RU2435272C1 - Method to increase efficiency of power usage (version 3) - 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, individually or jointly with the energy of harmonics of the main frequency, 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 current extracted from the power system, and after conversion into DC energy, it is recycled, by means of its usage for load supply.

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

1 dwg

Description

The invention relates to electrical engineering and can be used to increase energy efficiency, by reducing unproductive losses in the power flow of a power system.

A known method of compensating reactive "power" (1), adopted as an analogue, in which the inductive component of the current generated by the nonlinear load is compensated by the capacitive current of the capacitor banks (BC). The known method - the analogue has disadvantages, the main of which are the dependence of the reactive power generated by the BC, on the voltage and their sensitivity to distortion of 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) to improve the quality of electricity, adopted as a prototype, in which a part of the energy that causes its unproductive losses is extracted from the power flow, which is taken as an inactive load, and after conversion, it is used to “charge the batteries from which the electrical installations are powered current, as well as inverters, from which electrical installations of alternating current are fed and (or) with the help of which electric energy is returned back to the electric network, as well as iziruyut in electrical systems, for which the power quality is not significant (different heaters). " 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, from the power flux taken by the active-inductive load, its inductive component, the value of which is equal to a predetermined or less than it, is extracted, respectively: either individually or together with the fundamental energy, in the form of an equivalent sequence energy unipolar, periodically repeating pulse-width modulated current pulses, the duration of which varies according to the law of change of the extracted current, and utilize, by means of it used ia to power the DC load.

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 - voltage sensor

6 - nonlinear load

7 - block generating a logical signal

8 - block generating a modulating signal

9 - DC load

10 - voltage sensor

11 - control unit signal of the main frequency

12 - harmonic filter of the fundamental frequency current

13 - mixer

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 energy losses 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 energy flow used by the active-inductive load the inductive component and utilize it by using it to power the DC load.

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 ensured, 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 a time during which the inductive component of the current flows in the power system. The use of IGBT-transistors, when rectifying the current, allows you to use their control properties relative to currents. Transistors are controlled by a modulating signal with predetermined characteristics. In this case, if the power required by the DC load is less than or equal to the inductive component of the power extracted from the power system, the extraction of its current is controlled by a modulating signal, which is preliminarily generated as a result of comparing the signs of its two components, an analogue proportional to the current taken actively -inductive load, and component, which in case of equality of signs compared: voltage supplying the load, and voltage proportional to the mentioned analog with stavlyayuschey - formed into a logic signal. If the amount of power required by the aforementioned DC load exceeds the amount of extractable power of the inductive component, the harmonic power of the fundamental frequency is additionally extracted from the power system, in a fraction equal to the power missing from the DC load. In this case, the operation of the transistor rectifier is controlled by a modulating signal, including, inter alia, two components, one of which is formed as described above, and the other is formed in proportion to the harmonic of the current of the fundamental frequency. Thus, from the power system, both the inductive component of the power returned to the power system by the active-inductive load is extracted, as well as the additional harmonic power of the fundamental frequency, in parts necessary for the implementation of the claimed method. In this case, selective rectification of only the current component that is specified by the control signal is carried out. At the output of a controlled transistor PWM rectifier, there is a sequence of unipolar periodically repeating pulse-width modulated current pulses, the energy of which, for the period of their repetition, is equivalent (depending on the ratio of energies - the inductive component of energy extracted from the power system and the energy required by the DC load): or the extracted inductive component of energy, or the sum of the energies - the extracted inductive component of energy and the proportion of the additional energy of the harmonics of the basics th frequency deficient for normal operation of the DC load. Thus, the entire inductive component of the energy extracted from the power flow of the power system is consumed to power the DC load, and if this energy is insufficient, i.e. if its value is less than the amount of energy needed to power the aforementioned load, then the harmonic energy of the fundamental frequency is additionally used. In this case, the circuit in which the reactive component generated by the load is closed is limited by the connection point of the device providing its extraction, and the power system is thus unloaded from the inductive component of the current.

Consider an example implementation of the method. Preliminarily, the reactive component of the power returned to the power system by the active-inductive load is tentatively estimated and correlated with the power necessary to power one or more of the available DC loads. The power mismatch mode: extracted from the power system and the required DC load is monitored by the fact that the voltage in the capacitive storage 4 decreases, by means of a voltage sensor 10. In this case, if the power required by the DC load is greater than the power extracted from the power system, block 5 is formed a signal for additional selection from the power system of the missing power, in the form of harmonic power of the fundamental frequency, in a fraction necessary for the mentioned load for its normal operation. Moreover, if the inductive component of the power extracted from the power system is greater than or close to the power necessary for the normal functioning of the existing DC loads, as evidenced by the correspondence of the voltage in unit 4 to a predetermined value, the energy of the inductive component is disposed of independently by using it to power the DC load current. In accordance with the claimed method, in this case, the disposal process is as follows.

