A direct-drive wind turbine low voltage ride through control method and related device

Abstract

Embodiments of the application disclose a direct-drive wind turbine low-voltage ride-through control method and related equipment. The method comprises: generating a ride-through high-level signal to activate a low-voltage ride-through mode when a low-voltage ride-through trigger module detects that a current voltage value of a target power grid where a target direct-drive wind turbine is located is lower than a preset reference value; calculating a voltage drop depth according to the current voltage value and the preset reference value; a low-voltage period reactive power control module of a grid-side control system controls the target direct-drive wind turbine to output reactive power to the target power grid to support the power grid according to the voltage drop depth; and an active power control module of a machine-side control system controls output power of the target direct-drive wind turbine according to the voltage drop depth. The direct-drive wind turbine low-voltage ride-through control method overcomes the direct-current voltage overvoltage oscillation defect of the prior art and limits the machine-side electromagnetic power during the wind turbine low-voltage ride-through period from the source.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power electronic technology control, and particularly relates to a direct-drive wind turbine low-voltage ride-through control method and related equipment. BACKGROUND

[0002] Single-phase faults and three-phase faults occur in power systems from time to time. With large-scale wind turbines connected to the grid, it is necessary to ensure that the wind turbines do not disconnect from the grid during power grid faults, especially during low-voltage periods of the power grid, and to improve the low-voltage ride-through capability of the wind turbines during faults. At present, the low-voltage ride-through control method for direct-drive wind turbines mainly controls the grid-side converter.

[0003] The output power of the machine-side converter and the output power of the grid-side converter are controlled according to the formula If the grid-side converter cannot send out active power, the DC voltage will rise out of limit. In a common low-voltage ride-through control method for direct-drive wind turbines, when the grid voltage drops, the constant reactive power control of the grid-side converter is switched to low-voltage ride-through reactive current control that responds to changes in the grid voltage, and the grid-side converter adopts a strategy of maintaining constant active power or a strategy of maintaining constant current, but does not limit the output power of the machine-side converter, which will cause high-amplitude oscillation of the DC voltage of the converter during low-voltage ride-through, and poor stability of the DC voltage. SUMMARY

[0004] A series of simplified concepts are introduced in the summary section, which will be described in further detail in the detailed description section. The summary section of the present application does not mean to attempt to limit the key features and necessary technical features of the claimed technical solution, nor to determine the protection scope of the claimed technical solution.

[0005] In order to improve the control of the grid-side converter and the machine-side converter of the direct-drive wind turbine and ensure safe and reliable operation of the direct-drive wind turbine during low-voltage ride-through, in a first aspect, the present application provides a low-voltage ride-through control method for a direct-drive wind turbine, which comprises:

[0006] In a case where a low-voltage ride-through triggering module detects that the current voltage value of a target power grid where a target direct-drive wind turbine is located is lower than a preset reference value, a ride-through high-level signal is generated to activate a low-voltage ride-through mode, wherein the low-voltage ride-through control system for the direct-drive wind turbine comprises a grid-side control system and a machine-side control system, in the low-voltage ride-through mode, a voltage normal period reactive power control module of the grid-side control system is closed and a low-voltage period reactive power control module works, and a voltage normal period active power control module of the machine-side control system is closed and a low-voltage ride-through period active power control module works;

[0007] The voltage drop depth is calculated according to the current voltage value and the preset reference value.

[0008] The low-voltage period reactive power control module of the grid-side control system controls the target direct-drive wind turbine to output reactive power to the target power grid according to the voltage drop depth to support the power grid.

[0009] The low-voltage ride-through period active power control module of the machine-side control system controls the output power of the target direct-drive wind turbine according to the voltage drop depth.

[0010] Optionally, the low-voltage ride-through triggering module comprises an effective value calculator, a first-order hysteresis device, and a comparator.

[0011] The effective value calculator is configured to calculate the effective value of the three-phase AC voltage of the bus after phase change and voltage boost of the target direct-drive wind turbine.

[0012] The first-order hysteresis device is configured to low-pass filter the effective value of the three-phase AC voltage of the bus.

[0013] The comparator is configured to output the ride-through high level signal when the effective value of the three-phase AC voltage of the bus is lower than the preset low-voltage ride-through threshold value.

[0014] Optionally, the step of controlling the target direct-drive wind turbine to output reactive power to the target power grid according to the voltage drop depth to support the power grid comprises:

[0015] The low-voltage period reactive power control module of the grid-side control system calculates the reactive current corresponding to the reactive power according to the voltage drop depth by the following formula:

[0016] i ds_ref =1.5×(0.9-U pcc_pu )×1.1

[0017] wherein i ds_ref is the reactive current, 0.9-U pcc_pu is the voltage drop amplitude, and U pcc_pu is the effective value of the three-phase AC voltage of the bus.

[0018] The target direct-drive wind turbine is controlled to output the reactive current to the target power grid to support the power grid.

[0019] Optionally, the method further comprises:

[0020] The low voltage ride through trigger module generates a recovery low level signal to activate a voltage recovery mode when the current voltage value of the target power grid is restored to be greater than or equal to the preset reference value, wherein in the voltage recovery mode, the voltage normal period reactive power control module of the grid side control system is working and the low voltage period reactive power control module is closed, the voltage recovery period active power control module of the machine side control system is working and the low voltage ride through period active power control module is closed;

[0021] The voltage normal period reactive power control module of the grid side control system controls the target direct drive wind turbine to preferentially output active power to the target power grid.

