Yu Zeng

Nanyang Technological University | ntu · Division of Power Engineering (PE)

In the operation of the cascaded H-bridge converter-based battery energy storage system, the active power of each phase can be unevenly distributed among the submodules (SMs) for various reasons. In such conditions, conventional control methods yield unbalanced capacitor voltage ripple magnitudes among the SMs due to the active power disparity. Con...

Semiconductor-based solid-state power controllers (SSPCs) are a promising solution for dc system protection. During the connection of capacitive loads there is an inrush current because of zero initial energy in the capacitor, which can cause damage to the system. One of the main challenges of SSPCs is to suppress the current and voltage overshoot...

The common-mode choke (CMC) serves as a key component in mitigating electromagnetic interference noise across various applications. High-frequency (HF) impedance modeling of CMCs is essential for estimating their performance, typically involving two parts: impedance characterization and behavioral modeling. This article proposes a method for HF imp...

With the advancements in Industry 4.0 and the global demand for sustainable energy, power electronics devices are emerging as pivotal components for modern industrial, transportation, and energy delivery. Ensuring the security of these devices is of paramount importance for safeguarding the reliable operation of critical systems against any threats...

Operating cascaded H-bridge (CHB) static compen-sators (StatCom) at low dc capacitor voltages reduces voltage stress on submodule capacitors and switching semiconductors, resulting in enhanced system reliability and reduced power loss. Understanding the minimum allowable value for peak capacitor voltage is crucial for the optimal capacitor voltage...

The dc solid-state transformer (dcSST) plays a vital role in interconnecting diverse dc sources and loads in dc microgrids. However, output voltage regulation and submodule power balance control have always been two essential control challenges of the dcSST. To address these challenges, this article proposes a multiagent soft actor-critic-based act...

This article presents a swift and seamless start-up method for dual active bridge (DAB) converters, adhering to a predefined current limit. It explores all operation stage trajectories to identify the optimal switching sequence in both constant frequency (CF) and variable frequency (VF) modes. The method seamlessly integrates sophisticated modulati...

In this letter, a hybrid method of fault detection using data and models, based on easy knowledge transfer learning, is proposed. The proposed method is applied for multiple battery converters, where new systems that are integrated into a microgrid are trained using the knowledge acquired by the existing systems during the offline phase. The new Ta...

In-circuit impedances of power converters are pivotal for the prediction and mitigation of electromagnetic interference (EMI) in power electronics applications. Inductive coupling approaches, favored for their safety and non-intrusive nature, are the preferred solutions for in-circuit measurements. Given that the power converters are operational un...

Common-mode chokes (CMCs) are essential components of electromagnetic interference (EMI) filters. Obtaining precise common-mode (CM) and differential-mode (DM) impedance information of CMCs facilitates their performance evaluation and behavioral modeling, ultimately contributing to optimal EMI filter design. Among existing impedance extraction appr...

Single-phase common-mode chokes (CMCs) are key components in electromagnetic interference (EMI) filters to mitigate conducted emissions caused by the switching power converters. Finite-element analysis (FEA) has been adopted as one of the simulation tools to model a CMC for the extraction of its impedance frequency response. Most literatures focus...

Impedance characteristics of power converters are dependent on operating conditions, posing challenges to the stability-oriented design of control systems. This is because constant control parameters, designed according to a limited number of operating conditions, may cause instability in other conditions. In this letter, a deep reinforcement learn...

The use of three-phase common-mode (CM) chokes has become increasingly prevalent in power electronic systems due to their ability to effectively mitigate undesirable conducted electromagnetic interference (EMI) emissions. Accurate impedance information of the three-phase CM choke is critical for its circuit modelling and optimal selection to ensure...

Three-phase common-mode (CM) choke presents a large demand from the industry to mitigate the undesirable conducted emissions in power electronic applications. Accurate impedance information of three-phase CM choke provides useful insights for its circuit modeling so that optimal filter can be designed to comply with the relevant electromagnetic com...

This article proposes a distributed uniform control approach for a dc solid state transformer (DCSST) that feeds constant power loads. The proposed approach utilizes a multiagent deep reinforcement learning (MADRL) technique to coordinate multiple control objectives. During the offline training stage, each DRL agent supervises a submodule (SM) of t...

The neutral-point-clamped (NPC) dual-active-bridge (DAB) converter with hybrid semiconductors (Si and SiC devices) is a promising topology for high-power energy storage systems. The triple-phase-shift (TPS) modulation can achieve high efficiency with zero-voltage switching (ZVS) by adjusting three phase shift angles. However, when applied to hybrid...

This paper proposes a multi-agent (MA) deep reinforcement learning (DRL) based autonomous input voltage sharing (IVS) control and triple phase shift modulation method for input-series output-parallel (ISOP) dual active bridge (DAB) converters to solve the three challenges: the uncertainties of the dc microgrid, the power balance problem, and the cu...

This letter proposes a multiagent soft actor-critic (MASAC) enabled multiagent deep reinforcement learning (MADRL) algorithm for output current sharing of the input-series output-parallel dual active bridge converter. The modular converter is partitioned into different submodules, which are treated as DRL agents of Markov games. Furthermore, all ag...

The dual active bridge (DAB) converter has become a popular isolated solution to integrate energy storage systems (ESSs) and dc microgrids (MGs). However, constant power loads (CPLs) and pulsed power loads (PPLs) may reduce system damping and cause voltage oscillations in DAB converter-based ESSs (DAB-ESSs). An artificial neural network-based activ...

As a modular multilevel converter‐based medium‐voltage direct current (MMC‐MVDC) distribution grid mostly utilises small current grounding modes, the weak fault current for single‐pole‐to‐ground (SPTG) fault is very difficult to detect especially in the case of noises and fault resistance. Therefore, this study proposes a fast and accurate faulty f...

The large shunt capacitances on both sides of VSC-HVDC transmission line will block and reflect the travelling waves when a fault occurs on DC cable lines. When a forward fault occurs, the protection will detect the arrival of forward and backward travelling wave simultaneously. While for a backward fault, the arrival time difference of the forward...

Due to the labyrinthine topology of the MMC-MVDC system, identification of the faulty feeder especially for a single-pole-to-ground (SPTG) fault is a challenging task. Based on the characteristics analysis of capacitance charge–discharge, this article obtains the typical characteristics of the faulty feeder. To improve the sensitivity, the characte...

Nowadays, the efficient and reliable protection and location schemes for MMC-MVDC (Modular Multilevel Converter-Medium Voltage Direct Current) grid are few. This paper is the first to propose a scheme to not only protect the feeders and the busbar, but locate the segments in MMC-MVDC grid. To improve the reliability, this paper analyzes the transie...

This paper presents a novel pilot protection scheme of DC cable line in voltage-source-converter (VSC) based multi-terminal DC (MTDC) grids, which utilizes a novel phase-mode transformation to decouple the bipolar DC cable current into six mode and it uses the stationary wavelet transform to extract the modulus maxima of fault initial traveling wav...