DC-side soft-switching device for a converter and its startup and shutdown methods

Abstract

The present invention discloses a DC-side soft-switching device for a converter, comprising: a battery; a bus capacitor; a first relay switch disposed between the positive electrode of the battery and the bus capacitor; a first resistor connected in parallel with the first relay switch; a second relay switch disposed between the negative electrode of the battery and the bus capacitor; a second resistor connected in parallel with the second relay switch; and a third resistor connected in parallel with the bus capacitor. The present invention also discloses a method for performing startup and shutdown using the DC-side soft-switching device. By connecting a voltage-dividing resistor in parallel with the relay switch and a discharging resistor in parallel with the bus capacitor, and coordinating with the startup and shutdown timing control, the present invention reduces the voltage across the relay switch, thereby enabling the selection of a relay switch with a lower voltage rating, achieving miniaturization and low cost of the product.

Description

Technical Field

[0001] The present invention relates to the field of converters, and in particular to a DC-side soft-switching device for a converter and a method for performing startup and shutdown using the DC-side soft-switching device. Background Art

[0002] The energy storage converter system is composed of a bidirectional energy storage converter and an energy storage medium (such as a power battery). Its application can make the microgrid more intelligent and stable. As a core component of the future microgrid, users can benefit greatly.

[0003] As Figure 1-2 shown, where Figure 1 shows the structure of the energy storage converter system in the prior art, Figure 2 shows Figure 1 a simplified structural diagram of. Among them, a DC relay switch (DCrelay) generally needs to be set between the battery and the DC side of the converter. This DC relay switch must be selected with a rating corresponding to the battery voltage. For example, when the battery voltage is 1500V, the DC relay switch must be selected with a 1500V rating. However, the high-voltage DC relay switch has a high cost, a large volume, and a single model. This makes it very difficult for the energy storage converter system to develop towards miniaturization and low cost.

[0004] Therefore, it is very necessary to find a DC-side soft-switching device for a converter with low cost and small volume and a method for performing startup and shutdown using the DC-side soft-switching device. Summary of the Invention

[0005] In view of this, an object of the present invention is to provide a DC-side soft-switching device for a converter, which reduces the voltage across the relay switch by connecting a voltage-dividing resistor in parallel with the relay switch and connecting a discharging resistor in parallel with the bus capacitor, and at the same time cooperating with the startup and shutdown timing control, so that a relay switch with a lower voltage rating can be selected, realizing the miniaturization and low cost of the product.

[0006] To achieve the above object, according to one aspect of the present invention, there is provided a DC-side soft-switching device for a converter, the device comprising:

[0007] A battery;

[0008] A bus capacitor;

[0009] A first relay switch, disposed between the positive electrode of the battery and the bus capacitor;

[0010] A first resistor, connected in parallel with the first relay switch;

[0011] A second relay switch, disposed between the negative electrode of the battery and the bus capacitor;

[0012] A second resistor, connected in parallel with the second relay switch; and

[0013] A third resistor, connected in parallel with the bus capacitor.

[0014] According to another aspect of the present invention, the first resistor includes a plurality of resistors connected in series.

[0015] According to another aspect of the present invention, the second resistor includes a plurality of resistors connected in series.

[0016] According to another aspect of the present invention, the third resistor includes a plurality of resistors connected in series.

[0017] According to another aspect of the present invention, the DC-side soft-switching device further includes a pre-charging unit connected in parallel with the first relay switch, and the pre-charging unit includes a pre-charging relay switch and a fourth resistor connected in series.

[0018] According to another aspect of the present invention, in a state where both the first relay switch and the second relay switch are off, the voltages across the first resistor and the second resistor are both less than the voltage of the battery.

[0019] According to another aspect of the present invention, in a state where both the first relay switch and the second relay switch are off, the voltage across the first resistor or the second resistor is greater than or equal to 1 / 2 of the voltage of the battery.

[0020] According to another aspect of the present invention, the voltage of the battery is 1500V, and the voltages across the first resistor and the second resistor are 750V.

