Secrets of the Reliability of Smart PV Power Plant Solutions

-approaching GCTC

Smart PV power plant solutions feature intelligence, efficiency, safety, and reliability. Compared with traditional centralized solutions, the Smart PV power plant solutions take 'making power plants simpler' as the core concept. What we mean by making power plants simpler is that power plants have no non-essential facilities, like inverter rooms, DC solar junction boxes (SJBs), or fragile components, such as fuses, fans, so that the delivery of simplified and standard solutions is achieved. All the components can adapt to various harsh environments, including wind, sand, salt mist, high temperature, humidity, and altitude. Free of maintenance for 25 years, guarantee of reliable operation as well as simpler construction and O&M maximize the benefits of customers' investment.

It is known that the solar power generation system works under the sun exposure and is frequently challenged by such adverse elements as scorching heat, bitter cold, high humidity, strong sandstorms, heavy rain, and salt mist. Conventional electronic devices work in a relatively stable environment, but the components in the PV system, like inverters and SJBs, operate in a capricious environment, so the reliability of these components faces greater challenges. Many factories in this industry have poor reliability testing conditions and only conduct simple tests of high and low temperature performance, so they lack a good deal of other reliability testing evaluations.

As the core equipment of smart PV power plants, inverters are the key factor in ensuring the smooth operation of the plants. Then, how were the reliability of the smart PV power plant solutions realized? Let us approach GCTC to find the answer.

Huawei Global Compliance & Testing Center (Huawei GCTC) is a comprehensive laboratory that integrates EMC, RF, telecom, safety, and reliable environment, and is recognized by international authoritative organizations, including CNAS, ATLA, MET, ITS CETECOM. GCTC offers services of testing, compliance, and design consultations to Huawei products in accordance with the ISO/IEC17025. In addition to traditional testing equipment, the Huawei GCTC also has the combined stress testing equipment and testing methods for temperature, humidity, and corrosive dust, high temperature rain, solar radiation, of lightening attraction. This improves the adaptation of Huawei products dramatically.

    

Figure 1 GCTC Lab Figure 2 A Scenario of the GCTC Lab

 

Thoroughly-tested Huawei Inverters, Best of the Best

Huawei inverters need to pass the most strict tests of Huawei GCTC. The tests comprise of two parts: short-term and long-term reliability tests. Each part also contains many tests. The short-term tests include HALT test, high/low temperature tests, high temperature rain test, icing test, low pressure test, wet dust test, lightening attraction test, EMC tests (electromagnetic radiation, surge, static, lightening, and so on), and safety regulations test. The long-term tests include temperature cycle test (TC), temperature humidity bias test (THB), lifespan test (LLT), and outfield exposure test (high temperature, humidity, and salt). The time of long-term reliability tests all exceeds 1000 hours and some of the tests even last over a year. The reliability tests of Huawei inverters cover many real-world scenarios, such as high humidity, rain, salty and wet dust corrosion, solar radiation, capricious temperatures, lightening strikes, high altitudes, and extreme temperatures (from -60 ºC to over 100 ºC). Now, let's move to the main labs of Huawei GCTC and experience in person the testing process of Huawei inverters.

1.          HALT Test

HALT lab is short for Highly Accelerated Life Test lab. HALT test is one of the reliability tests that Huawei inverters must pass. The test is conducted at the development stage of products and mainly characterized by stepped high temperature limit test, stepped low temperature limit test (instant cooling of liquid nitrogen), stepped vibration test, and combined (temperature shock + vibration) stress test to reveal the weak points in design. The high temperature limit is 110 ºC, the low temperature limit is -60 ºC, and the vibration limit is 40 G acceleration. The test generally lasts 3 days. Inverters are powered on with loads in the whole process and the operating status of inverters is monitored.

Figure 3 HALT test of inverters

2.         Icing Test

Approaching the icing test chamber, you will feel the cold. This simulation test is to see whether Huawei inverters can adapt to the winter scenarios. This test is conducted under -40 ºC and lasts one week. During the test, water the sample intermittently and leave it to freeze. After three days of icing, warm the sample to thaw. Do it twice within the week. In the process, power on and off the inverter, with and without loads, and repeat these operations several times, to test all its functions.

Figure 4 Icing test of inverters

3.         Heat Dissipation Limit Test

After the icing test, here comes the heat dissipation limit test. The heat dissipation limit test simulates the contained scenarios Huawei inverters work in to reveal the design demerits of inverters. Entering the contained lab, heat waves are attacking you. The heat sinks or the top are stuffed with tree leaves. Installed in different modes, inverters are operating with full loads.

 

  

  

Figure 5 Heat dissipation limit test

4.         Low Pressure Test

High altitude is one of the typical application scenarios of inverters. Huawei is determined to send its inverters to Tibet and Mount Everest. Low pressure test simulates the application scenario of high altitude to check the power derating and safety performance of Huawei inverters. Low pressure test checks the operating status of grid-tied Huawei inverters at altitudes of 4,000 meters, 4,500 meters, 5,000 meters, and 5,500 meters respectively.

 Figure 6 Low pressure test of Huawei inverters

5.         Wet Dust Test

Created by Huawei, wet dust test is an integrated test of temperature, humidity, and corrosive dust (the formula of the dust is customized for different regions in the world), designed to verify the adaptation of Huawei inverters working in high temperature, humidity, and dust environments. The test casts dust on the inverter in the dust box, and then increases the temperature and humidity to check the anti-dust and anti-sand capability of the equipment. From the outside, it feels like that a sandstorm is coming.

