Method and corresponding device for controlling active power output of wind farm

Abstract

The present invention provides a method and corresponding device for controlling the active power output of a wind farm. The method comprises: when the wind farm enters a low voltage ride-through state due to a voltage drop at the grid connection point, determining the maximum active power value allowed to be output by the wind farm in the current low voltage ride-through state; determining whether the sum of the active power values ​​currently output by all wind turbines in the wind farm exceeds the determined maximum active power value; when it is determined that the sum of the active power values ​​exceeds the determined maximum active power value, controlling the wind turbines to adjust the active power output value so that the sum of the active power output values ​​of all wind turbines does not exceed the determined maximum active power value. According to the method and corresponding device, the wind farm can still ensure that the wind farm transmits active power to the outside during the low voltage ride-through period.

Description

Technical Field

[0001] The present invention generally relates to the field of wind power technology, and more specifically, to a method for controlling active power output of a wind farm and a corresponding device. Background Art

[0002] like Figure 1 As shown in the figure, the offshore full DC wind farm using parallel medium-voltage DC wind turbines can directly transmit the DC power output by the medium-voltage DC wind turbines to the onshore converter station via the DC transmission line, thereby eliminating the offshore converter platform and large-capacity converter station. Compared with the high-voltage AC transmission scheme with an offshore AC booster station, it has greater economic advantages. Among the various topologies of DC wind turbines, the DC wind turbines that use AC boost transformers and diode uncontrolled rectifier bridges as the key links of AC-DC power conversion have broader application prospects due to their good economy and high reliability.

[0003] In order to solve the problem of riding through a voltage drop at the onshore AC power grid connection point, the prior art sends a signal indicating low voltage riding through to the offshore DC wind turbine generator set, and the wind turbine generator set reduces the AC voltage amplitude output by the grid-side converter, so that the voltage input to the rectifier (i.e., the diode uncontrolled rectifier bridge) is lower than the rectifier rectification voltage threshold, thereby completely blocking the wind turbine generator set from outputting active power to the outside, and further completely blocking the entire wind farm from transmitting active power to the outside. This method not only leads to power generation loss, but is also not conducive to operation recovery after a power grid system failure. Summary of the invention

[0004] An exemplary embodiment of the present invention provides a method and a corresponding device for controlling active power output of a wind farm, which can ensure that the wind farm transmits active power to the outside during low voltage ride-through of the wind farm.

[0005] According to an exemplary embodiment of the present invention, a method for controlling the active power output of a wind farm is provided, the method comprising: when the wind farm enters a low voltage ride-through state due to a grid connection point voltage drop, determining a maximum active power value allowed to be output by the wind farm in the current low voltage ride-through state; determining whether the sum of the active power values ​​currently output by all wind turbines in the wind farm exceeds the determined maximum active power value; when it is determined that the sum of the active power values ​​exceeds the determined maximum active power value, controlling the wind turbines to adjust the active power output values ​​so that the sum of the active power output values ​​of all wind turbines does not exceed the determined maximum active power value.

[0006] Optionally, the step of determining the maximum active power value allowed to be output by the wind farm in the current low voltage ride-through state includes: determining the maximum apparent power value allowed by the converter station of the wind farm in the current low voltage ride-through state and the minimum reactive power value allowed for the converter station to output to the grid connection point; based on the maximum apparent power value allowed by the converter station in the current low voltage ride-through state and the minimum reactive power value allowed for the converter station to output to the grid connection point, determining the maximum active power value allowed to be output by the wind farm in the current low voltage ride-through state, wherein each wind turbine generator set in the wind farm is connected to the power grid via the converter station.

[0007] Optionally, the step of determining the maximum apparent power value allowed by the converter station of the wind farm in the current low voltage ride-through state and the minimum reactive power value allowed by the converter station to output to the grid connection point includes: based on the voltage value to which the grid connection point voltage of the wind farm currently drops, determining the maximum apparent power value allowed by the converter station of the wind farm in the current low voltage ride-through state and the minimum reactive power value allowed by the converter station to output to the grid connection point.

[0008] Optionally, the step of controlling the wind turbine generator sets to adjust the active power output values ​​so that the sum of the active power output values ​​of all the wind turbine generator sets does not exceed the determined maximum active power value includes: determining the active power output target value of each wind turbine generator set, wherein the sum of the active power output target values ​​of all the wind turbine generator sets does not exceed the determined maximum active power value; and controlling the wind turbine generator sets based on the determined active power output target value of each wind turbine generator set.

[0009] Optionally, the step of determining the active power output target value of each wind turbine generator set includes: determining the active power output target value of each wind turbine generator set based on the active power value currently output by each wind turbine generator set, so that the sum of the active power output target values ​​of all wind turbine generator sets is closest to the determined maximum active power value under the condition that the active power output target value of each wind turbine generator set does not exceed the active power value currently output by the wind turbine generator set;

[0010] Alternatively, the ratio between the determined maximum active power value and the total number of wind turbines in the wind farm is used as the maximum active power value allowed to be output by each wind turbine under the current low voltage ride-through state; and for each wind turbine, when the active power value currently output by the wind turbine exceeds the determined maximum active power value allowed to be output by each wind turbine, the determined maximum active power value allowed to be output by each wind turbine is used as the active power output target value of the wind turbine.

[0011] Optionally, based on the determined active power output target value of each wind turbine generator set, the step of controlling the wind turbine generator set includes: for each wind turbine generator set, when the active power value currently output by the wind turbine generator set exceeds the active power output target value of the wind turbine generator set, sending the determined active power output target value of the wind turbine generator set to the wind turbine generator set;

[0012] Alternatively, for each wind turbine generator set, when the active power value currently output by the wind turbine generator set exceeds the active power output target value of the wind turbine generator set, the amount of active power that needs to be absorbed by the unloading circuit in the converter of the wind turbine generator set in order for the wind turbine generator set to reach the corresponding active power output target value is calculated, and the calculated amount of active power that needs to be absorbed by the unloading circuit is sent to the wind turbine generator set;

[0013] Alternatively, for each wind turbine generator set, when the active power value currently output by the wind turbine generator set exceeds the active power output target value of the wind turbine generator set, a voltage reference value of the DC capacitor in the converter of the wind turbine generator set is calculated so that the wind turbine generator set can reach the corresponding active power output target value, and the calculated voltage reference value of the DC capacitor is sent to the wind turbine generator set.

