Patent ID: 12199520

The figures illustrate specific ways of implementing the present invention and are not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set.

DETAILED DESCRIPTION OF THE INVENTION

FIG.1illustrates a wind turbine system embodiment. The wind turbine has three rotor blades BL for driving an electric generator GN located inside the nacelle NC on top of a tower TW. A Medium Voltage (MV) power converter system CNV is connected to the electric generator of the wind turbine, and this converter CNV is positioned inside an enclosure MV_C provided by a housing H, preferably a housing with a floor, wall elements, and a top part serving to provide an enclosed space MV_C preventing unauthorized access to the MV equipment. In the following an automated procedure for access to the enclosure MV_C through access doors with controllable locks will be described. Such procedure allows fast and yet safe access for service of the MV converter and further MV equipment inside the enclosure MV_C.

FIG.2shows an embodiment of the housing H ofFIG.1. The housing H may be formed by a standard metal container in which two walls are inserted to provide three separate compartments: a control compartment CT_C in one end, an MV compartment MV_C which forms the enclosure for the MV converter system CNV connected to the wind turbine generator GN, and at the opposite end a switchgear compartment SWG_C enclosing switchgear SWG and a transformer TRM for connection of the wind turbine system to the public electric network NT, as well as necessary circuit breakers or contactors for electrically de-connecting the MV compartment MV_C. A door D allows a person to access the control compartment CT_C in which a user interface UI allows the person to request access to the MV compartment MV_C, e.g. by pushing a button, operating a handle or a touch sensitive display etc. An access door LD with a controllable locking mechanism serves to block access to the MV compartment MV_C unless the MV equipment therein has been disconnected and de-energized through a safety procedure to avoid any lethal accidents by access.

The user interface is connected to an access control system which in response to the access request initiates an automated safety procedure ending by unlocking the access door LD to the MV compartment MV_C.

The necessary circuit breaker(s) and/or contactor(s) and corresponding motorized draw-out actuator(s) used for disconnection of the MV converter system CNV are preferably positions inside the switchgear compartment SWG_C.

FIG.3illustrates a block diagram of an embodiment with the access control system ACS having a processor which is programmed to perform a safety access algorithm to allow access via the access door LD to the MV compartment in response to an access request from the user interface UI by controlling the locking mechanism of the access door LD to open after the safety procedure has been completed, thus ensuring that all necessary steps have been performed for eliminating personal contact with any electrically hazardous MV parts inside the MV compartment. The access control system ACS first opens a circuit breaker CB1to disconnect electrical connection between the circuit breaker and incoming or outgoing electric terminals connected to the MV converter system CNV. Next, a motorized actuator MA1is activated to draw out the circuit breaker CB1, or at least a part of it, to provide a physical separation between the circuit breaker CB1the incoming or outgoing electric terminals connected to the MV converter CNV. The access control system ACS awaits a feedback signal indicating that the physical separation of the circuit breaker CB1has been established, and in response, it transmits a feedback signal to the user interface UI indicating that the physical separation has been completed, Next, a self discharge procedure is activated to electrically discharge one or more AC-filter capacitors FCP connected to filter harmonic components from the MV converter system CNV. Further, a discharge circuit DCH including dump resistors can be activated to perform the discharging in a controlled manner, or the AC-filter capacitors FCP may be self-discharged by already connected discharge resistors. During the discharging, the access control system may determine whether a discharge criterion for the discharge of the AC-filter capacitor(s) FCP has been met, e.g. by sensing a charged voltage of the AC-filter capacitor(s) FCP and compare it with a predetermined threshold voltage, e.g. 75 V, or by merely starting a timer and wait for a predetermined period to lapse, e.g. 5 minutes or 10 minutes or the like. Further, a discharge procedure is activated for electrical discharge of DC cell capacitors forming part of the MV converter system CNV. When the discharge criterion for the AC filter capacitor(s) FCP and the DC cell capacitors are both met, and the physical separation of the circuit breaker CB1has been established by means of the motorized actuator, a ground switch GR1is activated to electrically ground the MV converter CNV. Finally, after this electrical grounding, the kick of the access door LD is controlled to open the access door LD to gain access to the MV compartment.

The safety access algorithm may comprise further steps of activating switches or circuit breakers, motorized physical separations as well as grounding switches to disconnect further electrical branches which have components placed inside the MV compartment, e.g. an electric branch serving to pre-charge the MV converter CNV before the ground switch GR1is activated to perform the electrical grounding. Furthermore, a further ground switch may be used to ensure safe access for further enclosures, e.g. switchgear SWG.

In some cases, further automated and/or motorized switches or circuit breakers as well as grounding switches are included in the safety access algorithm, and further the automated procedure may comprise providing access to the switchgear SWG and thus opening the HV switchgear for disconnecting from the public network NT as well as subsequently electrically grounding of the switchgear SWG.

FIG.4illustrates steps of a method embodiment starting with receiving a request R_RQ for access from outside the user interface outside the MV compartment. This initiates the following steps, including opening O_CB a circuit breaker to disconnect electrical connection between the circuit breaker and incoming or outgoing electric terminals connected to the MV converter. After this, drawing out DW_CB at least a part of the circuit breaker by activating a motorized actuator to provide physical separation between the circuit breaker and MV converter. When receiving R_FB_CB feedback that the circuit breaker has been physically separated from the MV converter, information is fed back FB_CB to the user interface that physical separation is completed. After this, a discharge procedures A_DCH1and A_DCH2are activated to electrically discharge AC-filter capacitors connected to filter harmonic components from the MV converter and to electrically discharge one or more DC capacitors inside the MV converter. The safety access algorithm then determines D_DCC if a discharge criterion for discharge of the AC-filter capacitors and the DC capacitors has been met, e.g. by checking a simple tinier to have reached a predetermined time period, or sensing if charging voltage has dropped to a predetermined charge voltage threshold. If the discharge criterion is met, a grounding switch A_GR is activated to electrically ground the MV converter. Finally, when grounded, activating A_LD the locking mechanism to unlock the access door to the enclosure to gain access to the enclosure.

