System for providing electrical power to a wind turbine component

Systems for providing electrical power to one or more wind turbine electrical components is provided comprising an electrical grid and an auxiliary power source for providing electrical power, and one or more wind turbines. Each of the wind turbines includes a wind turbine generator, one or more electrical components, a main voltage transformer for connecting the wind turbine generator to the grid and a switchgear arranged between the main voltage transformer and a point of connection to the grid. One or more switches for alternately connecting either said electrical grid or said auxiliary power source to the switchgears of the wind turbines are provided. The switchgears comprise a switchgear voltage transformer, the switchgear voltage transformer includes primary and secondary windings, the primary windings receiving power from the electrical grid or auxiliary power source, and the secondary windings delivering electrical power to the wind turbine electrical components.

This application claims the benefit of European Patent Application EP 13382116.5 filed on 27 Mar. 2013, the entire contents of which is hereby incorporated by reference for all purposes.

The present disclosure relates to systems and methods for providing electrical power to one or more wind turbine components.

BACKGROUND ART

Wind turbines may be arranged together forming a wind park, with a single point of connection, i.e. the PCC (“Point of Common Coupling”). Wind parks may comprise a substation including e.g. wind park transformers that convert power from the wind park voltage to a grid voltage. Such a substation may further include wind park control systems e.g. a supervisory control and data acquisition system (SCADA).

Wind parks may be arranged on land (“onshore”), or in the water (“offshore”), either as a plurality of floating wind turbines or wind turbines on pillars fixed in the sea bed.

It is known to provide an auxiliary power source, such as e.g. a diesel generator for supplying power to wind turbines when a connection with the grid is lost. Connection with the grid may be lost during planned maintenance, or during installation, but also during normal operation in case of a problem in the grid.

In a wind turbine, electrical components may be categorized into three levels, as follows: Level 1 electrical components are those components which are considered critical. These level 1 components are required to operate continuously, even during stand-by situations, i.e. when a wind turbine is disconnected from the electrical grid, and no electrical power is thus available.

Level 1 components may include components related to communication, and control and manoeuver of the gas insulated switchgear (GIS). It may further include air conditioning systems, sensors, PLCs, beacons and protective systems among others. The power required for these components may e.g. be around 15 kVA.

Level 2 electrical components may include those components which are less critical; these components may be required to operate only occasionally during stand-by situations. Level 2 components may include lubrication pumps, lighting systems, the service lift, pitch and yaw systems among others. The power required for these components may amount to e.g. around 30 kVA.

Finally, level 3 electrical components may not be required to operate during stand-by situations. Level 3 components may include e.g. cooling fans and pumps among others.

So at least for the level 1 components and at least occasionally for the level 2 components, electrical power supply must be available even in case of grid loss.

A plurality of auxiliary power generators, e.g. diesel generators, may be installed at individual wind turbines to be able to supply power to each wind turbine individually. If an auxiliary power generator is provided for each individual wind turbine, a problem is the high cost involved.

Alternatively, at least one more powerful auxiliary power generator may be provided at the central substation supplying all wind turbines simultaneously. If one auxiliary diesel generator is provided for a wind park, the logistics involved in providing fuel to each of the generators can be troublesome, in particular in the case of an offshore wind park.

Having a single more powerful auxiliary diesel generator providing electrical power to all wind turbines in the case of grid loss however may also have other disadvantages. One technical problem may be that the auxiliary diesel generator is over-dimensioned to take into account the in-rush of current at start-up, and the power losses associated with the reactive loads on the one or more transformers within each wind turbine.

One known approach is represented inFIG. 1. Reference sign100indicates the electrical grid, and reference sign200refers to an auxiliary power generator, for example a diesel generator. A switch150may be provided to alternatively connect the wind turbines either to the electrical grid or to the auxiliary power generator.

Each wind turbine may comprise a circuit breaker, which is commonly arranged in a gas insulated switchgear900for power ranges relevant to this sort of implementation, and a main wind turbine transformer300. The main transformer may convert power from 66 kV as delivered from the grid or from the auxiliary power generator to 0.9 kV, the voltage level of the generator600of the wind turbine. The rating of the main transformer may be e.g. 6500 kVA.

A secondary wind turbine transformer400will further transform the power from 0.9 kV to the voltage level required by the electrical components of the wind turbine, such as e.g. lighting systems, pitch systems, pumps, cooling fans, etc. This voltage level may be 0.4 kV. The rating of the secondary wind turbine transformer may be e.g. 200 kVA in order to be able to feed electrical components of all levels (levels 1, 2 & 3).

The electrical components may be divided into level 1 components800, which always need power supply and for which an interruption of the operation cannot be accepted and level 2 and 3 components700, for which interruption of the operation is not necessarily problematic. To this effect, an uninterruptible power supply500(UPS) may be added to the level 1 critical electrical components' circuit. Additionally, circuit breakers may be arranged both for the level 1 circuit and for the levels 2 and 3 components. The circuit breaker250may be opened in case of grid loss, and only selectively closed so that only power is delivered to those components when needed.

