RU2394346C1 - Vector method for control of three-phase static converter with asymmetric load - Google Patents

Abstract

FIELD: electric engineering.

SUBSTANCE: in vector method of control they measure instantaneous values of three-phase output value of converter, voltage or current, zero, direct and reverse sequences of output value are detected, values are transformed from three-phase abc-system of coordinates into double-phase system of coordinates. Reference signals are generated for double-phase system of coordinates, as well as comparison signals, control signals are generated proportionally to results of comparison, which are transformed from double-phase system of coordinates into three-phase abc-system of coordinates, three-phase modulating signal of converter is generated. Identified signal of zero sequence is used to generate a signal orthogonal to it, and it is received as the second component of double-phase system of coordinates of zero sequence. All sequences are transformed into rotary dq-system of coordinates, reference signal for d-component of direct sequence is generated according to rated value of output value, reference signals for remaining components of sequences are generated as zero. Specified signals of comparison are generated for each component of sequences by integration of differences in according reference signals and d- and q- component sequences, and modulating signal is generated by summation of transformed control signals of direct, reverse and zero sequences in abc-system of coordinates.

EFFECT: generation of three-phase symmetric signal of output value with asymmetric load.

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Description

The invention relates to the field of electrical engineering and can be used to control a three-phase static converter with an asymmetric load, which is part of an autonomous system for generating electrical energy, uninterruptible power supply systems, power supply systems, etc.

There is a vector method for controlling a three-phase static converter [RF Patent No. 2207698, Н02М 7/72, Н02Р 9/42, 21/00. Vector way to control a quadrant voltage inverter as part of an alternating current electric power generation system. / S.A. Kharitonov, A.A. Stennikov. - publ. 06/27/2003. - Bulletin No. 18], which measures the voltage and power of the synchronous generator, the network voltage and the voltage at the filter capacitor of the DC link, converts the voltage of the synchronous generator and network voltage from a three-phase abc coordinate system to a two-phase α, β coordinate system , for a two-phase coordinate system, a reference signal is generated for the zero phase angle of the output current for each output phase of the converter in phase with the voltage of the corresponding network phase and a reference signal for the static output power converter, and the power reference signal is 90 ° ahead of the reference signal at the zero phase angle of the output current, the α and β components of the reference signal at the zero phase angle of the output current are formed proportionally to the α and β components of the converted phase network voltages, the α component the signal of the task for the output power of the static converter is formed as the product of the β-component of the mains voltage and the signal generated as the difference of the signal proportional to the power supplied by the generator and the signal is determined much like the difference between the voltage reference signal at the filter capacitor and the voltage feedback signal at the filter capacitor, the β-component of the reference signal to the output power of the static converter is formed as the product of the α-component of the mains voltage taken with the opposite sign and the signal generated as the signal difference proportional to the power supplied by the generator, and a signal defined as the difference between the voltage reference signal at the filter capacitor and the voltage feedback signal at filter capacitor, form the α- and β-components of the control signal by summing respectively the α- or β-components of the reference signal to the zero phase angle of the output current and the reference signal to the output power of the static converter, form a modulating signal with an inverter by converting the α- and β-components of the control signal from a two-phase α, β-coordinate system to a three-phase abc-coordinate system.

This method is implemented with a symmetrical network voltage system and takes into account only the direct sequence of the three-phase network voltage system. In addition, the conversion to the α, β-coordinate system, where the components are sinusoidal signals, does not allow for high control accuracy due to the finiteness of the gain of the respective control loops.

The vector method of controlling the converter is known [RF Patent No. 2144729, Н02М 5/27, G05F 1/40. Vector way to control the converter. / S.A. Kharitonov, Mashinsky V.V. - publ. 01/20/2000. - Bulletin No. 2], which is the prototype of the present invention and consists in measuring the instantaneous values of a three-phase output value, inverter, voltage or current, isolating the zero sequence of a three-phase output voltage of the inverter, converting the values from a three-phase abc coordinate system to a two-phase α, β-coordinate system, for a two-phase coordinate system and zero sequence, reference signals are generated, comparison signals are generated by subtracting α, β-components and the zero sequence by the voltage of the three-phase output voltage of the inverter from the corresponding reference signals, proportionally to the comparison results form the corresponding control signals, which convert from the two-phase system of α, β-coordinates into a three-phase abc-coordinate system, form a three-phase modulating signal by summing the converted α- and β-components of the control signals and zero sequence control signal.

This method does not regulate the reverse sequence of the three-phase system of output voltages that occurs with an asymmetric load. The conversion to the α, β coordinate system used, where the components are sinusoidal signals, does not allow for high control accuracy due to the finiteness of the gain of the corresponding static control loops in the α and β components and the zero sequence. As a result, with an asymmetric load, the output voltage of the converter during the implementation of this method will be asymmetric.