[0014] Optionally, the step of calculating the voltage reference value of the DC capacitor in the converter of the wind turbine generator set that enables the wind turbine generator set to reach the corresponding active power output target value includes: calculating the active power amount P that needs to be absorbed by the unloading circuit in the converter of the wind turbine generator set in order for the wind turbine generator set to reach the corresponding active power output target value. chopper Based on the voltage value of the DC capacitor when the unloading circuit is fully operational, the resistance value of the discharge resistor of the unloading circuit, the on-resistance value of the switch device of the unloading circuit, and the voltage value of the DC capacitor when the unloading circuit starts to operate, calculate the active power P that can be absorbed by the unloading circuit chopper The voltage reference value of the DC capacitor.

[0015] Optionally, the calculation enables the unloading circuit to absorb the calculated active power amount P chopper The step of calculating the voltage reference value of the DC capacitor comprises: calculating the voltage reference value u of the DC capacitor by the following formula: c :

[0016]

[0017] Among them, u c,max Indicates the voltage value of the DC capacitor when the unloading circuit is fully operational, R d Indicates the resistance value of the discharge resistor of the unloading circuit, Ron Indicates the on-resistance of the switch device of the unloading circuit, u c,min Indicates the voltage value of the DC capacitor when the unloading circuit starts to operate, D max Indicates the maximum duty cycle corresponding to the unloading circuit.

[0018] Optionally, the method also includes: determining the current voltage value of the grid connection point based on the amplitude and / or frequency of other signals different from the DC signal on the DC bus used for power transmission between the wind turbine generator set and the converter station of the wind farm; when the current voltage value of the grid connection point is lower than a preset threshold, determining that the wind farm has entered a low voltage ride-through state due to a voltage drop at the grid connection point, wherein there is a preset mapping relationship between the amplitude and / or frequency of the other signal and the voltage value at the grid connection point, wherein each wind turbine generator set in the wind farm is connected to the power grid via the converter station, and the other signal is a sinusoidal signal or a square wave signal.

[0019] According to another exemplary embodiment of the present invention, a controller of a wind farm is provided, and the controller of the wind farm includes: a first communication module, which is used to realize communication between a first processor and a wind turbine generator set; the first processor is configured to perform the following operations: when the wind farm enters a low voltage ride-through state due to a voltage drop at a grid connection point, determining a maximum active power value allowed to be output by the wind farm in the current low voltage ride-through state; determining whether the sum of the active power values ​​currently output by all wind turbine generator sets in the wind farm exceeds the determined maximum active power value; when it is determined that the sum of the active power values ​​exceeds the determined maximum active power value, controlling the first communication module to send an active power control instruction to the wind turbine generator set, so that the sum of the active power output values ​​of all wind turbine generator sets does not exceed the determined maximum active power value.

[0020] Optionally, the first processor is also configured to: determine the maximum apparent power value allowed by the converter station of the wind farm in the current low voltage ride-through state and the minimum reactive power value allowed for the converter station to output to the grid connection point; and based on the maximum apparent power value allowed by the converter station in the current low voltage ride-through state and the minimum reactive power value allowed for the converter station to output to the grid connection point, determine the maximum active power value allowed for the wind farm to output in the current low voltage ride-through state, wherein each wind turbine generator set in the wind farm is connected to the power grid via the converter station.

[0021] Optionally, the first processor is further configured to: when it is determined that the sum of the active power values ​​exceeds the determined maximum active power value, determine the active power output target value of each wind turbine generator set, wherein the sum of the active power output target values ​​of all wind turbine generator sets does not exceed the determined maximum active power value; and based on the determined active power output target value of each wind turbine generator set, control the first communication module to send an active power control instruction to the wind turbine generator set.

[0022] Optionally, the first processor is further configured to: determine the active power output target value of each wind turbine generator set based on the active power value currently output by each wind turbine generator set, so that the sum of the active power output target values ​​of all wind turbine generator sets is closest to the determined maximum active power value under the condition that the active power output target value of each wind turbine generator set does not exceed the active power value currently output by the wind turbine generator set;

[0023] Alternatively, the ratio between the determined maximum active power value and the total number of wind turbines in the wind farm is used as the maximum active power value allowed to be output by each wind turbine under the current low voltage ride-through state; and for each wind turbine, when the active power value currently output by the wind turbine exceeds the determined maximum active power value allowed to be output by each wind turbine, the determined maximum active power value allowed to be output by each wind turbine is used as the active power output target value of the wind turbine.

[0024] Optionally, the first processor is further configured to: for each wind turbine generator set, when the active power value currently output by the wind turbine generator set exceeds the active power output target value of the wind turbine generator set, control the first communication module to send an active power control instruction including the determined active power output target value of the wind turbine generator set to the wind turbine generator set;

[0025] Alternatively, for each wind turbine generator set, when the active power value currently output by the wind turbine generator set exceeds the active power output target value of the wind turbine generator set, the amount of active power that needs to be absorbed by the unloading circuit in the converter of the wind turbine generator set is calculated in order for the wind turbine generator set to reach the corresponding active power output target value, and the first communication module is controlled to send an active power control instruction including the calculated amount of active power that needs to be absorbed by the unloading circuit to the wind turbine generator set;

[0026] Alternatively, for each wind turbine generator set, when the active power value currently output by the wind turbine generator set exceeds the active power output target value of the wind turbine generator set, a voltage reference value of the DC capacitor in the converter of the wind turbine generator set is calculated so that the wind turbine generator set can reach the corresponding active power output target value, and the first communication module is controlled to send an active power control instruction including the calculated voltage reference value of the DC capacitor to the wind turbine generator set.

[0027] Optionally, the first processor is further configured to: determine the current voltage value of the grid connection point based on the amplitude and / or frequency of other signals different from the DC signal on the DC bus used for power transmission between the wind turbine generator set and the converter station of the wind farm; and when the current voltage value of the grid connection point is lower than a preset threshold, determine that the wind farm enters a low voltage ride-through state due to a voltage drop at the grid connection point, wherein there is a preset mapping relationship between the amplitude and / or frequency of the other signal and the voltage value of the grid connection point, wherein each wind turbine generator set in the wind farm is connected to the power grid via the converter station, and the other signal is a sinusoidal signal or a square wave signal.

