Adjustable robust low-carbon dispatch for interconnected power systems in Northeast Asian countries

Interconnected power systems that link several countries and fully utilize their individual resources in a complementary manner are becoming increasingly important. As these systems enhance accommodation of renewable energy, they also represent a move toward low-carbon and low-emission power systems. In this paper, a low-carbon dispatch model is proposed to coordinate the generation output between several countries where the carbon emission constraint is a priority. An adjustable robust optimization approach is used to find the optimal solution under the worst-case scenario to address the uncertainties associated with renewable energy resources. A specific constraint is that the area control error for each country should be self-balanced. Furthermore, a reformation using participation factors is presented to simplify the proposed robust dispatch model. Simulation results for practical interconnected power systems in northeast Asian countries verify the effectiveness of the proposed model.     

Optimal dispatch strategy in remote hybrid power systems

For small villages in developing countries, local stand-alone power systems are often more cost-effective than utility grid extension. Various combinations of wind turbine generators, photovoltaic arrays, diesel gensets, and batteries—remote hybrid power systems—may be preferred to diesel-only systems. Dispatch strategy is the aspect of control strategy that pertains to energy flows among components. In systems with both batteries and diesel genset(s), dispatch affects the life-cycle cost through both the fuel usage and the battery life. In this study, dispatch strategies are compared using (1) an analysis of cost trade-offs, (2) a simple, quasi-steady-state time-series model, and finally (3) HYBRID2, a more sophisticated stochastic time-series model. An idealized predictive dispatch strategy, based on assumed perfect knowledge of future load and wind conditions, is developed and used as a benchmark in evaluating simple, non-predictive strategies. The results illustrate the nature of the optimal strategy and indicate that one of two simple diesel dispatch strategies—either load-following or full power for a minimum run time—can, in conjunction with the frugal use of stored energy (the Frugal Discharge Strategy), be virtually as cost-effective as the Ideal Predictive Strategy. The optimal choice of these two simple charging strategies is correlated to three dimensionless parameters, yielding a generalized dispatch design chart for an important class of systems.     

含电动汽车的气电互联虚拟电厂区间多目标优化调度策略

气电互联虚拟电厂能够推动分布式能源的高效利用,考虑诸多不确定因素的有效调度策略是保证其运行品质的关键.本文在构建含电动汽车的气电互联虚拟电厂风电、光伏、燃气轮机、电转气设备、电动汽车各单元模型的基础上,采用区间优化理论描述了该虚拟电厂中风电、光伏出力及电负荷、气负荷的不确定性;以运行经济效益、用户舒适度、二氧化碳排放作...     

一种适用于微电网的新型风电调度策略

微电网对风电功率波动较为敏感,适当的调度策略有助于微电网充分接纳风能。文章提出了一种适用于微电网的新型风电调度策略:通过模拟退火算法初步算出每一"时间窗口"的输出功率参考值,随后考虑输出容量可信度对曲线进行一定的修正,同时根据历史数据引入奖罚制度对曲线进行优化。采用该调度策略,有助于减少不可精确预测的风电波动对微电网的影响,提高风电的容量可信度,减少弃风。     

Optimization strategy for element sizing in hybrid power systems

This paper presents a procedure to evaluate the optimal element sizing of hybrid power systems. In order to generalize the problem, this work exploits the “energy hub” formulation previously presented in the literature, defining an energy hub as an interface among energy producers, consumers and the transportation infrastructure. The resulting optimization minimizes an objective function which is based on costs and efficiencies of the system elements, while taking into account the hub model, energy and power constraints and estimated operational conditions, such as energy prices, input power flow availability and output energy demand. The resulting optimal architecture also constitutes a framework for further real-time control designs.Moreover, an example of a hybrid storage system is considered. In particular, the architecture of a hybrid plant incorporating a wind generator, batteries and intermediate hydrogen storage is optimized, based on real wind data and averaged residential demands, also taking into account possible estimation errors. The hydrogen system integrates an electrolyzer, a fuel cell stack and hydrogen tanks. The resulting optimal cost of such hybrid power plant is compared with the equivalent hydrogen-only and battery-only systems, showing improvements in investment costs of almost 30% in the worst case.     

