Active Power Decoupling Circuit Research Articles

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.

Stability Analysis of a Single-Phase Active Power Decoupling Converter Based on Discrete Harmonic State Space Model

Digitally controlled single-phase active power decoupling converter is a continuous-discrete hybrid system with nonlinear time-periodic (NTP) nature, thus the conventional linear time-invariant (LTI) model cannot accurately describe the system dynamic behavior. This paper presents a discrete harmonic state space (DHSS) modeling method to analyze the small-signal stability of a digitally controlled single-phase current source converter (SCSC) with an active power decoupling circuit (APDC). The proposed model retains the switching details, it has the potentiality to accurately describe the high-frequency dynamics. Moreover, the DHSS model not only transforms NTP system into LTI system, but also includes harmonic interaction dynamics. Furthermore, a LTI Toeplitz matrix is developed to analyze the oscillation phenomenon and system stability, and the stability boundaries of system parameters are obtained based on the eigenvalues loci. Finally, the physical experiment results validate the correctness of the theory analysis.

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.

An online capacitance estimation method based on DC component applied in PFC converter with split-capacitor

Inaccurate capacitance significantly increases the DC-Link ripple voltage of active power decoupling circuit (APDC). To solve this problem, a high-precision online capacitance estimation method is proposed. This method converts the AC components of decoupling capacitor into the sum of DC component and AC component with 8 times grid frequency, which is beneficial to the extraction of DC component. This DC component replaces the AC component to effectively eliminate the periodic capacitance mutation, and accurately estimate the capacitance. Based on the capacitance, the DC-Link ripple is controlled with the set scope. Experimental results verify the effectiveness of the proposed method.

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.

Model Predictive Current Control for DC-Link Ripple Voltage Suppression in Electrolytic Capacitor-Less Drive System

Electrolytic capacitor-less drive systems have a higher lifespan and reliability. However, the DC-link voltage of ECL drive systems has a sudden change under dynamic conditions, which results in a serious degradation of the drive system performance. To solve the problem, this paper proposes a model predictive current control (MPCC) based on motor power change. A grid current predictive model based on motor power change is established. Motor power change is introduced into the cost function, so that grid power can quickly and accurately track the motor power under dynamic conditions, thereby effectively avoiding the sudden change of the DC-link voltage. Meanwhile, the current predictive model for decoupling inductor in the asymmetric split-capacitor active power decoupling circuit (APDC) is constructed. It realizes the high-precision complementary control of the split-capacitor voltages under various working conditions, and effectively reduces the DC-link voltage ripple. The experimental results verify the effectiveness of the proposed MPCC.

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.

Single‐phase small capacitor motor drive system with high‐efficiency buck active power decoupling converter

This paper proposes a novel active power decoupling circuit (APDC) based on modified Buck converter to reduce the DC-link voltage ripple of small capacitor motor drive systems. The APDC is placed between the Boost PFC circuit and the DC-link, and has two energy flow paths, and the sum of the power decoupling capacitor and the DC-link capacitor voltage equals to the output voltage of the Boost converter. With these configurations, the voltage of the decoupling capacitor can be precisely controlled to be the same as the AC component of the output voltage of the Boost converter, thereby effectively reducing the DC-link voltage ripple. Another unique feature of the proposed APDC is that the inductor works in discontinuous current mode and only work for half of the time, which not only reduces the current stress of power switches, but also further improves the efficiency of the proposed APDC. Then, an instantaneous voltage control method is investigated to reduce the DC-link voltage drop, which significantly improve the dynamic performance of the motor. The design guideline of key components is given in detail. The feasibility of the small capacitor motor drive system based on the proposed APDC is verified by experimental results.

Power decoupling capability with PR controller for Micro-Inverter applications

Micro-inverters have been known as promising structures for small-scale PV systems. However, these structures need energy storage elements to balance the instantaneous output and input power. Demanding a large size capacitor forces using an electrolytic type at the dc-link that affects the micro-inverter lifetime. This paper presents a new Active Power Decoupling (APD) circuit for the micro-inverters to reduce the capacitor size at the dc-link and utilize film capacitors instead of electrolytic types. The proposed APD circuit is based on a single-phase flyback converter. This structure is controlled based on the PQ theory and a Proportional Resonant (PR) controller for delivering the PV panel energy to the grid and eliminating the pulsation power through the switching pattern control. Simulations and experimental results of a 180 W single-phase micro-inverter prototype were performed to evaluate the performance of the proposed structure and the control scheme. It was found that this controller can accurately regulate the switching pattern to remove the ripples of input current and voltage. Furthermore, the robustness and fast dynamic performance of the proposed configuration have been confirmed during input power variation. In conclusion, this single-phase micro-inverter structure has an efficiency of ∼ 91%, THDi of 3.6%, and a long lifetime.

