Zaijun Wu

• Southeast University

The analysis and design of the grid-forming (GFM) power loop and decoupling control can be challenging due to the coupled high-order system, where active and reactive power controls are typically designed separately using a dual-input-dualoutput model. In this letter, we introduce a complex-power-phaseangle (CPPA) model, formulated as a single-inpu...

An innovative Improved Synchronous Rectification LLC (ISR LLC) resonant converter is proposed for applications that demand extended hold-up time, such as data center power supplies. The design greatly simplifies the hold up operation circuit by integrating only one switch into the conventional Synchronous Rectification(SR) LLC converter. Utilizing...

With rapidly growing penetration of renewable energy, there is an increasing need for real-time balance in the power system. In recent years, as a vital component of the end user side, residential distributed energy resources (RDER) have shown promising prospects in demand response (DR). This paper addresses the RDER optimal dispatch problem from a...

Active distribution networks utilize advanced sensors, communication, and control technologies to achieve flexible and intelligent power distribution management. Reliable state estimation (SE) is crucial for distribution management systems to monitor these networks. Historically, the scarcity of measurement resources has hindered the application of...

With the proliferation of advanced communication technologies and the deepening interdependence between cyber and physical components, power distribution networks are subject to miscellaneous security risks induced by malicious attackers. To address the issue, this paper proposes a security risk assessment method and a risk-oriented defense resourc...

Electrolyzers are recognized as promising equipment to improve power systems' operation flexibility. However, existing electrolyzer models used in power system operation optimization are either nonconvex or inaccurate when operating over a broad temperature range. Hence, this letter proposes an enhanced feasible operational area of electrolyzer (EF...

Phasor measurement unit (PMU) serves as a superior tool to monitor the dynamics of the power system, but its high cost remains a practical concern that requires optimal placement of the PMU (OPP). Traditionally, researchers relied on model-based approaches to analyze this problem. However, these methods not only suffer from inevitable parameter unc...

The uncertainty brought by the integration of distributed generations in distribution networks poses a higher demand for situation awareness in the distribution network. Accurate identification of distribution network line parameters is of great significance for the operation and control of the distribution network. This paper proposes a method for...

Fault ride-through (FRT) is key to DC distribution networks for both avoidance of system blocking and improvement of the safety of flexible DC devices in the face of faults. This paper proposes an FRT method for low-voltage DC distribution networks with a photovoltaic energy storage system, which achieves rapid fault detection and constraint of fau...

Owing to the advancements in industry information technology, the traditional distribution network has evolved into a cyber-physical distribution system (CPDS), thereby introducing new challenges in quantifying the vulnerability of the system to cyber attacks. In addressing this issue, this paper proposes a novel risk assessment model with the exam...

The power-to-hydrogen-and-heat (P2HH) method is a potential means of improving energy efficiency while reducing carbon emissions. However, existing P2HH methods are ineffective at low temperatures, and do not consider physical constraints on heat exchange between the electrolyzer and heating network. Hence, this paper proposes an improved P2HH (IP2...

Production cost minimization (PCM) simulation is commonly employed for assessing the operational efficiency, economic viability, and reliability, providing valuable insights for power system planning and operations. However, solving a PCM problem is time-consuming, consisting of numerous binary variables for simulation horizon extending over months...

Managing energy usage flexibility has been identified as an effective way to coordinate Internet of Things (IoT) technologies and transition to a low-carbon future. However, the various models of these flexibilities may not be fully understood, and some may even be characterized by black-box neural networks, such as those used for electric vehicles...

Modular Multilevel Resonant DC-DC Converters (MMRDCs) are emerging as a competitive solution for medium wide input voltage - low voltage (MV-LV) conversion, yet they often encounter output voltage overshoot when submodules (SMs) insert or extract. In this article, a novel K+D control scheme of MMRDCs is proposed, which combines both inserted submod...

With the advance in communication facilities and information technologies, the state estimation (SE) of distribution networks is subject to intensified cybersecurity threats caused by false data injection attacks (FDIAs). To address the issues, this paper proposes a novel FDIA detection strategy for unbalanced distribution networks. The SE model an...

This paper proposes an image-based algorithm for detecting and cleaning the wind turbine abnormal data based on wind power curve (WPC) images. The abnormal data are categorized into three types, negative points, scattered points, and stacked points. The proposed algorithm includes three steps, data pre-cleaning, normal data extraction, and data mar...

Synchronous rectification (SR) technology has been a critical technology for LLC converters to achieve high efficiency and power density. However, conventional SR driving methods face challenges in terms of light-load condition, module size, switching accuracy, and circuit complexity. This paper proposes an SR driving strategy based on resonant ind...

Multiarea parallel computing has emerged as a powerful tool for improving operation and control efficiency in the context of the expanding scale of new power systems. However, the existing partitioning methods cannot handle the problem of three-phase imbalance, the results are not stable enough and have not been verified in large-scale distribution...