In the event of an interruption of the power supply from the main grid100, the uninterruptable power supply associated with the level 1 critical electrical components may continue to function for e.g. approximately 30 minutes. However beyond these 30 minutes, the auxiliary power generator will have to deliver the required power via the transformers.

At least one problem related with this kind of arrangement is the major power losses in the main transformer300.

In examples of the present invention, at least some of the aforementioned problems are at least partially resolved.

SUMMARY

In a first aspect, a system for providing electrical power to one or more wind turbine electrical components is provided comprising an electrical grid and an auxiliary power source for providing electrical power, and one or more wind turbines. Each of the wind turbines includes a wind turbine generator, one or more electrical components, a main voltage transformer for connecting the wind turbine generator to the grid and a switchgear arranged between the main voltage transformer and a point of connection to the grid. One or more switches for alternately connecting either said electrical grid or said auxiliary power source to the switchgears of the wind turbines are provided. The switchgears comprise a switchgear voltage transformer, the switchgear voltage transformer includes primary and secondary windings, the primary windings receiving power from the electrical grid or auxiliary power source, and the secondary windings delivering electrical power to the wind turbine electrical components while bypassing the main voltage transformer.

A switchgear may be regarded as the combination of electrical disconnect switches, fuses or circuit breakers used to control, protect and isolate electrical equipment. A switchgear may generally include a voltmeter measuring the voltage in secondary windings of a voltage transformer. The voltmeter may be used to detect electrical power supply from the grid, i.e. as long as a voltage is present, electrical power is supplied by the grid. In alternative arrangements, a voltmeter or any other device suitable for detecting the presence of power supply in the electrical grid.

In accordance with this first aspect, a voltage transformer of the switchgear which ordinarily is only used for lowering the high line voltage e.g. approximately 66 kV down to e.g. approximately 120-400V, for measuring voltage and for detecting whether there is power supply from the grid or not is additionally used to supply power to one or more wind turbine components. By using this transformer, the main transformer may be bypassed and so the losses may be reduced. This may reduce the use of (diesel) fuel of an auxiliary power generator.

In some examples, the wind turbine electrical components may be divided according to at least two different levels, wherein a first level is defined for electrical components requiring permanent operation. In these examples, optionally a second level is defined for electrical components requiring occasional operation during stand-by situations and a third level is defined for electrical components not required during stand-by situations.

In some examples, a switch for alternately connecting the first level wind turbine electrical components to the switchgear voltage transformer secondary windings or the main transformer may be provided. In case of grid connection the level 1 components may receive electrical power in a conventional manner, i.e. through the main transformer and possibly a secondary transformer. In case of grid loss, the switch may ensure that electrical power is delivered through the transformer of the switchgear.

In alternative examples, instead of switches or in addition to switches, circuit breakers may be used to establish the same effect. In some examples, one or more circuit breakers for disconnecting the second level and/or third level wind turbines electrical components may be provided.

Optionally, a switch for alternately connecting the second level wind turbine electrical components to the switchgear voltage transformer secondary windings or to the main transformer may be also provided.

The auxiliary power source used may be a liquid fuel generator, optionally a diesel generator. However, in other examples, any other auxiliary power source may be used, including a renewable energy source. For instance, an offshore wind turbine may have solar power or wave power system for the collection, storage and supply of the minimum power required for the operation of first level electrical components, and occasionally, second level electrical components.

In another aspect, a method for providing electrical power to one or more wind turbine components when no power is supplied by a power grid is provided for systems substantially as hereinbefore described. The method comprises detecting a drop in power supply from the grid, switching the power supply to the switchgear from electrical grid to the auxiliary power source, connecting the first level electrical components to the secondary windings of the switchgear transformer, and operating the auxiliary power source.

In this aspect, a method of operating e.g. a wind park is provided in which electrical power supply may be ensured in an efficient manner, even when no power is delivered from the electrical grid.

In some examples, when no power is supplied by the power grid, the method may further comprise selectively connecting one or more electrical components other than first level electrical components to the secondary windings of the switchgear transformer. By selectively connecting one or more electrical components of e.g. second level electrical components or e.g. one wind turbine at a time, the power that needs to be supplied through the switchgear may be kept to a minimum.

Additional objects, advantages and features of examples of the present invention will become apparent to those skilled in the art upon examination of the description, or may be learned by practice of the invention.

DETAILED DESCRIPTION

FIG. 2schematically illustrates an example of a system for supplying power to one or more electrical components of a wind turbine.

The reference sign100refers to the electrical grid, or e.g. to a transformer of a substation connecting an offshore wind park to a high voltage transmission line (either High Voltage DC or High Voltage AC).

