Active Power Decoupling Research Articles

Evaluation and Control of a Three-Port Universal Input Integrated Converter With Power Factor Correction and Active Power Decoupling

Evaluation and Control of a Three-Port Universal Input Integrated Converter With Power Factor Correction and Active Power Decoupling

Reduced sensor Lyapunov‐based control for active power decoupling circuit

SummaryThe double‐line frequency ripple power exists inherently in single‐phase power converters. To address this problem, active power decoupling (APD) technique is widely used. It diverts the ripple power into a small energy storage element by introducing passive and active power devices. This inevitably involves more voltage and current sensors for corresponding control, which raises the cost while decreasing reliability and power density. In this paper, a Lyapunov‐based methodology is proposed to achieve APD control without adding any sensor. According to the designed controller laws, the practical decoupling capacitor voltage will converge to its reference. The decoupling voltage reference is given by taking into account buffering the double‐line frequency ripple power. Afterward, the robustness against parameter perturbations of the proposed method is discussed. Finally, the experimental results verify the feasibility of the proposed control strategy.

The Scope of Application of Power Decoupling Technology and Its Evolution

As energy consumption worldwide continues to escalate, the gap between energy supply and demand is becoming alarmingly evident. This disparity, combined with the mounting environmental threats impacting production and human existence, intensifies the energy challenges our nation confronts. At the heart of addressing these issues is the imperative to maximize energy efficiency. Within the realm of power electronics, the topic of power decoupling has emerged as a pivotal area of research. This paper delves into the application of power decoupling in power electronics, offering a comprehensive analysis of its characteristics and applicability. Tracing its evolutionary trajectory, the paper systematically explores the historical progression of power decoupling technology. It further segments the technology, elucidating its merits, limitations, and mechanisms for enhancement. By aggregating data, the study categorizes various inverters and contrasts their roles in the domain of power decoupling. Subsequently, the discourse distinguishes between active and reactive power decoupling, providing prevalent examples of the former. The paper concludes by affirming the trajectory of power decoupling towards increased cleanliness and efficiency. The emphasis on high-precision and high-efficiency apparatuses heralds the anticipated future direction of this field.

A Novel Single-Phase Non-Isolated Dual-Input Micro-inverter with Active Power Decoupling

A Novel Single-Phase Non-Isolated Dual-Input Micro-inverter with Active Power Decoupling

A simplified space vector modulation for the single-phase active power decoupling quasi-Z-source inverter

The double-line frequency ripple power of the single-phase quasi-Z source inverter (qZSI) will result in a large designed qZS impedance on the dc side, which can be greatly reduced by the coupled-type active power decoupling (APD) method. However, the traditional sinusoidal pulse width modulation (SPWM) for the APD-qZSI needs extravagant APD storage capacitance and may cause abnormal operation under low load conditions. Classical space vector modulation (SVM) has higher flexibility and dc-link voltage utilization, but it cannot be directly applied to the APD-qZSI. In this paper, a simplified SVM method for the coupled-type APD-qZSI is proposed, where the switching time sequence is transformed to carrier-based pulse width modulation, so the shoot-through control of the qZSI is easy to implement. Next, the passive component parameters and normal operation range of the traditional SPWM and the proposed SVM are analyzed and compared. The proposed SVM has a smaller APD storage capacitance but a slightly larger ac side filter inductance. In addition, the decreased current of the APD branch under SVM can help suppress the abnormal operation of the inverter, so the APD-qZSI can operate at a lower load condition. Finally, experimental results validate the effectiveness and superiority of the proposed SVM method.

