Fan electric structure and control strategy for actively compensating power prediction deviation

Abstract

The application discloses a fan electrical structure and a control strategy for actively compensating power prediction deviation, comprising an energy storage battery, the energy storage battery is connected to a direct current side of a converter through a DC / DC transformer; a plurality of DC / DC transformers are connected to the direct current side of the fan converter through a direct current circuit breaker or a direct current fuse and are connected through a direct current bus bar or a bus; the capacity of a grid-side converter exceeds the capacity of a machine-side converter; the scheme is applicable to full-power fans, including direct-drive type, semi-direct-drive type, a fan with all generator outputs connected to a grid through a converter and a fan with part of generator outputs connected to the grid through the converter, so that the fan can simultaneously track a maximum power point and a wind power prediction curve, the problem of power fluctuation of the fan itself, deviation between actual power and wind power prediction is solved, the adverse effect on the grid frequency is reduced, and the ability of the fan to participate in grid frequency modulation is improved to a certain extent.

Description

Technical Field

[0001] This invention belongs to the field of wind turbine technology, specifically relating to a wind turbine electrical structure and control strategy for actively compensating for power prediction deviations. Background Technology

[0002] Power fluctuations in wind turbines are a key factor limiting large-scale wind power development and grid connection. Wind power prediction systems can mitigate the impact of wind power fluctuations to some extent, reducing the difficulty of grid dispatch and frequency regulation. However, there are discrepancies between wind power predictions and actual turbine power. Short-term prediction accuracy is only 90%, and the impact of instantaneous gusts cannot be predicted. Therefore, the volatility of wind turbine power remains one of the challenges in increasing wind power installed capacity and power generation.

[0003] To mitigate the impact of wind turbine power fluctuations on grid frequency, wind farms typically incorporate energy storage systems accounting for 10% of their installed capacity, effectively reducing the influence of power fluctuations on grid frequency. However, centralized energy storage requires a large footprint and necessitates the configuration of battery management systems, energy management systems, grid-connected inverters, transformers, etc., significantly increasing wind farm investment. Currently, the electrical system of a wind turbine includes generators, turbine-side converters, DC capacitors, grid-side converters, AC filters, and transformers. Since it operates at less than full capacity most of the time, there is significant room for improvement in the utilization rate of electrical equipment, providing a foundation for enhancing the wind turbine's ability to limit power fluctuations. By utilizing this potential for improvement and designing appropriate electrical circuits and control strategies, wind turbines can capture maximum wind energy while actively compensating for power prediction deviations, delivering actual power equal to the predicted power curve. This reduces the adverse impact on grid frequency, decreases the scale of energy storage system construction, and may even eliminate the need for dedicated energy storage power stations, thereby lowering wind farm investment.

[0004] Therefore, it is necessary to propose a wind turbine electrical structure and control strategy that actively compensates for power prediction deviations to solve the above problems. Summary of the Invention

[0005] This invention provides an electrical structure and control strategy for wind turbines that actively compensate for power prediction deviations. This solution is applicable to full-power wind turbines, including direct-drive and semi-direct-drive wind turbines where all generator output is connected to the grid via a converter, and doubly-fed induction generators where part of the generator output is connected to the grid via a converter. This allows the wind turbine to simultaneously track the maximum power point and the wind power prediction curve, solving the problems of power fluctuations in the wind turbine itself and deviations between actual power and wind power predictions. It also reduces the adverse impact on grid frequency and, to some extent, enhances the wind turbine's ability to participate in grid frequency regulation.

[0006] To achieve the above-mentioned technical effects, the technical solution adopted by the present invention is as follows:

[0007] The wind turbine motor structure for actively compensating for power prediction deviation includes an energy storage battery, which is connected to the DC side of the converter via a DC / DC transformer. Multiple DC / DC transformers are connected to the DC side of the wind turbine converter via DC circuit breakers or DC fuses, and are connected via DC busbars or busbars. The turbine-side converter, grid-side converter, and DC / DC transformer adopt a coordinated control strategy to simultaneously track the MPPT and power prediction curves, and consider the charging and discharging strategy of the energy storage battery.

