Undisturbed dual-power switching loop for high-voltage frequency converter

Abstract

The utility model relates to the thermal power generation field, and discloses an undisturbed dual power supply switching loop used for a high voltage frequency converter, the undisturbed dual power supply switching loop comprises a main power supply loop and a standby power supply loop, the main power supply loop comprises a main power supply, two SSR solid state relays, a K4 relay, two K4 normally open contacts, and two K7 contacts; and the standby power supply loop comprises a standby power supply, two SSR solid-state relays, a K8 relay, two K8 contacts, a K7 relay and two K4 normally closed contacts. According to the scheme, the technical problem that a main circuit and a standby circuit cannot be switched when a control power supply loop DAC device or a UPS device of a conventional high-voltage frequency converter fails can be solved.

Description

Technical Field

[0001] The utility model relates to the field of thermal power generation, and particularly relates to a non-disturbing dual power supply switching circuit for a high-voltage frequency converter. Background Art

[0002] During the power generation process in a thermal power plant, some high-voltage auxiliary machines are controlled by high-voltage frequency converters, such as primary fans, condensate pumps, induced draft fans, etc. After being controlled by high-voltage frequency converters, the energy-saving effect is good. However, due to the design defects of the frequency converters themselves, the operating reliability of the frequency converters still needs to be improved.

[0003] In a thermal power plant, the control power supply circuit of a conventional high-voltage frequency converter adopts a dual power supply switching circuit. The first group of control power is taken from the DC control section of the unit, and the second group of control power is taken from the UPS device of the unit. As Figure 1 shown, two power supplies are provided for switching. Both power supplies are reliable in power supply. However, since the DAC (inverter power supply) device and the UPS device are single-configured, the actual dual power supply function cannot be truly reflected. After analysis, it is found that there are two bottlenecks in this circuit:

[0004] 1. The DAC (inverter power supply) device. When the DAC device is abnormal or fails, the inversion of the DC input power supply cannot be realized normally. When the UPS power supply disappears, the DC power supply cannot be inverted and cannot be used as a backup power supply, and the dual power supply switching circuit loses its meaning.

[0005] 2. The UPS device. Analyzing from the sources of the two power supplies taken, they both have high reliability. However, if the UPS power supply device used fails, both power supplies cannot normally supply the load, that is, the PLC, main control board, etc. lose power.

[0006] During the production process of the power plant, the control power supply has disappeared many times due to the damage of the UPS power supply device or the inverter in the control circuit, causing the frequency converter to trip and resulting in the boiler flameout. The reliability of the power supply circuit needs to be improved. Content of the Utility Model

[0007] The utility model aims to provide a non-disturbing dual power supply switching circuit for a high-voltage frequency converter to solve the technical problem that the main circuit and the standby circuit cannot be switched when the DAC device or the UPS device of the control power supply circuit of a conventional high-voltage frequency converter fails.

[0008] To achieve the above purpose, the utility model adopts the following technical scheme:

[0009] A disturbance-free dual power supply switching circuit for a high-voltage frequency converter, including a main power supply circuit and a standby power supply circuit. The main power supply circuit includes a main power supply, two SSR solid-state relays, a K4 relay, two K4 normally open contacts, and two K7 contacts. The K4 relay is connected across the main power supply. The two K4 normally open contacts are connected to the two ends of the K4 relay. The two K7 contacts are connected to the other ends of the two K4 contacts. The two SSR solid-state relays are connected in parallel. The K4 relay is connected to the input ends of the two SSR solid-state relays. The output ends of the two SSR solid-state relays are connected to the output control power supply.

[0010] The standby power supply circuit includes a standby power supply, two SSR solid-state relays, a K8 relay, two K8 contacts, a K7 relay, and two K4 normally closed contacts. The K8 relay and the K7 relay are connected in parallel across the standby power supply. The two K8 contacts are connected to the two ends of the K8 relay. The two K4 normally closed contacts are connected to the other sides of the two K8 contacts. The two SSR solid-state relays are connected in parallel. The K7 relay is connected to the input ends of the two SSR solid-state relays. The output ends of the two SSR solid-state relays are connected to the output control power supply. The standby power supply is taken from the tertiary winding of the phase-shifting transformer of the high-voltage frequency converter body.

