CN-121983989-A - New energy power grid impedance identification system with impedance self-adaptation characteristic

CN121983989ACN 121983989 ACN121983989 ACN 121983989ACN-121983989-A

Abstract

The application discloses a new energy power grid impedance identification system with an impedance self-adaption characteristic, and relates to the technical field of new energy power electronic converter control. The application adopts continuous mixed disturbance injection, real-time impedance identification, global optimization of multi-node cooperative control strategy, and a full-closed loop design for dynamically switching the operation mode of the distributed generation unit through the issuing of a high-speed communication interface, is applied to a large-scale micro-grid-connected system, remarkably improves the overall performance of the system, and realizes real-time adaptation of the new energy converter to the impedance of the time-varying grid. The application can rapidly respond to power fluctuation, thereby ensuring the stability and the electric energy quality of the micro-grid.

Inventors

MENG YANFENG
HU SHUJU
SHE LINLIN
LI FENGLIN
WANG YIBO

Assignees

中国科学院电工研究所

Dates

Publication Date: 20260505
Application Date: 20260115

Claims (8)

1. The new energy power grid impedance identification system with the impedance self-adaptation characteristic is characterized by comprising an impedance identification device, a high-speed communication interface and an energy management system; the impedance identification device is used for detecting the power grid impedance value of the power grid side in real time to construct power grid impedance matrix data, wherein the power grid side consists of a plurality of distributed power generation units, and the power grid impedance matrix data consists of impedance values corresponding to a plurality of continuous frequency bands; the high-speed communication interface is used for connecting the impedance identification device with the energy management system to realize the transmission of the power grid impedance matrix data to the energy management system; The high-speed communication interface is also used for connecting the energy management system with the plurality of distributed power generation units, providing time synchronization signals for the distributed power generation units, and transmitting control instructions generated by the energy management system, wherein the control instructions comprise preset control strategies of all distributed power generation sources; The energy management system is used for receiving the power grid impedance matrix data in real time and generating a control instruction according to the power grid impedance matrix data.
2. The system of claim 1, wherein the impedance recognition device comprises a power supply unit, an inversion unit, a filtering unit, a disturbance unit, a detection unit and a storage operation unit; The power supply unit is connected with the inversion unit and is used for providing a direct current power supply for the impedance identification device; The inverter unit is used for converting direct current into alternating current with a first frequency, and the first frequency is fundamental wave frequency of a power grid side; The filtering unit is used for filtering high-frequency harmonic waves introduced by the switching action of the inverter so as to generate fundamental wave signals; The disturbance unit is used for generating disturbance signals of a plurality of continuous frequency bands and injecting the disturbance signals into the inversion unit; The detection unit is used for collecting voltage and current signals at the power grid side in real time and sending the voltage and current signals to the storage operation unit; The storage operation unit is used for calculating a corresponding power grid impedance value according to the received voltage and current signals at the power grid side, and constructing power grid impedance matrix data.
3. The system according to claim 1, characterized in that the system comprises: Each distributed power generation unit is used for receiving a control instruction sent by the energy management system, wherein the control instruction comprises a power grid impedance per unit value, and a local controller of each distributed power generation unit switches between a voltage source mode and a current source mode according to the power grid impedance per unit value.
4. The system of claim 2, comprising the perturbation unit injecting perturbation signals into the inversion unit in a manner that: At the grid-side frequency of frequency f, harmonic current components are injected in the following time sequence in N m cycles of the grid-side voltage: N 0 -N 2 th cycle, namely injecting harmonic current component with the frequency nf and the size 10% of rated current; n 2 -N 4 th cycle, namely injecting harmonic current component with the frequency of (n+2) f and the size of 10% of rated current; N 4 -N 6 th cycle, namely injecting harmonic current component with the frequency of (n+4) f and the size of 10% of rated current; ...... stopping the injection disturbance until the frequency of the injection disturbance signal is greater than or equal to the preset highest frequency; The N m-4 -N m th cycle is used for data verification and the next cycle initialization, wherein N m-4 is the cycle corresponding to the preset highest frequency, and N m is the last cycle.
5. The system of claim 4, wherein the system further comprises: The storage operation unit is also used for judging whether the voltage and current signals on the power grid side after the disturbance signals are injected meet the dynamic security domain constraint, and if not, the injection mode of the disturbance signals is modified.
6. The system of claim 4, wherein the system comprises: The storage operation unit is used for intercepting any adjacent 4 cycles through fast Fourier analysis, identifying the fundamental wave component and the amplitude of each harmonic wave component in the voltage and current signals at the power grid side, and calculating the corresponding power grid impedance through a preset formula according to the amplitude of the corresponding harmonic current after the disturbance signals are continuously injected twice in the 4 cycles.
7. The system of claim 6, wherein the predetermined formula is: (1) Wherein, the 、 Is the inductance and resistance in the impedance of the power grid, 、 Is the detection frequency And The frequency of the corresponding grid side, Is at the detection frequency At the detected amplitude of the harmonic signal, Is at the detection frequency At the detected harmonic signal amplitude.
8. The system of claim 6, wherein the system comprises: the energy management unit is used for comparing and analyzing the power grid impedance matrix data acquired in real time with the historical impedance matrix data in the storage operation unit, identifying the current power grid working condition characteristics and generating a control instruction comprising a preset control strategy based on the current power grid working condition characteristics.

