JP2749306B2 - AC electric vehicle control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an electric vehicle of a system that uses an AC motor such as an induction motor as a propulsion motor and is driven by AC power using a voltage-type converter and a voltage-type inverter. In particular, the present invention relates to an AC electric vehicle control device suitable for an electric railway system in which there is a possibility that a fluctuation in a power supply voltage becomes large. [Prior art] In recent years, maintenance-free vehicles have been increasingly improved,
Accordingly, a drive system for an induction motor using a voltage-source converter and an inverter has been adopted as a drive system for a railway vehicle using an AC power supply. In this system, an AC voltage supplied from an overhead wire or the like is converted to DC by a converter and added to a smoothing capacitor.
In addition, a DC voltage of the smoothing capacitor is applied to the inverter to generate a variable voltage, a three-phase AC voltage having a variable frequency, and the voltage is applied to the induction motor for driving to drive the vehicle. The required electric power according to the operation state of the electric vehicle is controlled so as to be supplied as a DC input of the inverter. By the way, in the electric railway system, generally, a relatively large tolerance is given to the fluctuation rate of the power supply voltage,
For example, when there are a plurality of electric vehicles in a power supply section of the same substation, a voltage fluctuation as much as ± 20% appears. Thus, in the above-described drive system, the required DC power can always be supplied to the inverter by controlling the converter despite the fluctuation of the AC power supply voltage. However, there is a limit to this. However, when the AC power supply voltage is greatly reduced, the input current of the converter must be increased. Proceedings of the IEEJ National Convention (19
1987), pp. 1099-1100. That is, the converter includes a voltage regulator for controlling the DC output voltage and an input AC current regulator for controlling the AC input current.A limiter is provided at the output of the voltage regulator, and the output of the limiter is input. The reference value for the AC current regulator is used, and the limit value at this time is made to correspond to the limit of the current or disconnection capability of the main circuit element of the converter. Thus, in the above-described prior art, even at the time of a low input voltage, the input AC current does not exceed the current-carrying or disconnection ability of the main circuit element. As a result, as a matter of course,
In this prior art, the output power of the converter is also limited. On the other hand, in the electric railway system, power is supplied from a plurality of substations via overhead lines, and the overhead lines are divided for each substation. For this reason, when an electric vehicle crosses from a power supply section of a certain substation to a power supply section of another substation, there is a non-voltage period of about 0.5 seconds. Thus, during this non-voltage period, not only can the converter not be operated, but also when a voltage is applied again, an excessive voltage or current is applied to the switching element constituting the converter, and the switching element may be damaged. There is. Therefore, in the conventional AC electric vehicle control device, control is performed as described in, for example, JP-A-60-200790. That is, a monitoring means for input AC voltage or the like is provided, and if a no-voltage period is detected, the operation state of the inverter is switched so as to perform regenerative operation in preference to torque control of the electric motor,
As a result, during the no-voltage period, regenerative power is supplied from the inverter to the smoothing capacitor, and the DC output voltage of the converter is maintained substantially equal to the voltage in the power supply section. [Problems to be Solved by the Invention] In the above conventional technology, no consideration is given to the fact that the output power of the converter is limited when the input AC voltage of the converter is reduced. For this reason, if the inverter consumes more power than the maximum DC power that can be output by the converter during the power running operation of the electric vehicle, the DC voltage of the smoothing capacitor decreases, and the converter and the inverter cannot cooperate. There is a risk that the vehicle will become uncontrollable. Further, in the conventional technology, during regeneration operation, when the inverter regenerates power greater than the maximum power that can be regenerated to the power supply by the converter to the smoothing capacitor, the voltage becomes excessively large, and the main circuit elements and the like constituting the converter and the inverter are damaged. There is a risk of damage. An object of the present invention is to provide an AC electric vehicle control device capable of always operating stably without fear that the cooperative operation of the converter and the inverter is disrupted even if the input AC voltage fluctuates. [Means for Solving the Problems] The above object is achieved by controlling the current of an AC motor for electric vehicle propulsion to maintain the DC side voltage of the inverter. Specifically, the above object is to provide a voltage source converter for converting AC power to DC power by PWM control, and a voltage source for converting the DC power to AC power by PWM control and supplying power to an AC motor for propelling an electric vehicle. An AC electric vehicle control device, comprising: an inverter; a smoothing capacitor connected to a DC side coupling portion between the converter and the inverter; and current control means for controlling an AC input current of the converter to a command value. This is achieved by providing control means for controlling the AC input current of the converter to a constant value and reducing the output current of the inverter when the AC input current of the converter reaches the limit value when the motor is running. [Operation] When the input AC current of the