AC-DC Power Converter Research Articles

Performance analysis of mono-stage three-phase DC-AC converter with reduced logic power supply circuits

This paper presents the performance analysis of a mono-stage three-phase DC-AC converter with reduced logic power supply circuits. The power DC-AC power converter of the proposed system is formed by arrangement of one inductor, two power switches, and one capacitor in an opener-like configuration to yield each leg of the inverter. During the inversion process, the number of capacitor elements that charges up (builds electrical energy) or discharges across the power switches will be equal to the number of inductors that discharges or builds up magnetic energy that terminates in between the power switches and vice versa. Under this condition, the proposed system, boosts and converts DC power to AC power and at the same time maintains energy balance in the system in one stage power conversion phenomenon unlike conventional power inverters. The logic power supply circuit used in the proposed system has fewer component counts and performs optical isolation unlike its conventional counterparts which have larger component counts and isolate by electromagnetic induction. The proposed system achieved the following results: lower and cheaper logic power supply circuits, simulated phase voltages of 327.8 V and 326.6 V and 329.8 V at THDs of 0.09879 %, 0.2569 % and 0.2905 % and average phase currents of 6.30A, 6.32A and 6.26A, respectively, and experimented: scaled down phase-A, B, and C average voltages of 66.95 V, 65.6 V and 68.93 V at phase angles of 0°, 120°, and -120° respectively. The performance analysis of the mono-stage three-phase DC-AC converter with reduced logic power supply circuits can be used in home appliances, hospital equipment, communication-based power stations, and drive systems such as electric vehicles.

MPC based fault tolerance control of AC–DC power converters for offshore wind turbines

MPC based fault tolerance control of AC–DC power converters for offshore wind turbines

Power converter for battery charger of electric vehicle with controllable charging current

Research on electric vehicle chargers primarily focuses on improving charging technology to enhance the convenience, quality, efficiency, and affordability of charging electric vehicles. This paper discusses a different AC-DC power converter topology proposed as a potential candidate for electric vehicle battery charger. Using the proposed converter circuit, the charging process of electric vehicle battery can be simply adjusted to meet the battery requirement, and even for increasing the charging speed while avoiding overcharging of battery. During the charging process, if the voltage of battery approaches to the targeted battery voltage level, the charging current can be reduced gradually to zero. Hence it will prevent the battery from overcharging condition. Moreover, the ability of working at high power factor operation, low distortion of alternating current (AC) input current, and low direct current (DC) output current ripple are other features of the proposed charger circuits. Some test results of the proposed power converter were presented. The test results revealed potential features of the converter for battery charger of electric vehicle with power factor 0.9996, total harmonic distortion (THD) of AC current 2.73%, and low charging current ripple, i.e. 3.91%. Therefore, it minimizes the negative effects caused by ripples of charging current especially for lithium-ion batteries widely used in electric vehicles.

Self-Measurement of the Admittance Matrix of AC–DC Power Converter by Internal Harmonic Injection

Frequency-domain impedance or admittance model is widely applied to analyze harmonic stability of power electronic converters. Conventionally, the converter impedance is modeled holistically, without exhibiting the sole effect of different control and phase-locked loop (PLL). Besides, harmonic voltage or current injection external to the converter is usually adopted, which involves dedicated equipment and introduces unexpected inner impedance. In this paper, the response of voltage perturbation upon AC-DC power converter along various voltage signal flow paths is analyzed, based on superposition principle. Each part of admittance and its effect on stability can therefore be quantified explicitly. By injecting harmonic perturbation through the identified paths within the converter controller, each part of admittances, with and without the concerned control or PLL blocks, are measured and summed to be the total admittance. Harmonic voltage mitigation control implemented on a grid-forming converter creates an ideal grid with constant voltage and nearly zero inner impedance at the injected harmonic frequency. The proposed admittance analysis and measurement is successfully applied to power converter with different PLL, voltage feedforward, output power control, DC voltage control and grid-forming cascaded control. Effectiveness of the analysis and the proposed admittance measurement approach are validated by comprehensive simulation and hardware test.

