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SolarEdge•Unknown

Analysis by Marcus & Team

SolarEdge Inverter: DC Injection Error in Off-Grid Operation

Troubleshoot SolarEdge DC Injection errors during off-grid operation. Diagnose root causes & solutions for hybrid inverter faults. Follow NEC safety standards.

Frequently Asked Questions

•What are the typical causes of DC injection faults in grid-tie inverters?

Failed DC blocking capacitors, transformer saturation, or ground faults are common causes.

•How can I safely measure DC injection in an inverter's AC output?

Use a multimeter in DC voltage mode to measure the voltage between the AC neutral and ground. A value significantly above 0V indicates DC injection.

•What are the potential consequences of operating an inverter with DC injection?

Damage to connected AC loads, increased energy losses, and potential safety hazards due to overheating or fire.

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Marcus leads the technical research department at Storage Faults. Together with a team of systems analysts, he specializes in translating complex solar storage error codes into actionable diagnostic steps for the US market.

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Symptoms:

The SolarEdge inverter reports a "DC Injection" fault while operating in off-grid mode. The system may shut down or operate erratically, potentially disconnecting from the battery bank and AC loads. AC voltage may exhibit a DC offset.

How It Works:

DC injection refers to the presence of a DC voltage or current component in the AC output of the inverter. Hybrid inverters must generate a pure AC sine wave to avoid damaging connected AC loads. In off-grid mode, the inverter creates its own AC voltage and frequency reference, derived from the DC battery bank. The inverter's DC/AC conversion process should ideally eliminate any DC bias. Internal components such as capacitors and transformers play a crucial role in blocking DC.

Common Causes:

Failed DC blocking capacitor within the inverter's AC output filter.
Transformer saturation due to excessive DC current, causing distortion in the AC waveform.
Grounding issues, creating a DC current path between the DC and AC sides.
Firmware glitch in the inverter's control algorithms, leading to incorrect DC/AC conversion parameters.
Battery imbalance, creating a DC offset in the DC bus voltage.
Insulation breakdown in internal inverter components, leading to DC leakage.

Technical Recommendation:

Access the SolarEdge service menu (refer to the system manual for the key combination) to view detailed error logs and diagnostic data. Check the DC bus voltage stability and the output filter capacitor voltages. This data can provide clues about the source of the DC injection fault.

Important Warnings:

High DC voltage (up to 600V+) is present within the inverter. Always disconnect the DC input before performing any maintenance or troubleshooting. Arc flash hazards exist. Wear appropriate PPE (Personal Protective Equipment), including insulated gloves and eye protection. Ensure NEC 690 rapid shutdown compliance. A qualified electrician is mandatory for all electrical work.

Recommended Action:

1

Disconnect all AC loads from the inverter and cycle the inverter's AC breaker. Monitor the AC output voltage with a multimeter for any DC component (should be less than 0.5V). Record the AC voltage and frequency.
2

Disconnect the DC input (PV and battery) and measure the DC resistance between the AC neutral and ground. Should be very high (megohms). Any low resistance indicates a potential fault.
3

Use an oscilloscope to analyze the AC output waveform for distortion or a DC offset. Capture the waveform data.
4

Inspect the inverter's internal components (capacitors, transformers) for signs of damage, overheating, or bulging. Use an IR thermometer to check for hot spots.
5

Check the battery bank voltage and individual battery voltages for imbalances. Correct imbalances by rebalancing the battery string.
6

Consult the SolarEdge service manual for specific troubleshooting steps for the DC Injection fault. Check for firmware updates and apply if available.
7

If the DC injection fault persists, the inverter requires repair or replacement by a qualified technician. Adhere to NEC 690 for PV rapid shutdown.

Preventative Care:

Regularly check the inverter's firmware for updates.
Periodically inspect the inverter's internal components for signs of damage or overheating.
Monitor battery health and address any imbalances promptly.
Verify proper grounding of the system components.
Perform AC load audits to prevent overloading the inverter.