512results about "Flicker reduction in ac network" patented technology

The invention discloses a virtual double-fed induction generator inertia control method coordinated with secondary frequency regulation, which solves the problem of cooperation between the virtual inertia control of a wind turbine generator and the secondary frequency regulation of a power system. On the basis of an original virtual inertia control module, a module which is coordinated with the secondary frequency regulation of a power system is added, so that the overall frequency regulation effect is increased. Moreover, in the added module, the rotational speed of the rotor of the wind turbine generator is considered, so that the wind turbine generator can continuously operate within a safe rotational speed range; the problem of the affection of system frequency fluctuation on the active regulation capability of the wind turbine generator is solved; because the affection of system frequency fluctuation on the active regulation capability of the wind turbine generator is great, in order to ensure that the double-fed induction generator has better frequency regulation capability, the steady-state frequency response of the wind turbine generator is optimized, and moreover, accordingly, a control strategy is designed, so that the frequency regulation effect of the wind turbine generator is increased to a certain degree.

The invention discloses a low-frequency oscillation control parameter optimization method of a grid-connected double-fed fan with virtual inertia belonging to the technical field of power system stability analysis. The method is realized by a processing system comprising a sequentially connected information acquisition module, a robust random optimization parameter adjustment calculation module and a parameter adjustment result output module, comprising three steps of information acquisition, parameter adjustment calculation and output parameter adjustment result optimization, and obtaining aset of control parameter policy variables; Judging whether the doubly-fed fan is the cause of inducing low frequency oscillation can guide the optimization of control parameters. After the parameter optimization strategy is applied, the power angle response level of the fan is effectively improved, the fan no longer transmits oscillation energy to the power network, and the low-frequency oscillation of the fan-connected system is restrained.

The invention discloses a rapid robustness single-current feedback control method of an LCL type grid-connected inverter. Single-current feedback control is introduced, a rapid robustness PWM modulation method is combined, and grid-connected control of the inverter is realized. According to the method, the grid-connected current is sampled, extra sensors are not needed, the hardware cost is reduced, and the system reliability is improved. According to the rapid robustness PWM control method, the duty cycle limitation is not introduced, the calculation time delay of one-step delay of a grid-connected current outer loop and an active damping inner loop is completely eliminated, the essential requirement that the positive and negative dividing frequency of an equivalent damping resistor is higher than the design range of the LCL resonant frequency is realized, the method allows half of the switching period of sampling and duty cycle calculating time, and the overall robustness and the dynamic performance of the grid-connected inverter are enhanced.

The invention belongs to the field of an electric system, and specifically relates to a method for suppressing large-scale photovoltaic power station power system low-frequency oscillation by utilizing an active-disturbance-rejection additional damping controller to adjust active output of a photovoltaic system. The method, taking a large-scale photovoltaic power station as an object of study, designs a photovoltaic power station active additional damping control strategy with active disturbance rejection control and MPPT control being combined, and designs and sets an active disturbance rejection controller through a separation principle; the angular velocity of a synchronous generator serves as the input of the active disturbance rejection controller; and the output signal of the controller is added to a constant power control outer ring after amplitude limiting, thereby achieving an effect of suppressing the power system low-frequency oscillation. The method has a good control effect for single-machine and multi-machine power system low-frequency oscillation; and the controller has high robustness.

The invention relates to a self-adaptive damping control method of a virtual synchronous generator. The self-adaptive damping control method comprises the steps of: acquiring relevant parameters of avirtual synchronous generator system; judging whether low-frequency oscillation occurs in the virtual synchronous generator system according to the relevant parameters, if not, returning to the previous step to acquire data continuously, and if so, adjusting a virtual damping value in the virtual synchronous generator system in a self-adaptive manner according to the acquired relevant parameters;and realizing frequency adjustment of the virtual synchronous generator system according to the virtual damping value. Compared with the prior art, the self-adaptive damping control method has the advantage of being capable of effectively suppressing the low-frequency oscillation of the system.

