The voltage rise problem due to the reverse power flow is one of the main obstacles to expanding the photovoltaic systems (PVSs) in distribution networks. In this paper, a decentralized control method for coordinated control of on-load tap changer (OLTC) transformers and PV inverters, is proposed for the voltage regulation of radial distribution networks. In this method, the allowable voltage range is divided into several zones, and appropriate corrective actions are adaptively taken according to each zone. To reduce the tension on the OLTC, first, the reactive power capability of the PV inverters is employed for the voltage regulation, and if it is insufficient, OLTC is used as the last solution. In this regard, the unused capacity of PV inverters is utilized for the reactive power compensation, considering the grid codes reactive power requirements. Furthermore, decentralized control based on a signaling method is used for coordination between OLTC and PVSs, which eliminates the need for communication links. Finally, the effectiveness of the proposed method is validated by the simulation results for the IEEE 33-bus distribution network, and the impact of different reactive power control methods on the number of OLTC operation is investigated.

Decentralized Control of OLTC and PV Inverters for Voltage Regulation in Radial Distribution Networks With High PV Penetration

The voltage rise problem due to the reverse power flow is one of the main obstacles to expanding the photovoltaic systems (PVSs) in distribution networks. In this paper, a decentralized control method for coordinated control of on-load tap changer (OLTC) transformers and PV inverters, is proposed for the voltage regulation of radial distribution networks. In this method, the allowable voltage range is divided into several zones, and appropriate corrective actions are adaptively taken according to each zone. To reduce the tension on the OLTC, first, the reactive power capability of the PV inverters is employed for the voltage regulation, and if it is insufficient, OLTC is used as the last solution. In this regard, the unused capacity of PV inverters is utilized for the reactive power compensation, considering the grid codes reactive power requirements. Furthermore, decentralized control based on a signaling method is used for coordination between OLTC and PVSs, which eliminates the need for communication links. Finally, the effectiveness of the proposed method is validated by the simulation results for the IEEE 33-bus distribution network, and the impact of different reactive power control methods on the number of OLTC operation is investigated. 

By strategically curtailing active power and providing reactive power support, photovoltaic (PV) systems with advanced inverters can mitigate voltage and thermal violations in distribution networks. Quasi-static time-series (QSTS) simulations are increasingly being utilized to study the implementation of these inverter functions as alternatives to traditional circuit upgrades. However, QSTS analyses can yield significantly different results based on the availability and resolution of input data and other modeling considerations. In this paper, we quantified the uncertainty of QSTS-based curtailment evaluations for two different grid-support functions (autonomous Volt-Var and centralized PV curtailment for preventing reverse power conditions) through extensive sensitivity analyses and hardware testing. We found that Volt-Var curtailment evaluations were most sensitive to poor inverter convergence (−56.4%), PV time-series data (−18.4% to +16.5%), QSTS resolution (−15.7%), and inverter modeling uncertainty (+14.7%), while the centralized control case was most sensitive to load modeling (−26.5% to +21.4%) and PV time-series data (−6.0% to +12.4%). These findings provide valuable insights for improving the reliability and accuracy of QSTS analyses for evaluating curtailment and other PV impact studies.

Evaluating Distributed PV Curtailment Using Quasi-Static Time-Series Simulations

High penetration rates of distributed generation using photovoltaic systems (PVS) bring challenges for distribution network operation, mainly due to PVS presenting intermittent generation characteristics. Strategies such as controlling the active and reactive power supplied to the network by inverter connected to the PVS are adopted to overcome the challenges. The use of electric battery storage systems (EBSS) has proved to be a viable alternative to increase the host capacity of distribution networks. An EBSS charging strategy during the solar generation period and discharging during the period of highest demand can contribute to reducing consumers’ energy costs and network loading. This paper investigates the PVS hosting capacity variation in distribution networks, without EBSS and by a methodology for allocating EBSS on the network busbars. The results show that the most expressive increase in PVS hosting capacity is obtained in busbars with higher power loads and when the periods of highest demand are displaced from the period of photovoltaic generation.

Improving PV Hosting Capacity by Implementing Energy Storage Systems on Distribution Networks

With the distributed energy resources massive integration and the power electronic devices rapid proliferation, tremendous new challenges around power quality are emerging. Thus, new performance indicators are established, and several revisions of the power quality standardization corpus is being deployed. Moreover, different advanced control-based mitigation techniques are being developed to prevent power quality deterioration. This paper presents a review of the power quality disturbances, standards, and performance indicators along with some of its control-based mitigation techniques. 

Review on power quality disturbances assessment and advanced control-based mitigation techniques

This paper presents a review of case studies and operational experiences of smart inverters in increasing hosting capacity in real distribution systems, worldwide The phenomenal increase in penetration of solar PV systems has caused several grid integration challenges Overvoltage due to active power injection by solar PV systems is a prominent factor that restricts hosting capacity of PV systems in distribution networks Smart inverter functions on PV inverters have been shown to obviate this challenge and enhance hosting capacity This paper presents a comparative evaluation of different smart inverter functions such as constant power factor, volt-var, and volt-watt in improving hosting capacity Key takeaways from various simulation studies and operating experiences of smart inverters in actual distribution systems across the world are described This paper provides useful insights to utilities in understanding the impact of smart inverters for improving PV hosting capacity in their distribution systems

Vatandeep Singh

Papers

Review of Studies and Operational Experiences of PV Hosting Capacity Improvement by Smart Inverters