166results about How to "Improve transient stability" patented technology

The invention discloses an electromagnetic transient mathematical model of a distributed power-flow controller based on an MMC, control system and a modeling method. The distributed power-flow controller comprises a parallel connection side converter composed of a three-phase converter based on the MMC at the parallel connection side and a parallel connection side single-phase converter and a series connection side converter composed of multiple sets of series connection side single-phase converter; the electromagnetic transient mathematical model mainly comprises a parallel connection side converter model and a series connection side converter model; the control system comprises a parallel connection side control model and a series connection side control model, the parallel connection side control model comprises a three-phase converter control module based on the MMC at the parallel connection side and a parallel connection side single-phase converter module, and the series connection side control model comprises a series connection side third harmonic control module and a series connection converter active power reactive power control module. The electromagnetic transient mathematical model is designed by adopting modularization, the sub module switch-on and switch-off frequency is lowered, and the loss is lowered; the control system adapts to different voltage grades, and is applicable to flexible alternating current transmission occasions.

A ride-through and recovery method for DC short circuit faults of a hybrid modular multilevel converter based high-voltage direct current transmission (MMC-HVDC) system, the hybrid MMC including multiple full-bridge sub-modules and half-bridge sub-modules, and the method including: 1) detecting whether a DC short circuit fault occurs, and proceeding to step (2) if yes and continuing detecting if no; 2) realizing ride-through of the DC short circuit fault; 3) detecting whether a DC residual voltage increases, and proceeding to step (4) if yes and continuing detecting if no; and 4) realizing DC short circuit fault recovery.

The present invention discloses a reactive compensation coordination control method during the DC emergency power support process and belongs to the technical field of power systems and automation. According to the technical scheme of the invention, according to a current running state and a to-be-lifted DC power, a reactive power, required to be consumed additionally for the DC system after the active power thereof is boosted, is estimated. Before the DC boosting process, filters or parallel capacitors of a corresponding number are put to use in the emergency manner. After the DC boosting process, reactive-load compensation equipment is put to use additionally according to the actual control manner of a convertor station. Meanwhile, the AC bus voltage of the convertor station is monitored. As a result, the condition that the AC voltage of the convertor station is out of limit due to the usage of the reactive-load compensation equipment can be avoided. The method can effectively improve the amount of the actual emergency power support in the DC large modulation mode. Meanwhile, the power imbalance problem of the power grid of a receiving end can be effectively relieved, and the safety and the stability of the power grid are improved.

The invention discloses an integrated frequency and damping control method for a double-fed wind power generation unit. When the double-fed wind power generation unit normally operates, a maximum power tracking control policy is adopted; when system frequency is changed, a quick active control instruction is provided for participation in system frequency modulation of the wind power generation unit through a frequency controller, and the inertial frequency response of the wind power generation unit is simulated. The proportional differential control in the conventional frequency control of the wind power generation unit is improved into the proportional differential control with first-order inertia, so that the frequency control of the wind power generation unit is always shown as positive damping characteristics, the wind power generation unit have a frequency modulation control function and a system power oscillation suppression control function, and a foundation is laid for the wide application of the controller. After the frequency of a power grid is changed, the electromagnetic power of the wind power generation unit is quickly regulated by frequency control to participate in frequency modulation of the power grid; if a system is subjected to inter-area low-frequency oscillation, the wind power generation unit can suppress the power oscillation of the system under the control policy.

The invention discloses a hybrid pseudo-bipolar direct-current transmission method for supplying power to a passive network and a weak alternating-current network. The method is characterized in that two six-pulse current source converters are adopted in the rectification side, a six-pulse voltage source converter is adopted in the inversion side, and then a pseudo-bipolar direct-current transmission system is established. A constant-current control mode is adopted in the rectification side, a constant-alternating-current voltage-direct-current voltage control mode is adopted in the inversion side, stable power transmission is achieved, the voltage stability of a receiving system is guaranteed as well, and therefore it is made possible that the power is supplied to the passive network and the weak alternating-current network through the novel direct-current transmission system. Compared with a flexible direct-current transmission method, power transmission cost is reduced; compared with a traditional direct-current transmission method, the power can be supplied to the passive network; the novel direct current-transmission system has high transient stability.