Non-intrusive load monitoring (NILM) can infer load profiles for each individual appliance from aggregated power consumption signals without installing extra sub-meters. However, the performance of traditional energy disaggregation methods deteriorates in complex environments, especially susceptible to the presence of other high power consumption a...

Introduction: This paper proposes a sigmoid-based adaptive inertia control strategy for grid-forming (GFM) inverter to enhance frequency stability. Methods: Firstly, the frequency response characteristics under different disturbances are analyzed theoretically. Then, to solve the problem that fixed inertia leads to a contradiction between the maxim...

The extensive penetration of distribution energy resources (DERs) brings increasing uncertainties to distribution networks. Accurate topology identification is a critical basis to guarantee robust distribution network operation. Many algorithms that estimate the distribution network topology have already been employed. Unfortunately, most are based...

Photovoltaic (PV) power generation has highly penetrated in distribution networks, providing clean and sustainable energy. However, its uncertain and intermittent power outputs significantly impair network operation, leading to unexpected power loss and voltage fluctuation. To address the uncertainties, this paper proposes a multi-timescale affinel...

The discrete-time optimal control (DTOC) based tracking differentiator (TD) was first proposed by Han, (named fHan-TD). As for a nonlinear differentiator, it is difficult to evaluate the stability of the system containing fHan-TD. The application of the fHan-TD is also constrained by complex computation. Hence, in this paper, a linearized TD was pr...

The State Estimation (SE) method is troubled by heavy computational tasks and poor estimation tracking capability for the large-scale active distribution network. Given the aforementioned difficulty, this paper proposed a novel multi-area Forecasting Aided State Estimation (FASE) strategy to perceive the state of the system effectively. The propose...

The State Estimation (SE) method is troubled by heavy computational tasks and poor estimation tracking capability for the large-scale active distribution network. Given the aforementioned difficulty, this paper proposed a novel multi-area Forecasting Aided State Estimation (FASE) strategy to perceive the state of the system effectively. The propose...

Power distribution networks are evolving toward a modernized cyber-physical system that is vulnerable to mounting cybersecurity threats brought by false data injection attacks (FDIAs). To address the issue, this article innovatively proposes a multiarea probabilistic forecasting-aided interval state estimation (MPF-ISE) framework for FDIA identific...

As a critical session of cyber-energy system operation, the state estimation (SE) is becoming more vulnerable to various malicious cyber-attacks like false data injection attacks (FDIAs), which can circumvent the detection mechanism and tamper with the data transmission to cause abnormal state deviation. Driven by this motivation, this paper tries...

With the rapid development of demand-side management technologies, load serving entities (LSEs) may offer demand response (DR) programs to improve the flexibility of power system operation. Reliable load aggregation is critical for LSEs to improve profits in electricity markets. Due to the uncertainty, the actual aggregated response of loads obtain...

The bi-directional DC-DC converter (DDC) is commonly employed for the battery or supercapacitor (BA/SC) to accomplish the power management flexibility. The current and voltage control for the DDC is crucial for power management. Focusing on the control of the DDC, this paper first proposes a simple order-reduction control method for the first-order...

The intermittent and stochastic power injections of the penetration of photovoltaic (PV) generators make the processing of fault restoration in the distribution network need to consider more uncertainties. A new scheme of robust fault restoration methods, aiming to maximize the recovery of outage power, is proposed for unbalanced distribution netwo...

At present, the distributed resources with a high proportion in Regional Energy Internet are wildly involved in the optimized operation. This paper aggregates distributed resources into a "virtual generator" which considers the time-varying characteristics of distributed resources. Conventional optimization models often adopt components such as gen...

Modular multilevel converters (MMCs), as one of the core components of hybrid AC/DC power grids, become the preferred converter topology and show good developments. Urgently, a general MMC modeling scheme with good model accuracy needs to be developed to realize small-signal analyses and designs for the large-scale AC/DC power grids easily. This pa...

The increasingly close connections between multiple heterogeneous energy subsystems, the integrated energy system (IES) will play a critical role in ensuring future energy generations and distributions. As an essential function of the energy management system, state estimation provides data support for energy management of IES. Unfortunately, the e...

Widespread advanced metering infrastructure and wide-area monitoring systems generate a significant amount of electricity load consumption data, which can facilitate eliciting end users temperature flexibility for demand response programs. However, the direct delivery of users load profiles is a threat to users privacy. So this paper proposes a pri...

Modern energy systems are experiencing the transition towards renewable-powered ones. Some conventional thermal units based on synchronous machines are gradually decommissioned and replaced by power electronics interfaced renewables. Thus, the lack of natural inertia and governor damping, which are the features of synchronous machines, raises signi...