[0028] According to another exemplary embodiment of the present invention, a control device of a wind turbine generator set is provided, the control device comprising: a second communication module, used to enable a second processor to communicate with a controller of the wind farm as described above; the second processor is configured to perform the following operations: determine a voltage reference value of a DC capacitor in a converter of the wind turbine generator set based on an active power control instruction received from the controller of the wind farm through the second communication module; and control the voltage of the DC capacitor according to the voltage reference value of the DC capacitor.

[0029] Optionally, the second processor is further configured to: when the received active power control instruction is an active power control instruction including an amount of active power that needs to be absorbed by a load shedding circuit in a converter of the wind turbine generator set, calculate a voltage reference value of a DC capacitor in the converter based on the amount of active power that needs to be absorbed by the load shedding circuit;

[0030] And / or, the second processor is further configured to: when the received active power control instruction is an active power control instruction including an active power output target value, calculate the amount of active power that needs to be absorbed by the unloading circuit in the converter in order to achieve the active power output target value, and calculate the voltage reference value of the DC capacitor in the converter based on the calculated amount of active power that needs to be absorbed by the unloading circuit;

[0031] And / or, the second processor is further configured to: when the received active power control instruction is an active power control instruction including a voltage reference value of the DC capacitor in the converter, directly set the voltage reference value of the DC capacitor in the converter to the received voltage reference value.

[0032] According to another exemplary embodiment of the present invention, a system for controlling active power output of a wind farm is provided, the system comprising: a controller of the wind farm as described above; and control devices of a plurality of wind turbine generator sets as described above connected to the controller of the wind farm.

[0033] According to another exemplary embodiment of the present invention, a computer-readable storage medium storing a computer program is provided, and when the computer program is executed by a processor, the method for controlling active power output of a wind farm as described above is implemented.

[0034] According to the method and corresponding device for controlling the active power output of a wind farm according to an exemplary embodiment of the present invention, it is possible to ensure that the active power transmitted to the outside of the wind farm is not interrupted during the low voltage ride-through of the wind farm (i.e., during the period of deep voltage drop at the grid connection point), thereby maximizing the power generation of the wind farm and facilitating the operation recovery after a power grid system failure.

[0035] Additional aspects and / or advantages of the present general inventive concept will be set forth in part in the following description and in part will be obvious from the description, or may be learned through practice of the present general inventive concept. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The above and other objects and features of the exemplary embodiments of the present invention will become more apparent through the following description in conjunction with the accompanying drawings which exemplarily illustrate the embodiments, in which:

[0037] Figure 1 A schematic diagram showing an offshore all-DC wind farm;

[0038] Figure 2 A flow chart showing a method for controlling active power output of a wind farm according to an exemplary embodiment of the present invention;

[0039] Figure 3 A structural block diagram of a controller of a wind farm according to an exemplary embodiment of the present invention is shown;

[0040] Figure 4 A structural block diagram showing a control device for a wind turbine generator set according to an exemplary embodiment of the present invention;

[0041] Figure 5 A structural block diagram of a system for controlling active power output of a wind farm according to an exemplary embodiment of the present invention is shown. DETAILED DESCRIPTION

[0042] Reference will now be made in detail to embodiments of the present invention, examples of which are shown in the accompanying drawings, wherein like reference numerals refer to like parts throughout. The embodiments will be described below with reference to the drawings in order to explain the present invention.

[0043] Figure 2 A flow chart showing a method of controlling active power output of a wind farm according to an exemplary embodiment of the present invention is shown.

[0044] Reference Figure 2 In step S10, when the wind farm enters a low voltage ride-through state due to a voltage drop at the grid connection point, a maximum active power value allowed to be output by the wind farm in the current low voltage ride-through state is determined.

[0045] As an example, when the voltage value of the wind farm's grid connection point drops below a preset threshold, the wind farm enters the low voltage ride-through state. For example, the preset threshold may be 20% of the rated voltage value of the grid to which the wind farm is connected.

[0046] In one embodiment, the current voltage value of the grid connection point (i.e., the voltage drop depth of the grid connection point) can be directly received from the converter station of the wind farm, and when the current voltage value of the grid connection point is lower than a preset threshold, it is determined that the wind farm enters a low voltage ride-through state due to the voltage drop of the grid connection point. Each wind turbine generator set of the wind farm is connected to the grid via the converter station, that is, the output end of each wind turbine generator set is connected to the grid connection point via the converter station.

[0047] In another embodiment, the current voltage value of the grid connection point can be determined based on the amplitude and / or frequency of other signals different from the DC signal on the DC bus used for power transmission between the wind turbine generator set and the converter station of the wind farm; and when the current voltage value of the grid connection point is lower than a preset threshold, it is determined that the wind farm has entered a low voltage ride-through state due to a voltage drop at the grid connection point, wherein there is a preset mapping relationship between the amplitude and / or frequency of the other signal and the voltage value at the grid connection point. In other words, the converter station can inject other forms of signals different from the DC signal into the DC transmission line (that is, the DC bus) between the wind turbine generator set, and since different amplitudes (for example, less than 3% of the rated voltage of the DC bus) and / or different frequencies (for example, within 100H) of the signal are preset. Z The above) has a one-to-one correspondence with different grid connection point voltage values. Therefore, by controlling the amplitude and / or frequency of the signal, the notification of the current voltage value of the grid connection point can be achieved. Further, as an example, the other signal can be a sine signal or a square wave signal.

[0048] Considering that when the voltage value at the grid connection point drops below the preset threshold, the sum of the square of the active power P and the square of the reactive power Q injected by the wind farm converter station into the AC power grid system should not exceed the maximum apparent power S allowed by the converter station. max The square of, that is, Therefore, as an example, the maximum apparent power value S allowed by the converter station of the wind farm in the current low voltage ride-through state can be determined as max and the minimum reactive power value Q that the converter station is allowed to output to the grid connection point min ; and based on the maximum apparent power value S allowed by the converter station in the current low voltage ride-through state max and the minimum reactive power value Q that the converter station is allowed to output to the grid connection point min , determine the maximum active power value P that the wind farm is allowed to output under the current low voltage ride-through state max .

