Three-phase Current Source Rectifier Research Articles

Three-Phase Current Source Rectifier With Reduced Voltage Stress on Switching Devices and Common Mode Current Mitigation

Three-Phase Current Source Rectifier With Reduced Voltage Stress on Switching Devices and Common Mode Current Mitigation

Impact of Narrow Pulse on High-Switching Frequency Three-Phase Current Source Rectifier

Impact of Narrow Pulse on High-Switching Frequency Three-Phase Current Source Rectifier

An Improved Asymmetric Modulation of Current-Source Rectifier With CM Filter for Low Voltage Stress on Switching Devices

Common mode (CM) filters are usually utilized in high power density three-phase current source rectifier (3ph-CSR) to suppress the CM noise in the input currents. However, when CM filters are utilized, the inductor currents at the positive and the negative ends of the DC side of 3ph-CSR are unequal, which brings high voltage stress on switching devices. To reduce the voltage stress on the switching devices, an improved asymmetric modulation is proposed in this letter. In the proposed asymmetric modulation, two switching devices are always turned on in each sector, which clamps the voltage of the switching devices to the peak of the input line voltages. A 1kW experimental prototype of the 3ph-CSR is built to verify the analysis results.

Impact of Space Vector Selection and Input Displacement Angle on Switch Voltage Stress of Current Source Rectifier

Three-phase current source rectifier (CSR) is concerned due to its flexible output voltage regulation, high reliability and fast dynamic response. Excessive voltage stress on the switch will increase the cost of the rectifier and reduce the reliability of the system. Therefore, it is essential to optimize the voltage stress of the switch. In this letter, the voltage stress of switch caused by each current vector in space vector modulation (SVM) is analyzed. Then, the vectors with low voltage stress are selected for combination to reduce the voltage stress of the switch without changing the topology. In addition, the vectors are re-optimized considering the effects of displacement angle. The re-optimized SVM can reduce the voltage stress by up to 13% under the leading or lagging power factor operation. Furthermore, the dc-link current ripple and modulation index range of different modulation methods are compared, and the effectiveness of the proposed modulation schemes are verified by experiments.

Variable Pulse Density Modulation for a Buck-Type Three-Switch Current Source Rectifier

With flexible voltage adjustment without an intermediate DC/DC converter, short-circuit protection, self-starting, high reliability, and three-phase current source rectifiers (CSRs) are being widely used in high-power medium-voltage applications and low-power low-voltage applications. Modulation methods significantly affect the performance of CSRs and can be categorized into offline modulation methods, such as selective harmonic elimination/compensation pulse width modulation (SHE/SHC-PWM), and online modulation methods, such as space vector pulse width modulation (SV-PWM) and carrier-based pulse width modulation (CB-PWM). The SHE/SHC-PWM is popular in high-power medium-voltage applications that do not require a fast dynamic response and have a low switching frequency. Online modulations considerably improve the dynamic response and performance of the CSR; however, high computational power, such as digital signal processors (DSPs), is required at higher switching frequencies, leading to greater system complexity and cost. In this paper, an offline method based on variable pulse density modulation (VPDM) of power switches to synthesize sinusoidal input currents and control power transfer with pulse width modulation (PWM) is proposed. The proposed modulation is applicable to the three-switch buck-type VIENNA rectifier, showing the capability of improving the input current total harmonic distortion (THD) with respect to the SHE-PWM and is comparable to online modulations at a sufficiently high switching frequency. The simulation and experimental results basically prove the feasibility of the proposed modulation.

Conductance Emulating Control Strategy for Three-Phase Current Source Rectifier Under Unbalanced Grid Voltages

Power oscillation is a technical challenge for the grid-connected three-phase current source rectifiers (3ph-CSRs) under unbalanced grid voltage conditions. To manipulate the instantaneous power adapted to different grid requirements under unbalanced grid voltage conditions, a conductance emulating control method is proposed in this brief. The proposed method constructs a fictitious voltage pair with two individually adaptable parameters. One parameter regulates the distribution of oscillating power between active power and reactive power, and another parameter controls the average reactive power. Then, the rectifier imitates variable conductance under the fictitious voltage pair, regulating the average active power. As a result, the power control of the grid-connected 3ph-CSRs becomes flexible and adaptable to various grid requirements. The correctness and effectiveness of the proposed control scheme are verified by experimental results.

