1 Preface Statistical analysis shows that through proper simulation, 50% of design errors in the realization of power systems can be found. Therefore, simulation plays an important role in product design and production, which can shorten production cycle and reduce production cost. The more complex the simulation tools, the more realistic the circuit system is, and the more design errors are found, the more helpful the circuit design is. SPICE is a traditional circuit simulation software, its model library includes basic circuit components (resistors, inductors, capacitors, independent and controllable power supplies, transformers, transmission lines), switches and some semiconductor devices (diodes, BJT, JFFT, MESFET and MOSFET) and so on. SPICE is mainly used for simulation analysis of DC, AC, transient, pole, distortion, sensitivity and noise of electronic circuits and common circuits. Because SPICE uses the variable step integral node method, it can accurately simulate the switching power electronic circuit. However, in SPICE's model library, there are no special models for power systems and electric drives such as motors, circuit breakers, surge arresters, and thyristors. In order to simulate the power system, users must use the existing components in SPICE to construct the system. The model is needed, which will take time and effort. An easy-to-use engineering computing language, the latest version to date is MATLAB 5.3, which combines computation, visualization, and programming into an interactive work environment based on matrix operations. Here you can perform engineering calculations, algorithm research, modeling and simulation, data analysis and visualization, science and engineering drawing, application development and more. SIMULINK is one of the most widely used software packages for dynamic modeling and simulation in the MATLAB environment. It supports continuous, discrete, and a mixture of both linear and nonlinear systems, as well as multi-rate systems with multiple sample rates. Now, the version of SIMULINK has been developed from 1.0 to 3.0. It is more powerful and more convenient to use. Especially since the 2.0 version, the Power System Module (PSB) has been added, which shows great advantages in the simulation of the power system. Sex. The PSB uses a variable-step integration method that allows very accurate simulations of nonlinear, rigid, and non-continuous systems to accurately detect breakpoints and when switches occur, so PSB is a simulation of circuits including power electronics. Very handy tool. The PSB is compatible with MATLAB and SIMULWK. Users can easily create a chart in the PSB, use the modules in SIMULINK to assemble the control system, and use the digital design and analysis tools provided in MATLAB. 2 Circuit modeling and state space description In PSB, the dynamic description of the linear part of the circuit is realized by continuous time domain state space equation. N integrators can describe an N-order linear system with multiple inputs and multiple outputs. The output vector is obtained by linear combination of input and state variables. In the circuit, the inductor current and capacitor voltage are state variables. Since all components in the power system can be constructed with these two quantities, it is not difficult to obtain a state space expression for a system composed of inductors and capacitors. For example, a motor typically includes rotor current, stator current, and magnetic flux, while for a switching device such as a thyristor or GT0, selecting the associated state variable is less straightforward, depending on the macro model of the switch. In the PSB, it is described by a series RL circuit and logic circuits designed according to different switch types. In these models, the inductor current is the state variable of the switch. However, both the switch and the motor are non-linear, and their models look more like voltage-controlled current sources, except for the linear variable available state variable expressions. The current of these current sources is the input to the linear portion. 3 Basic Component Model PSB is used to simulate power systems and electric drives. There are seven types of models available for users to choose from (power, linear and nonlinear passive components, three-phase components, couplings, measuring devices, motors and Power electronics) Power supplies include an AC voltage (current) source, a DC voltage source, and a controllable voltage (current) source. Passive components include series and parallel RLC branches, linear and saturated transformer n-section lines and distributed lines, and switch and surge breaker models. The three-phase component is a combination of other types of models, providing the user with a basic three-phase library, and the user can also refer to these models to build other three-phase systems. Joints and measuring devices are used for coupling between different systems. The motor unit includes several models of synchronous and asynchronous. Power electronics models are especially important in the simulation of drives and power converters, and this section is highlighted below. A macroscopic model of a two-pole MOSEFT and an ideal switch is included in the power electronics library, where the diode can be considered as the core model of other semiconductor devices. The basic diode model is described