Power electronic circuit dynamic graph simulation method and system for teaching assistance

Abstract

The invention discloses a power electronic circuit dynamic graph simulation method and system for teaching assistance, and belongs to the technical field of power electronics. According to the method, basic elements of a circuit are configured, a semiconductor element is regarded as an ideal switch, a power electronic circuit model is established according to different equivalent topologies in different switching states, and a numerical solution of the power electronic circuit at each sampling time point is calculated through discretization iteration on a time domain. After steady-state detection, sampling data of circuit working voltage and current waveforms are output, and a message system is used for enabling the circuit waveforms to change along with input parameters in real time. The system comprises a starting module, an input module and an output module, and provides simulation demonstration of 18 power electronic circuit models. The method has the advantages of efficient modeling solution, interactive feedback implementation, fine parameter adjustment and the like, and can effectively improve the ability of students to understand and apply the power electronic technology.

Description

Technical Field

[0001] The present invention belongs to the technical field of power electronics, and in particular relates to a power electronic circuit dynamic graphic simulation method and system for auxiliary teaching. Background Art

[0002] In recent years, with the popularity of the new teaching trend of combining online and offline teaching, computer and multimedia technology have added diverse and flexible optional forms to the teaching process. However, there are some problems with the existing power electronics teaching, such as abstract and complicated course content, outdated and insufficient experimental equipment, and the disconnect between practical teaching and theoretical teaching. These problems make it difficult for students to master the principles of power electronic circuits and lack the ability to understand and solve practical engineering problems. Against the background of the widespread application of computer and multimedia technology in teaching, a graphics system developed for teaching can intuitively demonstrate the changing laws of circuit working states, compare the effects of different circuit parameters on circuit operation, provide an intuitive and comparative principle demonstration method for the teaching process, and enhance students' understanding and application capabilities of power electronics technology. Summary of the Invention

[0003] The present invention aims to overcome the shortcomings of the prior art and provide a method and system for dynamic graphical simulation of power electronic circuits for teaching purposes. This method is simple to operate, covers the basic teaching content of power electronics, and can display the voltage and current time-domain waveforms of an ideal power electronic circuit during stable operation based on set circuit parameters. The waveforms can also change in response to real-time user input of circuit parameters, enhancing the intuitiveness and interactivity of teaching.

[0004] The specific technical solutions adopted in the present invention are as follows:

[0005] In a first aspect, the present invention provides a method for dynamic graphics simulation of power electronic circuits for teaching assistance, as follows:

[0006] S1: Configuring basic circuit components; the basic circuit components include linear passive components, semiconductor components, power supplies, and transformers;

[0007] S2: Based on the basic circuit elements, the semiconductor elements are regarded as ideal switches. According to the equivalent topology under different switching states, the nonlinear power electronic circuit is converted into a linear time-varying circuit and a differential equation system is established to construct a power electronic circuit model;

[0008] S3: Based on the power electronic circuit model, through discretization iteration in the time domain, a numerical solution at each sampling point in a time period in which the switch state of the power electronic circuit remains unchanged is calculated, and the numerical solution is passed to the next switch state as an initial condition for discretization iteration to solve the power electronic circuit model;

[0009] S4: Based on the solved power electronic circuit model, set the steady-state criterion of the power electronic circuit to ensure that the model outputs voltage and current waveforms when working stably;

[0010] S5: Based on the power electronic circuit after the steady-state criterion is set, the dynamic simulation results of the power electronic circuit are output visually, so that the circuit waveform changes in real time according to the changes of the input parameters.

[0011] Preferably, the S1 is as follows:

[0012] S11: Arrange linear passive components including resistors, inductors, and capacitors so that: the resistance, inductance, or capacitance of the linear passive components are constant, and the withstand voltage and current are sufficiently high; the equivalent series resistance of the inductor is 0; and the equivalent series resistance of the capacitor is 0, with no leakage current.

[0013] S12: Configure semiconductor components to meet the following requirements: Ignore switching time, and treat the switching process as an instantaneous switch from on to off or off to on; the on-resistance is 0, the off-leakage current is 0, and no fault breakdown occurs within the operating voltage range; ignore various capacitive effects of semiconductor components, and there is no switching loss; for paired switching elements in power electronic circuits and full-bridge and half-bridge structures, no dead time is set for the switch control signal;

[0014] S13: Configure the power supply and transformer to meet the following requirements: the DC power supply, single-phase or three-phase AC power supply is an ideal voltage source, the output voltage waveform meets the ideal requirements, and will not change due to the influence of the output current; the internal resistance of the voltage source is 0, and the line parasitic inductance of the AC power supply is ignored; the voltage and current of the transformer model meet the following requirements:

[0015]

[0016] Where n is the number of windings in the transformer model, u j is the voltage of the jth winding, N j is the number of turns of the jth winding, i j is the current flowing through the jth winding.

[0017] Preferably, the S2 is as follows:

[0018] S21: Considering the semiconductor element as an ideal switch, and analyzing possible states of the power electronic circuit according to different equivalent topologies under different switching states;

[0019] S22: List the differential equations for each energy storage element, and apply the conclusions of Kirchhoff's voltage law and Kirchhoff's current law based on the equivalent topology to obtain a differential equation system containing four or more independent equations to represent the corresponding equivalent topology for solving the model in S3; the energy storage elements include inductors and capacitors;

[0020] S23: The process of modeling the power electronic circuit using a group of differential equations is completed by segmenting the time according to different working states of the power electronic circuit.

[0021] Preferably, the S3 is as follows:

[0022] S31: Convert the differential equations representing the topology in S22 into integral form;

[0023] S32: Discretize the power electronic circuit model in the time domain;

[0024] S33: After time domain discretization, each sampling point is numbered with 1, 2, ..., p in sequence;

[0025] S34: Given the voltage and current values of each energy storage element in the initial state, the voltage and current values of the next time sampling point are calculated using the voltage and current values of the previous time sampling point, and finally the numerical solution of the equation for each time sampling point is calculated sequentially through iteration;

[0026] S35: When a switch state transition is detected, the numerical solution obtained by the power electronic circuit under the current switch state condition will provide the initial state condition under the next switch state. Through continuous iteration and transfer, the voltage and current values of the power electronic circuit at each time sampling point in the entire time range are obtained;

[0027] S36: Based on the known voltage and current of the energy storage element, combined with Kirchhoff's voltage law and Kirchhoff's current law, obtain the voltage and current waveforms of other circuit components other than the energy storage element.

