ASSESSMENT OF PROSUMER PHOTOVOLTAIC INSTALLATION IMPACT ON VOLTAGE VARIATIONS IN LOW-VOLTAGE NETWORKS

Recent investigations on the evaluation of solar PV hosting capacity in LV distribution networks constrained by voltage rise

The objective of this paper is to show the characteristics of smart meters enabling to monitor and analyze the low-voltage (LV) network. This is achieved by developing use cases, where power quality and outage data are transferred from smart meters through distribution network to the control center. To visualize the monitoring process of LV network, the use cases are mapped into smart grid architecture model. The paper proposes a solution to analyze the LV network interruption and power quality problems (over-voltage, under-voltage, voltage sags, and swells). Thus, this paper provides a smart platform for monitoring LV network.

Active power management in low voltage networks with high photovoltaics penetration based on prosumers’ self-consumption

The increasing photovoltaic (PV) power sources connected to low-voltage (LV) distribution networks generate a new grid environment featuring various types of power generations near consumers and bidirectional active and reactive power flows. However, the large-scale deployment of PVs is hindered by the power quality problems, particularly voltage deviation. To overcome this obstacle, proper mitigation techniques should be developed to eliminate the negative impacts of high-PV penetration in LV networks. This article provides an in-depth review of recently developed technologies that prevent voltage deviation in LV grids with PVs. Following an investigation of the voltage fluctuation phenomena along the distribution feeder due to variable PV output and power demand, the mathematical relationship between power flow and voltage level is revealed. The solutions that mitigate the voltage variation are then investigated and classified. Their effectiveness, advantages, and disadvantages are illustrated. Finally, the current trend in grid integration of PVs and other distributed generators (DGs) under future grid framework is discussed. Voltage Deviation Challenge.

This paper presents the results of experiment-based simulation aimed at analyzing the harmonic distortion behavior of nonlinear loads and the background voltage distortion of power supply in building low-voltage (LV) distribution network. The procedure of constructing experiment-based simulation model and harmonic monitoring at various points of common coupling (PCCs) in LV network are introduced for analyzing voltage and current harmonic distortion behavior due to attenuation effect. The model is proposed for future microgrid modeling analysis at different PCCs in LV networks. The simulation model was constructed from captured harmonic data and the corresponding LV network topology. The simulation model has been verified by comparing with field measurement results. The VTHD and ITHD relationship curve and the attenuation effect curve for personal computers (PC) have been proposed by using the simulation model. In particular case study has been conducted to compare the conventional and state-of-art switch mode power supply (SMPS) used in PCs.

The paper proposes a new local method of controlling the on-load tap changer (OLTC) of a transformer to mitigate negative voltage phenomena in low-voltage (LV) networks with a high penetration of photovoltaic (PV) installations. The essence of the method is the use of the load compensation (LC) function with settings determined via artificial neural network (ANN) algorithms. The proposed method was compared with other selected local methods recommended in European regulations, in particular with those currently required by Polish distribution system operators (DSOs). Comparative studies were performed using the model of the 116-bus IEEE test network, taking into account the unbalance in the network and the voltage variation on the medium voltage (MV) side.

The growing penetrations of rooftop photovoltaics (PVs) into low-voltage (LV) distribution networks are challenging voltage regulation. Developing an effective volt-var (VV) control has been the focus of many researchers with various approaches proposed so far. However, assuming a single voltage level and balanced network model, widely adopted in existing literatures, tends to cause inaccurate and even infeasible control solutions. Besides, existing distribution VV control studies are usually based on the day-ahead predictions of PV generations and loads, introducing inevitable and non-negligible errors. To address the challenges above, this paper proposes a VV co-optimization across unbalanced medium-voltage (MV) and LV networks, by traditional and emerging techniques, to ensure the network operation with the required power quality. Specifically, the operation of MV delta-connected switched capacitors and LV distributed PV inverters is coordinated, under a three-stage strategy that suits integrated and unbalanced radial distribution networks. The proposal aims to simultaneously improve voltage magnitude and balance profiles while reducing network power loss, at the least controlling cost. To effectively solve the proposed VV optimization problem, a joint solver of the modified particle swarm optimization and the improved direct load flow is employed. Finally, the proposal is evaluated by simulations on real Australian distribution networks over 24 h.

Probabilistic framework for evaluating droop control of photovoltaic inverters

THE PURPOSE. Due to the increase in the number of farms in the Devashtichsky district of the Sughd region of Tajikistan, over the past 3-4 years, a disproportionate distribution of electricity in the 0.4 kV network has been observed. Unbalance currents of phase loads in relation to asymmetric phase voltages at the terminals of consumers of a three-phase network cause additional losses of electricity, which can reach 21% of the standard losses. In the decree of the President of the Republic of Tajikistan dated May 10, 2009 No. 29 “On energy saving and reduction of electricity losses” it is indicated that there is a need to study the quality of electricity in rural 0.4 kV networks and its compliance with GOST 32144. 2013, as well as an assessment of losses electricity in its distribution structure is an important task in the field of rural electricity. METHODS. A single-line diagram of a 0.4 kV network with initial parameters, which were refined during the survey of the network, and the current loads of outgoing lines were investigated. Experimental studies of the quality of electricity and assessment of the level of losses in the low- voltage network were carried out using a complex measuring device «Energotester» PKE - A - C4. RESULTS. The studies allowed obtaining data on the daily consumption of electricity in individual outgoing lines, information on the characteristics of consumers, digital information (database) on indicators of the quality of electricity in low-voltage networks. CONCLUSIONS. It has been established that the main factors influencing the losses of electricity in low-voltage networks are: incommensurability of the power of transformers of transformers and consumers, uneven loading of individual phases, a significant effect of individual converters on the quality of energy. Measures are forecasted to reduce losses and improve the quality of electricity in low-voltage rural networks of 0.4 kV.

