Wind power plant static var generator power oscillation suppression method considering third harmonic injection technology influence

Abstract

The invention discloses a wind power plant static var generator power oscillation suppression method considering the influence of a third harmonic injection technology, and relates to the technical field of wind power generation. A traditional oscillation suppression method is poor in suppression effect and dynamic adaptability. The method comprises the following steps: collecting grid-connected point voltage of a static var generator, outputting a reactive power actual value and an active power actual value through a control ring with third harmonic, and when the reactive power actual value or the active power actual value exceeds a corresponding power reference value, controlling a preset lead-lag corrector to be put into the control ring with the third harmonic, and inhibiting oscillation of reactive power and active power through phase compensation. The invention is used for suppressing power oscillation.

Description

Technical Field

[0001] This invention relates to the field of wind power generation technology. Background Technology

[0002] Static var generators (SVRs) are widely used in wind farms due to their rapid dynamic reactive power regulation capabilities to maintain stable voltage at the grid connection point and meet the reactive power and voltage control requirements of the power grid. Figure 1 As shown.

[0003] The existing method of interleaving third-order harmonics (TOH) into the control loop of a static var generator improves the utilization rate of the DC voltage of the static var generator and expands the reactive power output range of the static var generator without significantly increasing equipment costs, thus meeting the system requirements under high power generation conditions.

[0004] However, while injecting third harmonics expands the operating range of the equipment, this technology may induce power oscillations in the static var generator (SVR) under certain operating conditions. Although these oscillations have a low frequency, their amplitude is large, which may cause the SVR to shut down and disconnect from the grid due to overcurrent or power fluctuations, posing a serious threat to the safe and stable operation of the wind farm.

[0005] Traditional oscillation suppression methods are mostly designed for naturally occurring oscillations in the system. For oscillations induced by active harmonic injection with specific triggering conditions, there is a lack of targeted and rapid suppression methods. Therefore, traditional oscillation suppression methods have poor suppression effects and poor dynamic adaptability. Thus, there is an urgent need for a method that can effectively suppress power oscillations in static var generators without sacrificing the technical advantages brought by third harmonic injection. Summary of the Invention

[0006] The purpose of this invention is to solve the problems of poor suppression effect and poor dynamic adaptability of traditional oscillation suppression methods, and to propose a power oscillation suppression method for wind farm static var generators that takes into account the influence of third harmonic injection technology.

[0007] A method for suppressing power oscillations in a wind farm static var generator considering the influence of third harmonic injection technology, the method comprising the following:

[0008] Step 1: Collect the grid connection voltage of the static var generator, and output the actual values ​​of reactive power and active power through the control loop with third harmonic.

[0009] Step 2: If the actual value of reactive power or active power exceeds the corresponding power reference value, and if so, determine that power oscillation has occurred and proceed to step 3; otherwise, proceed to step 4.

[0010] Step 3: Control the preset lead-lag corrector to engage the control loop with the third harmonic, and suppress the oscillation of reactive power and active power through phase compensation;

[0011] Step 4: Generate a modulation signal based on the actual values ​​of reactive power and active power, and use the modulation signal to drive the static var generator to output voltage and current.

[0012] Preferably, the transfer function of the preset lead-lag corrector for:

[0013] ,

[0014] In the formula, To be ahead of time, For the time lag, For the Laplace operator, , The maximum phase angle occurs at the geometric center frequency of the zero and poles. For coefficients, , , This is the preset maximum compensation angle.

[0015] Preferably, the preset maximum compensation angle is set according to the preset target phase margin, which is 45°~60°.

[0016] The beneficial effects of this invention are:

[0017] This invention cleverly superimposes power oscillation suppression functionality on top of third harmonic injection technology. It retains the advantage of third harmonic injection technology in expanding the operating range of equipment while solving the potential power oscillation problem, achieving a synergistic effect by maximizing strengths and minimizing weaknesses.

[0018] This invention employs a lead-lag corrector, which can perform precise phase compensation and damping injection for power oscillations induced by third harmonic injection technology, making it highly targeted.

[0019] This method is based on the classic frequency domain correction theory. The physical meaning of the parameters is clear, making it easy for engineers to debug and adjust on-site. It does not require additional hardware equipment, is low in cost, and has strong engineering applicability.

[0020] This invention prevents the static var generator from locking up due to large power fluctuations by suppressing power oscillations, thereby improving the operational stability and reliability of the entire wind farm grid-connected system and exhibiting strong dynamic adaptability. Attached Figure Description

[0021] Figure 1A flowchart of a method for suppressing power oscillations in a wind farm static var generator that takes into account the influence of third harmonic injection technology;

[0022] Figure 2 A schematic diagram of the wind farm structure and the grid connection of the static var generator;

[0023] Figure 3 The diagram shows the control loop structure with third harmonics, which includes a preset lead-lag corrector.