[0028] Furthermore, the S32 is specifically as follows:

[0029] The time axis is divided into (p-1) segments at a constant sampling time interval Δt, and the numerical solutions at the obtained p sampling points are used as the solutions to the model equations.

[0030] Furthermore, the S35 is specifically as follows:

[0031] For an electrical quantity that is subject to delay interference of x discrete sampling time intervals, calculation is started using the equivalent topology after the switch state is converted at the (x+1)th sampling point. Before this point, calculation is still performed using the equivalent topology before the state conversion.

[0032] Preferably, the S4 is as follows:

[0033] S41: Based on the general conclusions of power electronics technology, the initial conditions of the power electronic circuit model are set to values as close to the steady state as possible, thereby shortening the transition process of the power electronic circuit;

[0034] S42: Sampling is performed at the same position in two adjacent switching cycles, and the obtained voltage or current change in one switching cycle is used as the basis for steady-state judgment. When this change is less than a set threshold, it is considered that the voltage or current waveform has reached stability;

[0035] S43: For scenarios prone to misjudgment, for power electronic circuits with a short startup process, the method of reducing the threshold is adopted. At this time, even at the peak or valley position, the power electronic circuit can still detect more obvious voltage or current changes in adjacent switching cycles; for power electronic circuit models that cannot use the method of reducing the threshold, the method of increasing the sampling period is adopted, that is, the change amount separated by multiple cycles is used instead of the change amount in adjacent cycles as the judgment basis, amplifying the measurement sensitivity of the voltage or current change amount, thereby improving the accuracy of steady-state judgment; in order to eliminate additional misjudgment risks, while detecting the voltage or current difference at the sampling point, the voltage or current change amount near the sampling moment is added as the second-level judgment basis.

[0036] Preferably, the S5 is as follows:

[0037] By applying the message system provided by the Qt system, the trigger condition is set to the change of the value entered by the user in the input field. Once the input parameters change, the program immediately replaces the old parameters with the new parameters, recalculates the corresponding waveforms of the power electronic circuit, and redraws the image. For all power electronic circuits involved, the calculation of replacing the old parameters with the new parameters and recalculating the corresponding waveforms of the power electronic circuit can be completed within 1 millisecond, that is, the displayed waveform can quickly follow the changes in the input.

[0038] In a second aspect, the present invention provides a power electronic circuit dynamic graphics simulation system for teaching assistance, comprising:

[0039] A startup module is used to select, start, or close the power electronic circuit model demonstration window and the system's user manual; the power electronic circuit model demonstration window provides simulation demonstrations of four types of 18 power electronic circuit models; the user manual provides an introduction to the power electronic circuit dynamic graphics simulation system, an interface description, and an operating guide;

[0040] The input module is used to input power electronic circuit parameters. Users can choose to enter the parameters accurately through the input box or drag the slider to quickly adjust the power electronic circuit parameters. Clicking the power electronic circuit parameter reset button can restore the power electronic circuit parameters to the default values set by the program. The input parameters include input power supply voltage Ud, control signal frequency f, control signal duty cycle D, main circuit inductance L, output capacitance C, and load resistance R.

[0041] The output module is used to output the dynamic simulation results of the power electronic circuit; the dynamic simulation results include the voltage and current time domain waveforms corresponding to the stable operation of the power electronic circuit, as well as the real-time average and peak-to-peak values of the output waveforms; the user can change the displayed waveform image in the waveform selection area, and the waveform image options provided include the voltage or current of the energy storage element, the voltage or current of the semiconductor element, and the voltage or current waveform of the power supply; the scaling coordinate axis switch can control the coordinate axis of the output waveform to automatically scale to the appropriate range according to the displayed waveform, or maintain the original coordinate axis unchanged, thereby reflecting the law of change of the power electronic circuit waveform with the power electronic circuit parameters in two different ways.

[0042] Preferably, the power electronic circuit model includes Buck converter, Boost converter, Buck-Boost converter, Cuk converter, Sepic converter, Zeta converter, isolated full-bridge Buck converter, forward converter, flyback converter, single-phase full-bridge uncontrolled rectifier circuit, single-phase single thyristor rectifier circuit, three-phase full-bridge uncontrolled rectifier circuit, three-phase full-bridge thyristor rectifier circuit, single-phase full-bridge square wave inverter circuit, single-phase full-bridge phase-shift voltage regulation inverter circuit, single-phase bipolar SPWM inverter circuit, single-phase unipolar SPM inverter circuit, and single-phase AC voltage regulation circuit.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] 1) Efficient modeling and solution methods: Common power electronic circuit modeling methods include switching cycle average models, small signal models, and linear analysis methods that use equivalent time-varying conductance models instead of ideal switches. These modeling methods each have advantages and disadvantages in terms of approximation and computational efficiency. The modeling method used in this invention treats the semiconductor components of the circuit as ideal switches. Based on the different equivalent topologies under different switching states, the equivalent topology of each circuit state is analyzed separately, thereby converting the nonlinear power electronic circuit into a linear time-varying circuit. This analysis is performed using linear circuit analysis methods, which can meet the high requirements for average values and ripple of voltage and current waveforms during teaching with a relatively small amount of computation.

[0045] 2) Real-time simulation result output: Currently popular engineering simulation analysis systems mostly use numerical analysis methods. Once the circuit structure or circuit parameters change, the circuit model must be recompiled, which is time-consuming and not conducive to comparative demonstration. The present invention does not require this recompilation process. Instead, it adopts a solution that precompiles the entire system. Utilizing the Qt development library and its accompanying message system tools, the system can immediately depict the circuit operating waveform according to the new circuit parameters whenever the circuit parameters change during the auxiliary teaching process, greatly improving the system's demonstration effect and enhancing the interactivity and real-time nature of teaching.

