Photovoltaic String Voltage-Limiting Circuit for 1500V Systems
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Solution Overview
Problem
The quantity of photovoltaic modules that can be connected in series is limited by the maximum voltage requirement of 1500V, leading to low utilization rates of direct voltage and PV-to-inverter ratio in conventional photovoltaic systems.
Innovation Solution
A circuit for component voltage limitation is connected to a photovoltaic-cell string, incorporating a detection-and-control unit and a switch unit to manage photovoltaic cells in voltage-limited modes, such as complete-short or chopping modes, to adjust output voltage based on detected parameters like voltage, current, or temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If more photovoltaic modules are connected in series to increase system voltage and power output, then the system power increases, but the maximum voltage limit of 1500V restricts the quantity of modules that can be connected
Solution Approach 1:
The patent applies dynamics by making the photovoltaic module voltage adjustable rather than fixed. Through the control circuit and switching device, the module voltage can be dynamically changed between a first voltage (normal operation) and a second voltage (reduced operation), allowing the system to adaptively manage the number of series-connected modules based on real-time voltage conditions
Solution Approach 2:
The patent changes the voltage parameter of individual photovoltaic modules from a fixed value to a variable value. By controlling at least one module to operate at a reduced second voltage when the string voltage approaches the 1500V limit, the system can connect more modules in series while maintaining compliance with the maximum voltage requirement
2Reliability
If the system operates at maximum voltage of 1500V with limited series connection, then voltage safety is maintained, but the direct voltage utilization rate and PV-to-inverter ratio are low
Solution Approach 1:
The patent implements dynamic voltage adjustment where modules can switch between normal voltage mode and reduced voltage mode. This dynamic capability allows the system to maintain voltage safety through active control while also optimizing voltage utilization by preventing excessive voltage buildup, thereby improving the PV-to-inverter ratio and direct voltage utilization rate
Solution Approach 2:
The patent employs feedback control through a control circuit that monitors the voltage of the photovoltaic string and adjusts the operating voltage of individual modules accordingly. When the string voltage approaches the safety limit, the feedback mechanism triggers voltage reduction in selected modules, ensuring both safety compliance and optimal voltage utilization
Data Source
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Figure 3a~3b
AI summary
A circuit for component voltage limitation and an apparatus for applying the same. A detection-and-control unit detects a parameter of a photovoltaic-cell string, and controls operation of a switch unit according to the parameter of the photovoltaic-cell string. The switch unit controls, according to control of the detection-and-control unit, at least one photovoltaic cell connected to the switch unit to operate in the voltage-limited mode, or a photovoltaic cell operating in a voltage-limited mode to resume a normal output. In a case that the switch unit controls the at least one photovoltaic cell connected to the switch unit to operate in the voltage-limited mode according to control of the detection-and-control unit, a voltage of the photovoltaic-cell string can be reduced. Thereby, a quantity of photovoltaic modules connected in series can be increased while the highest voltage of the system is guaranteed not to exceed a corresponding requirement, and a cost of the system is reduced. In a case that that the switch unit controls the photovoltaic cell operating in the voltage-limited mode to resume the normal output according to control of the detection-and-control unit, an output voltage of the photovoltaic-cell string can be increased. Thereby, the rate of utilization on the direct voltage and the PVIR of DC/AC are improved for the photovoltaic system.