Bidirectional Power Flow Control Research Articles

Bidirectional DC - DC Converter Topology for Electric Vehicles Using Fuzzy Logic Controller

This project organizes an application of hybrid electric vehicle systems operated with novel designed bidirectional dc-dc converter (BDC) which interfaces a main energy storage (ES1), an auxiliary energy storage (ES2) and dc bus of different voltage levels. Proposed BDC converter can operate both step up and step-down mode. In which step up mode represents low voltage dual source -powering mode and step-down mode represents high voltage dc link energy –regenerating mode, both the modes are operated under the control of bidirectional power flow. This model can independently control power flow between low voltage dual source buck/boost modes. Here in, the circuit configuration, operation, steady-state analysis, and closed-loop control of the proposed BDC are discussed according to its three modes of power transfer. In this project fuzzy logic controller is used and also system results are validating through MATLAB/SIMULINK software. Index Terms—Bidirectional dc/dc converter (BDC), dual battery storage, hybrid electric vehicle, Fuzzy logic controller.

A hybrid approach for PV based grid tied intelligent controlled water pump system

SummaryThis article proposes a hybrid POA‐RBFNN approach for PV (photovoltaic) based grid tied intelligent controlled water pump system. The proposed method is the hybrid wrapper of Pelican Optimization Algorithm (POA) and Radial Basis Function Neural Network (RBFNN) and later it is termed as POA‐RBFNN method. On the basis of bidirectional power grids, this research presents bidirectional power flow control for PV systems. The water pump is driven through a three‐phase synchronous reluctance motor (RSM). A novel Cuk integrated Landsman converter can operate at low duty cycles to provide larger DC voltages with negligible switching losses is used. In addition, to enhance the pumping system reliability, solar panels and electric pumps can be used to their maximum potential. Despite fluctuating weather conditions, the system supplies nominal displacement all over the day and surplus energy to the grid. Furthermore, if one of the sources fails, the pump performance is unaffected. Switching losses are minimized since the Voltage Source Inverter (VSI) operates at a fundamental frequency. In all operational modes, this control delivers unique grid‐side power quality and unity power factor functioning. Here, the performance of the proposed hybrid system is implemented in the MATLAB and is compared with several existing methods.

Multi-objective control strategy for multilevel converter based battery D-STATCOM with power quality improvement

Differences in battery state-of-charge (SOC) in a cascaded H-bridge multilevel converter (CHB-MLC) based distribution static synchronous compensator (D-STATCOM) in battery storage system (BSS) applications could result in undesirable efficiency and performance reductions, and even system failure. Moreover, faults occurring on batteries and/or H-bridges (modules) of CHB-MLC severely increase the risk of failure. Power quality at the output of CHB-MLC is reduced as results of those faults. Therefore, active power differences that are introduced by SOC balancing among modules and bypassing the faulty modules yield to undesired harmonics at the output of CHB-MLC. This paper proposes a multi-objective control strategy for CHB-MLC based BSS D-STATCOM. The proposed control strategy includes a bidirectional power flow controller with unity power factor operation (UPF) feature, a fault-tolerant (FT) controller, a SOC balancing scheme that is designed to work on fault conditions, and a harmonic minimization strategy to enhance the power quality at the output of the CHB-MLC. Performance of the proposed method is validated through different operating conditions including faults, unbalanced SOCs and dynamic load changes. Results indicate that charging and discharging of the batteries with 5 kW rated power are held successfully along with maintaining UPF operation under both normal and fault conditions. Moreover, grid currents are balanced with the help of the FT controller and SOC balancing is properly operated even in fault conditions. Negative impacts of faults and unbalanced operating conditions on the power quality are also mitigated with the help of the harmonic reduction controller with significant decreases on total harmonic distortion reaching up to 47% and 69% during normal operation and faulty operations, respectively.

Development of a Bidirectional DC/DC Converter with Dual-Battery Energy Storage for a Hybrid Electric Vehicle System

Abstract: This study develops a newly designed, patented, bidirectional DC/DC converter (BDC) that interfaces a main energy storage (ES1), an auxiliary energy storage (ES2), and a DC-bus of different voltage levels, for application in hybrid electric vehicle systems. The proposed converter can operate in a step-up mode (i.e., low-voltage dual-source-powering mode) and a stepdown (i.e., high-voltage dc-link energy-regenerating mode), both with bidirectional power flow control. In addition, the model can independently control power flow between any two low-voltage sources (i.e., low-voltage dual-source buck/boost mode). Herein, the circuit configuration, operation, steady-state analysis, and closed-loop control of the proposed BDC are discussed according to its three modes of power transfer.

