59 results about "Sub synchronous resonance" patented technology

A power distribution system comprising a point of common connection that receives electric power supplied by a first power generation system and a second generation system, with the second power generation system that comprises a renewable electric power generator; a transmission line operatively connected to the point of common connection for conducting the electric power between the point of common connection and an external AC electric network. The power distribution furthermore comprises a capacitive compensator connected in series with the transmission line to compensate for a reactive power component of the electric power conducted by the transmission line; and a shunt arranged flexible AC transmission system that mitigates a sub-synchronous resonance effect caused at least in part by the capacitive compensator. A flexible AC transmission system controller of the flexible AC transmission system comprises a damping effect on sub-synchronous oscillations included in the sub-synchronous resonance.

The invention relates to a sub-synchronous oscillation suppression method based on controlled series compensation, which is based on the concept of damping torque, adopts a design method of phase compensation, and carries out proper amplification and phase shift processing on speed signal delta omega to generate an additional control signal to modulate a TCSC (Thyristor Controlled Series Capacitor) trigger angle. Therefore, equivalent reactance of the TCSC is changed, the TCSC can provide positive electrical damping in the entire sub-synchronous frequency range, and the problem of SSR (Sub-Synchronous Resonance) caused by series compensation capacitors can be thoroughly eliminated.

The invention provides a method for using a controllable high-voltage shunt reactor to inhibit the sub-synchronous resonance of an electric power system. The shafting tachometry signal of the steam turbine generator unit in the electric power system is used as an input signal, and the shafting torsional oscillation property of the steam turbine generator unit can be discriminated from the input signal after being processed by digital signal algorithm. The method is characterized in that the shafting torsional oscillation property signal is calculated on line with a sub-synchronous resonance control strategy to gain the volume control command of the controllable high-voltage shunt reactor, so as to dynamically adjust the volume of the shunt reactor, thus correspondingly dynamically adjusting the reactive power, voltage, active power and rotating speed of the steam turbine generator unit, realizing the effect of inhibiting the sub-synchronous resonance of the steam turbine generator unit, and the effectiveness of the invention is validated by a numerical simulation aiming at certain planning system.

A method and arrangement for controlling a doubly-fed induction machine by a frequency converter including a rotor side converter (INU) connected to a rotor circuit of a doubly-fed induction machine (DFIG) and having a control system with rotor flux as a feedback variable, a grid side converter (ISU) connected to an AC power network, and a direct voltage intermediate circuit (DC) connected between the rotor side converter (INU) and the grid side converter (ISU). The method includes forming a rotor flux reference (ψr,ref), forming a damping signal (ψref,D), summing the damping signal and the rotor flux reference for obtaining a modified rotor flux reference (ψref), and feeding the modified rotor flux reference to a controller of the rotor side converter (INU) for damping sub-synchronous resonances.

Distributed static synchronous series compensators (DSSSCs) which may also be designated tower routers capable of injecting series inductive or capacitive impedances to enable distributed power-flow control. When a large number of these (a fleet of) DSSSCs are distributed over the grid for power-flow control, it is necessary to ensure that coordinated communication and control capabilities are also established, enabling fast reaction to changes that can exist across the grid. A system architecture and method for enabling localized high-speed low-latency intelligent control with communications between subsections (local network) of the grid along with communication to the central Grid operations center at the utility for supervisory control is disclosed herein. The architecture provides sub-cyclic (< 1 / 60 of a second) response capability, using the local DSSSCs with high-speed communication at the local network level to power-system disturbances, such as power-oscillation damping (POD), sub-synchronous resonance (SSR) etc.

The invention relates to an equivalent method for mitigating sub-synchronous resonance on a power frequency based on sub-synchronous frequency capacitance voltage, in particular to a flip-flop stage control algorithm of a thyristor controlled series compensation, which belongs to the technology of the thyristor controlled series compensation (TCSC). The method is characterized in that a structure with an additional damping control algorithm is adopted, and the method achieves the purpose of mitigating sub-synchronous resonance through trimming the trigger angle of the thyristor controlled series compensation. The method comprises the following steps: obtaining the sub-synchronous frequency components of the capacitance voltage, calculating the equivalent Uadd_s of the components in the half power frequency period, proximately calculating Uadd_s to cause a variable Delta x of the TCSC fundamental wave impedance lifting coefficient, and calculating a value added of the trigger angle Delta Alpha according to Delta x.

