A damping control method based on the two-dimensional motion distribution of output current vector amplitude and phase

Abstract

The present invention discloses a damping control method based on the two-dimensional motion distribution of the output current vector amplitude and phase. Specifically, in a power system containing a high proportion of power electronic equipment, electromagnetic conversion equipment may have various oscillation problems, including low-frequency oscillation and subsynchronous oscillation. The oscillation problems of the electromagnetic conversion equipment can be suppressed by adding damping control to the power electronic equipment. The present invention only needs to add the control signals generated by the signal measurement link, phase correction link, and motion distribution link to the d and q axis command values ​​of the power electronic equipment, and can fully utilize the two-dimensional motion of the amplitude and phase of the output current vector of the power electronic equipment to damp different types of oscillations of the electromagnetic conversion equipment. This method improves the adaptability of damping control to different types of oscillation problems and the variable operating points of power electronic equipment, ensuring the safe and stable operation of the power system.

Description

Technical Field

[0001] The present invention belongs to the field of safe operation of power systems, and more specifically, relates to a damping control method based on output current vector amplitude-phase two-dimensional motion distribution. Background Art

[0002] In modern power systems, with the widespread adoption of power electronics devices such as converters and flexible direct current transmission (HVDC), the system exhibits a "double high" characteristic: a high proportion of power electronics and a high proportion of renewable energy. While the introduction of power electronics improves system flexibility and controllability, it also introduces a series of new dynamic stability issues, including low-frequency oscillations (LFOs) and subsynchronous oscillations (SSOs) in electromagnetic converters.

[0003] In traditional power systems, the rotor of a synchronous generator is the primary energy storage element. Due to the large rotor inertia and the time constant of the excitation winding, the rotors of synchronous machines interact only on an electromechanical timescale, and the relative sway of the rotors is a direct manifestation of this interaction. Unlike electromagnetic conversion equipment, power electronics equipment incorporates multiple energy storage elements, including rotors, DC capacitors, and AC inductors. To maintain energy balance and state stability among these various energy storage elements, controllers with varying bandwidths (BW) are often used. In "dual-high" power systems, both low-frequency oscillations and subsynchronous oscillations may be related to the complex interactions between power electronics and electromagnetic conversion equipment.

[0004] In recent years, with the increasing adoption of power electronics in power systems, complex oscillations caused by these interactions have become increasingly common, ranging in frequency from a few Hz to thousands of Hz. These oscillations pose a serious threat to the safe and stable operation of power systems. To suppress these oscillations, damping control can be added to power electronics. However, existing damping control techniques are insufficiently adaptable to varying operating points. Therefore, there is an urgent need to optimize existing damping control techniques to enhance the adaptability of power electronics to diverse operating points. Summary of the Invention

[0005] In response to the need for improvement in the existing technology, the present invention provides a damping control method based on the two-dimensional motion distribution of the output current vector amplitude-phase, which aims to simultaneously suppress low-frequency oscillations and subsynchronous oscillations, and has better adaptability to changes in the operating point.

[0006] To achieve the above objectives, the present invention provides a damping control method based on output current vector amplitude-phase two-dimensional motion distribution, comprising:

[0007] S1. Collect the real-time three-phase voltage V of the power electronic equipment grid connection point tabc And the three-phase output current I cabc, by the three-phase voltage V tabc And the three-phase output current I cabc Calculate the active power P and reactive power Q, and obtain the AC grid frequency f and phase error θ by the phase-locked loop err , the difference between the active power P and the active power in steady state, the difference between the reactive power Q and the reactive power in steady state, the difference between the AC grid frequency f and the grid frequency in steady state, and the phase error θ err Perform linear combination and set two different sets of proportional coefficients for low-frequency oscillation and subsynchronous oscillation respectively to obtain signals s1 and s2;

[0008] S2. Signal s1 is low-pass filtered to obtain a low-frequency oscillation frequency band signal, which is then phase corrected and multiplied by a proportional coefficient to obtain a phase signal for damping the low-frequency oscillation.

[0009] S3. Signal s2 is filtered by a bandpass filter to obtain a subsynchronous frequency band signal, which is then phase corrected and multiplied by a proportional coefficient to obtain an amplitude signal for damping subsynchronous oscillations.

