A DC main and standby power supply automatic uninterrupted switching circuit

Abstract

The utility model discloses a direct current main and standby power automatic non-interruptible switching circuit, wherein the positive and negative poles of the main power supply are connected to one end of the main supply circuit switch through the main supply bus, and the other end of the main supply circuit switch is connected to the positive and negative poles of the system load through the output bus; the positive and negative poles of the standby power supply are connected to one end of the standby circuit switch through the standby bus, and the other end of the standby circuit switch is connected to the output bus, one of the diodes is connected between the standby bus connected to the positive pole of the standby power supply and the output bus connected to the positive pole of the system load, another diode is connected between the standby bus connected to the negative pole of the standby power supply and the output bus connected to the negative pole of the system load, the positive and negative poles of the undervoltage relay are connected to the main supply bus, and the signal end of the undervoltage relay is respectively connected to the main supply circuit switch and the standby circuit switch. The utility model can realize the automatic non-interruptible switching of the direct current main and standby power supplies without the support of complex control and detection systems.

Description

Technical Field

[0001] The utility model relates to an automatic non-interruption switching circuit of a DC main and standby power supply. Background Art

[0002] With the maturity and economic improvement of power electronics technology, coupled with the introduction of DC terminal power equipment, DC distribution networks have gradually emerged in recent years. The DC system has the characteristics of no harmonics and high safety, which makes it stand out in the low-voltage DC distribution network. In the DC system, in order to ensure the power supply of DC loads, DC dual power supplies from different rectifiers are used, especially for highly sensitive loads, requiring the power switching time to be no more than 2ms or uninterrupted power supply. In the AC system, the two power supplies are usually used as backup for each other: the bus load with power failure is switched to the non-faulty bus through the bus-connected switch device (circuit breaker or contactor, etc.). When the power supply is working normally, each carries the load, and both power supplies are in working state.

[0003] The dual DC power supplies are backup power supplies for each other. In normal operation, one power supply is the main power supply and the other is the backup power supply. When the main power supply fails, it switches to the backup power supply. In order to reduce system losses and improve efficiency, the backup power supply is usually in hot backup mode. The dual DC power supplies do not supply power to the same bus at the same time. Although this avoids internal circulation caused by inconsistent output voltages between the dual power supplies, there will be a time difference in the switching of the main and backup power supplies. Figure 1 As shown, the conventional DC main-standby power supply switching circuit includes a main power supply, a standby power supply, a KM1 main supply circuit switch, a KM2 standby circuit switch and a system load. The KM1 main supply circuit switch and the KM2 standby circuit switch are controlled by the control system through instructions to open and close. The positive and negative poles of the main power supply are connected to one end of the KM1 main supply circuit switch through the main supply bus, and the other end of the KM1 main supply circuit switch is connected to the positive and negative poles of the system load through the output bus; the positive and negative poles of the standby power supply are connected to one end of the KM2 standby circuit switch through the standby bus, and the other end of the KM2 standby circuit switch is connected to the output bus. The defects of this DC main-standby power supply switching circuit are:

[0004] ⑴ When the main power supply is switched to the backup power supply, the switch needs to be opened and closed and its instructions are given, and the switching time is as long as hundreds of milliseconds or longer.

[0005] (2) Use a high-speed sampling control system to generate opening and closing instructions. Even if the solution of closing the backup power supply first and then disconnecting the main power supply is adopted to ensure the continuity of load power supply, it is still subject to the influence of factors such as the reliability of the control system, sudden power failure of the main circuit, and power failure of the control circuit, resulting in output power failure. Utility Model Content

[0006] The utility model aims to provide a direct current main and standby power supply automatic non-interruption switching circuit, which can realize the direct current main and standby power supply automatic non-interruption switching without the support of complex control and detection systems.

[0007] The purpose of the utility model is achieved through the following technical solutions: a DC main and standby power automatic uninterruptible switching circuit, including a main power supply, a standby power supply, a main supply circuit switch, a standby circuit switch and a system load, the positive and negative poles of the main power supply are connected to one end of the main supply circuit switch through a main supply bus, and the other end of the main supply circuit switch is connected to the positive and negative poles of the system load through an output bus; the positive and negative poles of the standby power supply are connected to one end of the standby circuit switch through a standby bus, and the other end of the standby circuit switch is connected to the output bus, characterized in that the DC main and standby power automatic uninterruptible switching circuit includes two diodes and an undervoltage relay, one of which is connected between the standby bus connected to the positive pole of the standby power supply and the output bus connected to the positive pole of the system load, and the other diode is connected between the standby bus connected to the negative pole of the standby power supply and the output bus connected to the negative pole of the system load, the positive and negative poles of the undervoltage relay are connected to the main supply bus, and the signal ends of the undervoltage relay are respectively connected to the main supply circuit switch and the standby circuit switch.

