Grid-Connected Power Converter for Stable Frequency Support
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Solution Overview
Problem
Current grid forming control methods for power converters fail to provide stable and accurate frequency support for alternating current power grids due to fluctuations in power output and load requirements, leading to unstable frequency in photovoltaic and energy storage systems.
Innovation Solution
A grid-connected power converter with a power conversion circuit and controller that adjusts output power based on inertia and frequency regulation, simulating synchronous generator behavior to provide fast and accurate frequency support by dynamically adjusting power in response to frequency deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If grid forming control is used to actively provide frequency support, then frequency support capability is improved, but frequency stability deteriorates
Solution Approach 1:
The frequency support control is segmented into two distinct parts: inertia control that activates only during frequency changes to provide immediate support, and frequency regulation control that activates when frequency deviation exceeds a threshold to restore frequency. This segmentation allows each control mode to operate optimally without interfering with the other, resolving the contradiction between providing active frequency support and maintaining frequency stability.
Solution Approach 2:
The control system dynamically switches between different control modes based on real-time frequency conditions. The inertia control dynamically responds to frequency changes by adjusting power output proportional to the rate of frequency change, while the frequency regulation control dynamically activates when frequency deviation exceeds thresholds. This dynamic adaptation enables the system to provide frequency support when needed while maintaining stability during normal operation.
2Power
If power output is adjusted to match load requirements, then power balance is improved, but frequency stability deteriorates
Solution Approach 1:
The system continuously monitors frequency deviations and uses this feedback to control power output. The inertia control uses feedback from frequency change rate to adjust power, while the frequency regulation control uses feedback from frequency deviation magnitude to activate or deactivate. This feedback mechanism ensures power balance is maintained while frequency stability is preserved through controlled responses.
Solution Approach 2:
The control system changes operational parameters (power output) based on frequency conditions rather than continuously adjusting to match load requirements. By changing power output in response to frequency deviations and their rates of change, the system maintains power balance while avoiding excessive frequency fluctuations that would occur with continuous load-matching adjustments.
Data Source
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AI summary
This application provides a grid-connected power converter, a power control method therefor, and an energy storage system. In the grid-connected power converter, a controller is configured to: in response to a frequency of an alternating current power grid being a first frequency, control an output power of a power conversion circuit to be adjusted from a preset reference power to a first power, where the first power is a sum of the preset reference power and a first inertia power. Further, the controller is configured to: in response to the frequency of the alternating current power grid being a second frequency, control the output power of the power conversion circuit to be adjusted from the first power to a second power, where the second power is a sum of the first power and a first frequency regulation power, and an absolute value of a difference between the second frequency and a utility frequency of the alternating current power grid is greater than an absolute value of a difference between the first frequency and the utility frequency of the alternating current power grid. According to this application, the alternating current power grid can obtain more stable and accurate frequency support.