Oluwaseun M. Akeyo

Abstract: This paper analyzes the configuration, design, and operation of multi-MW grid connected solar photovoltaic (PV) systems with practical test cases provided by a 10-MW field development. In order to improve the capacity factor, the PV system operates at its maximum power point during periods of lower irradiance, and the power output is limited to a rated value at high irradiance. The proposed configuration also incorporates a utility scale battery energy storage system (BESS) connected to the grid through an independent inverter and benefits of the experience gained with a 1-MW 2-MWh BESS large demonstrator. The BESS power smoothing and frequency regulation capabilities are illustrated though combined theoretical and experimental studies. The behavior of the grid connected PV and BESS combined system is studied using a modified IEEE 14 bus test system implemented in PSCAD/EMTDC. This paper also includes a sizing exercise for energy storage in order to provide dispatchable PV power.

Abstract: The multi-megawatt grid connected photovoltaic (PV) system studied in the paper includes parallel arrays and power electronic units, each with their own DC-DC and DC-AC converters. In one configuration, the DC-AC converters of adjacent parallel sections are connected in cascade, in order to effectively operate as a multilevel inverter, thereby reducing the filtering requirements. Grid voltage oriented control is employed for inverters and a battery is incorporated for energy storage and performance improvement. Modeling is performed with the PSCAD/EMTDC software, such that both the power electronics components, controls and subsystem aspects, and the electric grid power system issues, can be studied during steady-state and transient operation. The system simulation is demonstrated on a modified IEEE 14-bus test case.

Abstract: Typically, solar inverters curtail or “clip” the available power from the photovoltaic (PV) system when it exceeds the maximum ac capacity. This article discusses a battery system connected to the dc link of an inverter to recuperate this PV energy. Contrary to conventional approaches, which employ two dc–dc converters, one each for the battery and solar PV system, the proposed configuration utilizes a single dc–dc converter capable of simultaneously operating as a charge controller and a maximum power point tracking (MPPT) device. In addition to improving the overall system capacity factor, increasing the conversion efficiencies, and ensuring MPPT stability, the proposed configuration offers a simple solution for adding energy storage to existing PV installations. With this configuration, the excess power that will otherwise be curtailed due to inverter rating limitations is stored in the battery and supplied to the grid during periods of reduced irradiance. Moreover, a systematic methodology for sizing a dc-bus connected battery to minimize total PV energy curtailed was developed using an annual PV generation profile at the Louisville Gas and Electric and Kentucky Utilities E. W. Brown solar facility at Kentucky. The detailed behavior of the proposed system and its power electronics controls and operations were validated with case studies developed in PSCAD/EMTDC software for variable power generation and PV output power smoothing.

Abstract: Solar photovoltaic (PV) renewable energy systems are undergoing major technological developments and large-scale field deployment and electric grid integration. This paper proposes a method of expanding the capacity of an existing irrigation farm with additional pumps powered by solar PV. The system includes PV arrays and battery energy storage connected to a common dc bus, which energizes an array of variable speed inverter driven pumps. Capacity modulation is achieved by energizing an optimal number of pumps required in order to meet a particular load demand with minimum supply energy. A grid connection to the dc bus of the power electronic system is established via a bidirectional converter, such that active and reactive power demands can be both serviced. The controls and the steady-state and transient performance of the system are implemented and simulated with the PSCADTM/EMTDCTM software.

Abstract: According to some utility schedules, the electricity rate is variable such that homes may be encouraged to buy and store power in a battery when it is inexpensive, and self-consume or sell to the grid during other times. Power arbitrage through a battery energy storage (BES), can help maintain consumer comfort and minimize residential electricity bills. This paper reports the calculated daily energy costs incurred by different types of homes for a given utility electricity rate schedule. The homes exchange power among each other behind a section of the distribution network. A free market system is formed and the electricity rate is a function of time, depending on the instantaneous supply and demand of power. A real time control for the BES based on its state of charge, residential power demand, and electricity rate is proposed. Relative savings in homes are achieved through rooftop solar photovoltaic systems, or BES, or both. It is shown that all types of houses benefit from the transactive power flow.

Abstract: Due to the possibility of providing energy with much less dependence on the fossil fuels, renew-competent energy sources, in specified sun photovoltaic (PV) conversion have received elevated acceptance and progress in latest times. Big benefits of PV panels comprise easy and trustworthy power production and suitability for disbursed iteration. In addition the costs for photovoltaic modules is drastically lowering. To comprehend this issue, a control plan with modulation compensation scheme is likewise proposed. An exploratory three-stage seven-level cascaded H-bridge inverter has been manufactured using nine H-bridge modules (three modules for each stage). Each H-bridge module is associated with a 185-W solar panel. Simulation results are introduced to confirm the practicality of the proposed approach.

Abstract: This paper analyzes the configuration, design, and operation of multi-MW grid connected solar photovoltaic (PV) systems with practical test cases provided by a 10-MW field development. In order to improve the capacity factor, the PV system operates at its maximum power point during periods of lower irradiance, and the power output is limited to a rated value at high irradiance. The proposed configuration also incorporates a utility scale battery energy storage system (BESS) connected to the grid through an independent inverter and benefits of the experience gained with a 1-MW 2-MWh BESS large demonstrator. The BESS power smoothing and frequency regulation capabilities are illustrated though combined theoretical and experimental studies. The behavior of the grid connected PV and BESS combined system is studied using a modified IEEE 14 bus test system implemented in PSCAD/EMTDC. This paper also includes a sizing exercise for energy storage in order to provide dispatchable PV power.

Abstract: This paper analyzes the stability of a battery energy storage system (BESS) connected to the grid using a power electronic interface. It is shown that the internal resistance and internal voltage of the battery affect system stability. Variations in these parameters may occur due to aging and changes in the state-of-charge (SoC). Using average-value modeling, this problem is framed into a nonlinear system formulation and the region of stability as a function of the internal resistance and the internal voltage of the battery is determined. This paper also extends its results in determining the configuration of a battery pack in terms of the number of battery cells in series and parallel to prevent instability while meeting demand power requirements.

Abstract: This paper illustrates the implementation and the study of a hybrid electric power system based on a 10kW-diesel generator associated to renewable energy sources including a 10kW wind turbine, 12kW photovoltaic, and 53Ah lithium-battery. These energy production sources are interfaced to micro-grid through three-level power electronics converters where the phase-to-phase RMS voltage is 600V. The variable speed diesel generator is considered as the main energy source which is used to control the DC-bus voltage. The wind turbine and PV system are controlled using the Maximum Power Point Tracking (MPPT) technique with bipolar DC-bus voltage equilibration approach. The battery pack is used to compensate the intermittent power fluctuations from the wind turbine and PV system. The hybrid system control is ensured by the three-level converters (AC/DC, DC/DC, and DC/AC) using energy management based on frequency components allocation approach.

Abstract: In this paper, it is proposed a robust Second-Order Super-Twisting Sliding Mode Control for a Grid-connected inverter of a PV power plant. The proposed control strategy is able to maximize the energy extracted from the PV while regulating the DC-link voltage and achieving a power factor compensation and the reduction of currents harmonic distortion. Both in balanced or unbalanced condition, the grid is supplied by the PV plant with the desired active power and with the developed strategy, it is possible to use the inverter as a reactive power compensator. In order to prove the goodness of the proposed algorithm in terms of high efficiency and performance, some simulated and experimental results are carried out.