Design and Analysis of High Power Density On-Board Charger with Active Power Decoupling Circuit for Electric Vehicles

This article presents a design method for the active power decoupling (APD) circuit of a PFC converter for high power density on-board chargers (OBCs) utilized in electric vehicles (EVs). The utilization of electrolytic capacitors to mitigate power ripple at the input is a common practice in PFC converters. However, these electrolytic capacitors are associated with issues such as limited lifetime and low current ratings, resulting in a significant portion of the OBC’s volume being occupied by them. To address these challenges and achieve power density, the relationship between the power of the APD circuit and DC-link voltage is derived, and a design method for the APD circuit for high power density is proposed. The feasibility of this design approach is validated through the PFC converter prototype designed for 6.6 kW OBC. Consequently, a substantial volume reduction of 19.7% is realized when compared to the utilization of the electrolytic capacitor approach, and a reduction of 36.2% is achieved in comparison to the conventional APD design method. This reduction in volume proves advantageous for fulfilling the requisites of high power density OBCs.

Active Power Decoupling by Closed-Loop Control of Power Oscillations for a Bidirectional Single-Phase DC–AC Converter

Active Power Decoupling by Closed-Loop Control of Power Oscillations for a Bidirectional Single-Phase DC–AC Converter

Topology synthesis of integrated active power decoupling converters using asymmetrical H-bridge circuits

Aiming to handle the inherent double-line frequency ripple power in single-phase power systems, a lot of active power decoupling (APD) topologies have been developed. In this paper, a general method is introduced to synthesize APD topologies. The main construction idea is to insert a rectifier/inverter into asymmetrical H-bridge circuits (AHCs) or replace the switch/diode in the AHCs with a rectifier/inverter. This approach not only reveals the formation process of existing APD topologies but also deduces new APD topologies. Finally, an experimental case study has been carried out to illustrate the feasibility and effectiveness of the proposed topology synthesis method.

Active power decoupling scheme of symmetrical LCL structure in single‐phase grid‐connected voltage source inverter for ultra‐high voltage transmission

SummaryThe voltage source converter (VSC) is an important component of ultra‐high voltage (UHV) technology, where the former is responsible for converting new energy sources into electricity and the latter enables the transmission of electricity over long distances. However, the VSC has a serious problem of oscillation power under three‐phase unbalance, which comes from the single‐phase voltage source inverter (VSI) that is the basic structure of VSC. So there is always the requirement for active power decoupling (APD). Conventional passive solutions increase the overall size significantly, and existing active solutions either require the addition of a decoupling topology or rely strongly on their own original topology and more complex control. To overcome this drawback, this paper proposes an improved APD method with a combination of topology‐type and control‐type decoupling features for single‐phase VSI based on the symmetrical LCL filter for solving the power oscillation problem of VSC at the source. The proposed structure can decrease common mode interference and can absorb the oscillation power by the original filter capacitors of the LCL filter. Besides, the original circuit components can be reused, and the decoupling is simple enough to achieve APD without affecting the full bridge control. Next, the control is optimized to reduce the compensation error and input voltage. Finally, the experimental device is carried out to verify the effectiveness of the proposed method.

An Integrated Power Decoupling Method for Single-Phase EV Onboard Charger in V2G Application

Instead of bulky passive filters, the active power decoupling (APD) method can be adopted to suppress the 2nd-order ripple power in the DC-bus of the single-phase electric vehicle (EV) onboard charging system. However, the traditional APD methods require additional power switches and energy storage devices, which increases the cost and significantly reduces the power conversion efficiency. To tackle these problems, an integrated method of utilizing the auxiliary power module to form a series-connected APD circuit is proposed in this paper. Without additional switches and energy storage devices, the APD circuit only needs to compensate less than 10% of the rated power, while realizing soft-switching operation. In addition, the corresponding control method can further reduce the voltage stress of the switches on the high-voltage side of the converter, and increase the efficiency of the system. Finally, a 2kW single-phase charging system prototype is built to verify the feasibility and effectiveness of the proposed method.

