Yghor Correa

Fake power is an English term that, in direct translation, would be expressed in Portuguese as “false power”. This term is used for equipment that does not reach the nominal power indicated in the datasheet, whether due to poor product quality, use of low-quality raw materials and components, low performance under normal operating conditions, or any other reason that may impair the correct functioning of the equipment. In the solar market, the topic has already been addressed previously, exposing photovoltaic modules that exhibited this behavior, not reaching the maximum power in Wp declared in the datasheet when subjected to laboratory tests. Fake power in solar inverters Recently, as has already occurred in the module market, fake power behavior has also been observed in inverters, bringing the subject back into discussion. The IEM (Institute of Energy and Mobility) laboratory, an organization linked to UFSM (Federal University of Santa Maria), carries out conformity assessment tests on photovoltaic inverters in accordance with the Inmetro ordinance. He carried out a series of tests and observed, in some equipment, a performance different from that expected and specified in the datasheet. SOFAR and the commitment to product quality In response to the resurgence of the issue of fake power in the market, already discussed above, SOFAR decided to voluntarily carry out tests on its own products to demonstrate the brand's quality and commitment to the Brazilian market. A sample of single-phase inverter and a sample of three-phase inverter were selected, models 5KTLM-G3 and 75KTLX-G4-LV respectively. To ensure the test was conducted impartially and with circulating products, the two inverters used for the tests were sent to the laboratory directly responsible for the inventory of Bold, a partner distributor, which has been selling SOFAR products in the national market since 2022. The laboratory that carried out the tests belongs to IEM. The test performed consisted of applying a constant DC voltage, a DC input power of 170% and 200% of the nominal power (70% and 100% overload) and during operation the temperature was varied from 25º to 60º. This made it possible to observe how the inverter's AC output behaved in each temperature range and within the conditions established for the tests. The chosen overload level is within current market practices, and above the standard overload used in some tests. The aim is to subject the equipment to tests, referring to its actual use and obtaining results that are more in line with the reality of its use in the field. To establish a reference, Inmetro ordinance 140 of 2022 brings some points that must be respected by equipment that is nationalized, two of which are relevant to the subject in question. The first one states that "On-grid inverters, when operating with overload on the photovoltaic port(s), must present a measured power value at the AC port." equal to the nominal power value declared by the manufacturer in the data sheet or in the product manual, at the declared nominal voltage, with a tolerance of ±2%” and also that “The reference ambient temperature must be 25 oC (±3ºC) and with the inverter in permanent thermal mode”. Another point addressed by the ordinance is that “The reduction of inverter power due to temperature cannot occur at ambient temperatures below 40°C”. When comparing these numbers with numbers observed in the field, it is clear that in some real operating situations the ambient temperature can exceed 40ºC, causing the inverter to operate in even more severe conditions than those subjected to in the tests. Test results: The results of the tests performed for each inverter are listed below. The tests were efficiency and performance, totaling 7 tests as shown in Table 1 below: Table 1: Tests performed on each Inverter model. Model No. Test Reference Test Type 5KTLM - G3 202411061748A Efficiency 5KTLM - G3 202411061748B Efficiency 5KTLM - G3 202411061748D Derating 5KTLM - G3 202411061748C Efficiency 75KTLX – G4 - LV 202411061748F Efficiency 75KTLX – G4 - LV 202411061748E Efficiency 75KTLX – G4 - LV 202411061748G Derating In the case of the 5kW inverter, a performance above that declared in the datasheet was observed, as can be seen in Table 2 and Figure 2 below, taken from the report issued after the test. Table 2: 5KTLM-G3 inverter operating power test results. Figure 1: Graphic result - Operating power test of the 5KTLM-G3 inverter. The graph shows the evolution of the output power (Y axis) in relation to the temperature variations (X axis) suffered by the device throughout the test. On the X axis there are two lines, the red one being the reference line and the blue one being the power measured during the test. The DC voltage used during the tests was 487,5Vdc and an overload of 100% (200% DC overload). In the test, it can be observed that the measured power (blue line in Figure 1) is always above the reference line (red line in Figure 1) for all temperatures tested. It can also be observed that the performance exceeded expectations, since the inverter's output power surpassed the datasheet data in all measurements performed, demonstrating the equipment's good construction and robustness in the face of temperature variations and applied overload. This reaffirms the operating capacity, even in the harshest environments in actual use of the inverter. The same test was repeated for the 75KTLX-G4-LV inverter and the result is shown in Table 3 and Figure 2 below. Table 3: 75KTLX-G4-LV inverter operating power test results. Figure 2: Graphic result - Operating power test of the 75KTLX-G4-LV inverter. As with the test performed on the 5kW inverter, it is possible to observe the variation in the output power of the 75kW LV inverter throughout the test temperature ranges. The purple line represents the test reference and the green line represents the actual power measured in each temperature range. The table above the graph shows the exact values measured during the test. For this test, an overload of 70% (170% DC overload) and a string voltage of 554V DC were used. As observed in the single-phase, the 75KTLX-G4-LV inverter also performed above expectations, delivering nominal power up to 40ºC as required by ordinance 140 and easily exceeding the test parameters, presenting derating in relation to the reference only at 55ºC. Again, it is possible to conclude that in real overload and temperature situations, the inverter has the capacity to operate with a certain margin of slack, guaranteeing the plant's performance. With the results of these tests, SOFAR clearly demonstrates not only that it seriously follows all the operating requirements of the inverters, but that it goes beyond, delivering equipment that will have guaranteed performance in the field, satisfying the customer and guaranteeing energy generation even in the most extreme environments. This performance is only possible with a well-built product designed to best serve the Brazilian market with affordable and reliable equipment that maintains a high standard of quality, with a low failure rate and high performance. When choosing the inverter for your project, Sofar recommends always taking into account the technical characteristics as well as the performance in real situations so that there are no surprises regarding the energy delivery to the customer as well as additional unforeseen costs inherent in premature replacements or rework due to the low quality of the equipment.

Yghor Correa

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