Five-level active neutral point clamped circuit structure and design method of average model

Abstract

This invention discloses a five-level active midpoint clamping circuit structure and design method based on an average model. Ignoring redundancy, the five-level active midpoint clamping circuit structure based on the average model includes two controlled voltage sources, two controlled current sources, two DC bus capacitors, and a floating capacitor. The series and parallel connection of the controlled voltage and current sources is shown in the attached figure of the abstract. The current of the controlled current source is determined by the output current of the five-level circuit, and the voltage of the controlled voltage source is determined by the positive and negative voltages of the two DC bus capacitors. This invention can simulate the voltage fluctuation of a five-level active midpoint clamping circuit switching model. It considers the impact of voltage fluctuations on the AC side and can control the voltage fluctuation of the five-level active midpoint clamping circuit within a reasonable range. It has strong versatility and greatly improves simulation speed.

Description

Technical Field

[0001] This invention relates to the field of modeling five-level active midpoint clamp circuit structures, specifically to the average model of five-level active midpoint clamp circuit structures and design methods. Background Technology

[0002] In recent years, five-level circuits have been widely used in photovoltaic power generation, charging piles, active filters, high-voltage direct current transmission systems and other applications because they have advantages over traditional two-level and three-level circuits, such as more output levels, lower output harmonics, and lower output voltage variation rate.

[0003] The high penetration rate of large-scale distributed photovoltaic (PV) systems into distribution networks introduces uncertainties in system characteristics, particularly stability and power quality assessment. Simulation modeling is a key method for analyzing the impact of large-scale power electronic devices integrated into power systems. Traditional switching device models are relatively accurate but overly complex and unsuitable for multi-machine or even cluster simulations in distributed applications.

[0004] Existing five-level active midpoint clamping circuit switching model technology suffers from drawbacks such as simulation difficulties, slow speed, or complex algorithms, and further improvements are needed. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention proposes a five-level active midpoint clamping circuit structure and design method based on an average model.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] The average model's five-level active midpoint clamping circuit structure includes two controlled voltage sources, two controlled current sources, two DC bus capacitors, and one floating capacitor. The current of the controlled current source is determined by the output current, and the voltage of the controlled voltage source is determined by the positive and negative voltages of each capacitor. The state of each controlled source is controlled by controlling the duty cycle component of the switching transistor.

[0008] The controlled voltage source and the controlled current source are calculated using the following formulas:

[0009]

[0010]

[0011]

[0012]

[0013] Where u pc The voltage across the upper bridge arm switching transistor; u cn This is the voltage across the lower bridge arm switch transistor;

[0014] i oc i is the current from the midpoint of the DC bus to the AC output; cf The current flowing through the floating capacitor;

[0015] i o The output current on the AC side of the converter; u c1 The voltage across capacitor PO on the upper bridge arm DC bus; u c2 This is the voltage across the ON terminal of the DC bus capacitor in the lower bridge arm;

[0016] d1, d3, d5, and d6 are the duty cycles of the corresponding switching transistors T1, T3, T5, and T6 in the five-level active midpoint clamping circuit structure.

[0017] A design method for a five-level active midpoint clamping circuit structure based on an average model is provided. The five-level active midpoint clamping circuit structure based on the average model includes two controlled voltage sources, two controlled current sources, and three capacitors. The current of the controlled current source is determined by the output current, and the voltage of the controlled voltage source is determined by the positive and negative voltages of each capacitor. The state of each controlled source is controlled by controlling the duty cycle component of the switching transistor.

[0018] The controlled voltage source and the controlled current source are calculated using the following formulas:

[0019]

[0020]

[0021]

[0022]

[0023] Where u pc The voltage across the upper bridge arm switching transistor; u cn This is the voltage across the lower bridge arm switch transistor;

[0024] i oc i is the current from the midpoint of the DC bus to the AC output; cf The current flowing through the floating capacitor;

[0025] i o The output current on the AC side of the converter; u c1 The voltage across capacitor PO on the upper bridge arm DC bus; u c2 This is the voltage across the ON terminal of the DC bus capacitor in the lower bridge arm;

[0026] d1, d3, d5, and d6 are the duty cycles of the corresponding switching transistors T1, T3, T5, and T6 in the five-level active midpoint clamping circuit structure.

[0027] The beneficial effects of this invention are:

[0028] This invention uses an average model instead of a switching model as the research object, which can simulate the voltage fluctuation of a five-level active midpoint clamp circuit switching model. It considers the impact of voltage fluctuation on the AC side and can control the voltage fluctuation of the five-level active midpoint clamp circuit to be within a reasonable range. It has strong versatility and greatly improves the simulation speed. Attached Figure Description

[0029] The invention will now be further described with reference to the accompanying drawings.