[0011] The principle of this solution is:

[0012] In actual use, the main power supply circuit is preferentially used for power supply. When the main power supply circuit is operating, the K4 relay is energized, the K4 normally open contacts are closed, the K7 contacts remain closed, and the two SSR relays are energized, forming a complete circuit. Its output control power supply continuously supplies power to the high-voltage frequency converter. At the same time, the power supply of the standby power supply circuit remains connected. The K8 relay is energized, the K8 contacts are closed, and the K4 normally closed contacts are opened, so that no current passes through the K7 relay, and the two SSR relays in the standby power supply circuit remain in an open state. When the main power supply circuit fails, the SSR solid-state relay is used to automatically switch the circuit to the standby power supply circuit. At this time, the main circuit is open, the K4 relay loses power, the K4 normally closed contacts are closed, the K4 normally open contacts are opened, the K8 relay remains energized, the K8 contacts remain closed, the K7 relay is energized, the K7 normally closed contacts are opened, and the two SSR solid-state relays in the standby power supply circuit are energized, forming a complete circuit, and the output control power supply continuously supplies power to the high-voltage frequency converter.

[0013] During the separate operation of the two circuits, the K4 relay, the normally open and normally closed contacts of K4, the K8 relay, the contacts of K8, the K7 relay, and the contacts of K7 form the locking of the standby power supply circuit when the main power supply circuit is operating and the locking of the main power supply circuit when the standby power supply circuit is operating by setting different closing and connection states respectively. In addition, the SSR solid-state relays on the main power supply circuit and the standby power supply circuit are used to complete the rapid switching of the circuit, ensuring that the high-voltage frequency converter will not stop running due to sudden power loss during the switching process. Again, in this solution, the standby power supply is taken from the tertiary winding B-N of the phase-shifting transformer of the high-voltage frequency converter itself, and the low-voltage side winding of the transformer is used as the standby power supply. There is no need to worry about the disappearance of the power supply. When the primary equipment is operating in frequency conversion, the low-voltage side winding of the phase-shifting transformer will surely be energized, and the output control power supply will not lose power. Only in one case will the low-voltage side winding of the phase-shifting transformer lose power, that is, when the frequency converter has stopped operating in frequency conversion. Naturally, there is no need to consider the harm caused by the loss of the control power supply.

[0014] The advantages of this solution are as follows:

[0015] 1. Under the existing technology, the control power supply circuit of the conventional high-voltage frequency converter also adopts a dual-power switching circuit, specifically including two power supplies taken from the DC control section of the unit and the UPS device of the unit, the DAC device and the UPS device jointly connected by the two power supplies. The DAC device is used to invert the power supply taken from the DC control section of the unit into alternating current, and the UPS device is used to temporarily supply power to the load when the DAC device fails or the two power supplies are lost. Since both power supply circuits are connected to the DAC device and the UPS device, when the DAC device or the UPS device fails, the two power supply circuits cannot work properly, let alone complete the circuit switching.

[0016] This solution cancels the DAC device and the UPS device in the original dual-power switching circuit, and mainly uses solid-state relays and "coil-reed contact type" relays to transform the dual-power switching circuit of the high-voltage frequency converter to improve the reliability of the control power supply and ensure the stable operation of the high-voltage frequency converter.

[0017] 2. The standby power supply of this solution is taken from the tertiary winding of the phase-shifting transformer of the high-voltage frequency converter body. This power supply is energized as long as the frequency converter is operating, which is more reliable than the power supply taken from the user side. Moreover, there is no need to lay cables again, which can save investment funds and has higher economy.

[0018] 3. If the switching time is too long during the circuit switching, it will also cause the control power supply to disappear and the frequency converter to trip. To avoid too long switching time, this solution uses an SSR solid-state relay as the switching component. Its switching action is rapid and the interference is small. The switching process does not exceed 5 ms, which can ensure that the power supply is uninterrupted during the switching process, and the switching process will not cause any interference to the operation of the high-voltage frequency converter, ensuring the continuous power supply of the PLC, the main control board, etc.

[0019] Preferably, as an improvement, a T1 isolation transformer is also connected in parallel across both ends of the output control power supply. The T1 isolation transformer is used to isolate impurities in the commercial power supply and maintain the equipment.

[0020] Preferably, as an improvement, a K1 relay is also connected in parallel across both ends of the output control power supply. The function of the K1 relay is to control power supply detection so that the user can confirm whether the output control power supply is powered on.

