Method of electric energy quality improvement and associated device

FIELD: power production.

SUBSTANCE: when non-sinusoidal shape of supply voltage is decreased, electric power is distributed between electronic devices distorting the shape of supply voltage and electronic devices improving the shape of supply voltage during the semi-wave of supply voltage. Device is connected in parallel with consumers introducing distortions of voltage shape. Main voltage is supplied to the device input. Device includes serial connection of phase-shifting chain, control pulse shaper, dc power supply and power switcher, which connects consumers improving the shape of supply voltage to the mains at a certain period of time.

EFFECT: improvement of supply voltage shape and simplification of device design.

2 cl, 4 dwg

 

The invention relates to electrical engineering and power industry, and in particular to methods and devices for improving power quality at the consumers, distorting the shape of the mains voltage.

In single-phase network all consumers are switched in parallel, with the instantaneous value of the current is determined by the sum of multiple values of currents of individual consumers. Among them are the consumers, distorting the shape of the supply voltage, such consumers have a circuit containing a rectifier device with filters. The instantaneous value of the current of such consumers is a short sequence of alternating pulses following with the power supply frequency (figure 1, feature - 1). Range of current pulses contains a very large number of harmonic components. Reduce the impact of consumers on the shape of the mains voltage is the actual problem.

There is a method of improving the quality of electrical energy, which consists in reducing the level of higher harmonics by configuring several groups of sequential circuits at resonance voltages of 5, 7, 11 and 13 harmonics (Zielonko IV "harmonics in power supply systems of industrial enterprises". M.: Energoatomizdat, 1984, pp.109). The principle of operation of such devices is based on the occurrence of resonance in their substancesleselena circuit, tuned to a specific frequency. Filters can be installed in the network for the separation of linear and nonlinear loads (barrier filters) or absorption (bypass) currents harmonics.

The main disadvantage of using filters is incomplete compensation of the higher harmonics.

As the prototype accepted way of improving the quality of electrical energy, which consists in the selection of the voltage harmonics voltage, and the first harmonic is determined by the voltage asymmetry, the straightening of the selected harmonic voltage, converting the rectified voltage into alternating voltage with a frequency equal to the frequency of the first harmonic of the network, and the return of the AC voltage in the electrical network (patent RU №2237334, H02J 3/01, H02J 3/26).

The disadvantage of this method is incomplete compensation of the higher harmonics is limited by the characteristics of the filters included in its composition.

As a prototype device adopted stabilizer, AC voltage, related to the sources of the secondary power supply (patent RU №2280271 C1, G05F 1/14). The AC voltage stabilizer is designed to reduce non-sinusoidal shape of the voltage supplied to the electricity consumer with a power of several kilowatts.

The disadvantages of this device is the tsya the complexity of the design, in addition, digital resistance changes stepwise, which reduces the accuracy of the magnitude of the output characteristics of the voltage.

The objective of the proposed method to improve the power quality is improving power quality by restoring the shape of the supply voltage to a sine wave by distributing energy consumption between different consumers.

To implement this task, divide consumers into groups:

- electronic devices, distorting the shape of the supply voltage;

- electronic devices that improve (correcting) the form of the supply voltage.

The way to improve the quality of electricity based on the distribution of energy consumption between different consumers during the half.

The way to improve the quality of electric energy is to reduce the nonsinusoidal shape of the supply voltage. Make the distribution of energy consumption between electronic devices that distort the shape of the supply voltage, and electronic devices that improve the shape of the supply voltage during the half-wave voltage network.

The method can be implemented using devices improve the quality of electric energy with the output load. At the entrance is trojstva installed phase-shifting chain, connected to the driver control pulses, a source of DC power and the power switching key, and outputs the driver control pulses, a source of DC power and the power switching key connected in series.

The method is illustrated in the drawings.

Figure 1 shows a form of instantaneous values of current of different consumers, where 1 is an electronic device that distort the shape of the supply voltage; 2 - electronic device that improves (correcting) the form of the supply voltage.

Figure 2 shows a connection diagram of the device And to improve the quality of electric power, electronic device, distorting the shape of the supply voltage, consisting of the diode bridge VD1...VD4, capacitor C1, resistor R1, and electronic devices that improve (correcting) the form of the supply voltage, consisting of a resistor R2, where u is the voltage in the connection point of the electrical load; i1- the instantaneous value of the current electronic devices, distorting the shape of the supply voltage; i2- the instantaneous value of the current electronic devices, which improve the form of the supply voltage; isum- the instantaneous value of the total current; ZNR- the internal impedance of the generator; fgenerators(t) - EMF of the generator.

