Novel fast techniques for online voltage and T/D power exchange control in smart distribution grids considering voltage stability issues

Abstract

The integration of Distributed Generation (DG) units into Distribution Networks (DNs) has been raised in the recent years. Hosting high penetration levels of DG units can add new challenges to power system operation, stability, and control. Such challenges are a) over/under voltage problems caused by the intermittent generation of DGs, b) operational conflicts between DG units and convention voltage control devices, c) voltage stability problem due to increase the electrical distances between the generator nodes and load nodes, and d) active and reactive power control problem at Transmission/Distribution (T/D) interface to meet the requirements issued by international Demand Connection Codes (DCC) at this point. Although numerous research efforts have focused to utilize DG units to solve the first two problems through Coordinated Voltage Control (CVC), the last two problems have not yet been fully studied. Besides, the calculation time needed to obtain the global control through CVC may not meet smart grid requirements. This thesis aims to develop novel online techniques for CVC and power exchange control at T/D interface for smart DNs while considering the voltage stability issues and high-voltage (HV) side support. The fast-computational speed associated with these techniques makes them unique. Including the cost in the analysis also adds an important feature to the techniques. The CVC and T/D power exchange control are mainly based on the relation between network voltages and control variables. Thus, a fast voltage sensitivity analysis method (ABCD model) is proposed via the direct derivative of system nodal quantities (power, current and voltage) with respect to power injections. Moreover, a new online CVC technique for choosing a global group of the most effective control variables considering the ones with low cost is proposed. This technique is based on the concept of electrical distances to define the effectiveness of control variables, and on top-down/bottom-up method for control selection. Besides, a new technique for online static voltage stability control for smart DNs is developed by using the sensitivity of the load and the equivalent impedances to control variables. The impedance sensitivities can be used to evaluate the Thevenin Load Impedance Margin (TLIM). Finally, an online multi-modes T/D power exchange control is developed by formulating the problem as Mixed-integer Quadratically Constrained Optimization Problem (MIQCP). Coordination among different types of control resources, including the customer-owned devices and utility-owned devices is achieved for this purpose.

Date	17 Dec 2020
Original language	American English
Awarding Institution	École de technologie supérieure
Supervisor	Maarouf Saad (Supervisor) & Hasan Mehrjerdi (Co-supervisor)