PV Module String Switching for Reverse Current Protection
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Solution Overview
Problem
Conventional solar arrays face inefficiencies due to the need for blocking diodes to prevent reverse current flow, which results in power dissipation and reduced efficiency, especially in low voltage bus architectures.
Innovation Solution
A power control and distribution unit (PCDU) with two-quadrant transistor based switches is used to connect or disconnect PV module strings from the main power bus, preventing reverse current flow without the need for blocking diodes, thereby maintaining efficient power transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If blocking diodes are used to prevent reverse current flow in PV module strings, then reverse current protection is achieved, but power dissipation increases and efficiency decreases
Solution Approach 1:
The patent removes blocking diodes from the PV module string circuitry entirely. Instead of using diodes to block reverse current, the system extracts this protection function to a separate power management integrated circuit (PMIC) that uses electronic switching elements (MOSFETs or BJTs) controlled by a control circuit to detect and prevent reverse current flow, thereby eliminating the continuous power dissipation associated with diode-based protection.
Solution Approach 2:
The patent replaces the passive mechanical/electronic diode-based reverse current protection with an active electronically-controlled switching system. The control circuit monitors current direction and uses switching elements to actively open or close circuit paths, substituting the always-on diode mechanism with a smart, condition-based electronic control system that minimizes power loss.
2Reliability
If blocking diodes are used to protect PV module strings, then reverse current is prevented, but device complexity increases
Solution Approach 1:
The patent combines the reverse current protection function with the existing power management integrated circuit (PMIC) that already controls the PV module strings. The control circuit within the PMIC performs both power management and reverse current protection functions, eliminating the need for separate blocking diodes and reducing overall circuit complexity despite adding electronic control capabilities.
Solution Approach 2:
The control circuit in the PMIC is designed to perform multiple functions: normal power management, reverse current detection, and reverse current protection by controlling the switching elements. This multi-functional approach replaces the single-function blocking diode while integrating protection into the existing power management architecture, thereby not increasing but potentially reducing overall system complexity.
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 eliminates the need for blocking diodes, reducing power dissipation and enhancing the overall efficiency of the solar array by directly managing reverse current flow through control circuitry, resulting in improved power transfer and utilization.
Implementation Method 1
A power control and distribution unit (PCDU) with two-quadrant transistor based switches is used to connect or disconnect PV module strings from the main power bus
Implementation Method 2
The control circuit determines whether a reverse current flows in the direction from the main power bus to any of the PV module strings connected to the main power bus
Data Source
AI summary
Technology is disclosed herein for reverse current protection for a photovoltaic module string. An apparatus has a switch connected between each respective PV module string and a power bus. A control circuit closes a set of the switches to connect a set of the PV module strings to the power bus to transfer power from the set of the photovoltaic PV module strings to the power bus. The control circuit determines whether a reverse current flows in the direction from the power bus to any of the PV module strings. The control circuit maintains the switch associated with a particular PV module string in an open state to prevent reverse current from flowing in the particular PV module string responsive to a determination that a reverse current flows in the particular PV module string when the particular PV module string is connected to the power bus.