CN210745029U - A single-resistor soft power-on circuit in a three-phase rectifier bridge - Google Patents

Abstract

The utility model discloses a soft last electric circuit of well single resistance in three-phase rectifier bridge, include: the air circuit breaker comprises first to third thyristors, first to third diodes, an electrolytic capacitor, an upper electric resistor, first and second air circuit breakers; cathodes of the first to third thyristors are connected; anodes of the first to third diodes are connected; the anode of the first thyristor is connected with the cathode of the first diode; the anode of the second thyristor is connected with the cathode of the second diode; the anode of the third thyristor is connected with the cathode of the third diode; the gate electrodes of the first to third thyristors are respectively connected with the controller by signals; the anode of the electrolytic capacitor is connected with the anode of the output direct current, and the cathode of the electrolytic capacitor is connected with the cathode of the output direct current; the upper resistor is connected between the anode and the cathode of the first thyristor in parallel; the input ends of the first air circuit breaker and the second air circuit breaker are connected with a three-phase power supply, and the output ends of the first air circuit breaker and the second air circuit breaker are respectively connected with the input ends of the a phase, the b phase and the c phase. Through the utility model discloses, simple structure, control are easy, go up the electric resistance loss little.

Description

A single-resistor soft power-on circuit in a three-phase rectifier bridge

technical field

The utility model relates to the technical field of power electronic conversion, in particular to a single-resistor soft power-on circuit in a three-phase rectifier bridge.

Background technique

Three-phase diode rectifier circuits or power electronic conversion circuits containing three-phase diode rectifier circuits are widely used in industrial frequency converters, active power filters, controllable rectifiers and other application fields, and become necessary circuits. The structure of the three-phase diode rectifier circuit adopts electrolytic capacitors, and after filtering, the DC voltage is obtained to provide the DC power supply for the subsequent power electronic inverter.

The three-phase diode rectifier circuit needs to adopt soft power-on (pre-charge) measures to form an RC charging circuit, so that the power-on process is slow, the electrolytic capacitor voltage is controllable, and the grid-side inrush current amplitude meets safety standards, otherwise the electrolytic capacitor voltage will rise rapidly. It is enough to break down the power switch contained in the circuit, and the rapid sudden change of the inrush current will burn the power switch and fuse, and cause the malfunction of the circuit circuit and serious EMI interference.

Common power-on and current-limiting measures for three-phase diode rectifier circuits: (1) DC positive current-limiting power resistors or PTC thermistors in series; (2) three-phase AC line three-phase current-limiting power resistors in series; (3) In the three-phase AC line, two of the two phases are connected in series with a current-limiting power resistor. Among them, the third measure is a common measure. The current-limiting power resistor plays a current limiting role during power-on. After the power-on is completed, the current-limiting power resistor is cut off by a relay, and the rectifier circuit enters the normal working state.

The soft power-on problem of single-phase or three-phase diode rectifier circuits or power electronic conversion circuits containing diode rectifier circuits has attracted extensive attention. Slow voltage rise and grid-side current peaks are suppressed.

After searching the prior art, it was found that Zhang Xiangjun et al., in their June 2011 "Journal of Electrical Machinery and Control" article, after summarizing two traditional soft-start circuits, proposed "a start-up inrush current suppression circuit". That is, the three-stage rush current suppression circuit, which can effectively suppress the primary rush current and the secondary rush current during startup. The utility model patent "Power Conversion Device" (P2001-238459A) discloses a rectifier bridge that changes a simple diode rectifier bridge to a high-end, low-end or full bridge thyristor, and makes the thyristor parallel with appropriate resistors and diode branches. It can realize the function of soft power-on. After power-on, the thyristor is turned on, and the trigger angle is zero, which acts as a diode.

There is a problem in the existing soft power-on schemes, especially for the three-phase diode rectifier circuit, the total loss of all power-on resistors during the power-on process is not considered, so no corresponding power-on circuit and power-on scheme are formulated. Due to the serious nonlinear problem of the circuit, it is very difficult to calculate the total loss of the power-on resistor during the power-on process, so there is no soft power-on solution that minimizes the total loss of the power-on resistor during the power-on process.