Novel Universal Power Electronic Interface for Integration of PV Modules and Battery Energy Storages in Residential DC Microgrids

This paper introduces the novel concept of a highly versatile smart power electronic interface for fast deployment of residential dc microgrids. The proposed approach has bidirectional power flow control capabilities, wide operating voltage range, and high efficiency resulting from the topology morphing control utilization. This enables universal compatibility with the majority of the commercial 60- and 72-cell photovoltaic modules, as well as the efficient charge/discharge control of the 24 V and 48 V battery energy storages using the same hardware platform. The proposed concept features fully autonomous operation where switching between the photovoltaic and battery interfacing modes is automatically done using the input source identification algorithm. Moreover, the proposed universal interface converter employs droop control and solid-state protection, making it fully compatible with the emerging standards and requirements for power electronic systems used in dc microgrid environments. A 350 W prototype was developed and tested in the residential 350 V dc microgrid with droop control to validate the proposed concept experimentally.

A versatile series‐parallel‐connected bidirectional DC power flow controller for HVDC and MVDC system

A versatile series‐parallel‐connected bidirectional DC power flow controller for HVDC and MVDC system

An Intelligent Control Scheme for Optimum Efficiency and Reduced Emission Operation of Marine Transportation System

This paper proposes an intelligent control scheme (ICS) for optimum efficiency and reduced emission operation in small marine transportation systems such as tugs, research vessels, and small scale cruiser ships. The diesel engines used in marine and other transport related applications are designed to provide optimum efficiency at a specific value of mechanical loading. Generally, these engines provide the best fuel efficiency near 80% of their rated load and also the break specific emission of CO (carbon mono oxide) and other harmful greenhouse gases are found to be lowest at this specific amount of mechanical loading. The proposed controller makes the diesel engine to operate continuously at 80% of loading in order to ensure an optimum efficiency operation even if the mechanical load is kept changing due to the variations and fluctuations in the ship propulsion load or electrical load. The intelligent control scheme (ICS) uses a battery bank as an energy balancing element to maintain a constant total mechanical loading on the engine shaft using a bidirectional power flow control through the battery bank thus changing effective mechanical loading on the engine for optimum efficiency operation of the marine transportation system. The output mechanical power (P) delivered by the engine on its shaft is sensed using a power sensor and compared with its optimum value in order to calculate the error. Thereafter, based on the information about the error in engine shaft power, the ICS regulates the power flow to the SPAG (single phase asynchronous generator) in such a manner that the mechanical load on the engine is restored to its optimum value immediately. The optimum efficiency operation is maintained under randomly varying mechanical power demanded by the ship propulsion system and it is also maintained under varying electrical loads in the marine transportation system. This ICS scheme has been implemented in the laboratory using a DSP controller. The detailed test results are presented to validate the claims.

Grid-connected solar photovoltaic-fed brushless DC motor drive for water pumping system using colliding body optimization technique

PurposeThis paper aims to present an improvement to the power quality of the grid by using a colliding body optimization (CBO) based proportional-integral (PI) compensated design for a grid-connected solar photovoltaic-fed brushless DC motor (BLDC)-driven water pumping system with a bidirectional power flow control. The system with bidirectional power flow allows driving the pump at full proportions uninterruptedly irrespective of the weather conditions and feeding a grid when water pumping is not required.Design/methodology/approachHere, power quality issue is taken care of by the optimal generation of the duty cycle of the voltage source converter. The duty cycle is optimally generated by optimal selection of the gains of the current controller (i.e. PI), with the CBO technique resulting in a nearly unity power factor as well as lower total harmonic distortion (THD) of input current. In the CBO technique, the gains of the PI controller are considered as agents and collide with each other to obtain the best value. The system is simulated using MATLAB/Simulink and validated in real time with OPAL RT simulator, OP5700.FindingsIt was found that the power quality of grid using the CBO technique has improved much better than the particle swarm optimization and Zeigler–Nichols approach. The bidirectional flow of control of VSC allowed for optimum resource utilization and full capacity of water pumping whatever may be weather conditions.Originality/valueImproved power quality of grid by optimally generation of the duty cycle for the proposed system. A unit vector tamplate generation technique is used for bidirectional power transfer.

