1675 results about "Voltage stability" patented technology

The present invention relates to a power system and provides a method for considering the network security constraints of in the operation of economic dispatch of power systems, which comprises the power flow constraint of branches, the static voltage stability constraint and the transient stability constraint, and provides an effective way for coordinating contradiction between the economy and security of power system operation. The security region based security-constrained economic dispatching method comprises the following steps: step 1, calculating the coefficients for the active power static security region, the cut-set voltage stability region and the dynamic security region respectively; step 2: building the models for security region based security-constrained economic dispatch; step 3: solving the unit on/off state optimal sub-problem through Social Evolutionary Programming; step 4: calculating the generation cost, the static voltage stability margin and the transient stability margin in the dispatching period; step 5: obtaining a feasible economic dispatching scheme, otherwise, return to step 3. The invention is mainly applied in load dispatching optimization.

The invention discloses a spirofluorene xanthene material and a preparation method and an application method thereof, and relates to application of the material in the fields such as organic electroluminescence, photovoltaic cell, organic electrical storage, organic nonlinear optics, chemical and biological sensing, organic laser and so on. The material has the following structure. The material has the advantages that (1) the material is prepared through a one pot process and has simple steps and mild conditions; (2) the material has the advantages of spirobifluorene materials, and shows high thermal stability and vitrification temperature; and (3) the material has high hole or electron mobility and so on. An electroluminescent device prepared by utilizing the material achieves satisfactory results in aspects such as illumination, luminous efficiency, voltage withstand stability and so on.

The invention relates to a control system of a flexible wind power DC convertor on the sea, which pertains to the technical field of power transmission in wind power generation and comprises the doubly closed loop control structure of a sending end rectifier on the sea and the doubly closed loop control structure of a receiving end inverter on the coast; the doubly closed loop control structure of the sending end rectifier on the sea is used for controlling the active power of a flexible DC transmission system and the voltage stability of a wind power AC system; the doubly closed loop control structure of the receiving end inverter on the coast is used for controlling the constant voltage of the DC side of a receiving end convertor and the dynamic regulation of the reactive power of the main network accessing end of the receiving end convertor; two control structures are mutually independent and no data communication exists between the two control structures. The control system can fast and correctly control the active power of wind power transmission on the sea as well as promote the stability of the wind power AC system on the sea and the transmission efficiency and the power quality of the whole DC transmission system.

A method of forming a CMOS structure, and the device produced therefrom, having improved threshold voltage and flatband voltage stability. The inventive method includes the steps of providing a semiconductor substrate having an nFET region and a pFET region; forming a dielectric stack atop the semiconductor substrate comprising an insulating interlayer atop a high k dielectric; removing the insulating interlayer from the nFET region without removing the insulating interlayer from the pFET region; and providing at least one gate stack in the pFET region and at least one gate stack in the nFET region. The insulating interlayer can be AlN or AlO_xN_y. The high k dielectric can be HfO₂, hafnium silicate or hafnium silicon oxynitride. The insulating interlayer can be removed from the nFET region by a wet etch including a HCl/H₂O₂ peroxide solution.

A means for improving the dynamic and voltage stability of utility transmission systems is provided by the coordinated control of windfarms. Electrical measurements of the system, which may include synchronized phasors, are supplied to one or more windfarm controllers, which in turn perform a regulation function improving the damping of electromechanical oscillations or voltage performance in the utility system. The control structure is of a decentralized nature, which maintains operation in case of communication failures. The benefits are improved damping to electromechanical oscillations and better voltage performance and ultimately increased utilization of assets, reducing the install additional network assets.

The invention discloses a dynamic power coordination control method for a battery energy storage system. The battery energy storage system comprises a plurality of power converters which supply power to a load and are connected in parallel for operation, and is characterized in that: the power converters connected in parallel for operation are divided into two types, and a master-slave control scheme is adopted, wherein one type comprises only one power converter which adopts a constant voltage constant frequency control mode and is called a master node, and the power converters of the other type adopt a constant power mode with a slight droop characteristic, and serve as slave nodes; generally, a power converter with a high capacity is selected to be the only one master node which is specified by an upper-layer monitoring system, and all the other power converters are the slave nodes; and under a stable state condition, active power and reactive power output by the power converters which serve as the slave nodes are set by a power instruction transmitted by the monitoring system, and the output power of the power converter which serves as the master node is dynamically regulated according to a load condition. The method adopting the master-slave control scheme has the advantages that: on the premise of sufficient power capacity, both the voltage stability and frequency stability of a micro-grid system are easily achieved, anti-load disturbance capability is high, and failure recovery time is short.