As the penetration of renewable energy resources increases, their intrinsic uncertainty and randomness raise significant concerns about the grid’s reliability. With the development of information technologies, residential air-conditioners serve increasing services, including secondary frequency regulation, peak load shaving, and capacity reserve. H...

At present, the distributed resources with a high proportion in Regional Energy Internet are wildly involved in the optimized operation. This paper aggregates distributed resources into a “virtual generator” which considers the time-varying characteristics of distributed resources. Conventional optimization models often adopt components such as gen...

The differentiator is widely used in power converter control to improve the control performance. However, the noise attenuation and phase lag always challenge the digital implementation of the differentiator. The existing differentiators, such as the high-pass filter (HPF), nonideal generalized integrator (nGI) and the discrete-time optimal control...

In island microgrids, the increasing integration of inverter-interfaced distributed generators (DGs) degrades the dynamic performance of the control system. The operation voltage and frequency may appear unacceptable overshoots and fluctuations under disturbances. To achieve rapid convergence while efficiently suppressing overshoot, this paper deve...

A rational partition is the key prerequisite for the application of distributed algorithms in the distribution networks. This paper proposes community-detection-based approaches to distribution network partition, including a non-overlapping partition and a border-node partitioning method. Firstly, a novel electrical distance is defined to quantify...

With the promotion of integrated energy technology and the diversification of energy trading, the trading prices and trading process of different types of energy show stronger coupling and relevance. In view of the strong correlation of integrated energy service providers in the dynamic pricing process of electric and thermal energy, and the game r...

The transient stability mechanism of grid-following inverter (GFL-inverter) and grid-forming inverter (GFM-inverter) in the power system has been extensively studied respectively, whereas the integration of GFM-inverters and GFL-inverters into the grid unavoidably change the transient stability of the power system. This paper aims to analyze the tr...

Load aggregators (LAs) play a coordinating role between the independent system operator and retail customers, which evaluate the regulatory value of small or medium users to achieve an efficient integration of discrete demand response resources. Dealing with the fluctuating electricity price of the day-ahead market, we established a bi-level optimi...

As the penetration of distributed renewable generation increases, their intrinsic uncertainty and random raise neutral concerns on the reliability of microgrid. Demand side resources are considered helpful in facilitating the operation of microgrid. In recent years, the development of Internet of Things and electric vehicle enables the capability o...

A grand challenge for the state estimation (SE) method in large-scale distribution networks lies in how to deal with the increasing computational tasks. This article addresses the issue and proposes a novel multiarea architecture for the unbalanced distribution network SE method. The first step of the method is to introduce an innovative multiarea...

Converter blocking in the case of pole-to-pole short circuit of the direct current (DC) distribution network can cause large-scale power outage and slow system recovery. Given this issue, a scheme of short circuit protection between poles of the DC distribution network based on the cooperation of fault current limiting module and DC circuit breaker...

交直流配电网中受端弱交流配电网电压调节能力较弱, 需要直流配电网提供功率支撑, 而直流配电网受到自身和交流配电网的双重影响, 导致直流电压偏差较大且低惯性特征更加明显. 对此, 文中引入柔性多状态开关 (SNOP), 并提出一种交直流电压自适应控制策略. 首先, 分析交流电网电压扰动对直流电压动态响应和惯性调节过程的影响机理, 通过设计电压前馈控制方法有效抑制了扰动作用. 其次, 针对弱交流配电网调节能力不足的问题, 设计自适应功率补偿控制方法, 使得 SNOP 能够根据工作点处电压变化量自适应地补偿功率缺额, 同时分析了该功率需求对于直流电压偏差的影响; 在此基础上针对直流系统, 综合考虑直流电压偏差与电压变化率设计了改进的自适应虚拟惯性控制方法, 并分析主要控制参数变化对直流系统稳定性的...

With the rapid development of renewable energy sources (RESs), adopting power‐to‐gas to improve the penetration of RESs is promising. This study designs a grid‐forming application for the fuel cell/electrolyser (FC/ELZ) system to supply the frequency support for the grid as well as the voltage source. The detailed control methods including the DC,...

电压控制型并网逆变器由于其特有的优点, 如便于孤岛运行, 可脱离锁相环, 有利于提高电网稳定性等, 受到越来越广泛的关注. 针对电压控制型并网逆变器瞬时功率控制需求, 文中提出了时间常数与功率幅度可自由调节的有功惯量支持控制与下垂控制. 所提算法采用前馈与零极点消除的方式, 将原有二阶有功控制系统降阶为一阶系统, 从而有效改善了功率控制的动态响应, 且由于前馈的引入, 有效提高了系统的控制自由度, 使得功率调节时间与功率-频率调节幅度可独立设计. 实验结果表明所提控制方法可以实现具有良好动态性能的惯量支持及下垂控制.

