CN212751892U

CN212751892U - Dual-power conversion device

Info

Publication number: CN212751892U
Application number: CN202021916416.5U
Authority: CN
Inventors: 章宽; 陈利东; 李福�
Original assignee: Changshu Switchgear Manufacturing Co Ltd
Current assignee: Changshu Switchgear Manufacturing Co Ltd
Priority date: 2020-09-04
Filing date: 2020-09-04
Publication date: 2021-03-19
Anticipated expiration: 2030-09-04

Abstract

The utility model discloses a dual power supply conversion device, including common power input end, stand-by power input end, mechanical type dual power supply change-over switch to and be used for getting energy and supplying energy for the load short-time in the power conversion process for the short-time energy supply unit from common power and/or stand-by power, the short-time energy supply unit includes inverter circuit and output filter circuit, output filter circuit includes the three groups of filter capacitors that concatenate respectively between N looks and A, B, C looks; the short-time energy supply unit further comprises at least one nonpolar capacitor, the three groups of filter capacitors are connected with the N to form a common connection point Nc, and the midpoint of the direct current side of the inverter circuit is connected with the common connection point Nc through the nonpolar capacitor or the midpoint of a direct current bus constructed by the nonpolar capacitor connected between the positive direct current bus and the negative direct current bus in series is connected with the common connection point Nc. Compared with the prior art, the utility model discloses can alleviate or eliminate generating line electrolytic capacitor's midpoint voltage skew problem to can play better supplementary arc extinguishing effect.

Description

Dual-power conversion device

Technical Field

The utility model relates to a dual power supply conversion equipment.

Background

In the fields of modern industry, medical treatment, business, daily life and the like, some electric equipment needing continuous power supply exists, and in order to meet the continuous power supply requirements of the electric equipment, a double-path power supply scheme is usually adopted, namely, a double-power automatic conversion device is utilized to realize the automatic switching of a main power supply and a standby power supply. The dual-power automatic switching device generally comprises a detection unit, a control unit and a dual-power change-over switch, wherein the detection unit is used for detecting the input voltage of a main power supply and an emergency power supply in real time, and the control unit controls the dual-power change-over switch according to the detection result of the detection unit so as to realize the automatic switching of the main power supply and the emergency power supply. In the process of power supply conversion of the conventional dual-power automatic conversion device, the execution logic of the dual-power change-over switch is firstly disconnected and then switched on, namely, a main power supply is firstly disconnected and then a standby power supply is connected, so that short power failure occurs, and the short power failure is unacceptable for some application occasions. In order to solve the problem, a chinese invention patent (publication No. CN105024450A, published as 2015/11/4) discloses a dual power supply automatic switching device with high reliability, which can meet the power supply requirement of a highly sensitive load, and its basic structure is shown in fig. 1, the device uses a mechanical dual power supply switch to switch the main power supply and the standby power supply, and uses an auxiliary power supply unit (hereinafter referred to as a short-time power supply unit) including an inverter unit to supply power to the load in a short time during the switching process of the mechanical dual power supply switch.

The short-time function loop in the double-power-supply conversion device has the main functions of assisting the mechanical switch to quickly extinguish arc in the conversion process of the mechanical switch and supplying energy to a load in a short time.

As shown in fig. 2, the standby power supply of the conventional power supply rectifies an ac voltage into a dc voltage through rectifier bridges, the dc voltages output by two rectifying circuits are connected in parallel, and are converted into a stable dc voltage after passing through a charging buffer circuit and a dc filter circuit, and then the dc voltage is inverted into a controllable pulse voltage through an inverter circuit, and the controllable pulse voltage forms a controllable ac voltage after passing through an output filter circuit and is injected into a load. Controllable alternating voltage is artificially injected into the load side, the current is forced to quickly pass zero to play a role in assisting arc extinction, the controllable alternating voltage is continuously applied to the load side after the arc extinction to play a role in supplying energy for a short time until the conversion of the mechanical switch is completed, the power grid supplies power to the load, the applied controllable alternating voltage is cancelled at the moment, and the function of quick conversion is completed.

