Bias Voltage Source for Grounded Photovoltaic Modules
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Solution Overview
Problem
Existing solar power plants with photovoltaic modules face challenges in maintaining the life of thin-film modules and achieving high inverter conversion efficiency due to the need for grounding, which often requires expensive solutions or reduced efficiency inverter topologies.
Innovation Solution
An additional direct voltage source is inserted between the neutral conductor and ground, or between one of the phases and ground, to set a bias voltage, preventing adverse field orientation and allowing the use of grounded photovoltaic generators with various inverter topologies, including transformerless inverters, without the need for galvanic isolation or special inverters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If photovoltaic modules are grounded to prevent early damage and extend life, then module reliability is improved, but inverter conversion efficiency is reduced due to the need for galvanic separation or transformerless inverters with special topologies
Solution Approach 1:
A bias voltage source is introduced as an intermediary element between the photovoltaic generator and ground. This bias voltage source shifts the potential of the photovoltaic strings, allowing the modules to be grounded while maintaining the necessary voltage polarity for efficient inversion. The bias voltage acts as a mediator that reconciles the conflicting requirements of module grounding and inverter efficiency.
2Reliability
If galvanically separating inverters or transformerless inverters with special topologies are used to ground modules, then module life is extended, but device complexity increases
Solution Approach 1:
The bias voltage source serves as a simple intermediary that enables grounding without requiring complex inverter topologies. By shifting the potential level, it allows the use of standard inverter designs while still protecting the modules, thereby reducing device complexity compared to galvanically separating inverters or transformerless inverters with special topologies.
3Reliability
If many devices are mounted to raise module potential in large solar plants with many photovoltaic generators, then module life is extended, but system cost increases
Solution Approach 1:
The bias voltage sources for multiple photovoltaic strings are merged into a common reference potential. Instead of requiring separate bias voltage devices for each string, the system combines them share a common ground reference, significantly reducing the number of devices needed in large solar plants while still extending module life.
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 solution extends the life of photovoltaic modules, maintains high inverter conversion efficiency, and reduces wiring costs, enabling the use of sensitive modules like thin-film modules with transformerless inverters in large solar power plants.
Implementation Method 1
an additional direct voltage source is inserted between the neutral conductor and ground in such a manner that the potential of the photovoltaic strings is displaced and that a bias voltage different from zero volts is set
Data Source
AI summary
A solar power plant includes at least one photovoltaic module for generating power to be fed in a multi-phase grid. At least one inverter is provided for converting a direct voltage generated by the at least one photovoltaic module into an alternating mains voltage. A mains transformer is coupled to receive the alternating mains voltage from the inverter. The inverter is coupled to a primary side of the mains transformer. A direct voltage source coupled between an output of the at least one inverter and an input of the mains transformer such that a potential of the at least one photovoltaic module is displaced and that a bias voltage is set which is different from zero volts.