RU68819U1 - ELECTRIC FILTER POWER DEVICE - Google Patents

Abstract

The proposal relates to power supplies for electrostatic precipitators, representing a load with a pronounced capacitive component. The purpose of this proposal is to increase the reliability and electrical efficiency of the device. To do this, in a device for powering an electrostatic precipitator, containing a three-phase rectifier network, a high-frequency bridge transistor inverter connected to its output, raising a high-frequency transformer with a primary winding included in the diagonal of the inverter, and a high-voltage secondary winding, through a rectifier connected to the load of the electrostatic precipitator, voltage sensors and the current of the electrostatic precipitator and the control unit, an intermediate capacitive storage is additionally introduced, included at the output of the network rectifier and two high-hours total chokes through which the primary winding of the high-frequency transformer is included in the diagonal of the bridge inverter. In this case, the network rectifier is made controllable, which ensures the maximum possible efficiency of the charger in the absence of inrush currents in the supply network. The inclusion of high-frequency chokes provides the formation of a high-frequency transformer current with gentle edges, which increases the efficiency of the device. In this case, the secondary winding of the high-frequency transformer is partitioned, each section is connected to its output rectifier, shunted by the corresponding high-frequency capacitor at the input and output. This allows you to provide a given symmetrical shape of the fronts, taking into account the influence of stray capacitances of the inputs of the high-frequency transformer on the "ground", which also increases the efficiency of the device. The control unit connected to the inputs with voltage and current sensors of the electrostatic precipitator, and the outputs to the control electrodes of the inverter transistors, is configured to control a network rectifier.

Description

This proposal relates to electrical engineering, namely to power supplies of electrostatic precipitators (EF), which are a load with a pronounced capacitive component.

Such sources should provide the necessary dust cleaning efficiency in the entire known range of specific electrical dust resistivities, at low operating costs and specific energy consumption for dust cleaning, high electrical efficiency, and the reliability of the high-voltage power supply EF in the mode of continuous standard breakdowns.

A high-voltage unipolar power device is known [patent No. EP 0192553, publication date 1986-08-27], which contains a network bridge rectifier, an L-shaped LC filter of a low-frequency network, a bridge transistor inverter, an output serial resonant oscillatory circuit, step-up transformer, two secondary windings connected to their diode bridges, storage capacitors are connected in parallel to the bridges, which are connected in series, the load is connected to the output ends of the series connected capacitors. The amplitude of the output voltage is controlled by changing the duration of the transistor control pulse. The voltage at the load is measured using a high voltage divider connected in parallel to the load. The amplitude of the voltage at the load is proportional to the duration of the pulses at the control electrodes of the transistors. However, when working on a capacitive load, such a device does not provide reliable operation in conditions of frequent breakdowns.

Also known is a device for unipolar power supply of an electrostatic precipitator adopted as a prototype [US patent No. US 5639294, published date 1997-06-17]. The device contains a network bridge rectifier, a high-frequency bridge transistor inverter, an output step-up transformer with a secondary winding connected to a diode bridge, the load-electrostatic precipitator is connected to the diode bridge through a damper. The amplitude of the output voltage is controlled by changing the duration of the transistor control pulse. Load voltage is measured

using a high voltage divider connected in parallel to the load, and the current using a shunt resistor. The amplitude of the voltage at the load is proportional to the duration of the pulses at the control electrodes of the transistors.

The disadvantage of this device is that the mains voltage is supplied directly to the switching devices after the rectifier. This inclusion leads to spasmodic energy consumption from the network when voltage is restored on the electrostatic precipitator after breakdown. The breakdown frequency of 1-0.5 breakdown per second. When there are many power sources, intense impulse noise arises from the mains supply in the primary network, which reduces the reliability of the entire system. In addition, the presence of a resistor in the output circuit reduces its efficiency.

The purpose of this proposal is to increase the reliability and electrical efficiency of the device.

