Using High Voltage Solar Inverter DC-AC board to develop a LCL inverter

Tong CHEN

Dear technicians,

I am now using High Voltage Solar Inverter DC-AC board to develop a LCL filter myself.

I add a extra 1.5mH inductor as the grid side inductor,

I use SOGI PLL for get the phase and a PR current control loop to control the grid side current to follow the current reference.

I use a bi-polar pwm modulation. currently I do the PR close loop without grid, the load is R=20ohms.

However, the result is here

the green line is output voltage , the red line is output current.

WHy there are so much switching frequency harmonics and so severe cross zero distortion?

over 7 years ago

0 Brian Johnson96 over 7 years ago

TI__Expert 3200 points

Hi Tong,

Can you provide a schematic and an idea of what controller you are using for this inverter application? You make reference to using the "SOGI PLL " so is this a C2000 based design? This way I can direct your question to the best application engineering group to help you.

0 Tong CHEN over 7 years ago in reply to Brian Johnson96

Prodigy 105 points

Dear Brian,
I use this board:C2000™ Solar DC/AC Single Phase Inverter (www.ti.com/.../tidm-solar-onephinv)
and add a 1.5mh inductor to substitute the upper relay to form a LCL inverter.
I use PR control to control the grid-side inductor current.
the DC side is a DC power supply and the AC side load is pure resistor of 20ohm.
I use mcu 28069 and use bi-polar pwm modulation,(90Mhz cpu)
the ocilliscope is used to detect inverter output voltage and output current as the image shows.

I don't know why there are so much switching frequency harmonics(20khz sampling freq)?
And also why there are abvious distortion when zero cross?
Do you have any idea about it?

0 Tong CHEN over 7 years ago in reply to Brian Johnson96

Prodigy 105 points

sure you can direct it, that will be a great help, thx!

0 Brian Johnson96 over 7 years ago in reply to Tong CHEN

TI__Expert 3200 points

Hi Tong,

I moved this to the C2000 Forum as the experts there will be able to help better. I hope your solution is easy to solve.

C2000™︎ microcontrollers

C2000 microcontrollers forum

Using High Voltage Solar Inverter DC-AC board to develop a LCL inverter