Reduced DC Link Voltage Research Articles

Bidirectional controller supported inductively coupled dual buck converter based DSTATCOM with passive filterfor PQ improvement

This research paper explains about the bidirectional controller (BC) supported inductively coupled dual buck converter (IC-DBC) based distributed static compensator (DSTATCOM) with passive filter (PF) for 3-ф 3-wire (3P3W) power distribution system (PDS). The most significant concern in the PDS is power quality (PQ) control. Hence, innovative approach is proposed by considering concept and benefits of BC, inductive coupled filtering transformer (IFCT), passive filter and dual buck converter. Equivalent circuit for IC-DBC based DSTATCOM is realized in view of impedance of transformer and direct coupled dual buck converter (DC-DBC) based DSTATCOM to disclose the filtering mechanism. The supremacy of the proposed DSTATCOM is introduced by comparing its simulation outcomes with DC-DBC based DSTATCOM and IC-DBC based DSTATCOM in terms of better harmonics curtailment, power factor advancement, load balancing & reduced DC link voltage compared to other approaches as per IEEE standard.

Analysis of Asymmetric Hybrid Modular Multilevel Topology for Medium-Voltage Front-End Converter Applications

Modular multilevel converters (MMCs) have been conceived as an alternative in front-end converter applications to enhance the converter system’s reliability, minimize total harmonic distortion, and improve power quality. These converters utilize several DC-link capacitors and power electronic switches, along with switches operating with high switching frequencies, to attain the desired characteristics. Thereby, this paper systematically proposes a novel three-phase asymmetric hybrid modular multilevel converter (AHMMC) for front-end converters used in lower-medium-voltage applications. The AHMMC configuration is based on a three-phase converter connected to a per-phase series arrangement with a cascaded converter module (CCM). The study investigates the AHMMC and proposes a control scheme, which minimizes the voltage range on switches and maintains the current to its reference value. Furthermore, the study also introduces an active balancing of voltage across DC-link capacitors based on the phase opposition disposition PWM (POD-PWM) method. Our new configuration has features such as low switching loss, reduced DC-link voltage, a wider modulation range for the unity power factor (PF), and low voltage and current harmonic distortion. The simulation results are added to verify the performance of the new AHMMC topology and the usefulness of the modular control scheme. In addition, a low-voltage laboratory prototype based on customized control and power boards is built to validate the proposed converter and its control scheme in practice.

Bi-directional Battery Charging/Discharging Converter for Grid Integration: A Step Towards Power Quality and Efficient Energy Management in Electric Vehicles

This paper presents the design and simulation of a bi-directional battery charging and discharging converter capable of interacting with the grid. The proposed converter enables Electric Vehicles (EVs) not only to charge their batteries from the grid but also to discharge excess energy back into the grid through the Vehicle-to-Grid (V2G) operating mode. The work discusses charger design considerations, including control strategies, and examines its potential contribution to efficient energy management and grid stability. Furthermore, a simulation study using MATLAB/Simulink validates the performance, efficiency, and dynamic response of the bi-directional converter, demonstrating its viability for real-world grid integration. The simulation shows better performance in various performance aspects, including high-power factor correction (PFC), minimized steady-state oscillations, reduced DC link voltage overshoot, increased overall efficiency, and both voltage and current Total Harmonic Distortions (THD maintained below 5%).

Topology, Modeling and Control Scheme for a new Seven-Level Inverter With Reduced DC-Link Voltage

This paper presents a novel single-source three-phase multilevel converter with voltage boosting capability for medium-voltage photovoltaic applications. This converter consists of different switched-capacitor networks, formed by 1 capacitor and 3 active switches, as a basic switching cell to generate variable dc-link voltage that boosts the input dc-source voltage, producing 2n+1 (n2) voltage levels at the output. It can reduce the dc-link voltage requirements by 50% in comparison to the traditional neutral point clamped (NPC), flying capacitors, active NPC (ANPC), hybrid and hybrid clamped ANPC and cascaded H-bridge topologies, and 75% to advanced ANPC topologies. It can also reduce the number of required switches and capacitors as well as their voltage stresses compared to these state-of-the-art topologies reported in the literature so far. A finite control set model predictive control algorithm is derived to control the converter, which has the capability to control the active and reactive power without distorting the generated grid current quality. The capacitor voltage balancing is inherent in the proposed topology, and thus, there is no need for any additional voltage balancing circuit, which reduces the control complexity. As an example, a 7-level version of the proposed topology is compared to other existing 7-level inverter topologies.

