WO2020169018A1

WO2020169018A1 - Converter having multiple dc ports and control method

Info

Publication number: WO2020169018A1
Application number: PCT/CN2020/075665
Authority: WO
Inventors: 谢晔源; 王宇; 李海英; 曹冬明; 连建阳; 张中锋; 杨晨
Original assignee: 南京南瑞继保电气有限公司; 南京南瑞继保工程技术有限公司
Priority date: 2019-02-19
Filing date: 2020-02-18
Publication date: 2020-08-27
Also published as: CN109873568A

Abstract

Disclosed is a converter having multiple DC ports. The converter comprises a multi-winding transformer, M unidirectional converter modules, and N bidirectional converter modules. The multi-winding transformer comprises a primary winding and M+N secondary windings. AC sides of the unidirectional converter modules and the bidirectional converter modules are correspondingly connected to the secondary windings on a one-to-one basis. DC sides of the N bidirectional converter modules form a cascade connection, and head and tail ends of said cascade connection form a low-voltage DC port. The low-voltage DC port further forms a cascade connection with DC sides of the M unidirectional converter modules, and head and tail ends of said cascade connection form a high-voltage DC port. The invention also proposes a corresponding control method. The converter having multiple DC ports in the present invention provides a plurality of DC ports, forms a DC bus, connects to a DC load and DC power supply, and has redundancy features, high reliability, and a good cost-performance ratio.

Description

Multi-DC port converter and control method

Technical field

The invention relates to a multi-DC port converter and a control method, belonging to the technical field of high-power power electronic converters.

Background technique

In recent years, the demand for DC distribution networks has grown continuously and power electronics technology has become more and more mature. Distributed power generation has become more and more widely used in the power grid, such as new energy distributed power generation, which consists of distributed power sources, loads and energy storage devices. In microgrids, many distributed power sources, loads and energy storage devices are of different types, including DC or AC, with different voltage levels and capacities. How to connect the above units economically and effectively and conduct unified management is a difficult problem to solve ; At present, the existing DC distribution network access architecture is relatively complex, and usually requires a high-voltage AC-DC converter, such as a modular multi-level AC-DC converter and multiple DC/DC converters to achieve cost and The difficulty of implementation is relatively high. As shown in Fig. 2, which includes two sets of high-voltage AC/DC converters and multiple DC/DC converters, the present invention provides a low-cost solution for multiple DC ports for high and low voltage access in DC distribution networks. Inverter.

Summary of the invention

In order to solve the above problems, the present invention proposes a multi-DC port converter and a control method. Only one set of converters can provide multiple DC ports of different voltage levels, and can be connected to multiple sets of DC buses without adding additional Investment, cost-effective.

The specific plan is as follows:

A multi-DC port converter. The multi-DC port converter includes a multi-winding transformer, M unidirectional converter modules and N bidirectional converter modules, where M is an integer greater than or equal to 2, and N is An integer greater than or equal to 1, the multi-winding transformer includes a primary winding and M+N secondary windings, the AC side and the secondary windings of the unidirectional converter module and the bidirectional converter module are connected in one-to-one correspondence, so The DC output side of the N bidirectional converter modules are cascaded, the cascade head end is defined as the positive pole of the low voltage DC port, and the cascade tail end is defined as the negative pole of the low voltage DC port; the low voltage DC port is then commutated with M unidirectional converters The DC output side of the converter module is cascaded, the head of the cascade is defined as the positive pole of the high voltage DC port, and the tail end of the cascade is defined as the negative pole of the high voltage DC port.

Further, the one-way converter module is composed of uncontrolled or semi-controlled power semiconductor devices.

Further, the bidirectional converter module is composed of a fully controlled power semiconductor device.

Further, the N bidirectional converter modules in the multi-DC port converter are located in the middle of all the converter modules.

Further, the low-voltage direct current port and the high-voltage direct current port are connected through a DC/DC converter, and the DC/DC converter is connected to direct currents of different amplitudes to realize a bidirectional flow of energy.

