Discharge device for a dc bus and energy storage converter

Abstract

The utility model discloses a discharging device and energy storage converter of direct current bus relates to power electronics technical field. The main contact of direct current switch unit is connected in series on the direct current bus, and the bus capacitor is connected between the direct current bus, the discharging device includes control unit and discharging unit, the control unit includes the auxiliary contact of direct current switch unit, the control unit is parallel with the bus capacitor, and is used for generating control signal, the discharging unit is parallel with the bus capacitor, and in the case where the main contact is disconnected, discharges the bus capacitor to the control signal. The device utilizes the auxiliary contact of direct current relay self and realizes discharging control, and the energy of bus capacitor can be discharged quickly, and the structure of discharging circuit is simplified, and the hardware cost is reduced.

Description

Technical Field

[0001] This utility model relates to the field of power electronics technology, specifically to a DC bus discharge device and an energy storage converter. Background Technology

[0002] Energy storage product standards have specific requirements for the discharge time of energy storage converters. Related discharge schemes usually rely on additional discharge devices to meet the discharge requirements. The discharge circuit structure is complex, which increases the hardware cost. Utility Model Content

[0003] The main purpose of this invention is to provide a discharge device and energy storage converter for a DC bus to solve the problems of complex discharge circuit structure and high hardware cost.

[0004] To solve the above-mentioned technical problems, the embodiments of this utility model disclose the following technical solutions:

[0005] In a first aspect, a discharge device for a DC bus is provided, wherein the main contacts of a DC switching unit are connected in series on the DC bus, and a bus capacitor is connected between the DC buses; the discharge device includes:

[0006] The control unit includes auxiliary contacts of the DC switching unit; the control unit 10 is connected in parallel with the bus capacitor and is used to generate control signals.

[0007] A discharge unit, connected in parallel with the bus capacitor, discharges the bus capacitor in response to the control signal when the main contacts are open.

[0008] In some embodiments, the DC switching unit is a DC contactor or a DC circuit breaker.

[0009] In some embodiments, the control unit includes:

[0010] A first resistor, the first end of which is connected to the positive terminal of the bus capacitor;

[0011] The auxiliary contact is connected in series between the second end of the first resistor and the negative terminal of the bus capacitor, and the second end of the first resistor is used to generate the control signal.

[0012] In some embodiments, the control unit further includes a second resistor, the first end of which is connected to the second end of the first resistor, and the second end of which is connected to the negative terminal of the bus capacitor.

[0013] In some embodiments, the discharge unit includes a discharge resistor and a switching unit, wherein the discharge resistor and the switching unit are connected in series and then connected in parallel with the bus capacitor.

[0014] In some embodiments, the first end of the discharge resistor is connected to the positive terminal of the bus capacitor, the second end of the discharge resistor is connected to the negative terminal of the bus capacitor through the switching unit, and the control terminal of the switching unit receives the control signal.

[0015] Alternatively, the control terminal of the switching unit receives the control signal, the first terminal of the switching unit is connected to the positive terminal of the bus capacitor, the second terminal of the switching unit is connected to the first terminal of the discharge resistor, and the second terminal of the discharge resistor is connected to the negative terminal of the bus capacitor.

[0016] In some embodiments, the auxiliary contact is mechanically linked to the main contact, and the main contact and the auxiliary contact close / open synchronously.

[0017] In some embodiments, the resistance of the first resistor is greater than or equal to 1MΩ.

[0018] In some embodiments, the discharge resistor is a kiloohm level resistor.

[0019] In a second aspect, an energy storage converter is provided, including a discharge device for a DC bus as described in any of the first aspects.