The invention discloses a transient stability control method for a microgrid with multiple virtual synchronizers, and belongs to the technical field of microgrid transient stability analysis and control. According to the method, the virtual inertia, the virtual damping, the virtual governor sag coefficient and the reactive power control loop sag coefficient are fully considered, an energy functionmodel of the microgrid with multiple virtual synchronizers operating in parallel is constructed and the stability of the system is analyzed and judged based on the energy function. Besides, an adaptive control method based on the energy function is applied to perform adaptive real-time adjustment on the virtual inertia, the virtual damping, the virtual governor sag coefficient and the reactive power control loop sag coefficient in VSG so as to reduce the system energy after the system failure, increase the attraction region of the system, slow down the process of the system energy reaching the critical energy, obtain the effective time for the failure removal and improve the transient stability of the system.

The invention discloses an enhanced droop control method capable of improving the transient stability of an inverter. A method of introducing a non-directional axis voltage component intro droop control as the feedback quantity is adopted; the virtual power-angle characteristic of the inverter is changed; the inverter reaches balance in a current saturation transient process; voltage orientation can also be achieved when the current is saturated, so that the transient stability of the inverter is ensured; and the inverter is prevented from entering a current source mode to lose the stability. The method prevents the inverter from entering a current source instability mode; the method does not change the power sharing characteristic of droop control; and the control method can be applied to other inverters, such as a virtual synchronous machine, employing double-loop control, can also be further popularized and applied to large disturbance scenes of a multi-machine passive isolated network, high-load switching of the isolated network and the like, and improves the transient stability of a system.

The invention discloses a double-fed fan crowbar adaptive cut-out control method for preventing repeated switching of a crowbar. The method comprises the following steps of: when an amplitude of a rotor current exceeds an operating value of a crowbar at the side of the rotor, placing the crowbar and simultaneously, locking a converter at the side of the rotor; if the rotor current is smaller than the operating value of the crowbar, calculating a rotor current maximum value which is to be generated when assuming that the crowbar is cut out at a current moment, and when the rotor current maximum value is smaller than the operating value of the crowbar, cutting out the crowbar and recovering working of the converter at the side of the rotor; and in a fault period, setting a q-axis component of the rotor current according to a preferred output reactive power of a double-fed wind driven generator, and enabling reference values of d-axis and q-axis components of the rotor current to meet constraint conditions. According to the double-fed fan crowbar adaptive cut-out control method disclosed by the invention, the crowbar is guaranteed to be cut out as soon as possible in the premise that the crowbar cannot be placed, so that placing time of the crowbar is shortened and effects that a slave system absorbs the reactive power a little and safety influence on a fan and a control device thereof is reduced are achieved.

The invention discloses a control method for inhibiting the offset of a transient virtual power angle curve of a drop-controlled inverter. A feedforward parameter adding method is adopted for calculating an output current of the inverter and carrying out feedforward control on the output current, so that the voltage tracking performance of the inverter is improved, and the transient stabilization of the inverter is kept. Two feedforward output voltage estimated values are added to two current reference values generated by original voltage outer rings of the inverter, so that neo current reference values are obtained. By adopting the method, the transient tracking performance of the voltage is improved, the transient offset of the virtual power angle curve is effectively inhibited, additional sensors are not needed, and the good transient state and the small interference performance of the system are ensured; in addition, the method can be applied to inverters under dual-loop control such as a virtual synchronous machine, the method can also be further popularized to large interference scenes such as multi-machine passive isolated grids and isolated grid large-load switching, and the transient stabilization of the system is improved.

