DC Bus Voltage Control During Power Converter Method Updates
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Solution Overview
Problem
In DC grid power systems, centralized control methods struggle to manage rapid changes in power demand and supply, leading to potential voltage instability and inadequate load sharing between devices.
Innovation Solution
A power system architecture that includes multiple power converters with primary control units performing feedback control based on drooping characteristics, and a central control device executing secondary control to update the control methods, ensuring that at least one power converter always performs voltage control during method updates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If centralized control is performed on the DC grid, then the entire DC grid can be controlled easily, but it is difficult to smoothly deal with rapid changes in power demand and supply
Solution Approach 1:
The patent divides the DC grid control into multiple independent control regions, each with its own controller that can autonomously manage local power converters. This segmentation allows each region to respond rapidly to local power changes while the overall system remains coordinated, resolving the contradiction between centralized ease of control and adaptability to rapid changes.
2Ease of operation
If constant voltage control is performed in multiple spots in a wide area, then voltage control can be distributed, but the voltage control would become unstable and lead to fluctuations in voltage of the DC bus
Solution Approach 1:
The patent implements different control strategies for different regions of the DC grid based on local conditions. Controllers in wide-area regions use droop control characteristics that account for local power converter capabilities and DC bus conditions, rather than uniform constant voltage control. This local differentiation maintains voltage stability while enabling distributed control.
3Adaptability or versatility
If control method is updated in power converters, then the control method can be optimized, but there is a risk of unintentional increase or decrease in voltage in the DC bus during update period
Solution Approach 1:
The patent requires that before a power converter updates its control method, it first switches to a safe control mode (such as constant voltage control or droop control with predetermined characteristics) that ensures DC bus voltage stability. The control method update is then performed, and only after successful completion does the converter return to its optimized control mode. This preliminary action prevents voltage instability during the update process.
Data Source
AI summary
A power system includes: power converters, each including a power conversion unit configured to convert an input power, and output the converted power, a controller configured to execute a primary control for controlling the output by controlling the power conversion unit based on: a reference function having a drooping characteristic defined according to an input value and a voltage of the bus or a power of the power converter to which the power conversion unit is connected, and an update unit configured to update a control method on the output; a central control device configured to execute a secondary control of controlling the power converter; the bus connected to the power conversion unit; and a power element connected to the power converter and configured to supply, consume and charge power. The central control device performs the secondary control on the power converter according to an update instruction to update the control method.