Control of a Three-Phase Current Source Rectifier for H2 Storage Applications in AC Microgrids

The share of electrical energy from renewable sources has increased considerably in recent years in an attempt to reduce greenhouse gas emissions. To mitigate the uncertainties of these sources and to balance energy production with consumption, an energy storage system (ESS) based on water electrolysis to produce hydrogen is studied. It can be applied to AC microgrids, where several renewable energy sources and several loads may be connected, which is the focus of the study. When excess electricity production is converted into hydrogen via water electrolysis, low DC voltages and high currents are applied, which needs specific power converters. The use of a three-phase, buck-type current source converter, in a single conversion stage, allows for an adjustable DC voltage to be obtained at the terminals of the electrolyzer from a three-phase AC microgrid. The voltage control is preferred to the current control in order to improve the durability of the system. The classical control of the buck-type rectifier is generally done using two loops that correspond only to the control of its output variables. The lack of control of the input variables may generate oscillations of the grid current. Our contribution in this article is to propose a new control for the buck-type rectifier that controls both the input and output variables of the converter to avoid these grid current oscillations, without the use of active damping methods. The suggested control method is based on an approach using the flatness properties of differential systems: it ensures the large-signal stability of the converter. The proposed control shows better results than the classical control, especially in oscillation mitigation and dynamic performances with respect to the rejection of disturbances caused by a load step.

A Novel Three-Phase Current Source Rectifier Based on an Asymmetrical Structure to Reduce Stress on Semiconductor Devices

This paper presents a novel three-phase current source rectifier (CSR) for AC/DC step-down voltage conversion to reduce voltage and current stress. The proposed converter features an asymmetrical connection between upper and lower arms compared with conventional CSRs, but has the same number of devices. With the proposed asymmetrical structure and modified space vector pulse width modulation (SVPWM) scheme, half of transistors only need to withstand half of the line-to-line voltage rather than the full line-to-line voltage, and its DC link current can be shared by multiple switches in freewheeling periods. Therefore, it is able to bring about a significant reduction in voltage and current stress, allowing for an improvement in the converter without additional cost. The topological structure, operation principles, and comparative analysis are specifically presented. Finally, an experimental prototype is built up to verify the performance of the proposed converter.

Integrated Battery Charger for Electric Vehicles Based on a Dual-Inverter Drive and a Three-Phase Current Rectifier

This paper presents a new three-phase battery charger integrated with the propulsion system of an electric vehicle. The propulsion system consists of a dual-inverter topology connected to an induction motor via open windings. The electrical vehicles (EV) batteries are divided by two inverters. This will result in a drive with multilevel characteristics reducing the total harmonic distortion (THD) of the voltage applied to the motor. The modularity of the multilevel inverter will be maintained since two classical three-phase inverters are used. The charger will be fed by a three-phase high power factor current source rectifier. The motor windings will take the role of the DC-inductor required by the rectifier. In this way, an intermediate storage element between the grid and the batteries of the vehicle exist. For the control system of the battery charger, we propose the use of the instantaneous power theory and a sliding mode controller for the three-phase charger input currents. Finally, to verify the behavior and characteristics of the proposed integrated battery charger and control system, several tests are be presented.

A novel three-phase current source rectifier with delta-type input connection to reduce the device conduction loss

The three-phase current source rectifier (CSR) features a step-down ac–dc voltage conversion function, smaller ac filter size compared with the traditional two-level voltage source rectifier, and inrush current limiting capability. However, large conduction loss of semiconductor devices has limited the wide application of traditional CSRs. In this paper, a new CSR topology, delta-type current source rectifier (DCSR), is proposed to reduce the conduction loss. The proposed rectifier has delta-type connections on its ac input side and its dc-link current can be shared by multiple devices at a given time. This paper introduces the DCSR's operation principle, modulation scheme, and design method. Based on the analysis, the conduction loss can be reduced by up to 20% with the proposed topology. An 8-kW prototype is then built to experimentally verify the performance of the DCSR.

Paralleled Three-Phase Current-Source Rectifiers for High-Efficiency Power Supply Applications

This paper presents the paralleling operation of three-phase current-source rectifiers (CSRs) as the front-end power conversion stage of data center power supply systems based on 400- $\hbox{V}_{\rm dc} $ power delivery architecture, which has been proven to have higher efficiency than traditional ac architectures. A control algorithm of paralleled three-phase CSRs is introduced to achieve balanced outputs and individual rectifier module hot swap, which are required by power supply systems. By using silicon carbide (SiC) power semiconductors, SiC MOSFETs, and Schottky diodes, the power losses of the front-end stage are reduced, and the power supply system efficiency can be further increased. The prototype of a 19-kW front-end rectifier to convert 480 $\hbox{V}_{{\rm ac},{\rm rms}}$ to 400 $\hbox{V}_{\rm dc} $ , based on three paralleled three-phase CSRs, is developed. Each CSR is an all-SiC converter and designed for high efficiency, and the front-end stage full-load efficiency is greater than 98% from experimental tests. The balanced outputs and individual converter hot swap are realized in the hardware prototype too.

