PV Combiner Box Power Control Without High-Speed Communication
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Solution Overview
Problem
The two-stage power conversion mode in photovoltaic power generation systems relies heavily on high-speed communication for power control between the DC-DC circuit and the DC-AC circuit, which can be affected by slow communication speeds.
Innovation Solution
A photovoltaic power generation system with a combiner box that includes multiple DC-DC circuits and a controller, allowing for independent power control without relying on high-speed communication. The combiner box is configured to output maximum power within a specific voltage range and decrease output power as the voltage increases beyond a preset threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If two-stage power conversion mode is used to improve power conversion efficiency, then power conversion efficiency is improved, but power control becomes dependent on high-speed communication which may be slow
Solution Approach 1:
The system divides the photovoltaic power generation system into multiple independent combiner boxes, each capable of autonomous power control. Each combiner box manages its own DC-DC circuits and photovoltaic strings independently, segmenting the overall system control function to eliminate dependency on high-speed communication between central controller and power conversion stages.
Solution Approach 2:
The combiner box is designed with autonomous control capability, where the controller within each combiner box independently manages power conversion based on local voltage measurements. The controller determines output power based on the output voltage of the combiner box itself, enabling self-service operation without requiring external communication instructions.
2Loss of energy
If two-stage power conversion mode is used to improve power conversion efficiency, then power conversion efficiency is improved, but power control speed is reduced due to communication delays
Solution Approach 1:
The controller is pre-configured with voltage thresholds (first preset voltage and second preset voltage) and corresponding power control strategies. When the output voltage falls within the specified range, the controller is ready to immediately command maximum power output without waiting for communication delays, enabling rapid response to voltage changes.
Solution Approach 2:
The system implements local feedback control where the controller continuously monitors the output voltage of the combiner box and adjusts the output power accordingly. The feedback loop operates within the combiner box itself, creating a closed-control system that responds instantly to voltage changes without external communication delays.
3Reliability
If independent power control in combiner box is implemented to eliminate high-speed communication dependency, then communication reliability is improved, but control complexity in combiner box increases
Solution Approach 1:
The controller changes operational parameters (output power) based on the measured output voltage parameter. When output voltage is between the first and second preset voltages, the controller sets output power to maximum; when output voltage exceeds the second preset voltage, the controller reduces output power. This parameter-based control strategy simplifies the control logic despite the autonomous operation.
Solution Approach 2:
The patent uses simple, readily available voltage comparison logic and basic DC-DC circuitry within the combiner box controller, avoiding complex communication infrastructure. The control mechanism relies on fundamental electrical parameters and simple decision logic rather than sophisticated communication protocols or advanced control algorithms.
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
Enables fast and independent power control in the photovoltaic power generation system, unaffected by communication speed between the inverter and the combiner box, thereby improving system efficiency and reliability.
Implementation Method 1
The combiner box includes a plurality of direct current-direct current DC-DC circuits
Data Source
AI summary
An example system includes an inverter and at least one combiner box. The combiner box includes a plurality of direct current-direct current (DC-DC) circuits and one controller. The controller is configured to: when an output voltage of the combiner box is greater than or equal to a first preset voltage and less than or equal to a second preset voltage, control the combiner box to output a maximum power. When the output voltage of the combiner box is greater than the second preset voltage, the controller controls an output power of the combiner box to decrease as the output voltage increases. The second preset voltage is greater than the first preset voltage, and the maximum power is a sum of maximum powers of all photovoltaic strings connected to the combiner box.