RU2435273C1 - Method to increase efficiency of power usage (version 1) - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: from a power flow extracted by an active-inductive load, by means of a fully controllable transistor PWM rectifier, an inductive component is extracted, as an equivalent energy of sequence of unipolar, periodically repeating width-modulated pulses of current, duration of which changes according to the law of change of envelope of inductive current component, and after its conversion, using a controlled power source, such as a PWM inverter extracted, is returned into a power system as active energy by means of current harmonics of the main frequency.

EFFECT: reduction of non-efficient losses in flow of power system capacity.

1 dwg

Description

The method relates to electrical engineering and can be used to increase the efficiency of electricity use, by reducing unproductive losses in the power flow of the power system.

A known method of reactive power compensation (1), adopted as an analogue, in which the inductive component of the current generated by the non-linear load is compensated by the capacitive current of capacitor banks (BC). The known analogue method has disadvantages, the main of which are the dependence of the reactive power generated by the BC from the voltage and their sensitivity to distortions in the shape of the supply voltage. In this case, there is a short service life of the battery and their insufficient electrical strength.

The known method (2), adopted as a prototype, in which a part of the energy that causes its unproductive losses is extracted from the power flow taken by an inactive load, and after conversion to the harmonic of the fundamental frequency, it is returned to the power system. In the known method, compensation for reactive “power” is not provided, and thus, unproductive energy losses due to reactive currents occur.

The problem solved by the invention is to increase the efficiency of electricity use.

This is achieved by the fact that according to the proposed method, the inductive component is extracted from the power flux selected by the active-inductive load, in the form of an equivalent energy sequence of unipolar, periodically repeating pulse-width modulated current pulses, the duration of which varies according to the law of the envelope of the inductive component of the current, and, after its conversion, they are returned to the power system in the form of active energy by means of a current of fundamental frequency.

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 - fully controlled transistor PWM rectifier

4 - capacitive storage

5 - controlled power converter

6 - voltage sensor

7 - nonlinear load

8 - block generating a logical signal

9 - block generating a modulating signal

The essence of the method is as follows. As you know, in a power grid, when active-inductive loads are supplied from it, during a quarter of a period the sign of instantaneous power changes to the opposite. This is due to the fact that part of the energy stored in the magnetic field of the reactive load returns back to the source in the form of reactive current. In this case, the flow of reactive current is provided by the self-induction EMF. In this case, the signs of the supply voltage and EMF of self-induction, as is known, are opposite. The negative effect associated with reactive currents is the additional unproductive loss of energy in the power system. In the claimed method, the task of increasing the efficiency of energy use is solved by reducing its unproductive losses. At the same time, it is proposed to extract from the flow of energy used by the active-inductive load, the inductive component, and after its accumulation and conversion into a current of fundamental frequency, return to the energy system in the form of active energy. The inductive component extraction problem is solved by means of a fully controlled transistor PWM rectifier built on IGBT modules. The flow of the inductive component of the current through each of the arms of a fully controlled transistor rectifier is provided, in each half-cycle of the supply voltage, by the action of the self-induction EMF. In this case, the transistors of each of the arms of the controlled bridge open for the time during which the inductive component of the current flows in the power system, and as already mentioned, its course is provided by the action of the self-induction EMF. Transistors are controlled by a modulating signal with predetermined characteristics. The use of IGBT-transistors, when rectifying the current, allows you to use their control properties relative to currents. In this case, selective rectification of only that current component is carried out, which is set by the control signal. At the output of a 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 extracted from the power system of the inductive component of the current, and the duration of which varies according to the law of variation of its envelope. Further, the extracted energy is accumulated in the capacitive storage, and after conversion by means of an additional power source, which is proposed to use a PWM inverter, it is returned to the power system in the form of active energy, by means of a fundamental frequency current. In this case, the circuit in which the reactive component of the current generated by the load is closed is limited by the connection point of the device that ensures its extraction. Thus, the power system is unloaded from the inductive component of the current.