The invention belongs to the technical field of stability and control of power systems and particularly relates to a VSC (Voltage Source Converter)-HVDC (High Voltage Direct Current Transmission) system class synchronization machine controller design method in consideration of transient stability. The method comprises steps: a dual-unit equivalent model for the VSC-HVDC system is built, wherein the dual-unit equivalent model comprises an inverter end and a rectifier end; and a class synchronization machine controller is designed. The idea of a synchronous inverter is applied to HVDC containing the VSC, and the dual-unit equivalent model for the VSC-HVDC system is built; on the basis of the dual-unit equivalent model, the class synchronization machine controller with droop characteristics is designed, and the traditional outer-loop voltage inner-loop current controller is replaced to improve the transient stability of the system; and the class synchronization machine controller with the droop characteristics can be well applied to the VSC-HVDC system, adding of the class synchronization machine controller can effectively increase the system damping, the oscillation is suppressed, and the transient stability of an AC/DC system after disturbance can be improved.

The invention discloses a dual-passage exciting control method of a doubly fed induction generator, which is based on a dynamical synchronous reference frame. The control method is characterized in that active power is only relevant to the component Urd on the d shaft of the dynamical synchronous reference frame under the dynamical synchronous reference frame when the doubly fed induction generator stably runs, reactive power is only relevant to the component Urq on the q shaft of the dynamical synchronous reference frame, and the independent control to the active power and the reactive power of the doubly fed induction generator is realized through controlling the projections of a rotor exciting voltage phasor Ur on the d shaft and the q shaft . The control method has good dynamic tracking ability, and improves the robustness of an exciting control system, each control coefficient respectively influences the dynamic response during the process of adjusting the active power, the reactive power and the rotating speed, the design of the exciting control system is facilitated, the independent adjustment to the active power, the reactive power and the rotating speed of the doubly fed induction generator is realized, and the doubly fed induction generator is enabled to have good dynamic and transient stability. The invention enables the doubly fed induction generator to be applied to water power generation, wind power generation, and the like, and has obvious advantages of good stability, wide operating range, high energy utilization rate, and the like.

The invention relates to a method for improving the transient stability of a system by combining a crowbar circuit and an energy storage device. The method is applied to a multi-machine system with afan; and a rotor-side crowbar protection circuit is employed and a superconducting energy storage device is installed at the exit of a wind power plant. The method comprises: when the system works normally, the superconducting energy storage device works in a work mode of stabilizing output fluctuation of the fan; when a short-circuit fault occurs at the system, the voltage at the grid-connected point of the fan is reduced, the rotor current reaches a set value, the rotor-side crowbar protection circuit starts to work, and the work mode of stabilizing output fluctuation of the fan is changed into a work mode with a fault after the superconducting energy storage device detects a crowbar signal change; the superconducting energy storage device starts detecting a power angle difference signalbetween two synchronous machines of the two-machine systems; and when the absolute value of a difference between a power angle difference signal at a current time and a power angle difference signalat a previous time is larger than a set value epsilon, the superconducting energy storage device works continuously in the work mode with a fault.

The present invention relates to a spectral clustering-based voltage source converter based high voltage direct current transmission (VSC-HVDC) AC-DC system optimal splitting section search method. The method is characterized by comprising the steps of constructing an undirected edge weight graph G of a power system according to a power system structure; calculating an adjacent weight matrix W and a degree matrix A according to trend data; determining whether the system is unstable due to large disturbance; dividing a generating unit into k homolog groups according to a rotor power angle rocking curve after a generator is disturbed, and updating the adjacent weight matrix W and the degree matrix A; updating the adjacent weight matrix W and the degree matrix A according to a VSC-HVDC converter station placement; calculating a standardized Laplacian matrix LN; and clustering, according to the homolog group number k, feature vectors corresponding to the first k smallest feature values of the standardized Laplacian matrix LN, so as to determine the optimal splitting section, wherein the feature vectors are calculated by using a k mean value clustering algorithm. The method is scientific and reasonable, has high applicability and high reliability.