[0010] S4. Using phase signal and amplitude signal By distributing motion, calculate the additional damping to control the D-axis signal and q-axis signal

[0011] Furthermore, step S1 is specifically to use the collected three-phase voltage V tabc And the three-phase output current I cabc Calculate active power P and reactive power Q, and use a phase-locked loop to obtain the AC grid frequency f and phase error θ err After low-pass filtering, the difference between the active power P and the active power in steady state, the difference between the reactive power Q and the reactive power in steady state, the difference between the AC grid frequency f and the grid frequency in steady state, and the phase error θ are converted into err Perform linear combination to obtain signals s1 and s2.

[0012] Furthermore, the time constant of the low-pass filter is generally 0.01s to 0.1s.

[0013] Furthermore, the calculation formulas of signals s1 and s2 are:

[0014] s1=k1(f-f0)+k2θ err +k3(P-P0)+k4(Q-Q0)

[0015] s2=k5(f-f0)+k6θ err +k7(P-P0)+k8(Q-Q0)

[0016] Among them, k1, k2, k3, k4, k5, k6, k7 and k8 are proportional coefficients, f0, P0, Q0 are the grid frequency, active power and reactive power in steady state, respectively, and f, P, Q are the real-time grid frequency, active power and reactive power, respectively.

[0017] Furthermore, step S2 specifically includes filtering the signal s1 using a low-pass filter, where the cutoff frequency of the low-pass filter is about 5 Hz.

[0018] Furthermore, step S3 specifically includes filtering the signal s2 using a bandpass filter, where the passband of the bandpass filter is 5 to 30 Hz.

[0019] Furthermore, step S4 calculates the additional damping control d-axis signal through the motion distribution link and q-axis signal The calculation formula is:

[0020]

[0021] Among them, I c0 is the output current in steady state, It is worth noting that the output current and power factor angle here can also use the real-time calculated values. The real-time output current is I c , real-time power factor angle The calculation formula is:

[0022]

[0023] Among them, P and Q are the active and reactive powers at the current moment.

[0024] In general, the technical solution conceived by the present invention requires measuring terminal voltage, current, grid frequency, and phase error information to generate signals s1 and s2. These signals, respectively, undergo a phase correction process to generate additional damping control phase and amplitude signals. Furthermore, through a motion distribution process, additional damping control d-axis and q-axis signals are obtained, which participate in the original AC current control process to simultaneously generate damping torque in the low-frequency oscillation and subsynchronous oscillation frequency bands. By directly controlling the amplitude and phase of the output current vector in two dimensions, the present invention achieves the effect of simultaneously damping low-frequency oscillations and subsynchronous oscillations, and can improve the adaptability of power electronic equipment to various operating points. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 1 is a schematic structural diagram of a grid-connected converter according to an embodiment of the present invention;

[0026] Figure 2 is a control structure diagram of a grid-connected converter according to an embodiment of the present invention;

[0027] Figure 3 This is a structural diagram of the motion allocation link of an embodiment of the present invention;

[0028] Figure 4 is another structural diagram of the motion distribution link of an embodiment of the present invention;

[0029] Figure 5 This is a typical application scenario of the embodiment of the present invention. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0031] The output current vector amplitude-phase two-dimensional motion distribution of the embodiment of the present invention includes the following steps:

[0032] S1. Collect the real-time three-phase voltage V of the power electronic equipment grid connection point tabc And the three-phase output current I cabc , by the three-phase voltage V tabc And the three-phase output current I cabc Calculate the active power P and reactive power Q, and obtain the AC grid frequency f and phase error θ by the phase-locked loop err , the difference between the active power P and the active power in steady state, the difference between the reactive power Q and the reactive power in steady state, the difference between the AC grid frequency f and the grid frequency in steady state, and the phase error θ err Perform linear combination and set two different sets of proportional coefficients for low-frequency oscillation and subsynchronous oscillation respectively to obtain signals s1 and s2;

[0033] S2. Signal s1 is low-pass filtered to obtain a low-frequency oscillation frequency band signal, which is then phase corrected and multiplied by a proportional coefficient to obtain a phase signal for damping the low-frequency oscillation.

[0034] S3. Signal s2 is filtered by a bandpass filter to obtain a subsynchronous frequency band signal, which is then phase corrected and multiplied by a proportional coefficient to obtain an amplitude signal for damping subsynchronous oscillations.

[0035] S4. Using phase signal and amplitude signal By distributing motion, calculate the additional damping to control the D-axis signal and q-axis signal

[0036] Furthermore, step S1 is specifically to use the collected three-phase voltage V tabc And the three-phase output current I cabc Calculate active power P and reactive power Q, and use a phase-locked loop to obtain the AC grid frequency f and phase error θ err After low-pass filtering, the difference between the active power P and the active power in steady state, the difference between the reactive power Q and the reactive power in steady state, the difference between the AC grid frequency f and the grid frequency in steady state, and the phase error θ are converted into err Perform linear combination to obtain signals s1 and s2.