This goal is achieved by the fact that in the device for powering the electrostatic precipitator, containing a three-phase network rectifier, a high-frequency bridge transistor inverter connected to its output, increasing the high-frequency transformer with a primary winding included in the diagonal of the inverter, and a high-voltage secondary winding, through a rectifier connected to the load-electrostatic precipitator , voltage and current sensors of the electrostatic precipitator and a control unit, an intermediate capacitive storage device is included, which is included at the output of the network o rectifier and two high-frequency chokes, through which the primary winding of the high-frequency transformer is included in the diagonal of the bridge inverter. In this case, the network rectifier is made controllable, which ensures the maximum possible efficiency of the charger in the absence of inrush currents in the supply network. The inclusion of high-frequency chokes provides the formation of a high-frequency transformer current with gentle edges, which increases the efficiency of the device. In this case, the secondary winding of the high-frequency transformer is partitioned, each section is connected to its output rectifier, shunted by the corresponding high-frequency capacitor at the input and output. This allows you to provide a given symmetrical shape of the fronts, taking into account the influence of stray capacitances of the inputs of the high-frequency transformer on the "ground", which also increases the efficiency of the device. The control unit connected to the inputs with voltage and current sensors of the electrostatic precipitator, and the outputs to the control electrodes of the inverter transistors, is configured to control a network rectifier.

To clarify the essence of the proposal, figure 1 shows the structurally-electric circuit of the source with high-frequency communication with the network

(IVES), providing the formation of a unipolar high voltage at a frequency of more than 10 kHz. Figure 2 shows the sequence diagram of the main timers of the control system (SU), figure 3 shows the structural and functional diagram of the SU, and figure 4 is a waveform of the voltage at the load when working out the sequence diagram of the change in high voltage on the EF during regular breakdown of the EF.

The device for powering the electrostatic precipitator, the circuit of which is shown in Fig. 1, contains a rectifier 5 connected to a three-phase network 1 through inductors 2, 3, 4. The rectifier 5 contains thyristors 6. At the output of the rectifier, a voltage divider 8 is connected to the input 7 of the control unit 29 The output 9 of the control unit 29 is connected to the submodulator 10 of the thyristors 6. The low-pass filter capacitor 11 is connected to the output of the rectifier 5 and to the input of the high-frequency bridge inverter 12. The sensor 13 of the charging current of the capacitor 12 is connected to the input terminals 20 and 0 of the control unit 28. The transistors 14-17 of the inverter 12 through the submodulators 18-21 are connected respectively to the output terminals 22-25 of the control unit 29. Through the inductors 26, 27, the primary winding 31 of the up-frequency transformer 32 connected by the capacitor 30 is included in the diagonal of the bridge inverter 12. Listed above the elements, except for the winding 31, form the low-voltage part 28 of the power source. The secondary windings 33, 34, 35 of the step-up high-voltage high-frequency transformer 32 are shunted by corrective capacitors 36, 37, 38 and feed rectifiers 39, 40, 41, the outputs of which are shunted by capacitors 42, 43, 44, connected in series and through parallel-connected inductor 45 and resistor 46 and also the shunt 47 closed to the load (EF) 52, which contains its own capacitance 53 and its own resistance 54. A voltage divider 48 is connected in parallel with the load 52. The shunt 47 and the divider 48 are connected respectively to the input terminals 49, 50 bl Single control 29. These circuit elements, except for load and control unit form part of a high voltage power supply 51.

In the initial state, all switches of the power circuit are closed and the voltage at the load is zero.

The electrical circuit (figure 1) works as follows:

- initial state - all voltages are absent;

- the power supply of the device 28 is turned on with a voltage of 220/380 V, for example, with a frequency of 50-60 Hz and is supplied to the “network” terminals 1 to the inductors 2, 3, 4 and then to the adjustable rectifier 6 of the rectifier unit 5 and the control unit (BU) 29;

- the obtained constant voltage with a ripple frequency of 100 Hz charges the low-pass filter capacitor 11, enters the drain of transistors 14, 16, using the divider 8 determines the level of the rectified voltage, information about the level of this voltage is transmitted to block 29 through channel 7, which has galvanic isolation with network (e.g. optical);

- all power sources of the block 29 are charged and the device is ready to start;

- the start button (P) on the block 29 starts the device (t ₁ - Fig. 2), while the block 29 sends a signal to the submodulator 10 through the communication channel 9, which generates unlocking pulses with a gradually increasing switching phase, ensuring a smooth charging to the maximum value of the power capacitor 11, while the voltage on the closed switches (transistors) 14, 15, 16, 17, for example, the bridge circuit of the inverter 12 gradually increases;

- the charging current is automatically kept constant, it is defined as the voltage drop across the resistor 13 and is transmitted through channel 20 with galvanic isolation to block 29;

- when the charging of the capacitor 11 ends, block 29 generates control impulses, for example, of a rectangular shape of minimum duration (starting from time t ₂ ), which are transmitted in pairs to submodulators 18, 21 and 19, through channels with galvanic isolation 22, 23, 24, 25, 20, the bridge inverter 12, while the pulse duration gradually increases, which leads to an increase in voltage at the load, and the absence of through currents is monitored automatically;

