WO2021068640A1

WO2021068640A1 - Dc boost conversion circuit and apparatus

Info

Publication number: WO2021068640A1
Application number: PCT/CN2020/108229
Authority: WO
Inventors: 尉志勇; 邓占锋; 周哲; 赵国亮; 刘海军; 陆振纲; 慕小斌; 徐云飞
Original assignee: 全球能源互联网研究院有限公司; 国家电网有限公司
Priority date: 2019-10-08
Filing date: 2020-08-10
Publication date: 2021-04-15
Also published as: CN110635693A

Abstract

A DC boost conversion circuit and apparatus. The circuit comprises: a fully controlled circuit (10), a transformer (20), and an uncontrolled circuit (30). The fully controlled circuit (10) is composed of multiple fully controlled H-bridge circuits connected in parallel; the DC side of the fully controlled circuit (10) is configured to receive DC power, and the AC side of the fully controlled circuit (10) is connected to the uncontrolled circuit (30) by means of the transformer (20); the uncontrolled circuit (30) is composed of multiple uncontrolled H-bridge circuits connected in series; the fully controlled circuit (10) is configured to perform equalization conversion on the DC power to obtain equalized AC power, and input the equalized AC power to the transformer; the transformer (20) is configured to boost the equalized AC power to obtain boosted equalized AC power, and input the boosted equalized AC power to the uncontrolled circuit (30); and the uncontrolled circuit (30) is configured to rectify and output the boosted equalized AC power.

Description

DC boost conversion circuit and device

This application claims the priority of a Chinese patent application filed with the Chinese Patent Office with an application number of 201910949416.0 on October 8, 2019. The entire content of this application is incorporated into this application by reference.

Technical field

This application relates to the field of power system transmission and distribution technology, for example, to a DC boost converter circuit and device.

Background technique

The DC distribution network is gradually being used in a variety of circuit systems. The DC distribution network has the advantages of high power supply reliability, low line cost, and low power transmission loss. The development of the DC distribution network provides new access methods for distributed new energy consumption, island power generation and low-voltage DC loads.

As an important form of distributed energy, photovoltaic power generation follows the principle of decentralized development and nearby consumption, which can solve the problem of power loss during boosting and long-distance transportation. However, the photovoltaic boost circuit in the related art has the problem of difficulty in voltage equalization and current control. In order to solve the voltage equalization problem in the boost circuit, a capacitor with a larger capacity is usually set in the circuit. The increase of the large capacitor not only improves the circuit design In addition, the total cost of the equipment is increased, and there are problems such as low efficiency and high cost.

Summary of the invention

The embodiments of the present application provide a DC boost conversion circuit and device to solve the technical problems of high cost and large volume of the DC boost circuit in the related art.

The embodiment of the present application provides a DC boost conversion circuit. The DC boost conversion circuit includes: a fully-controlled circuit, a transformer, and an uncontrolled circuit. The fully-controlled circuit is composed of a plurality of fully-controlled H-bridge circuits connected in parallel. Composition, the DC side of the fully-controlled circuit is set to receive DC power, the AC side of the fully-controlled circuit is connected to the uncontrolled circuit through the transformer; the uncontrolled circuit is composed of a plurality of uncontrolled circuits connected in series The control type H bridge circuit is composed; the full control type circuit is set to obtain the equalizing AC power after the DC power is voltage equalized, and the equalizing AC power is input to the transformer; the transformer is set to The voltage equalizing AC power is boosted to obtain the boosted equalizing AC power, and the boosted equalizing AC power is input to the uncontrolled circuit; the uncontrolled circuit is set to set the boosted The balanced AC power is output after rectification.

The embodiment of the present application also provides a DC boost conversion device. The DC boost conversion device includes: a DC source, a controller, and the DC boost conversion circuit as described in the above embodiments of the application, the DC boost conversion circuit The DC source is connected to receive the DC power output by the DC source; the controller is connected to the DC boost converter circuit and is configured to control the switching frequency of the full-control circuit.

Description of the drawings

In order to illustrate the specific embodiments of the present application or the technical solutions in the related technologies, the following will briefly introduce the drawings that need to be used in the description of the embodiments or related technologies.

