JP2008113543A - Power controller of railway car - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve braking performance and regeneration rate of regeneration power to a wire and to enable improvement in acceleration performance, when running at acceleration, without having to use an inverter incorporating special high-voltage, large-capacity switching elements. <P>SOLUTION: A main inverter 7 and a sub-inverter 8 are connected in parallel to a wire 1. AC side power lines L1-L3 of the main inverter 7, and power lines L7-L9 of an induction motor 10 are connected to one ends and to the other ends of the secondary windings (Ua, Va, Wa) of a three-phase transformer 9. AC-side power lines L4-L6 of the sub-inverter 8 are connected to one ends of the primary windings (Ub, Vb, Wb) of the transformer 9, and the other ends of the primary windings are short-circuited. The winding ratio λ of the transformer 9 is 0.4. When a motor-driven car 2 is braked during high-speed running, induced voltage of approximately 140%, caused by the main inverter 7 and the sub-inverter 8, is generated in the induction motor 10, so that the braking performance is improved. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a power control apparatus for a railway vehicle in which regenerative power induced by a regenerative brake using a traveling drive motor is returned to an overhead line via an inverter of a PWM control system, and a voltage addition transformer is provided. And at least the regenerative voltage during braking is increased.

  Conventionally, an electric power regenerative braking system is generally known as a braking system for railway vehicles such as electric locomotives and electric vehicles. This power regenerative braking system is generated by power generation by using a motor used for driving during braking as a generator to generate power using kinetic energy stored in the railway vehicle, and also applying braking force to the railway vehicle. In this method, the regenerative power is returned to the overhead line by an inverter.

  According to this power regenerative braking method, there is a great advantage that the regenerated electric power can be effectively used compared to a brake method in which the regenerated electric power is wastefully consumed as heat generation energy by resistance, such as a dynamic brake. .

  Therefore, for example, the regenerative control device for an electric vehicle described in Patent Document 1 converts a direct current collected from an overhead wire through a pantograph into a three-phase alternating current by an inverter (VVVF inverter) during powering, and this conversion By supplying the generated three-phase alternating current to the induction motor, the electric vehicle is driven to travel, while at the time of regeneration, the inverter is based on the modulation factor and the regenerative brake current pattern set according to the traveling state of the electric vehicle. Is controlled so as to act as a regenerative converter, and most of the kinetic energy of the electric vehicle is converted into electric energy by an induction motor acting as an induction generator and regenerated on an overhead line.

  In general, a VVVF inverter used for driving an induction motor to travel is designed to withstand a maximum voltage substantially equal to the overhead wire voltage. Therefore, in the electric vehicle regenerative control device described in Patent Document 1, the regenerative power generated by the power generation action of the induction motor acting as an induction generator is converted into DC electric energy by the VVVF inverter and regenerated on the overhead line. In doing so, as shown in FIG. 9, during high-speed running that decelerates from about 100 km / h to about 70 km / h, it is restricted so as not to exceed the overhead line voltage, and good braking performance cannot be obtained. In FIG. 9, the torque, power, current, and voltage of the electric motor are expressed with the maximum value during power running as 100%.

  By the way, when the regenerative brake is operated, generally, even if the regenerative voltage induced by the induction motor is increased, the upper limit voltage in use of the VVVF inverter is limited, and the overhead line transmitted from the substation to the overhead line The high voltage regenerative voltage which is restricted by the voltage and greatly boosted from the overhead line voltage cannot be regenerated to the overhead line. Therefore, the voltage induced in the induction motor and used for regeneration is limited to about 110% of the overhead line voltage at the maximum.

  Regarding the electric brake force and brake power during regeneration, the magnitude relationship is often discussed as compared with the case of a dynamic brake (resistance brake) of a DC motor-driven train. In a DC motor-driven train, in the high-speed region of power running, the induced electromotive force of the motor balances with the overhead line voltage and the current necessary for acceleration does not flow, so a current shunt is generally provided in parallel with the field winding. The field weakening control is used to reduce the induced electromotive force of the motor and increase the current from the overhead wire to secure the acceleration force while being weak.

  On the other hand, a dynamic brake is used as the brake, and in this case, the relationship with the overhead line is cut off. Therefore, field weakening control is not performed, and the entire field is used even at high speed. For this reason, the induced electromotive force of the motor is twice that of powering (in some cases, more than twice). If the current is the same as the powering current, the power at the brake start point is approximately 200%, in the range from high to low. Has realized a powerful electric brake.