In preferred embodiments, the method may comprise opening a second circuit breaker or contactor and providing physical separation by means of a motorized actuator, before the access door is opened to gain access to the enclosure with the MV converter system. Especially, such second circuit breaker or contactor serves to disconnect a pre-charge circuit branch from the MV converter system.

It is to be understood that the access control system is preferably further arranged to reverse the process after request from the user having left the MV compartment, e.g. by operating the user interface in the control compartment. The access door is then locked to block access, and the grounding switch(es), motorized actuator(s) and electric contactor(s) or circuit breaker(s) are then operated to a normal function mode where all MV components are connected,

FIG.5illustrates an electric circuit diagram of vital parts of a wind turbine system for 3-phase connection to the electric public network via a transformer and switchgear SWG. The circuit includes circuit breakers CB1, CB2, motorized actuators MA1, MA2to provide electric disconnection and physical separation of contact elements, and grounding switch GR1for electrically grounding to ensure zero voltage at electrically conducting elements before gaining access to the MV compartment, as explained in the above description. Grounding switch GR2can be activated in case access to the switchgear SWG compartment is necessary. Especially, access to the switchgear SWG compartment may be necessary to service circuit breakers/contactors CB1, CB2. The system comprises a modular MV converter system CNV including modular cells for DC-AC conversion of electric power from the wind turbine generator, and an AC filter capacitor bank ECP for filtering harmonic components from the line side converter (LSC). LSC is connected to the switchgear SWG via circuit breaker CB1, and further LSC is connected to the switchgear SWG via pre-charge resistors PCR, which can be disconnected by circuit breaker/contactor CB2. The pre-charge resistors PCR are further connected via fuses FS. Before electrically grounding by means of the grounding switches GR1and GR2, DC cell capacitors (not shown) in the MV converter system CNV should be discharged to a voltage below a predetermined threshold e.g. 50 V. Still further, the switchgear SWG is connected to still another circuit branch, namely to provide power to auxiliary circuits AUX, e.g. via a transformer. Such auxiliary circuits are preferred to operate also in case of service being performed on the MV converter system CNV and related circuits. Especially, the auxiliary circuits AUX include vital functions of the wind turbine, such as powering hydraulics and controlling yaw and pitch etc.

All of the components CB1, CB2, MA1, MA2, GR1, GR2, as well as 33/66 kV circuit breakers(s) are all intended to be physically positioned inside a separate switchgear compartment, i.e. an enclosure separate from the enclosure housing the MV converter system CNV. Normally, the switchgear SWG is associated with equipment for 33 or 66 kV circuit breakers in turbines having Low Voltage Converters. However, in a wind turbine with a MV converter system, the switchgear SWG involves33(or 66 kV) circuit breakers as well as MV (1-35 kV) circuit breakers and their related equipment (motorized actuators MA1, MA2and ground switches GR1, GR2).

The electrical switches or circuit breakers/contactors CB1, CB2with motorized actuators MA1, MA2for providing physical and visible separation of contact elements are commercially available and thus standard components for MV equipment. The discharge circuit necessary for automatically discharging the AC-filter capacitors FCP (as well as e.g. sensing charge voltage of the capacitors FCP) is not shown, but such circuit is also known by the skilled person.

The access control system may be implemented as a computerized system involving such as a DSP, a PLC, an FPPA or the like with a processor and associated memory in which the safety access algorithm is stored. The access control system may be wired and/or wirelessly connected to control the circuit breaker(s), motorized actuator(s), user interface (for receipt of request by a user and feeding back information of the safety access procedure), as well as to automatic discharge circuit and to operate the controllable access door locking mechanism.

To sum up: the invention provides a wind turbine system with a medium voltage (MV) converter system for converting electric power by the wind turbine generator. A housing, e.g. a placed on the ground near the wind turbine tower, encloses the MV converter system and some other related components, to block access. An access door with a controllable locking mechanism is controlled by an access control system which unlocks the access door after execution of a safety access algorithm. This algorithm involves activating electrical disconnection of the MV converter and activating motorized actuators to provide a physical separation between the electric terminals connected to the MV converter system. A feedback signal is transmitted to outside the enclosure, that the physical separation has been established. Further, a discharge procedure is activated to electrically discharge at least one AC-filter capacitor connected to filter harmonic components from the MV converter system as well as discharging of DC cell capacitors inside the MV converter system. When said physical separation is established and a discharge criterion is met for discharge of the AC-filter capacitor and DC cell capacitors, a grounding switch is activated to electrically ground the MV converter system, and subsequently, the access doors are unlocked. This allows a person to provide service to the potentially dangerous MV equipment in a safe and automated way after request. The housing preferably has a control compartment where a person can request access and await opening of the access door for safe access to the MV converter system.

Although the present invention has been described in connection with the specified embodiments, it should not be construed as being in any way limited to the presented examples. The scope of the present invention is to be interpreted in the light of the accompanying claim set. In the context of the claims, the terms “including” or “includes” do not exclude other possible elements or steps. Also, the mentioning of references such as “a” or “an” etc. should not be construed as excluding a plurality. The use of reference signs in the claims with respect to elements indicated in the figures shall also not be construed as limiting the scope of the invention. Furthermore, individual features mentioned in different claims, may possibly be advantageously combined, and the mentioning of these features in different claims does not exclude that a combination of features is not possible and advantageous.