Figure 3 shows the diagram of the device And improve power quality, consisting of the following blocks:

1 - phase-shifting chain consisting of parallel-connected capacitor C1 and resistor R2 which are connected in series to the resistor R1;

2 - driver control pulses, consisting of a series connected Zener diodes VD1 and VD2, parallel-connected capacitor C2 and resistor R3, which are connected in series to the resistor R4 in parallel to the resistor R4 connected optotransistor VT1 and VT2;

3 - the source of DC power, consisting of a step-down transformer T1, the primary winding of which is connected to the supply voltage, to the secondary winding of the transformer T1 are sequentially connected tomographically resistor R5 and a diode bridge VD3...VD6, the output of the diode bridge connected in parallel to the Zener diode VD7, capacitor C3 and resistor R6;

4 - the power switching key, consisting of the diode bridge VD8...VD11 and parallel connected power transistor VT3;

5 is an electronic device that improves the shape of the mains voltage, the resistor Rn.

Figure 4 shows the characteristics of the device to improve power quality, where

(a) the form of voltage;

b) the magnitude of the current supplied to the LEDs optotransistor VT1 and VT2 with regard to phase shift;

C) current control of the power transistor VT3;

g) the form of the voltage on the electronic device C.

It is known that electronic devices use power in a narrow time interval (figure 1, feature 1) and thereby distort the shape of the supply voltage. To restore the shape of the supply voltage to a sinusoidal you want another type of load consumed power in the time interval in which the electronic device, distorting the shape of the supply voltage, do not consume electricity (figure 1, feature 2).

When you enable parallel with consumers, distorting the shape of the supply voltage, other consumers instantaneous value of the total current is equal to the sum of the instantaneous values of the currents of individual consumers (figure 1, features 1 and 2). Thus, the total value of the instantaneous currents of different groups of consumers will reduce distortion of the supply voltage.

To implement the proposed method requires the device And improve power quality (figure 2), which produces the disabling of the electronic device, which improves the shape of the mains voltage (figure 2), in the time interval when the power consumption of the electronic device In distorting the shape of the supply voltage (figure 2).

The proposed device And improve the power quality of the art is meant to control the inclusion of the group of electronic devices, improving the shape of the mains voltage, at certain points in time (figure 1, feature 2)

Input device And improve the quality of electricity supplied voltage (3, u) for synchronization of time during which the electronic device, which improves the shape of the voltage connected to the network and to power the device.

For the formation of the desired time control pulses to open the power switching key is created by phase-shifting the chain consisting of capacitor C1 and resistor R1 (figure 3, box 1), which produces a shift of the current shape relative to the shape of the voltage angle is close to 90° (figure 4, b). To generate control pulses the circuit includes two optotransistor VT1 and VT2 (figure 3, box 2). They act as a logic element, which is triggered as a result of excessive current through the led relative to the threshold values. Optotransistor VT1 sets the threshold icrab, VT2 - icrab(figure 4, b). Optotransistor VT1 and VT2 are all similar in this regard, the threshold values of icraband icrabhave the same value. When triggered, optotransistor VT1 or VT2 is the opening of the phototransistor. Using the source DC power (figure 3, block 3) and the opening of the phototransistor (figure 3, block 2, VT1 and the and VT2) is the formation of control pulses (figure 4, in), coming on the power switching key. Power key by means of the power transistor VT3 (figure 3, block 4) in turn connects to the network at certain times of the electronic device, which improves the shape of the mains voltage. As a result, the voltage supplied to the electronic device connected to the network through the device And improve the quality of electricity takes the necessary form (figure 4, g or 1, feature 2). The necessary duration of the open and closed state of the power transistor VT3 (figure 3, block 4) is determined by selection of the values of the Zener diodes VD1 and VD2, and capacitor C2 (figure 3, box 2).

An advantage of the device improve the quality of electricity is simple structure, high stability, low energy consumption.

To restore the shape of the supply voltage necessary to produce the correct choice of device connectivity And improve power quality (figure 2). Otherwise, the device And improve the power quality will be not as proof, but as a source that introduces distortions in the form of the supply voltage. The device And improve the quality of electricity must be connected in parallel to the consumers, introduces distortions in the form of the supply voltage (figure 2).

The shape of the voltage set is initially is non-sinusoidal due to the fact, what is the internal resistance of the generator is active and inductive resistance:

where Rgenerators- the active resistance of the generator; Lgeneratorsthe inductance of the generator; isum- the total current of all consumers; u(t) is the voltage at the point of connection of consumers; fgenerators(t) - EMF of the generator.

Thus, when using the method of restoring the shape of the supply voltage is possible that the shape of the mains voltage will beto fit the shape of the voltage at idle generator.

The positive effect is in the shape recovery of the supply voltage, the maximum closer to a sine wave. When using the method to improve the quality of electrical energy is also observed and the economic effect is the reduction of non-production energy losses in power supply systems.

1. The way to improve the quality of electrical energy, which consists in reducing the nonsinusoidal shape of the supply voltage, characterized in that make the distribution of energy consumption between electronic devices that distort the shape of the supply voltage, and electronic devices, improving the mi form of the supply voltage, over half of the supply voltage.

2. The device improve the quality of electric energy connected in parallel with consumers, introduces distortions in the form of a voltage, the input of which is applied a voltage that contains one United vasodilatory chain, the driver control pulses, a source of DC power and the power switching key that connects to the network at certain times of consumers, improve the shape of the supply voltage.



 

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