Двойная инверторная система для питания шагового электродвигателя с уменьшенным напряжением звена постоянного тока

Двойная инверторная система для питания шагового электродвигателя с уменьшенным напряжением звена постоянного тока

Comparative Analysis of Chopper-Inverter Performances for Wind Conversion System Connected to Grid

PurposeThe purpose of this paper is to propose an efficient current control technique based on model predictive control (MPC) for grid-connected wind conversion system. This nonlinear strategy is applied for the chopper circuit and grid-tied inverter and compared with other two conventional schemes; a traditional proportional-integral (PI) and sliding mode controller (SMC) using the same switching frequency.Design/methodology/approachFirstly, the MPC scheme uses the mathematical model to predict future behaviors of the controlled converter outputs for possible switching states. After that, the optimal voltage vector is selected by minimizing a cost function, which is defined as a sum of the absolute values of the controlled current errors. Then, the corresponding switching signals are applied to the converter switches in the next sampling period to track correctly the reference current. Thus, the MPC scheme ensures a minimal error between the predicted and reference trajectories of the considered variables.FindingsThe MPC-based algorithm presents several benefits in terms of high accuracy control, reduced DC-link voltage ripples during steady-state operation, faster transient response, lower overshoots and disturbance rejection and acceptable total harmonic distortion.Originality/valueThe authors introduce several simulation case studies, using PSIM software package, which prove the reliability and effectiveness of the proposed MPC scheme. Therefore, the MPC performances, during dynamic and steady-state condition, are compared with those obtained by a PI regulator and SMC to highlight the improvements, specifically the transfer of smooth power to the grid.

Single-Phase to Three-Phase Power Converter With Reduced DC-Link Voltage Ripple and Grid Current Harmonics

This article presents a control technique to improve the power quality and performance of grid-connected single to three-phase power converter. The conventional five-leg (5L) topology is modified to parallel five-leg (P5L) topology that has fault tolerance capability and operates even either of the front end converter leg is open-circuited. In such topologies, lower order harmonics (3rd, 5th, 7th, 9th, 11th, 13th, and 15th) are dominant, which are eliminated using a proportional plus resonant controller in the inner current control loop of active front end converter (AFEC). The control technique implemented over single-phase AFEC controls the dc-link voltage and provides unity power factor operation at the grid side and also balances the individual capacitor voltages (Vc1 and Vc2) even under faulty conditions of power semiconductor switches. The dc-link voltage oscillation is the inherent problem of such converters, therefore, it is proposed to use advanced bus clamp PWM technique at the inverter side to reduce such ripples and also improves the inverter output voltage profile. The comparative improvement under operating conditions is presented through the simulation and verified on hardware setup to validate the efficacy of the control algorithm.

Development of PCS to utilize differential pressure energy in district heating systems with reduced DC-link voltage variation

This paper proposes a power conversion system (PCS) to utilize the differential pressure (DP) energy in district heating systems with reduced DC-link voltage variation. A differential pressure control valve (DPCV) is usually used to regulate pressure for heat transmission to remote areas in district heating systems. However, there is a high probability of malfunctions and failures of the DPCV, due to cavitation, since high-pressure fluids are used in district heating systems. Therefore, a PCS for utilizing DP energy in the district heating system replacing the DPCV is proposed in this paper. In addition, the DC-link voltage of the PCS greatly fluctuates when a sudden change occurs in a hydraulic turbine. It is effectively relieved by using the feed-forward control method. The effectiveness of the PCS for utilizing the DP energy in district heating systems with reduced DC-link voltage variation is verified by simulation and experimental results.