The objective of the invention is to form a symmetric three-phase output quantity, voltage or current, with an asymmetric load.

The problem is achieved in that in the known method of controlling a three-phase converter, which consists in measuring the instantaneous values of a three-phase output quantity of a converter, voltage or current, isolating a zero sequence of an output quantity, converting values from a three-phase abc coordinate system to a two-phase coordinate system, for two-phase coordinate systems form reference signals, form comparison signals, in proportion to the comparison results form regulatory signals that they transform from a two-phase coordinate system into a three-phase abc-coordinate system, form a three-phase modulating signal of the converter, form an orthogonal signal from the selected zero-sequence signal and take it as the second component of the two-phase coordinate system of the zero sequence, extract the direct and reverse sequences from the three-phase output value of the converter , the direct, reverse and zero sequences are converted into a rotating dq-coordinate system, the reference signal is I of the d-component of the direct sequence is formed according to the nominal value of the output quantity, the reference signals for the remaining components of the direct, reverse and zero sequences are formed by zero, these comparison signals are formed for each component of the direct, reverse and zero sequences by integrating the differences of the corresponding reference signals and d- and q-component sequences, and the specified modulating signal is formed by summing the converted control signal positive, negative and zero sequence in the abc-system coordinates.

и

(блоки 21 и 22), обратной последовательности

и

(блоки 23 и 24) и прямой последовательности

и

(блоки 25 и 26). Выходы соответствующих схем вычитания соединены с входами интеграторов d- и q-составляющих нулевой последовательности

и

(блоки 27 и 28), обратной последовательности

и

(блоки 29 и 30) и прямой последовательности

и

(блоки 31 и 32). Выходы интеграторов d- и q-составляющих каждой последовательности через пропорциональные звенья (блоки 33, …, 38) соединены с входами схем обратного преобразования координат ПК^-1 для нулевой последовательности (блок 39), обратной последовательности (блок 40) и прямой последовательности (блок 41). Выходы схем обратного преобразования координат ПК^-1 нулевой, обратной и прямой последовательностей пофазно соединены с входами сумматоров (блоки 42, 43 и 44). Выходы сумматоров (блоки 42, 43 и 44) соединены с входами системы импульсно-фазового управления СИФУ (блок 1).The drawing shows one of the possible structural schemes that implement the proposed method for stabilizing the output voltage of the Converter. It contains a SIPU pulse-phase control system (block 1), the outputs of which are connected to the power circuit of the inverter static frequency converter (block 2). The power circuit of the converter is also connected to the primary source of electricity with unstable parameters Uc (block 3). The output of the power circuit of the inverter static frequency converter (block 2) through the output filter Ф (block 4) is connected to the unbalanced load N (block 5). At the same time, the output of the converter is connected to the inputs of the allocation circuits of zero Z (block 6), reverse N (block 7) and direct P (block 8) of the output voltage sequences. The output of the zero sequence allocation circuit Z (block 6) through the orthogonal component formation circuit Δφ (block 9) and is directly connected to the inputs of the coordinate transformer PK2 (block 10). The outputs of the circuits for extracting the reverse N (block 7) and direct P (block 8) sequences through the corresponding coordinate converters PK1 (blocks 11 and 12) are connected to the input of the coordinate converters PK2 for the reverse (block 13) and direct (block 14) sequences. The outputs of the coordinate converters PK2 of the zero sequence (block 10), the negative sequence (block 13) and the direct sequence (block 14) are connected to the corresponding inputs of the subtraction schemes of the d- and q-components of the zero sequence (blocks 15 and 16), the negative sequence (blocks 17 and 18) and direct sequence (blocks 19 and 20). The second inputs of the indicated schemes for subtracting sequences are connected to the outputs of the schemes for the formation of reference signals of d- and q-components of the zero sequence

and

(blocks 21 and 22), reverse sequence

and

(blocks 23 and 24) and direct sequence

and

(blocks 25 and 26). The outputs of the corresponding subtraction schemes are connected to the inputs of the integrators of the d- and q-components of the zero sequence

and

(blocks 27 and 28), reverse sequence

and

(blocks 29 and 30) and direct sequence

and

(blocks 31 and 32). The outputs of the integrators of the d- and q-components of each sequence through proportional links (blocks 33, ..., 38) are connected to the inputs of the inverse coordinate transformation circuits PC ^-1 for the zero sequence (block 39), the reverse sequence (block 40) and the direct sequence (block 41). The outputs of the schemes of the inverse transformation of coordinates PC ^{-1 of} zero, reverse, and forward sequences are phase-connected to the inputs of the adders (blocks 42, 43, and 44). The outputs of the adders (blocks 42, 43 and 44) are connected to the inputs of the pulse-phase control system SIFU (block 1).