[0049] As an example, the maximum active power value P that the wind farm is allowed to output under the current low voltage ride-through state is max It can be calculated by formula (1):

[0050]

[0051] As an example, based on the voltage value to which the grid connection point voltage of the wind farm currently drops, the maximum apparent power value allowed by the converter station of the wind farm in the current low voltage ride-through state and the minimum reactive power value allowed for the converter station to output to the grid connection point can be determined.

[0052] As an example, the maximum apparent power value S allowed by the converter station of the wind farm under the current low voltage ride-through state can be calculated by formula (2): max :

[0053]

[0054] Among them, I max Indicates the maximum allowable effective current value that the converter station can inject into the grid connection point, U T Indicates the ratio between the current voltage value of the grid connection point and the rated voltage value of the grid.

[0055] As an example, the minimum reactive power value Q that the converter station is allowed to output to the grid connection point under the current low voltage ride-through state can be calculated by formula (3): min :

[0056]

[0057] Among them, during the low voltage ride-through period, the minimum reactive current I injected by the converter station into the grid connection point T,min =1.5×(0.9-U T)×I n , I n Indicates the rated current value of the converter station. As an example, 0.2≤U T ≤0.9.

[0058] In step S20, it is determined whether the sum of the active power values ​​currently output by all wind turbine generator sets in the wind farm exceeds the determined maximum active power value.

[0059] In step S30, when it is determined in step S20 that the maximum active power value is exceeded, the wind turbine generator sets are controlled to adjust the active power output values ​​so that the sum of the active power output values ​​of all wind turbine generator sets does not exceed the determined maximum active power value.

[0060] It should be understood that when it is determined in step S20 that it exceeds, all or part of the wind turbines in the wind farm may be controlled to adjust the active power output value so that the sum of the active power output values ​​of all wind turbines does not exceed the determined maximum active power value.

[0061] As an example, the active power output target value of each wind turbine generator set can be determined, wherein the sum of the active power output target values ​​of all wind turbine generator sets does not exceed the determined maximum active power value; and based on the determined active power output target value of each wind turbine generator set, the wind turbine generator set is controlled.

[0062] In one embodiment, the active power output target value of each wind turbine generator set can be determined based on the active power value currently output by each wind turbine generator set, so that the sum of the active power output target values ​​of all wind turbine generator sets is closest to the determined maximum active power value, while the active power output target value of each wind turbine generator set does not exceed the active power value currently output by the wind turbine generator set. In other words, the active power output target value of each wind turbine generator set can be allocated accordingly according to the active power value currently output by each wind turbine generator set, so that the sum of the active power output target values ​​of all wind turbine generator sets is closest to the determined maximum active power value on the basis of not exceeding the determined maximum active power value, and the active power output target value of the wind turbine generator set is guaranteed not to exceed its current actual active power output value, that is, the active power output value of each wind turbine generator set can only be adjusted downward but not upward.

[0063] In another embodiment, the determined maximum active power value P max The ratio of the total number of wind turbines in the wind farm (i.e., P max / N), as the maximum active power value allowed to be output by each wind turbine generator set under the current low voltage ride-through state; and for each wind turbine generator set, when the active power value currently output by the wind turbine generator set exceeds the determined maximum active power value allowed to be output by each wind turbine generator set, the determined maximum active power value allowed to be output by each wind turbine generator set is used as the active power output target value of the wind turbine generator set. In addition, for each wind turbine generator set, when the active power value currently output by the wind turbine generator set does not exceed the determined maximum active power value allowed to be output by each wind turbine generator set, the original active power output target value of the wind turbine generator set is not changed, that is, the active power output value of the wind turbine generator set is not adjusted. In other words, for each wind turbine generator set, the active power output value can only be adjusted downward with reference to the maximum active power value allowed to be output by each wind turbine generator set, but cannot be adjusted upward.

[0064] As an example, based on the determined active power output target value of each wind turbine generator set, the wind turbine generator set may be controlled in one of the following ways:

[0065] Method 1: For each wind turbine generator set, when the active power value currently output by the wind turbine generator set exceeds the active power output target value of the wind turbine generator set, the determined active power output target value of the wind turbine generator set is sent to the wind turbine generator set to control the active power output value of the wind turbine generator set to reach the active power output target value.

[0066] Method 2: For each wind turbine generator set, when the active power value currently output by the wind turbine generator set exceeds the active power output target value of the wind turbine generator set, the amount of active power that needs to be absorbed by the unloading circuit in the converter of the wind turbine generator set in order for the wind turbine generator set to reach the corresponding active power output target value is calculated, and the calculated amount of active power that needs to be absorbed by the unloading circuit is sent to the wind turbine generator set to control the wind turbine generator set to absorb the corresponding active power through its unloading circuit.

[0067] As an example, the active power P that needs to be absorbed by the unloading circuit in the converter of the wind turbine generator set in order for the wind turbine generator set to reach the corresponding active power output target value can be calculated by formula (4): chopper :

[0068] P chopper =P MPPT -P wt,loss -P wt,out (4)

[0069] Among them, P MPPT Indicates the active power value currently inputted from the generator of the wind turbine generator set to the converter of the wind turbine generator set, P wt,lossIndicates the loss value of the converter, P wt,out Indicates the active power output target value of the wind turbine generator set.

[0070] Method 3: For each wind turbine generator set, when the active power value currently output by the wind turbine generator set exceeds the active power output target value of the wind turbine generator set, the voltage reference value (i.e., voltage target value) of the DC capacitor in the converter of the wind turbine generator set that enables the wind turbine generator set to reach the corresponding active power output target value is calculated, and the calculated voltage reference value of the DC capacitor is sent to the wind turbine generator set to control the voltage value of the DC capacitor in the converter of the wind turbine generator set to reach the voltage reference value. Here, the DC capacitor in the converter is connected in parallel with the unloading circuit.