To improve the filtering capability of frequency-locked loop (FLL), the high-order bandpass filters FLL was proposed recently. This paper proposes a high-order FLL in synchronous (dq) reference frame where the high-order lowpass filter is adopted. A general analytical model is established for the high-order FLL. Based on the model, it is proven tha...

As the penetration of renewable energy continues to increase, stochastic and intermittent generation resources gradually replace the conventional generators, bringing significant challenges in stabilizing power system frequency. Thus, aggregating demand-side resources for frequency regulation attracts attentions from both academia and industry. How...

This paper introduces a scenario-adaptive online learning algorithm for aggregating demand side resources. The problem of dispatching demands is formulated under a contextual combinatorial multi-armed bandit framework with the objective to minimize the mismatch between actual aggregated demand adjustment and the reduction target from system operato...

In order to avoid overuse of a certain battery energy storage system (BESS) and prolong the cycle life of battery in AC microgrid, an improved SoC-based droop control based on multi-agent system (MAS) is proposed for achieving State of Charge (SoC) balance of multiple BESS units. A proportional-integral (PI) adjustment item using the average SoC is...

Owing to the limited operating regions of combined heat and power (CHP) units, the operation of integrated energy systems suffers from low flexibility, low‐cost efficiency, renewable curtailment etc. Meanwhile, as the capacity of renewable energies keeps growing and integrating into power systems, various methods, such as installing electric boiler...

The increasing penetration of photovoltaic (PV) generators has led to a reduction in the effectiveness of existing strategies for restoring the power distribution network. This article proposes a dynamic robust restoration (DRR) framework for the recovery of outage power considering uncertain PV outputs and demands. This framework is presented in t...

An enormous challenge for state estimation (SE) in power distribution networks with high penetration of photovoltaic generators lies in how to deal with measurement uncertainty. Driven by this motivation, an interval arithmetic (IA) based SE is proposed in this paper, which considers interval modeling for measurement uncertainty. The proposed SE is...

This paper proposes a distributed adaptive robust voltage/var control (DAR-VVC) method in active distribution networks to minimize power loss while keeping operating constraints under uncertainties. The DAR-VVC aims to coordinate on-load tap changers, capacitor banks and PV inverters in multiple operation stages through a distributed algorithm. To...

This letter proposes a new design of frequency-locked loop (FLL) which is based on synchronous (dq) reference frame instead of stationary ({\alpha}\b{eta}) reference frame. First, a synchronous reference frame FLL (briefly called SRF-FLL0) equivalent to the conventional FLL is proposed. Then the SRF-FLL0 is improved by utilizing the phase error to...

This letter proposes a new design of frequency-locked loop (FLL) which is based on synchronous (dq) reference frame instead of stationary ({\alpha}\b{eta}) reference frame. First, a synchronous reference frame FLL (briefly called SRF-FLL0) equivalent to the conventional FLL is proposed. Then the SRF-FLL0 is improved by utilizing the phase error to...

Future power distribution networks are characterized by changes of uncertain behavior due to the integration of distributed generators (DG) and prosumers, and the design of meter deployment is more critical for the safe and effective network monitoring system. The use of any available and the newly installed metering devices such as micro phasor me...

This paper proposes an image-based algorithm for detecting and cleaning the wind turbine abnormal data based on wind power curve (WPC) images. The abnormal data are categorized into three types, negative points, scattered points and stacked points. The proposed algorithm includes three steps, data pre-cleaning, normal data extraction and data marki...

Distribution networks with high penetration of distributed generation (DG) yield complicated and uncertain power flow, which make most existing faulted line identification methods not adaptable for industrial applications. Driven by this motivation, a novel single-phase-to-ground (SPTG) faulted line identification method is proposed based on hybrid...

The increasing penetration of photovoltaics (PVs) and fluctuating load exacerbate the risk of voltage and reactive power violations in distribution systems. The conventional regulation strategy is based on the nine-zone diagram control (NDC), which is difficult to quick response and meet the requirement with high precision. Utilizing the delay of N...

This paper proposes an extended-state-observer-based distributed robust secondary voltage and frequency control for an autonomous microgrid (MG) with inverter-based distributed generators (DGs) considering the uncertainties from models and measurement noise. The MG is considered as a multi-agent system where each DG is defined as an agent and its c...

This paper proposes a two stage decentralized optimal reactive power dispatch (D-ORPD) framework, which considers the network partitioning influence in distributed optimization. The first stage is to divide the distribution networks (DNs) into several high intra-cohesion and low coupling sub-networks while the mathematical model is constructed base...

This paper presents a novel distributed voltage control strategy to maintain the voltage of active distribution networks containing multiple microgrids. Local voltage regulation characteristics, such as power reserve, adjustment cost and regulating speed, are identified first. According to a neighbors’ voltage regulation characteristics, the microg...