converter reaches the limit value during the power running operation, the power consumption of the inverter is also limited accordingly, thereby keeping the power supply of the converter and the power consumption of the inverter equal. Prevent voltage drop of smoothing capacitor. On the other hand, when the current of the converter reaches the limit value during the regenerative operation, the regenerative power of the inverter is limited, which keeps the regenerative power of the converter and the inverter equal and the voltage of the smoothing capacitor becomes excessive. To prevent As a result, the voltage of the smoothing capacitor is maintained, and the electric vehicle can be operated continuously. Hereinafter, an AC electric vehicle control device according to the present invention will be described in detail with reference to the illustrated embodiments. FIG. 1 shows an embodiment of the present invention. In this embodiment, an AC voltage from a substation (not shown) is applied to the primary side of a transformer 3 via an overhead wire 1 and a pantograph 2, and the secondary voltage is applied to the transformer. the E _s through the reactor 4 and summer to apply the voltage type converter 5. Here, the converter 5 is composed of a self-extinguishing switching element such as a GTO thyristor and a diode,
The AC input terminal voltage E _c, by operating as described later, the magnitude and phase of the input current I _s is controlled. FIG. 2 shows these relationships in a vector diagram. That is, the secondary voltage E _s, when set as shown in the drawing the input terminal voltage E _c, the reactor voltage E _L the difference between the two is applied to the reactor 4. Where the input current _Is
And the reactor voltage E _L are orthogonal, so the input current
I _s is as shown in the figure. Was but connexion, by operating the imaginary axis component (component perpendicular to the secondary voltage E _s) E _ci of the input AC voltage E _c, the effective component of the input current I _s (secondary voltage E _s and phase component) is It is controlled by operating a real axis component E _cr of the input AC voltage E _c, the input current I _s of the phase (the fundamental wave power factor) is controlled. Then, a DC power equal to the input AC power is generated on the DC side, whereby the terminal voltage of the smoothing capacitor 6 becomes _Ed . On the other hand, voltage source inverter 7 is constructed from self-commutation of switching-element and a diode, based on the DC voltage E _d, the known PWM (Pulse Width Modulation, PWM) by control technology, variable voltage, variable A three-phase AC voltage having a frequency is generated and added to the induction motor 8 for propulsion. As a result, currents I _u , I _v , and I _w flow. Here, a method of controlling the supply current to the induction motor 8 will be described. First, among the currents I _u I _v and I _w of the motor 8, an effective motor current I _mr (a component in phase with the voltage) is detected by the current detector 9, and is compared with an effective motor current command I _mr ^* .
Motor current regulator 10, depending on the deviation, and outputs a slip frequency f _s. Further, the rotor rotational frequency f _r of the motor 8, and detected through the pulse diethyl Nereta 11 adds the slip frequency f _s, defines the inverter frequency f _i, the modulation degree control circuit 12, the voltage of the electric motor 8 is As proportional to the inverter frequency f _i ,
The modulation degree K is controlled. Then, PWM modulation circuit 13 performs pulse width modulation control in accordance with the inverter frequency f _i and the modulation factor K, is added to the inverter 7 generates a gate pulse. In this way, the effective motor current I _mr is controlled to be equal to the effective motor current command I _mr ^* . Here, the effective motor current command I _mr ^* has a polarity, and when this is positive, the slip frequency f _s is also positive,
The electric motor 8 generates a positive torque to perform a power running operation. Also,
At this time, the inverter input current _Ii has the illustrated polarity. On the other hand, when the effective motor current command I _mr ^* is negative, the slip frequency f _s also becomes negative, and the motor 8 generates a negative torque to perform regenerative braking operation. At this time, the inverter input current I _i And reverse polarity. Next, a description will be given of a control method of the DC voltage E _d by the converter 5. First, the DC voltage E _d compared to the DC voltage command E _d ^*, the voltage regulator 14 generates an output signal epsilon _ed in accordance with the deviation, in addition to Rimitsuta 15, Rimitsuta 15, the effective input current command I _sr
^*, And outputs the motor current correction command I _mrc. On the other hand, the input current detector 16, of the input current I _s, the secondary voltage E _s and phase component, i.e. detects the valid input current I _sr, compares it with valid input current command I _sr ^*, the deviation Is added to the current controller 17 and the input terminal voltage E _{c of the} converter 5 is
Outputs the imaginary axis component E _ci of. The phase detector 18 detects a phase difference phi between the input current I _s and the secondary voltage E _s, the phase adjuster the deviation between the phase command phi ^*
In addition to 19, the real axis component E of the input terminal voltage E _c of the converter 5
Output _cr . Then, the PWM modulation circuit 20 performs pulse width modulation control in accordance with the real axis component E _CR and the imaginary axis component E _ci of E _c , generates a gate pulse, and applies the gate pulse to the converter 5. In this manner, the effective component of the input current I _s, i.e. the effective input current I _sr is equal to the command I _sr ^*, phase difference phi is controlled to be equal to the phase command phi ^*. Here, the effective input current command I _sr ^* and the effective input current I _sr have polarities, and when positive, mean the same phase as the secondary voltage E _s , that is, power running operation, and the converter output current I _d is illustrated. Flow with the polarity. On the other hand, a negative value indicates a regenerative operation, and the converter output current _Id has a polarity opposite to that shown in the figure. Incidentally, Rimitsuta 15 has a characteristic shown in FIG. 3, in accordance with the output signal epsilon _ed voltage regulator 14, controls the effective input current command I _sr ^* and the motor current correction command I _mrc. Here, the input current limit I _SM is permissible maximum current of the input current I _s, which is determined from the current interruption capability and the like of the main circuit elements which constitute the converter 5. In a normal operation state, the output signal ε of the voltage regulator 14
