Output Filter Research Articles

Distributed Controller for the Parallel Operation of Power Converters With Small Output Filters

Distributed Controller for the Parallel Operation of Power Converters With Small Output Filters

Improving the Control Strategy of the DVR Compensator Based on an Adaptive Notch Filter with an Optimized PD Controller Using the IGWO Algorithm

One of the objectives of electrical distribution networks is to provide customers with access to high‐quality electricity. Because any disruptions in these systems result in voltage disorders, different devices are employed to offset these disruptions on consumers who are more susceptible. One of the most important and contemporary pieces of equipment that is connected in series with the network is dynamic voltage restoration (DVR), which shields delicate loads from network voltage issues by injecting the proper voltage. This article presents a DVR control scheme optimized with improved grey wolf optimization (IGWO) that uses a proportional derivative (PD) controller and adaptive notch filter (ANF). The output LC filter’s resistance has been removed, and the control system has actively engaged in oscillation damping in order to accelerate dynamic responsiveness and lower system losses. The major component of the voltage, which comprises its frequency, amplitude, and phase, is extracted using ANF. The capacitor current of the output filter in this structure is fed back to the control system and from the current mode control in the inner loop to boost stability. Owing to the occasionally complex dynamic behavior in distribution networks, particularly during a fault, the system’s frequency response has been altered and response speed has been accelerated using the PD controller. This kind of controller is distinguished by its accurate functioning in the presence of frequency deviations and its swifter dynamic reaction in the face of voltage swell and sag. In order to improve the THD and voltage sag indicators of the sensitive load, the PD coefficients were adjusted using the IGWO algorithm. As a consequence, the simulation results demonstrated that the suggested controller performed better than traditional controllers.

Analysis and Improved Behavior of a Single-Phase Transformerless PV Inverter

Transformerless inverters have an important role in the electrical energy market. The high-efficiency and reliable inverter concept is one of the most widely used inverters in single-phase photovoltaic systems because of its high efficiency, low cost, and reduced leakage ground current. However, the leakage ground current behavior depends on the power and weather conditions, which can increase the parasitic capacitance value, thus producing an increase in the leakage ground current magnitude. In this paper, it is proposed to add a passive inductive–capacitive output filter to the inverter structure in order to reduce the dependency of the leakage ground current on the system power and weather conditions. The inductive–capacitive output filter is designed in such a way that it can provide a low impedance path for the leakage ground current, different from the ground path. The proposed system was evaluated both through simulations and experimentally in a 1 kW laboratory prototype.

РОЗРАХУНОК ПРОЦЕСІВ У ПЕРЕТВОРЮВАЧІ ЗА ТОПОЛОГІЄЮ LUO З ВИКОРИСТАННЯМ МЕТОДА УСЕРЕДНЕННЯ НА ОСНОВІ ТЕОРЕМ ЛАГРАНЖА

The electromagnetic processes in elementary dc converter according to the Luo topology with inverting output in modes of continuous and discontinuous conduction were studied. Using the method of averaging in the state space based on Lagrange theorems, mathematical models of converter for mentioned modes of operation have been devel-oped. The use of developed models made it possible to obtain analytical expressions for calculating the average and pulsation values of currents and voltages in the reactive elements of the converter, as well as their ripple coefficients. Graphical dependences of the mentioned parameters were calculated in the entire commutation range of converter, taking into account the conduction modes. It is shown that, in comparison with traditional topology of buck-boost con-verter, the output filter in elementary Luo converter with inverting output significantly reduces the ripple coefficient of output voltage. It was determined that the amount of voltage ripple reduction is proportional to the product of the in-ductance and filter capacity values, as well as the square of the switching frequency and does not depend on the con-ductivity mode of the converter. Ref. 13, fig. 5, table. Key words: dc voltage converters, Luo converter, averaging method in state space, Lagrange theorems.

