Design of Reduced Order LADRC via Model Order Reduction Technique for Load Frequency Control in A Single-Area Power System

The performance of a higher-order power system deteriorates due to the sudden load variations, structural discrepancy, and uncertainties involved in the parameters. Thus, an effective control technique must be employed to resolve the load frequency control (LFC) related issues in such systems. For the performance analysis of a higher-order system, a reduced-order controller is used for its reduced-order model because the full-order controller meets some structural and computational complexities. This paper proposes a reduced order linear active disturbance rejection control (RDLADRC) technique to deal with the LFC issues in a single-area power system. This technique successfully combines the benefits of the model order reduction (MOR) scheme and LADRC. Merits of the proposed approach are highlighted based on a deep comparative analysis of the reduced-order LADRC (RDLADRC) technique with full-order linear active disturbance rejection control (LADRC) and pre-existing two degree of freedom-internal model control (TDF-IMC) technique. The robustness of the proposed controller is investigated via system responses under parametric variations. MATLAB and simulation results confirm the effectiveness of the proposed scheme.

I. Introduction

The overall electrical power system has become a complex structure with the rapid advancement of electric power technology. The generation, transmission, and distribution units in a typical power system are generally installed at different locations, but all are interconnected through common tie lines. In such large-scale power systems, the frequency and power of tie-lines frequently change due to the sudden load demand, uncertainty in system parameters, errors in modeling, and disturbance occurs due to variations in the environmental condition. Therefore, the stability of such a complex power system is a prime concern for maintaining synchronism and the specified voltage level under any short-term disturbances such as line faults or overload. In view of this, the prime responsibility for load frequency control (LFC) is to provide highly efficient and steady power in the electrical power system as well as in the tie-line. The essential features of LFC in large-scale power systems comprise; i) retaining the zero steady-state error in case of any frequency deviation, ii) minimizing the unplanned power flow between the tie-line and neighboring areas, iii) handling the problem of system's nonlinearities, iv) maintaining model uncertainties within a tolerable limit, and v) having an excellent performance quality under the frequency and power variations in the tie-line. Therefore, LFC is a matter of concern for the problem related to optimization, and robust control [1].