The SIFU pulse-phase control system (block 1) is a standard control system that implements the vertical control principle (see BC Rudenko, V. I. Senko, I. M. Chizhenko. Fundamentals of converting technology. - M.: Higher school, 1980). The power circuit of a static frequency inverter (block 2) is an autonomous voltage inverter using fully controllable switches (see BC Rudenko, V. I. Senko, I. M. Chizhenko. Fundamentals of converter technology. - M.: Higher school, 1980) ; primary source of electricity with unstable parameters Uc (block 3) - battery; output filter F (block 4) is a low-pass filter that suppresses the high-frequency components of the spectrum of the output value, for example, a single-link LC filter; unbalanced load N (block 5) - parallel or series connection of the resistor and inductor.

The schemes for isolating zero Z (block 6), reverse N (block 7) and direct P (block 8) of the output voltage sequences realize the decomposition of asymmetric three-phase systems into symmetrical components, known from the theoretical foundations of electrical engineering (see L.R. Neumann, K.S. . Demirchyan. Theoretical Foundations of Electrical Engineering: A Textbook for High Schools. - Volume 1. - L .: Energy Publishing House. Leningrad Department, 1981) and can be single-phase (block 6) and three-phase symmetric (blocks 7 and 8) sinusoidal shapers whose amplitudes are determined by known elations

,

,

- комплексные амплитуды фаз выходных несимметричных напряжений;

- комплексный множитель, обеспечивающий смещение фазы сигнала на

|…| - модуль комплексного числа.Where

,

,

- complex phase amplitudes of output unbalanced voltages;

- a complex factor that provides a phase shift of the signal by

| ... | is the module of a complex number.

The scheme for the formation of the orthogonal component Δφ (block 9) can be a 90 ° phase-shifting circuit at a constant frequency Ω with normalization of the amplitude of the phase-shifted signal (see. Theory of automatic control. Part 1. Theory of linear systems of automatic control. / Ed. A.A . Voronova. Textbook for universities. - M .: Higher school, 1977) or a digital filter (see Sergienko AB Digital signal processing. - St. Petersburg: Peter. - 2006. - 751 p.). Coordinate converters PK1 (blocks 11 and 12) implement the well-known Clarke transforms (see Vazhnov A.I. Transients in AC machines. - L .: Energy, Leningrad. Department, 1980) from a three-phase abc coordinate system to a two-phase orthogonal αβ coordinate system and can be a scheme of summing and subtracting analog signals on operational amplifiers (see. Theory of automatic control. Part 1. Theory of linear systems of automatic control. / Ed. by A.A. Voronov. Textbook for universities. - M .: High school, 1977). The coordinate converters PK2 for the zero (block 10), reverse (block 13), and direct (block 14) sequences realize the transformation of the Signal Park from the αβ coordinate system into a dq coordinate system rotating at a constant frequency Ω (see Vazhnov A.I. Transient processes in AC machines. - L.: Energy, Leningrad. Department, 1980) and can be analog signal multipliers (see Timoneev V.N., Velichko L.M., Tkachenko V.A. Analog signal multipliers in electronic equipment. - M .: Radio and communications. - 1982. - 112 p.). Subtraction schemes for the zero sequence (blocks 15 and 16), the reverse sequence (blocks 17 and 18) and the direct sequence (blocks 19 and 20), integrators (blocks 27, ..., 32), proportional links (blocks 33, ..., 38) and adders (blocks 42, ..., 44) are typical elementary units known from the theory of automatic control (see. Theory of automatic control. 41. Theory of linear systems of automatic control. / Under the editorship of A.A. Voronov. Textbook for universities . - M.: Higher School, 1977). Schemes of the formation of reference signals (blocks 21, ..., 26) are parametric voltage stabilizers (see Sources of power supply of electronic equipment: Reference / Edited by G.S. Naivelt. - M .: Radio and communication, 1986). Inverse coordinate transformation schemes PC ^-1 implements a transformation from a rotating two-phase dq-coordinate system to a three-phase abc-coordinate system (see Vazhnov A.I. Transients in AC machines. - L.: Energy, Leningrad. Department, 1980 ) and can be analog signal multipliers (see Timoneev V.N., Velichko L.M., Tkachenko V.A. Analog signal multipliers in electronic equipment. - M.: Radio and communications. - 1982. - 112 p. )

