PV DC Bus Grounding Control to Mitigate Module Polarization
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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 at positive and negative polarities.
Innovation Solution
Implementing a power system with dynamic control methods that monitor and regulate voltages, currents, and impedance across interconnected components, including PV generators, wind turbines, and batteries, using DC to DC 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 PV modules operate at higher voltages to increase power output, then power delivery efficiency is improved, but voltage-induced polarization degradation worsens
Solution Approach 1:
The patent applies voltage reversal by switching between positive and negative voltage polarities across the PV module terminals. This inversion principle directly counteracts the accumulated polarization charge that causes degradation, allowing the module to maintain higher operating voltages without suffering from progressive power loss. The controller periodically reverses the voltage polarity to neutralize harmful polarization effects.
Solution Approach 2:
The patent implements periodic voltage reversal cycles where the controller alternates between positive and negative voltage application to the PV module. This periodic action prevents permanent polarization degradation by regularly resetting the charge accumulation, enabling the system to operate at higher voltages for extended periods while maintaining reliability through cyclic polarity switching.
2Reliability
If DC to DC converters are added to regulate voltage and prevent polarization, then reliability is improved, but system complexity increases
Solution Approach 1:
The DC to DC converter is designed to perform multiple functions: voltage regulation to maintain optimal operating points, polarity reversal to counteract polarization effects, and potentially maximum power point tracking. By consolidating these functions into a single converter unit, the patent reduces overall system complexity compared to using separate devices for each function while maintaining improved reliability.
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 maintaining non-negative voltages, thus mitigating voltage-induced degradation and enhancing system reliability.
Implementation Method 1
a converter adapted to convert power from a source of AC voltage or a source of DC voltage to a DC output 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
a photovoltaic panel may connect to the input of the DC to DC converter
Data Source
AI summary
A method may include: applying a first voltage on at least one first terminal of a first direct current (DC) bus electrically connected to a power source, obtaining at least one indication that discharge of a second voltage related to the first voltage should be performed, and discharging the second voltage by electrically connecting at least one second terminal of a second DC bus to a ground in response to the at least one indication. Another method may include: injecting a current at least one terminal of a direct current (DC) bus that is electrically connected to a power source, simultaneous to injecting the current, measuring an insulation relative to ground, obtaining an electrical parameter related to the power source, and, in response to the electrical parameter, maintaining the current injected at the terminal of the DC bus without ceasing the measuring of the insulation relative to a ground.