[0024] Figure 4 Simulation diagram of power oscillation induced by third harmonic injection technology;

[0025] Figure 5 Simulation diagram showing the power oscillation suppression effect of enabling the lead-lag corrector in the power self-synchronization control loop. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the scope of the invention.

[0028] Example:

[0029] This embodiment retains the advantage of the extended operating range of the third harmonic injection system while effectively suppressing the power oscillations of the static var generator induced by the introduction of a lead-lag corrector.

[0030] A method for suppressing power oscillations in a wind farm static var generator considering the influence of third harmonic injection technology, the method comprising the following:

[0031] Step 1: Collect the grid connection voltage of the static var generator, and output the actual values ​​of reactive power and active power through the control loop with third harmonic.

[0032] Step 2: If the actual value of reactive power or active power exceeds the corresponding power reference value, and if so, determine that power oscillation has occurred and proceed to step 3; otherwise, proceed to step 4.

[0033] Step 3: Control the preset lead-lag corrector to engage the control loop with the third harmonic, and suppress the oscillation of reactive power and active power through phase compensation;

[0034] Step 4: Generate a modulation signal based on the actual values ​​of reactive power and active power, and use the modulation signal to drive the static var generator to output voltage and current.

[0035] Specifically, in step 3, after suppressing the oscillation of reactive power and active power through phase compensation, a modulation signal is generated based on the actual values ​​of the suppressed reactive power and active power. The modulation signal is then used to drive the static var generator to output the modulated voltage and current.

[0036] The system monitors power fluctuations. When periodic fluctuations are detected in the actual reactive power or active power of the static var generator, a lead-lag corrector is activated to suppress power oscillations. Once the fluctuations in the actual reactive power or active power disappear (indicating that power oscillations have been suppressed), the lead-lag corrector is removed from the power self-synchronization control loop of the static var generator.

[0037] The power oscillation frequency is only 0.1 to 0.15 Hz, which is a low-frequency oscillation. The main reason for this low-frequency oscillation is a problem with the active power control loop. Therefore, a lead-lag corrector is set in the active power control loop, such as... Figure 3 The location shown is indicated. By suppressing the active component oscillation in the active control loop, the reactive component oscillation is naturally eliminated.

[0038] Further defining the preset transfer function of the lead-lag corrector for:

[0039] ,

[0040] In the formula, To be ahead of time, For the time lag, For the Laplace operator, , The maximum phase angle occurs at the geometric center frequency of the zero and poles. For coefficients, , , This is the preset maximum compensation angle.

[0041] Further, the preset maximum compensation angle is set according to the preset target phase margin, which is 45°~60°.

[0042] Specifically, by introducing a transfer function as The correction stage suppresses power oscillations caused by third harmonic injection technology. The lead / lag time parameters are tuned, and D is determined. f and T fThe optimal parameter values ​​enable the corrector to provide sufficient phase margin for the static var generator system.

[0043] Further defining the static var generator (SVA) grid connection point voltage, the actual reactive power and active power are output via a control loop with third harmonics. The specific process is as follows:

[0044] Actual value of active power After passing through the preset lead-lag corrector, the processed active power output is compared with the preset active power reference value. Summation is performed, and the summation result is fed into the angular frequency transform coefficients to output the angular frequency. After the integration process, the virtual power angle is output. The virtual power angle Simultaneously, the gain coefficient of the first forward path is... Gain coefficient of forward path 2 and third harmonic coefficient Output the first result, the second result, and the third result respectively;

[0045] Actual value of reactive power Compared with the preset reactive power reference value The summation result is adjusted by the reactive power regulation coefficient. Adjustment is performed, and the process enters the integration stage. The output result is summed with the result from step three, and the summation result is simultaneously fed into the gain coefficient of the forward path from step three. and the gain coefficient of the fourth forward path Output results four and five respectively. Summing result four with result one yields the actual value of the suppressed active power; summing result five with result two yields the actual value of the suppressed reactive power.

[0046] Further specifying, the angular frequency transformation coefficients are: In the formula, For Laplace variables, It is the power frequency angular frequency. The damping coefficient is... This is the virtual moment of inertia.

[0047] Further specifying, the points system is as follows: .

[0048] Further specifying, the gain coefficient of the first forward path is: In the formula, The voltage at the grid connection point. This is the grid voltage. This is the smoothing reactance value.

[0049] Further specifying, the gain coefficient of the second forward path is: In the formula, This is the virtual power angle.

[0050] Further specifying, the gain coefficient of the third forward path is: .

[0051] Further specifying, the gain coefficient of the fourth forward path is: .

