A topology based on single-phase cascaded double-buck full-bridge type converter

Abstract

The utility model discloses a kind of topology structure based on single-phase cascaded double Buck full-bridge type converter, comprising: a plurality of module unit cascaded single-phase main power circuit, and a plurality of independent direct-current power supply, each direct-current power supply is connected with the direct-current side of corresponding module unit in main power circuit, and main power circuit output is connected with single-phase power grid after filter circuit. Compared with traditional single-phase two-level inverter and cascaded H-bridge type multilevel inverter, its advantage is that inverter switching loss is smaller, applicable to higher switching frequency, more suitable for high-power application, better modular expandability, improve the working efficiency of system. At the same time, due to the structural characteristics of double Buck full-bridge circuit itself, the shoot-through condition of upper and lower switching tubes on the same bridge arm can be effectively avoided, greatly improving its safety and reliability, with very wide application prospect.

Description

Technical Field

[0001] This utility model relates to the fields of new energy power generation technology and power electronics technology, specifically to a topology based on a single-phase cascaded double-Buck full-bridge converter. Background Technology

[0002] In recent years, the installed capacity of single units in new energy distributed generation systems has increased significantly, and correspondingly, higher requirements have been placed on transmission efficiency. Currently, the mainstream solution is to use higher voltage levels for transmission. Therefore, power electronic equipment is becoming increasingly popular in medium- and high-voltage, high-power applications. Due to the limited voltage withstand capability of power switching transistors, cascaded topologies, which utilize low-voltage devices to transmit medium- and high-voltage power, are widely used in the topology of medium-voltage direct-connected grid-connected inverters. Since each DC side of a cascaded grid-connected inverter requires an independent DC source, which perfectly matches the characteristics of photovoltaic power generation, cascaded medium-voltage direct-connected inverters are the most widely used power topology, with photovoltaic modules as the front-end. For example, patent document CN106253334A discloses a cascaded photovoltaic grid-connected inverter and its control method and device.

[0003] For new energy power generation systems, the grid-connected inverter serves as the primary interface between the photovoltaic array and the power grid; therefore, the inverter's performance determines the overall performance of the power generation system. In photovoltaic grid-connected power generation systems, improving system efficiency and grid-connected waveform quality are key issues to be addressed. For grid-connected power generation systems with cascaded photovoltaic grid-connected inverter structures, current considerations focus more on system efficiency. Since single-stage inverters have only one energy conversion stage, their efficiency is the highest. Therefore, the most common type of grid-connected inverter is based on a cascaded H-bridge circuit topology. However, in common cascaded H-bridge circuit structures, shoot-through may occur between the upper and lower switches of the same arm of the H-bridge circuit in any power conversion module, reducing system reliability. Correspondingly, to prevent shoot-through, a dead time must be added between drive signals, which causes distortion of the output current waveform. Currently, the mainstream modulation method is phase-shifted PWM modulation. Therefore, when the number of cascaded inverters increases to a certain extent, the phase shift of each modulation wave becomes very small, and the corresponding phase shift period is also very small. If the dead time set between drive signals is too large, it may lead to inverter failure or equipment damage, greatly reducing system reliability. On the other hand, H-bridge inverters lack independent freewheeling diodes, and the reverse recovery time of the MOSFETs and IGBTs' own diodes is long, resulting in significant switching losses in the switching transistors and limiting the drive frequency of the switching transistors. To address this issue, dual-buck half-bridge inverters and dual-buck full-bridge inverters are available for ordinary two-level inverters to solve problems such as shoot-through in the same bridge arm switch and high losses due to long reverse recovery times. However, dual-buck half-bridge inverters suffer from the common drawbacks of half-bridge inverters, namely, the need for a DC input voltage with a midpoint, resulting in high voltage stress on power devices. Additionally, dual-buck half-bridge inverters also suffer from low DC-side voltage utilization. Dual-Buck full-bridge inverters retain the advantages of dual-Buck half-bridge inverters while effectively improving their common drawbacks, and all power transistors and inductors operate at high frequency for half of the output cycle. Therefore, dual-Buck full-bridge inverters have greater advantages in future applications.

