Xiaoqing Han

• Taiyuan University of Technology

Under the background of "Dual Carbon" goals, the integration of many distributed power sources has increased harmonic injection into distribution networks, posing significant challenges to the system's static voltage stability. In this context, this article analyzes the impact of harmonics on static voltage stability post-distributed power source i...

The loads that have several working states cannot be accurately distinguished by the conventional Non-Intrusive Load Monitoring (NILM) methods. This paper proposed an improved NILM method based on the Resnet18 Convolutional Neural Network (CNN) and Support Vector Machine (SVM) algorithm to address the misidentification of multi-state appliances. Th...

Cascaded inverters may suffer from multiple opencircuit faults (OCFs) that occur in cascaded way, but most existing hardware-based fault-tolerant methods usually activate redundant submodules (SMs) after a long diagnosis process is finished, which leads to significant waveform distortion and power derating. This paper proposes a seamless fault-tole...

A modular Sigma DC/DC converter with wide input voltage range is proposed in this paper. The proposed converter is combined with a traditional LLC converter and two multi-resonant converters via Sigma architecture. Among them, the traditional LLC converter operates as a DC transformer (DCX) at resonant frequency to achieve maximum efficiency. Meanw...

Compared with isolated converters, transformerless converters are a preferred choice in low-voltage grids due to their efficiency and lower cost. However, leakage current and common mode (CM) voltage appear through the converter and ground in hybrid grids, which consist of AC and DC subgrids. The leakage current and CM voltage seriously influence o...

The connection of single-phase AC loads to a DC microgrid not only large secondary currents flowing into energy storage units with droop control cause, but also lead to secondary voltage ripples appeared on the DC bus, which seriously affects the normal operation of DC microgrids. In this paper, the secondary currents and voltages can be suppressed...

As a promising way to achieve energy transition, electric vehicles (EVs) are rapidly advancing. Dynamic charging price of charging network operator (CNO) guides the owners to vary travel decisions, which in return affect the operation of power distribution networks (PDNs) and transportation networks (TNs). Therefore, an appropriate dynamic charging...

With the increasing penetration of natural gas in power systems, the resilience of electric-gas coupled distribution networks under extreme fault perturbations has received increasing attention. Since the entire phase resilience of an electric-gas coupled distribution network after an extreme event depends on its system function, it is necessary to...

The real‐time monitoring technology of power line is an important guarantee for the digitization and intelligence of the modern power system. Traditional current transformers cannot provide continuous and stable energy when the power line current fluctuates in a large range. This paper proposes a comprehensive design method of an active electronic...

The stability of dual active bridge converter (DAB) is threatened when feeding the constant power loads (CPLs). This article proposes a deep reinforcement learning-based backstepping control strategy to solve this problem. First, a nonlinear disturbance observer is adopted to estimate the large-signal nonlinear disturbance. Then, a backstepping con...

The multi-energy synergy of electricity and natural gas distribution systems (EGDS) offers a more proactive potential for resiliency in extreme contingencies. The interests of energy systems owned by different agents are nonnegligible in resilience enhancement. Existing distributed coordinated operation models seldom consider the multiple resilienc...

The DC solid-state transformer (DCSST) is a key component of the DC microgrid, and stability issues due to operation with constant power loads (CPLs) have become increasingly prominent. To stabilize the system of DCSST with CPLs, in this paper, a novel intelligent backstepping controller based on a nonlinear disturbance observer (NDO) is proposed,...

The uncertainty associated with loads and renewable-energy sources affects active distribution networks in terms of the operation and voltage stability on different time scales. To address this problem, a multi-time-scale voltage stability constrained optimal scheduling framework is proposed, which includes a day-ahead model with a coarse-grained t...

DC circuit breaker is the key equipment to deal with the interruption of short-circuit current. Compared with the mechanical switch, the solid circuit breaker and the hybrid circuit breaker using the semiconductor device to interrupt the short-circuit current exhibit superiorities in response duration and arc-less characteristics. Massive power dev...

Energy load forecasting is essential to effectively optimise the use of energy for the purpose of smart grid operation. In this work, a focus is placed on Short-term Load Forecasts (STLF) using measured heat pump data from the UK utilising the Long Short-Term Memory (LSTM) method. A load forecasting program is developed to forecast the electricity...

This paper proposes a circulating current and second harmonic current (SHC) suppression method by introducing virtual impedance into the circulating current and output current feedback control loops of the DC solid state transformer (DCSST). The virtual impedance is employed to adjust impedance in the circulating current feedback control loop to de...

Abstract An active power filter (APF), which operates under the power‐balance‐based scheme (PB scheme), suffers heavier DC‐link voltage fluctuation when the loads change suddenly, so that it is apt to be interfered and degraded or even out of stable operation. By analyzing the cause of DC‐link voltage fluctuation, this study proposes an improved PB...

The grid voltage distortion represents a significant cause of the grid quality degradation when a renewable energy system is incorporated into the traditional grid. In this paper, a direct harmonic current control strategy is proposed for an LCL converter under distorted grid conditions. The proposed strategy improves the power quality and enhances...

The redundant design of multi-paralleled bidirectional power converters (BPCs) provides technical support for hybrid microgrid systems to consume more distributed generations (DGs) and DC loads. However, the multi-BPCs also provide paths for circulating current. In addition, the AC sub-grid may operate under unbalanced conditions due to the consump...

Silicon carbide-based solid-state circuit breaker (SSCB) exhibits superior performance in dealing with the interruption of dc short-circuit current compared with the mechanical switch. The blocking voltage of commercially available SiC devices still cannot meet the voltage requirements. Series-connected SiC mosfet s providing higher blocking volt...

