Guoqing Li

With the integration of high-proportion renewable energies, the independent operation of the transmission and distribution systems (T&DSs) makes it difficult to achieve optimal scheduling and ensure frequency security. Therefore, this paper proposes a two-stage robust frequency-constrained unit commitment (TRO-FCUC) model of T&DS. Firstly, the impacts of distributed energy resources (DERs) frequency regulation capabilities on inertial response and primary frequency response (PFR) are considered, and dynamic frequency constraints considering the cooperation of thermal units, wind farms, and DERs with their inertia-based frequency reserve are constructed. Then, the TRO-FCUC model is formulated to address uncertainties of wind farms (WFs) and distributed photovoltaics (DPVs) based on uncertainty sets. Further, the column and constraint generation (C&CG) algorithm and strong duality theory are utilized to transform the TRO-FCUC model into a mixed-integer second-order cone programming (MISOCP) model and then solve it iteratively. Finally, case analyses proposed demonstrate that the coordinated operation of T&DS can fully mobilize the frequency regulation potential of DERs and improve the operation’s economy while ensuring the frequency security of the system.

Forced oscillations (FO) in power systems are caused by sustained periodic disturbances, threatening the power system stability. Developing a fast and accurate FO detection and location approach is of great significance for mitigating FO. This manuscript proposes a novel FO detection and location method using synchrophasor measurements in bulk power systems. Firstly, based on the short-time Fourier transform (STFT) of measurements, an FO detection method is proposed using the energy ratio function in time-frequency domain. Then, the equivalence of dissipating energy flow and dissipating energy spectrum is demonstrated. On this basis, the cross power spectral density (CPSD) of governor and excitation system are defined. The amplitude and phase spectra of the governor and excitation system at FO frequency are then derived, and the criteria for control device collaborative location are presented. Furthermore, an index for evaluating the oscillation contribution of the disturbance device based on frequency band energy is proposed to identify the dominant FO disturbance control device. Finally, the proposed method is validated using the simulation data of WECC 179-bus test system and 2021 IEEE-NASPI oscillation source location contest, as well as the field data from ISO-New England. The results validate the effectiveness and feasibility of the proposed method.

Accurately and promptly extracting subsynchronous oscillation (SSO) components from measurements and locating SSO sources are crucial for SSO suppression. Existing transient energy flow (TEF) based SSO location methods suffer from low location accuracy and poor robustness. To cope with the shortcoming of the traditional TEF in SSO source location, this paper proposes a multivariate variational mode decomposition (MVMD) based SSO source location method to locate the SSO source from the measurements. Firstly, the multi-channel measurement matrix of each generator, including voltage and current measurements, is formed. Then, the multi-channel intrinsic mode functions (IMFs) are simultaneously decomposed from the formed multi-channel measurement matrix by using the MVMD approach, enabling the simultaneous decomposition of SSO components from measurements. Furthermore, the IMFs associated with the SSO mode are identified according to the Hilbert transform (HT). Using the identified IMFs, the MVMD-based TEF is calculated and the SSO source is located. Finally, the performance of the proposed method is evaluated using the simulation data of the modified 4-machine 11-bus test system and the field measurements from the Guyuan SSO event in the North China region. The results validate the accuracy and effectiveness of the proposed method in the SSO source location.

To solve the problems of weak inertia support and poor frequency regulation capability of power system, a novel coordinated control strategy for frequency regulation of MMC-HVDC connecting offshore wind farms (OWFs) is proposed to improve system frequency stability. In terms of inertia support, based on analyzing the available energy margin of MMC-HVDC, a virtual inertia control method based on decoupling control of DC voltage and capacitor voltage is proposed, which can fully utilize the energy margin of capacitors and improve its inertia support capability. The coupling relationship between the rotor speed of wind turbines and the frequency is directly established through DC voltage, an inertia support coordinated control strategy for MMC-HVDC and OWFs is designed to realize the rational utilization of available energy. In terms of primary frequency regulation, according to the local DC voltage, a primary frequency regulation control strategy is proposed for OWFs based on the variable speed control and pitch angle control. The overall coordination is realized through the reasonable design of control links and parameters, so as to improve the frequency stability of the system. Finally, the simulation model of MMC-HVDC connecting OWFs is built to verify the validity of the proposed control strategies.

Electromechanical transient (EMT) and transient stability hybrid simulations can make full use of their fast-solving ability and high-precision computing ability to accurately simulate the dynamic characteristics of large-scale AC/DC systems. This paper selects the bus as the hybrid simulation interface bus in the AC system near the DC system, which can effectively improve the simulation accuracy of the AC/DC system interaction. At the interface bus, Norton equivalent and Thevenin equivalent are applied to the EMT simulation side and electromechanical transient simulation side, respectively. The three-phase simulation data and three-sequence component simulation data are extracted respectively, and the serial iteration method is used for hybrid simulation calculation. This paper takes Zhangbei multi terminal AC/DC system as an example, compares the hybrid simulation results with the EMT simulation results, and tries to verify the accuracy and effectiveness of the hybrid simulation method.

In this paper, a regret-based risk-averse stochastic production task and energy management (PTEM) model for industrial microgrid is proposed, which is applied to a battery manufacturing plant (BMP) microgrid. We incorporate production task scheduling with production constraints in the energy management of industrial microgrid. The general PTEM of industrial microgrids is analyzed and the production processes and energy requirements of a BMP multi-energy microgrid prosumer are presented, in which thermostatically controlled loads (TCLs) in buildings are considered. Then, the regret-based risk-averse PTEM model is formulated as a mixed-integer linear programming (MILP) problem based on stochastic programming considering uncertainties of day-ahead electricity market price and photovoltaic (PV) power output. Conditional value-at-risk (CVaR) is introduced for risk control and utilized for minimizing the expected regret. Numerical studies are carried out to validate the proposed model by comparing with risk-neutral approach and deterministic model based on real market prices from PJM electricity market. The results show that the proposed PTEM approach is effectively risk-averse. In addition, the impacts of total target production task and risk-control parameter on expected cost and regret are analyzed.