WO2017174085A1 - Commande d'une centrale éolienne dans un réseau électrique faible - Google Patents

Commande d'une centrale éolienne dans un réseau électrique faible Download PDF

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Publication number
WO2017174085A1
WO2017174085A1 PCT/DK2017/050088 DK2017050088W WO2017174085A1 WO 2017174085 A1 WO2017174085 A1 WO 2017174085A1 DK 2017050088 W DK2017050088 W DK 2017050088W WO 2017174085 A1 WO2017174085 A1 WO 2017174085A1
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Prior art keywords
power
wind turbine
reactive
generator
turbine generator
Prior art date
Application number
PCT/DK2017/050088
Other languages
English (en)
Inventor
Amit Gupta
Ryan Arya PRATAMA
Arun Kumar SHIVARAMAN
Manoj Gupta
Original Assignee
Vestas Wind Systems A/S
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Publication of WO2017174085A1 publication Critical patent/WO2017174085A1/fr

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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
    • H02J3/16—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load by adjustment of reactive power
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03D—WIND MOTORS
    • F03D7/00—Controlling wind motors 
    • F03D7/02—Controlling wind motors  the wind motors having rotation axis substantially parallel to the air flow entering the rotor
    • F03D7/0272—Controlling wind motors  the wind motors having rotation axis substantially parallel to the air flow entering the rotor by measures acting on the electrical generator
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03D—WIND MOTORS
    • F03D7/00—Controlling wind motors 
    • F03D7/02—Controlling wind motors  the wind motors having rotation axis substantially parallel to the air flow entering the rotor
    • F03D7/028—Controlling wind motors  the wind motors having rotation axis substantially parallel to the air flow entering the rotor controlling wind motor output power
    • F03D7/0284—Controlling wind motors  the wind motors having rotation axis substantially parallel to the air flow entering the rotor controlling wind motor output power in relation to the state of the electric grid
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/18—Arrangements for adjusting, eliminating or compensating reactive power in networks
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/381—Dispersed generators
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
    • H02J3/466—Scheduling the operation of the generators, e.g. connecting or disconnecting generators to meet a given demand
    • H02J3/472—For selectively connecting the AC sources in a particular order, e.g. sequential, alternating or subsets of sources
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
    • H02J3/48—Controlling the sharing of the in-phase component
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
    • H02J3/50—Controlling the sharing of the out-of-phase component
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2270/00—Control
    • F05B2270/10—Purpose of the control system
    • F05B2270/103—Purpose of the control system to affect the output of the engine
    • F05B2270/1033—Power (if explicitly mentioned)
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • H02J2300/28—The renewable source being wind energy
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/70—Wind energy
    • Y02E10/72—Wind turbines with rotation axis in wind direction
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/70—Wind energy
    • Y02E10/76—Power conversion electric or electronic aspects
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/30—Reactive power compensation