by a first-order system consisting of Ron, Lon, and UF series branches. It represents the energy storage of the device and gives the state variable. Generally, Ln=10H is taken as the default value. This value is considered to be stable. Sex and computational speed are also suitable for most applications where the converter switching frequency is 20 kHz. Ron represents the dynamic resistance of the semiconductor, and the constant voltage source Uf is the forward voltage drop (junction voltage drop). In order to avoid the occurrence of algebraic rings, Lon can't take zero. Relatively speaking, the requirements for Ron and Uf are not so harsh when considering computational stability, so Ron can be set to zero; in the ideal switch and MOSFET model, There is no junction voltage drop in the on state and UF is automatically set to zero. In the off state, the state variable is and its microcomponent dis/dt is forced to zero. The basic macromodel of the diode has ON/OFF characteristics that characterize the basic behavior of the other four devices. In fact, the essential difference between the basic macro models of these types of power switches is the different switching logic. Therefore, the basic circuit model plus the appropriate switching logic can describe the components of all power electronics libraries. Since the semiconductor is a highly nonlinear current source that is driven by the voltage across the terminals, it cannot be directly connected in series with other semiconductor models or current source branches, so a node must be used to provide the branch containing the current source. A circulating circuit of instantaneous current difference. Conventional snubber circuits (like R~C, or R~CD, C) can be used in parallel with these devices to accomplish this additional task. The choice of snubber circuit parameters is based on common standards and depends on device type, topology, power and operating frequency. Selecting the appropriate parameters avoids internal high frequency oscillations caused by the interaction of the RL equivalent circuit and the RC buffer loop in the device. High-frequency oscillations force the variable-step algorithm to properly shorten the computational step size, which increases the simulation step size. An example of an application for PSB is an asynchronous motor powered by a sinusoidal PWM inverter. The frequency of the sinusoidal modulation wave is 50 Hz, and the frequency of the triangular carrier is 300 Hz. The PWM inverter in the figure is completely composed of a standard SIMULINK module. Its output is connected to the stator winding of the asynchronous motor through a controllable voltage source module, and the rotor of the motor is short-circuited. The model of the motor is more complicated. There are both electrical and mechanical parts. The ordinary motor model also has more than 10 equations and more than 20 parameters. In PSB, the electrical part of the motor model is composed of a fourth-order state space model, and the mechanical part is composed of a two-stage system. If you build your own model, it will not only take time and effort, but also be proficient in the principle and construction of the motor. With PSB, it is much more convenient to do simulation. The simulation waveform is as shown, where /s, n, and Te are rotor current, stator current, speed, and torque, respectively. The circuit is simulated and found that the simulation waveforms are the same, which shows that the simulation accuracy of the PSB is the same as that of the PSPICE. However, because PSB's model library is more powerful and the interface is more intuitive, it has greater advantages than PSPICE. 5 Conclusion Due to the rigidity and non-linearity of modern power systems, simulation tools are required to have comprehensive performance, and the graphical user interface has become an important part of measuring the quality of simulation tools. PSB can meet these requirements, and it can accurately detect system breakpoints, so it is more suitable for simulation analysis with switching device circuits. Another important advantage of PSB is that the models in the SIMULINK standard library can be assembled into new control modules in the PSB. Moreover, the PSB library contains models of power electronics and motors, so it is more suitable for simulating power systems and electric drives. The Waterproof and oil repellent fabric is also called [breathable fabric". It is a functional fabric that combines oil-proof, waterproof, moisture-permeable and warm-keeping properties after PU coating or film coating. It can resist the invasion of rain and stains. The body's hot air and sweat can be discharged in time to keep the body dry, warm and comfortable. Water Oil Repellent Fabric,Repellent Fabric,Waterproof Fabric,Oil Repellent Fabric Xinxiang Xinke Protective Technology Co, Ltd. , https://www.coverallsuits.com
The Waterproof and oil repellent fabric produced by Xinke Protective has excellent waterproof and moisture permeability. The products have been tested by the authoritative testing institutions SGS and ITS. The water pressure resistance can reach 10000 MM or above and the moisture permeability can reach 8000g/m2 for 24 hours.
Of course, you can also combine anti-static fabric and flame retardant fabrics or insect repellent fabric to combine their functions to choose the right multi-functional fabric.