Equipping a renewable energy collection station with Static Var Generator (SVG) contributes to the enhancement of the power quality, and system stability. To efficiently achieve the analysis of grid-connected stability and multi-parameter optimization of SVGs in renewable energy collection stations, the impedance models of SVG, considering various control modes, are first established. By using the frequency-domain admittance matrix to describe the whole system consisting of renewable power generation units, collecting network, SVGs and equivalent unity grid, the stability analysis is performed for typical operating conditions of the renewable energy collection station. Furthermore, damping ratio and its sensitivity calculation algorithm based on the frequency-domain admittance matrix is designed, and a multi-parameter coordinated tuning model for stability optimization using the damping ratio sensitivity is developed. Finally, the derived impedance model and the proposed method are validated through theoretical analysis using the frequency-domain admittance matrix and time-domain simulations in MATLAB/Simulink.

Hybrid power supply systems (HPSS), which include fuel cells (FC), lithium-ion batteries (LB), and supercapacitors (SC), are commonly used to power onboard electric loads in transportation electrification systems. To improve reliability, hybrid virtual impedance droop (HVID) control is typically employed to enable dynamic power sharing among different sources. However, when one of the main sources, such as the FC or battery, disconnects from the HPSS, maintaining both DC-bus voltage quality and the ability to share power dynamically becomes challenging. During faults, the load may lose power, potentially causing severe damage to the system. This article proposes a simple fault-tolerant control strategy for the FC-LB-SC HPSS. The strategy allows the SC unit to quickly provide power for the excessive load during LB’s outage by adding an adjustable virtual resistor in parallel with the SC unit's virtual capacitor. This ensures that the DC bus voltage quality and dynamic power-sharing capability are preserved even if one of the main power sources fails. The operational principle of this strategy is examined in detail, and its effectiveness is confirmed through experiments with a 5-kW HPSS prototype.

With the increasing penetration of converter-interfaced renewable energy sources, converter-dominated power systems (CDPS) have become increasingly vulnerable to wideband oscillations. Impedance-shaping control has been recognized as an effective solution for oscillation mitigation. However, existing impedance-shaping approaches offer suffer from inconsistent design objectives and complicated parameter tuning requirements, which limit their applicability in practical CDPS. To address these issues, this paper proposes a broadband admittance-shaping control strategy incorporating a fundamental-frequency reactance coefficient regulation mechanism to improve compatibility among diverse converter types. Furthermore, a coordinated admittance-shaping control scheme is developed for converters with dominant oscillatory dynamics. Specifically, distributed coordination among multiple converters is achieved through online adjustment of admittance-shaping coefficients according to oscillation participation factors, oscillation conditions, and converter capacities. Hardware-in-the-loop (HIL) experimental results validate the theoretical analysis and demonstrate the effectiveness of the proposed strategy in enhancing system stability and suppressing sideband oscillations.

Stochastic electromagnetic transient (EMT) simulation can provide a rigorous testing environment for converter-dominated power systems. To efficiently realize it, an algorithm in the framework of finite element methods is investigated in this paper. Taking a grid-connected three-phase VSC circuit as an example, the issues in performing the stochastic EMT simulation are first analyzed. By introducing the concept of simulation interval, the pseudo-Wiener process with piecewise linear interpolation is developed to reformulate the EMT model incorporating stochastic process. Furthermore, a large-stepping stochastic EMT simulation algorithm using the discontinuous Galerkin method is designed. In addition, an implementation scheme with specially tailored LU factorization techniques is introduced for enhancing the computational efficiency. The effectiveness and superiority of the proposed algorithm are verified by the simulation results on a dc distribution system and the physical experiments.

To meet the cross-timescale response requirements of new electrified loads, lithium batteries and supercapacitors are being integrated into onboard electrical power systems via DC/DC converters. Despite the rapid response and energy recovery capabilities of these storage units, the onboard hybrid power systems remain prone to significant power quality degradation and instability under transient conditions such as wide-range load transients, partial source failures, and pulsed loads with a high peak-to-average ratio. To address these issues, this article proposes a composite controller that integrates a fixed-time sliding mode disturbance observer (FTSMDO) with a prescribed performance controller (PPC). The FTSMDO is designed to estimate lumped disturbances, upon which a PPC is developed using the backstepping method. This approach enhances the system’s capability for rapid voltage recovery under various transient events and ensures large-signal stability. Finally, the effectiveness of the proposed composite control strategy is validated through both simulation and experimental results.

Hybrid power supply systems (HPSSs), which integrate the dynamic properties of different power sources, are a promising solution for transportation electrification systems. However, extreme cases such as large variations of load like large step-changing load and high peak-to-average ratio pulsed power load are highly susceptible to power supply system destabilization, which is beyond the scope of small-signal analysis. In this article, a comprehensive large-signal stability analysis for HPSSs considering variation in virtual impedance droop parameters and proportional and integral (PI) regulators under extreme load switching conditions is conducted based on the region of attraction estimation (ROA). On this basis, the impact of system parameters and load power on the large-signal stability is elaborated. The stability of the system is greatly improved by the adoption of active capacitors to absorb the pulsed power. The effectiveness of the proposed large-signal stability analysis method and the correctness of the analyzing results are verified through experiment results.