[0021] According to another aspect of the present invention, the DC-side soft-switching device further includes a voltage detection unit for detecting the voltage across the second relay switch in the off state.

[0022] According to another aspect of the present invention, there is also provided a method for performing startup and shutdown using a DC-side soft-switching device, including the following steps:

[0023] Closing the second relay switch;

[0024] Closing the pre-charging relay switch to charge the bus capacitor to a first predetermined voltage;

[0025] Closing the first relay switch;

[0026] Turning off the pre-charging relay switch to complete startup.

[0027] According to another aspect of the present invention, before closing the second relay switch, the voltage across the second relay switch is detected, and when the voltage across the second relay switch is less than the rated voltage of the second relay switch, the second relay switch is closed.

[0028] According to another aspect of the present invention, before closing the second relay switch, the voltage across the second relay switch is detected, and when the voltage across the second relay switch is less than the rated voltage of the second relay switch, the second relay switch is closed.

[0029] According to another aspect of the present invention, the method further includes the following steps:

[0030] Block the drive signal of the converter;

[0031] Turn off the first relay switch and the second relay switch, and maintain the voltage across the bus capacitor within a predetermined range during the process of turning off the first relay switch and the second relay switch.

[0032] According to another aspect of the present invention, after turning off the first relay switch and the second relay switch, the bus capacitor is discharged through the third resistor or through a forced discharge circuit.

[0033] According to another aspect of the present invention, the bus capacitor is discharged through the third resistor during the process of turning off the first relay switch and the second relay switch, and the voltage across the bus capacitor is maintained within the predetermined range.

[0034] By connecting a voltage-dividing resistor in parallel with the relay switch and a discharge resistor in parallel with the bus capacitor, and coordinating with the on-off timing control, the present invention reduces the voltage across the relay switch, so that a relay switch with a lower voltage rating can be selected, achieving miniaturization and low cost of the product.

[0035] The following will describe the above description in detail with embodiments, and provide a further explanation of the technical solution of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] To make the above and other objects, features, and advantages of the present invention more obvious and understandable, the description of the accompanying drawings is as follows:

[0037] Figure 1 is the structure of an energy storage converter system in the prior art;

[0038] Figure 2 shows Figure 1 a simplified structural diagram of the energy storage converter system of

[0039] Figure 3Shows a schematic structural diagram of a DC-side soft-switching device for a converter according to a preferred embodiment of the present invention;

[0040] Figure 4 Shows a flowchart of a method for performing startup using a DC-side soft-switching device according to a preferred embodiment of the present invention. Detailed implementation manners

[0041] To make the description of the present invention more detailed and complete, reference may be made to the accompanying drawings and the following various embodiments, where the same reference numerals in the drawings represent the same or similar components. On the other hand, well-known components and steps are not described in the embodiments to avoid unnecessary limitations to the present invention. In addition, for the sake of simplifying the drawings, some well-known conventional structures and elements will be shown in a simple schematic manner in the drawings.

[0042] As Figure 3 shown, it shows a schematic structural diagram of a DC-side soft-switching device for a converter according to a preferred embodiment of the present invention. The DC-side soft-switching device for the converter includes:

[0043] A battery (not shown in the figure), the positive electrode of the battery is connected to DC+, and the negative electrode of the battery is connected to DC-;

[0044] A bus capacitor C;

[0045] A first relay switch RLY1, arranged between the positive electrode (i.e., DC+) of the battery and the positive terminal of the bus capacitor C;

[0046] A first resistor R1, connected in parallel with the first relay switch RLY1;

[0047] A second relay switch RLY2, arranged between the negative electrode (i.e., DC-) of the battery and the negative terminal of the bus capacitor C;

[0048] A second resistor R2, connected in parallel with the second relay switch RLY2; and

[0049] A third resistor R3, connected in parallel with the bus capacitor C.

