RU2542749C2 - Corrector of power ratio - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: suggested device is related to power conversion equipment; it provides energetic pulsed control method for power transmitted to load. Technical result is attained due to introduction of the first and second capacitors of input filter, the second controlled key element, the second valve element, the second capacitor of output filter, addition of the second winding of magnetic energy storage. The circuit consisting of in-series first and second capacitors of input filter is coupled between outputs of the output circuit of alternating line voltage rectifier. One output in the second winding of magnetic energy storage is coupled to the second output in output circuit of alternating line voltage rectifier while the second output in the second winding of magnetic energy storage is coupled to the device output bus through output circuit of the second controlled power key, besides this output is coupled to output bus of the device through the circuit, which contains the second valve element and in-series second capacitor of output filter.

EFFECT: improved operational reliability of the device as well as reliability of pulse converters connected to output of the corrector of power factor and acting as the second power conversion stage thus ensuring galvanic isolation of the energy source and load.

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Description

The invention relates to power converting equipment and implements an energy-efficient pulsed method of regulating the power transmitted to the load.

Most industrial consumers of electric energy receive it from a three-phase AC network. In relation to the consumer, the energy source is presented in the form of three tires, which are usually denoted by the symbols "A", "B", "C". The voltages between these tires are sinusoidal with an amplitude value of 540 V (effective value of 380 V), and the sinusoidal functions are shifted to each other by an angle of 120 degrees.

In modern power supply systems, their power part is usually performed in two stages (cascades).

The first stage is the power factor corrector (CMC). In the simplest case, its input circuit is connected to one of the bus pairs (for example, between buses A and B). KKM contains a rectifier and a pulsed DC / DC converter, in which the input and output circuits are connected directly [1, p. 26, Fig. 1].

KKM provides performance of two functions. The first of them consists in converting an alternating voltage, the value of which has technological variation, into a stabilized constant voltage. The second function is the creation of a current of a given shape in the KKM input circuit. Usually, the task is to ensure that the values of this current averaged over short intervals (50-100 μs long) are proportional to the values of the low-frequency sinusoidal supply voltage averaged over the same intervals (usually 50 Hz).

The constant voltage to which the capacitors of the output filter KKM are charged cannot fundamentally be lower than the amplitude of the voltage between the supply lines (A and B). Given the technological variation of the supply voltage and with some margin, the constant voltage that is formed at the output of the KKM, at least, should be more than 600-700 V.

The second stage of the power supply system converts the DC voltage created by using KKM, into a set of voltages transmitted to the consumer. The second stage is represented in the form of one or more pulse converters with transformer coupling between the energy source and the consumer. In addition to solving the problem of galvanic separation of load circuits and an energy source, the second stage ensures that the quality parameters of electric energy are maintained with a given accuracy in accordance with the requirements of its consumer.

When building pulse converters of electric energy, it is most promising to perform power controlled keys in the form of field-effect transistors. The marked high voltage level at the output of the KKM reduces the reliability of their operation (this level is close to the permissible limit for most types of these devices). Improving the reliability of work on the basis of reducing the voltage on the power controlled keys is the goal of the technical solution proposed in this application.

The structural features of the power factor corrector, considered as a prototype [1, p. 26, Fig. 1], is that the known device contains:

- AC rectifier;

- pulse DC / DC converter.

Pulse DC / DC converter includes:

- magnetic energy storage;

- the first managed key element;

- the first valve element;

- the first capacitor of the output filter.

Known features of the topology of the proposed device are as follows:

- one terminal of the winding of the (first) magnetic energy storage device is connected to the first output terminal of the alternating voltage rectifier output circuit;

- the second terminal of the winding of the (first) magnetic energy storage device is connected to the output bus of the device through the output circuit of the first key element, and, in addition, the second terminal of the winding is connected to the output bus of the device through a circuit that contains the first valve element and the first output filter capacitor connected sequentially.

The presence of a rectified current sensor in the device is fundamentally necessary for the implementation of the function of generating the current consumed from the alternating current network, similar in shape to the mains voltage. To this end, the signal from the output of the sensor is transmitted to one of the inputs of the controller. In accordance with this signal, the controller generates control pulses.

