DC converter system

Abstract

The invention relates to a direct current converter system which comprises a plurality of DC-DC units, a controller and a plurality of switches. The input ends and the output ends of the plurality of DC-DC units are respectively connected through the switch, and the input ends and the output ends of the plurality of DC-DC units can be respectively connected in series and in parallel through switching on and switching off the switch; and the controller requests to send a control instruction to control the on and off of the plurality of switches so as to switch the input ends and the output ends of the plurality of DC-DC units between the parallel connection and the series connection.

Description

Technical Field

[0001] The invention relates to a direct current converter system, in particular to a direct current converter system with output voltage and output current adjustable in multiple gears. Background Art

[0002] DC converters are widely used in the power supply of various DC systems. DC converters are used to adjust the supply voltage so that the output voltage is suitable for the needs of the load. Usually the load has different working modes, and different working modes have different requirements for the voltage and current of the power supply. For example, high-power motors or energy storage systems have different working states, such as 1000V DC Low voltage and 2000V DC Two working modes of high voltage. Since the maximum power of the load is certain, the 1000V DC When the voltage is low, the required current is 2000A, and the 2000V DC When the voltage is high, the required current is reduced to 1000A accordingly.

[0003] However, for DC converters, the output voltage can be adjusted by controlling the on-time of switching elements such as IGBT, but the switching elements themselves need to meet the requirements of outputting 2000V. DC The requirements of high voltage and 2000A high current place very high demands on switch components, increasing equipment costs. In view of the above problems of the prior art, the object of the present invention is to reduce the requirements of the withstand voltage and allowable current of the switching element while meeting the requirements of multi-level changes of the output voltage and the output current. Summary of the invention

[0004] The present invention provides a technical solution for a direct current converter system, comprising: a plurality of DC-DC units, a controller, and a plurality of switches; the input ends and output ends of the plurality of DC-DC units are respectively connected through the switches, and the input ends and output ends of the plurality of DC-DC units can be respectively connected in series and in parallel by closing and opening the switches, and the controller requests to send a control instruction to control the closing and opening of the plurality of switches to switch the input ends and output ends of the plurality of DC-DC units between parallel connection and series connection.

[0005] Preferably, the invention comprises: two DC-DC units (1a, 1b), the input ends and output ends of the two DC-DC units (1a, 1b) are respectively connected to six switch elements (K1a, K2a, K3a, K1b, K2b, K3b), the switch elements (K1a, K2a, K3a) are respectively connected to the input ends of the DC-DC units (1a, 1b), the switch elements (K1a, K3a) are respectively connected to the positive pole and the negative pole of the input ends of the DC-DC units (1a, 1b), the switch element (K2a) is connected to the negative pole of the input end of the DC-DC unit (1a) and the positive pole of the input end of the DC-DC unit (1b), The switch elements (K1b, K2b, K3b) are connected to the output ends of the DC-DC units (1a, 1b) respectively, the switch elements (K1b, K3b) are connected to the positive and negative poles of the output ends of the DC-DC units (1a, 1b) respectively, and the switch element (K2b) is connected to the negative pole of the output end of the DC-DC unit (1a) and the positive pole of the output end of the DC-DC unit (1b).

[0006] Preferably, the switching elements (K1a, K2a, K3a, K1b, K2b, K3b) are contactors.

[0007] Preferably, the DC-DC unit (1a, 1b) comprises: a first switch tube (G1a), a second switch tube (G2a), a third switch tube (G3a), and a fourth switch tube (G4a); the first switch tube (G1a) and the second switch tube (G2a) are connected in series as an input end, the third switch tube (G3a) and the fourth switch tube (G4a) are connected in series as an output end, the first capacitor (C1a) and the second capacitor (C2a) are connected in parallel at both ends of the input end and the output end, respectively, and the connection point of the first switch tube (G1a) and the second switch tube (G2a) and the connection point of the third switch tube (G3a) and the fourth switch tube (G4a) are connected via an energy storage element.

[0008] Preferably, a connection point between the first switch tube (G1a) and the second switch tube (G2a) and a connection point between the third switch tube (G3a) and the fourth switch tube (G4a) are connected via an inductor (L).

[0009] Preferably, the first switch tube (G1a), the second switch tube (G2a), the third switch tube (G3a), and the fourth switch tube (G4a) are N-channel IGBT power elements.