[0008] Furthermore, the DC / DC transformer converts the DC voltage of the wind turbine converter into a DC voltage suitable for charging and discharging the energy storage battery pack, adapting to fluctuations in the DC voltage of the wind turbine converter within a certain range, allowing for bidirectional flow of electrical energy.

[0009] To increase the design capacity of the grid-side converter and transformer of the wind turbine, and further enhance the output power of the wind turbine when the generator is running at full capacity, the maximum capacity can be achieved through the following methods:

[0010]

[0011] Among them, S max P represents the maximum capacity of the grid-side converter and transformer; G_VSC The capacity of the turbine-side converter depends on the type of wind turbine; P DC / DC Q represents the capacity of the DC / DC transformer, and the formula includes the sum of the capacities of all DC / DC transformers. S_VSC The rated reactive power of the grid-side converter can be replaced with an expression that includes the power factor.

[0012] Furthermore, after the grid-side converter has increased capacity, it can be used to generate power exceeding the rated power of the wind turbine when participating in grid frequency regulation, or to store more surplus power from the grid; the capacity of the turbine-side converter is consistent with that of conventionally designed wind turbine units; and the energy storage battery can be of various types, including but not limited to lithium batteries, sodium batteries, or lead-acid batteries.

[0013] The control strategy for the wind turbine motor structure that actively compensates for power prediction deviation is as follows:

[0014] S1, the turbine-side converter, grid-side converter, and DC / DC transformer coordinate with each other to enable the wind turbine to capture wind energy according to the maximum power point tracking curve and output active power according to the wind power prediction curve within the allowable range of battery charging and discharging power and capacity; the coordinated control strategy is as follows:

[0015] S101, the generator-side converter performs torque control or excitation control on the generator according to the MPPT curve, so that the generator outputs the maximum power corresponding to the current wind speed. The generator output power is rectified by the generator-side converter and output to the DC side of the converter.

[0016] S102, the grid-side converter receives the power prediction curve for this wind turbine from the wind power prediction system, and the update frequency is consistent with the update frequency of the wind power prediction system; the grid-side converter can also actively participate in the primary and secondary frequency regulation of the power grid according to the primary frequency regulation curve or dispatch instructions, as follows:

[0017] The active power control of the grid-side converter adopts constant active power control. For full-power wind turbines, the active power command value is the power value on the power prediction curve or the power command participating in grid frequency regulation. For doubly-fed wind turbines, the active power command value should be the expected power command (power value on the power prediction curve or power command participating in grid frequency regulation) minus the real-time power of the generator stator.

[0018] The reactive power control of the grid-side converter can be selected as either constant reactive power control or constant AC voltage control, depending on the requirements.

[0019] S103, when there is only one DC / DC transformer branch, the DC / DC transformer controls the DC side voltage U of the converter. dc The specific method is as follows:

[0020] U dc When the command value is exceeded, the DC / DC transformer increases the charging power of the energy storage battery, thereby reducing the DC voltage;

[0021] U dc When the voltage is lower than the commanded value, the DC / DC transformer increases the discharge power of the energy storage battery, thereby increasing the DC voltage.

[0022] S104. When there are multiple DC / DC transformer branches, a hierarchical control architecture is adopted to avoid power circulation between branches. The specific method is as follows:

[0023] Upper-level control controls the DC-side voltage U of the converter. dc This generates the total power command P. ∑ Then, based on the current state of charge (SOC) of the energy storage batteries in each branch, the appropriate power allocation P for each branch is determined. DC / DCi The relationship between power and current SOC depends on the performance of the battery used;

[0024] The lower-level control is the power control of the DC / DC transformer itself, which receives power commands from the upper-level control to charge and discharge the energy storage battery;

[0025] Furthermore, the maximum power of a DC / DC transformer is limited not only by its own rated electrical capacity but also by the dual limits of the energy storage battery's maximum charging and discharging current and maximum charging voltage. When the energy storage battery is fully charged, the DC / DC transformer's charging power is 0; when the energy storage battery is fully discharged, the DC / DC transformer's discharging power is 0.