Definitions

  • the invention relates to controlling a power plant in a weak grid.
  • the invention relates to controlling a wind turbine generator in a weak grid for steady state power transfer.
  • Some wind power plants operate in 'weak grid' conditions, meaning that there is high impedance in a transmission line between wind turbine generators of the power plant and a main grid, specifically between a point of common coupling (PCC) of the wind turbine generators and the main grid.
  • PCC point of common coupling
  • a weak grid may arise, for example, as a result of locating wind turbine generators or a wind farm or park at a significant distance from the main grid to exploit wind energy at a particular location.
  • the long transmission line required means that there is a high impedance between the generators and the grid.
  • a weak grid is formally defined as one where the relevant bus has a short circuit ratio (SCR) below 3 at the PCC.
  • SCR short circuit ratio
  • the SCR is a measure of generator stability characteristics, and can be expressed mathematically as the quotient of the short circuit capacity of the bus and the rated power of the associated generator.
  • An alternative mathematical formula for the SCR, which is applicable for a wind power plant at the PCC, is:
  • SCR Fault level in MVA at PCC / MW rating of the plant.
  • a challenge for a wind power plant operating in weak grid conditions is to maintain system stability. This involves ensuring that the characteristics of the power delivered to the PCC are steady and consistent, including both the voltage amplitude and the frequency (or 'angle') of the waveform.
  • a reactive power target value is supplied by a power plant controller, which in turn may receive this value from a transmission system operator.
  • the reactive component of the output power is inadequate, the output l may become unstable. Instability can manifest as an uncontrollable rise or fall in voltage amplitude, a loss of synchronism, or both. In the extreme case, instability may cause the wind turbine generator to trip, for example if it is not able to ride-through the voltage droop.
  • An aspect of the invention provides a method of controlling a wind turbine generator comprising an electrical generator and a power converter, the power converter being configured to process electrical power produced by the electrical generator to supply output power to an electrical grid through a transmission line.
  • the method comprises determining a transmission line impedance value, calculating a reactive power reference based on the transmission line impedance value and an active power reference, and controlling the wind turbine generator to adjust the output power based on the calculated reactive power reference.
  • the method may comprise calculating a load angle at the power converter based on the transmission line impedance value and the active power reference, and then calculating the reactive power reference based on the load angle.
  • the load angle can be calculated based on the desired active power to be delivered to the grid along with data that is readily available such as the power converter voltage. Once calculated, elegantly the load angle can in turn be used to calculate a reactive power reference.
  • the method may comprise calculating the impedance of the power converter based on the transmission line impedance value.
  • the method may comprise determining a reactive current reference based on the reactive power reference, and delivering the reactive current reference to a current controller of the wind turbine generator.
  • determining the reactive current reference may include measuring a voltage output of the wind turbine generator, and dividing the reactive power reference by the measured wind turbine generator voltage.
  • the method may include obtaining from a voltage controller of the wind turbine generator a control value based on a voltage error of the wind turbine generator, in which case the control value may be a generator reactive current value, and determining the reactive current reference may include converting the reactive power reference to a reactive current value, and combining the reactive current value with the generator reactive current value.
  • control value may be a generator reactive power reference
  • the method may comprise combining the reactive power reference with the generator reactive power reference to produce a combined reactive power reference, and determining the reactive current reference based on the combined reactive power reference.
  • the method may comprise obtaining from a power plant controller of the wind power plant a plant control value based on a voltage error of the wind power plant.
  • the plant control value may be a power plant reactive power reference, in which case determining the reactive current reference may include processing the reactive power reference and the power plant reactive power reference to determine a power plant reactive current value, and combining the power plant reactive current value with the generator reactive current reference.
  • Another aspect of the invention provides a control system for controlling a wind turbine generator, the wind turbine generator comprising an electrical generator and a power converter, the power converter being configured to process electrical power produced by the electrical generator to supply output power to an electrical grid through a transmission line.