[0071] As an example, the active power amount P that needs to be absorbed by the unloading circuit in the converter of the wind turbine generator set in order for the wind turbine generator set to reach the corresponding active power output target value can be calculated. chopper ; and based on the voltage value of the DC capacitor when the unloading circuit is fully put into operation, the resistance value of the discharge resistor of the unloading circuit, the on-resistance value of the switch device of the unloading circuit, and the voltage value of the DC capacitor when the unloading circuit starts to operate, calculate the active power P that can be absorbed by the unloading circuit chopper The voltage reference value of the DC capacitor.

[0072] As an example, the active power P that can be absorbed by the unloading circuit can be calculated by formula (5): chopper The voltage reference value u of the DC capacitor c :

[0073]

[0074] Among them, u c,max Indicates the voltage value of the DC capacitor when the unloading circuit is fully operational (i.e., the switch device of the unloading circuit is fully turned on), R d Indicates the resistance value of the discharge resistor of the unloading circuit, R on Indicates the on-resistance of the switch device of the unloading circuit, u c,min The voltage value of the DC capacitor when the unloading circuit starts to operate (i.e., the switch device of the unloading circuit starts to close), D max is the maximum duty cycle corresponding to the unloading circuit. max The correct answer is 1.

[0075] As an example, when u c <u c,min When P chopper=0. When the wind turbine generator is working normally, the voltage value of the DC capacitor is equal to the rated value u c,rated , that is u c =u c,rated <u c,min , the unloading circuit does not work, P chopper =0, at this time the active power output of the wind turbine is equal to the maximum input power P of the converter MPPT Subtract the inverter loss P wt,loss Therefore, the unloading circuit will not affect the normal power transmission of the wind turbine generator set. In addition, by adjusting the voltage reference value of the DC capacitor, the amount of active power absorbed by the unloading circuit (i.e., the braking circuit) can be controlled, thereby limiting the active power output by the wind turbine generator set to reduce the amount of active power output by the wind turbine generator set to reach the active power output target value.

[0076] According to an exemplary embodiment of the present invention, one of an active power output target value, an active power amount to be absorbed by a load shedding circuit, and a voltage reference value of a DC capacitor may be sent to a wind turbine generator set. When the active power output target value is sent to the wind turbine generator set, the wind turbine generator set may calculate the active power amount to be absorbed by its load shedding circuit based on the active power output target value, and then calculate the voltage reference value of the DC capacitor based on the active power amount to be absorbed by the load shedding circuit, and control the voltage of the DC capacitor based on the calculated voltage reference value of the DC capacitor. When the active power amount to be absorbed by its load shedding circuit is sent to the wind turbine generator set, the wind turbine generator set may calculate the voltage reference value of the DC capacitor based on the active power amount to be absorbed by the load shedding circuit, and control the voltage of the DC capacitor based on the calculated voltage reference value of the DC capacitor. When the voltage reference value of the DC capacitor is sent to the wind turbine generator set, the wind turbine generator set may directly control the voltage value of the DC capacitor to reach the voltage reference value of the DC capacitor.

[0077] It should be understood that when the active power value currently output by the wind turbine generator set does not exceed the active power output target value of the wind turbine generator set, the active power output value of the wind turbine generator set will not be adjusted, that is, the active power output target value, the active power amount to be absorbed by the unloading circuit and the voltage reference value of the DC capacitor will not be sent to the wind turbine generator set.

[0078] When it is determined in step S20 that it does not exceed, each wind turbine generator set can still operate according to its actual active power, that is, there is no need to control the wind turbine generator set to adjust the active power output value, the active power output target value of the wind turbine generator set remains unchanged, and it can continue to operate according to the current operating conditions.

[0079] As an example, the method for controlling the active power output of a wind farm according to an exemplary embodiment of the present invention may further include: when the grid connection point voltage of the wind farm returns to normal, the wind turbine generator set may be controlled to adjust the active power output value so that the wind farm enters a normal operating state.

[0080] Figure 3 A structural block diagram of a controller of a wind farm according to an exemplary embodiment of the present invention is shown.

[0081] like Figure 3 As shown, a controller 100 of a wind farm according to an exemplary embodiment of the present invention includes: a first communication module 101 and a first processor 102 .

[0082] Specifically, the first communication module 101 is used to implement communication between the first processor 102 and the wind turbine generator set. Specifically, it is used to implement communication between the first processor 102 and a processor of a control device of the wind turbine generator set.

[0083] The first processor 102 is configured to perform the following operations: when the wind farm enters a low voltage ride-through state due to a grid connection point voltage drop, determine the maximum active power value allowed to be output by the wind farm in the current low voltage ride-through state; determine whether the sum of the active power values ​​currently output by all wind turbines in the wind farm exceeds the determined maximum active power value; when it is determined that the sum of the active power values ​​exceeds the determined maximum active power value, control the first communication module 101 to send an active power control instruction to the wind turbines so that the sum of the active power output values ​​of all wind turbines does not exceed the determined maximum active power value.

[0084] As an example, the first processor 102 can also be configured to: determine the maximum apparent power value allowed by the converter station of the wind farm in the current low voltage ride-through state and the minimum reactive power value allowed for the converter station to output to the grid connection point; and based on the maximum apparent power value allowed by the converter station in the current low voltage ride-through state and the minimum reactive power value allowed for the converter station to output to the grid connection point, determine the maximum active power value allowed for the wind farm to output in the current low voltage ride-through state, wherein each wind turbine generator set in the wind farm is connected to the power grid via the converter station.

[0085] As an example, the first processor 102 can also be configured to: when it is determined that the sum of the active power values ​​exceeds the determined maximum active power value, determine the active power output target value of each wind turbine generator set, wherein the sum of the active power output target values ​​of all wind turbine generator sets does not exceed the determined maximum active power value; and based on the determined active power output target value of each wind turbine generator set, control the first communication module 101 to send an active power control instruction to the wind turbine generator set.

[0086] As an example, the first processor 102 can also be configured to: determine the active power output target value of each wind turbine generator set based on the active power value currently output by each wind turbine generator set, so that the sum of the active power output target values ​​of all wind turbine generator sets is closest to the determined maximum active power value while ensuring that the active power output target value of each wind turbine generator set does not exceed the active power value currently output by the wind turbine generator set.