An optimum load management strategy for stand-alone photovoltaic power systems

The subject of load management for stand-alone photovoltaic (SAPV) power systems is addressed. The objective is to minimize the total life-cycle cost of the system while, at the same time, the battery is protected and the load priorities are observed. The first step in this approach involves a general load classification. The idea is to manipulate the controllable loads in order to reduce battery size. For this reason, optimum curves are obtained for the controllable loads. Then an optimum load management strategy is mathematically formulated. Finally, a tracking algorithm has been devised in order to implement the optimum load management scheme. The previously described method yields cost optimum SAPV systems. An illustrative example using data similar to the first village PV power system of Schuchuli, Arizona shows the practical application of the proposed optimum load management strategy.     

An effortless hybrid method to solve economic load dispatch problem in power systems

This paper proposes a new approach and coding scheme for solving economic dispatch problems (ED) in power systems through an effortless hybrid method (EHM). This novel coding scheme can effectively prevent futile searching and also prevents obtaining infeasible solutions through the application of stochastic search methods, consequently dramatically improves search efficiency and solution quality. The dominant constraint of an economic dispatch problem is power balance. The operational constraints, such as generation limitations, ramp rate limits, prohibited operating zones (POZ), network loss are considered for practical operation. Firstly, in the EHM procedure, the output of generator is obtained with a lambda iteration method and without considering POZ and later in a genetic based algorithm this constraint is satisfied. To demonstrate its efficiency, feasibility and fastness, the EHM algorithm was applied to solve constrained ED problems of power systems with 6 and 15 units. The simulation results obtained from the EHM were compared to those achieved from previous literature in terms of solution quality and computational efficiency. Results reveal that the superiority of this method in both aspects of financial and CPU time.     

Environmental/economic power dispatch with wind power

Economic environmental dispatch (EED) is a significant optimization problem in electric power system. With more wide spread use of wind power, it is necessary to include wind energy conversion system (WECS) in the EED problem. This paper presents a model to solve the EED problem incorporating wind power. In addition to the classic EED factors, the factors accounting for overestimation and underestimation of available wind power in both economic and environmental aspects are also considered. In order to obtain some quantitative results, the uncertain characteristic of available wind power and the performance of WECS are determined on the basis of the statistical characteristic of wind speed. The optimization problem is numerically solved by a scenario involving two conventional generators and two wind-powered generators. The results demonstrate that the allocation of system generation capacity may be influenced by multipliers related to the cost for overestimation and underestimation of available wind power, and by the multiplier related to the emissions for underestimation of available wind power. Nevertheless, the multiplier related to the emissions for overestimation of available wind power has little impact on the allocation. Taking account of economic factors, environmental factors and impacts of wind power penetration, the proposed EED model is beneficial to finding the right balance between radical and conservative strategy for wind power development.     

Dispatch strategy and model for hybrid photovoltaic and trigeneration power systems

The advent of small scale combined heat and power (CHP) systems has provided the opportunity for in-house power backup of residential-scale photovoltaic (PV) arrays. These hybrid systems enjoy a symbiotic relationship between components, but have large thermal energy wastes when operated to provide 100% of the electric load. In a novel hybrid system is proposed here of PV-trigeneration. In order to reduce waste from excess heat, an absorption chiller has been proposed to utilize the CHP-produced thermal energy for cooling of PV-CHP system. This complexity has brought forth entirely new levels of system dynamics and interaction that require numerical simulation in order to optimize system design. This paper introduces a dispatch strategy for such a system that accounts for electric, domestic hot water, space heating, and space cooling load categories. The dispatch strategy was simulated for a typical home in Vancouver and the results indicate an improvement in performance of over 50% available when a PV-CHP system also accounts for cooling. The dispatch strategy and simulation are to be used as a foundation for an optimization algorithm of such systems.     

