Resilience-oriented Transmission Expansion Planning with Optimal Transmission Switching Under Typhoon Weather

This paper presents resilience-oriented transmission expansion planning(RTEP)with optimal transmission switching(OTS)model under typhoon weather.The proposed model carefully considers the uncertainty of component vulnerability by constructing a typhoon-related box uncertainty set where component failure rate varies within a range closely related with typhoon intensity.Accordingly,a min-max-min model is developed to enhance transmission network resilience,where the upper level minimizes transmission lines investment,the middle level searches for the probability distribution of failure status leading to max worst-case expected load-shedding(WCEL)under typhoon,and the lower level optimizes WCEL by economic dispatch(ED)and OTS.A nested decomposition algorithm based on benders decomposition is developed to solve the model.Case studies of modified IEEE 30-bus and 261-bus system of a Chinese region illustrate that:a)the proposed RTEP method can enhance resilience of transmission network with less investment than widely used RTEP method based on attacker and defender(DAD)model,b)the influence of OTS on RTEP is closely related with contingency severity and system scale and c)the RTEP model can be efficiently solved even in a large-scale system.

Resilience-oriented Hardening and Expansion Planning of Transmission System Under Hurricane Impact

In this paper,we propose a two-stage transmission hardening and planning(TH&P)model that can meet the load growth demand of normal scenarios and the resilience requirements of hurricane-induced damage scenarios.To better measure the resilience requirements,the proposed TH&P model includes two resilience assessment indexes,namely,the load shedding(LS)under the damage scenario and the average connectivity degree(ACD)at different stages.The first-stage model,which aims to meet the load growth demand while minimizing the LS,is formulated as a mixed-integer linear program(MILP)to minimize the total planning and hardening cost of transmission lines,the operating cost of generators,and the penalty cost of wind power and load shedding in both normal and damage scenarios.The second-stage model aims to further improve the ACD when the ACD of the scheme obtained from the first-stage model cannot reach the target.Specifically,the contribution of each transmission line to the ACD is calculated,and the next hardened line is determined to increase the ACD.This process is repeated until the ACD meets the requirements.Case studies of the modified IEEE RTS-24 and two-area IEEE reliability test system-1996 indicate the proposed TH&P model can meet the requirements for both normal and damage scenarios.

Frequency-constrained Co-planning of Generation and Energy Storage with High-penetration Renewable Energy

Large-scale renewable energy integration decreases the system inertia and restricts frequency regulation. To maintain the frequency stability, allocating adequate frequency-support sources poses a critical challenge to planners. In this context, we propose a frequency-constrained coordination planning model of thermal units, wind farms, and battery energy storage systems (BESSs) to provide satisfactory frequency supports. Firstly, a modified multi-machine system frequency response (MSFR) model that accounts for the dynamic responses from both synchronous generators and grid-connected inverters is constructed with preset power-headroom. Secondly, the rate-of-change-of-frequency (ROCOF) and frequency response power are deduced to construct frequency constraints. A data-driven piecewise linearization (DDPWL) method based on hyperplane fitting and data classification is applied to linearize the highly nonlinear frequency response power. Thirdly, frequency constraints are inserted into our planning model, while the unit commitment based on the coordinated operation of the thermal-hydro-wind-BESS hybrid system is implemented. At last, the proposed model is applied to the IEEE RTS-79 test system. The results demonstrate the effectiveness of our co-planning model to keep the frequency stability.

Demand Response Based and Wind Farm Integrated Economic Dispatch

Increased penetration of intermittent renewable energy resources is pushing the grid to prepare more reserves to meet the supply and demand balance.Demand response(DR)is an efficient strategy to reduce the overall load at peak times.In order to fully utilize the application of DR and make DR capable of actively supporting grid operations at all times,this paper builds a DR and wind farm integrated economic dispatch model.The objective is to minimize the total operation costs,such as fuel cost,startup cost,greenhouse gas(GHG)emission costs,and DR cost.DR maximum participating time and DR ramp rate constraints are considered.A system with 10 traditional units,one large-scale wind farm,three types of DR,including interruptible load,direct load control,and load as capacity resource are selected to verify the proposed model.Four DR penetration rates are analyzed:0%,10%,20%and 30%.The results indicate that DR penetration can decrease total operation costs.The lower price DR resource gets the priority to be committed.The DR and wind farm integration is indispensable in the future economic dispatch.

Reliability Evaluation of Electricity-heat Integrated Energy System with Heat Pump

Integrated energy system(IES)has the advantages of improving the efficiency of energy utilization and promoting the consumption of renewable energy.It is of great importance to evaluate the reliability of an IES.This paper proposes a novel reliability evaluation method for the electricity-heat IES with heat pump.First,the load-point reliability indices and systemlevel reliability indices are defined according to the characteristics of electricity-heat IES.Second,the model of maximum output heat power of heat pump at the user-side considering the safety criterion of distribution network is established,and the stepvaried repeated power flow method is applied to solve the model.Third,the reliability evaluation procedure of electricityheat IES with heat pump based on the Monte Carlo simulation is presented.Case studies are carried out on the electricityheat IES of an industrial park,and the results show that the configuration site,capacity and coefficient of performance of heat pump as well as the security constraints of distribution network can significantly affect the reliability indices.