[0026] S2, when the maximum power of the DC / DC transformer reaches the limit and still cannot meet the control U dc When the active power difference between the generator-side converter and the grid-side converter is constant, i.e., when the active power difference is greater than the maximum power of the DC / DC transformer, U dc Gradually increase or decrease until exceeding the allowable upper or lower limits; at this point, the grid-side converter will take over U dc The control function no longer operates in constant active power control mode.

[0027] Preferably, in step S3 of the control strategy for the wind turbine motor structure that actively compensates for power prediction deviation, the grid-side converter takes over U dc The methods for controlling functions include the following two:

[0028] a. A control mode switching command is issued from a higher-level control layer:

[0029] The grid-side converter switches to constant DC voltage control mode, still controlling the DC voltage to the rated value; the DC / DC transformer switches to constant power control mode, and its power command is determined according to the remaining charge of the energy storage battery.

[0030] b. Automatic switching is achieved using voltage margin control, by setting appropriate upper and lower limits U of the DC voltage. dc_max U dc_min This is used as the DC voltage command for the grid-side converter, which will automatically control the DC voltage at U. dc_max or U dc_min .

[0031] The beneficial effects of this invention are as follows:

[0032] 1. This invention allows for the flexible arrangement of multiple sets of energy storage batteries and DC / DC transformer branches within the wind turbine tower and foundation, improving space utilization and layout flexibility. By utilizing multiple sets of energy storage batteries and DC / DC transformers, the wind turbine can actively compensate for deviations in wind power prediction. This invention can be used to design and construct grid-friendly wind turbines and upgrade existing wind turbines, reducing the adverse effects of wind power fluctuations on grid frequency and decreasing wind curtailment rates. This, to a certain extent, solves the technical challenges of large-scale wind power construction and grid connection.

[0033] 2. This invention utilizes multiple sets of energy storage batteries and DC / DC transformers to optimize the capacity of the turbine-side converter, grid-side converter, and transformer. This enables the wind turbine to actively participate in the primary and secondary frequency regulation of the power grid according to the primary frequency regulation curve or dispatch instructions, and to generate power exceeding or less than the maximum power corresponding to the current wind speed, or even exceeding the rated power of the wind turbine for a certain period of time.

[0034] 3. The present invention enables a wind farm to obtain more benefits when participating in the power grid spot market. When the real-time electricity price is high, it actively discharges the energy of the energy storage battery to participate in spot market transactions. It can reduce the scale of the energy storage power station supporting the wind farm, or even not build a supporting energy storage power station, thereby reducing the investment of the wind farm.

[0035] 4. The present invention provides a method for coordinating the control of the machine-side converter, the grid-side converter, and the DC / DC transformer, enabling the wind turbine to simultaneously meet the requirements of maximum power point tracking control, compensating for the deviation of the wind power prediction curve, responding to the primary and secondary frequency regulation requirements of the power grid, and the battery charging power limit. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is the electrical structure diagram of a doubly-fed wind turbine for actively compensating the power prediction deviation in Embodiment 1 of the present invention;

[0037] Figure 2 It is the electrical structure diagram of a full-power wind turbine for actively compensating the power prediction deviation in Embodiment 2 of the present invention;

[0038] Figure 3 It is the control strategy of the DC / DC transformer (group) in the present invention;

[0039] Figure 4 It is the steady-state operation curve of the machine-side converter, the grid-side converter, and the DC / DC transformer (group) in the present invention; DETAILED DESCRIPTION OF THE EMBODIMENTS

[0040] Embodiment 1:

[0041] As Figure 1 shown, an embodiment based on a doubly-fed wind turbine is provided, specifically as follows:

[0042] The wind turbine motor structure for actively compensating the power prediction deviation includes an energy storage battery, and the energy storage battery is connected to the DC side of the converter through a DC / DC transformer; multiple groups of DC / DC transformers are connected to the DC side of the wind turbine converter through a DC circuit breaker or a DC fuse, and are connected through a DC busbar or a bus; the machine-side converter, the grid-side converter, and the DC / DC transformer adopt a coordinated control strategy to simultaneously track the MPPT and the power prediction curve, and consider the charge and discharge strategy of the energy storage battery;

[0043] Embodiment 2:

[0044] As Figure 2 shown, an embodiment based on a full-power wind turbine is provided, specifically as follows:

[0045] Three groups of energy storage batteries and DC / DC transformer branches are arranged on the DC side of the wind turbine converter; the capacity of the grid-side converter and the transformer is designed according to the maximum value.

