DC Link Voltage Of Converter Research Articles

Interval Type-2 Fuzzy Logic Controlled Shunt Converter Coupled Novel High-Quality Charging Scheme for Electric Vehicles

The deployment of electric vehicle charging stations degrades the quality of power in the distribution grid. This article proposes an interval type-2 fuzzy logic controlled shunt converter coupled novel high-quality charging scheme for electric vehicles. This system includes three-phase bidirectional front-end ac-dc pulsewidth modulation (PWM) converter, backend dc-dc PWM converter and three-phase three-wire distribution static compensator. The bidirectional converters help to perform both grid to vehicle and vehicle to grid mode of operations. The combination of dc-link voltage with decoupled current control technique is exploited for ac-dc converter. A multistep constant current control technique is proposed for the dc-dc converter to charge and discharge the battery. A fuzzy logic controller based instantaneous reactive power theory control method is proposed for shunt converter. The performance of type-1, interval type-2, and real coded genetic algorithm optimized fuzzy logic controllers are evaluated by the shunt converter dc-link voltage and the total harmonic distortion of the source current. Lithium-ion batteries are utilized as an energy storage device for electric vehicles in the proposed system. The entire system is modeled and evaluated in the MATLAB/Simulink environment. An interval type-2 and real coded genetic algorithm optimized fuzzy logic controller affords the better performance during V2G and G2V operations, respectively.

Three-Phase Four-Wire PV System for Grid Interconnection at Weak Grid Conditions

A photovoltaic (PV) system for reliable interconnection of a PV array to the grid is presented in this article. A boost converter ensures operation of the PV array at its maximum power point, and it also enables the adaptive adjustment of the dc link voltage of the interfacing voltage source converter according to the variations in the grid voltages. This prevents system tripping during the voltage sag, and helps to maintain the grid current power quality at voltage swell conditions. Even in the weak grid scenarios of unbalanced or distorted voltages, the grid currents are maintained distortion free and balanced. Furthermore, the system eliminates the dc offset in the sensed grid voltages, and ensures absence of dc offset in the grid currents. The fast dynamic response of the system to sudden load variations is obtained by employing a total least squares-based control technique, which swiftly extracts the fundamental active weights from the distorted load currents. Moreover, the PV system performs grid power quality conditioning, such as neutral current mitigation, harmonics reduction, power factor correction, and balancing of grid currents, even under the absence of PV power, such as during nights. The system performance is validated by test results at unbalanced load currents, unbalanced grid voltages, distorted grid voltages, grid voltage sag and swell, PV power variations, and dc offset in the sensed grid voltage.

Analytic Spectral Analysis Technique for Converters Operating With Oscillatory DC-Link Voltage Components

Converters are playing an ever increasing role in electric power grids. To help facilitate a design of power grids that ensures stable and efficient transfer of power, the harmonic pollution injected by converters must be quantified. At present, analytic expressions used to describe modulated converter waveforms have been derived while assuming that the converter dc-link voltage contains only a dc component. This is a reasonable assumption in many converter applications. However, there is a large number of converters that operate with superimposed oscillatory dc-link components, such as single-phase and cascaded multilevel converters. Grid and/or load imbalance can also lead to oscillatory dc-link voltage components. Given this context, the main contribution of this article is to derive analytic expressions for converter output harmonics when oscillatory components are present in the dc-link voltage. Experimental verification of the proposed spectral analysis technique is performed on a $\text{1}\,\text{kVA}$ , 3-level, $\text{240}\,\text{V}$ single-phase full-bridge inverter.

Current Compensation in Grid-Connected VSCs using Advanced Fuzzy Logic-based Fluffy-Built SVPWM Switching

