JPS6328817B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power feeding method for an AC electric railway feeding system, and more particularly to a power feeding method for an AC electric railway that controls reactive power in the AC electric railway system.

Figures 1A and 1B schematically show the power supply system of a commercial frequency single-phase AC electric railway.
Generally, as shown in Figure 1A, the power supply area is divided for each substation, and the so-called individual power supply state of one substation and one power supply section is standard.

In commercial frequency single-phase AC electric railways where rectifier-type AC electric cars are operated, the electric car load current contains many high-frequency components, and electric railways generally use single-phase AC with single-line grounding that uses the rail as a conductor. Since it is a circuit, there is a risk that the electric car current flowing through the rails will cause electromagnetic induction interference to communication lines near the tracks. Therefore, for the purpose of reducing electromagnetic induction, the electric current line on the induction side adopts a circuit structure as shown in Fig. 2A and B.

Figure 2A shows an AC railway power supply circuit using a suction transformer feeding circuit system. In the figure, 4 is a single-phase AC power source with a voltage E _t equal to the contact line voltage, and 5 is the number of tightly wound turns. A siphon transformer with a ratio of 1:1, 6 is a negative wire, 7 is a rail, 8 is a contact wire, 9 is a siphon wire that connects the rail 7 and the negative wire 6 at approximately the center of the installation interval, 10 is a train A suction transformer section is provided on line 8, 11 is a series capacitor, and 12 is an electric car.

In Fig. 2A, an electric car 12 with a load of current I _t is shown.
The current distribution is shown when the electric car is operated at the position shown in the figure, and between points B and C of the rail 7, the electric car current I _t and the current I _t generated by the action of the siphon transformer 5 are Since it flows in the opposite direction, the rail current in this portion becomes zero, and only the current due to the action of the siphon transformer 5 remains in the C-D portion. After all, the electric car current is C of the rail
It flows through the -D section and returns to the power source from point D through the suction wire 9 and the negative wire 6.

In other words, in this method, even when the electric car is operated at any position, the part where the electric car current flows on the rail is limited to a relatively short section between the electric car 12 and the suction line 9 that does not include the suction transformer 5. Therefore, compared to a single-phase AC electric railway feeding circuit configured with overhead contact line rails, it has a greater effect of reducing induction on communication lines and the like. However, it requires a suction transformer section 10 on the overhead contact line, and the impedance of the suction transformer 5 is inserted in series with the feeding circuit, which reduces the reliability of the overhead contact line equipment and reduces the voltage drop rate of the line. It has disadvantages such as increased size.

Figure 2B shows a conventional power feeding system using an autotransformer. In Figure 2B, 4a is a single-phase AC power supply with a voltage of 2E _t , 13 is a positive wire, and 14 is a contact line 8.
and rail 7, and an autotransformer with a turns ratio of 1:1 between the positive electric wire 13 and the rail 7, and 15 is an automatic voltage regulator.

The feeding system in Figure 2B shows the current distribution when an electric car carrying a load of current I _t is operated at the position shown in the figure, and shows the current distribution between the autotransformers 14 where the electric car is operated. The rail current between rails B-C-D is branched from the electric car position C in directions B and D to the left and right, and the induced voltage from the B-C-D portion to the proximity communication line is C-B, C- Since this is the difference in induced voltage from each part of D, the effect of reducing communication induction is greater than that of a single-phase AC feeding circuit made up of contact line rails, similar to the wicking transformer feeding circuit. In addition, in the impedance of the commercial frequency single-phase AC power supply circuit as described above, the ratio of resistance to reactance is approximately 1:4, and the electric car load power factor lags behind the contact line voltage at the electric car position. It is 0.8-0.85 (%).

Therefore, the methods for resolving voltage drops in power control of commercial frequency single-phase AC railway power supply circuits include compensating the line reactance with a series capacitor 11 in the circuit system shown in Figure 2A, and the method shown in Figure 2B. In general, a method is adopted in which an automatic voltage regulator 15 is provided in the middle of the power supply circuit to obtain a compensation voltage e for relief.