  • the control system comprises an input configured to receive a transmission line impedance value and an active power reference, a processor configured to calculate a reactive power reference based on the transmission line impedance value and the active power reference, and a controller configured to adjust the output power of the wind turbine generator based on the calculated reactive power reference.
  • the invention also extends to a wind turbine system comprising at least one wind turbine generator and a control system according to the above aspect.
  • Figure 1 is a schematic diagram of a wind turbine generator that is suitable for use with embodiments of the invention
  • Figure 2 is a schematic diagram of a wind power plant comprising a plurality of wind turbine generators such as that illustrated in Figure 1 ;
  • Figure 3 is a schematic diagram of an architecture of a full-scale converter based wind turbine generator that is suitable for use with embodiments of the invention
  • Figure 4 is a schematic diagram showing a grid-side portion of the wind turbine generator of Figure 3 and its connections to a grid;
  • Figure 5 is a flow diagram showing a first stage of a process according to an embodiment of the invention for providing steady state power transfer in weak grid conditions
  • Figure 6 is a flow diagram showing a second stage of a process according to an embodiment of the invention for providing steady state power transfer in weak grid conditions
  • Figure 7 is a flow diagram showing a second stage of a process for providing steady state power transfer in weak grid conditions according to another embodiment of the invention.
  • Figure 8 is a flow diagram showing a second stage of a process for providing steady state power transfer in weak grid conditions according to yet another embodiment of the invention.
  • Embodiments of the invention provide methods and a control system for controlling one or more wind turbine generators of a wind power plant so as to provide steady state power transfer in a weak grid. Three alternative methods for achieving this are described below, but it is noted at this stage that all of the described methods involve controlling the wind turbine generator according to a reactive power reference that is calculated based on the impedance of the grid.
  • controlling the wind turbine generator might involve providing a target value for reactive current to a current controller governing an output signal from a power converter of a wind turbine generator. Determining what this value should be is not straightforward.
  • 'pu' refers to the 'per-unit' system for representing voltage or current values, in which a base or reference value in the system is selected, and all other corresponding values in the system are divided by that base value to be represented as a fraction of the base value.
  • the base value might be the voltage at the wind turbine generator.
  • the per-unit system simplifies calculations in power transmission systems as the quantities do not change when crossing a transformer.
  • Determining the grid impedance may involve obtaining values for a grid fault level (in MVA) and X/R at the PCC from a transmission system operator, for example, and calculating the grid impedance based on these values and the voltage rating of the transmission line. Transmission system operators make such data available to offer third parties knowledge of fault levels in the grid.
  • control system includes an input at which a value of the grid impedance and an active power reference can be received and then passed to a processor of the control system, to be used in determining a target reactive power for controlling the wind turbine generator.
  • Figure 1 shows an individual wind turbine generator 1 of a kind that may be controlled in the manner described above. It should be appreciated that the wind turbine generator 1 of Figure 1 is referred to here by way of example only, and it would be possible to implement embodiments of the invention into many different types of wind turbine systems.
  • the wind turbine generator 1 shown is a three-bladed upwind horizontal-axis wind turbine (HAWT), which is the most common type of turbine in use.
  • the wind turbine generator 1 comprises a turbine rotor 2 having three blades 3, the rotor 2 being supported at the front of a nacelle 4 in the usual way. It is noted that although three blades is common, different numbers of blades may be used in alternative embodiments.
  • the nacelle 4 is in turn mounted at the top of a support tower 5, which is secured to a foundation (not shown) that is embedded in the ground.
  • the nacelle 4 contains a generator (not shown in Figure 1) that is driven by the rotor 2 to produce electrical energy.
  • the wind turbine generator 1 is able to generate power from a flow of wind passing through the swept area of the rotor 2 causing the rotation of the blades 3.
  • FIG. 2 shows the wind turbine generator 1 in the context of a wind power plant 6 having a plurality of individual wind turbine generators 1 ; specifically, three wind turbine generators 1 are present in the wind power plant 6 shown in Figure 2.
