CN1808883A - Excitation circuit of DC chopped-wave voltage-regulating independently excited DC motor - Google Patents

Abstract

The invention relates to a separately excited DC motor excitation circuit with DC chopping and voltage regulation. On the basis of the original three-phase uncontrolled rectifier bridge, it is composed of absorbing capacitors, absorbing resistors, power switches, freewheeling diodes, filter capacitors and filter inductors. The chopper voltage regulator circuit, the absorption capacitor and the absorption resistance are connected in parallel to the output positive and negative poles of the rectifier bridge, the drain of the power switch is connected to the output positive pole of the rectifier bridge, the source is connected to the cathode of the freewheeling diode and one end of the filter inductor The other end of the filter inductor is connected to one end of the filter capacitor, and the other end of the filter capacitor and the anode of the freewheeling diode are connected to the output negative pole of the rectifier bridge. In the present invention, a high-precision adjustable DC voltage is generated at the output end by a chopping voltage regulating circuit, which is used for excitation of the excitation coil, and at the same time, the three-phase input current is a symmetrical high-frequency PWM waveform, which is beneficial to filtering and reduces the level of harmonic current. It has the characteristics of simple structure, fast and reliable response, and strong versatility.

Description

Exciting Circuit of Separately Excited DC Motor with DC Chopper Voltage Regulation

technical field

The present invention relates to a separately excited DC motor excitation circuit with DC chopping and voltage regulation, in particular to a DC excitation circuit suitable for various separately excited DC motor transmissions. The matching matrix rectifier can be used together to meet the needs of higher power DC drives and DC motors. Applications of DC power generation.

Background technique

For a long time, the power supply and excitation power supply of separately excited DC motors generally adopt the silicon controlled rectifier scheme, which causes serious distortion of the grid current waveform, reduces the power factor, and reduces the power utilization rate. Since the thyristor is a half-controlled device, the rectifier can only use the phase control scheme. With the improvement of power switch manufacturing technology, many high-power fully-controlled devices continue to appear, such as IGBT (insulated gate bipolar transistor) and MOSFET (metal oxide semiconductor field-effect transistor), etc., the application range of fully-controlled devices is becoming more and more Wide, there is a tendency to replace semi-controlled devices in many fields. In addition, as the power sector continues to strengthen power environmental protection, it is imperative to eliminate the harmonic current pollution from power electronic converters to the grid. For this reason, the silicon controlled rectifier scheme used before is no longer popular, and new full-control devices are used The controllable rectifier scheme is increasingly favored. Among them, the DC power supply scheme using a high-performance four-quadrant matrix rectifier is more eye-catching (Vladimir Blasko.DC motor matrix converter with field and armature circuits.United States Patent, Patent Number: 6636693B2, Date of Patent: Oct.21, 2003.), using two sets of matrix rectifier systems to supply power and excite separately excited DC motors, not only can realize the rectifier function, but also have regenerative power generation capability, not only can continuously adjust the output DC voltage level and change the output voltage polarity, but also essentially The input current waveform is a sinusoidal waveform, which can eliminate harmonic current pollution to the grid. However, the inevitable result of this configuration is that although the power factor of the power grid is very high, the system structure is complex, the safety commutation strategy and control algorithm are relatively complex, and the cost is relatively high. It does not take into account the very large transmission power of the power supply circuit and the very low power consumption of the excitation circuit. The actual situation, so this scheme needs to be further simplified.

Contents of the invention

The purpose of the present invention is to aim at the deficiencies of the prior art, and to design and provide a separately excited DC motor excitation circuit with DC chopping and voltage regulation, which has the advantages of simple structure, easy control, low cost and high power support.