An auxiliary power source, such as e.g. a diesel generator200may be provided at the substation as well. Any form of auxiliary power source could be used, but diesel generators are the most common. In some examples, a single auxiliary power source may be sufficient to supply power to all wind turbines during standby situations. The single auxiliary power source may be arranged at an offshore substation in case of an offshore wind park. In another example, a plurality of auxiliary power sources may be arranged at the substation.

A switch150may alternatively connect a wind turbine to either the electrical power from the grid or the auxiliary power source. Reference sign300refers to the wind turbine main transformer (as before) that transforms power to the voltage level of the wind turbine generator600.

As before, a secondary transformer400may further transform the voltage to a suitable level for various electrical components of a wind turbine, e.g. 0.4 kV.

A switchgear, optionally a gas insulated switchgear900is arranged “upstream” from the main transformer and may generally serve to control, protect and isolate electrical equipment. A transformer which ordinarily is used only in connection with a voltmeter, may be used to supply electrical power to electrical components of a wind turbine. Depending on which electrical components are involved, and depending on the electrical power required at any moment, it may be necessary to “upgrade” a standard switchgear transformer to be able to deliver sufficient power.

In this example, electrical components of the wind turbine may be divided into level 1 components800and level 2&3 components700. The level 1 components' operation may never be interrupted, and to this end a standard Uninterruptable Power Supply (UPS)500may be foreseen. In case of grid loss, it will generally not be possible to have electrical power immediately delivered from the auxiliary power source. For example, a diesel generator needs to be started up and warmed up before being able to deliver full power. The UPS500may be able to deliver electrical power for e.g. up to approximately 30 minutes or more. By then, the electrical power supply from the auxiliary power source should be established.

In this example, a switch450may alternatively connect the level 1 electrical components800to the transformer of the switchgear900or to the main and secondary transformers300and400. A first circuit breaker “upstream” from the UPS may be arranged for isolating the level 1 components. Similarly, a second circuit breaker may isolate, and disconnect level 2 and level 3 components.

In accordance with this arrangement, when electrical power is available from the grid, all electrical components may be connected to the grid through the main transformer300. When power is not available from the grid, power may be supplied to the level 1 components through the switchgear or the UPS.

A control signal indicating a switch from grid supply to auxiliary power supply may be generated at the level of a supervisory control and data acquisition system (SCADA) of a wind park and may be sent to all individual wind turbines.

FIG. 3schematically illustrates a similar example. In this illustrated example, a wind park comprising at least three wind turbines1000,2000and3000are shown. Each wind turbine1000,2000,3000comprises similar components, i.e. each wind turbine includes a switchgear with a voltage transformer for supplying power to the wind turbines' electrical components. However, they are only illustrated for one of them, namely wind turbine1000.

FIG. 4schematically illustrates a slightly different arrangement. The same reference signs used inFIGS. 2 and 3may denote the same or similar components. As in the previous examples, switchgear900may be used to supply power to various electrical components.

A slightly different arrangement of switches and circuit breakers is provided in this example. A first level switch450(as in the examples ofFIGS. 2 and 3) may alternatively connect the level 1 electrical components800to the transformer of the switchgear900or to the main and secondary transformers300and400. A second level switch550may alternatively connect the level 2 (and level 3) components to the transformer of the switchgear900or to the main and secondary transformers300and400. As in the previous example, first and second circuit breakers350and250may be provided.

In this example, selectively one or more level 2 components may also receive power from the switchgear. In order to keep the rating of the transformer of the switchgear to a reasonable limit, it is preferable that only very selectively level 2 components request electrical power. For example, only some level 2 components of wind turbine1000are provided with power in a first instance. In a second instance, only some level 2 components of wind turbine2000are provided with power. At that point in time, the level 2 components of wind turbines1000,3000and others may be disconnected.

It will be clear that further alternative arrangements of circuit breakers and switches may be used to selectively supply power to the different electrical components from either one source (the grid) or the other (the auxiliary power source).

FIG. 5schematically illustrates a part of a switchgear900that may be used in the different disclosed examples. Switchgear900may comprise a transformer having primary windings (or primary sets of windings)910and secondary windings (or secondary sets of windings)920. A voltmeter930may measure the voltage of the secondary windings. In case of grid loss, no voltage will be detected.

In the disclosed examples, the same voltage transformer that is normally used for voltage metering may be used to supply power to components of one or more wind turbines.

In alternative examples, the voltmeter (or any other device suitable for detecting the presence of power supply in the grid) does not necessarily need to be integrated in the switchgear. For example, a voltmeter may be arranged outside the switchgear. Alternatively, a portable voltmeter could also be used.

Although only a number of particular embodiments and examples of the invention have been disclosed herein, it will be understood by those skilled in the art that other alternative embodiments and/or uses of the invention and obvious modifications and equivalents thereof are possible. Furthermore, the present invention covers all possible combinations of the particular embodiments described. Thus, the scope of the present invention should not be limited by particular embodiments, but should be determined only by a fair reading of the claims that follow.