[0022] The voltage recovery period active power control module of the machine side control system controls the output power of the target direct drive wind turbine to be raised to a rated value at a fixed raising speed.

[0023] Optionally, the method further comprises:

[0024] When the current voltage value is restored to be greater than or equal to the preset reference value, the target direct drive wind turbine controls the power according to the following formula:

[0025] T e = 1.5pΨ f i q

[0026] In the formula, T e is the electromagnetic torque of the direct drive wind turbine, p represents the number of pole pairs, Ψ f is the rotor flux of the direct drive wind turbine, i q is the component of the stator current of the direct drive wind turbine in the q-axis.

[0027] Optionally, the low voltage ride through period active power control module comprises an adder and a limiter.

[0028] The adder is used to calculate the difference between the target power grid voltage and the preset reference value.

[0029] The limiter is used to limit the output value of the adder within an acceptable range.

[0030] Optionally, the voltage recovery period active power control module comprises a sample and hold, an OR gate, a first adder, a divider, a pulse generator, a NOT gate, an integrator and a second adder.

[0031] The sample and hold is used to lock the active current value in the inner loop of the machine side converter when the target power grid voltage is still not restored to the preset reference value or the output active power of the wind turbine side is not restored to the rated value.

[0032] The first adder is used to calculate the difference between the active current command value in the low voltage ride through mode and the active current value in the inner loop of the wind turbine side converter.

[0033] The pulse generator receives a low-level signal through the input end and sends a high-level signal with a time length of the output value of the divider through the output end in the voltage recovery mode;

[0034] The NOT gate is used for maintaining a low-level signal in the voltage recovery mode;

[0035] The integrator is used for integrating according to a fixed slope value and outputting a change value of the inner loop active current instruction during voltage recovery;

[0036] The second adder is used for summing the change value of the inner loop active current instruction output by the integrator and an active current instruction value in the low voltage ride through mode to obtain an active current instruction in the voltage recovery mode.

[0037] In the second aspect, the application further provides a direct-drive wind turbine low voltage ride through control device, comprising:

[0038] The detection unit is used for generating a ride through high-level signal to activate a low voltage ride through mode when it is detected that a current voltage value of a target power grid where a target direct-drive wind turbine is located is lower than a preset reference value, wherein the direct-drive wind turbine low voltage ride through control system comprises a grid-side control system and a machine-side control system, in the low voltage ride through mode, a voltage normal period reactive power control module of the grid-side control system is closed and a low voltage period reactive power control module works, a voltage normal period active power control module of the machine-side control system is closed and a low voltage ride through period active power control module works;

[0039] The calculation unit is used for calculating a voltage drop depth according to the current voltage value and the preset reference value;

[0040] The first control unit is used for controlling the target direct-drive wind turbine to output reactive power to the target power grid to support the power grid according to the voltage drop depth;

[0041] The second control unit is used for controlling output power of the target direct-drive wind turbine according to the voltage drop depth.

[0042] In the third aspect, the application further provides a direct-drive wind turbine low voltage ride through control system, which can realize any one of the direct-drive wind turbine low voltage ride through control methods in the first aspect, and comprises a low voltage ride through triggering module, a voltage normal period reactive power control module, a low voltage period reactive power control module, a voltage normal period active power control module, a low voltage ride through period active power control module and a voltage recovery period active power control module.

[0043] In the fourth aspect, the application further provides a direct-drive wind turbine comprising the direct-drive wind turbine low voltage ride through control system in the third aspect.

[0044] The embodiment of the present application has the following beneficial effects:

[0045] The low-voltage ride-through control method of the direct-drive wind turbine provided in the present application overcomes the overvoltage oscillation of the prior art direct-current voltage, and comprehensively considers the control systems of the grid-side and machine-side converters of the direct-drive wind turbine, so that the direct-drive wind turbine can provide reactive power support for the power grid during low voltage and ensure the stability of the direct-current voltage. According to the change of the grid voltage, the machine-side active current command value during low voltage ride-through is quickly adjusted to limit the machine-side electromagnetic power from the source during low voltage ride-through. The imbalance of the grid-side and machine-side active power, overcharging of the direct-current capacitor and the low-voltage ride-through direct-current voltage oscillation problem are avoided. BRIEF DESCRIPTION OF DRAWINGS

[0046] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed in the following embodiment or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0047] Among them:

[0048] Figure 1 A low-voltage ride-through control method flowchart of a direct-drive wind turbine is provided for the embodiment of the present application;

[0049] Figure 2 A direct-drive wind turbine power flow diagram is provided for the embodiment of the present application;

[0050] Figure 3 A low-voltage ride-through control system structure diagram of a direct-drive wind turbine is provided for the embodiment of the present application;

[0051] Figure 4 A low-voltage ride-through trigger module RTDS simulation control block diagram of a grid-side converter control system of a direct-drive wind turbine is provided for the embodiment of the present application;

[0052] Figure 5 A low-voltage ride-through reactive power control module RTDS simulation control block diagram of a grid-side converter control system of a direct-drive wind turbine is provided for the embodiment of the present application;

