I-V curve diagnosis algorithm for intelligent O&M for PV systems-IoT Platform (Deprecated)(IoT)-阿里云帮助中心

Data Service provides an I-V curve diagnosis algorithm for intelligent O&M for PV systems. This algorithm analyzes the current-voltage (I-V) curve of a PV string, considering influencing factors such as ambient irradiance and temperature. It detects potential system faults to improve equipment efficiency and ensure the PV plant operates efficiently. This topic explains how to use the I-V curve diagnosis algorithm.

Basic information

In the IoT Platform console, on the instance overview page, click the card for your target Enterprise Edition instance.
In the left-side navigation pane, choose Data Service > Data Intelligence.
In the list of algorithm templates, find I-V Curve Diagnosis and click View in the Actions column.
On the template details page of the algorithm, view the Basic Information tab.

The Basic Information tab includes Template Introduction, Typical Scenarios, and Competitive Edges & Highlights.

Instructions

On the template details page of the algorithm, click the Instructions tab.
Click IV Detection Input and IV Detection Output to view the input and output data formats for I-V curve diagnosis.

The input parameters include irradiance (INTEGER, ambient irradiance), temperature (DOUBLE, ambient temperature), np (INTEGER, number of parallel strings), iv_curve (JSON, I-V curve data), and electrical_params (INTEGER, number of series-connected modules). The output parameter is detectResult (JSON, detection result).

PV array fault conditions

PV array partial shading

Partial shading is a common type of fault in PV systems. It occurs when external factors block part of a PV array.

Partial shading has the following effects:

It reduces array power output and causes financial loss.
Shaded modules can cause the hot spot effect, acting as loads on the array. This generates high localized temperatures that can damage or destroy the modules, posing a serious safety hazard.
It can cause uneven aging, which degrades the performance and lifespan of the entire array.

PV array resistance aging

Every solar cell has internal resistance. The following figure shows the equivalent circuit diagram of a solar cell.

Series resistance aging

Series resistance (Rs) arises from the internal connections of solar cells and the inherent resistance of the materials. It mainly includes the bulk resistance of semiconductor materials, the resistance of metal parts, the contact resistance of connections, and the resistance introduced by metal-to-semiconductor contacts.

Many factors can increase series resistance, such as corrosion of metal parts inside a module, poor contact due to thermal expansion and contraction of internal connectors, solar cell aging, and damage from mechanical stress.

Increased series resistance has the following effects:

It reduces the current output of the entire PV array, which lowers power generation and causes energy losses.
It can cause uneven heat dissipation and trigger local hot spots in the array. This affects array performance and shortens its lifespan. Additionally, unstable voltage and current can affect the connected power grid and energy storage systems.

Parallel resistance aging

Parallel resistance (Rsh), also known as shunt resistance, is mainly caused by imperfections in the P-N junction or impurities near it. These can lead to short circuits, especially at the edges of the cell. Parallel resistance indicates the amount of current leakage in the solar cells of a PV module.

Many factors can cause parallel resistance to decrease, such as performance degradation from long-term operation, poor manufacturing processes, module delamination, fine cracks at solder joints, delamination in high-humidity environments, and damage from mechanical stress.

Decreased parallel resistance has the following effects:

It reduces the open-circuit voltage of the solar cell.
Photocurrent flowing through the Rsh branch reduces output power.

String open circuit

A string open circuit is a break in the connection between series-connected cells or modules within a PV string.

In a PV string, multiple solar cells or modules are connected in series to produce a higher voltage output. If an open circuit occurs, current cannot flow between certain cells or modules. This interrupts the circuit of the PV system, preventing it from generating an output current.

Common causes include physical damage during transportation and installation, non-uniform aging, damage from high temperatures, corrosion, and loose connections.

Module short circuit

A module short circuit is a short circuit between series-connected cells or cell groups within a PV module.

In a PV string, multiple solar cells or modules are connected in series to produce a higher voltage output. If a short circuit occurs, current can bypass a portion of the cells or modules, leading to a significant voltage drop.

Common causes include physical damage during transportation and installation, non-uniform aging, and corrosion due to poor waterproofing.