[0020] This utility model discloses a DC bus discharge device that utilizes the auxiliary contacts of a DC relay to achieve discharge control, rapidly dissipating energy from the bus capacitor, simplifying the discharge circuit structure, and reducing hardware costs. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0022] Figure 1 Structural block diagram of the discharge device for the DC bus provided in this embodiment of the utility model;

[0023] Figure 2 One of the circuit diagrams of the discharge device for the DC bus provided in the embodiments of this utility model;

[0024] Figure 3 A schematic diagram of DC relay contacts provided in an embodiment of this utility model;

[0025] Figure 4 The second circuit diagram of the discharge device for the DC bus provided in this embodiment of the utility model.

[0026] Explanation of reference numerals in the attached figures:

[0027] 10: Control unit; 20: Discharge unit;

[0028] R1: First resistor; R2: Second resistor; R3: Discharge resistor;

[0029] Q1: Switching unit; Cbus bus capacitor; S1: Auxiliary contact;

[0030] G: Gate; D: Drain; S: Source. Detailed Implementation

[0031] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0032] Furthermore, descriptions in this utility model involving terms such as "first" and "second" are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, features defined with "first" and "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. If the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed by this utility model.

[0033] The DC bus discharge device provided by this utility model can be used to quickly discharge residual electrical energy stored in the bus capacitor when the system is powered off or shut down, ensuring equipment maintenance safety and compliance with electrical safety standards. The device uses auxiliary contact linkage control of the DC switching unit and automatically generates control signals through the control unit to control the discharge unit to form a discharge circuit, achieving safe and rapid release of the bus voltage.

[0034] Please see Figure 1 , Figure 1This is a structural block diagram of a DC bus discharge device provided in an embodiment of the present invention. A DC bus discharge device includes a main contact of a DC switching unit connected in series on the DC bus, and a bus capacitor connected between the DC buses. The discharge device includes a control unit 10 and a discharge unit 20. The control unit 10 includes auxiliary contacts of the DC switching unit; the control unit 10 is connected in parallel with the bus capacitor and is used to generate a control signal; the discharge unit 20 is connected in parallel with the bus capacitor; in response to the control signal, the bus capacitor is discharged when the main contacts are open.

[0035] Optionally, the DC switching unit is a DC contactor, a DC circuit breaker, or a DC relay.

[0036] It is understood that the DC bus discharge device provided by this utility model simplifies the discharge circuit structure and reduces hardware costs by utilizing the auxiliary contacts of the DC switching unit (such as a DC relay, DC contactor, or DC circuit breaker) as a control signal source. Specifically, the device directly utilizes the mechanical linkage characteristics of the main contacts and auxiliary contacts of the DC switching unit. When the main contacts are open, the auxiliary contacts operate synchronously and trigger the control unit to generate a control signal, causing the discharge unit to automatically conduct and form a discharge circuit without the need for additional isolation devices or complex control circuits. This design not only makes full use of the idle auxiliary contact resources of existing DC switching units, but also achieves rapid discharge of bus capacitor energy through a hardware self-triggering mechanism. Compared with traditional solutions, it reduces the number of components, significantly simplifies the circuit structure, and reduces hardware costs while ensuring discharge performance.

[0037] Based on Figure 1 Based on the described DC bus discharge device, the various unit modules of the DC bus discharge device are further described in detail through specific embodiments.

[0038] Please refer to Figure 2 , Figure 2 This is one of the circuit diagrams of a DC bus discharge device provided in an embodiment of the present invention. Optionally, the control unit 10 includes a first resistor R1, the first end of which is connected to the positive terminal of the bus capacitor Cbus; an auxiliary contact S1 is connected in series between the second end of the first resistor R1 and the negative terminal of the bus capacitor Cbus, and the second end of the first resistor R1 is used to generate a control signal.

[0039] Optionally, the auxiliary contact S1 is mechanically linked to the main contact, and the main contact and auxiliary contact S1 close / open synchronously. Specifically, the on / off state of the auxiliary contact S1 is controlled by a DC switching unit. The control signal is taken from the connection node between the first resistor R1 and the auxiliary contact S1. When the DC switching unit controls the auxiliary contact S1 to close or open, it changes the connection of the circuit containing the first resistor R1, thereby affecting the voltage of the connection node, which is the control signal voltage. For example, when the auxiliary contact S1 is closed, the voltage at this node will be equal to the negative terminal voltage of the bus capacitor Cbus; when the auxiliary contact S1 is open, the first resistor R1 and the bus capacitor Cbus form a loop, generating a specific control signal voltage at this node.

