Photovoltaic Optimizer Voltage-to-Ground Control for MPPT Headroom
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Solution Overview
Problem
In photovoltaic power generation systems using optimizers and distributed maximum power point tracking (MPPT) technology, the limited voltage headroom between normal working voltage and output voltage upper limit value leads to energy loss when photovoltaic components are blocked, causing optimizers to operate in a power limited state instead of MPPT state.
Innovation Solution
Setting an upper limit value for the output voltage to ground for each converter in the photovoltaic power generation system, allowing the system to limit the output voltage to ground based on this value, thereby increasing the voltage headroom and ensuring optimizers operate in the MPPT state even in abnormal scenarios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a BUS voltage upper limit value is set for the photovoltaic string, then the system voltage safety is ensured, but the voltage headroom of each optimizer becomes small, causing energy loss when photovoltaic components are blocked
Solution Approach 1:
The patent divides the centralized BUS voltage control into individual optimizer-level voltage to ground upper limit settings. Each optimizer independently manages its own output voltage to ground based on its position in the series string, allowing granular control that prevents energy loss while maintaining overall system safety.
Solution Approach 2:
The patent introduces a new control dimension by switching from controlling only the series output voltage to controlling the voltage to ground for each optimizer. This additional dimensional control parameter enables independent optimization of each converter's operating range without affecting others, resolving the contradiction between system safety and energy efficiency.
2Productivity
If the output voltage upper limit value of each optimizer is set close to the BUS voltage upper limit value, then the voltage utilization is maximized, but the optimizers enter power limited state when components are blocked, reducing productivity
Solution Approach 1:
The patent pre-configures each optimizer with an individual voltage to ground upper limit value that accounts for its position in the series string and potential blocking scenarios. This preliminary setting ensures that even when photovoltaic components are blocked, the optimizer has sufficient voltage headroom to maintain MPPT operation and avoid entering the power limited state.
3Power
If the quantity of optimizers in series is increased, then the system power output is increased, but the voltage headroom of each optimizer decreases, causing more frequent power limited states
Solution Approach 1:
The patent segments the voltage control authority from the centralized inverter to individual optimizers. Each optimizer independently manages its voltage to ground within its allocated upper limit, ensuring that increasing the number of series-connected optimizers does not reduce individual voltage headroom. This segmentation allows system power output to increase while maintaining energy efficiency.
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 effectively reduces photovoltaic energy loss by maintaining optimizers in the MPPT state, even when photovoltaic components are blocked, without the need for active intervention, by providing a larger voltage headroom and ensuring all optimizers operate efficiently.
Implementation Method 1
Each photovoltaic module includes a photovoltaic unit and a converter (also referred to as an optimizer). The photovoltaic unit and the converter in each photovoltaic module are connected
Data Source
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AI summary
Embodiments of this application disclose a control method for a photovoltaic power generation system and a photovoltaic power generation system, to reduce a photovoltaic energy loss in the photovoltaic power generation system. The method in the embodiments of this application includes: presetting, by the photovoltaic power generation system, an upper limit value for each converter in the photovoltaic power generation system, where the upper limit value is a maximum voltage value of an output voltage to ground of the converter, and the output voltage to ground is a voltage difference between a positive output end of the converter and a ground point of the photovoltaic power generation system; and limiting, by the photovoltaic power generation system, an output voltage to ground of a target converter based on an upper limit value corresponding to the target converter, where the target converter is any converter in the photovoltaic power generation system.