[0004] To address the reliability and efficiency challenges in new energy grid-connected power generation systems constructed with cascaded H-bridge inverters, it is crucial to study how to ensure that grid-connected inverter systems can transmit power at higher voltage levels, improve the transmission efficiency of inverter systems, and, especially for photovoltaic grid-connected systems, simultaneously ensure the reliability and safety of grid-connected inverters while enhancing the DC-side voltage utilization rate of inverters. Utility Model Content

[0005] To achieve the above objectives, this utility model provides a topology based on a single-phase cascaded double-Buck full-bridge converter, which aims to enable medium- and high-voltage power transmission in grid-connected inverter systems while improving their safety and transmission efficiency.

[0006] The embodiments of this utility model adopt the following technical solutions, as detailed below:

[0007] The present invention relates to a topology based on a single-phase cascaded double-Buck full-bridge converter, characterized by comprising: a main power circuit and a filter circuit; the main power circuit includes N cascaded double-Buck full-bridge circuits and N independent DC power supplies V1, V2, ... V i …、V N , where V i Let N represent the i-th DC power source, where N is a positive integer.

[0008] The input DC power supply V of any i-th double Buck full-bridge circuit si The positive terminal is connected to the i-th DC power supply V i The positive terminal is connected to the positive terminal, and the input DC power supply V of any i-th double-Buck full-bridge circuit is... si The negative terminal is connected to the i-th DC power supply V i The negative terminal is connected;

[0009] Among them, any i-th double-Buck full-bridge circuit includes four power diodes D. i1 D i2 D i3 D i4 and four power switching transistors S i1 S i2 S i3 S i4 The bridge circuit consists of two inductor coils L i1 L i2 and a DC capacitor C i ;

[0010] The first power diode D i1 With the first power switch S i1 Located in the same bridge arm, the first power diode D i1 The anode of the first power switch S i1 The first terminal p is connected, and the first power diode D i1 The cathode and the DC capacitor C i The first terminal p is connected to form a DC positive bus and connected to the input DC power supply V. si The positive terminal is connected; the first power switch S i1 The second terminal n is connected to the DC capacitor C iThe second terminal n is connected to form a DC negative bus and connected to the input DC power supply V. si The negative terminal is connected;

[0011] The second power diode D i2 With the second power switch S i2 Located in the same bridge arm, the second power diode D i2 The anode of the second power switch S i2 The first terminal p is connected, and the second power diode D i2 The cathode is connected to the DC positive bus, and the second power switch S i2 The second terminal n is connected to the DC negative busbar;

[0012] The third power diode D i3 With the third power switch S i3 Located in the same bridge arm, the third power diode D i3 The cathode and the third power switch S i3 The second terminal n is connected to the third power switch S. i3 The first terminal p is connected to the DC positive bus, and the third power diode D i3 The anode is connected to the DC negative busbar;

[0013] The fourth power diode D i4 With the fourth power switch S i4 Located in the same bridge arm, the fourth power diode D i4 The cathode and the fourth power switch S i4 The second terminal n is connected to the fourth power switch S. i4 The first terminal p is connected to the DC positive bus, and the fourth power diode D i4 The anode is connected to the DC negative busbar;

[0014] First inductor L i1 The first terminal p is connected to the first power diode D i1 The anode of the first inductor L is connected to the anode of the first inductor. i1 The second terminal n and the third power diode D i3 The cathodes are connected, and the connection point between them is denoted as . a , and serve as the first output terminal of the i-th double Buck full-bridge circuit;

[0015] The second inductor L i2 The first terminal p and the second power diode D i2 The anode of the second inductor L is connected to the anode of the second inductor.i2 The second terminal n is connected to the fourth power diode D i4 The cathodes are connected, and the connection point between them is denoted as . b It serves as the second output of the i-th double Buck full-bridge circuit and is connected to the first output of the (i+1)-th double Buck full-bridge circuit; the second output of the N-th double Buck full-bridge circuit is connected to the first output of the first double Buck full-bridge circuit through the filter circuit and the AC power grid.

[0016] The characteristic of the topology based on a single-phase cascaded double-Buck full-bridge converter described in this utility model is that the filter circuit includes: a filter inductor L f and a filter capacitor C f Wherein, the filter inductor L f The two ends of the capacitor are connected in series with the first output terminal of the first double-Buck full-bridge circuit and the AC mains, respectively; the filter capacitor C f The two ends are connected in parallel with the first output terminal of the first double-Buck full-bridge circuit and the second output terminal of the Nth double-Buck full-bridge circuit, respectively.