Voltage sag is one of the most frequent issues affecting power quality, can lead to abnormal operation of equipment, resulting in significant economic losses. This paper proposes a novel topology for voltage sag mitigation utilizing the solid-static transfer switch (SSTS) and power conversion system (PCS), and the operational principles are analyzed thoroughly. Under normal grid conditions, the PCS operates in grid-connected mode, supporting the grid in peak shaving and valley filling. Upon the detection of a voltage sag in the grid, the SSTS promptly activates, and the PCS switches to off-grid mode to ensure the continuous and reliable supply of power to the loads. A dual closed-loop control structure is devised to optimize both the dynamic and steady state performance of the PCS, with the inner-loop employing state feedback control, and the outer-loop employing a proportional-integral (PI) controller. The effectiveness of the proposed topology for voltage sag mitigation and the superior performance of the employed control structure for PCS are validated through MATLAB/Simulink.

The impedance analysis, as a well-established technique to analyze the small-signal stability of interconnected systems, has gained increasing popularity in recent years. To promote the performance of impedance analysis in the multiparameter coordinated tuning, the exclusive sensitivity for Nyquist plot and its computing algorithm are developed in this article, thus a sensitivity- and optimization-based parameter tuning method is further proposed. Finally, a multiterminal dc distribution system and a two-stage power supply system are studied to demonstrate the effectiveness of the proposed sensitivity and parameter tuning method.

In recent years, impedance-based stability analysis and improvement methods have become very popular in DC distribution systems. However, the existing stability criteria such as the impedance-ratio and impedance-sum criteria, require the additional calculation of the number of right-half-plane (RHP) poles when applied in the DC distribution systems with multiple voltage sources, which makes the stability analysis complex. In this paper, a stability analysis method for a DC distribution system with two voltage sources and one converter-based load is proposed, which does not require evaluating the RHP poles. On this basis, an impedance reshaping strategy based on the first-order high-pass filter is proposed to suppress system oscillations. Finally, the feasibility of the proposed methods is verified through impedance analysis and experiments.

Due to the distributed integration of renewable energy sources, storage devices, and DC loads, DC distribution systems are facing constantly evolving stability challenges. The complex system architecture and network of line impedances render the system instability characteristic analysis increasingly complex. In this paper, we propose an instability participation analysis method for DC distribution systems, utilizing the impedance determinant criterion, to precisely assess each converter's contribution to system instability, identifying critical instability converter. Case studies and experimental validation confirm the feasibility and accuracy of the proposed method.

The impedance-based stability analysis method is widely used in DC distribution systems. However, most existing methods are based on the one-dimensional impedance transfer functions and overlook the system's complex network. This paper investigates the small-signal stability of DC distribution systems with complex networks. First, the small-signal equivalent circuit model of the system is established and the closed-loop transfer function from all input variables to bus node voltages is derived. Second, based on the control theory of multi-input multi-output systems, two system-level stability criteria based on admittance matrix sum and equivalent loop gain are proposed, respectively. Finally, a typical DC distribution system consisting of four nodes and four converters was designed for case analysis and simulation, and the results show the correctness of the proposed stability criteria.

The large-signal stability analysis of two-stage cascaded dc-dc converter systems is still a troublesome problem due to various limitations of existing stability analysis methods. To address this problem, a large-signal stability analysis method based on Lyapunov's stability theory and the sum-of-squares programming technique is proposed. With the proposed method, one can not only obtain the maximum stability boundary of the system under large disturbances, which helps understand the system's transient behaviors, but also can analyze the influences of system parameters on the stability region and identify the dominant parameters. The proposed stability analysis method could provide a practical guide for designing system parameters. The effectiveness of the large-signal stability analyzing results is verified by experimental results.

In multi-terminal DC distribution system,due to the diversity of operating points and the complexity of impedance environ-ment,it is often difficult to provide sufficient improvement effect of stability by the active damping control with single point configuration in the converter station.In order to meet the multi-source configuration requirements of active damping in complex system,this paper takes the phase-shifted full-bridge DC converter as the research object from the perspective of load.On the basis of establishing the average equivalent circuit,the reduced-order impedance model and the transformation relation between input side and output side parallel impedances in low-frequency range,the origin of active damping control strategy using input voltage feedforward is traced,and the active damping control strategy of output voltage feedback is proposed.Finally,the dual-terminal DC distribution system is taken as the application abject,the accuracy of the reduced-order impedance model for the phase-shifted full-bridge DC converter and the effectiveness of the active damping strategy are verified by the time-domain simulation results,the small-signal eigenvalue trajectories and hardware-in-the-loop experiments.

"直流配电系统分析与控制"是南京航空航天大学电气工程系新开设的研究生课程,旨在让学生了解电气工程领域直流配电的发展现状,掌握直流配电的技术内涵.通过分析该课程的定位与教学目标,并以陆上系统为主体和航空航天应用为特色,规划和实践了课程教学内容,从而服务于一流学科建设和直流配电专业人才培养.