[0046] 3) Fine parameter adjustment operation: The present invention realizes "quasi-stepless adjustment" of circuit parameter input, that is, it allows fine adjustment in extremely small steps, thereby accurately demonstrating the impact of parameter changes on the circuit. The system's waveform display function can accurately respond to such continuous changes in parameters, making the comparison of circuit operating states under different parameter settings simple and intuitive.

[0047] 4) Rich teaching application scenarios: The present invention can provide computer simulation functions for circuit models commonly used in the teaching of basic power electronics technology. It has the functions of real-time input of circuit parameters and real-time display of circuit time domain waveforms. When used in the teaching process, it can intuitively show students the working principles of power electronic circuits, the idealized voltage and current waveforms under the stable working state of the circuit, and the average value, ripple and other characteristics of the circuit waveform, helping students to more deeply grasp the basic principles of power electronics technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 It is a schematic diagram of the overall process of the present invention;

[0049] Figure 2 The equivalent topology of the Buck circuit in different switching states according to the embodiment of the present invention;

[0050] Figure 3 A schematic diagram of a simulation system panel of the present invention;

[0051] Figure 4 1 is the output voltage and inductor current waveform of the Buck circuit according to an embodiment of the present invention. DETAILED DESCRIPTION

[0052] The present invention will be further described and illustrated below with reference to the accompanying drawings and specific embodiments. The technical features of each embodiment of the present invention may be combined accordingly, provided that there is no conflict between them.

[0053] like Figure 1 As shown in FIG, a power electronic circuit dynamic graphic simulation method for teaching assistance provided by the present invention is provided. The steps of the power electronic circuit dynamic graphic simulation method are as follows:

[0054] S1: Configure basic circuit components. Basic circuit components include linear passive components, semiconductor components, power supplies, and transformers.

[0055] As a preferred embodiment of the present invention, the steps are as follows:

[0056] S11: Arrange linear passive components including resistors, inductors, and capacitors so that the linear passive components meet the following conditions:

[0057] Linear passive components have constant resistance, inductance, or capacitance, and sufficiently high withstand voltage and current ratings. The equivalent series resistance of an inductor is zero. The equivalent series resistance of a capacitor is also zero, with no leakage current.

[0058] S12: Configure the semiconductor components so that they meet the following conditions:

[0059] Ignoring switching times, the switching process is considered an instantaneous transition from on to off or off to on. The on-resistance is zero, the off-leakage current is zero, and no breakdown will occur within the operating voltage range. Ignoring the various capacitive effects of semiconductor components, there are no switching losses. For paired switching elements in power electronic circuits, as well as full-bridge and half-bridge structures, no dead time is set for the switch control signals.

[0060] S13: Configure the power supply and transformer to meet the following conditions:

[0061] The DC power supply, single-phase or three-phase AC power supply is an ideal voltage source. The output voltage waveform meets the ideal requirements and is not affected by the output current. The internal resistance of the voltage source is 0, and the parasitic inductance of the AC power supply line is ignored. The voltage and current of the transformer model meet the following requirements:

[0062]

[0063] Where n is the number of windings in the transformer model, u j is the voltage of the jth winding, N j is the number of turns of the jth winding, i j is the current flowing through the jth winding.

[0064] S14. The transformer model of the simulation model is based on the ideal transformer model and incorporates the excitation inductance required by the corresponding power electronic circuit. When the excitation inductance is taken into consideration, it is clearly marked in the corresponding circuit topology.

[0065] S2: Based on the basic circuit elements, semiconductor elements are regarded as ideal switches. According to the equivalent topology under different switching states, the nonlinear power electronic circuit is converted into a linear time-varying circuit and a set of differential equations is established to construct a power electronic circuit model.

[0066] As a preferred embodiment of the present invention, the steps are as follows:

[0067] S21: Consider semiconductor components as ideal switches and analyze the possible states of power electronic circuits based on different equivalent topologies under different switching states.

[0068] For example, when the Buck circuit operates in CCM (continuous current mode) or BCM (critical conduction mode), the circuit alternates between the T-on and D-on states, corresponding to two equivalent topologies; when the Buck circuit operates in DCM (discontinuous current mode), the circuit alternates between the T-on, D-on, and L-off states, corresponding to three different equivalent topologies.

[0069] S22: List the differential equations for each energy storage element. Combined with the equivalent topology, apply the conclusions of Kirchhoff's voltage law and Kirchhoff's current law to obtain a differential equation system containing four or more independent equations. This system is used to represent the corresponding equivalent topology and is used to solve the model in S3. The energy storage elements include inductors and capacitors.

[0070] For example, when the Buck circuit operates in the T-on, D-on, and L-off states, the differential equations representing the topology are:

[0071] T conduction: D is on: L cut-off:

[0072] Where, L is the inductance of the inductor, i L is the current flowing through the inductor, u L is the voltage across the inductor, C is the capacitance of the capacitor, i C is the current flowing through the capacitor, u0 is the voltage across the capacitor (i.e. output voltage), U d is the input voltage, and R is the resistance of the load resistor.

[0073] S23: The process of modeling the power electronic circuit using a group of differential equations is completed by segmenting the time according to different working states of the power electronic circuit.

[0074] S3: Based on the power electronic circuit model, through discretization iteration in the time domain, the numerical solution at each sampling point in the time period when the power electronic circuit switch state remains unchanged is calculated and passed to the next switch state as the initial condition of the discretization iteration to solve the power electronic circuit model.

[0075] As a preferred embodiment of the present invention, the steps are as follows:

[0076] S31: Convert the system of differential equations representing the topology in S22 into integral form.

[0077] For example, when the circuit is in the T-on state, the differential equations are converted into integral form, that is:

[0078]

[0079] Where, t is the time, Δt is the time interval, L is the inductance of the inductor, i L (t) is the current flowing through the inductor at time t, u L (τ) is the voltage across the inductor at time τ, C is the capacitance of the capacitor, u o (t) is the voltage across the capacitor at time t (i.e., output voltage), i c (τ) is the current flowing through the capacitor at time τ, U d is the input voltage, and R is the resistance of the load resistor.