[0021] Preferably, as an improvement, a circuit breaker is also connected between the main power supply and the K4 relay, and between the standby power supply and the K8 relay. The two circuit breakers are respectively used to control the total power supply of the main power supply circuit and the standby power supply circuit, and automatically disconnect when the current in the two circuits exceeds the rated current. Description of the Drawings

[0022] Figure 1 It is a schematic structural diagram of a dual-power switching circuit before improvement;

[0023] Figure 2 It is a schematic structural diagram of a dual-power switching circuit after improvement. Detailed Embodiments

[0024] The following is a further detailed description through specific embodiments:

[0025] The reference numerals in the accompanying drawings of the specification include: main power supply 1, standby power supply 2, circuit breaker I 3-1, circuit breaker II 3-2, K4 relay 4, K4 normally open contact 5, SSR1 solid-state relay 6, SSR2 solid-state relay 7, K1 relay 8, T1 isolation transformer 9, output control power supply 10, K8 relay 11, K8 contact 12, K4 normally closed contact 13, K7 relay 14, K7 contact 15, SSR3 solid-state relay 16, SSR4 solid-state relay 17.

[0026] The embodiment is basically as shown in the attached Figure 2 figures:

[0027] As Figure 2 shown, a non-interference dual-power switching circuit for a high-voltage frequency converter includes a main power supply circuit and a standby power supply circuit. The main power supply circuit includes a main power supply 1, a circuit breaker I 3-1, a K4 relay 4, two K4 normally open contacts 5, two K7 contacts 15, two SSR solid-state relays, a K1 relay 8, a T1 isolation transformer 9, and an output control power supply 10; the standby power supply circuit includes a standby power supply 2, a circuit breaker II 3-2, a K8 relay 11, two K8 contacts 12, two K4 normally closed contacts 13, a K7 relay 14, and two solid-state relays.

[0028] The main power supply 1 is AC220V, taken from the unit's UPS device and used as the main power supply during normal operation. Both ends of the main power supply 1 are connected to the circuit breaker I3-1. The K4 relay 4 is connected across the circuit breaker I3-1. Two normally open contacts 5 of K4 are respectively connected to both ends of the K4 relay 4. Two K7 contacts 15 are respectively connected after the normally open contacts 5 of K4. The two SSR solid-state relays are the SSR1 solid-state relay 6 and the SSR2 solid-state relay 7 respectively. Both the SSR1 solid-state relay 6 and the SSR2 solid-state relay 7 include three input terminals A, C, D and one output terminal B. The input terminals A, D of the SSR1 solid-state relay 6 and the input terminal D of the SSR2 solid-state relay 7 are connected to the upper K7 contact 15. The input terminals C of the SSR1 solid-state relay 6, the input terminals A, C of the SSR2 solid-state relay 7 are connected to the lower K7 contact 15. The output terminals B of the SSR1 solid-state relay 6 and the SSR2 solid-state relay 7 are both connected to the K1 relay 8. Both ends of the K1 relay 8 are connected to the T1 isolation transformer 9. Both ends of the T1 isolation transformer 9 are connected to the output control power supply 10, and the output control power supply 10 is AC220V.

[0029] The standby power supply 2 is taken from the tertiary winding B-N of the phase-shifting transformer of the high-voltage frequency converter itself and used as the standby power supply when the main power supply 1 fails. Both ends of the standby power supply 2 are connected to the circuit breaker II3-2. The K8 relay 11 is connected across the circuit breaker II3-2. Two K8 contacts 12 are respectively connected to both ends of the K8 relay 11. Two normally closed contacts 13 of K4 are connected after the two K8 contacts 12. The K7 relay 14 is connected after the two K8 contacts 12. The two SSR solid-state relays are the SSR3 solid-state relay 16 and the SSR4 solid-state relay 17 respectively. Their input terminals and output terminals are the same as those of the aforementioned SSR1 solid-state relay 6. The input terminals A, D of the SSR3 solid-state relay 16 and the input terminal D of the SSR4 solid-state relay 17 are connected to the upper end of the K7 relay 14. The input terminals A, C of the SSR4 solid-state relay 17 and the input terminal C of the SSR3 solid-state relay 16 are connected to the lower end of the K7 relay 14. The output terminals B of the SSR3 solid-state relay 16 and the SSR4 solid-state relay 17 are both connected to the K1 relay 8.

