JP3186495B2 - Power converter for AC electric vehicles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power converter for converting alternating current into direct current and direct current into alternating current, and more particularly to a power converter for an AC electric vehicle capable of controlling a power factor of one.

[0002]

2. Description of the Related Art A power conversion facility for an AC electric vehicle to which power is supplied from an AC overhead line includes a distance relay for detecting that the overhead line has been grounded (ground fault) and stopping the power system quickly. When a grounding accident occurs in an AC overhead line far from a substation, the current is limited by a reactance component of the overhead line, and an overcurrent detector that detects an overcurrent and detects a grounding accident may not operate. Therefore, a distance relay is employed to detect a distant grounding accident.
This distance relay detects a grounding accident by detecting a delay current limited by a reactance component of the overhead wire.

[0003] On the other hand, as a power converter for converting alternating current received from an overhead line mounted on an electric vehicle traveling in an alternating current feeding section into direct current by means of a diode bridge (without regenerative action) or a thyristor bridge. PW using a separately-excited converter (with regenerative action) and a self-extinguishing type semiconductor element that controls the AC phase and controls the DC voltage
A self-excited converter capable of reversible operation of powering and regenerative realizing a power factor of 1 by performing M control is used. This self-excited converter is described in JP-A-62-213961.

[0004]

[SUMMARY OF THE INVENTION] those who are occupied Umate mainstream of the power converter of the current of the AC train is separately excited converter. In recent years, GTO (gate turn-off thyristor) and I
GBT is self-excited converter with the development of large-capacity self-extinguishing semiconductor switching elements, such as (in-scan Federated gate bipolar transistor) is beginning to be adopted. With the adoption of this self-excited converter, there is a possibility that the above-mentioned distance relay may malfunction.

An object of the present invention is to provide a control device for an AC electric vehicle which can prevent a malfunction of a distance relay.

[0006]

The object of the present invention is to provide a ground fault for an overhead line.
AC feeder where distance relays are installed to detect accidents
Convert AC to DC by wire and separately excited converter
The vehicle is driven on a route on which
The flow side is connected via a transformer, and the DC side is for driving electric vehicles
Connected to the motor control device to control the DC voltage to a specified value
And a self-excited converter (pulse
Power converter for AC electric vehicles
In the regenerative operation of the AC electric vehicle of the self-excited converter
To prevent malfunction of the distance relay due to the
The power factor of the self-excited converter
This is achieved by providing means for controlling the delay from 1 "to the delay side .

[0007]

The distance relay detects a reactive current in order to detect a distant overhead wire grounding accident. On the other hand, the power factor of the separately-excited converter is about 0.75, and that of the self-excited converter is 1. During power running of a separately excited converter type electric car,
It is assumed that the self-excited converter electric vehicle is performing regenerative operation. Since the power factor of the self-excited converter is 1, the effective component of the current taken by the separately-excited converter is supplied from the self-excited converter. The remaining inactive components taken by the separately-excited converter are supplied from the substation because the self-excited converter does not output. At this time, the distance relay at the substation detects this reactive current and determines that a grounding accident has occurred. Since the means for lowering the power factor during the regeneration supplies not only the active current but also the reactive current to the overhead line, the reactive current supplied by the substation is reduced to the inoperative area of the distance relay. Therefore, the possibility of malfunction of the distance relay is reduced.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The operation of a distance relay which is a protection relay for detecting a short circuit and a ground fault in an AC feeding circuit will be described with reference to FIG. The overhead power line 3 is installed in the power conversion equipment of AC electric vehicles.
There is a distance relay that detects the grounding of 0 and stops the power system quickly. In the case of AC overhead line, if a grounding accident occurs far from the substation, the reactance component X of the overhead line
Therefore, the current is limited, and the overcurrent detector that detects the magnitude and the rate of increase of the current may not operate. The distance relay has a role of detecting a ground at a distance, and detects a delay current limited by a reactance component X of the overhead line.

The operating area of the distance relay is as shown in the figure.
It is made to operate when the impedance of the overhead wire is mainly composed of the reactance X component. When a current enters the illustrated parallelogram, it is detected as a ground fault and protection for operating the circuit breaker of the substation is performed. Therefore, as a power converter for an AC electric vehicle, it is necessary to operate while avoiding the operating region of the distance relay.