High voltage gain quasi Z‐source inverter unified with switched three‐winding coupled inductor

SummaryThis paper presents a new high voltage gain quasi Z‐source inverter consisting of a switched‐inductor unit. A coupled inductor including three windings is utilized in structure of the switched inductor in a way to increase voltage gain effectively. In addition, the configuration includes an active switch with low number of components that has positive effects on voltage gain and two of its components recycles stored energy of the coupled inductor similar to a clamp circuit. The converter boosts voltage appropriately in low shoot‐through duty cycles and transfers power with a continuous input current, leading to a reduction in losses, requiring smaller output filter and improving the efficiency. Also, the converter can operate in high modulation index for similar voltage gains compared to the other works which improves quality of outputs. Low number of components and fewer cores for inductors are considered during the design of the converter, causing some superiorities for it in comparisons. In addition, the presented converter has appropriate condition from the viewpoint of voltage stress on its diodes. To validate quality of the converter performance, a 240‐W prototype is prepared that converts 35‐ to 60‐V DC to three‐phase sinusoidal voltages where effective voltage of each phase is equal to 110 V.

Nonfragile high‐gain observers for nonlinear systems with output uncertainty

AbstractIn this paper, we present the definitions of nonfragile high‐gain observers and design method for lower‐triangular nonlinear systems with output uncertainty. Radial basis function neural networks (RBFNNs) are used to approximate the output uncertainty. By inserting an output filter and an input‐output filter, a new augmented adaptive observable canonical form is derived. Then, a corresponding observer with gain perturbations is designed to estimate the states and the coefficients of the RBFNNs, and a disturbance observer is designed to estimate the approximation error. The maximum allowable gain perturbation is also given. Then, the obtained results are extended to nonlinear systems in adaptive observer form with output uncertainty. Finally, some numerical simulations are offered to corroborate the theoretical results.

Soft switching modulation strategy based on bipolar (PSM) with improved efficiency in high-frequency link inverters

High Frequency-Link (HFL) Inverters have been employed to integrate renewable energy sources into utility grids and electric vehicles. The soft-switching range of High-Frequency Link Inverters (HFLI) is increased using auxiliary inductors and capacitors. The application of auxiliary components increases the conduction loss and the complexity of the circuit. The literature indicates that the existing soft-switching methods suffer from higher duty cycle loss, voltage spikes, and lower efficiency owing to the resonance between the parasitic capacitance of switches and the leakage inductance of the transformer. Therefore, it is imperative to develop a modulation strategy that can improve the efficiency of HFLI. In this context, the proposed study develops a cycloconverter-type High-Frequency Link Inverter (CHFLI) based on a Bipolar Phase Shift Modulation (BPSM) strategy without the use of auxiliary components. The proposed modulation strategy enables the semiconductor switches to operate under zero voltage switching. The full-bridge inverter and Full Bridge Active Clamper Circuit (FBAC) switches operate at the same gating signals with a constant duty cycle of 50%. The proposed topology uses built-in magnetizing inductance to achieve zero voltage switching and reduce the duty cycle loss. The leakage energy is recycled from the output filter inductor to the load side using the FBAC. The results indicate that the proposed modulation strategy achieves ZVS and simultaneously achieves an efficiency of 95%. The proposed modulation strategy is easy to implement and does not require complex circuitry.

Harmonic analysis and filter design based on high power electromagnetic transmitter

In order to effectively suppress the higher harmonics contained in the output voltage of high-power electromagnetic transmitter, the waveform expression of the output voltage of bipolar pulse width modulation (SPWM) circuit is derived, which can accurately obtain the fundamental wave and each harmonic content in the inverter bridge transmission voltage, and provide a theoretical basis for the design of output filter. At the same time, a design method of output LC filter based on high power electromagnetic transmitter is proposed based on MATLAB simulation calculation and considering the fundamental voltage drop, inductor current ripple and reactive power capacity on the filter inductor. Finally, the feasibility of this design method is verified by the field experiment of transmitter, and the output filtering effect is good.

