RT23 | HIL validation of advanced voltage controller of DC/DC converters in an MTDC grid

The presentation demonstrates the HiL validation of the active disturbance rejection control (ADRC) applied for the voltage regulation of DC/DC converters in a three-terminal DC grid. The ADRC is a disturbance oberver-based control, which estimates the total disturbance and rejects it through the feedback controller. The main HiL set-up consists of two OPAL-RT targets, the OP5707 and the OP4510. In the FPGA of OP5707 target the DC grid is modelled, with one buck converter, one boost converter and one constant power load (CPL). The OP5707 target provides analog measurements to the OP4510 target. In the CPU of the OP4510 target, the ADRC voltage digital controllers of the buck and the boost converters are modelled, as well as the PID current digital controller of the CPL. In the FPGA of this OPAL-RT target the PWM signals of the DC/DC converters are generated. The OP4510 target provides the digital switching signals to the DC/DC converters modelled in the OP5707 target. The PWM signals of the two ADRC-controlled converters, generated both in OP4510 target, are shifted randomly for a more realistic representation of non-synchronised PWM of different converters in the grid. The HiL results are compared with the results of offline simulations of the continuous system and of the discrete system, with/without digital controllers. The effect of delays, noise and PWM modelling in these simulations is also investigated. The same HiL set-up and the comparison approach is followed for two different ADRC models, one linear and one non-linear. These challenge differently the control discretisation and thus the realisation of the digital controllers in the OPAL-RT target. The HiL results validate both ADRC models, as compared to the offline simulations. It is proven that the digital controllers manage to estimate fast the total disturbance and reject it through the feedback control, to handle different disturbances in the DC grid in real time, while providing very good dynamics and tight voltage regulation.