Further, the multi-DC port converter further includes a Kth DC port, where K is an integer greater than or equal to 2 and less than or equal to (M+N); there are M unidirectional converter modules and N bidirectional converter modules. K continuous modules are randomly selected from the module series chain of the module, the positive lead-out port of the module close to the positive pole of the high-voltage DC port is the positive of the Kth DC port, and the negative lead-out port of the module close to the negative of the high-voltage DC port is the negative of the K-th DC port.

Further, the low-voltage DC port and the Kth DC port are connected through a DC/DC converter.

Further, the N is an even number greater than or equal to 2, counted from the positive pole of the low-voltage DC port to the negative pole of the low-voltage DC port, and the negative pole of the N/2th bidirectional converter module is led out and grounded.

Further, the DC output sides of any two or more bidirectional converter modules are connected in parallel, that is, the positive poles of the DC output sides of any two or more bidirectional modules are connected, and the negative poles of the corresponding DC output sides are connected.

Further, the DC output sides of any two or more unidirectional converter modules are connected in parallel, that is, the anodes of the DC output sides of any two or more unidirectional modules are connected, and the cathodes of the corresponding DC output sides are connected .

Further, the DC output sides of the unidirectional converter module and the bidirectional converter module are also connected in parallel with a bypass switch respectively.

Further, the DC output sides of the unidirectional converter module and the bidirectional converter module are respectively connected in series with a power electronic unit.

Further, the power electronic unit can quickly break the output DC current, can bypass the DC output side of the converter module, and can adjust the output voltage.

Further, the power electronic unit is composed of two fully-controlled power semiconductor device IGBT half-bridge modules, the positive electrode of the input side of the power electronic unit is the collector of the upper tube IGBT, and the negative electrode of the input side of the power electronic unit is the lower tube IGBT The emitter electrode of the half-bridge is led out as the output positive pole, and the emitter electrode of the down tube IGBT is led out as the output negative pole.

Further, the power electronic unit is composed of a full-bridge module of four fully-controlled power semiconductor devices IGBT.

Further, the power electronic unit is composed of a half-bridge module, an inductor and a DC capacitor, the input side of the power electronic unit is connected to both ends of the half-bridge module, the midpoint of the half-bridge module is connected to the inductor as the output side of the power electronic unit, and the output side is connected in parallel DC capacitors.

Further, the power electronic unit is composed of a half-bridge module, an inductor and a DC capacitor, the input side of the power electronic unit is connected to the midpoint of the half-bridge module via the inductor, and the two ends of the half-bridge module are connected in parallel with the DC capacitor as the output side of the power electronic unit .

Further, the multi-DC port converter according to claim 1, wherein: between the AC side of the unidirectional converter module and the bidirectional converter module and the secondary winding of the multi-winding transformer An AC switch is connected in series.

Further, the phases of the secondary windings of the multi-winding transformer are different by a certain angle to eliminate the primary harmonics.

Further, the unidirectional converter module includes an AC-DC converter composed of diodes or thyristors and a DC capacitor. The DC side of the AC-DC converter is connected in parallel with the DC capacitor, and the AC side of the AC-DC converter is connected to the multi-winding transformer. The secondary side is connected.

Further, the bidirectional converter module includes an AC-DC converter, a DC capacitor, and a filter unit composed of fully-controlled power semiconductor devices. The DC side of the AC-DC converter is connected in parallel with the DC capacitor, and the AC-DC converter After the side is connected to the filter unit, it is then connected to the secondary side of the multi-winding transformer.

The present invention also includes a control method of the multi-DC port converter:

(1) When the multi-DC port converter starts, the following steps can be used:

Step 1: Close the AC switch of the single and bidirectional converter module;

Step 2: The primary side of the multi-winding transformer is charged, and the DC capacitors of the single and bidirectional converter modules enter the charging state;

Step 3: After the charging is completed, the DC capacitor voltage is stable, the bidirectional converter module is started, the power semiconductor device is unlocked, and the output DC voltage of the bidirectional converter module is adjusted to reach the target value.

(2) When the DC voltage of the high-voltage DC port needs to be adjusted after the multi-DC port converter is started, one of the following four control methods can be used:

Method 1: Adjust the DC voltage of the low-voltage DC port, and the DC voltage of the high-voltage DC port will change accordingly;

Method 2: When the one-way converter adopts a semi-controlled device, calculate the output voltage of the one-way converter module according to the set target value, control the conduction time of the semi-controlled device of the one-way converter, and control the unit The output voltage to the converter module.

