Multi-objective optimisation method for coordinating battery storage systems, photovoltaic inverters and tap changers

The many well-established advantages of distributed generation (DG) make their usage in active distribution networks prevalent. However, uncontrolled operation of DG units can negatively interfere with the performance of other equipment, such as tap-changers, in addition to resulting in sub-optimal usage of their potential. Thus, adequate scheduling/control of DG units is critical for operators of the distribution system to avoid those adverse effects. A linearised model of a multi-objective method for coordinating the operation of photovoltaics, battery storage systems, and tap-changers is proposed. Three objective functions are defined for simultaneously enhancing voltage profile, minimising power losses, and reducing peak load power. The formulated multi-objective problem is solved by means of the epsilon-constraint technique. A novel decision-making methodology is offered to find the Pareto optimality and select the preferred solution. To assess to proposed model's performance, it is tested using 33-bus IEEE test system. Consequently, tap-changers suffer lessened stress, the batteries state-of-charge is kept within adequate limits, and the DG units operation is at higher efficiency. The obtained results verify the effectiveness of this approach.fi=vertaisarvioitu|en=peerReviewed

Benefits of on-load tap changers coordinated operation for voltage control in low voltage grids with high photovoltaic penetration

3noThe transformers that connect the Medium Voltage (MV) grid with the Low Voltage (LV) system are classically equipped with tap changers with tap positions variable only at no load. The evolution of the technologies and the increasing needs of controlling the voltage profile in the LV networks require better control capabilities. The use of MV/LV transformers with On Load Tap Changers (OLTCs) is increasing, to provide further control capabilities in LV grids with high penetration of distributed generation. In this paper, centralised voltage control is evaluated by simulating the operation of an OLTC installed inside the MV/LV transformer substation. The goal is to stabilise the voltage at the LV bus of the transformer. It is supposed that the OLTC does not communicate with other devices in the grid; thus, it does not know the voltage levels at the other nodes. At the same time, the distributed PV inverters control the voltage in their grid connection points without any information about the other nodes. The expected benefits of exploiting OLTCs in LV grids with high photovoltaic (PV) penetration are determined through indicators that assess the voltage deviations with energy flows, the global overvoltage or undervoltage persistence, and the overvoltage or undervoltage duration. The results show that the use of an OLTC can help the mitigation of voltage fluctuations, especially limiting the undervoltages. The effectiveness strongly depends on the control parameters, especially the maximum number of daily taps.partially_openopenCiocia A.; Chicco G.; Spertino F.Ciocia, A.; Chicco, G.; Spertino, F

Ancillary Services in Hybrid AC/DC Low Voltage Distribution Networks

In the last decade, distribution systems are experiencing a drastic transformation with the advent of new technologies. In fact, distribution networks are no longer passive systems, considering the current integration rates of new agents such as distributed generation, electrical vehicles and energy storage, which are greatly influencing the way these systems are operated. In addition, the intrinsic DC nature of these components, interfaced to the AC system through power electronics converters, is unlocking the possibility for new distribution topologies based on AC/DC networks. This paper analyzes the evolution of AC distribution systems, the advantages of AC/DC hybrid arrangements and the active role that the new distributed agents may play in the upcoming decarbonized paradigm by providing different ancillary services.Ministerio de Economía y Competitividad ENE2017-84813-RUnión Europea (Programa Horizonte 2020) 76409

Reducing Voltage Volatility with Step Voltage Regulators: A Life-Cycle Cost Analysis of Korean Solar Photovoltaic Distributed Generation

To meet the United Nation’s sustainable development energy goal, the Korean Ministry of Commerce announced they would increase renewable energy generation to 5.3% by 2029. These energy sources are often produced in small-scale power plants located close to the end users, known as distributed generation (DG). The use of DG is an excellent way to reduce greenhouse gases but has also been found to reduce power quality and safety reliability through an increase in voltage volatility. This paper performs a life-cycle cost analysis on the use of step voltage regulators (SVR) to reduce said volatility, simulating the impact they have on existing Korean solar photovoltaic (PV) DG. From the data collected on a Korean Electrical Power Corporation 30 km/8.2 megawatts (MW) feeder system, SVRs were found to increase earnings by one million USD. SVR volatile voltage mitigation increased expected earnings by increasing the estimated allowable PV power generation by 2.7 MW. While this study is based on Korean PV power generation, its findings are applicable to any DG sources worldwide.11Nsciescopu