- on the inductors 26, 27 of the capacitor 30, and the primary winding 31 of the high-frequency transformer 32 included in the diagonal of the bridge inverter, this high-frequency voltage is allocated;

- on the secondary windings 33, 34, 35 of the step-up high-voltage high-frequency transformer 32 and correction capacitors 36, 37. 38 there appears a high-frequency voltage of increased amplitude, which is rectified with the help of diode bridges 39, 40, 41 and charges the capacitors 42, 43, 44, respectively;

- the rectified direct voltage obtained at the capacitors 42, 43, 44 is summed up and a unipolar constant high voltage is obtained, which, through the inductor 45 (for example, with a ferrite core), the resistor 46 and the shunt 47, giving current information, is fed to the high-voltage divider 48 giving information about the voltage of the EF, through the channels with galvanic isolation 49, 50, the signals are fed to the block (28), then the high voltage received from the transformer-rectifier

block 51, is supplied to the load 52 (EF) containing its own capacitance 53 and its own resistance 54.

- after the voltage reaches its nominal value, set in advance by the setting, the increase in the duration of the control pulse of transistors 22, 23, 24, 25 stops;

- in the future, an automatic change in the duration of the control pulses is carried out when the load resistance changes to maintain a constant voltage on it, the duration decreases when the resistance increases and the duration increases when the resistance decreases, in addition, the voltage amplitude on the load changes according to a previously defined algorithm;

- when the IVCH is turned off normally, the start signal is removed, the adjustable rectifier 5 is turned off first (time t ₃ ), and then the control pulse duration decreases and after reaching the minimum duration (time 14), the control from the inverter 12 is removed.

To improve the reliability of the high-frequency inverter in the conditions of regular regular electrical breakdowns in the electrostatic precipitator, high-frequency chokes 26, 27 are included in the diagonal of the inverter 12 bridge in series with the load - the primary winding 31 of the high-frequency transformer 32 and the capacitor 30, connected in parallel with the primary winding 31.

The task of block 28 (figure 3) is to ensure the operability of all systems of a high-voltage device, monitoring, diagnostics and indication of parameters. Block 28 is carried out:

- development of control pulses;

- maintaining the hierarchy of time delays timers;

- diagnostics of the operating mode of the entire device;

- automatic monitoring of the maximum value of the amplitude of the high voltage at the load according to the control algorithm previously set in block 28.

Block 29 (figure 3) consists of two controllers: the first 101 provides a smooth charging of the power capacitor, and the second 102 controls the operation of the inverter when working out a given algorithm.

Mains voltage 1 is supplied to the zero-crossing sensor 104, the output signal of which includes a timer 105 for smoothly changing the opening phase of the thyristors of the rectifier unit 5, which is controlled by a photo amplifier 10 through an optical channel 9 with a light pulse after a photo emitter 106. Operation parameters

the timer is determined by the control unit 107 according to a predetermined algorithm (setting the slew rate of the voltage across the storage capacitor 11).

The second controller 102 performs a smooth decrease or increase in the duration of the control pulses of the power inverter transistors and thus change the output voltage at the load 52. After the Start command is turned on (time t ₂ ), the shutter timer 108 is turned on, which includes a pulse repetition rate generator 109 inverter 12. On channels 50 and 49 relative to the ground (or zero bus), the amplitude of voltage 110 and load current 111 is continuously determined 54. At the same time, channel 1 is monitored by device 1 12 the number of breakdowns per unit time in the load. Next, using the comparator 113 according to the setting 114, the allowable number of breakdowns is monitored, and the comparator 115 according to the setting 116 monitors the maximum allowable value of the load current 54. The maximum voltage value is monitored by the comparator 117 according to the setting 118. All three parameters of the load voltage limiting are supplied to the logic element 119, which determines the maximum allowable duration of the control pulses of the power transistors of the inverter 12. The device 120 generates control pulses of the timers 121 which are coupled to control pulse duration generator 122, and further to the corresponding optical control devices 123, 124, 125, 126 forming the optical control channels 22, 23, 24, 25 podmodulyatorami 18, 19, 20, 21, 12 transistors of the bridge inverter.

The form of voltage at the load (Fig. 4) represents a high unipolar voltage at a very low level of ripple and is determined, in addition to the nature of the load, by a given control algorithm.

