JPS6115642B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power conversion control method for an AC electric vehicle, and particularly to a power regeneration control method in a high speed range.

First, a conventional power conversion control method for electric vehicles will be explained.

FIG. 1 is a main circuit configuration diagram of an AC electric vehicle equipped with a power regenerative brake during regenerative braking. In this figure, 1 is the overhead contact line, 2 is the pantograph, 3 is the main transformer, 31 is its primary winding, 32 and 33 are its armature secondary windings, and 34 is its field secondary winding. It is a line. 4 is a power converter, 41 to 48 are thyristors for controlling the armature circuit, 49 and 52 are thyristors for controlling the field circuit, and 50 and 51 are diodes for controlling the field circuit. 6 is the main smoothing reactor for current smoothing, 7 is the armature of the drive DC motor, 8 is the armature series resistance for supplementing the lack of regenerative braking force in the high-speed range with the generating brake, and 9 is the armature series resistance 8. A resistance control device 10 for controlling the resistance value is a field winding of the DC motor 7.

In such a main circuit, in order to convert the energy of an electric car with a certain kinetic energy into electric power regeneration energy, the armature 7 of the DC motor must be
The direction of the induced voltage generated in is given by the direction of the solid arrow in the figure. On the other hand, the DC voltage (average value) of the thyristor bridge constituted by the thyristors 41 to 48 is controlled by controlling the phase control angle so that the voltage is output in the opposite direction to that during power running, as indicated by the broken line arrow in the figure. Then, due to the action of the main smoothing reactor 6, the current flows in the opposite direction to the voltage of the thyristor bridge, that is, in the same direction as the induced voltage of the armature 7, and the power converter 4 consumes negative power. This means that power is being regenerated.

FIG. 2 shows a control block of the current control system during regenerative braking. In this figure, 11 is a brake notch command, 12 is a speed signal, 13 is a brake force pattern generator, 14 is a brake force/current converter, 15, 18, 20 are comparators, 16, 21 are phase shifters, 17 is a thyristor bridge for the armature circuit of the power conversion device, 19 is the main circuit constant, 22 is the thyristor for the field circuit of the power conversion device, 23 is the field circuit constant, 24 is the DC motor characteristic, 25 and 26 are current detection It is a vessel.

When a regenerative braking operation is performed on an electric vehicle having a certain speed, the brake force pattern generator 13
A predetermined braking force BE pattern given by the speed V and the size of the brake notches BN1 to BN3 is generated. This brake force BE pattern passes through the brake force/current converter 14 and becomes the armature current I _a pattern, which is then commanded to the comparator 15 . The comparator 15 compares the magnitude of this armature current pattern with the actual inorganic current, applies the deviation to the phase shifter 16, and outputs the output of the phase shifter 16 to the armature circuit thyristor bridge 17. given to control the rectifier voltage. On the other hand, the armature of the DC motor generates an induced voltage E _M under the control described below, and the difference from the rectifier voltage is taken on the main circuit connection.
Through the main circuit constant 19, armature current I _a is generated. The main circuit constant 19 is generally expressed as 1/(R+SL), where L is the inductance of the main circuit, R is the DC resistance of the main circuit, and S is the Laplace operator. Actually, the armature current I _a is detected by the current detector 26
The signal is converted through the , and is provided to the comparator 15 as a feedback input. Generally, the field of a DC motor is separately excited controlled during regenerative braking, and I _a = I _f
In the total field control, as shown in the figure, the output signal of the current detector 26 of the armature current I _a is given to the comparator 20 as the command value of the field current If, and the output signal of the current detector 25 of the actual field current _{I f is} applied to the comparator 20 as the command value of the field current If. This is done by comparing the output signal and applying the deviation to the field circuit thyristor 22 via the phase shifter 21. When a field current If flows through the DC motor, an induced voltage E _M is generated which is determined by the speed _V and the characteristics 24 (saturation characteristic curve) of the DC motor. The electric brake power is this induced power E _M
It is given by the product of the armature current Ia and the armature current _Ia .

Further, FIG. 3 is a control characteristic diagram for speed during electric power regenerative braking. In this figure, BE is the required braking force, which is shown by the characteristics of the broken line ABCD,
It is assumed that the total field control characteristic (I _a =I _f ) for obtaining this necessary braking force is approximated by a broken line EFGH. Moreover, the curve ab is the commutation failure limit of the power converter 4 when the armature series resistance 8 shown in FIG. 1 is zero ohm. In other words, the shaded area CDI
This shows that the braking force at is in a range that exceeds the commutation capacity of the thyristor.