A power flow controller responsive to power circulation demand for optimizing power transfer is disclosed. When a power flow controller operates at its rated capacity, it can no longer regulate from-bus voltage set-points, line power flow set-points, or both. In such cases, the power flow controller switches to power circulation set-point control without exceeding the rated capacities of the voltage-sourced converters in the power flow controller. Power-voltage (PV) curves associated with voltage stability analysis for maximizing power transfer can be generated and stored for use with a power flow controller operating in automatic power flow control mode.

The invention provides a fault protection circuit for a submodule of a modular multilevel converter. When a second switch tube T2 is on, and a first switch tube T1 is off and is short circuited, a submodule controller 101 controls the second switch tube T2 to block the conduction between a pulse and a second thyristor D4, and sends an off signal to a by-pass switch at the same time. Due to the long action time of the by-pass switch K, the conduction of the second thyristor D4 can implement the rapid bypass of a fault submodule. According to the fault protection circuit and method for the submodule of the modular multilevel converter provided by the invention, when the second switch tube T2 is on, and the first switch tube T1 is short circuited, fault current can be prevented from expanding to a system effectively, so that the voltage stability at a direct current side is ensured and the requirements of the system on high reliability and safe operation are met.

The invention discloses a micro-grid system voltage stability control method based on robust control. The control structure of an intelligent micro-grid system is composed of a system control layer, a concentrated control layer and a local control layer, and energy optimization and voltage and frequency stability control of the micro-grid system are realized through multi-layer coordination control. According to the micro-grid system voltage stability control method based on robust control, a comprehensive load module of an induction motor is established, wherein dynamic loads are connected with static loads in parallel. On the premise that the constraint conditions of system performance and robust stability are met, a micro-grid voltage stability robust controller is designed by the adoption of a method of solving the problem of mixed sensitivity so as to improve the micro-grid voltage stability. The micro-grid system voltage stability control method based on robust control can be adapted to wide-range change of load parameters, has high robustness for the situations that due to the factors such as changes of running conditions, influences of external environment and frequency switching of the loads, perturbation is generated in model parameters of a micro-grid and uncertainty exists in the topologic part and the unmolded part and can better restrain parameter drift and noise interference, and meanwhile, the controller is simple in structure and easy to realize.

The invention discloses a hybrid energy-storage DC micro grid hierarchical control method. The DC micro grid comprises a photovoltaic power generation unit, a hybrid energy storage unit, a load unit, a networking interface unit and a DC bus, wherein each unit is connected with the DC bus respectively. By adopting the hierarchical control method, a system control layer and a current converter control layer are used for controlling the DC micro grid, the system control layer acquires networking operation mode parameters, DC bus voltage and a battery charge state to judge the current operation mode of the DC micro grid, a control mode of each unit of the DC micro grid is given, and a control instruction is sent to the current converter control layer. Each current converter can adjust the self control mode according to a different DC micro grid operation state, network voltage stability and power balance can be maintained effectively, and relative to master-slave control, excessive dependence on the master current converter is reduced; relative to a multi-agent control mode, communication is simpler; and relative to a voltage sag control mode, the network voltage is more stable and controllable.

Provided is a method and device for assessing and monitoring voltage security in a power system. More specifically, a method and device for assessing and monitoring the value of reactive power load when changes in reactive power outputs of at least some of the generators in the electrical power system cause all of the generators in the system to reach the combined operating limit of their reactive power output. In response thereto, the method and device are further adapted to initiate suitable control measures such as switching of transformer banks and/or capacitor/reactor banks, as well as shedding loads whenever necessary to mitigate an impending voltage stability problem.

