Active Rectifier Research Articles

Performance Comparison of Numerical Methods in a Predictive Controller for an AC–DC Power Converter

The use of model-based predictive control in power converters has substantially increased in recent years. This control technique always needs a discrete system model to be implemented. There are several methods to obtain a discrete model; in this paper, all common methods are examined from a practical point of view. Their precision, simplicity, and implementation requirements are analyzed to establish their advantages and disadvantages. From this analysis, it is shown that different discretization methods result in different closed-loop converter performance. A model-based predictive control AC–DC converter is used to show that different discretization procedures result in different total harmonic distortion. For this evaluation, a simulation of a 1 kW three-phase active rectifier was performed in Matlab-Simulink.

ELECTROMAGNETIC COMPATIBLE CURRENT SOURCES WITH RELAY CONTROL

The development of industry leads to an increase in nonlinear loads, which are generators of higher harmonics in the network. The quality indicators of voltage and current consumed from the network are established by international standards for the quality of electricity. The simplest method of filtering harmonics is passive filters, lack of low quality harmonic compensation. The use of active filters improves the quality of the current. But active filters have a complex control system. The use of active rectifiers as part of semiconductor power supplies solves the problem of generating higher harmonics in the network and provides a power factor equal to 1.
 Six variants of three-phase and single-phase power supplies have been developed. They operate as a current source. All circuits consist of two parts: an active rectifier and a DC-DC converter. The scope of use of such sources is different: a direct current electric drive, an electric power system of wind turbines, an electric system of aircraft. The control system of the relay converters provides the formation of current and the maximum speed in the processing of disturbances. 
 Oscillograms of the current sources are obtained by digital modeling. They confirm the efficiency of the proposed sources, the electromagnetic compatibility of the power sources with the mains and the value of the power factor close to unity. Current sources are invarant to the action of disturbances: changes in load resistance, mains voltage. The study of electromagnetic processes made it possible to obtain analytical expressions for the maximum and minimum frequency of the relay mode, the capacitance of the capacitors and the operating conditions of the sources. 
 The developed program allows you to get the parameters for choosing the power elements of the circuit: inductance, capacitance, switching frequency of transistors. 
 The quality of the consumed current is analyzed by calculating the total harmonic distortion (THD). For all considered sources, the THD value is less than 5%, which meets the quality standards for the consumed current.

Determination of the input filter parameters of the active rectifier with a fixed modulation frequency

Goal. Development of a methodology for calculating the parameters of the active rectifier-voltage source input filter operating with a fixed modulation frequency to ensure electromagnetic compatibility with the supply network acceptable by standards at minimum values of the input inductance and checking its main characteristics on a mathematical model. Methodology. The authors have developed a methodology for calculating the parameters of the input filter of an active rectifier-voltage source. The calculation results are verified on the constructed mathematical model of a frequency converter, the scheme of which is an active rectifier and an autonomous voltage inverter. A series of experiments was carried out on a mathematical model to study the dependence of the total harmonic distortion of current and mains voltage on the value of the input inductance for various parameters of the input filter. Results. The structure and calculation procedure the input filter of an active rectifier operating with a fixed modulation frequency are proposed. The simulation results showed that the inclusion of a filter at the input of the active rectifier significantly improves its electromagnetic compatibility with the supply network in the entire range of variation of the input inductance of the circuit and makes it possible to achieve the values of the total harmonic distortion permissible by the norms. Originality. A structure and a calculation procedure the input filter of an active rectifier-voltage source operating with a fixed modulation frequency are proposed. Practical significance. The dependencies obtained in the article allow us to evaluate the relationship between the parameters of the filter elements and its characteristics among themselves and come to a compromise between them when designing a scheme for specific technical conditions.