[0017] Compared with the prior art, the beneficial effects achieved by this utility model are:

[0018] This invention provides a cascaded double-Buck full-bridge converter topology that ensures grid-connected inverter systems can transmit power at medium and high voltage levels. It also avoids shoot-through issues that might occur between the upper and lower switches on the same arm of an H-bridge circuit, thus improving safety and reliability. Furthermore, it reduces the switching time of the switches, thereby reducing losses during the switching process and improving operating efficiency. Attached Figure Description

[0019] Figure 1 This is a topology diagram of the single-phase cascaded double Buck full-bridge converter of this utility model;

[0020] Figure 2 This is the circuit diagram of the double-Buck full-bridge converter topology based on the single-phase cascaded double-Buck full-bridge converter of this utility model. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention.

[0022] In this embodiment, a topology based on a single-phase cascaded double-Buck full-bridge converter includes: a main power circuit and a filter circuit; the main power circuit includes N cascaded double-Buck full-bridge circuits and N independent DC power supplies V1, V2, ... Vi …、V N , where V i Let N represent the i-th DC power source, where N is a positive integer.

[0023] The input DC power supply V of any i-th double Buck full-bridge circuit si The positive terminal is connected to the i-th DC power supply V i The positive terminal is connected to the positive terminal, and the input DC power supply V of any i-th double-Buck full-bridge circuit is... si The negative terminal is connected to the i-th DC power supply V i The negative terminals are connected, such as Figure 1 As shown, the connection method of each DC power supply has already been... Figure 1 It is drawn in the middle.

[0024] Among them, any i-th double-Buck full-bridge circuit includes four power diodes D. i1 D i2 D i3 D i4 and four power switching transistors S i1 S i2 S i3 S i4 The bridge circuit consists of two inductor coils L i1 L i2 and a DC capacitor C i ,like Figure 2 As shown.

[0025] The first power diode D i1 With the first power switch S i1 Located in the same bridge arm, the first power diode D i1 The anode of the first power switch S i1 The first terminal p is connected, and the first power diode D i1 Cathode and DC capacitor C i The first terminal p is connected to form a DC positive bus and connected to the input DC power supply V. si The positive terminal is connected; the first power switch S i1 The second terminal n is connected to the DC capacitor C i The second terminal n is connected to form a DC negative bus and connected to the input DC power supply V. si The negative terminal is connected;

[0026] The second power diode D i2 With the second power switch S i2 Located in the same bridge arm, the second power diode D i2 The anode and the second power switch S i2 The first terminal p is connected, and the second power diode Di2 The cathode is connected to the DC positive bus, and the second power switch S i2 The second terminal n is connected to the DC negative busbar;

[0027] The third power diode D i3 With the third power switch S i3 Located in the same bridge arm, the third power diode D i3 The cathode and the third power switch S i3 The second terminal n is connected, and the third power switch S i3 The first terminal p is connected to the DC positive bus, and the third power diode D... i3 The anode is connected to the DC negative busbar;

[0028] The fourth power diode D i4 With the fourth power switch S i4 Located in the same bridge arm, the fourth power diode D i4 The cathode and the fourth power switch S i4 The second terminal n is connected to the fourth power switch S. i4 The first terminal p is connected to the DC positive bus, and the fourth power diode D... i4 The anode is connected to the DC negative busbar;

[0029] First inductor L i1 The first terminal p is connected to the first power diode D i1 The anodes of the first inductor coil L are connected. i1 The second terminal n and the third power diode D i3 The cathodes are connected, and the connection point between them is denoted as . a And as the first output terminal of the i-th double-Buck full-bridge circuit, the specific connection method is already in Figure 2 It is drawn in the middle.

[0030] The second inductor L i2 The first terminal p and the second power diode D i2 The anode of the first inductor is connected to the second inductor L. i2 The second terminal n is connected to the fourth power diode D i4 The cathodes are connected, and the connection point between them is denoted as . b It serves as the second output of the i-th double Buck full-bridge circuit and is connected to the first output of the (i+1)-th double Buck full-bridge circuit; the second output of the N-th double Buck full-bridge circuit is connected to the first output of the first double Buck full-bridge circuit through a filter circuit and an AC power grid.

