Dynamic frequency coordination control method combining frequency synchronous control in vsc-hvdc with bilateral frequency limit control in lcc-hvdc

Patent metadata

Field	Value
Publication number	US-2026074520-A1
Application number	US-202519026429-A
Country	US
Kind code	A1
Filing date	Jan 17, 2025
Priority date	Sep 12, 2024
Publication date	Mar 12, 2026
Grant date	—

Abstract

A dynamic frequency coordination control method combining frequency synchronous control in VSC-HVDC and bilateral FLC in LCC-HVDC includes: when a disturbance occurs in a system, the frequency synchronous control in VSC-HVDC is preferentially used to stabilize a grid frequency, and a power adjustment output by the frequency synchronous control in VSC-HVDC is taken as an activation criterion for the bilateral FLC control in LCC-HVDC; when the power adjustment exceeds a preset limiting range and a system frequency deviation exceeds a control dead zone of the bilateral FLC control in LCC-HVDC, the bilateral FLC control in LCC-HVDC is used to determine and output the power adjustment for LCC-HVDC; based on the power adjustment for LCC-HVDC, an additional reactive power control of VSC-HVDC is utilized to provide additional reactive power to LCC-HVDC to regulate a voltage stability of a grid.

First claim

What is claimed is:

1 . A dynamic frequency coordination control method combining frequency synchronous control in voltage source converter based high voltage direct current (VSC-HVDC) with bilateral frequency limit control in line commutated converter based high voltage direct current (LCC-HVDC), comprising the following steps:
Step 1: during system disturbances, prioritizing the frequency synchronous control in the VSC-HVDC to stabilize a grid frequency, and using a power adjustment output by the frequency synchronous control as an activation criterion for the bilateral frequency limit control in the LCC-HVDC: Step 2: when the power adjustment exceeds a preset limit range and a system frequency deviation exceeds a control dead zone of the bilateral frequency limit control in the LCC-HVDC, utilizing the bilateral frequency limit control to determine and output a conventional direct current (DC) power adjustment; Step 3: based on the conventional DC power adjustment, employing additional reactive power control of the VSC-HVDC to provide additional reactive power to the LCC-HVDC to regulate a voltage stability of a grid; Step 4: using a VSC-HVDC power adjustment as an input signal for a judgment logic; Step 5: converting the input signal into additional reactive power for the VSC-HVDC; Step 6: superimposing the additional reactive power on an original reactive power command of the VSC-HVDC to generate a new reactive power command for the VSC-HVDC; and Step 7: adjusting an actual operating reactive power of the VSC-HVDC based on the new reactive power command; wherein Step 4 comprises: Step 4.1: when the VSC-HVDC power adjustment is greater than a maximum power adjustment threshold of a frequency synchronous controller, or when the VSC-HVDC power adjustment is less than a minimum power adjustment threshold of the frequency synchronous controller, then allowing the bilateral frequency limit control in the LCC-HVDC to output the conventional DC power adjustment; and Step 4.2: when the VSC-HVDC power adjustment is greater than or equal to the minimum power adjustment threshold of the frequency synchronous controller and less than or equal to the maximum power adjustment threshold of the frequency synchronous controller, allowing the bilateral frequency limit control in the LCC-HVDC to output 0; Step 3.1: wherein in Step 3, the additional reactive power mentioned is the additional reactive power for the VSC-HVDC, and a method to calculate the additional reactive power for the VSC-HVDC is as follows: a product of the conventional DC power adjustment and tang is calculated, wherein φ represents a power factor of a valve side of the conventional DC connected to the VSC-HVDC.

2 . The dynamic frequency coordination control method according to claim 1 , wherein inputs of the frequency synchronous control in the VSC-HVDC are respectively a first difference between a sending-end grid frequency and a system frequency reference value and a second difference between a receiving-end grid frequency and the system frequency reference value, and the dynamic frequency coordination control method further comprises:
determining the VSC-HVDC power adjustment based on preprocessed first and second differences; superimposing the VSC-HVDC power adjustment on an original power reference value of the VSC-HVDC to determine an active power command for the VSC-HVDC; and adjusting an actual operating active power of the VSC-HVDC based on the active power command.

