RU2442275C1 - Method for controlling three-phase static converter with unbalanced load - Google Patents

Abstract

FIELD: electrical engineering; three-phased static converter with unbalanced load. ^ SUBSTANCE: according to the method, the instantaneous value of the three-phase output variable of the converter, the voltage or current are measured, the zero-phase sequence of the output variable is separated out, the calibration signal for the zero-phase sequence equal to zero is formed, a comparison signal is formed by substracting the zero-phase sequence from the calibration signal, a three-phase control signal is formed for stabilization or adjustment of the output variable, voltage or current parameters, a three-phase modulating converter signal is formed, harmonic components with high amplification gain are separated out in the comparison signal, a feedback signal of the zero-phase sequence is formed by combining the separated harmonic components, and the said modulating signal is formed by combining the feedback signal with the control signals of all phases. ^ EFFECT: increase of the three-phase output signal (voltage or current) quality by means of suppressing the zero-phase sequence which appears in the output signal if the load in unbalanced. ^ 1 dwg

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.

A known method of controlling a three-phase static Converter [RF Patent No. 2207698 Н02М 7/72, Н02Р 9/42, 21/00. A vector way to control a quadrant voltage inverter as part of an alternating current electric energy 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 the 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 in proportion 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, 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. The method does not realize the reduction of the reverse and zero sequences with an asymmetric system of voltages, the last of which is the most dangerous, since it causes the magnetization of electromagnetic elements powered by the voltage generated by the converter.

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

When using a static converter to convert the energy of the primary source into the output energy with the specified parameters as a result of switching the converter valves, the output quantity, voltage or current will contain a wide range of harmonic components. In this case, the main harmonic component and harmonic components that are multiples of three, with an asymmetric load form a zero sequence. Therefore, the quality of the generated energy will be low due to the presence of components of the zero sequence, and their suppression will be ineffective due to the finiteness of the gain of the corresponding control loop.

The objective of the invention is to improve the quality of the generated electricity (voltage or current) by suppressing in the output signal the components of the zero sequence that occur 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 value of the converter, voltage or current, extracting a zero sequence of the output quantity, generating a reference signal for a zero sequence equal to zero, generating a comparison signal by subtracting the zero sequence of the signal from the reference signal of the zero sequence, form a three-phase control signal to stabilize or adjusting the parameters of the output quantity, voltage or current, a three-phase modulating signal of the converter is generated, harmonic components with a high gain are extracted in the zero-sequence comparison signal, a zero-sequence feedback signal is generated by summing the selected harmonic components, and the specified modulating signal is formed by summing the zero-sequence feedback signal with control signals of each phase.

(блок 7) и

(блок 8) соединены с соответствующими вычитаемыми входами схем вычитания d- и q-составляющих (блоки 9 и 10). Вторые уменьшаемые входы указанных схем вычитания последовательностей соединены с выходами схем формирования эталонных сигналов d- и q-составляющих напряжения

и

(блоки 11 и 12). Выходы соответствующих схем вычитания соединены с входами пропорционально-интегральными регуляторами d- и q-составляющих PI^d и PI^q (блоки 13 и 14). Выходы пропорционально-интегральных регуляторов d- и q-составляющих соединены с входами схем обратного преобразования координат ПК^-1 (блок 15). Выходы схем обратного преобразования координат ПК^-1 соединены с входами сумматоров (блоки 16, 17 и 18). Выходы сумматоров (блоки 16, 17 и 18) соединены с входами системы импульсно-фазового управления СИФУ (блок 1). Выходные фазы нагрузки соединены с входами сумматора (блок 19) и через пропорциональное звено 1/3 (блок 20) соединены с вычитающим входом схемы вычитания (блок 21). Уменьшаемый вход схемы вычитания (блок 21) соединен с выходом схемы формирования эталонного сигнала нулевой последовательности U_ЭТ0 (блок 22). Выход схемы вычитания (блок 21) соединен с входами схем выделения гармонических составляющих нулевой последовательности W_p1 (блок 23), W_p2 (блок 24), W_pN (блок 25). Выходы схем выделения гармонических составляющих нулевой последовательности (блоки 23, 24, 25) соединены с входами сумматора (блок 26). Выход сумматора соединен со вторыми входами сумматоров (блоки 16, 17, 18).Figure 1 shows one of the possible structural schemes that implement the proposed method. Figure 2 and figure 3 presents the simulation results, confirming the effectiveness of the proposed method. The block diagram (Fig. 1) 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 converter output is directly connected to the inputs of the PC coordinate converter (block 6). Outputs of PC coordinate converters via proportional links