[0080] S32: Discretize the power electronic circuit model in the time domain. This step is as follows:

[0081] The time axis is divided into (m-1) segments at a constant sampling time interval Δt, and the numerical solutions at the m sampling points are used as the solutions to the model equations.

[0082] For example, the integrals when the circuit is in the T-on state are approximated as follows:

[0083] ∫ t t+Δt u L (τ)dτ≈∫ t t+Δt u L (t)dτ=Δt·u L (t)

[0084] ∫ t t+Δt i C (τ)dτ≈∫ t t+Δt i C (t)dτ=Δt·i C (t)

[0085] Among them, t is the time, Δt is the time interval, u L (τ) is the voltage across the inductor at time τ, u L (t) is the voltage across the inductor at time t, i C (τ) is the current flowing through the inductor at time τ, i C (t) is the current flowing through the inductor at time t.

[0086] S33: After time domain discretization, each sampling point is numbered with 1, 2, ..., m in sequence.

[0087] For example, when the circuit is in the T-on state, the equations are converted into the following after discretization approximation:

[0088]

[0089] Among them, Q is the sampling point number, L is the inductance value of the inductor, i L is the current flowing through the inductor, u L is the voltage across the inductor, C is the capacitance of the capacitor, i C is the current flowing through the capacitor, u0 is the voltage across the capacitor (i.e. output voltage), U d is the input voltage, and R is the resistance of the load resistor.

[0090] S34: Given the voltage and current values of each energy storage element in the initial state (sequence number 1), the voltage and current values of the next time sampling point are calculated using the voltage and current values of the previous time sampling point, and finally the numerical solution of the equation for each time sampling point is calculated in sequence through iteration.

[0091] S35: When a switch state transition is detected, the numerical solution obtained by the power electronic circuit under the current switch state condition will provide the initial state condition under the next switch state. Through continuous iteration and transfer, the voltage and current values of the power electronic circuit at each time sampling point in the entire time range are obtained. This step is specifically as follows:

[0092] For an electrical quantity that is subject to delay interference of x discrete sampling time intervals, calculation is started using the equivalent topology after the switch state is converted at the (x+1)th sampling point. Before this point, calculation is still performed using the equivalent topology before the state conversion.

[0093] S36: Based on the known voltage and current of the energy storage element, combined with Kirchhoff's voltage law and Kirchhoff's current law, obtain the voltage and current waveforms of other circuit components other than the energy storage element.

[0094] S4: Based on the solved power electronic circuit model, set the steady-state criterion of the power electronic circuit to ensure that the model outputs the voltage and current waveforms when working stably.

[0095] As a preferred embodiment of the present invention, the steps are as follows:

[0096] S41: Based on the general conclusions of power electronics technology, the initial conditions of the power electronic circuit model are set to values as close to the steady state as possible, thereby shortening the transition process of the power electronic circuit.

[0097] For example, the initial conditions of the Buck circuit model are set to values close to the CCM steady-state values, while the initial conditions of more complex circuits are set to 0.

[0098] S42: Sampling is performed at the same position in two adjacent switching cycles, and the obtained change in voltage or current in one switching cycle is used as the basis for steady-state judgment. When this change is less than a set threshold, it is considered that the voltage or current waveform has reached stability.

[0099] S43: For scenarios prone to misjudgment, for power electronic circuits with short startup processes, a threshold reduction method is used. In this case, even at peak or valley positions, the power electronic circuit can still detect significant voltage or current changes in adjacent switching cycles. For power electronic circuit models where the threshold reduction method cannot be used, the sampling period is increased. That is, the change between adjacent cycles is replaced by the change between multiple cycles as the judgment basis, amplifying the measurement sensitivity of the voltage or current change, thereby improving the accuracy of steady-state judgment. To eliminate the additional risk of misjudgment, the voltage or current change near the sampling moment is added as a second-level judgment basis in addition to detecting the voltage or current difference at the sampling point.

[0100] S5: Based on the power electronic circuit after the steady-state criterion is set, the dynamic simulation results of the power electronic circuit are output visually, so that the circuit waveform changes in real time according to the changes of the input parameters.

[0101] As a preferred embodiment of the present invention, the steps are as follows:

[0102] By applying the message system provided by the Qt system, the trigger condition is set to the change of the value entered by the user in the input field. Once the input parameters change, the program immediately replaces the old parameters with the new parameters, recalculates the corresponding waveforms of the power electronic circuit, and redraws the image. For all power electronic circuits involved, the calculation of replacing the old parameters with the new parameters and recalculating the corresponding waveforms of the power electronic circuit can be completed within 1 millisecond, that is, the displayed waveform can quickly follow the changes in the input.

[0103] The present invention also provides a power electronic circuit dynamic graphics simulation system for teaching assistance, which mainly includes:

[0104] The startup module is used to select, start, or close the power electronic circuit model demonstration window and the system's user manual. The power electronic circuit model demonstration window provides simulation demonstrations for 18 power electronic circuit models across four different types. These include the Buck converter, Boost converter, Buck-Boost converter, Cuk converter, Sepic converter, Zeta converter, isolated full-bridge Buck converter, forward converter, flyback converter, single-phase full-bridge uncontrolled rectifier circuit, single-phase single thyristor rectifier circuit, three-phase full-bridge uncontrolled rectifier circuit, three-phase full-bridge thyristor rectifier circuit, single-phase full-bridge square wave inverter circuit, single-phase full-bridge phase-shifted voltage-regulating inverter circuit, single-phase bipolar SPWM inverter circuit, single-phase unipolar SPM inverter circuit, and single-phase AC voltage regulator circuit. The user manual provides an introduction to the power electronic circuit dynamic graphical simulation system, its interface, and operational guidelines.

[0105] Input module: This module is used to input power electronic circuit parameters. Users can choose to enter parameters accurately through the input box, or drag the slider to quickly adjust the power electronic circuit parameters. Clicking the power electronic circuit parameter reset button can restore the power electronic circuit parameters to the default values set by the program.

