SU920677A1 - Device for stabilizing self-contained inverter output voltage - Google Patents

Description

The invention relates to electrical engineering, in particular, to control systems of devices of converter equipment and can be used in autonomous stabilized voltage inverters.

A device for stabilizing the output voltage of an autonomous inverter is known, in which a current transformer, a rectifying bridge loaded on a resistor, and a live RC filter are applied to the resistor to obtain current correction signals. The device generates a signal that is linearly dependent on the average value of an AC current transformer measured by 1.

A disadvantage of this device with respect to the stabilization of the voltage of a single-phase inverter is the inertia caused by the large time constant of the smoothing RC filter and the impossibility of obtaining the dependence of the output signal on the phase of the measured current.

The closest in technical essence to the present invention is a device for stabilizing the voltage of an autonomous inverter with a control system, comprising a constant voltage regulator connected to the input of the inverter, a voltage setting device, the output of which is connected to the first input of the comparison element, the second the input of which is connected to the output of the constant voltage regulator, and the output to its control input 2.

The disadvantage of this device is the impossibility of obtaining the dependence of the output signal on the measured input phase and, as a consequence, the low static accuracy of maintaining the output voltage of the inverter when using the device to obtain a load current correction signal. In addition, the device is characterized by the complexity of the circuit (14 operational amplifiers, 7 nonlinearity blocks, and a number of auxiliary units).

The aim of the invention is to increase the static accuracy of stabilizing the output voltage while maintaining speed.

The goal is achieved by the fact that in the device for stabilizing the output voltage of an autonomous inverter, the voltage setter is equipped with a current-to-voltage converter, a filter, two sample-storage cells, an adder, a quadrant and a reference voltage source, and the current converter is the voltage is connected to the load of the inverter, its output through the filter is connected to two cell-sample-storage, the clock inputs of which are connected to the inverter control system, the output of the first cell directly, and the second output through A quadrant is connected to an adder to which a reference voltage source is also connected, and the output of the adder is the output of the voltage setpoint device. : FIG. 1 shows a structural diagram of the device; Fig. 2 shows the century: the torn voltage diagram on the output filter with active-inductive load: The device contains a constant voltage regulator 1, the output of which is connected to an inverter with the voltage NIN 2 with a control system. The output of the inverter 2 is connected through a current flow filter 3 to the load 4 "The device has a voltage master 5, the input of which is connected to the load output, and the output is connected to the first input of the reference element 6. Two clock inputs of the voltage master are connected to the inverter control system, the second input of the comparison element b is connected to the output of the regulator, and the output is connected to its control inputs. The voltage setter, designed to generate the load signal, contains a current converter to voltage 7, which is connected through a filter 8 kami sample storage 9 and 10. In the adder 11 is supplied with signals of a reference voltage source 12 and through the quad cell 13 with the sample-storage. The output of the adder is the output of the voltage master. As the inverter 2, an autonomous single-phase unregulated inverter can be used, which converts the DC voltage to an alternating rectangular with a constant transmission coefficient.

AC output filter is made according to an L-shaped structure of the series element - inductance., parallel - resonant parallel LC circuit, carried out by | rectangular filtering: inverter w apr. Load 4 is active-inductive. A current transformer can be used as a current converter in voltage 7, which converts the load current into a voltage signal. Filter 8 serves to suppress pulse noise and can be implemented in the form

inertial link. The sampling circuit 9 is designed to fix the analog correction signal, corresponding to the product of the load current and the sine of the angle between this current and the output voltage of the inverter, during the output frequency period. Sampling-storage circuit 10 is intended for fixing an analog correction signal corresponding to the product of the magnitude of the load current and the cosine of the angle between this current and the output voltage of the inverter. A quadrant 13 squares a signal proportional to the product of the magnitude of the load current and the cosine of the angle between this current and the output voltage of the inverter, and can be implemented, for example, by a piecewise-linear diode circuit, the adder 11 combines the signals from the cells 9 and 11 and can be implemented on an operational amplifier. The reference voltage source 12 serves to set the exhaust voltage at idle and is realized at the zener diode. Comparison element 6 compares the DC voltage input to the input of inverter 2 with the output voltage of the setpoint generator 5 and generates a control signal for the regulator 1. As an element of the comparison, an operational amplifier, I -, can be used.

FIG. 1 and 2, the following notation is used:

Uj, - input voltage

torus 1 ;,

Ufg is the output voltage of the regulator 1; U-rt - first harmonic vector

rectangular voltage from the output of inverter 2; Ugbix the vector of the output voltage of the filter 3 - the vector pa, value the voltage

on filter 3;

IH load current vector; LfH is the angle between the vector of the load current and the vector of the output voltage of the filter 3; / 1 - the angle between the current vector

the load and the vector of the first harmonic of the rectangular voltage of the inverter; Uj signal from the set point

stress;

The magnitude of the voltage drop across the filter 3 is equal to

. Ui. j bf ..., (1) where the magnitude of the voltage drop

on the filter; IH is the load current;

u) is the circular frequency of the inverter; Lcp is a consistent inductance filter.

From the vector diagram (Fig. 2), the magnitude of the first harmonic of the rectangular voltage at the output of the inverter

is equal to) g (1n «LfsLsL) H-1„ and) Lfs1nl, (2)

where UTI is the magnitude of the first harmonic of the rectangular voltage at the output of the inverter; Ufibtx output voltage at

filter)

1n - load current; I is the circular frequency of the inverter; bf — the inductance of the filter is consistent; L is the angle between the vector of the load current and the vector of the first harmonic of the rectangular voltage of the inverter.

