CN-122017351-A - Impedance measurement method, device and equipment of grid-formed inverter and storage medium

CN122017351ACN 122017351 ACN122017351 ACN 122017351ACN-122017351-A

Abstract

The invention belongs to the field of electric power, and discloses an impedance measurement method, device, equipment and storage medium of a grid-formed inverter, which comprise the steps of obtaining an active power reference instruction of an impedance test inverter, a filter capacitor voltage amplitude and a filter capacitor voltage amplitude of a tested inverter; the method comprises the steps of generating an active power reference instruction, inputting the active power reference instruction, the dynamic power angle difference, the filter capacitor voltage amplitude of an impedance test inverter and the filter capacitor voltage amplitude of a tested inverter into a line impedance calculation module, and calculating the resistance and the inductance of a connecting line between the impedance test inverter and the tested inverter by the line impedance calculation module according to a preset impedance calculation formula.

Inventors

FANG LE
WANG CHENXU
HAN BING
DONG WEI
FANG JINGYANG
LU CHENGYU
YANG YING
HUA WEN
MA JUNCHAO
LIU JIANING

Assignees

国网浙江省电力有限公司电力科学研究院

Dates

Publication Date: 20260512
Application Date: 20260319

Claims (10)

1. The method is applied to a controller of a grid-connected inverter parallel system, the grid-connected inverter parallel system comprises an impedance test inverter and a tested inverter which are connected in parallel and connected to a public connection point through a connection line, the impedance test inverter and the tested inverter respectively comprise a direct current power supply, a three-phase full-bridge inverter and an LCL filter, the controller comprises a power calculation module, an active power control module, a reactive power control module, a voltage and current double closed-loop control module and a line impedance calculation module, and the modules are sequentially or parallelly connected to form a closed-loop control loop of power and voltage and current, and the method comprises the following steps: Acquiring an active power reference command Pg_ref of the impedance test inverter, a filter capacitor voltage amplitude vgf _ref and a filter capacitor voltage amplitude vtf _ref of the tested inverter; Based on the deviation between the active power reference command Pg_ref and the actual measured active power Pg, performing virtual synchronous machine control through the active power control module to generate a dynamic power angle difference delta g; Inputting the active power reference command Pg_ref, the dynamic power angle difference delta g, the filter capacitor voltage amplitude vgf _ref of the impedance test inverter and the filter capacitor voltage amplitude vtf _ref of the tested inverter into the line impedance calculation module; according to a preset impedance calculation formula, the circuit impedance calculation module calculates the resistance Rcs and the inductance Xcs of the connecting circuit between the impedance test inverter and the inverter to be tested, wherein the impedance calculation formula is as follows: ; 。
2. The method of claim 1, wherein the virtual synchronous machine control by the active power control module comprises: The deviation amount of the active power reference command Pg_ref and the actual measured active power Pg is subjected to per unit conversion and is input to a VSM controller with a transfer function of 1/(2H g s+Dg) to obtain per unit conversion frequency deviation Δfg_pu, wherein H g is a virtual inertia coefficient, and Dg is a damping coefficient; and carrying out inverse per unit on the frequency deviation delta fg_pu and integrating to obtain the dynamic power angle difference delta g.
3. The method as recited in claim 1, further comprising: The power calculation module collects the filter capacitor voltage v_gf_abc and the network side inductance current i_gg_abc of the impedance test inverter, and the filter capacitor voltage v_gf_abc and the network side inductance current i_gg_abc are based on a voltage phase command thetag output by the active power control module; Performing dq coordinate transformation on the filter capacitor voltage and the network side inductance current to obtain a direct current component of the filter capacitor voltage and the network side inductance current under a dq rotating coordinate system; Based on the direct current component, the actual active power Pg and the reactive power Qg transmitted by the line are calculated.
4. A method according to claim 3, characterized in that the formula for calculating the active power Pg and the reactive power Qg is: ; ; Wherein vgf _d and vgf_q are d-axis and q-axis components of the filter capacitor voltage, respectively, and igg _d and igg_q are d-axis and q-axis components of the net inductor current, respectively.
5. A method according to claim 3, further comprising: The reactive power control module performs per unit on the deviation amount of the reactive power reference command Qg_ref and the actually measured reactive power Qg, and obtains the per unit amount of the voltage deviation through PI control; and carrying out inverse per unit on the per unit quantity of the voltage deviation and adding the per unit quantity of the voltage deviation with the rated voltage amplitude Vg_ref to generate a voltage ring d-axis voltage amplitude reference command vgf _d_ref.
6. The method as recited in claim 5, further comprising: The voltage-current double closed-loop control module takes a voltage amplitude reference instruction vgf _d_ref generated in the reactive power control step as a d-axis voltage reference, takes 0 as a q-axis voltage reference, and respectively makes differences with capacitance voltage components on a dq axis to obtain voltage deviation values; PI control is carried out on the voltage deviation amount, and a dq axis reference component of the network side inductance current is generated; the current reference component is differenced with the dq axis component of the inverter side inductance current obtained through coordinate transformation, and the current deviation value is obtained; and performing PI control on the current deviation amount to generate a pulse width modulation signal for driving the impedance test inverter.
7. The method as recited in claim 1, further comprising: And controlling the active power transmitted between the impedance test inverter and the tested inverter by changing the active power reference command Pg_ref so as to calculate the impedance of the connecting line in real time in the dynamic power adjustment process, thereby realizing continuous tracking of the impedance of the line.
8. The device is arranged in a controller of a grid-connected inverter parallel system, the grid-connected inverter parallel system comprises an impedance test inverter and a tested inverter which are connected in parallel and connected to a public connection point through a connection line, the impedance test inverter and the tested inverter respectively comprise a direct current power supply, a three-phase full-bridge inverter and an LCL filter, the controller comprises a power calculation module, an active power control module, a reactive power control module, a voltage and current double closed-loop control module and a line impedance calculation module, the modules are sequentially or parallelly connected to form a closed-loop control loop of power and voltage and current, and the device comprises: The acquisition unit is used for acquiring an active power reference instruction Pg_ref, a filter capacitor voltage amplitude vgf _ref of the impedance test inverter and a filter capacitor voltage amplitude vtf _ref of the tested inverter; The first control unit is used for performing virtual synchronous machine control through the active power control module based on the deviation between the active power reference instruction Pg_ref and the actually measured active power Pg so as to generate a dynamic power angle difference delta g; The input unit is used for inputting the active power reference instruction Pg_ref, the dynamic power angle difference delta g, the filter capacitor voltage amplitude vgf _ref of the impedance test inverter and the filter capacitor voltage amplitude vtf _ref of the tested inverter into the line impedance calculation module; The first calculating unit calculates the resistance Rcs and the inductance Xcs of the connection line between the impedance test inverter and the inverter to be tested according to a preset impedance calculating formula, where the impedance calculating formula is: ; 。
9. an electronic device, comprising: A processor; A memory for storing processor-executable instructions; wherein the processor is configured to implement the steps of the method according to any of claims 1-7 by executing the executable instructions.
10. A computer readable storage medium having stored thereon computer instructions which, when executed by a processor, implement the steps of the method of any of claims 1-7.