[0040] The control unit 10 operates based on the voltage across the bus capacitor Cbus, and generates control signals according to this voltage. When the bus capacitor Cbus stores electrical energy, a voltage is applied across the first resistor R1; when discharge is required, a change in the state of the auxiliary contact S1 (e.g., opening) will cause a control signal to be generated at the second terminal of the first resistor R1. For example, during the operation of the energy storage converter, when the bus capacitor Cbus stores a certain amount of electrical energy, the opening of the auxiliary contact S1 will trigger the control unit 10 to generate the necessary control signals at the second terminal of the first resistor R1.

[0041] Optionally, the control unit 10 also includes a second resistor R2, the first end of which is connected to the second end of the first resistor R1, and the second end of the second resistor R2 is connected to the negative terminal of the bus capacitor Cbus. The function of the second resistor R2 is to adjust the voltage amplitude of the control signal. By changing the resistance value of the second resistor R2, the total resistance value of the series circuit of the first resistor R1 and the second resistor R2 can be changed, thereby changing the voltage value of the control signal output node (i.e., the connection point of the first resistor R1 and the second resistor R2) to adapt to different operating conditions or requirements, increasing the flexibility and adjustability of the device.

[0042] Optionally, the discharge unit 20 includes a discharge resistor R3 and a switching unit Q1. The discharge resistor R3 and the switching unit Q1 are connected in series and then in parallel with the bus capacitor Cbus. The switching unit Q1 acts as a switch, and its on or off state is determined by the control signal received at its control terminal. When the control signal voltage meets the on-condition of the switching unit Q1, the switching unit Q1 is turned on, allowing the discharge resistor R3 to form a discharge circuit with the bus capacitor Cbus; when the control signal voltage does not meet the on-condition, the switching unit Q1 is turned off, preventing the discharge process.

[0043] Optionally, the first terminal of the discharge resistor R3 is connected to the positive terminal of the bus capacitor Cbus, and the second terminal of the discharge resistor R3 is connected to the negative terminal of the bus capacitor Cbus through the switching unit Q1. The control terminal of the switching unit Q1 receives a control signal. Specifically, the switching unit Q1 can be a transistor, with its gate G connected to the second terminal of the first resistor R1, its drain D connected to the second terminal of the discharge resistor R3, and its source S connected to the negative terminal of the bus capacitor Cbus.

[0044] The auxiliary contact S1 is mechanically linked to the main contact. When the DC switching unit is energized, the main contact closes and the auxiliary contact S1 closes simultaneously. At this time, the auxiliary contact S1 pulls the control signal voltage down to the negative terminal voltage of the bus capacitor Cbus, causing the control terminal voltage of the switching unit Q1 to be too low, thus turning off the switching unit Q1 and preventing discharge. When the DC switching unit is de-energized, the main contact opens and the auxiliary contact S1 opens simultaneously. The first resistor R1 and the bus capacitor Cbus form a circuit, generating a control signal voltage at the connection node. When this control signal voltage meets the conduction condition of the switching unit Q1, the switching unit Q1 conducts, thereby forming a discharge circuit from the positive terminal of the bus capacitor Cbus through the discharge resistor R3 and the switching unit Q1 to the negative terminal of the bus capacitor Cbus, realizing the discharge of the bus capacitor Cbus.

