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Xiaodong Zheng - IEEE Xplore Author Profile

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The increasing penetration of renewable energy sources, coupled with the variability of loads such as Electric Vehicles (EVs), is leading to stability issues in power systems. Addressing this problem requires dynamic measurements. However, there may be a limited number of High-Resolution (HR) meters, such as Phasor Measurement Units (PMUs), especially in distribution grids. In contrast, there are ...Show More
Incipient faults (IFs) are the precursors of power equipment failures. Due to the low occurrence frequency, IF data are scarce. The scarcity of IFs leads to the difficulty of identifying IFs. Traditional methods lack the ability to learn rich and meaningful representations of IF data, especially under the circumstance of limited IF data. Besides, some methods that involve transforming waveforms in...Show More
Power systems are integrating uncertain generations, demanding transient analyses using dynamic measurements. However, High-Resolution (HR) Phasor Measurement Units are few. The aim is to interpolate dynamic data for extensive but Low-Resolution (LR) meters. Existing interpolation methods capture data correlations but ignore the governing equations, i.e., Ordinary Differential Equations (ODEs) or ...Show More
With the integration of large-scale renewable energy, the fault characteristics of the renewable energy outgoing line have undergone significant changes, leading to the sensitivity decrease or even rejection of traditional ratio restraint current differential protection. Through rewriting the protection criterion and constructing the composite sequence network during fault, this paper investigates...Show More
The inertia of power grid has decreased recently as a result of the widespread connection of wind power, which has negatively impacted the frequency stability of the system. This paper proposes an inertia demand-based wind-storage combined system inertia control strategy to overcome these issues. First, the minimum inertia demand of new energy is estimated based on system frequency safety constrai...Show More
The traditional flexible HVDC system protection scheme based on boundary conditions uses current-limiting reactors to extract fault features. When the size of the reactor is limited by the actual engineering, there is a problem that the protection is difficult to identify the fault. This paper takes the flexible HVDC transmission line as the research object. Considering the limited value of the cu...Show More
Unlike synchronous generators (SGs), inverter-based resources (IBRs) exhibit unique fault behaviors. These fault behaviors include limited fault current amplitude, controlled fault current phase, and unsteady sequence impedance. The unique fault behaviors of IBRs, combined with the absence of zero-sequence current, can lead to the malfunction of IBR-side distance protection on outgoing lines of IB...Show More
When single-phase-to-ground (SPG) or phase-to-phase (PP) faults occur on collection lines of an offshore wind farm with modular multilevel converter-based high voltage direct current (MMC-HVDC) transmission, the fault current level may be low or even approach zero due to the controlled current at both ends of the collection line. As a result, the traditional current differential protection may mal...Show More
Uncertain power generations and loads are continually integrated into the power system, causing high risks of dynamic events. To better monitor systems, advanced meters like Phasor Measurement Units (PMUs) can record high-resolution system dynamic states in real time. However, due to the high cost, the placement of PMUs is limited in a system. Thus, it's hard to obtain all the dynamic system state...Show More
The fault characteristics of photovoltaic (PV) power plant are influenced by inverter control strategy, resulting in the malfunction of traditional power frequency phase selection method. Theoretical analysis indicates that inverters can be approximate to linear components in high-frequency superimposed network and its impedance tends to stabilize. On this basis, we analyse the characteristics of ...Show More
With the application of large-scale renewable power generation and power electronic equipment, the fault characteristics of power grids have been significantly altered. Unlike synchronous generators, the fault characteristics of power electronics are primarily determined by their control strategy, resulting in reduced adaptability of traditional protection methods. Therefore, it is imperative to r...Show More
With the vigorous development of renewable energy and the popularization of HVDC transmission, the structure of power sources has changed a lot. The output current amplitude of power electronic devices is limited, the phase angle of current is controlled, and the characteristics of the sequential component are affected by the converter control strategy, which are different from fault characteristi...Show More
