Abstract
Considering the possible overvoltage caused by the high proportion of photovoltaic systems (PVs) accessing distribution networks in the future, traditional centralized control methods will be too complex to satisfy the control response time demands. To solve this problem this paper presents a two-level voltage control method. At the day-ahead level, based on the PV-output and load-demand forecast, a community detection algorithm using an improved modularity index is introduced to divide the distribution network into clusters; a day-ahead optimal scheduling is drawn up on the basis of the network partition, and the objective is to minimize the operation costs of the distribution networks. At the real-time level, under the day-ahead optimal scheduling and network partition of the upper level, a real-time optimal voltage control algorithm is proposed based on the real-time operation data of the distribution networks, and the objective is to correct the day-ahead optimal scheduling through modifications. Thus, the algorithm realizes the combination of day-ahead scheduling and real-time control and achieves complete zonal voltage control for future distribution networks with high proportion of PVs. The proposed method can not only optimize the tap operation of an on-load tap changer (OLTC), improving the PV hosting capacity of the distribution network for a high proportion of PVs, but can also reduce the number of control nodes and simplify the control process to reduce the optimization time. The proposed approach is applied to a real, practical, 10 kV, 62-node feeder in Zhejiang Province of China to verify its feasibility and effectiveness.
Highlights
The increasing demand for renewable energy and the escalating concerns over environmental issues have driven the rapid and continuous growth of photovoltaic (PV) generation [1]
At the real-time level, on the basis of the day-ahead optimal scheduling and network partitioning of the day-ahead level, a real-time optimal voltage control algorithm is proposed based on the real-time operation data of the distribution networks; the objective is to minimum deviating from the day-ahead scheduling
In this work, taking advantage of the zonal control, the day-ahead optimal scheduling is created on the basis of distribution network partition at the day-ahead level to maintain the economic operation of distribution networks whilst reducing on-load tap changer (OLTC) tap operations, and the OLTC service life can be prolonged
Summary
The increasing demand for renewable energy and the escalating concerns over environmental issues have driven the rapid and continuous growth of photovoltaic (PV) generation [1]. To solve the problem of the over-voltage and complex control process due to the high proportion of PVs in future distribution networks, as well as the inadequacies of existing OLTC controlled methods, this paper presents a two-level voltage control method with the combination of day-ahead optimal scheduling and real-time optimal control, which are based on zonal control. At the day-ahead level, based on the forecast of PV output and load demand, a community detection algorithm using an improved modularity index is introduced to divide the distribution network into clusters On this basis, a day-ahead optimal scheduling is drawn up for the OLTC, PVs and distributed Shunt Capacitors (SC) in each sub-network, while the objective is to minimize the operation costs of the distribution networks. Taking an actual feeder as an example, this paper proves that the proposed method can effectively and efficiently solve the overvoltage problem caused by the high proportion of PVs in future distribution networks
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