FIG. 1 is a schematic structural diagram of a DC boost converter circuit provided by an embodiment of the application;

2A is a schematic structural diagram of a DC boost converter circuit provided by another embodiment of the application;

2B is a schematic structural diagram of a DC boost converter circuit provided by another embodiment of the application;

2C is a schematic structural diagram of a DC boost converter circuit provided by another embodiment of the application;

3 is a schematic structural diagram of a DC boost converter circuit provided by another embodiment of the application;

4 is a schematic structural diagram of a DC boost converter circuit provided by another embodiment of the application;

FIG. 5 is a structural block diagram of a DC boost converter device provided by an embodiment of the application;

Fig. 6 is a modulation principle diagram of a DC boost converter provided by an embodiment of the application.

Detailed ways

The technical solution of the present application will be described below in conjunction with the accompanying drawings. Obviously, the described embodiments are a part of the embodiments of the present application, rather than all of the embodiments.

In the description of this application, the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. indicate the orientation or position The relationship is based on the orientation or position relationship shown in the drawings, only for the convenience of describing the application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specified orientation, be constructed and operated in a specified orientation, therefore It cannot be understood as a restriction on this application. In addition, the terms "first", "second", and "third" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance.

In the description of this application, unless expressly stipulated and limited otherwise, the terms "installed", "connected", and "connected" shall be interpreted broadly, for example, it may be a fixed connection, a detachable connection, or an integral Connection; It can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or it can be the internal connection of the two components, which can be a wireless connection or a wired connection. For those of ordinary skill in the art, the meaning of the above-mentioned terms in this application can be understood according to the situation.

The embodiment of the present application provides a DC step-up conversion circuit. As shown in FIG. 1, the DC step-up conversion circuit includes: a fully-controlled circuit 10, a transformer 20, and an uncontrolled circuit 30. The fully-controlled circuit 10 consists of multiple It consists of a parallel fully-controlled H-bridge circuit, the DC side of the fully-controlled circuit 10 is set to receive DC power, and the AC side of the fully-controlled circuit 10 is connected to an uncontrolled circuit 30 through a transformer 20; the uncontrolled circuit 30 consists of multiple The uncontrolled H-bridge circuit is composed of a series-connected uncontrolled H-bridge circuit; the fully-controlled circuit 10 is set to obtain equalized AC power after voltage equalization and conversion of DC power, and input the equalized AC power to the transformer 20; the transformer 20 is set to equalize the AC power After boosting, the boosted equalized AC power is obtained, and the boosted equalized AC power is input to the uncontrolled circuit 30; the uncontrolled circuit 30 is set to rectify the boosted equalized AC power and output .

In the DC boost converter circuit provided by the embodiment of the application, a plurality of parallel fully-controlled H-bridge circuits are arranged on the low-voltage side, and a plurality of uncontrolled H-bridge circuits in series are arranged on the high-voltage side, and the high-voltage side and the low-voltage side are connected by a transformer Therefore, the DC boost conversion circuit avoids the DC-AC-DC conversion link, and can achieve a high boost ratio through the structure of parallel connection on the low-voltage side and cascade connection on the high-voltage side. At the same time, the DC boost converter circuit does not need to be equipped with other components, and the voltage equalization of the circuit can be realized through a plurality of parallel fully-controlled H-bridge circuits, which improves the boost efficiency of the circuit and reduces the volume and cost of the circuit. In addition, the DC boost conversion circuit provided by the embodiment of the present application can be used for the unidirectional flow of energy of the distributed power generation unit, and can realize the power transmission from the low-voltage DC port to the high-voltage DC port.

In the DC boost converter circuit provided by the embodiment of the present application, during the normal triggering of the fully-controlled circuit 10, the fully-controlled circuit 10, the transformer 20, and the uncontrolled circuit 30 may have a strong coupling connection, and multiple non-controllable circuits may be connected. The working state of the controlled H-bridge circuit can be completely the same. At this time, the DC power received by the low-voltage stage can be induced to the high-voltage stage via the transformer 20 to realize the circuit voltage equalization. In addition, it is also possible to realize current sharing among multiple uncontrolled H-bridge circuits through carrier phase-shift modulation and equal output time of the circuit.