Maximum torque per ampere controlled induction motor drive with reduced DC link capacitor

ABSTRACT This paper presents a three-phase induction motor (IM) drive comprising a single-phase Pulse Width Modulated (PWM) converter with an active power decoupling (APD) as an active front-end converter (AFEC) to reduce the size of a DC link capacitor. Consequently, film capacitors can be used in place of bulky electrolytic capacitors that improve the power density, reliability, and cost of AFECs. A control scheme for an APD circuit is developed to mitigate the ripple power, and to control the three-phase IM, a maximum torque per ampere (MTPA) control scheme is implemented. A Simulink model of the proposed system rated for 3.73 kW, 200 V, and 50 Hz three-phase IM drive and its equivalent prototype model are developed in a laboratory and the APD and the MTPA control schemes are implemented with the help of STM32F407VG, a 32-bit microcontroller and dSPACE 1104, respectively. This paper demonstrates the experimental verification of the concepts for APD and MTPA control. Further, a significant reduction in motor current at starting/light load conditions is observed that leads to lower energy requirements. The prospective application of these schemes includes railway traction drive, electric vehicles, and so on, where compactness, reliability, and lower energy requirements are the prime concerns.

Active Power-Decoupling Methods for Photovoltaic-Connected Applications: An Overview

This study compares ripple port, stacked switched capacitor, and capacitive energy storage architectures for active power decoupling, comparing the number of components, performance, energy density, DC-link capacitor reduction, efficiency, and frequency operation to highlight their main benefits and drawbacks for single-phase grid-connected applications. The overview reveals equivalent effective energy density without electrolytic capacitors, as well as enhanced simplicity, performance, and durability, thereby providing stacked switched capacitors as an attractive power-decoupling alternative for multi-stage connected applications, based on the principle that its individual buffer capacitors absorb and deliver energy without tightly constraining their individual terminal voltages, while maintaining a narrow range voltage at the buffer DC port.

Active Power Decoupling Control for PWM Converter Considering Sensor Failures

The power converters integrated with active power decoupling (APD) may handle the ripple power in dc link and then reduce the volume of the filter capacitor dramatically. Generally, voltage and current signals of the LC branch are required for the closed-loop APD control. However, sensor failures could degrade the control performance and even lead to the breakdown of the converter system. This article proposes a detection method for sensor failures in the APD circuit of the single-phase converter. The voltage and current of the LC branch in the APD circuit are estimated by a dual sliding mode observer (SMO). The residuals of the estimated and measured signals are calculated, and they have high sensitivity to specific sensor faults, namely, the current residual is sensitive to the fault of the current sensor and the voltage residual is sensitive to the fault of the voltage sensor, which could be employed to locate the faulty sensors. Finally, the effectiveness of the proposed method is verified by the simulation and experimental results.

An Active Power Decoupling-Integrated Reduced-Switch Current-Fed Switched Inverter

In recent literature, high-gain dc–ac inverters are employed in grid-connected photovoltaic (PV) systems. These inverters can have several features, such as shoot-through immunization and buck/boost capabilities achieving a wide range of operations with reliability and minimum distortion. One such example is the single-phase reduced-switch current-fed switched inverter (RSCFSI). This article proposes the enhanced boost control-based pulsewidth modulation (EBC-PWM) strategy for RSCFSI to improve the inverter’s dc–ac gain. Being a single-phase inverter, RSCFSI suffers from the double-line frequency ripple problem. However, a low-frequency (LF) ripple analysis reveals that the RSCFSI is also plagued with fundamental frequency ripple, which poses additional challenges for the active power decoupling (APD) integration and corresponding closed-loop controllers. Although both LF ripples can be alleviated using markedly large passive elements, the power density and reliability of the inverter worsen. In this article, an APD-integrated RSCFSI (APDRSCFSI) is introduced as a solution that deflects the aforementioned LF ripple energy to an auxiliary capacitor without adding more active switches. As a result, the inverter can employ smaller passive elements. In addition, the EBC-PWM strategy is also extended for APDRSCFSI, improving its dc–ac voltage gain and voltage stress. A closed-loop control technique that combines output voltage control and APD functionality is also illustrated. A hardware prototype is used to corroborate the advantages of APDRSCFSI.