[0053] Figure 6 A low-voltage ride-through active power control module RTDS simulation control block diagram of a machine-side converter control system of a direct-drive wind turbine is provided for the embodiment of the present application;

[0054] Figure 7 A voltage recovery active power control module RTDS simulation control block diagram of a machine-side converter control system of a direct-drive wind turbine is provided for the embodiment of the present application;

[0055] Figure 8 A low voltage ride through RTDS simulation test waveform schematic diagram of a direct drive wind turbine provided by the embodiment of the present application is provided;

[0056] Figure 9 A RTDS simulation result diagram of a direct current voltage controlled by the method of the present application provided by the embodiment of the present application is provided;

[0057] Figure 10 A RTDS simulation comparison diagram of a direct current voltage controlled by the existing method provided by the embodiment of the present application is provided;

[0058] Figure 11 A RTDS simulation result diagram of a direct current machine side converter dq axis inner ring current controlled by the method of the present application provided by the embodiment of the present application is provided;

[0059] Figure 12 A RTDS simulation result diagram of a direct current machine side converter dq axis inner ring current controlled by the existing method provided by the embodiment of the present application is provided;

[0060] Figure 13 A low voltage ride through control device structure schematic diagram of a direct drive wind turbine provided by the embodiment of the present application is provided;

[0061] Figure 14 A direct drive wind turbine low voltage ride through control electronic equipment structure schematic diagram provided by the embodiment of the present application is provided. DETAILED DESCRIPTION

[0062] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0063] The terms "first", "second", "third", "fourth", and the like in the description and in the claims of the present application and above-described drawings, if any, are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the use of the terms so construed herein is merely for convenience and brevity and does not necessarily imply a serial or chronological order unless expressly so defined by their content. Further, the terms "comprise", "have" and any variations thereof are intended to cover a non-exclusive inclusion, for example, a process, method, system, product or apparatus that comprises a list of steps or units is not necessarily limited to those steps or units which are expressly listed, but can include other steps or units not expressly listed or inherent to such process, method, product or apparatus. The technical solutions in the embodiments of the present application will be described clearly and completely in the following with reference to the drawings of the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all.

[0064] Please refer to Figure 1 A direct-drive wind turbine low-voltage ride-through control method flowchart provided by the embodiments of the present application can specifically include:

[0065] S110, generating a ride-through high-level signal to activate a low-voltage ride-through mode in the case that a low-voltage ride-through triggering module detects that the current voltage value of the target power grid where the target direct-drive wind turbine is located is lower than a preset reference value, wherein the direct-drive wind turbine low-voltage ride-through control system includes a grid-side control system and a machine-side control system, in the low-voltage ride-through mode, the voltage normal period reactive power control module of the grid-side control system is closed and the low-voltage period reactive power control module works, and the voltage normal period active power control module of the machine-side control system is closed and the low-voltage ride-through period active power control module works;

[0066] S120, calculating a voltage drop depth according to the current voltage value and the preset reference value;

[0067] S130, the low-voltage period reactive power control module of the grid-side control system controls the target direct-drive wind turbine to output reactive power to the target power grid according to the voltage drop depth;

[0068] S140, the low-voltage ride-through period active power control module of the machine-side control system controls the output power of the target direct-drive wind turbine according to the voltage drop depth.

[0069] For example, Figure 2 A direct-drive wind turbine power flow diagram, the direct-drive wind turbine converts mechanical energy into electrical energy by capturing wind energy, and transmits the electrical energy into the power grid through the conversion of the machine-side converter and the grid-side converter. Figure 3A direct-drive wind turbine low-voltage ride-through control system structure schematic diagram provided for an application, comprising: a low-voltage ride-through triggering module of a grid-side converter control system, a low-voltage period reactive power control module, a voltage normal period reactive power control module, an active power control module during a low-voltage ride-through period of a machine-side converter control system, an active power control module during voltage recovery, an active power control module during voltage normal period. When the power grid fails, the low-voltage ride-through triggering module detects the voltage drop of the power grid, generates a triggered high-level signal (i.e. ride-through high-level signal), and the wind turbine enters the low-voltage ride-through mode. The grid-side converter control system (i.e. grid-side control system) of the direct-drive wind turbine is switched from the voltage normal period reactive power control module to the low-voltage period reactive power control module (i.e. the voltage normal period reactive power control module of the grid-side control system is closed and the low-voltage period reactive power control module works), according to the voltage drop depth, the grid-side converter reactive current command Ids_ref value is adjusted, the reactive power is preferentially output to the grid side, and the grid voltage is supported. At the same time, the machine-side converter control system of the direct-drive wind turbine is switched from the voltage normal period active power control module to the low-voltage ride-through period active power control module (i.e. the voltage normal period active power control module of the machine-side control system is closed and the low-voltage ride-through period active power control module works), according to the grid-side voltage drop amplitude, the machine-side converter active current command Iqr_ref value is adjusted, the wind turbine machine-side torque current is rapidly reduced, the wind turbine machine-side electromagnetic power is limited, thereby reducing the wind turbine machine-side output power, avoiding overcharging of the direct current capacitor during the fault period, and causing direct current voltage overvoltage oscillation problem, it needs to be explained that the grid-side control system (i.e. grid-side control system) of the direct-drive wind turbine includes the machine-side converter, and the machine-side control system (i.e. machine-side control system) of the direct-drive wind turbine includes the grid-side converter.