The invention relates to a primary frequency regulation closed loop control method for a generator set. The method comprises steps: a frequency difference signal between an actual power grid frequency and a power grid standard frequency is acquired; whether the above frequency difference signal is out of a frequency regulation dead zone is judged, if the frequency difference signal exceeds the frequency regulation dead zone, the frequency difference signal is used to obtain a theoretical frequency regulation power according to a corresponding function between the frequency difference signal and a frequency regulation load, and the theoretical frequency regulation power and an instantaneous generator set power in the case of frequency regulation action are overlapped to obtain a power target value for the frequency regulation closed loop control; and the power target value and an actual generator set generation power form a PID closed-loop circuit, and a frequency regulation load instruction is outputted. The method of the invention can accurately control the generator set primary frequency regulation contribution rate, improve the generator set primary frequency regulation qualified rate, and improve the power grid stability and safety.

The invention discloses a coordination control method of VSC-HVDC (voltage source converter based high voltage direct current) alternating-current voltage-frequency for improving the transient stability of an alternating-current system. An alternating-current voltage-frequency coordination control target is increased in a transient state control target of a VSC station; the control strategy can be involved in transient state control of voltage and frequency of the alternating-current system by utilizing reactive and active rapid adjustment capability of VSC-HVDC respectively on the premise of guaranteeing the running safety of VSC-HVDC equipment. Based on the strategy, the invention designs a VSC controller structure capable of controlling the target priority ranking seriously, so that the transient state stability of voltage and frequency of a weak alternating-current power grid linked to the VSC can be improved effectively.

The invention discloses a WAMS-based ultra-low-frequency oscillation monitoring and emergency control method therefor. A WAMS-based ultra-low-frequency oscillation online monitoring method and a modelfor judging whether ultra-low-frequency oscillation occurs or not are given; by performing online judgment on whether a hydroelectric generating set provides negative damping or not, a speed regulator is further controlled in a targeted manner; and by combination with switching of speed regulator networking / isolated network mode, ultra-low-frequency oscillation can be quite down while certain primary frequency modulation capacity is maintained, so that a practical emergency control measure is provided for ultra-low-frequency oscillation control by a power grid dispatching operation staff, andtherefore, the control method is of significant practical meaning to power grid dispatching operation.

The present invention relates to a resonance elimination apparatus and method of ferromagnetic resonance, wherein the apparatus is electrically connected to an electromagnetic voltage transformer in a power distribution network, and comprises: a power source module, a resonance judging module, a resonance elimination module, and a current transformer, wherein the power source module is electrically connected to the resonance judging module and the resonance elimination module; the current transformer is electrically connected to a connecting wire between a neutral point of the electromagnetic voltage transformer and the earth, and the current transformer is electrically connected to the resonance judging module; the resonance elimination module comprises a resonance elimination resistor and a first control switch, both ends of the resonance elimination resistor are connected to both ends of an open triangular loop of the electromagnetic voltage transformer in series, the first control switch is connected between the resonance elimination resistor and the open triangular loop in series; and the resonance judging module is electrically connected to the first control switch. The apparatus provided in this embodiment can accurately and fast eliminate ferromagnetic resonance and improve resonance elimination efficiency of ferromagnetic resonance.

The invention discloses a node disturbance power transfer distribution balance degree analyzing method. The method comprises the steps of conducting load flow calculation on an electric system when the electric system operates and obtaining a sensitivity matrix of branch power to node injection power, obtaining a load flow transfer rate matrix according to the sensitivity matrix and the active power margin of a branch, obtaining the probability distribution condition of each element in a column vector corresponding to each node in the load flow transfer rate matrix in a load flow transfer rate statistical interval, calculating the improved information entropy according to the probability distribution condition to serve as the index for reflecting each node disturbance power transfer distribution balance degree, and conducting safety assessment on the system under the disturbance of each node according to the transfer distribution balance degree indexes. The method is used for quick assessment of the node injection power anti-interference capacity of the large-scale electric system, computing speed and accuracy can meet the requirements for online safety assessment of the large-scale electric system, and guidance can be provided for load management of the electric system and error control of a grid-connected wind power unit.