3 . The dynamic frequency coordination control method according to claim 1 , wherein inputs of the bilateral frequency limit control in the LCC-HVDC are respectively a first difference between a sending-end grid frequency and a system frequency reference value and a second difference between a receiving-end grid frequency and the system frequency reference value, and the dynamic frequency coordination control method further comprises:
determining the conventional DC power adjustment output by the bilateral frequency limit control in the LCC-HVDC based on preprocessed first and second differences;
performing logical judgment, normalization, and Proportional-Integral (PI) control on the conventional DC power adjustment based on the judgment logic to obtain a result, and then converting the result into a firing angle adjustment; and
adjusting an actual operating active power of the conventional DC based on the firing angle adjustment.

4 . The dynamic frequency coordination control method according to claim 1 , wherein an active power command and a reactive power command of the VSC-HVDC are processed through a dynamic limiting link with PI control to generate a target active power command and a target reactive power command required for an inner loop control of the VSC-HVDC, wherein the target active power command and the target reactive power command satisfy preset dynamic limiting constraints.

5 . The dynamic frequency coordination control method according to claim 1 , wherein a method for calculating the maximum power adjustment threshold of the frequency synchronous controller in the VSC-HVDC comprises:
calculating a first product value corresponding to a rated power of the VSC-HVDC and an overload capacity coefficient of the VSC-HVDC, and calculating a third difference between the first product value and an actual power of the VSC-HVDC, and using the third difference as the maximum power adjustment threshold; wherein a method for calculating the minimum power adjustment threshold of the frequency synchronous controller in the VSC-HVDC comprises: calculating a second product value corresponding to a minimum operating level coefficient of the VSC-HVDC and the rated power of the VSC-HVDC; and calculating a fourth difference between an actual operating power of the VSC-HVDC and the second product value, and using the fourth difference as the minimum power adjustment threshold.

6 . The dynamic frequency coordination control method according to claim 1 , wherein the control dead zone of the bilateral-frequency limit control in the LCC-HVDC ranges from ±0.1 Hz to ±0.14 Hz.

7 . The dynamic frequency coordination control method according to claim 1 , wherein a power adjustment for the bilateral frequency limit control in the LCC-HVDC also corresponds to an upper limit and a lower limit of the power adjustment, wherein a method for calculating the upper limit of the power adjustment comprises:
calculating a third product value corresponding to a rated power of the LCC-HVDC and an overload capacity coefficient of the LCC-HVDC; calculating a fifth difference between the third product value and an actual operating power of the LCC-HVDC, and using the fifth difference as the upper limit of the power adjustment; wherein a method for calculating the lower limit of the power adjustment comprises: calculating a fourth product value corresponding to a minimum operating level coefficient of the LCC-HVDC and the rated power of the LCC-HVDC; and calculating a sixth difference between the actual operating power of the LCC-HVDC and the fourth product value, and using the sixth difference as the lower limit of the power adjustment.

Assignees

• Univ Kunming Science & Technology

Inventors

• Shu Hongchun
• Shao Zongxue
• Lei Shunguang
• Wang Guangxue
• Tang Yutao
• Shi Botao
• Hu Yinan

Classifications

• H02J3/16

  by adjustment of reactive power · CPC title

• H02J3/34

  Arrangements for transfer of electric power between networks of substantially different frequency · CPC title

• H02J3/36 Primary

  Arrangements for transfer of electric power between AC networks via high-voltage DC [HVDC] links; Arrangements for transfer of electric power between generators and networks via HVDC links · CPC title

• Y02E60/60

  Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD] · CPC title

• H02J3/00142 Primary

  Oscillations concerning frequency · CPC title