[0045] For details, please refer to Figure 3 , Figure 3 This is a schematic diagram of a DC relay contact provided in an embodiment of the present invention. From top to bottom, the components are the load, auxiliary part, and coil. The load refers to a component in the circuit that consumes electrical energy or performs a specific function, and the auxiliary part is the part associated with the auxiliary contacts of the DC relay. The working principle of the DC relay is as follows:

[0046] The coil is the control core of the DC relay and has positive and negative polarities. When the DC relay energizes the coil, the coil generates a magnetic field. Under the action of this magnetic field, the main contacts close. Since the moving contact of the auxiliary contact S1 of the DC relay is an integral structure with the moving contact of the main contacts, the auxiliary contact S1 closes synchronously and conducts. At this time, the voltage divider unit does not generate a drive signal, and the switching unit Q1 connected in the circuit is cut off due to the lack of a suitable drive signal.

[0047] When the DC relay de-energizes the coil, the magnetic field generated by the coil disappears. The main contacts open under the action of the relevant mechanical structure, and the auxiliary contact S1 also opens synchronously. At this time, a control signal is generated through voltage division by the first resistor R1. This control signal is transmitted to the control terminal (i.e., gate G) of the switching unit Q1. When the drive signal meets the conduction condition of the switching unit Q1, the switching unit Q1 turns on. The whole process demonstrates that the DC relay controls the switching unit Q1 by energizing and de-energizing the coil, with the synchronous action of the main contacts and the auxiliary contact S1.

[0048] Optionally, the first end of the discharge resistor R3 is connected to the positive terminal of the bus capacitor Cbus, and the second end of the discharge resistor R3 is connected to the drain D of the switching unit Q1, forming a discharge circuit from the positive terminal of the bus capacitor Cbus through the discharge resistor R3 and the switching unit Q1. In this discharge circuit, when the switching unit Q1 is turned on, the electrical energy stored in the bus capacitor Cbus is dissipated as heat through the discharge resistor R3, completing the discharge process.

[0049] Optionally, the first resistor R1 is a megohm-level resistor with a resistance greater than or equal to 1MΩ. Using such a high-resistance resistor serves two purposes: firstly, it forms a microampere-level leakage circuit when the auxiliary contact S1 is closed, effectively making the control unit an open circuit; secondly, it ensures specific voltage distribution requirements are met during voltage division, allowing for the generation of appropriate drive voltages under different bus capacitor Cbus voltages.

[0050] Optionally, the discharge resistor R3 is a kiloohm-level resistor. This resistance range ensures that the discharge speed meets the relevant standard requirements, while preventing excessive discharge current due to insufficient resistance, which could damage other components in the circuit, or excessive discharge time due to excessive resistance, which could fail to meet the standard requirements for bus capacitor discharge time.

[0051] exist Figure 2 In the circuit structure shown, whether the switching unit Q1 is turned on or off plays a crucial role in the current flow direction of the entire circuit. The current direction before and after the switching unit Q1 is turned on is as follows:

[0052] (a) Before the switching unit Q1 is turned on.

[0053] When the main contacts of a DC switching unit (such as a DC contactor / DC circuit breaker) close, the auxiliary contact S1 closes simultaneously. At this time, the current path of the control signal is: from the positive terminal of the bus capacitor Cbus → the first resistor R1 → the closed auxiliary contact S1 → the negative terminal of the bus capacitor Cbus. The closing of the auxiliary contact S1 pulls the potential at the second terminal of the first resistor R1 down to the potential of the negative terminal of the bus capacitor Cbus. The voltage at the control terminal of the switching unit Q1 (such as the gate of a MOSFET) is below the conduction threshold, the switching unit Q1 remains off, and no current flows through the series branch of the discharge resistor R3 and the switching unit Q1. The bus capacitor Cbus forms a microampere-level leakage loop (negligible) only through the first resistor R1 and the auxiliary contact S1.

[0054] (ii) After the switching unit Q1 is turned on.