Method 3: Calculate the output voltage of the unidirectional converter module according to the set target value, and use the power electronic unit in the unidirectional converter module to control the output voltage of the unidirectional converter module;

Method 4: Use the power electronic unit in the unidirectional converter module to bypass a certain number of unidirectional converter modules.

Wherein, when the converter module includes a bypass switch, the following control method can be adopted: according to the set target value, calculate the number of one-way converter modules required, and use the bypass switch in the one-way converter module. Circuit switch to bypass a certain number of unidirectional converter modules;

(3) When the load on the low-voltage DC port has power reverse, one of the following two control methods can be used:

Method 1: Detect the voltage increase at the low-voltage DC port, the bidirectional converter module transmits the remaining energy to the primary side through the secondary side of the transformer;

Method 2: Detect the voltage increase of the low-voltage DC port, and transfer the remaining energy to the high-voltage DC port through the DC/DC converter.

(4) When the load on the high-voltage DC port has power reverse, one of the following two control methods can be used:

Method 1: Detect the voltage increase at the high-voltage DC port, and transfer the remaining energy to the low-voltage DC port through the DC/DC converter.

Method 2: The low-voltage DC port transmits part of the energy to the load. When the voltage of the low-voltage DC port is detected to increase, the bidirectional converter module transmits the remaining energy to the primary side through the secondary side of the transformer;

The beneficial effects of the present invention:

1. The present invention proposes a multi-DC port converter, which constructs multiple sets of DC ports by cascading the DC capacitors of multiple converter modules, and the low-voltage DC ports formed by the bidirectional converter modules can realize bidirectional power flow. It is suitable for the connection of power supply or load. The high-voltage DC port formed by the unidirectional converter module is suitable for the connection of the load. The invention also includes a bidirectional DC/DC converter between the high-voltage DC port and the low-voltage DC port. In the case of reverse power, the reverse power can be transferred to another port through a bidirectional DC/DC converter, or to the primary side of the transformer. A multi-DC port converter can provide both high voltage DC and low voltage DC ports at the same time, and can handle reverse power at the same time . Facilitate the access of DC distribution network. The program has low cost and high cost performance.

2. The unidirectional converter module and the bidirectional converter module of the present invention are connected to the secondary side of the multi-winding transformer, and are isolated from each other by the secondary side winding. At the same time, it is also equipped with power electronic units and AC switches, which can be conveniently based on actual needs. , Adjust the number of input converter modules, or change the series-parallel mode on the output side of the converter modules. When the voltage is higher, the cascade scheme is adopted. When the current is higher, the output side of the module can be connected in parallel. The flexibility of the scheme is improved. At the same time, when the module fails, the faulty module can be quickly removed, which greatly improves the reliability of the scheme.

Description of the drawings

Figure 1 is a schematic diagram of the composition of the multi-DC port converter of the present invention;

Figure 2 is a typical topology diagram of a DC distribution network in the prior art;

Figure 3 is a first embodiment of a power electronic unit;

Figure 4 is a second embodiment of a power electronic unit;

Figure 5 is a third embodiment of a power electronic unit;

Figure 6 is a fourth embodiment of a power electronic unit;

Figure 7 is the second embodiment of the multi-DC port converter of the present invention;

Figure 8 is a third embodiment of the multi-DC port converter of the present invention;

Figure 9 is a fourth embodiment of the multi-DC port converter of the present invention;

Label name in the figure: 1. Multi-winding transformer; 2. One-way converter module; 3. Two-way converter module; 4. High voltage DC port positive; 5. High voltage DC port negative; 6. Low voltage DC port positive; 7 , Low voltage DC port negative; 8. AC switch; 9. Power electronic unit; 10. DC/DC converter; 11. Bypass switch.

detailed description

The present invention will be further described below in conjunction with the drawings.

