Abstract: A method for operating a wind farm having a string (S1-S3) of wind turbines (100-100c) which are electrically connectable with each other and a grid (510, 550) is disclosed. Each wind turbine includes a rotor (106) with rotor blades (108), a power conversion system (118, 210, 238) mechanically connected with the rotor (106), and at least one auxiliary subsystem (105, 109).

Abstract: A common reference signal is used by a plurality of serially-connected power optimizers to manage a plurality of photovoltaic panels. It is determined whether an individual voltage output exceeds an individual limit. If so, a corresponding photovoltaic panel in the plurality of photovoltaic panels is adjusted to reduce the individual voltage output and the combined voltage output, where the combined voltage output is based at least in part on (a) the individual voltage output and (2) at least one other individual voltage output associated with another power optimizer. It is determined whether the combined voltage output relative to the common reference signal exceeds a maximum offset. If so, the corresponding photovoltaic panel in the plurality of photovoltaic panels is adjusted to reduce the individual voltage output and the combined voltage output.

Abstract: According to some embodiments, system and method are provided comprising calculating an output power setpoint for a thermal generation system for a first calculation cycle of a time window having at least one calculation cycle; calculating a net demand for dispatchable power to satisfy a required load demand after calculating an available renewable power generation; determining, responsive to determining that the net demand for dispatchable power exceeds the output power setpoint for the thermal generation system, whether a discharge power of an energy storage device satisfies a power gap; generating, responsive to determining that the discharge power is not larger than a power rating, a discharge command to discharge the energy storage device at the discharge power; and increasing, responsive to determining that the discharge of the energy storage device fails to satisfy the power gap, the output power setpoint for the thermal generation system for the first calculation cycle.

Abstract: This application discloses a photovoltaic power generation system and method, and the system includes an inverter and at least one shutdown apparatus. A type of the shutdown apparatus includes at least one of a shutdown device and an optimizer; and an input end of each shutdown apparatus is connected to a corresponding PV module, and power of the corresponding PV module is output. In the system, when a parameter of the inverter meets a preset condition, some shutdown apparatuses are turned off to lower an input voltage of the inverter, and ensure that an input end of the inverter has a direct current source, and the system can operate as usual; and the preset condition is that the input voltage of the inverter is greater than a first preset voltage, or an input current of the inverter is less than a first preset current.

Abstract: A system and a method of black start for a combined operation of wind power, photovoltaic power, energy storage, and thermal power includes a renewable energy alternating current microgrid module, a power transmission and distribution module, and a thermal power generation module, the power transmission and distribution module is coupled to the renewable energy alternating current microgrid module and the thermal power generation module respectively. The renewable energy alternating current microgrid module includes a photovoltaic unit, a wind power unit, and an energy storage unit. The power transmission and distribution module is configured to transmit the electrical energy generated by the renewable energy alternating current microgrid module to the thermal power generation module. The thermal power generation module is configured to start an auxiliary equipment using the electrical energy transmitted by the power transmission and distribution module.

Abstract: A common reference signal is used by a plurality of serially-connected power optimizers to manage a plurality of photovoltaic panels. It is determined whether an individual voltage output exceeds an individual limit. If so, a corresponding photovoltaic panel in the plurality of photovoltaic panels is adjusted to reduce the individual voltage output and the combined voltage output, where the combined voltage output is based at least in part on (a) the individual voltage output and (2) at least one other individual voltage output associated with another power optimizer. It is determined whether the combined voltage output relative to the common reference signal exceeds a maximum offset. If so, the corresponding photovoltaic panel in the plurality of photovoltaic panels is adjusted to reduce the individual voltage output and the combined voltage output.

Abstract: A wind farm for supplying electrical power into a supply grid. The farm includes wind power installations, a farm grid connecting the installations, and a power flow control device. The power flow control device is configured to connect the farm grid and the supply grid such that an electrical power generated by the installations can be supplied into the supply grid. The power flow control device has at least: a DC link configured to conduct at least the electrical power generated by the installations, an electrical energy store connected to the DC link, an inverter connected to the DC link and configured to inject at least the electrical power generated by the installations into the supply grid, and a controller configured to drive the inverter in such a way that the farm, at the supply grid, in the steady state appears to be dynamic like an electromechanical synchronous machine.

