LCL filter for grid tie inverters - why not CLC?

[Magnethicc]

Hello everyone,
I was searching for any grid tie inverters why CLC grid-side filters for Grid Tie Inverters but all I find is LCL filters.

Anyone knows why LCL is preferred to an CLC filter?

 

[enertechups]

An LCL filter is often preferred over a CLC filter in power electronics, especially in grid-connected inverter systems, due to its better harmonic attenuation, improved efficiency, and cost-effectiveness. Here's a breakdown of why LCL filters are usually favored:

1. Superior Harmonic Attenuation​

• The LCL filter offers higher attenuation of high-frequency harmonics compared to a CLC filter.
• It provides a steeper roll-off (-60 dB/decade) after the resonance frequency, while a CLC filter typically offers -40 dB/decade.
• This makes LCL filters more effective in reducing switching noise and meeting stringent grid code requirements.

2. Smaller Component Size​

• Due to better harmonic filtering, the LCL filter allows for smaller inductors and capacitors, leading to reduced size and weight.
• The first inductor in an LCL filter can be designed with a lower value compared to the single inductor in a CLC filter, reducing core losses and cost.

3. Improved Efficiency​

• The reduced inductance in the LCL filter lowers the conduction losses.
• As the current ripple is handled effectively, the filter minimizes energy losses, enhancing overall system efficiency.

4. Cost-Effectiveness​

• While the LCL filter has three components (two inductors and a capacitor) compared to the CLC's two (inductor-capacitor-inductor), the ability to use smaller inductors often results in a more cost-effective design.
• Lower core and copper losses further reduce operational costs.

5. Flexibility with Damping​

• The LCL filter's inherent resonance can be easily controlled using passive or active damping methods, ensuring system stability.
• This makes LCL filters adaptable to various grid conditions and inverter designs.

 

[FvM]

CLC filter would short the inverter with a capacitor, inverter side L is PFC choke and can't be omitted. If you are adding a second capacitor, the filter becomes LCLC (seen from the inverter side). A real inverter has typically more than one shunt capacitor, because LCL filter is accompanied by additional EMI filters.

--- Updated Feb 23, 2025 ---

Additional comment. Above answer, which is 100% AI generated according to AI detector is a typical example how AI is missing the point by not understanding the actual problem.

 

[Magnethicc]

Oh I see, I understand now the 2nd inductor is the PFC inductor!
Thank you FvM.

 

[D.A.(Tony)Stewart]

It is also assumed that the filter is a T type from a voltage source rather than a Pi filter.
Some GTI's may be using just LC to absorb external harmonics and contribute to passive PFC of the external grid.
It depends on what source impedance and all s-parms you want.

100% on AI missing the point.

 

[tuchichi takkaida]

Unfortunately..........AI-generated replies are becoming commonplace across many, many forums.