Low threshold DC–AC power converter with optimized standby power consumption

The quest for universal energy access continues to be a major concern globally. Renewable energy technologies such as solar PV are viable options to meet this energy poverty with DC–AC power converters playing a major role in solar PV systems. Current designs of these converters suffer from high standby energy consumption and high input threshold voltage. This paper presents the design and implementation of a single-phase DC–AC power converter with low threshold input voltage and optimized standby power consumption. A multivibrator, pulse width modulation signal generator, MOSFETs, and a multiple secondary winding center tap transformer were used in the system design. The results show an optimized power converter having a low input threshold voltage of 10.5V and power consumption of 9.49W.

Cooperative Voltage-Balancing Control for Medium-Voltage Electric–Spring System Based on Diode-Clamped Converter and Dual Active Bridges

Electric spring (ES) is an emerging smart grid technology for stabilizing the voltage and frequency in a power network. Being fast demand-side-management technology, ES has recently been extended to the medium-voltage (MV) level in an AC-DC power conversion system that connects the distribution line of 6.6/11/22 kV to a DC grid of 800 V. To interface with the MV power grid, a diode-clamped converter (DCC) and multiple dual active bridges (DABs) can be employed to construct the MV-ES system. The balance of the capacitor voltages is crucial for DCCs, and thereby also for the MV-ES system. Conventional voltage-balancing approaches for DCCs generally compromise the quality of the grid-side voltage and current, which is undesirable especially in high-voltage high-power occasions. In this paper, a voltage-balancing control solution is proposed for the MV-ES system via cooperation of the DCC and DABs. By taking advantage of the DABs in voltage balancing, the DCC can adopt simple modulation and ensure grid-friendly voltage and current injection into the grid. The proposed voltage-balancing solution is verified using simulations in a five-level system and with practical experiments for a three-level system.

Switched Inductor Z Source Inverters for High Boost Applications

Abstract—This paper analyses a different configuration for the classical Z-Source Inverters (ZSI) which is named as Switched Inductor Z-Source Inverters (SL-ZSI) through simulation results. This configuration uses a unique impedance network that helps in the voltage adjustability. Comparing with the ordinary Z-source inverter, the new configuration provides more voltage inversion ability and enhances the output power quality of the main circuit considerably. The various applications of this configuration include DC-AC, AC-AC, DC-DC and AC-DC power conversions. Index Terms—Inverter, voltage source inverter (VSI), Z-source inverter (ZSI), switched inductor Z-source inverter (SI-ZSI)

A novel triangular wave quadrature oscillator without passive components for sinusoidal pulse width modulation DC-AC power conversion

In this study, a low-cost quadrature triangle oscillator using a voltage-controlled closed-loop dual operational amplifier (Op-Amp) architecture is proposed. Unlike other typical designs, this oscillator does not require any passive components. The use of an Op-Amp-based circuit is attractive for a triangle oscillator because it is more cost-effective than a microcontroller-based solution. This is especially true for sinusoidal pulse width modulation (SPWM) DC-AC power conversion applications. The slew-rate restriction of an Op-Amp is a useful characteristic for producing a triangle waveform when seen from the perspective of wave shaping techniques. The MC4558 and the JRC4558D are two examples of dual Op-Amps that are evaluated, contrasted, and described in this article. At supply voltages of +7 V and -7 V, the suggested quadrature triangle oscillator that uses Op-Amps MC4558 and JRC4558D has the same oscillation frequency, which is 63 kHz, as demonstrated by simulation and experimental data. The frequency stability is estimated to be around 0.23%. In addition, the findings from the experiment demonstrate that the proposed oscillator is a practical solution for the SPWM DC-AC power conversion application.

A Modulation Strategy With Transformer Leakage Inductance Energy Management for a Three-Phase Matrix-Based Isolated AC–DC Converter

Three-phase matrix-based ac-dc power conversion has recently gained popularity, considering its higher conversion efficiency and power density compared to the conventional two stage solutions. In the literature, several modulation strategies have demonstrated improved total harmonic distortion (THD) of the ac current in the matrix converters through independent control of the anti-series combination of active devices that form a matrix switch (i.e., two gate drivers per matrix switch). In this paper, a matrix-based ac-dc power converter that utilizes only one gate driver per matrix switch is proposed without compromising the quality of ac current. Managing energy stored in high-frequency transformer’s leakage inductor is an issue while utilizing single driver per matrix switch. An additional short-circuit leg is proposed to circulate stored energy in the leakage inductance during zero vector periods of the proposed converter, thereby ensuring continuous path for the leakage inductor’s energy flow. Steady-state analysis of the proposed ac-dc converter along with its loss modelling are presented with necessary mathematical expressions. The presented analysis and design of the proposed converter are experimentally validated on a 2 kW hardware prototype in the laboratory environment. A pertinent comparison of the proposed matrix-based conversion methodology with the conventional matrix-based conversion strategy is also provided.

