Linearized Modeling Method for Real-Time Simulation of Power Electronic Converters
By establishing the state space equation and improving Euler's method to derive the constant admittance model, the problems of large amount of power electronic converters and virtual power loss are solved, and high-precision power electronic converter simulation is realized, which is suitable for the simulation of multi-power electronic converters.
Patent Information
- Application Number
- CN202410936646.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-12
- Publication Date
- 2025-07-25
- Estimated Expiration
- 2044-07-12
AI Technical Summary
The node admission matrix of the power electronic converter changes with the change of the switching state, resulting in large calculation amounts and virtual power loss and high-frequency oscillation. The existing constant admission model fails to effectively solve the overall linear modeling problem of the converter.
By establishing the state space equations of the inductance on the AC side and the DC side capacitor, combining it with the power electronic switching state, the constant admittance model is derived using the improved Euler method, and the AC side and DC side are equivalent to the accompanying circuit, and the equivalent resistance is a fixed value, realizing the constant admittance characteristics of the converter.
Linearized constant admittance modeling of different power electronic converter topology is realized, the node admittance matrix order is reduced, virtual power consumption and oscillation is eliminated, simulation accuracy is improved, switch unlocking and locking modes are supported, and delays between the equivalent model and the system global solution is eliminated.
Smart Images
Figure CN118940473B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of electromagnetic transient simulation, and particularly to a linearized modeling method for real-time simulation of a power electronic converter. Background Art
[0002] Due to the time-varying nodal admittance matrix caused by switching in a power electronic converter, the computational amount for its solution is huge, which limits the scale of electromagnetic transient simulation of a power electronic power system. The traditional constant admittance modeling of power electronics is based on the Associated Discrete Circuit (ADC) model equivalent to L / C. By setting the parameters of inductors and capacitors, ensuring that the equivalent resistances of the inductor and capacitor are equal can ensure that the ADC model has the advantage that the system admittance matrix remains unchanged when the switching state changes. Although the L / C equivalent model ensures that the admittance matrix is constant, during the switching state transition, due to the non-negligible magnitudes of the equivalent inductor and capacitor, oscillations will occur in the transient process. And each switching operation will charge the equivalent inductor and capacitor, so virtual power losses greater than the actual ones will be generated, affecting the simulation accuracy. At the same time, the high order of the converter also affects the solution speed. Summary of the Invention
[0003] The technical problem to be solved by the present invention is:
[0004] The nodal admittance matrix of a power electronic converter changes with the switching state, resulting in a large computational amount for its solution. Existing constant admittance models of power electronic converters are all for individual switching devices, and no constant admittance model is established for the whole converter. And there are virtual power losses and high-frequency oscillations.
[0005] The present invention adopts the following technical solutions to solve the above technical problems:
[0006] First, establish the state space equations of the AC-side inductor and the DC-side capacitor and combine them with the power electronic switching state. Secondly, use the improved Euler method to derive a constant admittance model representing the port characteristics of the power electronic converter. This model is similar to the classical nodal equation expression and can be compatible with traditional electromagnetic transient software. Then, according to the discretized nodal equation, the AC side and the DC side are equivalent to an adjoint circuit, and the equivalent resistance is a fixed value related to the actual inductor and capacitor, realizing the constant admittance characteristic of the converter.
[0007] As a further improvement of the present invention, the state space equation is:
[0008]
[0009] Wherein, v sj and i j are the voltage and current on the AC side, v con_jThe output voltage of the converter, SW upj and SW lowj respectively represent the upper and lower switches of each phase of the converter, v dc_p and v dc_n are respectively the upper and lower capacitor voltages on the DC side, i dc_p and i dc_n are respectively the upper and lower currents on the DC side; L and C are respectively the inductance value on the AC side and the capacitance value on the DC side.
[0010] As a further improvement of the present invention, the improved Euler method is as follows:
[0011]
[0012] Wherein, is the next predicted value.
[0013] As a further improvement of the present invention, the state space equation (1) is discretized by the improved Euler method to obtain:
[0014]
[0015] Wherein, x v and x I respectively represent the DC side capacitor voltage and the AC side inductor current in (1), u v and u I respectively represent the AC side voltage and the DC side current in (1);
[0016] After organizing the above formula (3), we get:
[0017]
[0018] Wherein, and
[0019] The above formula is written in the form of a nodal equation to obtain:
[0020]
[0021] Wherein, The historical term is
[0022]
[0023] It can be seen from the above formula (5) that the AC-DC system is completely decoupled, as shown below respectively
[0024]
[0025] Wherein, the value of the equivalent inductor is The value of the equivalent capacitor is
[0026] As a further improvement of the present invention, the power electronic converter topology includes two-level, three-level, and multi-level voltage source converters.
[0027] As a further improvement of the present invention, the connection points of the power electronic converter on the three-phase AC side are equivalent to three Norton equivalent circuits.
[0028] As a further improvement of the present invention, the resistance of the Norton equivalent circuit is a fixed value, and the resistance value is 2 times the AC side inductance value divided by the simulation step size.
[0029] As a further improvement of the present invention, if the neutral point of the DC side capacitor is grounded, the connection points of the power electronic converter on the DC side are equivalent to two Thevenin equivalent circuits.
[0030] As a further improvement of the present invention, the resistance of the Thevenin equivalent circuit is a fixed value, and the resistance value is the simulation step size divided by 2 times the DC side capacitance value.
