CN-121984326-A - Method, system, equipment and medium for eliminating common-mode voltage of three-phase four-bridge-arm flexible interconnection device based on model predictive control

CN121984326ACN 121984326 ACN121984326 ACN 121984326ACN-121984326-A

Abstract

The invention relates to the technical field of power system application and discloses a method, a system, equipment and a medium for eliminating common-mode voltage of a three-phase four-bridge-arm flexible interconnection device based on model predictive control. The common-mode voltage is eliminated efficiently, the direct-current voltage utilization rate is not required to be sacrificed, and excellent output electric energy quality and quick dynamic response can be ensured. And the damage of common mode voltage is eradicated, so that the service lives of sensitive equipment such as the interconnection device and an in-network motor are effectively prolonged, and the reliability and electromagnetic compatibility of the whole power distribution system are improved.

Inventors

ZHENG YOUZHUO
DOU CHEN
WU PENG
YAN JIANGFENG
ZUO HONGYU
ZHANG WANCHENG
LI CHUN
LI XINHAO
LIU ANJIANG
HAO SHUQING
LI YUE
HUA LONG
MIAO YU
XU YUTAO
WENG DI

Assignees

贵州电网有限责任公司

Dates

Publication Date: 20260505
Application Date: 20251224

Claims (10)

1. The common-mode voltage elimination method for the three-phase four-bridge arm flexible interconnection device based on model predictive control is characterized in that the three-phase four-bridge arm flexible interconnection device comprises a first converter and a second converter which are connected back to back, and the first converter and the second converter are two-level three-phase four-bridge arm voltage source type converters; The method comprises the following steps: establishing a discretized mathematical model of the first transformer and the second transformer; Constructing a multi-objective cost function comprising current tracking performance and a common mode voltage suppression objective; Traversing all switch state combinations which enable the conduction quantity of the upper bridge arm of the first converter to be equal to that of the upper bridge arm of the second converter in each control period; predicting the output phase current of the next control period for each group of switch state combinations by using the discretization mathematical model; Substituting the predicted phase current into the multi-objective cost function, and calculating a cost function value corresponding to each switch state combination; And selecting a switch state combination which minimizes the multi-objective cost function value as an actual switch instruction of the next control period.
2. The method for eliminating the common-mode voltage of the three-phase four-leg flexible interconnection device based on model predictive control according to claim 1, wherein the step of establishing a discretized mathematical model of the first converter and the second converter comprises the following steps: And respectively writing voltage equations of each phase loop of the first converter and the second converter based on kirchhoff voltage law, and converting the voltage equations of the continuous time domain into current prediction expressions of the discrete time domain by adopting a discretization method.
3. The method for eliminating the common-mode voltage of the three-phase four-leg flexible interconnection device based on model predictive control according to claim 2, wherein the step of constructing a multi-objective cost function containing current tracking performance and common-mode voltage inhibition targets comprises the following steps: Taking the sum of squares of deviations between the predicted phase currents of the first converter and the second converter in the next control period and the corresponding reference phase currents as a current tracking term, and implying the constraint condition that the common mode voltage is zero in the screening process of the selectable switch state combination.
4. The method for eliminating the common-mode voltage of the three-phase four-leg flexible interconnection device based on model predictive control according to claim 3, wherein the step of traversing all the switch state combinations for enabling the number of the upper leg conduction of the first converter to be equal to the number of the upper leg conduction of the second converter comprises the following steps: Enumerating all possible four-leg switch states of the first converter, enumerating all possible four-leg switch states of the second converter, and reserving the combination that the conduction quantity of the legs on two sides is equal.
5. The method for eliminating the common-mode voltage of the three-phase four-leg flexible interconnection device based on model predictive control according to claim 4, wherein the step of predicting the output phase current of the next control period comprises the steps of: substituting the phase current of the current control period, the power grid voltage and the bridge arm voltage corresponding to the candidate switch state into the discretization mathematical model, and calculating the phase current predicted value of the next control period.
6. The method for eliminating the common-mode voltage of the three-phase four-leg flexible interconnection device based on model predictive control as claimed in claim 5, wherein the step of obtaining the reference phase current comprises the following steps: And carrying out phase locking processing on the grid voltage connected with the first converter and the second converter respectively, generating voltage phase information under a synchronous rotation coordinate system, and obtaining reference phase current under a static coordinate system through coordinate transformation based on a power instruction or a current instruction.
7. The method for eliminating the common-mode voltage of the three-phase four-leg flexible interconnection device based on model predictive control according to claim 6, wherein after the step of selecting the switch state combination with the minimum multi-objective cost function value is completed, the selected switch state combination is directly mapped into driving signals of power switching devices of each leg of the first converter and the second converter without a pulse width modulation module.
8. A system for eliminating common-mode voltage of a three-phase four-bridge arm flexible interconnection device based on model predictive control, which is characterized by comprising the following steps of: the model building module is used for building a discretized mathematical model of the first converter and the second converter; the function construction module is used for constructing a multi-objective cost function comprising current tracking performance and a common-mode voltage suppression target; The combination module is used for traversing all switch state combinations which enable the conduction quantity of the upper bridge arms of the first converter to be equal to that of the upper bridge arms of the second converter in each control period; the current prediction module is used for predicting the output phase current of the next control period for each group of switch state combinations by utilizing the discretization mathematical model; the calculation module is used for substituting the predicted phase current into the multi-objective cost function and calculating a cost function value corresponding to each switch state combination; and the instruction selection module is used for selecting a switch state combination which minimizes the multi-objective cost function value as an actual switch instruction of the next control period.
9. An electronic device comprising a memory and a processor, wherein the memory stores a computer program, and the method is characterized in that the processor realizes the steps of the method for eliminating the common-mode voltage of the three-phase four-bridge arm flexible interconnection device based on model predictive control according to any one of claims 1 to 7 when executing the computer program.
10. A computer readable storage medium having stored thereon a computer program, wherein the computer program when executed by a processor implements the steps of a method for eliminating common mode voltage of a three-phase four-leg flexible interconnection device based on model predictive control as claimed in any one of claims 1 to 7.