The invention discloses a control method for increasing asymmetrical fault ride-through capability of a wind power system. In the method, a super capacitance energy storage system is assessed between a machine side rectifier and a net side inverter on the basis of the prior art. On the control aspect, besides the control for the machine side rectifier and the net side inverter, the control for a super capacitance energy storage system is additionally provided in the method. Through controlling the coordination of the machine side rectifier and the net side inverter, a unit can realize the maximum wind energy tracking, grid-connected active and reactive power adjusting and grid-connected three-phase current symmetry and the stability of the voltage for a direct-current busbar between the machine side rectifier and the net side inverter when a power grid is normal is assured. The additionally provided super capacitance energy storage system is further controlled, the voltage stability of the direct-current busbar of the unit while the power grid has asymmetrical faults is assured, especially the grid-connected three-phase current symmetry is assured and the double power frequency ripple wave of the voltage of the direct-current busbar while the power grid has asymmetrical faults is removed so that the asymmetrical fault ride-through capability of the wind power system is enhanced.

The invention provides a dynamic reactive power reserve optimization method for improving transient voltage stability of an alternating-current and direct-current power grid. The method comprises the steps of determining a key fault set and a key node set which influence the transient voltage stability of a power system, and sequentially ranking nodes; adjusting reactive power output of dynamic reactive power compensation equipment and calculating the trajectory sensitivity of the dynamic reactive power compensation equipment; ranking m dynamic reactive power compensation equipment and calculating the weight coefficients of the nodes in the dynamic reactive power compensation equipment; calculating the capacities of the dynamic reactive power compensation equipment, establishing a dynamic reactive power reserve optimization model and solving the dynamic reactive power reserve optimization model. The dynamic reactive power reserve optimization method for improving the transient voltage stability of the alternating-current and direct-current power grid provides auxiliary decision-making support for improving the transient voltage stability of the multi-direct-current-drop-point power grid, and has great importance in improving the allowance of the transient voltage stability of the large-scale alternating-current and direct-current power grid, establishing a smooth power transmission passage between a transmitting end and a receiving end, improving the transmission capacity of the alternating-current and direct-current power transmission passage and improving the operation economy and the power quality of the power grid.

A system for accurately determining real-time Available Transfer Capability and the required ancillary service of large-scale interconnected power systems in an open-access transmission environment, subject to static and dynamic security constraints of a list of credible contingencies, including line thermal limits, bus voltage limits, voltage stability (steady-state stability) constraints, and transient stability constraints.

The invention discloses a voltage detection and power failure protection device, which is used for keeping the voltage stability of a load. The device comprises a voltage detection module, a voltage stabilization circuit module, an energy storage and power supply module, a control module, a switch module and a power supply switching voltage stabilization module, wherein the switch module comprises a second switch and a third switch; a power supply is connected with one end of each of the second switch, the energy storage and power supply module and the voltage detection module; the other end of the second switch is connected with one end of the voltage stabilization circuit module; the other end of the energy storage and power supply module is connected with one end of the third switch; the other end of each of the voltage stabilization circuit module and the third switch is connected with the load by the power supply switching voltage stabilization module; and the control module is connected with the second switch, the third switch, the voltage detection module and the power supply switching voltage stabilization module. The voltage detection and power failure protection device provided by the invention can keep the power supply voltage stability of the load when the output of the power supply is instable, and may not cause voltage fluctuations of the load, thereby meeting the requirements of a user on the voltage stability of the load.

The invention provides a receiving-end network voltage stabilization overall process situation assessment and prevention and control method based on responses. The method comprises the steps of S1, obtaining various off-line simulation data or real-time measuring data; S2, constructing equivalent power transmission models of nodes according to node practical transfer power; S3, obtaining a node quiescent voltage stability margin index Vsi of equivalent power transmission model parameters of each node; S4, constructing a node reactive compensation assessment index according to the equivalent power transmission model parameters of each node; S5, setting an early warning threshold value Ncr of the node quiescent voltage stability margin index, and calculating a load shedding estimation of a weaker node when the quiescent voltage stability margin index Vsi of each node is smaller than the Ncr. According to the receiving-end network voltage stabilization overall process situation assessment and prevention and control method based on the responses, a weak node or a weak area in a current operating mode can be found out, a rapid estimation of reactive compensation levels and load shedding of each node is achieved, and the method can be widely applied to the fields of power network planning and online security monitoring.