Abstract: A method for controlling a wind power installation or a wind farm is provided. The method includes establishing that there is a grid fault within an electrical power supply grid operated by a grid operator and to which the wind power installation or the wind farm is electrically connected via a point of common coupling; switching electrical switches of the wind power installation or the wind farm using a control unit of the wind power installation or the wind farm which is operated by a low-voltage power supply, so that the wind power installation or the wind farm is voltage-free; testing an electrical store for ensuring the low-voltage power supply once the grid fault has been established; and switching further electrical switches of the wind power installation or the wind farm to a predefined switching state in which start-up of the wind power installation or the wind farm is possible.

Abstract: Provided is a method of feeding electric power at a grid connection point into an electric power grid having a grid voltage using a converter-controlled feeder, in particular using a wind energy system and/or of a storage unit. The method includes feeding the electric power into the electric power grid in a normal operating mode when no grid fault or grid malfunction has been detected in the electric power grid, and switching to a fault mode when a grid fault or grid malfunction has been detected, in which the grid voltage is increased or decreased. In the normal operating mode an active current is fed in in order to feed active electric power into the grid and if the need arises a reactive electric power is additionally fed into the grid by a reactive current. The combination of the active and reactive currents results in an apparent current.

Abstract: A power system includes an AC power supply, an AC filter circuit, an AC circuit breaker, and a first switch. The AC filter circuit includes an inductor having one end connected in series to an output end of the AC power supply, and a capacitor having one end receiving a voltage at another end of the inductor. The AC circuit breaker exists between the other end of the inductor and an electric power grid. The first switch switches a state between the one end of the capacitor and a wire connecting the other end of the inductor to the AC circuit breaker, between a connected state and a disconnected state. The AC power supply may be a generator and include a generator control unit controlling the generator. The generator control unit may turn off the first switch when the AC power supply operates in a predetermined standby mode.

Abstract: Electrical systems for connecting rotary electric machines to dc networks operating at different voltages V and W where V>W are provided, along with gas turbine engine arrangements incorporating such systems.

Abstract: A control system for controlling the power output of a plurality of renewable energy generators, a power network connecting those generators to a Point of Interconnection (PoI) with which the power network is connected to an external power grid, and measurement means configured to measure electrical parameters associated with the Point of Interconnection, wherein the control system is configured to: operate each renewable energy generator to achieve a respective current level at a terminal of the generator that is equal to a current set point; implement, during a grid fault event, a feedback control routine in which the control system: determines a measured value of an electrical parameter at the Point of Interconnection, determines a target value of the electrical parameter; and modifies the current set point based on the measured value and the target value of the electrical parameter.

Abstract: A method and apparatus for minimizing circulating currents on a power distribution line. In one embodiment, the method comprises dynamically adjusting a turns ratio of a tap changing transformer, the tap changing transformer coupled to a power grid distribution line that is also coupled to a plurality of microgrid branches wherein at least one microgrid branch of the plurality of microgrid branches comprises a distributed energy resource (DER), based on a reactive power measured locally to the tap changing transformer, to minimize current circulating on the power grid distribution line.

Abstract: The invention concerns a method for coupling to the grid a hydraulic unit having a synchronous generator, a runner, and wicket gates, the method comprises: a) a step of increasing the flow of water into the runner from a time t0 to a time t1 so that the rotation frequency of the rotor of the synchronous generator is, at time t1 equal to the frequency of the grid; b) a step of closing the circuit breaker at time t1, step a) further comprises a sub-step a1) executed from a time t2 to time t1, wherein the flow of water is adjusted so that, at time t1, the phase of the synchronous generator is aligned with the grid phase.

Abstract: A method and apparatus for no-break power transfer in a power distribution system, including providing, from a first power source, a first power supply to a power bus, disabling the first power supply from the power bus, and providing, from a second power source, a second power supply to the power bus, the second power supply having the second set of electrical characteristics.

Abstract: A method involves receiving power data measurements at nodes of an electrical power grid, the electrical power grid having multiple buses. For a first bus of the electrical power grid, an objective function is repeatedly minimized using the received power data measurements to determine estimated admittances between the first bus and other buses of the electrical power grid. The minimization of the objective function is linearly constrained by a repeatedly estimated sum of conductances and susceptances connected to the first bus. A minimum value of the objective function for the first bus is determined that corresponds to a maximum value of the estimated sum of conductances and susceptances. A topology of the electrical power grid associated with the first bus is determined based on the estimated admittances that correspond to the minimum value of the objective function and to the maximum value of the estimated sum of conductances and susceptances.

