Power Conditioner Control Circuit for Photovoltaic Systems
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Solution Overview
Problem
In photovoltaic systems, non-insulating type power conditioners face challenges in maintaining the negative electrode of thin film solar cells at ground potential, leading to degradation due to differing reference potential levels between DC and AC sides, which affects the accuracy of switch element control in power conversion.
Innovation Solution
A power conditioner with a chopper circuit and control circuit that includes a differential amplifier for measuring capacitor voltages, calibrating in-phase errors to improve the accuracy of switch element control, ensuring the negative electrode is grounded and reducing degradation of thin film solar cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a non-insulating type power conditioner is used to improve power conversion efficiency, then power conversion efficiency is improved, but the negative electrode of thin film solar cells cannot be maintained at ground potential due to differing reference potential levels between DC and AC sides, causing degradation
Solution Approach 1:
The patent introduces a measurement intermediary (differential amplifier) that measures the potential difference between the DC side negative electrode and AC side ground. This intermediary enables the control system to detect the potential offset and apply compensatory control, allowing the negative electrode to be maintained at ground potential even in a non-insulating configuration. The measurement intermediary bridges the gap between the two reference potential levels, enabling precise control to prevent degradation while maintaining high efficiency.
2Reliability
If the negative electrode of thin film solar cells is maintained at ground potential to prevent degradation, then reliability is improved, but the reference potential levels between DC and AC sides must be made identical, complicating the non-insulating type configuration
Solution Approach 1:
The patent implements a feedback control mechanism where the differential amplifier continuously measures the potential difference between the DC negative electrode and AC ground, and this measurement is fed back to the control circuit. The control circuit adjusts the operating point or adds compensatory voltage based on the feedback signal, creating a closed-loop system that automatically maintains the negative electrode at ground potential. This feedback approach simplifies the overall configuration by using automatic control rather than complex hardware modifications to align reference potentials.
3Productivity
If switch elements are controlled with high accuracy to improve power conversion, then productivity is improved, but measurement precision of capacitor voltage is affected by in-phase components in differential amplifier output
Solution Approach 1:
The patent extracts and separates the in-phase component from the differential amplifier output signal. By identifying and removing this unwanted component, the measurement system obtains a clean signal that accurately represents only the capacitor voltage. This extraction approach allows high-speed switching control to proceed with precise voltage measurement, as the in-phase component (which causes measurement errors) is eliminated from the control signal path.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The calibration of in-phase errors in the differential amplifier output enhances the accuracy of switch element control, leading to more precise operation of the power conditioner and preventing degradation of thin film solar cells by maintaining the negative electrode at ground potential.
Implementation Method 1
the measurement circuit section includes a differential amplifier circuit for differentially amplifying (that differentially amplifies) the inter-end voltage of the capacitor
Data Source
AI summary
A power conditioner of a photovoltaic system is configured operate at higher accuracy. A chopper circuit, a capacitor connected in parallel to the chopper circuit, and a control circuit that controls an ON/OFF status of switch elements in the chopper circuit to control charging and discharging of the capacitor are provided. The control circuit includes a measurement control section that measures an inter-end voltage of the capacitor and a control circuit section that performs a predetermined control operation from a measurement output of the measurement circuit section. The measurement circuit section includes a differential amplifier circuit that differentially amplifies the inter-end voltage of the capacitor. The circuit control section calibrates an in-phase component in the output of the differential amplifier circuit as an in-phase error and performs the control from the calibrated output from the differential amplifier circuit.