Control and operation of a power converter

Abstract

Methods of operating a wind turbine (1) having a generator (10) and a power converter (60). The methods may comprise: determining a first reduced power setpoint (94) in response to an operating condition; reducing the active power from a line-side converter (66) to an electrical network (80) according to the first reduced power setpoint (94); determining a reduced power setpoint (92) for a machine-side converter (62); reducing a torque applied to the generator (10) by the machine-side converter (62) so that the generator (10) produces active power according to the second reduced power setpoint (92); and dissipating excess power in one or more resistive elements (68), provided that the second power setpoint is higher than the first power setpoint. Wind turbines configured for such methods are also provided.

Description

Control and operation of a power converter

[0001] The present invention relates to methods for operating a wind turbine. The present invention also relates to wind turbines that include a generator connected to a power converter. BACKGROUND

[0002] Modern wind turbines are commonly used to supply electricity to the power grid. Wind turbines of this type generally consist of a tower and a rotor mounted on the tower. The rotor, which typically consists of a hub and a plurality of blades, is set in rotation by the wind acting on the blades. This rotation generates torque that is normally transmitted through a rotor shaft to an electric generator, either directly ("direct drive") or by using a gearbox. In this way, the electric generator produces electricity that can be supplied to the power grid.

[0003] The generator may be connected to the electrical grid through a power converter. Such a power converter may include a line-side converter connected to the grid, a machine-side converter connected to a generator rotor, and a DC link between the line-side converter and the machine-side converter.

[0004] The power converter regulates the generator's power output to the grid and can control the torque applied to the generator's stator. In normal wind turbine operation, the active power produced by the generator is fed into the grid. The power a generator can produce depends on the prevailing wind speed, but it also depends on the torque applied to the generator's stator. Wind turbine control generally depends on the prevailing wind speed, and the blade pitch angle and stator torque are typically selected to maximize power generation and grid feed-in.

[0005] However, under certain circumstances, a grid anomaly may occur, such as a high frequency. According to some grid codes, the wind turbine must be able to reduce the active power output of the generator to the grid. For example, a grid code may prescribe the ability to reduce the active power output by 25% per second. Other grid conditions may also exist where there is no anomaly (yet), but a reduction in the active power output of a wind turbine, or of a wind farm, is required.

[0006] Document WO2010002402 describes a system for connecting a wind turbine generator to a public electric grid with low-voltage transmission capacity. The system includes a first power converter that converts an AC signal from the wind turbine generator into a DC signal and supplies a controlled amount of reactive current to the wind turbine generator. The system also includes a second power converter, connected in series with the first converter, which converts the DC signal from the first power converter into a line-side AC signal and supplies a controlled amount of current to the electric utility grid. A power dissipation element is coupled to the first and second power converters to dissipate the power from the first power converter.

[0007] US2010320762 A1 discloses a wind power installation having a doubly fed asynchronous generator and a converter control and a method for controlling a converter of a wind power installation. The converter is connected to the rotor of a doubly fed asynchronous generator to inject electrical power into an electrical grid and comprises a generator-side inverter, a grid-side inverter, and at least one converter regulator for regulating and / or controlling the current output from at least one of the inverters to the doubly fed asynchronous generator and / or to the electrical grid.The method includes detecting a change in actual output power, determining whether the detected change satisfies a predefined condition, and changing a nominal reactive power output value in the opposite direction to a change in actual power at the grid-side inverter and in the same direction as the generator-side inverter when the predefined condition is satisfied.

[0008] The present invention relates to methods and systems designed to be able to cope with such network conditions. SUMMARY

[0009] The present invention is defined by a method of operating a wind turbine having a generator and a power converter with the stages of independent claim 1, and by a wind turbine with the technical characteristics of independent claim 12.