[0055] When the main contacts of the DC switching unit open, the auxiliary contact S1 opens simultaneously. At this time, the current path of the control signal is: positive terminal of bus capacitor Cbus → first resistor R1 → second resistor R2 → negative terminal of bus capacitor Cbus, forming a loop; a control signal voltage is generated at the connection point of the first resistor R1 and the second resistor R2. When the control signal voltage exceeds the conduction threshold of the switching unit Q1, the discharge loop is activated, i.e., positive terminal of bus capacitor Cbus → discharge resistor R3 → conducting Q1 → negative terminal of bus capacitor Cbus. When the second resistor R2 is configured, the control signal voltage is determined by the voltage division of the first resistor R1 and the second resistor R2. By adjusting the R1 / R2 ratio, the conduction threshold of the switching unit Q1 can be precisely set.

[0056] Please refer to Figure 4 , Figure 4 The second circuit diagram of the discharge device for the DC bus provided in this embodiment of the utility model. Figure 2 The discharge resistor R3 is connected between the drain D of the switching unit Q1 and the positive terminal of the bus capacitor Cbus, forming a discharge circuit; while Figure 4 The position of the discharge resistor R3 is changed, and it is connected between the source S of the switching unit Q1 and the negative terminal of the bus capacitor Cbus.

[0057] Optionally, the first terminal of switching unit Q1 is connected to the positive terminal of bus capacitor Cbus, the second terminal of switching unit Q1 is connected to the first terminal of discharge resistor R3, and the second terminal of discharge resistor R3 is connected to the negative terminal of bus capacitor Cbus. The control terminal of switching unit Q1 receives a control signal. This connection method means that the control signal acts on the control terminal of switching unit Q1. When the control signal meets the conduction condition of switching unit Q1, switching unit Q1 is turned on; otherwise, it is turned off.

[0058] exist Figure 4 In the circuit structure shown, the current direction before and after the switching unit Q1 is turned on is as follows:

[0059] (a) Before the switching unit Q1 is turned on.

[0060] When the main contacts of the DC relay close, the auxiliary contact S1 also closes. At this time, the current path of the control signal is: positive terminal of bus capacitor Cbus → first resistor R1 → closed auxiliary contact S1 → negative terminal of bus capacitor Cbus. The closure of the auxiliary contact S1 pulls the potential of the control signal node (i.e., the R1-S1 connection point) down to the negative potential, and the voltage at the control terminal of the switching unit Q1 is 0V, ensuring reliable cutoff. The discharge circuit state is as follows: the discharge resistor R3 is in a high-resistance state due to the cutoff of Q1, the voltage of the bus capacitor remains stable, and the energy loss mainly comes from the R1 branch.

[0061] (ii) After the switching unit Q1 is turned on.

[0062] When the main contacts of the DC relay open, the auxiliary contact S1 also opens. At this time, the current path of the control signal is: positive terminal of bus capacitor Cbus → first resistor R1 → second resistor R2 → negative terminal of bus capacitor Cbus. The conduction condition is: when the control signal voltage is greater than the threshold voltage, the switching unit Q1 enters the saturation conduction state. The current path of the discharge circuit is: positive terminal of bus capacitor Cbus → switching unit Q1 → discharge resistor R3 → negative terminal of Cbus. The function of the first resistor R1 is to limit the power consumption of the control circuit, the discharge resistor R3 ensures a safe discharge rate, and the second resistor R2 provides the gate drive voltage divider.

[0063] Accordingly, this embodiment of the invention also provides an energy storage converter, which includes the DC bus discharge device described in any of the above embodiments. This energy storage converter can be applied to various energy storage systems, photovoltaic power generation systems, and other new energy power conversion equipment; this embodiment does not impose any special limitations on it.