Abstract: Electrical power distribution system for supplying a set of fixed-frequency loads and a set of variable-frequency loads, includes a set of at least one fixed-frequency AC voltage generator and a set of at least one variable-frequency AC voltage generator, a DC distribution network supplying the variable-frequency loads by means of inverter stages, a first set of rectifier stages connected between the fixed-frequency generators and the distribution network, and a second set of rectifier stages connected between the variable-frequency generators and the DC distribution network. The first set of rectifier stages includes bidirectional rectifiers capable of providing a bidirectional transfer of power and protection means against fault currents connected between the bidirectional rectifiers and the distribution network.

Abstract: A method for operating an inverter-based resource includes monitoring a current magnitude in the inverter-based resource. The method also includes monitoring a voltage magnitude in the inverter-based resource. Further, the method includes comparing the current magnitude in the inverter-based resource to a primary current threshold. Moreover, the method includes comparing the voltage magnitude in the inverter-based resource to a voltage threshold. As such, the method also includes disabling switching of the switching elements of the power converter when the current magnitude increases above the primary current threshold and the voltage magnitude decreases below the voltage threshold to bypass the switching elements of the power converter until excess energy in the inverter-based resource is dissipated.

Abstract: Systems and methods are disclosed to manage a microgrid with a hybrid energy storage system (HESS) includes deriving a dynamic model of a bidirectional-power-converter (BPC)-interfaced HESS; applying a first neural network (NN) to estimate a system dynamic; and applying a second NN to calculate an optimal control input for the HESS through online learning based on the estimated system dynamics.

Abstract: A parallel Marx generator topology capable of producing high power, high current output pulses is provided. The parallel Marx generator topology can include a plurality of Marx generators that operate in parallel to one another to jointly generate an output pulse. The topology can further include a pulse transformer configured to step up the voltage of the pulse created by the plurality of generators and also ensure that each Marx generator of the plurality of Marx generators is outputting substantially the same amount of current. The system can include a common interface that allows for fault detection and control of all the Marx generators using one common control panel. The parallel Marx generator topology can allow for a high voltage, high current pulse to be generated using import/export compliant switches.

Abstract: A new system for producing electricity and fuel to produce electricity has 1) at least two sources of electricity, comprising any two of photovoltaic energy, tidal energy capture, wind mills and the utility interconnect system; 2) an alkaline electrolyzer including an alkaline fluid container, an alkaline fluid, an anode, a cathode and a thin foil; 3) the alkaline electrolyzer positioned downstream from a means for generating low voltage waves sufficient to lower the ground energy of the water, the low voltage means being connected to the electrical distribution box and providing treated water; 4) a fuel cell being connected to an electrical distribution box that is capable of routing electricity from the fuel cell, the fuel cell also being connected to the hydrogen storage area to receive hydrogen gas to convert to electrical energy for dispersion to the utility interconnect system and/or the system for producing electricity; 5) an electricity distribution box, connected to the current best energy source to

Abstract: The disclosure provides a wind turbine generator and a control method thereof. The wind turbine generator comprises at least two power transmission systems connected each other in parallel and a control system comprising an upper controller and control subsystems corresponding to the power transmission systems and comprising bottom controllers. The bottom controllers monitor operating state parameters of functional units in corresponding power transmission systems, and when determining corresponding functional units meet abnormal conditions according to operating state parameters, send operating state parameters of corresponding functional units to the upper controller; the upper controller generates operating instructions when determining faults of the corresponding functional units occur according to operating state parameters of corresponding functional units, to control power transmission systems to work according to operation instructions.

Abstract: An electrical power system includes a system-level controller and a plurality of clusters of subsystems defining a stator power path and a converter power path for providing power to the power grid. The converter power path includes a partial power transformer. The system further includes a cluster transformer connecting each cluster to the power grid and a plurality of cluster-level controllers communicatively coupled with the system-level controller. Each of the clusters is communicatively coupled with one of the cluster-level controllers. Thus, the system-level controller regulates system-level active and/or reactive power based on required active or reactive power for the system, respectively, and compares the system-level active or reactive power with preferred values thereof.

Abstract: An electric power generation system and a method in an electric power generation system.

Abstract: Methods for arc detection in a system including one or more photovoltaic generators, one or more photovoltaic power devices and a system power device and/or a load connectible to the photovoltaic generators and/or the photovoltaic power devices. The methods measure voltage, voltage noise and/or power delivered to the load or system power device. The methods may compare one or more measurements, an aggregation of measurements and/or values estimated from the measurements to one or more thresholds, and upon a comparison indicating a potential arcing condition, an alarm condition may be set. Embodiments include an arrangement of photovoltaic generators and photovoltaic power devices for reduced-impedance voltage loops which may enhance arc-detection capabilities.