[0046] Furthermore, the DC / DC transformer converts the DC voltage of the wind turbine converter into a DC voltage suitable for charging and discharging the energy storage battery pack, adapting to fluctuations in the DC voltage of the wind turbine converter within a certain range, allowing for bidirectional flow of electrical energy.

[0047] Example 3:

[0048] like Figure 3 As shown, Figure 3 This is a DC / DC transformer (group) control strategy; the upper-level control target is DC voltage, which is achieved through a DC voltage controller, U dc_ref For DC voltage command, U dc This is a DC voltage measurement; P ∑ The total power of each branch; the power distribution module determines the distribution of the total power among the branches based on the SOC of the energy storage battery, Q. n Let P be the remaining charge of the energy storage battery in the nth branch. n The power limiter sets the power command based on the maximum power of the DC / DC transformer and the maximum charging / discharging power of the energy storage battery, P, to allocate the charging / discharging power to the nth branch. ref n This is the final power command after limitation; the DC / DC charging control is based on the power command and the charging current I. bn Adjust the charging voltage U output by the DC / DC transformer. bn U bn This forms a closed-loop feedback loop.

[0049] The specific control strategies for DC / DC transformers (groups) are as follows:

[0050] First, increase the capacity of the grid-side converter and transformer of the wind turbine to further increase the output power of the wind turbine when the generator is running at full capacity. The maximum capacity method is as follows:

[0051]

[0052] Among them, S max P represents the maximum capacity of the grid-side converter and transformer; G_VSC The capacity of the turbine-side converter depends on the type of wind turbine; P DC / DC Q represents the capacity of the DC / DC transformer, and the formula includes the sum of the capacities of all DC / DC transformers. S_VSC The rated reactive power of the grid-side converter can be replaced with an expression that includes the power factor.

[0053] Furthermore, after the grid-side converter has increased capacity, it can be used to generate power exceeding the rated power of the wind turbine when participating in grid frequency regulation, or to store more surplus power from the grid; the capacity of the turbine-side converter is consistent with that of conventionally designed wind turbine units; and the energy storage battery can be of various types, including but not limited to lithium batteries, sodium batteries, or lead-acid batteries.

[0054] S1, the turbine-side converter, grid-side converter, and DC / DC transformer coordinate with each other to enable the wind turbine to capture wind energy according to the maximum power point tracking curve and output active power according to the wind power prediction curve within the allowable range of battery charging and discharging power and capacity; the coordinated control strategy is as follows:

[0055] S101, the generator-side converter performs torque control or excitation control on the generator according to the MPPT curve, so that the generator outputs the maximum power corresponding to the current wind speed. The generator output power is rectified by the generator-side converter and output to the DC side of the converter.

[0056] S102, the grid-side converter receives the power prediction curve for this wind turbine from the wind power prediction system, and the update frequency is consistent with the update frequency of the wind power prediction system; the grid-side converter can also actively participate in the primary and secondary frequency regulation of the power grid according to the primary frequency regulation curve or dispatch instructions, as follows:

[0057] The active power control of the grid-side converter adopts constant active power control, and its active power command value is the power value on the power prediction curve or the power command participating in grid frequency regulation.

[0058] The reactive power control of the grid-side converter can be selected as either constant reactive power control or constant AC voltage control, depending on the requirements.