Single-Phase Grid-Forming Strategy with Power Decoupling Implementation for Electrolytic-Capacitor-Free EV Smart Battery Charger

Smart Battery Chargers (SBCs) implementing grid-forming (GFM) control strategies are a promising solution to provide voltage and frequency support, increasing the grid reliability. Typically, GFM studies consider inverters with high DC-link capacitance. Therefore, there is a research gap in two-stage DC-AC converters with small DC-link capacitance implementing GFM strategies. This article proposes a novel approach to implement a GFM control strategy along with active power decoupling (APD) in an isolated, single-phase, electrolytic-capacitor-free two-stage DC-AC structure. The structure is composed of a voltage source inverter (VSI), DC-linked by film capacitors, with a dual-active-bridge series-resonant (DABSR) DC-DC converter. High DC-link ripple is allowed and managed by the APD. Hence, electrolytic capacitors are avoided, increasing the converter lifetime. In the proposed approach, the VSI implements the GFM strategy, operating in the four quadrants of the active and reactive power plane. However, the DABSR allows galvanic isolation, average DC-link voltage control, and suppression of the low-frequency ripple on the battery current, minimizing the impact in the battery lifetime. Design criteria are given for the DC-link voltage controller, active-reactive power controllers, inner inverter controllers, and APD technique. The control strategy is validated for vehicle-to-grid and stand-alone vehicle-to-home applications, using hardware-in-the-loop for a 2kW test setup.

Differential Single-Phase Inverters With Active Power Decoupling: A Survey

This paper provides an overview of differential single-phase inverter topologies with active power decoupling (APD) and their main control techniques. Owing to the advantage of achieving APD without additional semiconductor devices, thus boosting inverter reliability at a minimum cost, these topologies have gained increasing interest, especially for small-scale photovoltaic applications. Therefore, in this study, we consider it essential to synthesize the main differential single-phase inverters, their operating principles, and provide a unified mathematical description for each topology. The study identified and analyzed three main structures: buck, boost, buck–boost, and derived topologies. First, a comparative analysis, including a hardware assessment in terms of the DC-link voltage requirements, voltage and current stresses on the switches, and losses, shows the performance of various inverter topologies under different operating parameters (e.g., input voltage and decoupling capacitance). Second, this paper discusses the main control strategies applied to this class of inverters to achieve both primary control (autonomous or grid-connected operation) and APD functions, while highlighting the development of control algorithms that are less dependent on parameter variations and more robust to external disturbances. Finally, the need for further research on reliability improvement in single-phase differential inverters, particularly in the context of emerging technologies, such as high-speed switches (e.g., wide-bandgap semiconductors) and advanced control techniques, is emphasized.

A modified submodule of modular multilevel converter using active power decoupling method for reducing capacitor voltage ripple under low‐frequency operation

AbstractIn this paper, a modified submodule (MSM) method is proposed to reduce capacitor voltage fluctuation by integrating a bidirectional buck‐boost type active power decoupling (APD) circuit into each SM for the low‐frequency operation of a converter system. The capacitor voltage fluctuation of the proposed MSM‐MMC can be significantly reduced compared to conventional SMs with the same capacitance by transferring the low‐frequency ripple power components to the auxiliary energy storage capacitor, resulting in a lower voltage fluctuation of the main capacitor in the SM, which requires a lower total SM capacitance. Additionally, a closed‐loop controller is proposed to control the APD capacitor voltages by inheriting the advantages of the repetitive controller and proportional‐integral (PI) controller to enhance the performance of SM capacitor voltage ripple suppression. The method can improve the start‐up performance of medium voltage drives without injecting high‐frequency components, which can avoid the common‐mode voltage imposed on the AC side of the system. The operating principle, auxiliary capacitor voltage control, and capacitor voltage ripple suppression control of the proposed MSM‐MMC method are analyzed in detail. The feasibility of the proposed method has been confirmed by simulation results based on case studies using MATLAB/SIMULINK software and further verified with hardware‐in‐the‐loop simulation (HILS) using the real‐time simulator OPAL‐RT platform.

