SU1686667A1 - Method for controlling inverter having transformer output - Google Patents

Abstract

The invention relates to power converter technology. The purpose of the invention is to reduce overloads in start-up modes caused by saturation of the output transformer. This goal is achieved by the fact that before supplying control pulses to the keys of the inverter, the sign of the residual magnetic flux is determined and control pulses are fed to those keys that provide a transformer re-magnetization with a flux sign opposite to the above. 2 Il.

Description

The invention relates to electrical engineering, in particular to a class of inverters with a transformer output.

The aim of the invention is to reduce overloads in start-up modes.

FIG. 1 shows a device that implements the method; in fig. 2 is a diagram explaining his work.

The device contains a block 1 of reference signals, a block 2 of correction, a block 3 of logic, one of the inputs of which is connected to the output of block 2 of correction, and the outputs - to the corresponding control inputs of keys 4-7 connected by a bridge circuit, and the diagonal of which is switched on primary transformer winding 8. In parallel, the latter is connected to the sensor 9 magnetic flux. The device also contains a delay circuit 10, two inputs of which are connected to the corresponding outputs of the reference signal unit 1, a comparator 11, the output of which is connected to the third input of the delay circuit 10. One of the outputs of the delay circuit 10 is connected to one of the inputs of the logic block 3, and the second output through the correction block 2 to the second input of the logic block 3.

The output of the sensor 9 of the magnetic flux is connected to the input of the correction unit 2 and simultaneously to the input of the comparator 11.

At the outputs of the reference signal block, voltage pulses Ui, U .. are formed. In logic unit 3, pulses Uz, U4, Us, Ue of the inverter key 4-7 are generated. At the same time, a primary voltage Us is formed on the primary winding of the transformer 8.

Prior to supplying control signals to the keys 4-7, the magneto conductor of the transformer 8 may be in two stable states characterized by residual induction + SH and -Gr.

Suppose, for definiteness, that the magnetic circuit was in the 4Bg state

O 00 O O O XI

then the heaviest starting mode corresponds to an increase in induction. When this happens, the transformer is saturated, the inverter is overloaded.

In order to eliminate this phenomenon, before applying the control pulses to the keys 4-7, the sign of the magnetic flux is determined using the comparator 11, and the signal Ug is fed to the input of the delay circuit 10. Depending on this, one of the pulses Ui or Da passes through the start-up circuit, with which the control pulses are applied to the keys, re-magnetizing the core of the transformer with the flow sign opposite to the original one. For example, if the initial value of the induction is + Br and when the switches of keys 5 and 6 are closed, the transformer re-magnetized from + ВГI to-Br. then after the start of the inverter - the moment of time to - the delay circuit forms primarily a pulse Uf, identical to the signal UL

The correction unit 2 operates in a stationary mode and does not affect the control signal U2 if the voltage on the primary winding of the transformer 8 and, therefore, the output signal of the sensor 9 measuring the magnetic flux does not contain a constant component. If the symmetry of the signals Ue and, therefore, the signal F is broken, for example, as shown in the diagram by a dotted line, then in accordance with

the deviation of the signal AF is corrected by the leading edge of the pulse U / and, accordingly, the signals t) 4, lie. As a result, a pulse Ua is generated at the output of the correction unit. by which the flow bias is eliminated.

The proposed method was implemented

on autonomous voltage inverter

power 45 kW. It was noted

reliable operation during start-ups, and start-ups

currents decreased by 15-20%.

Using the proposed method of controlling inverters with a transformer output reduces overloads in start-up modes and increases their overall reliability.

Claims (1)

Claims The method of controlling an inverter with a transformer output, consisting in generating and applying control pulses to anti-phase switches, measuring flux and correcting control pulses in accordance with measurement results, in order to reduce overloads start-up modes, before applying the specified pulses to the keys, determine the sign of the residual magnetic flux and apply control pulses to those keys that provide transformer over-restraint with the opposite stream sign. 1 H b ъ four C B H f s / 5 P1 tffe / .2