[0010] According to the invention, a different power setpoint is provided for the line-side converter than for the machine-side converter. The power setpoint for the line-side converter can be selected to meet, for example, a grid requirement at a given time. A different power setpoint is selected for the machine-side converter. A divergence between the two setpoints is permitted to avoid operational problems with the generator or the wind turbine connected to it. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The following are non-limiting examples of this disclosure, with reference to the accompanying drawings, in which: Figure 1 illustrates a perspective view of a wind turbine according to an example in this disclosure; Figure 2 illustrates a simplified interior view of a wind turbine nacelle according to an example in this disclosure; Figure 3 schematically illustrates a method of operation of a wind turbine and a power converter according to an example from the previous material; Figure 4 schematically illustrates a method of operation of a wind turbine and a power converter according to an example in this disclosure; Figure 5 schematically illustrates a method of operation of a wind turbine and a power converter in the event of a grid disturbance according to an example in this disclosure; and Figure 6 schematically illustrates a method of operation of a power converter according to another example. DETAILED DESCRIPTION OF THE EXAMPLES

[0012] In these figures, the same reference symbols have been used to designate the matching elements.

[0013] Figure 1 illustrates a perspective view of an example of a wind turbine 1. As shown, the wind turbine 1 includes a tower 2 extending from a support surface 3, a nacelle 4 mounted on the tower 2, and a rotor 5 coupled to the nacelle 4 at a front region. The rotor 5 includes a rotating hub 6 and at least one rotor blade 7 coupled to the hub 6 and extending outward. For example, in the illustrated example, the rotor 5 includes three blades 7. However, in an alternative embodiment, the rotor 5 may include more or fewer than three blades 7. Each rotor blade 7 may be separated from the hub 6 to facilitate the rotation of the rotor 5 and allow kinetic energy to be transferred from the wind to usable mechanical energy and subsequently to electrical energy.For example, the hub 6 may be rotatably coupled to an electric generator 10 (Figure 2) located within the nacelle 4 or forming part of the nacelle to enable the production of electrical power. The rotor's rotation may be transmitted directly, for example in direct-drive wind turbines, or via a gearbox to a generator.

[0014] Figure 2 illustrates a simplified internal view of an example of the nacelle 4 of the wind turbine 1 of Figure 1. As shown, the generator 10 can be arranged within the nacelle 4. In general, the generator 10 can be coupled to the rotor 5 of the wind turbine 1 to generate electrical power from the rotational energy generated by the rotor 5. For example, the rotor 5 can include a main rotor shaft 8 coupled to the hub 6 to rotate with it. The generator 10 can be coupled to the rotor shaft 8 such that the rotation of the rotor shaft 8 drives the generator 10. For example, in the illustrated embodiment, the generator 10 includes a generator shaft 11 rotatably coupled to the rotor shaft 8 via a gearbox 9. In alternative examples, the hub can be directly coupled to a generator rotor, and the rotation of the hub can thus drive the generator rotor.

[0015] Generator 10 can be electrically coupled to the converter. The wind turbine converter can adapt the generator's electrical output power to the requirements of the electrical grid.

[0016] It should be noted that the rotor shaft 8, gearbox 9 and generator 10 can generally be supported within the nacelle 4 by a support frame or rack 12 placed at the top of the wind turbine tower 2.

[0017] The nacelle 4 is rotatably coupled to the tower 2 by means of a slewing system 20. The slewing system comprises a slewing bearing (not visible in Figure 2) having two bearing components configured to rotate relative to each other. The tower 2 is coupled to one of the bearing components, and the base or support frame 12 of the nacelle 4 is coupled to the other bearing component. The slewing system 20 comprises a ring gear 21 and a plurality of slewing drives 22 with a motor 23, a gearbox 24, and a pinion 25 for meshing with the ring gear to rotate one of the bearing components relative to the other.

[0018] The nacelle 4 further comprises a cover structure 50 for housing the wind turbine components. In this example, the wind turbine components housed in or enclosed by the cover structure 50 comprise the generator 10, the converter, the gearbox 9, and the shaft 8. In other examples, the wind turbine components arranged within the nacelle may refer to the converter and the generator.

[0019] Figure 3 schematically illustrates a method of operating a wind turbine and a power converter according to an example of the prior art. In the example in Figure 3, a wind turbine comprises a generator 10, which is connected to an electrical network 80 via a power converter 60. In this particular example, the generator 10 is a permanent magnet generator, which includes a generator rotor carrying a plurality of permanent magnets. The permanent magnet generator can be driven directly (i.e., without a gearbox) by the rotor of the wind turbine 5. In this example, the wind turbine can be an offshore wind turbine. In this particular example, the stator of the generator 10 is connected to a machine-side converter 62. The machine-side converter is connected to a line-side converter 66 via a DC link 64.