A method which is suitable for a system having a frequency converter and a generator, both of which are connected to a power grid, includes obtaining sub-synchronous components of the grid voltage and determining damping current set points according to the sub-synchronous components to compensate for sub-synchronous resonances of the grid. Damping current set points are determined by receiving the sub-synchronous components of the grid voltage and returning damping current set points as outputs. A variable damping gain is adjusted according to the sub-synchronous frequency of the grid, such that the required compensation level can be adapted to the frequency converter for damping sub-synchronous resonance of the grid.

The invention discloses a method and a device for assessing sub-synchronous resonance, and belongs to the technical field of stability analysis of a power system. The method comprises the following steps of: acquiring electric damping and mechanical damping of a machine screen system; acquiring total damping of the machine screen system according to the electric damping and the mechanical damping of the machine screen system; and assessing the sub-synchronous resonance of the machine screen system according to the total damping of the machine screen system. The device comprises a first acquisition module, a second acquisition module and an assessment module. The method and the device can comprehensively and accurately assess the sub-synchronous resonance of the machine screen system by acquiring the total damping according to the electric damping and the mechanical damping of the machine screen system and assessing the sub-synchronous resonance of the machine screen system according to the total damping.

The present invention discloses a control method and device of restraining sub-synchronous resonance, wherein the method comprises the steps of selecting an input signal of an additional damping controller; determining the access position of the additional damping controller; carrying out the filtering, proportional phase shift and amplitude limiting operations on the input signal to obtain an output control signal; restraining the sub-synchronous resonance of a system according to the output control signal and the access position. According to the method of the present invention, the sub-synchronous resonance of the system is restrained effectively, and the safe and stable operation of a draught fan and the system is guaranteed. The present invention also provides a control device of restraining the sub-synchronous resonance.

The invention relates to a method for controlling the sub-synchronous resonance of a wind power station series compensated transmission system and belongs to the electric power system control technical field. A sub-synchronous current reference signal is given through appropriate signal processing so as to control a switch arranged in a power electronic converter to be on and off and accordingly a sub-synchronous current signal is generated to be injected into the series compensated transmission system, the resonance energy in the wind power station series compensated transmission system is consumed, and accordingly the sub-synchronous resonance in the wind power station series compensated transmission system is effectively inhibited. According to the method for controlling the sub-synchronous resonance of the wind power station series compensated transmission system, the method is based on the modern power electronic technology and the capability of the inhibition on the wind power station SSR (Sub-Synchronous Resonance) is high and the defect that the SSR inhibition capability is limited by the capacity of a fan converter by the traditional decentralized control method is overcome, wherein a sub-synchronous resonance damping control ring can be attached to a converter control system of a doubly-fed fan in the traditional decentralized control method.

The invention relates to an experimental method for simultaneously exciting out unit shafting torsional oscillation of a plurality of turbo-generator units in a large thermal power plant, which discloses an excitation method for realizing the synchronous torsional oscillation of a plurality of generating sets based on a synchronous torsional oscillation excitation device through GPS time tick, the synchronous torsional oscillation excitation device sends out synchronous torsional oscillation excitation signals having the same frequency with the unit mode to each generating set, the signals act on excitation systems of turbo-generator units and generate controllable electric torque in the turbo-generator units through the excitation systems, the shafting torsional oscillation on the plurality of units can be further excited out simultaneously, meanwhile, the strength of shafting torsional oscillation of each generating set can be detected for confirming the safety of the unit shafting. The method can accurately and controllably generate shafting torsional oscillation synchronously on the plurality of large turbo-generator units, and provides a test means for researching the effectiveness and setting of various measures for restricting sub-synchronous oscillation (SSO) and sub-synchronous resonance (SSR).

The invention discloses a method for rapidly assessing a sub-synchronous resonance of a complex AC / DC interconnected system comprising multiple series compensation. The method is characterized in that: in a system where a plurality of series compensations simultaneously exist, the theory of a two-point method is utilized to carry out effective and equivalent simplification on a vast AC / DC interconnected system network to rapidly obtain a plurality of simplified system networks; each simplified system comprises the single series compensation or the adjacent series compensation; and a frequency scanning method is combined to analyze each simplified power system model to obtain a curve that a real part and an imaginary part of a sub-synchronous equivalent impedance change along with the frequency so as to rapidly assess whether the system has a danger that the sub-synchronous resonance occurs or not.