A Hybrid Modulation Control for Wireless Power Transfer Systems to Improve Efficiency Under Light-Load Conditions

Traditional wireless power transfer (WPT) systems usually adopt the triple-phase-shift control method to maintain a constant output voltage, track the maximum system efficiency point (MEPT), and achieve zero-voltage-switching (ZVS) operation for various applications. However, these three targets are achieved at the cost of high reactive power on both primary and secondary sides, especially under light-load conditions, leading to low efficiency. This has become one of the challenges that hinder a further deployment of WPT technologies in practice. To address this vital problem, in this article, how the reactive power lowers the system efficiency is revealed based on a mathematical model established. Then, a hybrid modulation control strategy based on a proper selection between the full-bridge and half-bridge modes of the inverter and active rectifier is developed. An experimental prototype is constructed to verify the effectiveness of the proposed control method. Experimental results show that the proposed method can reduce the reactive power, maintain a constant output voltage, and realize the MEPT and ZVS operation, with high efficiencies up to 94.29% in a wide load range.

Load-Independent Push–Pull Class E$ ^2$ Topology With Coupled Inductors for MHz-WPT Applications

This article investigates the modeling and implementation of the load-independent operation for the push–pull Class E topology with coupled inductors. The analytical modeling is first presented and provides a new design methodology, which distantly improves the soft-switching performance, load regulation, and efficiency compared with the conventional inductor-coupled Class E topology. An <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC-S</i> resonant Class E <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ ^2$</tex-math></inline-formula> converter, which combines the load-independent inductor-coupled inverter and active rectifier, is proposed for MHz-wireless power transfer (MHz-WPT) applications. The active inductor-coupled Class E rectifier maintains soft switching, constant voltage gain, and zero-phase-angle input at various loads. A three-winding magnetic structure is also proposed to improve the coupled inductors by enhanced self-inductance, which features more effective harmonic suppression with lower magnetic losses and volumes. By the proposed methodology and the improved magnetic structure, the converter features negligible harmonic contents and maintains soft switching with a constant voltage conversion ratio over the entire load range. A 6.78-MHz WPT prototype was built to verify the proposed methodology with detailed parameter design and hardware implementation. The prototype realizes load-independent zero-voltage switching and maintains an approximately constant voltage gain with +5/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-$</tex-math></inline-formula> 4% variance from no-load to 320-W output power. The measured dc–dc efficiency reaches 89.3% at 210 W.

Load Independent Constant Current and Constant Voltage Control of LCC-Series Compensated Wireless EV Charger

In this article, load-independent constant current/voltage control operations of an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC</i> -Series compensated wireless electrical vehicle (EV) chargers are presented. The parameters of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC</i> -Series compensation topology are designed based on load-independent zero phase angle and soft switching operation in the constant current charging operation. Then, the load independent soft switching conditions are achieved for constant voltage charging operation with a semibridgeless active rectifier using pulse density modulation control. Thus, high efficiency power transfer to the load is performed during the entire charging period. The wireless communication is not needed to achieve the output voltage regulation in the proposed EV charging system. The soft switching operations of the switches on the primary and the secondary side are achieved in a wide load range. The performance of the proposed charging system is validated by a prototype. At the full load condition, the output voltage of the system is regulated at 210 V while the output current is 5 A. The maximum efficiency is measured 93.8% at 1 kW output power with 150 mm air gap. The efficiency performance of the system is also evaluated based on the misalignment conditions.

The use of frequency converter and active rectifier of voltage for the power quality improvement in coal longwalls

Improvement of productivity and performance in coal longwall mining is achievable via transition to longwalls to 250&ndash;400 m long and by increasing installed capacity of longwall equipment systems up to 4200&ndash;5600 kW. The up-to-date longwall mining uses energy- and resource-saving machines equipped with variable frequency motors. In this case, inclusion of the frequency converters in the machinery electrics results in essential distortion of voltage from the nominal sine waveform and leads to the power quality degradation in longwalls. With a view to enhancing power quality in longwall networks, the authors propose to use variable frequency motors with frequency converters with active rectifiers of voltage. When selecting a frequency converter with the active rectifier for voltage in underground power network, it is recommended to take into account the longwall power supply specifics, the cross-effect of the frequency converters operating in neighbor lines, the variable nature of power system loads and the change in the number of the frequency converters in simultaneous operation. To that end, the power supply model is developed to study consumed power quality with regard to the power network topology, parallel-operating frequency converters and actual loads of electric motors. The modeling has determined the mechanisms of effect exerted by the frequency converters on the power quality in operation with active rectifiers of voltage. The carrier frequency and inductance of the buffer reactor of the threelevel active rectifier, which ensure the standard quality power supply in longwall, are substantiated.