Design and Analysis of Solid State DC-AC Transformer

Multimodal single/dual stage conversion (BSDC) based on a new solid-state DC-AC transformer (SDAT) is proposed. The suggested conversion can perform variable or constant DC voltage operation. A variable DC voltage is controlled dynamically in response to changes in DC input side voltage, allowing the DC-DC conversion stage to always operate at its best. New DC-AC power conversion of 2 port two-way choppers (TBDC) and two-way rectifier/inverter conversion (BRIC) was planned for the implementation of the proposed SDAT. SDAT, consisting of a bi-directional step-down-step-up converter and a bi-directional step-up-step-down converter, has been used as a prototype model to check the suggestion system. Functional concepts of this BSDC converter with TBDC are designed and simulated on the MATLAB/simulink environment network. PWM and control methods have been applied for SDAT to accomplish a wide variety of voltage and power loss reduction in the proposed device. Test bench model hardware is designed and tested to validate the effectiveness and benefits of the proposed approach.

An Examination of Power Converter Architectures for Utility-Scale Hybrid Solar Photovoltaic and Battery Energy Storage Systems: The Features of Several Power Conversion Architectures

Recently, the falling costs of photovoltaic (PV) and battery storage (BS) technologies have raised interest in the creation of hybrid PV+BS power plants. Together with increasing energy storage capacity by storing clipped energy, hybrid plants broaden a power plant’s grid services by featuring fast dispatch flexibility and voltage-ampere reactive support. Although many proposed PV plants are being developed with colocated batteries, the dominant architecture of ­utility-scale PV+BS power plants is uncertain. Moreover, power architectures are expected to evolve over time based on future trends. The primary goal of this article is to critically examine and compare several dc–dc and dc–ac power converter architectures that are suitable candidates for hybrid PV+BS power plants. In particular, the article presents characteristics of several power conversion architectures from the point of view of power semiconductor requirements, efficiency, reactive component requirements, modularity, control complexity, and so forth. Detailed analytical models are utilized, along with a benchmark design example to present a comparative evaluation of the alternatives for performing engineering tradeoff studies.

A Single-Stage Bridgeless Isolated AC–DC Conversion System for Light Electric Vehicles Charging Application

A 1- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\phi $ </tex-math></inline-formula> single-stage ac–dc power conversion unit employing bridgeless isolated modified single-ended primary inductor converter (BLIMSEPIC) is presented in this work for the light electric vehicles (LEVs) charger applications. Unlike the existing SEPIC and Cuk high-power factor (HPF) ac–dc converters, the presented BLIMSEPIC HPF ac–dc converter incorporates continuous input and output current features while operating under discontinuous current mode (DCM) condition. Therefore, it demonstrates excellent applicability in charging applications. The DCM operation considerably simplifies overall control architecture, as the presented BLIMSPEIC ac–dc converter exhibits inherent power factor correction capability under DCM operation, and therefore, significantly reduces the cost of control implementation. Besides, the continuous input and output currents attribute lessen the filter’s size and associated losses. Furthermore, the reduced voltage stress and zero current switching of semiconductor devices, together with the front-end bridgeless structure, considerably improve the conduction and switching losses of the charger. The operation, design, control, and performance of the BLIMSEPIC HPF ac–dc converter are experimentally verified, and corresponding results are presented to justify its efficacy for LEVs charging applications.

Cascaded AC-DC Power Conversion Interface for Charging Battery

This paper develops a cascaded AC-DC power conversion interface (CADPCI) to convert AC power to charge the battery set. The proposed CADPCI is composed of a cascaded converter (CC) and a dual-input buck converter (DIBC). The CC is formed by connecting a full-bridge converter (FBC) and a bridgeless rectifier (BLR) in series. The CADPCI generates an 11-level input voltage and performs unity power factor correction. The switching loss is reduced because only the FBC with a lower DC port voltage is switched at a high frequency. The DIBC uses a buck converter and a selection switch set to generate a two-level DC voltage on the DC port of the BLR. By controlling the DC input voltage of the buck converter, the injected power of the BLR can match the input power of the utility. Therefore, the FBC does not require to handle the real power, saving an isolated converter for regulating the DC port voltage of the FBC, thus simplifying the power circuit of the CC. The buck converter also acts as a DC active filter to filter out low-frequency ripples of the charging current. A prototype is constructed to verify the performance of the proposed CADPCI.