The control system of the high-voltage power supply with high-frequency communication provides automatic time-based control of the amplitude of the high voltage of negative polarity supplied to the EF according to the algorithm laid down earlier in block 29. The control algorithm is determined in advance according to an experimental study of the electrophysical features of dust cleaning of a particular type of dust and the physicochemical parameters of solid particles of a dusty air mixture.

The operation of the device is controlled from the control unit 29 by a secondary power source with high-frequency communication, its transistor switches 14, 15, 16, 17 through communication channels 22, 23, 24, 25 by means of: pulse devices providing galvanic isolation (isolation transformers, optical fiber channel, optocouplers or other).

The amplitude of the supply voltage is regulated by changing the duration of the control pulses supplied to the transistor switches 14, 15, 16, 17 of a high-frequency-coupled power supply installed in the primary circuit of the winding 31 of the high-voltage high-frequency transformer 32. The inductance parameters of the chokes 26. 27 in the inverter 12 are thus to help suppress the high-frequency component of the first voltage harmonic in the primary winding 31 of the high-voltage power transformer 32 and highlight The main frequency of the first harmonic of the inverter 12, as well as its reactance, contribute to limiting the amplitude of the current of the transistors during a short circuit in the secondary winding between themselves or to earth.

A power rectifier provides rectification of the mains voltage, which is supplied to the "bridge" circuit 3 of the high-frequency inverter 18 of the device for powering the electrostatic precipitator. The inclusion of transistors 14, 15, 16, 17 is carried out in pairs so that through the primary winding 31 of the high-voltage high-frequency transformer 32 passed an alternating current.

The voltage amplitude (Fig. 4) U ₁ , U ₂ , U ₃ at the load (EF) 54 is constantly measured using a high voltage divider 48. After reaching the first maximum value of U ₁ after a time Δt ₅ , block 29 stops the rapid increase in the duration of the pulse controlling power transistors 14, 15, 16, 17 of the inverter 12, thus, proceeding to a further smooth increase in duration to a maximum value of U ₂ . After a time Δt _{6, the} rate of increase in the duration of the control pulses by transistors 14, 15, 16, 17 decreases even more. After a time Δt _{7, the} duration of the control pulses, and, accordingly, the voltage amplitude at the load U _3, becomes so large that the EF breaks through, and the EF capacitance of the corona electrode - the precipitation electrode is discharged, during the discharge time in EF Δt _{8 the} voltage drops to almost zero. After the deionization time of the dusty air stream Δt ₉ between the electrodes of the EF, the voltage begins to increase again. It grows to the level of U ₁ during the time Δt ₅ . In the future, the whole process of increasing the duration of the control pulses, and, accordingly, the voltage on the EF U _{2 is} repeated until a new breakdown at a voltage of U ₃ . The duration Δt _{7 of} the operating time of the EF in these cycles each time from breakdown to breakdown is changed in such a way as to maintain the maximum possible voltage U ₃ on the EF. The voltage-free time Δt ₁₀ should be as short as possible since the EF does not work at this time. The breakdown in the EF must be of a spark nature, that is, at the time of the breakdown, the high-frequency inverter 12 is turned off.

The device for limiting the maximum voltage U ₃ and the current EF works so that the increase in the duration of the control pulses stops when any of the parameters: maximum breakdown voltage, current, number of breakdowns per unit time reaches the value set in advance. Block 29 provides for the accumulation of breakdown pulses at a voltage of U ₃ in an EF by converting the number of pulses to a logical voltage. If the number of pulses (logical voltage) is greater than the set, then this also helps to stop the increase in the duration of the pulse control transistors 14, 15, 16, 17.

Claims (1)

A device for powering an electrostatic precipitator, comprising a three-phase rectifier network, a high-frequency bridge inverter on transistors connected at its output, raising a high-frequency transformer with a primary winding included in the diagonal of a bridge inverter, and a high-voltage secondary winding, through an output bridge rectifier electrically connected to the electrostatic precipitator, voltage sensors and the current of the electrostatic precipitator, and the control unit connected by the corresponding inputs to the outputs of the sensors, and the outputs to the control inputs t anzistors of a high-frequency inverter, characterized in that an intermediate capacitive storage is added to it, included at the output of a network rectifier, made adjustable, and two high-frequency chokes, through which the primary winding of the high-frequency transformer is included in the diagonal of the bridge inverter, while the high-voltage secondary winding of the transformer is made sectional , each section is connected to its output rectifier, the input and output shunted by the corresponding high frequency condenser, the outputs of all output rectifiers are connected in series, and the control unit is configured to control a network rectifier.