Distributed photovoltaic (PV) accessed to DC distribution power system (DPS) from multi-port is a major form to promote the consumption of renewable energy, but the increase of PV permeability will ...lead to the deterioration of the system stability. Traditional analysis usually concentrates on the DC micro-grid and the analysis of DC DPS with multi-voltage levels, such as medium and low voltage DC DPS, is rarely involved. This paper proposes a decentralized unified control strategy for the medium and low voltage DC DPS. It is composed of two parts, one is the decentralized control strategy based on the DC bus voltage signal (DBS) for the PV, storage and fuel cell units on the DC bus; one is the unified control strategy for the DC transformer integrating the power control, medium voltage and low voltage DC bus voltage regulation functions. Consequently, it avoids the control mode switching of DC transformer and can achieve the global power sharing of the system. Finally, the equivalent simulation model of medium and low voltage DC DPS is built in Matlab/Simulink and simulation analysis of multiple operating states and scenarios is carried out to validate the effectiveness of the proposed control strategy.
For power shortage and no electricity areas, building wind/pv hybrid islanded DC microgrid with multiple energy storages can reduce the power supply insufficient or imbalance caused by single energy. ...It can improve system performance and power supply reliability, and is advantageous to the complementary advantages and coordination control between various micro-sources. Ring topology is adopted with more flexibility and higher reliability. Then three different operation modes are proposed, that is energy storage voltage regulation mode, wind/pv power reduction mode, and load shedding mode. According to the regulation of DC voltage operating range, the voltage segment control strategy is proposed, to ensure energy storage units, power generation unit and loads are all involved in the coordinated control. They can adjust the DC voltage automatically according to their priorities. For multiple energy storage units, droop coefficient of droop control is adjusted dynamically based on load power share. In addition, control methods of converters in each voltage segment are analyzed to meet different operation requirements, such as changes of wind speed, intensity of light and loads, or energy storage reaching limit value. The control strategy can be extended to other distributed power-based DC microgrids. Finally, the proposed control is validated by simulations using MATLAB/Simulink.
Most of the photovoltaic (PV) power plants in operation are equipped with a certain proportion of Static VAR Generator (SVG). The reactive power and voltage control system in PV power station ...achieves the control objectives of the dispatching mechanism by controlling SVG, without considering the reactive power and voltage regulation ability of the inverters themselves. To better exert the reactive power and voltage support ability of the PV inverters, reduce the SVG system investment and later O&M costs. It is necessary to introduce new voltage regulation methods. This paper focused on a hybrid reactive voltage regulation, method and control strategy based on energy storage system and PV inverters. By combine the good response characteristics of energy storage battery and optimizing the configuration and coordination control, it can not only respond to the second-level steady-state reactive power demand of PV power station, but also respond to the millisecond-level reactive power demand. The ability of second-order transient voltage fluctuation was verified by the example of Luneng Haixi Demonstration Project, which satisfies the power system requirements for ability and speed of reactive power regulation, and plays a role in replacing SVG to a certain extent.
To manage the growing penetration of renewables and electric vehicles (EVs), a concept of clean energy on wheels (CEW) is presented for active distribution networks in smart cities. The CEW is an EV ...fully equipped with battery energy storage systems and EV chargers to improve the performance of modern distribution systems, especially in peak load hours. A multi-area power flow calculation method is employed to predict energy surplus and deficit feeders and locations at the same time. A bi-level optimisation framework is developed to determine the integration buses and capacities of PV systems and CEW vehicles in multiple distribution systems in smart cities. A Peer-to-Peer (P2P) energy trading scheme is adopted to obtain optimal scheduling and power dispatch of CEW in different areas of the city. An improved version of the genetic algorithm is adopted to determine optimisation variables of both the levels. To demonstrate the applicability of the proposed model, eight low-voltage feeders of different areas are selected from the city. Moreover, multiple scenarios are proposed and investigated. The simulation results obtained are found to be promising to accommodate a high penetration of EVs and renewables while increasing the operational flexibility of associated distribution systems.