However, the current sensor, being a necessary element of the control circuit, practically does not affect the processes in the power circuit. This is because the voltage drop across the sensor is negligible with respect to other voltages in the circuit where the sensor is turned on. For this reason, the presence of the sensor in the power circuit and its specific design can be considered as non-essential features of the proposed device. The same remark applies to the controller, which generates control signals.

The goal formulated above is solved by the proposed device, due to the combination of well-known and distinctive features.

Distinctive structural features of the proposed device are that it additionally introduced:

- the first and second capacitors of the input filter;

- the second managed key element;

- the second valve element;

- second capacitor of the output filter;

- The magnetic energy storage device is supplemented by a second winding.

Distinctive features of the topology of the proposed device are as follows:

- a circuit in the form of the first and second input filter capacitors, which are connected in series, is connected between the outputs of the output circuit of the AC voltage rectifier, and the common point of the first and second input filter capacitors is connected to the output bus of the device;

- one terminal of the second winding of the magnetic energy storage device is connected to the second terminal of the output circuit of the rectifier of an alternating mains voltage;

- another output of the second winding of the magnetic energy storage device is connected to the output bus of the device through the output circuit of the second power controlled key, and, in addition, this output of the winding is connected to the output bus of the device through a circuit that contains a second valve element and a second output filter capacitor connected in series ;

- in a circuit that contains in series the first winding of the magnetic energy storage, the first valve element, the first output filter capacitor, the second output filter capacitor, the second valve element and the second winding of the magnetic energy storage, said first and second windings have the same number of turns and are turned on according , and, in addition, the directions of direct conductivity of the first and second valve elements are made the same.

A variant of the device according to claim 2 is a device according to claim 1, in which the input circuits of additional DC / DC converters having transformer coupling between input and output circuits and the output circuits of additional DC / DC are connected to the first and second capacitors of the output filter - converters are combined (connected in parallel or in series).

A variant of the proposed device according to claim 3 is a device according to any one of claims 1 and 2, where:

- a rectifier of alternating mains voltage is made according to a single-phase bridge circuit;

- introduced the first and second capacitors of the additional input filter, connected in series with each other;

- the circuit formed by the first and second capacitors of the additional input filter is connected between the terminals of the input circuit of the AC voltage rectifier, the middle point of this circuit, i.e. the common point of the capacitors of the additional input filter is connected to the output bus of the device.

A variant of the device according to claim 4 is a device according to any one of claims 1 and 2, where the rectifier is made in the form of a multiphase bridge circuit, and the input circuit of this rectifier is connected to the terminals of all phases of the multiphase AC voltage source, the number of which is "m", where m≥3.

An embodiment of a power factor corrector circuit that corresponds to claim 1 is shown in FIG.

In the circuit of FIG. 1, the AC network is considered to be three-phase (phases A, B, and C), and it is represented by power buses 1, 2, and 3, respectively.

The power factor corrector comprises a single-phase bridge rectifier 4 and a pulsed DC / DC converter 5.

The input circuit of a single-phase bridge rectifier 4 is connected to the power bus 1 and 2. The name of the power bus to which the input circuit of the rectifier is connected is not essential for the operation of the proposed device, i.e. it is possible to connect the input circuit to the power buses 1 and 3 or 2 and 3.

The positive terminal of the output circuit of the rectifier 4 is connected to the bus 6 (positive), and the negative terminal of the output circuit of the rectifier 4 is connected to the bus 7 (negative).

Between the positive and negative buses 6 and 7, a circuit is formed formed by the capacitors 8 and 9 of the input filter of the DC / DC converter 5 connected in series. The midpoint of this chain, i.e. the common point of the capacitors 6 and 7 is directly connected to the output bus 10 of the device.

One terminal of the first winding 11 of the magnetic energy storage device 12 is connected to the positive bus 6. Another terminal of the winding 11 is connected to the output bus 10 through the output circuit of the first power controlled key 13. In addition, another terminal of the winding 11 is connected to the output bus 10 through a circuit that contains a first valve element 14 and a first output filter capacitor 15 connected in series.

One terminal of the second winding 16 of the magnetic energy storage device 12 is connected to the negative bus 7. Another terminal of the second winding 16 is connected to the output bus 10 through the output circuit of the second power key 17. In addition, the other terminal of the second winding 16 is connected to the output bus 8 through the circuit, which comprises a second valve element 18 and a second output filter capacitor 19 connected in series.

