Low carbon and economic dispatch of the multi-microgrid integrated energy system using CCS-P2G integrated flexible operation method

ABSTRACT

The multi-microgrid integrated energy system offers multiple effective approaches to promote clean energy utilization as well as carbon emission reduction, etc. Combined with stepped carbon trading mechanism, it proposes a multi-microgrid (MMG) system with CCS-P2G integrated flexible operation method for optimal scheduling. Firstly, based on the microgrids’ “source-load” characteristic, electricity sharing between the source and load type microgrids can be achieved. Secondly, the CCS-P2G integrated flexible operation method is proposed, i.e. introducing HFC (Hydrogen Fuel Cell) and HES (Hydrogen Energy Storage) in P2G can enhance the utilization effect of hydrogen. Moreover, introducing carbon storage equipment in CCS, which can effectively solve the situation of unsynchronized operation times of CCS and P2G. Finally, introducing stepped carbon trading mechanism can be a further way of limiting carbon emission. Based on the above, MMG’s optimal dispatch model has established with objective of minimizing total operation cost by considering economic performance and carbon emission of the MMG system. Above optimal dispatch model is a mixed integer linear problem, which is solved using CPLEX solver. Simulation results show that electric energy interaction between source-type and load-type microgrids enhances renewable energy utilization rate. Compared to CCS-P2G cooperative operation method, the single-day carbon emissions and total operation cost of multi-microgrid system using CCS-P2G integrated flexible operation method are reduced by 37.02% and 6.80%, respectively. Meanwhile, when the stepped carbon trading mechanism was introduced, multi-microgrid system’s single-day carbon emissions is reduced to 5.40% compared to when normal carbon trading was considered, further constraining MMG’s carbon emissions.

KEYWORDS:

• Multi-microgrid integrated energy system
• CCS-P2G integrated flexible operation method
• hydrogen
• stepped carbon trading
• low-carbon economic dispatch