As shown in Figure 1, the multi-DC port converter of the present invention includes a multi-winding transformer 1, M unidirectional converter modules 2 and N bidirectional converter modules 3, where M is an integer greater than or equal to 2, and N is An integer greater than or equal to 1, the multi-winding transformer includes a primary winding and M+N secondary windings, the AC side and the secondary windings of the unidirectional converter module and the bidirectional converter module are connected in one-to-one correspondence, so The DC output side of the N bidirectional converter modules are cascaded, the cascade head end is defined as the low-voltage DC port positive 6 and the cascade tail end is defined as the low-voltage DC port negative 7; the low-voltage DC port is connected to M unidirectional The DC output side of the converter module is cascaded, the head of the cascade is defined as the positive 4 of the high-voltage DC port, and the tail end of the cascade is defined as the negative 5 of the high-voltage DC port; the unidirectional converter module is uncontrolled or semi-controlled The two-way converter module is composed of a fully-controlled power semiconductor device.

Wherein, in this embodiment, the N bidirectional converter modules in the multi-DC port converter are located in the middle of all the converter modules. As shown in Figure 1, the upper and lower sides of the two-way inverter module each contain the same number of one-way inverter modules.

Wherein, the low-voltage direct current port and the high-voltage direct current port are connected through a DC/DC converter 10, and the DC/DC converter is connected to direct currents of different amplitudes and realizes bidirectional flow of energy.

The multi-DC port converter further includes a Kth DC port, where K is an integer greater than or equal to 2 and less than or equal to (M+N); in the modules of M unidirectional converter modules and N bidirectional converter modules K continuous modules are randomly selected in the series chain, the positive lead-out port of the module close to the positive pole of the high-voltage DC port is the positive pole of the Kth DC port, and the negative lead-out port of the module close to the negative pole of the high-voltage DC port is the negative of the Kth DC port. In the embodiment of the present invention, the serial link port formed by any continuous module can be led out.

Wherein, the low-voltage DC port and the Kth DC port are connected through a DC/DC converter.

Wherein, N is an even number greater than or equal to 2, counted from the positive pole of the low-voltage DC port to the negative pole of the low-voltage DC port, and the negative pole of the N/2th bidirectional converter module is led out and grounded. As shown in Figure 7, when N=2, the midpoint of the two bidirectional converter modules, that is, the negative pole of the first bidirectional converter module is led out and grounded, forming a true bipolar system.

Wherein, the DC output sides of any two or more bidirectional converter modules can be connected in parallel, that is, the positive pole of the DC output side of each bidirectional module is connected, and the negative pole of the corresponding DC output side is connected.

Wherein, the DC output sides of any two or more unidirectional converter modules can also be connected in parallel, that is, the positive pole of the DC output side of each one-way module is connected, and the negative pole of the corresponding DC output side is connected. As shown in Figure 8, every two single-phase modules are connected in parallel to form a group, and then cascaded.

Wherein, a bypass switch 11 is also connected in parallel on the DC output side of the unidirectional converter module and the bidirectional converter module.

Wherein, a power electronic unit 9 is connected in series on the DC output side of the unidirectional converter module and the bidirectional converter module.

Wherein, the power electronic unit can quickly break the output DC current, can bypass the DC output side of the converter module, and can adjust the output voltage.

As shown in Figure 3, it is the first embodiment of the power electronic unit. The power electronic unit is composed of two fully-controlled power semiconductor device IGBT half-bridge modules. The positive pole of the input side is the collector of the upper tube IGBT, and the negative pole of the input side is The emitter electrode of the lower tube IGBT is led out from the midpoint of the half-bridge as the output anode, and the emitter electrode of the lower tube IGBT is led out as the output cathode. In normal operation, the upper tube IGBT is turned on and the lower tube IGBT is turned off. When it is necessary to switch off, the upper tube IGBT is turned off and the lower tube IGBT is kept turned off. When bypass is needed, the upper IGBT is turned off and the lower IGBT is turned on. As shown in Fig. 4, it is the second embodiment of the power electronic unit. The power electronic unit is composed of a full-bridge module with four fully-controlled power semiconductor devices IGBT. Figures 5 and 6 show the third and fourth embodiments with voltage regulation function, which are composed of half-bridge modules, inductors and capacitors. The input side of the power electronic unit in Figure 5 is connected to both ends of the half-bridge module. The midpoint of the power electronic unit is connected to the inductor as the output side of the power electronic unit, and the output side is connected in parallel with a DC capacitor; Figure 6 side.