The invention belongs to the field of flexible alternating current transmission of power systems, and particularly relates to a latent series compensation device of the power system. The device comprises a capacitor bank, an over-voltage protection device, a damping device and a bypass circuit breaker, wherein the capacitor bank and the damping device are connected in series and then connected in parallel with the over-voltage protection device and the bypass circuit breaker. When the system runs normally, the latent series compensation device is not used, namely the latent series compensation device is in a bypass state; and when short-circuit failures occur, the latent series compensation device detects the short-circuit failures, is used for a circuit in different ways according to different failure types, and is bypassed after a certain time. By the latent series compensation device, the transient state stability of the system is improved, and the voltage distribution of the circuit is optimized; and risks in sub-synchronous resonance (SSR) are eliminated. The latent series compensation device can be used both independently and together with a conventional series compensator.

The invention discloses a method for screening a sub-synchronous resonance risk based on series compensation effect coefficients in the technical field of electric power system operation and control. The method comprises the steps that (1) according to a multi-machine alternating current system with a series compensation alternating current line, all electric generators are equivalent to a series branch of a power source and an inductor; (2) according to the well equivalent multi-machine alternating current system in the step (1), an instant three-phase short circuit ground fault is triggered on the series compensation alternating current line, and when the multi-machine alternating current system recovers the steady state, CIF values of series compensation effect coefficients of the electric generators are calculated; (3) if the CIF value of the series compensation effect coefficient of one electric generator is larger than or equal to a TCIF value, the sub-synchronous resonance risk exists in the electric generator; if the CIF value of the series compensation effect coefficient of the electric generator is smaller than the TCIF value, the sub-synchronous resonance risk does not exist in the electric generator. According to the method, the calculated amount is small, the amount of information required for calculation is small, and the electric generator with the sub-synchronous resonance risk can be effectively and accurately judged.

The invention discloses a doubly-fed wind turbine sub synchronous resonance hardware in-loop test system and a doubly-fed wind turbine sub synchronous resonance hardware in-loop test system method. The system comprises a power electronics real-time simulation platform and a to-be-tested doubly-fed wind turbine controller; a real-time digital simulation model comprising a power grid, wind power plant equipment and doubly-fed wind turbine equipment is built on the power electronics real-time simulation platform; after being subjected to real-time transformation, the real-time digital simulation model is downloaded to the simulation machine of the power electronics real-time simulation platform; and the to-be-tested doubly-fed wind turbine controller is connected with the real-time digital simulation model through the input and output interface of the simulation machine. With the doubly-fed wind turbine sub synchronous resonance hardware in-loop test system and the doubly-fed wind turbine sub synchronous resonance hardware in-loop test system method of the invention adopted, a doubly-fed wind turbine sub synchronous resonance hardware in-loop test can be realized flexibly and conveniently, and test results can be close to engineering practice, and test results is more accurate.

The invention discloses a detection method and a detection system of a generator sub-synchronous resonance generator terminal damping controller. The detection method includes that electrical power system simulation environment, a 12-chain cascade H-bridge voltage source converter model and a boosting transformer of the 12-chain cascade H-bridge voltage source converter model are established, the electrical power system simulation environment provides electric signals for a control cabinet of the generator sub-synchronous resonance generator terminal damping controller, the control cabinet of the generator sub-synchronous resonance generator terminal damping controller generates window signals according to the electric signals, the window signals controls an insulated gate bipolar translator (IGBT) of each bridge of the 12-chain cascade H-bridge voltage source converter model to be powered on or powered off, a restraining sub-synchronous resonance damping current is generated and injected into a generator terminal of a generator model through the boosting transformer model, disturbance is arranged so as to stimulate the electrical power system simulation environment to generate sub-synchronous resonance of self natural mode of vibration, and the restraining effect of the sub-synchronous resonance of the restraining sub-synchronous resonance damping current to the self natural mode of vibration of the electrical power system simulation environment is detected.

The invention relates to a control method for suppressing sub-synchronous resonance of a wind power station series compensated transmission system, and particularly provides a sub-synchronous resonance control method based on a high-power power electronic converter. According to the invention, series compensated line current signals or series compensated capacitive voltage signals are measured at first to act as input signals, sub-synchronous voltage reference signals are acquired through signal processing, the sub-synchronous voltage reference signals are inputted into a high-capacity power electronic converter so as to generate actual sub-synchronous voltage, and the sub-synchronous voltage is coupled to the series compensated transmission system through a transformer which is connected to the series compensated line in series. Therefore, the power electronic converter is equivalent to a pure resistor connected in the line in series at the sub-synchronous frequency where resonance occurs, and resonance energy is consumed, and SSR (sub-synchronous resonance) is suppressed; and the power electronic converter is equivalent to a short circuit at the power frequency, and the power frequency operating state of the system is ensured to be constant.