Here, using a self-extinguishing type semiconductor device,
A power converter that performs reversible operation of powering and regeneration will be referred to as a self-excited converter.

Since the impedance of the self-excited converter is controlled by the excitation impedance jX _{T of the} transformer and the power factor 1, it becomes a combined impedance of the resistance component R _CS . In addition, the accessory impedance R _A + jX _A of the AC vehicle is further added. The overhead line impedance seen from the substation is
Further overhead line impedance R _L + jX _L is added.

FIG. 3 shows the impedance of the self-excited converter as viewed from the overhead line.

As an example, the impedance of the overhead wire viewed from a substation when a self-excited converter is used in an AC vehicle is calculated. 16 MW while the control power of the self-excited converter is running,
Regenerative brake is -16MW, transformer excitation impedance is j6KΩ, auxiliary capacity is 1200KVA, power factor is 0.8
And The control power is power corresponding to a case where six trains of AC electric cars enter four trains in the same substation section and simultaneously control peak power of powering and regeneration. Assuming that the overhead wire voltage is 20000 V, the accessory impedance R _A + jX _A at this time is 179 + j280Ω, and the resistance component of the self-excited converter is at least 25Ω during power running and -25Ω during regenerative braking. The overhead line impedance as viewed from the substation in this case is shown in FIG.

Now, when the power running operation is performed from the coasting or the stop state and the control power gradually increases, the impedance of the overhead wire viewed from the substation approaches the vicinity of the origin 0 clockwise from the upper right A. On the contrary, during the regenerative braking, the vehicle approaches the vicinity of the origin 0 counterclockwise from the upper left B. Since the self-excited converter controls the power factor to "1", it can be understood that the operation area of the distance relay can be avoided because the delay component is small.

On the other hand, a separately-excited converter, which is currently dominant as a power converter for an AC electric vehicle, will be examined.
The configuration shown in FIG. 4 is considered as a separately excited converter. AC power supply 1, transformer (transformer) 2, separately excited converter 8, main smoothing reactor 7, smoothing capacitor 6, inverter 4,
It is composed of a main circuit such as an induction motor 5. In the case of the separately-excited converter, the power factor is about 0.75, and the delay component flowing through the overhead wire becomes considerably large. Here, consider a case where the self-excited converter is regenerating while the separately-excited converter is controlling the peak power of power running. FIG.
Shows the current supplied from the substation when the self-excited converter regenerates while the separately-excited converter is running.

Since the regenerative current of the self-excited converter supplies the in-phase component of the current of the separately-excited converter, it can be seen that the current supplied from the substation mainly includes a delay component. Since the above-mentioned distance relay operates when the current flowing through the substation mainly includes a delay component, there is a concern that the distance relay may malfunction in this mode.

FIG. 6 shows the impedance of the overhead wire viewed from the substation when the self-excited converter and the separately-excited converter are simultaneously present.

The excitation impedance of both transformers is j1
It is assumed that 2 KΩ, the auxiliary equipment capacity is 600 KVA, the power factor is 0.8, the regenerative power of the self-excited converter is 8 MW at the maximum, the powering control power of the separately-excited converter is 8 MVA, and the power factor is 0.75. This control power corresponds to a case where a self-excited converter car of 6 cars performs regenerative braking at the same time for 2 cars and a separately-excited converter car of 6 cars performs power running in the same manner as 2 cars.

If the overhead line voltage is similarly set to 20000 V,
Both accessory impedance R _A + jX _A is 359 + j560
Ω, the resistance component of the self-excited converter is −50 Ω, and the impedance of the separately-excited converter is 29.3 + j40.5 Ω.

[0020] Figure 7, separate excitation converter, in a state in which power running, when the self-excited converter performing regenerative braking, showing the overhead line impedance seen from the substation. From the point of the impedance C of the overhead wire when the separately-excited converter is running, it can be seen that the impedance of the overhead wire changes counterclockwise, crosses the operating region of the distance relay, and the distance relay malfunctions.