[0050] Preferably, the first resistor R1 is directly connected in parallel across the two ends of the first relay switch RLY1. Similarly, the second resistor R2 is directly connected in parallel across the two ends of the second relay switch RLY2. The third resistor R3 is directly connected in parallel across the two ends of the bus capacitor C.

[0051] Advantageously, the battery of the present invention can be a high-voltage battery, such as a battery with a voltage of 1500V or higher, and the first relay switch RLY1 and the second relay switch RLY2 can be selected with a rated voltage compared to the battery voltage (V battery)A lower relay switch, for example, a relay switch with a rated voltage less than the battery voltage and greater than or equal to 1 / 2 of the battery voltage can be selected. For example, when the battery voltage is 1500V, a 750V or 1000V relay switch can be selected, so as to achieve miniaturization and low cost. It should be noted that the DC-side soft-switching device of the present invention can be used in various converters, Figure 3 taking the inverter as an example. In some other embodiments, it can also be a DC / DC converter, etc.

[0052] According to another preferred embodiment of the present invention, the first resistor R1 includes a plurality of resistors connected in series. As Figure 3 shown, the first resistor R1 includes 3 resistors connected in series, but the number of resistors is not limited to this. In some embodiments, the first resistor R1 is a high-voltage resistor, and as the voltage level increases, the number of series resistors can be adjusted appropriately.

[0053] According to another preferred embodiment of the present invention, the second resistor R2 includes a plurality of resistors connected in series. As Figure 3 shown, the second resistor R2 includes 3 resistors connected in series, but the number of resistors is not limited to this. Similarly, in some embodiments, the second resistor R2 is a high-voltage resistor, and as the voltage level increases, the number of series resistors can be adjusted appropriately.

[0054] As Figure 3 shown, the third resistor R3 is a single resistor, but in some other embodiments of the present invention, the third resistor R3 can include a plurality of resistors connected in series. The number of resistors R3 is not limited in the present invention.

[0055] According to another preferred embodiment of the present invention, the DC-side soft-switching device further includes a pre-charge unit connected in parallel with the first relay switch RLY1. The pre-charge unit includes a pre-charge relay switch RLY3 and a fourth resistor R4 connected in series, where the fourth resistor R4 can be a single resistor or a plurality of resistors connected in series, and the present invention is not limited thereto.

[0056] According to another preferred embodiment of the present invention, in a state where both the first relay switch RLY1 and the second relay switch RLY2 are disconnected, the voltage difference (V battery -V bus)Perform voltage division, and the voltages across the first resistor R1 and the second resistor R2 are both less than the voltage of the battery. Preferably, when the resistance values of the first resistor R1 and the second resistor R2 are the same, the voltages across the first resistor R1 and the second resistor R2 are equal. Correspondingly, at this time, the voltages borne by the first relay switch RLY1 and the second relay switch RLY2 are also both less than the voltage of the battery. Preferably, the voltage borne by the first relay switch RLY1 is equal to the voltage borne by the second relay switch RLY2.

[0057] According to another preferred embodiment of the present invention, in the state where both the first relay switch RLY1 and the second relay switch RLY2 are disconnected, if the voltage of the bus capacitor C is zero and the resistance value of the first resistor R1 is greater than or equal to the resistance value of the second resistor R2, according to the voltage division principle, the voltage across the first resistor R1 is greater than or equal to 1 / 2 of the voltage of the battery. Correspondingly, the voltage across the second resistor R2 is less than or equal to 1 / 2 of the voltage of the battery; vice versa. It can be understood that at this time, the voltages borne by the first relay switch RLY1 and the second relay switch RLY2 are both less than the voltage of the battery.

[0058] Taking the voltage of the battery as 1500V as an example, when the voltage on the bus capacitor C is zero, if the resistance values of the first resistor R1 and the second resistor R2 are the same, then the voltages across the first resistor R1 and the second resistor R2 are both 750V, that is, the voltages across the first relay switch RLY1 and the second relay switch RLY2 are both 750V.

[0059] According to another preferred embodiment of the present invention, the DC-side soft-switching device further includes a voltage detection unit for detecting the voltage across the second relay switch RLY2 in the off state.