[0020] Generator 10 is configured to convert mechanical energy into AC electrical energy and supplies the generated AC to the machine-side converter 62. The generator's AC has a variable frequency due to fluctuating wind conditions. The machine-side converter 62 is configured to convert or rectify the AC into DC voltage and current supplied to the DC link 64. The line-side converter 66 converts the DC from the DC link 64 into fixed-frequency AC for the grid 80. The line-side converter 66 can be connected to the grid 80 via a main transformer 70.

[0021] According to this example, the power converter 60 receives a single setpoint 92 from a wind turbine controller 90. Setpoint 92 is based on optimal wind turbine operation according to the prevailing weather conditions. By controlling the generator torque, the generator's rotational speed can be controlled. The generator's rotational speed, in turn, determines the rotational speed of the wind turbine rotor 5. The rotational speed can be selected according to a predefined operating program. In particular, it is known that the wind turbine can be controlled differently at different wind speed ranges. At wind speeds below a nominal speed, the rotational speed can be selected so that the wind strikes the rotor blades at an optimal angle of attack.This method of operation can be maintained until a maximum rotation speed is reached.

[0022] At higher wind speeds, and particularly above the nominal wind speed, the rotational speed can be controlled to maintain a constant rate. Maximum torque can be applied to the stator and the blades can be pitched to ensure a constant rotational speed. Variations from this optimized operation are possible.

[0023] According to the predefined operation, a wind turbine controller can send a torque signal 92 to the machine-side converter. The resulting active power 100 is injected into the grid. The wind turbine controller 90 can be a local wind turbine controller or, for example, a wind farm controller.

[0024] Figure 4 schematically illustrates a method of operating a wind turbine and a power converter according to an example in this disclosure. As in the example in Figure 3, the wind turbine may comprise a permanent magnet generator 10 having a rotor carrying a plurality of magnets. As in the example in Figure 3, the generator is connected to the electrical grid 80 through a power converter 60.

[0025] The power converter includes a line-side converter 66, a machine-side converter 62, and a DC link 64. The wind turbine further includes a controller 90, wherein the controller is configured to determine a first power setpoint 94 in response, for example, to a grid condition and send the first power setpoint 94 to the line-side converter 66 and to determine a second power setpoint 92 in response to the grid condition and send the second power setpoint 92 to the machine-side converter 62. The second power setpoint 92 is higher than the first power setpoint 94.

[0026] According to the second instruction, generator 10 has a power of 100. However, according to the first instruction, an amount of active power 104 is supplied to the network.

[0027] The wind turbine includes one or more resistive elements in the DC link, and the power converter is configured to dissipate excess generator power in the resistive elements. The DC link may include a DC chopper 68 to dissipate excess generator power that cannot be absorbed by the grid. When necessary, a switch on the DC chopper can be closed to divert electrical current through the chopper.

[0028] The power supplied by the machine-side converter, on the one hand, and the power supplied to the grid by the line-side converter, on the other, indirectly control the operation of the DC chopper. The setpoints are power setpoints, unlike in the previous subject, where it is common to have a setpoint for the DC link voltage and operate a chopper based on the DC link voltage.

[0029] Operation based on independent power setpoints allows the converter and wind turbine to reliably cope with different situations, including different grid anomalies.

[0030] According to this example, a method of operating a wind turbine is provided. The method comprises determining a first reduced power setpoint 94 in response to an operating condition; reducing the active power 104 according to the first reduced power setpoint 94 from a line-side converter 66 to the grid 80; determining a reduced power setpoint for a machine-side converter; and reducing a torque applied to the generator 10 by a machine-side converter 62 so that the generator produces active power according to the second reduced power setpoint 92. The method further comprises dissipating excess power (10-104) in one or more resistive elements 68 while the second power setpoint is higher than the first power setpoint.

[0031] The operating condition may be a grid condition, which may be an abnormal grid condition. The grid condition may be a grid frequency above a predefined threshold. The grid frequency may be controlled by the amount of active power supplied to the grid. In response to a high frequency, the wind turbine may be forced to reduce the active power supplied to the grid. Such a response may be defined in a grid code. According to the operating procedures, the generator torque may be reduced. If the generator torque is reduced, the rotor speed 5 will tend to increase. This could be counteracted by a braking system and / or by adjusting the blade pitch to reduce the converted aerodynamic energy. Depending on the wind turbine, these actions may not be sufficient to reduce the active power output in accordance with the grid disturbance and the grid code.