[0010] Preferably, the controller (10) comprises: a mode switching module (11), a driving module (12), and an output voltage regulating module (13). The output voltage regulating module (13) generates a signal for outputting a control output voltage, and the driving module (12) generates a driving signal for driving each switch tube of the DC-DC unit (1a, 1b) according to the control signal of the output voltage regulating module (13), and the driving signal is input to the control electrodes of the first switch tube (G1a), the second switch tube (G2a), the third switch tube (G3a), and the fourth switch tube (G4a) in the DC-DC unit 1a and the first switch tube (G1b), the second switch tube (G2b), the third switch tube (G3b), and the fourth switch tube (G4b) in the DC-DC unit (1b).

[0011] Preferably, the first switch tube (G1a), the second switch tube (G2a), the third switch tube (G3a), and the fourth switch tube (G4a) in the DC-DC unit 1a and the first switch tube (G1b), the second switch tube (G2b), the third switch tube (G3b), and the fourth switch tube (G4b) in the DC-DC unit (1b) use IGBT switch elements. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is the overall structural diagram of the DC converter system; Figure 2 is a circuit diagram of a DC-DC unit; Figure 3 It is a schematic diagram of the module structure of the controller; Figure 4 It is the control timing diagram of the DC-DC unit; Figure 5 It is a schematic diagram of the status of each contactor when switching to high current mode; Figure 6 This is the equivalent circuit diagram when switching to high current mode; Figure 7 It is a schematic diagram of the status of each contactor when switching to high voltage mode; Figure 8 This is the equivalent circuit diagram when switching to high voltage mode. DETAILED DESCRIPTION

[0013] The specific implementation modes of the present invention are described below by way of examples.

[0014] Figure 1The overall structural diagram of the DC converter system. First, the principle of the present invention is explained. The DC converter system is composed of multiple DC-DC units, a controller, and multiple switching elements. The DC-DC unit is also called a DC-DC converter, which is a device used to output the voltage of a DC power supply after stepping up or down. The input and output ends of multiple DC-DC units are respectively connected through multiple switching elements. By switching the switching elements, multiple DC-DC units can be used in series or in parallel. When the working state is in the high current gear, the controller controls the switching element so that multiple DC-DC units are used in parallel to increase the input and output currents of the DC conversion system; when the working state is switched to the high voltage gear, the controller switches the switching element so that multiple DC-DC units are switched to the series state to increase the input and output voltages of the DC conversion system.

[0015] For example, in a DC converter system with two DC-DC units, when the two DC-DC units are connected in parallel, the input and output currents of the DC converter system can reach twice the output current of a single DC-DC unit, and when the two DC-DC units are connected in series, the input and output voltages of the DC converter system can reach twice the input and output voltages of a single DC-DC unit. Compared with simply increasing the input, output current and voltage of the DC-DC unit, it can reduce the withstand voltage and current requirements of the switch elements in the DC-DC unit while meeting the requirements for multi-level changes in output voltage and output current, which can significantly reduce equipment costs.

[0016] The following describes an embodiment of the present invention by taking a DC converter system with two groups of DC-DC units as an example.

[0017] Figure 1 Figure 1 is a schematic diagram of the overall structure of the DC converter system. Figure 1 As shown, the DC converter system includes: two DC-DC units 1a, 1b, six contactors K1a, K2a, K3a, K1b, K2b, K3b and a controller 10.

[0018] The input and output ends of the two DC-DC units 1a and 1b are connected to six contactors K1a, K2a, K3a, K1b, K2b, and K3b respectively. The contactors K1a, K2a, and K3a are connected to the input ends of the DC-DC units 1a and 1b as switching elements at the input ends, respectively. The contactors K1a and K3a are connected to the positive and negative poles of the input ends of the DC-DC units 1a and 1b respectively, and the contactor K2a is connected to the negative pole of the input end of the DC-DC unit 1a and the positive pole of the input end of the DC-DC unit 1b.

[0019] Contactors K1b, K2b, and K3b are connected as switching elements at the output ends of the DC-DC unit 1a and the DC-DC unit 1b, respectively. Contactors K1b and K3b are connected to the positive and negative poles of the output ends of the DC-DC unit 1a and the DC-DC unit 1b, respectively. Contactor K2b is connected to the negative pole of the output end of the DC-DC unit 1a and the positive pole of the output end of the DC-DC unit 1b.