A stability analysis system (SAS) for non-invasive estimation of damping torque associated with a power generator in an electric power network includes a processor in communication with a PMU associated with the generator. The processor is configured to receive a first data sample set from the PMU. The first data set is substantially representative of at least one measurement of the generator. The processor is also configured to determine an estimated torque of the generator based at least in part on the first data set. The processor is further configured to determine an estimated average torque and one or more estimated torque components based at least in part on the estimated torque. The processor is also configured to output the estimated average torque and the one or more estimated torque components to an operator for use in stability analysis of one or more of the generator and the network.

The invention provides a convertor station electrical signals-based subsynchronous oscillation monitoring analysis method. The method includes the following steps that: step 1, acquiring and selecting appropriate converter station electrical signals x (k); and step 2, adopting a windowed interpolation FFT algorithm and an ESPRIT algorithm to identify the subsynchronous oscillation information of the electrical signals x (k). Compared with the prior art, and according to the convertor station electrical signals-based subsynchronous oscillation monitoring analysis method provided by the invention, the windowed interpolation FFT algorithm and the ESPRIT algorithm are applied to electrical signal analysis, and therefore, analysis precision can be improved; and monitoring and prevention of subsynchronous oscillation can be performed based on the method, so that the security and economical efficiency of the operation of a power grid and a unit can be improved.

A distributed power flow controller and a control method therefor are disclosed. The controller is mounted on a power transmission line, wherein the distributed power flow controller comprises shunt-wound side equipment and series-wound side equipment; each phase of power transmission line is split into multiple split conductors; the series-wound side equipment comprises multiple groups of single-phase power flow compensators connected with each phase of power transmission line in series separately; each group of certain-phase power flow compensators shares a set of converter, controller, current transformer, voltage transformer and communication module; each group of certain-phase power flow compensators also comprises multiple single-turn transformers matched with the number of the split conductors; and the alternating current side of the corresponding converter is connected to each split conductor through each single-turn transformer separately. The control method is carried out by the steps of comparing the each-phase transmission power target value with an actually collected and calculated transmission power parameter difference value; trigging control on the converter; optimizing and switching switch sequences of the converter; and realizing transmission power compensation for the power transmission line. According to the distributed power flow controller and the control method therefor, the transmission power of the power transmission system with multiple split conductors is realized; due to the control method, balanced power flow distribution is achieved; and the flexibility and reliability of equipment control are improved.

The invention discloses an electric system low frequency oscillation mode identification method based on correlation functions. The method includes the following steps that firstly, a section of an active power signal of a circuit having high observability for a low frequency oscillation mode under the circumstance that no large disturbance exists in an electric system is read and serves as a signal to be analyzed, and a sampling time interval Ts is determined; secondly, the read active power signal is preprocessed to obtain a corresponding power fluctuation signal; thirdly, a self-correlation function of the power fluctuation signal is solved, and a system free oscillation signal is obtained; fourthly, based on an extended Prony method, mode identification is carried out on the free oscillation signal to obtain a low frequency oscillation mode frequency and a damping ratio. The electric system low frequency oscillation mode identification method has the advantages that the method is only based on random response signals, operation is simple, the calculation amount is small, and identification accuracy is good.

The invention discloses a unified power flow controller additional damping control system capable of restraining subsynchronous oscillation. The unified power flow controller additional damping control system comprises a subsynchronous damping controller, wherein the additional control signals are superimposed in current inner loop control instructions of reactive control circuits of a shunt-wound side converter and a series-wound side converter of the unified power flow controller; the subsynchronous damping controller comprises multiple subsynchronous modal control circuits; each subsynchronous modal control circuit comprises a modal filter, a proportion amplifying module and a phase shifter for realizing phase compensation separately; the output signals of each subsynchronous modal control circuit are subjected to signal superposition and amplitude limiting to form the additional control signals output by the subsynchronous damping controller; and the subsynchronous damping controller takes generator shaft system rotating speed deviation as the input control signal. The unified power flow controller additional damping control system provided by the invention is capable of restraining subsynchronous oscillation of the power system successfully and the normal and steady operation of the system and the unified power flow controller is not affected.