In these conventional methods, (a) In the method shown in Figure 2 A, when an unloaded electric car is on the line, the transformer winding and capacitor mounted on the electric car are installed in series with the substation power supply. As a result, when the power supply voltage fluctuates, or when power is first transmitted, or when the cable is cut and reclosed, series resonance occurs between the excitation impedance of the vehicle transformer and the capacitor, and subharmonic oscillations occur and continue, causing the capacitor terminal voltage to decrease. If the voltage becomes too large, the capacitor voltage may be added to the power supply voltage, causing an overvoltage in the circuit. Countermeasures such as installing a fractional harmonic suppressor at the capacitor terminal have been taken to suppress the continuation of the capacitor voltage and subharmonic vibration, but this makes the equipment complex.

(b) Furthermore, in the method shown in FIG. 2A, when the load current contains many harmonics, the line reactance compensation effect by the capacitor is reduced.

(C) In the method shown in Figure 2B, the control to obtain the compensation voltage is performed at high speed, and the compensation voltage is not affected by harmonics much, so it is possible to perform reasonable relief from voltage drops, but the circuit loss tends to increase.

(d) Conventional power control methods such as the methods shown in FIGS. 2A and 2B do not improve the power factor because reactive power cannot be controlled.

The present invention has been made in view of the above points, and its purpose is to control reactive power including harmonics of electric car load power in the feeding system of a commercial frequency single-phase AC electric railway, and to control the voltage of the electric line. An object of the present invention is to provide a high-performance and economical power supply method for electric vehicles by reducing line drop and line loss and improving power supply efficiency of substations.

A power supply method for an electric vehicle according to an embodiment of the present invention will be described below with reference to FIGS. 3 and 4.

FIG. 3 shows the main circuit configuration for high-speed dynamic reactive power compensation when a single-phase AC current type reactive power compensator is used. In FIG. 3, reference numeral 16 indicates a load device such as the electric vehicle 12. A filter 17 is composed of reactors 18, 19 and a capacitor 20. 21 is an inverter, and thyristors 22a, 22b, 22c and 22d,
Diodes 23a, 23b, 23c and 23
d, consisting of capacitors 24a and 24b. 25 is a load reactor of the inverter 21. The filter 17, the inverter 21, and the reactor 25 constitute a reactive power compensator 26. A filter 17 is provided on the input side of the reactive power compensator 26, and a load reactor 25 is provided in parallel on the output side.

In the main circuit with the above configuration, the power supply voltage is E _a ,
When the load current is I _t , these general formulas are expressed as follows.

E _a = Asinωt (1) I _t =Bsinωt+Ccosωt+ZB _o sinωt +ZC _o cos nωt (2) where A, B, and C are constants, and n indicates the harmonic order.

Furthermore, a negative feedback control system is created so that the input current of the reactive power compensator 26 becomes a current expressed as I _i =Bsinωt−I _t (3).

The current supplied from the power source 4 is a combination of I _i and I _t , and only the current B sin ωt flows through the power source 4, reducing harmonics and improving the power factor.

As shown in FIG. 4, the present invention provides a reactive power compensator having the above-mentioned performance at the end of a commercial single-phase AC power supply circuit, compensates for reactive power including harmonics of electric vehicle loads, and This will reduce voltage drop and line loss, and improve substation power factor.

In FIG. 4, 27 is a train track, and 28 is a rail. When a single electric car is operated on the overhead contact line 27, the maximum voltage drop occurs at the load position where the maximum load is taken at the end of the line. Figure 4 is an example of the case where the maximum load is taken at the end of the electric line. In the figure, x _s is the reactance of the power supply impedance, D is the track length and the distance from substation 1 to the load point, x _t , r _t is the reactance and resistance components per unit length of the overhead contact line impedance.
E _sp is the no-load power supply voltage, E _s is the substation supply voltage under load, E _t is the contact line voltage at the load point of the electric car, and I _t is the load current of the electric car, with only the fundamental wave component at the load point.
Let us take the lagging power factor cost for E _t .

In this case, the line voltage drop is ΔV _t , the substation feeding point power factor is cos _s , and the loss in the train track ω _t is ΔV _t = DI _t r _t cos _t + (x _s + Dx _t ) I _t sin _t …( 4) ∴E _t ≒E _s −ΔV _t …(5) ω _t =I _t ² Dr _t (7) The reactive power compensator 26 compensates for the reactive component of I _t so that cos _t =1. In this case, if the line voltage drop is ΔV _t ′, the electric car position contact line voltage is E _t ′, the substation feed point power factor is cos _s ′, and the line loss is ω _t ′, then ΔV _t ′≒DI _t r _t cos _t …(8) E _t ′＝E _s −ΔV _t ′ …(9) ω _t ′=Dr _t (I _t cos _t ) ² …(11). Substituting general values for commercial frequency single-phase AC electric railway lines into equations (4) to (9) and looking at numerically how much the voltage drop, power factor, etc. are improved, we get the following: Become.