Control Methodologies to Mitigate and Regulate Second-Order Ripples in DC–AC Conversions and Microgrids: A Brief Review

Second-order ripples occur in the voltage and current during any DC–AC power conversion. These conversions occur in the voltage source inverters (VSIs), current source inverters (CSIs), and various single-stage inverters (SSIs) topologies. The second-order ripples lead to oscillating source node currents and DC bus voltages when there is an interconnection between the AC and DC microgrids or when an AC load is connected to the DC bus of the microgrid. Second-order ripples have various detrimental effects on the sources and the battery storage. In the storage battery, they lead to the depletion of electrodes. They also lead to stress in the converter or inverter components. This may lead to the failure of a component and hence affect the reliability of the system. Furthermore, the second-order ripple currents (SRCs) lead to ripple torque in wind turbines and lead to mechanical stress. SRCs cause a rise in the temperature of photovoltaic panels. An increase in the temperature of PV panels leads to a reduction in the power generated. Furthermore, the second-order voltage and current oscillations lead to a varying maximum power point in PV panels. Hence, the maximum power may not be extracted from it. To mitigate SRCs, oversizing of the components is needed. To improve the lifespan of the sources, storage, and converter components, the SRCs must be mitigated or kept within the desired limits. In the literature, different methodologies have been proposed to mitigate and regulate these second-order ripple components. This manuscript presents a comprehensive review of different effects of second-order ripples on different sources and the methodologies adopted to mitigate the ripples. Different active power decoupling methodologies, virtual impedance-based methodologies, pulse width modulation-based signal injection methodologies, and control methods adopted in distributed power generation methods for DC microgrids have been presented. The application of ripple control methods spans from single converters such as SSIs and VSIs to a network of interconnected converters. Furthermore, different challenges in the field of virtual impedance control and ripple mitigation in distributed power generation environments are discussed. This paper brings a review regarding control methodologies to mitigate and regulate second-order ripples in DC–AC conversions and microgrids.

Hybrid Dynamical Control for Discharging Rate Consensus in AC-Bus Microgrids

In this work, a robust distributed hybrid algorithm is proposed for the primary and secondary control loops of an island AC-bus microgrid to provide large-signal stability of the complete system. A secondary control loop is designed from droop control and multi-agent systems theory to ensure that the State Of Charge (SOC) of the batteries in discharging mode converges to a consensus. Furthermore, this distributed strategy ensures robustness with respect to any plug-and-play event or communication failure. The DC-AC power converter of each battery in discharging mode is controlled in the primary loop by using hybrid dynamical system theory, which considers non-trivial issues in the model (switching and affine terms) and in the signals (constraints in the dwell time). A suited selection of gains allows using singular perturbation analysis to provide large-signal stability properties for the complete nonlinear model.

AC-DC Fuzzy Linear Active Disturbance Rejection Control Strategy of Front Stage of Bidirectional Converter Based on V2G

Aiming at the problems of output voltage fluctuation and current total harmonic distortion (THD) in the front stage totem-pole bridgeless PFC of two-stage V2G (Vehicle to Grid) vehicle-mounted bi-directional converter, a fuzzy linear active disturbance rejection control strategy for V2G front-stage AC-DC power conversion system is proposed. Firstly, the topological working mode of the totem-pole bridgeless PFC is analyzed, and the mathematical model is established. Combined with the system model and the linear active disturbance rejection theory, a double closed-loop controller is designed with the second-order linear active disturbance rejection control as the voltage outer loop and PI control as the current inner loop. The controller can realize self-adaptive tuning of the proportional gain coefficient of the active disturbance rejection controller through fuzzy reasoning and realize self-adaptive control. Simulation and experimental results show that this method can better solve the problems of slow system response and high total harmonic distortion rate of input current and effectively improve the system’s robustness.

