PV String Voltage Control to Mitigate Potential-Induced Degradation
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Solution Overview
Problem
Photovoltaic (PV) module reliability and service lifetime are compromised due to polarization effects, leading to power degradation and potential safety issues, particularly in crystalline silicon wafer-based systems, where reversible polarization affects n-type and p-type cells differently, and voltage-induced degradation is pronounced.
Innovation Solution
Implementing a power system with dynamic control methods that monitor and regulate voltages, currents, and impedance in interconnected components, using DC to AC inverters and converters to maintain reference voltages above or below ground potential, thereby alleviating Potential Induced Degradation (PID) and extending the lifespan of PV strings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If higher voltage is applied to PV modules to increase power output, then power delivery efficiency is improved, but voltage-induced degradation and polarization effects worsen, reducing module reliability
Solution Approach 1:
The system dynamically adjusts the voltage potential of PV module strings by switching between different grounding configurations (positive grounding, negative grounding, and floating configurations). This dynamic reconfiguration allows the system to operate at higher voltages when conditions permit while mitigating degradation effects when polarization occurs, thus resolving the contradiction between power output and reliability
Solution Approach 2:
The invention changes the electrical parameter of voltage potential reference by switching the grounding configuration of PV strings. By changing which terminal (positive or negative) is grounded, the system can reverse the polarity stress on cells, preventing permanent polarization degradation while maintaining high voltage operation for increased power output
2Productivity
If PV strings are extended to increase system capacity, then productivity is improved, but voltage potential differences relative to ground increase, worsening PID effects
Solution Approach 1:
The system uses dynamic switching of grounding configurations to manage voltage potential in extended PV arrays. By periodically or conditionally switching between positive and negative grounding modes, the system prevents cumulative PID effects while maintaining the extended string configuration for increased capacity
Solution Approach 2:
The invention applies periodic reversal of voltage polarity by alternating grounding configurations over time. This periodic action prevents permanent ion migration and cell degradation in extended PV strings, allowing the system to maintain high capacity operation without suffering from progressive PID effects
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
This approach ensures efficient power delivery, reduces power losses, and extends the service life of PV modules by regulating voltages to non-negative levels, mitigating voltage-related degradation effects and enabling the extension of photovoltaic strings within regulatory limits.
Implementation Method 1
A converter may be included in the system and may be adapted to convert a source of AC voltage to a source of DC voltage
Implementation Method 2
A DC to AC inverter may include a first input terminal and a second input terminal. The first input terminal and the second input terminal may be connectable to the first output terminal and the second output terminal respectively
Implementation Method 3
photovoltaic (PV) modules
Data Source
AI summary
An apparatus may determine a parameter related to a voltage value at a midpoint terminal of a system power device, and may adjust a voltage applied to a second terminal of the system power device based on the parameter and a reference value. The second terminal may be different from the midpoint terminal.