A V2G Enabled Bidirectional Single/Three-Phase EV Charging Interface Using Modular Multilevel Buck PFC Rectifier

The battery charging power electronics interface of an electric vehicle (EV) must be capable of bidirectional power flow to enable both grid-to-vehicle (G2V) and vehicle-to-grid (V2G) operations. In the presence of a single/three-phase AC supply, the front-end of the EV charger employs a power factor correction (PFC) rectifier, which should have the bidirectional capability to facilitate V2G mode. A conventional active rectifier functions in boost mode while performing PFC and voltage regulation. In most of the currently available EVs, however, the battery nominal voltage is low and, hence, a downstream high step-down DC-DC converter and high voltage DC bus capacitor are required in the charging interface. To overcome these issues, this work proposes a bidirectional AC-to-DC buck rectifier topology that can operate in G2V and V2G modes, both in single- and three-phase versions. The proposed topology utilizes the switched capacitors principle to achieve self-balancing of voltages in the capacitors. In addition, it is highly modular in structure. This paper describes the proposed topology, its working and modulation and its applications. The hardware proto model is used to validate the proposed power converter and the control approach to achieve PFC and voltage regulation. In addition, a comparison with other topologies is presented to demonstrate its competence.

Design Procedure and Efficiency Analysis of a 99.3% Efficient 10 kW Three-Phase Three-Level Hybrid GaN/Si Active Neutral Point Clamped Converter

High-efficient and power-dense ac–dc power electronic converters are demanded for a wide range of applications, such as motor drives and active rectifiers. The utilization of wide bandgap devices, such as gallium-nitride (GaN) transistors, is a key feature to improve both the efficiency and the power density of power electronic converters. Owing to the superiority of GaN switches, this article achieves a high-efficiency three-level active-neutral-point-clamped converter. However, using GaN transistors is critically dependent on the layout configuration to achieve smooth switching transient and, as equally important, efficient cooling. Therefore, this article presents layout optimization and considers different layout configurations to achieve a low power loop inductance and as efficient heatsink assembly/performance. Two configurations of the switch boards are built by GaN/Si <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> s, and a power loop inductance comparison is presented. Furthermore, a comprehensive loss model is performed to fine-tune the switching frequency from the efficiency and the size point of view. A 10 kW laboratory prototype voltage source converter, including an electromagnetic interference (EMI) filter, is built with the switching frequency of 140 kHz. The efficiency measurement is performed and confirmed the full load efficiency of 99% and peak efficiency of 99.34%. Moreover, the CISPR11 Class A conducted EMI standard is fulfilled.

Efficiency Improvement of Dual-Receiver WPT Systems Based on Partial Power Processing Control

In wireless power transfer (WPT) system for light electric vehicles (LEVs), adopting dual receivers on the receiver side is an available way to offer a high-current power supply. In this article, the partial power processing (PPP) control method is proposed for optimizing the power loss of the dual-receiver WPT system. With the PPP control method, only one of the active rectifiers will be regulated by the variable angle phase-shift (VAPS) modulation to adjust the required power under different load power demands and misalignment situations. As a result, the switching loss of the two active rectifiers, which accounts for a considerable part of the overall power loss with a high operating frequency, can be dramatically reduced. At last, 24 V-50 A-1200 W LEV wireless charging experimental setup to verify the effectiveness of the proposed PPP control method. Compared with the conventional power distribution method based on impedance matching with VAPS, the proposed PPP control method can increase the efficiency by 6%–7% with misalignment situations, achieving the overall efficiency as high as >92% at the heavy load.

