Three-phase alternating current generating system with voltage inverter

FIELD: electricity.

SUBSTANCE: invention is related to the field of electric engineering and power electronics and can be used for manufacturing of HV three-phase alternating current generating systems for aircraft. The suggested three-phase alternating current generating system with voltage inverter contains a three-phase synchronous generator, a static electric energy transducer based on a three-phase bridge rectifier which inputs are connected to outputs of the synchronous generator, two filter capacitors in the direct current link connected in-series and switched on in parallel to the output terminals of the rectifier and a three-phase bridge voltage inverter which inputs are connected to the rectifier outputs and outputs are connected to inputs of three low-frequency LC filters; a neutral load wire of the generation system is connected to the average point of filter capacitors in the direct current link; an inductance coil is connected by its one output to the neutral load wire of the generation system and by its other output to the neutral wire of the stator three-phase winding of the synchronous generator.

EFFECT: reducing electric losses in elements and improving efficiency ratio of the system as a whole.

2 dwg

 

The invention relates to the field of electrical and power electronics and can be used to build systems generate electrical energy (SGAE) three-phase alternating current for aircraft in which to achieve qualitative indicators output energy applied static Converter of electrical energy (SPAA) with voltage inverter (JN). The primary sources with unstable parameters of the input energy in such systems is synchronous generator with variable speed of rotation of the shaft. Ensuring quality indicators generated electric power is vested in the static Converter and the output power low-pass filter.

For the specified application generation systems important indicator is the weight and dimensions of all elements of the system, the design of which must be pursued to its reduction. Weight and dimensions of the system generate largely determined by the magnitude of the coefficient (η) of its individual elements, so the challenge is to increase the value of this ratio.

A known system for generating electric energy of three-phase AC voltage inverter [Kharitonov S.A. Integral parameters and characteristics invert the ditch voltage in the systems of generating alternating current type variable speed - constant frequency for wind turbines. Scientific Bulletin of the NSTU, Novosibirsk, 1999. No. 2 (7). 92-120 S.], containing three-phase synchronous generator with output neutral wire, static Converter of electrical energy on the basis of the three-phase bridge rectifier, two filter capacitors in the DC link connected in series, and a three-phase bridge voltage source inverter with three low-pass LC filters, zero wire load system connected with the zero wire of the generator and the middle point of the filter capacitors in the DC link.

This system has a number of disadvantages. The connection of the neutral wire synchronous generator with system load generation and the middle point of the filter capacitors in the DC link leads to an increase in current of the generator is approximately2[Kharitonov S.A. Integral parameters and characteristics of voltage source inverters in the systems of generating alternating current type variable speed - constant frequency for wind turbines. Scientific Bulletin of the NSTU, Novosibirsk, 1999. No. 2 (7). 92-120 C.]. This leads to increased electrical losses in the synchronous generator and, as consequence, to decrease in efficiency IR increase the weight and dimensions of the system generation. In addition, changes the operation mode of the bridge rectifier, the resulting decrease in twice the pulsation frequency and twice the amplitude of the ripple in the current of each of the filter capacitors in the DC link, resulting in higher electrical losses in the capacitors, i.e. to decrease the efficiency of the system generation and increase its weight and size.

In addition, the known system for generating electric energy of three-phase AC voltage inverter [Kharitonov S.A., Korobkov A.R., A.S. Khlebnikov and Some other results of the development of power systems for aircraft. Technical electrodynamics, special issue "Power electronics and energy efficiency". Kyiv. Institute of electrodynamics of national Academy of Sciences, 2010, T.1. P.88-89], which is the prototype of the present invention containing three-phase synchronous generator, a static Converter of electrical energy on the basis of the three-phase bridge rectifier, the input of which is connected to the outputs of the synchronous generator, two filter capacitors in the DC link connected in series and connected in parallel to the output terminals of the rectifier, and a three-phase bridge voltage source inverter, the input of which is connected to the outputs of the rectifier, and o the dy - to the inputs of three low-pass LC filters, zero wire load system generation is connected to the middle point of the filter capacitors in the DC link (figure 1).

The disadvantage of this system is that you must install in parallel with the filter capacitors of the DC link current is relatively low ohmic resistors R, which are necessary to reduce the DC component in the output voltage of the system generation, arising from the difference between the static and dynamic characteristics of the power transistors of the inverter, and also in connection with the inaccuracy playback of law control the power transistors of the inverter [Grabovetskaya, GV, Korobkov D.V., Kharitonov, S.A. Features of the operation of the inverter voltage in the system generating electric energy of the aircraft. No. 1 (18), January-June, pp.69-79]. In this work, in particular, it is shown that for the suppression of the DC component in the output voltage of the system generation using negative feedback with integral regulator, provided that the sum of a permanent component without feedback was equal to 1.6, you need to meet the conditions of R<(8÷10)RH0where RH0- load resistance systems generate DC. Given that the voltage across the resistor R is approximately equal to the Ud2Unmaxwhere Un max- the amplitude of the voltage on the load of the system generation, the capacity of each of the resistors R can be (1.6÷2)% of system power generation. Thus, the installation of these resistors will lead to a significant increase of electrical losses in the system generation (in this example, (3.2÷4)% of system power generation), and consequently, to decrease the efficiency and increase the weight and size SHEA.

