Fujin Deng

• PhD
• Professor at Southeast University

The voltage tracking capability of conventional moving‐discretized‐control‐set model‐predictive‐control (MDCS‐MPC) in the dual‐active‐bridge (DAB) converter is affected by parameter mismatch and measurement noise. To address these issues and enhance voltage tracking capability, a continuous‐control‐set model‐free predictive voltage control with noi...

The increasing demand for DC power loads across various applications such as railway systems, data centers, electric vehicle charging stations, and hydrogen electrolyzers necessitates efficient rectifiers capable of converting medium-voltage AC (MVAC) to low-voltage DC (LVDC) while accommodating a wide DC voltage range. This paper presents a novel...

The valve-side single-phase-to-ground (SPG) fault is one of the key challenges for hybrid modular multilevel converter (HMMC)-based bipolar high voltage direct current systems. In this paper, the valve-side SPG fault characteristics of HMMCs are analyzed in detail, revealing that not only the submodules (SMs) in upper arms are severely overcharged,...

The detailed temperature field distribution of high-power Insulated Gate Bipolar Transistor (IGBT) modules is important information for the reliability analysis and thermal design of power electronic systems and it is difficult to obtain quickly. This paper proposes a hybrid model for temperature field prediction based on Dynamic Mode Decomposition...

The magnetic network energy router (MNER) is promising for applications integrating multiple renewable sources, storages, and loads with the advantages of low component requirement, high efficiency and high controllability. Power density is essential for MNERs, which is mainly restricted due to the use of multiple magnetic components, including the...

Parameter mismatch in LC -filtered voltage source inverters (VSIs) can affect the capacitor voltage performance under conventional model predictive control with optimal switching sequence (MPC-OSS), including prediction error and total harmonic distortions. To improve the parameter robustness of the conventional MPC-OSS, this article proposes a vol...

Modular multilevel converters (MMCs) have been considered as one of the most promising topologies in medium- and high-voltage applications. Capacitors are heavily used for submodules energy storage in MMCs. Due to the vulnerability and large quantity, the failure of capacitors has been recognized as one of the major challenges that threaten the hea...

This paper provides a novel real-time fault diagnosis unified approach of stator interturn short circuit faults (ISCFs) and open-switch faults (OSFs) in voltage source inverter (VSI)- fed three-phase induction motor (IM) drive systems without requiring additional hardware even for ISCFs involving fewer turns. The proposed diagnosis approach leverag...

AC-AC converter plays a pivotal role in low-frequency alternating current (LFAC) transmission. This article proposes a bipolar modular AC-AC converter (BMAC) for lowfrequency transmission, which consists of six arms and a triplewinding transformer referred to as bipolar transformer. Considering the unbalance of the grid voltage, the mathematical mo...

A compact model could be an efficient tool and general solution to accurately predict the short-circuit (SC) dynamics of the SiC mosfet . In this article, an SC test setup is constructed to collect the model data, where no physical information of the SiC mosfet is required. The SC trajectory in the safety state and failure state is measured, an...

DC-side short-circuit fault is one of the key challenges for the modular multilevel converter (MMC)-based high-voltage direct current (HVDC) systems. In this paper, a thyristor branch loop (TBL)-based hybrid MMC (HMMC), where the thyristor branches are adopted to connect the upper arm inductors in three phases, is proposed to handle the DC faults....

This paper proposes a novel real-time fault diagnosis approach for open-switch faults of three-phase pulse width modulated voltage source inverter (PWM-VSI) induction motor drive system. The diagnosis method relies only on the observed current via processing the extracted DC components and current absolutes using dynamic resonant filters (DRFs). By...

The modulated model-free predictive control (MFPC) is affected by the noise effect and the parameter mismatch in LC -filtered voltage source inverters (VSIs). To improve the noise suppression capability and parameter robustness of the MFPC, this article proposes a modulated parameter less (PL) prediction and reference-based predictive control wit...

An ac-fed PMSM drive system with reduced dc-link capacitance easily suffers from fluctuations of dc-link voltage which may aggravate modulation error and severe current ripple at low frequency. The occurrence and impact of the dc-link voltage fluctuations are discussed firstly. Then, a current ripple suppression method is proposed by the adoption o...