In order to achieve the above object, the present invention adds a chopper voltage regulation circuit on the basis of the existing three-phase uncontrolled rectifier bridge, the rectifier bridge is composed of six rectifier diodes connected in accordance with the three-phase H-bridge structure, and the chopper voltage regulation circuit consists of absorbing capacitors , Snubber resistor, power switch, freewheeling diode, filter capacitor and filter inductor. In the three-phase uncontrolled rectifier bridge, every two rectifier diodes are connected in series, and their common terminal is connected to a phase input. The cathodes of the three series connected diodes are connected together to form the positive pole, and their anodes are connected together to form the negative pole. In the chopper voltage regulating circuit, one end of the parallel connection of the absorbing capacitor and the absorbing resistor is connected to the output positive pole of the three-phase uncontrolled rectifier bridge, the other end is connected to the output negative pole of the three-phase uncontrolled rectifier bridge, and the drain of the power switch is connected to the rectifier bridge The positive output of the power switch is connected to the cathode of the freewheeling diode and one end of the filter inductor, the other end of the filter inductor is connected to one end of the filter capacitor, the other end of the filter capacitor and the anode of the freewheeling diode are connected to the rectifier bridge The negative pole of the output is connected, and the filter capacitor is connected in parallel with the excitation coil circuit, that is, the excitation coil of the separately excited motor.

When the three-phase AC voltage is applied to the three input terminals of the three-phase uncontrollable rectifier bridge, a six-pulse DC voltage is generated between the positive pole and the negative pole of the output terminal, which is buffered by the absorption capacitor and the absorption resistor and then sent to the power switch for high frequency PWM (Pulse Width Modulation) chopping and voltage regulation, the generated voltage pulse is filtered again by the filter circuit composed of filter inductor and filter capacitor, and then supplies power to the excitation winding. The freewheeling circuit of the filtered inductor current is composed of freewheeling diodes. In this way, the voltage supplied to the excitation winding after filtering is a DC voltage source with very high voltage accuracy, voltage regulation rate, and load regulation rate. At the same time, the three-phase input current presents a high-frequency PWM waveform, which is convenient for filtering by the grid-side input filter.

The present invention adds a chopper voltage regulating circuit in the rear stage of the three-phase uncontrolled rectifier bridge, on the basis of the closed-loop adjustment of the output voltage and the voltage detection after rectification, it can stably and continuously adjust the final output DC voltage level, and at the same time, the three-phase input current is The symmetrical high-frequency PWM waveform is beneficial to the filtering of the input filter and reduces the harmonic current level. It has the characteristics of fast and reliable response, strong versatility, etc., and has the advantages of simple structure, low additional cost, and easy implementation. It is especially suitable for use as an excitation power supply in a separately excited DC motor drive system powered by a matrix rectifier.

Description of drawings

Fig. 1 is the schematic circuit diagram of the present invention.

Fig. 2 is a schematic circuit diagram of an embodiment of the present invention applied to a separately excited DC motor drive system together with a matrix rectifier.

Detailed ways

The technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and embodiments. The following examples are further illustrations of the present invention, but do not constitute a limitation of the present invention.

The separately excited DC motor excitation circuit designed by the present invention is shown in Figure 1. On the basis of the existing three-phase non-controlled rectifier bridge 1, a chopper voltage regulation circuit 2 is added, and the three-phase non-controlled The rectifier bridge 1 is composed of six rectifier diodes D1-D6, and the chopper voltage regulation circuit 2 is composed of absorbing capacitor C1, absorbing resistor R1, power switch S1, freewheeling diode D7, filter capacitor C2 and filter inductance L1. The absorption capacitor C1 is connected to the output of the three-phase uncontrolled rectifier bridge 1, and the filter capacitor C2 is connected to the excitation coil circuit 3, that is, the excitation coil of the separately excited motor.

In the three-phase uncontrolled rectifier bridge 1, the rectifier diode D1 and the rectifier diode D2 are connected in series to form a bridge arm. The rectifier diode D3 is connected in series with the rectifier diode D4 to form a bridge arm. The rectifier diode D5 is connected in series with the rectifier diode D6 to form a bridge arm. The common cathode of D1, D3 and D5 forms the positive output of the rectifier bridge, and the common anode of D2, D4 and D6 forms the negative output of the rectifier bridge. The common point formed by D1 anode and D2 cathode is connected to the input Ua phase voltage, the common point formed by D3 anode and D4 cathode is connected to the input Ub phase voltage, and the common point formed by D5 anode and D6 cathode is connected to the input Uc phase voltage.