Abstract: Methods for arc detection in a system including one or more photovoltaic generators, one or more photovoltaic power devices and a system power device and/or a load connectible to the photovoltaic generators and/or the photovoltaic power devices. The methods measure voltage, voltage noise and/or power delivered to the load or system power device. The methods may compare one or more measurements, an aggregation of measurements and/or values estimated from the measurements to one or more thresholds, and upon a comparison indicating a potential arcing condition, an alarm condition may be set. Embodiments include an arrangement of photovoltaic generators and photovoltaic power devices for reduced-impedance voltage loops which may enhance arc-detection capabilities.

Abstract: A power maintaining method of electric vehicle includes the following step. In step 01, an energy power is provided by a main battery pack to drive a first electric vehicle (EV) moving to a first power supply station. In step 02, a first swappable battery pack is installed on the first EV at the first power supply station, and the first swappable battery pack is electrically connected to the main battery pack of the first EV so that the main battery pack is charged by the first swappable battery pack. In step 03, the first EV is driven to a second power supply station from the first power supply station. In step 04, the first swappable battery pack is uninstalled from the first EV at the second power supply station. In addition, an electric vehicle and a power supply station is disclosed in the present application.

Abstract: A method for determining a speed (nG) of a generator unit which has an electric machine (100) with a rotor winding (110) and a stator winding (120) and a rectifier (130) connected thereto, via which rectifier the electric machine (100) is connected to an electrical system (150) of a motor vehicle, the speed (nG) being determined depending on the plot of an excitation current (IE) flowing through the rotor winding (110) of the electric machine (100). In particular, the speed is determined from a known relationship between the speed, the frequency of the excitation current, the number of pole pairs and optionally the number of phases when there is an error that leads to a constant phase voltage being output.

Abstract: The present invention relates to a fault diagnosis for a photovoltaic system. A fault diagnosis apparatus includes a temperature sensor unit measuring both an internal temperature value of the junction box and a surface temperature value of the solar module; a voltage sensor provided in the junction box; and an operation unit determining where a fault occurs among the solar module, an inside of the junction box, and the inverter by comparing measured values of the temperature sensor unit with a measured value of the voltage sensor. According to the present invention, initial investment cost is inexpensive. In addition, it is possible to detect solar module faults that are difficult to be checked by the naked eye.

Abstract: A method and associated control device for synchronizing a turbine with an alternating current network having a network frequency, having the following steps: A) accelerating the turbine up to a frequency in the range of the network frequency; B) sensing an angle difference between the turbine and the alternating current network; C) sensing a speed difference between the turbine and the alternating current network; D) accelerating or decelerating the turbine such that the turbine follows a desired trajectory, wherein the desired trajectory is a trajectory calculated in advance that indicates, in dependence on the angle difference, a desired speed difference that should be present such that a target angular position between the turbine and the alternating current network suitable for synchronous feed-in is achieved when the speed of the turbine and the speed of the alternating current network correspond.

Abstract: A method of generating electricity by an alternator and a generator is disclosed. The method includes: connecting in series stator coils of two multi-pole permanent-magnet generators that can generate equiamplitude alternating currents of different frequencies to generate equiamplitude alternating currents of different frequencies that are superimposed to generate an amplitude-modulation alternating current with envelope lines having an amplitude that changes with a voltage difference between two equiamplitude alternating currents; rectifying the amplitude-modulation alternating current positively and negatively through a controllable rectifying circuit; and filtering to output an alternating current having frequency of the envelope lines.

Abstract: A method, system and computer program product enhance the commercial value of electrical power produced from a wind turbine production facility. Features include the use of a premier power conversion device that provides an alternative source of power for supplementing an output power of the wind turbine generation facility when lull periods for wind speed appear. The invention includes a communications infrastructure and coordination mechanism for establishing a relationship with another power production facility such that when excess electrical power is produced by the wind turbine facility, the excess may be provided to the power grid while the other energy production facility cuts back on its output production by a corresponding amount. A tracking mechanism keeps track of the amount of potential energy that was not expended at the other facility and places this amount in a virtual energy storage account, for the benefit of the wind turbine facility.

