CN-121981057-A - Modeling method and device for soft direct current converter

CN121981057ACN 121981057 ACN121981057 ACN 121981057ACN-121981057-A

Abstract

The invention relates to the technical field of simulation modeling of power electronics technology and discloses a modeling method and device of a soft direct current converter, wherein the modeling method comprises the steps of constructing a simplified model of the soft direct current converter, replacing a plurality of soft direct current sub-modules of an upper bridge arm and a lower bridge arm of each phase of the soft direct current converter with a controlled voltage source in an electric primary topology, and setting a modulation delay link between a modulation wave output end of a control loop and an input end of the controlled voltage source; the method comprises the steps of constructing a virtual direct current bus based on an energy balance relation of a soft direct current converter, collecting electrical parameters of a simplified model of the soft direct current converter through a sampling link, inputting the electrical parameters into a control loop, outputting three-phase modulation waves after closed-loop adjustment of the control loop, and carrying out delay processing on the three-phase modulation waves through a modulation delay link to generate a control signal of a controlled voltage source. The controlled voltage source replaces the traditional switching device, so that the number of electrical nodes of the model is reduced, nonlinear links introduced by the sub-module switching device are eliminated, and the simulation speed is remarkably improved.

Inventors

SONG YANG
GOU LIFENG
LI XIAOTONG
LI ZONGSHANG
WANG CE
LIAO ANRAN
WANG YIFAN
XUE YINGLIN
WANG YIN
GUO YONGQI
TANG BOJIN
CHANG YONG
CHEN MEIFU
GAO WEI

Assignees

中国长江三峡集团有限公司

Dates

Publication Date: 20260505
Application Date: 20260121

Claims (10)

1. A method of modeling a flexible direct current converter, the method comprising: A soft direct current converter simplified model is built, the soft direct current converter simplified model comprises an electric primary topology, a sampling link, a control loop and a modulation delay link, in the electric primary topology, a plurality of soft direct current sub-modules of an upper bridge arm and a lower bridge arm of each phase of the soft direct current converter are replaced by a controlled voltage source, and the modulation delay link is arranged between a modulation wave output end of the control loop and an input end of the controlled voltage source; Constructing a virtual direct current bus based on an energy balance relation of the soft direct current converter; Collecting electrical parameters of the simplified model of the soft direct current converter through the sampling link, and inputting the electrical parameters into the control loop; After closed-loop adjustment by the control circuit, outputting three-phase modulation waves; And carrying out delay processing on the three-phase modulation wave through the modulation delay link to generate a control signal of the controlled voltage source.
2. A method of modeling a soft dc converter according to claim 1, wherein collecting electrical parameters of the soft dc converter simplified model through the sampling segment and inputting the electrical parameters into the control loop comprises: collecting power grid voltage and converter output current; converting the power grid voltage and the converter output current into d-axis voltage, q-axis voltage, d-axis current and q-axis current under a synchronous rotation coordinate system through abc-dq coordinate transformation respectively; The d-axis voltage, the q-axis voltage, the d-axis current, and the q-axis current are input to the control circuit.
3. The modeling method of a soft dc converter according to claim 2, wherein the outputting of the three-phase modulated wave after the closed-loop adjustment of the control circuit includes: The d-axis current reference instruction and the q-axis current reference instruction are obtained by controlling the PI regulator of the outer ring; Based on the d-axis current reference instruction and the q-axis current reference instruction, combining the d-axis voltage, the q-axis voltage, the d-axis current and the q-axis current, and obtaining d-axis modulation waves and q-axis modulation waves through current closed-loop control adjustment of a control inner ring; and converting the d-axis modulation wave and the q-axis modulation wave into three-phase modulation waves through dq-abc inverse transformation.
4. The method of modeling a soft dc converter according to claim 2, wherein the virtual dc bus includes a virtual capacitance.
5. The method of modeling a soft dc converter according to claim 4, wherein the voltage calculation process of the virtual capacitor includes: Calculating the input power of the soft direct current converter according to the power grid voltage and the output current of the converter; obtaining the output power of a soft direct current converter, wherein the output power is obtained by manually simulating the output characteristic of the inverter-side converter or modeling the inverter-side direct current converter; dividing the input power and the output power by real-time voltage values of a virtual direct current bus respectively to obtain input current and output current of the bus; And subtracting the output current from the input current, integrating the subtraction result, and dividing the subtraction result by the capacitance value of the virtual capacitor to obtain the virtual direct current voltage.
6. The method of modeling a soft dc converter according to claim 1, further comprising: In the electric primary topology, the bridge arm reactors of the soft direct current converter are subjected to parallel equivalent treatment, and the inductance value after equivalent is 1/2 of the inductance value of the actual bridge arm reactors.
7. The modeling method of a soft dc converter according to claim 6, wherein an LR series circuit is provided between the equivalent bridge arm reactor output and the grid.
8. A flexible direct current converter modeling apparatus, the apparatus comprising: The model construction module is used for constructing a simplified model of the soft direct current converter, the simplified model of the soft direct current converter comprises an electric primary topology, a sampling link, a control loop and a modulation delay link, in the electric primary topology, a plurality of soft direct current sub-modules of an upper bridge arm and a lower bridge arm of each phase of the soft direct current converter are replaced by controlled voltage sources, and the modulation delay link is arranged between a modulation wave output end of the control loop and an input end of the controlled voltage sources; the bus construction module is used for constructing a virtual direct current bus based on the energy balance relation of the soft direct current converter; the sampling module is used for collecting electrical parameters of the simplified model of the flexible direct current converter through the sampling link and inputting the electrical parameters into the control loop; the modulation module is used for outputting three-phase modulation waves after closed-loop adjustment by the control circuit; and the delay module is used for carrying out delay processing on the three-phase modulation wave through the modulation delay link and generating a control signal of the controlled voltage source.
9. An electronic device, comprising: A memory and a processor communicatively coupled to each other, the memory having stored therein computer instructions that, upon execution, perform the method of modeling a flexible direct current converter of any of claims 1-7.
10. A computer-readable storage medium having stored thereon computer instructions for causing a computer to perform the method of modeling a soft inverter according to any one of claims 1 to 7.

