RU1794274C - Method of control over bridge inverter - Google Patents

Abstract

Usage: in the control of pulse converters, in electric drives for controlling AC motors, Summary of the invention: the keys 1-4 of the bridge inverter are turned off for a fixed period of time when the instantaneous value of the load current is in the interval between the additional constant positive and additional constant negative levels fixed relative to the zero value of the load current in the positive and negative sides, respectively, and reaches either variable in upper or alternating lower levels, fixed relative to a given value of the load current. The corresponding keys of the bridge inverter are turned on until the end of the fixed time interval. 2 ill.

Description

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The invention relates to electrical engineering and can be used in the control of pulse converters in electric drives to control AC motors.

Closest to the proposed method of controlling a bridge inverter by autosw. NJ 604123, CL H 02, M 7/48, 1975, which consists in generating control signals for the bridge keys depending on the fixed levels of the load current, the keys of the first diagonal of the load bridge turning on when the instantaneous value of the load current is in the interval between the zero level corresponding to zero load current and an alternating upper level fixed in a positive direction relative to a given value of the load current and turn off these keys when the instantaneous value of the load current reaches an alternating lower level, and the keys of the second diagonal are turned on when the instantaneous value of the load current is in the interval between the zero level corresponding to the zero load current and the alternating lower level fixed in the negative direction relative to the set value of the load current and turn off these keys when the instantaneous value of the load current reaches the variable upper level.

A disadvantage of the known method is the possibility of the occurrence of through currents in the case when the switching of the keys of the bridge inverter occurs at zero instantaneous value of the load current.

The purpose of the invention is to increase reliability by eliminating the passage of through current.

The goal is achieved by the fact that according to the proposed method of controlling a bridge inverter, which means that they generate control signals for the bridge keys depending on the fixed levels of the load current, the keys of the first diagonal of the bridge turning on when the instantaneous value of the load current is in the interval between the zero level, corresponding to the zero load current, and an alternating upper level fixed in the positive direction relative to the set value of the load current, and these keys are turned off when the instantaneous value of the load current reaches a variable upper level, and the keys of the second diagonal turn on when the instantaneous value of the load current is between the zero level corresponding to the zero load current and the alternating lower level fixed in the negative direction relative to the set value of the load current .. and turn off these keys when the instantaneous value of the load current

reaches a variable lower level, the keys of the bridge inverter are turned off for a fixed period of time when the instantaneous value of the load current is in the interval between the additional

0 constant positive and additional constant negative levels, fixed relative to the zero value of the load current in the positive and negative direction, respectively, and reaches either an alternating upper or alternating lower level, fixed relative to a given value of the load current, and include the corresponding keys of the bridge inverter at the end of a fixed time interval,

In FIG. 1 shows a bridge inverter; in FIG. 2 is a timing diagram explaining the operation of a bridge inverter according to the proposed method.

The bridge inverter contains keys 1–4, reverse diodes 5–8, and active-inductive load 9.

The following notation is adopted in the diagram of Fig. 2: I is the set value of the load current. II - load current, 111 - additional constant positive level, IV - additional constant negative level, V - alternating

5 is the upper level, V is the variable lower level, a are the key control signals 1, 2 of the first diagonal of the bridge inverter, b are the key control signals 3, 4 of the second diagonal of the bridge inverter, AM special moments of time.

A positive value of the load current corresponds to the direction of current flow indicated by the arrow in Fig. 1.

The control signals to turn on the key of the 5th bridge inverter correspond to log. 1 (see, Fig. 2).

According to the proposed method, the bridge inverter operates as follows. At time point, the keys 3.4 of the second diagonal of the bridge are turned on. The load current begins to flow in the negative direction until the moment that corresponds to. indicates that the load current reaches an alternating lower level. At this time, keys 3 and 4 are turned off, and the current, under the action of the energy stored in the load 9, diodes 7 and 8 tends to zero. At the moment, the load current reaches zero, and switches on keys 1 and 2 of the first diagonal.

through which the load current begins to rise until it reaches an alternating upper level V. This happens at the moment, and since the load current at this point in time is between the additional constant positive and negative levels III and IV, keys 1 and 2 are turned off. and keys 3 and 4 are not yet included in the time from to. At the moment, switches 3 and 4 are turned on, which will be turned on until t E, when the load current reaches an alternating low level. In the time interval between and the load current flows through the inverse diodes 7 and 8.

Claims (1)

The claims A method of controlling a bridge inverter, which consists in generating control signals for the bridge keys depending on the fixed levels of the load current, the keys of the first diagonal of the bridge turning on when the instantaneous value of the load current is in the interval between the zero level corresponding to the zero load current and the alternating upper level fixed in the positive direction relative to the set value of the load current, and turn off these keys when the instantaneous value of the load current reaches alternately top level, and the keys of the second diagonal include when the instantaneous value of the load current is in the interval between the zero level corresponding to the zero value of the load current and the variable lower level fixed in the negative. Subsequently, the keys 1 and 2 of the first diagonal will be included in the time intervals between and . and, and the keys 3 and 4 of the second diagonal will be turned on at the moment and off at the moment. The existence of fixed time intervals (CD and IK) between turning on the keys of the same diagonal and turning off the other switches out the possibility of the occurrence of through currents through series-connected switches 1 and 4 and 3 and 2, which increases the reliability of the bridge inverter. the back side relative to the set value of the load current, and turn off these keys when the instantaneous value of the load current reaches an alternating low level, characterized in that, in order to increase reliability by eliminating the passage of through current, the keys of the bridge inverter are turned off for a fixed time interval, when the instantaneous the value of the load current is in the interval between the additional constant constant positive and additional constant negative levels, fixed relative to zero values of the load current in the positive and negative sides, respectively, and reaches either an alternating upper or alternating lower level, fixed relative to a given value of the load current, and include the corresponding keys of the bridge inverter at the end of a fixed time interval. Phil. 2.