An apparatus for controlling a thyristor controlled series capacitor connected to a power transmission line. A thyristor firing control includes a unit for effectuating a desired capacitor voltage zero crossing in dependence of a line current and a capacitor voltage in response to a command signal. A command control provides the command signal to the thyristor firing control. The command control includes a damping control including a damper configured to damp at a least one discrete frequency.

Method and apparatus for mitigating SSR in power transmission system are provided. The method comprises: checking whether the sub-synchronous resonance (SSR) happens in the power transmission system; checking whether the sub-synchronous resonance is undamped; providing a command to bypass the SC unit when the SSR happens and is undamped. In some embodiments, the method further comprises providing a command to reinsert the SC unit into the power transmission system when the transmission level of the power transmission system is determined to be higher than a predetermined level and there is no fault in the power system. The invention also relates to a corresponding apparatus which can implement the method of the invention.

The invention discloses a wind power plant sub-synchronous resonance suppression method based on a parallel voltage source current converter, and belongs to the technical field of the stability analysis and control of the power system. The method comprises the following steps: measuring current on a wind power cluster convergence line to obtain connecting line current; designing a low-pass filterand a band rejector filter to filter the connecting line current so as to obtain the connecting line sub-synchronous current; designing phase compensation and proportion gain loop so as to obtain sub-synchronous damping current, wherein a voltage outer ring enables the device DC voltage to track a reference value under the effect of a PI regulator, and an output value is converted through a phaseangle so as to obtain DC voltage compensation current; adding the DC voltage compensation current and the sub-synchronous damping current to obtain an output current reference value, wherein a currentinner ring enables the SSO-DS output current to track the output current reference value under the effect of the PI regulator, the current is injected into the wind power cluster system to provide positive damping for the system, thereby achieving the effect of depressing the sub-synchronous resonance. The method disclosed by the invention has important significance for depressing the sub-synchronous resonance problem caused by the wind power integration in a centralized way.

The invention discloses a prediction method for the sub-synchronous resonance frequency of a direct-drive wind farm and a terminal device. The method comprises the following steps: an output signal ofa network-side converter of a wind farm system is collected; a network-side converter model, a phase-locked loop model and a network-side converter controller model are established according to the output signal and the internal physical quantity relationship. According to the grid-side converter model, the phase-locked loop model and the grid-side converter controller model, the sub-synchronousresonance prediction model is established. According to the sub-synchronous resonance frequency prediction model, the resonance frequency point is predicted, and the wind farm system is adjusted according to the resonance frequency point to suppress the sub-synchronous resonance. The invention utilizes the sub-synchronous resonance prediction model established by the state space equation, the resonance frequency of the wind farm system is predicted by the sub-synchronous resonance prediction model, and the resonance frequency point is predicted according to the resonance frequency point, and protection measures are added in the system according to the resonance frequency point in advance to avoid the occurrence of sub-synchronous resonance and ensure the continuous, safe and stable operation of the system.

The invention belongs to the thyristor controlled series compensation (TCSC) technology and relates to a method for inhibiting the sub-synchronous resonance on the basis of the phase variation of the circuit current relative to working frequency, in particular to a triggering-level control algorithm of the controlled series compensation, which adopts an additional damping control structure and achieves the purpose of inhibiting the sub-synchronous resonance by the fine-tuning of a controlled series compensation triggering angle. The invention particularly comprises the steps of calculating and obtaining the phase variation Delta t of measurement circuit current relative to the working frequency, which is caused by the sub-synchronous frequency circuit current component, and calculating the additional value Delta Alpha of the triggering angle according to the Delta t, etc.

The invention discloses a method for analyzing the sub-synchronous resonance of an alternating-current system in the technical field of running and control of a power system. The method comprises the following steps of: calculating the natural frequency of each decoupling modal of a multi-mass-block model of a generator shaft system, and scanning the frequency of a power transmission system to beresearched by using a frequency scanning method to acquire the resonance frequency feA of an asynchronous generator effect and the resonance frequency feC of a transient torque amplification function; if the feA and / or the feC accords with a condition shown in the specifications, determining that f0(i) is partial main resonance frequency of the sub-synchronous resonance, calculating a line seriescompensation degree KS according to the feA and the feC and determining the minimum value KSmin of the line series compensation degree; establishing a full system equation, and calculating a curve ofeach modal electric damp which is changed with the series compensation degree in a range of between 0 and KSmin by using a characteristic value method; and further obtaining all the main resonance frequencies of the sub-synchronous resonance and a secure series compensation region. By the method, a characteristic of quickness of the frequency scanning method and a characteristic of the precision of characteristic value method are combined, the shortcoming of low precision of the frequency scanning method and the shortcoming of large calculation quantity of the characteristic value method are overcome, and the obtained secure series compensation region has a great significance for engineering practice.