  • Each wind turbine generator 1 has an output line 7a that connects to a transmission line 7b that takes electrical power generated within the wind power plant 6 to an electrical grid.
  • Each wind turbine generator 1 of the wind power plant 6 is connected to a power plant controller (PPC) 8 that controls operation of the wind power plant 6.
  • the PPC 8 is responsible for monitoring operating conditions and for issuing reactive power references to each wind turbine generator 1 based on an active power demand.
  • the PPC 8 therefore represents part of the control system referred to above.
  • the PPC 8 includes an input 9 at which operational data is received from each wind turbine generator 1.
  • the PPC 8 further includes a processor 10 that uses the data received at the input 9 to determine, among other things, the required reactive power references for the wind turbine generators 1 , as shall be described in more detail below.
  • FIG. 3 an example of a wind power plant 12 to which methods according to embodiments of the invention may be applied is shown.
  • the example shown is representative only and the skilled reader will appreciate that the methods described below may be applicable to many different configurations.
  • the components of the wind power plant 12 are conventional and as such familiar to the skilled reader, and so will only be described in overview.
  • the wind power plant 12 shown in Figure 3 includes a single wind turbine generator 1 such as that shown in Figure 1 , but in practice further wind turbine generators may be included as shown in Figure 2.
  • the wind turbine generator 1 comprises an electrical generator 20 that is driven by a rotor (not shown in Figure 3) to produce electrical power.
  • the wind turbine generator 1 includes a low voltage link 14 defined by a bundle of low voltage lines 16 terminating at a coupling transformer 18, which acts as a terminal that connects the wind turbine generator 1 to a grid transmission line, which is described later with reference to Figure 4. Electrical power produced by the wind turbine generator 1 is delivered to the grid through the coupling transformer 18.
  • the power produced in the electrical generator 20 is three-phase AC, but is not in a form suitable for delivery to the grid, in particular because it is typically not at the correct frequency or phase angle.
  • the wind turbine generator 1 includes a power converter 22 and a filter 24 disposed between the electrical generator 20 and the coupling transformer 18 to process the electrical generator 20 output into a suitable waveform having the same frequency as the grid and the appropriate phase angle.
  • the power converter 22 provides AC to AC conversion by feeding electrical current through an AC-DC converter 26 followed by a DC-AC converter 28 in series.
  • the AC-DC converter 26 is connected to the DC-AC converter 28 by a conventional DC link 30, which includes a switched resistor 32 to act as a dump load to enable excess energy to be discharged, and a capacitor 34 providing smoothing for the DC output.
  • the smoothed DC output of the AC-DC converter 26 is received as a DC input by the DC- AC converter 28 and creates a three-phase AC output for delivery to the coupling transformer 18.
  • the DC-AC converter 28 is configured to provide a level of control over the characteristics of the AC power produced, for example to increase the relative reactive power in dependence on grid impedance, as shall be explained later.
  • a current controller 36 is provided for this purpose, the current controller forming part of an overall control system that controls operation of the wind turbine generator 1.
  • the current controller 36 is configured to receive target values for the active current and the reactive current contained in the AC output, and to adjust the AC output accordingly.
  • a voltage controller 37 acts to maintain the voltage of the AC output at the required level.
  • control system also includes a power plant controller 6 having an input 9 and a processor 10 for receiving and processing grid operating values to determine the target reactive power as shown in Figure 2.
  • power plant controller 6 having an input 9
  • processor 10 for receiving and processing grid operating values to determine the target reactive power as shown in Figure 2.
  • these elements of the control system are not shown in Figure 3.
  • the AC output leaves the power converter 22 through the three power lines 16, one carrying each phase, which together define the low voltage link 14.
  • the low voltage link 14 includes the filter 24, which in this embodiment comprises a respective inductor 38 with a respective shunted filter capacitor 40 for each of the three power lines 16, to provide low-pass filtering for removing switching harmonics from the AC waveform.
  • the low voltage link 14 terminates at the coupling transformer 18 which provides a required step-up in voltage.
  • a high voltage output from the coupling transformer 18 defines a wind turbine generator terminal 42, which acts as a PCC for the wind power plant 12.
  • Figure 4 shows how a grid-side portion of the wind power plant 12 connects to a grid 44.
  • the grid-side portion involves the DC-AC converter 28 of the power converter 22, which may also be referred to as the 'line-side converter', along with the filter 24 and the coupling transformer 18.