[0070] In summary, the method provided by the embodiment of the application overcomes the direct current voltage overvoltage oscillation defect of the prior art, and comprehensively considers the grid-side and machine-side converter control systems of the direct-drive wind turbine, so that the direct-drive wind turbine can provide reactive power support for the power grid during the low-voltage period and ensure the stability of the direct current voltage. According to the change of the grid voltage, the machine-side active current command value during the low-voltage ride-through period is quickly adjusted, the machine-side electromagnetic power during the low-voltage ride-through period of the wind turbine is limited from the source, the imbalance between the grid-side and machine-side active powers is avoided, the direct current capacitor is overcharged, and the direct current voltage oscillation problem during the low-voltage ride-through period is avoided.

[0071] In some embodiments, the low-voltage ride-through triggering module comprises an effective value calculator, a first-order lag and a comparator.

[0072] The effective value calculator is used to calculate the effective value of the three-phase alternating current voltage of the busbar after phase change and voltage boost of the target direct-drive wind turbine.

[0073] The first-order lag is used to low-pass filter the effective value of the three-phase alternating current voltage of the busbar.

[0074] The comparator is used to output the high-level crossing signal when the effective value of the three-phase AC voltage of the bus is lower than the preset low-voltage crossing threshold.

[0075] For example, such as Figure 4 As shown, the three-phase AC voltages WF1Vtr1SecA, WF1Vtr1SecB, and WF1Vtr1SecC of the busbar after the wind turbine is stepped up by the transformer are monitored online in real time. The effective value of the three-phase voltage of the busbar is calculated as WTPCC. After normalization and low-pass filtering, the per-unit value of the busbar voltage WTPCCpu is obtained and compared with 0.9pu. When the grid voltage drops by 10% or more, a high-level signal LVRT_Det is output, and the direct-drive wind turbine is triggered to achieve low-voltage ride-through.

[0076] In some embodiments, the step of the reactive power control module of the grid-side control system controlling the target direct-drive wind turbine to output reactive power to the target grid to support the grid during low voltage periods, based on the voltage drop depth, includes:

[0077] The reactive power control module of the above-mentioned grid-side control system calculates the reactive current corresponding to the reactive power during the low-voltage period based on the voltage drop depth using the following formula:

[0078] i ds_ref =1.5×(0.9-U pcc_pu )×1.1

[0079] In the formula, i ds_ref For reactive current, 0.9-U pcc_pu U represents the voltage drop. pcc_pu This represents the effective value of the three-phase AC voltage at the busbar.

[0080] Control the aforementioned target direct-drive wind turbine to output the aforementioned reactive current to the aforementioned target power grid in order to support the power grid.

[0081] For example, after triggering a low-voltage ride-through, the grid-side converter control system of the direct-drive wind turbine adjusts the reactive current command value according to i ds_ref =1.5×(0.9-U pcc_pu )×1.1 generates reactive power; during low voltage periods, the reactive power control module, such as Figure 5 As shown. Reactive power is prioritized, while active power output is limited. The inner loop active current reference value of the grid-side converter is determined according to... Limit the amplitude.

[0082] In some embodiments, the above method further includes:

[0083] The low voltage ride through trigger module generates a recovery low level signal to activate a voltage recovery mode when the current voltage value of the target power grid is restored to be greater than or equal to the preset reference value, wherein in the voltage recovery mode, the voltage normal period reactive power control module of the grid side control system works and the low voltage period reactive power control module is closed, the voltage recovery period active power control module of the machine side control system works and the low voltage ride through period active power control module is closed;

[0084] The voltage normal period reactive power control module of the grid side control system controls the target direct drive wind turbine to preferentially output active power to the target power grid.

[0085] The voltage recovery period active power control module of the machine side control system controls the output power of the target direct drive wind turbine to increase to a rated value according to a fixed increase speed.

[0086] For example, when the power grid fault disappears, the low voltage ride through trigger module detects the recovery of the power grid voltage, generates a falling edge low level signal, and the wind turbine enters a recovery active power stage, preferentially outputs active power, and the machine side converter control system of the direct drive wind turbine is switched from the low voltage ride through period active power control module to the voltage recovery period active power control module, the active current command Iqr_ref value of the machine side converter is increased according to a fixed slope, and the output power of the wind turbine machine side is gradually recovered to the rated value. The control logic of the machine side converter control system is as follows: when the voltage of the power grid drops, the active current command value of the machine side converter in the low voltage ride through period is calculated according to the voltage drop amplitude of the grid side, so as to limit the output active power of the machine side converter during the low voltage ride through period. When the voltage of the power grid recovers, the active current command value of the machine side converter is recovered according to a preset fixed slope, so as to gradually recover the output active power of the machine side converter.

[0087] In some embodiments, the method further comprises:

[0088] When the current voltage value is restored to be greater than or equal to the preset reference value, the target direct drive wind turbine controls the power according to the following formula:

[0089] T e = 1.5pΨ f i q

[0090] In the formula, T e is the electromagnetic torque of the direct drive wind turbine, p represents the number of pole pairs, Ψ f is the rotor flux of the direct drive wind turbine, i q is the component of the stator current of the direct drive wind turbine in the q axis.