After careful and repeated computer-aided analysis, it is found that in the process of filtering or charging the energy storage electrolytic capacitor, the total loss of the power-on resistor is different in different technical solutions. Therefore, we can make full use of this finding and involve a reasonable power-on scheme in order to reduce Power-on loss, to achieve the purpose of energy saving and emission reduction.

Specifically, (1) when the DC power supply is powered, the ratio of the total loss of the power-on resistor to the energy storage of the electrolytic capacitor is the highest, which is 100%; (2) in the three-phase AC diode rectifier circuit, the power-on resistor is placed on the positive electrode of the DC, and the power is turned on. The ratio of the total loss of the resistance to the energy storage of the electrolytic capacitor is very high, about 92.6%; (3) In the three-phase AC diode rectifier circuit, the three power-on resistors are respectively placed on the three-phase AC line, and the total loss of the power-on resistor is relatively high compared to the electrolytic capacitor. The proportion of energy storage is relatively high, about 89.3%; (4) In the three-phase AC diode rectifier circuit, two power-on resistors are placed on any two-phase AC line, and the ratio of the total loss of the power-on resistor to the energy storage of the electrolytic capacitor is relatively high. (5) In the single-phase AC diode rectifier circuit, regardless of whether the power-on resistor is on the AC side or the DC side, the ratio of the total loss of the power-on resistor to the energy storage of the electrolytic capacitor is the lowest, about 78.7%. The above ratios are all started when the grid voltage crosses zero or the phase voltage ua crosses zero, and the result has nothing to do with the resistance value.

The above ratios are all started when the grid voltage crosses zero or the phase voltage ua crosses zero, and the result has nothing to do with the resistance value.

Therefore, the single-phase diode rectifier circuit can be selected to perform soft power-on for the three-phase diode rectifier circuit to achieve energy saving and consumption reduction.

Based on the above, the retrieval of the existing circuit structure of the rectifier circuit for soft power-on shows that there is still no application example of using a single-phase diode rectifier circuit for a three-phase diode rectifier circuit for soft power-on, and there is also a lack of related scientific papers.

Utility model content

Aiming at the above problems in the prior art, the utility model proposes a single-resistor soft power-on circuit in a three-phase rectifier bridge, which only needs to use a single power-on resistor on the AC line, and has the advantages of simple circuit structure and easy control. , and minimizes power-on resistive losses.

In order to solve the above-mentioned technical problems, the utility model is realized through the following technical solutions:

The utility model provides a single-resistor soft power-on circuit in a three-phase rectifier bridge, which comprises: a three-phase rectifier bridge, an electrolytic capacitor, a power-on resistor, a first air circuit breaker and a second air circuit breaker; wherein,

The three-phase rectifier bridge includes: a first thyristor, a second thyristor, a third thyristor, a first diode, a second diode and a third diode; wherein,

The cathode of the first thyristor, the cathode of the second thyristor and the cathode of the third thyristor are connected to form the output DC positive pole of the three-phase rectifier bridge;

The anode of the first diode, the anode of the second diode and the anode of the third diode are connected to form the output DC negative electrode of the three-phase rectifier bridge;

The anode of the first thyristor is connected to the cathode of the first diode to form a phase input; the anode of the second thyristor is connected to the cathode of the second diode to form a phase b input; the The anode of the third thyristor is connected to the cathode of the third diode to form a c-phase input;

The gate electrode of the first thyristor, the gate electrode of the second thyristor and the gate electrode of the third thyristor are respectively connected with the controller signal;

The positive pole of the electrolytic capacitor is connected to the output DC positive pole of the three-phase rectifier bridge, and the negative pole of the electrolytic capacitor is connected to the output DC negative pole of the three-phase rectifier bridge;

One end of the power-on resistor is connected to the anode of the first thyristor, and the other end is connected to the cathode of the first thyristor;

The input end of the first air circuit breaker is connected to the a and b-phase power sources, and the a and b-phase output ends of the first air circuit breaker are respectively connected to the a-phase input and the b-phase input;

The input end of the second air circuit breaker is connected to the c-phase power supply, and the c-phase output end of the second air circuit breaker is connected to the c-phase input.

