RU2183378C1 - Former of synchronizing pulses - Google Patents

Abstract

FIELD: electrical engineering. SUBSTANCE: former of synchronizing pulses can be employed to control thyristor converter on A C electrified rolling stock with regenerative braking, it is able to operate under heavy distortion of form of supply voltage without any static and dynamic errors. Former of synchronizing pulses incorporates instrument transformer, comparator, integrating element, phase-shifting element, former of reference pulses, sawtooth voltage generator, half-adder, storage and retrieval unit, comparison element, front pulse former and frequency divider. Output of instrument transformer is coupled to inputs of comparator and phase-shifting element which output is connected to inputs of sawtooth voltage generator and frequency divider via former of reference pulses and to second input of integrating element which first input is connected to output of comparator. Output of sawtooth voltage generator is coupled to second inputs of half- adder and comparison element. Output of integrating element is connected to first input of half-adder which output is coupled to first input of storage and retrieval unit which second input is connected to output of frequency divider. Output of storage and retrieval unit is coupled to first input of comparison element which output is connected to input of front pulse former and its output is output of former of synchronizing pulses. Application of integrating element makes it feasible to decrease effect of variation of supply voltage at moment of its transition through zero which in its turn raises accuracy of formation of synchronizing pulses which is technical result of invention. Results of simulation with model demonstrated that distortions of supply voltage related to multiple transition of it through zero do not lead to shift of synchronizing pulses relative to non-distorted form of supply voltage. EFFECT: raised accuracy of formation of synchronizing pulses. 3 dwg

Description

 The invention relates to a pulse technique and can be used, in particular, for controlling a thyristor converter on an electrically-moving AC composition with regenerative braking.

 During operation of AC electric locomotives with regenerative braking in some sections of the railway, unstable operation of electronic control equipment is observed with severe distortions in the shape of the supply voltage curve. The essence of this phenomenon is to change the moment of formation of synchronizing pulses designed to synchronize the operation of control equipment. Synchronization is carried out at the moment of transition of the network (supply) voltage through zero. In the event of a distortion in the shape of the supply voltage curve, for example, with the appearance of switching and post-switching voltage fluctuations, the inverter’s reserve angle, measured from the moments of the appearance of the clock pulses, changes, which affects the energy performance of the electric locomotive.

 With severe distortions of the supply voltage, unstable operation occurs, crashes and failure of the control system of an electric locomotive.

 A device is known that allows the generation of pulses synchronized with the network to set the angle of the inverter supply when the shape of the supply voltage curve is distorted [1]. Synchronization is carried out by replacing the distorted curve of the supply voltage with its first harmonic component and approximating its phase to the phase of the supply voltage. Phase regulation is carried out by an automatic phase adjustment circuit, while at the moments of the passage of the voltage of the first harmonic through zero, sync pulses are formed [2].

 The adjustable reference pulse generator comprises a measuring transformer, a rectifier bridge, a transistor switch, a bias voltage adjuster, a comparison element, an integrating and phase-shifting element.

 The secondary winding of the power transformer is connected to the primary winding of the measuring transformer. Its output is connected to the input of the rectifier bridge. The output of the rectifier bridge is connected to the first input of the transistor switch. The bias voltage adjuster is connected to the first input of the comparison element, the second input of which is connected to the output of the transistor switch. The output of the comparison element is connected to the input of the integrating element, the output of which is connected to the input of the phase-shifting element, the output of which is connected to the second input of the transistor switch and is the output of the driver of adjustable reference pulses.

 The adjustable reference pulse generator performs the functions of the inverter reserve angle setter and corrects the reserve angle depending on the distortion of the voltage shape on the secondary winding of the transformer. The shaper provides pulse synchronization by automatically approaching the voltage phase of the secondary winding of the transformer of the phase of its first harmonic. The phase shifting element of the shaper generates rectangular pulses equal in duration to the specified value of the inverter’s reserve angle, which are synchronized with the mains voltage.

 Thus, the shaper of adjustable reference pulses allows to increase the stability of inverters in operating modes, accompanied by distortions in the shape of the supply voltage curve, as the correction of the value of the specified angle of the inverter reserve, depending on the arising distortions.