In the chopper voltage regulating circuit 2, the absorbing capacitor C1 is connected in parallel with the absorbing resistor R1, and one end of the parallel connection is connected to the output positive pole of the three-phase uncontrolled rectifier bridge 1, and the other end is connected to the output negative pole of the three-phase uncontrolled rectifier bridge 1. The drain of the power switch S1 is connected to the positive output of the rectifier bridge, the source of the power switch S1 is connected to the cathode of the freewheeling diode D7 and one end of the filter inductor L1, and the other end of the filter inductor L1 is connected to one end of the filter capacitor C2. The other end of the capacitor C2 and the anode of the freewheeling diode D7 are both connected to the output cathode of the rectifier bridge.

In the excitation coil circuit 3, the resistor R2 is connected in series with the inductor L2, and then connected in parallel with the filter capacitor C2 in the chopper voltage regulating circuit 2, that is, the other end of R2 is connected to one end of C2, and the other end of L2 is connected to the other end of C2.

Working principle of the present invention is:

(1) In the three-phase uncontrolled rectifier bridge 1, D1-D6 form a natural rectifier, which rectifies the three-phase input AC voltage into a six-pulsating DC voltage, and supplies power to the subsequent stage chopper voltage regulating circuit 2;

(2) In the chopping and voltage regulating circuit 2, C1 and R1 form an absorbing circuit, which can buffer the transient of the input DC voltage and protect S1 and D7 of the subsequent stage. Under the action of the PWM drive signal, S1 performs high-frequency turn-on and turn-off actions. When turned on, the input DC voltage is transmitted to the subsequent stage, and when it is turned off, the transmission of the input DC voltage is prohibited. In this way, a high-frequency PWM voltage is formed at the input end of the low-pass filter circuit formed by the subsequent stage L1 and C2, and a relatively straight DC voltage output is obtained after filtering, which is used for the exciting coil circuit 3 . The role of D7 is to provide a path for the current to flow for L1 to prevent the generation of high-amplitude induced voltages that endanger the safety of the power switch and the insulation of the excitation winding.

(3) The PWM signal generation method of the power switch S1 is: increase the input DC voltage detection and output DC voltage feedback link, so that the generated PWM signal can resist the pulsation of the input DC voltage and the disturbance generated by the excitation coil, and obtain high-performance DC The output voltage. At the same time, a high-frequency PWM current waveform of 120 electrical angles is formed on the three-phase input Ua, Ub and Uc lines, which is very beneficial to the filtering of the input filter.

The chopping and voltage regulating circuit in the present invention is an additional circuit, only needs one absorbing capacitor, one absorbing resistor, one power switch, one freewheeling diode, one filter inductor and two filter capacitors, and can rely on The switching on and off of the power switch S1 chops the rectified voltage of the three-phase uncontrolled rectifier bridge 1 into a PWM voltage, and the average value after filtering by L1 and C2 is the desired output DC voltage, which is used as the power supply voltage of the excitation coil. At the same time, the three-phase input current waveform is a high-frequency PWM current, which is beneficial to input current filtering.

In the present invention, a chopper voltage regulating circuit including a low-pass LC filter circuit is added to the output end of the three-phase uncontrolled rectifier bridge, and the pulse width of the PWM pulse of the power switch is increased to adapt to the fluctuation and excitation of the rectified voltage. When the load changes, a high-precision DC voltage is output. Due to the high-frequency chopping effect, the capacity of the filter inductor and filter capacitor can be small, which reduces the cost.