Evolution of China’s power dispatch principle and the new energy saving power dispatch policy

With social economic reform in the past decades, the power industry of China is gradually evolving from a highly integrated one toward an electricity market, which can be characterized based on the transition of the power dispatch principle. To attract investment in the power generating industry, China introduced non-state-owned power plants to the original system of a highly vertically integrated power industry with annual power generation quota guarantees, which makes the traditional economic dispatch principle not applicable. The newly debuted energy saving power dispatch (ESPD) is an attempt to fully exploit the maximum energy savings and was implemented by an administrative code. Starting in August 2007, the pilot operation of the ESPD was implemented in five provinces, but after two years, it is still not widely applied all over the country. This paper details the transition of China’s power dispatch principle with particular attention to its origin and content. Moreover, the factors that influence the ESPD’s actual energy saving effect are discussed, as well as the sustainability of the policy.     

规模化电池储能系统的无功功率控制策略研究

无功功率补偿是电池储能系统并网运行时的重要应用。电池储能系统主要包括电池组、变流器以及设备监控系统等。电池储能用变流器可向电网提供无功功率。文章提出了规模化电池储能电站中各储能机组间的无功功率分配方法。采用仿真软件对电池储能系统的无功功率分配策略进行仿真分析,并基于张北储能试验基地的电池储能机组实例验证了控制策略的有效性。     

Emission operational strategy for combined cooling,heating, and power systems

Integrated Energy Systems (IES), as technology that use thermal activated components to recover waste heat, are energy systems that offer key solution to global warming and energy security through high overall energy efficiency and better fuel use. Combined Cooling, Heating, and Power (CCHP) Systems are IES that use recovered thermal energy from the prime mover to produce heating and cooling for the building. The CCHP operational strategy is critical and it has to be considered in a well designed system since it defines the ultimate goal for the benefits expected from the system. One of the most common operational strategies is the cost-oriented strategy, which allows the system to operate at the lowest cost. A primary energy strategy (PES) optimizes energy consumption instead of cost. However, as a result of the worldwide concern about global warming, projects that target reduction of greenhouse gas (GHG) emissions have gained a lot of interest. Therefore, for a CCHP system, an emission strategy (ES) would be an operational strategy oriented to minimize emission of pollutants. In this study, the use of an ES is proposed for CCHP systems targeted to reduce emission of pollutants. The primary energy consumption (PEC) reduction and carbon dioxide (CO₂) emission reduction obtained using the proposed ES are compared with results obtained from the use of a PES. Results show that lower emission of CO₂ is achieved with the ES when compared with the PES, which prove the advantage of the ES for the design of CCHP systems targeted to emissions reduction.     

考虑相关性的含风电电力系统日前灵活性调度方法

含风电电力系统的传统调度侧重于时段内功率平衡,而忽略了相邻调度时段间的功率波动,因此造成大量弃风,文章针对该问题提出了灵活性调度方法。首先,将风电场依据相关性分组,采用通用生成函数方法建立由风源风速预测信息到每组风电场总出力的爬坡状态概率分布,结合由预测序列建立的负荷爬坡概率分布得到系统净负荷爬坡概率,引入风险价值理论得到系统上下灵活性需求;其次,根据所建立的常规机组和抽水蓄能电站灵活性调节模型,以运行成本与灵活性服务费用之和最小为目标,考虑灵活性需求约束与网络安全约束,提出了一种含风电电力系统灵活性优化调度模型;最后,通过改造的IEEE-118测试系统验证了文章所提出方法的正确性与有效性。     

Output power dispatch control for a wind farm in a small power system

Nowadays, a wind turbine generator (WTG) is required to provide control capabilities as the output power of WTG fluctuates. Under this scenario, this paper proposes an output power control method of a wind farm (WF) connected to a small power system using pitch angle control. In this control approach, the WF output power control is achieved by two control levels: central and local. In the central control, the WF output power command is determined by considering the frequency deviations and wind speeds using a fuzzy function. Then, the local output power commands for each of the WTGs are based on the proposed dispatch control. In the proposed dispatch control, the output commands of each WTG are determined by considering wind conditions for each of the WTGs. The simulation results by using an actual detailed model for the wind power system show the effectiveness of the proposed method. Copyright © 2010 John Wiley & Sons, Ltd.     