(block 7) and

(block 8) are connected to the corresponding deductible inputs of the subtraction schemes of d- and q-components (blocks 9 and 10). The second diminished inputs of these sequence subtraction schemes are connected to the outputs of the d-and q-component voltage generating circuits

and

(blocks 11 and 12). The outputs of the corresponding subtraction circuits are connected to the inputs of the proportional-integral regulators of the d- and q-components PI ^d and PI ^q (blocks 13 and 14). The outputs of the proportional-integral regulators of the d- and q-components are connected to the inputs of the inverse coordinate transformation circuits PC ^-1 (block 15). The outputs of the schemes of the inverse coordinate transformation PC ^{-1 are} connected to the inputs of the adders (blocks 16, 17 and 18). The outputs of the adders (blocks 16, 17 and 18) are connected to the inputs of the pulse-phase control system SIFU (block 1). The output phases of the load are connected to the inputs of the adder (block 19) and through the proportional link 1/3 (block 20) are connected to the subtracting input of the subtraction circuit (block 21). The reduced input of the subtraction circuit (block 21) is connected to the output of the zero sequence reference signal generating circuit U _ET0 (block 22). The output of the subtraction circuit (block 21) is connected to the inputs of the zero sequence harmonic components W _p1 (block 23), W _p2 (block 24), W _pN (block 25). The outputs of the circuits for the allocation of harmonic components of the zero sequence (blocks 23, 24, 25) are connected to the inputs of the adder (block 26). The output of the adder is connected to the second inputs of the adders (blocks 16, 17, 18).

The SIFU pulse-phase control system (block 1) is a standard control system that implements the vertical control principle (see BCRudenko, 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.

или

, реализуемые в аналоговом виде (см. Теория автоматического управления. Ч.1. Теория линейных систем автоматического управления. Под ред. А.А.Воронова. Учеб. пособие для вузов. - М.: Высш. школа, 1977), а для исключения температурной зависимости параметров звеньев в цифровом виде (см. Сергиенко А.Б. Цифровая обработка сигналов. - СПб.: Питер. - 2006. - 751 с.).The PC coordinate converter (block 6) implements the conversion of the Signal Park from the abc coordinate system to the dq coordinate system rotating at a constant frequency Ω (see Vazhnov A.I. Transient processes in AC machines. - L.: Energy, Leningrad. -nie, 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.). Proportional links (blocks 7, 8 and 20), subtraction schemes (blocks 9, 10 and 21), proportional-integral controllers (blocks 13 and 14) and adders (blocks 16, 17, 18, 19 and 26) are typical elementary links known from the theory of automatic control (see. Theory of automatic control. 41. Theory of linear systems of automatic control. Edited by A.A. Voronov. Textbook for universities. - M.: Higher school, 1977). Schemes of the formation of reference signals (blocks 11, 12 and 22) are parametric voltage stabilizers (see Sources of power supply of electronic equipment: Reference / Edited by G.S. Naivelt. - M .: Radio and communication, 1986). Schemes for the inverse transformation of coordinates PK ^-1 (block 15) implement the conversion 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 -nie, 1980) and can be multipliers of analog signals (see Timoneev V.N., Velichko L.M., Tkachenko V.A. Analog signal multipliers in electronic equipment. - M.: Radio and communications. - 1982. - 112 p.). The allocation schemes of the harmonic components W _pi (blocks 23, 24 and 25) can be resonant links, for example,

or

implemented in analog form (see. Theory of automatic control. Part 1. The theory of linear systems of automatic control. Edited by A.A. Voronov. Textbook for universities. - M .: Higher school, 1977), and for exceptions for the temperature dependence of link parameters in digital form (see Sergienko AB, Digital Signal Processing. - St. Petersburg: Peter. - 2006. - 751 p.).

