As the cost of photovoltaic (PV) systems has sharply fallen over the recent years, they have been enormously installed, whether in open racks, rooftop or even floating on water. Today, the integration of PV systems into the power system is mostly seen on the low voltage distribution network. This adoption is envisaged to bring both technical and environmental benefits to the traditional distribution network such as reliability, minimization of line loss, line capacity improvement, and investment deferement associated with network upgrade. However, extensive integration may also bring some detrimental impacts such as voltage rise, reverse power flow, harmonics, etc. Therefore, the limit of penetration needs to be determined so as all the desired benefits are acquired. Lately, Karabuk University has begun installing PV generators on some of its buildings, aiming ultimately for autonomus supply; yet, the effect of increasing the capacity of such systems is not yet investigated. In this paper, Electrical Transient and Analysis Program (ETAP) software is used to simulate and analyze the low voltage distribution grid of Karabuk University under multiple PV penetration levels. It is concluded that, considering different power quality metrics, the penetration level of PV as distributed generations should not exceed 75% of the maximum demand of Karabuk University. 

Power Quality Assessment of Karabuk University'S Grid-Connected Microgrid Under High Penetration of PV Generation

As the cost of photovoltaic (PV) systems has sharply fallen over the recent years, they have been enormously installed, whether in open racks, rooftop or even floating on water. Today, the integration of PV systems into the power system is mostly seen on the low voltage distribution network. This adoption is envisaged to bring both technical and environmental benefits to the traditional distribution network such as reliability, minimization of line loss, line capacity improvement, and investment deferement associated with network upgrade. However, extensive integration may also bring some detrimental impacts such as voltage rise, reverse power flow, harmonics, etc. Therefore, the limit of penetration needs to be determined so as all the desired benefits are acquired. Lately, Karabuk University has begun installing PV generators on some of its buildings, aiming ultimately for autonomus supply; yet, the effect of increasing the capacity of such systems is not yet investigated. In this paper, Electrical Transient and Analysis Program (ETAP) software is used to simulate and analyze the low voltage distribution grid of Karabuk University under multiple PV penetration levels. It is concluded that, considering different power quality metrics, the penetration level of PV as distributed generations should not exceed 75% of the maximum demand of Karabuk University.

Photovoltaic (PV) systems are used to generate electricity and they are considered less aggressive in their environmental impact. These systems require no further maintenance once they are installed, they do not pollute the environment and their average lifespan is high. These are the reasons why they are considered a good alternative for electricity generation. However, PV systems have different challenges to solve when they are connected to low voltage distribution grids and one of them is related to the power quality when there is a high penetration of PV systems, when voltage variations usually appear. In this paper, a central energy storage system (ESS) is considered to alleviate grid voltage variations under a high penetration scenario of PV systems instead of using multiples ESS. The proposal controls the energy injected into the grid to maintain the voltage variation within the standard, no limitations are imposed on the PV systems, and then as an advantage of the proposal, the PVs’ available energy is fully delivered to the grid. In addition, in the absence of sunlight the ESS may provide power to the grid. An analysis and experimental setup were built to validate the proposed scheme.

Central Energy Storage System to Reduce the Harmful Effects of PV Systems under a High Penetration Scenario

Although PV systems are one of the most widely used alternatives as a renewable energy source due to their well-known advantages, there are significant challenges to address related to voltage fluctuations and reverse power flow caused by high PV penetration scenarios. As a potential solution to this problem, an active power management strategy is proposed in this work using a residential cluster as a benchmark. The proposed strategy is analyzed and experimentally verified, offering a simple way to reduce the voltage fluctuations by regulating the active power delivered by the PV system, achieving also relevant functionalities for the system, such as the regulation of the DC bus voltage, maximum power point tracking (MPPT), synchronization with the grid voltage, detection of high penetration conditions, and a simple strategy for the main controller with an effective performance. The proposal system shows satisfactory results being able to maintain grid voltage fluctuations within the voltage standard specifications.

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Elso Rodriguez

Papers

Active Power Management for PV Systems under High Penetration Scenario

Central Energy Storage System to Reduce the Harmful Effects of PV Systems under a High Penetration Scenario