The bridge arm of the hybrid modular multilevel converter (MMC) is composed of half-bridge and full-bridge sub-modules cascaded together. Compared with the half-bridge MMC, it can operate in the boost-AC mode, where the modulation index can be higher than 1, and the DC voltage and the AC voltage level are no longer mutually constrained; compared wi...

The valve-side single-phase-to-ground (SPG) fault is one of the key challenges for the MMC-based bipolar HVDC system. In this paper, a grounded thyristor loop (GTL)-based hybrid MMC (HMMC) is proposed to protect the bipolar HVDC system under valve-side SPG faults. In the GTL-HMMC, the thyristor branches are proposed to connect the different arm ind...

The modular multilevel converter (MMC) is a research hotspot in medium-voltage and high-voltage applications. The measurement offset error would cause an increase in the monitoring error of the submodule (SM) capacitance of the MMC, affecting the estimation accuracy of the SM capacitance monitoring. This paper proposes a capacitor monitoring strate...

The model predictive control (MPC) is sensitive to parameter variations in LCL -filtered voltage source inverters (VSIs). To improve the robustness of the MPC, this article proposes a parameter less prediction and reference-based predictive control (PLPR-PC) for LCL -filtered VSIs, where the proposed PLPR-PC not only obtains the parameter less...

Nonlinearities of inductor’s soft magnet, converter’s time-varying mode and control delays limit the grid-side power quality improvement capability of interleaved boost Power Factor Correction (PFC) circuit. The traditional internal model principle-based approaches are widely used to improve the power quality, but the expense is the reduce of certa...

Integrating renewable energy resources into the existing generation capacity can handle the additional load resulting from the EV charging system, even when the majority of the EVs are charged during off-peak hours. This paper comprehensively analyzes EV charging methods with a particular focus on both grid-based direct charging and the utilization...

Grid-tied inverter performance is degraded by its inherent nonlinear characteristics, which can be suppressed by internal model principle-based controllers. However, designing these controllers requires a tradeoff between time consumption and model uncertainties. This paper proposes a data-driven approach that can eliminate the influences of nonlin...

This paper proposes a novel voltage estimation scheme for the modular multilevel converter (MMC) based on model predictive control (MPC). The developed strategy is presented by combining a disturbance observer (DOB) with an adaptive neural network (ANN) for voltage estimation in the MMC. Firstly, the ac-side and dc bus voltages are estimated as the...

In this paper, an optimized space vector modulation (SVM) method is proposed for the isolated three-phase matrix-type AC/DC converter, where the four-quadrant operation ability of the bidirectional power switch can be fully used. The primary-side transformer current can be eliminated naturally during zero current vectors without extra switching act...

This paper offers an in-depth analysis of the hybrid modular multilevel converter (MMC) working steadily under boost AC mode and proposes an improved capacitance design approach reducing its overall capacitance without affecting the performance. This enables more cost-effective and space-efficient applications of hybrid MMC in distribution networks...

Power loss management is one of the most important challenges for improving the reliability of modular multilevel converters (MMCs). This paper proposes a current integral comparison (CIC) based power loss balancing control (PLBC) for full-bridge submodule (FBSM) based MMCs, where two types of bypassed modes of the FBSM are selected by comparing th...

The crossing thyristor branches (CTB) based hybrid modular multilevel converter (HMMC) can effectively protect high-voltage direct-current (HVDC) system under dc-line short-circuit fault with advantages of low percentage of unipolar full-bridge (UFB) submodules (SMs), short dc current interruption time and high efficiency. However, the faulty UFB-S...

A compact SPICE model is proposed in this article, which predicts the avalanche dynamics of the planar SiC mosfet in high accuracy. Different to the existing models, the proposed model takes the dynamic avalanche resistance into consideration, so the avalanche trajectory in safety state can be accurately simulated. In novelty, the proposed model...

The modular multilevel converter (MMC) is one of the most appropriate topologies for high power applications due to its high modularity and low harmonic distortion. As faulty submodules (SMs) are bypassed, the capacitor voltage and switching frequency of healthy SMs in faulty arm will rise, which causes unbalanced power losses distribution among th...

My current interests are applications research of modular multilevel converters, such as High-Voltage Direct Current, Machine Drive, Low-Frequency Transmission, etc. as well as multi-port DC/DC converters.