[0020] In addition to controlling the operation of the switching elements in the DC-DC units 1a and 1b to enable the DC-DC units 1a and 1b to complete voltage conversion, the controller 10 also controls six contactors K1a, K2a, K3a, K1b, K2b, and K3b to switch the operating state of the DC converter system, that is, to switch between a high input and output voltage state and a high input and output current state.

[0021] Figure 2 The circuit diagram of the DC-DC unit is as follows: Figure 2 As shown, the DC-DC unit 1a includes: a first switch tube G1a, a second switch tube G2a, a third switch tube G3a, a fourth switch tube G4a, an inductor L, a first capacitor C1a, and a second capacitor C2a.

[0022] In this embodiment, the first switch tube G1a, the second switch tube G2a, the third switch tube G3a, and the fourth switch tube G4a are N-channel IGBT switch elements.

[0023] One end of the first capacitor C1a is connected to the emitter of the second switch tube G2a, the other end of the first capacitor C1a is connected to the collector of the first switch tube G1a, and the emitter of the first switch tube G1a is connected to the collector of the second switch tube G2a; one end of the second capacitor C2a is connected to the emitter of the fourth switch tube, the other end of the second capacitor C2a is connected to the collector of the third switch tube G3a, and the emitter of the third switch tube G3a is connected to the collector of the fourth switch tube G4a; the connection point between the first switch tube G1a and the second switch tube G2a is connected to one end of the inductor L, and the connection point between the third switch tube G3a and the fourth switch tube G4a is connected to the other end of the inductor L. As the energy storage inductor, an isolated inductor can also be used.

[0024] The structure of the DC-DC unit 1b in this embodiment is the same as that of the DC-DC unit 1a, except that the subscript a of each component symbol in the DC-DC unit 1a is replaced with b. The details are referred to above and will not be repeated here.

[0025] Figure 3 The module structure diagram of the controller is as follows: Figure 3As shown, the controller 10 includes: a mode switching module 11, a driving module 12, and an output voltage regulating module 13. The output voltage regulating module 13 generates a signal for outputting a control output voltage, and the driving module 12 generates a driving signal for driving each switch tube of the DC-DC unit 1a and 1b according to the control signal of the output voltage regulating module 13, and the driving signal is input to the gates of the first switch tube G1a, the second switch tube G2a, the third switch tube G3a, and the fourth switch tube G4a in the DC-DC unit 1a and the first switch tube G1b, the second switch tube G2b, the third switch tube G3b, and the fourth switch tube G4b in the DC-DC unit 1b.

[0026] The mode switching module 11 receives a request from the power system or the user, and sends a control instruction to the mode switching module 11 according to the request. The mode switching module 11 generates a signal to control the contactors K1a, K2a, K3a, K1b, K2b, and K3b according to the control instruction, switches the states of the contactors K1a, K2a, K3a, K1b, K2b, and K3b, and makes the DC-DC units 1a and 1b work in parallel or in series, thereby realizing the gear switching of the output voltage and output current of the DC converter system.

[0027] In this embodiment, the mode switching module 11 works as a part of the controller 10, but an independent component can also be set as a mode switching module. When switching the working state, the controller 10 sends a control instruction to the switching module, and after receiving the control instruction sent by the controller 10, the switching module controls the operation of each contactor K1a, K2a, K3a, K1b, K2b, K3b according to the control instruction.

[0028] The following describes a driving example of the DC-DC conversion unit by taking the DC-DC unit 1a as an example. Figure 4 This is the control timing diagram of the DC-DC conversion unit. Figure 4 As shown, during the period t1 - t2 , the first switch tube G1a and the third switch tube G3a are turned on, and the second switch tube G2a and the fourth switch tube G4a are turned off. At this time, the current of the inductor L gradually increases with time, and the inductor L stores energy.

[0029] During the period t2-t3, the first switch tube G1a and the fourth switch tube G4a are turned off, the second switch tube G2a and the third switch tube G3a are turned on, and the current of the inductor L remains unchanged and continues to flow.

