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    What is a power conversion system?

    4 min readLast reviewed: August 2026
    Short answer

    A power conversion system, or PCS, is the bidirectional converter that sits between a battery and the AC network. It controls how fast the battery charges and discharges, synchronises with the grid, and in grid forming mode can create a stable AC network on its own during an outage. It is the component that turns a battery into a usable energy system.

    In a storage project the battery gets the attention and the PCS does the work. Its rating and control modes define what services the system can sell or save.

    Power versus energy

    The PCS is rated in kW or MW and sets how fast energy moves. The battery is rated in kWh or MWh and sets how much there is. A 1 MW PCS with a 2 MWh battery discharges for two hours; the same battery behind a 2 MW PCS discharges for one. Choose the ratio from the application, not from a catalogue.

    Grid following and grid forming

    A grid following PCS injects or absorbs power relative to an existing grid reference and cannot operate without it. A grid forming PCS sets its own voltage and frequency, which is what allows a microgrid or a black start. If backup or islanded operation is a requirement, it must be specified explicitly, because most standard units are grid following.

    Efficiency and losses

    Round trip efficiency of a modern lithium system is typically 85 to 92 percent measured at the AC terminals, including PCS losses, auxiliary consumption, and thermal management. Auxiliary load is often ignored in early calculations and can consume several percent of throughput on a container system in summer.

    Frequently asked

    Is a PCS the same as a solar inverter?
    No. A solar inverter is one directional, DC to AC. A PCS is bidirectional and includes battery control, state of charge management, and grid service modes a solar inverter does not have.
    Can one PCS serve solar and a battery?
    Yes, hybrid units combine an MPPT solar input with bidirectional battery control. This suits smaller sites; large plants usually keep solar and storage conversion separate for availability.
    What does the C rate mean?
    The C rate is the ratio of power to energy. A 0.5C system discharges fully in two hours, a 1C system in one hour, a 2C system in thirty minutes. It drives cell selection and cooling design.

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