The regenerative braking of the self-excited converter, powering the separately excited converter, at the same time if the overlap, in order to solve the problem would cause malfunction of the distance relay becomes a delay component main current supplied from the substation By making the regenerative current of the self-excited converter have a further delay component from the power factor “−1”, the delay component (reactive current) of this current
By supplying the delay component of the separately excited converter, the delay component supplied from the substation can be reduced. FIG. 8 shows a vector diagram of the regenerative current of the self-excited converter and the powering current of the separately-excited converter when control based on this concept is performed.
It can be seen that the in-phase component and the quadrature component cancel each other, and the delay component supplied from the substation can be reduced. Although the ideal case where the vector of the self-excited converter and the vector of the separately-excited converter are 180 ° has been described, if the self-excited converter supplies any delay component, the delay component supplied from the substation becomes small. In addition, the malfunction of the distance relay can be prevented.

FIG. 9 shows a control vector diagram of the self-excited converter in this case. By increasing the output voltage E _{C of the} converter from the AC power supply voltage E _S and setting E _C higher than in the case where the power factor is controlled to “−1”, E E
Differential voltage between _S and E _C, that is, the voltage applied to the inductance L _T in the transformer 2, it is possible to delay than the case of controlling the power factor "-1".

On the other hand, since the output voltage E _C cannot output 1 / √2 or more of the voltage V _d of the smoothing capacitor,
It is expected that E _C > V _d / √2. In this case, it is sufficient that according also set high when the voltage V _d of the smoothing capacitor 6 of power running.

FIG. 10 shows the overhead line impedance as viewed from the substation in this case.

From the point marked by the impedance X of the overhead wire when the separately-excited converter is running, the line shifts counterclockwise to the right and the impedance changes from upper left to counterclockwise.
Operation that avoids the operation area of the distance relay can be performed.

One embodiment based on the above-described concept is shown in FIG.
This will be described with reference to FIG.

An AC from an AC power supply 1 such as a substation obtained through an overhead wire is collected by a pantograph (not shown) and supplied to a transformer 2. The transformer 2 has a pulse width modulation (PWM) converter 3 which is a self-excited converter via an inductance LT (shared with the transformer winding).
Connected to. The DC side of the PWM converter 3 is connected to a three-phase PWM inverter 4 via a smoothing capacitor 6. The induction motor 5 which is a load is driven by the variable voltage / variable frequency alternating current generated by the PWM inverter 4.

The PWM converter 3 operates so that the DC voltage _Vd becomes a set value. The DC voltage command V _d * is compared with a DC voltage detection value V _d detected as a voltage across the smoothing capacitor 6 by an adder 10, and the deviation is input to a voltage regulator 11. Voltage regulator 11 outputs the peak value command I _sm of the current I _s flowing through the AC side of PWM converter 3.

On the other hand, the voltage of the AC power supply 1 detected from the secondary side of the transformer 2 is converted by the divider 14 into a unit sine wave si.
is converted to n wt, this sin wt and the peak value command I _sm are multiplied by the multiplier 12, the instantaneous AC current command I _s *. The instantaneous alternating current command I _S * and the PWM converter output current I _s is the deviation is compared with the adder 13 is input to the current regulator 17. The current regulator 17 outputs a modulated wave corresponding to the AC voltage command of the PWM converter, and the comparator 19 compares the modulated wave with the triangular wave generated by the triangular wave generator 18 to output a pulse width modulation signal. . This signal is amplified by the gate circuit 20 to control ON / OFF of the self-extinguishing type switching element constituting the PWM converter 3.

The powering / regenerative operation mode of the PWM converter 3 will be described with reference to a vector diagram. FIG.
(A) has shown the power running operation mode. The voltage phase output from the converter is delayed from the power supply voltage E _S , and E _S and E
Voltage difference between _C, that the voltage applied to the inductance L _T in the transformer 2, 90 ° with respect to the power supply voltage E _S
Control so that the phase is advanced. As a result the current flowing in L _T I _s becomes the power supply voltage E _S and phase.

FIG. 3B shows a regenerative operation mode. Contrary to the power running mode, the output voltage E _{C of the} converter
Was advanced than the power supply voltage E _S, the differential voltage between E _S and E _C, i.e. the voltage applied to the inductance L _T in the transformer 2, the power supply voltage E _S as a 90 ° phase delayed with respect to Control. Current resulting flowing in L _T I _s becomes the power supply voltage E _S and reverse phase.