[0032] According to the example disclosed here, a first nominal power setpoint 94 is sent to the line-side converter 66. The line-side converter 66 receives the first setpoint and injects electricity 104 into the grid according to this (reduced) setpoint 94. Simultaneously, a second setpoint 92 is sent to the machine-side converter 62. In some examples, the second reduced power setpoint 92 is reduced according to a maximum reduction rate. In some examples, the maximum reduction rate may be determined to prevent overspeeding of a wind turbine rotor 5. In other examples, the maximum reduction rate may be determined to prevent loads above an acceptable level.

[0033] Controller 90 can measure electrical variables on the grid (e.g., voltage, frequency, phase angle, etc.) and autonomously determine a grid condition or anomaly. The wind turbine controller can calculate or otherwise determine a suitable setpoint reduction signal. Alternatively, controller 90 can receive a setpoint reduction signal 98 from the grid. The grid condition could be a particularly high grid frequency. Another condition could be a voltage anomaly.

[0034] By applying this control, a wind turbine may be able to meet grid code requirements. In other cases, the control may serve to reduce the loads on the wind turbine.

[0035] In some examples, the first reduced power setpoint may be received by the wind turbine from a grid operator. In other examples, the first reduced power setpoint may be determined by the wind turbine or by the wind turbine controller. Specifically, the wind turbine may measure a grid frequency and determine an appropriate response. In other examples, the wind turbine may receive a measured grid frequency from another entity, for example, a grid operator or the controller of a wind farm.

[0036] In another example, the network condition or anomaly could be a voltage dip. A voltage dip, or "sag," is a sudden increase in the voltage of the electrical network. In such a dip, the voltage can drop to, for example, 90% or less of the nominal voltage. Specifically, in a dip, the network voltage can drop to 30, 20, or 10% of the nominal voltage and even reach 0 V. The duration of a voltage dip can be very short, but it can last for a few seconds.

[0037] Grid codes may prescribe that, under these conditions, the wind turbine must remain connected to the grid. As before, first and second power setpoints may be generated for the machine-side and line-side converters. And excess power may be burned off in resistive elements, for example, a chopper in the DC link.

[0038] In another example, the operating condition might be the necessary or anticipated shutdown of the wind turbine. When operation is to be interrupted, similarly to the previous example, first and second power setpoints can be generated. In this case, the setpoint for the line-side converter is not necessarily prescribed by a grid code.

[0039] In some examples, while reducing the generator torque, the method may also include pitching the rotor blades of a wind turbine to reduce the rotational speed of the wind turbine rotor. According to the reduction in the rotational speed of the wind turbine rotor, the second reduced power setpoint 92 may be further reduced. An excess of electrical energy could continue to be dissipated in resistive elements. The second reduced power setpoint 92 may be reduced depending on the circumstances until the active power produced by the generator 100 can feed the grid 80. Until this situation is reached, the excess electrical energy may be dissipated in resistors.

[0040] In some examples, the method may further comprise monitoring the operation of resistive elements to prevent them from reaching an operating limit. For example, the method may comprise measuring the temperature of one or more resistive elements, for instance, in the DC chopper 68. The temperature of the resistive elements may be measured to ensure that they do not reach a critical temperature at which they may fail. Alternatively, the cumulative amount of energy dissipated in the resistive elements may be monitored or calculated. Based on the amount of energy dissipated, it may be calculated or estimated whether the resistive elements are close to their operating limits.

[0041] In some examples, the method may further involve dissipating less energy if one or more of the resistive elements reach one of their operating limits. For example, less energy may be dissipated in the resistive elements if their temperature exceeds a threshold, if the operating time of the resistive elements exceeds a time threshold, or if the amount of energy dissipated reaches a predetermined level. In some circumstances, this may mean that it is necessary to supply more active power to the grid than is desirable or prescribed by a grid code. This may be done to prevent the disconnection of the converter or the wind turbine.

[0042] In some examples, the method may also include increasing the power output once the grid condition has been resolved. Once the problem is resolved, the wind turbine can be restarted to optimize power output. Under these conditions, the power converter control can switch back to normal operation, in which a single setpoint is sent to the power converter to determine the generator torque.