The controller 20, which generates control signals of a pulsed DC / DC converter 5, is connected to the input circuits of the first and second power controlled keys 13 and 17, through the first and second communication circuits 21 and 22, respectively.

Parallel to the first and second capacitors 15 and 19 of the output filter of the DC / DC converter 5, loads 23 and 24 are included, respectively.

A variant of the power factor corrector circuit corresponding to claim 2 is presented in FIG. 2.

A variant of the proposed device according to claim 2, presented in figure 1, has all the features of the device depicted in figure 1. The device in FIG. 2 differs from the device in FIG. 1 in that the loads 23 and 24 connected in parallel with the first and second capacitors 15 and 19 of the output filter of the DC / DC converter 5 are input circuits of additional DC / DC converters. with transformer coupling between input and output. In this case, the output circuits of additional DC / DC converters are combined (connected in parallel, as in FIG. 2, or in series).

A variant of the proposed device according to claim 3, having all the features of the device depicted in figure 1 or figure 3, differs from them in that the first and second capacitors 25 and 26 of the additional input filter are introduced. Capacitors 25 and 26 are connected in series with each other. The circuit formed by them is connected between the terminals of the input circuit of a single-phase bridge rectifier of alternating voltage, the middle point of this circuit, i.e. the common point of the capacitors 25 and 26 is connected to the output bus 10 of the device.

A variant of the proposed device according to claim 4, presented in figure 4, having all the features of the device shown in figure 1 or figure 2, differs from them in that the rectifier 4 is made according to the "m" -phase bridge circuit (in this case m = 3) and the rectifier inputs are connected to all buses of a multiphase AC network (in this case, to three buses A, B and C).

The principle of operation of the proposed device, the circuit of which is presented in figure 1, ensuring the achievement of the goal, is as follows.

By the control pulses generated by the controller 20, the power controlled keys 13 and 17 (hereinafter, the term “power controlled key” is replaced by the term “power transistor” to shorten the text) are simultaneously transferred to a state of high or low conductivity. Moreover, the switching frequency of the power transistors 13 and 17 is many times higher than the frequency of the alternating voltage of the supply network. Because of this, without a significant error, we can assume that during one cycle of operation of a pulsed DC / DC converter 5, the voltage applied to the input circuit of rectifier 4 is almost unchanged. It is equal to the instantaneous value of the mains voltage at the beginning of this cycle of operation of the pulse DC / DC converter 5.

Let, for example, at the moment of unlocking the power transistors 13 and 17, the potential of the power bus 1 (phase A) is higher than the potential of the power bus 2 (phase B).

Unlocking power transistors 13 and 17 causes the formation of a series circuit. It contains:

- power bus 1;

- rectifier diode 4, connected by the anode to the power bus 1;

- positive tire 6;

- the first winding 11 of the magnetic energy storage 12;

- output circuit of the power transistor 13;

- a common output bus 10 of the device;

- output circuit of the power transistor 17;

- the second winding 16 of the magnetic energy storage 12;

- negative bus 7;

- a rectifier diode 4 connected by a cathode to a power bus 2;

- power bus 2.

A current flows in the indicated series circuit. Its direction corresponds to the order of the above elements of this chain. The current flowing through the mentioned rectifier diodes 4 means that between the buses 6 and 7 a potential difference is established (plus - on the bus 6, minus - on the bus 7), which practically coincides with the potential difference between the power buses 1 and 2 (up to a voltage drop on rectifier diodes 4).

Since the power transistors 13 and 17 are converted into a conducting state by the control signals, the voltage drops at their output circuits are negligible in comparison with the potential difference between the buses 6 and 7. Therefore, this potential difference is almost completely applied to the windings 11 and 16 of the magnetic energy storage device 12. which are connected in series and according.

The action of voltage applied to the windings 11 and 16 causes an increase in the current of these windings. This means that in the interval of conductivity of the power transistors 13 and 17, the magnetic energy storage device 12 stores energy that enters it from the AC mains through the rectifier 4.

Due to the equality of the number of turns of the windings 11 and 16 of the magnetic energy storage device 12, the voltage applied to these windings is divided equally between them. Therefore, the potential of the common output bus 10 is equal to half the potential difference between the power lines 1 and 2. Accordingly, the capacitors 8 and 9 of the input filter of the pulsed DC / DC converter 5 in the proposed device are charged to the same voltage.