The method is as follows. The asymmetric three-phase load voltage N (block 5) is supplied to the allocation circuits of zero Z (block 6), reverse N (block 7) and direct P (block 8) of the output voltage sequences. At the outputs of these circuits, alternating voltages of the fundamental frequency Ω are formed: single-phase (block 6) and three-phase (blocks 7 and 8) of a certain amplitude, in accordance with expressions (1). The circuit for the formation of the orthogonal component Δφ (block 9) shifts the phase of the input signal by 90 ° and normalizes the amplitude of the output signal, making it equal to the amplitude of the input signal. The output signal of the zero sequence extraction circuit Z (block 6) is adopted as the α-component of the zero sequence, and the output signal of the formation circuit of the orthogonal component Δφ (block 9) as the β-component of the zero sequence. The coordinate converters PK1 of the reverse (block 11) and direct (block 12) sequences form the α- and β-components of the reverse and direct sequences. From these α- and β-components for the zero, reverse and direct sequences in the coordinate converters PK2, the own phase angle φ _i is determined, using which the d- and q-components of zero (block 10) and symmetric inverse are formed at the outputs of the coordinate converters PK2 (block 13) and direct (block 14) sequences, which are DC voltages. At the outputs of the subtraction schemes (blocks 15, ..., 20), the difference between the corresponding reference signals (DC voltage) and the d- and q-components is formed of zero (blocks 15, 16), reverse (blocks 17, 18) and direct (blocks 19, 20) sequences (DC voltage). These differences are integrated (blocks 27, ..., 32), and at the outputs of the corresponding integrators, signals are generated for comparing the d and q components of the zero (blocks 27, 28), reverse (blocks 29, 30) and direct (blocks 31, 32) sequences which are scaled by linear links (blocks 33, ..., 38). The control signals generated at the outputs of the linear links for each sequence (blocks 33, ..., 38) are converted by inverse coordinate schemes PC ^-1 (blocks 39, 40, 41) from the dq coordinate system to a three-phase abc coordinate system. The output voltages of the inverse coordinate transformation circuits PC ^-1 (blocks 39, 40, 41) are phase-summed in the adders (blocks 42, 43, 44), at the output of which modulating signals are generated for the SIFU pulse-phase control system (block 1). Based on these modulating signals, the SIFU pulse-phase control system (block 1) generates control pulses that are supplied to the controlled keys of the power circuit of the inverter static frequency converter (block 2). The power keys are switched in accordance with the change in the modulating signals, and thereby the conversion of the electric energy of the primary source of electricity with unstable parameters Uc (block 3) into a three-phase voltage of a given frequency and magnitude is realized. The output filter F (block 4) significantly reduces the high-frequency components in the spectrum of the output voltage, approximating the shape of the output voltage to a sinusoidal one.

The formation of a symmetric three-phase output voltage under an unbalanced load is achieved due to the fact that when converting signals from a three-phase abc coordinate system to a rotating dq coordinate system of the selected symmetrical voltages, the d- and q-components of each sequence are DC voltages, and when integrating the corresponding difference DC signals in steady state and in the linear range of operation of all elements of the control system, astatism is realized zero th order in the regulation of each component. In this case, the relations

- d(q)-составляющая одной из последовательностей; i=Z, N, P - нулевая, обратная или прямая последовательность.Where - a reference signal for the d (q) component of one of the sequences;

- d (q) is a component of one of the sequences; i = Z, N, P - zero, reverse or direct sequence.

If the reference signals of the d- and q-components of the zero and reverse and q-component of the direct sequence are formed as zero, and the reference signal of the d-component of the direct sequence is formed according to the nominal value of the output voltage, then according to expressions (2), the output voltage will be a direct sequence with specified value of the amplitude. The amplitudes of the reverse and zero sequences will be zero. Thus, the output voltage will be a three-phase, symmetrical voltage with an unbalanced load.

Claims (1)

The vector way to control a three-phase static converter with an asymmetric load, which consists in measuring the instantaneous values of a three-phase output value of a converter, voltage or current, extracting a zero sequence of an output quantity, converting values from a three-phase abc coordinate system to a two-phase coordinate system, for a two-phase coordinate system form reference signals, form comparison signals, in proportion to the comparison results form regulatory signals that convert They are connected from a two-phase coordinate system to a three-phase abc-coordinate system, a three-phase modulating signal of the converter is formed, characterized in that a signal orthogonal to it is formed from the extracted zero-sequence signal and accepted as the second component of the two-phase zero-coordinate coordinate system, and the converter is isolated from the three-phase output value direct and reverse sequences, direct, reverse and zero sequences are transformed into a rotating dq-coordinate system, etal The reference signal for the d-component of the direct sequence is formed according to the nominal value of the output quantity, the reference signals for the remaining components of the forward, reverse and zero sequences are zero, these comparison signals are generated for each component of the forward, reverse and zero sequences by integrating the differences of the corresponding reference signals and d - and q-component sequences and the specified modulating signal is formed by summing the converted control direct signals, reverse and zero sequences in the abc coordinate system.