[0030] During the period t3-t4, the first switch tube G1a and the third switch tube G3 are turned on, and the second switch tube G2a and the fourth switch tube G4a are turned off. The current of the inductor L gradually increases with time, and the inductor L continues to store energy.

[0031] During the period t4-t5, the first switch tube G1a and the fourth switch tube G4a are turned on, the second switch tube G2a and the third switch tube G3a are turned off, and the current of the inductor L gradually decreases.

[0032] After that, the above cycle is repeated. That is, during t5-t9, the control between t1-t5 is repeated.

[0033] The input voltage Vin of the DC-DC unit 1 a is high, and the output voltage Vout is low.

[0034] The on and off of the first switch tube G1a, the second switch tube G2a, the third switch tube G3a, and the fourth switch tube G4a are controlled by the pulse voltage output to the gate of each switch tube by the driving module 12 of the controller 10.

[0035] In this embodiment, the output voltage of the DC-DC units 1a and 1b is lower than the input voltage. Therefore, the withstand voltage parameter of each switch element can be selected according to the output voltage.

[0036] The working process of the DC-DC unit 1b is the same as that of the DC-DC unit 1a, which will not be repeated here.

[0037] The DC-DC unit and control are prior art, and other structures and control methods may be adopted.

[0038] Figure 5 It is a schematic diagram of the status of each contactor when switching to high current mode; Figure 6 This is the equivalent circuit diagram when switching to high current mode; Figure 7 It is a schematic diagram of the status of each contactor when switching to high voltage mode; Figure 8 This is the equivalent circuit diagram when switching to high voltage mode.

[0039] When switching to high current mode, Figure 5 As shown, contactors K1a, K2a, K1b, and K2b are in a connected state, and the remaining contactors are in a disconnected state. The connection state of DC-DC unit 1a and DC-DC unit 1b is as shown in FIG. Figure 6 As shown, the positive and negative electrodes of the input terminals of the DC-DC unit 1a and the DC-DC unit 1b are connected to the positive and negative electrodes of the power supply as Vin+ and Vin- respectively, and similarly, the positive and negative electrodes Vout+ and Vout- of the output terminals of the DC-DC unit 1a and the DC-DC unit 1b output voltages.

[0040] When switching to high voltage mode, Figure 7As shown, contactors K3a and K3b are in a connected state, and the other contactors are in a disconnected state. The connection state of DC-DC unit 1a and DC-DC unit 1b is shown in the figure. The input ends of DC-DC unit 1a and DC-DC unit 1b are in a series state, the positive electrode of the input end of DC-DC unit 1a serves as Vin+, and the negative electrode of the input end of DC-DC unit 1b serves as Vin- to be connected to the power supply. Similarly, the output ends of DC-DC unit 1a and DC-DC unit 1b are in a series state, the positive electrode of the output end of DC-DC unit 1a serves as Vout+, and the negative electrode of the output end of DC-DC unit 1b serves as Vout- to output voltage.

[0041] As an example, the load device powered by the DC converter system has two gears. Gear 1: Low voltage (1000V DC ), high current (2000A), in this case, two DC-DC units in parallel circuit can meet the needs of this scenario. Gear 2: High voltage (2000V DC ), low current (1000A), in this case, the series circuit can meet the needs of this scenario. When selecting switch components, as long as the withstand voltage is 1000V DC , a switch element with an allowable current of 1000A is sufficient. A withstand voltage of 2000V is required DC Compared with the existing DC converter with switch elements of 2000A or above, the requirements for switch elements are reduced, saving equipment costs. In addition, since the DC-DC unit 1a and the DC-DC unit 1b can work independently, redundancy is formed in function, which improves the safety of the equipment.

[0042] That is, as the working mode changes, the driving voltage required by the load device will be different. Since the power of the load device does not change accordingly, the required current is relatively small in the high voltage driving mode, and conversely, the required current is relatively high in the low voltage driving mode. For the DC converter system, it is not necessary to work in high voltage and high current states at the same time. Therefore, in the above usage scenario, a single DC-DC unit only needs to be designed with a rated power of 1MW (1000V×1000A). When in use, the two DC-DC units 1a and 1b can be connected in series or in parallel as needed to meet the working requirements, which greatly reduces the requirements and production costs of the DC-DC units.