[0064] It is understood that the energy storage converter of this utility model integrates the aforementioned DC bus discharge device, utilizes the existing auxiliary contacts of the DC contactor as a control signal source, and cooperates with the control unit to convert the bus voltage into a control signal to directly control the on / off state of the switching unit. This design has the following outstanding features: 1) When the main contacts of the contactor open, its auxiliary contacts open simultaneously, and the control unit automatically generates a control signal voltage to turn on the switching unit, forming a discharge circuit; 2) When the main contacts of the contactor close, its auxiliary contacts close simultaneously, forcibly pulling down the control terminal of the switching unit to ensure reliable disconnection of the discharge circuit; 3) It eliminates the isolation devices, dedicated drive circuits, and other components in traditional solutions, reducing system costs; 4) The discharge process is completely controlled autonomously by the hardware circuit, avoiding possible abnormalities in software control.

[0065] This application utilizes existing resources such as contactor auxiliary contacts to achieve safe, economical, and reliable discharge of the bus capacitor in an energy storage converter. The discharge time can be reasonably set by adjusting the discharge resistor value, making it suitable for energy storage applications requiring frequent charge-discharge switching.

[0066] The discharge device and energy storage converter for a DC bus provided by the embodiments of this utility model have been described in detail above. Specific examples have been used to illustrate the principle and implementation of this utility model. The description of the above embodiments is only for the purpose of helping to understand the technical solution and core idea of ​​this utility model. Those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this utility model.

Claims

1. A discharge device for a DC bus, characterized in that, The main contacts of a DC switching unit are connected in series on the DC bus, and a bus capacitor (Cbus) is connected between the DC buses; the discharge device includes: The control unit (10) includes an auxiliary contact (S1) of the DC switching unit; the control unit (10) is connected in parallel with the bus capacitor (Cbus) to generate a control signal; The discharge unit (20) is connected in parallel with the bus capacitor (Cbus); in response to the control signal, it discharges the bus capacitor (Cbus) when the main contacts are open.

2. The discharge device according to claim 1, characterized in that, The DC switching unit is a DC contactor, a DC circuit breaker, or a DC relay.

3. The discharge device for a DC bus according to claim 1, characterized in that, The control unit (10) includes: The first resistor (R1) has its first terminal connected to the positive terminal of the bus capacitor (Cbus); The auxiliary contact (S1) is connected in series between the second end of the first resistor (R1) and the negative terminal of the bus capacitor (Cbus), and the second end of the first resistor (R1) is used to generate the control signal.

4. The discharge device for a DC bus according to claim 3, characterized in that, The control unit (10) further includes a second resistor (R2), the first end of which is connected to the second end of the first resistor (R1), and the second end of which is connected to the negative terminal of the bus capacitor (Cbus).

5. The discharge device for a DC bus according to any one of claims 1-4, characterized in that, The discharge unit (20) includes a discharge resistor (R3) and a switch unit (Q1). The discharge resistor (R3) and the switch unit (Q1) are connected in series and then connected in parallel with the bus capacitor (Cbus).

6. The discharge device according to claim 5, characterized in that, The first terminal of the discharge resistor (R3) is connected to the positive terminal of the bus capacitor (Cbus), and the second terminal of the discharge resistor (R3) is connected to the negative terminal of the bus capacitor (Cbus) through the switching unit (Q1). The control terminal of the switching unit (Q1) receives the control signal; or, The first terminal of the switching unit (Q1) is connected to the positive terminal of the bus capacitor (Cbus), the second terminal of the switching unit (Q1) is connected to the first terminal of the discharge resistor (R3), the second terminal of the discharge resistor (R3) is connected to the negative terminal of the bus capacitor (Cbus), and the control terminal of the switching unit (Q1) receives the control signal.

7. The discharge device for a DC bus according to any one of claims 1-4, characterized in that, The auxiliary contact (S1) is mechanically linked to the main contact, and the main contact and the auxiliary contact (S1) close / open synchronously.

8. The discharge device for a DC bus according to claim 3 or 4, characterized in that, The resistance of the first resistor (R1) is greater than or equal to 1MΩ.

9. The discharge device for a DC bus according to claim 5, characterized in that, The discharge resistor (R3) is a kiloohm level resistor.

10. An energy storage converter, characterized in that, The discharge device includes the DC bus as described in any one of claims 1-9.

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