Wherein, an AC switch 8 is connected in series between the AC side of the unidirectional converter module and the bidirectional converter module and the secondary winding of the multi-winding transformer.

Wherein, the phases of the secondary windings of the multi-winding transformer are different by a certain angle to eliminate the primary harmonics.

Wherein, the unidirectional converter module includes an AC-DC converter composed of diodes or thyristors and a DC capacitor. The DC side of the AC-DC converter is connected in parallel with the DC capacitor, and the AC side of the AC-DC converter is connected to the multi-winding transformer. The secondary side is connected.

Wherein, the bidirectional converter module includes an AC-DC converter, a DC capacitor, and a filter unit composed of a fully-controlled power semiconductor device. The DC side of the AC-DC converter is connected in parallel with the DC capacitor, and the AC side of the AC-DC converter After connecting with the filter unit, connect with the secondary side of the multi-winding transformer.

(1) When the multi-DC port converter starts, the following steps can be used:

Step 1: Close the AC switch of the single and bidirectional converter module;

Method 2: The low-voltage DC port transmits part of the energy to the load. When the voltage of the low-voltage DC port is detected to increase, the bidirectional converter module transmits the remaining energy to the primary side through the secondary side of the transformer.

An application scenario is listed below to further illustrate the application scenarios and control methods of the present invention. The multi-DC port converter of the present invention can be applied to the DC distribution network, as shown in FIG. 9.

Wherein, the N bidirectional converter modules in the converter are located in the middle of all the modules. In this application, M=10, N=2, this embodiment summarizes 2 two-way converter modules located in the middle position, the upper and lower sides of the two-way converter module each contain 5 one-way converter modules, of which two-way The converter module outputs a rated DC voltage of ±375V, and the output voltage of 10 unidirectional converter modules is 1.925kV. The voltage is superimposed directly after series connection. The total rated voltage is ±10kV. The high voltage DC port is connected to the load bus. The load bus is ±10kV DC. The low-voltage DC port leads as the interface of the DC distribution network, and the energy storage system or photovoltaic system is connected to or DC load through the DC/DC converter.

(1) When the multi-DC port converter starts:

Step 1: Close the AC switch of the single and bidirectional converter module;

(2) When the multi-DC port converter needs to adjust the DC voltage of the high-voltage DC port, one of the following two control methods can be used:

Method 1: Adjust the DC voltage of the low voltage DC port, and the DC voltage of the high voltage DC port will change accordingly;

Method 2: According to the set target value, calculate the required number of unidirectional converter modules, and use the power electronic unit or bypass switch in the unidirectional converter module to bypass a certain number of unidirectional converter modules .

In this application, if the output voltage is adjusted to ±10.5kV, method 1 can be used to adjust the low-voltage DC port voltage to ±400V by adjusting the output DC voltage of the bidirectional converter module.

If the output voltage is adjusted to ±8kV, method 2 can be used, using the power electronic unit in the one-way converter module to bypass the two one-way converter modules, which can bypass each of the upper and lower modules to achieve the output voltage adjust.

Method 3: The above-mentioned unidirectional converter module can use semi-controlled devices, such as thyristors. The bridge circuit composed of thyristors has the function of output DC voltage regulation. Specifically: according to the set target value, calculate the output voltage of the unidirectional converter module, control the on-time of the thyristor of the unidirectional converter, and control the output voltage of the unidirectional converter module.

Method 4: The above-mentioned power electronic unit can use the circuit shown in Figure 5, which is a typical step-down regulator circuit, which can reduce the output DC voltage of the unidirectional converter module to ±8kV.

In this application, if the output power of the low-voltage DC photovoltaic power generation unit is greater than the DC load, and reverse transmission occurs, choose between two methods. When the high-voltage DC port needs this part of energy, you can choose method 2 or method 1. Send excess energy back to the grid.

In this application, when the load on the high-voltage DC port has power reversal, choose between two methods. When the low-voltage DC port can absorb this part of energy, you can choose method 1 to transfer energy to the low-voltage DC port; if If the energy is too large, method 1 cannot be completely consumed, and method 2 can also be selected. Another part of the excess energy is sent back to the grid through the transformer through the bidirectional converter module.