The invention discloses an alternating current and direct current coordination control method improving the system stability, and belongs to the field of electric power system operation control. The method comprises the steps of carrying out quadratic polynomial curve fitting on the power of a connecting line after smoothing and stopping are carried out on the power of the connecting line under the condition that an alternating current and direct current series-parallel power grid goes wrong, judging whether the power increase condition or the power decrease condition is met and then increasing or decreasing the direct current power. Meanwhile, the effect is more remarkable with cooperation with an additional PSS4B excitation controller. According to the alternating current and direct current coordination control method, the regional power balance relation in the swinging process of a generator set can be effectively controlled, power angle swinging can be restrained, generator tripping can be reduced, and the transient stability level and the dynamic stability level of an alternating current and direct current system can be increased.

The invention discloses a fixed time dynamic surface high-order sliding-mode suppression method for chaotic oscillation of a power system. The suppression method comprises the steps of (1) determining the reactive power of the to-be-compensated power system; (2) establishing a mathematical model of a current source type static synchronous compensation controller, and determining the output and reference value of the current source type static synchronous compensation controller; (3) determining a control target value, wherein the output can achieve an adjacent domain with an arbitrarily small reference value within finite time, and the upper bound of the convergence time does not depend on the initial value; (4) designing a fixed time dynamic surface high-order sliding-mode surface and control law to realize target control; and (5) determining the control parameter of the designed control law according to stability analysis of the Liapunov function. By adoption of the method, system stability can be realized within predetermined time under any initial starting condition of the system; and in addition, a buffeting phenomenon is overcome, higher transient response is obtained, the convergence speed is accelerated and the stability of the power system is improved.

The invention discloses a new grid-connection / disconnection seamless switching strategy in an optical storage alternating current and direct current micro grid. The strategy comprises the following steps: at first, designing a new micro grid pre-synchronization algorithm, thus guaranteeing an alternating current bus voltage phase to be smooth and continuous, and laying a foundation for grid-connected / disconnected seamless switching; and then putting forward an improved outer ring which is used as an energy storage control outer ring and an inverter control outer ring according to a system structure of the micro grid and in combination with an outer ring output characteristic during switching micro grid system grid-connection / disconnection operating modes. The improved outer ring realizes a resetting function required by instant output of grid-connection / disconnection mode switching, so as to make up for overshoot caused by line power flow changes when a traditional PI adjuster switches; the problem of alternating current and direct current bus voltage fluctuation in the switching process can be better solved; and seamless switching is realized. By adopting an improved voltage outer ring adjusting strategy, serious overshooting in a transient process can be inhibited; the voltage fluctuation of an alternating current and direct current bus is reduced; and smoothness during switching is guaranteed.

The present invention provides a doubly-fed wind farm sub-synchronous oscillation SVG suppressing method and a device. The method comprises the following steps: acquiring voltage signal(s), current signal(s) and wind farm parameters of the output end(s) of a doubly-fed wind farm, wherein the wind farm parameters comprises a wind speed and a power-transmission line series compensation degree; determining active power signal(s), voltage oscillation amplitude(s) and current oscillation amplitude(s) according to the voltage signal(s) and the current signal(s); determining the working mode of a SVGcontroller; determining module parameter(s) of the SVG controller according to the determined working mode, the voltage oscillation amplitude(s), the current oscillation amplitude(s), oscillation frequencies, the wind farm parameters and a pre-established SVG parameter table, wherein the SVG parameter table is a pre-established corresponding table of the SVG function module parameter(s) and system operation information under different working modes; and performing sub-synchronous oscillation SVG suppressing on the wind farm by using the SVG controller with the determined parameter(s). According to the method, sub-synchronous frequency band signal(s) are filtered from sampling signal(s), and the doubly-fed wind farm is subjected to sub-synchronous oscillation SVG suppressing by using the voltage(s) and the active power(s).

The invention discloses an optimal configuration closing method for an energy storage system of an independent type micro power grid. The method comprises the steps that a self-sufficiency probability requirement of the micro power grid is determined; an optimal configuration module of the energy storage system of the micro power grid is established; aimed at the optimal configuration module of the energy storage system, a rain-flow counting method is used to estimate the service life of a storage battery, and an investment coefficient is obtained; and load data and wind power data of one year are predicted, a proper operation strategy is adapted in the simulated operation process, and according to the optimization searching range, a traversal algorithm or particle swarm optimization is used to search configuration of the energy storage system. The method satisfies economical performance, provides the self-sufficiency probability requirement, and pursuits the system stability; the system stability is kept when the economical performance is optimal; and a balance is made among investment, operation and pollution treatment cost.

