Damping control method based on output current vector amplitude-phase two-dimensional motion distribution

Abstract

The invention discloses a damping control method based on output current vector amplitude-phase two-dimensional motion distribution. Particularly, in a power system containing high-proportion power electronic equipment, various oscillation problems including low-frequency oscillation and subsynchronous oscillation possibly occur in the electromagnetic transformation equipment, and the oscillation problem of the electromagnetic transformation equipment can be suppressed by adding damping control to the power electronic equipment. According to the method, only control signals generated through a signal measurement link, a phase correction link and a motion distribution link need to be added to d-axis and q-axis instruction values of the power electronic equipment, and different types of oscillation of the electromagnetic transformation equipment can be damped by fully utilizing amplitude and phase two-dimensional motion of a current vector output by the power electronic equipment. According to the method, the adaptability of damping control to different types of oscillation problems and variable working points of power electronic equipment is improved, and safe and stable operation of a power system is guaranteed.

Description

Technical Field

[0001] The present invention belongs to the field of safe operation of electric 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 application of power electronic devices such as converters and flexible direct current transmission, the system presents the "double high" characteristics of a high proportion of power electronic devices and a high proportion of renewable energy. The introduction of power electronic devices improves the flexibility and controllability of the system, but also brings a series of new dynamic stability problems, including low-frequency oscillation (LFO) and subsynchronous oscillation (SSO) of electromagnetic conversion equipment.

[0003] In traditional power systems, the rotor of a synchronous generator is the main energy storage element. Due to the large rotor inertia and the time constant of the excitation winding, only electromechanical time scale interaction occurs between the rotors of synchronous machines, and the relative swing of the rotors is a direct reflection of this interaction process. Different from electromagnetic conversion equipment, power electronic equipment has multiple energy storage elements including rotors, DC capacitors, and AC inductors. In order to maintain the energy balance and state stability of different energy storage elements, controllers with different bandwidths (Band Width, BW) are often equipped accordingly. In "double-high" power systems, low-frequency oscillations and subsynchronous oscillations may be related to the complex interaction between power electronic equipment and electromagnetic conversion equipment.

[0004] In recent years, with the continuous deepening of power electronics in power systems, complex oscillation problems caused by interactions have emerged one after another, covering a frequency range from a few Hz to thousands of Hz, which has seriously threatened the safe and stable operation of power systems. In order to suppress these oscillation problems, damping control can be added to power electronic equipment. However, the existing damping control technology is not adaptable enough to the working point. Therefore, it is urgent to optimize the existing damping control technology to enhance the adaptability of power electronic equipment to various working points. Summary of the invention

[0005] In response to the need for improvement in the prior art, 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 sub-synchronous oscillations and has better adaptability to changes in the operating point.

[0006] To achieve the above object, 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, set two different sets of proportional coefficients for low-frequency oscillation and subsynchronous oscillation, and obtain signals s1 and s2 respectively;

[0008] S2. The 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 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 specifically includes using the collected three-phase voltage V tabc And the three-phase output current I cabc Calculate the active power P and reactive power Q, and use the 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 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 with a low-pass filter, and the cut-off frequency of the low-pass filter is about 5 Hz.

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

[0019] Further, 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, 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 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 above technical scheme conceived by the present invention requires measuring terminal voltage, current, grid frequency, phase error and other information, generating signals s1 and s2, respectively generating additional damping control phase signal and amplitude signal through the phase correction link, and then obtaining additional damping control d-axis signal and q-axis signal through the motion distribution link, participating in the original AC current control link, thereby generating damping torque of low-frequency oscillation and subsynchronous oscillation frequency band at the same time. The present invention achieves the effect of simultaneously damping low-frequency oscillation and subsynchronous oscillation by directly controlling the amplitude and phase two-dimensional motion of the output current vector, and can improve the adaptability of power electronic equipment to various working points. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 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 It 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 allocation 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 solution and advantages of the present invention more clear, the present invention is further described in detail below in conjunction with 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 used to limit the present invention.

[0031] The output current vector amplitude-phase two-dimensional motion allocation 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, set two different sets of proportional coefficients for low-frequency oscillation and subsynchronous oscillation, and obtain signals s1 and s2 respectively;

[0033] S2. The 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 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 specifically includes using the collected three-phase voltage V tabc And the three-phase output current I cabc Calculate the active power P and reactive power Q, and use the 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 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 with a low-pass filter, and the cut-off frequency of the low-pass filter is about 5 Hz.

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

[0044] Further, 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 values ​​calculated in real time, and 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 in conjunction with specific embodiments.

[0050] Embodiment 1

[0051] Figure 1 The structure diagram 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 embodiments 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 The phase-locked phase θ is calculated 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 Using PARK transformation to obtain 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 voltage at the d-axis end is 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 The q-axis component of the internal potential is obtained After calculation, a 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 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 A typical application scenario of the embodiment of the present invention is shown, where the grid-connected converter equipped with the embodiment of the present invention is connected in parallel with the synchronous generator set and connected to the busbar to access the power grid. When the synchronous generator set has low-frequency oscillation or sub-synchronous oscillation, the grid-connected converter equipped with the embodiment of the present invention can effectively suppress the oscillation phenomenon through additional damping control.

[0056] It will be easily understood by those skilled in the art that the above description 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 protection scope of the present invention.

Claims

1. A damping control method based on output current vector amplitude-phase two-dimensional motion distribution, characterized in that: The steps include: S1. Collect the real-time three-phase voltage V of the power electronic equipment grid connection point tabc With the three-phase output current I cabc , by the three-phase voltage V tabc With 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, set two different sets of proportional coefficients for low-frequency oscillation and subsynchronous oscillation, and obtain signals s1 and s2 respectively; S2. The 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 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. A 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 the active power P and reactive power Q, and use the 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 err Perform linear combination to obtain signals s1 and s2.

3. A damping control method based on output current vector amplitude-phase two-dimensional motion distribution according to claim 2, characterized in that: The calculation formula of signals s1 and s2 is: 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 is 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 is characterized in that: In step S3, a bandpass filter is used to perform bandpass filtering on the signal s2, and the passband of the bandpass filter is 5 to 30 Hz.

6. A 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. A 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: A computer readable storage medium and a processor; The computer-readable storage medium is used to store executable instructions; The processor is used 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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