Installers and professionals working in the solar photovoltaic energy market often encounter an increase in electrical voltage during the operating hours of inverters. Many inexperienced professionals may consider this phenomenon a defect or equipment misconfiguration, but the increase in electrical voltage is normal and expected, as long as it operates within a voltage range. It is important to note that no matter the brand of the inverter, the operation is the same. In this article, we will discuss the origin of this phenomenon, the likely causes of stoppages due to overvoltage alarms, and how to avoid them.
Photovoltaic grid-tie or on-grid inverters, which are connected to the grid do not regulate voltage but rather the current injected into the grid based on local voltage sampling. To inject the generated power into the electrical grid, there must be a potential difference (voltage) between the inverter terminals and the grid connection point; without this difference, there is no current flow from the inverter to the utility's electrical grid. However, the voltage increase must not occur uncontrollably.
The standard "NBR16149: Photovoltaic (PV) systems - Characteristics of the connection interface with the distribution electrical grid" establishes the criteria as shown in the image below, where the voltage increase cannot exceed 10% of the nominal grid voltage. Therefore, based on this information, we verify that when inverters are connected to the 220V grid, they must disconnect (OVR failure) at 242V. For Renac inverters, this setting is done through the "Brazil-180s" country configuration. When connected to rural grids with a nominal voltage of 254V, they must indicate OVR failure at 279V; this configuration is done through the "Brazil-W-180" country setting. If you want to learn how to change the country, we suggest the video "Adjust the country of Renac inverters".
The voltage increase when connecting the photovoltaic inverter to the grid is normal; however, it can cause problems when it exceeds the established limits. Consequences of an overvoltage alarm include revenue loss due to inverter stoppage and possible interference with loads more sensitive to voltage levels.
To avoid unwanted stoppages due to overvoltage alarms, it is essential to analyze the voltage level provided by the utility, local generation and demand, cable sizing, and checking for faulty connectors or improper use. In addition, overvoltage can be caused by issues related to the internal grid of the photovoltaic system, such as inadequate conductor sizes, poorly made or defective connections, or by the utility's grid itself, especially in rural areas with few nearby consumer units to absorb the excess generation - called weak grids.
In these cases, where the utility's grid is considered weak, it is crucial to contact the utility so they can make the necessary improvements to the electrical grid, thus ensuring the proper operation of the photovoltaic system and avoiding generation stoppages due to overvoltage.
Overvoltage in photovoltaic inverters is a common phenomenon that occurs due to increased electrical voltage during inverter operating hours. To avoid overvoltage alarms and generation stoppages, it is necessary to analyze the voltage level provided by the utility, consider local generation and demand, perform proper cable sizing, and check connections. If the problem is in the utility's grid.
Author: Leonardo Burtet - April 5, 2023 - Technical Articles