In the auxiliary arc extinguishing process, after any phase of L1, L2, L3, N is extinguished successfully, the controllable alternating current voltage is stopped being continuously applied to the current phase until all phases of L1, L2, L3, N are extinguished successfully, and then the short-time functional mode is entered, so that the arc extinguishing sequence is inevitably generated in the working process, and finally the situation that one phase is not extinguished occurs, at this time, in a non-isolated system, N phases of a common power supply and a standby power supply are mutually connected, so that a path on the circuit is formed, and an equivalent circuit of the path is shown in fig. 3.

In the figure, C1 and C2 are filter capacitors in the dc filter circuit in fig. 2, Q1 and Q2 are a group of IGBT modules in the inverter circuit in fig. 2, Lg is a filter inductor connected to outputs of Q1 and Q2, Cf is a filter capacitor connected to Lg, K1 is a contact of a mechanical dual power transfer switch, and D is a rectifier diode in a rectifier bridge. Nm and Ns are N lines of a common power supply and a standby power supply respectively, and in a non-isolated system, the N lines of the two power supplies are connected together. The conventional filter circuit has filter capacitances only between L1, L2, L3, N, and when only 1 phase remains without extinguishing an arc, the Nc point becomes an isolated floating point. As shown in fig. 3. At this time, the high-frequency pulsating voltage output by the Q1 and the Q2 passes through the inductor Lg and is directly applied to the contact of the K1, and the filter capacitor Cf is ineffective due to one end floating, so that the high-frequency pulse voltage directly exists on the K1, even if the arc current on the contact of the mechanical switch is subjected to zero-crossing arc extinction, the high-frequency pulse voltage existing on the contact of the switch is far larger than the medium recovery voltage intensity, according to the arc gap medium intensity recovery theory proposed by Stabin, the arc can be re-ignited, and the phenomenon that the high-frequency current is subjected to zero-crossing but effective arc extinction is always caused can occur. Since the dielectric recovery strength is related to the opening distance of the switch, the phenomenon continues until the high-frequency ripple voltage is less than the dielectric recovery voltage after the contact opening distance of the mechanical switch reaches a certain value. The arc extinguishing time can be obviously prolonged, so that the function of quick switching cannot be effectively realized.

The following improvements are made in the prior art: nc is directly connected with the midpoint of the preceding-stage bus capacitor, and the potential of the Nc point is fixed, so that the problems can be effectively solved, but a loop has large ripple current, the large ripple current can cause the midpoint voltage of the electrolytic capacitor of the direct-current bus to deviate in a short time, and if the bus voltage is higher at the moment, the overvoltage of one electrolytic capacitor can occur.

SUMMERY OF THE UTILITY MODEL

The utility model aims to solve the technical problem that it is not enough to overcome prior art, provide a dual power conversion equipment, improve the circuit topology of energy supply unit wherein for a short time to can alleviate or eliminate generating line electrolytic capacitor's midpoint voltage skew problem, and can play better supplementary arc extinguishing effect.

The utility model discloses specifically adopt following technical scheme to solve above-mentioned technical problem:

a dual-power conversion device comprises a common power input end, a standby power input end, a mechanical dual-power conversion switch and a short-time energy supply unit, wherein the short-time energy supply unit is used for acquiring energy from a common power and/or a standby power and supplying energy to a load in a short-time manner in the power conversion process, the short-time energy supply unit comprises an inverter circuit and an output filter circuit, and the output filter circuit comprises three groups of filter capacitors which are respectively connected between an N phase and an A, B, C phase in series; the three groups of filter capacitors are connected with N to form a common connection point Nc, and the DC side midpoint of the inverter circuit is connected with the common connection point Nc through a nonpolar capacitor or the DC bus midpoint constructed by the nonpolar capacitors connected in series between the positive and negative DC buses is connected with the common connection point Nc.