[0060] According to another preferred embodiment of the present invention, the DC-side soft-switching device may include multiple voltage detection units, which are respectively used to detect the voltage of the battery, the voltage across the bus capacitor C, and the voltage across the second relay switch RLY2, and can also calculate the voltage across the first relay switch RLY1 based on the detected voltages, thereby realizing the judgment of whether the second relay switch RLY2 and the first relay switch RLY1 are faulty before starting up.

[0061] According to another preferred embodiment of the present invention, taking the rated voltages of the first relay switch RLY1 and the second relay switch RLY2 as both 1 / 2 of the voltage of the battery as an example, the present invention provides a method for using the DC-side soft-switching device to perform startup and shutdown, including the following steps:

[0062] Close the second relay switch RLY2;

[0063] Close the pre-charge relay switch RLY3 to charge the bus capacitor C to a first predetermined voltage;

[0064] Close the first relay switch RLY1;

[0065] Turn off the pre-charge relay switch RLY3 to complete the startup.

[0066] Preferably, the first predetermined voltage is more than 50% of the battery voltage to ensure that the voltage across the first relay switch RLY1 does not exceed its rated voltage (i.e., half of the battery voltage) when the first relay switch RLY1 is closed.

[0067] According to another preferred embodiment of the present invention, before closing the second relay switch RLY2, the voltage across the second relay switch RLY2 is detected. When the voltage across the second relay switch RLY2 is less than the rated voltage of the second relay switch RLY2, the second relay switch RLY2 is closed. It should be noted that in this embodiment, there are various ways to detect the voltage across the second relay switch RLY2. It can either be directly detected by a detection unit across the second relay switch RLY2 or be calculated. For example, by detecting the voltage of the battery, the voltage of the bus capacitor, and the voltage across the first relay switch RLY1 by a detection unit, and then calculating the voltage across the second relay switch RLY2 based on the above voltages.

[0068] In this embodiment, before closing the first relay switch RLY1, in order to ensure that the voltage across the first relay switch does not exceed its rated voltage when it is closed, the voltage across the first relay switch RLY1 can also be detected. When the voltage across the first relay switch RLY1 is less than its rated voltage, the first relay switch RLY1 is then closed.

[0069] According to another preferred embodiment of the present invention, the method further includes the following steps:

[0070] Block the drive signal of the converter;

[0071] Turn off the first relay switch RLY1 and the second relay switch RLY2, and maintain the voltage across the bus capacitor C within a predetermined range during the process of turning off the first relay switch RLY1 and the second relay switch RLY2.

[0072] Preferably, the predetermined range is greater than or equal to 1 / 2 of the battery voltage. The rated voltage of the first and / or second relay switch RLY2 is, for example, half of the battery voltage. In extreme cases, it can ensure that the operating voltage when the first and / or second relay switch RLY2 is turned off is less than its rated voltage. It can be understood that this predetermined range depends on the rated voltage of the first and / or second relay switch RLY2, and it is necessary to ensure that the voltage when the relay switch is turned off does not exceed its own rated voltage.

[0073] Advantageously, the present invention utilizes the characteristics that the relay switch has a short turn-off time, the bus capacitor has a long discharge time, and the voltage of the bus capacitor does not change suddenly. After the relay switch turn-off process is completed, the bus capacitor is forced to discharge through software control.

[0074] Preferably, the turn-off timing of the first relay switch RLY1 and the second relay switch RLY2 is optional, and they can be turned off simultaneously or successively.

[0075] According to another preferred embodiment of the present invention, after turning off the first relay switch RLY1 and the second relay switch RLY2, the bus capacitor is discharged through the third resistor R3 or through a forced discharge circuit.

[0076] According to another preferred embodiment of the present invention, during the period when the first relay switch RLY1 and the second relay switch RLY2 are turned off, the bus capacitor is discharged through the third resistor R3, and the voltage across the bus capacitor is maintained within the predetermined range.