Power Loss Minimization for Distribution Networks with Load Tap Changing Using Genetic Algorithm and Environmental Impact Analysis

This paper presents an investigation of the IEEE 34 bus test system benefits with deployment of distribution static compensator (DSTATCOM) and distributed generation (DG) in the aspect of power loss minimization, bus voltage stability and greenhouse gas emission mitigation. Power loss minimization is carried out by adjusting tap changer positions of the load tap changing transformer with one of the well-known metaheuristic algorithms, Genetic Algorithm (GA). To check the voltage stability of the system after minimization, bus voltage profile index is developed. Similarly, environmental profile is evaluated by three different indices. The behaviour of the system is analysed for four different cases as follows. In Case 1, voltage and reactive power control is provided by capacitor banks. In Case 2, capacitor banks are replaced with DSTATCOM. In Case 3 and Case 4, Case 1 and Case 2 are reinvestigated in the presence of additional DG. All cases are evaluated with both traditional Newton- Raphson optimization algorithm and evolutionary-based GA optimization algorithm. The results indicate that GA optimization provides more energy savings than traditional optimization in all cases with bus voltage index within the allowed range. Besides voltage profile of the system in all cases with two algorithms supports the fact that evolutionary-based metaheuristics offer the best choices for a non-linear optimization problem in comparison with the traditional optimization methods. The overall results reveal that Case 4, test system with DSTATCOM and DG, is the best case which provides minimum power losses and a significant amount of emission savings with greenhouse payback time (GPBT) of 0.458 years

On Accelerated Aging of Mechanical Assets in Distribution Systems with Renewable Generation

The integration challenges associated with the widespread adoption of the photovoltaic generation can be divided into operational and the maintenance issues. Work done in recent years has addressed issues like voltage rise and unbalance. Less attention was directed to the maintenance challenges like accelerated aging of mechanically controlled voltage support assets under rapidly changing conditions. In particular, there is need for analysis on the mechanism of accelerated wear and tear of devices such as on-load tap changers and capacitor banks exposed to rapid voltage fluctuations. Such an analysis relies on development of lifetime models of switching devices to study the impact of increased stress, whether electrical or mechanical, on operational life. This article focuses on developing such models and proposes the framework to study the impact of non-scheduled distributed generation on aging of mechanically-switched devices commonly used in distribution feeders

Secure High DER Penetration Power Distribution Via Autonomously Coordinated Volt/VAR Control

Traditionally voltage control in distribution power system (DPS) is performed through voltage regulating devices (VRDs) including on load tap changers (OLTCs), step voltage regulators (SVRs), and switched capacitor banks (SCBs). The recent IEEE 1547-2018 from March 2018 requires inverter fed distributed energy resources (DERs) to contribute reactive power to support the grid voltage. To accommodate VAR from DERs, well-organized control algorithm is required to use in this mode to avoid grid oscillations and unintended switching operations of VRDs. This paper presents two voltage control strategies (i) static voltage control considering voltage-reactive power mode (IEEE 1547-2018), (ii) dynamic and extensive voltage control with maximum utilization of DER capacity and system stability. Further, effective time-graded control is implemented between VRDs and DER units to reduce the simultaneous and negative operation. The proposed voltage control strategies are tested in a realistic 140-bus southern California distribution power system through extensive time-domain simulation studies. The results show that voltage quality in a distribution system is effectively achieved through the proposed voltage control strategies with a significantly reduction in the number of switching operations of VRDs. In addition, proposed voltage control strategies increase reliability and security of the DPS during unexpected failures

太陽光発電の最大利用に向けた低圧配電系統の需要・供給側におけるエネルギーマネジメントに関する研究

早大学位記番号:新7825早稲田大