  Compared to the above, since the field weakening is performed in the induction motor during regeneration at high speed, the regenerative power is only about 140%, and the braking torque is smaller than about 100% at low speed. It has become. Therefore, good braking performance cannot be ensured. For this reason, dynamic brakes and mechanical brakes that are standard equipment on electric vehicles are used in combination during regeneration at high speeds. However, when the vehicle speed is reduced to about 70 km / h, the braking torque recovers to the maximum of about 100%, so that a relatively large braking force can be obtained at about 70 km / h or less.

  On the other hand, when the electric vehicle is powered, as shown in FIG. 10 (the torque, power, current, and voltage of the electric motor are expressed with the maximum value during power running as 100%, respectively) / F = Constant acceleration (where V is voltage and F is frequency) is performed, and the pulse mode is sequentially switched to the high speed side to become a three-pulse mode. Furthermore, when driving at high speed, the driving voltage is maximized (about 100%) by switching to the 1-pulse mode. Thereafter, traveling control is performed in which the field is weakened while the voltage is constant and the power is constant and only the frequency is changed.

FIG. 11 shows another example of the regenerative braking characteristics of a currently used railway vehicle. As shown in this figure, in order to reduce the weight of the motor, the transition point from V / F = constant control region to constant voltage frequency control is set as low as possible. In the constant voltage region, the motor current is controlled. The range of constant torque is expanded as much as possible to reach the limit of the stopping torque of the motor, and the high speed region is used to control the torque in the characteristic region of the motor.
JP-A-8-251706 (pages 2-4, FIG. 3)

  As described above, when the vehicle speed is high speed of about 100 km / h to about 70 km / h, the brake performance is poor, and therefore dynamic brakes and mechanical brakes must be used together. Therefore, there is a method of increasing the regenerative voltage or regenerative current induced by the induction motor when the braking performance is increased by increasing the braking torque at high speed without using such a dynamic brake or mechanical brake. .

  However, when the regenerative voltage induced by the induction motor is increased, the upper limit voltage for use of the VVVF inverter is almost limited to the overhead line voltage, and is limited by the overhead line voltage transmitted from the substation to the overhead line. The high-voltage regenerative voltage that is significantly higher than the overhead line voltage cannot be regenerated on the overhead line. On the other hand, it is impossible to increase the regenerative current induced by the induction motor because it is limited by the electric capacity of the VVVF inverter and the induction motor.

  In any case, the braking performance of the regenerative brake when the electric vehicle is traveling at high speed could not be improved, and the mechanical brake had to be used with the intention of energy loss. As described above, when dynamic brakes and mechanical brakes are used in combination, the regenerative power induced by the induction motor is released into the atmosphere as heat, which reduces the recovery rate of regenerative power and is extra for mechanical brake maintenance. There are problems such as cost and work being required.

  On the other hand, in the power running of the electric vehicle, as shown in FIG. 10, when the vehicle speed reaches about 50 km / h, the voltage is constant and the power is constant, so that the motor torque decreases as the speed increases. Therefore, since the current is constant, the voltage is constant, and the power is constant when the vehicle speed is about 50 km / h or higher, the V / F ratio decreases when the vehicle is further accelerated. The VVVF inverter is controlled so as to be small so that the motor torque does not exceed the stationary torque, and there is a problem that the acceleration performance is inferior.

  The object of the present invention is to improve the braking performance and improve the regeneration rate of regenerative power to the overhead line while effectively utilizing the existing inverter without depending on the inverter using a special high-voltage large-capacity switching element. For example, to improve acceleration performance during acceleration traveling.

  The power control apparatus for a railway vehicle according to claim 1 is a three-phase induction motor for driving driving, and electric power that can be supplied to the induction motor by converting the direct current of the overhead wire into three-phase alternating current during traveling and regenerated by the induction motor during braking. In a railroad vehicle power control apparatus comprising: a variable voltage / variable frequency type first inverter that can convert DC into DC and supply it to an overhead line; and an inverter control means that performs PWM control on the first inverter. A variable voltage / variable frequency type second inverter connected in parallel with the first inverter and controlled by the inverter control means; a secondary winding provided between the AC power line of the first inverter and the induction motor; A voltage addition transformer for boosting the regenerative voltage of the induction motor at least during braking, and a primary winding connected to the AC power line of the second inverter The inverter control means operates the first and second inverters until decelerating to a predetermined speed from the high speed side during regeneration, and operates only the first inverter when decelerating at a vehicle speed equal to or lower than the predetermined speed. The second inverter is controlled when only operating, and the primary winding of the voltage adding transformer is short-circuited to prevent a voltage drop of the secondary winding.

