Power Converter Output Impedance Control for Accurate Status Detection
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Solution Overview
Problem
The existing methods for determining the working status of power conversion apparatuses, such as photovoltaic optimizers, in photovoltaic power systems suffer from low accuracy due to voltage deviations and wire voltage drops, making it difficult to ensure precise control and normal operation.
Innovation Solution
A power conversion apparatus comprising a power conversion circuit, an impedance adjustable circuit, and a control circuit that adjusts the output impedance based on start conditions, allowing for accurate representation of the working status by setting distinct impedance values when the apparatus is functioning correctly or not, thereby improving the accuracy of status determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If voltage testing method is used to determine working status, then the determination process is simple, but the measurement precision is low due to voltage deviations and wire voltage drops
Solution Approach 1:
The patent changes the measurement parameter from voltage to impedance. By measuring the impedance of the optimizer and comparing it with a threshold value, the system can accurately determine working status without being affected by voltage deviations or wire voltage drops. The impedance measurement reflects the actual working state of the optimizer more reliably than voltage measurement.
2Ease of operation
If output voltage is controlled to 1V for testing, then the testing method is straightforward, but the control precision is difficult to ensure due to low voltage level
Solution Approach 1:
The patent changes the testing parameter from voltage level to impedance magnitude. Instead of controlling and measuring at a specific low voltage level (1V) which is difficult to control precisely, the system measures impedance which can be accurately determined even at low power levels. This maintains operational simplicity while significantly improving measurement and control precision.
3Power
If multiple optimizers are connected in series, then the system power capacity increases, but the accumulation of voltage deviations and wire voltage drops causes specific deviation from tested output voltage
Solution Approach 1:
The patent changes the measurement parameter from voltage to impedance for determining working status. Since impedance is an intrinsic property of the optimizer and does not accumulate with series connections like voltage drops do, this method maintains high measurement precision even when multiple optimizers are connected in series to increase system power capacity.
Solution Approach 2:
The patent introduces impedance as an intermediary measurement parameter that indirectly reflects the working status of the optimizer. This intermediary parameter is not affected by wire voltage drops or voltage deviations that accumulate in series connections, allowing accurate determination of individual optimizer status even in high-power series configurations.
Data Source
AI summary
A power conversion apparatus and a method for controlling an output impedance of a power conversion apparatus are provided to resolve a prior-art problem of relatively low accuracy of a method for determining a working status of a power conversion apparatus. The method includes: adjusting the output impedance of the power conversion apparatus to a first impedance when the power conversion apparatus does not satisfy a start condition; or adjusting the output impedance of the power conversion apparatus to a second impedance when the power conversion apparatus satisfies a start condition, where the first impedance is not equal to the second impedance.