The present invention provides a power system emergency reserve capacity configuration method. The method comprises: a system secondary frequency modulation reserve R2 is determined according to a cost effectiveness method; the system secondary frequency modulation reserve R2 is taken as a basis, and the maximum steady state frequency fluctuation [Delta]fw,0 of a system after the occurrence of an extra high-voltage direct current bipolar locking fault is simulated and determined; if the [Delta]fw,0 is larger than an allowable limit, a generation side and a load side are taken as reserved sources, a lowest cost is the standard, and an added primary frequency modulation reserve [Delta]R1,w is determined, or else, the [Delta]R1,w is equal to zero; the R2 and the [Delta]R1,w are taken as a basis, the maximum frequency fluctuation [Delta]fh,0 of the system after the occurrence of an extra high-voltage direct current bipolar locking fault is simulated and determined; if the [Delta]fh,0 is larger than an allowable limit, the generation side and the load side are taken as reserved sources, the lowest cost is the standard, and an added inertia response reserve [Delta]R1,h is determined, or else, the [Delta]R1,h is equal to zero; and finally, an optimum emergency reserve capacity R in an electrical area in the whole process of frequency fluctuation after a large-scale direct current locking fault is determined. The power system emergency reserve capacity configuration method is able to improve the transient state safety level of a system after the occurrence of faults so as to comprehensively guarantee the safety of the system after the occurrence of faults.

The invention discloses an energy storage primary frequency modulation control method based on a dynamic droop coefficient and an SOC recovery base point. The method is characterized by dividing an energy storage frequency modulation process into a frequency modulation stage and an SOC recovery stage by taking a power grid frequency modulation dead zone as a segmentation boundary; at the frequencymodulation stage, using the SOC and the maximum frequency deviation as controlled variables to adaptively adjust the energy storage output depth so as to prevent the energy storage SOC from being saturated or exhausted; at the SOC recovery stage, adopting a dynamic SOC recovery base point adjustment method adapting to load changes, then designing an energy storage output determination method considering SOC recovery requirements and power grid bearing capacity, and finally designing a double-layer fuzzy controller to achieve the determination of a dynamic SOC base point value and an energy storage output value. The method has the advantages of being scientific, reasonable, being high in applicability, being capable of guaranteeing the frequency modulation effect and the state of the energy storage SOC, being capable of maintaining the long-term stable output of energy storage and the like.

The invention discloses an optimization method of phase compensation link time constants of a power system stabilizer. The optimization method comprises the following steps of (1) measuring non-compensation phase-frequency characteristics of a unit excitation system by adopting a dynamic signal analyzer on the spot and reading a phase angle within a range of 0.1-2.0Hz; (2) converting the power system stabilizer into the PSS of a rotating speed deviation single-input mode according to structure characteristics of an electric power and rotating speed deviation double-input signal of a PSS4B-W; and (3) building a parameter optimization model of the PSS4B-W by employing third-order lead-lag phase compensation link time constants of the PSS4B-W as optimization variables and in-phase additional moment generated by the PSS and [delta]omega shaft as an optimization target and solving the time constants through an adaptive weight particle swarm optimization algorithm. According to the optimization method, optimized parameters, meeting the industry standard requirements, of the PSS4B-W can be quickly and efficiently found out.

The invention relates to a power system intelligent low-frequency low-voltage load reduction method based on an intelligent household electrical appliance. The method comprises the following steps: when large disturbance in a system is monitored, determining whether the frequency and the voltages of the system are decreased to preset load reduction motion values, and once the frequency and the voltages reach the load reduction motion values, obtaining power shortage in the system and determining a load capacity which should be cut from the system; starting an intelligent household electrical appliance load reduction module; starting low-frequency low-voltage load reduction; and if intelligent household electrical appliance load reduction cannot enable the system frequency and voltages to restore to normal operation scopes and the frequency and voltages are continuously decreased to preset values of the low-frequency low-voltage load reduction, starting the low-frequency low-voltage load reduction, according to a residual load reduction amount, successively starting a basic round and a special round of low-frequency load reduction for cutting off loads until the frequency is restored to the normal operation scope, and embedding one low-voltage load reduction module in each round of low-frequency load cutting. According to the invention, after a power system is disturbed, the frequency and voltages can be effectively and rapidly inhibited from dropping and even collapsing, the load cutting amount is small, and the economic loss is small.

