Filter compensating device for three-phase power system

 

(57) Abstract:

Usage: to reduce electricity losses by introducing into the design of the transformer. The inventive filter compensating device has three transformers, three winding of each phase which are located on the same rod, the first same conclusions first and second windings connected to the mains power supply system, the first conclusions of the third windings connected in a star schema, the second the conclusions of the first winding connected to the capacitor Bank, main conclusions of the second winding is connected to the reactor, the second the third winding is connected to the resistor, the ratio of the number of turns of the second winding W2the number of turns of the first winding W1choose from the equation , where is the angular frequency of the supply network; C is the capacity of the phase capacitor Bank; L is the inductance of the phase of the reactor. 1 Il.

The invention relates to electrical engineering, namely for industrial power generation.

Reduce losses and improve power quality in power supply systems of industrial plants is achieved by reactive power compensation and filtering harmonics.

It is known that DL is the harmonic content of the mains voltage, especially in respect of high-order harmonics, since capacitive reactance is inversely proportional to the frequency [1]

However, in connection with the specified filtering properties of the capacitor battery, the low order harmonics are not. Meanwhile, for many industrial installations, for example for excavators with AC drives based on direct frequency converters, is required, along with reactive power compensation, filtering a wide range of harmonics.

For reactive power compensation and filtering of harmonics of both the low and high order known use of the broadband filter [2] represents a capacitor battery, serially connected with the parallel reactor and a resistor.

However, this filter compensating device (PKU) has a significant drawback: large energy loss in the resistor at the power supply frequency.

The aim of the invention is to increase the efficiency of PKU by reducing the power loss in the resistor.

The objective is achieved by the fact that in PKU, condenser containing a battery, a reactor and a resistor prompted to enter the three-winding conclusions of the first and second windings are intended for connection to an electrical power supply system, and the first conclusions of the third windings connected in a star schema". Second, the conclusions of the first winding connected to the capacitor Bank, main conclusions of the second winding of the reactor, the second the third winding resistor. The ratio of turns of the first and second windings of the transformer is chosen from the equality

CL (0,95-1,05) where the angular frequency of the supply network;

With the capacity of the phase capacitor Bank;

L the inductance of the phase reactor;

W2the number of turns of the second winding;

W1the number of turns of the first winding.

The necessity and sufficiency of the specified confirmed by the following.

In the prototype resistor, where the main energy losses in the circuit, directly connected with the mains supply. In the inventive PKU between the network and the resistor (as between the network and the reactor network and the capacitor Bank) is incorporated winding of the transformer. The parameters of the elements are selected (in accordance with the formula) that the resistor excluded the loss at the frequency of the mains supply. This is due to the fact that the magnetomotive force of the winding connected to the inductance, and winding connected to the capacitor Bank, is balanced at a frequency of bicause the er in it.

Specified is displayed in the physico-mathematical circuit analysis PKU.

The coefficient in the formula takes into account the design requirements to the elements, the parameters of which are calculated according to the formula. The range of values of the coefficient is determined based on the preservation conditions of practical balance magnetomotive forces of the first and second windings, i.e., conditions to ensure the cost effectiveness of the decision.

Costs caused by the introduction in PKU transformer, significantly less funds obtained by reducing energy losses, which is confirmed by the calculations.

The drawing shows a schematic diagram of the inventive PKU.

PKU contains capacitor battery 1, the reactor 2, the resistor 3.

The transformer has 4 windings 5, 6, 7, each of which is located on three cores of the magnetic circuit 8. The beginning (or end) 9 winding 5 and the beginning (or end) 10 winding 6 are intended for connection to the mains supply 11. In this case, the findings 9 and 10 are connected together inside the transformer, forming a three pin 12 located outside the transformer and connected to the mains supply 11. In other cases, depending on konkretnyh ends of the windings. The latter findings 13 winding 5 is connected with the capacitor Bank 1, the second conclusions 14 winding 6 with the reactor 2. Some conclusions 15 winding 7 is connected in a star schema, other findings 16 is connected to the resistor 3.

The calculation of orbits let us consider a specific example of PKU for power system dragline ESH-25.90 actuators pressure, lift, turn on "direct frequency Converter induction motor". Angular frequency 314 is set.

Using a mathematical model of the power system, defined values=99 f and L=mH 613.

Ratio 2CL 5,983

Based on the optimization calculations of the transformer, select the optimal diameter of the magnetic circuit, which, at a given induction uniquely identifies the number of turns of one of the windings, for example the first:

W1=51. Then W2=5,h=305,13.

Because structurally, the number of turns must be a value, accept W2=305.

5,98

In this case, the coefficient before relation W2/W1equal to one.

Thus, the equality relationship W2/W1work 2CL is sustained. In this case, the magnetomotive force of the windings 5 and 6 osnovnom the absence of losses in the resistor unlike the prototype, where they take place.

Higher harmonics of the mains causes the currents in the capacitor battery 1, the reactor 2 and the resistor 3. Since the inductive impedance of the reactor is proportional to the frequency, the higher harmonic current is significantly suppressed in the reactor.

In the resistor the energy of the higher harmonics is dissipated, as in the prototype. However, the total loss at the fundamental frequency and higher harmonics in the inventive device is much less than in the prototype.

Filter compensating DEVICE FOR three-PHASE POWER SYSTEM, condenser containing a battery, a reactor and a resistor, characterized in that it additionally introduced three three-winding transformer, the windings of each phase which are located on the same rod, with the first same conclusions first and second windings are used for connection of the mains power supply system, the first conclusions of the third windings connected in a star schema, the second the conclusions of the first winding connected to the capacitor Bank, main conclusions of the second winding of the reactor, the second the third winding with a resistor, the ratio of the number of vidoy second winding W2the number of turns of the first winding W1area;

L the inductance of the phase of the reactor.

 

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