[0106] Output module, which is used to output the dynamic simulation results of power electronic circuits. The dynamic simulation results include the voltage and current time domain waveforms corresponding to the stable operation of the power electronic circuit, as well as the real-time average and peak-to-peak values of the output waveforms. Users can change the displayed waveform image in the waveform selection area. The waveform image options provided include the voltage or current of the energy storage element, the voltage or current of the semiconductor element, and the voltage or current waveform of the power supply. The scaling axis switch can control the coordinate axis of the output waveform to automatically scale to the appropriate range according to the displayed waveform, or maintain the original coordinate axis unchanged, thereby reflecting the law of the power electronic circuit waveform changing with the power electronic circuit parameters in two different ways.

[0107] Specifically, the input parameters and output waveform selection range of the power electronic circuit dynamic graphics simulation system are shown in the following table:

[0108]

[0109]

[0110] Among them, the corresponding meanings of the symbols in the table are: U refers to DC voltage, u refers to dynamic voltage value, i refers to dynamic current value, R refers to linear resistance, L refers to linear inductance, C refers to linear capacitance, n refers to the number of winding turns, m refers to modulation index, α refers to control angle, f refers to main frequency, and D refers to duty cycle; in the subscript, d refers to DC, o refers to output, i refers to input, M refers to excitation inductance, m refers to amplitude, D refers to diode, and T refers to transistor.

[0111] The method and system of the present invention will be specifically described below through examples.

[0112] Example

[0113] This embodiment provides a method for dynamic graphics simulation of power electronic circuits for teaching assistance, the method comprising:

[0114] S1. Configure basic circuit components, including linear passive components, semiconductor components, power supplies, and transformers;

[0115] S2. Build a power electronic circuit model. The core is to treat semiconductor components as ideal switches. Based on the equivalent topology under different switching states, the nonlinear power electronic circuit is converted into a linear time-varying circuit and a set of differential equations is established.

[0116] S3. Solve the power electronic circuit model, calculate the numerical solution at each sampling point in the time period when the power electronic circuit switch state remains unchanged through discretization iteration in the time domain, and pass it to the next switch state as the initial condition of the discretization iteration;

[0117] S4. Set the steady-state criterion of the power electronic circuit to ensure that the circuit model outputs the voltage and current waveforms when working stably;

[0118] S5. Visually output the dynamic simulation results of the power electronic circuit so that the circuit waveform changes in real time according to the changes in the input parameters.

[0119] In this embodiment of the present invention, step S1 specifically includes:

[0120] S11. Configure linear passive components to meet the following requirements: the resistance, inductance, or capacitance of the components are constant, and the withstand voltage and current values are sufficiently high; the equivalent series resistance of the inductor is 0; the equivalent series resistance of the capacitor is 0, and there is no leakage current.

[0121] S12. Configure semiconductor elements to meet the following requirements: Ignore switching time, and the switching process is regarded as an instantaneous switch from on to off or off to on; the on-resistance is 0, the off-leakage current is 0, and there will be no fault breakdown within the operating voltage range; ignore various capacitance effects of semiconductors, and there is no switching loss; for switching elements that exist in pairs in power electronic circuits, as well as full-bridge, half-bridge and other structures, no dead time is set for the switch control signal.

[0122] S13. Configure the power supply and transformer to meet the following requirements: the DC power supply and single-phase / three-phase AC power supply are ideal voltage sources, the output voltage waveform meets the ideal requirements, and will not change due to the influence of the output current; the internal resistance of the voltage source is 0, and the parasitic inductance of the AC power supply line is ignored; the voltage and current of the transformer model meet the following requirements:

[0123]

[0124] Where n is the number of windings in the transformer model, u j is the voltage of the jth winding, N j is the number of turns of the jth winding, i j is the current flowing through the jth winding.

[0125] S14. The transformer model of the simulation model is based on the ideal transformer model and incorporates the excitation inductance required by the corresponding power electronic circuit. When the excitation inductance is taken into consideration, it is clearly marked in the corresponding circuit topology.

[0126] In this embodiment of the present invention, step S2 specifically includes:

[0127] S21. Consider the semiconductor components of the circuit as ideal switches and analyze the possible states of the circuit according to the different equivalent topologies under different switching states (such as Figure 2 As shown in Figure 2): When the Buck circuit operates in CCM (continuous current mode) or BCM (critical conduction mode), the circuit alternates between T-on and D-on states, corresponding to two equivalent topologies. When the Buck circuit operates in DCM (discontinuous current mode), the circuit alternates between T-on, D-on, and L-off states, corresponding to three different equivalent topologies.

[0128] S22. List the differential equations for each energy storage element. Combined with the conclusions of Kirchhoff's voltage law and Kirchhoff's current law in the equivalent topology, a differential equation system containing four or more independent equations is obtained to represent the corresponding equivalent topology for subsequent model solving. When the Buck circuit operates in the T on, D on, and L off states, the following differential equation system representing the topology is obtained:

[0129] T conduction:

[0130] D is on:

[0131] L cut-off:

[0132] Where, L is the inductance of the inductor, i L is the current flowing through the inductor, u Lis the voltage across the inductor, C is the capacitance of the capacitor, i C is the current flowing through the capacitor, u0 is the voltage across the capacitor (i.e. output voltage), U d is the input voltage, and R is the resistance of the load resistor.

[0133] S23. The circuit is segmented in time according to different working states of the circuit, and the process of modeling the circuit using a group of differential equations is completed.

[0134] In this embodiment of the present invention, step S3 specifically includes:

[0135] S31. Convert the differential equations representing the topology into integral form. When the Buck circuit is in the T-on state, we can obtain:

[0136]

[0137] Where, t is the time, Δt is the time interval, L is the inductance of the inductor, i L (t) is the current flowing through the inductor at time t, u L (τ) is the voltage across the inductor at time τ, C is the capacitance of the capacitor, u o (t) is the voltage across the capacitor at time t (i.e., output voltage), i c (τ) is the current flowing through the capacitor at time τ, U d is the input voltage, and R is the resistance of the load resistor.