Since the value of the inverter input voltage and the first harmonic voltage of the rectangular voltage at the inverter output are related by a constant factor / determined by an unregulated autonomous voltage inverter required to stabilize the output voltage of the signal;

(l4 cpcos L. UuJJLoiJbi D

where and. - voltage at the output of the voltage adjuster; k is the coefficient of the inverter circuit 2; , UQ is the required value of the output voltage; 1c - load current; IO - circular frequency inverter; Bf is the inductance of the filter; L - the angle between the current vector

the load and the vector of the first harmonic of the rectangular voltage of the inverter.

The coefficient of the inverter circuit is determined by the formula.

L k ...,, (4) where Uj is the output voltage of the regulator 1;

/ Un / is the voltage value of the first harmonic of the rectangular voltage from the output of the inverter 2.

Decomposition of the radical in the power series and neglecting the higher order terms, we obtain a simpler expression for the voltage setting of 5

0 A + BlrtSin L- CdrtCOsAj. .. (5) where Uj is the set point output voltage;

fljbfC - constant coefficients; JH is the load current; A is the angle between the current / load vector and the first harmonic vector of the rectangular across the inverter voltage.

The constant coefficients are determined by the formula

 kU

0 /

(6):

ktfLcj)

(7)

ku) Let (8)

2Ue

The second and third terms in formula 5 are output perturbation correction signals and provide compensation for the voltage drop across the filter 3.

The device works as follows.

A constant voltage regulator 1 changes the magnitude of the incoming input voltage to it in accordance with the error signal. incoming from the element of comparison 6 Constant output voltage of the regulator voltage is supplied to the inverter 2, where it is converted into a rectangular alternating voltage and after filtering in filter 3 is applied to the load 4. The load current flowing in the output buses of the converter after the transformer 7 passes through a filter 8 to suppress noise and harmonics that may be present in a real load current. Phase distortions on the main harmonic filter 8 almost do not introduce. The sampling clock pulses for sample storage cells 9 and 10, the duration of the order of 0.01 period of the inverter frequency, are formed in the discrete part of the inverter control system and are rigidly connected to the square voltage of inverter 2. Pulse C1 is fed to cell 9 and formed when the sign of the first harmonic of the rectangular voltage from the output of the inverter changes from plus to minus, and the pulse C2 supplied to cell 10 is formed when the first harmonic of the same voltage reaches its maximum. The instantaneous values of the current signal at the moment of action of C1 are proportional to the product of the load current per sine of the angle between the ethnm current and the first harmonic of the rectangular voltage of inverter 2, and at the time of the action of the clock pulse C2 are proportional to the product of the load current by the cosine of the angle between this current and the first harmonic of pr coal pressure. Due to the short duration of the clock pulses, these instantaneous values are practically undistorted and are stored in an analog sample-storage memory 9 and 10, the output of which is a constant voltage proportional to the corresponding works and updated for a period. Further, the signal equal to the magnitude of the load current at the cosine of the angle between the vector of this current and the vector of the first harmonic of the rectangular voltage of the inverter 2 is raised to the square by block 13 and, together with the signal, the equality of the product of the value of the load current by the sine angle between the vector of this current and the first vector rat oHHKH of the rectangular voltage of the inverter 2 and the reference voltage from the source 12 is supplied to the analog adder 11, where the sum is calculated; signals, taking into account the coefficients of formula 5. When switching load 4, a change in the magnitude or phase of the load current occurs and, with delay, baths of not more than one period are detected by the device and, as a voltage correction signal, are transferred to the regulator 1 through the comparison element than and is achieved. a combination of accuracy and speed of maintaining the voltage unchanged on the filter 3,

The use of the proposed device allows improving the quality of the output voltage of stabilized autonomous sources of alternating current power. An increase in static voltage accuracy and a reduction in the duration of transients leads to a longer service life of powered electrical equipment, a reduction in the operating costs associated with its repair and a decrease in the likelihood of information | Power failures in electronic equipment, i.e. to improve the reliability of consumers of AC energy.

Claims (2)

Invention Formula A device for stabilizing the output voltage of an autonomous inverter with a control system containing a constant voltage regulator connected to the inverter input p a voltage source, the output of which is connected to the first input of the reference element, the second input of which is connected to the output of the constant voltage regulator and the output is from its control input, characterized in that l in order to increase the static accuracy of output voltage stabilization while maintaining speed, the voltage setting unit is equipped with a current-to-voltage converter, a filter, two sample-storage cells, an adder, a quad and a voltage source, and the current-to-voltage converter is connected to the inverter load, its output through the filter is connected to two sample-storage cells, the clock inputs of which are connected to the inverter control system, the output of the first cell directly, and the output of the second cell The quad cutter is connected to cyt aTopyj f: to which the source of the reference voltage is also connected, and the output of the adder is the output of the voltage generator. 0 Sources of information taken into account in the examination 1 Pugachev E.V. and L. Kozelkov, Multifunctional thyristor converter I Electrotechnical with industry, Ser. Conversion Technique, 1978, No. 12, p. 18, 2. Egorov V.A., et al. Regulation and stabilization of the output voltage of the inverter voltage. Sat . Modern tasks of converting equipment, K, 1975, h. 4, s, 157.