[0087] As an example, the first processor 102 can also be configured to: use the ratio between the determined maximum active power value and the total number of wind turbines in the wind farm as the maximum active power value allowed to be output by each wind turbine under the current low voltage ride-through state; and for each wind turbine, when the active power value currently output by the wind turbine exceeds the determined maximum active power value allowed to be output by each wind turbine, use the determined maximum active power value allowed to be output by each wind turbine as the active power output target value of the wind turbine.

[0088] As an example, the first processor 102 can also be configured to: for each wind turbine generator set, when the active power value currently output by the wind turbine generator set exceeds the active power output target value of the wind turbine generator set, control the first communication module 101 to send an active power control instruction including the determined active power output target value of the wind turbine generator set to the wind turbine generator set.

[0089] As an example, the first processor 102 can also be configured to: for each wind turbine generator set, when the active power value currently output by the wind turbine generator set exceeds the active power output target value of the wind turbine generator set, calculate the amount of active power that needs to be absorbed by the unloading circuit in the converter of the wind turbine generator set in order for the wind turbine generator set to reach the corresponding active power output target value, and control the first communication module 101 to send an active power control instruction including the calculated amount of active power that needs to be absorbed by the unloading circuit to the wind turbine generator set.

[0090] As an example, the first processor 102 can also be configured to: for each wind turbine generator set, when the active power value currently output by the wind turbine generator set exceeds the active power output target value of the wind turbine generator set, calculate the voltage reference value of the DC capacitor in the converter of the wind turbine generator set that can enable the wind turbine generator set to reach the corresponding active power output target value, and control the first communication module 101 to send the active power control instruction including the calculated voltage reference value of the DC capacitor to the wind turbine generator set.

[0091] As an example, the first processor 102 can also be configured to: determine the current voltage value of the grid connection point based on the amplitude and / or frequency of other signals different from the DC signal on the DC bus used for power transmission between the wind turbine generator set and the converter station of the wind farm; and when the current voltage value of the grid connection point is lower than a preset threshold, determine that the wind farm enters a low voltage ride-through state due to a voltage drop at the grid connection point, wherein there is a preset mapping relationship between the amplitude and / or frequency of the other signal and the voltage value of the grid connection point, wherein each wind turbine generator set in the wind farm is connected to the power grid via the converter station, and the other signal is a sinusoidal signal or a square wave signal.

[0092] It should be understood that the specific details of the processing performed by the first processor 102 of the controller 100 of the wind farm according to the exemplary embodiment of the present invention have been referred to. Figure 2 The details have been described in detail and will not be repeated here.

[0093] Figure 4 A structural block diagram of a control device for a wind turbine generator set according to an exemplary embodiment of the present invention is shown.

[0094] Reference Figure 4 According to an exemplary embodiment of the present invention, the control device of a wind turbine generator set includes: a second communication module 201 and a second processor 202 .

[0095] Specifically, the second communication module 201 is used to enable the second processor 202 to communicate with the controller 100 of the wind farm as described in the above exemplary embodiment.

[0096] The second processor 202 is configured to perform the following operations: determine the voltage reference value of the DC capacitor in the converter of the wind turbine generator set based on the active power control instruction received from the controller of the wind farm through the second communication module 201; and control the voltage of the DC capacitor according to the voltage reference value of the DC capacitor.

[0097] As an example, the second processor 202 can also be configured to: when the received active power control instruction is an active power control instruction including the amount of active power that needs to be absorbed by the unloading circuit in the converter of the wind turbine generator set, calculate the voltage reference value of the DC capacitor in the converter based on the amount of active power that needs to be absorbed by the unloading circuit.

[0098] As an example, the second processor 202 may also be configured to calculate the active power P that can be absorbed by the unloading circuit based on the voltage value of the DC capacitor when the unloading circuit is fully operational, the resistance value of the discharge resistor of the unloading circuit, the on-resistance value of the switch device of the unloading circuit, and the voltage value of the DC capacitor when the unloading circuit starts to operate. chopperThe voltage reference value of the DC capacitor.

[0099] As an example, the active power P that can be absorbed by the unloading circuit can be calculated by formula (5): chopper The voltage reference value u of the DC capacitor c .

[0100] As an example, the second processor 202 can also be configured to: when the received active power control instruction is an active power control instruction including an active power output target value, calculate the amount of active power that needs to be absorbed by the unloading circuit in the converter in order to achieve the active power output target value, and calculate the voltage reference value of the DC capacitor in the converter based on the calculated amount of active power that needs to be absorbed by the unloading circuit.

[0101] As an example, the active power P that needs to be absorbed by the unloading circuit in the converter of the wind turbine generator set in order to achieve the active power output target value can be calculated by formula (4): chopper .

[0102] As an example, the second processor 202 can also be configured to: when the received active power control instruction is an active power control instruction including a voltage reference value of the DC capacitor in the converter, directly set the voltage reference value of the DC capacitor in the converter to the received voltage reference value.

[0103] Figure 5 A structural block diagram of a system for controlling active power output of a wind farm according to an exemplary embodiment of the present invention is shown.

[0104] Reference Figure 5 According to an exemplary embodiment of the present invention, a system for controlling the active power output of a wind farm comprises a controller 100 of the wind farm as described in the above exemplary embodiment and a plurality of control devices 200 of wind turbine generator sets as described in the above exemplary embodiment. The control devices 200 of the plurality of wind turbine generator sets communicate with the controller 100 of the wind farm to realize coordinated control of the active power output of the wind farm.

[0105] It should be understood that the communication module and processor in the controller of the wind farm and the control device of the wind turbine generator set according to the exemplary embodiment of the present invention can be implemented as hardware components and / or software components. Those skilled in the art can implement the communication module and the processor, for example, using a field programmable gate array (FPGA) or an application specific integrated circuit (ASIC) according to the processing performed by the defined communication module and the processor.

[0106] An exemplary embodiment of the present invention provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements a method for controlling the active power output of a wind farm as described in the above exemplary embodiment. The computer-readable storage medium is any data storage device that can store data read by a computer system. Examples of computer-readable storage media include: read-only memory, random access memory, read-only optical disk, magnetic tape, floppy disk, optical data storage device, and carrier wave (such as data transmission through the Internet via a wired or wireless transmission path).