Description

Impedance measurement method, device and equipment of grid-formed inverter and storage medium Technical Field The invention belongs to the field of electric power, and particularly relates to an impedance measurement method, an impedance measurement device, impedance measurement equipment and an impedance measurement storage medium of a grid-formed inverter. Background The grid-structured inverter is used as core power electronic equipment for new energy grid connection, has the capabilities of active voltage regulation and frequency modulation, and can provide auxiliary services such as inertia support and damping for a power grid. Compared with the traditional grid-connected inverter, the grid-connected inverter can realize grid-connected operation without a phase-locked loop by virtue of the phase self-synchronization capability of the grid-connected inverter, and shows better stability under a weak current network. In the micro-grid equal-proportion new energy application scene, a plurality of grid-structured inverters are operated in parallel mode so as to improve the system capacity, the reliability and the modularization degree. However, since the distances between the inverters and the common connection point are different, the impedance of the connection lines of the inverters is different, so that reactive power among the parallel inverters is difficult to be equally divided, and further problems such as circulation, system oscillation and even equipment damage can be caused. Therefore, accurate estimation of line impedance is critical to achieving power sharing and analysis system stability. In the related art, impedance measurement schemes are largely divided into passive techniques and active techniques. The passive technology collects inherent harmonic signals of the port to be measured through equipment such as a Kalman filter, a phasor measurement unit and the like to carry out impedance estimation, but the method is too dependent on random events of a power grid, and has low measurement precision and poor real-time performance. The active technology actively injects specific disturbance signals (such as harmonic waves, pulses and the like) into the system, impedance is calculated through measurement response, accuracy is high, but the design of the injection device increases complexity and cost of the system, and improper disturbance can pollute the power quality of a power grid to influence stable operation of the system. Disclosure of Invention In view of the above, the present invention discloses a method, an apparatus, a device and a storage medium for measuring impedance of a grid-formed inverter, which can solve the disadvantages of the related art. In order to achieve the above purpose, the technical scheme disclosed by the invention is as follows: According to a first aspect of the present invention, an impedance measurement method of a grid-connected inverter is provided, the method is applied to a controller of a grid-connected inverter parallel system, the grid-connected inverter parallel system includes a parallel impedance test inverter and a tested inverter, the parallel impedance test inverter and the tested inverter are connected to a common connection point through a connection line, the impedance test inverter and the tested inverter each include a direct current power supply, a three-phase full-bridge inverter and an LCL filter, the controller includes a power calculation module, an active power control module, a reactive power control module, a voltage-current double-closed-loop control module and a line impedance calculation module, each module is connected in sequence or in parallel to form a closed-loop control loop of power and voltage current, the method includes: Acquiring an active power reference command Pg_ref of the impedance test inverter, a filter capacitor voltage amplitude vgf _ref and a filter capacitor voltage amplitude vtf _ref of the tested inverter; Based on the deviation between the active power reference command Pg_ref and the actual measured active power Pg, performing virtual synchronous machine control through the active power control module to generate a dynamic power angle difference delta g; Inputting the active power reference command Pg_ref, the dynamic power angle difference delta g, the filter capacitor voltage amplitude vgf _ref of the impedance test inverter and the filter capacitor voltage amplitude vtf _ref of the tested inverter into the line impedance calculation module; according to a preset impedance calculation formula, the circuit impedance calculation module calculates the resistance Rcs and the inductance Xcs of the connecting circuit between the impedance test inverter and the inverter to be tested, wherein the impedance calculation formula is as follows: ; 。 According to a second aspect of the present invention, an impedance measurement device of a grid-connected inverter is provided, the device is installed in a controller of