The invention relates to a low frequency oscillation modal identification method based on improved generalized morphological filtering and aims to the low frequency oscillation modal identification of power system. A generalized morphological filtering is utilized to carry out de-noising processing to low frequency oscillation signals, and TLS-ESPRIT algorithm in adopted to do modal identification. For a problem of determining the order in the process of the TLS-ESPRIT algorithm being used to do the low frequency oscillation model identification, a ratio method between singular value difference and maximum singular value is adopted to determine the older. The method has the advantages of less calculation, fast speed, and less influence from subjective factors in the process of the order determination. According to the invention, the accurate identification of the low frequency oscillation mode under the noise interference is achieved, and a good application prospect is achieved.

A power supply system including a battery module and a converter unit. The system includes a bidirectional DC-DC converter as a component of a battery module voltage control device that is connected between a load and a secondary battery and that changes a discharge voltage of the secondary battery and outputs the discharge voltage to the load. Moreover, a voltage control unit, which can include a control unit and the bidirectional DC-DC converter, changes the discharge voltage of the secondary battery to an output voltage target value to be outputted to the load.

The invention discloses a double-fed wind turbine generator subsynchronous oscillation suppression method of a broadband rotor additional damping, which is implemented in control of a rotor-side converter of a doubly-fed fan and used for suppressing subsynchronous oscillation of a doubly-fed wind turbine generator; the three-phase currents of a double-fed fan rotator is detected; after the rotor current is detected, Park transform is performed on the three-phase currents to form a DQ axis system; filtering is performed by using a filter, sub-synchronous frequency band components of the rotor currents are extracted in real time, and then phase compensation and proportional amplification control is performed, the virtual additional rotor damping is added to an original converter DQ-axis rotor voltage control command. A control strategy of a fan rotor-side converter is changed to perform subsynchronous oscillation suppression, broadband additional damping control is increased on the rotor-side so as to enhance the damping characteristics of a subsynchronous frequency band of the wind turbine generator, the electrical damping of the whole wind turbine generator is enhanced, the subsynchronous oscillation of the system is suppressed; and the method can avoid additional devices, and is conductive to engineering implementation.

The invention provides an electronic regulator model for a water turbine adjusting system. The model has an openness control mode, a power control mode and an isolated-network control mode. The openness control mode or the power control mode can be manually selected as a control mode of a normal grid-connected unit. The openness control mode or the power control mode can be automatically switched with the isolated-network control mode. The power control mode has two sets of PID control parameters which can be automatically switched. The electronic regulator model is clear in structure and strong in universality, the parameter meaning of the model is definite, and the parameters can be conveniently obtained through measurement on site. The modeling process is efficient, the precision is high, and the actual control function can be accurately simulated, so that the actual engineering demands can be satisfied. Moreover, the universality of model application is improved. The meaning of the control parameters of the model is clear, and the parameters are conveniently obtained through a field test, so that the model has actual engineering application value. A reliable and accurate basis is provided for stable analysis and calculation of an electric power system, so that the stability of the electric power system is ensured.

The invention discloses a method for positioning and suppressing an ultralow-frequency oscillation disturbance source. The method comprises the following steps of SS1, positioning an ultralow-frequency oscillation disturbance source unit; SS2, identifying the system low-order linear model of the disturbance source unit; SS3, providing the disturbance source unit with an additional damping controller, and optimizing the parameters of the additional damping controller by using an intelligent algorithm; and SS4: performing disturbance suppression by using the additional damping controller. The method for positioning the ultralow-frequency oscillation disturbance source is characterized by constructing a corresponding Hamilton expression according to a rotor motion equation, obtaining the energy change rate of each generator input into a power grid, and determining the ultralow-frequency oscillation disturbance source according to the energy variation amount input into the power grid. Themethod suppresses system ultralow-frequency oscillation, and improves the stability of small interference.