[0030] In actual use, during normal operation, it is powered by the main power supply circuit. When the main power supply circuit is operating: Circuit breaker I3-1 is closed, K4 relay 4 is energized, normally open contact 5 of K4 is closed, contact 15 of K7 remains closed, SSR1 solid-state relay 6 and SSR2 solid-state relay 7 are energized, K1 relay 8 is energized, T1 isolation transformer 9 is energized, and the current is output to the output control power supply 10. At this time, the states of the components on the standby power supply circuit are as follows: Circuit breaker II3-2 is closed, K8 relay 11 is energized, contact 12 of K8 is closed, normally closed contact 13 of K4 is opened, K7 relay 14 is de-energized, SSR3 solid-state relay 16 and SSR4 solid-state relay 17 are de-energized;

[0031] When a fault occurs in the main power supply circuit, it switches to the standby power supply circuit. At this time, K4 relay 4 on the main circuit is de-energized, normally open contact 5 of K4 is opened, normally closed contact 13 of K4 is closed, K8 relay 11 on the standby power supply circuit continues to be energized, contact 12 of K8 continues to remain closed, K7 relay 14 is energized, contact 15 of K7 is opened, SSR3 solid-state relay 16 and SSR4 solid-state relay 17 are energized, K1 relay 8 is energized, TI isolation transformer 9 is energized, and the current is output to the output control power supply 10.

[0032] During the circuit switching process, to avoid too long switching time of the dual-power switching circuit, SSR solid-state relays are connected in both circuits. Since the SSR solid-state relay is composed of all-solid-state electronic components and has no movable mechanical parts and no mechanical actions during operation, the SSR solid-state relay realizes the switching function of "on" and "off" through the transformation of the circuit working state. The switching process is stable and rapid. When the main power supply 1 is de-energized, SSR1 solid-state relay 6 and SSR2 solid-state relay 7 on the main power supply circuit quickly cut off the main power supply circuit, and SSR3 solid-state relay 16 and SSR4 solid-state relay 17 quickly connect the standby power supply circuit. The switching process between the two does not exceed 0.5 ms, ensuring that the power supply is uninterrupted during the circuit switching process to avoid the power loss of components such as PLC and the main control board due to too long switching time and causing accidents.

[0033] The above are only the embodiments of the present invention. Specific technical solutions and / or common knowledge such as characteristics well known in the art are not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several deformations and improvements can still be made, which should also be regarded as the protection scope of the present invention, and these will not affect the implementation effect of the present invention and the practicability of the patent. The protection scope required by this application should be based on the content of its claims, and the specific implementation manners described in the specification can be used to explain the content of the claims.

Claims

1. A non-disturbance dual power switching circuit for a high-voltage frequency converter, comprising a main power circuit and a backup power circuit, characterized in that: The main power supply circuit includes a main power supply, two SSR solid-state relays, a K4 relay, two K4 normally open contacts, and two K7 contacts. The K4 relay is connected to both ends of the main power supply, the two K4 normally open contacts are connected to both ends of the K4 relay, and the two K7 contacts are connected to the other ends of the two K4 contacts. The two SSR solid-state relays are connected in parallel, the K4 relay is connected to the input ends of the two SSR solid-state relays, and the output ends of the two SSR solid-state relays are connected to the output control power supply; The backup power supply circuit includes a backup power supply, two SSR solid-state relays, a K8 relay, two K8 contacts, a K7 relay, and two K4 normally closed contacts. The K8 relay and the K7 relay are connected in parallel at both ends of the backup power supply, the two K8 contacts are connected at both ends of the K8 relay, and the two K4 normally closed contacts are connected to the other side of the two K8 contacts; the two SSR solid-state relays are connected in parallel, the K7 relay is connected to the input ends of the two SSR solid-state relays, the output ends of the two SSR solid-state relays are connected to the output control power supply, and the backup power supply is taken from the tertiary winding of the phase-shifting transformer of the high-voltage inverter body.

2. The disturbance-free dual power switching circuit for a high-voltage frequency converter according to claim 1, characterized in that: The two ends of the output control power supply are also connected in parallel with a T1 isolation transformer.

3. The non-intrusive dual power switching circuit for a high voltage frequency converter according to claim 2, characterized in that: The two ends of the output control power supply are also connected in parallel with a K1 relay.

4. The non-intrusive dual power switching circuit for a high voltage frequency converter according to claim 3, characterized in that: A circuit breaker is also connected between the main power supply and the K4 relay, and between the backup power supply and the K8 relay.

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