This paper proposes a novel adaptive droop (ADC) control for voltage source converter (VSC)-based multiterminal medium-voltage direct current (MT-MVDC) distribution systems with heterogeneous energy storage system (ESS) participation. The proposed ADC scheme can achieve MVDC bus voltage management and power sharing between VSCs with overloading operation, solving the issue that all VSCs on the rectifier/inverter side reach their power limits concurrently after a large system disturbance. This is accomplished by factoring in the real-time power/voltage values at VSC stations along with an extended power component. This component is contingent on the actual operational state of the ESSs and inversely correlated with the power delivered/absorbed by the ESSs. Moreover, the controllers of the battery and ultracapacitor systems incorporate two additional control loops, a novel VSC excess power reduction (VEPR) loop as well as inner expanded excess power reduction (EEPR) loop, to obtain the power reference values. The two loops ensure all VSCs operate within individual power limits after the engagement of the ESS. The effectiveness of proposed ADC strategy is confirmed through real-time simulations in a hybrid AC/MT-MVDC system.

This paper addresses the challenge of high peak loads on local distribution networks caused by fast charging stations for electric vehicles along highways, particularly in remote areas with weak networks. It presents a multi-stage, multi-objective optimization algorithm to determine the battery energy storage system (BESS) specifications required to support the infrastructure. The algorithm results in the minimum BESS capacity and power rating required, subject to the various specific constraints to comply with distribution grid power quality standards by limiting the peak grid demand whilst taking into account several factors over one day, i.e., daily traffic patterns (used to estimate charging system demand), and details of the local electricity network (demand patterns). The optimization method was demonstrated using actual data from an intercity highway and electricity distribution network in a remote highway mid-way between two cities in New South Wales, Australia. The results showed that no BESS is needed up to a critical EV penetration rate, above which both the required BESS capacity and output power capability increase rapidly with the EV penetration rate.

AbstractCapacitive power transfer (CPT) has emerged as a promising alternative to traditional inductive methods. CPT offers advantages like cost‐effectiveness, reduced weight and volume, and greater tolerance to alignment errors. However, the high‐Q resonant circuits used as matching networks can be susceptible to high voltage stress, especially when transmitting substantial power. Consequently, designing matching networks for CPT systems necessitates consideration of multiple parameters, including practical constraints such as component losses and breakdown thresholds. In this work an innovative algorithm is presented for designing practical matching networks in CPT systems. The algorithm conducts a methodical search of potential solutions, and converges on component values that maximize power transfer efficiency whilst also minimizing component voltage stress. The proposed algorithm is demonstrated theoretically and experimentally.

Within the context of multi-coil inductive power transfer (IPT) systems, the presence of mutual induction between same side coils has been a considerable challenge since it directly impacts system stability and performance. In this paper, a mathematical model is presented to accurately estimate the location of a null point in mutual inductance between two planar spiral circular coils. The impact of coil design parameters such as vertical separation, fill factor and outer radius are investigated for impact on null point location. This model is then verified against finite element analysis simulation results. The identified location of the null point is within a maximum of 0.39% error. The findings of this work are directly applicable to the design of multi-coil inductive power transfer systems where decoupling between same-side coils is advantageous to achieving high efficiency and power capability.

In hybrid ac/multi-terminal medium -voltage dc (AC/MT-MVDC) systems with multiple voltage source converters (VSCs) and dc/dc converters, it is essential to attain accurate initial power flow (PF) and post -event power distribution solutions efficiently. This paper proposes: (i) a novel sequential PF algorithm for hybrid AC/MTMVDC systems by a Fibonacci search -based Newton-Raphson (FSNR) approach with uniform MVDC bus type definition, while considering power losses and varied control schemes of different converters; (ii) a zero error steady-state post -event power distribution calculation method under droop control by the introduction of dynamic I/V droop coefficients based on the FS algorithm. The FSNR approach simplifies the MVDC PF derivation by only requiring the definition of the dc current bus type, effectively eliminating the need to solve multiple sub-Jacobian matrices. Furthermore, the post -event power distribution analysis offers precise power redistribution calculation approach following disturbances by considering both open- and closed -loop operation in an MT-MVDC distribution system. The computational efficiency and validity of the proposed PF algorithm, along with the accuracy of presented post -event power distribution calculation method are verified through Python and RTDS real-time simulators in an extended MT-MVDC distribution network incorporated with the IEEE 14/33/69 bus transmission/distribution systems.