The method is as follows. An asymmetric three-phase load voltage N (block 5) is supplied to the outputs of the adder (block 19) and then to the input of the proportional link (block 20), at the output of which a zero sequence of load voltage is formed. The zero sequence of the load voltage is fed to the subtracting input of the subtraction circuit (block 21). At the reduced input of the subtraction circuit (block 21), a zero reference signal of the zero sequence of the load voltage U _{ET0 is supplied} (block 22). From the output of the subtraction circuit (block 21), the harmonic components of the zero sequence of the output voltage with a high gain, which are to be excluded from the zero sequence, are selected by the resonant links W _pi (blocks 23, 24, and 25). These selected harmonic components are summed (block 26), and a zero sequence feedback signal is generated at the output of the adder.

и

(блоки 11 и 12) пропорциональными звеньями

и

(блоки 7 и 8). На выходах схем вычитания (блоки 9 и 10) формируется разность соответствующих эталонных сигналов и d- и q-составляющих выходного напряжения. Эти разности преобразуются пропорционально-интегральными регуляторами d- и q-\3+At the same time, an asymmetric three-phase load voltage N (block 5) is supplied to the output of the PC coordinate converter (block 6), at the output of which d- and q-components of the output voltage are formed, which are consistent in magnitude with the reference signals

and

(blocks 11 and 12) by proportional links

and

(blocks 7 and 8). At the outputs of the subtraction schemes (blocks 9 and 10), a difference is formed between the corresponding reference signals and the d- and q-components of the output voltage. These differences are transformed by proportional-integral controllers d- and q- \ 3+

components PI ^d and PI ^q (blocks 13 and 14), and at the outputs of the respective proportional-integral controllers, comparison signals of d and q components (blocks 13 and 14) are generated. The signals generated at the outputs of the proportional-integral regulators are converted by the inverse coordinate transformation circuit PC ^-1 (block 15) from the dq-coordinate system to a three-phase abc-coordinate system. The output voltage of the inverse coordinate transformation circuit PC ^-1 (block 15), which are the control signals of the converter phases, are summed with the zero sequence feedback signal in the adders (blocks 16, 17, and 18), at the outputs of which modulating signals are generated for the pulse-phase system SIFU control (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) reduces its high-frequency components in the spectrum of the output voltage, approximating the shape of the output voltage to a sinusoidal one.

The exception of the harmonic components of the zero sequence of the load voltage is achieved due to the fact that in the proposed control method, in contrast to the prototype method, for each excluded harmonic component of the zero sequence, its own is used, and a very large gain and selection of each component occurs with a phase shift close to to zero, and not the same gain for all harmonic components, as in the prototype method.

Compare the presence of harmonic components in the zero sequence for the prototype method and the proposed control method.

For the prototype method, the output phase load voltage can be represented as:

;

;

- изображение фазного напряжения нагрузки;Where

- image of the phase voltage of the load;

- изображение эталонного сигнала нулевой последовательности;

- image of the reference signal of the zero sequence;

- изображение нулевой последовательности выходного напряжения;

- image of the zero sequence of the output voltage;

- конечный коэффициент усиления сигнала сравнения;

- final gain of the comparison signal;

- управляющий сигнал i-ой фазы, определяющий прямую и

- the control signal of the i-th phase, which determines the direct and

reverse sequence of load voltage;

- коэффициент усиления силовой схемы преобразователя с учетом СИФУ;

- gain of the power circuit of the converter taking into account SIFU;

- изображение передаточной функции линейной части

- image of the transfer function of the linear part

converter taking into account load asymmetry;

i = a, b, c.

We define the image of the zero sequence by relations (1) as 1/3 of the sum of the phase load voltages, express the zero sequence from the resulting sum, and obtain the expression:

=0 величина гармонических составляющих нулевой последовательности определяется вторым слагаемым числителя выражения (2) и при ограниченном значении К_OC будет иметь конечную величину.When performing equality

= 0, the value of the harmonic components of the zero sequence is determined by the second term of the numerator of expression (2) and, with a limited value of K, _OC will have a finite value.

