Yuguang Niu

Genetic algorithm-based multi-variables nonlinear boiler model identification for 300 MW power unit

A kind of improve genetic algorithm for identifying multi-variables nonlinear boiler model of 300 MW power unit is introduced. In the algorithm, floating-point coding, rank-based selection, elitist reservation and grouping method are used, and the premature convergence is restrained, and the searching ability is improved. The genetic algorithm-based model identification MATLAB program is designed and the model parameters can be gotten with it according to the operating data log files. It is shown by simulation research that the multi-variables nonlinear model can be identified accurately no matter what kind of input signal is used.

Economic dispatch of wind-thermal power system by using aggregated output characteristics of virtual power plants

The use of renewable energy sources, such as wind power, is of major importance in future power grids for economic and environmental reasons, while the intermittent and stochastic nature of such energy brings challenges to system dispatch. Application of the virtual power plant (VPP) concept is one of the promising ways to improve utilization of renewable power. Among the many issues of practically using VPP, the aggregated output characteristics of a set of generators have not been well studied yet. In this paper, a two-phase economic dispatch model considering the aggregated VPPs is presented for wind-thermal power systems. In phase 1, outputs of VPPs consisting of several wind and thermal generators are decided by the grid operator, with characteristics of such VPPs obtained by aggregating those of individual generators. Then in phase 2, an output dispatch is performed among individual generators within each VPP by its aggregator. The model of the above two phases are both solved by using linear programming methods, and numerical tests are performed on a 3-bus system by using CPLEX. Results show that compared with conventional economic dispatch models, our model leads to substantial improvements in wind power utilization, and lower generator costs.

Economic dispatch of wind-thermal power system with MW and ramp rate dependent generator costs

Making use of the steam heat storage in thermal generators enables them to operate in a “fast mode” to ramp up or down faster than regular, so as to better catch up with the fluctuations of wind power to improve system wind utilization. In such fast mode, generators have MW-dependent ramp rates and, distinguished from regular units, MW and ramp rate dependent coal consumption costs. Existing economic dispatch models usually use MW-dependent generator cost functions and constant ramp rate limits, and are thus not applicable to systems containing fast mode generators. This paper presents a new formulation of dynamic economic dispatch for wind-thermal power systems, to take into account ramping capabilities and costs of generators in their fast mode. In our model, the objective is to minimize a two-variable quadratic generator cost function depending on both output levels and ramp rates, and generator ramp rate limits are MW-dependent piece-wise linear functions. The formulation can be solved by using existing quadratic programming methods. In numerical examples implemented by using CPLEX, our model is demonstrated on the IEEE 30-bus system containing two 600MW thermal units with real data. Results show that by using our model, unit ramping capabilities are better utilized in system dispatch to substantially save curtailed wind energy, and total generator costs are reduced.

Dispatch of wind-thermal power system containing heat storage units with fast ramping capabilities

Wind energy is beneficial both economically and environmentally, while its utilization levels are still far from satisfactory and has plenty of room to be improved. One way to achieve this is to make use of the heat storage in some of the thermal generators to obtain fast ramping capabilities, so that they can catch up with the fluctuating and intermittent wind energy. Output characteristics of such thermal units are distinguished from conventional ones in that their ramping rates are dynamic and with memory, thus new models of system dispatch need to be established. In this paper, we present a mixed integer linear formulation with decisions of thermal unit heat usage for the dispatch of wind-thermal power systems containing heat storage units, and network security constraints of power balance and transmission limits are considered. Numerical tests are performed for a 3-bus system and the IEEE 30-bus system by using CPLEX, and results show that additional ramping capabilities from heat storage units lead to substantial improvements in wind power utilization.

Sensitivity analysis of system wind penetration to thermal generation ramp rates

Operating thermal generators flexibly enables them to achieve higher ramping up or down rates than usual. In this way, thermal generation can better follow the fluctuations of wind power, and the allowable penetration level of wind energy can thus be increased in the grid. In this paper, we analyze the sensitivity of allowable system wind penetration level to thermal generation ramp rates in an economic dispatch problem formulated as a linear programming. By using the “100% rule,” it is theoretically shown that the allowable wind power levels in the system are subject to an analytical joint constraint coupling all decision periods. Numerical tests on an IEEE 30-bus system are performed to demonstrate the theoretical results.

Dispatch of wind-thermal power system by using aggregated outputs of virtual power plants

Usage of renewable energy sources, such as wind power, is of major importance in future power grids for economic and environmental reasons, while the intermittent and stochastic nature of such energy brings challenges to system dispatch. Application of the virtual power plant (VPP) concept is one of the most promising ways to better accommodate and utilize renewable power in the grid. Among the many issues of applying VPPs in practice, the aggregated output characteristics of a VPP containing several wind and thermal generators have not been well studied yet. In this paper, a two-phase economic dispatch model considering the aggregated outputs of VPPs is presented for wind-thermal power systems. In phase 1, outputs of VPPs are decided by the grid operator, with characteristics of such VPPs obtained by aggregating those of individual generators. Then in phase 2, a local dispatch among individual generators within each VPPis performed by its aggregator. Both of the above two phase shave linear programming formulations, and numerical tests are performed on an illustrative 3-bus system. Results show that compared with conventional economic dispatch models, our model leads to substantial improvements in wind power utilization and lower generator costs.