As an optional implementation of the embodiments of the present application, the uncontrolled H-bridge circuit is a rectifier circuit composed of multiple diodes. The fully-controlled H-bridge circuit includes a voltage equalization circuit composed of multiple fully-controlled devices. Fully-controlled devices can use insulated gate bipolar transistors (IGBT), metal-oxide half field effect transistors (Metal-Oxide-Semiconductor Field-Effect Transistor, MOSFET), fast switching, or devices with the same function. 2A is a schematic structural diagram of a DC boost conversion circuit provided by another embodiment of the application; FIG. 2B is a schematic structural diagram of a DC boost conversion circuit provided by another embodiment of the application; FIG. 2C is another implementation of the application The schematic diagram of the structure of the DC boost converter circuit provided by the example. 2A-2C show a DC boost converter module in the DC boost converter circuit. The DC boost converter module includes a fully controlled H-bridge circuit, a transformer, and an uncontrolled H-bridge circuit. As shown in Figure 2A, when T1 and T4 in the fully-controlled H-bridge circuit are turned on, the voltage across the low-voltage winding of the transformer 20 is positive, and the voltage across the high-voltage winding is induced to be positive. At this time, the DC input The DC power of the boost converter module can be transmitted to the high-voltage stage via D1 and D4 of the uncontrolled H-bridge circuit; as shown in Figure 2B, when T2 and T3 in the fully-controlled H-bridge circuit are turned on, the low-voltage winding of the transformer 20 The voltage at both ends is negative, and the voltage at both ends of the high-voltage stage winding is induced to be negative. At this time, the DC power input to the DC boost converter module can be transmitted to the high-voltage stage via D2 and D3 of the uncontrolled H-bridge circuit; As shown in 2C, when the fully-controlled H-bridge circuit is blocked or T1 and T3 are turned on at the same time or T2 and T4 are turned on at the same time, the low-voltage winding of the transformer 20 has no current, and the high-voltage uncontrolled H-bridge circuit is connected to the power grid. The current in the H-bridge circuit can be freewheeled through the diode in the uncontrolled H-bridge circuit and flow back to the grid.

As an optional implementation of the embodiment of the present application, as shown in FIG. 3, the fully-controlled H-bridge circuit may be connected to a DC source 40 to receive the DC power output by the DC source 40. The DC source 40 may be a photovoltaic array or other devices that can provide DC power, which is not limited in this application. In the working process of the DC boost converter circuit, the fully-controlled H-bridge circuit can realize the maximum power tracking of photovoltaic power generation, and the maximum power tracking can be realized by adjusting the duty cycle of the fully-controlled H-bridge circuit.

Optionally, when adjusting the duty cycle of the fully-controlled H-bridge circuit, a maximum power point tracking (max point power trace, MPPT) algorithm may be used. The controller can be used to collect the voltage and current of the external DC bus, generate the reference voltage of the DC bus according to the MPPT algorithm, and input the difference between the voltage of the DC bus and the reference voltage into the proportional integral controller (PI regulator), PI The regulator can output the duty ratio of the DC boost converter circuit according to the calculation. According to the duty cycle, the full-control H-bridge circuit can be adjusted to realize the maximum power tracking of photovoltaic power generation.

As an optional implementation of the embodiments of the present application, as shown in FIG. 4, the number of transformers 20 is multiple, each transformer includes a primary coil and multiple secondary coils, and the primary coil of each transformer is connected to one Fully controlled H-bridge circuit, each secondary coil of each transformer is connected to an uncontrolled H-bridge circuit. That is, the transformer can adopt three-winding and multi-winding structures. Taking the three windings as an example, one winding of the three windings is connected to a fully controlled H-bridge circuit, and the other two windings are respectively connected to an uncontrolled H-bridge circuit. Compared with the double-winding transformer structure, the transformer structure can reduce the number of transformers and increase the output voltage of the DC step-up converter circuit.

As an optional implementation manner of the embodiment of the present application, the transformer 20 is an intermediate frequency transformer or a high frequency transformer. The operating frequency of the transformer 20 may exceed 10 kHz. When an intermediate frequency transformer or a high frequency transformer is used in the DC step-up conversion circuit, the number of transformers can be reduced, thereby reducing the volume of the circuit and saving costs.

As an optional implementation of the embodiment of the present application, as shown in FIG. 3 or FIG. 4, the DC boost conversion circuit further includes: a capacitor C, the capacitor C is connected to the DC side of the full-control circuit 10, and the DC power It is input to the fully-controlled circuit 10 through the capacitor C. Providing a capacitor C in the DC boost conversion circuit can buffer the fluctuating power of the photovoltaic array 40, thereby making the DC power of the input circuit more stable.

