Tianqi Hong

A Reconfigurable Auto-Loop Microgrid

This letter proposes a novel reconfigurable auto-loop microgrid (ALMG). The new configuration combines the advantages of auto-loops and microgrids. In addition, the ALMG offers the possibility of balancing loads for economic operation.

Dynamic Demand Response Using Customer Coupons Considering Multiple Load Aggregators to Simultaneously Achieve Efficiency and Fairness

This paper discusses the feasibility of using customer coupon demand response in meshed secondary networks. Customers are rewarded by coupons to achieve the objective of optimal operation cost during peak periods. The interdependence of the locational marginal price and the demand is modeled by an artificial neural network. The effect of multiple load aggregators participating in customer coupon demand response is also investigated. Because load aggregators satisfy different proportions of the objective, a fairness function is defined that guarantees that aggregators are rewarded in correspondence with their participation toward the objective. Energy loss is also considered in the objective as it is an essential part of the distribution system. A dynamic coupon mechanism is designed to cope with the changing nature of the demand. To validate the effectiveness of the method, simulations of the proposed method have been performed on a real heavily-meshed distribution network in this paper. The results show that customer coupon demand response significantly contributes to shaving the peak, therefore, bringing considerable economic savings and reduction of loss.

Design algorithm of a uniform magnetic field transmitter intended for the wireless charging of electric vehicles

This paper proposes to use uniform magnetic fields for wireless electric vehicle charging in order to resolve the problem of positioning the receiver (on the vehicle) over the transmitter (on the parking spot). A novel funnel-shaped coil structure is introduced to generate uniform magnetic fields, together with a design algorithm for determining the geometric parameters of the coil structure. This algorithm can be applied to the design of uniform magnetic fields of any size. Results show that magnetic fields produced by our design have fairly good uniformity; more than 71% of the coil area has a uniform field with a maximum percentage difference of the vertical component of the magnetic below 10%. The uniformity of the example is validated with finite element analysis (FEA).

An Online Data-Driven Technique for the Detection of Transformer Winding Deformations

This paper presents a novel online diagnostics method capable of detecting winding deformations in two-winding single-phase transformers. The main idea is to identify changes in the short-circuit impedance. The combination of 3-D Lissajous curve methods with a Butterworth low-pass filter allows for the accurate determination of winding deformation of large power transformers in real time. The method is very robust and capable of detecting deformations at the early stage even when the measurements are noisy. Only information already available to the differential protection relay is needed. The proposed diagnostics method has been validated with circuit and finite-element simulations plus a lab experiment. The results show that the proposed online diagnostics technique has the ability to identify winding deformation problems under severe conditions, such as nonsinusoidal input, nonlinear loading, and measurement noise. Under ideal conditions (no signal noise), the inductive identification error of the proposed online diagnostics method identifies the parameters with less than 0.09% error. When accepting a measurement noise of 1%, the error on the identification of inductance is less than 0.13%.

Supplementary damping controller of grid connected dc micro-grids based on Q-learning

In this paper, a new near optimal supplementary damping controller is proposed for grid connected dc microgrids with small power capacities using the Q-learning algorithm. A novel system discretization approach is presented to formulate the power system stability problem into a Q-learning solvable format. A numerical example is provided for illustration of the performance of the proposed supplementary damping controller.

Optimal Power Dispatch Under Load Uncertainty Using a Stochastic Approximation Method

This paper applies a known stochastic approximation method to solve a two-phase optimal power dispatch problem under load uncertainty using a novel realistic model for random loads. The stochastic power dispatch problem is solved with the Robbins-Monro method applied with the Kiefer-Wolfowitz procedure with random directions. The constraints of this optimization problem have been investigated and considered by truncated algorithms. Two numerical examples are presented for illustration of the significant improvement obtained with the proposed method. In the first example, the optimizable cost of the system can be reduced by 1.6% under 2.68% load variation. In the second example, the results show that the possibility of voltage violations is reduced from 49.5% to 0.01%. All the improvements are compared with deterministic optimal solutions validated with scenario-based Monte Carlo simulations. The method is 60 times faster than scenario-based Monte Carlo for similar accuracy for the IEEE 30-bus test system.

Benefits of a Nonsynchronous Microgrid on Dense-Load LV Secondary Networks

This paper describes the advantages of using nonsynchronous microgrids in networked systems containing densely concentrated loads. The nonsynchronous bus arrangement, in addition to allowing for the integration of substantially larger distributed generation, completely isolates transient disturbances from and to the network and the microgrid. Significant is the fact that distributed generators installed in the microgrid do not contribute to the short-circuit current that needs to be interrupted by the substation breakers. The behavior of the grid and the microgrid is investigated by comparing: the occurrence of faults, voltage reduction, and losses, in the presence and absence of the microgrid. The benefits of the dc microgrid are made evident with steady-state and transient studies performed on a real distribution network in New York City.

Optimal Dispatch of Electrical Transmission Systems Considering Interdependencies with Natural Gas Systems

This chapter presents a novel model to assess the interdependencies between electric power systems interconnected with natural gas systems. The impact from natural gas systems in the electric power system can be evaluated with the proposed model in normal operation and contingency situations. To reduce the impact of interdependencies, additional constraints to the optimal dispatch problem are formulated. The interdependency constraints can be integrated into the normal optimal power flow problem and security-constrained optimal power flow problem to improve the robustness of the electric power system. A co-simulation platform is built in MATLAB environment. We evaluate the proposed model using the IEEE 14-bus system and a corresponding natural gas transmission system. According to the simulation results, the reliability of the power system is improved when interdependency constraints are considered.

Centralized Unbalanced Dispatch of Smart Distribution DC Microgrid Systems

This paper proposes three new operation strategies such that a set of dc microgrids in distribution systems can cooperate pursuing particular objectives: 1) loss reduction; 2) full unbalance compensation; and 3) partial unbalance compensation. Loss reduction is a regular strategy for distribution utilities operating their systems efficiently by optimal dispatch of three-phase in/out powers of dc microgrids. Full and partial unbalance compensation strategies can solve single- or two-phase overloading problems of substation transformers temporarily and slow down their aging process. To validate the performance of the proposed operation strategies, several steady-state studies are performed in the IEEE 123-bus test system. According to the simulation results, the operation losses can be reduced by up to 34% with 15.2% DG penetration. The maximum single-phase loading of the substation transformer can be reduced by up to 30%.

Novel control architecture for programmable electronic AC load to achieve harmonic load profiles

A programmable power electronic load solution is usually needed for comprehensive test of generator and power supplies. An Active Programmable Electronic AC Load (APEL) based on a Voltage Source Inverter (VSI) is introduced to emulate a variety of load characteristics such as resistive, inductive, capacitive and harmonic loads. This paper focuses on the development of a novel control structure to emulate harmonic load behaviors. Resonant control method is presented to track high order harmonic components. Standard harmonic loads such as six-pulse and twelve-pulse diode rectifiers are emulated by configuring the amplitude and phase of programmable dominant odd harmonics. Experimental results have been carried out to validate the effectiveness of the proposed control structure.