[0031] Compared with the prior art, the present invention adopts the above technical solutions and has the following technical effects:
[0032] Realize the linearized constant admittance modeling of different power electronic converter topologies. By establishing a constant admittance model for the entire converter, the order of the node admittance matrix can be greatly reduced. This method does not require the introduction of virtual inductors and capacitors, so there is no virtual power consumption and oscillation. At the same time, this model supports both switch unlocking and locking modes, and there is no need to switch the circuit in the locking mode. In addition, the proposed method can eliminate the delay between the equivalent model and the global solution of the system, thereby effectively improving the accuracy of multi-power electronic converter simulation. Description of the Drawings
[0033] Figure 1 is a general linearized modeling method for power electronic converters;
[0034] Figure 2 is a parallel equivalent model of multi-power electronic converters. Detailed Description of the Invention
[0035] The technical solutions of the present invention will be further described in detail below with reference to the drawings:
[0036] The present invention provides a general linearized modeling method for power electronic converters based on port characteristic constant admittance, without introducing virtual inductors and capacitor equivalent switches. By establishing a state space equation for the port characteristics of the converter and combining it with the internal switch states, a constant admittance adjoint circuit model of the power electronic converter is derived based on the improved Euler method. The specific steps are as follows: By Figure 1The state - space equations are established by combining the inductor current on the AC side and the capacitor voltage on the DC side of the shown converter with the switching states.
[0037]
[0038] Where, v sj and i j are the voltage and current on the AC side, v con_j is the output voltage of the converter, SW upj and SW lowj represent the upper and lower switches of each phase of the converter respectively, v dc_p and v dc_n are the upper and lower capacitor voltages on the DC side respectively, i dc_p and i dc_n are the upper and lower currents on the DC side respectively. L and C are the inductor value on the AC side and the capacitor value on the DC side respectively.
[0039] The improved Euler method can be expressed as
[0040]
[0041] Where is the predicted value for the next step.
[0042] By discretizing the state - space equation (1) using the improved Euler method, we can obtain
[0043]
[0044] Where, x v and x I represent the capacitor voltage on the DC side and the inductor current on the AC side in (1) respectively, u v and u I represent the voltage on the AC side and the current on the DC side in (1) respectively.
[0045] After arranging the above formula (3), we can obtain
[0046]
[0047] Where And
[0048] Writing the above formula in the form of a nodal equation, we can obtain
[0049]
[0050] Where The historical term is
[0051]
[0052] It can be seen from the above formula (5) that the AC-DC system is completely decoupled, as shown below
[0053]
[0054] where Figure 1 the value of the equivalent inductance is the value of the equivalent capacitance is
[0055] According to the above formula derivation, as Figure 1 shown, the converter can be equivalent to a Norton circuit on the AC side and a Thevenin circuit on the DC side, and the order of the system admittance matrix is constant, which is 3-order and 2-order respectively, and has nothing to do with the converter topology structure.
[0056] As Figure 2 shown, the power electronic converters connected to the same bus can be in-phase and equivalent to a Norton equivalent circuit, and the value of the equivalent current source is the sum of the equivalent current sources of each converter. At the same time, the equivalent resistance is the original resistance value divided by the number of converters.
Claims
1. A general linearized electromagnetic transient modeling method for power electronic converters, characterized in that: First, establish the state - space equations of the AC - side inductor and the DC - side capacitor and combine them with the states of the power - electronic switches; then, use the improved Euler method to derive a constant - admittance model representing the port characteristics of the power - electronic converter, which can be compatible with traditional electromagnetic transient software; finally, according to the discretized nodal equations, the AC - side and the DC - side are equivalent to adjoint circuits, and the equivalent resistance is a fixed value related to the actual inductor and capacitor, realizing the constant - admittance characteristics of the converter. The state - space equations are as follows: Among them, v sj and i j are the voltage and current on the AC side, v con_j is the output voltage of the converter, SW upj and SW lowj respectively represent the upper and lower switches of each phase of the converter, v dc_p and v dc_n are the upper and lower capacitor voltages on the DC side respectively, i dc_p and i dc_n are the upper and lower currents on the DC side respectively; L and C are the inductance value on the AC side and the capacitance value on the DC side respectively; The improved Euler method is as follows: Among them, is the predicted value for the next step; Discretize the state - space equation (1) by the improved Euler method to obtain: Among them, x v and x I respectively represent the DC-side capacitor voltage and the AC-side inductor current in (1), u v and u I respectively represent the AC-side voltage and the DC-side current in (1); After arranging the above formula (3), we get: Among them, and Among them, The historical item is From the above formula (5), it can be seen that the AC - DC system is completely decoupled, as shown below respectively Among them, the value of the equivalent inductance is The value of the equivalent capacitance is 2. The general linearized electromagnetic transient modeling method for a power electronic converter according to claim 1, characterized in that: The power - electronic converter topology includes two - level, three - level, and multi - level voltage - source converters.
3. A general linearized electromagnetic transient modeling method for a power electronic converter according to claim 1, characterized in that: The connection points of the power - electronic converter on the three - phase AC side are equivalent to three Norton equivalent circuits.
4. A general linearized electromagnetic transient modeling method for a power electronic converter according to claim 3, characterized in that: The resistance of the Norton equivalent circuit is a fixed value, and the resistance value is 2 times the AC - side inductor value divided by the simulation step size.
5. A general linearized electromagnetic transient modeling method for a power electronic converter according to claim 1, characterized in that: If the neutral point of the DC - side capacitor is grounded, the connection points of the power - electronic converter on the DC side are equivalent to two Thevenin equivalent circuits.
6. A general linearized electromagnetic transient modeling method for a power electronic converter according to claim 5, characterized in that: The resistance of the Thevenin equivalent circuit is a fixed value, and the resistance value is the simulation step size divided by 2 times the DC - side capacitor value.