Coordinated Control for Series Voltage Source Converter Valve Groups
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Solution Overview
Problem
Current technologies lack an effective method for achieving DC voltage balance in series voltage source converter valve groups, which is crucial for the stable operation of series hybrid and flexible DC transmission systems, as the coordinated control methods for thyristor converter valve groups are not applicable to voltage source converter valve groups.
Innovation Solution
A coordinated control method and device for series voltage source converter valve groups that involves calculating DC voltage deviations and using proportional or integral methods to determine active power compensation, applying current inner loop limits to maintain DC voltage balance between valve groups, and configuring control units for active power and DC voltage control to ensure balanced operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If series voltage source converter valve groups are used to improve DC voltage level and transmission capacity, then the transmission capability is improved, but the DC voltage balance between valve groups becomes difficult to control
Solution Approach 1:
The patent implements a coordinated control system that continuously monitors the DC voltage output of each series-connected valve group and uses feedback signals to adjust the active power reference of individual valve groups. The control device calculates the DC voltage deviation of each valve group and dynamically adjusts the active power compensation amount based on these deviations, ensuring voltage balance is maintained while operating at high transmission capacity.
Solution Approach 2:
The patent dynamically changes the active power reference parameter of each valve group based on real-time DC voltage measurements. By adjusting the active power compensation amount ΔPVi according to the DC voltage deviation ΔUdV-i, the system optimizes the operating parameters of each valve group to maintain voltage balance while maximizing transmission capacity.
2Adaptability or versatility
If coordinated control methods for thyristor converter valve groups are applied, then control experience is available, but the methods are not applicable to voltage source converter valve groups due to different device characteristics
Solution Approach 1:
The patent develops a specialized control strategy that accounts for the fundamental differences between thyristor and voltage source converter characteristics. The control method uses proportional and integral calculations to determine active power compensation amounts, with the formula ΔPVi = Kv·ΔUdV-i + Ki·∫ΔUdV-idt, which is specifically tailored to the dynamic characteristics of voltage source converters rather than directly applying thyristor-based control methods.
Solution Approach 2:
The patent divides the control of each series-connected valve group into independent controllable units, with each valve group having its own active power reference adjustment mechanism. This segmentation allows the control system to independently manage the active power output of each valve group based on its specific DC voltage deviation, enabling precise coordinated control that respects the unique characteristics of voltage source converters.
3Reliability
If active power compensation is dynamically adjusted to achieve DC voltage balance, then the DC voltage balance is improved, but the control system complexity increases
Solution Approach 1:
The patent implements a universal coordinated control framework that can be applied to series-connected valve groups regardless of the specific number of groups or their configuration. The control device performs multiple functions including monitoring DC voltage, calculating deviations, determining active power compensation amounts using proportional and integral methods, and adjusting active power references, all within a single integrated control system that scales to different system configurations.
Data Source
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AI summary
A coordinated control method for series voltage source converter valve groups comprises: allocating a total direct-current voltage reference value or a total active power reference value at the end where a direct-current electrode series voltage source converter valve group is located according to the total number of voltage source converter valve groups in series; for a direct-current voltage control end, controlling the direct-current voltage of each valve group according to the assigned direct-current voltage reference value for each valve group; for an active power control end, controlling the active power of each valve group according to the assigned active power reference value for each valve group and based on adding the active power compensation amount of the valve group which has voltage equalization effects on the valve group. Correspondingly, also providing a coordinated control device for series voltage source converter valve groups. The direct-current voltage equalization of each valve group in operation of the direct-current voltage control end or the active power control end of the series voltage source converter valve group is achieved.