 However, with severe distortions in the shape of the supply voltage curve, a significant error occurs in the formation of clock pulses, leading to malfunctions of the control equipment of the electric locomotive.

 At the same time, the inverter’s angle control device controlled by a known shaper lowers the energy performance of an electric locomotive when the shape of the supply voltage curve is distorted due to a static error in the formation of clock pulses.

 Static error in the formation of clock pulses due to the error of the automatic control system and is in the steady state 1-2 e. hail [2].

 With a sharp increase in switching voltage dips when starting the motor-compressor of the electric locomotive, as well as when the protection is disconnected on its own or neighboring electric locomotive, the dynamic error in the formation of clock pulses increases, amounting to 2-9 e. hail [2].

 A shaper is also known in a thyristor converter multi-phase control device [3], which eliminates malfunctions in the operation of the driver of the reference pulses due to severe distortions in the shape of the supply voltage curve due to the diversity in time of the beginning and end of switching between two sections of the electric locomotive. In this case, the free post-switching voltage components of the sections are opposite in phase, which leads to their reduction in the form of the supply voltage and, accordingly, allows to improve the voltage form on the secondary winding of the transformer.

 The adjustable reference pulse generator in [3] contains a measuring transformer, a rectifier bridge, a transistor switch, a bias voltage adjuster, a comparison element, integrating and phase-shifting elements.

 The secondary winding of the power transformer of the electric locomotive is connected to the primary winding of the measuring transformer of the shaper. Its output is connected to the input of the rectifier bridge. The output of the rectifier bridge is connected to the first input of the transistor switch. The bias voltage adjuster is connected to the first input of the comparison element, the second input of which is connected to the output of the transistor switch. The output of the comparison element is connected to the input of the integrating element, the output of which is connected to the input of the phase-shifting element, the output of which is connected to the second input of the transistor switch and the input of the pulse delay unit, the output of which is the output of the adjustable reference pulse shaper.

 Shaper of adjustable reference pulses with a delay unit provides asynchronous inclusion of two inverters of each section of the electric locomotive. The fixed angle of the pulse delay specified by the delay unit is equal to the half-period of free post-switching voltage fluctuations that occur in the network with strong distortions of the supply voltage. Mutual compensation between the sections of free voltage fluctuations having the opposite sign leads to a decrease in the free components in the form of a supply voltage curve and an improvement in the shape of the voltage curve supplied to the former from the secondary winding of an electric locomotive transformer.

 However, with a fixed angle of pulse delay, full compensation of free post-switching voltage fluctuations can be carried out with the same value of the half-cycle of the voltage oscillations. This can be achieved only when the electric locomotive is operating at a fixed distance from the traction substation of a certain power. Under other operating conditions, it is impossible to achieve full compensation of free post-switching voltage fluctuations, which in turn leads to an error in the formation of clock pulses with respect to the moments when the mains voltage passes through zero and the energy performance of the electric locomotive worsens.

 A sharp increase in switching voltage dips and, accordingly, free post-switching voltage fluctuations at startup, for example, an electric locomotive motor compressor, or other transient processes is also accompanied by an error in the formation of clock pulses, since the free component of voltage fluctuations increases.

 In addition, with the automatic control scheme stored in the device during the generation of clock pulses, the static error in the generation of clock pulses is inevitable, as in the first device considered. Static error due to the error of the automatic control system.

 Thus, the multi-phase control scheme due to compensation of free post-switching voltage fluctuations allows working without failures with strong distortions of the supply voltage, but with incomplete compensation of this voltage it does not solve the problem of generating clock pulses that must form at the moments when the supply voltage passes through zero.

 The basis of the invention is the task of creating a generator of synchronizing pulses, which works without failures with strong distortions in the shape of the supply voltage and is devoid of static and dynamic errors in the formation of clock pulses due to the fact that the device only works when the mains voltage passes through zero.

