A modular parallel power supply DC input side short-circuit cooperative protection circuit

Abstract

This invention discloses a modular parallel power supply DC input side short-circuit coordinated protection circuit. This protection circuit consists of two levels: the first level is a DC bus input side explosion bridge; the second level includes a fuse, thyristor, resistor, capacitor, and contactor. The positive terminal of the common DC bus is connected to the first terminal of the fuse, the second terminal of the fuse is connected to the first terminal of the resistor and the anode of the thyristor, and the second terminal of the resistor and the cathode of the thyristor are connected to the capacitor and the positive terminal of the module. The negative terminal of the common DC bus is connected to the first terminal of the contactor, and the second terminal of the contactor is connected to the capacitor and the negative terminal of the module. Each power module is independently configured with a set of second-level protection circuits. By adopting a two-level protection approach, short-circuit protection coordination between the device and other devices on the common bus, short-circuit protection coordination between the entire device and its internal modules, and short-circuit protection coordination between modules can be achieved. The circuit is simple and has a wide range of applications.

Description

Technical Field

[0001] This invention relates to the field of power supply technology, and more specifically to a modular parallel power supply DC input side short-circuit cooperative protection circuit. Background Technology

[0002] Modular parallel power supplies are composed of multiple power modules connected in parallel on both the input and output sides. This parallel connection method improves the reliability of the power supply, reduces the current stress requirements on the converter's switching devices, and allows for flexible and convenient capacity expansion, offering significant advantages in high-capacity power conversion applications.

[0003] The power supply unit adopts a modular parallel design scheme, which requires higher coordination of short-circuit protection on the DC input side. Specifically, it needs to achieve coordination of short-circuit protection between the unit and other units on the common DC bus, coordination of short-circuit protection between the unit as a whole and its internal power modules, and coordination of short-circuit protection between power modules.

[0004] Figure 1 The block diagram of the DC input terminal circuit of the modular parallel power supply is shown. The DC input terminal can be divided into four sections: Section 1 is the DC bus section, Section 2 is the whole machine input side component section, Section 3 is the branch input side component section, and Section 4 is the power module input side section. The short-circuit protection targets for each section are as follows:

[0005] The first short-circuit protection objective is: when the common DC bus is short-circuited, the explosion bridge of the whole machine should not be protected, and the device itself should be able to achieve fault passage. Specifically, the DC capacitors in sections 2, 3, and 4 should not discharge through the bus short-circuit point, or the discharge current should not be sufficient to trigger the explosion bridge to operate.

[0006] The second short-circuit protection objective is: when a short circuit occurs in a component on the input side of the whole machine, the explosion bridge of the whole machine will realize the protection action, requiring that the protection circuits of each module branch will not operate;

[0007] The third short-circuit protection objective is: when a short circuit occurs on the input side of a branch, the branch fault must be quickly cleared so that the overall explosion bridge does not activate; and the capacitors inside other branches or modules must not discharge at the short-circuit point, or the discharge current must be insufficient to cause the protection of other branches to activate or the capacitor voltage to drop.

[0008] The target of the fourth stage of short circuit protection is the same as that of the third stage.

[0009] Existing typical modular parallel power supply DC input side circuits, such as Figure 2As shown, all power modules share a common circuit, which includes resistors, a soft-on switch, and a bus support capacitor. The soft-on switch is typically a contactor or a thyristor. This circuit has a simple structure and can achieve soft-on of the bus support capacitor, but it fails to achieve the aforementioned combination... Figure 1 The aforementioned whole-machine short-circuit collaborative protection will actually reduce the power supply reliability of the entire device, thus losing the advantage of modular parallel power supply. Summary of the Invention

[0010] The purpose of this invention is to address the shortcomings of the above-mentioned problems by providing a modular parallel power supply DC input side short-circuit collaborative protection circuit. By adopting this circuit scheme, short-circuit protection collaboration between the device and other devices on the same bus, short-circuit protection collaboration between the device as a whole and its internal power modules, and short-circuit protection collaboration between power modules can be achieved, thus greatly improving the reliability of the power supply of the entire device.

[0011] Specifically, this invention provides a modular parallel power supply DC input side short-circuit cooperative protection circuit, which is divided into two levels: the first level protection circuit is a DC bus input side explosion bridge; the second level protection circuit includes a fuse FCI, a thyristor Ti, a resistor Ri, a capacitor Ci, and a contactor Si. The positive terminal of the common DC bus is connected to the first terminal of the fuse FCI, the second terminal of the fuse FCI is connected to the first terminal of the resistor Ri and the anode of the thyristor Ti, the second terminal of the resistor Ri and the cathode of the thyristor Ti are connected to the positive terminal of the capacitor Ci and the power module i; the negative terminal of the common DC bus is connected to the first terminal of the contactor Si, and the second terminal of the contactor Si is connected to the negative terminal of the capacitor Ci and the power module i, where i∈1,2,3…n, and n is the number of power modules.