[0138] S32. Discretize the circuit model in the time domain, i.e., divide the model into (n-1) segments at a constant sampling time interval Δt on the time axis. Use the numerical solutions at the obtained n sampling points as the solutions to the model equations, and make the following approximations for the above integrals:

[0139] ∫ t t+Δt u L (τ)dτ≈∫ t t+Δt u L (t)dτ=Δt·u L (t)

[0140] ∫ t t+Δ i C (τ)dτ≈∫ t t+Δ i C (t)dτ=Δt·i C (t)

[0141] Among them, t is the time, Δt is the time interval, u L (τ) is the voltage across the inductor at time τ, uL (t) is the voltage across the inductor at time t, i C (τ) is the current flowing through the inductor at time τ, i C (t) is the current flowing through the inductor at time t.

[0142] S33. After time domain discretization, use 1, 2, ..., n to number each sampling point in sequence. The above equations are transformed into:

[0143]

[0144] Among them, Q is the sampling point number, L is the inductance value of the inductor, i L is the current flowing through the inductor, u L is the voltage across the inductor, C is the capacitance of the capacitor, i C is the current flowing through the capacitor, u0 is the voltage across the capacitor (i.e. output voltage), U d is the input voltage, and R is the resistance of the load resistor.

[0145] S34. Given the voltage and current values of each energy storage element in the initial state (sequence number 1), the voltage and current values of the next time sampling point are calculated using the voltage and current values of the previous time sampling point, and finally the numerical solution of the equation for each time sampling point is calculated sequentially through iteration;

[0146] S35. When a switch state transition is detected, the numerical solution obtained by the circuit under the current switch state condition will provide the initial state condition under the next switch state. Through continuous iteration and transfer, the voltage and current values of the power electronic circuit at each time sampling point in the entire time range are obtained. The core method of this process is that for an electrical quantity that is subject to delay interference of n discrete sampling time intervals, the equivalent topology after the transition is used for calculation at the (n+1)th sampling point after the switch state transition. Before that, the equivalent topology before the state transition is still used for calculation.

[0147] S36. Based on the known voltage and current of the energy storage element, combined with Kirchhoff's voltage law and Kirchhoff's current law, obtain the voltage and current waveforms of other circuit components other than the energy storage element.

[0148] In this embodiment of the present invention, step S4 specifically includes:

[0149] S41. Based on the general conclusions of power electronics technology, the initial conditions of the circuit model are set to values as close to the steady-state as possible to shorten the circuit transition process. The initial conditions of the Buck circuit model are set to values close to the steady-state values of the CCM mode.

[0150] S42. Sampling the same position in two adjacent switching cycles, and using the obtained voltage / current variation in one switching cycle as the basis for steady-state determination. When this variation is less than a set threshold, the voltage / circuit waveform is considered to be stable.

[0151] S43. For scenarios prone to misjudgment, for circuits with a short startup process, a method of reducing the threshold is adopted. At this time, even at the peak / valley position, the circuit can still detect obvious voltage / current changes in adjacent switching cycles.

[0152] In an embodiment of the present invention, step S5 specifically includes: applying the message system provided by Qt, setting the trigger condition to a change in the value entered by the user in the input field, and once the input parameters change, the program immediately replaces the old parameters with the new parameters and recalculates the corresponding waveforms of the circuit operation, and redraws the image. For all power electronic circuits involved, the calculation of replacing the old parameters with the new parameters and recalculating the corresponding waveforms of the circuit operation can be completed within 1 millisecond, that is, the displayed waveform can quickly follow the changes in the input.

[0153] like Figure 3 As shown in FIG. 1 , a power electronic circuit dynamic graphics simulation system for teaching assistance provided by this embodiment includes:

[0154] A startup module is used to select, start, or close the circuit model demonstration window and the system's user manual. The circuit model demonstration window provides simulation demonstrations of 4 types, totaling 18 power electronic circuit models: Buck converter, Boost converter, Buck-Boost converter, Cuk converter, Sepic converter, Zeta converter, isolated full-bridge Buck converter, forward converter, flyback converter, single-phase full-bridge uncontrolled rectifier circuit, single-phase single thyristor rectifier circuit, three-phase full-bridge uncontrolled rectifier circuit, three-phase full-bridge thyristor rectifier circuit, single-phase full-bridge square wave inverter circuit, single-phase full-bridge phase-shift voltage regulation inverter circuit, single-phase bipolar SPWM inverter circuit, single-phase unipolar SPM inverter circuit, and single-phase AC voltage regulation circuit. The user manual provides an introduction to the power electronic circuit dynamic graphic simulation system, an interface description, and an operating guide.

[0155] The input module is used to input circuit parameters. Users can choose to enter the parameters accurately through the input box, or drag the slider to quickly adjust the circuit parameters. Clicking the circuit parameter reset button can restore the circuit parameters to the default values set by the program;

[0156] The output module is used to output the dynamic simulation results of the power electronic circuit, including the voltage and current time domain waveforms corresponding to the stable operation of the power electronic circuit, as well as the real-time average and peak-to-peak values of the output waveform. The user can change the displayed waveform image in the waveform selection area. The provided circuit image options include the voltage / current waveforms of the energy storage element, the voltage / current waveforms of the semiconductor element, and the voltage / current waveforms of the power supply. The scaling axis switch can control the coordinate axis of the output waveform to automatically scale to the appropriate range according to the displayed waveform, or maintain the original coordinate axis unchanged, thereby reflecting the law of circuit waveform changes with circuit parameters in two different ways.

[0157] In the embodiment of the present invention, click the "Start Window" button corresponding to the right side of the Buck converter in the first row of the startup module list, and the word "Buck Converter" will be displayed in the upper left corner of the opened Buck converter sub-window panel; the circuit topology area displays the circuit topology of the Buck converter; 6 adjustable input parameters can be observed in the circuit parameter input area, including: power supply voltage Ud, control signal frequency f, control signal duty cycle D, main circuit inductance L, output capacitance C, load resistance R, and the circuit parameters can be accurately set in the input box, or the circuit parameters can be quickly adjusted by dragging the slider; click the circuit parameter reset button to restore the circuit parameters to the default value; the time domain waveform display area can instantly display the corresponding voltage or current waveform according to the input parameters on the left; the waveform parameter measurement area can output the real-time average value and peak-to-peak value of the two waveforms; the waveform selection area provides 8 selectable waveforms, including u o 、i L 、u L 、i C 、u D 、i D 、u T 、u Gate ; The axis scaling control check box can control the scaling of the waveform axis.

