Analytical LVRT analysis of doubly fed induction generator with MPC‐basedDSCC/DRCC

Abstract

Under the low-voltage ride-through (LVRT) of the doubly fed induction generator, extra efforts are required for the model predictive control (MPC)-based direct stator/rotor current controls (DSCC/DRCC) against the stator flux oscillation. Constant stator/rotor currents are maintained at the cost of rotor/stator current oscillations, respectively, due to stator flux oscillation. Necessity to incorporate the stator flux transient in the MPC-based DSCC/DRCC under the LVRT is analysed based on tracking effects of the current references. To quantify LVRT effect with the MPC-based DSCC/DRCC, analytical expressions of the stator current, rotor current and rotor voltage are proposed, whose accuracy is validated based on comparison with the time-domain simulations. On the basis of analytical study, advantages and disadvantages of the DSCC/DRCC are analysed considering impacts of the current oscillations on the security of the rotor-side converter. With the DRCC, rotor voltage increase is suppressed with damping to the stator flux oscillation and rotor current constraint is satisfied without decreasing stator output power; thus, the LVRT effect is desirable compared with the DSCC. The MPC-based DSCC/DRCC is extended to LVRT under the asymmetrical fault to realise effective control to both the positive and negative sequence stator/rotor currents.

Hierarchical Predictive Control to Frequency of DFIG‐Integrated Power System Based on Improved Dynamic Power Flow

“…Alternatively, the MPC‐based DRCC is applied to directly quantify the response of the rotor current based on the relationship between the rotor current and voltage [35], $$$$ {\displaystyle \begin{array}{ll}& \frac{{\boldsymbol{I}}_{\mathrm{r}}^{\left(n+1\right)}-{\boldsymbol{I}}_{\mathrm{r}}^{(n)}}{T_{\mathrm{MPC}}}=-\frac{R_{\mathrm{r}}}{L_{\mathrm{r}}^{\prime }}{\boldsymbol{I}}_{\mathrm{r}}^{(n)}-\mathrm{j}{s}_{\mathrm{r}}{\omega}_{\mathrm{s}}\left(\frac{L_{\mathrm{m}}}{L_{\mathrm{s}}{L}_{\mathrm{r}}^{\prime }}{\boldsymbol{\psi}}_{\mathrm{s}}^{(n)}+{\boldsymbol{I}}_{\mathrm{r}}^{(n)}\right)\\ {}& \kern5em -\frac{L_{\mathrm{m}}}{L_{\mathrm{s}}{L}_{\mathrm{r}}^{\prime }}\left({\boldsymbol{V}}_{\mathrm{s}}^{(n)}-{R}_{\mathrm{s}}{\boldsymbol{I}}_{\mathrm{s}}^{(n)}-\mathrm{j}{\omega}_{\mathrm{s}}{\boldsymbol{\psi}}_{\mathrm{s}}^{(n)}\right)+\frac{{\boldsymbol{V}}_{\mathrm{r}}^{(n)}}{L_{\mathrm{r}}^{\prime }}\end{array}} $$$$ where T MPC is the step of the DRCC. Then the rotor voltage that directly controls the rotor current to the reference is obtained.…”

Generation of second harmonic component of fault current in a doubly‐fed induction generator and mitigation measures for transformer protection

“…where i rd-er1 and i rq-er1 is the fundamental frequency component in (28) and (29), respectively. The second harmonic component of rotor current in abc SRF is as follows:…”

R-SFCL and RRCOCS-TVC Based Cooperative Control for Enhancing LVRT Capability of DFIG System

“…The controller's performance was robust to perturbation in wind speed and machine parameters and proved to enhance the LVRT ability during faults. Employment of a model predictive control (MPC) scheme has proved in improving the damping, accuracy, and speed of the controller to track reference currents during fault [14].…”

“…A rotor reference current orientation control strategy (RRCOCS) is proposed in which the current reference is modified for the rotor current loop by following an orientation scheme with the stator circuit current to overturn the rotor circuit high current and reduce the rotor emf [18]. The software control schemes [12][13][14][15][16][17][18] underperform under a severe grid fault condition. Due to extremely low voltage at the common coupling point (PCC) under a severe fault condition, the reactive power available to DFIG is not sufficient to support the voltage at the PCC [19].…”