BESS
Battery energy storage system
A complete battery plant block combining batteries, power conversion and controls, shown as one source or sink on an SLD.
SLD
Symbols · PCS
Battery power conversion system
The bidirectional inverter stage of a battery plant that charges and discharges the DC battery from the AC network.
In plain English
What does Battery power conversion system mean?
The power conversion system is the bidirectional converter that sits between the battery DC bus and the AC network in a storage plant. It charges the battery by rectifying AC and discharges it by inverting DC, under the direction of a plant controller that sets active and reactive power or operates in a grid-forming mode.
A simple example
Drawings show a converter box with both AC and DC marks and a bidirectional energy-flow arrow, a DC breaker or switch on the battery side, and an AC breaker, filter and often a medium-voltage skid transformer on the network side. Several PCS units may share one transformer.
What the drawings help you do
The symbol does not tell you whether the unit can black-start a dead bus, how much overload it can supply or how it limits fault current. Those features drive protection settings and must be read from the converter specification.
This particular reference
The bidirectional inverter stage of a battery plant that charges and discharges the DC battery from the AC network. A PCS is a utility or commercial storage converter; an inverter-charger is a smaller low-voltage unit with an integral AC transfer relay.
- DC
- Direct current: electricity flowing in one direction.
- AC
- Alternating current: electricity whose direction changes periodically.
- Winding
- A coil of conductor inside an electrical machine or transformer.
Read the source: Battery energy storage and power conversion · Autodesk IEC-60617 preview: Energy-flow qualifiers
SLD · PCS
What it represents
The power conversion system is the bidirectional converter that sits between the battery DC bus and the AC network in a storage plant. It charges the battery by rectifying AC and discharges it by inverting DC, under the direction of a plant controller that sets active and reactive power or operates in a grid-forming mode.
Drawings show a converter box with both AC and DC marks and a bidirectional energy-flow arrow, a DC breaker or switch on the battery side, and an AC breaker, filter and often a medium-voltage skid transformer on the network side. Several PCS units may share one transformer.
The symbol does not tell you whether the unit can black-start a dead bus, how much overload it can supply or how it limits fault current. Those features drive protection settings and must be read from the converter specification.
How to read it
- Look for the bidirectional energy-flow qualifier to confirm charge and discharge capability.
- Check the transformer and filter on the AC side.
Information to show or reference
- State kW, kVA and DC voltage window.
- Show DC and AC switching and filters.
- Reference control modes and black-start capability.
A distinction that matters
A PCS is a utility or commercial storage converter; an inverter-charger is a smaller low-voltage unit with an integral AC transfer relay.
Sources you can follow
These public references support the explanation and provide further detail. Their graphics and downloadable files remain with their publishers.
Battery energy storage and power conversion
Public power conversion context for battery storage.
Autodesk IEC-60617 preview: Energy-flow qualifiers
Public IEC-context energy-flow qualifier family used for the bidirectional mark.
About this graphic
This illustration was authored independently by Elora Grid to explain the concept. It is not reproduced from a customer drawing, an official standard graphic or a manufacturer CAD file. Its correspondence to an exact IEC or IEEE symbol identifier has not been certified.
SVG and DXF downloads contain this original artwork. DXF uses unscaled drawing units; a GA envelope supplies no product dimensions, clearances or fabrication information. Original artwork is available under CC BY 4.0. Third-party references retain their own terms.
Explore related references
Q020508
Bidirectional-energy-flow qualifier
This qualifier identifies an energy interface intended to operate in both directions.
IEC
INV/CHG
Bidirectional inverter-charger
A battery converter that charges from an AC source and inverts back to AC, with an internal transfer relay for the load.
SLD / Schematic
GFM
Grid-forming inverter
An inverter controlled as a voltage source that sets its own voltage and frequency, able to energise and hold up an island.
SLD
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