How To Choose Capacitors For Solar/Smart Inverter?

According to the requirment of energy buffer, the suitable choice is film capacitor and aluminum electrolytic capacitors.

    Solar inverter between the solar panels and the main power grid plays an interface role.In the solar inverter have two power process.
1)DC / DC converter controls the operating point of the solar panel, so as to achieve maximum power output.
2)DC / AC conversion transfer the power to the main power grid, while performing a variety of management and control rules set up by the main grid operator.

    Film capacitors and aluminum capacitors have some factor, it will affect the solar inverter service life and reliability. So you need to consider all technical charactors, for example, working temperature, operating voltage, ripple current and duration.

    Film Capacitors VS Aluminum Electrolytic Capacitors

    Film capacitors are a good choice. Capacity of this capacitor does not vary significantly with temperature, almost no heat in the charge / discharge (ripple current). Cause of the structure of the capacitor, the current loop is short-circuited, the inductance is very low, so that it can be used over a wide frequency range, usually up to a few Mhz.

    Problems of aluminum capacitors to be more. Pores plus general electrolyte conductivity, make its capacitance change with temperature and frequency. This capacitors will have a fever when charge and discharge, so its ripple current have limited.

    Finally, there is especially important, since the electrolyte capacitor will work with other materials chemical reaction characteristics will change over a period of time, after the end of life of the capacitor failure rate will increase. As the speed of a chemical reaction with the decrease in capacitor temperature decreases the life of the capacitor needs to be calculated according to the working conditions of the solar inverter.

Design Points film capacitors and aluminum capacitors

    When you need to make a choice between these two capacitors, performance not all, the size is also very important, the price is a factor.

    Space efficiency of aluminum capacitors will certainly be higher than film capacitors. 470uF/450V aluminum electrolytic capacitors' size only have 15% of 470uF/450V film capacitor.

    On the other side, aluminum capacitor life is limited. if the solar inverter need to work for 20 years or a high power level, better choice is film capacitor, because it has lower loss and unlimited life.

    On costs, the aluminum capacitor has an absolute advantage, the same spefication 470uF/450V, the cost of film capacitor is five times or more than aluminum capacitors. However, aluminum capacitors generally require additional protection circuitry. But film capacitors no need. In high power rating of the solar inverter, can handle the heat problem is a better choice, because it helps to significantly reduce costs, for example, does not need water to cool the components.