Description

Method, system, equipment and medium for eliminating common-mode voltage of three-phase four-bridge-arm flexible interconnection device based on model predictive control Technical Field The invention relates to the technical field of power system application, in particular to a method, a system, equipment and a medium for eliminating common-mode voltage of a three-phase four-bridge-arm flexible interconnection device based on model predictive control. Background With the high-proportion access of renewable energy sources to the power system, the load types in the power system are more and more diversified, so that higher requirements are also put on energy scheduling and power flow control in the power system at present. The flexible interconnection device is used as key equipment for realizing flexible interconnection of regional power grids and optimizing resource allocation, is of great importance to energy scheduling and distribution of a power distribution network, is designed into a development trend based on transformerless design of the flexible interconnection device, and becomes a current technical bottleneck in the design process. The common-mode voltage mentioned above is a voltage common component of the output end of the power electronic converter, the switching tube in the three-phase voltage source converter acts to make the output voltage have a high-frequency common-mode component, the traditional three-phase three-bridge arm topology specific switching state can generate a high-amplitude common-mode voltage pulse, the common-mode voltage formed in the high-amplitude common-mode voltage pulse can form a channel through parasitic capacitance and generate common-mode current, and the generated common-mode current can cause various problems, such as shortening the mechanical life of a motor, polluting the environment of a power grid, accelerating the aging of insulating materials and the like. The model predictive control is an advanced control model at present, utilizes a discretization model to predict the state behavior of a switch, can inhibit and eliminate the common-mode voltage, does not need a complex modulation module, and has advantages in general in three-phase four-bridge arm topology and model predictive control, but has less researches for combining the two and concentrating on eliminating the common-mode voltage. Disclosure of Invention The present invention has been made in view of the above-described problems occurring in the prior art. Therefore, the invention provides a method, a system, equipment and a medium for eliminating the common-mode voltage of a three-phase four-leg flexible interconnection device based on model predictive control, which can solve the problems that the common-mode voltage problem is prominent due to transformerless design of the existing flexible interconnection device, and the traditional model predictive control has high calculation complexity and difficult control target weight distribution to achieve the current tracking precision and the common-mode voltage elimination effect when processing common-mode voltage inhibition of three-phase four-leg topology. In order to solve the technical problems, the invention provides the following technical scheme: The invention provides a common-mode voltage elimination method of a three-phase four-leg flexible interconnection device based on model predictive control, which comprises a first converter and a second converter which are connected back to back, wherein the first converter and the second converter are two-level three-phase four-leg voltage source type converters; The method comprises the following steps: establishing a discretized mathematical model of the first transformer and the second transformer; Constructing a multi-objective cost function comprising current tracking performance and a common mode voltage suppression objective; Traversing all switch state combinations which enable the conduction quantity of the upper bridge arm of the first converter to be equal to that of the upper bridge arm of the second converter in each control period; predicting the output phase current of the next control period for each group of switch state combinations by using the discretization mathematical model; Substituting the predicted phase current into the multi-objective cost function, and calculating a cost function value corresponding to each switch state combination; And selecting a switch state combination which minimizes the multi-objective cost function value as an actual switch instruction of the next control period. As a preferable scheme of the three-phase four-bridge arm flexible interconnection device common-mode voltage elimination method based on model predictive control, the method for establishing the discretization mathematical model of the first converter and the second converter comprises the following steps: And respectively writing voltage equations of each phase loop of the first con