Power electronic converter (PEC)-interfaced renewable energy generators (REGs) are increasingly being integrated to the power grid. With the high renewable power penetration levels, one of the key power system parameters, namely reactive power, is affected, provoking steady-state voltage and dynamic/transient stability issues. Therefore, it is imperative to maintain and manage adequate reactive power reserve to ensure a stable and reliable power grid. This paper presents a comprehensive literature review on the reactive power management in renewable rich power grids. Reactive power requirements stipulated in different grid codes for REGs are summarized to assess their adequacy for future network requirements. The PEC-interfaced REGs are discussed with a special emphasis on their reactive power compensation capability and control schemes. Along with REGs, conventional reactive power support devices (e.g., capacitor banks) and PEC-interfaced reactive power support devices (e.g., static synchronous compensators) play an indispensable role in the reactive power management of renewable rich power grids, and thus their reactive power control capabilities and limitations are thoroughly reviewed in this paper. Then, various reactive power control strategies are reviewed with a special emphasis on their advantages/disadvantages. Reactive power coordination between support devices and their optimal capacity are vital for an efficient and stable management of the power grid. Accordingly, the prominent reactive power coordination and optimization algorithms are critically examined and discussed in this paper. Finally, the key issues pertinent to the reactive power management in renewable rich power grids are enlisted with some important technical recommendations for the power industry, policymakers, and academic researchers.

Reactive Power Management in Renewable Rich Power Grids: A Review of Grid-Codes, Renewable Generators, Support Devices, Control Strategies and Optimization Algorithms

Low voltage ride-through (LVRT) is one of the main requirements of the new grid codes for integration of wind farms (WFs) to power system. In this paper, to enhance the LVRT capability of doubly-fed induction generator (DFIG)-based WFs, a capacitive bridge-type fault current limiter (CBFCL) is proposed. The CBFCL is based on the conventional inductive bridge-type fault current limiter (IBFCL), in which the limiting impedance (LI) of the IBFCL is adapted according to WFs requirement to provide the reactive power needed of WFs after fault clearance. The WF has been modeled based on an equivalent aggregated DFIG. To check the effectiveness of the CBFCL, its performance is compared with the IBFCL. The PSCAD/EMTDC simulation results show that the CBFCL is an effective and novel solution for LVRT augmentation and short circuit current limitation of WFs. Also, it was found that the CBFCL is more competent to satisfy the LVRT requirements than the IBFCL.

LVRT Performance Enhancement of DFIG-Based Wind Farms by Capacitive Bridge-Type Fault Current Limiter

This article proposes a model reference adaptive control (MRAC) of static synchronous compensator (STATCOM) for enhancing the integration of driven wind turbine-based self-excited induction generator (SEIG) into electrical grids. An MRAC-based Massachusetts Institute of Technology adaptive mechanism is utilised to control the reactive power flow of grid-integrated SEIG. The voltage-source inverter sinusoidal pulse width modulation of the STATCOM is used to overcome the abnormal operating conditions in the wind energy conversion system. This accordingly increases the low-voltage ride through (LVRT) capability. The abnormal operating conditions are faults occurring at the point of common coupling between the generator and the grid. The proposed MRAC is compared to proportional-integral (PI) controllers tuned by genetic algorithm (GA). To evaluate the proposed control of STATCOM for enhancing grid-integrated SEIG, a part of the Egyptian 220 kV network integrated with Zafarana Wind Energy System is used. The results provide evidence of an efficient and robust proposed adaptive control performance rather than static PI controller whose parameters tuned by GA in the voltage, currents, and wind generator speed responses. Moreover, the proposed controller increases the capability of continuous operation of the wind turbines under different abnormal operating conditions and also increases the LVRT capability.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/iet-epa.2017.0662

Model reference adaptive control of STATCOM for grid integration of wind energy systems

LVRT capability enhancement of DFIG-based wind farms by using capacitive DC reactor-type fault current limiter

Modified rotor-side converter control design for improving the LVRT capability of a DFIG-based WECS

This study proposes optimal rating and location of static synchronous compensator (STATCOM) for enhancing transient voltage stability of a real distribution network with wind power generation. The test network consists of fixed and variable speed wind turbines connected to a rural load centre. To ensure reliable and secure operation of the grid, the wind farm (WF) has to comply with the grid code for its low-voltage ride through operation. Loads play significant role in voltage stability analysis. Induction motors and general loads are modelled according to real-time data available with the system operator. In this study, dynamic reactive power requirement of WFs is considered for determination of rating of the STATCOM. Reactive power margin (Q margin) of load bus is used as an index to identify the location of the STATCOM. Extensive simulation has been carried out in DIgSILENT to show the validity of the proposed approach.

https://ietresearch.onlinelibrary.wiley.com/doi/epdf/10.1049/iet-rpg.2016.0022

Veerakumar Boominathan

Papers

Enhancement of transient stability of distribution system with SCIG and DFIG based wind farms using STATCOM