Preferably, two sets of capacitors C1 with the same capacitance value and polarity are connected in series between the dc positive bus and the dc negative bus, two sets of capacitors C1 are each connected in parallel to one set of resistors R, the resistances of the two sets of resistors R are the same, the connection point of the two sets of capacitors C1 is the dc side midpoint of the inverter circuit, and the non-polar capacitor is connected in series between the connection point of the two sets of capacitors C1 and the dc side midpoint of the inverter circuit and the common connection point Nc.

Preferably, the non-polar capacitors include two same sets of capacitors, the two sets of non-polar capacitors are connected in series between the positive and negative buses on the dc side of the inverter circuit, and the connection midpoints of the two sets of non-polar capacitors are directly connected to the common connection point Nc.

Preferably, the voltage withstanding value of the non-polar capacitor is at least twice as large as that of the filter capacitor.

Preferably, the filter capacitor is an electrolytic capacitor, and the non-polar capacitor is a thin film capacitor.

Compared with the prior art, the utility model discloses technical scheme has following beneficial effect:

the utility model provides a circuit topology can solve among the prior art the electric capacity damage problem that the electrolytic capacitor mid point unbalance of direct current filter circuit arouses. The electrolytic capacitor mid point unbalance can appear when two power conversion device take great single-phase load in conventional circuit topology, needs to use the electrolytic capacitor of large capacity to solve this problem, and the utility model discloses a circuit topology only needs less generating line electrolytic capacitor just can satisfy mid point balance, can effectively reduce volume and reduce cost.

The utility model discloses can effectively improve the supplementary arc extinguishing effect of short-term energy supply unit in the conversion process.

Drawings

Fig. 1 is a schematic diagram of a basic principle of a conventional dual power automatic switching device;

FIG. 2 is a schematic circuit diagram of a conventional dual power automatic transfer device;

FIG. 3 is a schematic diagram of an equivalent circuit of a conventional short-time energy supply unit assisting arc extinguishing process of a mechanical switch;

fig. 4 is an equivalent circuit schematic diagram of the short-time energy supply unit assisting the arc extinguishing process of the mechanical switch in the technical scheme of the invention;

fig. 5 is a schematic circuit diagram of an embodiment of the present invention;

FIG. 6 is a schematic diagram of the circuit connections between the output filter circuit and the DC filter circuit in an embodiment;

FIG. 7 is another circuit connection between the output filter circuit and the DC filter circuit.

Detailed Description

Not enough to prior art exists, the utility model discloses a solution thinking is to improve filter circuit's topological structure in the energy supply unit for a short time to need to use large capacity electric capacity to prevent the electric capacity damage problem that the unbalanced neutral point potential brought among the direct current filter circuit of overcoming the contravariant unit front end, and improve the supplementary arc extinguishing function of energy supply unit for a short time.

Particularly, the utility model discloses a dual power supply conversion equipment, including common power input end, stand-by power input end, mechanical type dual power change-over switch to and be used for getting energy and supplying energy for the load short-time in the power conversion process for power supply unit from common power and/or stand-by power, short-time energy supply unit includes inverter circuit and output filter circuit, output filter circuit includes the three group's filter capacitance who concatenates respectively between N looks and A, B, C looks; the three groups of filter capacitors are connected with N to form a common connection point Nc, and the DC side midpoint of the inverter circuit is connected with the common connection point Nc through a nonpolar capacitor or the DC bus midpoint constructed by the nonpolar capacitors connected in series between the positive and negative DC buses is connected with the common connection point Nc.

As shown in FIG. 4, the present invention provides a set of non-polar capacitors C in the existing short-time power supply unit_fN' connected to a dc side midpoint O of the inverter circuit and a common connection point Nc of the three sets of filter capacitors and the N-phase. When Nc point passes through the capacitor C_fNAfter the high-frequency pulsating voltage output by the Q1 and the Q2 is connected with the midpoint O of the capacitors C1 and C2, the high-frequency pulsating voltage is filtered by an LC filter circuit formed by Lg and Cf to form controllable alternating current voltage, and the controllable alternating current voltage is not the high-frequency pulsating voltage at the contact end of the mechanical switch K1, so that the effects of quickly extinguishing the arc and not re-igniting can be achieved.