Light rail vehicles (LRVs) are increasingly in demand to sustainably meet the transport needs of growing populations in urban centres. LRVs have commonly been powered from the grid by direct-contact overhead catenary systems (OCS); however, catenary-free direct-contact systems, such as via a "hidden rail", are popular for new installations. Wireless power transfer (WPT) is an emerging power transfer (PT) technology for e-transport with several advantages over direct contact systems, including improved aesthetics and reduced maintenance requirements; however, they are yet to be utilised in LRV systems. This paper provides a review of existing direct-contact and wireless PT technologies for LRVs, followed by an in-depth critical assessment of inductive power transfer (IPT) and capacitive power transfer (CPT) technologies for LRVs. In particular, the feasibility and advantages of CPT for powering LRVs are presented, highlighting the efficacy of CPT with respect to power transfer capability, safety, and other factors. Finally, limitations and recommendations for future works are identified.

A novel adaptive droop control (ADC) is proposed in this paper for voltage source converter (VSC)-based medium-voltage direct current (MVDC) distribution systems. The proposed ADC can achieve MVDC bus voltage management and power sharing between VSCs with overloading operation consideration, solving the issue that all VSCs on the rectifier/inverter side reach their power limits concurrently after a large system disturbance. It is accomplished by factoring in the real-time power/voltage values at VSC stations and a newly introduced extended power component. This component is contingent on the actual operational state of the energy storage systems (ESSs) in MVDC systems and inversely correlated with the power delivered/absorbed by the ESSs. The effectiveness of proposed ADC is confirmed through an MVDC distribution system model built in RTDS real-time digital simulators.

In order to address the gap in comprehensive power flow (PF) analysis of multi-terminal medium-voltage direct current (MT-MVDC) distribution systems, this paper proposes a novel decoupled sequential PF algorithm based on Newton-Raphson (NR)/estimation-correction method. The presented algorithm is designed for an MT-MVDC distribution network and takes into account the PF equations of both generic ac/dc and dc/dc converters. The MVDC PF study is the main focus and the power losses of voltage source converters (VSCs) & dc/dc converters are considered for accurately deriving the dc powers at MVDC links. The proposed algorithm only requires to define a single dc power or current bus type, hence the bus type definition is simplified and the solution of multiple sub-Jacobian matrices can be avoided. A binary search method is employed to correct the estimated initial dc power/current values, which contributes to the searching time reduction. Although an external correction iteration is required in the dc PF derivation, the proposed algorithm still improves on the computation efficiency in comparison with coupled sequential ac/dc PF algorithms. An MT-MVDC distribution network incorporated into IEEE 14 bus system verifies the validity and efficiency of the proposed algorithm.

We demonstrate the use of the electrooptic effect to control the propagation constant of the guided modes in silicate few mode fibers with internal electrodes. The electrooptic effect induces a perturbation of the fiber’s refractive index profile that controls intermodal interference. To increase the electrooptic effect the silicate fibers are poled. The response time is in the nanosecond range.

As the number and range of electric vehicles in use increases, and the size of batteries in those vehicles increases, the demand for fast and ultra-fast charging infrastructure is also expected to increase. The growth in the fast charging infrastructure raises a number of challenges to be addressed; primarily, high peak loads and their impacts on the electricity network. This paper reviews fast and ultra-fast charging technology and systems from a number of perspectives, including the following: current and expected trends in fast charging demand; the particular temporal and spatial characteristics of electricity demand associated with fast charging; the devices and circuit technologies commonly used in fast chargers; the potential system impacts of fast charging on the electricity distribution network and methods for managing those impacts; methods for long-term planning of fast charging facilities; finally, expected future developments in fast charging technology and systems.

Transmission and distribution networks based on medium voltage direct current (MVDC) solutions have the potential to provide higher power quality, greater power transmission/conversion efficiency, enhanced power supply reliability/stability, improved power supply capacity, and more efficient corridor utilisation compared to an equivalent ac system. Moreover, MVDC networks can facilitate the integration of renewable energy sources (RESs), energy storage systems (ESSs), and the increasing number of dc loads. However, these systems are still in early development stages; their advantages in need of clear demonstration before large-scale commercial adoption. This paper explores general MVDC network structures and different application scenarios focusing on cases of particular interest to Australian power systems and to Australia in general. Areas of interest are identified and equipment requirement, protection schemes and related challenges are also discussed, highlighting both technical barriers and possible development directions.

