36results about How to "Good for engineering practice" patented technology

The invention relates to a method for designing a crowbar resistor for passing through the low voltage of a double-fed type wind generator system, belonging to the technical field of wind power generation and comprising the following steps: firstly, acquiring the rotor turns ratio, the rotor resistance, the rotor rated current and the rotor current upper limit of a double-fed generator of the wind generator system; computing current overload multiples according to the rotor rated current and the rotor current upper limit; acquiring the DC bus voltage of the wind generator system; computing a per-unit parameter kc of the crowbar resistor according to the DC bus voltage, the current overload multiples, the rotor rated current and the rotor resistance; obtaining a modified per-unit parameter kc after properly increasing the per-unit parameter kc; and finally, designing the resistance value of the crowbar resistor to be Rc=kcRr. The method designs the crowbar resistor according to a principle of the LVRT process of a DFIG system, adopts the clamping effect of a DC bus in the LVRT process, ensures the LVRT property while having less current and ensures the safety of a fly-wheel diode of a rotor current transformer.

The invention discloses a pile top stiffness adjustment device based on a variable-strength supporting material, which comprises: a cover plate and a cylinder body, the cylinder body is in the structural form of an upper part opening and a lower part sealing, and a variable-strength metal supporting material is arranged in the cylinder body; The cover plate is arranged on the cylinder body and is in contact with the upper end of the variable-strength metal support material; the rigidity of the variable-strength metal support material is greater than that of the side wall of the cylinder body. The invention effectively utilizes the appearance parameters of the variable-strength metal support material to change its own compression performance, and overcomes the fact that the volume of the support material itself cannot be changed in the existing pile top stiffness adjustment device, and the vertical compression can only be caused by the crushing or discharge of the support material. Disadvantages of displacement, high adjustment accuracy, stable operation, simple preparation process, low manufacturing cost, convenient installation, the load-displacement curve of the stiffness adjustment device under the action of the upper load has a significant linear change characteristic, without any fluctuation phenomenon, there is It is beneficial to further promote the engineering practice of pile-raft foundation with controllable stiffness.

The invention discloses a fuzzy control method of a direct current transmission converter based on command filtering. A fuzzy logic system is employed to approach unknown nonlinear terms in a power grid side converter system of a voltage source type direct current transmission converter system. A command filtering technology is introduced to solve the inevitable problem of 'calculation explosion'in the back-stepping control technology, the error of the filter is reduced by introducing a filtering compensation mechanism, and the command filtering technology has good inhibition effect on higherharmonics; the problems of unknown system parameters and uncertain disturbance intervention can be solved by introducing a self-adaptive control technology; under the control method of the invention,only one self-adaptive parameter exists in the controller, thereby reducing the on-line calculation burden and facilitating engineering practice. Simulation results show that the method can achieve quick and stable response to power and can achieve control of the power grid side converter.

The invention, which belongs to the field of the anti-interference technology of the radar, discloses an optimized station distribution method for a netted radar unit under deceptive jamming. The method comprises: a deceived probability of a netted radar is calculated; a target function of a minimized deceived probability is constructed; coverage ranges of all node radars in the netted radar unit are calculated and a target function of a maximized coverage range is constructed; according to the target function of the minimized deceived probability and the target function of the maximized coverage range, a combined optimized target function is established; a constraint condition of station distribution of the netted radar unit is determined; on the basis of the constraint condition of station distribution of the netted radar unit and the combined optimized target function, an optimization formula of station distribution of the netted radar unit is constructed under deceptive jamming; and station distribution positions of all node radars in the netted radar unit are obtained based on the optimization formula of the station distribution of the netted radar unit under deceptive jamming. Therefore, the radar system resources are saved and precise and effective inhibition of the deceptive jamming can be realized.

The invention discloses a method for judging and controlling the dynamic stability of flexible direct current transmission. The judgment method includes the following steps: unlocking the converter station of the flexible direct current transmission system, allowing the flexible direct current transmission system to operate in a non-island control mode; extracting the flexible direct current The corresponding parameters of the power transmission system, the parameters include the effective value of the AC system voltage U t0 , flexible DC output reactive power Q vsc0 , the gain k of the phase-locked loop PLL p and the proportional-integral time constant k of the phase-locked loop PLL i ; Calculate the short circuit ratio SCR, and calculate U t0 , Q vsc0 The per unit value of ; calculate the key stability component; check the sign of the key stability component and determine the stability of the HVDC system. The method of the invention only needs to simply calculate the value of the key stable component, and judge the stability of the system through the sign of the value, which is simple and easy to implement, and is beneficial to engineering practice.

The invention discloses a receiving-end cascaded hybrid direct current coordinated control method based on dynamic limiting, comprising the following steps: under the master-slave control mode adopted by the MMC, the overall UI characteristic curve of the receiving-end cascaded hybrid direct current transmission system is clarified ; The dynamic limiting link is set in the fixed power flexible converter station of cascaded hybrid direct current transmission at the receiving end. The method of the invention can release the reactive power support potential of the flexible DC to the AC system to enhance the voltage stability of the AC system when the receiving end system fails, and can automatically limit the active power output of the constant power station to avoid the flexibility of the constant DC voltage. The finishing and inverter mode of the converter station is changed, which improves the system stability in terms of active frequency and reactive voltage.

The invention discloses an open-type magnetic field shielding device capable of adjusting at full frequency band, and belongs to the technical field of electromagnetic compatibility. The magnetic field shielding device comprise a magnetic field searching coil, a magnetic field detection oil, a driving circuit, a magnetic field adjustment coil and a corresponding matched sample table, wherein the magnetic field detection coil is used for monitoring change of an environmental magnetic field, the magnetic field adjustment coil is driven to offset with an external magnetic field by the driving circuit after a power is amplified, the magnetic field searching coil is placed right above the device, the sample table is placed in the center of the magnetic field adjustment coil, the magnetic fielddetection coil is connected with a magnetic field detection probe and is placed on the sample table, the driving circuit is placed at an outer side of the magnetic field adjustment coil, and a shielded magnetic field is arranged above the driving circuit. The magnetic field shielding device capable of adjusting at full frequency band is more beneficial for engineering practice.