[0043] In some examples, the method may further include ensuring that the wind turbine rotor speed does not fall below a threshold at which the wind turbine becomes difficult to control. If necessary, the power output may be increased to guarantee a minimum rotor speed.

[0044] In this particular example, the generator is a permanent magnet generator and the power converter is a full power converter. In this particular example, the wind turbine may be a direct-drive offshore wind turbine. In another example (Figure 6), the generator may be a doubly fed induction generator (DFIG), and the drive train may include a gearbox.

[0045] Figure 5 schematically illustrates a method of operation of a power converter in the event of a network disturbance, according to an example in this disclosure. In particular, the power converter may be connected to a turbine driven by a generator, specifically a generator driven by a wind turbine.

[0046] An operating method for a power converter connected to an electrical network is illustrated. The power converter comprises a machine-side converter, a DC link, and a line-side converter. The method comprises determining a network anomaly; determining a first setpoint for the active output power of the line-side converter according to the network anomaly; and determining a second setpoint for the active output power of the rotor-side converter, wherein the second setpoint is different from the first setpoint.

[0047] During the first part (left side of the graph), the converter operates normally. There are no specific grid anomalies or grid conditions requiring a reduction in active power. Under these circumstances, the only command the power converter receives is a command related to the machine-side converter. In this particular example, a nominal power Pnom can be generated. In the case of an offshore wind turbine, Pnom could be, for example, 6 MW, 10 MW, or 12 MW.

[0048] When a frequency increase occurs on the grid, two setpoints, P1 and P2, can be sent instead. The "frequency control mode" can be activated. In this frequency control mode, a first setpoint P1 for the grid-side converter and a second setpoint P2 for the machine-side converter are determined (e.g., calculated) separately. It can be seen from the graph that the setpoint P1 for the grid-side converter can be rapidly reduced to adjust to the grid conditions. The second setpoint P2 cannot be rapidly reduced because this could lead to unsafe conditions for the wind turbine or high loads due to excessive wind turbine rotor speed. The ramp rate of the second setpoint can be as high as possible to avoid these problems. In one example, the ramp rate might be 0.4 MW / s.In comparison, the ramp for the reduction of P1 can be, for example, two to four times greater and the reduced power can be achieved in you.

[0049] It can be seen in the graph that, as long as the second power setpoint P2 is higher than the first setpoint Pi (up to t2), energy must be dissipated. This can be done by passing electric current through one or more resistors in the DC link.

[0050] At t2, the second setpoint is equal to the first setpoint. This means that the power produced by the generator is injected into the grid and no further electrical energy needs to be dissipated. The power produced by the generator Pred may be lower than during normal operation before the grid anomaly.

[0051] At t = t3, a network condition still exists, but the frequency increase is less than at the beginning of the network condition. Therefore, the first setpoint of the converter on the Pi machine side can be increased, and at the same time, the second setpoint P2 can also be increased. In this way, the power can be increased without dissipating energy in the resistors.

[0052] At t = t4, the network returns to normal conditions. The frequency control mode can be deactivated and normal operation resumed. The first setpoint for the network-side converter is no longer sent to the converter. The machine-side converter is controlled to gradually increase the output power to return to normal conditions at t5.

[0053] Figure 6 schematically illustrates a method of operation of a power converter 60 according to another example.

[0054] In this particular example (similar to the arrangement in Figure 4), the wind turbine comprises a wind turbine rotor 5 with a plurality of blades, and a generator 10 operatively connected with the wind turbine rotor 5, and a power converter 60 electrically connecting the generator 10 to an electrical network 80, wherein the power converter 60 includes a line-side converter 66, a machine-side converter 62, and a DC link 64. The wind turbine in this example further comprises a controller 90.The controller may be configured to determine a first power setpoint 94 in response to a grid condition and send the first power setpoint 94 to the line-side converter 66 and to determine a second power setpoint 92 in response to the grid condition and send the second power setpoint 92 to the machine-side converter 62, wherein the second power setpoint 92 is higher than the first power setpoint 94.

[0055] In this particular example in Figure 6, the generator 10 can be a doubly fed induction generator (DFIG). The generator 10 can be driven by a gearbox 9. With this specific generator topology, the machine-side converter 62 is electrically connected to the generator rotor. The generator stator is directly connected to the electrical grid. "Directly," as used here, means that there is no converter between the stator and the electrical grid. Depending on the circumstances, a transformer 80 may be provided between the grid and the stator.