  • the coupling transformer 18 comprises a low voltage side 18a which is directly connected to the filter 24, and a high voltage side 18b which defines an output from the wind turbine generator 1.
  • the filter 24 is represented by a single line having a resistor and an inductor to represent the resistance and inductance of the line.
  • a transmission line 46 is connected to the high voltage side 18b of the coupling transformer 18 to connect the wind turbine generator 1 to the grid 44.
  • the resistance and inductance of the transmission line 46 are represented by a resistor and an inductor respectively.
  • Figure 5 shows a first stage 50 of a control process for controlling the wind turbine generator 1 that would be performed by the PPC 8, in which values for resistance and reactance at the power converter 22 are obtained. Determining these values is a precursor to calculating a reactive power reference, which as already noted is used in each embodiment of the invention to control the wind power plant 12 to achieve steady state transfer of electrical power to the grid 44. Accordingly, the first stage of the control process, namely the sub-process 50 shown in Figure 5, is common to each embodiment.
  • the first stage 50 of the control process begins by obtaining at step 52 a value for the grid impedance Z g as seen from the wind turbine generator terminal 42.
  • the grid impedance value may be supplied by a transmission system operator.
  • the grid impedance Z g defines the resistance R g and reactance X g Of the grid from the high voltage side 18b of the coupling transformer 18b, which corresponds to the impedance presented by the resistor and inductor of the transmission line 44 shown in Figure 4.
  • corresponding values for the resistance R T and reactance X T at a terminal of the power converter 22 can be determined at step 54, noting that the total impedance between the power converter 22 and the grid 44 is equal to the sum of the grid impedance Z g and the respective impedances of the filter 24 and the coupling transformer 18, which are already known as characteristics of the wind turbine generator 1.
  • R T and X T can be used to determine at step 56 the impedance Z T at the power converter terminal, as well as the impedance angle ⁇ ⁇ .
  • this first stage 50 of the control process in which the impedance Z T and impedance angle ⁇ ⁇ at the power converter terminal are determined is used in all embodiments. Also common to all embodiments is that the ultimate objective of the control process is to provide a final reactive current reference l d to supply to the current controller 36 of the wind turbine generator 1 for steady state power transfer.
  • Figures 6, 7 and 8 show respective embodiments of a second stage 60a, 60b, 60c of the control process to achieve this objective.
  • the impedance Z T and the impedance angle ⁇ ⁇ at the power converter terminal that have been obtained using the first stage 50 shown in Figure 5, as well as an active power reference P REF , are used as initial inputs to the second stage 60a.
  • the active power reference P REF is supplied by the PPC 8, and represents the desired active power that should be delivered to the grid to meet grid demand, taking into account instantaneous operating conditions such as wind speed.
  • a first step in the second stage 60a of this embodiment is to use the active power reference P REF , the power converter impedance Z T and the impedance angle ⁇ ⁇ to determine at step 62 the load angle ⁇ of the electrical generator 20, namely the difference in angle between the converter terminal v c and the grid voltage source v g .
  • the load angle ⁇ can be calculated using equation (1), shown below:
  • v g represents the grid voltage and v c represents the generator 42 output voltage. It is noted that v g and v c are all assumed to be 1 pu in the calculation, but in practice each can take a value in the range 0.9pu - 1.1 pu, or between 0.85pu and 1.15 in some grid codes.
  • the second stage 60a moves on to a second step 64 in which the load angle ⁇ is used to determine a reactive power reference Q REF , representing the required reactive power to deliver the active power indicated by the active power reference P REF - This is achieved using equation (2), shown below:
  • equations (1) and (2) are standard equations that can be readily implemented into the PPC 8 for executing the above calculations.
  • equation (1) can be reorganised in terms of ⁇ , and then the result substituted for ⁇ in equation (2).
  • the reactive power reference Q REF can thereby be calculated directly from the active power reference P REF in a single calculation without the intermediate step of calculating the load angle ⁇ .
  • the reactive power reference Q REF is converted directly at step 66 into a corresponding reactive current reference, which is used to calculate the final reactive current reference that is used to control the wind turbine generator 1 to achieve steady state transfer.
  • the final reactive current reference l d is composed of two components: a main component l d1 ; and a minor component l d2 .
  • the main component l d1 is obtained by dividing the reactive power reference Q RE F by the turbine voltage. For this calculation, instead of using an assumed value of 1 pu as above, a direct measurement of the turbine voltage is used.
