A Three-Phase Unbalanced Linear Power Flow Solution With PV Bus and ZIP Load

Hongwei Li,Fengzhu Zhang,Xinli Yan,Jiaxin Yan,Anan Zhang

doi:10.1109/access.2019.2940229

Hongwei Li, Fengzhu Zhang + Show 3 more

Open Access

https://doi.org/10.1109/access.2019.2940229

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Abstract

With the penetration of distributed generators (DGs) into active distribution network (ADN), the voltage controlled buses (PV buses) are becoming more common, to maintain a normal voltage level in the distribution network. Moreover, there are many load modes in ADN which need to be taken into account. In this paper, the approximations of three-phase line model have been analyzed and the ZIP loads with star and delta connections were discussed in detail. And then based on the basic three-phase power flow equations, a general three-phase LPF solution under a polar coordinate system has been presented. The proposed method can account for various connections of ZIP loads, multi-phase feeders and single-phase or three-phase DGs. The effectiveness and advantages of the proposed method are validated with the IEEE 13-bus, 37-bus, 123-bus and an improved 615-bus unbalanced networks.

Highlights

The high penetration of distributed renewable generation, such as photovoltaic generators, into distribution power system (DPS) has increased quickly
The linear power flow (LPF) models should account for the distributed generators (DGs) and different load modes in active distribution network (ADN)
The proposed method is referred as IPLPF, other methods consist of AGLPF[14], LALPF[16], POLPF[17]

Summary

INTRODUCTION

The high penetration of distributed renewable generation, such as photovoltaic generators, into distribution power system (DPS) has increased quickly. H. Li et al.: Three-Phase Unbalanced Linear Power Flow Solution With PV Bus and ZIP Load voltage angle difference is close to 0. In [7], [8], two similar LPF methods have been derived under polar coordinates with respect to the voltage magnitude U and the phase angle difference θ based on cos θ ≈ 1, sin θ ≈ θ and selectively setting U ≈ 1.0. In [10], based on LPF equations, it proposes an improved decoupled linearized power flow models including PV buses. In [15], considering the fact that voltage angles and magnitudes vary within the relatively narrow boundaries in DPS, a three-phase LPF formulation has been derived and the ZIP load was approximated with their linear equivalents using a curve-fitting technique. EXTENSION TO THE NETWORK WITH ZIP LOADS AND PV BUS Because the proposed method can just deal with the phaseground loads, that is, star connection load (Y-load in abbreviation), so the delta connection load (D-load in abbreviation) must be specially dealt with

THE D-LOAD TO Y-LOAD CONVERSION

THE IMPROVED LPF SOLUTION CONSIDERING ZIP LOAD

G LL G LV

SIMULATION RESULTS

CONCLUSION