Hybridization of battery and ultracapacitor for electric vehicle application with dynamic energy management and non-linear state feedback controller

• Proposed a dynamic energy management system for hybrid sources in an electric vehicle. • Buck-boost H-bridge converters are introduced for bidirectional power flow control. • System non-linearities are addressed using a nonlinear state feedback controller. • The proposed system accurately delivers instantaneous vehicle speed and torque. This paper describes a methodology to control a multi-source battery-capacitor hybrid EV incorporating a dynamic power splitting strategy. Considering the requirement for precise speed control characteristics of the EV and the non-linear behavior of traction motor with system disturbances, a non-linear state feedback controller (NLSFC) with a disturbance observer is suggested as the speed control technique for the EV traction motor. To interface a parallel configured multi-source system, a non-inverted buck-boost H-bridge is proposed as the source side converter for effective recovery of the braking energy. Detailed control design for traction motor and converter is also presented for efficient control of EV. Besides, an adaptive energy management strategy considering power profile and dynamic source characteristics is incorporated into the overall control system. The simulation results from various case studies indicate that the proposed system can follow the required vehicle speed and torque despite the sudden change in EV load torque. Furthermore, the comparative analysis between NLSFC and PI controller shows improvement with steady-state error reduction from 0.43 to 0.0014 and peak overshoot drop from 12.07% to 3.51% during acceleration of the system when proposed NLSFC is adopted. The proposed solutions will be implemented in a prototype EV system in the future.

Dc-Dc Bidirectional Cascaded Converter for Hvdc Network Using Bidirectional Power Flow Controller

Dc-Dc Bidirectional Cascaded Converter for Hvdc Network Using Bidirectional Power Flow Controller

Wireless Power Supply Design for Precharging Circuit of SST in Railway Vehicles

Frequency modulation control-based wireless power supply (WPS) system adopted for the operating signals of a precharging circuit in solid-state-transformer (SST) is proposed in this article. To guarantee high voltage insulation capability between trolley line and railway vehicle and to decrease the voltage level of railway feeder, a large and heavy main transformer (MTr) operating at 50/60 Hz is conventionally used in railway vehicles. The SST, operating at high frequency for compact size and active control of bidirectional power flow, is an emerging technology in order to substitute a conventional MTr. At initial start of the SST, it is important to slowly charge the capacitor voltages by a precharging circuit connected in series with the trolley line. To operate a precharging circuit in the SST, the proposed WPS system can be utilized for high voltage insulation capability in this article. To transfer operating signals wirelessly through the air, long slim dipole coils for transmitter (Tx) and receiver (Rx) are adopted to fabricate a small size of the whole WPS system. The proposed WPS can be operated at a maximum power efficiency point w.r.t. the wide ranges of the coil distance and load conditions by the proposed frequency modulation control method in the primary side. A 3-30 W prototype of the Tx and Rx coils for the proposed WPS were fabricated and verified by simulation and experiments, showing that 84.0% and 80.2% of high dc-dc efficiencies for P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</sub> = 30 and 12 W at d <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> = 30 mm, respectively. As a result, the proposed control method without communication circuits between Tx and Rx sides has been successfully verified when coil distance and load resistance are widely varied.

Overview of grounding schemes for solid‐state transformers in distribution networks

Proposed to be the critical enabling component for future distribution networks, solid-state transformers (SSTs) have drawn much attention lately. They have a massive potential to help reduce size and weight, improve efficiency, integrate microgrids, renewables and energy storages in distribution systems, and can fulfil multiple grid functions such as bidirectional power flow control, fault isolation, system reconfiguration, and post-fault restoration. The introduction of these power electronics devices in distribution systems, however, also brings new challenges to the grid. Extra levels of electromagnetic interference, stray current, and personnel safety are among the most prominent practical issues that proper grounding arrangements can address. In this paper, considerations that should be factored into the grounding scheme design for SST ports with different voltage forms and levels are thoroughly reviewed and summarised. The characteristics of various grounding schemes used in AC and DC distribution systems are evaluated and compared in detail from different perspectives. Based on the comprehensive review, several combinations of grounding schemes are recommended for typical SSTs. In addition, the inclusion of new relay protection devices in the SST grounding scheme design, considering their characteristics and unique requirements, to enhance protection and reliability is also discussed.