  • the main component l d1 alone cannot maintain a stable generator output voltage of 1 pu as it takes no account of error.
  • the minor component l d2 is also used.
  • the minor component l d2 is obtained directly at step 68 from a voltage controller of the electrical generator 20, which calculates the value for the minor component l d2 based on a voltage error, namely a difference between the generator output voltage v c and a reference generator output voltage v* c .
  • the minor component l d2 therefore accounts for the voltage error, and thus can be used to maintain voltage stability.
  • the main component l d1 and the minor component l d1 are then combined at step 70 to produce the reactive current reference l d , which is then transmitted to the current controller 36 of the power converter 22 to control the form of the AC output waveform accordingly.
  • FIG. 7 shows a variation of the above described process.
  • a reactive power reference Q RE F is calculated at steps 62 and 64 based on the impedance Z T and impedance angle ⁇ ⁇ at the power converter 22.
  • the reactive power reference Q RE F is treated as a main component Qi of a final reactive power reference Q RE F to be calculated by combining at step 72 the main component Qi with a minor component Q 2 .
  • the minor component Q 2 corresponds to the minor component l d2 of the reactive current reference l d of the Figure 6 process, in that the minor component Q 2 is obtained at step 74 from the voltage controller, and is based on the generator voltage error.
  • the main and minor components Qi , Q 2 are combined to produce the final reactive power reference Q REF .
  • the final reactive power reference Q REF is then divided at step 76 by the measured generator output voltage to produce the final reactive current reference l d , which is fed to the current controller 36 as in the Figure 6 process.
  • FIG. 8 shows a further embodiment of the invention in which the wind turbine generator 1 forms part of a wind power plant 6 comprising one or more further wind turbine generators 1 such as that shown in Figure 2, which wind power plant is managed by a PPC 8.
  • the process 60c shown in Figure 8 begins in the same way as the above described processes of Figures 6 and 7 by determining at steps 62 and 64 a reactive power reference Q REF based on the impedance Z T and impedance angle ⁇ ⁇ at the power converter 22.
  • the PPC 8 monitors a voltage error for the combined output of the wind turbine generators 1 of the installation and generates at step 78, based on this error, a power plant reactive power reference Q PPC .
  • the reactive power reference Q REF and the power plant reactive power reference Q PPC are both delivered at step 80 to a reactive power manager, which is configured to determine the correct amount of reactive power to deliver based on current operating conditions.
  • the reactive power manager makes this decision using an equation of the form: a*Q REF + b*Q PP c; where 'a' and 'b' are real numbers that are chosen based on instantaneous operating conditions. It is noted that optionally the reactive power manager could be used in other embodiments in a similar manner, such as the option described above with reference to Figure 7 in which two reactive power references are combined.
  • the reactive power manager processes the reactive power reference Q REF and the power plant reactive power reference Q PPC to generate a main component l d1 of the final reactive current reference l d .
  • a minor component l d2 of the final reactive current reference l d is provided at step 82 by the generator voltage controller based on a local voltage error of the wind turbine generator 1.
  • the main and minor components I en , Id2 3 ⁇ combined at step 84 to produce the final reactive current reference l d , which in this case accounts for both local voltage error and plant-wide voltage error.
  • This reactive current reference l d is delivered to the current controller 36 to ensure steady state power transfer.
  • a reactive power reference is output from the PPC 8 and combined with a reactive power reference from the voltage controller 37 to produce a combined reactive power reference, which is then converted to a current reference.
  • embodiments of the invention provide for steady state transfer of power in weak grid conditions by calculating a reactive current reference for input to the current controller 36, the reference being derived from a reactive power reference which in turn is based on instantaneous grid impedance as seen from a power converter 22 of the wind turbine generator 1.
  • Each embodiment also takes into account any error in an output voltage from the wind turbine generator 1 to ensure stability over a range of operating conditions.
  • a Q REF value is calculated based on the instantaneous grid impedance seen at the generator, and not based on an external target provided by a transmission system operator, as is conventional.
  • This approach offers the advantage that the reactive power can be adjusted to respond to changes in grid impedance resulting from varying grid loads or grid faults more quickly than is possible in known arrangements, thereby enabling the system to maintain steady state power transfer during changing operational conditions.

