RU2436215C1 - Method to increase quality and efficiency of power usage (version 2) - Google Patents

Abstract

FIELD: electricity. ^ SUBSTANCE: levels of higher harmonics, in a flow of power extracted by a non-linear load, are reduced by extraction of their energy in the form of equivalent energy of sequence of unipolar, periodically repeating width-modulated pulses of current, by means of a fully controllable WPM-rectifier of transistor type, which is controlled by a modulating signal, which has been previously formed as a geometric difference of two signals, one of which is equivalent to the current of the non-linear load, the other one - to the current of the main frequency harmonic. Power usage efficiency is increased by utilising power of higher harmonics, by means of its accumulation in the form of DC power. ^ EFFECT: increased quality of power, reduction of non-efficient losses of power in the main flow of power system capacity. ^ 1 dwg

Description

The method relates to electrical engineering and can be used to improve the quality, efficiency of use and reduce unproductive losses of electricity in the main power flow of the power system, as well as increase efficiency by reducing resource consumption in the implementation of these processes.

A known method [1] of improving the quality of electricity, which consists in the fact that the first harmonic, determined by the asymmetry voltage, is isolated from the "voltage of the electric network, and the higher harmonic components rectify the selected voltage harmonics, convert the rectified voltage to alternating voltage with a frequency equal to the frequency of the main harmonic of the network, and return the alternating voltage to the electrical network. " The known method, adopted as an analogue, has several disadvantages, the main of which are as follows. In a known method for improving the quality of electricity, the authors propose the utilization of higher harmonic voltage components. However, it is known that the percentage of harmonics in the supply voltage does not repeat the percentage of harmonics in the current flowing in the power system, which is formed under the influence of a nonlinear load. It is also known that it is the current taken by the nonlinear load that determines the harmonic composition and percentage of harmonics in the power supply network. Thus, a significant decrease in the amplitudes of higher harmonics in the phases of the power system, when implementing the known analogue method, will not occur. The limitations of the known method also lies in the "reduction" of harmonic voltage levels of strictly defined frequencies. In addition, in the implementation of the analogue method, a power transformer is used, which causes additional unproductive power losses.

A known method [2] of improving the quality of electricity, adopted as a prototype, in which to “increase the efficiency of use of electric energy, compare the voltage of the network with the voltage of the reference source of high-quality electric energy, allocate a voltage that is determined by the difference between the voltage of the network and the voltage of the reference source of high-quality electric energy, and the resulting voltage is supplied to consumers of electric energy. " The known prototype method has several disadvantages, one of which is the presence of additional energy costs associated with the use of a “reference source of high-quality electric energy”, the power of which is commensurate with the power taken by the protected loads. It should also be noted that in connection with the use of a combination of voltages in the prototype method for extracting higher harmonics — the supply and reference and the fact of the transformation of higher voltage harmonics, without “special” means of processing them, the prototype method has the same disadvantages as the method analogue, in relation to solving the problem of reducing the influence of higher voltage harmonics, while it has already been pointed out that the harmonic components of the current of the fundamental frequency taken by the nonlinear load have a significant effect oh, whose spectrum does not coincide with the spectrum of voltage harmonics. The resource intensity of the known prototype method is associated, inter alia, with the use of a power transformer in it.

Further, it should be noted about the disadvantages of the prototype method in relation to the utilization of the energy of higher harmonics. Thus, in the known method, it is proposed to “use the obtained voltage after rectification” to “charge the batteries from which DC electrical installations are fed, as well as inverters from which AC electrical installations are fed and (or) by means of which electric energy is returned back to the electric network , and also be disposed of in electrical installations for which the quality of electrical energy is not significant (various electric heaters). ” Thus, in the known method it is proposed to utilize the voltage harmonics, while the higher harmonics of the current generated by the non-linear load, the recycling process does not affect. Thus, on the basis of these shortcomings, the prototype method has low efficiency.

The problem solved by the invention is to improve the quality, efficiency of use and reduce unproductive losses of electricity in the main power flow of the power system and increase efficiency by reducing resource consumption in the implementation of the claimed method.

This is achieved by the fact that according to the proposed method, the total energy of the higher harmonics, the proportion of which must be reduced, is extracted in the form of equivalent energy from a sequence of unipolar, periodically repeating latitudinally modulated current pulses, the duration of which varies according to the law of variation of the envelope of the total current of the above harmonics, and disposed of by storage in the form of direct current energy.

The drawing shows a diagram explaining the essence of the claimed method. The following notation is introduced:

1 - power system

2 - load current sensor

3 - harmonic current filter of the fundamental frequency

4 - phase shifting device

5 - mixer

6 - fully controllable transistor PWM rectifier

7 - energy storage

8 - nonlinear load

The essence of the method is as follows. As you know, in the power network, when non-linear loads are supplied from it, the current shape is distorted due to the appearance of higher harmonic components of the fundamental frequency in it. In this case, when using higher harmonics in the energy extraction process, a transistor PWM rectifier built on IGBT modules, in which the amplifying properties of IGWT transistors and PWM modulation are used simultaneously to form the envelope of the extracted current and to regulate its magnitude, such a rectifier is frequency-selective and can functionally solve the problem of extracting energy of a given harmonic component, or group thereof, from the power flow of a power system selected by a non-linear load, in the form, at one for its further use. In this case, the control of such a rectifier must be carried out using a signal of a given shape.

