The invention discloses a distributed wind turbine generator power quality test method. The method comprises the following steps of using a virtual power grid model to determine a voltage fluctuationand flicker generated by a wind turbine generator; determining a test voltage fundamental electrical angle through a pole-symmetric mode decomposition algorithm; using the virtual power grid model todetermine a function relationship between the voltage fluctuation and flicker and a power grid impedance angle; determining a relationship between a power grid and volatility of the wind turbine generator according to the function relationship between the voltage fluctuation and flicker and the power grid impedance angle; building a power quality detection platform based on an information physicssystem; and through the power quality detection platform, converting hidden data into explicit data, converting the explicit data into understandable information, and forming an optimal strategy andknowledge through intelligent analysis and decision making. A distributed wind turbine generator power quality test platform based on the information physics system is constructed, an impact of the power grid on the distributed wind turbine generator power quality is accurately assessed, and detection accuracy and reliability are improved.

Distributed wind turbine generator power quality test method

The invention belongs to the technical field of power electronic device control, and relates to a power decoupling control method and system for a virtual synchronous generator based on voltage feedforward compensation. The method comprises the steps of firstly, acquiring output power Pvsg and Qvsg of the virtual synchronous generator; giving a reactive power reference value Qref, subtracting thereactive power Qvsg output by the virtual synchronous generator from the reactive power reference value Qref to obtain d-axis initial reference voltage V through an inertia equation of a reactive power loop, setting the q-axis initial reference voltage V to be 0 at the same time, then presetting voltage feedforward equivalent inductive reactance Xv, and generating feedforward voltage Xviod; and obtaining a voltage control loop reference instruction V according to the d-axis initial reference voltage V , subtracting the feedforward voltage Xviod from the q-axisinitial reference voltage V to obtain a voltage control loop reference instruction V , and finally generating an SVPWM control instruction through a voltage control loop and a currentcontrol loop according to the voltage control loop reference instruction. According to the invention, the coupling problem between active power output and reactive power output is significantly improved, and the capacity requirement of the inverter is reduced.

Power decoupling control method and system for virtual synchronous generator based on voltage feedforward compensation

The invention discloses a wind power grid-connected inverter frequency modulation control method and system. The control method is applied to frequency modulation control in a wind power grid-connected system. The control method comprises the following steps that the wind power grid-connected system uses a double-closed-loop control strategy of a output voltage outer loop and a output current inner loop; a virtual synchronous motor is used for control; the operation frequency of the wind power grid-connected system is obtained; whether the operation frequency is in a frequency range or not isjudged; if so, the virtual synchronous motor is used for performing primary frequency modulation on the wind power grid-connected system; otherwise, the virtual synchronous motor is used for performing secondary frequency modulation on the wind power grid-connected system. The double feed control is performed according to the frequency deviation; the frequency self restoration is realized; meanwhile, the power fluctuation is reduced; no limiting exceeding in the whole frequency regulation process occurs is ensured.

Wind power grid-connected inverter frequency modulation control method and system

The invention relates to a grating moire fringe denoising method based on VMD. The method comprises the following steps of S1, decomposing an original signal into an intrinsic mode function through the VMD; S2, carrying out Hilbert transformation on the intrinsic mode function to obtain function time-frequency information; S3, filtering a high-frequency IMF component containing noise signals; S4,separating and recombining the high-frequency IMF component and a low-frequency IMF component to obtain noise-reduced signals, carrying out VMD on a moire fringe simulation signal to decompose the moire fringe simulation signal into multiple intrinsic mode functions (IMF) with different frequency bands, then analyzing the time-frequency characteristics of the IMF component by means of the Hilberttransformation, and filtering out the high-frequency noise signals. The VMD algorithm can well inhibit a mode aliasing phenomenon, accurately decompose the signals with different frequency bands, improve the signal-to-noise ratio of the denoised signals and have a good denoising effect. Compared with the prior art, the method has the advantages of high signal-to-noise ratio, good denoising effectand the like.

Grating moire fringe denoising method based on VMD

The invention discloses an improved method for droop control of a flexible direct current converter. An active frequency droop module outputs a power grid synchronization signal. A reactive voltage droop module outputs a converter voltage amplitude given signal, the converter valve output voltage phase and amplitude are synchronized with a power grid through the reactive voltage droop module and the reactive voltage droop module, the stability of the converter valve connected into a weak alternating current system can be improved without depending on a phase-locked loop, and meanwhile convenient conditions are provided for switching of an island control mode and a networking control mode. The transient active power regulation module utilizes an error between a transient active power givenvalue and a feedback value, to calculate a compensation signal of a transient active current given value, the active dynamic response process of droop control is accelerated, a proportional differential link is arranged in the transient active adjustment module, the transient active adjustment module outputs compensation components in the transient process that the output is basically 0 and the power step is equal in the steady state, and active power tracking giving is accelerated. And meanwhile, the droop characteristic of the converter during steady-state operation is kept, and the system stability is ensured.

