Abstract
Voltage control devices are employed in power distribution systems to reduce the power consumption by operating the system closer to the lower acceptable voltage limits; this technique is called conservation voltage reduction (CVR). The different modes of operation for system's legacy devices (with binary control) and new devices (e.g. smart inverters with continuous control) coupled with variable photovoltaic (PV) generation results in voltage fluctuations which makes it challenging to achieve CVR objective. This paper presents a two-timescale control of feeder's voltage control devices to achieve CVR that includes (1) a centralized controller operating in a slower time-scale to coordinate voltage control devices across the feeder and (2) local controllers operating in a faster timescale to mitigate voltage fluctuations due to PV variability. The centralized controller utilizes a three-phase optimal power flow model to obtain the decision variables for both legacy devices and smart inverters. The local controllers operate smart inverters to minimize voltage fluctuations and restore nodal voltages to their reference values by adjusting the reactive power support. The proposed approach is validated using the IEEE-123 bus (medium-size) and R3-12.47-2 (large-size) feeders. It is demonstrated that the proposed approach is effective in achieving the CVR objective for unbalanced distribution systems.
Highlights
D ISTRIBUTION Driven by the requirement for improved energy efficiency, conservation voltage reduction (CVR) has emerged as a popular approach to reduce the power consumption of voltage dependent loads by operating the feeder at the lower limits of the acceptable voltages
The overall contributions of this work are threefold: (1) we propose low-compute algorithms for the coordinated control of system’s legacy devices and smart inverters for CVR; (2) we propose fast local control methods for smart inverters to mitigate the effects of local generation/load variability on nodal voltage fluctuations; (3) we propose lowcompute and low-communication algorithms to coordinate the central and local controllers to achieve the CVR objectives for a system with significant levels of local generation variability
The proposed control framework is validated using the modified IEEE-123 bus system and the modified R3-12.472 feeder with simulation done on Matlab and OpenDSS
Summary
D ISTRIBUTION Driven by the requirement for improved energy efficiency, conservation voltage reduction (CVR) has emerged as a popular approach to reduce the power consumption of voltage dependent loads by operating the feeder at the lower limits of the acceptable voltages. The related literature designs a centralized controller to achieve the CVR objective by solving a three-phase optimal power flow (OPF) problem to obtain decision variables for both legacy devices and smart inverters. A centralized controller is proposed that solves an OPF and obtains control set-points for feeder’s voltage control devices for a three-phase unbalanced radial distribution system at discrete time intervals (every 5 to 15-min). The overall contributions of this work are threefold: (1) we propose low-compute algorithms for the coordinated control of system’s legacy devices and smart inverters for CVR; (2) we propose fast local control methods for smart inverters to mitigate the effects of local generation/load variability on nodal voltage fluctuations; (3) we propose lowcompute and low-communication algorithms to coordinate the central and local controllers to achieve the CVR objectives for a system with significant levels of local generation variability.
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