Thus, in any cycle of operation of a pulsed DC / DC converter 5, the instantaneous voltage values at the capacitors 8 and 9 of the input filter of the DC / DC converter 5 are the same and equal to half the instantaneous value of the potential difference between the power buses 1 and 2.

With the simultaneous transfer of power transistors 13 and 17 to the low conductivity state, which is provided by the controller 20, the current through the windings 11 and 16 continues to flow in the same direction, thanks to the energy that was previously stored in the magnetic drive 12.

The circuit through which the current of the windings 11 and 16 flows after locking the power transistors 13 and 17 changes with respect to the circuit, which was on the interval of the transistors' conducting state. In the circuit along which the current of the windings 11 and 16 flows after locking the power transistors 13 and 17, are:

- power bus 1;

- rectifier diode 4, connected by the anode to the power bus 1;

- positive tire 6;

- the first winding 11 of the magnetic energy storage 12;

- the first valve element 14;

- the first capacitor of the output filter 15;

- common output bus 10;

- the second capacitor of the output filter 19;

- the second valve element 18;

- the second winding 16 of the magnetic energy storage 12;

- negative bus 7;

- a rectifier diode 4 connected by a cathode to a power bus 2;

- power bus 2.

The direction of the current in the circuit, which was formed after the locking of power transistors 13 and 17, corresponds to the order of the above elements of this circuit.

After locking the power transistors 13 and 17, it turns out that the potentials of the buses 6 and 7 are identical in magnitude but different in sign with respect to the common output bus 10. This is due to the current flowing through the mentioned rectifier diodes 4, as well as the fact that the capacitors 8 and 9 on the conductivity interval of the power transistors 13 and 17 were charged to the same voltage.

The first and second windings 11 and 16 of the magnetic energy storage 12 are magnetically coupled and have the same number of turns. Therefore, the positive potential difference in sign between the first terminal of the capacitor 15 connected through the valve element 14 to the winding 11 and the positive bus 6 is identical in modulus with the negative potential difference between the first terminal of the capacitor 19 connected through the valve element 18 to the winding 16, and negative bus 7. This means that with respect to the common output bus 10 are identical in modulus and opposite in sign in the potentials of the first terminals of the capacitors 15 and 19 of the output filter, taking into account the fact that with respect to to the common output bus 10, the potentials of the buses 6 and 7 are set equal in modulus, but differing in sign.

Thus, in the proposed device, the capacitors 15 and 19 of the output filter are charged to the same potential difference. Therefore, the output voltage of the pulsed DC / DC converter 5, which, as noted, is of the order of 700-800 V, is distributed evenly between the capacitors 15 and 19 of the output filter, i.e. each of them is charged to a voltage of 350-400 V.

As follows from the description of the pulse processes in the diagram above, the equality of the voltages at the capacitors 8 and 9 of the input filter of the DC / DC converter 5, as well as the equality of the voltages at the capacitors 15 and 19 of the output filter is due to the magnetic coupling between the first and second windings 11 and 16 magnetic energy storage 12, which have equal numbers of turns. Due to this, the voltages at the windings 11 and 16 are equal at both intervals of the pulse process in the circuit, and the voltage equality at the capacitors 15 and 19 of the output filter is forcibly established, even if the loads 23 and 24 are connected in parallel to the capacitors 15 and 19, respectively.

In the interval when the power transistor 13 is in a low conductivity state, the voltage that is applied to its output circuit is higher than the voltage to which the capacitor 15 is charged by the magnitude of the direct voltage drop across the gate element 14. Thus, the voltage applied to the output circuit power transistor 13 in its locked state, almost equal to 350-400 B.

Similarly, in the interval when the power transistor 17 is in a low conductivity state, the voltage that is applied to its output circuit is higher than the voltage to which the capacitor 19 is charged by the magnitude of the direct voltage drop across the gate element 18. Thus, the voltage applied to the output the circuit of the power transistor 17 in its locked state, is also about 350-400 B.

If the loads 23 and 24 are the input circuits of additional DC / DC converters, which are made with transformer coupling between the input and output (see the device according to claim 2), then a voltage of about 350-400 V is applied to their input circuits. additional DC / DC converters can be used as power keys modern field-effect transistors, while having a significant margin of their allowable voltage.

