MLPE Photovoltaic String Voltage Control for Backflow Current
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Module level power electronics (MLPE) devices in photovoltaic systems are vulnerable to backflow currents, which can cause damage due to their weaker ability to withstand such currents, especially when connected in parallel with other photovoltaic strings, leading to potential risks in MLPE systems.
Innovation Solution
A method and system for photovoltaic string control in MLPE systems, where a control unit detects output currents of each string and adjusts the voltage of strings connected to the same inverter to reduce backflow currents to a preset range, either by reducing the voltage of strings with higher output currents or increasing the voltage of those with lower output currents, without requiring additional hardware, thereby protecting MLPE devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If photovoltaic strings are connected in parallel to an inverter, then system power output is improved, but backflow current damage risk to MLPE devices increases
Solution Approach 1:
The patent implements dynamic voltage adjustment for photovoltaic strings based on real-time current detection. When backflow current is detected, the system dynamically changes the voltage of affected strings to prevent current reversal, transforming the static parallel connection into a dynamically controlled system that adapts to prevent MLPE device damage while maintaining power output
Solution Approach 2:
The system employs feedback control by detecting output currents of each photovoltaic string and using this information to adjust string voltages. The control unit continuously monitors current flow and implements voltage adjustments based on detected backflow conditions, creating a closed-loop control system that prevents MLPE device damage while maintaining system power output
2Measurement precision
If MLPE devices are added to photovoltaic modules, then system control precision is improved, but vulnerability to backflow current increases
Solution Approach 1:
The system applies preliminary anti-action by detecting potential backflow current conditions before actual damage occurs. When abnormal current patterns are detected indicating potential backflow, the control unit proactively adjusts string voltages to prevent the harmful current reversal from occurring, protecting the MLPE devices before damage can happen
Solution Approach 2:
The patent changes operating parameters (voltage) of photovoltaic strings in response to detected backflow conditions. By adjusting the voltage parameter of affected strings, the system alters the electrical characteristics to prevent current reversal, thereby protecting the precision MLPE devices while maintaining their control capabilities
3Reliability
If voltage adjustment control is implemented to reduce backflow current, then MLPE device protection is improved, but system complexity increases
Solution Approach 1:
The control unit performs multiple functions: it detects output currents of photovoltaic strings, determines backflow conditions, calculates required voltage adjustments, and implements control signals to MLPE devices. By consolidating these functions into a single multi-functional control unit, the system achieves comprehensive protection without proportionally increasing overall system complexity
Solution Approach 2:
The system implements self-service by having the control unit automatically detect backflow conditions and adjust string voltages without external intervention. The photovoltaic system monitors itself and performs self-correction when abnormal conditions are detected, reducing the need for additional complex external protection systems
Data Source
AI summary
A module level power electronics (MLPE) photovoltaic system and a method for photovoltaic string control are provided. The method is applied to a control unit in the MLPE photovoltaic system. The control unit detects an output current of each photovoltaic string in the MLPE photovoltaic system, and then controls, for photovoltaic strings connected in parallel to a same inverter in the MLPE photovoltaic system, a voltage of a photovoltaic string with larger output current to be reduced, or controls a voltage of a photovoltaic string with smaller output current to be increased, so that backflow current can be reduced to preset range tolerable for MLPE device. The method is from a perspective of the MLPE photovoltaic system, the backflow current is limited by controlling voltage change of associated photovoltaic string without additional hardware cost, effectively protecting MLPE device in the MLPE photovoltaic system.