[0091] For example, when the grid voltage is normal, the direct-drive wind turbine's machine-side and grid-side converters employ active power control modules and reactive power control modules during normal voltage periods, i.e., dual-closed-loop vector typical control. The grid-side converter's outer loop uses constant reactive power control and constant DC voltage control to ensure a constant DC voltage and maximum active power output to the grid with unity power factor. The machine-side converter's outer loop employs maximum power point tracking (MPPT) control and i... d =0 control, according to MPPT capture wind energy output active power, by controlling the stator current i q Controlling the electromagnetic torque of the direct-drive fan, i.e., T e =1.5pΨ f i q In the formula: T e For the electromagnetic torque of the direct-drive fan, p represents the number of pole pairs, and Ψ represents the number of pole pairs. f For direct-drive fan rotor flux linkage, i q Let be the q-axis component of the stator current of the direct-drive wind turbine. It can be seen that the electromagnetic torque of the direct-drive wind turbine is determined by the active current i of the machine-side converter. q This decision, in turn, controls the output active power P of the machine-side converter. r During a grid fault, the grid-side converter outputs power P. s If the power cannot be transmitted, it will cause a power imbalance between the turbine side and the grid side. That is, the DC capacitor bears the unbalanced energy caused by the active power imbalance on both sides. When the DC voltage is greater than 1.4 pu, the energy is released by external hardware through the Chopper-controlled unloading circuit. This invention limits the output active power of the turbine-side converter during low voltage periods, reduces the unbalanced energy between the turbine side and the grid side, and improves the stability of the DC voltage. At the same time, the reactive power output by the grid-side converter supports the grid voltage, enabling direct-drive wind turbines to achieve low voltage ride-through more safely and reliably.

[0092] In some implementations, the active power control module during the low voltage ride-through includes an adder and a limiter.

[0093] The above adder is used to calculate the difference between the target grid voltage and the preset reference value;

[0094] The aforementioned limiter is used to limit the adder output value to an acceptable range.

[0095] For example, such as Figure 6 As shown, the adder is used to calculate the difference between the grid voltage and the adjustment constant; the limiter is used to limit the adder output to between 0 and 1, ensuring that the active power on the generator side is greater than or equal to 0 during the low voltage ride-through period. After limiting, the active current command Ir_IqLVRT_0 during the low voltage ride-through period is obtained.

[0096] In some implementations, the active power control module for voltage recovery includes a sample-and-hold circuit, an OR gate, a first adder, a divider, a pulse generator, a NOT gate, an integrator, and a second adder.

[0097] The aforementioned sample-and-hold circuit is used to lock the active current value of the inner loop of the generator-side converter when the target grid voltage has not yet recovered to the preset reference value or the active power output of the wind turbine has not recovered to the rated value.

[0098] The first adder mentioned above is used to calculate the difference between the active current command value and the active current value of the inner loop of the wind turbine-side converter under low voltage ride-through mode.

[0099] In the voltage recovery mode, the pulse generator receives a low-level recovery signal at its input and outputs a high-level signal with a duration equal to the divider's output value.

[0100] The NOT gate described above is used to maintain a low-level signal in the voltage recovery mode described above;

[0101] The integrator described above is used to integrate at a fixed slope value and output the inner loop active current command change value during voltage recovery.

[0102] The second adder is used to sum the inner loop active current command change value output by the integrator and the active current command value in low voltage ride-through mode to obtain the active current command in voltage recovery mode.

[0103] For example, such as Figure 7 As shown, the active power control module during voltage recovery includes a sample-and-hold circuit, an OR gate, a first adder, a divider, a pulse generator, a NOT gate, an integrator, and a second adder. The sample-and-hold circuit locks the active current value of the generator-side converter's inner loop when entering low-voltage recovery, provided the grid voltage has not yet recovered to 0.9 pu or the generator-side output active power has not recovered. The first adder calculates the difference between the active current command value during low-voltage recovery and the active current value of the generator-side converter's inner loop when entering low-voltage recovery. The output of the first adder is divided by a fixed slope value by a divider to obtain the recovery time value of the generator-side converter's inner loop active current as it gradually increases to the active current value when entering low-voltage recovery. The pulse generator is used to change from a high level to a low level when the grid voltage recovers. The falling edge signal of the gate outputs a high-level signal with a duration equal to the divider output value. The input of the NOT gate is the pulse generator output, which outputs 0 after negating the high-level signal during the low-voltage recovery process. The NOT gate is used to maintain a low-level signal during the low-voltage recovery period. The integrator integrates at a fixed slope value and outputs the change value of the inner loop active current command during the voltage recovery period. The second adder is used to sum the change value of the inner loop active current command output by the integrator and the active current command value during the low-voltage recovery period to obtain the active current command Iqr_ref during the voltage recovery period.

[0104] In some examples, the direct-drive wind turbine generator machine-side converter control system triggers low-voltage ride-through active power control during low voltage, and the active power control module is as shown in Figure 6 When the voltage difference is limited in amplitude, the active current instruction value Ir_IqLVRT_0 during low-voltage ride-through is obtained.