This paper provides an analysis on the main voltage regulation techniques, PF(P) and Q(U) that can be applied in the low voltage (LV) network with standard photovoltaic (PV) inverter technology. The investigations are done by simulating the power flow in the LV and MV network over one year, with real load and irradiance profiles. The conclusion is that by installing a certain amount of solar PV in the LV network, the losses in the network can be reduced. For Denmark with around 70 000 distributions transformers and underlying LV networks, the yearly reduction of losses in the LV network could supply approximately 14 500 households. Another results is, that a normal distribution transformer can host up to 140% solar PV power without being significantly over-loaded.

The intermittent injection of power and the nature of power electronic devices used for photovoltaic (PV) systems can affect the power quality (PQ) of the grid to which they are connected. This study proposes to quantify and evaluate the impact of PV injection on the PQ of a low-voltage (LV) network by applying a statistical analysis through hypothesis testing for the mean comparison of populations of parameters with and without a PV system. The effects of PV power injection and load demand at the point of common coupling on PQ are monitored. The methodology includes the selection and monitoring of PQ, the use of a matrix for classification of data with similar load and PV power injection conditions, and the application of the Wilcoxon rank sum test. This methodology was applied to evaluate the impact of a 9.8 kWp PV system on the PQ of an LV network.

The decarburization of heat and transport using electric vehicles (EVs) and heat pumps (HPs) needs an important investment in low-voltage (LV) networks. This article proposes an optimization approach to estimate the availability of headroom for domestic EV charging and optimization on LV networks under various penetrations of heat pumps. The proposed optimization approach is called dynamic differential annealed optimization (DDAO). The objective of the proposed approach is to maximize the hosting capability of low-voltage networks for EVs and HPs by optimizing the flexibility of EV charging. The DDAO is used to optimize different aspects of EV charging and LV networks. The DDAO approach is implemented in three steps: (a) HP headroom assessment, (b) EV optimization, and (c) validation. The performance of the proposed method is validated on a MATLAB platform and compared with the existing Binary Spring Search Algorithm (BSSA), Manta Ray Foraging Optimization Algorithm (MRFO), and Chaos Game Optimization methods. In comparison to the total prices of 3.5£ in BSSA, 4.5£ in MRFO, and 5.5£ in CGO, the proposed DDAO method achieves a lower total price of 3.2£. This suggests that the DDAO method is more cost-effective than the existing techniques.

This paper deals with power quality (PQ) problem in low-voltage network. It is focused on voltage variations, unbalance, fluctuation, harmonic and their impact on customers. The introduction concerns with general resources and impacts of the deterioration PQ in networks. A measurement was focused on consumers in the Czech Republic who are supplied by the power line from the Slovak Republic. Next part was focused on processing measurement values in this point with using PQ analyser. This values were used for creating simulation. The paper includes initial recommendations for improve PQ in this problematic area.

The increasing deployment of residential photovoltaic (PV) systems poses a significant operational challenge to low-voltage (LV) distribution networks. Most PV systems in Malta are installed in a uniform south-facing orientation with low tilt angles, to maximize energy yield throughout the year. However, the synchronized generation peaks accentuate reverse power flows through the network, resulting in overvoltage issues and the exceedance of line current ratings. This paper investigates how PV orientation and tilt angles can be used as a passive mitigation measure to reduce technical issues in LV networks. Using a synthetic Maltese residential feeder, four PV deployment scenarios have been investigated. These combined two tilt angles (10° and 35°), and two orientation strategies (uniform south-facing and mixed south-east-west) within a Monte Carlo simulation. Results show that both increasing the tilt angle from 10° to 35° and changing the orientation strategy from uniform south-facing to mixed reduces overvoltage issues and flattens the utilization factor curves. The total energy yields are also quantified for each scenario. This demonstrates that simple design choices can maintain high PV hosting capacity without the need for active control or costly grid reinforcement.

The paper presents aspects related to Smart Grid observability and Power Quality assessment in medium and low voltage networks, by using the Unbundled Smart Meter (USM) concept [1]. Smart meters are placed at the border of connection point to the network, for any prosumer and when deployed through large roll-outs, become the most abundant equipment in active distribution networks. With this near future in mind, our approach is securing Smart Grid observability and improved Power Quality (PQ) assessment based on distribution of probabilities, to improve operation & control of active networks in the presence of distributed energy resources and to provide Smart Grid services such as voltage secondary control and congestion avoidance in medium / low voltage networks. The paper presents also some results of using Unbundled Smart Meter solution already deployed in real environments pilots in two distribution networks: Alginet/Spain and Bucharest/Romania.