Inverter Neutral Point Voltage Control for PV PID Suppression
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Solution Overview
Problem
Existing photovoltaic power systems face challenges in reducing lead costs and complex wiring due to the need for direct connections between photovoltaic panel electrodes and voltage sources to mitigate potential-induced degradation (PID) effects, which complicates the operation and increases costs.
Innovation Solution
A power supply system incorporating a voltage controller with a sampling unit, control unit, and inverter unit that adjusts the duty cycle of PWM signals to control the output of alternating current voltage, allowing for charge or discharge of an energy storage circuit to balance voltages between photovoltaic panel electrodes and ground, thereby reducing the need for additional leads and simplifying connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a direct voltage source is connected between photovoltaic panel electrodes and ground to suppress PID effect, then PID effect is suppressed, but lead costs increase and wiring becomes complex
Solution Approach 1:
The patent combines the PID suppression function with the existing inverter neutral point by connecting the voltage source to the neutral point instead of requiring separate connections to each photovoltaic panel electrode. This merging of functions eliminates the need for additional leads and complex wiring while maintaining PID suppression capability.
Solution Approach 2:
The inverter neutral point serves as an intermediary connection point that enables voltage control to suppress PID effects without requiring direct connections between the voltage source and photovoltaic panel electrodes. This intermediary approach simplifies the wiring structure while achieving the same protective function.
2Reliability
If a direct voltage source is connected between photovoltaic panel electrodes and ground to suppress PID effect, then PID effect is suppressed, but lead costs increase
Solution Approach 1:
The patent merges the PID suppression function with the inverter's existing neutral point connection, eliminating the need for separate leads to connect voltage sources to photovoltaic panel electrodes. This reduces the total quantity of leads required while maintaining effective PID suppression.
Solution Approach 2:
The inverter neutral point is designed to serve multiple functions: it acts as the return path for inverter current and simultaneously serves as the connection point for PID suppression voltage control. This multi-functionality eliminates the need for dedicated leads for PID suppression, reducing overall lead quantity.
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 effectively reduces lead costs and simplifies wiring by allowing the power supply system to operate without direct connections between photovoltaic panel electrodes and voltage sources, thereby addressing PID effects and enhancing system efficiency.
Implementation Method 1
determine, according to a difference between the initial voltage and a first voltage, a duty cycle of a pulse width modulation, PWM signal outputted by the control unit
Implementation Method 2
the control unit controls the energy storage circuit to discharge, to lower a voltage of a neutral point of an alternating current side of the inverter; or if the peak amplitude of the first alternating current voltage is less than a peak amplitude of a second alternating current voltage
Data Source
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AI summary
The present invention relates to the photoelectric field, and provides a power supply system and a power supply method, so as to reduce costs of a lead between a positive electrode or a negative electrode of a photovoltaic panel and a direct current voltage source. The power supply system includes: a photovoltaic panel string, an inverter connected to the photovoltaic panel string, and a transformer connected to the inverter. The power supply system further includes a voltage controller. The voltage controller includes a first terminal, a second terminal, and a third terminal. The first terminal is connected to a first output end of the inverter, the second terminal is connected to a second output end of the inverter, and the third terminal is connected to a third output end of the inverter. The voltage controller further includes: a first sampling unit, a control unit connected to the first sampling unit, and an inverter unit connected to both the first sampling unit and the control unit.