Understanding Huawei SUN2000 Log Files

Learn how Huawei SUN2000 inverters record, store, and manage binary EMAP log files, and when to export them before data is overwritten.

Huawei SUN2000 inverters continuously record operational data into a set of proprietary binary log files. Understanding how these files are structured, stored, and eventually overwritten is the foundation for effective O&M work — whether you are tracking daily performance, investigating a fault, or building a legal case against your grid operator.

What are EMAP files?

Most log files on the SUN2000 use the .emap extension. EMAP is a proprietary Huawei binary format used for command scripts and binary data throughout the SUN2000 ecosystem. Huawei has not publicly documented what the acronym stands for.

The reason logs are stored in binary rather than plain text is straightforward: text formats such as .txt or .log consume 5–10 times more storage space and require significantly more CPU time to write. Because EMAP writes raw data structures directly from ARM processor memory, the inverter can commit a log entry almost instantly — even during a critical fault event.

The circular buffer (FIFO) mechanism

The inverter’s internal Flash memory is finite — typically 128 MB to 1 GB depending on the model. To prevent it from filling up, Huawei implements a FIFO circular buffer:

1. Segmentation — Flash is divided into logical blocks (sectors).
2. Sequential writes — new data is written to the next available block.
3. Automatic overwrite — when free space runs out, the system erases the oldest block and writes new data in its place.

You must export logs within 30–90 days of any event you want to investigate. Once the circular buffer overwrites an old block, that data is gone permanently and cannot be recovered.

Log lifecycle: from sensor to Flash

Every data point passes through three stages before it is permanently stored:

1. Sampling — The DSP processor polls current and voltage sensors thousands of times per second.
2. Aggregation — The ARM processor collects DSP samples, averages them (typically into 5-minute intervals for logs like his_inv_rd), or isolates peaks (for alarmg_history).
3. Commit — Aggregated data accumulates in RAM and is flushed to Flash in large batches to reduce Flash wear (wear leveling).

Log persistence and reliability

SUN2000 logs are power-loss safe. If AC grid power and solar irradiance both disappear simultaneously, any data already committed to Flash remains intact. Two mechanisms guarantee this:

• Atomic writes — the file system uses journaling so that a .emap file is never left in a corrupt state, even if power is cut mid-write.
• 20+ year wear leveling — write operations are distributed across the full Flash chip so the inverter can reliably store logs throughout its entire service life.

Four functional groups of logs

The SUN2000 log set is organized into four functional groups. Each group serves a distinct O&M purpose:

Heartbeat

Daily monitoring logs that record voltage, current, energy yield, and insulation resistance at 5-minute intervals.

Black Box

Fault investigation logs including alarm history, oscillography waveforms, and frequency analysis for post-event diagnosis.

Hardware Health

Preventive diagnostics for panels (IV curves), cooling fans, DC bus capacitors, and per-panel optimizers.

Communication & Audit

Security and communication logs covering user access, power-line communication quality, system events, and configuration state.