In the claimed method, the task of increasing efficiency with respect to lowering the levels of higher harmonics in the main power flow of the power system is solved by extracting the total energy of the higher harmonics, the proportion of which must be reduced, by means of a fully controlled PWM rectifier based on IGBT transistors. In this case, in addition to the fact that the latter are used as controlled valves, it is proposed to use their amplifying (control) properties relative to currents. The operation of the transistor rectifier is controlled by a signal of a given shape containing a spectrum of harmonics, the energy of which must be extracted from the power flow of the power system. In this case, selective rectification of the current components of only those frequencies that are contained in the control signal is carried out. Thus, the controlled transistor PWM rectifier provides the minimum harmonics with the mentioned higher harmonics, while the harmonics that are not contained in the spectrum of the control signal do not allow the controlled gates to pass at all. At the output of the controlled transistor PWM rectifier, there is a sequence of unipolar periodically repeating pulse-width modulated pulses, the energy of which for the period of their repetition is equivalent to the energy of the higher harmonics currents extracted from the power system. Moreover, the energy of higher harmonics extracted in this way is utilized by means of its accumulation in the form of direct current energy.

The method is as follows. A signal proportional to the current sampled by the nonlinear load 8, in which there are higher harmonics of the fundamental frequency, is supplied to the input of the harmonic current filter of the fundamental frequency 3 by the load current sensor 2, and to one of the inputs of the mixer 5, the second input of which receives a signal from the output of the phase shifting device 4, proportional to the harmonic current of the fundamental frequency and inverse with respect to it. Thus, the phase-shifting device 4, the signal proportional to the harmonic current of the fundamental frequency, fed to its input from the output of the harmonic current filter of the fundamental frequency 3, is inverted. At the output of the mixer 5, a control signal is generated that is fully controlled by a transistor PWM rectifier 6, which is proportional to the geometric difference of the signals: a signal equivalent to a signal of a non-sinusoidal load current and a signal equivalent to a harmonic current signal of the fundamental frequency. The current generated by a fully controlled transistor PWM rectifier 6 and proportional to the geometric difference of the signals, the spectrum of which contains all the higher harmonics, the power of which must be extracted from the power flow of the power system, enters the energy storage 7. As a result, the percentage of the power of the higher harmonics in the main power network can be reduced to zero, and their energy is utilized through storage.

On the implementation of the claimed method, the following should be noted. The use in the claimed method of a fully controlled PWM rectifier transistor type, operating in key mode at frequencies higher than the frequency of the modulated control signal, is optimal. Moreover, due to the fact that a fully controlled transistor PWM rectifier allows you to arbitrarily, depending on the task, to form the envelope of the rectified current consumed from the supply network, the fraction of energy of the harmonic group redirected for utilization is maximum, and the fraction of their energy remaining in the power network - minimized. Thus, almost the entire power of the group of higher harmonics generated by a nonlinear load is utilized (converted for further useful use), thereby unloading the main power system from itself. The interference from the operation of a fully controlled transistor PWM rectifier can be filtered out using standard solutions with minimal energy and material costs.

In the proposed method, a fully controlled PWM rectifier, while acquiring frequency-selective properties, is used as a rectifier without distortion, with minimal switching losses. In this regard, the use of a fully controlled transistor PWM rectifier for the process of controlled energy extraction of higher harmonics is a necessary condition for its feasibility and at the same time solves the problem of increasing its efficiency. The following fact should also be noted. One of the advantages of extracting a current of a given frequency through a fully controlled transistor PWM rectifier is the simplicity of its reconstruction when changing the conditions of the task. In this case, it is possible to extract energy of both one and a group of harmonics. To do this, just change the modulating control signal. In addition, the possibility of resonance. For the execution of other blocks used to implement the claimed method, well-known standard solutions are used.

Thus, as a result of the sequence of actions reproduced in accordance with the claimed method of improving the quality and efficiency of electricity use, the percentage of the group of higher harmonics in the main power network can be minimized. In this case, almost all the energy of the mentioned group of harmonics, the spectrum of the current taken by the nonlinear load, is utilized through the accumulation in the form of direct current energy. In addition, increasing efficiency in the implementation of the claimed method is achieved by increasing its efficiency by reducing resource consumption, by reducing unproductive losses and material consumption in the process.

INFORMATION SOURCES

1. RF patent No. 2237334, published 2004.05.20.

2. RF patent No. 2320067, published 2007.01.20.

Claims (1)

A way to improve the quality and efficiency of energy use, in which the main power stream of a power system reduces the proportion of higher harmonic components of the fundamental frequency, and their energy is utilized, characterized in that the energy of a group of higher harmonic components, the proportion of which must be reduced in the power flow of a power system selected by a non-linear load , extract in the form of equivalent energy a sequence of unipolar periodically repeating pulse-width modulated current pulses, The number of which changes according to the law of variation of the envelope of the total current of the aforementioned group of higher harmonics, by means of a fully controlled PWM rectifier of a transistor type, and utilized by its accumulation in the form of direct current energy, while the energy extraction process of the aforementioned group of higher harmonics is controlled by a signal preformed as geometric difference: a signal proportional to the current sampled by the nonlinear load and a signal proportional to the harmonic current of the mains Noah frequency.