Photovoltaic Power Control via String Current Sensing
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Solution Overview
Problem
In photovoltaic power generation systems, existing power conversion structures face challenges with high power loss and reliability issues due to the parallel connection of power conversion modules to photovoltaic modules, leading to increased size and cost, and operational inefficiencies when dealing with varying string currents and power differences.
Innovation Solution
A power control method that senses string current and voltage values across photovoltaic modules, calculates conversion power values, and adjusts string current to find a minimum power point tracking control, minimizing the sum of absolute conversion power values and optimizing power processing by the power conversion modules.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If power conversion modules are connected in parallel to photovoltaic modules, then power conversion capability is improved, but power loss increases and reliability decreases
Solution Approach 1:
The patent extracts only the differential power (power difference) between photovoltaic modules for processing, rather than converting all power. The differential power processing converter processes only the deviation from the average power, leaving the majority of power transmission unaffected, thus reducing power loss while maintaining conversion capability
Solution Approach 2:
The patent changes the operating parameters of the power conversion system by operating the differential power processing converter only when power difference exceeds a threshold value. This parameter-based control optimizes the balance between conversion capability and power loss by activating conversion only when necessary
2Productivity
If power conversion modules are connected in parallel to photovoltaic modules, then power conversion capability is improved, but reliability decreases
Solution Approach 1:
The patent segments the power conversion function into two independent parts: string converters that handle total power transmission and a differential power processing converter that handles only power differences. This segmentation isolates failures, so that issues in the differential processing unit do not affect the main power transmission path
Solution Approach 2:
The differential power processing converter acts as an intermediary that handles only the deviation between modules, mediating power differences without disrupting the main power flow. This intermediary structure protects the primary power transmission path from failures in the conversion process
3Power
If string current is increased to handle power differences, then power processing capacity is improved, but power loss in converter increases
Solution Approach 1:
The patent applies partial action by processing only the differential power portion rather than the entire power flow. The differential power processing converter handles only the excess or deficit power between modules, significantly reducing the power processing burden and associated losses compared to processing total power
Data Source
AI summary
A power control method for controlling power of a plurality of power conversion modules that are respectively connected in parallel to a plurality of photovoltaic, includes: sensing a string current value flowing between outermost opposite ends of the plurality of photovoltaic modules, and voltage and current values of each of the photovoltaic modules; changing the string current value and respectively calculating conversion power values of the plurality of power conversion modules per the changed string current value by using the voltage and current values; searching a string current value for a minimum power point tracking control among the changed string current values by using the conversion power values; and controlling the plurality of power conversion modules to track the searched string current value.