Capacitors 8 and 9 of the input filter of the DC / DC converter 5 reduce the level of high-frequency impulse noise that occurs during operation of the converter and is transmitted to the low-frequency alternating voltage network. The pulsed interference signals are caused, in particular, by the transmission of current pulses to the input buses 6 and 7 of the DC / DC converter 5 through the stray capacitances of the windings 11 and 16. Current pulses occur at the moments of switching power transistors, when the voltages between the terminals of their output circuits change stepwise.

The suppression of interference is all the more significant, the higher the capacitance of the capacitors 6 and 7. However, an increase in this capacitance lengthens the intervals during which the diodes of the rectifier 4 are in a non-conductive state. At these intervals, the DC / DC converter 5 is actually disconnected from the AC mains, which is why it is not capable of correcting the shape of the current consumed from the mains.

Reducing the level of impulse noise transmitted to the supply network, without increasing the duration of the intervals during which the DC / DC converter 5 ceases to perform the correction function, is achieved by introducing additional filtering capacitors 25 and 26, as shown in Fig.3.

The circuit in Fig. 4, by appropriate control of power transistors 13 and 17, allows for the constancy of the current consumed from the multiphase AC network at the conduction intervals of the diodes of the bridge rectifier 4. In this mode of operation, there is practically no low-frequency ripple (at a frequency multiple of the frequency of the AC voltage ) the current that is transferred to the capacitors of the output filter. Thus, the capacitance of the output filter capacitors can be significantly reduced.

The source of information

1. Meleshin V.I., Ovchinnikov D.A. Management of transistor power converters. - Moscow: Technosphere, 2011 .-- 516 p. ISBN 978-5-94836-260-1.

Claims (4)

1. The power factor corrector, comprising a rectifier for the alternating voltage of the supply network and a pulsed DC / DC converter, which includes a magnetic energy storage device, a first controllable key element, a first gate element and a first output filter capacitor, wherein one terminal of the (first) magnetic coil the energy storage device is connected to the first output terminal of the rectifier of the alternating mains voltage, and the second output of the winding of the (first) magnetic energy storage device is connected to the output bus the output circuit of the first key element and, in addition, the second output of the winding is connected to the output bus of the device through a circuit that contains the first gate element and the first capacitor of the output filter connected in series, characterized in that, in order to increase the reliability of operation, in DC / DC the converter additionally introduced the first and second capacitors of the input filter, the second controlled key element, the second valve element, the second capacitor of the output filter, and the magnetic energy storage is supplemented by a second By the way, a circuit in the form of the first and second input filter capacitors, which are connected in series, is connected between the outputs of the output circuit of the AC voltage rectifier, and the common point of the first and second input filter capacitors is connected to the output bus of the device, one output of the second winding of the magnetic energy storage device is connected to the second terminal of the output circuit of the rectifier AC voltage, the other terminal of the second winding of the magnetic energy storage device is connected to the output bus of the device the circuit of the second power controlled key, and, in addition, this output of the winding is connected to the output bus of the device through a circuit that contains a second valve element and a second capacitor of the output filter connected in series, and in a circuit that contains the first winding of a magnetic energy storage device connected in series the first valve element, the first capacitor of the output filter, the second capacitor of the output filter, the second valve element and the second winding of the magnetic energy storage, the first and the second windings have the same number of turns and are included according to, and, in addition, the direct conductivity directions of the first and second valve elements are made the same. 2. The power factor corrector according to claim 1, characterized in that the input circuits of the additional DC / DC converters having transformer coupling between the input and output circuits are connected to the first and second capacitors of the output filter, and the output circuits of the additional DC / DC converters are combined (connected in parallel or in series). 3. The power factor corrector according to any one of claims 1, 2, characterized in that the input rectifier is made in the form of a single-phase bridge circuit, and the first and second capacitors of an additional input filter are connected in series, connected in series with each other, and the circuit formed by the first and the second capacitors of the additional input filter, is connected between the terminals of the input circuit of a single-phase bridge rectifier of alternating voltage, and the middle point of this circuit, i.e. the common point of the capacitors of the additional input filter is connected to the output bus of the device. 4. The power factor corrector according to any one of claims 1, 2, characterized in that the rectifier is made in the form of a multiphase bridge circuit, and the input circuit of the rectifier is connected to the terminals of all phases of the multiphase AC voltage source, the number of which is equal to "m", and m≥ 3.

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