[0037] Furthermore, the time constant of the low-pass filter is generally 0.01s to 0.1s.

[0038] Furthermore, the calculation formulas of signals s1 and s2 are:

[0039] s1=k1(f-f0)+k2θ err +k3(P-P0)+k4(Q-Q0)

[0040] s2=k5(f-f0)+k6θ err +k7(P-P0)+k8(Q-Q0)

[0041] Among them, k1, k2, k3, k4, k5, k6, k7 and k8 are proportional coefficients, f0, P0, Q0 are the grid frequency, active power and reactive power in steady state, respectively, and f, P, Q are the real-time grid frequency, active power and reactive power, respectively.

[0042] Furthermore, step S2 specifically includes filtering the signal s1 using a low-pass filter, where the cutoff frequency of the low-pass filter is about 5 Hz.

[0043] Furthermore, step S3 specifically includes filtering the signal s2 using a bandpass filter, where the passband of the bandpass filter is 5 to 30 Hz.

[0044] Furthermore, step S4 calculates the additional damping control d-axis signal through the motion distribution link and q-axis signal The calculation formula is:

[0045]

[0046] Among them, I c0 is the output current in steady state, is the power factor angle in steady state. It is worth noting that the output current and power factor angle here can also use the real-time calculated values. The power factor angle calculation formula is:

[0047]

[0048] Among them, P and Q are the active and reactive powers at the current moment.

[0049] In order to enable those skilled in the art to better understand the present invention, a damping control method based on output current vector amplitude-phase two-dimensional motion distribution of the present invention is described in detail below with reference to specific embodiments.

[0050] Example 1

[0051] Figure 1 The structure of the grid-connected converter is shown in Figure 1: One side of the grid-connected converter is the DC side, and the AC side is connected to the grid through the LCL filter circuit. tabc , current I cabc , active power P and reactive power Q are signals that need to be collected or calculated in accordance with the embodiment of the present invention.

[0052] Figure 2 The structure diagram of the damping control based on the output current vector amplitude-phase two-dimensional motion distribution provided by the present invention is shown: the controller includes DC voltage control, reactive power control, AC current control and additional damping control. The phase-locked loop is connected to the grid through the AC three-phase voltage V tabc Calculate the phase-locked phase θ pll DC voltage reference value and DC voltage V dc The PI controller controlled by DC voltage obtains the d-axis output current reference value The reactive power reference value and reactive power are passed through the PI controller of reactive power control to obtain the q-axis output current reference value. Phase lock phase θ pll and current I cabc Use PARK transformation to get the d-axis output current and q-axis output current Three-phase voltage V tabc , three-phase output current I cabc , AC grid frequency f, phase-locked phase θ pll and phase error θ err The information is passed through the information measurement link, phase correction link, and motion distribution link in the additional damping control to obtain the additional damping control d-axis signal and q-axis signal D-axis output current reference value d-axis output current Additional damping control d-axis signal The result of the PI controller controlled by AC voltage plus the d-axis terminal voltage Get the d-axis component of the internal potential q-axis output current reference value q-axis output current Additional damping controls the q-axis signal The result of the PI controller controlled by AC voltage plus the voltage at the q-axis end is Get the q-axis component of the internal potential After calculation, the converter driving signal is obtained to drive the grid-connected converter.

[0053] Figure 3 A structural diagram of the motion distribution link of an embodiment of the present invention is shown, showing the phase signal controlled by additional damping and additional damping control amplitude signal Get the additional damping control d-axis signal and q-axis signal The calculation process shown in the figure is c0 is the output current in steady state, is the power factor angle in steady state.

[0054] Figure 4 Another structural diagram of the motion distribution link of the embodiment of the present invention is shown, showing the phase signal controlled by the additional damping and additional damping control amplitude signal Get the additional damping control d-axis signal and q-axis signal The calculation process shown in the figure is c is the real-time output current, is the real-time power factor angle.

[0055] Figure 5 This illustrates a typical application scenario of an embodiment of the present invention. A grid-connected converter equipped with this embodiment operates in parallel with a synchronous generator set, connected to a busbar for grid access. When the synchronous generator set experiences low-frequency or subsynchronous oscillations, the grid-connected converter equipped with this embodiment of the present invention can effectively suppress the oscillations through additional damping control.