[0107] The control device of a wind farm according to an exemplary embodiment of the present invention comprises: a processor (not shown) and a memory (not shown), wherein the memory stores a computer program, and when the computer program is executed by the processor, the method for controlling the active power output of the wind farm as described in the above exemplary embodiment is implemented. As an example, the control device may be a controller of a wind farm.

[0108] Although some exemplary embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that modifications may be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for controlling active power output of a wind farm, It is characterized in that The method comprises: When the wind farm enters a low voltage ride-through state due to a voltage drop at the grid connection point, determine the maximum active power value allowed to be output by the wind farm in the current low voltage ride-through state; Determining whether the sum of active power values ​​currently output by all wind turbine generator sets in the wind farm exceeds the determined maximum active power value; When it is determined that the sum of the active power values ​​exceeds the determined maximum active power value, determining the active power output target value of each wind turbine generator set, wherein the sum of the active power output target values ​​of all wind turbine generator sets does not exceed the determined maximum active power value; Based on the determined active power output target value of each wind turbine generator set, control the wind turbine generator set so that the sum of the active power output values ​​of all wind turbine generator sets does not exceed the determined maximum active power value, and ensure that the active power transmitted to the outside of the wind farm during the low voltage ride-through period is not interrupted; Wherein, based on the determined active power output target value of each wind turbine generator set, the step of controlling the wind turbine generator set includes: For each wind turbine generator set, when the active power value currently output by the wind turbine generator set exceeds the active power output target value of the wind turbine generator set, the determined active power output target value of the wind turbine generator set is sent to the wind turbine generator set; or, For each wind turbine generator set, when the active power value currently output by the wind turbine generator set exceeds the active power output target value of the wind turbine generator set, the amount of active power that needs to be absorbed by the unloading circuit in the converter of the wind turbine generator set is calculated in order for the wind turbine generator set to reach the corresponding active power output target value, and the calculated amount of active power that needs to be absorbed by the unloading circuit is sent to the wind turbine generator set; or, For each wind turbine generator set, when the active power value currently output by the wind turbine generator set exceeds the active power output target value of the wind turbine generator set, a voltage reference value of the DC capacitor in the converter of the wind turbine generator set that can enable the wind turbine generator set to reach the corresponding active power output target value is calculated, and the calculated voltage reference value of the DC capacitor is sent to the wind turbine generator set, wherein the DC capacitor in the converter is connected in parallel with the unloading circuit.

2. The method according to claim 1, It is characterized in that The steps of determining the maximum active power value allowed to be output by the wind farm under the current low voltage ride-through state include: Determine the maximum apparent power value allowed by the converter station of the wind farm and the minimum reactive power value allowed to be output by the converter station to the grid connection point under the current low voltage ride-through state; Based on the maximum apparent power value allowed by the converter station in the current low voltage ride-through state and the minimum reactive power value allowed to be output by the converter station to the grid connection point, the maximum active power value allowed to be output by the wind farm in the current low voltage ride-through state is determined. Wherein, each wind turbine generator set in the wind farm is connected to the power grid via the converter station.

3. The method according to claim 2, It is characterized in that The step of determining the maximum apparent power value allowed by the converter station of the wind farm in the current low voltage ride-through state and the minimum reactive power value allowed to be output by the converter station to the grid connection point comprises: Based on the voltage value to which the grid connection point voltage of the wind farm currently drops, the maximum apparent power value allowed by the converter station of the wind farm and the minimum reactive power value allowed to be output by the converter station to the grid connection point are determined in the current low voltage ride-through state.

4. The method according to claim 1, It is characterized in that The steps of determining the active power output target value of each wind turbine generator set include: Based on the active power value currently output by each wind turbine generator set, determine the active power output target value of each wind turbine generator set, so that the sum of the active power output target values ​​of all wind turbine generator sets is closest to the determined maximum active power value, while the active power output target value of each wind turbine generator set does not exceed the active power value currently output by the wind turbine generator set; or, The ratio between the determined maximum active power value and the total number of wind turbines in the wind farm is used as the maximum active power value allowed to be output by each wind turbine under the current low voltage ride-through state; and for each wind turbine, when the active power value currently output by the wind turbine exceeds the determined maximum active power value allowed to be output by each wind turbine, the determined maximum active power value allowed to be output by each wind turbine is used as the active power output target value of the wind turbine.

5. The method according to claim 1, It is characterized in that The step of calculating a voltage reference value of a DC capacitor in a converter of the wind turbine generator set that enables the wind turbine generator set to reach a corresponding active power output target value comprises: Calculate the active power P that needs to be absorbed by the unloading circuit in the converter of the wind turbine generator set in order for the wind turbine generator set to reach the corresponding active power output target value. chopper ; Based on the voltage value of the DC capacitor when the unloading circuit is fully operational, the resistance value of the discharge resistor of the unloading circuit, the on-resistance value of the switch device of the unloading circuit, and the voltage value of the DC capacitor when the unloading circuit starts to operate, the active power P that can be absorbed by the unloading circuit is calculated. chopper The voltage reference value of the DC capacitor.

6. The method according to claim 5, It is characterized in that Calculate the active power P that can be absorbed by the unloading circuit chopper The steps of determining the voltage reference value of the DC capacitor include: The voltage reference value u of the DC capacitor is calculated by the following formula: c : Among them, u c,max Indicates the voltage value of the DC capacitor when the unloading circuit is fully operational, R d Indicates the resistance value of the discharge resistor of the unloading circuit, R on Indicates the on-resistance of the switch device of the unloading circuit, u c,min Indicates the voltage value of the DC capacitor when the unloading circuit starts to operate, D max Indicates the maximum duty cycle corresponding to the unloading circuit.

7. The method according to claim 1, It is characterized in that The method further comprises: Determine the current voltage value of the grid connection point based on the amplitude and / or frequency of other signals different from the DC signal on the DC bus used for power transmission between the wind turbine generator set and the converter station of the wind farm; When the current voltage value of the grid connection point is lower than the preset threshold, it is determined that the wind farm has entered the low voltage ride-through state due to the voltage drop at the grid connection point. There is a preset mapping relationship between the amplitude and / or frequency of the other signal and the grid connection point voltage value. Wherein, each wind turbine generator set of the wind farm is connected to the power grid via the converter station, and the other signal is a sinusoidal signal or a square wave signal.