Economic dispatch is a critical problem in operation of power grids. A consensus-based algorithm was recently proposed to solve the economic dispatch problem in a distributed manner. In this paper, we propose a novel secure scheme for the consensus-based economic dispatch algorithm using the Paillier cryptosystem. This secure scheme ensures that not only the network transmitted information is protected from external malicious party but also the privacy information of each node remains intact. The proposed secure scheme has two features. First, it relies on the solution to the so-called structural consensus problem with time-varying network weights. Second, it contains a strategy for transmitting encrypted information and generating network weights with randomness, as well as treatment of the practical issues like quantization error and computation overflow/underflow. The performance in terms of cost optimization and privacy-preserving is verified by rigorous theoretical analysis and numerical simulation.

High penetration of electric vehicles with unmanaged clustered charging will cause unwanted peaks in the electric network. It is important for the system operator to manage the impact of EV charging on the power system. This work developed a model to construct the aggregated charging load due to EVs in a parking lot while considering EV travel patterns, usage and charging needs. The EV charging load was combined with the system load to determine the reliability of the composite power system. IEEE-RTS 24 bus was used as a test system to demonstrate the efficacy of the proposed method. The DC load flow with linear programming having an objective function of minimum load curtailment was carried out to evaluate the reliability index (i.e. loss of load probability (LOLP)). The model has been validated for Shopping Center Parking Lots. Results showed that due to uncontrolled charging of EVs, the LOLP of the power system could reach up to 2.3% in peak hours, whereas acceptable LOLP is <; 1%. However, to maintain the reliability of the power system, it is recommended to either manage or limit the load assigned to parking lots equipped with EV chargers.

The increasing penetration of electric vehicles (EVs) brings challenges and opportunities for power systems. One particular opportunity concerns the use of parked EVs to provide energy and associated services to the grid. In this work, the potential energy storage capacity of parking lots (PLs) of EVs is computed using the proposed stochastic model which considers the sporadic nature of the EV' behaviours (i.e. arrival/departure, battery degradation, travel pattern, charge/discharge rates). The analysis was performed for two types of PLs with very different occupancy distributions, i.e. a shopping centre PL, and a workplace PL. In both cases, the available energy storage capacity of EVs was estimated hourly using real household travel data, i-MiEV data and car park occupancy records. The results show that the aggregated energy storage capacity closely follows the occupancy of EVs in the PLs, and is substantial, with little sensitivity to charging rate. The proposed stochastic modelling considered the variations in energy consumption, battery degradation, and user behaviour, predicted 13.4% less peak capacity than deterministic modelling. Moreover, the authors conclude that the shopping centre PL is a viable energy resource to the grid, with their scale and throughput compensating for the relatively low occupancy.

This study investigates a single-phase common-ground transformerless inverter topology for grid-connected photovoltaic (PV) systems. The inverter shares a common ground with the grid and utilizes minimal components for power conversion, making it suitable for use as an integrated microinverter for solar PV modules. The peak of the ac output voltage is the same as the input DC voltage, and a virtual DC bus capacitor is used to provide power during the negative cycle of the inverter. A simple unipolar sinusoidal pulse-width modulation technique is used to modulate the inverter minimizing switching loss, output filter requirements, and output current ripple. Moreover, a double-charging process is employed to minimize the inrush charging current of the virtual DC bus capacitor. Various operating states along with the design guidelines for choosing the constituent components are presented. Finally, some simulation and experimental results are presented for a 1 kW prototype to validate the proposed topology.

With the continuous increase in distributed energy resources that are being integrated into the utility grid, it becomes necessary for inverters to estimate the grid impedance online to be used for several applications. Despite the fact that online grid impedance estimation techniques using grid-connected inverters gained more attention recently, no comprehensive study has been evaluating the performance of different estimation techniques under several grid conditions. This study proposes an extensive comparison to assess the accuracy of two online frequency-based grid impedance estimation techniques at the fundamental frequency. These two techniques are based on the 75 Hz frequency injection technique and pseudo-random binary sequence injection, respectively. Results from MATLAB/Simulink and PLECS RT Box present the advantages and disadvantages of these estimation techniques and the required trade-offs. This comparison study analyses the effects of disturbance magnitude and its injection time, the variation of grid impedance and non-ideal grid voltage. Furthermore, solutions are proposed to enhance the estimation accuracy of both techniques for non-ideal grid voltage containing inter-harmonics and sub-harmonics. The study concludes with recommendations regarding the best use of these two frequency-based grid impedance estimation techniques to suit a particular low voltage grid scenario.

