Abstract
The voltage and reactive power control (Volt/VAR Control, VVC) in distribution networks has become a challenging issue with the increasing utilization of distributed generations (DGs). In this paper, a heuristic-based coordinated voltage control scheme that considers distribution voltage control devices, i.e., on-load tap changers (OLTC) and step voltage regulators (SVR), as well as reactive power control devices, i.e., DGs, are proposed. Conventional voltage control methods using non-linear node voltage equations require complex computation. In this paper, the formulation of simplified node voltage equations accounting for changes in tap position of distribution voltage control devices and reactive power changes of reactive power control devices are presented. A heuristic coordinated voltage control scheme using the proposed simplified node voltage equations is proposed. A coordinated voltage control scheme to achieve voltage control for nominal voltage and conservative voltage reduction (CVR) is presented. The results of the proposed schemes are compared with the results from the quadratic optimization method to confirm that the proposed schemes yields suitably similar results. Furthermore, a tap scheduling method is proposed to reduce the number of tap changes while controlling network voltage. The tap position is readjusted using a voltage control performance index (PI). Simulation results confirm that when using this method the number of tap changes is reduced. The proposed scheme not only produces reasonable performance in terms of control voltage of networks but also reduces the number of tap changes made by OLTC. The proposed control method is an alternative candidate for a system to be applied to practical distribution networks due to its simplified calculations and robust performance.
Highlights
The voltages of distribution networks are conventionally regulated by changing the tap position of the on-load tap changer (OLTC) at distribution substation and step voltage regulator (SVR) or by switching shunt capacitor banks at feeders
The “Opt” graph in Figure 15 is determined by the voltage control for nominal voltage
The schedule readjustment results confirm is significantly larger than the performance index (PI) at each tap position
Summary
The voltages of distribution networks are conventionally regulated by changing the tap position of the on-load tap changer (OLTC) at distribution substation and step voltage regulator (SVR) or by switching shunt capacitor banks at feeders. The voltage control characteristics of tap changing devices, i.e., OLTC and SVR, and reactive compensation devices, i.e., reactive power of DGs, are represented by simplified node voltage equations. DGs, in the second stage, the voltage profiles of the distribution networks are leveled by adjusting the tap position of the OLTC. A simplified linear voltage equation is proposed to reduce the computation times of the voltage estimation process and heuristic-based coordinated algorithms for voltage control devices, such as tap changing devices and reactive power sources, are proposed to reduce the computational complexity of the search process for an optimal solution. It is expected that the proposed method is very useful for the practical distribution systems due to the simplified calculation process, robust performance, and practical consideration for limitation of tap changing operations
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