Description

Modeling method and device for soft direct current converter Technical Field The invention relates to the technical field of simulation modeling of power electronics technology, in particular to a modeling method and device for a soft direct current converter. Background With the increase of energy demand and the upgrade of environmental protection requirement, offshore wind power and new energy are becoming large-scale development emphasis, but such large-capacity stations are more remote, and remote power transmission becomes a core challenge. The flexible direct-delivery system becomes a preferred delivery scheme of the field station due to the advantage of long-distance transmission efficiency. In the early design stage of the project when new energy is sent out flexibly and directly, key problems such as overvoltage and short-circuit current of a system are needed to be analyzed through modeling, and basis is provided for parameter design and equipment model selection. In the current modeling process of the current collecting system of the new energy station, the flexible direct system usually adopts a complete modeling mode, namely, a complete model comprising all flexible direct sub-modules and a control system is established. With the continuous increase of the capacity of the new energy station, the flexible direct-delivery system needs to adopt a power device with large through current, and the voltage class of the system is improved so as to meet the power delivery requirement of the high-capacity station. The increase in the voltage level of the soft-direct system necessarily results in a substantial increase in the number of sub-modules of the bridge arm of the soft-direct converter valve. The increase of the number of the sub-modules enables the electrical nodes of the flexible-direct system model to be increased sharply, meanwhile, the capacitance voltage equalizing problem of the plurality of sub-modules is also needed to be considered in the control algorithm, and therefore the system simulation speed is greatly reduced. For the modeling of the current collecting system of the large-scale new energy station, because of the numerous devices, when a complete current collecting system model comprising a flexible direct system and all new energy power generation devices is established, the model scale is extremely huge, the simulation efficiency is seriously reduced, and even the upper limit of the number of electrical nodes which can be accommodated by simulation software is possibly exceeded. In order to reduce the number of electrical nodes of the current collection system model, in the prior art, a single-machine model of the new energy power generation equipment is multiplied generally so as to realize the equivalence of a plurality of equipment at a station level. Although the scale of the simulation model is greatly reduced, the current collecting system is completely simplified, and the method can only be used for evaluating the electrical characteristics of partial nodes between the current collecting bus and the flexible and straight system, and cannot effectively evaluate key nodes in the current collecting system. To achieve complete modeling of the current collection system, the soft dc converter model needs to be simplified to reduce the simulation model scale. The current simplified modeling mode mostly adopts a state space method and a switch function method to establish a small signal model, and the mode converts a system model from an electric model to a pure mathematical model, which is not beneficial to electric characteristic evaluation under the transient working condition of the system. Disclosure of Invention The invention provides a modeling method and device for a soft direct current converter, which are used for solving the problem of how to model the soft direct current converter in a simulation manner. In a first aspect, the present invention provides a method for modeling a soft dc converter, the method comprising: A soft direct current converter simplified model is built, the soft direct current converter simplified model comprises an electric primary topology, a sampling link, a control loop and a modulation delay link, in the electric primary topology, a plurality of soft direct current sub-modules of an upper bridge arm and a lower bridge arm of each phase of the soft direct current converter are replaced by a controlled voltage source, and the modulation delay link is arranged between a modulation wave output end of the control loop and an input end of the controlled voltage source; Constructing a virtual direct current bus based on an energy balance relation of the soft direct current converter; Collecting electrical parameters of the simplified model of the soft direct current converter through the sampling link, and inputting the electrical parameters into the control loop; After closed-loop adjustment by the control circuit, outputting three-phase modulati