[0056] It will be easily understood by those skilled in the art that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A damping control method based on the two-dimensional motion distribution of output current vector amplitude-phase, characterized in that: The steps include: S1. Collect the real-time three-phase voltage V of the power electronic equipment grid connection point tabc And the three-phase output current I cabc , by the three-phase voltage V tabc And the three-phase output current I cabc Calculate the active power P and reactive power Q, and obtain the AC grid frequency f and phase error θ by the phase-locked loop err , the difference between the active power P and the active power in steady state, the difference between the reactive power Q and the reactive power in steady state, the difference between the AC grid frequency f and the grid frequency in steady state, and the phase error θ err Perform linear combination and set two different sets of proportional coefficients for low-frequency oscillation and subsynchronous oscillation respectively to obtain signals s1 and s2; S2. Signal s1 is low-pass filtered to obtain a low-frequency oscillation frequency band signal, which is then phase corrected and multiplied by a proportional coefficient to obtain a phase signal for damping the low-frequency oscillation. S3. Signal s2 is band-pass filtered to obtain a subsynchronous frequency band signal, which is then phase corrected and multiplied by a proportional coefficient to obtain an amplitude signal for damping subsynchronous oscillations. S4. Using phase signal and amplitude signal By distributing motion, calculate the additional damping to control the D-axis signal and q-axis signal 2. The damping control method based on output current vector amplitude-phase two-dimensional motion distribution according to claim 1, characterized in that: Step S1 specifically includes using the collected three-phase voltage V tabc And the three-phase output current I cabc Calculate active power P and reactive power Q, and use a phase-locked loop to obtain the AC grid frequency f and phase error θ err After low-pass filtering, the difference between the active power P and the active power in steady state, the difference between the reactive power Q and the reactive power in steady state, the difference between the AC grid frequency f and the grid frequency in steady state, and the phase error θ are converted into err Perform linear combination to obtain signals s1 and s2.

3. The damping control method based on output current vector amplitude-phase two-dimensional motion distribution according to claim 2, characterized in that: The calculation formulas for signals s1 and s2 are: s1=k1(f-f0)+k2θ err +k3(P-P0)+k4(Q-Q0) <h2 style=";text-align:left;direction:ltr">s2=k5(f-f0)+k6θ<h2 style=";text-align:left;direction:ltr"> err <h2 style=";text-align:left;direction:ltr"> +k7(P-P0)+k8(Q-Q0) Among them, k1, k2, k3, k4, k5, k6, k7 and k8 are proportional coefficients, f0, P0, Q0 are the grid frequency, active power and reactive power in steady state, respectively, and f, P, Q are the real-time grid frequency, active power and reactive power, respectively.

4. The damping control method based on output current vector amplitude-phase two-dimensional motion distribution according to claim 1, characterized in that: In step S2, a low-pass filter is used to perform low-pass filtering on the signal s1, and the cut-off frequency of the low-pass filter is 5 Hz.

5. The damping control method based on output current vector amplitude-phase two-dimensional motion distribution according to claim 1, characterized in that: In step S3, a band-pass filter is used to perform band-pass filtering on the signal s2, and the passband of the band-pass filter is 5 to 30 Hz.

6. The damping control method based on output current vector amplitude-phase two-dimensional motion distribution according to claim 1, characterized in that: Step S4 calculates the additional damping control d-axis signal by motion distribution and q-axis signal The calculation formula is: Among them, I c0 is the output current in steady state, is the power factor angle in steady state.

7. The damping control method based on output current vector amplitude-phase two-dimensional motion distribution according to claim 1, characterized in that: Step S4 calculates the additional damping control d-axis signal by motion distribution and q-axis signal The calculation formula is: Among them, I c is the real-time output current, is the real-time power factor angle. The real-time power factor angle calculation formula is: Among them, P and Q are the active and reactive powers at the current moment.

8. An electronic device, characterized in that: include: Computer-readable storage medium and processor; The computer-readable storage medium is used to store executable instructions; The processor is configured to read the executable instructions stored in the computer-readable storage medium and execute the method according to any one of claims 1 to 7.

9. A computer-readable storage medium, characterized in that The computer-readable storage medium stores computer instructions, and the computer instructions are used to enable a processor to execute the method according to any one of claims 1 to 7.

10. A computer program product comprising a computer program or instructions, characterized in that When the computer program or instruction is executed by a processor, the method according to any one of claims 1 to 7 is implemented.

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