8. A controller for a wind farm, It is characterized in that The controller of the wind farm comprises: A first communication module, used to implement communication between the first processor and the wind turbine generator set; The first processor is configured to perform the following operations: When the wind farm enters a low voltage ride-through state due to a voltage drop at the grid connection point, determine the maximum active power value allowed to be output by the wind farm in the current low voltage ride-through state; Determining whether the sum of active power values ​​currently output by all wind turbine generator sets in the wind farm exceeds the determined maximum active power value; When it is determined that the sum of the active power values ​​exceeds the determined maximum active power value, determine the active power output target value of each wind turbine generator set, wherein the sum of the active power output target values ​​of all wind turbine generator sets does not exceed the determined maximum active power value; and based on the determined active power output target values ​​of each wind turbine generator set, control the first communication module to send an active power control instruction to the wind turbine generator set, so that the sum of the active power output values ​​of all wind turbine generator sets does not exceed the determined maximum active power value, and ensure that the active power transmitted to the outside of the wind farm during the low voltage ride-through period is not interrupted; Wherein, the first processor is further configured to: For each wind turbine generator set, when the active power value currently output by the wind turbine generator set exceeds the active power output target value of the wind turbine generator set, control the first communication module to send an active power control instruction including the determined active power output target value of the wind turbine generator set to the wind turbine generator set; or, For each wind turbine generator set, when the active power value currently output by the wind turbine generator set exceeds the active power output target value of the wind turbine generator set, the amount of active power that needs to be absorbed by the unloading circuit in the converter of the wind turbine generator set is calculated in order for the wind turbine generator set to reach the corresponding active power output target value, and the first communication module is controlled to send an active power control instruction including the calculated amount of active power that needs to be absorbed by the unloading circuit to the wind turbine generator set; or, For each wind turbine generator set, when the active power value currently output by the wind turbine generator set exceeds the active power output target value of the wind turbine generator set, a voltage reference value of the DC capacitor in the converter of the wind turbine generator set is calculated so as to enable the wind turbine generator set to reach the corresponding active power output target value, and the first communication module is controlled to send an active power control instruction including the calculated voltage reference value of the DC capacitor to the wind turbine generator set, wherein the DC capacitor in the converter is connected in parallel with the unloading circuit.

9. The wind farm controller according to claim 8, It is characterized in that The first processor is further configured to: determine the maximum apparent power value allowed by the converter station of the wind farm in the current low voltage ride-through state and the minimum reactive power value allowed for the converter station to output to the grid connection point; and determine the maximum active power value allowed for the wind farm to output in the current low voltage ride-through state based on the maximum apparent power value allowed by the converter station and the minimum reactive power value allowed for the converter station to output to the grid connection point in the current low voltage ride-through state, Wherein, each wind turbine generator set in the wind farm is connected to the power grid via the converter station.

10. The wind farm controller according to claim 8, It is characterized in that The first processor is further configured to: Based on the active power value currently output by each wind turbine generator set, determine the active power output target value of each wind turbine generator set, so that the sum of the active power output target values ​​of all wind turbine generator sets is closest to the determined maximum active power value, while the active power output target value of each wind turbine generator set does not exceed the active power value currently output by the wind turbine generator set; or, The ratio between the determined maximum active power value and the total number of wind turbine generator sets in the wind farm is used as the maximum active power value allowed to be output by each wind turbine generator set in the current low voltage ride-through state; And for each wind turbine generator set, when the active power value currently output by the wind turbine generator set exceeds the determined maximum active power value allowed to be output by each wind turbine generator set, the determined maximum active power value allowed to be output by each wind turbine generator set is used as the active power output target value of the wind turbine generator set.

11. The wind farm controller according to claim 8, It is characterized in that The first processor is further configured to: determine the current voltage value of the grid connection point based on the amplitude and / or frequency of other signals different from the DC signal on the DC bus used for power transmission between the wind turbine generator set and the converter station of the wind farm; and when the current voltage value of the grid connection point is lower than a preset threshold, determine that the wind farm enters a low voltage ride-through state due to a voltage drop at the grid connection point, There is a preset mapping relationship between the amplitude and / or frequency of the other signal and the grid connection point voltage value. Wherein, each wind turbine generator set of the wind farm is connected to the power grid via the converter station, and the other signal is a sinusoidal signal or a square wave signal.

12. A control device for a wind turbine generator set, It is characterized in that The control device comprises: A second communication module, configured to enable the second processor to communicate with the controller of the wind farm according to any one of claims 8 to 11; The second processor is configured to perform the following operations: Based on the active power control instruction received from the controller of the wind farm through the second communication module, a voltage reference value of the DC capacitor in the converter of the wind turbine generator set is determined; and the voltage of the DC capacitor is controlled according to the voltage reference value of the DC capacitor.

13. The control device according to claim 12, It is characterized in that The second processor is further configured to: when the received active power control instruction is an active power control instruction including an amount of active power that needs to be absorbed by a load shedding circuit in a converter of the wind turbine generator set, calculate a voltage reference value of a DC capacitor in the converter based on the amount of active power that needs to be absorbed by the load shedding circuit; and / or, The second processor is further configured to: when the received active power control instruction is an active power control instruction including an active power output target value, calculate the amount of active power that needs to be absorbed by the unloading circuit in the converter in order to achieve the active power output target value, and calculate a voltage reference value of the DC capacitor in the converter based on the calculated amount of active power that needs to be absorbed by the unloading circuit; and / or, The second processor is further configured to: when the received active power control instruction is an active power control instruction including a voltage reference value of the DC capacitor in the converter, directly set the voltage reference value of the DC capacitor in the converter to the received voltage reference value.

14. A system for controlling active power output of a wind farm, It is characterized in that The system comprises: A wind farm controller according to any one of claims 8 to 11; A plurality of control devices of wind turbine generator sets according to any one of claims 12 to 13 connected to a controller of the wind farm.

15. A computer-readable storage medium storing a computer program, It is characterized in that When the computer program is executed by a processor, the method for controlling active power output of a wind farm as claimed in any one of claims 1 to 7 is implemented.

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