[0105] When the grid fault disappears and the grid voltage starts to recover, the voltage recovery active power control module of the direct-drive wind turbine generator machine-side converter control system is as shown in Figure 7 As long as the grid voltage has not recovered to 0.9 pu or the active current has not recovered to the locked value at the time of low-voltage ride-through, the low-voltage trigger signal LVRT_Det and the recovery trigger signal LVRT_Rcov output a high-level signal after an OR gate, thereby maintaining the active current value WT1IqSTPURef0 at the time of low-voltage ride-through. The difference between the value and the active current instruction value Ir_IqLVRT_0 during low-voltage ride-through is calculated, and the result is divided by the preset active current fixed slope recovery value LV_Rate to obtain the time of recovery to the active current value WT1IqSTPURef0 at the time of low-voltage ride-through. As the voltage gradually recovers, when the voltage is greater than 0.9 pu, the input end of the pulse generator receives a falling edge signal with a low level, and the output end outputs a high-level signal with a time length of the output value of the divider. This makes the integrator always integrate according to the preset fixed slope value during the recovery time of the active current instruction, and outputs the inner loop active current instruction recovery value during voltage recovery. The value is then summed with the active current instruction value Ir_IqLVRT_0 during low-voltage ride-through to obtain the active current instruction Iqr_ref during voltage recovery, thereby controlling the wind turbine generator to gradually recover the active power to the value before low-voltage ride-through according to the fixed slope.

[0106] When the grid voltage is normal, the direct-drive wind turbine generator grid-side converter adopts the voltage normal period reactive power control module, i.e. constant control with zero reactive power. When the grid voltage is normal and the active power of the direct-drive wind turbine generator recovers to the rated state, the active power control of the machine-side converter adopts the voltage normal period active power control module, i.e. capturing wind energy according to maximum power tracking to output active power.

[0107] During the simulation experiment, the low-voltage ride-through control method and system of the direct-drive wind turbine generator are constructed by RTDS real-time simulation and applied to the full electromagnetic transient simulation system of the direct-drive wind farm connected to an infinite power source. A low-voltage fault is set on the grid side, the grid side voltage drops to 20%, and the fault is removed after a duration of 625 ms. The simulation waveforms of the active power pu and the reactive power pu of the wind turbine generator, and the bus voltage pu are as shown in Figure 8The direct-drive wind turbine provides reactive power support for the power grid when the voltage drops to 20%, and the active power is restored to the value before the fault at a power change rate of 500% Pn / s after the low penetration ends.

[0108] The results obtained by using the application are compared with the simulation results of the conventional control (only control the grid-side converter), and the comparison results of the DC voltage are as follows Figure 9 、 Figure 10 The DC voltage under the conventional control has an oscillation problem, the DC voltage under the control of the application is as low as 0.8 pu during the low penetration, and the DC voltage rapidly rises to 1.3 pu at the voltage recovery moment, and then gradually recovers to the steady state. The comparison results of the dq-axis inner loop current of the machine-side converter are as follows Figure 11 、 Figure 12 The active current under the control of the application is limited to 0 during the low penetration, and the dq-axis current under the conventional control continuously oscillates during the low penetration.

[0109] Please refer to Figure 13 The application further provides a direct-drive wind turbine low voltage ride-through control device, which comprises:

[0110] A detection unit 21 is configured to generate a ride-through high level signal to activate a low voltage ride-through mode when it is detected that a current voltage value of a target power grid where a target direct-drive wind turbine is located is lower than a preset reference value, wherein the direct-drive wind turbine low voltage ride-through control system comprises a grid-side control system and a machine-side control system, the voltage normal period reactive power control module of the grid-side control system is closed and the low voltage period reactive power control module is in operation under the low voltage ride-through mode, and the voltage normal period active power control module of the machine-side control system is closed and the low voltage ride-through period active power control module is in operation.

[0111] A calculation unit 22 is configured to calculate a voltage drop depth according to the current voltage value and the preset reference value.

[0112] A first control unit 23 is configured to control the target direct-drive wind turbine to output reactive power to the target power grid according to the voltage drop depth.

[0113] A second control unit 24 is configured to control the output power of the target direct-drive wind turbine according to the voltage drop depth.

[0114] As shown in Figure 14 The application further provides an electronic device 300, which comprises a memory 310, a processor 320, and a computer program 311 stored in the memory 320 and capable of running on the processor, and the processor 320 implements the steps of any method for controlling the outlet temperature of a slot-type solar heat collection field when executing the computer program 311.

[0115] Since the electronic device introduced in the embodiment is the device used in the implementation of the slot type solar heat collection field outlet temperature control device in the embodiment of the application, based on the method introduced in the embodiment of the application, the person skilled in the art can understand the specific implementation of the electronic device in the embodiment and various changes thereof, so how the electronic device implements the method in the embodiment of the application is not described in detail here, as long as the device used by the person skilled in the art to implement the method in the embodiment of the application belongs to the scope of the application.

[0116] In the specific implementation process, the computer program 311 can realize the functions of the method, the device and the electronic equipment in the embodiment of the application when the computer program 311 is executed by the processor. Figure 1 Any of the embodiments in the corresponding embodiment.

[0117] It should be noted that in the above embodiments, the description of each embodiment has its own emphasis, and the parts not described in detail in a certain embodiment can be referred to the related description of other embodiments.

[0118] Those skilled in the art should understand that the embodiments of the application can be provided as a method, a system, or a computer program product. Therefore, the application can adopt a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Moreover, the application can adopt the form of a computer program product implemented on one or more computer usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer usable program codes.

