency converter, said network being powered by the heat engines when the bow thrusters are supplied by the said network.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Other objects, characteristics and advantages of the invention will become apparent on reading the following description, given by way of non-limiting example, with reference to the accompanying drawings, in which:

[0035] FIG. 1 illustrates the general architecture of a propulsion system for a ship comprising an electrical energy distribution system according to an embodiments of the invention; and

[0036] FIG. 2 illustrates an embodiment of a propulsion system according to the invention

[0037] FIG. 3 illustrates an embodiment of a propulsion system according to the invention

[0038] FIG. 4 illustrates an embodiment of a propulsion system according to the invention

DETAILED DESCRIPTION

[0039] This propulsion system firstly comprises heat engine 1 which drives motor shaft 2 provided with propeller 3 which is equipped with auxiliary electrical motor 4 of the SGM type (for “Shaft Generator Motor”) which is supplied by a distribution network 5 of the AC type with a fixed frequency.

[0040] Network 5 is supplied by assembly of generators G, here four in number, each driven by auxiliary heat engines, e.g. 6, in this case two-stroke diesel engines.

[0041] In addition to distribution network 5 and auxiliary heat engines 6 associated with the generators, the electrical power distribution system is provided with means for recovering heat energy WHRS comprising heat exchanger 7 receiving the exhaust gas of auxiliary motors 6 for vaporizing a working fluid, in this case water, and steam turbine 8 receiving the steam from the exchanger via an adjustment valve 9 controlled by control device 10.

[0042] The control device acts on valve 9 so as to control it in the fully open position as soon as the steam pressure upstream of the steam turbine exceeds a Pmin minimum value. The control device thus comprises member 10a for measuring the pressure upstream of steam turbine 8 and comparator 10b which compares the measured pressure value with the minimum value for controlling valve 9.

[0043] As shown in the figure, auxiliary electrical motor 4 is supplied by distribution network 5 via frequency converter 11.

[0044] Converter 11 is a reversible converter and constitutes a fixed frequency—variable frequency converter for converting the available AC voltage on the fixed frequency network 5 into a variable frequency voltage for supplying auxiliary motor 4.

[0045] On the distribution network side, it comprises filter input stage 12, then active rectifier circuit 13, smoothing circuit 14, inverter circuit 15 and filtering inductor L.

[0046] Distribution network 5 essentially comprises a principal bus supplied by the auxiliary motors and the gas turbine associated with generators G.

[0047] It also comprises secondary bus 5a supplied by the principal bus via distribution transformers 16.

[0048] It can also be seen that the system comprises a number of circuit breakers 17, 18 and 19 capable of isolating distribution network 5 from generators G, frequency converter 11 and the distribution transformers.

[0049] Additional circuit breakers, e.g. 20, make it possible to isolate portions of principal supply bus 5 and secondary supply bus 5a.

[0050] Finally, the distribution system is supplemented by a stage for controlling the frequency of the distribution network.

[0051] This stage firstly comprises transformer 21 for measuring the voltage available on network 5 as well as phase-locked loop 22 for converting the measured voltage into frequency.

[0052] Comparator 23 provides a comparison of the frequency of the distribution network with a reference frequency FREF. Comparator 23 is associated, at the output, with hysteresis function 24 which, when active, reproduces the input at the output when the difference between the measured frequency and the reference frequency is above the thresholds ΔFmin and ΔFmax. When the difference is less than these thresholds, the output of the hysteresis function is zero.

[0053] The output of the hysteresis function is supplied to a proportional integral corrector 25 to maintain the frequency within the hysteresis band.

[0054] In addition, comparator 27 receives a power reference value Pref and the output of corrector 25 for controlling the frequency converter.

[0055] Finally, it must be noted that the distribution network is also intended to supply various electrical charges onboard the ship.

[0056] Indeed, the propulsion system is supplemented by complementary motors, in this case bow motors 28 driving a shaft carrying a propeller and supplied by network 5 via autotransformers 29.

[0057] The distribution system described above operates as follows.

[0058] In the first place, when auxiliary motors 6 operate, when the pressure of the steam admitted to the input of steam turbine 8 increases, this causes an acceleration of the steam turbine and a consequent increase in the frequency of distribution network 5, and the SGM motor is controlled to increase its active power consumption, if it is in motor mode, or to decrease its active power production, if it is in generator mode.

[0059] Depending on the consumption of auxiliary motor 4, or if the energy supplied by the steam turbine is available in excess, frequency converter 11 is controlled so as to reinject the available energy into the line shafting via auxiliary electrical motor 4.

[0060] If the steam pressure available at the input of the steam turbine decreases, the SGM motor is controlled to increase its active power consumption, if it is in engine mode, or to decrease its active power production, if it is in generator mode, in order to reduce the power generated by the steam turbine. The reversibility of frequency converter 11 enables it to switch from generator mode to motor mode or vice versa.

[0061] However, the pressure available at the input of the steam turbine is controlled and compared with a Pmin limit value (FIG. 1). As soon as the pressure exceeds this limit value, valve 9 is controlled in the fully open position and the frequency of the fixed frequency AC voltage of the distribution network 5 is regulated by acting at the power level supplied by the SGM motor via the frequency converter.

[0062] Finally, it is noted that the invention is not limited to the described embodiment.

[0063] Indeed, in the embodiment described with reference to FIG. 1, the propulsion system comprises bow thrusters, each comprising electrical bow motor 28 driving a shaft equipped with a propeller and supplied by the distribution network 5 via autotransformers 29.

[0064] As shown in FIGS. 2, 3 and 4, in which we recognize principal heat engine 1 equipped with auxiliary electrical motor 4 which jointly drive motor shaft 2 provided with propeller 3 and frequency converter 11 connected to the distribution network 5 via circuit breaker 18 and transformer T, it is also possible, as a variant, to supply bow motors 28 from converter 11.

[0065] The bow thrusters can thus be supplied by the frequency converter when the ship is maneuvering, i.e. when the ship is moving at low speed and distribution network 5 is powered by auxiliary motors 6 associated with the respective generators G.

[0066] In the embodiment of FIG. 2, a number of bow motors, in this case two, can be supplied by a single frequency converter.

In the embodiment of FIGS. 3 and 4, the bow motors can be supplied by a number of frequency converters 11 connected in parallel.