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Transformer Temperature Management and Voltage Control in Electric Distribution Systems with High Solar PV Penetration

Amirhossein Ghorbansarvi, Dakota Hamilton, Mads R. Almassalkhi, Hamid R. Ossareh

Abstract

The increasing penetration of photovoltaic (PV) systems in distribution grids can lead to overvoltage and transformer overloading issues. While voltage regulation has been extensively studied and some research has addressed transformer temperature control, there is limited work on simultaneously managing both challenges. This paper addresses this gap by proposing an optimization-based strategy that efficiently manages voltage regulation and transformer temperature while minimizing the curtailment of PV generation. In order to make this problem convex, a relaxation is applied to the transformer temperature dynamics constraint. We also provide analysis to determine under which conditions this relaxation remains tight. The proposed approach is validated through simulations, demonstrating its effectiveness in achieving the desired control objectives.

Transformer Temperature Management and Voltage Control in Electric Distribution Systems with High Solar PV Penetration

Abstract

The increasing penetration of photovoltaic (PV) systems in distribution grids can lead to overvoltage and transformer overloading issues. While voltage regulation has been extensively studied and some research has addressed transformer temperature control, there is limited work on simultaneously managing both challenges. This paper addresses this gap by proposing an optimization-based strategy that efficiently manages voltage regulation and transformer temperature while minimizing the curtailment of PV generation. In order to make this problem convex, a relaxation is applied to the transformer temperature dynamics constraint. We also provide analysis to determine under which conditions this relaxation remains tight. The proposed approach is validated through simulations, demonstrating its effectiveness in achieving the desired control objectives.

Paper Structure

This paper contains 12 sections, 1 theorem, 25 equations, 13 figures, 2 tables.

Table of Contents

  1. Introduction
  2. Distribution System Modeling
  3. Network model
  4. Inverter model
  5. Transformer temperature model
  6. MPC Framework and Problem Formulation
  7. Convex Relaxation and Tightness Guarantee
  8. Numerical Case Study Results
  9. Voltage and temperature issues without PV curtailment
  10. Impact of objective function on closed-loop performance
  11. Performance of the proposed MPC approach
  12. Conclusion and Future Work

Key Result

Theorem 1

If, at optimality, there exists a time step $h^*$ and a node $j^*$ such that $p_{j^*}^{cr}(h^*) > 0$, and the voltage constraints eq:vol_inequality are not binding for all $j\in\mathcal{N}$ at time $h^*$, then the relaxation is tight for all $h \in \{0, 1, 2, \ldots, h^*\}$.

Figures (13)

  • Figure 1: Illustration of radial distribution network.
  • Figure 2: Block diagram of centralized MPC framework.
  • Figure 3: Plot of available PV generation at node 6 during time window of interest.
  • Figure 4: Plot of bus voltage magnitudes in the feeder for the case when no PV curtailment is applied.
  • Figure 5: Plot of substation transformer hot-spot temperature for the case when no PV curtailment is applied.
  • ...and 8 more figures

Theorems & Definitions (2)

  • Theorem 1
  • proof