Nonlinear control of permanent magnet synchronous generators (PMSG) using feedback linearization

This paper presents nonlinear control of permanent magnet synchronous generators using feedback linearization. Permanent-magnet synchronous generators (PMSGs) are commonly used for small variable-speed wind turbines to produce highefficiency, high-reliability, and low-cost wind power generation. To eliminate the effects of nonlinearity caused by magnetic saturation, an input–output feedback linearization technique is applied to design the high-performance nonlinear current controllers. With this nonlinear control scheme, output voltage responses become faster than those in cascade control structures. Thus, the size of the output filter capacitor can be much reduced since fast voltage control is feasible. As with usual PWM power converters, in addition, the input current is regulated in a sinusoidal waveform. The proposed control scheme provides the wind generation system with the maximum efficiency and high dynamic performance.

Multi-objective optimization of two-stage AC–DC power supply for reliability and efficiency using NSGA-II and meta-heuristic honey bee algorithms

This paper introduces a novel approach to simultaneously optimize the reliability and efficiency of a switching power supply (SPS) using the Non-dominated Sorting Genetic Algorithm (NSGA-II) and Honey Bee Algorithm (HBA). The proposed method uses a Markov model to evaluate the reliability of the converter and maximizes objective functions, including efficiency and reliability, using optimization algorithms to identify the optimum values of the converter parameters. The optimization algorithm determines the optimal values for converter parameters, such as switching frequency, transformer turn ratio, and DC-link voltage. It also fine-tunes circuit components, such as the power factor correction inductor, DC-link capacitor, and output filter components. A sensitivity analysis is carried out to assess the impact of various parameters on the multi-objective functions of the converter. The converter’s reliability and mean time to failure (MTTF) are evaluated using the Markov reliability model, considering all components’ short and open circuit faults. The failure rates of converter components are calculated using the MIL-HDBK-217 methodology. The results obtained from the NSGA-II and HBA are compared to identify the superior algorithm with the best-optimized parameters. Simulation results indicate that the proposed optimization technique enhances the converter’s reliability performance while maintaining its efficiency. Furthermore, this paper presents comprehensive analyses, comparisons, and experimental findings to demonstrate the converter’s fault-tolerant capability. The multi-objective optimization approach offers a practical and effective strategy for optimizing switching power supplies for efficiency and reliability

Calculation of the Output Filters of Power Supply Systems with Multizone Control

Calculation of the Output Filters of Power Supply Systems with Multizone Control

Technology and Applications of Wide Bandgap Semiconductor Materials: Current State and Future Trends

Silicon (Si)-based semiconductor devices have long dominated the power electronics industry and are used in almost every application involving power conversion. Examples of these include metal-oxide-semiconductor field-effect transistors (MOSFETs), insulated-gate bipolar transistors (IGBTs), gate turn-off (GTO), thyristors, and bipolar junction transistor (BJTs). However, for many applications, power device requirements such as higher blocking voltage capability, higher switching frequencies, lower switching losses, higher temperature withstand, higher power density in power converters, and enhanced efficiency and reliability have reached a stage where the present Si-based power devices cannot cope with the growing demand and would usually require large, costly cooling systems and output filters to meet the requirements of the application. Wide bandgap (WBG) power semiconductor materials such as silicon carbide (SiC), gallium nitride (GaN), and diamond (Dia) have recently emerged in the commercial market, with superior material properties that promise substantial performance improvements and are expected to gradually replace the traditional Si-based devices in various power electronics applications. WBG power devices can significantly improve the efficiency of power electronic converters by reducing losses and making power conversion devices smaller in size and weight. The aim of this paper is to highlight the technical and market potential of WBG semiconductors. A detailed short-term and long-term analysis is presented in terms of cost, energy impact, size, and efficiency improvement in various applications, including motor drives, automotive, data centers, aerospace, power systems, distributed energy systems, and consumer electronics. In addition, the paper highlights the benefits of WBG semiconductors in power conversion applications by considering the current and future market trends.