Active-inductive load 6 selects from the power system together the active, inductive component of the energy. In this case, the latter loads the power system with reactive current. By means of a current sensor 2 and a supply voltage sensor 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 6 lags the voltage by a certain angle, which determines the power factor in the power system. In the block of formation of the logical signal 7, the signs of the inputs arriving at its inputs, from the outputs of the current sensor 2 and the sensor of the supply voltage 5, signals are compared, 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 block 7 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 6 selects active power from the power system. Further, the signal from the output of block 7 is supplied to one of the inputs of the block for generating the modulating signal 8, the second input of which receives a signal proportional to the current taken by the load 6. Thus, at those moments during which a logical zero coming from the output of block 7 , coincides at the input of block 8 with the positive half-wave selected by the load of 6 current, modulating voltage pulses are generated at the output of block 8, which are proportional to the inductive component of the current taken by load 6 and in-phase with respect to it. From the output of block 8, the generated modulating voltage pulses are supplied to one of the inputs of the mixer 13, at the second input of which there is no signal, due to its blocking by the control unit of the main frequency signal 11. During the duration of the voltage pulses generated by blocks 8 and 13, at the control inputs fully controlled transistor PWM rectifier 3, the power of the latter is due to the EMF of self-induction. Thus, by means of a controlled transistor PWM rectifier 3, the inductive component of the current selected by the active-inductive load 6 is extracted in a form that contributes to its accumulation. At the same time, at its output, sequences of unipolar, periodically repeating pulse-width modulated current pulses are formed, 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 varies according to the law of the envelope of the mentioned inductive component, which is stored through the energy storage is converted into direct current energy used to power the load 9.

As already noted, this case corresponds to the fact that the energy of the highest dominant harmonic is deficient, which is necessary to power the DC load 9. The voltage in the capacitive storage 4 is equal to the specified value, and a signal is generated at the output of the voltage sensor 10, blocking the passage of a signal equivalent to current the main harmonic formed by a chain consisting of blocks 12 and 11 to the second input of the mixer 13. Moreover, by means of a fully controlled transistor PWM rectifier 3, from the power system from only the inductive component of the energy is taken.

If the energy of the inductive component is not enough to power the DC load 9, the formation of the signal that controls the operation of the transistor PWM rectifier 3 is as follows. The signal equivalent to the inductive current taken by the load 6, and generated by the method described above, is fed to one of the inputs of the mixer 13, the second input of which, from the output of the control unit of the main frequency signal 11, whose operation is controlled by a signal generated by the voltage sensor 10 and characterizing the degree of use of the inductive component of the energy extracted from the power system — a DC load of 9 — a signal is received that is equivalent to the harmonic current of the fundamental frequency and generated by tion chain consisting of a load current sensor 2 and the current fundamental frequency of the filter 12. The harmonic load capacity mismatch Viewed mode DC 9 and inductive component of the energy used to power it, defined upon a voltage drop of buffer storage 4 less than the predetermined. In this case, at the output of the voltage sensor 10, a signal is generated that controls the operation of the control unit of the signal of the fundamental frequency 11, arriving at its control input and allowing the signal to pass through it, equivalent to the harmonic current of the fundamental frequency from the output of the harmonic current filter of the fundamental frequency 12 to the second input of the mixer 13, which controls the transistor PWM rectifier 3, through which the inductive component of the energy is completely extracted from the power system, and, the proportion of the harmonic energy of the fundamental frequency, Missing DC load 9 for normal operation.

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 of production: Reference, allowance [Text] / Rekus G.G. - M .: Higher. school., 2007, p.334.

2. RF patent №2320067, published: 2007.01.20.

Claims (1)

A method of increasing the efficiency of energy use, in which the non-productive losses that cause it are removed from the power flow and partially utilized after conversion, characterized in that the inductive component of the energy is utilized, the latter being used after conversion to direct current energy load, and if its value is less than a predetermined value, to power said load, additionally, after conversion to energy They use direct-current harmonic energy of the fundamental frequency, while the inductive component of the energy is extracted from the power system either independently or together with the harmonic energy of the fundamental frequency, by means of a fully controlled transistor-type PWM rectifier controlled by a modulating signal in the form of an equivalent energy of a sequence of unipolar, periodically repeating pulse-width modulated current pulses, the duration of which varies according to the law of the envelope of the signal, is proportional current, which determines the type of energy extracted from the power system, while the harmonic energy of the fundamental frequency is extracted in proportion to the fraction corresponding to the difference: the energy needed to power the DC load, and the inductive component of the energy to be disposed of, and if the difference is equal to the predetermined value , the inductive component of the energy is extracted, independently, in each half-cycle of the voltage supplying the load, by means of the pre-modulated signal ala, - if the signs of its two components: analog, proportional to the current taken by the active-inductive load, and the component, which in case of equality of the signs of the compared: voltage supplying the load and voltage proportional to the mentioned analog component, form in the form of a logical of the signal are opposite, and if the inductive component of the energy is extracted together with a fraction of the harmonic energy of the fundamental frequency, the process of extraction of the mentioned energies is controlled by modulating a needle, including, among other things, two components, one of which is proportional to the inductive current characterizing the extracted inductive component of energy, and which is formed by the two components mentioned above: analog and in the form of a logical signal, and the other is proportional to the fraction of the extracted harmonic current of the fundamental frequency.