A main focus in microgrids is the power quality issue. The used renewable sources fluctuate and this fluctuation has to be suppressed by designing a control variable to nullify the circulating current caused by voltage fluctuations and deviations. The switching losses across power electronic switches, harmonics, and circulating current are the issues that we discuss in this article. The proposed intelligent controller is an interface between a voltage-sourced converter and a utility grid that affords default switching patterns with less switching loss, less current harmonic content, and overcurrent protection, and is capable of handling the nonlinearities and uncertainties in the grid system. The interfaced controller needs to be synchronized to a utility grid to ensure that the grid–lattice network can be fine-tuned in order to inject/absorb the prominent complex reactive energy to/from the utility grid so as to maintain the variable power factor at unity, which, in turn, will improve the system’s overall efficiency for all connected nonlinear loads. The intelligent controller for stabilizing a smart grid is developed by implementing a fuzzy-built advance control configuration to achieve a faster dynamic response and a more suitable direct current link performance. The innovation in this study is the design of fuzzy-based space vector pulse width modulation controller that exploits the hysteresis current control and current compensation in a grid-connected voltage source converter. By using the proposed scheme, a current compensation strategy is proposed along with an advanced modulation controller to utilize the DC link voltage of a voltage source converter. To demonstrate the effectiveness of the proposed control scheme, offline digital time-domain simulations were carried out in MATLAB/Simulink, and the simulated results were verified using the experimental setup to prove the effectiveness, authenticity, and accuracy of the proposed method.

Analysis and Suppression for Frequency Oscillation in a Wind-Diesel System

In a wind-diesel system with weak network architecture, many techniques are utilized to enhance its stability. However, the frequency oscillation between the grid-side converter and the diesel generator may be caused by their interactions, and there are only a few studies considering this issue, which is a major challenge for the stability. To tackle this challenge, the cause of frequency oscillation is studied, and an adaptive fuzzy PI controller based on the variable universe is proposed to suppress oscillation in this paper. The control parameter of the wind turbine generator (WTG) converter's dc-link voltage loop and wind speed has an important influence on the oscillation. Our main idea is to suppress frequency oscillation by the optimizing control parameter. In order to analyze the interaction between WTG and diesel generator, we develop the small-signal models of the wind-diesel generator. Subsequently, the adaptive fuzzy PI controller based on the variable universe is proposed in the dc-link voltage loop to optimize control parameter instead of gain-scheduled PI controller, and its key feature is the innovative use of an extension factor with d-axis current in the output universe. The function of the extension factor is to adapt WTG to different wind speeds. The experimental results demonstrate that the proposed controller can significantly suppress frequency oscillation. The oscillation amplitude of isolated grid frequency is also significantly reduced by up to 0.175 Hz.

Parameters tuning of doubly fed induction generator systems with static synchronous compensator based on Chaos orthogonal particle swarm optimization

For Double-Fed Induction Generator (DFIG) wind farm systems with Static Synchronous Compensator (STATCOM), by optimizing multiple proportional integral (PI) controllers parameters of DFIG and STATCOM, the performance of the wind power system is significantly improved and the voltage of point of common coupling (PCC) is quickly restored when a low voltage due to a grid fault. Chaos orthogonal particle swarm optimization is proposed to make the integral time absolute error (ITAE) of active power of DFIG, DC-link voltage of converter of DFIG and voltage of PCC minimum. The orthogonal method is used to get the range of parameters and identify the weight relations between different indicators. And then the chaos algorithm is used to initialize the algorithm. Finally, the particle swarm optimization (PSO) can effectively improve the efficiency of the optimization. Based on MATLAB/Simulink, the simulations of wind farm containing STATCOM incorporated into the infinite system under different conditions both show that the application optimized PI controllers have good dynamic performance, which validates the effectiveness of the optimization algorithm.

Design of solar‐powered agriculture pump using new configuration of dual‐output buck–boost converter

This paper proposed a new structure of single switch dual output Zeta derived DC-to-DC converter for an efficient harvesting of photovoltaic (PV) power for a 4-phase switched reluctance motor (SRM) driven agriculture pump. The system is essentially developed to minimise both cost and complexity, while synchronously guaranteeing optimal operation of the PV array. The proposed converter is derived from a hybrid of a ‘Zeta’ and Landsman converters and so it contains all the benefits of both converters including balanced outputs. Due to an identical instantaneous duty cycle, the switching node is shared by both Zeta and Landsman converters. The proposed converter offers continuous power to drive, a low ripple in output current, and balanced dual output supply. The PV power optimisation and to deliver smooth start of SRM, are the two major objectives of proposed DC-to-DC converter. A new maximum power point tracking (MPPT) technique is also used in the system to optimise the performance of PV array. Moreover, the proposed MPPT control has an additional advantage of regulating the flow rate of water pumping by adjusting the duty cycle of DC-to-DC converter. The motor speed is smoothly regulated through the variable DC link voltage of a mid-point converter.