  When only the first inverter is operated, the second inverter must always short-circuit the primary winding of the voltage addition transformer so that the voltage drop of the secondary winding of the voltage addition transformer does not occur. is there. In the case of this short circuit, control is performed so that the load of each switching element is equal so that the current is not concentrated on a limited element among the plurality of switching elements included in the second inverter. Therefore, in the following description, when only the first inverter is operated, it is assumed that the short-circuit condition that the second inverter short-circuits the primary winding of the voltage addition transformer is satisfied.

  When the railway vehicle is decelerated from the high speed side to a predetermined speed, the inverter control means not only PWM-controls the first inverter but also PWM-controls the second inverter at the same time. Thereby, these two first and second inverters are regenerative circuits (load circuits) that regenerate regenerative power to the overhead wire with respect to the induction motor via the voltage addition transformer (three-phase transformer). The regenerative voltage becomes higher by the amount of voltage generated in the secondary winding via the second inverter and the primary winding of the voltage addition transformer than in the case of collecting only by the first inverter.

  In this way, the regenerative voltage is increased by the amount of operation of the second inverter until it is decelerated from the high speed side to the predetermined speed, so that the regenerative power can be increased with a constant braking torque. Therefore, since the braking torque of the induction motor can be kept constant during braking during high-speed running of the railway vehicle, the regenerative brake can be applied with this braking torque kept constant, and the braking performance is improved.

  By the way, when the railway vehicle is decelerated at a vehicle speed equal to or lower than a predetermined speed, the inverter control means performs PWM control only on the first inverter. In this case, since the inverter control means controls the second inverter to short-circuit the primary winding of the voltage addition transformer, the voltage drop due to the transformer is prevented and the braking operation by the first inverter is adversely affected. It does not affect.

  A power control apparatus for a railway vehicle according to a second aspect is the power control apparatus for a railway vehicle according to the first aspect, wherein the inverter control means operates only the first inverter until acceleration to a set speed during acceleration traveling, and accelerates at or above the set speed. Operates the first and second inverters, and when only the first inverter is operated, the second inverter is controlled to short-circuit the primary winding of the voltage addition transformer, thereby causing a voltage drop in the secondary winding. It is characterized by not.

  The power control apparatus for a railway vehicle according to claim 3 is a three-phase induction motor for driving driving, and electric power that can be supplied to the induction motor by converting the direct current of the overhead wire into three-phase alternating current during traveling and regenerated by the induction motor during braking In a railroad vehicle power control apparatus comprising: a variable voltage / variable frequency type first inverter that can convert DC into DC and supply it to an overhead line; and an inverter control means that performs PWM control on the first inverter. A variable voltage / variable frequency type second inverter connected in parallel with the first inverter and controlled by the inverter control means; a secondary winding provided between the AC power line of the first inverter and the induction motor; A voltage addition transformer for boosting the regenerative voltage of the induction motor at least during braking, and a primary winding connected to the AC power line of the second inverter Converter control means is characterized in that actuating during regeneration and acceleration both the first and second inverters over the entire speed range.

  In this power control device, the inverter control means operates the first inverter and the second inverter over the entire speed range during regeneration and during acceleration travel. Here, the output voltage E1 of the first inverter and the output voltage of the second inverter in claim 1 are shown in FIG. 3, respectively, and the output voltage E1 of the first inverter and the output voltage E2 of the second inverter in claim 2 are shown in FIG. As shown in FIG.

  The output voltage E1 of the first inverter increases in proportion to the speed V1 from zero to the maximum voltage E1M (“100%” during power running in FIG. 2 and “110%” during regeneration in FIG. 3). The speed when the output voltage E1 of the first inverter reaches the maximum voltage E1M is V1M, and the frequency is F1M. Thereafter, the output voltage E1 of the first inverter is constant, and only the frequency F1 changes. From this time, the second inverter starts to operate, and the output voltage E2 of the second inverter increases in proportion to the speed difference between the actual speed V and the maximum voltage speed V1M when the maximum voltage E1M is reached.