To meet the diversified requirements of active damping configuration in a dc distribution system, the input-series-output-parallel (ISOP) load converter based on phase-shifted full-bridge (PSFB) modules is investigated in this article. The reduced-order impedance model of the PSFB-based ISOP converter with common-duty-ratio control is established first, and then the active damping control strategies using the primary- and secondary-side voltages are proposed, respectively. By reformulating the stability criterion in the form of impedance-frequency curves and using the impedance sensitivity, the sensitivity of resonance frequency is derived to develop a method for designing the parameters of active compensators. Finally, the experimental results demonstrate the effectiveness of the proposed active damping control strategies and parameter design method.

To investigate the impact of uncertain variability on multiterminal dc distribution systems and provide an efficient simulation tool, this article develops a stochastic transient simulation method based on dynamic phasor (DP). Starting from the lumped elements, the dynamic phasor models of the elements with parameter migration are established first, as well as the corresponding dynamic companion circuits used in digital simulation. By introducing the switching function and low-frequency approximation, the DP-based companion circuit of the voltage source converter is formulated, and the revised nodal voltage equations that can be solved in the framework of Electromagnetic Transients Program are also derived. Then, combined with the discussion on the ill condition of the nodal admittance matrix, the main process of DP-based stochastic transient simulation and the hybrid simulation scheme integrating electromagnetic transient (EMT) simulation are further proposed. Through the comparison with the full EMT simulation and physical experiments, the effectiveness of the DP-based dynamic companion circuits is validated, as well as the efficiency of the proposed simulation method.

为了高效地实现多端直流配电系统的准确动态仿真,在动态相量–电磁暂态混合仿真框架下,文章首先分析应用于直流配电系统时所涉及的子系统建模、接口机制和数据交互时序等执行要素.然后以混合仿真误差产生机理为切入点,以电磁暂态子系统为主要关注对象,详细分析简单阻感支路和复杂系统两种情况下混合仿真的误差传递过程,并推导了数值稳定的必要条件.其次,以串行时序为例,设计直流配电系统动态相量–电磁暂态混合仿真算法的主流程,并提出动态相量提取修正、直流量特征纹波添加等精度提升方法.最后,基于MATLAB/Simulink搭建多端直流配电系统同构串行混合仿真平台,通过对比全电磁暂态仿真,验证混合仿真的高效性及精度提升方法的有效性.

To investigate the impact of uncertain variability and provide a rigorous testing environment for converter-dominated power systems, this article develops a testing tool called stochastic electromagnetic transient simulation. The tool is derived from the stochastic differential equation (SDE) representing the stochastic process of parameter migration. By inheriting the principle of companion circuit, the dynamic companion circuits of the lumped elements with parameter migration are further established. Combined with the analysis of the numerical stability in discrete simulation as well as the stability of the continuous system with parameter migration, a numerical algorithm that is compatible with the electromagnetic transients program (EMTP) framework is designed, as well as a C program package. The verification results on a grid-connected three-phase two-level rectifier and a two-terminal dc distribution system demonstrate that the developed tool can simulate the parameter migrations and the stimulated system dynamic process simultaneously, which can also be used to efficiently reflect the real performance of various control subsystems and their coordination in extreme cases.

分散式风电高渗透率接入直流受端电网后,系统频率问题逐渐突出,而调频单元分散化与多样化会加剧系统频率特性分析的复杂度,如何准确高效评估各单元调频作用于系统频率特性己是直流受端电网重要需求之一.首先推导了同步发电机、分散式风电场、直流受端换流站等单元的调频作用线性化表达式,进而以直流潮流集成各调频单元建立了直流受端电网频率响应模型.为解决模型阶数高不便于在复杂系统中应用这一缺陷,针对分散式风电场调频作用表征和复杂系统频率响应特性集成2个建模阶段,提出了采用劳斯近似法和Pade逼近法的双重降阶建模方法.最后,以扩展IEEE-30节点系统为测试对象,通过对比MATLAB/Simulink电磁暂态仿真结果,验证了所提分散式风电接入直流受端电网频率响应特性降阶建模的准确性和高效性,并从频率耐受水平方面对分散式风电渗透率进行了案例分析.

In order to improve the stability of high voltage direct current power supply system for more electric aircraft, reduce the cost and popularize the application of DC microgrid control technology in aviation. Firstly, this paper introduces the conventional PWM rectifier system based on the permanent magnet synchronous generator and its control strategy. Then, combining the advantages of the diode rectifier and active rectifier, a two-path hybrid rectifier system based on a permanent magnet synchronous generator is proposed, and the origin of the system topology and the corresponding control strategy is analyzed. Next, the small signal model of the power supply system is established, and the corresponding impedance model is further derived. Finally, based on MATLAB/Simulink, a simulation model of a two-path hybrid rectifier power supply system is built to verify the effectiveness of the proposed scheme and the accuracy of small-signal modeling, which provides a reference for the subsequent research on the power system architecture and stability of more electric aircraft.