In recent years, the integration of large-scale wind/Photovoltaic (PV) generation with inherent uncertainties has played a vital role in the stability of modern power system, especially in the low ...frequency oscillation (LFO) regarding weather changes. This paper aims to conduct the LFO analysis when wind farm and PV power station are integrated into the existing power system. Based on eigenvalue analysis, the small signal analysis models of the Doubly-fed induction generator (DFIG) type wind farm and the PV station are built. The low frequency oscillation characteristics of the multimachine power system with integration of wind farm equipped with PMSG and PV power station are elaborately studied under the MatlabTM environment. In addition, the influence on LFO modes is investigated in depth when the wind speed and light intensity fluctuate independently. In particular, a multivariate probability distribution of wind speed and light intensity is applied to simulate the real conditions of the multimachine system incorporating wind/PV generation. The Monte Carlo simulation technique based probabilistic small signal stability analysis is conducted to explore and exploit the impacts on the LFO stability. Some meaningful conclusions and comments are obtained by studying the damping ratios of the system.
Modern isolated microgrid requires flexible and intelligent control of inverter to minimize the power mismatch between renewable generators and load. Maintaining the voltage at load connection is one ...of the critical aspects of voltage regulation in the isolated microgrid. The power generation from renewable generators is not constant as well as load parameters. Also, the power flow control between renewable generators is another major issue in an isolated microgrid. In this study, the intelligent fuzzy-logic based inverter control (FLIC) is used to regulate the voltage at the load connected considered the change in load-parameter and variation in the renewable power generation. The power output from the renewable generators is converted in DC to make the DCbus, which helps to maintain the power flow control between renewable generators and battery storage. The variation in the DC bus voltage is kept within acceptable limit using PI battery controller. The FLIC uses the error in the reference voltage and difference between the line-to-line voltage to generate firing pulses based on if-then rules. PV and renewable wind generator modeled with MPPT control for optimal power generation.
Overcoming local limitations in distribution grids with high photovoltaic (PV) penetration may be a challenging issue with non-optimal costs if appropriate planning strategies and regulations are not ...utilized. The installation of PV systems should be done according to local grid capability in order to avoid costly reinforcements. Careful consideration of the PV hosting capacity limits can help significantly in maintaining the secure and healthy operation of the electricity grid and can help avoid damages caused by violating thermal limits or by exceeding the voltage limits set by EN 50160 during times of high PV power production. In this paper, the methodology and approach followed to define the maximum PV capacity of a typical urban distribution grid is presented and analysed. The application of alternative measures at distribution grid level such as the local voltage support via reactive power regulation is investigated in finding optimal operating conditions for increasing PV capacity. It has been demonstrated that the urban distribution grid under consideration can accommodate a PV hosting capacity that is comparable to the firm capacity (the allowed operating capacity of the substation by adapting the requirement of the Grid Rules for one contingency) of the transmission substation.
This paper investigates the effect of modelling of different aspects of renewable energy sources (RES) namely wind farms (WF) and photovoltaics (PV) plants as a first step towards development of the ...equivalent harmonic model of RES plant for harmonic propagation and mitigation studies in large transmission networks. The paper proposes a set of scaling factors that can be used when modelling the whole RES plant as a single harmonic source, considering different weather conditions, configurations, and harmonic cancellation effects of RES plants. The results facilitate the assessment of global contribution of power electronics connected RES to harmonic levels in transmission networks and more generally harmonic propagation studies in large power electronics reach transmission networks.
This paper proposes a topology of electric vehicle (EV) DC fast charging station (FCS) considering the access and applications of distributed PV (DPV) generation (such as rooftop PV, carport PV and ...building integrated PV) and hybrid energy storage systems (HESS), all the PV generation systems, hybrid energy storage systems and EV DC chargers are connected to a common DC bus in the way of plug and play. Considering the state of charge of super-capacitor energy storage system and power flow variation rate of DC bus, a fuzzy control based power flow control strategy (namely an optimal power allocation strategy between battery and super-capacitor (SC) according to the variation of PV output power, power dispatch order of AC distribution network and EV fast charging power) is designed to achieve the maximum utilization of DPV and guarantee the safe and stable operation of EV DC fast charging station. Simulation results in Matlab/Simulink verify the effectiveness of the proposed strategy, which can improve the voltage stability of DC bus and control flexibility of power flow.
The GCC countries has a good location for the solar energy with high intensity of the solar radiation. This means that renewable energy provides many benefits for our climate, health and our economy. ...Photovoltaic PV becomes the new competitive energy resources of the planet and it can be engaged in both Distribution and Transmission systems. In the present study, considering design of solar cell for both Kingdom of Bahrain and United Kingdom (UK) with the same specification. The Panel Generation Factor (PGF) considered satisfying the specification of the cells, which depends on the climate. For both Kingdom of Bahrain and UK the total (kWp) of PV panel capacity, number of PV panels needed for design of 110 Wp PV module and Solar Charge Controller Rating are calculated based on PGF of each country.
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