Energy load forecasting is essential to effectively optimise the use of energy for the purpose of the smart grid operation. Accurate energy load forecasting can provide an unprecedented level of flexibility in energy management. Home Energy Management Systems (HEMS) optimisation algorithms usually require reliable Short-term Load Forecasts (STLF) w...

Multiple uncertainties from renewable energy sources, power loads and bidirectional AC/DC converter have brought great challenges to the energy management of AC/DC hybrid microgrid. In view of the issues, this paper proposes a temporally coordinated energy management strategy for AC/DC hybrid microgrid considering dynamic conversion efficiency of b...

Active damping methods are widely adopted to present a damping effect on the resonance phenomenon without the power loss of LCL-type converters connected to a grid. However, extra sensors are used to implement the damping strategy. In this paper, a sensorless damping strategy where only the grid current is sampled has been proposed. Furthermore, th...

To improve the fault ride-through capability and power quality of a hybrid microgrid (HMG), a series compensation link (SCL) is inserted between an AC–DC HMG and a utility grid, which forms a new HMG topology. Correspondingly, a decoupling coordinated control strategy for the SCL and a bidirectional AC–DC interlinking converter (BIC) is proposed ba...

A model of the AC/DC converter based on the harmonic state space (HSS) theory is developed, and the AC/DC harmonic coupling characteristics of the converter have been analyzed in depth. Firstly, through the mathematical derivation, the three-phase AC/DC converter is modeled based on the HSS theory. The HSS model includes each harmonic on the AC and...

The demand for energy, particularly electricity, has increased over the past years due to economic development and the utilisation of electricity intensive technologies for heating, cooling and transportation. As a result, smart grid technology is being developed to address these new challenges. In order for a smart grid to achieve its full functio...

HybridAC/DC microgrids(HMG) are emerging as an attracting method for integrating the AC/DC distributed energy resources(DERs) with the features of high-performance and low-cost. In the isolated hybrid AC/DC microgrid (IHMG), the key problem is how to balance the power variation and regulate the voltage and frequency. Various energy storage systems...

With the further development of the world economy and society, the demand for electricity is rising significantly. To account for this growing electricity demand, smart grid technology development has ensued. Furthermore, Energy Management Systems (EMSs), especially Home Energy Management System (HEMS) are critical for a smart grid to function effe...

Smart grids are the developmental trend of power systems and they have attracted much attention all over the world. Due to their complexities, and the uncertainty of the smart grid and high volume of information being collected, artificial intelligence techniques represent some of the enabling technologies for its future development and success. Ow...

In order to facilitate access of DC micro-sources and loads of different voltage levels to DC microgrid, a DC microgrid with two DC buses based on power pool was designed in this paper. Its coordination control strategy was also proposed. The DC microgrid is composed of two sub-microgrids with different voltage levels and a power pool in connection...

Owing to intermittency of wind power and slow ramp rates of conventional generators (CGs), a considerable amount of wind energy cannot be effectively utilized during frequency control processes. This paper proposes a technique for power system planners and operators to select or commit power capacity and energy capacity of BESS for mitigating the e...

A high performance three-phase pulse width modulation (PWM) converter with reduced DC-link capacitor under unbalanced AC voltage conditions is proposed in this paper. The unique feature of the converter lies in that sinusoidal symmetrical AC currents and ripple free DC voltage can be achieved simultaneously without using a bulky capacitor, which wa...

This paper proposes a modified one cycle control (OCC) for active power filter (APF) to compensate only harmonic components of load currents. The conventional OCC-based APF cannot differentiate between the harmonic and reactive components of load currents, which leads to the increment in device current rating because of compensation of large reacti...

This chapter titled “Hybrid AC/DC Micro-grids: Solution for High Efficient Future Power Systems” presents a new configuration for future power systems which is the hybrid AC/DC gird for high efficient connection of the inherent AC and DC sources and loads. Three-phase AC power systems have been in dominant position for over hundred years due to inv...

With high renewable power penetration, uncertainty and intermittence of renewable sources become major concerns of power system planning and operation. Large and fast wind speed change may cause great variation of active power generation which may lead to system stability and reliability problems. The response speeds of the committed conventional g...

The one cycle control (OCC) scheme for active power filters (APFs) has shown excellent harmonic suppression and implementation simplicity. However, its real world application is limited because the non-ideal supply voltage for APFs can influence its performance so that the source currents are still distorted after compensation. This paper proposes...

Fatigue and destruction in the shafts of a wind turbine caused by sub-synchronous oscillations during power system faults is critical for wind turbine reliability. This paper investigates a three-mass shaft model according to a MW class doubly-fed wind generator shaft mechanical structure and obtains the electromagnetic torque of a wind turbine by...

A major concern for wind farm connection to power systems is large variation of power output caused by the variability and unpredictability of wind speed. For a power system with high wind power penetration, the frequency control process of conventional generators (CGs) to match load and wind power variation becomes an important operation issue. En...

Distributed generators and micro-grid connection in distribution network has changed power flow from unidirectional to bidirectional. Therefore, it is necessary to install directional components to locate the fault position accurately when there is a short circuit fault in distribution network. However, voltage information is not available because...

Voltage stability analysis has been highly concerned by researchers. However, probabilistic techniques cannot handle fuzzy factors in power system. In this paper, a voltage stability analysis method based on adaptive fuzzy logic with consideration of random factors of loads is proposed. System states are classified, fuzzy mathematical model and fuz...

This paper proposes an advanced non-harmonic detection control strategy for three-phase four-wire Active Power Filter (APF) based on improved Vector-Resonant Control (VRC). The mathematical model of the split-capacitor configuration is established with the source currents and the DC bus voltage as state variables. The proposed control scheme detect...