Duty Cycle Control Strategy for Dual-Side LCC Resonant Converter in Wireless Power Transfer Systems

The dual-side inductor–capacitor–capacitor (LCC) topology circuit has been widely adopted in wireless power transfer (WPT) systems due to its constant output current characteristic. However, most conventional control methods need specific synchronization techniques between the primary and secondary sides to avoid the oscillation in the system, which increases the cost and control complexity. To solve this issue, this article proposes a new duty cycle control (DCC) strategy for a dual-side LCC resonant converter with a semibridgeless active rectifier (SAR). With such a control strategy, gate signals of the primary- and secondary-side circuits do not need to be synchronized, which could reduce the complexity and the cost of the WPT system. Besides, the switching frequency of the secondary side can be decreased significantly. This article first presents the modal analysis of phase shift control (PSC) and DCC. Then, generalized state-space averaging (GSSA) modeling with PSC and the hybrid average modeling with DCC are performed. In addition, controllers’ design for both strategies is conducted to achieve the constant output voltage. Finally, the eigenvalues’ analysis is used to determine the stability region of the WPT system. The theoretical analysis has been validated by both simulation and experimental results.

SYNTHESIS OF THE OUTPUT VOLTAGE REGULATOR OF THE ACTIVE FOUR-QUADRANT RECTIFIER

The analysis of known control systems of the active four-quadrant rectifier with pulsewidth modulation applied on a rolling stock of electric railway transport, and methods of definitionof modal and symmetric optimum is carried out. The necessity of the automatic regulation system forstabilization of the output voltage under the condition of current change is established. The controlsystem of the active three-phase four-quadrant rectifier on the basis of pulse-width modulation isdeveloped. The static control characteristic of the output voltage of the active rectifier as a functionof the value of the load current and the value of the control factor is determined. It is shown that the control characteristic is nonlinear, and the static transmission coefficient of the active rectifierdepends on the load current. The amplitude-frequency characteristic of the control channel of theoutput voltage of the active rectifier is determined, which is obtained by adding additional frequenciesto the control signal and measuring these frequencies in the form of the output voltage. The dynamiccontrol characteristic and transfer function of the active rectifier are determined. The simulation ofan active rectifier with a control system and a pulse-width modulation frequency of 10 kHz in theMatlab / Simulink software environment was performed. The synthesis of the output voltage regulatorof an active three-phase four-quadrant rectifier with pulse-width modulation is performed, which ismade on the basis of the modal optimum. The oscillograms of the transient process of the outputvoltage during autoregulation are obtained. Given the fact that the static transmission factor of thecontrol system of the active rectifier depends on the load current, to obtain the uniqueness of thetransient process when regulating the output voltage, it is necessary to create an adaptive regulatorfor the output current of the active rectifier.

Comparative Analysis on AC and DC Distribution Systems for Electric Propulsion Ship

Decarbonization is an ongoing issue in the shipping industry, and electric propulsion systems are being proposed as alternative solutions to satisfy this requirement. To answer the fundamental questions of “Are electric propulsion systems the green solution?” and “Can DC distribution systems contribute to the decarbonization in shipping?”, this paper analyzed DC distribution system electrical characteristics, economic feasibility, and environmental evaluation for a full-scale AC-DC hybrid distribution electric propulsion system facility. By applying the actual ship’s operating profile as inputs, a DC distribution system with an active front end rectifier and a variable speed generator engine was proven to guarantee the same electric stability as the conventional AC distribution system. The life cycle assessment results achieved economic and life cycle environmental benefits of about 10% (8.9% for Case 1 and 12.4% for Case 2). These research findings offer meaningful insights into the DC distribution system to minimize fuel consumption and emissions toward cleaner shipping.