The above embodiments are only used to illustrate the technical solutions of the present invention, not to limit them. Various modifications or changes made with reference to the above embodiments are all within the protection scope of the present invention.

Claims

A multi-DC port converter, characterized in that the multi-DC port converter includes a multi-winding transformer, M unidirectional converter modules and N bidirectional converter modules, where M is greater than or equal to 2 Integer, N is an integer greater than or equal to 1. The multi-winding transformer includes a primary winding and M+N secondary windings. The AC side and secondary windings of the unidirectional converter module and the bidirectional converter module are one by one Correspondingly, the DC output sides of the N bidirectional converter modules are cascaded, the cascade head end is defined as the positive pole of the low-voltage DC port, and the cascade tail end is defined as the negative pole of the low-voltage DC port; the low-voltage DC port is then connected to M The DC output side of the unidirectional converter module is cascaded, the head of the cascade is defined as the positive pole of the high voltage DC port, and the tail end of the cascade is defined as the negative pole of the high voltage DC port.
The multi-DC port converter according to claim 1, wherein the unidirectional converter module is composed of uncontrolled or semi-controlled power semiconductor devices.
The multi-DC port converter of claim 1, wherein the bidirectional converter module is composed of a fully-controlled power semiconductor device.
The multi-DC port converter according to claim 1, wherein the N bidirectional converter modules in the multi-DC port converter are located in the middle of all the converter modules.
The multi-DC port converter according to claim 1, wherein the low-voltage DC port and the high-voltage DC port are connected through a DC/DC converter, and the DC/DC converter is connected with DC power of different amplitudes. , And realize the two-way flow of energy.
The multi-DC port converter according to claim 1, wherein the multi-DC port converter further comprises a Kth DC port, and K is an integer greater than or equal to 2 and less than or equal to M+N; K continuous modules are randomly selected from the module series chain of M unidirectional converter modules and N bidirectional converter modules. The positive lead-out port of the module near the positive pole of the high voltage DC port is the positive pole of the Kth DC port, which is close to the high voltage DC port. The negative terminal of the negative module is the negative terminal of the Kth DC port.
The multi-DC port converter according to claim 6, wherein the low-voltage DC port and the Kth DC port are connected through a DC/DC converter.
The multi-DC port converter according to claim 4, wherein said N is an even number greater than or equal to 2, and the number is counted from the positive pole of the low-voltage DC port to the negative pole of the low-voltage DC port, and the N/2th bidirectional converter The negative pole of the inverter module is led out and grounded.
The multi-DC port converter according to claim 1, wherein the DC output sides of any two or more bidirectional converter modules are connected in parallel.
The multi-DC port converter according to claim 1, wherein the DC output sides of any two or more unidirectional converter modules are connected in parallel.
The multi-DC port converter according to claim 1, wherein the DC output side of the unidirectional converter module and the bidirectional converter module are respectively connected in parallel with a bypass switch.
The multi-DC port converter according to claim 1, wherein the DC output sides of the unidirectional converter module and the bidirectional converter module are also connected in series with a power electronic unit.
The multi-DC port converter according to claim 12, wherein the power electronic unit can quickly break the output DC current, can bypass the DC output side of the converter module, and can adjust the output voltage.
The multi-DC port converter according to claim 12, wherein the power electronic unit is composed of two fully-controlled power semiconductor device IGBT half-bridge modules, and the positive electrode of the input side of the power electronic unit is upper The collector of the IGBT, the negative electrode of the input side of the power electronic unit is the generator electrode of the down tube IGBT, the half-bridge lead as the output positive electrode, and the generator electrode of the down tube IGBT as the output negative electrode.
The multi-DC port converter of claim 12, wherein the power electronic unit is composed of a full-bridge module of four fully-controlled power semiconductor devices IGBT.
The multi-DC port converter of claim 12, wherein the power electronic unit is composed of a half-bridge module, an inductor and a DC capacitor, and the input side of the power electronic unit is connected to both ends of the half-bridge module, The midpoint of the bridge module is connected to the inductor as the output side of the power electronic unit, and the output side is connected in parallel with a DC capacitor.
The multi-DC port converter according to claim 12, wherein the power electronic unit is composed of a half-bridge module, an inductor and a DC capacitor, and the positive pole of the input side of the power electronic unit passes through the inductor and the half-bridge module. Point connection, DC capacitors are connected in parallel at both ends of the half-bridge module as the output side of the power electronic unit.
The multi-DC port converter according to claim 1, characterized in that: the AC side of the unidirectional converter module and the bidirectional converter module are connected in series with the secondary winding of the multi-winding transformer. AC switch.
The multi-DC port converter according to claim 1, wherein the phase difference between the secondary windings of the multi-winding transformer is a certain angle.
The multi-DC port converter according to claim 1, wherein the unidirectional converter module includes an AC-DC converter composed of diodes or thyristors and a DC capacitor, and the DC side of the AC-DC converter It is connected in parallel with the DC capacitor, and the AC side of the AC-DC converter is connected with the secondary winding of the multi-winding transformer.
The multi-DC port converter according to claim 1, wherein the two-way converter module includes an AC-DC converter, a DC capacitor and a filter unit composed of fully-controlled power semiconductor devices, and the AC-DC The DC side of the converter is connected in parallel with the DC capacitor, and the AC side of the AC-DC converter is connected with the filter unit, and then connected with the secondary winding of the multi-winding transformer.
A control method based on the multi-DC port converter of claim 18, characterized in that: when the multi-DC port converter is started, the following steps can be adopted:

Step 1: Close the AC switch of the single and bidirectional converter module;

Step 2: The primary winding of the multi-winding transformer is energized, and the single and bidirectional converter modules enter the charging state;

Step 3: After charging is completed, start the bidirectional converter module and adjust the output DC voltage of the bidirectional converter module to reach the target value.
A control method based on the multi-DC port converter according to claim 2, characterized in that: when the DC voltage of the high-voltage DC port needs to be adjusted after the multi-DC port converter is started, one of the following two control methods is adopted :

Method 1: Adjust the DC voltage of the low voltage DC port, and the DC voltage of the high voltage DC port will change accordingly;

Method 2: When the one-way converter module adopts a semi-controlled device, calculate the output voltage of the one-way converter module according to the set target value, and control the conduction time of the semi-controlled device of the one-way converter module. Control the output voltage of the unidirectional converter module.
A control method based on the multi-DC port converter according to claim 13, characterized in that: when the DC voltage of the high-voltage DC port needs to be adjusted after the multi-DC port converter is started, one of the following two control methods is adopted :

Method 1: According to the set target value, calculate the output voltage of the unidirectional converter module, and use the power electronic unit in the unidirectional converter module to control the output voltage of the unidirectional converter module;

Method 2: Use the power electronic unit in the unidirectional converter module to bypass a certain number of unidirectional converter modules.
A control method based on the multi-DC port converter of claim 11, characterized in that: when the DC voltage of the high-voltage DC port needs to be adjusted after the multi-DC port converter is started, the following control method can be adopted: Set the target value, calculate the number of unidirectional converter modules required, and use the bypass switch in the unidirectional converter module to bypass a certain number of unidirectional converter modules.
A control method based on the multi-DC port converter according to claim 5, characterized in that: when the load on the low-voltage DC port has power reverse, one of the following two control methods can be used:

Method 1: Detect the voltage increase of the low-voltage DC port, the bidirectional converter module transmits the remaining energy to the primary winding through the secondary winding of the multi-winding transformer;

Method 2: Detect the voltage increase of the low-voltage DC port, and transfer the remaining energy to the high-voltage DC port through the DC/DC converter.
A control method based on the multi-DC port converter of claim 5, characterized in that: when the load on the high-voltage DC port has power reverse, one of the following two control methods can be used:

Method 1: Detect the high voltage DC port voltage increase, and transfer the remaining energy to the low voltage DC port through the DC/DC converter;

Method 2: The low-voltage DC port transmits part of the energy to the load. When the low-voltage DC port voltage is detected to increase, the bidirectional converter module transmits the remaining energy to the primary winding through the secondary winding of the multi-winding transformer.