[0158] Furthermore, enter the parameters in the circuit parameter input area on the left side of the Buck converter sub-window and set the power supply voltage U d Set to 5V, set the control signal frequency f to 100kHz, set the control signal duty cycle D to 0.5, set the main circuit inductor L to 1mH, set the output capacitor C to 100μF, and set the load resistance R to 51Ω. At this time, the Buck circuit operates in CCM (continuous current mode), and the circuit operates alternately in the two states of T conduction and D conduction. Select the output voltage and inductor current waveforms in the waveform selection area. The obtained Buck circuit output voltage and inductor current waveforms are as follows Figure 4 As shown, it shows that the system can draw the working waveform of the ideal power electronic circuit, and the drawn waveform is consistent with the theory.

[0159] Furthermore, the real-time average value and peak-to-peak value of the two waveforms output from the waveform parameter measurement area are recorded. According to theoretical calculations, the average output voltage of the circuit is 2.5V, the peak-to-peak value of the output voltage ripple is 0.0002V, the average inductor current is 0.049A, and the peak-to-peak value of the inductor current ripple is 0.0125A; the numerical measurement results of the present invention are: the average output voltage is 2.5001V, the peak-to-peak value of the output voltage ripple is 0.0003V, the average inductor current is 0.0493A, and the peak-to-peak value of the inductor current ripple is 0.0128A. Compared with the theoretical value, the error value of each measurement result is less than 8%.

[0160] In other embodiments of the present invention, users can select the remaining 17 different power electronic circuits for learning. The operation method is similar to the above embodiment. The input parameters and output waveform selection ranges of the corresponding circuits are shown in the following table:

[0161]

[0162]

[0163] Among them, the corresponding meanings of the symbols in the table are: U refers to DC voltage, u refers to dynamic voltage value, i refers to dynamic current value, R refers to linear resistance, L refers to linear inductance, C refers to linear capacitance, n refers to the number of winding turns, m refers to modulation index, α refers to control angle, f refers to main frequency, and D refers to duty cycle; in the subscript, d refers to DC, o refers to output, i refers to input, M refers to excitation inductance, m refers to amplitude, D refers to diode, and T refers to transistor.

[0164] The method of the present invention configures basic circuit components, treating semiconductor components as ideal switches, and establishes power electronic circuit models based on different equivalent topologies under different switching states. Through discretization iteration in the time domain, the numerical solution of the power electronic circuit at each sampling time point is calculated. After steady-state detection, the sampled data of the circuit operating voltage and current waveforms are output, and a message system is used to ensure that the circuit waveforms follow the changes of input parameters in real time. The system includes a startup module, an input module, and an output module, and provides simulation demonstrations of 18 power electronic circuit models. The present invention has the advantages of efficient modeling and solution, interactive feedback implementation, and precise parameter adjustment, and can effectively enhance students' understanding and application capabilities of power electronics technology.

[0165] The embodiment described above is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Persons skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, any technical solution obtained by equivalent substitution or equivalent transformation falls within the scope of protection of the present invention.

Claims

1. A dynamic graphics simulation method for power electronic circuits for teaching assistance, characterized in that: The details are as follows: S1: Configuring basic circuit components; the basic circuit components include linear passive components, semiconductor components, power supplies, and transformers; S2: Based on the basic circuit elements, the semiconductor elements are regarded as ideal switches. According to the equivalent topology under different switching states, the nonlinear power electronic circuit is converted into a linear time-varying circuit and a differential equation system is established to construct a power electronic circuit model; S3: Based on the power electronic circuit model, through discretization iteration in the time domain, a numerical solution at each sampling point in a time period in which the switch state of the power electronic circuit remains unchanged is calculated, and the numerical solution is passed to the next switch state as an initial condition for discretization iteration to solve the power electronic circuit model; S4: Based on the solved power electronic circuit model, set the steady-state criterion of the power electronic circuit to ensure that the model outputs voltage and current waveforms when working stably; S5: Based on the power electronic circuit after the steady-state criterion is set, the dynamic simulation results of the power electronic circuit are output visually, so that the circuit waveform changes in real time according to the changes of the input parameters.

2. The power electronic circuit dynamic graphics simulation method for teaching assistance according to claim 1, characterized in that: The S1 is specifically as follows: S11: Arrange linear passive components including resistors, inductors, and capacitors so that: the resistance, inductance, or capacitance of the linear passive components are constant, and the withstand voltage and current are sufficiently high; the equivalent series resistance of the inductor is 0; and the equivalent series resistance of the capacitor is 0, with no leakage current. S12: Configure semiconductor components to meet the following requirements: Ignore switching time, and treat the switching process as an instantaneous switch from on to off or off to on; the on-resistance is 0, the off-leakage current is 0, and no fault breakdown occurs within the operating voltage range; ignore various capacitive effects of semiconductor components, and there is no switching loss; for paired switching elements in power electronic circuits and full-bridge and half-bridge structures, no dead time is set for the switch control signal; S13: Configure the power supply and transformer to meet the following requirements: the DC power supply, single-phase or three-phase AC power supply is an ideal voltage source, the output voltage waveform meets the ideal requirements, and will not change due to the influence of the output current; the internal resistance of the voltage source is 0, and the line parasitic inductance of the AC power supply is ignored; the voltage and current of the transformer model meet the following requirements: Where n is the number of windings in the transformer model, u j is the voltage of the jth winding, N j is the number of turns of the jth winding, i j is the current flowing through the jth winding.

3. The power electronic circuit dynamic graphics simulation method for teaching assistance according to claim 1, characterized in that: The S2 is specifically as follows: S21: Considering the semiconductor element as an ideal switch, and analyzing possible states of the power electronic circuit according to different equivalent topologies under different switching states; S22: List the differential equations for each energy storage element, and apply the conclusions of Kirchhoff's voltage law and Kirchhoff's current law based on the equivalent topology to obtain a differential equation system containing four or more independent equations to represent the corresponding equivalent topology for solving the model in S3; the energy storage elements include inductors and capacitors; S23: The process of modeling the power electronic circuit using a group of differential equations is completed by segmenting the time according to different working states of the power electronic circuit.