The method is as follows. Active-inductive load 7, selects from the power system instead of the active, inductive component of energy. In this case, the latter loads the power system with reactive current. By means of the current sensor 2, and the sensor of the supply voltage 6, signals proportional to them are formed. At the same time, at the output of the current sensor 2, the signal proportional to the inductive current generated by the load 7 lags the voltage by a certain angle, which determines the power factor in the power system. In the block for generating a logical signal 8, the signs of the signals arriving at its inputs, from the outputs of the current sensor 2 and the sensor of the supply voltage 6, are compared, the signals are generated, and a digital sequence of zeros and ones is generated at its output, and if the signs of the signals are proportional to the current and voltage, the output of block 8 is formed by a logical unit, and in other cases, a logical zero. Thus, the logical unit corresponds to that part of the period during which the load 7 takes active power from the power system. Further, the signal from the output of block 8 is supplied to one of the inputs of the block for generating the modulating signal 9, the second input of which receives a signal proportional to the current taken by the load 7. Thus, at those moments during which a logical zero coming from the output of block 8 , coincides at the input of block 9, with a positive half-wave selected by the load 7 - current, modulating voltage pulses are generated at the output of block 9, proportional to the inductive component of the current taken by load 7, and in-phase with respect to it. During the duration of the voltage pulses generated by block 9, at the control inputs of a fully controlled transistor PWM rectifier 3, the latter is powered by self-induction EMF. Thus, by means of a controlled transistor PWM rectifier 3, the inductive component of the current selected by the active-inductive load 7 is extracted in a form that contributes to its accumulation. At the same time, at its output, a sequence of unipolar, periodically repeating pulse-width modulated current pulses is formed, which, through the capacitive storage 4, enters a controllable power converter 5, which uses a PWM inverter. In a capacitive storage device, a sequence of unipolar, periodically repeating pulse-width modulated current pulses, the energy of which, for the period of their repetition, is equivalent to the inductive component of the current extracted from the power system, and their duration changes according to the law of the envelope of the mentioned inductive component, is accumulated in the form of direct current energy . The voltage thus obtained is used to power a controlled power converter 5, by which the stored energy is converted into harmonic energy of the fundamental frequency and returned to the power system. In this case, the control unit 5 is carried out by a signal generated by the supply voltage, setting the phase (equal to zero in relation to the supply voltage) of the current returned to the power system.

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. In this case, a fully controllable 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 interference from the operation of a fully controlled transistor PWM rectifier can be filtered out using standard solutions with minimal energy and material costs.

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 adjustment when the current power factor in the power system changes. To do this, just change the modulating control signal.

Thus, as a result of the sequence of actions reproduced in accordance with the claimed method of increasing energy efficiency, the inductive component of the current taken by the active-inductive load is extracted and disposed of from the power system.

INFORMATION SOURCES

1. Rekus G.G. Electrical equipment production: Ref. allowance [Text] / Rekus G.G. M .: Higher. school., 2007, p.334.

2. RF patent No. 2237334, published: 2004.05.20.

Claims (1)

A method of increasing the efficiency of energy use, in which a part of the energy that causes its unproductive losses is extracted from the power flow taken by an inactive load, and after conversion to the harmonic of the fundamental frequency is generated into the power system, characterized in that the fundamental frequency current generated in the power system is generated by the inductive component energy that is extracted from the power system using a fully controlled transistor type PWM rectifier controlled by a modulator signal in the form of an equivalent energy of a sequence of unipolar, periodically repeating latitudinally modulated current pulses, the duration of which varies according to the law of the envelope of the said modulating signal, which is preliminarily generated as a result of comparing the signs of two components: an analog one proportional to the current taken by the active-inductive load, and component, which in case of equality of signs compared: voltage supplying the load, and voltage proportional to a coherent analog component is formed in the form of a logical signal, in this case, if the signs of the components are opposite, the modulating signal is generated and, by means of it, the inductive component of the current is extracted, during each half-cycle supplying the load voltage, while the current of the main frequency generated in the power system is generated by means of an additional controlled power source, the power of which is carried out due to the extracted inductive component of energy, and which is controlled by a modulating signal, the envelope of which is formed in proportion to the voltage supplying the active-inductive load.