[0059] S103, when there is only one DC / DC transformer branch, the DC / DC transformer controls the DC side voltage U of the converter. dc The specific method is as follows:

[0060] U dc When the command value is exceeded, the DC / DC transformer increases the charging power of the energy storage battery, thereby reducing the DC voltage;

[0061] U dc When the voltage is lower than the commanded value, the DC / DC transformer increases the discharge power of the energy storage battery, thereby increasing the DC voltage.

[0062] S104. When there are multiple DC / DC transformer branches, a hierarchical control architecture is adopted to avoid power circulation between branches. The specific method is as follows:

[0063] Upper-level control controls the DC-side voltage U of the converter. dc This generates the total power command P. ∑ Then, based on the current state of charge (SOC) of the energy storage batteries in each branch, the appropriate power allocation P for each branch is determined. DC / DCi The relationship between power and current SOC depends on the performance of the battery used;

[0064] The lower-level control is the power control of the DC / DC transformer itself, which receives power commands from the upper-level control to charge and discharge the energy storage battery;

[0065] Furthermore, the maximum power of a DC / DC transformer is limited not only by its own rated electrical capacity but also by the dual limits of the energy storage battery's maximum charging and discharging current and maximum charging voltage. When the energy storage battery is fully charged, the DC / DC transformer's charging power is 0; when the energy storage battery is fully discharged, the DC / DC transformer's discharging power is 0.

[0066] S2, when the maximum power of the DC / DC transformer reaches the limit and still cannot meet the control U dc When the active power difference between the generator-side converter and the grid-side converter is constant, i.e., when the active power difference is greater than the maximum power of the DC / DC transformer, U dc Gradually increase or decrease until exceeding the allowable upper or lower limits; at this point, the grid-side converter will take over U dc The control function no longer operates in constant active power control mode.

[0067] Preferably, in step S3 of the control strategy for the wind turbine motor structure that actively compensates for power prediction deviation, the grid-side converter takes over U dc The methods for controlling functions include the following two:

[0068] a. A control mode switching command is issued from a higher-level control layer:

[0069] The grid-side converter switches to constant DC voltage control mode, still controlling the DC voltage to the rated value; the DC / DC transformer switches to constant power control mode, and its power command is determined according to the remaining charge of the energy storage battery.

[0070] b. Automatic switching is achieved using voltage margin control, by setting appropriate upper and lower limits U of the DC voltage. dc_max U dc_min This is used as the DC voltage command for the grid-side converter, which will automatically control the DC voltage at U. dc_max or U dc_min .

[0071] like Figure 4 As shown, Figure 4 The figure shows the steady-state operating curves of the machine-side converter, grid-side converter, and DC / DC transformer under mode b. The power in the figure is positive when flowing into the DC side of the wind turbine converter; that is, the DC power is positive when the machine-side converter and grid-side converter are in rectification mode, and the DC power is positive when the DC / DC transformer is in discharge mode. dc_ref This is the DC voltage command for normal operation; U dc_max U dc_min These are the high-voltage command and low-voltage command for the grid-side converter, respectively; PGVSC P SVSC P represents the power of the machine-side converter. charge P discharge These represent the maximum DC power of the DC / DC transformer (group); when the DC / DC transformer (group) reaches its maximum DC power, the DC voltage increases or decreases, and the grid-side converter gradually takes over the DC voltage control, ultimately reaching U. dc_max U dc_min .

