Photovoltaic String Controller Voltage Regulation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional photovoltaic systems face challenges in efficiently regulating voltage to prevent overloading and stress on power converters, often requiring overdesigning, which reduces efficiency and increases complexity, and existing solutions like pre-loads can be costly and pose safety risks.
Innovation Solution
A photovoltaic system with a configurable string controller that monitors voltage and selectively connects or disconnects strings to regulate power output, using switches to manage power flow and adjust voltage levels in response to changes in the power sink, thereby maintaining safe and efficient operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the power converter is overdesigned to handle PV open circuit voltage levels, then the system can reliably operate with high PV voltage, but the system efficiency decreases and complexity increases
Solution Approach 1:
The controller proactively monitors PV voltage and preemptively disconnects strings before the PV voltage reaches levels that would stress the power converter. This preliminary action prevents the need for overdesigning the power converter while maintaining reliable operation.
Solution Approach 2:
The system continuously monitors PV voltage and provides feedback to the controller, which adjusts string connections in real-time. This closed-loop feedback mechanism ensures the PV voltage remains within safe operating limits without requiring an overdesigned power converter.
2Reliability
If a pre-load is used to maintain PV voltage at safe levels, then the PV voltage stress on the power converter is reduced, but the system cost increases and fire risk is introduced
Solution Approach 1:
The invention extracts the voltage regulation function from the pre-load resistor and relocates it to the string connection system. By disconnecting strings directly at the source, the system eliminates the need for dissipative pre-loads and their associated fire risks while maintaining PV voltage control.
Solution Approach 2:
The controller acts as an intermediary between the PV generator and power converter, managing string connections to regulate voltage. This intermediary control mechanism replaces the need for passive pre-load resistors, eliminating fire hazards while maintaining voltage regulation.
3Power
If all PV strings are connected to maximize power generation, then the power output is increased, but the PV voltage increases toward open circuit level causing stress on the power converter
Solution Approach 1:
The system dynamically adjusts the number of connected PV strings based on real-time voltage conditions. Rather than a static all-or-nothing connection, the controller continuously optimizes string connections to balance power generation with voltage stress prevention.
Solution Approach 2:
The PV generator is segmented into multiple independently controllable strings. This segmentation allows the controller to selectively connect or disconnect individual strings, providing granular control over power output and voltage levels to prevent converter stress while maximizing generation.
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 regulates voltage, reducing stress on power converters, enhancing efficiency, and avoiding the need for overdesigning, while also mitigating safety risks and costs associated with traditional solutions.
Implementation Method 1
The solar cells are solid state devices that convert the energy of sunlight directly into electricity by the photovoltaic effect
Implementation Method 2
The DC switch 202 can be closed to connect the solar cell array 201 to DC capacitor bank 204
Implementation Method 3
The inverter 205 converts the DC voltage output from the capacitor bank 204 into a 3-phase (or in some cases 2-phase) pulsed AC voltage
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A photovoltaic system includes: a photovoltaic generator comprising strings that each includes one or more photovoltaic cells; a power converter; switches; and a controller. The power converter is configured to convert direct current (DC) power provided by the photovoltaic generator into alternating current (AC) power, and to output the AC power. Each switch is associated with one of the strings and is configured to connect the associated string to the power converter when set to a first setting, such that power generated by the first string can flow to the power converter. Each switch is also configured to disconnect the string from the power converter when set to a second setting. The controller is configured to control the power provided by the photovoltaic generator by selectively connecting the strings of the photovoltaic generator to the power converter by controlling the settings of the switches.