For the proposed method in accordance with figure 1, the output phase load voltage can be represented as:

- передаточная функция схемы выделения i-ой гармонической составляющей нулевой последовательности.Where

- the transfer function of the allocation circuit of the i-th harmonic component of the zero sequence.

We define the zero sequence by relations (3) as 1/3 of the sum of the phase load voltages, express the zero sequence from the resulting sum and obtain the expression:

Define by expression (4) the value of the k-th harmonic component ω _k in the zero sequence of the load voltage for the proposed control method. To do this, we present in the sums of the numerator and denominator of expression (4) the transfer function of the allocation scheme of the k-th harmonic component ω _k in the form:

The image of the reference signal of the zero sequence can be represented as:

- постоянный, нулевой сигнал.Where

- constant, zero signal.

, которое равно нулю, обращаются в ноль. Выражение (4) преобразуется к виду:After that, we bring to the common denominator the expressions of the numerator and denominator in formula (4) and replace the complex variable S with jω _k . As a result, all terms of the numerator and denominator of expression (4) multiplied by

, which is zero, vanish. Expression (4) is converted to the form:

=0, то это означает, что амплитуда к-ой гармонической составляющей в нулевой последовательности напряжения на нагрузке так же равна нулю. Таким образом, происходит исключение к-ой гармонической составляющей в нулевой последовательности напряжения на нагрузке.If the value

= 0, then this means that the amplitude of the k-th harmonic component in the zero sequence of voltage at the load is also equal to zero. Thus, the kth harmonic component is eliminated in the zero sequence of voltage at the load.

Arguing in a similar way, it can be shown that in the zero sequence of the voltage across the load with the proposed control method, all selected components of the zero sequence of the voltage across the load will be excluded. Therefore, with the proposed control method, an improvement in the quality of the output three-phase signal (voltage or current) is achieved by suppressing in the output signal the zero sequence that occurs with an asymmetric load.

A similar result is obtained if a link of the form is used as a scheme for distinguishing harmonic components of the zero sequence of a three-phase asymmetric quantity:

Figure 2 presents the simulation results in Matlab Simulink of a bridge voltage inverter that generates a voltage of 400 Hz and operates with a phase voltage of 115 V (airborne electrical energy generation system) without regulating the harmonic components of the zero voltage sequence. The switching frequency of the inverter keys is 20 kHz. Active load resistances for phases A, B and C are respectively 2 Ohms, 3 kOhms and 3 kOhms. Figure 2 shows the phase voltage of the load (first graph), d- (upper curve) and q- (lower curve) components of the load voltage (second graph) and the zero sequence of the load voltage (third graph). Figure 3 presents the curves similar to those in figure 2 when implementing the proposed control method and highlighting the first and third harmonic components of the zero sequence of the load voltage. The simulation results confirm the improvement in the quality of the output three-phase signal (voltage or current) due to the suppression in the output signal of the zero sequence that occurs with an asymmetric load for the proposed control method.

Thus, the task of the proposed control method, namely: improving the quality of the generated electricity (voltage or current) by suppressing in the output signal the components of the zero sequence that occur with an asymmetric load, is proved.

Claims (1)

A method of controlling a three-phase static converter with an asymmetric load, which consists in measuring the instantaneous values of a three-phase output value of the converter, voltage or current, extracting the zero sequence of the output quantity, generating a reference signal for the zero sequence equal to zero, generating a comparison signal by subtracting the zero sequence of the signal from reference signal of the zero sequence, form a three-phase control signal for stabilization or regulation I parameters of the output quantity, voltage or current, form a three-phase modulating signal of the converter, characterized in that harmonic components with a high gain are extracted in the zero-sequence comparison signal, a zero-sequence feedback signal is formed by summing the selected harmonic components, and the specified modulating signal is formed by summing the feedback signal communication of the zero sequence with the control signals of each phase.

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