Huawei Smart IV Curve Diagnosis — Fast, Comprehensive, Automated Fault Detection for PV Modules
A global investigation by TÜV Rheinland into PV plants with output totaling 12 GW has shown that 30% of the plants had severe defects, among which 50% were from PV module faults. PV module faults directly affect the energy yields and benefits of PV plants. Locating PV string faults accurately and promptly is an urgent problem for plant owners. However, conventional PV module inspection methods are both time and labor intensive, driving up costs.
A large-scale PV plant has many PV modules and strings scattered over a large area. For example, a typical 100 MW PV plant contains about 400,000 PV modules grouped into 20,000 PV strings and occupying 2.5 km2. It is impossible to compare every two PV modules by comparing their voltages and currents because of the huge number of PV modules and complex outdoor testing environment. This means that only spot checks are feasible.
There are currently two common methods of spot checking PV modules. The first is using a dedicated IV scanner to test site PV modules. The second is sending PV modules to a professional testing organization to obtain IV curves, which are then used to determine PV module faults. Both methods, however, are time consuming and costly. With a spot-check ratio of just 0.1%, a spot-check on a 10 MW PV plant costs 400,000 rupees.
A further problem is that these methods usually identify PV module faults by comparing the output power, open-circuit voltage, short-circuit current, operating voltage, and operating current. The fault identification rate is low and errors of measurement or calculation are common.
Smart IV Curve Diagnosis: Locating Faults Quickly and Accurately to Implement Proactive Maintenance
To solve the pain points caused by the conventional inspection methods, Huawei has developed smart IV curve diagnosis. This technology allows the inverter to export IV curves, deploys algorithms on the management system, and analyzes data. It also identifies modes to scan all PV strings of a PV plant and identify hidden PV module faults.
This technology, along with the smart PV management system and smart PV controller, can detect all PV strings of a PV plant online with 0.5% precision (more than six times the industry level and equal to the precision of a professional outdoor IV tester).
Huawei’s latest SUN2000-43KTL requires only 1 second to finish scanning and 10 minutes to output a report including data about a PV array in one-click mode, with no testing personnel and testers onsite. This greatly lowers the labor and cost requirements for testing. Test personnel are forewarned about PV module faults using smart PV string diagnosis, and the health status of the PV plant can be estimated comprehensively to achieve proactive maintenance. The diagnosis precision and efficacy have been certified by TÜV.
A successful trial was carried out at Huanghe Hydropower, finding that 0.17% of PV modules in a PV array were faulty. The big difference is based on Huanghe Hydropower’s previous spot-check ratio of 0.3%, 97.6% of these faulty PV modules would have escaped detection.
Fault Types and Fault Analysis with Online IV Curve Detection
In the Huanghe Hydropower project, faults such as PV module glass breakages, PV string open circuits, and faulty diodes were detected using online IV curve detection. The technology can detect many common types of PV string faults.
Common PV string fault types that can be detected
| PV string open circuit | PV string performance attenuation | PID | Single PV module shielded | Cell output abnormal
(cracking or shielded by foreign matter) |
| PV string current mismatch | Diode short circuit | Single cell failure | PV module overheating | PV module glass breakage |
| PV module interconnection fault (disconnected) | PV module interconnection fault (interconnection strip corroded) | PV module delamination | EVA discoloration | – |
IV curve characteristics for typical faults
Professional instruments used in conventional spot-checks can test PV strings but cannot perform analysis. Smart IV curve diagnosis not only allows every PV string to be scanned, but also assesses the health of PV strings, exports fault reports, and provides recommendations for proactive maintenance. This helps to achieve automatic O&M and intelligent management.
Comparison between Huawei IV curve scanning solution and professional IV testers
| Item | Huawei IV Curve Scanning Solution | Professional IV Tester | Huawei Solution Evaluation and Risk | |||
| Hardware | ||||||
| Scan speed | < 1s | 0.3–5s | The scan speed is less than 1 second, which is within the same range as professional outdoor testers. | |||
| Scan precision | 128 points | 101 points | Scan precision reaches the level of a professional outdoor tester. | |||
| Scan accuracy | Current < 0.5%
Voltage < 0.5% |
Voltage < 1%
Current < 1% |
Accuracy is higher than that of a tester. | |||
| Convenience | Fixed, PV string IV curve | Movable, PV string/module IV curve | No need to remove terminals or enter the site. | |||
| System | ||||||
| Scan consistency | The entire PV array is scanned, providing high-accuracy power comparison among PV strings. | One PV string is scanned at a time. Power comparison among PV strings is indefinite due to the variety of environments. | The test has little influence on energy yield.
Power comparison among PV strings has high credibility. |
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| Comprehensiveness | The entire PV plant is scanned, and no PV module is missed. | A sample of PV modules is tested randomly, and many PV modules escape inspection. | Provides great value for PV plant inspection.
Dramatically decreases PV plant inspection cost. |
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| Automatic startup | Monitors the PV string output and checks PV strings with low output for potential issues. | Test objective is hard to select. | Scans PV strings with low output to find potential issues and reduce the PV module failure rate. | |||
| Function | ||||||
| Environment data | Reads the environment data automatically. | Environment data is collected manually, posing a risk of collecting incorrect data. | Provides a data port, through which environment data is collected automatically as required. This reduces manual recording workload and potential for errors. | |||
| Availability | The scan is performed remotely in one-click mode and no professional skill is required. | Test personnel must carry out the scan onsite, which is difficult and labor intensive. | Decreases test workload and cost. | |||
| Data analysis | Analyzes the IV curve automatically and identifies faulty PV strings.
Generates analysis reports automatically. |
The IV curve is analyzed manually and data is collected manually, creating high workload. | Reduces requirements for technical personnel and cost. | |||
Benefits of PV String IV Curve Detection
The online IV curve detection function enables the features and health status of PV strings of large-scale PV plants to be inspected. This facilitates O&M by detecting and processing low-efficiency PV strings, improving energy yields, and preventing faults from propagating. The online IV curve detection function brings four key benefits:
Benefit 1: Timely Discovery of PV Module Faults
- All PV modules in the PV plant are scanned rapidly and periodically through annual inspection, detecting faulty PV strings. Timely processing of the faulty PV strings helps improve energy yields and prevents faults from propagating.
- Carrying out IV tests for PV strings with low output power on an irregular basis helps detecting and preventing faults.
Benefit 2: Inspection Quality Improvement
- The IV curve can be used to accept PV modules after a PV plant is constructed, detecting faulty products, improving PV plant quality, and reducing acceptance cost.
- Tests the faulty PV strings reported by the system by combining the IV curve detection result. This significantly improves PV plant inspection efficiency and fault detection rate, as well as lowering inspection workload.
Benefit 3: High Automation
- One-click remote operation greatly reduces PV plant test intensity, requirements on test personnel, and test cost.
- Automatic analysis of IV curves lowers requirements on test personnel.
- Automatic generation of reports reduces workloads for test personnel.
Benefit 4: Mining the Value of Historical Data
- The system automatically collects statistics about PV string fault types and attenuation rate based on PV modules and historical runtime. Using the collected statistics, it provides suggestions for the future construction of the PV plant.
- When the array attenuation rate changes rapidly or a certain type of faults propagates throughout the system, the PV plant owner can adjust the O&M policy accordingly. This improves O&M efficiency, reduces costs, and increases the plant PR.
PV modules function as the main body of a PV system, making PV module quality a vital consideration. Huawei’s smart IV curve diagnosis technology is a significant step toward freeing PV plants of the consequences of PV module faults.