INCREASING THE ENERGY PARAMETERS OF THE MAINS SUPPLY BY ACTIVE RECTIFIERS IN THE COMPOSITION OF FREQUENCY CONVERTERS

The total power consumed by electrical loads from the electric mains consists of their two components – active and reactive. Most electric drives of modern industrial enterprises operate with a reactive power index of 0.7–0.8. This leads to increased consumption of full power, which increases the load on the mains supply. Modern electric drives are built according to the principle: power supply – rectifier – DC link-inverter – asynchronous motor. Full power consumption occurs at the junction of the “power supply-rectifier”, where the required active power factor of the converter device can be formed. The higher the active power factor, the lower the reactive component in the total energy consumed. Thus, the article proposes a solution to the problem of creating highly efficient converter devices for powering electric motors with the formation of the necessary power factor, since frequency-controlled electric drives of modern mechanisms in industrial enterprises are the main consumers of electricity, which have a significant impact on the state of the supply network. The article considers the possibility of increasing the power factor of the mains input of electric drives with two-link frequency converters based on active (controlled) rectifiers with current inverters and voltage inverters. New methods of control of active rectifiers based on the use of AC rectifiers on fully controlled thyristors GTO, GCT, as well as IGBT transistors with pulse width adjustment are proposed. The variants of the construction of these rectifiers and the results of modeling the proposed control methods are presented, confirming a decrease in the passive components of the mains current, and as a consequence, an increase in the power factor of the network input. The simulation results are performed in the MATLAB 10 program, and are the basis for confirming the method of increasing the active power factor at the network input of a controlled frequency converter with a two-link structure.

Optimization of AC–DC Converters for Regenerative Train Suspensions

This article focuses on the dynamic optimization of the operating conditions of two types of ac–dc converters, a diode bridge rectifier and a full bridge active rectifier, which are used for interfacing regenerative rail vehicle suspensions based on ac electromagnetic generators. A theoretical analysis shows that, for both types of converters, the optimal operating conditions, leading to the maximization of the extracted power, can be predicted from the measurement of the generator speed. In particular, as regards the diode bridge rectifier, it is shown that the optimal value of the dc side voltage is related to the generator speed. As regards the active full-bridge rectifier, it is shown that a relationship exists between the optimal converter duty cycle and the generator speed. Experimental results validate the proposed theoretical models both in case of ideal constant generator speeds, and in case of more realistic time-variable generator speeds. The proposed analysis enables the design of high-performance speed-driven maximum power point tracking techniques for regenerative vehicle suspensions.

A Single-Stage Rectifier-Less Boost Converter Circuit for Piezoelectric Energy Harvesting Systems

In this paper, a single-stage rectifier-less boost converter circuit (SSRBC) for piezoelectric energy harvesting from ambient vibration was proposed. The proposed rectifier-less circuit acted as a boost converter to extract energy from a piezoelectric device (PD). It combined the conventional boost, buck-boost methods using two split inductors and single filter capacitor. The proposed integrated circuit topology functioned in both positive and negative half cycles generated by the PD. In the proposed topology, inductors were invigorated by being enveloped with the current, which was produced by the PD through the switches. This facilitated active rectification of ultra-low AC (amplitude < 0.5 V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P</sub> ). Theoretical analysis, control strategies, simulation and experimental study were presented. The proposed circuit was capable of converting a low amplitude AC voltage of 0.5 V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P</sub> into 5.1 V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dc</sub> . The highest output power extracted by the proposed circuit was 281.1 μW, which outperformed existing circuits. It could potentially facilitate the advancement of vibration-based energy harvesting systems for low power demand applications such as sensors, quartz watches and portable charging devices.