[0056] The operation of the wind turbine and converter can be, in general, the same as described above with reference to Figures 4 and 5. The operating methods may be more efficient in the configuration with a permanent magnet generator and a full power converter because all the electrical power passes through the converter, unlike the DFIG configuration in Figure 6.

[0057] This written description uses examples to disclose the invention, including preferred embodiments, and also to enable any person skilled in the art to implement the invention. The scope of the invention is defined by the claims and may include other examples that occur to those skilled in the art. Such other examples are included within the scope of the claims if they have structural elements that do not differ from the literal language of the claims.

Claims

1. A method of operating a wind turbine (1) having a generator (10) and a power converter (60) electrically coupled to the generator (10), wherein the power converter (60) comprises a machine-side converter (62) connected to the generator (10), a line-side converter (66) connected to an electrical network (80), and a DC link (64) through which the machine-side converter (62) is connected to the line-side converter (66), the method comprising: determining a first reduced active power setpoint (94) in response to an operating condition; reducing the active power of the line-side converter (66) to the electrical network (80) based on the first reduced active power setpoint (94); determining a second reduced active power setpoint (92) for the machine-side converter (62),the second reduced power setpoint (92) being higher than the first reduced active power setpoint (94); reducing a torque applied to the generator (10) by the machine-side converter (62) so that the generator (10) produces active power in accordance with the second reduced active power setpoint (92); and dissipating excess active power from the generator (10) in one or more resistive elements (68) in the DC link (64) while the second reduced active power setpoint is higher than the first reduced active power setpoint.

2. The method according to claim 1, wherein the operating condition is a power grid condition.

3. The method according to claim 2, wherein the power grid operating condition is a power grid frequency increase.

4. The method according to claim 2,wherein the operating condition of the electrical grid is a voltage drop.

5. The method according to any of claims 1-4, wherein the second reduced active power setpoint (92) is reduced according to a maximum reduction rate.

6. The method according to claim 5, wherein the maximum reduction rate is determined to prevent overspeeding of a rotor (5) of the wind turbine (1).

7. The method according to any of claims 1-6, wherein the first reduced active power setpoint (92) is received by the wind turbine (1) from a grid operator.

8. The method according to any of claims 1-6, wherein the first reduced active power setpoint (92) is determined by the wind turbine (1) in response to a measured variable of the electrical grid.

9. The method according to any of claims 1-8,further comprising pitching the blades (7) of a wind turbine rotor (5) to reduce the rotational speed of the wind turbine rotor (5).

10. The method according to any one of claims 1-9, further comprising monitoring the operation of the resistive elements (68) to prevent the resistive elements (68) from reaching an operating limit, and dissipating less energy in the resistive elements (68) if one or more of the resistive elements (68) reach an operating limit.

11. The method according to any one of claims 2-10, further comprising increasing the output power of the generator (10) once the power grid condition (80) has been resolved.

12. A wind turbine (1) comprising: a wind turbine rotor (5) with a plurality of blades (7), a generator (10) operatively connected to the wind turbine rotor (5), a power converter (60) electrically connecting the generator (10) to an electrical network (80),wherein the power converter (60) includes a line-side converter (66) connected to the electrical network (80), a machine-side converter (62) connected to the generator (10), and a DC link (64) through which the machine-side converter (62) is connected to the line-side converter (66), and a controller (90), wherein the controller (90) is configured to determine a first reduced active power setpoint (94) in response to a network condition and send the first reduced active power setpoint (94) to the line-side converter (66) and to determine a second reduced active power setpoint (92) in response to the network condition and send the second reduced active power setpoint (92) to the machine-side converter (62), wherein the second reduced power setpoint (92) is higher than the first reduced active power setpoint (94), and in the that,The DC link comprises one or more resistive elements (68), and the power converter (60) is configured to dissipate excess power from the generator (10) in the resistive elements (68) while the second reduced active power setpoint is higher than the first reduced active power setpoint.

13. The wind turbine according to claim 12, wherein the regulator is configured to reduce the second active power setpoint (92) to 0.4 MW / s.

14. The wind turbine according to any of claims 1-13, wherein the generator (10) is a permanent magnet generator, and the power converter is a full-power converter.

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