Preferably, the gate electrode of the first thyristor, the gate electrode of the second thyristor and the gate electrode of the third thyristor are respectively connected to the controller signal through a current mode driver. The controller signal is at a high level after power-on, and is at a low level before power-on and in standby.

Compared with the prior art, the utility model has the following advantages:

(1) The single-resistor soft power-on circuit in the three-phase rectifier bridge provided by the utility model, the power-on process of the three-phase diode rectifier bridge is actually the power-on process of the single-phase diode rectifier bridge, and the power-on resistance total loss in the power-on process Minimum, and has nothing to do with the resistance value;

(2) The single-resistor soft power-on circuit in the three-phase rectifier bridge provided by the utility model only needs one power-on resistor and two power-on air circuit breakers, the circuit structure is simple, and the control is convenient.

Of course, any product implementing the present invention does not necessarily need to simultaneously achieve all of the above-mentioned advantages.

Description of drawings

Embodiments of the present utility model are further described below in conjunction with the accompanying drawings:

FIG. 1 is a schematic diagram of a single-resistor soft power-on circuit in a three-phase rectifier bridge according to an embodiment of the present invention.

Detailed ways

The embodiments of the present utility model are described in detail below. The present embodiment is implemented on the premise of the technical solution of the present utility model, and provides detailed implementation methods and specific operation processes, but the protection scope of the present utility model is not limited to the following described embodiment.

As shown in FIG. 1 , it is a schematic diagram of a single-resistor soft power-on circuit in a three-phase rectifier bridge according to an embodiment of the present invention.

Please refer to FIG. 1, the circuit includes: a three-phase rectifier bridge, an electrolytic capacitor C1, a power-on resistor R1, a first air circuit breaker SW1 and a second air circuit breaker SW2; wherein,

The three-phase rectifier bridge includes: a first thyristor T1, a second thyristor T2, a third thyristor T3, a first diode D1, a second diode D2 and a third diode D3; wherein,

The cathode of the first thyristor T1, the cathode of the second thyristor T2 and the cathode of the third thyristor T3 are connected to form the output DC positive pole of the three-phase rectifier bridge;

The anode of the first diode D1, the anode of the second diode D2 and the anode of the third diode D3 are connected to form the output DC cathode of the three-phase rectifier bridge;

The anode of the first thyristor T1 is connected to the cathode of the first diode D1 to form a phase a input; the anode of the second thyristor T2 is connected to the cathode of the second diode D2 to form a phase b input; the anode of the third thyristor T3 Connected to the cathode of the third diode D3 to form a c-phase input;

The gate electrode of the first thyristor T1, the gate electrode of the second thyristor T2 and the gate electrode of the third thyristor T3 are respectively connected with the controller signal Dr through the current mode driver;

The positive pole of the electrolytic capacitor C1 is connected to the output DC positive pole of the three-phase rectifier bridge, and the negative pole of the electrolytic capacitor C1 is connected to the output DC negative pole of the three-phase rectifier bridge;

One end of the power-on resistor R1 is connected to the anode of the first thyristor T1, and the other end is connected to the cathode of the first thyristor T1;

The input end of the first air circuit breaker SW1 is connected to the a and _b -phase power supplies ua and ub, and the _a and b-phase output ends of the first air circuit breaker SW1 are respectively connected to the a-phase input and the b-phase input;

The input end of the second air circuit breaker SW2 is connected to the _c -phase power supply uc, and the c-phase output end of the second air circuit breaker SW2 is connected to the c-phase input.

In this embodiment, the controller signal is at a high level after power-on, and is at a low level before power-on and in standby.