An Inductive Hybrid UPQC for Power Quality Management in Premium-Power-Supply-Required Applications

Voltage sag and harmonic pollution have a serious impact on the medium-voltage premium-power-supply-required park represented by optical semiconductors, data storage, precision instruments and biopharmaceuticals. Which makes existing equipment require higher voltage capacity of power electronics, higher economic cost and compensation performance. In this paper, an Inductive Hybrid Unified Power Quality Conditioner (IH-UPQC), which is characterized as high integration, reduced DC-link voltage and satisfactory harmonic isolation of transformer, is presented to realize the bi-directional power quality improvement for medium-voltage premium-power-supply-required park. First, the three-phase equivalent circuit and mathematical model are established to reveal the mechanism of harmonic suppression and voltage regulation. Based on the theoretical analysis, the compound control strategy of series and shunt Hybrid Active Power Filter (HAPF) as well as the synchronous method sliding Goertzel discrete Fourier transformation-pre-filtering Phase Lock Loop (PLL) are designed. Then, the main circuit components design including Double Resonant Passive Filter (DRPF), L-C-R low pass filter and the special designed filtering winding for implementing inductive filtering method are described. Finally, the performance of IH-UPQC is validated in 10kV distribution network by MATLAB/Simulink. The simulation results demonstrate that the IH-UPQC is effective to perform grid voltage regulation, load harmonic current suppression and reactive power compensation.

High Step-Up Y-Source Inverter With Reduced DC-Link Voltage Spikes

Impedance-source inverters using coupled inductors have been investigated as alternatives for providing high step-up voltages. However, leakage inductances of the coupled inductors have commonly led to lower overall effectiveness, in addition to generating high dc-link voltage spikes. The latter raises voltage stresses of switches, which in turn, may reduce the power levels of the inverters. A high step-up Y-source inverter has therefore been proposed in this paper to provide a high boost with a smooth dc-link voltage ensured by proper recycling of the leakage energy. These features have been verified by comparing simulation and experimental results of an existing Y-source and the proposed inverters. Factors compared are their respective boost ratios, voltage stresses, current stresses, and dc-link voltage spikes.

Advanced Active Filter AAF with Reduced DC Link Voltage

Advanced Active Filter AAF with Reduced DC Link Voltage

Frequency support from PMSG-based wind turbines with reduced DC-link voltage fluctuations

Frequency droop control is widely used in permanent magnet synchronous generators (PMSGs) based wind turbines (WTs) for grid frequency support. However, under frequency deviations, significant DC-link voltage fluctuations may occur during the transient process due to sudden changes in real power of such WTs. To address this issue, a current feedforward control strategy is proposed for PMSG-based WTs to reduce DC-link voltage fluctuations when the WTs are providing frequency support under grid frequency deviations. Meanwhile, the desired frequency support capability of the PMSG-based WTs can be ensured. Simulation results verify the rationality of the analysis and the effectiveness of the proposed control method.

Optimal Control of a Compact Converter in an AC Microgrid

This paper presents an optimal control method for a compact reduced switch count AC/AC converter in an AC microgrid. The AC/AC converter is adopted to interconnect dual three-phase renewable energy sources (RESs) and a three-phase permanent magnet synchronous motor (PMSM) to the grid to form an example of a mixed grid-feeding-drive system. For the adopted converter, a generalized pulse width modulation (PWM) scheme employing the third harmonic injection and a control method are proposed. Moreover, to achieve reduced dc link voltage ripple, good reference tracking and disturbance rejection, the gains of the controllers are optimized by minimizing a weighted sum of different objective functions. Each objective function represents a specific aspect to be minimized and the optimization problem is solved employing particle swarm optimization (PSO) method, while ensuring that the total harmonic distortion (THD) of the current at the points of common coupling (PCC) are less than 5%. For this mixed grid-feeding-drive system, simulation results under fast transient are provided to demonstrate the applicability of the adopted converter in the AC microgrid, the effectiveness of the proposed PWM, and the proposed optimal control method.

3-Phase 4-wire UPQC Topology with reduced DC-link Voltage rating for Power Quality Improvement using Fuzzy Controller

3-Phase 4-wire UPQC Topology with reduced DC-link Voltage rating for Power Quality Improvement using Fuzzy Controller

A Novel Design of Fuzzy Controlled D-STATCOM with Reduced DC Link Voltage

A Novel Design of Fuzzy Controlled D-STATCOM with Reduced DC Link Voltage

Conventional DC Voltage Operating System for High Speeed Traction Power Supplies Using LLC-HPQC Control

<p>In this paper a hybrid power quality compensator (HPQC) is proposed for compensation in cophase traction power supply and minimum dc operation voltage is achievable for high-speed traction power supply. The parameter design procedure for minimum dc operation voltage in HPQC as well as minimum voltage rating with load PF is discussed. The detailed discussions of proposed circuit configurations of HPQC are provided in section II, together with comparison with conventional RPC. In comparison with conventional railway power compensator proposed HPQC can achieve reduced dc link voltage level. It is also verified through simulations results that the LLC-HPQC would operate at the minimum voltage with the proposed parameter design. HPQC is able to provide system unbalances, reactive power, and harmonic compensation in cophase traction power with reduced operation voltage. The cophase traction power supply with proposed HPQC is suitable for high-speed traction applications.</p>