A Novel Dynamic Switching Table Based Direct Power Control Strategy for Grid Connected Converters

Direct power control (DPC) has gained much attention for medium-voltage applications due to its fast power control capability. However, a conventional static switching table based DPC can lead to unsatisfactory response when the converter is connected to an electric grid because it is commonly designed assuming ideal and constant voltages of the grid and the dc link. Therefore, the actual grid voltage and the actual converter dc-link voltage should be considered while designing the switching table. This paper proposes a novel dynamic switching table for the DPC, considering actual grid and dc-link voltages variation. The proposed dynamic switching table incorporates a new definition of power influence crossover angles of each converter space vector. The proposed scheme dynamically adapts the switching table by feeding forward the actual grid and dc-link voltages, and hence the converter's power is precisely controlled. The proposed technique is verified for the three-level neutral point clamped converters connected to a standard IEEE 9-bus test system. Moreover, the real-time simulations are performed in a real-time digital simulator, OPAL-RT. The obtained results verified the effectiveness of the proposed DPC strategy under different grid fault scenarios.

Control strategy of wind turbine based on permanent magnet synchronous generator and energy storage for stand-alone systems

This paper investigates a variable speed wind turbine based on permanent magnet synchronous generator and a full-scale power converter in a stand-alone system. An energy storage system(ESS) including battery and fuel cell-electrolyzer combination is connected to the DC link of the full-scale power converter through the power electronics interface. Wind is the primary power source of the system, the battery and FC-electrolyzer combination is used as a backup and a long-term storage system to provide or absorb power in the stand-alone system, respectively. In this paper, a control strategy is proposed for the operation of this variable speed wind turbine in a stand-alone system, where the generator-side converter and the ESS operate together to meet the demand of the loads. This control strategy is competent for supporting the variation of the loads or wind speed and limiting the DC-link voltage of the full-scale power converter in a small range. A simulation model of a variable speed wind turbine in a stand-alone system is developed using the simulation tool of PSCAD/EMTDC. The dynamic performance of the stand-alone wind turbine system and the proposed control strategy is assessed and emphasized with the simulation results.

Microgrid Control based on a DFIG Integrated with a BESS

This study presents an improved doubly fed induction generator (DFIG) that is integrated with a battery energy storage system (BESS) for microgrid control. The proposed DFIG can generate independently the power output of the rotor-side converter (RSC), grid-side converter (GSC), and battery-side converter. The maximum power point tracking (MPPT) is included in the RSC to maximize the generated power of DFIGURE. The power of the GSC is used to smooth total wind power of DFIG and to maintain stably AC voltage and frequency in the island mode. The battery-side converter is used to keep the dc link voltage of a back-toback converter. The effective of the proposed DFIG is validated by simulations on Matlab / Simulink environment.

High dynamic performance of a BLDC motor with a front end converter using an FPGA based controller for electric vehicle application

This paper focus on a novel operation of a brushless dc (BLDC) motor fed by a proportional integral (PI) controlled buck--boost converter supplemented with a battery to provide the required power to drive the BLDC motor. The operational characteristics of the proposed BLDC motor drive system for constant as well as step changes in dc link voltage of a front end converter controlled by a Xilinx System Generator (XSG) based PI controller for two quadrant operations are derived. Thus a field programmable gate array (FPGA) based PI controller manages the energy flow through the battery and the front end converter. Moreover, speed to voltage conversion logic, made to control the BLDC motor through the PI controller, improves the performance and gives optimum control under the unstable driving situation or varying load condition when the complete system becomes a subject of application to electric vehicles (EVs) and hybrid electric vehicles (HEVs). The dual closed loop control implemented for end to end speed control of the proposed drive system facilitates the system with high accuracy integrated with excellent dynamic and steady state performance. In this paper, the proposed controller was designed for a 5 kW/480 V BLDC motor drive system. The feasibility of the proposed dual loop control topology for the BLDC motor drive system is validated and verified with extensive dynamic simulation in MATLAB/SIMULINK and XSG environment.