Therefore, since the predetermined braking force cannot be obtained as it is, an armature series resistor 8 and a resistance control device 9 are provided as shown in FIG. It is necessary to push it outward. That is, by inserting the armature series resistor 8, the resistor R of the main circuit constant 19 in Fig. 2 is increased, and the induced voltage in the armature is increased by the voltage drop, and the In other words, the braking force obtained can be increased, that is, the commutation failure limit can be increased. However, it goes without saying that the braking force increased by the armature series resistor 8 is not regenerated power but generated braking force. The resistance control device 9 is configured such that after inserting a predetermined armature series resistor 8 at a speed K shown in FIG. 3, the resistance value of the armature series resistor 8 is continuously changed according to the speed, It is ideal to use, for example, a chopper device, which completely shorts the armature series resistor 8 at . It is also possible to use a unit switch for resistor shorting without using such a chopper device, but in the case of using this unit switch, the line CI below the shaded area CDI has a stepped shape. , and the drawback that regenerated power decreases is unavoidable.

As described above, in conventional power conversion control methods, it is common for braking force to be insufficient due to the commutation failure limit, especially at high speeds.In order to compensate for this lack of braking force, electrical A secondary series resistor 8 and a resistance control device 9 are required. Further, as can be easily inferred from the above explanation, increasing the number of thyristor bridges in the power conversion device in order to increase the commutation failure limit is an effective means for countering insufficient braking force. however,
In this case as well, a high voltage control device will be added,
Similar to the former method, there are major problems in that it increases weight, increases the number of maintenance equipment, and increases the price of control electrical components. Furthermore, it may be possible to supplement the lack of braking force with an air brake rather than an electric brake, but this may cause wear and tear on the brake shoe.
Considering the adoption of electro-pneumatic brake blending control, the advantages of an electric regenerative braking vehicle are being diminished in one step, as it requires increased maintenance compared to a regenerative braking vehicle.

The present invention has been made in view of these points,
The purpose is to omit or reduce armature series resistance to compensate for insufficient braking force.
Moreover, it is an object of the present invention to provide a power conversion control method for an AC electric vehicle that can obtain good electric braking characteristics.

In order to achieve this objective, the present invention focuses on the fact that the commutation failure limit of a power conversion device increases with the magnitude of the armature current.
In the high-speed range, the armature current is increased to increase the commutation failure limit, and the required braking force is inversely proportional to the increase in armature current, and the induced voltage is reduced, in other words, the field current is controlled to be small. As a result, the armature series resistance can be omitted or reduced.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 4 is a main circuit configuration diagram during regenerative braking of an AC electric vehicle with power regenerative braking to which the method of the present invention is applied. In this figure, the same symbols as in Figure 1 indicate equivalent parts, and the armature series resistance 8
and the resistance control device 9 are omitted.
It is exactly the same as the figure.

FIG. 5 is a control block diagram of a current control system during regenerative braking for carrying out the method of the present invention. In this figure, the same reference numerals as in FIG. 3 indicate the same or equivalent parts, and 27 is a speed detector for pattern conversion, 28 is an armature current pattern generator, 29 is a field current pattern generator, and 30 is a logic It is a product circuit.

In order to control the armature current I _a to be larger than the I _a =I _f characteristic value in the high speed range, a pattern conversion speed detector 27 is provided. The detection speed is
When there is no armature series resistor 8 for supplementing brake force, it is effective to keep the induced voltage of the DC motor close to the speed determined by the commutation failure limit of the power converter. In response to the output of the speed detector 27, the armature current pattern generator 28 generates a predetermined pattern. Here, only the armature current I _a of the BN1 notch is controlled to a greater extent than the detection speed V ₀ , but the armature current pattern of the BN2 notch can also be changed if necessary.

Corresponding to such conversion of the armature current pattern, the field current pattern is controlled by the field current pattern generator 29. That is, the field current pattern generator 29 uses the output of the speed detector 27 to switch from the full field control characteristic of I _a = _If (indicated by the solid line in the figure) to the weak field characteristic shown by the broken line as shown in the figure. This is performed in response to the output of the circuit 30 which performs an AND with the contents of the brake notch. Note that the field current pattern generator 29 can also control the weakest field rate determined from the rectification characteristics of the DC motor.

FIG. 6 shows the control characteristics for speed in this case. In Fig. 3, the armature current I _a is increased as GL from around the speed J where the commutation failure limit when the armature series resistance is 0 ohm intersects with the required braking force BE characteristic at point C, thereby increasing the commutation failure limit. As shown by the curve aCf, the required braking force BE characteristic is pushed up. The reason why the commutation failure limit rises as the armature current I _a increases is as follows.