A method and arrangement for controlling a doubly-fed induction machine by a frequency converter comprising a rotor side converter (INU) connected to a rotor circuit of a doubly-fed induction machine (DFIG) and having a control system with rotor flux as a feedback variable, a grid side converter (ISU) connected to an AC power network, and a direct voltage intermediate circuit (DC) connected between the rotor side converter (INU) and the grid side converter (ISU). The method comprises forming a rotor flux reference (psi r,re ), forming a damping signal (psi re ,D ), summing the damping signal and the rotor flux reference for obtaining a modified rotor flux reference (psi re ), and feeding the modified rotor flux reference to a controller of the rotor side converter (INU) for damping sub-synchronous resonances.

The invention relates to a sub-synchronous resonance monitoring method. The method comprises the following steps: 1) acquiring line current in a series compensation system, and performing low-pass filtering on the line current; 2) sampling the line current after low-pass filtering, wherein the sampling indicates sampling one sampling value every M sampling values so as to convert sampling values with high sampling rate into sampling values with low sampling rate, and M is more than 1; 3) performing band-pass filtering on the sampled sampling values to generate sub-synchronous resonance current; and 4) calculating the effective value ISSR of the sub-synchronous resonance current, judging whether the ISSR is greater than the fixed value of the sub-synchronous resonance current, and if so, bypassing the series compensation system. The method eliminates circuit parameter conditions generated by sub-synchronous resonance, protects the safety of a generator shaft system, and improves the stability and the reliability of a system; and the measures of sectional calculation, sectional update, accumulation and the like can be taken by adopting sampling and a long-window effective value algorithm, so that the calculation quantity is small and relay protection can be realized.

The present invention relates to a method of controlling a doubly fed induction generator wind turbine converter system in case of a sub-synchronous resonance event, the method comprising the steps of detecting the sub-synchronous resonance event, and switching from a first control mode to a second control mode in response to detecting the predetermined event, wherein the second control mode comprises the step of setting at least one rotor current controller parameter on the basis of a generator speed of the doubly fed induction generator. The predetermined event may also be a fault ride through event. The present invention further relates to a doubly fed induction generator wind turbine converter system being capable of handling such events.

This disclosure provides a PSR-PWM technique for high power active front-end inverters to damp a specific inter-harmonic that may cause relative sub-synchronous resonance in power system. Due to the strong interaction between wind power converters, photovoltaic converters, FACTS devices and HVDC transmission, low-frequency oscillations occur from a few Hz to dozens of Hz, or even high-frequency oscillations ranging from about 300-2000 Hz. Meanwhile, low-frequency oscillations ranging from 0.6 Hz to 7 Hz occur in the power supply systems of many electric locomotives. Even in the case of large-scale train outage, low-frequency oscillation will lead to abnormal locomotive dispatching system; in addition, the power grid voltage disturbance and flicker caused by a large number of high-power are furnaces and other nonlinear loads in the industrial field with a passband inter-harmonic frequency ranging from 0.05 Hz-90 Hz and so on are detected.

The invention discloses a method for identifying modeling boundary of a sub-synchronous resonance actual system. The method comprises the following steps: injecting unit current in a certain frequency range into voltage equations of system nodes at a system study set node, injecting 0 current into other system nodes, by calculating impedance of a driving point, searching for a natural resonant frequency of driving point impedance of the system and a driving point equivalent resistance value under the frequency, then respectively calculating sensitivity factors I1 and I2 of power components; dividing power components in the system into three classes, expanding a study area formed by a first class of power components to the exterior by one node, and determining the sub-synchronous resonance modeling area and a molding boundary of an actual system; determining the specific sub-synchronous resonance boundary of the actual system by defined sub-synchronous resonance frequency sensitivity factors of the power components and impedance sensitivity factors of the power component. The accuracy of identifying the sub-synchronous resonance boundary and the modeling efficiency are improved.