[0077] It can be understood that the turn-off period of the first relay switch RLY1 and the second relay switch RLY2 may last from several milliseconds to dozens of milliseconds. Preferably, the two relay switches can start turning off simultaneously, and the time period from when both relay switches are completely disconnected is the turn-off period. However, there may also be a situation where the two relay switches are not synchronized. In this case, the "period" refers to the time period from when the first relay switch starts to turn off to when both relay switches are completely disconnected.

[0078] In this embodiment, advantageously, the rated voltage of the relay switch is selected to be greater than 1 / 2 of the battery voltage and less than the battery voltage. For example, when the battery voltage is 1500V, the rated voltages of the first relay switch RLY1 and the second relay switch RLY2 are selected to be 1000V, which can further improve the stability of the system.

[0079] The present invention reduces the voltage across the relay switch by connecting a voltage-dividing resistor in parallel with the relay switch and a discharge resistor in parallel with the bus capacitor, and at the same time, cooperating with the control of the on-off timing sequence, so that a relay switch with a lower voltage rating can be selected, realizing the miniaturization and low cost of the product.

[0080] Although the present invention has been disclosed above in the form of embodiments, it is not intended to limit the present invention. Any person skilled in the art can make various modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the appended claims.

Claims

1. A DC-side soft-switching device for a converter, characterized in that, Comprising: a battery; a bus capacitor; a first relay switch, disposed between the positive electrode of the battery and the bus capacitor; a first resistor, connected in parallel with the first relay switch; a second relay switch, disposed between the negative electrode of the battery and the bus capacitor; a second resistor, connected in parallel with the second relay switch; and a third resistor, connected in parallel with the bus capacitor; further comprising a pre-charging unit connected in parallel with the first relay switch, the pre-charging unit including a pre-charging relay switch and a fourth resistor connected in series.

2. The DC-side soft-switching device according to claim 1, wherein The first resistor includes a plurality of resistors connected in series.

3. The DC-side soft-switching device according to claim 2, characterized in that, The second resistor includes a plurality of resistors connected in series.

4. The DC-side soft-switching device according to claim 1, characterized in that, The third resistor includes a plurality of resistors connected in series.

5. The DC-side soft-switching device according to claim 1, wherein In a state where both the first relay switch and the second relay switch are off, the voltages across the first resistor and the second resistor are both less than the voltage of the battery.

6. The DC-side soft-switching device according to claim 5, characterized in that, In a state where both the first relay switch and the second relay switch are off, the voltage across the first resistor or the second resistor is greater than or equal to 1 / 2 of the voltage of the battery.

7. The DC-side soft-switching device according to claim 6, characterized in that The voltage of the battery is 1500V, and the voltages across the first resistor and the second resistor are 750V.

8. The DC-side soft-switching device according to claim 1, characterized in that Further comprising a voltage detection unit for detecting the voltage across the second relay switch in the off state.

9. A method for performing startup and shutdown using the DC-side soft-switching device according to any one of claims 1-8, characterized in that, Comprising the following steps: closing the second relay switch; closing the pre-charging relay switch to charge the bus capacitor to a first predetermined voltage; closing the first relay switch; turning off the pre-charging relay switch to complete startup.

10. The method according to claim 9, wherein Before closing the second relay switch, detect the voltage across the second relay switch, and when the voltage across the second relay switch is less than the rated voltage of the second relay switch, close the second relay switch.

11. The method according to claim 9, characterized in that, Further comprising the following steps: blocking the drive signal of the converter; turning off the first relay switch and the second relay switch, and maintaining the voltage across the bus capacitor within a predetermined range during the process of turning off the first relay switch and the second relay switch.

12. The method according to claim 11, wherein After turning off the first relay switch and the second relay switch, discharge the bus capacitor through the third resistor or through a forced discharge circuit.

13. The method according to claim 11, wherein Discharge the bus capacitor through the third resistor during the process of turning off the first relay switch and the second relay switch, and maintain the voltage across the bus capacitor within the predetermined range.

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