Preferably, the non-polar capacitors include two same sets of capacitors, the two sets of non-polar capacitors are connected in series between the positive and negative buses on the dc side of the inverter circuit, and the connection midpoint (i.e., the dc bus midpoint) of the two sets of non-polar capacitors is directly connected to the common connection point Nc.

For the public understanding, the technical solution of the present invention is further explained in detail by a specific embodiment as follows:

as shown in fig. 5, the dual power supply switching device of the present embodiment includes a common power supply input terminal, a standby power supply input terminal, a mechanical dual power supply switch, and a short-time power supply unit for obtaining power from the common power supply and/or the standby power supply and supplying power to a load in a short time during the power supply switching process. When the short-time energy supply unit detects that the power supply is frequently used and falls, and if stand-by power supply is normal this moment, then drive mechanical type dual power transfer switch and change, in the dual power transfer switch conversion process, the short-time energy supply unit is through the controllable voltage of grid-connected control circuit's output assistance mechanical switch quick arc extinguishing, and at the in-process of mechanical type dual power transfer switch conversion, the short-time energy supply unit provides the energy for the load, avoids load power supply interruption time overlength.

As shown in fig. 5, the short-time power supply unit in the present embodiment includes: the charging circuit comprises two rectifier bridges, a charging buffer circuit, a direct current filter circuit, an inverter circuit, an output filter circuit, a grid-connected control circuit, an output current sampling circuit, a load current sampling circuit and a control circuit. The two rectifier bridges respectively take electricity from a common power supply and a standby power supply, rectify an alternating current power supply and then output the rectified alternating current power supply in parallel to a direct current filter circuit; a charging buffer circuit is arranged between the output positive end of the rectifier bridge and the positive end of the direct current filter circuit, the charging buffer circuit comprises a charging resistor and a bypass switch, the bypass switch can be a contactor, a relay, a thyristor and the like, and the main function of the charging buffer circuit is to prevent pulsating direct current output by the rectifier bridge from being directly supplied to the direct current filter circuit to form large impact which can possibly cause the damage of the rectifier bridge, so that the current-limiting charging is carried out on a capacitor in the direct current filter circuit through the resistor of the charging buffer circuit, and after the charging is finished, the bypass switch is closed to bypass the charging resistor; the direct current filter circuit filters the pulsating direct current output by the rectifier bridge into a smooth direct current power supply which is provided for the inverter circuit; the inverter circuit inverts the direct-current power supply into a controllable alternating-current power supply and sends the controllable alternating-current power supply to the load end of the mechanical dual-power transfer switch to assist the dual-power transfer switch to rapidly extinguish arcs in the transfer process, and provides the alternating-current power supply for the load, so that the power supply interruption time of the load is shortened.

The main functions of the control circuit are: the control circuit sends out a driving signal to drive the mechanical dual-power transfer switch to convert, and simultaneously, the control circuit samples load voltage, load current and inverter circuit output current, and combines the collected signals with the common power voltage signal and the standby power voltage signal to carry out operation processing, and then outputs a controllable driving signal to drive the inverter circuit to work, the inverter circuit is connected with an output filter circuit, the output filter circuit filters pulse voltage of the inverter circuit into continuous alternating voltage, and then the continuous alternating voltage is output to the load and the mechanical dual-power transfer switch through a grid-connected control circuit. The alternating current power supply with controllable output of the short-time energy supply unit assists the double-power-supply change-over switch to rapidly extinguish arc in the change-over process, and the purpose of providing the alternating current power supply for the load is achieved.

