PID Compensation in Photovoltaic Inverters
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Solution Overview
Problem
Conventional methods for preventing potential induced degradation (PID) in photovoltaic modules are costly and ineffective in repairing degraded modules, especially in high-voltage grid-connected systems, and do not adequately address the power generation capacity reduction caused by PID effects.
Innovation Solution
A photovoltaic inverter system with a PID effect compensation method and device that includes a direct current voltage sampling unit, processing control unit, isolation AC/DC conversion unit, and switching protection unit, which calculates and applies a compensation voltage between the positive electrode terminals of photovoltaic modules and ground to mitigate PID effects, optimizing compensation based on real-time voltage signals and impedance conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If grounding of the negative electrode of the photovoltaic string is implemented, then PID effect is prevented, but the solution is only adaptive to grid-connected inverters and cannot repair degraded modules
Solution Approach 1:
The patent implements a universal PID compensation method that works for both grid-connected and off-grid inverters. The compensation device is integrated into the inverter system and can operate in different modes (prevention during daytime, repair during nighttime) regardless of grid connection status, making the solution adaptable to various inverter types and application scenarios.
Solution Approach 2:
The patent employs dynamic compensation voltage adjustment based on real-time detection of module voltage and PID degradation level. The compensation voltage is dynamically modified during operation, and the system can switch between prevention mode (daytime) and repair mode (nighttime), providing adaptive response to changing operating conditions.
2Reliability
If raising the potential of the virtual neutral point at the AC power grid side is implemented, then PID effect is prevented indirectly, but the solution cannot repair photovoltaic modules where PID effect has already occurred
Solution Approach 1:
The patent implements preliminary PID effect prevention during daytime operation by applying compensation voltage before significant degradation occurs. The system continuously monitors module voltage and applies preventive compensation during normal operation, addressing PID issues before they manifest as serious degradation that would require repair.
Solution Approach 2:
The patent employs periodic compensation cycles where the inverter operates in prevention mode during daytime and switches to repair mode during nighttime. This periodic alternation between prevention and repair operations ensures both proactive protection and active remediation of PID effects.
3Reliability
If conventional PID prevention solutions are implemented, then PID effect is prevented to a certain degree, but the cost is high and degraded modules cannot be repaired
Solution Approach 1:
The patent implements a self-service PID compensation system where the inverter itself generates and applies the compensation voltage using its existing power conversion capabilities. The system uses its own resources (DC bus voltage, control circuitry) to provide PID compensation, eliminating the need for external high-cost power supplies or specialized equipment.
Solution Approach 2:
The patent modifies operational parameters (compensation voltage magnitude, application timing, duration) to optimize PID prevention and repair effectiveness while minimizing cost. The compensation voltage is adjusted based on detected module conditions, applying only the necessary correction rather than continuous high-level compensation.
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
Effectively prevents and repairs PID-induced degradation in photovoltaic modules, enhancing power generation capacity while reducing maintenance costs and improving operational reliability compared to conventional solutions.
Implementation Method 1
a high negative bias voltage is formed between a battery panel and the grounded metal frame in a photovoltaic module close to a negative electrode terminal of the string, such that charges transfer occurs, and a surface of the module is polarized
Data Source
Figure 1~2
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AI summary
A photovoltaic inverter system and a method and a PID effect compensation device (400) for the photovoltaic inverter system are provided comprisng a processing control unit (102), a direct current voltage sampling unit (101), an isolation AC/DC conversion unit (103) and a switching protection unit (104). A processing control unit (102) records operation conditions of photovoltaic modules, determines whether a PID effect compensation condition is met, calculates a compensation voltage optimally and controls the integrated PID compensation device to perform PID effect compensation on the photovoltaic modules. By performing the PID effect compensation and repair, a problem of degradation of photovoltaic modules in a photovoltaic power station can be effectively solved to improve the power generation capacity of a system. As compared with the conventional technical solution, the provided solution has a high operation reliability and a low maintenance cost.