[0008] The utility model can realize automatic and uninterrupted switching of the DC main and standby power supplies without the support of complex control and detection systems, that is, the utility model can realize autonomous switching without relying on control system signals, and solves the problems of output power failure and output voltage disturbance caused by the time difference of opening and closing actions during the switching of two power supplies.

[0009] The voltage of the main power supply of the utility model is 1-2V higher than the system voltage.

[0010] The voltage of the backup power supply of the utility model is 1-2V lower than the system voltage.

[0011] The undervoltage setting value of the undervoltage relay of the utility model is 0.85 times of the main power supply voltage, and the undervoltage recovery value is 1.15 times of the undervoltage setting value.

[0012] Compared with the prior art, the utility model has the following significant effects:

[0013] (1) The utility model can realize automatic and uninterrupted switching of the DC main and standby power supplies without the support of complex control and detection systems, that is, the utility model can realize autonomous switching without relying on control system signals, and solves the problems of output power failure and output voltage disturbance caused by the time difference of opening and closing actions during the switching of the two power supplies.

[0014] (2) The utility model has a simple structure and low cost, and is particularly suitable for scenarios where the DC load is not allowed to be powered off. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The utility model is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0016] Figure 1 It is a schematic diagram of the structure of a conventional dual-channel main and standby power supply switching circuit;

[0017] Figure 2 It is a schematic diagram of the composition structure of the utility model;

[0018] Figure 3 It is a schematic diagram of the normal main power supply mode of the utility model system;

[0019] Figure 4 It is a schematic diagram of the short-term low voltage support working mode of the system of the utility model;

[0020] Figure 5 It is a schematic diagram of the normal switching mode of the main and standby modes of the utility model;

[0021] Figure 6 It is a schematic diagram of the utility model in the standby switching back to the main power supply mode. DETAILED DESCRIPTION

[0022] like Figure 2 As shown, the utility model is a DC main and standby power automatic non-interruptible switching circuit, including a main power supply, a standby power supply, a main supply circuit switch KM1, a standby circuit switch KM2, two diodes D1, D2, an undervoltage relay and a system load. The positive and negative poles of the main power supply are connected to one end of the main supply circuit switch KM1 through the main supply bus 1L+, 1L-, and the other end of the main supply circuit switch KM1 is connected to the positive and negative poles of the system load through the output bus 3L+, 3L-; the positive and negative poles of the standby power supply are connected to one end of the standby circuit switch KM2 through the standby bus 2L+, 2L-, and the other end of the standby circuit switch KM2 is connected to the output bus On lines 3L+, 3L-, diode D1 is connected between the standby bus 2L+ and the output bus 3L+, the anode of diode D1 is connected to the positive electrode of the standby power supply, and the cathode of diode D1 is connected to the positive electrode of the system load; diode D2 is connected between the standby bus 2L- and the output bus 3L-, the cathode of diode D2 is connected to the negative electrode of the standby power supply, and the anode of diode D1 is connected to the negative electrode of the system load; the positive electrode of the undervoltage relay is connected to the main supply bus 1L+, the negative electrode of the undervoltage relay is connected to the main supply bus 1L-, and the signal end of the undervoltage relay is respectively connected to the main supply circuit switch KM1 and the standby circuit switch KM2.

[0023] The main power supply is output by the front-end rectifier. The output voltage is set slightly higher than the system voltage. The output voltage can be 1V higher than the system voltage. If the system voltage is 220VDC and the fluctuation is allowed to be ±0.5%, the rectifier output voltage is set to 221VDC. If the system allows large fluctuations, the rectifier output voltage can be set to 2V or slightly higher than the system voltage, so that the 1L+ and 1L- buses maintain a 221VDC output. Similarly, the output voltage of the rectifier of the backup power supply is set to be 1V lower than the system voltage. Under the above conditions, the output voltage is set to 219VDC, so that the 2L+ and 2L- buses maintain a 219VDC output.

[0024] The undervoltage setting value of the undervoltage relay is 0.85 times the output voltage (about 188V), and the undervoltage recovery value is 1.15 times the undervoltage setting value (about 216V). The signal of the undervoltage relay is used to control the main supply circuit switch KM1 and the standby circuit switch KM2.

[0025] The working principle of the utility model is as follows:

[0026] 1. When the main power supply is normal, the undervoltage relay output signal closes KM1 and opens KM2 to maintain normal main power supply output. Because the 1L+, 1L- branch voltage is 2V higher than the 2L+, 2L- voltage, the diode is reversely cut off and the backup power supply does not output.

[0027] 2. The voltage of the main power supply drops slightly, but it is not enough to activate the undervoltage relay. Keep KM1 closed. When the main power supply is lower than 219V, the diode is forward-conducted to provide short-term support until the main power supply is restored and then reverse-cut off again.