The objective of the invention is to reduce the weight and dimensions of the system generation by increasing the magnitude of the efficiency of its individual elements.

This object is achieved in that in the known system, the generation of electric energy of three-phase AC voltage inverter, containing three-phase synchronous generator, a static Converter of electrical energy on the basis of the three-phase bridge rectifier, the input of which is connected to the outputs of the synchronous generator, two filter capacitors in the DC link connected in series and connected in parallel to the output terminals of the rectifier, and a three-phase bridge inverter voltage, the turns of which are connected to the outputs of the rectifier, and outputs to the inputs of three low-pass LC filters, zero wire load system generation is connected to the middle point of the filter capacitors in the DC link, enter the inductor, which one output is connected to a zero load wire system generation, and the other to a zero output three-phase stator winding of the synchronous generator.

Scheme of the proposed system generating electric energy of three-phase AC voltage inverter is shown in figure 2.

The generation system includes a synchronous generator (1) with excitation from permanent magnets and three-phase winding on the stator () with output neutral wire (NSG), the static Converter of electrical energy (2) and low-pass LC filter (3). In the static Converter (2) includes a rectifier (4), which can be both unmanaged and managed, in the latter case it can be implemented on any managed security keys; two capacitor DC link (5, 6), connected in series with the output midpoint NWiththe voltage inverter (7). Low-pass LC filter (3) can be implemented by any known scheme such filters in figure 2 as an example, a diagram of the l-shaped LC filter of the second order. It should be noted, Thu is the filter capacitors can be included in the triangle.

Conclusions three-phase winding (THAT) generator (1) connected to respective three-phase inputs (TV) static Converter (2), in which they are connected with three-phase input rectifier (4). Parallel to the findings DC rectifier (4) is connected capacitors (5, 6)connected in series, and their average point NWithconnected with the zero wire of the Nnthe load of the system generation (9) and one of the conclusions of the inductor (8), the second output of which is connected to the output neutral conductor NSGsynchronous generator. Inputs DC voltage inverter (7) is connected with the conclusions of the DC rectifier (4), three output AC inverter connected to the same inputs of low-pass LC filter, the findings of which are connected to the load of the system generation (9).

The proposed system operates as follows.

The inductance L0coil inductance (8) is selected:

3ωWith aGminL0>>23ωWith aGminC,(1)

where ωSG min- minimum cyclic frequency of the synchronous generator voltage, C is the capacitance value of the capacitors (5, 6).

The choice of a value for L0in accordance with equation (1) preserves the "chistipolsky" mode rectifier, because currents with frequency 3ωSG minthe electrical circuit between the points NSGand NWithhas a very high resistance. When this DC this circuit has almost zero resistance, the role of the resistance R in the circuit in figure 1 will perform output impedance DC three-phase zero-circuit rectification (REQ), the maximum value of which according to [I. Kaganov Electron and ion probes. Part III / Ilegenes. - M.: State energy publishing house, Moscow, 1956. - 528 S., Il.] will be equal to:

ReKin32πωWith aGmaxLd+Lq2,(2)

where ωSG max- maximum cyclic frequency of the synchronous generator voltage, Ld, Lqthe Indus is aktivnosti SG along the longitudinal and transverse axes.

It is obvious that the resistance value will satisfy the inequality

ReKin<<Rn0,(3)

because the value ofωWith aGmaxLd+Lq2is the output resistance of the phase synchronous generator, which should be obviously less than the load resistance.

Thus, in the proposed scheme system generating no problems with working DC component in the output voltage of the system generation, as is the inequality (3)is excluded, the resistor R, which reduces the electrical losses in the elements of the system generation, increased efficiency and, consequently, decrease the weight and dimensions of the system.

The system of generating electric energy of three-phase AC voltage inverter, containing three-phase synchronous generator, static transformed the Converter of electrical energy on the basis of the three-phase bridge rectifier the inputs of which are connected to the outputs of the synchronous generator, two filter capacitors in the DC link connected in series and connected in parallel to the output terminals of the rectifier, and a three-phase bridge voltage source inverter, the input of which is connected to the outputs of the rectifier, and the outputs to the inputs of three low-pass LC filters, zero wire load system generation is connected to the middle point of the filter capacitors in the DC link, wherein introducing the inductor, which one output is connected to a zero load wire system generation, and the other to a zero output three-phase stator winding of the synchronous generator.



 

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