In this embodiment, the circuit connection between the output filter circuit and the dc filter circuit is as shown in fig. 6, the dc filter circuit includes two sets of capacitors C1 with the same capacitance value and polarity connected in series between the dc positive and negative buses, each of the two sets of capacitors C1 is connected in parallel to a set of resistors R, the resistances of the two sets of resistors R are the same, and the connection point of the two sets of capacitors C1 is the dc side midpoint O of the inverter circuit; the output filter circuit comprises three groups of filter capacitors C2 which are respectively connected between A, B, C phase and N phase in series; a group of non-polar capacitors C3, which may be one capacitor or a plurality of capacitors connected in series, are connected in series between the common connection point Nc of the three groups of filter capacitors and the N phase and the dc side midpoint O. The circuit topology can limit ripple current and relieve the condition of point voltage deviation of the direct current bus capacitor. But in some extreme cases, the protection of the midpoint voltage deviation of the bus can still be triggered.

Fig. 7 shows another circuit connection structure between the output filter circuit and the dc filter circuit, in which two sets of the same non-polar capacitors C3 are connected in series between the positive and negative bus bars, and the connection midpoint of the two sets of capacitors C3 (i.e., the dc bus bar midpoint) is connected to Nc. The Nc point is connected with the connection midpoint of a non-polar capacitor on the direct current bus, after the two ends of the capacitor are connected with the circuit, the self characteristic of the capacitor is the jump of the suppression voltage, and if only one end of the capacitor is connected with the circuit and one end of the capacitor is floated, the capacitor is invalid and cannot suppress the jump of the voltage, when the potential of the Nc point does not jump any more, the voltage of the output end of the Lg is the controlled alternating voltage, and the voltage is controlled to force the current in the K1 to pass through zero rapidly, so that the auxiliary arc extinguishing function is realized. Meanwhile, the circuit can enable high-frequency components in the output current of the power module to flow through the corresponding filter capacitor C and the N bridge filter capacitor C (N) and then flow back to the bus capacitor, so that the injection of ripple current of an arc port is reduced, the influence of the ripple current on arc extinction is reduced, and the auxiliary arc extinction function of the short-time functional loop is more stable.

Among them, the polar capacitors C1 and C2 are preferably electrolytic capacitors, and the nonpolar capacitor C3 is preferably a high-withstand-voltage thin-film capacitor, and the withstand voltage thereof is preferably more than twice as high as that of the capacitors C1 and C2.

Claims

1. A dual-power conversion device comprises a common power input end, a standby power input end, a mechanical dual-power conversion switch and a short-time energy supply unit, wherein the short-time energy supply unit is used for acquiring energy from a common power and/or a standby power and supplying energy to a load in a short-time manner in the power conversion process, the short-time energy supply unit comprises an inverter circuit and an output filter circuit, and the output filter circuit comprises three groups of filter capacitors which are respectively connected between an N phase and an A, B, C phase in series; the three groups of filter capacitors are connected with N to form a common connection point Nc, and the DC side midpoint of the inverter circuit is connected with the common connection point Nc through a nonpolar capacitor or the DC bus midpoint constructed by the nonpolar capacitor connected in series between the positive and negative DC buses is connected with the common connection point Nc.

2. The dual-power conversion device as claimed in claim 1, wherein two sets of capacitors C1 with the same capacitance value and polarity are connected in series between the dc positive bus and the dc negative bus, two sets of capacitors C1 are each connected in parallel with a set of resistors R, the two sets of resistors R have the same resistance value, the connection point of the two sets of capacitors C1 is the dc-side midpoint of the inverter circuit, and the non-polarity capacitor is connected in series between the connection point of the two sets of capacitors C1 and the dc-side midpoint of the inverter circuit and the common connection point Nc.

3. The dual power supply switching device according to claim 1, wherein the non-polar capacitors include two same sets of capacitors connected in series between the positive and negative busbars on the dc side of the inverter circuit, and the connecting midpoints of the two sets of non-polar capacitors are directly connected to the common connection point Nc.

4. The dual power supply switching device of claim 1, wherein the non-polar capacitor has a withstand voltage value at least twice that of the filter capacitor.

5. The dual power transfer device of claim 1, wherein the filter capacitor is an electrolytic capacitor and the non-polar capacitor is a thin film capacitor.