The capacitor voltage fluctuation suppression is essential for the reliable and safe operation of the MMC. This paper proposes a shared capacitor (SC) based modular multilevel converter (MMC) with suppressed capacitor voltage fluctuation, where the SC in each submodule is utilized as the power channel for three phases of the MMC. A multivariate sor...

The cascaded modular multilevel converter (MMC) and cycloconverter (CCV) based machine drive system is a promising solution for the high-power machine drive applications. However, its output frequency is limited due to the characteristic of CCV. In this paper, an extended frequency range operation for the cascaded MMC and CCV based drive system is...

In the state-of-the-art fault location of modular multilevel converters(MMC),capacitor voltage deviations between the faulty and healthy submodules are extensively utilized to identify open-circuit faults. However, there is a potential risk of overlooking the ineffectiveness of the fault location under light load conditions. This paper presents an...

This paper investigates and discusses the interaction stability issues of a wind farm with weak grid connections, where the wind turbines (WTs) are controlled by a new type of converter control strategy referred to as the voltage source (VS) control. The primary intention of the VS control method is to achieve the high-quality inertial response cap...

Modular multilevel converter (MMC) faces challenges ofcost and footprint in medium and high voltage grid applications. By adding a three-phase switching bridge on the basis of MMC, this article proposes a three-phase multiplexing arm modular multilevel converter (TPMA-MMC) with high power density and small volume. The multiplexing principle for TPM...

The over-modulation capability of the hybrid modular multilevel converter (MMC), mixed by half-bridge and full-bridge submodules (SMs), has acquired widespread attention recently, which can significantly increase the design freedom of the hybrid MMC. When the hybrid MMC is applied in the medium-voltage occasions, an improved carrier phase shift pul...

A bleeding resistor is usually adopted to be parallel with the capacitor in the submodule (SM) to avoid static voltage imbalance caused by auxiliary power supply during start-up process of modular multilevel converters (MMCs). However, the bleeding resistor causes unnecessary power loss during normal operation. In this article, a resistor controlla...

High temperature superconducting generators (HTSGs) have great potential of high power density for future large direct-drive wind turbines. As synchronous machines, HTSGs have rapid rise of field currents during a sudden short circuit fault which cause AC losses in the HTS tapes. This paper applies H-A formulation of Maxwell equations for finite...

Low-speed drive is one of the challenges for modular multilevel converters (MMCs) due to large capacitor voltage fluctuation. In this paper, a cascaded MMC and cycloconverter (CCV) based machine drive system is proposed to ensure stable operation of medium- -voltage and low-speed machine. The MMC provides medium-frequency ac voltage for the CCV, an...

The hybrid modular multilevel converter (MMC), applied in high voltage direct current (HVDC) transmission systems, can operate in over-modulation mode to handle the abnormal situations of reduced HVDC voltage due to the extreme atmospheric environment. However, it might suffer from severe voltage imbalance between the half-bridge submodule (HBSM) a...

Fault localization is one of the most important issues for modular multilevel converters (MMCs) consisting of numerous switches. This paper proposes an Isolation Forest (IF) based SM switch open-circuit fault localization method for MMCs. Based on the continuous sampling SM capacitor voltages, a number of Isolation Trees (ITs) are produced to const...

Parallel operation of multiple AC/DC inverters is favorable in hybrid AC/DC microgrids to avert consecutive conversion stages and increase the system’s efficacy. Yet, several emerging technical challenges impede the expansion of such layout such as the circulating currents, sensitiveness to the input voltage disturbances, load variations and comple...

An improved SiC MOSFET model is proposed in this article, which predicts the dynamics accurately in the wide operation range of the SiC mosfet . The temperature-sensitive effect (TSE), the short channel effect (SCE), and the interface state effect are comprehensively taken into consideration in the modeling of the transfer characteristics. A dyna...

High-power machine drive systems are the heart of the modern power industry and have been used in a broad range of industry applications. Extensive R&D efforts have been carried out on the design and implementation of high-power machine drive systems. In this article, various converter topologies and research progress for high-power machine drive s...

In this article, a novel diagnosis strategy including both open-circuit faults (OCFs) and short-circuit faults (SCF) is proposed for the switches in modular multilevel converter topology based on half-bridge energy storage submodules. The OCF diagnosis strategy is to analyze the current flow path of the open-circuit submodule in each OCF state, and...