In one embodiment, the selection of the above-mentioned components is:

Three-phase power supply: three-phase AC power supply 380V±15%;

Three-phase rectifier bridge transmission power: according to needs, several kW to several hundred kW;

The first diode - the third diode (D1-D3): 1200V, the current level is based on the transmitted power, which constitutes a three-phase diode rectifier circuit;

The first thyristor - the third thyristor (T1-T3): 1200V, the current level is based on the size of the transmitted power, forming a three-phase diode rectifier circuit;

Electrolytic capacitor (C1): 450V withstand voltage, adopt the structure of parallel first and then series, the capacitance value is based on the size of the transmitted power;

Power-on resistance (R1): 49Ω～100Ω, the power level is more than tens of watts, according to the size of the transmitted power, it is used to limit the current during the power-on process;

Controller signal (Dr): high level after power-on, low level before power-on and standby;

The working principle of the single-resistor soft power-on circuit in the above-mentioned three-phase rectifier bridge is as follows: when the first air circuit breaker SW1 is closed, the electrolytic capacitor C1 starts to charge, and only the line voltage uab formed by the a-phase and the b-phase (ie the phase voltage) Charge the electrolytic capacitor C1. After a period of time, the electrolytic capacitor C1 rises to the amplitude of the single-phase voltage uab, that is, the grid line voltage amplitude, and then closes the second air circuit breaker SW2, turns on the power supply phase c, and then the controller Send a high-level signal Dr, and start the post-stage load of the rectifier circuit, forcing the three thyristors at the high end of the rectifier bridge to be in a conducting state with zero control angle, forming a true three-phase rectifier bridge (D1~D3, T1~T3 ) to complete the power-on process.

The single-resistor soft power-on circuit in the three-phase rectifier bridge provided by the above embodiment can be applied to the application field where the three-phase AC-DC converter is used as the front-stage circuit, can realize automatic soft power-on and energy-saving power-on at the same time, and has a circuit structure The advantages of simplicity, low device count and cost reduction.

What is disclosed here is only the preferred embodiments of the present invention, and the present specification selects and specifically describes these embodiments to better explain the principles and practical applications of the present invention, rather than limiting the present invention. Any modifications and changes made by those skilled in the art within the scope of the description should fall within the scope of protection of the present invention.

Claims (3)

1. A single-resistor soft power-on circuit in a three-phase rectifier bridge is characterized by comprising: the three-phase rectifier bridge, the electrolytic capacitor, the upper resistor, the first air circuit breaker and the second air circuit breaker; wherein,

the three-phase rectifier bridge includes: the thyristor comprises a first thyristor, a second thyristor, a third thyristor, a first diode, a second diode and a third diode; wherein,

the cathode of the first thyristor, the cathode of the second thyristor and the cathode of the third thyristor are connected to form an output direct-current positive electrode of the three-phase rectifier bridge;

the anode of the first diode, the anode of the second diode and the anode of the third diode are connected to form an output direct current cathode of the three-phase rectifier bridge;

the anode of the first thyristor is connected with the cathode of the first diode to form a-phase input; the anode of the second thyristor is connected with the cathode of the second diode to form a phase b input; the anode of the third thyristor is connected with the cathode of the third diode to form a c-phase input;

the gate electrode of the first thyristor, the gate electrode of the second thyristor and the gate electrode of the third thyristor are respectively connected with the controller by signals;

the anode of the electrolytic capacitor is connected with the output direct current anode of the three-phase rectifier bridge, and the cathode of the electrolytic capacitor is connected with the output direct current cathode of the three-phase rectifier bridge;

one end of the upper resistor is connected with the anode of the first thyristor, and the other end of the upper resistor is connected with the cathode of the first thyristor;

the input end of the first air circuit breaker is connected with a phase a and a phase b power supply, and the phase a and the phase b output ends of the first air circuit breaker are respectively connected with the phase a input and the phase b input;

the input end of the second air circuit breaker is connected with a c-phase power supply, and the c-phase output end of the second air circuit breaker is connected with the c-phase input.

2. The single-resistor soft power-on circuit in a three-phase rectifier bridge as claimed in claim 1, wherein the gate of the first thyristor, the gate of the second thyristor and the gate of the third thyristor are respectively connected to the controller signal through current-mode drivers.

3. The single-resistor soft power-on circuit in a three-phase rectifier bridge according to claim 1 or 2, wherein the controller signal is at a high level after the power-on is finished, and at a low level before the power-on is finished and during standby.

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