[0031] In this embodiment, the filtering circuit includes: a filter inductor L f and a filter capacitor C f Among them, the filter inductor L f The two ends are connected in series with the first output terminal of the first double-Buck full-bridge circuit and the AC mains, respectively; the filter capacitor C f The two ends are connected in parallel with the first output terminal of the first double-Buck full-bridge circuit and the second output terminal of the Nth double-Buck full-bridge circuit, respectively, as follows: Figure 1 As shown, the cascaded connection method on the output side of each dual-Buck full-bridge circuit has already been implemented. Figure 1 It is drawn in the middle.

[0032] The embodiments of this utility model have been described above. The specific embodiments described above are merely illustrative and not intended to limit the technical solutions. Therefore, this utility model is not limited to the specific embodiments described above. All simple substitutions and variations of the technical solutions of this utility model made by those skilled in the art without departing from the spirit and concept of this utility model are within the protection scope of this utility model.

Claims

1. A topology based on a single-phase cascaded dual-Buck full-bridge converter, characterized in that, include: Main power circuit and filter circuit; the main power circuit includes N cascaded double Buck full-bridge circuits and N independent DC power supplies V1, V2, ... V i …、V N , where V i This represents the i-th DC power source, where N is a positive integer; The input DC power supply V of any i-th double Buck full-bridge circuit si The positive terminal is connected to the i-th DC power supply V i The positive terminal is connected to the positive terminal, and the input DC power supply V of any i-th double-Buck full-bridge circuit is... si The negative terminal is connected to the i-th DC power supply V i The negative terminal is connected; Among them, any i-th double-Buck full-bridge circuit includes four power diodes D. i1 D i2 D i3 D i4 and four power switching transistors S i1 S i2 S i3 S i4 The bridge circuit consists of two inductor coils L i1 L i2 and a DC capacitor C i ; The first power diode D i1 With the first power switch S i1 Located in the same bridge arm, the first power diode D i1 The anode of the first power switch S i1 The first terminal p is connected, and the first power diode D i1 The cathode and the DC capacitor C i The first terminal p is connected to form a DC positive bus and connected to the input DC power supply V. si The positive terminal is connected; the first power switch S i1 The second terminal n is connected to the DC capacitor C i The second terminal n is connected to form a DC negative bus and connected to the input DC power supply V. si The negative terminal is connected; The second power diode D i2 With the second power switch S i2 Located in the same bridge arm, the second power diode D i2 The anode of the second power switch S i2 The first terminal p is connected, and the second power diode D i2 The cathode is connected to the DC positive bus, and the second power switch S i2 The second terminal n is connected to the DC negative busbar; The third power diode D i3 With the third power switch S i3 Located in the same bridge arm, the third power diode D i3 The cathode and the third power switch S i3 The second terminal n is connected to the third power switch S. i3 The first terminal p is connected to the DC positive bus, and the third power diode D i3 The anode is connected to the DC negative busbar; The fourth power diode D i4 With the fourth power switch S i4 Located in the same bridge arm, the fourth power diode D i4 The cathode and the fourth power switch S i4 The second terminal n is connected to the fourth power switch S. i4 The first terminal p is connected to the DC positive bus, and the fourth power diode D i4 The anode is connected to the DC negative busbar; First inductor L i1 The first terminal p is connected to the first power diode D i1 The anode of the first inductor L is connected to the anode of the first inductor. i1 The second terminal n and the third power diode D i3 The cathodes are connected, and the connection point between them is denoted as . a , and serve as the first output terminal of the i-th double Buck full-bridge circuit; The second inductor L i2 The first terminal p and the second power diode D i2 The anode of the second inductor L is connected to the anode of the second inductor. i2 The second terminal n is connected to the fourth power diode D i4 The cathodes are connected, and the connection point between them is denoted as . b It serves as the second output of the i-th double Buck full-bridge circuit and is connected to the first output of the (i+1)-th double Buck full-bridge circuit; the second output of the N-th double Buck full-bridge circuit is connected to the first output of the first double Buck full-bridge circuit through the filter circuit and the AC power grid.

2. The topology based on a single-phase cascaded dual-Buck full-bridge converter as described in claim 1, characterized in that, The filtering circuit includes: a filter inductor L f and a filter capacitor C f Wherein, the filter inductor L f The two ends of the capacitor are connected in series with the first output terminal of the first double-Buck full-bridge circuit and the AC mains, respectively; the filter capacitor C f The two ends are connected in parallel with the first output terminal of the first double-Buck full-bridge circuit and the second output terminal of the Nth double-Buck full-bridge circuit, respectively.

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