PV Module I-V Measurement Using a Parallel Variable Load
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Solution Overview
Problem
Current methods for measuring the current-voltage (I-V) characteristics of photovoltaic modules in solar energy production systems disrupt the power output and require module disconnection, limiting the ability to monitor performance effectively in situ.
Innovation Solution
A device and method that utilize a variable load and DC-DC switching power converter to shift the I-V operating point of a photovoltaic module within a string, allowing for in-situ measurement of I-V curves without disconnecting the module from the string, using a controller to vary the load current and duty cycle to record module current and voltage readings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional I-V measurement methods are used, then I-V characteristics can be measured, but module disconnection is required and power output is disrupted
Solution Approach 1:
A current injection circuit is introduced as an intermediary component between the PV module and the measurement system. This circuit allows current to be injected into the module during operation, enabling I-V curve measurement without disconnecting the module from the string, thus maintaining power output continuity while achieving measurement precision
Solution Approach 2:
The measurement device is designed to perform multiple functions: it can measure I-V characteristics, inject current into the module, and operate in both measurement mode and pass-through mode. This multi-functionality allows the system to maintain productivity by enabling continuous operation while providing precise measurement capabilities when needed
2Measurement precision
If a variable load is connected in parallel to measure I-V characteristics, then in-situ measurement is enabled, but device complexity increases
Solution Approach 1:
The variable load, current injection circuit, and measurement circuits are merged into a single integrated measurement device. This combination reduces device complexity by eliminating the need for separate components while enabling in-situ I-V measurement capability through the unified structure
3Adaptability or versatility
If DC-DC switching power converter is used to shift operating point, then measurement flexibility is improved, but device complexity and power loss increase
Solution Approach 1:
A DC-DC switching power converter is implemented with dynamically adjustable duty cycle control to shift the PV module operating point along its I-V curve. The switching converter provides measurement flexibility by enabling operation at different points, while the duty cycle adjustment mechanism allows precise control of the operating condition
4Measurement precision
If measurement is performed during operation, then continuous monitoring is achieved, but power loss occurs due to variable load
Solution Approach 1:
The variable load is designed to draw only the minimum necessary current required for measurement purposes rather than excessive current. This partial action approach enables continuous monitoring capability while minimizing power loss, as the load current is kept just sufficient to shift the operating point for measurement without causing significant energy waste
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 precise, non-disruptive measurement of I-V characteristics, minimizing power loss and allowing continuous operation of the PV module, thereby improving monitoring and assessment of solar energy production without significant disruption to the power output.
Implementation Method 1
said coupling circuit is configured as a DC-DC switching power converter, comprising at least a release transistor configured to alternately enable and disable current flow, wherein a duty cycle of said release transistor is controlled by said controller
Implementation Method 2
measuring current-voltage characteristics of at least one photovoltaic module connected to a photovoltaic array powering a load or inverter
Data Source
AI summary
In one respect, disclosed is an in-situ current-voltage (I-V) measurement device for photovoltaic modules in a photovoltaic array, comprising a variable load, wherein the variable load is configured to be connected in parallel with a module, wherein the module is connected in series with at least one other module in a string, such that the module supplies current simultaneously to the string and to the variable load, and wherein the variable load is controlled by a controller, and wherein the controller is configured to shift an I-V operating point of the module, based at least upon varying the variable load.