 The problem is solved in that in the synchronizing pulse generator, comprising an integrating and phase-shifting element, a comparison element and a measuring transformer connected to the output of the power transformer, an additional comparator, a reference pulse generator, a sawtooth generator, a half-adder, a sampling and storage device, a pulse shaper are additionally introduced along the front and the frequency divider, while the output of the measuring transformer is connected to the inputs of the comparator and phase-shifting element, output for which, through the reference pulse generator, it is connected to the inputs of the sawtooth generator and the frequency divider, as well as to the second input of the integrating element, the first input of which is connected to the output of the comparator, the output of the sawtooth generator is connected to the second inputs of the half-adder and the comparison element, the output of the integrating element is connected to the first input of the half-adder, the output of which is connected to the first input of the sampling and storage device, the second input of which is connected to the output of the frequency divider, the output of The sampling and storage device is connected to the first input of the comparison element, the output of which is connected to the front of the pulse shaper input, and its output is the output of the device.

The introduction of a set of new elements into the device (comparator, a reference pulse shaper, a sawtooth generator, a half-adder, a sampling and storage device, a front pulse shaper and a frequency divider) and their interconnections allows converting the voltage u ₂ from the output of the measuring transformer (Fig. 2, a ) in a sequence of rectangular pulses of different polarity (Fig.2, c), the edges and slices of which coincide with the moments of the transition of the supply voltage through zero. The use of an integrating element makes it possible to reduce the influence of fluctuations in the supply voltage at the moments of its transition through zero and to approximate the form of the voltage at the output of the integrator u _int to the voltage (shown by the dotted line in FIG. 2, d) corresponding to the smooth form of the supply voltage u ₂ (shown by the dotted line in FIG. 2a). In addition, the use of a half-adder in the device _{halves the} error in the formation of voltage u _Δ = (u _GPN + u _int ) / 2 at its output (Fig.2, g). Since the synchronizing pulses at the output of the device (figure 2, g) are formed depending on the voltage u _Δ , this, in turn, allows to increase the accuracy of their formation.

 In FIG. 1 shows a diagram of a driver of synchronizing pulses, in FIG. 2 are diagrams explaining the operation of the generator of synchronizing pulses.

 The synchronizing pulse generator comprises a measuring transformer 1, a comparator 2, an integrating element 3, a phase-shifting element 4, a reference pulse shaper 5, a sawtooth voltage generator 6, an adder 7, a sampling and storage device 8, a comparison element 9, a pulse shaper along the front 10 and a frequency divider eleven.

 The output of the measuring transformer 1 is connected to the inputs of the comparator 2 and the phase-shifting element 4, the output of which is connected to the inputs of the sawtooth voltage generator 6 and the frequency divider 11 through the reference pulse shaper 5, as well as to the second input of the integrating element 3, the first input of which is connected to the output of the comparator 2 , the output of the sawtooth voltage generator 6 is connected to the second inputs of the half-adder 7 and the comparison element 9, the output of the integrating element 3 is connected to the first input of the half-adder 7, the output of which is connected with the first input of the sampling and storage device 8, the second input of which is connected to the output of the frequency divider 11, the output of the sampling and storage device 8 is connected to the first input of the comparison element 9, the output of which is connected to the input of the pulse shaper at the front 10, and its output is the output of the device.

 Shaper synchronizing pulses works as follows.