_ed changes between a and b in FIG. 3. In this range, the effective input current command I _sr ^* is proportional to the output signal ε _ed , and the motor current correction command _Imrc is zero. Therefore, during power running, i.e., when the operation command I _p is positive, small converter output current I _d from the inverter input current I _i, the DC voltage E _d is decreased, the voltage regulator
The 14 output signal ε _ed increases, the effective input current command I _sr ^* increases, and the converter output current I _d increases. In this way, regardless of the value of the inverter input current I _i, the DC voltage E _d is controlled to be constant. On the other hand, during regenerative braking, the inverter input current I _i
, The current flows from the inverter 7 to the smoothing capacitor 6. As a result, when the DC voltage _Ed increases,
The output signal ε _ed of the voltage regulator 14 becomes negative, and the effective input current command I _sr ^* also becomes negative. As a result, the converter 5 is reversed polarity of the converter output current I _d Te summer and regenerative operation, current flows from the smoothing capacitor 6 to the converter 5, the DC voltage E _d is kept constant. The above is the description of the operation during normal operation, that is, when the output signal ε _ed of the voltage regulator 14 is in the range from a to b in FIG. Then, when the secondary voltage E _s during power running is reduced, decreased input power of the converter 5, the converter output current I _d is decreased. As a result, the DC voltage _Ed decreases and the voltage regulator
The 14 output signal ε _ed increases. When the output signal ε _ed becomes larger than b in FIG. 3, the effective input current command I _sr
^* It is kept in the input current limit I _SM. As a result, it is also the converter output current I _d is maintained constant, the motor current correction command I _mrc is increased. Therefore, the fourth
As shown by the dashed line in the figure, the effective motor current command I _mr
^* Decreases, the inverter input current I _i be decreased, the DC voltage E _d is kept constant. On the other hand, when the secondary voltage E _s is decreased at the time of regenerative braking operation, reduces the regenerative power of the converter 5, is reduced (opposite polarity to that of the illustrated) converter output current I _d. As a result, the DC voltage _Ed increases, and the output signal ε of the
_ed decreases. Here, when the output signal ε _ed becomes smaller than “a” in FIG. 3, the effective input current command I _sr ^* has an absolute value equal to the input current I _SM and a negative polarity. As a result, although the converter output current I _d is maintained constant, as shown in FIG. 4 in two-dot chain line, the absolute value of the effective motor current command I _mr ^* is decreased, the absolute value of the inverter input current I _i also it decreases, the DC voltage E _d is kept constant. Accordance connexion, according to this embodiment, the secondary voltage E _s is reduced,
Even when the effective input current command I _sr ^* is kept at the current limit I _SM , the electric vehicle can be operated by controlling the DC voltage _Ed to be constant. Further, according to this embodiment, even in the no-voltage period when the electric vehicle is crossing the feeder section, as in the case where the secondary voltage E _s is decreased, the effective motor current command I _mr ^* is operated, a DC voltage E It is clear that _d is kept constant. [Effects of the Invention] According to the present invention, the AC power supply voltage is reduced, and as a result,
Even if the converter input current is limited to a limit value determined by the current capacity of the main circuit element, etc., the DC voltage is kept constant by operating the motor current, so that the stable operation of the electric vehicle continues even at low input voltage. There is an effect that becomes possible.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram showing an embodiment of an AC electric vehicle control device according to the present invention, FIG. 2 is a vector diagram for explaining operation, and FIGS. FIG. 3… Transformer, 4… Reactor, 5… Voltage converter, 6… Smoothing capacitor, 7… Voltage inverter, 8…
Propulsion induction motor, 9 current detector, 10 motor current regulator, 11 pulse generator, 12 modulation degree controller, 13 PWM modulation circuit, 14 voltage regulator, 15 ... limiter, 16 ... input current detector, 17 ... current regulator, 18 ... phase detector, 19 ... phase regulator, 20 ... PWM modulation circuit.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-62-210866 (JP, A) JP-A-62-213503 (JP, A) JP-A-60-59904 (JP, A) JP-A-59-210 99902 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) B60L 9/08-9/30

Claims (1)

(57) [Claims] A voltage-source converter that converts AC power into DC power by PWM control, a voltage-source inverter that converts the DC power into AC power by PWM control, and supplies power to an AC motor that propels the electric vehicle, An AC electric vehicle control device comprising: a smoothing capacitor connected to a side coupling portion; and current control means for controlling an AC input current of the converter to be a command value. When the input current reaches a limit value, the AC electric vehicle control device is provided with control means for controlling the AC input current of the converter to a constant value and reducing the output current of the inverter.