[0072] The above embodiments are merely preferred technical solutions of the present invention and should not be considered as limitations on the present invention. The embodiments and features described in this application can be arbitrarily combined with each other without conflict. The scope of protection of the present invention should be limited to the technical solutions described in the claims, including equivalent substitutions of the technical features described in the claims. That is, equivalent substitutions and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. A control strategy for a wind turbine motor structure that actively compensates for power prediction deviations, the control structure including an energy storage battery, characterized in that: The energy storage battery is connected to the DC side of the converter via a DC / DC transformer; multiple DC / DC transformers are connected to the DC side of the wind turbine converter via DC circuit breakers or DC fuses, and are connected via DC busbars or busbars. The control strategy for wind turbine motor structures that actively compensate for power prediction deviations includes the following steps: S1, increase the design capacity of the grid-side converter and transformer of the wind turbine; S2, the turbine-side converter, grid-side converter, and DC / DC transformer adopt a coordinated control strategy to enable the wind turbine to capture wind energy according to the maximum power point tracking curve and output active power according to the wind power prediction curve within the allowable range of battery charging and discharging power and capacity; the coordinated control strategy is as follows: S201, the generator-side converter performs torque control or excitation control on the generator according to the MPPT curve, so that the generator outputs the maximum power corresponding to the current wind speed. The generator output power is rectified by the generator-side converter and then output to the DC side of the converter. S202, the grid-side converter receives the power prediction curve for this wind turbine from the wind power prediction system, and its update frequency is consistent with the update frequency of the wind power prediction system; the grid-side converter actively participates in the primary and secondary frequency regulation of the power grid according to the primary frequency regulation curve or dispatch instructions, and the specific methods are as follows: The active power control of the grid-side converter adopts constant active power control; for full-power wind turbines, the active power command value is the power value on the power prediction curve or the power command participating in grid frequency regulation; for doubly-fed wind turbines, the active power command value should be the expected power command minus the real-time power of the generator stator. The reactive power control of the grid-side converter can be selected as either constant reactive power control or constant AC voltage control, depending on the requirements. S203, When there is only one DC / DC transformer branch, the DC / DC transformer controls the DC side voltage of the converter. U dc The specific method is as follows: U dc When the command value is exceeded, the DC / DC transformer increases the charging power of the energy storage battery, thereby reducing the DC voltage; U dc When the voltage is lower than the commanded value, the DC / DC transformer increases the discharge power of the energy storage battery, thereby increasing the DC voltage. S204. When there are multiple DC / DC transformer branches, a hierarchical control architecture is adopted to avoid power circulation between branches. The specific method is as follows: Upper-level control controls the DC-side voltage of the converter. U dc Generate total power command P ∑ Then, based on the current state of charge (SOC) of the energy storage batteries in each branch, the appropriate power allocation for each branch is determined. P DC / DCi The relationship between power and current SOC depends on the performance of the battery used; The lower-level control is the power control of the DC / DC transformer itself, which receives power commands from the upper-level control to charge and discharge the energy storage battery; S3, when the maximum power of the DC / DC transformer reaches the limit and still cannot meet the control requirements. U dc When the active power difference between the generator-side converter and the grid-side converter is constant, that is, when the active power difference is greater than the maximum power of the DC / DC transformer, U dc Gradually increase or decrease until exceeding the allowable upper or lower limits; at this point, the grid-side converter will take over. U dc The control function no longer operates in constant active power control mode.

2. The control strategy for the wind turbine motor structure with active compensation for power prediction deviation as described in claim 1, characterized in that: In step S3, the grid-side converter is connected to the mains. U dc The methods for controlling functions include the following two: a. A control mode switching command is issued from a higher-level control layer: The grid-side converter switches to constant DC voltage control mode, still controlling the DC voltage to the rated value; the DC / DC transformer switches to constant power control mode, and its power command is determined according to the remaining charge of the energy storage battery. b. Automatic switching is achieved using voltage margin control, by setting appropriate upper and lower limits for the DC voltage. U dc_max , U dc_min This is used as the DC voltage command for the grid-side converter, which will automatically control the DC voltage at... U dc_max or U dc_min .

3. The control strategy for the wind turbine motor structure with active compensation for power prediction deviation as described in claim 1, characterized in that: In step S1, the design capacity of the wind turbine grid-side converter and transformer is increased to further enhance the wind turbine's output power when the generator is running at full capacity. The maximum capacity calculation method is as follows: ； in, S max This refers to the maximum capacity of the grid-side converter and transformer. P G_VSC The capacity of the turbine-side converter depends on the type of wind turbine. P DC / DC The formula takes into account the sum of the capacities of all DC / DC transformers, representing the capacity of the DC / DC transformer. Q S_VSC The rated reactive power of the grid-side converter can be replaced with an expression that includes the power factor.

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