H‐bridge modular multi‐level converter: control strategy for improved DC fault ride‐through capability without converter blocking

This study presents a control scheme that separates control of the fundamental current associated with AC power control from the DC and harmonic components in the arms of the H-bridge modular multi-level converter (MMC). In addition, this control scheme fully exploits the subtractive and additive switch states of the H-bridge MMC to maintain capacitor voltage balance when the converter DC-link voltage collapses during DC faults. The significance of this control scheme is that it permits the H-bridge MMC to ride through DC faults without the need for converter blocking, as is presented in the literature. This study provides comprehensive discussion of MMC fundamental theory, including a logical mathematical derivation of the relationships that governed its operation and modulation. The validity of the presented control scheme is confirmed using simulations and experimentations. Besides DC fault survival, this study presents operating the H-bridge-MMC from bi-polar DC-link voltages; thus, creating the possibility of complex hybrid DC grids with reversible DC-link voltage where the conventional line commutated current-source converters can operate alongside voltage-source converters. Operation of the H-bridge-MMC with reversible DC-link voltage is validated using simulation.

Active and Reactive Power Control of a Doubly Fed Induction Generator

Wind turbine WT occupies gradually a large part in world energy market, Doubly fed induction generator DFIG is mostly used in WT, it allow highly flexible active and reactive power generation control. This paper presents dynamic modeling and simulation of a doubly fed induction generator based on grid-side and rotor-side converter control. The DFIG, grid-side converter, rotor-side converter, and its controllers are performed in MATLAB/Simulink software. Dynamic response in grid connected mode for variable speed wind operation is investigated. Simulation results on a 3 MW DFIG system are provided to demonstrate the effectiveness of the proposed control strategy during variations of active and reactive power, rotor speed, and converter dc link voltage.

Active and Reactive Power Control of a Doubly Fed Induction Generator

Doubly fed induction generators (DFIG) are increasingly used in grid interfaced wind energy systems to address voltage regulation and provide adequate reactive power support. This paper presents dynamic modeling and simulation of a doubly fed induction generator based on grid-side and rotor-side converter control. The DFIG, grid-side converter, rotor-side converter, and its controllers ar e performed in MATLAB/Simulink software. Dynamic response in grid connected mode for variable speed wind operation is investigated. Simulation results on a 3.6 MW DFIG system are provided to demonstrate the effectiveness of the proposed control strategy during variations of active and reactive power, rotor speed, and converter dc link voltage.

An Adaptive Hysteresis Band Current Controller Based DSTATCOM for Enhancement of Power Quality with Various Load

The Distribution Static Compensator (DSTATCOM) is used for development of power quality in power distribution network with various loads such as linear, nonlinear and variable load. The dc link capacitor voltage is directly affected by any alteration made in the load. Proper operation of DSTATCOM requires maintenance of capacitor voltage within the limits. Right from the beginning, conventional controller has been used to maintain the converter dc-link capacitor voltage. In spite of it, the transient response of the PI and Hysteresis controller is still slow. In this paper, an adaptive hysteresis band current controller is proposed for DSTATCOM to eliminate harmonics and compensate the reactive power of three-phase converter. The adaptive hysteresis band current controller is varied from the hysteresis bandwidth with respect to modulation frequency, source voltage, dc link voltage and slope of the reference compensator current wave. Mathematical expressions are given to design the adaptive hysteresis band current controller to achieve the fast transient response. The results of simulation study of the proposed method have been carried out using MATLAB simulation software.

Input Power Quality Improvement in Switched Reluctance Motor Drive using Minnesota Rectifier

This paper deals with an input power quality improvement in a midpoint converter based switched reluctance motor (SRM) drive at ac mains using Minnesota rectifier. Normally a midpoint converter is used as a power converter for SRM drive. Conventionally three phase ac mains fed bridge rectifier is used as a dc source to feed this power converter which produces high content of harmonics at ac mains with a very low power factor. The proposed Minnesota rectifier with a midpoint converter fed SRM drive improves the power factor at ac mains with low current harmonics. This method provides constant dc link voltage and balanced capacitor voltages of the midpoint converter. The Minnesota rectifier fed SRM drive is modelled and its performance is simulated in Matlab/Simulink environment. The performance of Minnesota rectifier is compared with a conventional bridge topology for SRM drive to demonstrate improved power quality at ac mains.