The voltage u _{2 of the} secondary winding of the measuring transformer 1 (figure 2, a) is supplied to the inputs of the comparator 2 and the phase-shifting element 4 and has dips associated with the switching processes in the converter of the electric locomotive. Using a comparator 2, this voltage is converted into rectangular pulses of voltage u _to positive and negative polarity (figure 2, c). The transition of the voltage of the secondary winding of the measuring transformer 1 through zero is accompanied by the formation of a front and a cut in voltage u _to the output of the comparator 2. In this case, the output voltage of the comparator 2 stores voltage transitions from zero to high and back, which are associated with switching distortions of the voltage of the secondary winding of the measuring transformer 1. Using the phase-shifting element 4 and the reference pulse shaper 5, the generation of reference clock pulses SI1 (Fig. 2, b) by the first harmonics voltage u ₂ of the secondary winding of the measuring transformer 1. This method of pulse-applied in dilator 541, the locomotive locomotive VL85 unit [4]. Using the SI1 pulses, a sawtooth voltage u _{GPN is generated} at the output of the sawtooth voltage generator 6, and the beginning and end of the voltage conversion u _int in the integrator 3 is also controlled. The frequency divider 11 reduces the repetition rate of the SI1 pulses arriving at its input, the SI2 output pulses of the frequency divider 11 are shown in FIG. 2, e. Using a half-adder 7, voltage signals u _GPN and u _int are compared, as a result of which the voltage u _Δ at the output of the half-admitter 7 is half its input s ignals. The sampling and storage device 8 stores the voltage u _{Δ of the} half- _admitter 7. for a period of time. Updating the voltage u _uh at the output of the sampling and storage device 8 is carried out at the moment of supply of SI2 pulses (Fig. 2, d). Using the comparison element 9 and the pulse shaper on the front 10, the formation of SI synchronizing pulses occurs (Fig.2, g) when the sawtooth voltage exceeds the voltage at the output of the sampling and storage device 8. The fronts of the received SI synchronizing pulses coincide with the moments of the supply voltage passing through zero .

 Thus, changes in the input voltage associated with switching and transient modes of operation of an electric locomotive do not lead to a change in the moments of formation of synchronizing pulses. In addition, the serial connection of the elements of the device eliminates the static error characteristic of the automatic control system.

The operability of the generator of synchronizing pulses is confirmed by modeling its operation using the software package Design Lab 8.0 [5]. The calculation results on the model are shown in figure 3, from which it follows that the distortion of the supply voltage u ₂ associated with its repeated passage through zero does not lead to a shift of the SI clock pulses relative to the undistorted form of the supply voltage u.

Sources of information
1. A.S. 1018189. Device for controlling a thyristor inverter. The inventors O.R. Kalabukhov, S.A. Kramskov. Publ. in BI, 1983, 18, cl. H 02 M 1/08.

 2. S. A. Kramskov, B. M. Naumov, O. R. Kalabukhov. Synchronization of control systems for thyristor converters of AC electric locomotives. Publ. on Sat Proceedings of the All-Union Scientific Research, Design and Technological Institute of Electric Locomotive Engineering. t.25, Novocherkassk, 1984.

 3. Yu. M. Kulinich, VV Nakhodkin and others. Tests of an electric locomotive VL85 with different-phase control of rectifier-inverter converters. - Vestnik VNIIZHT, 1986, 4.

 4. Electric locomotive VL85: Operation manual / B.A. Tushkanov and others. - M.: Transport, 1992, - 480 p.

 5. V. D. Razevig. System of end-to-end design of electronic devices Design Lab 8.0. - M .: "Solon", 1999, - 693 p.

Claims (1)

 A synchronizing pulse generator containing an integrating and phase-shifting elements, a comparison element and a measuring transformer connected to the output of the power transformer, characterized in that a comparator, a reference pulse generator, a sawtooth generator, a half-adder, a sampling and storage device, and the front and the frequency divider, while the output of the measuring transformer is connected to the inputs of the comparator and phase-shifting element, the output of which through a reference pulse former is connected to the inputs of the sawtooth generator and the frequency divider, as well as to the second input of the integrating element, the first input of which is connected to the output of the comparator, the output of the sawtooth generator is connected to the second inputs of the half-adder and the comparison element, the output of the integrating element is connected to the first input half-adder, the output of which is connected to the first input of the sampling and storage device, the second input of which is connected to the output of the frequency divider, the output of the device is the storage and storage is connected to the first input of the comparison element, the output of which is connected to the input of the pulse shaper at the front, and its output is the output of the device, while the voltage at the output of the half-adder is half the sum of its input voltages, and the pulses generated by the reference voltage shaper control the beginning and the end of the voltage conversion in the integrator, the sampling and storage device stores the voltage from the output of the half-adder during a period, and updating the voltage at the output CTBA sampling and storage is performed at the time of the output pulses of the frequency divider.

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