That is, the armature induced voltage E _M corresponding to the commutation failure limit is given by the following equation.

E _M = 0.9E ₂ × cosβmin + 2/πXId + (R _ac + R _dc ) I _d ... (1) Here, E ₂ : Main transformer secondary conversion voltage βmin: Minimum control advance angle of power converter X: Main transformer Commutation reactance I _d : DC total current R _ac : DC resistance value of AC circuit of main transformer secondary conversion R _dc : DC resistance value of DC circuits such as main smoothing reactor and armature On the other hand, The brake force BE generated is shown by the following relational expression.

BE∝(E _M ′・I _d )/V …(2) Here, E _M ′: Actual armature induced voltage V: Speed From equation (1) above, if the DC current I _d is increased, cooβ
Although min decreases slightly, the magnitudes of the second and third terms increase, and the armature induced voltage E _M in equation (1)
It is clear that (that is, the commutation failure limit) increases. Of course, there is an overvoltage limit value for the armature induced voltage E _M that is determined by the structure of the DC motor, but in the case of AC electric cars, it is suppressed to the maximum DC voltage of the power converter, so most of the overvoltage limit values are determined by the DC motor's overvoltage limit value. Electricity regeneration will be performed below.
Therefore, the overvoltage limit of DC motors will not be mentioned below.

On the other hand, the required braking force at a certain speed is usually
From the deceleration performance of the electric vehicle, the braking force BE characteristic is given as shown in Figures 3 and 6, so if we increase the DC current to raise the commutation failure limit, the armature-induced It is necessary to reduce the voltage E _M ' to obtain the required braking force. That is, the field current I _f is reduced as shown by the curve GM to perform weak field operation.

Therefore, according to this embodiment, the armature series resistance and the resistance control device are not required, and the weight, size and economic effects are significant.

Note that in weak field operation of a DC motor, there is a weakest field rate due to its rectification characteristics, so it cannot always be said that it is possible to ideally eliminate the armature series resistance, but at least the armature series resistance can be reduced as compared to the conventional one. It is possible to design it much smaller than the conventional design.

As described above, according to the present invention, it is possible to omit or reduce the armature series resistance for supplementing insufficient braking force, and therefore, weight, size, and economic effects can be expected.

[Brief explanation of the drawing]

Fig. 1 is a main circuit configuration diagram of a conventional AC electric car with power regenerative brake during regenerative braking, Fig. 2 is a control block diagram of the current control system of the same AC electric car during regenerative braking, and Fig. 3 is the same AC electric car. A control characteristic diagram for speed during regenerative braking of an electric vehicle. FIG. 4 is a main circuit configuration diagram during regenerative braking of an AC electric vehicle with electric power regenerative brake to which the method of the present invention is applied. FIG. 5 is a diagram showing the implementation of the method of the present invention. FIG. 6 is a control characteristic diagram for explaining a control method according to an embodiment of the present invention. 3...Main transformer, 4...Power converter, 7...
Armature of driving DC motor, 10... Field winding of driving DC motor, 11... Brake notch command, 12... Speed signal, 13... Brake force pattern generator, 15, 18, 20... Comparator, 1
6, 21... Phase shifter, 17... Thyristor bridge for armature circuit of power converter, 19... Main circuit constant, 22... Thyristor for field circuit of power converter, 23... Field circuit Constant, 24...Driving DC motor characteristics, 25, 26...Current detector, 27
... Speed detector for pattern conversion, 28 ... Armature current pattern generator, 29 ... Field current pattern generator, 30 ... AND circuit, BE ... Brake force, I _a ... Armature current, I _f ...field current, V...
…speed.

Claims (1)

[Claims] 1. A power converter comprising: an AC power source, a transformer connected to the AC power source, and a driving DC motor connected to a secondary circuit of the transformer via a power converter; The device supplies DC power to the drive DC motor during power running, and during power regenerative braking, converts the generated power of the drive DC motor to the AC power source side to perform power regeneration. At high speeds, the armature current and field current are made larger and at the same time smaller than the values of the armature current and field current during full field operation of the drive DC motor to obtain the same braking force. 1. A power conversion control method for an AC electric vehicle, characterized by performing power regenerative brake control. 2. A power conversion control method for an AC electric vehicle according to claim 1, wherein the high speed range is a speed range that substantially corresponds to a commutation failure limit range of the power converter. 3. In claim 1, the alternating current electric current is characterized in that the control of the armature current and field current in the high speed range is performed by switching the armature current pattern and the field current pattern using a speed signal. Vehicle power conversion control method.