Multi-Objective Comparative Analysis of Active Modular Rectifier Architectures for a More Electric Aircraft

Aircraft electrification requires reliable, power-dense, high-efficient, and bidirectional rectifiers to improve the overall performance of existing aircrafts. Thus, traditional bulky passive rectifiers must be substituted by active rectifiers, satisfying the requirements imposed by up-to-date standards. However, several challenges are found in terms of power controllability, due to the standardized passive rectifier-based operating conditions. This work presents the implementation of an active rectifier modular architecture for aircraft applications. An analysis of the technical difficulties and limitations was performed and three innovative modular architectures are proposed and designed. In order to find the most suitable architecture, a comparison framework is proposed, focusing on efficiency, volume, and reliability parameters. From the comparative analysis, it can be concluded that the two-stage configuration architecture is a good solution in terms of semiconductor life expectancy and low volume. However, if converter redundancies are required, the single-stage with STATCOM configuration is an excellent trade-off between low volume, redundancy, and cost-effectiveness.

Winding Layout Considerations for an Integrated Generator–Rectifier System

An integrated generator–rectifier system is a promising architecture to harvest energy in offshore wind turbines. The system processes the majority of the incoming power using reliable, efficient, and inexpensive passive diodes operating at the generator line frequency. Elimination of capacitors at the diode rectifiers’ output by appropriately phase shifting the voltages of a multiport generator further improves the reliability of the overall architecture. This article creates a generalized framework to evaluate the interactions among different generator ports, diode-bridge rectifiers, and the active rectifier that is used to control the power flow. The framework enables quantifying the effect of integration on the dc bus power ripple and power imbalance among different generator ports. An exemplary winding layout is proposed that ensures theoretically zero interaction between the passive ports, although all the ports are mounted on a magnetic structure. A 10-MW integrated generator–rectifier design and simulation proves the accuracy of the framework using coupled circuit and finite-element simulation. Finally, a laboratory prototype shows the realization of the winding layout. The proposed inductance-matrix-based framework can be used to evaluate other winding layouts to estimate the effect of magnetic coupling on the performance of the system.

Non-Linear Switching Circuit for Active Voltage Rectification and Ripples Reduction of Piezoelectric Energy Harvesters

This paper describes an improved non-linear switching circuit (INLSC) for active rectification of voltage and reduction of ripples in the voltage waveform for the piezoelectric energy harvesting (PEH) system. The proposed converter controls the alternating current (AC) generated by the piezoelectric device (PD) under mechanical vibration. The proposed circuit combines the boost and buck-boost processes through a switching process, which functions in both positive and negative cycles. In addition, it controls the voltage and frequency of the load capacitor. In this process, the passive components in the circuit are energised by being short with the AC voltage using switching signals, which facilitates the active rectification of ultra-low AC voltage. Design considerations, theoretical analysis, simulations and experimental results are presented. It was shown that the circuit was able to control the switching signal and to convert low AC voltage (0.44 Vi) to high direct current (DC) voltage (6.5 Vdc) while achieving an output power of 469 µW which outperforms the existing similar circuits and synchronous rectifier circuit. The ripples in the rectified voltage were also comparatively less. Application-wise, the proposed circuit could power a manually connected 7-segments display, commonly used for traffic applications.

A multi-rotor medium-voltage wind turbine system and its control strategy

With the continuous increase in wind turbine power ratings, the growing turbine size makes the turbine manufacture, transport and installation more challenging. At MWs power level, the conventional two-level converters with a 690V voltage have to handle very high current, which causes substantial losses and high cost of power cables, switchgears, etc. To solve this issue, a multi-rotor medium-voltage modular wind turbine configuration is proposed in this paper. Each cell is composed of a turbine rotor, a permanent magnet synchronous generator (PMSG) and a converter. Each PMSG is driven directly by each rotor. The input and output power stages of each converter consist of a three-phase active rectifier and an H-bridge inverter. H-bridge inverters are connected in series to achieve medium-voltage grid connection. This wind turbine configuration has advantages such as more wind power capture, higher reliability, lower transport and installation cost, easy extension to higher power and grid voltage ratings and fault-tolerant operation capability. A control strategy of the wind turbine with maximum wind power capture is proposed. An imbalance compensation control scheme is also proposed to keep three phase output current balanced. Simulation results and experimental tests have validated the proposed wind turbine topology and control strategy.