Abstract: A lip shroud for a dragline lip configured to prevent wear on the dragline lip and to prevent decoupling therefrom during operations. The lip shroud comprises of a first sidewall having a first abutment surface provided with an opening; a second sidewall having a second abutment surface wherein the second sidewall has a securing portion configured for coupling to a lock device on the dragline lip; and a center- wall having a third abutment surface, the center wall connecting the first sidewall and the second sidewall wherein the first, second and third abutment surfaces define a channel to receive an edge portion of the dragline lip.

Abstract: A hollow motor module as a combination of a motor and a speed reducer is disclosed. The motor includes an outer stator, a first rotor and a plurality of second rotors. The first rotor is peripherally provided with a first coil and is installed in the outer stator. Each of the plural second rotors is peripherally provided with a second coil and is installed in the first rotor. The second rotor has a coupling portion extending out of the first rotor. The outer stator has first magnets that work with the first coil to magnetically excite the first rotor to rotate. The first rotor has second magnets for the second rotors. The second magnets work with the corresponding second coils to magnetically excite the second rotors to rotate synchronously. The speed reducer is connected to the coupling portions of the second rotors.

Abstract: The invention relates to a control loop (10) which is installed in a voltage regulator of a motor vehicle alternator and controls an output voltage of the latter by adjusting an excitation current of the alternator. The control loop includes, at the input, means for measuring (31) the output voltage by sampling, generating a measurement signal (Um), error-calculation means (13) generating an error signal (e) equal to a difference between the measurement signal (Um) and a set value (Uo), means for processing the error signal (e) including an amplifier (14) and generating a control signal (Ysat) and, at the output, means (35) for generating a control signal (PWM) controlling excitation control means in accordance with the control signal (Ysat). According to the invention, the processing means also include a phase-advance filter (24).

Abstract: A direct current power system includes a common direct current (DC) bus configured to supply power to a plurality of loads. A plurality of alternating current (AC) to DC converter bridges supply DC power to the common CD bus. Each of the AC to DC converter bridges is connected to the common DC bus by at least one split DC link. The at least one split DC link includes a small capacitor connected across output terminals of the respective AC to DC converter bridge and at least one diode coupled between two terminals of the small capacitor and the large capacitor in a way to block an instantaneous current flow from the common DC bus to the respective AC to DC converter bridge in case of a fault of the AC to DC converter bridge.

Abstract: A method and a controller for continuously operating a plurality of electric energy generating machines during a high voltage condition at a point of common coupling of the plurality of electric energy generating machines are provided herein. The method includes a) sensing a voltage level at the point of common coupling exceeding a permitted voltage level; b) curtailing an active power output of the plurality of electric energy generating machines such that a reactive capability of the plurality of electric energy generating machines is increased; c) establishing a set point of an electric quantity being present at the point of common coupling such that a reactive electric component providable by the electric energy generating machines is increased; and d) controlling an electric energy generating machine based on the set point of the electric quantity such that the high voltage condition at common coupling is at least partially remedied.

Abstract: Systems and methods for controlling an auxiliary power unit (APU) are provided. The systems and methods may comprise detecting an operating condition of the APU, determining an optimal APU frequency in response to the operating condition, and setting an angular velocity of the APU to the optimal APU frequency.

Abstract: The present invention concerns a method of feeding electric power into an electric network wherein the feed is effected by means of at least one wind power installation with a first feed-in arrangement at a feed-in point into the electric network, and the feed is effected in dependence on electric parameters in the network and measurement values of the electric parameters or measurement values for determining the electric parameters are detected at measurement times at predetermined time intervals and wherein the measurement times are synchronized to an external time signal available outside the first feed-in arrangement.

Abstract: A power integration module includes a first input connector, a second input connector, an output connector, a switch unit, a determining unit. The first input connector and the second input connector are electrically connected to a first power supply and a second power supply of a power supply module. The output connector is electrically connected to an electrical load. The switch unit is coupled between the first input connector, the second input connector and the output connector. When the switch unit is turned on, the first input power supply and the second input power supply are integrated in parallel and outputted to the output connector to the electrical load. Moreover, an electronic device with a plurality of power integration modules is provided. Thus, the wrong connection is prevented and the condition that the power supplies of different electrical parameters are connected in parallel is avoided.

Abstract: The cascaded multilevel inverter is considered to be a promising topology alternative for low-cost and high-efficiency photovoltaic (PV) systems. However, the leakage current issue, resulting from the stray capacitances between the PV panels and the earth, remains a challenge in the photovoltaic cascaded multilevel inverter application. The present invention presents leakage current suppression solutions for the PV cascaded multilevel inverter by introducing properly arranged and designed passive filters. The embodiments of the invention do not include an active semiconductor device, and as such, the leakage current suppression techniques of the present invention retain the simple structure of the cascaded inverter and do not complicate the associated control system.