The invention provides a multi-infeed direct-current auxiliary power/frequency combination controller coordination optimization control method, which comprises the following steps of: establishing a mathematical model of a multi-infeed direct-current power transmission system according to a connection relationship of the multi-infeed direct-current power transmission system; solving a multi-infeedinteraction factor, a multi-infeed effective short-circuit ratio and a multi-infeed power support factor of the multi-infeed direct-current power transmission system in a mode of applying small disturbance; determining the final DC power boosting amount of each loop; judging the tie line fault by measuring whether the power of the tie line is suddenly reduced to 0 or not; obtaining a multi-infeeddirect-current auxiliary power/frequency combined controller structure by adopting an active power large-mode controller and a bilateral frequency difference controller structure. The multi-infeed effective short-circuit ratio proportionality coefficient and the multi-infeed power support factor proportionality coefficient are adopted to perform emergency control on an internal fault of the alternating current system and a tie line fault disturbance form, so that coordination and optimization of emergency control of the multi-infeed direct current interconnected power system are realized, andthe transient stability of the system is improved.

The invention discloses a power support capacity distribution method of different DC lines in a multi-DC system, and belongs to the technical field of an electric power system and automation thereof. The method comprises: calculating the contribution of the different DC lines in improving transient power angle stability, the DC line maximum voltage controllable amount satisfying voltage safety constraints, and a support capacity integrated contribution index of each DC line, then determining a power support capacity distribution mode, and performing power support capacity distribution on each DC line. The method provided by the invention can be used for solving the problems of priority order determination and support capacity distribution of DC emergent power support of a multi-DC system, is helpful in fully utilizing the controllability characteristic of the DC system, improves transient stability of the system, prevents motor tripping or reduces motor tripping, and improves operation economic benefits and safety of an electric power system.

The invention provides a damping control method of a permanent magnetic direct-driven wind generating set, and is used for improving transient-state stability of an electric network. The technical scheme is as follows: the damping control method comprises active damping control and reactive damping control, wherein the active damping control is realized by quickly adjusting the active output of the wind generating set and injecting damping power into the electric network according to the variation of the electric network frequency on the basis of maximum power tracking control policy, thereby further increasing the system damping; and the reactive damping control is realized by rapidly providing reactive power for the electric network by utilizing the net side convertor of the permanent magnetic direct-driven wind generating set according to the variation of the electric network frequency, thereby inhibiting system power oscillation. According to the invention, the characteristic of independent adjusting of active power and reactive power of the permanent magnetic direct-driven wind generating set is utilized, and the system damping is increased by active and reactive adjusting, thus the problem that the regional electric network with higher wind electricity permeability is lack of system damping is well solved, the transient-state stability of the electric network is improved and the safe and stable operation of the electric system is guaranteed.

The invention discloses a rapid assessment method for performance indexes of different emergency control measures in an electric power system, and belongs to the technical field of the electric power system and automation thereof. According to a transient calculation model of the electric power system, candidate emergency control information and time domain simulation data when no control is implemented, and the electromagnetic power of an emergency control moment synchronous machine is calculated directly after different candidate emergency control measures are implemented, thereby rapidly determining the variation in difference between the electromagnetic power and the mechanical power of a single machine infinite-bus equivalent machine under different emergency control measures at the emergency control moment. Furthermore, the increment of a retardation area under different emergency control measures is calculated based on an extended equal area criterion, thereby determining the performance indexes of the different emergency control measures. The rapid assessment method disclosed by the invention can be applied to offline emergency control strategy calculation or online pre-decision emergency control measure calculation, thereby being conducive to optimization and coordination among the different emergency control measures, improving the transient stability of the system, and improving the economy and the safety of operations of the electric power system.