Reliability and sensitivity analysis of loop-designed security and stability control system in interconnected power systems

Security and stability control system (SSCS) in power systems involves collecting information and sending the decision from/to control stations at different layers; the tree structure of the SSCS requires more levels. Failure of a station or channel can cause all the execution stations (EXs) to be out of control. The randomness of the controllable capacity of the EXs increases the difficulty of the reliability evaluation of the SSCS. In this study, the loop designed SSCS and reliability analysis are examined for the interconnected systems. The uncertainty analysis of the controllable capacity based on the evidence theory for the SSCS is proposed. The bidirectional and loop channels are introduced to reduce the layers and stations of the existing SSCS with tree configuration. The reliability evaluation and sensitivity analysis are proposed to quantify the controllability and vulnerable components for the SSCS in different configurations. By aiming at the randomness of the controllable capacity of the EXs, the uncertainty analysis of the controllable capacity of the SSCS based on the evidence theory is proposed to quantify the probability of the SSCS for balancing the active power deficiency of the grid.     

A market‐oriented wind power dispatch strategy using adaptive price thresholds and battery energy storage

In this paper, an adaptive dispatch strategy is presented to maximize the revenue for grid‐tied wind power plant coupled with a battery energy storage system (BESS). The proposed idea is mainly based on time‐varying market‐price thresholds, which are varied according to the proposed algorithm in an adaptive manner. The variable nature of wind power and market price signals leads to the idea of storing energy at low price periods and consequently selling it at high prices. In fact, the wind farm operators can take advantage of the price variability to earn additional income and to maximize the operational profit based on the choice of best price thresholds at each instant of time. This research study proposes an efficient strategy for intermittent power dispatch along with the optimal operation of a BESS in the presence of physical limits and constraints. The strategy is tested and validated with different BESSs, and the percentage improvement of income is calculated. The simulation results, based on actual wind farm and market‐price data, depict the proficiency of the proposed methodology over standard linear programming methods.     

Developing a global interconnected power system model

Decarbonizing the power sector is a necessary step towards a low-carbon future. Interconnecting power systems on different continents could be a method to contribute to such a future, by utilizing highly efficient renewable resources around the globe, while simultaneously providing additional benefits of power system integration. In this paper, we describe the process of constructing and simulating a global interconnected power system model with high technical and temporal resolution. Being the first of its kind on the global scale, this paper is designed to showcase the proof of concept as an intermediate step to a high resolution global model, by integrating an existing European power system model with the North-American continent. The work to date has been focused on testing the methodology and building up necessary knowledge to realistically simulate the functionality of a possible future global grid. Some initial results are analysed to support the viability of the model and the concept in general. Furthermore, key factors influencing the development and optimal performance of the global interconnected power system model are identified.     

电动汽车与风电协同入网的双层优化策略

文章提出了一种电动汽车(EV)与风电协同入网的双层优化模型.该模型上层以电动汽车与风电协同入网时负荷方差与充电站运营商购电成本最小为目标,得到电动汽车与风电联合的负荷指导曲线.模型下层以电动汽车和风电实际等效负荷与负荷指导曲线偏差最小为目标,进行实时负荷跟随.为保证电动汽车进行有序的充放电,提出了用户综合评价系数和放电...     

基于PSASP和Power Factory的分解协调式输配一体化潮流计算

大量分布式电源的并网改变了配电网单向潮流特性,输电网和配电网之间的耦合更加紧密,电力系统呈现出主配网一体化的特点。文章提出了基于分解协调的主配一体化潮流计算方法,分别采用PSASP和Power Factory进行输电网和配电网的计算,设计了主网和配网潮流的边界协调方程,并采用Jacobian-Free Newton-GMRES(m)方法进行求解。测试结果表明,文章所提方法收敛性较好,计算精度高。