SU1367115A1 - Method of controlling independent voltage inverter - Google Patents

Abstract

The invention relates to the field of electrical engineering and can be used for a frequency-controlled electric drive, as well as in sources of electrical energy, which are subject to high demands on the quality of the output current. The aim of the invention is to improve the accuracy of controlling the output current of the inverter by reducing the relative error in the formation of the instantaneous value of the load current. This is achieved by generating comparison signals that change as a function of the reference signal, which ensures an almost constant relative error of the instantaneous value of the sinusoidal load current, independent of its phase and amplitude. 3 IDs | (L

Description

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The invention relates to electrical engineering and can be used in voltage inverters designed for a frequency-controlled electric drive, as well as in sources of electrical energy, which are subject to higher requirements for the quality of the output current.

The aim of the invention is to increase the accuracy of controlling the output current of the inverter by reducing the relative error in the formation of the instantaneous value of the load current.

Fig. 1 shows a functional control circuit of a voltage inverter implementing the proposed method; Fig. 2 shows plots of formation of the levels of reference signals; 3 shows the output current output plots with the proposed control method.

The device (Fig. 1) implementing the proposed control method comprises an oscillator 1, an error extracting node 2, an output parameter extracting signal node 3 — a load current, an integrator 4, a comparator 5, a full-wave rectifier 6, a voltage divider 7, a source 8 constant voltage, non-inverting adder 9, inverting adder 10, analog switch II, inverter 12. One of the inputs of the error isolation node 2 is connected to the output of the master oscillator 1, another input through the yaeji 3 signal parameter (load currents) to at The output of the inverter is 12, and the output is to the input of the integrator 4, the output of which is connected to the output of the analog switch 11. The output of the comparator 5 is connected via an inverter 12 to the load (not shown) and to the control input of the analog switch 11. The input of the full-wave rectifier 6 connected to the output of the master oscillator 1, and the output to the input of the voltage divider 7, the output of which is connected to the first inputs of the non-inverting 9 and inverting 1 O adders, the second inputs of which are connected to a constant-voltage source 8. The output of the non-inverting adder 9 is connected to the first input of the analog switch I 1, the second input of which is connected to the output of the inverting adder 10.

The essence of the method is as follows.

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The driver V is fed to one of the inputs of the error extracting unit 2, where it is compared with a signal proportional to the instantaneous value of the output parameter, the load current, coming from the node 3 of the load current signal. The error signal obtained from this signal is fed to the input of the integrator 4. The error signal integral from the integrator output is fed to one of the inputs of the comparator 5, to the other input of which the switching level is applied. When the integral of the switching level error signal is exceeded, the comparator 5 outputs the switching signal that affects the power switches of the inverter 12 and the control input of the analog switch 1 1, which changes the polarity of the switching level.

Under the influence of the signal from the output of the comparator 5, the inverter 12 changes its state and the sign of the output voltage changes to the opposite. Simultaneously with a change in the polarity of the output voltage, the load current changes, which leads to a change in the sign and magnitude of the error signal at the output of the error extractor 2. The integrator 4 perceives an error signal, as a result of which the signal at the integrator output begins to change from the opposite derivative. Further, the processes are repeated.

At the same time, the driving signal U is fed to the input of a full-wave rectifier 6, from the output of which the signal goes to a voltage divider 7, where it is divided by an amount determined by a given error in the formation of an instantaneous current value. From the output of the voltage divider 7, a signal is fed to the first inputs of the non-inverting 9 and the inverting 10 totalizers, the second inputs of which supply a signal from the source 8 of a constant voltage. As a result, the output of the adders 9 and 10 generates a switching level, the level of which varies simultaneously with the change in the instantaneous value of the reference current (Fig. 2).

Forming such an uroblic switching allows to increase the accuracy of forming the output load current by reducing the relative error of the instantaneous value of current.

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load. In the proposed method, the variable component of the switching level is several times greater than its constant component, which ensures the relative error in the formation of the instantaneous load current almost constant, independent of its amplitude and phase.

The constant switching level component limits the maximum switching frequency of the inverter valves.

Claims (1)

Invention Formula A method of controlling an autonomous voltage inverter, comprising forming a reference signal, generates a signal proportional to the instantaneous value of the output current. 15 the inverter, compare it with the reference signal, as a result of the comparison, generate an error signal, integrate it, form two equal switching polarity levels, compare the integral of the error signal with the switching levels, and at the moments of their equality switch the key elements of the inverter, In order to increase the control accuracy of the output current of the inverter, they form a signal proportional to the module of the reference signal, sum it with a signal of a constant value, and thereby form one of the levels switching, invert it and thereby form the switching level of the opposite polarity. FIG. one Editor N.Shvydka (rig. 3 Compiled by A.Pridatkov Tehred M. Hodankch Proofreader A.Obruchar 1367115 Ui