Description

New energy power grid impedance identification system with impedance self-adaptation characteristic Technical Field The invention relates to the technical field of control of new energy power electronic converters, in particular to a new energy power grid impedance identification system with impedance self-adaption characteristics. Background With the rapid increase of the permeability of the photovoltaic, wind power and other distributed power generation units in the micro-grid, the installed capacity and the number of access nodes are exponentially increased, and the grid operation faces serious challenges. A large number of distributed power generation units are connected with each other through a power electronic converter to form a multi-node and multi-level power electronic network, a power grid structure mainly taking a synchronous machine is overturned, the inertia of the system is obviously reduced (typical value is less than 2 s), and the disturbance rejection capability is rapidly deteriorated; in a micro-grid system, the fluctuation of the output of a distributed power supply (such as a photovoltaic power generator and a fan) is large, so that the impedance of a power grid is frequently changed, and the quality of electric energy is further affected. The different impedances may cause resonance problems, especially in the presence of a large number of power electronics, which amplify harmonics of certain frequencies, resulting in equipment damage or system instability. When wind and light power fluctuates or loads suddenly change, the impedance of the power grid changes, so that linkage voltage/frequency instability is easily caused, and the vulnerability of the power grid structure is aggravated; The existing impedance identification method is generally based on off-line impedance measurement under preset working conditions, and control parameters thereof are relatively fixed. The adaptability of such static models to offline parameters is limited in the face of dynamically changing grid impedance due to load switching, distributed power on and off. In addition, the description accuracy of the simplified model on the wide frequency domain characteristics of the complex power grid is still to be improved, which may affect the stable operation performance of the grid-connected system under the real complex working condition; The voltage source mode and current source mode switching has significant advantages when the grid impedance changes. The voltage source mode is usually used for a main power supply to maintain stable voltage and frequency, and the current source mode is usually used for a grid-connected inverter to control output current. Switching the two modes can improve the flexibility and adaptability of the system and optimize the operation of the system. For example, when the load changes greatly, the switching mode can better distribute power and reduce loss, and when in fault (such as short circuit), the switching mode is switched to the current source mode to limit current, so that equipment can be protected. By flexibly switching between the voltage source mode (Voltage Source Mode, VSM) and the current source mode (Current Source Mode, CSM), problems with changes in grid impedance can be effectively addressed. Therefore, the problem of stability and reliability degradation of the micro grid caused by large-scale distributed power generation access is needed to be solved. Disclosure of Invention In order to solve the above problems, the present invention provides a new energy grid impedance identification system with impedance self-adaptation characteristics, which can identify the grid impedance in real time, dynamically reconstruct the operation mode of the converter, and realize the collaborative optimization of a plurality of distributed power generation units. The first aspect discloses a new energy power grid impedance identification system with impedance self-adaptation characteristics, which comprises an impedance identification device, a high-speed communication interface and an energy management system, wherein the impedance identification device is used for detecting a power grid impedance value at a power grid side in real time to construct power grid impedance matrix data, the power grid side consists of a plurality of distributed power generation units, and the power grid impedance matrix data consists of impedance values corresponding to a plurality of continuous frequency bands; The high-speed communication interface is used for connecting the impedance identification device with the energy management system to realize the transmission of the power grid impedance matrix data to the energy management system, and is also used for connecting the energy management system with a plurality of distributed power generation units, providing time synchronization signals for the distributed power generation units and transmitting control instructions generated by the energy m