[0119] The application is described with reference to flowcharts and / or block diagrams according to the method, device (system), and computer program product of the embodiment of the application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of the flows and / or blocks in the flowcharts and / or block diagrams can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded computer, or other programmable data processing devices to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices produce a device for implementing the functions specified in the flowcharts and / or block diagrams. Figure 1 The functions specified in one flow or multiple flows and / or blocks. Figure 1 The functions specified in one block or multiple blocks.

[0120] These computer program instructions can also be stored in a computer readable storage medium that can guide the computer or other programmable data processing devices to work in a specific way, so that the instructions stored in the computer readable storage medium produce a manufactured product including instruction devices, which implement the functions specified in the flowcharts and / or block diagrams. Figure 1 The functions specified in one flow or multiple flows and / or blocks. Figure 1 The functions specified in one block or multiple blocks.

[0121] These computer program instructions can also be loaded into a computer or other programmable data processing devices, so that a series of operation steps are performed on the computer or other programmable devices to generate a computer implemented process, so that the instructions executed on the computer or other programmable devices provide a process for implementing the functions specified in the flow Figure 1 one flow or multiple flows and / or the functions specified in the block Figure 1 one block or multiple blocks.

[0122] The embodiments of the present application also provide a computer program product, which comprises computer software instructions, when the computer software instructions are run on a processing device, so that the processing device executes the functions as ​ The flow of the low-voltage ride-through control method of the direct-driven wind turbine in the corresponding embodiments.

[0123] The computer program product comprises one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the flow or function according to the embodiments of the present application is generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable devices. The computer instructions can be stored in a computer readable storage medium or transferred from one computer readable storage medium to another computer readable storage medium, for example, the computer instructions can be transmitted from one website, computer, server or data center to another website, computer, server or data center through wired (such as coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (such as infrared, wireless, microwave, etc.) mode. The computer readable storage medium can be any available medium that the computer can store or be integrated into a data storage device such as a server, data center, etc. containing one or more available media sets. The available media can be a magnetic medium (for example, a floppy disk, a hard disk, a magnetic tape), an optical medium (for example, a DVD), or a semiconductor medium (for example, a solid state disk (SSD)) and the like.

[0124] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working process of the above-described system, device and unit can refer to the corresponding process in the foregoing method embodiments, which will not be described here.

[0125] In several embodiments provided in the present application, it should be understood that the disclosed system, device and method can be implemented in other manners. For example, the division of the units is only a logical function division, and there can be another division manner for the actual implementation, for example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the displayed or discussed mutual couplings or direct couplings or communication connections between different units, or the among different units, can be indirect couplings or communication connections through some interfaces, devices or units, and can be in electrical, mechanical or other forms.

[0126] The units described as separated components can or can not be physically separated, and the components displayed as units can or can not be physical units, i.e., can be located in one place, or can be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purposes of the embodiments of the present application.

[0127] In addition, each functional unit in the embodiments of the present application can be integrated in a processing unit, or each unit can exist physically, or two or more units can be integrated in one unit. The integrated unit can be implemented in the form of hardware, or in the form of a software functional unit.

[0128] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer readable storage medium. Based on such an understanding, the technical solutions of the present application essentially, or the part that contributes to the prior art, or all or a part of the technical solutions can be embodied in the form of a software product. The computer software product is stored in a storage medium, and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods in the embodiments of the present application. The foregoing storage medium includes: a U disk, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk, and various other media that can store program codes.

[0129] The above only describes the preferred embodiments of the present application, and of course cannot limit the scope of the rights of the present application, so the equivalent changes made according to the claims of the present application are still within the scope of the present application.

Claims

1. A direct drive wind turbine low voltage ride through control method for a direct drive wind turbine low voltage ride through control system, characterized in that, The method comprises the following steps: In the case that the low voltage ride-through triggering module detects that the current voltage value of the target power grid where the target direct-driven wind turbine is located is lower than the preset reference value, a ride-through high level signal is generated to activate the low voltage ride-through mode, wherein the direct-driven wind turbine low voltage ride-through control system comprises a grid-side control system and a machine-side control system, in the low voltage ride-through mode, the voltage normal period reactive power control module of the grid-side control system is closed and the low voltage period reactive power control module works, the voltage normal period active power control module of the machine-side control system is closed and the low voltage ride-through period active power control module works; The voltage drop depth is calculated according to the current voltage value and the preset reference value; The low voltage period reactive power control module of the grid-side control system controls the target direct-driven wind turbine to output reactive power to the target power grid according to the voltage drop depth to support the target power grid; The low voltage ride-through period active power control module of the machine-side control system controls the output power of the target direct-driven wind turbine according to the voltage drop depth; The active power control module when the current voltage value recovers comprises a sample and hold, an OR gate, a first adder, a divider, a pulse generator, a NOT gate, an integrator and a second adder; The sample and hold is used to lock the machine-side converter inner loop active current value when the target power grid voltage has not recovered to the preset reference value or the wind turbine side output active power has not recovered to the rated value; The first adder is used to calculate the difference between the active current instruction value in the low voltage ride-through mode and the wind turbine side converter inner loop active current value; The pulse generator receives the recovery low level signal through the input end in the voltage recovery mode, and sends out the high level signal with the time length of the divider output value through the output end; The NOT gate is used to maintain the low level signal in the voltage recovery mode; The integrator is used to integrate according to the fixed slope value, and output the inner loop active current instruction change value in the voltage recovery period; The second adder is used to sum the inner loop active current instruction change value output by the integrator and the active current instruction value in the low voltage ride-through mode to obtain the active current instruction in the voltage recovery mode.