An active parallel power decoupling circuit with a dual loop control scheme for micro‐inverters

AbstractAn important challenge in single‐stage single‐phase micro‐inverters is reducing required capacitance by various active power decoupling (APD) techniques in order to use film capacitors with a longer lifetime instead of electrolytic capacitors. In this paper, a photovoltaic (PV)‐side parallel APD circuit based on a bidirectional flyback converter is proposed. This topology is able to increase the average and ripple voltages for the capacitor due to having a transformer and thus can reduce the required capacitance. In the control scheme, dual control loops on the main and decoupling circuits manage the micro‐inverter operation. The primary control loop is based on the instantaneous active and reactive power theory and a proportional resonant (PR) controller that is responsible for delivering the PV panel energy to the grid. The secondary control loop regulates the pulsation power on the dc‐link capacitor through the PR controller. Simulation results demonstrated that the proposed APD circuit and the control method could properly damp the pulsation power in the normal and reference tracking operations. Furthermore, the good robustness of the micro‐inverter was confirmed in shutdown and start‐up. Finally, the experimental results with a 180‐W single‐phase micro‐inverter prototype are presented, which validates the advantages of the proposed configuration.

Active Power-Decoupling Circuit to Reduce Ripple Currents of Recycling Batteries used with Single-Phase Voltage Source Inverters

Active Power-Decoupling Circuit to Reduce Ripple Currents of Recycling Batteries used with Single-Phase Voltage Source Inverters

Elimination of DC-Link Voltage Ripple in PMSM Drives With a DC-Split-Capacitor Converter

This article presents an electrolytic capacitorless (ECL) motor drive based on a dc-split-capacitor converter. In order to decrease the dc-link voltage ripple of ECL motor drive, an active power decoupling circuit (APDC) with a dc-split-capacitor is proposed. The APDC is composed of two converters, among which the boost converter is named the main converter and the buck-boost converter is named the auxiliary converter. The output capacitors of the two converters are connected in series to increase the dc-link voltage, which expands the speed range of the internal permanent magnet synchronous motor. When there is voltage ripple on the capacitor of the main converter, the auxiliary converter will produce complementary voltage on another capacitor. In addition, an instantaneous current control strategy is proposed in the auxiliary converter to reduce the voltage ripple, while the conventional control strategy is applied in the main converter. The main converter can achieve unity power factor, and the auxiliary converter is used to suppress the dc-link voltage ripple. Experiments are conducted, and the results verify the feasibility and effectiveness of the APDC.

A Novel SiC-Based Multifunctional Onboard Battery Charger for Plug-In Electric Vehicles

This article proposes a simple and effective method to reduce the bulky capacitor in onboard battery charger (OBC) where low-voltage (LV) battery charging circuit is utilized as an active power decoupling (APD) circuit to filter out the second-order ripple power. When the OBC is connected to the grid to charge the high-voltage (HV) battery, the switches on the primary side of the LV charging circuit are operated as those of an ac-dc converter with APD function. Consequently, small dc-link capacitors can be used instead of large capacitor banks. In the proposed OBC, the switching devices are shared for the ac-dc converter, APD circuit, and primary-side of the LV charger. For a simultaneous charging of the LV and HV batteries, a dc-dc converter is added, which shares the same transformer core and secondary side with the LV charging circuit. So the functions of the OBC are maintained in the proposed topology whereas the volume and cost are decreased by 52.3% and 46.9% compared with the conventional nonisolated OBC, respectively. A 2-kW SiC-based prototype has been designed and tested to verify the validity of the proposed system. The peak efficiencies of the OBC and LV charger are 96.1% and 95.3%, respectively.

Power Loss Reduction in Buck Converter Based Active Power Decoupling Circuit

Active power decoupling (APD) circuits enable the use of long lifetime capacitors (film or ceramic capacitors) in single-phase power converters. Owing to the inclusion of the APD circuits, the literature reports 1.5%-1.8% drop in efficiency of single-phase converter at rated power. This reduction in conversion efficiency is one of the significant challenges in the practical use of APD circuits. This article proposes an approach to reduce the power loss in the bidirectional buck converter based APD circuit. This approach is presented with the help of analytical calculations and graphical representation of operation of APD circuit. The proposed approach requires rapid variation in the average voltage of the buffer capacitor with a change in inverter power. To achieve this, an enhanced control technique is suggested with a duty ratio injection controller. The steady state and transient response of the proposed control technique are validated with simulation and experimentation. Further, the reduction in power losses realized by the proposed approach is verified with the help of a developed laboratory prototype. The proposed approach obtains up to 1% improvement in efficiency of single-phase converter at rated power, when compared with existing APD approaches.