The New High-Efficiency Hybrid Neutral-Point-Clamped Converter

This paper introduces a novel three-level voltage-source converter (VSC) as an alternative to known three-level topologies, including the conventional neutral-point-clamped converter (NPCC), many T-type VSCs, and active NPCC. It is shown that, operating in the low converter dc-link voltage range, this new solution not only can achieve higher efficiency than many typical three-level structures but also can overcome their drawback of asymmetrical semiconductor loss distribution for some operating conditions. Therefore, a remarkable increase of the converter output power capability and/or system reliability can be accomplished. The switching states and commutations of the converter, named here as hybrid NPCC (H-NPCC), are analyzed, and a loss-balancing scheme is introduced. Five- and seven-level H-NPCC topologies with loss-balancing features are also presented. Finally, a semiconductor-area-based comparison is used to further evaluate many three-level VSC systems. Interestingly, the total chip area of the proposed H-NPCC is already the lowest for low switching frequencies.

DC Link Voltage Effects on the Performance of the Two Current Control Strategies of Voltage Source Converters

This paper investigates the effects of the DC link voltage of a voltage source converter (VSC)on the performance oftwo current control strategies of the VSCsfrom point of views: capability of tracking the references signals with a zero steady-state error and imposing less transients during the step changes in the references signals of the controllers. Two conventional and multivariable proportional-integral (PI) based dqcurrent controllerstrategy has been represented. Then based on the considering the worst step changes in the references signals of the VSC while the DC link voltage (Vdc) is varying, a specified range has been obtained for theVdc.It has been depicted thatthe multivariable control strategy has less transient and more decoupling capability between d and q axis components of the current during the step changes which have been occurred in the various DC link voltage of the VSC. Alsofor tracking the reference signals,Vdc of the inverter must be in a particular range.Otherwise tracking the reference signals verifies that the axes are not fully decoupled or in some cases the system would be unstable.

Improved Power Quality IHQRR-BIFRED Converter Fed BLDC Motor Drive

This paper presents an IHQRR (Integrated High Quality Rectifier Regulator) BIFRED (Boost Integrated Flyback Rectifier Energy Storage DC-DC) converter fed BLDC (Brushless DC) motor drive. A reduced sensor topology is derived by utilizing a BIFRED converter to operate in a dual DCM (Discontinuous Conduction Mode) thus utilizing a voltage follower approach for the PFC (Power Factor Correction) and voltage control. A new approach for speed control is proposed using a single voltage sensor. The speed of the BLDC motor drive is controlled by varying the DC link voltage of the front end converter. Moreover, fundamental frequency switching of the VSI's (Voltage Source Inverter) switches is used for the electronic commutation of the BLDC motor which reduces the switching losses in the VSI. The proposed drive is designed for a wide range of speed control with an improved power quality at the AC mains which falls within the recommended limits imposed by international power quality standards such as IEC 61000-3-2.

DICM and DCVM of a PFC-based SEPIC-fed PMBLDCM Drive

This paper deals with two different discontinuous conduction modes of a Power Factor Corrected (PFC) Single Ended Primary Inductor Converter (SEPIC) -fed Permanent Magnet Brushless DC Motor (PMBLDCM) Drive. A novel scheme of speed control of PFC-based SEPIC-fed PMBLDCM drive is proposed using a single voltage sensor. The SEPIC is operated in a Discontinuous Inductor Current Mode (DICM) and Discontinuous Capacitor Voltage Mode (DCVM) feeding PMBLDCM Drive. A Diode Bridge Rectifier (DBR) fed from a single-phase AC supply followed by a SEPIC DC-DC converter is used for power factor correction. A three-phase Voltage Source Inverter (VSI) is used for the electronic commutation of the PMBLDC motor. The speed control is achieved by controlling the DC link voltage of the VSI. A voltage follower approach is used to control the DC link voltage of the front-end SEPIC converter. The developed model of the system is used to simulate the performance of the drive system to achieve improved power quality at AC mains with a wide range of speed control.