2. The method of claim 1, wherein, The low voltage ride-through triggering module comprises an effective value calculator, a first-order hysteresis and a comparator; The effective value calculator is used to calculate the effective value of the three-phase alternating current voltage of the bus bar after the phase change and voltage boost of the target direct-driven wind turbine; The first-order hysteresis is used to low-pass filter the effective value of the three-phase alternating current voltage of the bus bar; The comparator is used to output the ride-through high level signal when the effective value of the three-phase alternating current voltage of the bus bar is lower than the preset low voltage ride-through threshold value.

3. The method of claim 1, wherein, The step that the low voltage period reactive power control module of the grid-side control system controls the target direct-driven wind turbine to output reactive power to the target power grid according to the voltage drop depth to support the power grid comprises: The low voltage period reactive power control module of the grid-side control system calculates the reactive current corresponding to the reactive power according to the voltage drop depth through the following formula: In the formula, is the reactive current, 0.9- is the voltage drop amplitude, is the bus three-phase AC voltage effective value; The target direct-driven wind turbine outputs the reactive current to the target power grid to support the power grid.

4. The method of claim 1, wherein, The method further comprises the following steps: The low-voltage ride-through trigger module generates a recovery low-level signal to activate a voltage recovery mode when the current voltage value of the target power grid is restored to be greater than or equal to the preset reference value, wherein in the voltage recovery mode, a voltage normal period reactive power control module of the grid-side control system is in operation and a low-voltage period reactive power control module is closed, and a voltage recovery period active power control module of the machine-side control system is in operation and a low-voltage ride-through period active power control module is closed; The voltage normal period reactive power control module of the grid-side control system controls the target direct-drive wind turbine to preferentially output active power to the target power grid; The voltage recovery period active power control module of the machine-side control system controls the target direct-drive wind turbine to increase output power to a rated value at a fixed increase speed.

5. The method of claim 4, wherein, Further comprising: When the current voltage value is restored to be greater than or equal to the preset reference value, the target direct-drive wind turbine controls power according to the following formula: where: T e is the electromagnetic torque of the direct drive fan, p represents the number of pole pairs, is the rotor flux of the direct drive fan, i q is the component of the stator current of the direct drive fan in the q-axis.

6. The method of claim 1, wherein, The low-voltage ride-through period active power control module comprises an adder and a limiter; The adder is used to calculate a difference between the target power grid voltage and the preset reference value; The limiter is used to limit the adder output value within an acceptable range.

7. A wind turbine low voltage ride through control device, characterized by Comprising: A detection unit is configured to generate a ride-through high-level signal to activate a low-voltage ride-through mode when a current voltage value of a target power grid in which a target direct-drive wind turbine is located is detected to be lower than a preset reference value, wherein the direct-drive wind turbine low-voltage ride-through control system comprises a grid-side control system and a machine-side control system, and in the low-voltage ride-through mode, a voltage normal period reactive power control module of the grid-side control system is closed and a low-voltage period reactive power control module is in operation, and a voltage normal period active power control module of the machine-side control system is closed and a low-voltage ride-through period active power control module is in operation; A calculation unit is configured to calculate a voltage drop depth according to the current voltage value and the preset reference value; A first control unit is configured to control the target direct-drive wind turbine to output reactive power to the target power grid to support the target power grid according to the voltage drop depth; A second control unit is configured to control output power of the target direct-drive wind turbine according to the voltage drop depth; The device is further configured to: The low-voltage ride-through trigger module generates a recovery low-level signal to activate a voltage recovery mode when the current voltage value of the target power grid is restored to be greater than or equal to the preset reference value, and the voltage recovery period active power control module comprises a sample-and-hold device, an OR gate, a first adder, a divider, a pulse generator, a NOT gate, an integrator and a second adder; The sample-and-hold device is used to lock the machine-side converter inner loop active current value at the time of entering the low-voltage ride-through mode when the target power grid voltage is still not restored to the preset reference value or the wind turbine side output active power is not restored to the rated value; The first adder is used to calculate a difference between an active current instruction value in the low-voltage ride-through mode and the wind turbine side converter inner loop active current value; The pulse generator receives the recovery low-level signal through an input end and sends a high-level signal with a time length of the divider output value through an output end in the voltage recovery mode; The NOT gate is used to maintain a low-level signal in the voltage recovery mode; The integrator is configured to integrate with a fixed slope value, and output a value of change of inner loop active current command during voltage recovery period; The second adder is configured to sum the value of change of inner loop active current command output by the integrator and a value of active current command in low voltage ride through mode to obtain a value of active current command in voltage recovery mode.

8. A direct drive wind turbine low voltage ride through control system, capable of implementing the direct drive wind turbine low voltage ride through control method of any of claims 1-6, characterized by, The method comprises: The low voltage ride through triggering module, the reactive power control module during normal voltage period, the reactive power control module during low voltage period, the active power control module during normal voltage period, the active power control module during low voltage ride through period and the active power control module during voltage recovery period.

9. A direct drive blower, characterized by, The direct drive wind turbine low voltage ride through control system comprises the direct drive wind turbine low voltage ride through control system according to claim 8.

Images