CN-114614493-B - Positive and negative sequence decoupling power grid voltage feedforward control method

Abstract

The invention relates to a positive and negative sequence decoupling power grid voltage feedforward control method, which comprises the following steps that a feedforward signal calculation module can adjust the amplitude of a feedforward value high-frequency component, realize lead or lag compensation by adjusting phase angle compensation parameters, compensate the phase of the high-frequency component, reasonably adjust two degrees of freedom, and enable a grid-connected inverter to be stably connected in grid under a weak power grid, wherein the feedforward signal calculation module finally outputs 4 variables , , , 4 Variables obtained by the feedforward signal calculation module , , , Respectively carrying out inverse Park transformation according to the positive and negative sequence coordinate systems to obtain the positive sequence coordinate system , And under a negative sequence coordinate system , And synchronously obtaining positive and negative sequences And . The invention has better performance when the voltage of the power grid is unbalanced, realizes independent control of positive and negative sequence currents, and can improve the stability of grid-connected operation of the inverter under the condition of weak power grid.

Inventors

• WANG YIMING
• LIU CONGZHE
• WANG HAIPENG
• XU JUN
• XU PO

Assignees

• 锦浪科技股份有限公司

Dates

Publication Date

20260512

Application Date

20220321

Claims (4)

1. 1. The positive and negative sequence decoupling power grid voltage feedforward control method is characterized by comprising the following steps of: Step 1, collecting grid voltage of grid connection points, and decoupling positive and negative sequences of the grid voltage to obtain 4 variables , , , Wherein, the method comprises the steps of, , , , All contain higher harmonics; Step 2, adopting positive sequence component Performing software phase locking to enable the system to stably follow the phase angle theta of the positive sequence component of the power grid voltage; Step 3, positive and negative sequence components , , , Inputting a feedforward signal calculation module; Step 4, the feedforward signal calculation module can adjust the amplitude of the feedforward value high-frequency component, realize lead or lag compensation by adjusting the phase angle compensation parameter, compensate the phase of the high-frequency component, reasonably adjust the two degrees of freedom, and enable the grid-connected inverter to be stably connected under a weak current network , , , Wherein, the feedforward signal calculating module comprises a low-pass filter LPF and a regulating parameter K, , , , Sequentially passing through low pass filters LPF and K, and compensating the phase of high frequency component by itself; step 5, 4 variables obtained by the feedforward signal calculation module are processed , , , Respectively carrying out inverse Park transformation according to the positive and negative sequence coordinate systems to obtain the positive sequence coordinate system , And under a negative sequence coordinate system , And synchronously obtaining positive and negative sequences And Wherein the inverse Park transformation stably follows the phase angle theta of the positive sequence component of the grid voltage; step 6, performing inverse Clack transformation to obtain a three-phase stationary coordinate system PWM modulation is carried out by using the value as a final feedforward value, so that positive and negative sequence decoupling grid voltage feedforward control can be realized.
2. 2. The positive and negative sequence decoupling power grid voltage feedforward control method of claim 1, wherein in step 1 , , , The four variables are calculated according to a positive-negative sequence decoupling formula, when the three-phase power grid voltage value changes simultaneously or a certain phase voltage value changes, different four variable values can be obtained, and the four variable values change in real time.
3. 3. The positive and negative sequence decoupling power grid voltage feedforward control method of claim 1, wherein the positive sequence current d, the positive sequence current q, the negative sequence current d and the negative sequence current q of the current loop are respectively added to the output values before the reverse Park conversion in the step 5 , , , And (3) upper part.
4. 4. A photovoltaic grid-connected inverter is characterized in that the photovoltaic grid-connected inverter is applied to the positive and negative sequence decoupling grid voltage feedforward control method in any one of claims 1-3.

Description

Positive and negative sequence decoupling power grid voltage feedforward control method Technical Field The invention belongs to the technical field of power electronic control, and particularly relates to a positive and negative sequence decoupling grid voltage feedforward control method of a photovoltaic grid-connected inverter, which can adapt to an unbalanced grid. Background In order to improve the quality of grid-connected current and reduce the influence of grid-connected voltage fluctuation on the current, grid voltage feedforward control is added to the mainstream grid-connected inverter control, and the current general voltage feedforward control method mainly adopts the following means that three-phase grid voltage signals are collected, three-phase alternating current signals are converted into direct current signals under a dq coordinate system through Park conversion (Park conversion), but because the grid-connected voltage generally has a plurality of harmonic components and high-frequency interference which is inevitably introduced in the sampling process, the interference can have bad influence on the running stability of the grid-connected inverter, so that the variable under the dq coordinate system is generally subjected to low-pass filtering, and the filtered value is used as a grid voltage feedforward value. As described above, the existing feedforward control method generally does not compensate for higher harmonics, and cannot alleviate the influence caused by high-frequency components of the voltage of the grid-connected point and sampling interference. However, when the power grid voltage is unbalanced, the control requirement is difficult to meet, and the specific reason is that a negative sequence component is generated when the power grid voltage is unbalanced, and when the Park conversion is performed on the power grid voltage according to the above, the conversion is performed on the basis of a positive sequence component, and at the moment, the negative sequence component cannot be completely reflected, so that the grid-connected current control effect is poor, and even the machine is disconnected or even damaged due to the fact that an uncontrolled negative sequence current component is generated. Disclosure of Invention The invention designs a positive and negative sequence decoupling power grid voltage feedforward control method, which solves the technical problems that when the existing power grid voltage is unbalanced, a negative sequence component is generated, when the power grid voltage is subjected to Park conversion, the conversion is performed based on the positive sequence component, and at the moment, the negative sequence component cannot be completely reflected, so that the grid-connected current control effect is poor, and even a machine is disconnected or even damaged due to the fact that an uncontrolled negative sequence current component is generated. In order to solve the technical problems, the invention adopts the following scheme: A positive and negative sequence decoupling power grid voltage feedforward control method comprises the following steps: step 1, collecting grid voltage of grid connection points, and decoupling positive and negative sequences of the grid voltage to obtain 4 variables ,,,; Step 2, adopting positive sequence componentPerforming software phase locking to enable the system to stably follow the phase angle theta of the positive sequence component of the power grid voltage; Step 3, positive and negative sequence components ,,,Inputting a feedforward signal calculation module; Step 4, the feedforward signal calculation module can adjust the amplitude of the feedforward value high-frequency component, realize lead or lag compensation by adjusting the phase angle compensation parameter, compensate the phase of the high-frequency component, reasonably adjust the two degrees of freedom, and enable the grid-connected inverter to be stably connected under a weak current network ,,,; Step 5, 4 variables obtained by the feedforward signal calculation module are processed,,,Respectively carrying out inverse Park transformation according to the positive and negative sequence coordinate systems to obtain the positive sequence coordinate system,And under a negative sequence coordinate system,And synchronously obtaining positive and negative sequencesAnd; Step 6, performing inverse Clack transformation to obtain a three-phase stationary coordinate systemPWM modulation is carried out by using the value as a final feedforward value, so that positive and negative sequence decoupling grid voltage feedforward control can be realized. Preferably, in step 1,,,All contain higher harmonics, which provides a foundation for the subsequent processing of fundamental waves and harmonics respectively. Preferably, in step 1,,,The four variables are calculated according to a positive-negative sequence decoupling formula, when the three-phase power grid voltage v