Optimal Sizing and Energy Management of Microgrids with Vehicle-to-Grid Technology: A Critical Review and Future Trends

The topic of microgrids (MGs) is a fast-growing and very promising field of research in terms of energy production quality, pollution reduction and sustainable development. Moreover, MGs are, above all, designed to considerably improve the autonomy, sustainability, and reliability of future electrical distribution grid. At the same time, aspects of MGs energy management, taking into consideration distribution generation systems, energy storage devices, electric vehicles, and consumption components have been widely investigated. Besides, grid architectures including DC, AC, or hybrid power generation systems, energy dispatching problems modelling, operating modes (islanded or grid connected), MGs sizing, simulations and problems solving optimization approaches, and other aspects, have been raised as topics of great interest for both electrical and computer sciences research communities. Furthermore, the United Nations Framework Convention on Climate Change and government policies and incentives have paved the way to massive electric vehicle (EV) deployment. Hence, several research studies have been conducted to investigate the integration of EVs in national power grid and future MGs. Specifically, EV charging stations’ bi-directional power flow control and energy management have been considerably explored. These issues index challenging research topics, which are in most cases still under progress. This paper gives an overview of MGs technology advancement in recent decades, taking into consideration distributed energy generation (DER), energy storage systems (ESS), EVs, and loads. It reviews the main MGs architecture, operating modes, sizing and energy management systems (EMS) and EVs integration.

Bidirectional Power Flow Control and Hybrid Charging Strategies for Three-Phase PV Power and Energy Storage Systems

The objective of this article is to propose a photovoltaic (PV) power and energy storage system with bidirectional power flow control and hybrid charging strategies. In order to optimize the battery charging performance, five charging strategies, including the constant-current charging, the pulse-ripple-current charging, the sinusoidal-ripple-current charging, the bidirectional pulse-ripple-current, and the bidirectional sinusoidal-ripple-current charging, are adopted. Traditionally, in order to realize these charging strategies, the PV charger should abandon the maximum power point tracking function to maintain the power flow balance. As a result, the output power of the PV array will be decreased. Therefore, bidirectional power flow control strategies are proposed to achieve the maximum PV power utilization as well as to realize the hybrid charging methods. In addition, with the proposed strategies, the bidirectional charging/discharging capability of the battery is able to achieve the maximum PV power utilization. All the proposed strategies can be realized by the digital signal processor without adding any additional circuit, component, and communication mechanism. Theoretical analysis and control principles will also be revealed. Finally, a 5-kW prototype circuit with both simulation and experimental results demonstrate the performance and feasibility of the proposed strategies.

WITHDRAWN: A high gain multi-port bidirectional converter with reduced voltage stress

Abstract The energy storage becomes an essential part to exploit the intermittent form of renewable resources more effectively. Further it is mandate for a battery source to have a built in port for charging and discharging phenomena. A novel idea on multi port non-isolated bidirectional converter (M-NIBC) is proposed and experimented for improved voltage gain and reduced voltage stress in this paper. M-NIBC topology is devised with four electronic switches with a freewheeling diode across each and moreover two inductors and three capacitors certainly make the passive circuitry operation. Energy derived from the regenerative braking is sufficient to charge the battery and it can be done through the feedback control of bidirectional power flow. The voltage is shared in the respective module and thereby the stress across the switch is minimized to an extent. The successive reduction in voltage stress controls the ON state resistance of the semiconductor device eventually. Voltage gain of the proposed M-NIBC is comparatively lower than the conventional cascaded bidirectional converter (CBC) during the charging cycle whereas it is relatively higher in discharging cycle. The proposed M-NIBC is configured in a simpler way to control and this approach is tested in the simulation laboratory for validating its novel performance under the charging and discharging cycles respectively.

Bi-directional power flow control with improved power quality using intelligent controller for AC-DC coupled hybrid micro-grid system

Grid connected renewable sources are affected by harmonic distortion due to non-linear power electronics interfaces. Depending upon the nature of the load, many conversion stages are incorporated in the micro-grid which leads to increase in the losses. Therefore, in this paper, the AC-DC coupled hybrid micro-grid system is presented in which AC renewable sources and AC loads are connected to AC sub-grid and DC renewable sources and DC loads are connected to DC sub-grid. The shunt active power filter based 3φ 4-leg bi-directional intermediate converter using d-q load current technique is proposed to achieve the power flow between AC and DC sub-grids. The MATLAB simulation is carried out, and the performance of the proposed system is analysed using the d-q load current technique based fuzzy logic and PI controller. The obtained results demonstrate that the overall system performance is improved with the d-q load current technique based fuzzy logic controller.