Abstract: An integrated oscillator circuit comprises an oscillator configured to be switched between a first frequency and a second frequency. A switching circuit receives an input representing a target frequency and switches the oscillator between the first and second frequencies at intervals determined by the input, so as to cause the average output frequency of the oscillator to approximate the target frequency.

Abstract: An exemplary method and apparatus for detecting islanding conditions of a distributed grid are disclosed, wherein transfer of power through a power electrical unit is controlled on the basis of a control reference. The apparatus includes a first stage and a second stage performing a respective portion of the method. The first stage injects a reactive component to the control reference, and, for at least one electrical quantity of the grid, determines a change in the quantity induced by the injected component, and determines, on the basis of the change in the electrical quantity, whether to move to the second stage of the method.

Abstract: Described is a controller, wherein the controller is adapted: to control a transformation ratio of a park transformer of a wind turbine park including wind turbines connected to a first node. The park transformer is connected between a first node and a second node which is connected to a utility grid to which electric energy produced by the wind turbines is to be delivered. Further a wind park and a control method are described.

Abstract: A method and a system are described for island operation of at least two wind turbines associated with a wind farm, wherein said wind farm is configured for providing power generated by wind turbines in said wind farm to a main grid and wherein the method comprises: detecting at least two or more deactivated wind turbines in said wind farm, said deactivated wind turbines being disconnected from said main grid; configuring at least one islanded local grid for electrically connecting said two or more deactivated wind turbines; activating at least one of said deactivated wind turbine using a black start operation; and, connecting said at least one activated wind turbine and at least one of said deactivated wind turbines to said local grid, said activated wind turbine acting as a power supply for said at least one deactivated wind turbine connected to said local grid.

Abstract: A system for supplying power to a drilling rig has an engine/generator with an output line so as to transfer power therefrom, an energy storage system connected to the engine/generator, and a load connected to the energy storage system such that power from the energy storage system is directly transferred to the load and such that power from the engine/generator is electrically isolated from the load. The engine/generator has a capacity greater than an maximum power requirement of the load. The energy storage system can include at least one battery.

Abstract: A power transmission system may include a plurality of renewable-energy devices such as wind turbines or subsea turbines. The devices are connected together in parallel to a subsea cable that carries an ac transmission voltage. Each device includes a turbine assembly that is rotated by wind or water current flows, and a variable speed ac induction generator. A power converter is connected to the subsea cable and is used to interface the generators to a supply network or power grid. The power transmission system is operated such that an indicated operating speed of one or more of the devices is used to control the power converter (e.g. the PWM strategy that is used to open and close the power semiconductor devices) to achieve desired stator electrical quantities at each generator.

Abstract: An electric power control system is provided. The power control system includes a first node to which a plurality of power production entities are connectable for combining their power output signals as a first power signal, a transformer adapted to transformer the first power signal at the first node to a second power signal at a second node connectable to a load, the second power signal having a higher voltage than the first power signal, at least one capacitor connectable to the first node and/or to the second node, a control unit adapted to control the connection of the at least one capacitor to the first node and/or to the second node such that a power loss caused by transmission loss of the power output signals from the power production entities to the load is minimized.

Abstract: The present invention addresses the problem of avoiding that wind turbine voltage levels within a wind power plant do not exceed predetermined overvoltage and/or undervoltage protection levels. In particular, the present invention relates to shifting of an output voltage level of a wind power plant in order to protect an internal power plant grid against overvoltages.

Abstract: An apparatus for collecting energy in connection with a sheave system in a hoisting apparatus provided with a sheave system. The apparatus includes at least one generator including a rotor and at least one stator. The rotor is connected rigidly to a sheave of the sheave system, and the at least one stator is connected rigidly to the sheave system such that when the load of the hoisting apparatus is rising or lowering, said at least one sheave rotates, whereby the rotor rotates simultaneously but the stator does not rotate, whereby electric energy is induced in the stator. The apparatus further includes electric energy storage, a device for modifying induced electric energy and storing it in energy storage; and a device for supplying energy from the energy storage to at least one consumption device. The consumption device may be, for example, a working lamp, sensor, measuring device, communications device, signal device, charging plug or a combination of these mounted in connection with the sheave system.