[0030] Figure 1 This is a schematic diagram of the five-level active midpoint clamping circuit structure based on the average model proposed in this invention.

[0031] Figure 2 It is a three-phase topology of a five-level active neutral-point clamping converter, where A, B, and C represent the three phases of the AC side of the five-level active neutral-point clamping converter.

[0032] Figure 3 It is a single-phase five-level active midpoint clamping circuit topology, with T1-T8 being the IGBTs in the five-level circuit.

[0033] Figure 4 This is a schematic diagram of the three-phase five-level active neutral-point clamping converter structure based on the average model proposed in this invention. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] Combination Figures 1 to 4 The technical solution and principles of this invention are described. To accelerate simulation, a general average model for a five-level active midpoint clamping circuit based on a controlled source is proposed, and its implementation method is as follows:

[0036] Based on the converter topology, each single-phase five-ANPC topology is replaced by two controlled voltage sources and two controlled current sources; the current of the controlled current source is determined by the output current, and the voltage of the controlled voltage source is determined by the positive and negative voltages of each capacitor; the state of each controlled source is controlled by controlling the duty cycle component of the five-ANPC.

[0037] The controlled voltage source and the controlled current source are calculated using the following formulas:

[0038]

[0039]

[0040]

[0041]

[0042] Where u pc The voltage across the upper bridge arm switching transistor; u cn This is the voltage across the lower bridge arm switch transistor;

[0043] i oc i is the current from the midpoint of the DC bus to the AC output; cf The current flowing through the floating capacitor;

[0044] i o The output current on the AC side of the converter; u c1 The voltage across capacitor PO on the upper bridge arm DC bus; u c2 This is the voltage across the ON terminal of the DC bus capacitor in the lower bridge arm;

[0045] d1, d3, d5, and d6 are the duty cycles of the corresponding switching transistors T1, T3, T5, and T6 in the five-level active midpoint clamping circuit structure.

[0046] Figure 2 Three-phase topology of a five-level active neutral-point clamping converter. Figure 3 This is a single-phase five-level active neutral-point clamping circuit topology. As shown in the diagram, each phase arm of the five-phase ANPC consists of eight IGBT switches (T1-T8) connected in series and parallel, with D1-D2 representing accompanying diodes. The DC-side bus voltage is Udc, the arm reactance is L, and the arm resistance is R.

[0047] For simulations of five ANPCs under the switching model, it is necessary to build a simulation system in the PLECS software. Figure 2 Combination Figure 3 The topology used in this design results in a very slow simulation speed, which is not conducive to the design of control parameters.

[0048] At a certain level of precision, this invention utilizes PLECS simulation software. A comparison with simulations using a five-level ANPC (Automatic Processing Unit) model based on a switching model reveals that the circuit structure simulation speed based on the five-level ANPC average model is significantly faster. For a three-phase five-level clamped converter with 24 switches and a switching frequency of 15kHz, a 10-second simulation of the switching model takes 115 seconds, while the average model proposed in this paper only takes 23 seconds, greatly reducing the simulation time. This is because the proposed technique abandons the traditional switching model; after adopting the average model, the output waveform no longer exhibits switching ripple, yet maintains dynamic performance consistent with the original detailed model. Therefore, the simulation speed is greatly improved.

[0049] In summary, the traditional five-level active neutral-point clamped converter circuit suffers from slow simulation speed due to the large number of switches. This invention abandons the traditional switching model and, in the average model, replaces all eight switches on each phase arm of the converter with two controlled voltage sources and two controlled current sources. Under a certain level of simulation accuracy, it can simulate the normal operation performance of the five-level active neutral-point clamped converter, with no switching ripple in the output waveform, greatly improving the simulation speed. It also considers the impact of voltage fluctuations on the AC side and can control the output voltage fluctuations of the five-level active neutral-point clamped converter to be within a reasonable range.

[0050] In the description of this invention, it should be understood that the terms "opening", "upper", "lower", "thickness", "top", "middle", "length", "inner", "around", etc., which indicate orientation or positional relationship, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the components or elements referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting this invention.