4. The power electronic circuit dynamic graphics simulation method for teaching assistance according to claim 1, characterized in that: The S3 is as follows: S31: Convert the differential equations representing the topology in S22 into integral form; S32: Discretize the power electronic circuit model in the time domain; S33: After time domain discretization, each sampling point is numbered with 1, 2, ..., p in sequence; S34: Given the voltage and current values of each energy storage element in the initial state, the voltage and current values of the next time sampling point are calculated using the voltage and current values of the previous time sampling point, and finally the numerical solution of the equation for each time sampling point is calculated sequentially through iteration; S35: When a switch state transition is detected, the numerical solution obtained by the power electronic circuit under the current switch state condition will provide the initial state condition under the next switch state. Through continuous iteration and transfer, the voltage and current values of the power electronic circuit at each time sampling point in the entire time range are obtained; S36: Based on the known voltage and current of the energy storage element, combined with Kirchhoff's voltage law and Kirchhoff's current law, obtain the voltage and current waveforms of other circuit components other than the energy storage element.

5. The power electronic circuit dynamic graphics simulation method for teaching assistance according to claim 4, characterized in that: The S32 is specifically as follows: The time axis is divided into (p-1) segments at a constant sampling time interval Δt, and the numerical solutions at the obtained p sampling points are used as the solutions to the model equations.

6. The power electronic circuit dynamic graphics simulation method for teaching assistance according to claim 4, characterized in that: The S35 is specifically as follows: For an electrical quantity that is subject to delay interference of x discrete sampling time intervals, calculation is started using the equivalent topology after the switch state is converted at the (x+1)th sampling point. Before this point, calculation is still performed using the equivalent topology before the state conversion.

7. The power electronic circuit dynamic graphics simulation method for teaching assistance according to claim 1, characterized in that: The S4 is specifically as follows: S41: Based on the general conclusions of power electronics technology, the initial conditions of the power electronic circuit model are set to values as close to the steady state as possible, thereby shortening the transition process of the power electronic circuit; S42: Sampling is performed at the same position in two adjacent switching cycles, and the obtained voltage or current change in one switching cycle is used as the basis for steady-state judgment. When this change is less than a set threshold, it is considered that the voltage or current waveform has reached stability; S43: For scenarios prone to misjudgment, for power electronic circuits with a short startup process, the method of reducing the threshold is adopted. At this time, even at the peak or valley position, the power electronic circuit can still detect more obvious voltage or current changes in adjacent switching cycles; for power electronic circuit models that cannot use the method of reducing the threshold, the method of increasing the sampling period is adopted, that is, the change amount separated by multiple cycles is used instead of the change amount in adjacent cycles as the judgment basis, amplifying the measurement sensitivity of the voltage or current change amount, thereby improving the accuracy of steady-state judgment; in order to eliminate additional misjudgment risks, while detecting the voltage or current difference at the sampling point, the voltage or current change amount near the sampling moment is added as the second-level judgment basis.

8. The power electronic circuit dynamic graphics simulation method for teaching assistance according to claim 1, characterized in that: The S5 is specifically as follows: By applying the message system provided by the Qt system, the trigger condition is set to the change of the value entered by the user in the input field. Once the input parameters change, the program immediately replaces the old parameters with the new parameters, recalculates the corresponding waveforms of the power electronic circuit, and redraws the image. For all power electronic circuits involved, the calculation of replacing the old parameters with the new parameters and recalculating the corresponding waveforms of the power electronic circuit can be completed within 1 millisecond, that is, the displayed waveform can quickly follow the changes in the input.

9. A dynamic graphics simulation system for power electronic circuits used for teaching assistance, characterized in that: include: Startup module, used to select, start or close the power electronic circuit model demonstration window and the system manual; The power electronic circuit model demonstration window provides simulation demonstrations of 4 types, a total of 18 power electronic circuit models; The user manual presents an introduction to the power electronic circuit dynamic graphics simulation system, an interface introduction, and an operation guide; The input module is used to input power electronic circuit parameters. Users can choose to enter the parameters accurately through the input box or drag the slider to quickly adjust the power electronic circuit parameters. Clicking the power electronic circuit parameter reset button can restore the power electronic circuit parameters to the default values set by the program. The input parameters include input power supply voltage Ud, control signal frequency f, control signal duty cycle D, main circuit inductance L, output capacitance C, and load resistance R. An output module is used to output dynamic simulation results of power electronic circuits; the dynamic simulation results include the voltage and current time domain waveforms corresponding to the stable operation of the power electronic circuit, as well as the real-time average and peak-to-peak values of the output waveforms; the user can change the displayed waveform image in the waveform selection area, and the waveform image options provided include the voltage or current waveform of the energy storage element, the voltage or current of the semiconductor element, and the voltage or current waveform of the power supply; The axis scaling switch can control the coordinate axis of the output waveform to automatically scale to the appropriate range based on the displayed waveform, or maintain the original coordinate axis unchanged, thereby reflecting the law of power electronic circuit waveform changes with power electronic circuit parameters in two different ways.

10. The power electronic circuit dynamic graphics simulation system for teaching assistance according to claim 9, characterized in that: The power electronic circuit models include Buck converter, Boost converter, Buck-Boost converter, Cuk converter, Sepic converter, Zeta converter, isolated full-bridge Buck converter, forward converter, flyback converter, single-phase full-bridge uncontrolled rectifier circuit, single-phase single thyristor rectifier circuit, three-phase full-bridge uncontrolled rectifier circuit, three-phase full-bridge thyristor rectifier circuit, single-phase full-bridge square wave inverter circuit, single-phase full-bridge phase-shift voltage regulation inverter circuit, single-phase bipolar SPWM inverter circuit, single-phase unipolar SPM inverter circuit, and single-phase AC voltage regulation circuit.

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