www.panasonic.com/global/industry/ SOLAR POWER 21 www.power-mag.com Issue 3 2023 Power Electronics Europe continuously as the earth rotates. Detecting and tracking the live position of the sun and adjusting the angles of the panel to ensure that it always faces the sun, maximises the solar energy harvested. Conventional solar inverters have a centralised power conditioner that controls the entire module but, ironically can cause the modules to become shaded, resulting in a decrease in energy output (Figure 3). An example of conductive polymer solid aluminium capacitors is Panasonic’s OSCON series. Conductive polymer solid aluminum capacitors play a major role in the optimisation of solar inverters. To resolve this, micro inverters are installed on each module to keep the panel facing the sun, while only one centralised power conditioner is necessary for several modules (Figure 4). These micro inverters demand a long lifetime of five to 10 years and must save space as well as reduce costs. For example, a single OS-CON can replace seven MLCCs (multi-layer ceramic capacitors) in a micro inverter design, reducing PCB space by 31% without reducing capacitance, whereas using MLCCs reduces capacitance due to DC bias. The 10 year life span is more than three times that of an electrolytic device, enabling OS-CON capacitors to replace aluminium electrolytic versions to increase the life of the micro inverter. Two OS-CON capacitors can replace three electrolytic ones to save space. Resistors for solar inverters Many resistors are used in a solar inverter circuit (Figure 6). Current requirements focus on high voltage, high efficiency for energy saving, and long life. For the resistor this means high reliability with long life, high voltage-withstand capability and high accuracy. For the regulator and voltage-sense functions, resistors with a small case size (e.g., Panasonic’s ERJP series) can be used. (Pansonic claims the resistive element trimming shape ensures antisurge and anti-pulse-withstand performance.) Gate driver resistors are normally required to have a high power capacity and to be able to survive the high temperatures caused by heat generated within the IGBT and inverter. Panasonic’s ERJH series resistors use newly developed materials to achieve high heat resistance, says the Figure 3: The role of a centralised power conditioner. Figure 4: The position of a micro inverter. Figure 5: An example of a solar inverter circuit.
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