Double voltage vector model predictive control for grid-connected cascade H-bridge multilevel inverter with fixed switching frequency

Model predictive control (MPC) is an outstanding control method which can achieve superior dynamic response, nonlinear control and multi-objective collaborative control. However, because of unfixed switching frequency, the harmonic spectrum of the output current is dispersed, which would make it difficult to design the output filter. In this work, a double voltage vector model predictive control (DVV-MPC) algorithm for grid-connected cascade H-bridge (CHB) multilevel inverter is presented. The algorithm not only has the advantages of MPC but also produces fixed the switching frequency of the inverter. It is realized by a modulation stage with two adjacent voltage vectors in one switching cycle. And the duty cycle of the associated voltage level is obtained by minimizing an additional cost function. This method is suitable for the cascades of n cells inverter. For reducing the computation burden and eliminating the computation delay, adjacent regions prediction method and time-delay compensation method are applied to the inverter. Finally, in this paper, the proposed strategy is applied to a single-phase grid-connected 7-level CHB inverter. Simulation and experiment are executed to show the advantages of the proposed control algorithm in dynamic state and steady state.

DEVELOPMENT OF A BIDIRECTIONAL DC/DC CONVERTER WITH DUAL BATTERY ENERGY STORAGE FOR HYBRID ELECTRIC VEHICLE SYSTEM

This thesis focuses on the analysis, design, and control of a bidirectional DC/DC converter for electric vehicles. The converter aims to recover energy during regenerative braking. A stable converter topology with an output filter is proposed and a 1.5-kW prototype is designed. Sliding-mode control is chosen for the current loop, while voltage PI control is used for the converter. Interleaving multiple converters is explored to increase power rating. Experimental tests confirm the stability of the converter under realistic driving conditions.

Cascaded Inverters Increasing the Number of Levels and Effective Switching Frequency in Output Using Coupled Inductors

In this paper, a new coupled-inductor based modular multilevel cascaded inverter using a new phase-shift control is presented. The proposed inverter can generate a high output ac voltage using standard low voltage rating devices. The number of levels in the output pulse width modulation (PWM) voltage and the effective switching frequency of the output filter are increased using coupled inductors and phase-shift control. The switching signals of the cascaded units in the proposed inverter are phase-shifted by 360°/4n, where n is the number of cascaded units. The proposed phase-shift control results in (4n+1) levels in the output PWM voltage of the proposed inverter and increases the effective switching frequency of the output filter by 4n times of the actual switching frequency fsw. As a result, the output waveforms can be generated with better quality and less distortion. In addition, the output filter can be decreased dramatically in size. Besides, fewer coupled inductors are used to reduce the footprints, the number of inductors, and magnetic volume. Moreover, the proposed inverter is exceptionally reliable due to no short-circuit risk in the circuit.

A Novel High-Frequency Inverter With ZVT in a Wide Range of Duty Cycles and PFs

This paper presents a wide-range zero-voltage-transition (ZVT) high-frequency single-phase inverter. The proposed inverter consists of a full-bridge inverter and two auxiliary switches that are magnetically coupled to the output filter inductor via an additional winding. The auxiliary circuit provides zero-voltage switching (ZVS) for the full-bridge converter switches, while the auxiliary switches are turned on and off with zero current switching (ZCS). A combination of unipolar and bipolar modulation is used as the modulation technique to ensure soft-switching over a wide range of duty cycles and power factors. The proposed auxiliary circuit has a simple structure and does not require floating gate drives for the auxiliary switches. A 1.5 kW-400 kHz prototype has been developed to verify the theoretical analysis, demonstrating a significant increase in efficiency for both unity and non-unity power factors.