Flexible direct-current transmission converter control method based on improved droop controller

The invention relates to a frequency self-recovery control method based on a virtual synchronous generator. When the virtual synchronous generator is put into a microgrid, a small moment of inertia Jis provided to avoid dynamic power oscillation. When small disturbance occurs, the primary frequency modulation method based on virtual synchronous generator is adopted. When the disturbance is large,the frequency offset exceeds a certain value to start the secondary frequency modulation, and the fast charging and discharging characteristics of the energy storage battery are utilized to make it participate in the secondary frequency modulation process, so that the frequency can be quickly restored to the threshold range; after that, the energy storage output is gradually reduced and the secondary frequency modulation is slowly withdrawn, and other frequency modulation devices play a major role in restoring the frequency to the rated value. The invention can effectively restrain the frequency exceeding the limit when the heavy load disturbance occurs, enable the frequency to be recovered quickly, combine the primary and secondary frequency modulation in the whole frequency modulation range, and give full play to the energy storage function.

Frequency self-recovery control method based on virtual synchronous generator

The invention relates to a method for switching from off network to gird connection of a virtual synchronous power generator. Seamless switching between off network and grid connection of the virtualsynchronous power generator is achieved by employing a three-phase bridge-type inverter grid-connected structure and a virtual synchronous power generator control method and by combining a secondary frequency modulation and voltage adjustment strategy and a direct voltage phase identification principle. The method comprises the steps of firstly, detecting a voltage value and a frequency value of apower grid output by an electric energy quality detection device; secondly, taking the voltage value and the frequency value as given values of a micro grid during island running, achieving secondaryfrequency modulation by frequency deviation integration feedback, and achieving secondary voltage adjustment by voltage deviation integration feedback; and finally, calculating a micro grid phase voltage and a power line voltage, identifying two same phases when the micro grid phase voltage and the power line voltage are perpendicular to each other, and achieving seamless switching between off network and grid connection without a phase-locked ring. The phase-locked ring is not needed, only the strategy is needed to be switched, seamless switching between off network and grid connection can be achieved at relatively small overshoot and relatively short time, and the stability of the power grid is further improved.

Method for switching from off network to gird connection of virtual synchronous power generator

The invention relates to a voltage flicker parameter detection method based on extreme point symmetry mode decomposition. Based on the extreme symmetry mode decomposition theory and algorithm, a voltage flicker parameter detection step based on ESMD extreme point symmetry mode decomposition is given. Firstly, a voltage flicker signal is decomposed into single-frequency amplitude-modulated waves bythe ESMD method, and then the instantaneous amplitude and instantaneous frequency information of each single-frequency amplitude-modulated wave is obtained by the direct interpolation DI method. Theover-fitting and under-fitting of an envelope of the EMD method is overcome, and the modal aliasing phenomenon of the EMD method can be effectively avoided in the detection without adding noise; the defect that the detection result of the EEMD method strongly depends on the selected noise is overcome. The voltage flicker parameter detection method has strong self-decomposing ability in the detection of voltage flicker parameters, high detection precision, good real-time performance, less false mode, small end-end distortion of an amplitude-frequency curve, and small fluctuation.

Voltage flicker parameter detection method based on extreme point symmetry mode decomposition

The invention relates to a harmonic detection method combining extreme symmetry mode decomposition and Hilbert transform, which is aimed at the problem that the existing power system harmonic signal detection methods are not high in precision, and the problem that well-studied empirical mode decomposition has modal aliasing in harmonic detection, can provide a specific harmonic detection step based on a combination of the extreme symmetry mode decomposition ESMD and Hilbert transform (HT) according to the extreme symmetry mode decomposition theory and algorithm Firstly, a signal is subjectedto extreme symmetry mode decomposition to obtain a series of intrinsic mode functions of different feature scales Then, Hilbert transform is performed on the IMF component to obtain the instantaneousamplitude and instantaneous frequency information of each harmonic The invention has strong self-adaptive decomposition ability in harmonic detection, high detection precision and good real-time performance, and can effectively avoid the modal aliasing phenomenon of the EMD method in harmonic detection without adding noise

Harmonic detection method combining extreme symmetry mode decomposition and Hilbert transform

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Papers

Frequency self-recovery control method based on virtual synchronous generator

Method for switching from off network to gird connection of virtual synchronous power generator

Voltage flicker parameter detection method based on extreme point symmetry mode decomposition

Harmonic detection method combining extreme symmetry mode decomposition and Hilbert transform