The invention provides an electrical network operation risk assessment method of a wind electricity large-scale tripping. The method comprises the following steps of: simulation of a wind electricity large-scale tripping accident caused by a fault, a risk assessment of electrical network transient stability after disturbance, the risk assessment of system frequency stability after the disturbance, and the risk assessment of voltage stability after the disturbance. The method of the invention quantizes the risk of the wind electricity large-scale tripping from each aspect of the electrical network operation, so that the effects of preventing the wind electricity tripping and improving the electrical network safety are achieved.

The invention provides a multiterminal flexible direct current power transmission system included power grid operation control system and method. The method comprises the following steps of detecting alternating current bus voltage, alternating current bus phase angles and direct current bus voltage of various current converting terminals of a multiterminal flexible direct current power transmission system in real time; when a power grid is failed, and when the power grid is in a transient fault operation mode, performing transient stability operation control on the power grid; when the power grid is in a static fault operation mode, performing static stability operation control on the power grid; and uploading fault information and control information to a control center. According to a power voltage control decision model disclosed by the invention, a control strategy for the static security and stability operation of the multiterminal flexible direct current power transmission network included power grid is carried out, while in the transient fault operation of the power grid, a target function and a boundary condition for the transient stability operation control are established; as a control vector is solved, the corresponding current converting terminals are controlled through the calculated control vector, and thus, the voltage stability of the multiterminal direct current network and the emergency command strategy when the alternating current power grid is in the transient fault operation are effectively realized.

Based on the definition and classification of the power system stability both at home and abroad in combination with an appraisal procedure of the power system reliability, the invention provides a concept of voltage stability in case of large disturbance probability, based on the concept a reliability index of voltage stability in case of large disturbance probability is established, the reliability index can comprehensively take into account temporary and long-term voltage stability, and a comprehensive evaluation principle of probability voltage stability is formulated. Based on the reliability index and the comprehensive evaluation principle, a method for appraising voltage stability in case of large disturbance probability based on power system reliability appraisal is invented, and an applied algorithm process for the probability voltage stability appraisal established by the method can provide a quantitative appraisal result on the security feature of the system voltage stability.

The invention discloses a determination method for a partition D-STATCOM integrated optimization configuration scheme of a large-scale power grid. The method comprises the steps of first starting from a dynamic analysis method theory of a non-analytic complex power system, establishing a power system non-linear equivalent model, rapidly and accurately calculating system integration dynamic equivalence impedance and load static equivalence impedance of an a load node of a study area to obtain limit margin; enabling areas with total loads ranking at the top to be weak areas according to researched network load flow calculation analysis results, enabling dispatching partitions in the weak areas to be study objects, comparing voltage stability strength indexes of every partition to determine weak partitions so as to enable the weak partitions to serve as configuration study objects, utilizing the fact that an average value of substation impedance modulus margins of the partitions is a threshold value to determine reactive power compensation to-be-selected point sets, shrinking configuration point hunting zones, and comprehensively utilizing trace sensitivity index maximum points to determine configuration points; and finally utilizing an optimal model considering voltage dip risk cost to determine an optimal capacity.

An electric network transformer monitoring device comprises a data acquisition unit, a communication unit, a data processing unit, a control unit and a power supply unit, wherein the data acquisition unit consists of a filter circuit, a sampling circuit and a GPS timing circuit. The monitoring method provided by the invention applies unified time labels on the acquired transformer parameters through the GPS timing circuit of each electric network transformer monitoring device, transmits the monitored transformer parameters to an electric network dispatching center, judges and positions the internal faults of each transformer winding in the electric network, carries out the voltage stability analysis of the whole electric network according to the state of each transformer at the same time, reliably guarantees the safe and stable operation of local electric networks, and realizes the real-time monitoring of the wide-area electric network.