Active Thermal Control for Buck Converter-Based Active Power Decoupling Circuit

Aluminum electrolytic capacitors (AECs) and power semiconductor devices (PSDs) are typically identified as weak links in the reliable design of power converters. To eliminate the AECs from the design, active power decoupling (APD) circuits are preferred in single-phase power converters. However, in an attempt to eliminate AECs, this approach introduces the latter weak link in the design, i.e., PSDs in the APD circuit. This article proposes an active thermal control technique to improve the reliability of PSDs in the buck APD circuit. The proposed technique reduces the swing in junction temperature of PSDs using noninvasive power loss modulation. The power loss in PSDs is changed by varying the average voltage across the buffer capacitor. Further, a control technique is suggested to synthesize the reference for average voltage across buffer capacitor. This controller accounts for nonlinearities and minimum/maximum limits of power loss modulation. Further, the additional energy loss due to power loss modulation is restricted to a predefined limit. The proposed technique is validated with the help of circuit simulations and experimental studies with a 500 W laboratory prototype. For the selected mission profile, an increase of 28.5% in the lifetime of PSDs in buck APD circuit is estimated.

Predictive Direct DC-Link Control for 7.2 kV Three-Port Low-Inertia Solid-State Transformer With Active Power Decoupling

Promising for applications including renewable energy and electric vehicle fast charging, a medium-voltage (MV) solid-state transformer (SST) typically has multiple modules series stacked, which requires the modules to be single phase. One critical issue of the single-phase SST is the double-line-frequency power ripple. Traditionally, large passives are used to buffer the ripple, resulting in significantly increased volume and cost. This article for the first time proposes active power decoupling (APD) for the SST and a predictive direct dc-link control method, using a current-source (CS) single-stage SST as an example. An electrolytic capacitorless buffer port is used to absorb the ripple, which tolerates up to a 30% voltage ripple for small capacitance. The APD SST control is challenging. First, the CS SST realizes isolation, dc-link, and multiport in a single stage. Second, different from conventional SSTs or APD converters, the low-inertia dc-link in this SST has a 40% switching ripple, which is difficult to stabilize. To address the control challenge, a direct dc-link control architecture and a predictive control method are proposed. Simulation and experimental results verify the proposed control method on an MV SiC modular soft-switching solid-state transformer (M-S4T) prototype. The proposed APD reduces the SST volume by 53.8%. Importantly, the proposed concept is not limited to the M-S4T, but is generic to other SSTs or APD converters.

7.2 kV Three-Port SiC Single-Stage Current-Source Solid-State Transformer With 90 kV Lightning Protection

This article proposes a multiport modular single-stage current-source solid-state transformer (SST) for applications like photovoltaic, energy storage integration, electric vehicle fast charging, data center, etc. The 7.2 kV 50 kVA current-source SST consists of five input-series output-parallel modules, each based on 3.3 kV SiC reverse-blocking <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> -plus-diode modules. The proposed SST has some unique features. First, compared with the voltage-source or matrix converter-based SSTs, the current-source SST has a unique advantage of single-stage isolated ac/dc or ac/ac conversion with an inductive dc link, but no medium-voltage (MV) ac experiments have been reported. This article for the first time demonstrates MV ac current-source SST up to 7.5 kV peak. Second, the multiport SST has a buffer port for active power decoupling (APD) or energy storage integration. The double-line-frequency power ripple from single-phase ac grid normally results in a large capacitor size in MV SSTs. The APD scheme is proposed in MV applications for the first time to enable a reduced dc link and the electrolytic capacitor-less SST with high reliability. Third, for a direct grid-connected converter without line-frequency transformer, insulation and protection are critical. A medium-frequency transformer design passes 55 kV basic-insulation level (BIL) and 60 kV high potential dielectrics withstand test with only 0.09% leakage inductance. Importantly, a lightning protection scheme is presented to protect the SST itself from 90 kV BIL impulse. Fourth, the proposed current-source SST topology is a modular soft-switching solid-state transformer (M-S4T) with full-range zero-voltage switching and controlled <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dv/dt</i> for low electromagnetic interference. These concepts are verified in a three-port M-S4T prototype with forced oil cooling under single-module, stacked-module, steady-state, and dynamic operations.