[Condition]: Example of suction transformer feeding system (conventional line) E _s = 22 [Kv] I _t = 300 [A] D = 30 [Km] x _s = 3 [Ω] r _t = 0.2 [Ω/Km] x _t = 0.8 [Ω/Km] Equation (4) is ΔV _t = 6.300 [V] Equation (5) is E _t = 15.700 [V] (6) is cosω _s = 0.654 (7) The formula is ω _t = 540 [Kw] After compensating for the reactive power of the load and improving the power factor, formula (8) is ΔV′ = 1.440 [V] (9) is E _t ′ = 20.560 [V] (10 ) formula becomes ω _t ′=345.6 [Kw].

In other words, by controlling the reactive power to make the power factor at the load point 1, the load point power line voltage can be reduced.
It is possible to improve the voltage from 15.700 [V] to 20.560 [V], the substation power supply rate from 65.4 [%] to 99.8 [%], and furthermore, the electric train line voltage can be improved from 540 [Kw] to 345.6 [Kw].
Reduced to [Kw].

FIG. 5 shows a control device for controlling the inverter 21 of the main circuit shown in FIG. A pulse width control (PWM) or current type inverter is used. The inverter performs constant voltage control at the load end, and by adjusting the control advance angle on the inverter side, it compensates for the lagging power on the load side. Give and compensate.

In other words, in Fig. 5, 29 is the line voltage signal.
A comparator that compares S ₁ with the reference voltage signal S ₂ of the reference voltage setter 30; 31 is the deviation signal S ₃ from the comparator 29;
This is an amplifier for automatic voltage adjustment with input. 3
2 is a rectifier that detects the load current and converts it into a voltage signal _S5 ; 33 is a limiter circuit that receives the amplified signal _S4 from the amplifier 31 and the voltage signal _S5 from the rectifier 32; and 34 is a limiter circuit for the limiter circuit 33. An automatic pulse phase shift circuit that receives the limiter voltage signal _S6 as an input; 35 is a pulse generation circuit that generates a pulse signal _S8 in accordance with the phase shift angle signal _S7 of the automatic pulse phase shift circuit 34 _; is supplied as the gate signal of the inverter 21.

In the control device of FIG. 5, the automatic pulse phase shift circuit 34 adjusts the leading phase of the gate signal supplied to the thyristor in accordance with the deviation output signal _S8 of the comparator 29. Further, the load current is detected and the maximum output value of the limiter circuit 33 is limited only when the load current exceeds the maximum set value, thereby preventing commutation failure of the inverter from excessive input. Normally, an inverter performs constant voltage control of the load.

As explained above, according to the present invention, a reactive power compensator is installed at the end of the line to constantly maintain the load power factor.
Since the control can be improved to 100% condition,
Line current is reduced, line voltage drop and loss are reduced. In addition, the substation power supply rate is constantly improved according to the load, eliminating the need for parallel capacitors for power factor improvement, which were conventionally installed at substations, making capital investment more economical and reducing electricity purchasing costs. will be promoted. Further, according to the present invention, since the high frequency current generated by the electric car is also compensated, excellent effects such as being able to reduce the influence of the harmonic current of the electric car on power system equipment can be obtained.

[Brief explanation of the drawing]

Figures 1A and 1B are schematic diagrams showing general AC electric railway power supply circuits, Figures 2A and 2B are electrical circuit diagrams of conventional single-phase AC electric railway power supply circuits, respectively. The figure is a main circuit diagram of a single-phase AC power supply circuit according to an embodiment of the present invention, FIG. 4 is a schematic diagram of a single-phase AC power supply circuit according to an embodiment of the present invention, and FIG. 1 is a block diagram of a gate control device for controlling an inverter of a circuit; FIG. 4...Power supply, 12...Electric vehicle, 17...Filter, 21...Inverter, 25...Load reactor, 26...Reactive power compensator.

Claims (1)

[Claims] 1. An AC electric railway characterized in that a reactive power compensator for removing harmonics is disposed at the end of a commercial frequency AC electric railway feeding system, and the reactive power of the load is compensated by the reactive power compensator. Power supply method.