Abstract: A method for estimating a state of a combined heat and power system is provided. The method include: establishing an objective function; establishing constraints under a steady-state operating stage; converting the objective function and the constraints by utilizing a Lagrangian multiplier to obtain a Lagrange function; obtaining a steady-state estimation result of the combined heat and power system based on the Lagrange function; calculating an energy transmission delay produced by each pipe; establishing a dynamic constraint of each pipe based on the steady-state estimation result and the energy transmission delay; converting the objective function, the constraints, and the dynamic constraint by utilizing the Lagrangian multiplier to update the Lagrange function; obtaining a dynamic-state estimation result of the combined heat and power system during a dynamic-state operating stage of the combined heat and power system based on the updated Lagrange function.

Abstract: A state estimation method for a heat supply network in a steady state based on a bilateral equivalent model is provided. The method includes: establishing the bilateral equivalent model based on a mass flow rate in each supply branch of the heating network, a mass flow rate in each return branch of the heating network, a mass flow rate in each connecting branch of the heating network, a pressure and a temperature of each node in the heating network, wherein each heat source is configured as a connecting branch and each heat load is configured as a connecting branch; and repeatedly performing a state estimation on the heating network based on the bilateral equivalent model, until a coverage state estimation result is acquired.

Abstract: A method for calculating a voltage stability margin of a power system considering electric-gas system coupling is provided. The method includes: establishing constraint equations for stable and secure operation of an electric-gas coupling system; establishing a continuous energy flow model of the electric-gas coupling system using a load margin index ? based on a correlation between an electric load of the power system and a natural gas load of the natural gas system; setting inequality constraints for the stable and secure operation of the electric-gas coupling system based on the limits of pressure and gas supply amount of the natural gas system; and solving the energy flow equation established based on the constraints and the continuous energy flow model to obtain the voltage stability margin of the power system considering electric-gas system coupling.

Abstract: A state estimation method for a heat supply network in a steady state based on a bilateral equivalent model is provided. The method includes: establishing the bilateral equivalent model based on a mass flow rate in each supply branch of the heating network, a mass flow rate in each return branch of the heating network, a mass flow rate in each connecting branch of the heating network, a pressure and a temperature of each node in the heating network, wherein each heat source is configured as a connecting branch and each heat load is configured as a connecting branch; and repeatedly performing a state estimation on the heating network based on the bilateral equivalent model, until a coverage state estimation result is acquired.

Abstract: A method for estimating a state of a combined heat and power system is provided. The method include: establishing an objective function; establishing constraints under a steady-state operating stage; converting the objective function and the constraints by utilizing a Lagrangian multiplier to obtain a Lagrange function; obtaining a steady-state estimation result of the combined heat and power system based on the Lagrange function; calculating an energy transmission delay produced by each pipe; establishing a dynamic constraint of each pipe based on the steady-state estimation result and the energy transmission delay; converting the objective function, the constraints, and the dynamic constraint by utilizing the Lagrangian multiplier to update the Lagrange function; obtaining a dynamic-state estimation result of the combined heat and power system during a dynamic-state operating stage of the combined heat and power system based on the updated Lagrange function.

Abstract: A method and a device for controlling a local voltage are provided. The method includes: obtaining a first voltage value of a high-voltage side bus in a local transformer substation; determining a control strategy according to a starting threshold value for a voltage enhancement control, a starting threshold value for an under-voltage load shedding and the first voltage value of the high-voltage side bus; and performing the control strategy to control a charging power of an electric vehicle charging station corresponding to the local transformer substation, so as to control the local voltage of the local transformer substation.

Abstract: A method and a device for controlling a local voltage are provided. The method includes: obtaining a first voltage value of a high-voltage side bus in a local transformer substation; determining a control strategy according to a starting threshold value for a voltage enhancement control, a starting threshold value for an under-voltage load shedding and the first voltage value of the high-voltage side bus; and performing the control strategy to control a charging power of an electric vehicle charging station corresponding to the local transformer substation, so as to control the local voltage of the local transformer substation.

Abstract: A security and economy coordinated automatic voltage control method based on a cooperative game theory is provided. The method includes: establishing a multi-objective reactive voltage optimizing model of a power system; resolving the multi-objective reactive voltage optimizing model into an economy model and a security model; solving the economy model and the security model based on the cooperative game theory to obtain the automatic voltage control instruction; and performing an automatic voltage control for the power system according to the automatic voltage control instruction.

Abstract: A static security constrained automatic voltage control method is provided, which includes: performing a single automatic voltage control calculation for a control snapshot of a power system in each control cycle. The single automatic voltage control calculation comprises: obtaining a single-time severe contingency sequencing table and a periodical severe contingency sequencing table from a historical severe contingency information database, and selecting severe contingencies; performing a contingency assessment for the active contingency set, and iterating between a result of the contingency assessment for the active contingency set and a solution of the optimal power flow model to obtain a single automatic voltage control instruction; and performing a contingency assessment for a contingency set, and updating the single-time severe contingency sequencing table and the periodical severe contingency sequencing table according to a comprehensive result of the contingency assessment.

Abstract: A static security constrained automatic voltage control method is provided, which includes: performing a single automatic voltage control calculation for a control snapshot of a power system in each control cycle. The single automatic voltage control calculation comprises: obtaining a single-time severe contingency sequencing table and a periodical severe contingency sequencing table from a historical severe contingency information database, and selecting severe contingencies; performing a contingency assessment for the active contingency set, and iterating between a result of the contingency assessment for the active contingency set and a solution of the optimal power flow model to obtain a single automatic voltage control instruction; and performing a contingency assessment for a contingency set, and updating the single-time severe contingency sequencing table and the periodical severe contingency sequencing table according to a comprehensive result of the contingency assessment.

Abstract: A security and economy coordinated automatic voltage control method based on a cooperative game theory is provided. The method includes: establishing a multi-objective reactive voltage optimizing model of a power system; resolving the multi-objective reactive voltage optimizing model into an economy model and a security model; solving the economy model and the security model based on the cooperative game theory to obtain the automatic voltage control instruction; and performing an automatic voltage control for the power system according to the automatic voltage control instruction.