The invention discloses a transient state stability control method and device based on a trend to a stable state. The method includes the following steps of obtaining different balance points which can be operated according to basic parameters of a power system, and determining an initial state set which can maintain the stability of the system, namely the initial state set trending to the stablestate; setting a multi-objective function constraint according to preset requirements, when the power system fails, obtaining the distance between the system state after the fault is cleared and the initial state trending to the stable state, and determining the initial state trending to the stable state which is the most similar to the current state of the system; through coordinated control of various power electronic devices in the power system, making the power system smoothly and rapidly transit to the most similar initial state trending to the stable state to achieve stable control overthe power system. According to the method, the system can smoothly transit to the most similar stable initial state trending to the stable state through coordinated control of the power electronic devices, so that there is no need to determine whether or not the system is unstable, stable control over the system is achieved, and the stability of the system is effectively improved.

The present invention discloses an asymmetric operation and frequency offset information identification combined load equivalence motor method which belongs to load model building technology field in modern electrical power system, particularly takes three phase unsymmetrical pressure instantaneous value information of bus where the load motor group in recorded by a load characteristic wave recorder as input, takes three phase unsymmetrical electrical current consumed by user load motor group under three phase unsymmetrical pressure as output, and performs coordinate transform of three-phase voltage three-phase current instantaneous value to build model of combined load equivalence motor, optimize function of current component under rotary coordinate system, apply mixing optimizing algorithm of combined differential evolution and simplex to identify combined load equivalence motor parameter; change formerly taking pressure positive sequence phasor as input and taking positive sequence power as output; also use default electric network frequency as 50Hz to identify limitation of combined load equivalence motor, enhance accuracy and credibility of model building, precision of combined load equivalence motor identification and range of application.

The invention discloses an enhanced current-limiting control method aimed at a drop-controlled inverter. A current-limiting adding method is adopted, the current limiting in the inverter is enhanced without influencing the stable state performance of the inverter, the output frequency is emergently lowered so as to adjust a virtual power angle, current saturation of the inverter is prevented, and the transient stabilization of the inverter is maintained; in addition, an amplitude limit value is set, when an output current amplitude of the inverter exceeds the amplitude limit value, the frequency of the inverter is lowered, and the virtual power angle is reduced, so that the output current of the inverter is reduced, the operation returns to a non-saturation power angle curve, and the inverter is prevented from entering a current source mode for operation and further losing stability. According to the invention, the inverter is prevented from entering the current source instability mode, the stable state operation characteristics of the system are not changed, the control method can be applied to inverters under dual-loop control such as a virtual synchronous machine, the method can also be further popularized to large interference scenes such as multi-machine passive isolated grids and isolated grid large-load switching, and the transient stabilization of the system is improved.

The invention relates to a strip-shaped loudspeaker box with mirror image type low-frequency radiators. A box body is in a long flat strip shape. Low-frequency radiator installation holes symmetrical in position are formed in the upper and lower surfaces of the right half part, in the long axis direction, of the box body respectively, and the two low-frequency radiators are correspondingly installed in the two upper and lower low-frequency radiator installation holes in a mirror symmetry mode. A mid-low-pitch loudspeaker installation hole is formed in the left half part, in the long axis direction, of the box body, a mid-low-pitch loudspeaker is installed in the mid-low-pitch loudspeaker installation hole, and the mid-low-sound loudspeaker radiates sounds towards the part over the box body. A high-pitch loudspeaker installation table is arranged on the front side face of the left end, in the long axis direction, of the box body, a high-pitch loudspeaker is installed on the high-pitch loudspeaker installation table, and the high-pitch loudspeaker radiates sounds towards the part right ahead of the box body. The strip-shaped loudspeaker box has the acoustic properties of being small in distortion, good in low frequency, capable of bearing high power and excellent in high-frequency performance; the transient stability of the loudspeaker box can be improved, and thus the loudspeaker box can achieve a good sound effect when radiating low-frequency sounds.