Sliding Mode Control of a Four-Leg Dynamic Voltage Restorer in a Natural Reference Frame

This paper focuses on designing a sliding mode control (SMC) for a dynamic voltage restorer (DVR) using a four-leg voltage source converter and its output filters in the natural reference frame. The coupling of filter-capacitor voltages through the control inputs of the DVR system leads to cross-coupling in the dynamics of conventional sliding variables with respect to four control input variables, making the design of SMC using Lyapunov stability criteria difficult. To overcome this, a new sliding variable for each converter leg is proposed, which is a function of the respective filter-capacitor voltage and a fictitious voltage that depends on the converter neutral-point voltage (NPV). This allows control of both the compensator voltages and the converter NPV using the proposed scheme. This paper also presents the calculation of the optimum sliding coefficient to maximize the sliding existence region for a four-leg DVR. The performance of the proposed control scheme is experimentally validated under various operating conditions using a laboratory prototype of a four-leg DVR.

Zero-Level Control Design in AC Microgrids: A Robust Multivariable Approach

In this paper, a multi-input multi-output (MIMO) robust proportional-integral (PI) controller is designed for zero-level control of AC microgrids. The study system is a voltage-sourced converter connected to the rest of the microgrid through a distribution line and an AC output filter. The design procedure of the proposed high-gain PI controller is independent from the state matrix of the distributed energy resources. Severe local load changes are considered as the system unknown disturbances. It is proved that the closed-loop system behaves like a first-order system with stable internal dynamics. As the bandwidth of the suggested zero-level control can be systematically adjusted, it can properly operate in both high and medium frequencies without considerable fluctuations and overshoots at the output. It is also shown that circulating currents, which can cause overcurrent conditions in power electronic devices and damage DC-link capacitors, are limited without using any limiters. By considering some realistic scenarios and through time-domain simulations in MATLAB/SIMULINK and a supporting experimental test, it is shown that the proposed strategy can successfully attenuate adverse effects of unknown disturbances on the load voltage of islanded microgrids.

A bidirectional single‐phase Z‐source AC‐AC converter with reduced voltage stress on switches and safe commutation strategy

SummaryIn this paper, a bidirectional single‐phase Z‐source ac‐ac converter is proposed. Common features between the proposed converter and its counterparts are the capability of boost in‐phase, buck out‐of‐phase, and common ground. The output voltage gain of the proposed converter is improved compared with previous Z‐source ac‐ac converters, while the total standing voltage (TSV) of the switches has also been significantly reduced. Owing to the reduction of voltage stress of semiconductor elements, the switching device power (SDP) of the proposed converter is reduced. As a result, the cost of the converter is also reduced. A bidirectional switch is replaced instead of the output filter inductor to reduce the volume and weight of the converter. A safe commutation strategy is applied to eliminate voltage spikes on switches. Furthermore, the proposed converter can transfer power in both directions. By evaluating the converter in different operating modes, the key relationships and parametric design of the converter are presented. A laboratory prototype is made to confirm the proposed converter performance.

A novel pulse multiplication circuit for reducing harmonic distortion of 12 pulse rectifiers in aircraft electrical power systems

AbstractTo improve the performance and reduce the total harmonic distortion (THD) of the autotransformer 12‐pulse rectifier, a novel pulse multiplication circuit (PMC) based on two tapped inter‐phase reactors (TIPRs) is proposed to improve performance and reduce the THD of the autotransformer 12‐pulse rectifier. The proposed rectifier includes a phase‐shifting autotransformer based on a polygon connection, two 6‐pulse diode bridge rectifiers (DBRs), and a PMC. The novel PMC consists of two TIPRs (TIPR1 and TIPR2), an auxiliary single‐phase diode bridge (including four diodes D1 to D4), and two auxiliary diodes D21 and D22, which are connected directly to the output terminal of the DBRs (DBR1 and DBR2). The simulation and experimental results confirm the high capability of the proposed PMC to reduce the harmonic distortion of the input current, so that by using the proposed PMC, the input current is almost sinusoidal and the THD of the input current is less than 3%. Also, the results show that the proposed 12‐pulse rectifier meets the standard requirements of aircraft electrical systems (DO‐160G) without the need for any input and output filters.