[0051] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0052] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A five-level active midpoint clamping circuit structure for an average model, characterized in that, include: Two controlled voltage sources and Two controlled current sources and Two DC bus capacitors and and a floating capacitor The DC bus capacitor The DC bus capacitor is connected between the positive terminal P of the DC bus and the midpoint O of the DC bus. The controlled voltage source is connected between the midpoint O of the DC bus and the negative terminal N of the DC bus. The controlled voltage source is connected between the positive terminal P and the common terminal C of the DC bus. The controlled current source is connected between the common node C and the negative node N of the DC bus. Connect between the midpoint O of the DC bus and the common node C; The controlled voltage source With DC bus capacitor The controlled voltage source is connected in series. With DC bus capacitor Two series structures connected in series with the controlled current source The controlled current source is connected in parallel. With floating capacitor Series; Excluding redundant states, the five-level active midpoint clamping circuit operates under only five conduction states: (T1, T4, T7, T8), (T2, T4, T5, T7), (T1, T3, T7, T8), (T1, T3, T6, T8), and (T1, T3, T5, T6). The controlled voltage source and controlled current source are then calculated using the following formulas: in, This is the voltage across the upper bridge arm switch transistor; This is the voltage across the lower bridge arm switch transistor; This is the current output from the midpoint of the DC bus to the AC side; The current flowing through the floating capacitor; This refers to the output current on the AC side of the converter. u c1 This is the voltage across capacitor PO on the upper bridge arm DC bus. u c2 This is the voltage across the ON terminal of the DC bus capacitor in the lower bridge arm; d1, d3, d5, and d6 are the duty cycles of the corresponding switching transistors T1, T3, T5, and T6 in the five-level active midpoint clamping circuit structure.

2. The five-level active midpoint clamping circuit structure of the average model according to claim 1, characterized in that, The current of the controlled current source is determined by the output current of the five-level circuit, and the voltage of the controlled voltage source is determined by the positive and negative voltages of each capacitor.

3. The five-level active midpoint clamping circuit structure of the average model according to claim 1, characterized in that, The circuit structure controls the state of each controlled source by controlling the duty cycle component of the switching transistor.

4. The five-level active midpoint clamping circuit structure of the average model according to claim 1, characterized in that, The circuit structure controls the duty cycle component of the switching transistor to keep the output voltage fluctuation of the five-level active midpoint clamp converter within a reasonable range.

5. A design method for a five-level active midpoint clamping circuit structure based on an average model, characterized in that, include: Two controlled voltage sources and Two controlled current sources and Two DC bus capacitors and and a floating capacitor The DC bus capacitor The DC bus capacitor is connected between the positive terminal P of the DC bus and the midpoint O of the DC bus. The controlled voltage source is connected between the midpoint O of the DC bus and the negative terminal N of the DC bus. The controlled voltage source is connected between the positive terminal P and the common terminal C of the DC bus. The controlled current source is connected between the common node C and the negative node N of the DC bus. Connect between the midpoint O of the DC bus and the common node C; The controlled voltage source With DC bus capacitor The controlled voltage source is connected in series. With DC bus capacitor Two series structures connected in series with the controlled current source The controlled current source is connected in parallel. With floating capacitor Series; Excluding redundant states, the five-level active midpoint clamping circuit operates under only five conduction states: (T1, T4, T7, T8), (T2, T4, T5, T7), (T1, T3, T7, T8), (T1, T3, T6, T8), and (T1, T3, T5, T6). The controlled voltage source and controlled current source are then calculated using the following formulas: in, This is the voltage across the upper bridge arm switching transistor; This is the voltage across the lower bridge arm switch transistor; This is the current output from the midpoint of the DC bus to the AC side; The current flowing through the floating capacitor; This refers to the output current on the AC side of the converter. u c1 This is the voltage across capacitor PO on the upper bridge arm DC bus. u c2 This is the voltage across the ON terminal of the DC bus capacitor in the lower bridge arm; d1, d3, d5, and d6 are the duty cycles of the corresponding switching transistors T1, T3, T5, and T6 in the five-level active midpoint clamping circuit structure.

6. The design method of the five-level active midpoint clamp circuit structure of the average model according to claim 5, characterized in that, The current of the controlled current source is determined by the output current of the five-level circuit, and the voltage of the controlled voltage source is determined by the positive and negative voltages of each capacitor.

7. The design method of the five-level active midpoint clamp circuit structure of the average model according to claim 5, characterized in that, The circuit structure controls the state of each controlled source by controlling the duty cycle component of the switching transistor.

8. The design method of the five-level active midpoint clamp circuit structure of the average model according to claim 6, characterized in that, The circuit structure controls the duty cycle component of the switching transistor to keep the output voltage fluctuation of the five-level active midpoint clamp converter within a reasonable range.

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