37 results about "Mean value model" patented technology

The invention provides an average value modeling and control method applicable to a VSC-MTDC (Voltage Sourced Converters Multi-terminal Direct Current) system. The method comprises the following steps of 1, building a mathematical model of a VSC based on d and q rotational coordinates, and calculating active power and reactive power of an AC side of a converter by combining a VSC-MTDC power transmission system; 2, building a VSC-MTDC controller by taking the active power and the reactive power of the AC side of the converter as reference values to achieve cooperative control of a plurality of converter stations; and 3, simplifying a control process of the VSC-MTDC, and building a VSC-MTDC average value model. The average value model can be applied to a multi-terminal direct current power transmission system, the simulation speed is greatly increased, the simulation efficiency is improved, and the mathematical calculation amount is reduced.

The invention relates to an average value model of an MMC and belongs to the technical field of power transmission and distribution. Through an average value model of a prior MMC, direct-current faults of an MMC system and converter blocking can not be precisely simulated. According to the core technical scheme of the improved average value model, firstly, a diode is connected to an equivalent capacitor of the direct-current side of the average value model in parallel so that the capacitor voltage of the equivalent capacitor can be a nonnegative number all the time under serious double-pole direct-current short circuit fault conditions; then, the alternating-current side of the average value model is connected with the direct-current side of the average value model through a cascading switch very large in turn-off resistance, and it can be simulated that alternating-current side voltage bias can be accurately generated when single-pole direct-current grounding faults happen; finally, a fly-wheel diode is connected to an alternating-current side bridge of the average value model in series through a cascading bypass switch, and a reverse fly-wheel diode is connected with an equivalent capacitor branch circuit of the direct-current side in series through a bypass switch so that the average value model can have functions like simulating converter blocking or starting and locking after direct-current faults.

The invention provides an ADPSS-based distributed power flow controller modeling and simulation method. Electromagnetic transient simulation of a distributed power flow controller on a power system digital simulation system ADPSS platform can be realized. The method comprises the steps that a double-loop power transmission system simulation model is established under the ADPSS / ETSDAC simulation environment, a DPFC device is appropriately simplified by using the UDM function module of the ADPSS / ETSDAC, a series side current converter equivalent mathematical model is established by using an equivalent voltage source, and a parallel side current converter equivalent mathematical model is established by using an MMC mean value model. The dynamic and static characteristics of the DPFC device and the regulation and control function for the system power flow can be reflected under the premise of guaranteeing the simulation scale so that the simulation accuracy can be guaranteed and the simulation time can be shortened; and the more reliable, more comprehensive and more detailed theoretical support can be provided for actual power grid safe and stable operation of the DPFC device, and the foundation can be laid for popularization and application of the distributed power flow controller.

The invention discloses a method for calculating the thermal performance of a marine main engine cylinder in the working process. The invention is based on an average value model and a seiliger model, and takes the equal-volume pressurization ratio a and the equal-pressure pre-expansion ratio b as the cycle parameters of the seiliger model, based on a large number of measured data and related theories to fit the equal-volume supercharging ratio a and the equal-pressure pre-expansion ratio b, and apply it to the simulation of the working process of the ship's main engine cylinder. The invention can be used for the steady-state calculation of the working process in the cylinder of the main engine, can improve the calculation accuracy, and reduce the parameters needed for the calculation.

The invention provides a modeling method suitable for VSC-HVDC system. The modeling method suitable for the VSC-HVDC system comprises the steps: step 1: average simplifying rectification loop; step 2: average simplifying inverter loop; and step 3: average simplifying direct current transmission loop. The invention further provides a relevant converter and a synchronous prototype. The rectification loop, direct current transmission loop and inverter loop of the synchronous prototype use an average value model to form a whole converter average value model. The modeling method suitable for the VSC-HVDC system is suitable for the grid-connected wind farm, and can satisfy most simulation requests under the situation without involving the converter control method.

The invention discloses an engine hardware-in-the-loop testing method and system. The method includes: the real-time processor receives the simulation test instruction carrying the simulation model setting parameters, uses the real-time simulation composite model to simulate the engine test condition corresponding to the simulation model setting parameters, acquires the engine measurement signal, and sends the engine measurement signal to the engine control unit, wherein the real-time simulation composite model includes a subsystem simulation Gaussian model and a subsystem simulation mean value model; the engine control unit receives the engine measurement signal, uses the control program to be tested to process the engine measurement signal, obtains the target control signal, and sends the target control signal to to the real-time processor; the real-time processor receives the target control signal, uses the real-time simulation composite model to adjust the model running state according to the target control signal, and obtains the simulation test running result. This method can ensure both simulation calculation accuracy and real-time performance during the testing process.

The invention relates to a mean value model in a modular multilevel converter (MMC), and a simulation method of the same, and belongs to the field of flexible power transmission, and power electronics. The mean value model in a modular multilevel converter, and the simulation method of the same aim at improving the accuracy of a mean value simulation model in a modular multilevel converter and accelerating dynamic response. The mean value model in a modular multilevel converter includes an alternating current side equivalent model, a direct current side equivalent model and a capacitor equivalent model. The mean value model in a modular multilevel converter, and the simulation method of the same can improve the dynamic response speed of the system by means of a method of extracting the equivalent capacitors individually from sub modules and utilizing the controlled voltage source to control the direct current side. The mean value model in a modular multilevel converter, and the simulation method of the same can control the switches of the alternating current side equivalent model and the direct current side equivalent model, and the equivalent capacitors and equivalent voltage of sub modules at the same time to control the simulation model to realize simulation of stable operation of the MMC, operation in fault, of the MMC, and starting of pre charging at the same time.

The invention relates to a key error source identification method that affects the precision decay of a three-axis machining center, and belongs to the field of precision design of numerical control machine tools. The method first uses a precision measuring device to obtain the error values ​​of various precision of the machine tool at different measurement time nodes, and calculates each precision The error mean value of each item from the first measurement to each measurement time node is determined, and the error mean value distribution interval of each precision is determined; then, the error mean value of each item is integrated at the tool forming point, and the error mean value of the spatial distribution is integrated in the space dimension , and then establish the comprehensive spatial error mean value model of the three-axis machining center; finally, according to the distribution interval of each error mean value, the sensitivity analysis method is used to analyze the influence of the error mean value of each precision index in the interval on the comprehensive spatial error mean value, and determine the comprehensive spatial error value For the sensitivity of various precision indicators, the identification of key error sources is completed.

The invention discloses a multi-terminal VSC-HVDC (Voltage Source Converter Based High Voltage Direct Current) system droop control coefficient determining method comprising the following steps: first, a DC system state space model containing droop control is built based on a mean value model of VSC, and the action mechanism of droop control is analyzed using the model; and then, a droop coefficient determining problem is converted into an optimization problem with minimum system hybrid sensitivity Frobenius-Hankel norm as the objective based on the system model, and the eigenvalue constraint and steady-state error constraint of a closed-loop system are considered to optimize the stability and robustness of the system. The method can maximize the stability of the system under disturbance and make the system have certain fault ride-through capability. Moreover, the method can be combined with other droop coefficient determining methods, and a droop controller meeting different requirements or achieving different functions can be designed by increasing constraint conditions or changing the optimization objective.