Modified DSTATCOM Topology with Reduced DC Link Voltage for Reactive and Harmonic Power Compensation of Unbalanced Nonlinear Load in Distribution System

Abstract This paper proposes a modified four-leg distribution static compensator (DSTATCOM) topology for compensation of unbalanced and nonlinear loads in three-phase four-wire distribution system. DSTATCOM, connected in parallel to the load, supplies reactive and harmonic powers demanded by unbalanced nonlinear loads. In this proposed topology, the voltage source inverter (VSI) of DSTATCOM is connected to point of common coupling (point of interconnection of source, load, DSTATCOM) through interface inductor and series capacitance, unlike the conventional topology which consists of interface inductor alone. Load compensation with a lower value of input DC link voltage of VSI is possible in this modified topology compared to conventional topology. A comparative study on modified and conventional topologies in terms of voltage rating of inverter power switches, switching losses in VSI and power rating of input DC capacitor of VSI is presented. The detailed design aspects of DC link capacitor and interface series capacitor are also presented. The reference filter currents are generated using instantaneous symmetrical component theory and are tracked using hysteresis current control technique. A detailed simulation study is carried out, to compare the compensation performances of conventional, modified topologies using PSCAD simulator and experimental studies are done to validate the simulation results.

Three-Phase Four-Wire UPQC Topology with Reduced DC-Link Voltage Rating Using Z-Source

The unified power quality conditioner (UPQC) is a custom power device, which mitigates voltage and current-related PQ issues in the power distribution systems. In this paper, the Z-source is combined with UPQC topology for application with non-stiff source is proposed. The existing topology enables UPQC to have a reduced dc-link voltage without compromising its compensation capability. This proposed topology also helps to match the dc-link voltage requirement of the shunt and series active filters of the UPQC. The topology uses a Z-source is connected between the series and the shunt active filter, and the system neutral is connected to the negative terminal of the dc-link voltage to avoid the requirement of the fourth leg in the voltage source inverter (VSI) of the shunt active filter. The average switching frequency of the switches in the VSI also reduces, consequently the switching losses in the inverters reduce. Detailed design aspects of the series capacitor and VSI parameters have been discussed in the Project.

Mitigation of Power Quality Problems Using DSTATCOM with Reduced DC Link Voltage

This paper mainly presents the DSTATCOM (Distribution Static Compensator) and its control methodology of DC capacitor voltage. Generally, the dc capacitor voltage is regulated using a PI controller where various control algorithms are used for load compensation. Whenever there is a change in load there is considerable variation in dc capacitor voltage which might affect compensation. In this work, a supervisory method is proposed to reduce the dc link rating. The reduction in dc link voltage leads to the reduction in switching frequency and hence switching losses A considerable reduction in the in dc link capacitor voltage is obtained without compromising the compensating capability. The major power quality issues discussed in this work are harmonics and power factor reduction. The performance of the proposed strategy is proved using the detailed MATLAB simulation studies.

A Modified Three-Phase Four-Wire UPQC Topology With Reduced DC-Link Voltage Rating

The unified power quality conditioner (UPQC) is a custom power device, which mitigates voltage and current-related PQ issues in the power distribution systems. In this paper, a UPQC topology for applications with non-stiff source is proposed. The proposed topology enables UPQC to have a reduced dc-link voltage without compromising its compensation capability. This proposed topology also helps to match the dc-link voltage requirement of the shunt and series active filters of the UPQC. The topology uses a capacitor in series with the interfacing inductor of the shunt active filter, and the system neutral is connected to the negative terminal of the dc-link voltage to avoid the requirement of the fourth leg in the voltage source inverter (VSI) of the shunt active filter. The average switching frequency of the switches in the VSI also reduces, consequently the switching losses in the inverters reduce. Detailed design aspects of the series capacitor and VSI parameters have been discussed in the paper. A simulation study of the proposed topology has been carried out using PSCAD simulator, and the results are presented. Experimental studies are carried out on three-phase UPQC prototype to verify the proposed topology.