Figure 7 Wet dust test of inverters

6.         Vibration Test

 The vibration lab is an independent lab. You will hear the strong vibration noise when nearing it. Vibration test is a test for an object or model to check its anti-vibration capability in a simulated environment of its actual use. Influence on vibration on a product includes: 1. Broken structure, for example, the structure becomes misshapen or the product cracks or breaks. 2. Impaired functions, for example, there are poor contact and relay misoperation. These are irreversible damages. 3. Process damage, for example, the screws or connectors become loose, or a soldering point fails.

A Huawei inverter is fastened on a large vibration test platform. During the test, the inverter is powered on with full loads and monitored. Throughout the process, there is no alarm and the operating data is normal. After the test, no abnormality is found in any component.

Figure 8 Vibration test of inverters

7.         High Temperature Rain Test

High temperature rain test simulates the scenario that it rains suddenly on a day of high temperature and humidity, and then temperature drops dramatically. This test is designed to check whether Huawei inverters can adapt to the environments of tropical rainforest, and check their capability of IP65 protection and anti-condensation.

The rain test is conducted in a big T/H box with a special sprinkler. After working in an environment of 70 ºC/95% for a certain time, cool water is sprinkled on the inverter. Before the test, paste moisture-sensitive test papers on the internal board, interior of the shell, key components and the radiator. After the test, determine whether there is condensation according to the color of the test papers. During the test, the inverter is powered on and monitored.

 

Before the test Unchanged after the test

    Figure 9 Sequence diagram of rain test Figure 10 Test papers on internal board before and after the test

8.         Powered-On Temperature Cycle Test

Inverters work in daytime and stop working at night, so they have one temperature cycle every day. The lifecycle of a power plant is 25 years, so its temperature cycles total 9,125 times (365 x 25). Huawei has a very good understanding of this application scenario and implemented the most stringent standard (cycles: ≥ 1500 times; lowest working temperature: -40 ºC; highest temperature: 70 ºC; temperature variation: 15 ºC/minute), while the industry standard (for example, IPC9592) of powered-on temperature cycle is only 300 times. During the test, the inverter is powered on and monitored.

Figure 11 Powered-on temperature cycle test

9.         High Temperature & Humidity Test

In Southeast Asian countries as well as in the South China, there are many days of high temperature and humidity. This T/H test is to check the adaptation of Huawei inverters to such environments, and the anti-corrosion and insulation capabilities of inverter boards and shells.

After operating in the T/H box (70 ºC/95%) for over 6 months, the Huawei inverter has unimpaired electrical performance and appearance.

Figure 12 Powered-on temperature cycle test

10.     Outfield Exposure Test

Huawei Hainan Specialized Cooperation Test Outfield is close to the equator, has strong ultraviolet radiation and is frequently hit by typhoons. The maximum temperature in summer well exceeds 40 ºC. This outfield represents the typical scenario of high temperature, humidity, and salt. It also has an offshore test platform, and 350-meter and 1000-meter test sites. The Huawei inverter is in the 350m test site. After grid-tied operation over three years, the adaptation of Huawei inverters to solar radiation, salt mist, and high temperature and humidity has been fully proven.

  

  Figure 13 Offshore test platforms                                           Figure 4 Inverter outfield exposure test in the 350m test site

11.     Lightening Attraction Test

GCTC conducted the lightening attraction test with a rocket in the outfield. The rocket successfully attracted the lightening and the thunderbolt, like a huge sickle, splitting the cloudy sky. It is quite a spectacle. By launching a rocket shell in the field, the lightening is attracted to the equipment so as to test the surge protection capability of Huawei inverters.

Figure 15 Outfield lightening attraction test

Summary:

Huawei GCTC has always attached importance to the testing capacity building and has the most complete simulation tests for products in all scenarios, including climate, machines, wind, rain, solar radiation and icing, within the industry, and advanced reliability tests, such as HALT and accelerated dust corrosion test. At the same time, it has also conducted long-term research in testing standards and effectiveness, and thus accumulated abundant data and rich experience in this regard.

All Huawei products must pass the stringent quality tests. So, Huawei products can survive all the harsh environments, be it mind-numbing cold in the Arctic Ocean, scorching heat in Africa, coastal regions of high salt mist, or inner regions of deserts. 

The design concept of Huawei PV inverters as well as all smart PV power plant solutions is based on reliable operation of 25 years without maintenance. Therefore, the IP65 protection is implemented so that the internal and external environments are separated, ensuring a stable operation environment for components, and reducing the influence of external environment (temperature, wind, sand, salt mist, and so on) on the lifespan of components. The system eliminates fragile components, like fuses and fans, so that it is free of maintenance. Drawing on the design and quality management experience of massively delivered products and the product deployment from Huawei communications base stations, the components and the whole system adopt designs of high reliability and long service life to ensure the 25-year lifecycle. Besides, they must also live up to the strict standard tests. In this way, the components do not need replacing within their lifecycle so as to achieve reliable and economical operation. We have always upheld this concept 'quality is life, data is real & customers come first'. Huawei Smart PV power plant solutions are best of the best. These solutions are widely used around the world and highly recognized by consumers. In a word, choose wise, choose Huawei.