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Sustainable Development (AREA)
  • Sustainable Energy (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Control Of Eletrric Generators (AREA)
  • Supply And Distribution Of Alternating Current (AREA)

Abstract

L'invention concerne un procédé de commande d'un générateur d'éolienne (1) comprenant un générateur électrique (20) et un convertisseur de puissance (22), le convertisseur de puissance (22) étant conçu pour traiter une puissance électrique produite par le générateur électrique (20) en vue de fournir une puissance de sortie à un réseau électrique (44) par l'intermédiaire d'une ligne de transport d'électricité (46), le procédé consistant à : déterminer une valeur d'impédance de ligne de transport d'électricité ; calculer une référence de puissance réactive sur la base de la valeur d'impédance de ligne de transport d'électricité et d'une référence de puissance active ; et commander le générateur d'éolienne (1) pour ajuster la puissance de sortie sur la base de la référence de puissance réactive calculée.
PCT/DK2017/050088 2016-04-04 2017-03-27 Commande d'une centrale éolienne dans un réseau électrique faible WO2017174085A1 (fr)

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CN109638894A (zh) * 2019-01-31 2019-04-16 张欣 一种用于并网逆变器和弱电网之间的串联自适应稳定器
CN110542791A (zh) * 2019-09-06 2019-12-06 福建工程学院 电网连锁跳闸时初始故障支路的极限功率计算方法
US10855079B1 (en) 2019-07-19 2020-12-01 General Electric Company System and method for reducing oscillations in a renewable energy power system
US20210036639A1 (en) * 2019-07-30 2021-02-04 North China Electric Power University Stability evaluation method and system of direct-drive wind turbine generator
US11268496B2 (en) 2019-08-09 2022-03-08 Inventus Holdings, Llc Distributed wind park control
EP4002632A1 (fr) * 2020-11-13 2022-05-25 Wobben Properties GmbH Procédé de fourniture de puissance réactive
DE102022117824A1 (de) 2022-07-17 2024-01-18 Sma Solar Technology Ag Verfahren zur regelung eines leistungswandlers

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EP2612414A2 (fr) * 2010-08-31 2013-07-10 Vestas Wind Systems A/S Commande du rendement électrique d'un parc éolien
US20150069978A1 (en) * 2012-04-19 2015-03-12 Panasonic Corporation Voltage control apparatus, voltage control method, and power adjustment apparatus
US20150137520A1 (en) * 2012-06-12 2015-05-21 Vestas Wind Systems A/S Wind-power-plant control upon low-voltage grid faults

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EP2612414A2 (fr) * 2010-08-31 2013-07-10 Vestas Wind Systems A/S Commande du rendement électrique d'un parc éolien
US20130134779A1 (en) * 2011-10-31 2013-05-30 Panasonic Corporation Voltage control apparatus, voltage control method, and power regulating apparatus
US20150069978A1 (en) * 2012-04-19 2015-03-12 Panasonic Corporation Voltage control apparatus, voltage control method, and power adjustment apparatus
US20150137520A1 (en) * 2012-06-12 2015-05-21 Vestas Wind Systems A/S Wind-power-plant control upon low-voltage grid faults

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109638894A (zh) * 2019-01-31 2019-04-16 张欣 一种用于并网逆变器和弱电网之间的串联自适应稳定器
US10855079B1 (en) 2019-07-19 2020-12-01 General Electric Company System and method for reducing oscillations in a renewable energy power system
US20210036639A1 (en) * 2019-07-30 2021-02-04 North China Electric Power University Stability evaluation method and system of direct-drive wind turbine generator
US11677344B2 (en) * 2019-07-30 2023-06-13 North China Electric Power University Stability evaluation method and system of direct-drive wind turbine generator
US11268496B2 (en) 2019-08-09 2022-03-08 Inventus Holdings, Llc Distributed wind park control
CN110542791A (zh) * 2019-09-06 2019-12-06 福建工程学院 电网连锁跳闸时初始故障支路的极限功率计算方法
CN110542791B (zh) * 2019-09-06 2021-10-22 福建工程学院 电网连锁跳闸时初始故障支路的极限功率计算方法
EP4002632A1 (fr) * 2020-11-13 2022-05-25 Wobben Properties GmbH Procédé de fourniture de puissance réactive
US11994110B2 (en) 2020-11-13 2024-05-28 Wobben Properties Gmbh Method for providing reactive power
DE102022117824A1 (de) 2022-07-17 2024-01-18 Sma Solar Technology Ag Verfahren zur regelung eines leistungswandlers

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