The embodiment of the present application also provides a DC boost conversion device. As shown in FIG. 5, the DC boost conversion device includes a DC source 40, a controller 2 and the DC boost conversion circuit 1 as described in the above embodiment. The boost converter circuit 1 is connected to the DC source 40 and is configured to receive the DC power output by the DC source 40; the controller 2 is connected to the DC boost converter circuit 1 and is configured to control the switching frequency of the full-control circuit 10. Optionally, the controller 2 can control the switching frequency of the fully-controlled circuit according to a frequency multiplication modulation algorithm or a carrier phase shift algorithm. The DC source 40 may be a photovoltaic array or other devices that can provide DC power, which is not limited in this application.

In this embodiment, the controller 2 is connected to the control end of the fully-controlled device in the fully-controlled circuit 10 of the DC boost converter circuit 1.

Frequency doubling modulation algorithms can be divided into unipolar modulation and bipolar modulation. The equivalent switching frequency of unipolar modulation is twice that of bipolar modulation. The DC boost converter provided by the embodiment of the present application takes unipolar modulation as an example for description. Unipolar modulation is realized by comparing the triangular carrier wave and the power wave. As shown in Figure 6, taking a DC boost converter module as an example, compare the modulation wave u _{ref1 of the} DC boost converter module with the triangular wave u _c1 , when When the modulating wave u _{ref1 is} greater than the triangular wave u _c1 , the output pulse 1 acts on the fully-controlled device T1, so that the fully-controlled device T2 and T1 are reversed. While the modulation wave u _ref1 reversed compared with the triangular wave u _c1, when the reverse modulated wave -u _ref1 is greater than u _c1, two output pulses, applied to full-controlled devices T3, T4 such that the full-controlled devices and reverse T3 , So as to achieve the effect of unipolar modulation and frequency multiplication. Vt is the output voltage of the DC boost converter module at time t.

When the controller controls the switching frequency of the fully-controlled circuit according to the carrier phase-shifting algorithm, the carrier of multiple fully-controlled H-bridge circuits is phase-shifted, and multiple sets of triangular carriers are used to modulate the multiple fully-controlled H-bridge circuits respectively. Since multiple sets of triangular carriers have the same frequency and amplitude, and the phases are sequentially different by a fixed angle, after modulation, the pulse width modulation (PWM) pulses output by multiple fully-controlled H-bridge circuits can be staggered by a certain amount. Angle, thereby improving the equivalent switching frequency of the fully-controlled circuit.

Claims

A DC step-up conversion circuit, including: a fully-controlled circuit, a transformer, and an uncontrolled circuit,

The fully-controlled circuit is composed of a plurality of fully-controlled H-bridge circuits connected in parallel, the DC side of the fully-controlled circuit is set to receive DC power, and the AC side of the fully-controlled circuit is connected to the Uncontrolled circuit;

The uncontrolled circuit is composed of a plurality of uncontrolled H-bridge circuits connected in series;

The fully-controlled circuit is configured to obtain equalized AC power after voltage equalization and transformation of the DC power, and input the equalized AC power to the transformer;

The transformer is configured to boost the equalized AC power to obtain a boosted equalized AC power, and input the stepped up equalized AC power to the uncontrolled circuit;

The uncontrolled circuit is configured to rectify and output the boosted voltage equalizing AC power.
The DC boost converter circuit according to claim 1, wherein the uncontrolled H-bridge circuit is a rectifier circuit composed of a plurality of diodes.
The DC boost converter circuit of claim 1, wherein the fully-controlled H-bridge circuit includes a voltage equalization circuit composed of a plurality of fully-controlled devices.
The DC step-up conversion circuit according to claim 1, wherein the number of the transformers is multiple, each of the transformers includes a primary coil and a plurality of secondary coils, and the primary coil of each transformer is connected to one In a fully controlled H-bridge circuit, each secondary coil of each transformer is connected to an uncontrolled H-bridge circuit.
The DC boost conversion circuit according to claim 1, further comprising: a capacitor connected to the DC side of the fully-controlled circuit, and the DC power is input to the fully-controlled circuit through the capacitor.
The DC step-up converter circuit according to claim 1, wherein the transformer is an intermediate frequency transformer or a high frequency transformer.
A DC boost conversion device, comprising: a DC source, a controller, and the DC boost conversion circuit according to any one of claims 1-6,

The DC boost conversion circuit is connected to the DC source and is configured to receive the DC power output by the DC source;

The controller is connected to the DC boost conversion circuit, and is configured to control the switching frequency of the full-control circuit.
The DC boost converter device according to claim 7, wherein:

The controller is configured to control the switching frequency of the fully-controlled circuit according to a frequency multiplication modulation algorithm or a carrier phase shift algorithm.