With the wide application of distributed generations (DGs) and microgrids (MGs), the inverter control becomes a hot research topic. For the inverter control in MG applications, first, a complex variable state-feedback-based switch control frame is proposed. In the proposed control frame, the state feedback leads to a generalized control objective (...

Three-phase electric spring (TPES) was originally proposed to solve three-phase imbalance issues in power systems. So far, several attempts have been reported on proposing power control methods for it. However, existing solutions on TPES either depend on circuit parameters or have relatively slow dynamic responses. In this paper, a novel power cont...

A submodule (SM) capacitor voltage reduction control (SCVRC) can reduce voltage stress of power devices and capacitors in a modular multilevel converter (MMC) and also improve reliability. However, the SCVRC may deteriorate the harmonic performance of the MMCs output. This paper proposes a harmonic optimization strategy for the carrier phase-shifti...

The 2 N +1 submodule unified pulsewidth modulation (SUPWM) is attractive for modular multilevel converters (MMCs). To generate 2 N +1 voltage levels, the SUPWM results in voltage pulses imposed on the arm inductors, which produces large high-frequency current ripple in the dc link of the MMC and deteriorates the dc-link performance. In this artic...

Recently, solar power generation systems are more and more popular and widely used in grid connected power generation, intelligent buildings, and power supply in remote areas. For photovoltaic panels, due to the influence of factors such as light intensity and ambient temperature, their output voltage and current become uns, and the output voltage...

The modular multilevel converter (MMC) is attractive for medium-voltage and high-power applications because of the advantages of its high modularity, availability and high power quality. Due to unbalanced grid voltages, the arm current among three phases of the MMC would unbalance, which would cause unbalanced temperature distribution among three p...

In this paper, a modular current-fed high-frequency transformer isolated matrix converters (CF-HFT-MC) based wind energy conversion system (WECS) is proposed. The CF-HFT-MC module utilizes the high-frequency transformer instead of the low-frequency input transformer, and eliminates the bulky and vulnerable electrolytic capacitors in the WECS. There...

The modular multilevel converter (MMC) is attractive for high-voltage direct current (HVdc) applications. The dc line short-circuit fault is one of the key challenges for the HVdc system. In this article, a crossing thyristor branches (CTB)-based hybrid MMC (HMMC) with current interruption capability is proposed to protect the HVdc system under dc...

The hybrid modular multilevel converter (MMC) has the advantages of DC fault blocking and over-modulation capability as the promising candidate in future multi-port HVDC systems. Especially, the over-modulation ability could increase the modulation index higher than 1 without voltage distortions on the AC side. However, the hybrid MMC under the ove...

This paper proposes a novel type of piecewise and modular energy storage topology. Compared to the modular multilevel converter (MMC), the proposed topology is not only different in structure but also in concept. Firstly, the capacitors within the submodules of MMC are all replaced by lithium batteries, which can avoid the voltage imbalance among c...

In grid-tied power converters, the grid parameters such as the frequency, phase angle of the fundamental component, and the harmonics are essential to the control of power converters, the fast and accurate estimation of the grid parameters is a challenge especially for high-order harmonics. This paper proposes a one-step-prediction (OSP) discrete o...

Modular multilevel converters (MMCs) are regarded as promising topologies in medium/high‐voltage and high‐power applications. The reduction of power losses is an important issue for MMCs. This paper proposes a power loss minimization control (PLMC) by injecting optimal second‐ and fourth‐order harmonic circulating current into the arm current of MM...

In the hybrid modular multilevel converter (MMC), the voltage imbalance between the capacitors of half-bridge submodule (HBSM) and full-bridge submodule (FBSM) would occur when the over-modulation index exceeds certain range, which is caused by the different charging/ discharging properties of the HBSM and FBSM. An improved hybrid MMC with self-bal...

Thermal management is one of the most significant challenges for reliability improvement of modular multilevel converters (MMCs). The thermal stress difference caused by the uneven loss distribution between top and bottom IGBTs/diodes will lead to lifetime difference of the IGBTs/diodes which will decrease the reliability of the MMC. In this paper,...

This paper investigates the effect of filter inductor nonlinearity due to current and temperature variation on power control performance in microgrids. Output impedance model of inverters considering nonlinear inductor is first derived to analyze the effect of nonlinear inductor on system power control performance. Furthermore, a parameter estimato...