Pyrolysis is a well-established method of converting biomass to different types of value-added products, such as high energy density biofuels and chemicals. In this work, chicken-litter waste and rice husk were pyrolyzed at different temperatures with the aim of investigating the thermal behavior and energy recovery potential of the feedstocks. Computer aided thermal analysis and thermogravimetric analysis were employed to study the pyrolysis properties of each biomass in a temperature-controlled regime. The specific heats of chicken litter and rice husk samples during their pyrolysis and the energy content of their pyrolysis products were investigated to determine the energy required to complete the pyrolysis of each sample and the energy recovery potential of each pyrolytic product. Most of the volatile products were evolved at 350 to 450 degrees C with CO2, CO, and CH4 being the dominant gas products from both samples throughout the pyrolysis process. At 500 degrees C and at a heating rate of 10 degrees C/min, the gas, bio-oil, and biochar yields from chicken litter and rice husk were in the ranges of 18 to 19, 35 to 39, and 42 to 47 wt %, respectively, with a total recoverable energy value of 12.7 MJ/kg from chicken litter and 13.9 MJ/kg from rice husk. The energy consumed to heat the samples to the final pyrolysis temperature of 500 degrees C was also estimated to be 1.2 and 0.8 MJ per kilogram of chicken litter and rice husk, respectively. With the measured values, the efficiency of the pyrolysis of chicken litter and rice husk samples is estimated to be 84% and 89%, respectively, assuming the heat required to carry out the pyrolysis process is supplied by combustion of the evolved pyrolytic gas products. If the pyrolysis is instead driven by solar thermal energy, the overall efficiency will increase to 92% for the chicken litter and 94% for the rice husk pyrolysis.

Buildings and transport consume two thirds of the total global energy. It is desirable to maximize the use of renewable generation in these sectors, and to optimize the use of that energy by managing diverse sources and loads. This is particularly challenging in high-density residential premises where the space for such infrastructure is limited, and storage can have significant impact on energy utilization and demand. In this paper, we have proposed an aggregator-based-strategy (ABS) to optimally utilize the available energy resources and storage in an apartment building with twenty households, each having an electric vehicle (EV), and an aggregated solar photovoltaic (PV) energy and stationary battery storage (BS) system. The strategy is flexible and can be applied to any building with EVs, solar PV and BS to minimize the cost of energy consumption without compromising the flexibility of energy usage or travel requirements. The model also accounts for the battery capacity degradation and its associated cost to make it more realistic. The model is evaluated using real data and the results show that the strategy not only reduces the cost of energy consumption but also reduces the amount of energy drawn from the grid significantly.

The application of the pseudo random binary sequence (PRBS) estimation technique for wideband grid impedance estimation using grid-connected inverters has gained more attention recently because of its several advantages. This includes its simple implementation in the control loop of the inverters and the small disturbance amplitude produced. In this context, this paper aims to evaluate the performance influences of the PRBS design parameters bit length, frequency resolution, and disturbance amplitude. This goal is achieved by exploring their effects on the grid impedance estimation accuracy and the produced total distortion (THD%+PRBS noise) of the inverter output current. A 3-phase balanced inverter system is simulated and investigated using MATLAB/Simulink based on a discrete-time model to show the trade-off of a real implementation such as the PRBS disturbance amplitude and the sampling frequency of the analog-to-digital converters. Simulation results show the trade-off between the investigated PRBS parameters and the accuracy and frequency range of the estimated grid impedance as well as the total distortion.

This paper presents a quasi-Z-source based isolated bidirectional DC-DC converter (qZIBDC) for renewable energy applications. The converter utilizes a dual active bridge circuit with a quasi-Z-source network on both sides, so the converter works as buck/boost converter from either side. It has a wider input/output voltage operating range, soft-switching capabilities without additional devices, and...