Due to the influence of MMC control mode, the differential protection of AC transmission line in MMC-HVDC system has low sensitivity. To solve this problem, a high sensitivity differential protection scheme based on phase correction is proposed. The phase offset affected by the control link is calculated and the additional phase Angle is obtained. The additional phase Angle is introduced in the ca...Show More
In the context of building a new power system dominated by renewable energy sources, the integration of high proportion of renewable energy and high proportion of power electronic equipment imposes stricter requirements on power system protection. The current differential protection, as the main protection for the outgoing line of renewable energy stations, has a significant impact on the developm...Show More
Towards the carbon neutrality, more renewable energy sources (RESs) are integrated to the power system whose inevitably intermittent nature and sudden fluctuations may jeopardize the system stability. Therefore, the conventional robustly optimal energy management alone is not sufficient because the negative impact on the small-signal should be mitigated. This paper proposes a robust optimization m...Show More
In the photovoltaic connected distribution system, the photovoltaic is connected to the AC grid through the inverter. It brings great challenges to the protection of the AC outgoing line. When a fault occurs on the AC side, the fault current phase presents a controlled characteristic. The control mode of the inverter has great influence on the fault current, and the negative sequence current suppr...Show More
To achieve carbon peaking and carbon neutrality goals, it is necessary to build a new power system with renewable energy as the main body. In this context, the integration of high proportion of renewable energy and high proportion of power electronic equipment imposes stricter requirements on power system relay protection. The current differential protection, as the main protection for the outgoin...Show More
The flexible DC transmission system based on modular multilevel converter (MMC) responds quickly, and the control signal changes rapidly after DC fault. This paper analyzes the response characteristics of current control signal and voltage control signal in the MMC after a fault, and proposes a new protection scheme for flexible DC transmission lines based on calculated impedance. The calculated i...Show More
Nonlinear fault response of power electronics poses challenges to the reliability of protection. As the power electronic converters being connected to both ends of the AC collection line in the VSC-HVDC system with offshore wind farm integration, the fault characteristics of the AC collection line has completely changed, and the adaptability of protection is seriously affected. Distance protection...Show More
With more renewable energy integrated to the grid in the form of inverter based resources (IBRs), traditional current-based fault phase selector encounters limitations. The causes of this problem are the weak infeed feature and variation of source impedance of IBRs. This paper proposes an improved fault phase selection scheme to solve this problem. Firstly, the reasons for the failure of tradition...Show More
Hybrid cascaded high voltage direct current (HVDC) transmission adopts the form of modular multilevel converter (MMC) and line-commuted converter (LCC) in series, which not only reduces the investment cost, but also reduces the fault current. In this paper, the topology and control strategy of the hybrid cascade HVDC transmission system is introduced firstly. Then, the fault characteristics of cur...Show More
For the abnormal phenomenon of non-faulty MMC after fault MMC blocking in Hybrid Cascaded Ultra High Voltage Direct Current (HC-UHVDC) transmission system, a coordinated control strategy based on control signals is proposed. The mechanism of overcurrent and overvoltage in non-fault MMC was analyzed. Additional current was added in the LCC rectifier control to suppress overcurrent and overvoltage. ...Show More
Due to the influence of inverter control, the short-circuit current provided by distributed photovoltaics (PVs) exhibits new characteristics, such as a controlled amplitude and phase angle, resulting in the malfunction of the current protection and differential protection of distribution networks with high PV penetration. In this paper, the equivalent high-frequency impedance model (EHFIM) of PV p...Show More
The output current phase of photovoltaic power generation unit is affected by inverter control, and photovoltaic power generation unit presents weak feedback characteristics, resulting in the current differential protection and pilot protection of collection line in photovoltaic station may malfunction. This paper analyzes the fault high-frequency additional network of the collection line of photo...Show More
Accurate fault location method is beneficial since it reduces the power outage time and operational costs. This paper proposes a time domain Bergeron model based method to accurately locate faults in HVDC transmission lines. The line mode and high frequency component of measurements are utilized. In addition, the method utilizes wavelets to choose the proper line parameters used in the fault locat...Show More