Optimal OLTC voltage control scheme to enable high solar penetrations

Abstract

High solar Photovoltaic (PV) penetration on distribution systems can cause over-voltage problems. To this end, an Optimal Tap Control (OTC) method is proposed to regulate On-Load Tap Changers (OLTCs) by minimizing the maximum deviation of the voltage profile from 1 p.u. on the entire feeder. A secondary objective is to reduce the number of tap operations (TOs), which is implemented for the optimization horizon based on voltage forecasts derived from high resolution PV generation forecasts. A linearization technique is applied to make the optimization problem convex and able to be solved at operational timescales. Simulations on a PC show the solution time for one time step is only 1.1 s for a large feeder with 4 OLTCs and 1623 buses. OTC results are compared against existing methods through simulations on two feeders in the Californian network. OTC is firstly compared against an advanced rule-based Voltage Level Control (VLC) method. OTC and VLC achieve the same reduction of voltage violations, but unlike VLC, OTC is capable of coordinating multiple OLTCs. Scalability to multiple OLTCs is therefore demonstrated against a basic conventional rulebased control method called Autonomous Tap Control (ATC). Comparing to ATC, the test feeder under control of OTC can accommodate around 67% more PV without over-voltage issues. Though a side effect of OTC is an increase in tap operations, the secondary objective functionally balances operations between all OLTCs such that impacts on their lifetime and maintenance are minimized.

Coordination of PV Smart Inverters Using Deep Reinforcement Learning for Grid Voltage Regulation

“…An SI is able to help voltage regulation through modulating real and/or reactive power of the PCC, i.e. it can change the P k and/or Q k in (1,2) if bus k has a PV connection. In this way, the SI can change the voltage for bus k as well as other buses per (1,2).…”

“…Step 1: at the beginning of one episode (one operation scenario of the power network), the power flow (PF) will be solved to get the system information and assemble the state vector. The PF is performed by the AC power flow solver OpenDSS [26], which takes in load consumption and PV generation information, solves the corresponding PF equations (1,2), and gets voltage at each bus.…”

“…The amount of renewable distributed generation (DG) connection has been significantly increasing in recent years due to the technical, economic, and environmental benefits it brings [1]. However, increasing penetration of variable DG like PV generation can cause voltage problems on the distribution power grid [2].…”

Voltage regulation system for OLTC in distribution power systems with high penetration level of embedded generation

“…In Khan et al, a SCADA‐based voltage control strategy that ensures coordination between the OLTC, capacitor banks, and the embedded generators is proposed. The proposed voltage control determines the optimal tap settings for the OLTC and control the reactive power dispatch of the capacitors and embedded generators …”

“…The proposed voltage control determines the optimal tap settings for the OLTC and control the reactive power dispatch of the capacitors and embedded generators. 25,26 In this paper, a voltage regulation control algorithm is proposed. The proposed voltage regulation aim is to alter the conventional OLTC operation and hence optimizes the voltage regulation process in the presence of embedded generators.…”