[0052] Specifically, the effectiveness of this embodiment is verified based on an electromagnetic simulation model. A wind farm grid-connected system model containing a static var generator (SVM) is built in the simulation platform to verify the effectiveness of the SVM power oscillation suppression method. The simulation results are then used to verify this. Figures 4 to 5 It is known that the third harmonic injection technology can induce power oscillations, and after adding a lead-lag corrector, the power oscillations of the static var generator are completely suppressed.

[0053] This embodiment retains the advantage of the third harmonic injection technology in expanding the operating range, while effectively suppressing the power oscillation phenomenon induced by it, thus improving the operational reliability of the static var generator.

[0054] While the invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the invention. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that different dependent claims and features described herein can be combined in ways different from those described in the original claims. It is also understood that features described in conjunction with individual embodiments can be used in other described embodiments.

Claims

1. A method for suppressing power oscillations in a wind farm static var generator considering the influence of third harmonic injection technology, characterized in that, The method includes the following: Step 1: Collect the grid connection voltage of the static var generator, and output the actual values ​​of reactive power and active power through the control loop with third harmonic. Step 2: If the actual value of reactive power or active power exceeds the corresponding power reference value, and if so, determine that power oscillation has occurred and proceed to step 3; otherwise, proceed to step 4. Step 3: Control the preset lead-lag corrector to engage the control loop with the third harmonic, and suppress the oscillation of reactive power and active power through phase compensation; Step 4: Generate a modulation signal based on the actual values ​​of reactive power and active power, and use the modulation signal to drive the static var generator to output voltage and current.

2. The method for suppressing power oscillations in a wind farm static var generator considering the influence of third harmonic injection technology, as described in claim 1, is characterized in that... Preset transfer function of the lead-lag corrector for: ， In the formula, To be ahead of time, For the time lag, For the Laplace operator, , The maximum phase angle occurs at the geometric center frequency of the zero and poles. For coefficients, , , This is the preset maximum compensation angle.

3. The method for suppressing power oscillations in a wind farm static var generator considering the influence of third harmonic injection technology, as described in claim 1, is characterized in that... The preset maximum compensation angle is set according to the preset target phase margin, which is 45°~60°.

4. A method for suppressing power oscillations in a wind farm static var generator considering the influence of third harmonic injection technology, as described in claim 1, is characterized in that... The grid-connected voltage of the static var generator is used to output the actual values ​​of reactive power and active power through a control loop with third harmonics. The specific process is as follows: Actual value of active power After passing through the preset lead-lag corrector, the processed active power output is compared with the preset active power reference value. Summation is performed, and the summation result is fed into the angular frequency transform coefficients to output the angular frequency. After the integration process, the virtual power angle is output. The virtual power angle Simultaneously, the gain coefficient of the first forward path is... Gain coefficient of forward path 2 and third harmonic coefficient Output the first result, the second result, and the third result respectively; Actual value of reactive power Compared with the preset reactive power reference value The summation result is adjusted by the reactive power regulation coefficient. Adjustment is performed, and the process enters the integration stage. The output result is summed with the result from step three, and the summation result is simultaneously fed into the gain coefficient of the forward path from step three. and the gain coefficient of the fourth forward path Output results four and five respectively. Sum results four and one to obtain the actual value of the suppressed active power. Summing result 5 with result 2 yields the actual value of the suppressed reactive power.

5. A method for suppressing power oscillations in a wind farm static var generator considering the influence of third harmonic injection technology, as described in claim 4, is characterized in that... The angular frequency transformation coefficients are: In the formula, For Laplace variables, It is the power frequency angular frequency. The damping coefficient is... This is the virtual moment of inertia.

6. A method for suppressing power oscillations in a wind farm static var generator considering the influence of third harmonic injection technology, as described in claim 5, is characterized in that... The points system is as follows: .

7. A method for suppressing power oscillations in a wind farm static var generator considering the influence of third harmonic injection technology, as described in claim 6, is characterized in that... Forward path gain coefficient for: In the formula, The voltage at the grid connection point. This is the grid voltage. This is the smoothing reactance value.

8. A method for suppressing power oscillations in a wind farm static var generator considering the influence of third harmonic injection technology, as described in claim 7, is characterized in that... Gain coefficient of the second forward path for: In the formula, This is the virtual power angle.

9. A method for suppressing power oscillations in a wind farm static var generator considering the influence of third harmonic injection technology, as described in claim 8, is characterized in that... Gain coefficient of forward path 3 for: .

10. A method for suppressing power oscillations in a wind farm static var generator considering the influence of third harmonic injection technology, as described in claim 9, is characterized in that... Gain coefficient of forward path 4 for: .

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