Bidirectional Power Flow Control Integrated With Pulse and Sinusoidal-Ripple-Current Charging Strategies for Three-Phase Grid-Tied Converters

The objective of this paper is to propose bidirectional charging/discharging strategies for three-phase grid-tied converters. The bidirectional power flow control feature of the converter is able to realize both charging and discharging capability. Besides, in order to achieve high charging efficiency as well as extend the life of the battery, five charging strategies are adopted and developed: 1) the constant current (CC) charging, 2) the pulse-ripple-current (PRC) charging, 3) the sinusoidal-ripple-current (SRC) charging, 4) the bidirectional pulse-ripple-current (BPRC) charging and 5) the bidirectional sinusoidal-ripple-current (BSRC) charging. The direct quadrature (d-q) transformation is utilized for the converter to realize different charging methods. These methods can be achieved by the digital signal processor (DSP) without adding extra circuit components. In addition, the charging power differences between each strategy are considered and analyzed in this paper. Finally, both simulation and experimental results obtained from a 5-kW prototype circuit verify the performance and feasibility of the proposed bidirectional charger.

Evaluation of the Emission Impact of Cold-Ironing Power Systems, Using a Bi-Directional Power Flow Control Strategy

Even though cold ironing is not a new technology applied to reduce the impact of emissions from ships at berth, commonly used arrangements for shore-side power substations only allow a unidirectional power flow, from port to ship side. Although these applications have a positive contribution to port community health and global reduction of greenhouse gases (GHG), especially when the energy is supplied from renewable sources, emissions during loading/unloading operations are directly related to the operating profiles of auxiliary engines of a ship. The present work evaluates a ship’s emission impact when applying cold-ironing technology using a bi-directional power flow control strategy while at berth, thus optimizing the auxiliary engine operating profile and enabling regeneration into the port installations. The methodology applied considers the establishment of the operational profile of the ship, the adaptation and use of carbon intensity indicators (CII) used by the International Maritime Organization (IMO) to evaluate the impact of shipping, and the strategy considering the capacities of the ship to obtain and provide electric power from and to the port when at berth. Results show that the strategy can be applied to any ship with a high demand for electric power while at berth, and that the adaptation and use of different CIIs allows operational profiles of electric power generation on board to be optimized and to reduce emission generation, which affects port community health.

Simplified hybrid reliability simulation approach of a VSC DC grid with integration of an improved DC current flow controller

In this paper, different reliability simulation approaches of an improved DC current flow controller (CFC) integrated voltage-sourced converter (VSC) based DC grids are investigated with the following contributions: (1) In order to achieve bidirectional power flow control and fault current blocking capability, an improved DC CFC topology with a set of reversed switches is analysed to enhance the controllable path and control margins; (2) Two different reliability simulation approaches of the improved DC CFC integrated meshed multi-terminal DC (M2TDC) grid are analysed. In Approach 1, the VSCs and their AC sides are modelled without simplification. In Approach 2, the VSCs and their AC sides are represented by ideal DC voltage/current sources to simplify the system modelling; (3) Synthesizing the merits of both approaches while avoiding the deficiencies, a hybrid reliability simulation approach is proposed with high efficiency of simulation while maintaining the accuracy; (4) In order to further enhance the simulation efficiency, a different reliability simulation approach of the ideal DC current source, namely improved ideal DC current source, is proposed. Simulation systems are established in PSCAD/EMTDC for verification.

A New Topology of Three-Port Power Hub Converter With Power Quality Compensation for Remote Area Residential Power Supply

In remote areas, the distribution networks are usually underdeveloped; thus, three-phase medium-voltage grids may provide a low-cost power supply solution for residential buildings. A new centralized approach topology of three-port power hub converter, which consists of a V/V transformer, a back-to-back inverter, and a static volt-ampere reactive (VAR) compensator with adaptive impedance, is proposed for remote area power supply. The proposed three-port converter interfaces two bidirectional power ports connecting three-phase ac grid and dc grid, respectively, and one unidirectional power port connects ac loads. The functions of the proposed converter are the bidirectional power flow control between three-phase ac grid and dc grid and power quality compensation to the three-phase ac grid. Finally, to verify the validity of the proposed three-port converter and its control performance, different simulation and experimental cases are implemented under different operation conditions.