Parallel Inverter PLL Feedback for Frequency Convergence
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Solution Overview
Problem
Inverters providing independent outputs in parallel operation face instability due to non-converging frequencies when using traditional phase locked loops, leading to uncontrollable situations.
Innovation Solution
Implementing frequency feedback processing in phase locked loops with proportional integral operations to stabilize frequency convergence, using controllers to adjust frequency detection values based on alternating-current voltage, and incorporating proportional operations to manage voltage deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional phase locked loops are used for frequency detection in parallel inverter operation, then the system structure remains simple, but frequency convergence fails and operation becomes unstable
Solution Approach 1:
The patent introduces frequency feedback processing into the phase locked loop by adding a frequency correction value obtained through proportional integral operation on the comparison between previous frequency detection value and frequency reference value. This feedback mechanism enables the system to automatically adjust and converge to the target frequency, resolving the instability issue in parallel inverter operation.
Solution Approach 2:
The patent modifies the frequency detection operation by incorporating proportional integral operations that dynamically adjust the frequency correction value. This parameter change transforms the static frequency detection into a dynamic adaptive process, enabling frequency convergence while maintaining system stability in parallel operation.
2Reliability
If frequency feedback processing with proportional integral operation is added to phase locked loop, then frequency convergence is stabilized, but the control processing complexity increases
Solution Approach 1:
The frequency feedback processing uses proportional integral operation to generate a frequency correction value that is added to the frequency detection value. This feedback mechanism systematically reduces the frequency deviation over time, ensuring stable convergence while maintaining manageable control processing through well-established control theory methods.
3Productivity
If multiple inverters operate in parallel with independent outputs, then power distribution capacity increases, but cross-currents and operational instability occur
Solution Approach 1:
The frequency feedback processing stabilizes the frequency detection in each inverter's phase locked loop, ensuring that all parallel-operating inverters converge to the same target frequency. This frequency synchronization eliminates the frequency differences that cause cross-currents, enabling stable parallel operation with increased power distribution capacity.
Data Source
AI summary
An inverter according to the present disclosure is an inverter connected in parallel to an alternating-current circuit to which an alternating-current power source is connected, and configured to provide an independent output to the alternating-current circuit. The inverter includes a power converter configured to convert a direct-current power into an alternating-current power to supply power to the alternating-current circuit, a voltage sensor configured to detect an alternating-current voltage of the alternating-current circuit, and a controller configured to control the power converter. The controller is configured to add frequency feedback processing to an operation of calculating a frequency detection value in a phase locked loop to be executed based on the alternating-current voltage, the frequency feedback processing being processing of adding a frequency correction value obtained by performing a proportional integral operation on a comparison result between a previous value of the frequency detection value and a frequency reference value.