The invention provides a magnetic field shielding system based on a closed superconducting coil group, which includes a first-level superconducting coil and a second-level superconducting coil arranged coaxially and coplanarly around the same central axis of symmetry, the first-level superconducting The coil is connected in series with the second-level superconducting coil to form a closed loop, and a shimming area is formed inside the second-level superconducting coil to shield the external magnetic field. The present invention further provides a magnetic field shielding device. The process of the magnetic field shielding system in the invention has a simple realization route and is beneficial to engineering practice.

The invention relates to a method used for balancing three phases of direct current side voltages of a chain power regulating device, and belongs to the technical field of the control of power electronic devices. The method comprises the following steps of: acquiring direct current side voltages of each H-bridge unit in the three phases of a chain power regulating system; filtering ripples from the direct current side voltages; taking the direct current side voltages of which the ripples are filtered as feedback signals; calculating an average value of the three phases of the direct current side voltages based on the direct current side voltages; taking difference values between the three phases of the direct current side voltages and the average value as command signals; calculating an amplitude value and a phase angle of a negative sequence voltage according to the difference values by utilizing corresponding formulae; obtaining a required negative sequence according to an electric angle of a power supply voltage at a device grid place; and after the negative sequence voltage is superposed to an output voltage command used for power control in the device, driving the device to output an alternating current voltage so as to realize the balance control of the three phases of the direct current side voltages. The method of the invention has the characteristics of software implementation, simple algorithm, obvious effect and contribution to engineering application.

The invention discloses a coordinated control method for improving the stability of a cascaded hybrid direct current transmission system. When a fault occurs, according to the transmission power of the line, the output power of the LCC on the inverter side, and the steady-state output power of the constant direct current voltage MMC, the multi-drop point MMC is controlled. The active power command value is regulated to avoid the conversion of the constant DC voltage station from inverter to rectifier, and to prevent the phenomenon of large-scale transfer of power on the AC side of the receiving end. At the same time, after the fault is cleared, the problem of large fluctuations in the system recovery process can still be alleviated, so that the system can quickly and smoothly return to the rated operating state. The invention can realize the smooth transition of the system under typical faults of AC and DC, and improve the stability of the DC receiving end system.

The invention discloses a neural network output feedback self-adaptive robust control method based on a launch platform. The steps of the method are as follows: firstly, a mathematical model of the launch platform is established, and secondly, a neural network state observer and a neural network state observer based on the neural network state observer are designed. Network output feedback adaptive robust controller; Finally, the stability of the neural network state observer and neural network output feedback adaptive robust controller is proved by using Lyapunov stability theory. The invention solves the problem that the real value of the state quantity in the motor servo system of the launch platform is difficult to obtain.

The invention discloses a method for evaluating the impact of the topology of a DC power grid on fault currents. First, the equivalent circuit of the grounding mode of the metal return line and the earth return line is established, and a three-dimensional mesh circuit diagram decoupling method is proposed, so that the equivalent circuit plane An improved high-frequency equivalent model was proposed, and fault current calculation methods were deduced for radial and ring networks, and the theory was extended to n terminal network, and then analyzed the influence of topology parameters and structure on fault current; proposed the evaluation index of topology influence on fault current k , which can effectively evaluate the impact of the initial fault current level on the grid topology; k The magnitude of the value determines which converter stations the DC grid unipolar short-circuit fault current mainly comes from at the initial stage. The evaluation method proposed by the invention avoids cumbersome calculations, and can directly and quickly evaluate the influence of the topology on the fault current.

The present invention provides a networked radar site layout method based on the particle mechanism immune crowd search, including: establishing the deception probability model and detection range model of the networked radar under deceptive interference; constructing a joint optimization objective function, and determining its constraint conditions ; Initialize the key parameters of the network radar system and the basic parameters of the search team, determine the number of iterations of the particle mechanism immune crowd search; establish the fitness function, initialize the best position of each searcher and the best position of the search team group; use crowd search Method to prepare the vaccine; update the position of each searcher and vaccinate the search team; use elite selection and annealing selection to perform immune selection on the search team and update the best position; use crowd search method to perturb the prematurely convergent search team; judge whether the termination criteria are met. The present invention can quickly and accurately find the optimal radar deployment position without falling into local optimum.

The invention discloses a flexible DC power transmission oscillation frequency prediction and control method under a non-island control mode. The prediction method comprises the following steps: unlocking a convertor station of a flexible DC power transmission system, and running the flexible DC power transmission system in the non-island control mode; extracting corresponding parameters of the flexible DC power transmission system, wherein the corresponding parameters comprise an AC system voltage effective value UtO, a gain kp of the phase-locked loop PLL and the proportion integral time constant ki; taking the AC system voltage as a reference value, computing the prediction oscillation frequency; and checking whether the prediction oscillation frequency is a non-zero real number; if theprediction oscillation parameter is the non-zero real number, regarding that the flexible DC power transmission system is unstable, the flexible DC power transmission system has the oscillation at the frequency band and cannot be put into the flexile DC power transmission; if the virtual number is equal to zero, regarding that the flexible DC power transmission system is stable, the frequency band oscillation mode is inexistent, and the system can be put into the flexible DC power transmission. The corresponding oscillation frequency can be computed through simple parameter, the prediction issimple and practicable, and in favor of engineering practice.