[0012] In this modular parallel power supply, each power module is independently configured with a set of second-level protection circuits.

[0013] The operating time of the fuse FCI is shorter than that of the thyristor Ti and the exploding bridge.

[0014] The resistor Ri and thyristor Ti enable a soft-on process for capacitor Ci, preventing current surges caused by sudden voltage changes during power-on. Contactor Si isolates power modules that are not short-circuited, ensuring uninterrupted operation of other power modules. Each contactor is independently controlled by its corresponding power module.

[0015] This invention enables coordinated protection during DC input side short circuits, specifically as follows:

[0016] (1) When a short circuit occurs in the first section, since the thyristor Ti is reverse cut off, the input capacitor Ci of each branch and the power module can only provide short circuit current to the short circuit point through the resistor Ri, which is insufficient to trigger the explosion bridge and fuse FCI protection action.

[0017] (2) When a short circuit occurs in the second section, the explosion bridge protection will be activated. Since the thyristor Ti is reverse cut off, the capacitor Ci on the input side of each branch and the power module can only provide short circuit current to the short circuit point through the resistor Ri, which is insufficient to trigger the fuse FCI protection.

[0018] (3) When the third and fourth short circuits occur, taking the third and fourth short circuits of power module 1 as an example, the capacitor Ci from module 2 to module n is blocked by the reverse thyristor Ti, and can only provide short circuit current to the short circuit point through the resistor Ri, which is insufficient to trigger the protection action of fuse FCI; at the same time, fuse FC1 quickly blows, realizing the isolation of the faulty branch and power module 1, without affecting the normal operation of other branches and modules. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the DC input terminal circuit of a modular parallel power supply;

[0020] Figure 2 It is a typical existing modular parallel power supply DC input side circuit;

[0021] Figure 3 This invention provides a schematic diagram of a modular parallel power supply DC input side short-circuit cooperative protection circuit;

[0022] Figure 4 This is a schematic diagram of a specific example of the circuit using the present invention. Detailed Implementation

[0023] Figure 3 This invention provides a schematic diagram of a modular parallel power supply DC input side short-circuit collaborative protection circuit. This short-circuit collaborative protection circuit consists of two levels: the first level is a DC bus input side explosion bridge, which can be implemented using existing technology; the second level relies on fuses and thyristors. Each power module in the modular parallel power supply is independently configured with a set of the aforementioned second-level protection circuit.

[0024] The second-level protection circuit includes: a fuse FC, a thyristor T, a resistor R, a capacitor C, and a contactor S. The positive terminal of the common DC bus is connected to the first terminal of the fuse FC, the second terminal of the fuse FC is connected to the first terminal of the resistor R and the anode of the thyristor T, and the second terminal of the resistor R and the cathode of the thyristor T are connected to the capacitor C and the positive terminal of the power module. The negative terminal of the common DC bus is connected to the first terminal of the contactor S, and the second terminal of the contactor S is connected to the capacitor C and the negative terminal of the power module.

[0025] Thus, for n power modules, each independently configured with n secondary protection circuits, there are: fuse FCI, thyristor Ti, resistor Ri, capacitor Ci, and contactor Si. The positive terminal of the common DC bus is connected to the first terminal of fuse FCI, the second terminal of fuse FCI is connected to the first terminal of resistor Ri and the anode of thyristor Ti, and the second terminal of resistor Ri and the cathode of thyristor Ti are connected to capacitor Ci and the positive terminal of power module i. The negative terminal of the common DC bus is connected to the first terminal of contactor Si, and the second terminal of contactor Si is connected to capacitor Ci and the negative terminal of power module i, where i∈(1, 2, 3...n), and n is the number of power modules.

[0026] The operating time of the fuse FCI needs to be less than that of the thyristor Ti and the exploding bridge.

[0027] The resistor Ri and thyristor Ti enable a soft-on process for capacitor Ci, preventing current surges caused by sudden voltage changes during power-on. Contactor Si isolates power modules that are not short-circuited, ensuring uninterrupted operation of other power modules. Each contactor is independently controlled by its corresponding power module.

[0028] The principle of the DC input side short-circuit cooperative protection circuit of the present invention will be explained below with reference to specific embodiments.

[0029] Taking a certain power supply unit as an example, the input of this power supply unit is powered by a storage battery with a rated voltage of DC240V. The thyristor T is selected as TZ800N12KOF, the fuse FC is selected as RSG-2690V / 630A-ZK, and the resistor R is 300Ω. The following is in conjunction with... Figure 4 Detailed explanation.