[0028] 3. The voltage of the main power supply drops, the undervoltage relay is activated or the power is lost. When the main power supply is lower than 219V, the diode outputs until KM2 is closed. The diode is cut off after being bypassed, and the system switches to the backup power supply output; when the main power supply is restored, KM1 is closed and KM2 is opened. Usually, the closing time of the contactor is slower than the opening time. At the moment KM2 is opened, the diode is turned on until KM1 is closed stably, the 3L+, 3L- bus voltage is higher than the backup power supply, and the diode is reversely cut off, completing the process of restoring the main power supply.

[0029] Description of the working status of the utility model under different working conditions:

[0030] 1. System normal main power supply mode: The main power supply is normal, the output is at the set value (221V), the backup power supply is normal, the output is at the set value (219V), the undervoltage relay does not work, use its normally closed point to close KM1, the normally open point controls KM2, KM1 is closed, the 3L bus voltage is higher than the 2L bus, the diode is cut off and KM2 is open. Figure 3 shown.

[0031] 2. Short-term low-voltage support working mode of the system: When the system has short-term conditions such as large load input, fluctuations on the main power supply side, and load short circuit, but the bus voltage value is not lower than the undervoltage setting value (undervoltage setting value: 0.85U1n < main power supply U1 < U1n (221V)), the system keeps KM1 closed and KM2 open. However, because the voltage of the 3L bus is lower than that of the 2L bus, the diode conducts to support the load power supply. When the main power supply voltage is low, reverse injection protection will be executed until the state is eliminated and the main power supply is restored, and the output of the main power supply is maintained. As Figure 4 shown.

[0032] 3. Normal main-backup switching mode: When the main power supply fails or loses power (main power supply U1 < undervoltage setting value 0.85U1n), the bus voltage quickly drops below the setting value of the undervoltage relay. At this time, the relay simultaneously gives the signals of opening KM1 and closing KM2. When the power supply drops below the voltage of the 2L bus, the diode conducts until KM2 is stably closed, bypassing the diode. For the output load, it satisfies uninterrupted output, and the system enters the normal standby power supply mode. As Figure 5 shown.

[0033] 4. Standby power supply switching back to the main power supply mode: When the main power supply resumes normal power supply (main power supply U1 > undervoltage setting value 0.85U1n × 1.15), the undervoltage relay resumes, KM2 is opened, and KM1 is closed. Due to the mechanical action duration, the closing time is usually longer than the opening time. Before KM1 reaches the steady state of closing, the diode conducts until KM1 reaches the steady state of closing. When the voltage of the 3L bus resumes higher than that of the standby power supply, the diode naturally cuts off, satisfying uninterrupted output during the switching process, and the system resumes to the main power supply mode, completing the switching from standby power to main power. As Figure 6 shown.

[0034] The embodiments of the present utility model are not limited thereto. Based on the above content of the present utility model, according to the common technical knowledge and conventional means in the art, without departing from the above basic technical idea of the present utility model, the present utility model can also be modified, replaced or changed in many other forms, all of which fall within the scope of the protection of the rights of the present utility model.

Claims

1. A DC main and standby power automatic uninterrupted switching circuit, comprising a main power supply, a standby power supply, a main supply circuit switch, a standby circuit switch and a system load, wherein the positive and negative electrodes of the main power supply are connected to one end of the main supply circuit switch through a main supply bus, and the other end of the main supply circuit switch is connected to the positive and negative electrodes of the system load through an output bus; the positive and negative electrodes of the standby power supply are connected to one end of the standby circuit switch through a standby bus, and the other end of the standby circuit switch is connected to the output bus, characterized in that: The automatic uninterruptible switching circuit of the DC main and standby power supplies includes two diodes and an undervoltage relay, wherein one diode is connected between a standby bus connected to the positive pole of the standby power supply and an output bus connected to the positive pole of the system load, and the other diode is connected between the standby bus connected to the negative pole of the standby power supply and the output bus connected to the negative pole of the system load, the positive and negative poles of the undervoltage relay are connected to the main supply bus, and the signal ends of the undervoltage relay are respectively connected to the main supply circuit switch and the standby circuit switch.

2. The automatic uninterrupted switching circuit of the DC main and standby power supplies according to claim 1 is characterized in that: The voltage of the main power supply is 1 to 2V higher than the system voltage.

3. The automatic uninterrupted switching circuit of the DC main and standby power supplies according to claim 2 is characterized in that: The voltage of the backup power supply is 1 to 2V lower than the system voltage.

4. The automatic uninterrupted switching circuit of the DC main and standby power supplies according to claim 3 is characterized in that: The undervoltage setting value of the undervoltage relay is 0.85 times the main power supply voltage, and the undervoltage recovery value is 1.15 times the undervoltage setting value.

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