What are the effects of harmonics in bidirectional inverter chargers

With the rapid development of renewable energy and electric vehicle technology, the application field of bidirectional inverter charger (Bi-directional Inverter Charger) as a key device connecting power supply and load is constantly expanding. However, the ensuing harmonic problem has gradually emerged, posing severe challenges to the stability of the power system and the reliability of equipment.

Definition and Cause of Harmonics
Harmonics refer to current or voltage waveforms in the power system with frequencies that are integer multiples of the fundamental frequency, usually 50Hz or 60Hz. Harmonic components include various frequencies higher than the fundamental frequency, such as 2 times (100Hz or 120Hz), 3 times (150Hz or 180Hz), etc. The generation of harmonics is closely related to the working characteristics of nonlinear loads and switching devices. In the process of bidirectional inverter charger converting DC to AC, due to the characteristics of its switching operation, harmonics are often introduced, thus affecting the overall performance of the system.

Impact of Harmonics on Equipment
Equipment Overheating: Harmonics can cause additional heat inside the equipment, especially in equipment such as transformers and motors. The increase in harmonic components will increase the effective value of the current, causing the equipment to generate more heat than normal during operation, which not only shortens the service life of the equipment, but also may cause safety hazards.
Increased power loss: The additional current caused by harmonics will increase the heating of the wire, resulting in ineffective energy transmission and additional losses. This phenomenon not only reduces the overall efficiency of the system, but may also cause a significant increase in electricity costs, bringing economic burdens to enterprises.
Electrical equipment failure: High-order harmonics may cause electrical equipment failures, especially in key equipment such as motors and transformers. The presence of harmonics will cause vibration and noise in the equipment, increase mechanical wear, and may cause premature failure of the equipment, bringing unnecessary downtime costs to corporate operations.
Shortened battery life: In bidirectional inverter chargers, the battery management system (BMS) needs to effectively handle harmonics during charging and discharging. If the harmonic level is too high, the battery charging and discharging process will become unstable, which will affect the battery's cycle life and overall performance.

Impact of harmonics on power quality
Voltage waveform distortion: The presence of harmonics will cause voltage waveform distortion, which will affect power quality. Distortion of the voltage waveform may cause the equipment to not work properly, especially for sensitive equipment (such as computers, medical equipment, etc.), which may cause data loss or equipment failure.
Total Harmonic Distortion (THD): The presence of harmonics will cause the total harmonic distortion (THD) index to rise. THD is an important parameter to measure the distortion of voltage or current waveforms. Too high THD values ​​will not only affect the quality of power, but also may interfere with the normal operation of equipment.
Grid stability: The increase of harmonics may have a negative impact on the stability of the grid. Harmonics can cause oscillations in the grid and may even cause grid failures and power outages. In the case of large-scale grid connection, the impact of harmonics is particularly obvious, which may reduce the overall safety of the system.