Nomenclature

Abbreviations	=
MG	=	Microgrid
MMG	=	Multi-microgrid
CCS	=	Carbon Capture System
P2G	=	Power to Gas
EL	=	Electrolyzer
MR	=	Methane Reactor
CHP	=	Combined Heat and Power unit
HFC	=	Hydrogen Fuel Cell
HES	=	Hydrogen Energy Storage
WT	=	Wind Turbine
PV	=	Photovoltaic
EB	=	Electric Boiler
EES	=	Electrical Energy Storage
TES	=	Thermal Energy Storage
GES	=	Gas Energy Storage
Index	=
m	=	The kind of energy storage device
i	=	The ith MG
j	=	The jth MG
Parameters and Variables	=
$F_{\mathrm{CHP},t}$	=	Gas consumption of CHP
$P_{\mathrm{CHP},t}$	=	Electrical power output by CHP
$H_{\mathrm{CHP},t}$	=	Heat power output by CHP
${\eta }_{\mathrm{C}\mathrm{H}\mathrm{P}}^{\mathrm{e}}$${\eta }_{\mathrm{C}\mathrm{H}\mathrm{P}}^{\mathrm{h}}$	=	Efficiencies of the CHP unit consuming gas for convertion to electrical and heat energy, respectively
$H_{\mathrm{C}\mathrm{H}\mathrm{P}}^{\mathrm{m}\mathrm{i}\mathrm{n}}$$H_{\mathrm{C}\mathrm{H}\mathrm{P}}^{\mathrm{m}\mathrm{a}\mathrm{x}}$	=	The minimum and maximum heat power outputs by CHP unit in respect
$\mathrm{\Delta }{H}_{\mathrm{C}\mathrm{H}\mathrm{P}}^{min}$$\mathrm{\Delta }{H}_{\mathrm{C}\mathrm{H}\mathrm{P}}^{max}$	=	The CHP unit’s lower and upper heat power creep output limits, respectively
$P_{\mathrm{EB},t}$	=	The electric consumption of EB
$H_{\mathrm{EB},t}$	=	Heat output by EB
${\lambda }_{\mathrm{EB}}$	=	Electrical energy conversion efficiency
$P_{\mathrm{E}\mathrm{B}}^{\mathrm{m}\mathrm{i}\mathrm{n}}$$P_{\mathrm{E}\mathrm{B}}^{\mathrm{m}\mathrm{a}\mathrm{x}}$	=	Minimum and maximum electrical values consumed by EB, separately
$E_{\mathit{m},\mathit{t}}$	=	Capacity in the mth storage device
$P_{\mathrm{c}\mathrm{h},m}^{max}$$P_{\mathrm{d}\mathrm{i}\mathrm{s},m}^{max}$	=	Maximum store and discharge power of mth storage device, respectively
$E_m^{min}$$E_m^{max}$	=	Minimum and maximum capacity in mth storage device in respect
${\eta }_{\mathrm{ch},m}$${\eta }_{\mathrm{dis},m}$	=	Store and discharge efficiency of mth storage device in respect
$P_{\mathrm{CCS},t}$	=	Consumed electrical input to CCS in time period t
$C_{\mathrm{CCS},t}$	=	Captured CO2 quality output of CCS in time period t
${\eta }_{\mathrm{CCS}}$	=	Electrical energy conversion efficiency of CCS
$P_{\mathrm{C}\mathrm{C}\mathrm{S}}^{\mathrm{m}\mathrm{i}\mathrm{n}}$$P_{\mathrm{C}\mathrm{C}\mathrm{S}}^{\mathrm{m}\mathrm{a}\mathrm{x}}$	=	The CCS’s minimum and maximum values of consumed electrical power, respectively
$E_{\mathit{c},\mathit{t}}$	=	Capacity of carbon storage facility
$C_{\mathrm{ch},t}$$C_{\mathrm{dis},t}$	=	CO2 flow in and out of carbon storage device in respect
$E_c^{min}$$E_c^{max}$	=	Minimum and maximum value of carbon storage facility’s capacity, separately
$C_{\mathrm{MR},t}$	=	The consumed quality of carbon feedstock by MR at time t
$P_{\mathrm{EL},t}$	=	Electric consumption of EL in time period t
$M_{\mathrm{EL},t}$	=	Hydrogen energy output of EL
${\eta }_{\mathrm{EL}}$	=	Electrical conversion efficiency of EL
$M_{\mathrm{MR},t}$	=	Hydrogen power consumed of MR
$F_{\mathrm{MR},t}$	=	Gas power exports of MR
${\eta }_{\mathrm{M}\mathrm{R}}^{\mathrm{m}}$${\eta }_{\mathrm{M}\mathrm{R}}^{\mathrm{c}}$	=	The efficiency of the conversion of consumption hydrogen and CO2 to gas, respectively
$M_{\mathrm{HFC},t}$	=	Hydrogen power input to HFC in time period t
$P_{\mathrm{HFC},t}$	=	Electric power output of HFC
$H_{\mathrm{HFC},t}$	=	Heat power output of HFC
${\eta }_{\mathrm{H}\mathrm{F}\mathrm{C}}^{\mathrm{e}}$${\eta }_{\mathrm{H}\mathrm{F}\mathrm{C}}^{\mathrm{h}}$	=	Efficiencies of converting hydrogen energy consumed by the HFC into electric and heat energy, respectively
$C_{\mathrm{quota},t}$	=	Carbon emission allowances in time period t
${\chi }_{\mathrm{CHP}}$	=	Carbon emission allowances corresponding to the per electric power exported from CHP
${\epsilon }_{\mathrm{CHP}}$	=	Carbon emissions corresponding to the unit fuel gas consumed by CHP unit
$C_{\mathrm{CHP},t}$	=	Actual carbon emissions produced from CHP operation
$C_{\mathrm{out},t}$	=	System’s net carbon emissions
$f_{\mathrm{C}{\mathrm{O}}_2}^{\mathrm{trade}}$	=	Stepped carbon trading cost
$\mathit{\lambda }$	=	Carbon trading base price
$\mathit{l}$	=	Length of the carbon emission interval
$\mathit{\alpha }$	=	Price increase level
F	=	Total operating cost of MMG
$f_{\mathrm{buy},i}$	=	Energy purchase cost
$f_{\mathrm{C}{\mathrm{O}}_2,\mathit{i}}^{\mathrm{trade}}$	=	Carbon trading cost
$f_{\mathrm{C}{\mathrm{O}}_2,\mathit{i}}^{\mathrm{fix}}$	=	Carbon sequestration benefit
$f_{\mathrm{R}\mathrm{E},i}^{\mathrm{c}\mathrm{u}\mathrm{t}}$	=	The wind and solar abandonment cost
$f_{\mathrm{mg},i}$	=	Inter-microgrid power interaction cost
$f_{\mathrm{em},i}$	=	Operation and maintenance cost
$P_{\mathrm{buy},t}$	=	Purchased electricity power
$F_{\mathrm{buy},t}$	=	Purchased gas power
${\alpha }_t$${\beta }_t$	=	Electricity and gas prices in respect
${\lambda }_{\mathrm{fix}}$	=	Carbon sequestration benefit gain per unit quality of CO2 consumed by MR
${\delta }_{\mathrm{RE}}$	=	Penalty factor of wind and solar abandonment per unit
$P_{\mathrm{R}\mathrm{E},t}^{\mathrm{c}\mathrm{u}\mathrm{t}}$	=	Sum of the wind and solar abandonment power in time period t
$r_{\mathrm{mg}}$	=	Electricity price per unit for the interaction among “source-load” microgrids
$P_{\mathrm{mg},j,t}$	=	The electrical power of MGi interacting with MGj at time t
$P_{\mathrm{RE},t}$	=	The power output in renewable energy
$P_{\mathrm{ch},t}$$P_{\mathrm{dis},t}$	=	EES store and discharge power
$P_{\mathrm{Load},t}$	=	Electrical load demand
$H_{\mathrm{ch},t}$$H_{\mathrm{dis},t}$	=	TES charge and discharge heat power
$H_{\mathrm{Load},t}$	=	Heat load demand
$F_{\mathrm{ch},t}$$F_{\mathrm{dis},t}$	=	GES charge and discharge gas power
$F_{\mathrm{Load},t}$	=	The gas load demand
$M_{\mathrm{ch},t}$$M_{\mathrm{dis},t}$	=	HES store and discharge hydrogen

Acknowledgements

This work was supported by the National Science Foundation of China (61364027) and the Natural Science Foundation of Guangxi (2019 G×NSFAA185011).

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Notes on contributors

Zhilin Lyu

The paper was a collaborative effort among authors.

Zhilin Lyu carried out the relevant theoretical research, implemented the research process, compiled and analyzed the simulation data, and wrote the paper.

Yongfa Lai

Yongfa Lai carried out the relevant theoretical research, implemented the research process, compiled and analyzed the simulation data, and wrote the paper.

Jiaqi Yi

Jiaqi Yi also participated in the analysis of the simulation data.

Quan Liu

Quan Liu also participated in the analysis of the simulation data.