Improved Control Strategy Based on Space Vectors for Suppressing Grid-Side Current Harmonics in Three-Phase Current Source Rectifiers with a Hybrid Switch

This paper analyses the harmonic pollution to power grids caused by several high-power rectifiers, summarizes the requirements for rectifiers in suppressing grid-side current harmonics and optimizes a new-type of current source PWM rectifier with a hybrid switch. The rectifier with a hybrid switch boasts significant current characteristics and cost advantages in the high-power area. To further enhance the working frequency of the current source rectifier with a hybrid switch for suppressing grid-side harmonics and reducing the inductance size, this paper proposes an optimal control strategy based on space vector. It also verifies that the optimal control strategy based on space vector can reduce the total harmonic distortion of the grid-side current of the rectifier with a hybrid switch via circuit simulation and experimental results.

Current Source Rectifiers in Discontinuous Conduction Modes of Operation

Although the operation of a three-phase current source rectifier (CSR) for ac-to-dc conversion using phase control or low-frequency pulse control is well established in a wide variety of applications, CSR realization using high-frequency pulsewidth-modulation control has been recently studied as a potentially competitive alternative to a voltage source rectifier. In the CSR, reverse blocking gate turn-off switches are realized using series-connected diodes, which prevent any reversal of the dc-link current. A significant consequence of this limitation occurs at light load conditions. The dc-link inductor current enters the discontinuous mode of operation and leads to the loss of the control of the output voltage and a highly distorted input current, which compromise the potential advantages of the approach. This paper characterizes the CSR while operating in the discontinuous conduction mode and proposes a modulation strategy that restores the control of the output voltage and ensures a nearly sinusoidal current at light loads. Simulation and hardware results are provided for a 3-kW laboratory-scale prototype system.

Selective harmonic elimination and current/voltage control in current/voltage-source topologies: a unified approach

This paper presents a unified approach for generating pulsewidth-modulated patterns for three-phase current-source rectifiers and inverters (CSR/Is) that provides unconstrained selective harmonic elimination and fundamental current control. The approach uses the chopping angles or gating patterns developed for voltage-source rectifiers and inverters in combination with a logic circuit to generate the gating patterns for CSR/Is. The circuit also includes naturally and symmetrically distributed shorting pulses. Thus, the approach avoids the hassle of positioning the shorting pulses and defining and solving a set of nonlinear equations dedicated to CSR/Is. Moreover, the approach can eliminate an even or odd arbitrary number of harmonics (e.g., fundamental current control and elimination of the 5th, 7th, and 11th harmonics). This is an improvement over existing techniques and a new approach to pattern generation. Simulated and experimental results for both static and dynamic operating conditions are presented in order to validate the effectiveness of the approach.

DSP-based space-vector PWM pattern generators for three-phase current source rectifiers and inverters

Current source converters (rectifiers and inverters) are usually modulated using off-line pattern generators, due to the complex requirements of the switch gating signals. However, on-line patterns (carrier- and space-vector-based) offer a number of control advantages, such as tracking-error minimization, zero steady-state error, and potential implementation of enhanced control strategies. With the capability of microprocessors and digital signal processors (DSPs), digital space-vector modulation offers an interesting alternative to standard carrier-based modulation techniques. This paper addresses practical issues such as switching-frequency minimization, uncharacteristic-harmonic reduction, and delay compensation. Improved space-vector algorithms are derived that (a) reduce switching frequency, (b) improve reference tracking, and (c) reduce harmonic distortion. Experimental results on a 2-kVA current source rectifier are used to validate the proposed algorithms and control techniques.

Three-Phase Step-Up/Down Current-Source Rectifier with Sinusoidal Supply Currents.

This paper presents three-phase current-source rectifier, which is based on the cascade combination of buck-boost and buck DC-DC converters and has the step-up and step-down characteristics of output current, whereas the conventional current-source rectifiers have no step-up characteristics. The introduction of pulsewidth modulation makes it possible to obtain the widely controllable output current and to sinusoidally waveshape the supply currents with a near unity power factor. Three insulated-gate bipolar transistors (IGBTs) provide the necessary control over the currents for unidirectional power flow. To countract the oscillatory transient operations with single-loop output current feedback, the tested system includes the minor loop for the current in flyback inductor. The controllability of the output current is examined for the variation in its reference. The experimental results and state-space simulations for steady-state and transient conditions confirm the relevance of the presented configuration as an useful rectifier with near unity power factor sinusoidal supply currents and satisfactory output current regulation.