SU919037A1 - Method of controlling adjustable frequency converter with direct coupling - Google Patents

Description

one

The invention relates to power converter technology and can be used in all sectors of the national economy in which an adjustable electric drive is used.

A known method of controlling variable frequency converters with direct communication and natural commutation is carried out by applying control pulses to the converter C valves.

The disadvantage of this system is a low power factor.

Closest to the present invention is a method of controlling an adjustable frequency converter with direct connection to direct current valves with natural switching and series-connected rectifier and dependent inverter, consisting in that modulated according to frequency, phase and order are fed following the phases of the output network control pulses to the control electrodes of the direct current valves to regulate the time of their opening, measure the voltage of the output network and depending on this alter the depth of modulation .. upravdeni L2 signal. The disadvantages of the known method are low power factor

10 and insufficiently good harmonic composition of the output network voltage.

The purpose of the invention is to increase the power factor of the converter and to improve the harmonic power of the output network voltage while regulating the voltage value of the output network of the converter.

Claims (2)

This goal is achieved by the fact that in the method of controlling an adjustable frequency converter with non-frequency. By means of direct communication with direct current valves with natural commutation and series-connected rectifier and dependent inverter whose set of actions is partially described above, 2, the modulation depth is performed by the duty cycle of the control of direct current valves inversely proportional to the output network voltage, moreover, the value of the angle of regulation of the direct current is kept constant and equal to zero. Fig. 1 is a schematic diagram implementing the proposed method; in fig. 2 - time diagrams corresponding to the single phase of the converter. In the figures, there are: 18 - direct current valves of the frequency converter; 19-2 - dependent inverter valves; 25-30 - rectifier valves; 33 — Inductive-capacitive filter —circuit for control of direct current valves; - control circuit of the dependent inverter valves; 36 — voltage curves of the input network (and output network (Uj.), Output network current curve) with a modulating signal bore ratio of 3 and active-inductive load; 37 and 38 are the curves of the modulating signals of the control pulses of the valves with common cathodes and with common anodes, respectively, with a skase of 3; 39 - voltage curves, Ui current (2 with a modulating signal porosity equal to 4 and 5, and active-inductive load; 40 and 41 modulating signal curves, respectively, with a duty cycle of 4 and 5; 42 - voltage curves U, Ug and current 12. when the modulating signal has a duty cycle of 4 and 5 and the active load; 43 and 44 are modulating signal curves, respectively, when the modulating signal has a duty cycle of 4 and 5. The implementation of the proposed method is possible in controlled conversion of frequency bodies with direct connection to direct controlled valves With natural switching and series-connected rectifier and dependent inverter with any number of input and output converter networks. Figure 1 shows a three-phase voltage converter into a three-phase voltage. The control impulses of the direct current valves are generated by the control system 34 and are applied to the valves 1 The angle of regulation of each valve is set to zero. Control pulses applied to separate groups (with common anodes or with common cathodes} of each phase voltage yhodnoy network promudulirovany transducer in accordance with the frequency range order and Phase sequencer phases. Thus, control pulses are applied to the valves of each separate group at those intervals in which the modulating signal of this group is not equal to zero. With the equalization of the modulating signal to zero, the control pulses cease to flow to the valves of a separate group. However, the valve that is turned on up to this point is not immediately turned off and leads the current either up to the point in time determined by the zero voltage of the phase of the input circuit to which the valve is connected with the active load 42, or until the point of time determined by the equality of the voltage the input network to which the valve is connected and the input voltage of the dependent inverter, with the active-inductive load 39- Reducing the duration of the modulating signal compared to the duration of the voltage period of the output network, increasing its well spine, decrease the relative time during which the valves are a separate group are in the open state and a current is passed from the input transducer to the output network of the network, thereby varies the magnitude of the voltage output network. The use of the invention makes it possible to increase the power factor of the converter, and due to this it allows to reduce the loading of the valves with current, reduce the power losses in the valves and, thereby, increase the efficiency of the converter. In addition, the harmonic composition of the output voltage curve of the converter allows to reduce the losses in the converter load from higher harmonics. Claims The method of controlling an adjustable frequency converter with direct connection to direct current valves with natural commutation and series-connected rectifier and dependent inverter, consisting in the fact that modulated in accordance with the frequency, phase and phase following order are supplied the output network control pulses to the control electrodes of the direct current valves to control the time of their opening, measure the voltage of the output network and, depending on this, change the mode depth control signal, which, in order to increase the power factor and improve the voltage composition of the output network, the specified modulation depth is performed by the duty cycle of the control of the direct current valves is inversely proportional to the value of voltage 1 and the output network, and the value of the angle of regulation of the direct current valves is kept constant and equal to zero. Sources of information taken into account during the examination 1. G. Zhemerov, TirKstorny frequency converters with direct communication. M., Energie, 1977, 2. USSR author's certificate for application No. 25b9777 / 2-07, 1978.