Average Current Mode Control of a DC–DC Boost Converter to Reduce the Decoupling Capacitance at the PV Array Output

Due to the full-wave AC–DC power conversion, second-order frequency oscillations of current and voltage are created in single-phase PV-grid-connected inverters. These oscillations propagate toward the input and adversely affect the PV power utilization ratio. Large power decoupling capacitors are the preliminary solution for coping with voltage ripples across PVs, and they decrease the lifetime of the overall system. This paper proposes the average current mode control (ACMC) of the input inductor in a DC–DC boost converter in a double-stage PV power conversion system. Through extensive explanations of the modeling and control of a DC–DC boost converter, it is shown that the ACMC reduces the propagation of the second-order frequency components (SOFCs) toward the input PV array. Two controllers—a proportional–integral controller and an integral single-lead controller—are considered to adjust the average value of the PV output current in a single-loop control structure. This control approach is simple to implement and exhibits high impedance to current oscillatory components, which, in turn, reduces the size of the required capacitance.

Diagnosis fault of power converters in solar photovoltaic system with battery storage connected to grid

In recent years the increasing demand for electricity and the nonrenewable nature of fossil energy makes the move towards renewableenergies required. However, the common problem of renewable sources, which is the intermittence, is overcome by the hybridizationof complementary sources. Thus, whenever the load demand is not fully covered by the primary source, the second one will absolutelysupport it. Moreover, the solar photovoltaic system with battery connected to grid the One of the most used connections, In order toensure the continuity of power energy supply. Also, monitoring and diagnosing errors in the various installations of these systems is verynecessary in order to avoid falling into serious damage that leads to a complete shutdown of the system.In this paper, we are interested to study the common fault in the semiconductors (switches) of power converters, especially openswitch fault in the inverter (Bidirectional DC-AC power converter), and we are proposed a fuzzy-based fault diagnosis approach presentsa fault detection and localization (FDL) method for open-circuit faults (OCF) in the switching devices (IGBT) of a grid-connectedthree level inverter in photovoltaic (PV) system. The global model of the system is built using MATLAB/Simulink

A Common-Ground-Type Five-Level Inverter with Dynamic Voltage Boost

Today, transformerless inverters (TIs) are widely applicable in different solar photovoltaic (PV) grid-connected applications owing to their promising features, such as higher efficiency and power density. However, high-frequency common-mode voltage (CMV) in these topologies can result in high leakage current, electromagnetic interference, and lack of safety, reducing the whole system’s reliability. To resolve the problems associated with TIs, this paper proposes a novel hybrid switched capacitor (SC)-based common-ground (CG) transformerless inverter (TI) topology, which can be applied in grid-connected photovoltaic (PV) applications. The boost inductor is integrated to achieve continuous input current and dynamic voltage gain. In addition, the proposed circuit comprises nine switches and two SCs with a single input DC source. It can generate five-level AC voltage with voltage boosting within a single-stage DC–AC power conversion. The working principles of the proposed topology, circuit description, and control technique are presented. Furthermore, the proposed inverter is comprehensively compared with other five-level TIs to show its superiority. Finally, a laboratory prototype is developed and tested to validate the practical viability of the proposed configuration.

Three-Level T-Type qZ Source Inverter as Grid-Following Unit for Distributed Energy Resources

Distributed energy resources (DERs), such as solar photovoltaics (PVs), are required to achieve a high performance and an efficient use of generated renewable power in grid-integrated applications, both in normal and fault operating conditions. In this article, a grid-following (GFL) multifunctional control strategy for a three-phase three-level T-type quasi-impedance source inverter (3L-T-type qZSI) is studied through simulation and experimental tests. The GFL functionality is achieved by a proportional–integral (PI)-based dq current controller for the active and the reactive power tracking. A PI-based dc controller is used for the dc-link voltage control by taking advantage of the quasi-impedance source (qZS) network ability for input voltage boosting. The dc–ac power conversion is accomplished through a space vector pulsewidth modulation (SVPWM) with inner capacitors voltages balancing capability and minimum common-mode voltage (CMV) generation. Besides, a low-voltage ride-through (LVRT) strategy was implemented to fulfill the fault requirements imposed by the Spanish standard. The simulation and experimental results demonstrate the abovementioned functionalities and validate the stability and good dynamic response of the grid-connected 3L-T-type qZSI. Thus, this work supposes a novel contribution due to the few works previously reported in the literature concerning the performance of this relatively recent inverter topology in grid-tied applications.