A contingency-aware method for N-2 security-constrained transmission expansion planning

In this paper,a novel contingency-aware method for N-2 security-constrained transmission expansion planning is proposed.To ensure that the transmission construction plan satisfies the N-2 security criterion,the proposed method takes advantage of the adjustable robust optimization(ARO)framework and upgrades it.We construct a discrete uncertainty set in which component failures are treated as uncertain events that are handled as binary variables.In addition to the failure of existing lines and generators,we explicitly model the failure of candidate lines.The proposed model comprises a master problem that makes the transmission construction decision,and a series of subproblems that can detect not only the worst contingency,but also the potential contingencies.Computational studies on the IEEE RTS 24-bus and IEEE 118-bus test systems are carried out to validate the effectiveness of the proposed method.Compared with the deterministic method and ARO method in the literature,the proposed method has higher computational efficiency.

Optimal Siting and Sizing of Distributed Renewable Energy in an Active Distribution Network

The distributed generation (DG) plays an important role in the context of the environmental problems and sustain- able development throughout the world. This paper proposes a DG siting and sizing model in an active distribution network (ADN). The objective is to minimize the total cost, including investment, operation and maintenance costs. The proposed model is transferred to a Mixed Integer Second-Order Cone Programming (MISOCP) model based on a distribution network forward backward-sweep power flow and constraint relaxation. The CVX platform and GUROBI solver are used for the solution. The scenario analysis is used for the uncertainties of load and DG. Different numbers of operational scenarios are considered in order to analyze the effect of a non-network solution to the final planning result and total investment. The planning results with and without consideration of active managements, and the planning results with and without taking environmental profits into consideration, are compared and analyzed. The proposed methodology is verified with a modified IEEE 33 example.

Dynamic VAR planning methodology to enhance transient voltage stability for failure recovery

In recent years, failure recovery after faults is concerned and discussed worldwide as an important and hot topic. Facing the challenge of heavy loads and ultrahigh voltage transmission, it's urgent to propose some solutions to enhance transient voltage stability for failure recovery. Therefore, a novel dynamic volt ampere reactive(VAR) planning methodology is proposed in this paper to help failure recovery and improve transient voltage stability after contingencies. First, a transient voltage fluctuation(TVF) index is proposed to evaluate transient voltage condition after faults. Then dynamic compensationsensitivity is presented for searching the best candidate locations. Following that, the dynamic VAR planning methodology based on an improved Tent chaos multi-objective algorithm is discussed in detail. There are two optimization objects in the optimization. One is to minimize TVF to enhance transient voltage stability for failure recovery. And the other optimization is to minimize dynamic VAR investment cost and operation cost. Finally,IEEE 39 power system and a practical power system are analyzed and discussed. The proposed dynamic VAR planning methodology can support enough reactive power for failure recovery. With the least SVC planning amount and the power loss cost, it can greatly decrease the system TVF index and enhance the transient voltage stability. It's proved that the proposed dynamic VAR planning optimization is effective and helpful for safety operation of power system.

Accommodating Uncertain Wind Power Investment and Coal-fired Unit Retirement by Robust Energy Storage System Planning

Increasing wind power integration and coal-fired unit retirements increases the strain on the power system’s spinning reserve and increases the pressure on peak regulation.With the ability to stock extra power generation and supply the peak load,the energy storage system(ESS)can alleviate the rising demand on the spinning reserve and play an increasingly important role in the power system.In this paper,a trilevel robust ESS planning model is proposed to accommodate uncertain wind power investment as well as coal-fired unit retirement.The upper-level of this model is to determine the planning scheme of ESSs,which iteratively takes the worst-case scenario of wind power investment and coal-fired unit retirement into consideration.The middle-level and lower-level of this model are to make the optimal daily economic dispatch under the worst-case realizations of uncertainties.We derive an equivalent reformulation of the proposed robust ESS planning model and solve it with a dual column-and-constraint generation algorithm.Case studies are conducted using the IEEE RTS-79 system.The results demonstrate the superiority of the proposed planning method in comparison with other methods.Furthermore,the effects of the capital cost of ESS,the expected proportion of wind power,and the uncertainty budget on the development of ESS are studied.Taking the uncertainties of unit retirement and wind power investment into consideration achieves a better trade-off between the ESS investment cost and the operational cost.

An Extended DC Power Flow Model Considering Voltage Magnitude

A quasi-linear relationship between voltage angles and voltage magnitudes in power flow calculation is presented.An accurate estimation of voltage magnitudes can be provided by the quasi-linear relationship when voltage angles are derived by classical DC power flow.Based on the quasi-linear relationship,a novel extended DC power flow(EDCPF)model is proposed considering voltage magnitudes.It is simple,reliable and accurate for both distribution network and transmission network in normal system operation states.The accuracy of EDCPF model is verified through a series of standard test systems.