Zero-Voltage-Switching Single-Phase Full-Bridge Inverter With Active Power Decoupling

Single-phase zero-voltage-switching (ZVS) inverter with wide bandgap devices has higher efficiency and power density. However, the dc-side capacitor of the inverter will suffer double line frequency ripple and reduces the lifetime of the dc bus capacitor. Active power decoupling (APD) is an effective method to replace the short lifetime electrolytic capacitor with a smaller film capacitor. In order to help achieving the ZVS condition for ZVS inverter and the additional APD circuit, this article presents a ZVS topology for single-phase full-bridge inverter with APD circuit by adding an auxiliary branch between the dc source and the bridge legs. The auxiliary branch is composed of a clamping capacitor, an auxiliary switch, and a resonant inductor. A ZVS pulsewidth modulation scheme is proposed for a single-phase inverter with APD. The gate drive pulses are designed to realize the ZVS turn-on for the main switches of both APD circuit and single-phase full-bridge inverter. Circuit operation stages are analyzed and ZVS conditions are given. Finally, the proposed ZVS inverter with APD circuit is verified on a 1.5-kW inverter prototype.

Buck-Plus-Unfolder as the Superior Active Power Decoupling Solution for 400 Vdc/kW-Level Applications

In single-phase ac/dc applications where reliability and/or power-density are critical, active power decoupling (APD) circuits can be employed to reduce the required capacitance on the dc-link. Various APD circuits have been proposed so far, all with their advantages and disadvantages. However, many confusions still exist in the literature on this topic which is mainly attributed to a lack of unified and comprehensive assessment criteria. In this paper, first the decisive criteria for a modern APD circuit are established, and the buck APD is identified as the current state-of-the-art, based on them. Then the buck-plus-unfolder topology with triangular current mode (TCM) modulation is proposed as an improvement, and a simple, yet solid foundation is introduced to choose the superior decoupling solution at different specifications. The operation equations for the APD with TCM modulation are derived next, and the operation of the proposed solution is demonstrated using a hardware prototype.

A new active power‐decoupling topology and control mechanism to extend the lifespan and reduce the number of passive components

In this article, a new active power‐decoupling (APD) circuit without an additional discharging inductor is proposed for single‐phase power systems. In an APD circuit, a small film capacitor is used to extend the lifespan and remove ripple power derived from power systems. However, to manipulate power pulsation, additional circuits such as inductors, capacitors, and switches are required, which increase the manufacturing cost and parametric uncertainties. In the proposed circuit, rectification and a decoupling function are conducted on a coupled‐inductor at the same time to reduce the number of passive elements. Furthermore, a sliding mode control is used to ensure stable operation under parameter variation and disturbance. A design example is presented and the operation of the proposed topology is also verified with a simulation study and experimental results. The results show that the proposed APD method was able to remove passive components and reduce the withstand voltage of a buffer capacitor and insulated gate bipolar transistors (IGBT) while ensuring that both the input current and output voltage of the converter were well regulated under load variation. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Single-phase single-stage dual-buck photovoltaic inverter with active power decoupling strategy

Abstract This paper proposes a single-phase single-stage dual-buck photovoltaic (PV) inverter with an active power decoupling (APD) strategy. Using this strategy, the dc-link voltage pulsating caused by a low-frequency power fluctuation in single-phase systems can be reduced without using a bulky dc-link storage. A simple active damping control is adopted to suppress the resonance of the APD circuit, so that the design of the feedback control becomes simple and reliable. Furthermore, the APD circuit directly regulates the dc-link voltage, which is identical to the PV voltage in single-stage PV inverters. Hence, the dc-link voltage control in the given power stage, where the unidirectional dual-buck topology is employed, is supplemented. The APD strategy can be universally applied in single-stage PV inverters regardless of the topology connected to the utility grid. To verify the proposed scheme, both simulations and experiments on a 2.1 kW single-phase single-stage dual-buck PV inverter are conducted. The results confirm that the proposed method not only reduces the dc-link voltage pulsating but also improves the MPPT accuracy. Compared to the power stage using electrolytic capacitors, the proposed scheme decreases the physical size and implementation cost of the dc-link storage.