SLYY234 December 2024 AMC0106M05 , AMC0106M25 , AMC0136 , AMC0311D , AMC0311S , AMC0386 , AMC0386-Q1 , AMC1100 , AMC1106M05 , AMC1200 , AMC1200-Q1 , AMC1202 , AMC1203 , AMC1204 , AMC1211-Q1 , AMC1300 , AMC1300B-Q1 , AMC1301 , AMC1301-Q1 , AMC1302-Q1 , AMC1303M2510 , AMC1304L25 , AMC1304M25 , AMC1305M25 , AMC1305M25-Q1 , AMC1306M05 , AMC1306M25 , AMC1311 , AMC1311-Q1 , AMC131M03 , AMC1336 , AMC1336-Q1 , AMC1350 , AMC1350-Q1 , AMC23C12 , AMC3301 , AMC3330 , AMC3330-Q1
Figure 89 shows a generic voltage controller and equivalent model of the power plant.
As Figure 89 shows, the term derived analytically before (Equation 47 ) was introduced in the loop as a disturbance to check the voltage control performance. By observing the control loop topology, it can be demonstrated that, thanks to the presence of an integrative part of a PI controller, the steady-state error caused by the DC disturbance Equation 47 is completely rejected. Conversely, the AC component of the disturbance cannot be rejected completely, thus leading to a voltage ripple.
To evaluate the maximum acceptable gain error of a current sensor used in the AC side, simulations were run by applying the following hypothesis:
Figure 90 shows simulation results of an AC/DC converter working with sensors having different gain error.
The following results are present in Figure 90:
In this example a 400-Hz bandwidth of the voltage control loop, paired with 3.7% gain error of the current sensor, leads to a THD of 3.3 % compared to a 3% THD with an ideal current sensor without gain error. Alternatively, a low bandwidth of the voltage control loop leads to low THD on the grid-side but the ripple voltage on the DC link can increase to an unacceptable level. Having a voltage ripple in the DC link can lead to power ripple on the battery which cannot be tolerated. Furthermore, low voltage control loop bandwidth leads to poor load-step response.
In conclusion, a current sensor located in the switching node with a gain error of 3.7% can lead to an increment of the grid current THD of more than 10%. To compensate for this increase, the input filter has to grow by more than 4% in volume to meet the design goal of < 3% THD at the grid-side of the converter.