Next, the adjustment of the power factor according to the present invention will be described. The voltage signal of the AC power supply 1 detected as described above is used to calculate the unit sine wave signal sin wt by the divider 14 and then to determine the powering / braking.
0, at the time of regenerative braking, a unit sine wave sin (wt−α) having a phase delayed by α from the phase of the AC power supply E _S is output by an α setting device which sets a positive value to α. Then on multiplying the I _smr, the I _sr for commanding an instantaneous value of the alternating current to flow in the inductance L _T of the transformer 2.

As described above, the regenerative current of the self-excited converter can be made to have a component that is further delayed from the power factor "-1" by adding the α setting device which determines the powering / braking to set α. It is possible to supply the delay component of the separately-excited converter during power running by this current delay component, and to reduce the delay component of the current supplied from the substation.
It is possible to operate the AC electric vehicle stably without causing the distance relay installed in the substation to malfunction.

Although it is conceivable to detect the delay component of the separately-excited converter and correct the phase to cancel it, this is not practical. As described above, even if there is some error, if the delay component supplied by the substation is reduced, the distance relay does not malfunction, so it is effective to select α in advance in which the most likely malfunction is assumed. Can be expected.

FIG. 12 shows that in order to flow a current delayed by α from the power factor “−1”, the output voltage of the converter and the power factor need to be set higher than when the power factor is controlled to “−1”. However, the maximum output voltage of the converter is V _d / √2
This is an embodiment for compensating for this.

[0036] That is, provided the function of determining the power-running brake the setter V _dr, V in powering the V _dr in the brake
provided V _d setter 16 for setting higher than _dr.

In the above embodiment, the electric motor for driving the electric vehicle is described as an induction motor. However, the present invention is not limited to this, and a DC motor controlled by a chopper or a camshaft may be used.

In the above embodiment, the PWM converter is described as a two-level converter, but the same effect can be obtained with a three-level converter.

[0039]

As described above, according to the present invention, it is possible to prevent a malfunction of a distance relay installed in a substation.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of the present invention.

FIG. 2 is a diagram illustrating the operation of a distance relay.

FIG. 3 is a diagram showing the impedance of a self-excited converter.

FIG. 4 is a configuration diagram of a separately excited converter.

FIG. 5 is a diagram showing the impedance of the overhead wire viewed from the substation when the separately-excited converter performs power running and the self-excited converter performs regenerative braking operation.

6 is a diagram showing the impedance of the overhead wire as viewed from the substation in FIG.

FIG. 7 is a diagram showing a relationship with an operation area of a distance relay.

FIG. 8 illustrates the principle of the present invention.

FIG. 9 illustrates the principle of the present invention.

FIG. 10 illustrates the principle of the present invention.

FIG. 11 illustrates an operation of a self-excited converter.

FIG. 12 is a diagram showing one embodiment of the present invention.

[Explanation of symbols]

1. AC power supply, 2. Transformer, 3. PWM converter,
4 PWM inverter, 5 induction motor, 6 smoothing capacitor, 15 α setting device, 21 DC voltage setting device.

Continuation of the front page (51) Int.Cl. ⁷ identification code FI H02P 3/18 101 H02P 3/18 101B (58) Investigation field (Int.Cl. ⁷ , DB name) B60L 7/14 B60L 9/28 B60M 3/00 H02M 7/162 H02M 7/72 H02P 3/18 101

Claims (2)

(57) [Claims] 1. An AC electric vehicle on which a distance relay is installed to detect a ground fault of an overhead line, and a line on which an AC electric vehicle having a function of converting AC into DC by a separately excited converter runs. , The AC side is connected via a transformer, the DC side is connected to the electric vehicle drive motor control device,
In a power converter for an AC electric vehicle comprising a self-excited converter (pulse width modulation converter) capable of controlling a DC voltage to a predetermined value and controlling a power factor to “1”, a regenerative operation of the AC electric vehicle using the self-excited converter To prevent the distance relay from malfunctioning due to the self-excited converter, the power factor of the self-excited converter for the AC electric vehicle having means for controlling the power factor from "-1" to the lag side during the regenerative operation of the AC electric vehicle. Conversion device. 2. The power converter for an AC electric vehicle according to claim 1, further comprising means for increasing the DC voltage during regeneration rather than during power running.