[0043] If a single DC-DC unit is used, it needs to be designed for a high voltage of 2000V and a high current of 2000A. A device with a rated power of 4MW requires switching elements that can work normally under the conditions of 2000V high voltage and 2000A high current. This is not only costly but also causes great waste.

[0044] It should be noted that the above embodiments illustrate the present invention rather than limit the present invention, and those skilled in the art may design alternative embodiments without departing from the scope of the appended claims. For example, a contactor is used for switching in the embodiments of the present application, but other switch elements may also be used.

Claims

1. A DC converter system, comprising: Multiple DC-DC units, controllers, multiple switches; The input ends and output ends of the plurality of DC-DC units are connected through the switches, respectively. By closing and opening the switches, the input ends and output ends of the plurality of DC-DC units can be connected in series and in parallel, respectively. The controller requests to send a control instruction to control the closing and opening of the plurality of switches to switch the input terminals and the output terminals of the plurality of DC-DC units between parallel connection and series connection.

2. The DC converter system according to claim 1, characterized in that: include: Two DC-DC units (1a, 1b), The input and output ends of the two DC-DC units (1a, 1b) are respectively connected to six switch elements (K1a, K2a, K3a, K1b, K2b, K3b), the switch elements (K1a, K2a, K3a) are respectively connected to the input ends of the DC-DC units (1a, 1b), the switch elements (K1a, K3a) are respectively connected to the positive and negative poles of the input ends of the DC-DC units (1a, 1b), the switch element (K2a) is connected to the negative pole of the input end of the DC-DC unit (1a) and the positive pole of the input end of the DC-DC unit (1b), The switch elements (K1b, K2b, K3b) are connected to the output ends of the DC-DC units (1a, 1b) respectively, the switch elements (K1b, K3b) are connected to the positive and negative poles of the output ends of the DC-DC units (1a, 1b) respectively, and the switch element (K2b) is connected to the negative pole of the output end of the DC-DC unit (1a) and the positive pole of the output end of the DC-DC unit (1b).

3. The DC converter system according to claim 2, characterized in that: The switching elements (K1a, K2a, K3a, K1b, K2b, K3b) are contactors.

4. The DC converter system according to claim 2, characterized in that: The DC-DC unit (1a, 1b) comprises: a first switch tube (G1a), a second switch tube (G2a), a third switch tube (G3a), and a fourth switch tube (G4a); the first switch tube (G1a) and the second switch tube (G2a) are connected in series as an input end; the third switch tube (G3a) and the fourth switch tube (G4a) are connected in series as an output end; the first capacitor (C1a) and the second capacitor (C2a) are connected in parallel at both ends of the input end and the output end respectively; and the connection point of the first switch tube (G1a) and the second switch tube (G2a) and the connection point of the third switch tube (G3a) and the fourth switch tube (G4a) are connected via an energy storage element.

5. The DC converter system according to claim 4, characterized in that: A connection point between the first switch tube (G1a) and the second switch tube (G2a) and a connection point between the third switch tube (G3a) and the fourth switch tube (G4a) are connected via an inductor (L).

6. The system according to claim 1, characterized in that The first switch tube (G1a), the second switch tube (G2a), the third switch tube (G3a) and the fourth switch tube (G4a) are N-channel IGBT power elements.

7. The DC converter system according to any one of claims 1 to 6, characterized in that: The controller (10) comprises: a mode switching module (11), a driving module (12), and an output voltage regulating module (13). The output voltage regulating module (13) generates a signal for outputting a control output voltage, and the driving module (12) generates a driving signal for driving each switch tube of the DC-DC unit (1a, 1b) according to the control signal of the output voltage regulating module (13), and the driving signal is input to the control electrodes of the first switch tube (G1a), the second switch tube (G2a), the third switch tube (G3a), and the fourth switch tube (G4a) in the DC-DC unit 1a and the first switch tube (G1b), the second switch tube (G2b), the third switch tube (G3b), and the fourth switch tube (G4b) in the DC-DC unit (1b).

8. The DC converter system according to claim 7, characterized in that: The first switch tube (G1a), the second switch tube (G2a), the third switch tube (G3a), and the fourth switch tube (G4a) in the DC-DC unit 1a and the first switch tube (G1b), the second switch tube (G2b), the third switch tube (G3b), and the fourth switch tube (G4b) in the DC-DC unit (1b) use IGBT switch elements.

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