In a specific embodiment of the present invention, the accuracy of the rectifier diodes D1 - D6 , absorbing capacitor C1 , absorbing resistor R1 , filter inductor L1 and filter capacitor C2 in the above devices is not required. The withstand voltage of D1~D6 is 1200V, and the carrying capacity is calculated according to the actual excitation power. The distributed inductance content of C1 is low, and the capacitance value is 0.1μF～4.7μF. The distributed inductance content of R1 is low, the resistance value is 47kΩ～470kΩ, and the power is 20W. D7 is a reverse fast recovery power diode, the smaller the reverse recovery time, the better, generally less than 40nS. The power switch S1 selects IGBT, the switching frequency is not lower than 60kHz, the withstand voltage is 1200V, and the rated current is calculated according to the actual excitation power. The value of the filter inductance L1 is 1mH to 25mH, and the carrying capacity is calculated according to the actual excitation power. The value of the filter capacitor C1 is 4.7μF-470μF, and the withstand voltage is 1000V.

Fig. 2 is an embodiment of the application of the separately excited DC motor excitation circuit of the present invention to the separately excited DC motor drive system.

As shown in Figure 2, the separately excited DC motor drive system requires DC voltage power supply and DC voltage excitation. The DC voltage source is provided by a matrix rectifier, and the matrix rectifier is powered by a three-phase AC voltage source. The output voltage can be continuously adjusted by using the switching function algorithm or the input current space vector algorithm, and at the same time, it can ensure that the input current is distributed in a sinusoidal waveform.

The excitation circuit of the separately excited DC motor with DC chopper voltage regulation of the present invention can continuously adjust the DC excitation voltage, and at the same time, the input current of the excitation circuit is a high-frequency PWM waveform, and considering that the excitation power is very small, the amplitude of the PWM current is relatively low. In this way, after the matrix rectifier and the input current of the present invention pass through the input LC filter, a current waveform with a very high sine degree is obtained on the grid side, which satisfies the limit standard of the relevant harmonic current. In the separately excited DC motor drive system, the three-phase AC input is Ua, Ub and Uc, and the filtered three-phase AC is Ua', Ub' and Uc'.

Claims (3)

1. A separately excited DC motor excitation circuit for DC chopper voltage regulation, comprising a three-phase uncontrolled rectifier bridge (1) composed of six rectifier diodes (D1-D6) connected in accordance with a three-phase H-bridge structure, characterized in that It also includes a chopping and voltage regulating circuit (2) composed of a snubber capacitor (C1), a snubber resistor (R1), a power switch (S1), a freewheeling diode (D7), a filter capacitor (C2) and a filter inductor (L1) , one end of the parallel connection of the absorption capacitor (C1) and the absorption resistance (R1) is connected to the output positive pole of the three-phase uncontrolled rectifier bridge (1), and the other end is connected to the output negative pole of the three-phase uncontrolled rectifier bridge (1), and the power switch The drain of (S1) is connected to the positive output of the rectifier bridge, the source of the power switch (S1) is connected to the cathode of the freewheeling diode (D7) and one end of the filter inductor (L1), and the other end of the filter inductor (L1) is connected to One end of the filter capacitor (C2) is connected, the other end of the filter capacitor (C2) and the anode of the freewheeling diode (D7) are connected to the output negative pole of the rectifier bridge, and the filter capacitor (C2) is connected to the excitation coil circuit (3) that is separately excited Motor field coils are connected in parallel. 2. The separately excited DC motor excitation circuit according to claim 1, characterized in that the withstand voltage of the rectifier diodes (D1-D6) is 1200V, and the capacitance value of the absorbing capacitor (C1) is 0.1 μF～4.7μF, the resistance value of the absorption resistor (R1) is 47kΩ～470kΩ, the power is 20W, the freewheeling diode (D7) is a reverse fast recovery power diode, the reverse recovery time is less than 40nS, the power The switch (S1) selects IGBT, the switching frequency is not lower than 60kHz, the withstand voltage is 1200V, the value of the filter inductor (L1) is 1mH-25mH, the value of the filter capacitor (C1) is 4.7μF-470μF, and the withstand voltage is 1000V . 3. The separately excited DC motor excitation circuit of claim 1, characterized in that said filter capacitor (C2) and filter inductor (L1) constitute an LC low-pass filter, and the filter capacitor (C2) is an AC capacitor .

Images