[0030] When a short circuit occurs in the first stage, because the thyristor Ti is reverse cut off, the capacitor Ci on the input side of each branch and the power module can only provide short circuit current (less than 1A) to the short circuit point through the resistor Ri, which is insufficient to trigger the explosion bridge and fuse FCI protection action.

[0031] When a short circuit occurs in the second stage, the battery provides short-circuit current to the short-circuit point through the DC bus, and the explosion bridge protection is activated. Since the thyristor Ti is reverse cut off, the capacitor Ci on the input side of each branch and the power module can only provide short-circuit current (less than 1A) to the short-circuit point through the resistor Ri, which is insufficient to trigger the fuse FCI protection.

[0032] When the third and fourth short circuits occur, taking the third and fourth short circuits of power module 1 as an example, the capacitor Ci from module 2 to module n is blocked by the reverse thyristor Ti, and can only provide short circuit current to the short circuit point through the resistor Ri, which is insufficient to trigger the protection action of the corresponding branch fuse FCI; at the same time, the fuse FC1 blows quickly to isolate the faulty branch and power module 1, without affecting the normal operation of other branches and modules.

[0033] In particular, the design and selection of the thyristor T, fuse FC, and explosion bridge need to achieve selective protection, that is, the explosion bridge should not trip and the thyristor should not be damaged when the fuse trips; that is, the tripping time of the fuse must be shorter than the tripping time of the thyristor and the explosion bridge. This will be explained in detail below.

[0034] The parasitic parameters of the battery discharge circuit are mainly determined by the internal parasitic parameters of the battery. In this embodiment, the total parasitic inductance of the battery is 52.28uH, and the total parasitic resistance is 5.19mΩ. The discharge current formula when the battery voltage is 240V is:

[0035]

[0036] The explosion bridge parameters are: when the short-circuit current continues to rise at 15A / μs, the arc-precession i of the current-limiting fuse... 2 t value < 1500kA 2 s, arc pre-arc time <3ms; when the short-circuit current continues to rise at 3A / μs, the arc pre-arc time of the current-limiting fuse is i 2 t value < 3000kA 2 The arc pre-arc time is <14ms. According to the battery short-circuit current curve, the short-circuit current rise rate is around 3A / μs, reaching 3000kA. 2 The time is approximately 10ms.

[0037] The thyristor model is TZ800N, and the short-circuit parameter i 2 t is 4500kA 2 According to the battery short-circuit current curve, the time required to reach the thyristor short-circuit damage value is approximately 11ms.

[0038] According to the product manual of fuse RSG-2 690V / 630A-ZK and the short-circuit current curve of the battery, the time required for the fuse protection to operate is approximately 3ms.

[0039] Therefore, the operating time of the fuse FC is shorter than that of the thyristor T and the explosion bridge. When the 3rd and 4th short circuits occur, selective protection can be achieved. That is, when the input side of a power module is short-circuited, the fuse of that branch will blow first to protect it, without causing the explosion bridge of the whole machine to operate or the thyristor T of that branch to be damaged, thus meeting the above short circuit protection design requirements.

[0040] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the present invention. Therefore, all changes, modifications, or equivalent substitutions made to the specific embodiments of the invention are within the scope of the claims of the present invention.

Claims

1. A modular parallel power supply DC input side short-circuit cooperative protection circuit, characterized in that... The short-circuit collaborative protection circuit is divided into two levels: the first level protection circuit is an explosion bridge on the DC bus input side; the second level protection circuit includes a fuse FCI, a thyristor Ti, a resistor Ri, a capacitor Ci, and a contactor Si. The positive terminal of the common DC bus is connected to the first terminal of the fuse FCI, the second terminal of the fuse FCI is connected to the first terminal of the resistor Ri and the anode of the thyristor Ti, the second terminal of the resistor Ri and the cathode of the thyristor Ti are connected to the positive terminal of the capacitor Ci and the power module i; the negative terminal of the common DC bus is connected to the first terminal of the contactor Si, the second terminal of the contactor Si is connected to the negative terminal of the capacitor Ci and the power module i. The operating time of the fuse FCI is less than the operating time of the thyristor Ti and the explosion bridge, where i∈1,2,3…n, and n is the number of power modules.

2. The short-circuit cooperative protection circuit according to claim 1, characterized in that, Each power module in the modular parallel power supply is independently configured with a set of second-level protection circuits.

3. The short-circuit cooperative protection circuit according to claim 1, characterized in that, The branch capacitor Ci can be slowly energized by resistor Ri and thyristor Ti, and the power module with non-short-circuit fault is isolated by contactor Si. Each contactor is independently controlled by the corresponding power module.

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