  After the output voltage E2 of the second inverter reaches the maximum voltage E2M, the output voltage E2 is constant, and only the frequency F2 increases in proportion to the speed difference between the actual speed V and the maximum voltage speed V2M. The size of the voltage adding transformer is the ratio between the maximum voltage E2M of the output voltage E2 of the second inverter and the maximum voltage speed V2M when the maximum voltage E2M is reached, that is, the maximum frequency F2M at the maximum voltage speed V2M. That is, it is determined by E2M / F2M. In the first and second aspects described above, the output voltage E2 of the second inverter changes in proportion to the speed difference between the actual speed V and the maximum voltage speed V2M, not the actual speed V at that time.

  Therefore, the magnetic flux density of the voltage addition transformer becomes maximum at the maximum voltage speed V2M. In the range where the speed is higher than the maximum voltage speed V2M, the field weakening region is obtained. Therefore, the voltage adding transformer becomes a field weakening and the magnetic flux density is lowered. In the region where the speed is lower than the maximum voltage speed V2M, the output voltage E2 of the second inverter is changed in proportion to the speed difference between the actual speed V and the maximum voltage speed V1M, not the actual speed V at that time. At the maximum voltage speed V1M, the output voltage E2 = 0, and the magnetic flux density of the voltage addition transformer becomes zero.

  Therefore, this voltage addition transformer can be used under the condition of E2 / F = E2M / F2M = constant, but it is used under a condition with a sufficient margin. The output voltage E2 can be used under the condition that the output voltage E2 is changed to “zero to E2M” in proportion to the change “0 to F2M” of the frequency F2. From another point of view, it is suggested that it can be used under the conditions of claim 3.

  Therefore, as in claim 3, if a control method is adopted in which the first inverter and the second inverter are synchronized and the operation control is performed over the entire speed, the same gate signal is sent to the first inverter and the second inverter. Since it is sufficient to provide two inverters, one inverter control means may be provided, and gate drive circuits for operating the first inverter and the second inverter may be provided individually. Therefore, the inverter control means can be simplified.

  On the other hand, in the PWM control of the VVVF inverter, in general, a switching point between a triangular wave that is a modulated wave and a U-phase, V-phase, and W-phase sine wave having a phase difference of 120 degrees is obtained. When the sine wave of each phase is larger than the triangular wave for two IGBTs connected in series up and down so as to correspond to each phase, a gate signal is given to the IGBT above the corresponding phase. When the sine wave of each phase is smaller than the triangular wave, a gate signal is given to the lower IGBT. Therefore, the potential at the output terminal of the VVVF inverter is a rectangular wave voltage that changes between the DCLINK voltage and the zero voltage.

  In this case, since the crossing point with the triangular wave is different for each phase, different rectangular wave voltages are obtained at the output terminals of the respective phases. Therefore, the voltage of the difference between the U-phase rectangular wave and the V-phase rectangular wave of the VVVF inverter is applied between the U-phase and V-phase terminals of the three-phase induction motor, and the V-phase rectangular is between the V-W terminals. A difference voltage between the wave and the W-phase rectangular wave is applied, and a difference voltage between the W-phase rectangular wave and the U-phase rectangular wave is applied between the W-U terminals.

  When the speed is zero, a voltage having a frequency corresponding to the slip frequency necessary for generating the acceleration torque required for the three-phase induction motor is generated, and acceleration is performed at a constant V / F. In order to avoid torque pulsation in the low speed range, the modulation triangle wave uses an asynchronous triangle wave in the order of kHz, and switches to the synchronous method according to the acceleration. The number of pulses is sequentially changed from 9 pulse mode to 3 pulse mode to 1 pulse mode. Go down.

  That is, in the case of claim 3, as in claims 1 and 2, the first inverter and the second inverter are not given different control signals, but the first inverter and the second inverter are It is sufficient to give the same control signal to the two inverters at the same time.

  Further, in claims 1 and 2, during operation of the first inverter, a signal is given to the gate of the second inverter to prevent a voltage drop due to the voltage addition transformer, and the winding is short-circuited. However, according to the third aspect, there is no need for such short-circuit control, and rational regenerative control and acceleration control are possible. Therefore, the output voltage E1 of the first inverter and the output voltage E2 of the second inverter relating to the regeneration are as shown in FIG. 6 according to the embodiment, and the output voltage E1 of the first inverter relating to the acceleration (powering). The output voltage E2 of the second inverter is as shown in FIG. 5 according to the embodiment.

  The power control apparatus for a railway vehicle according to claim 4 includes a three-phase induction motor for driving and a power that can be supplied to the induction motor by converting the direct current of the overhead wire into a three-phase alternating current during traveling and regenerated by the induction motor during braking. In a railroad vehicle power control apparatus comprising: a variable voltage / variable frequency type inverter capable of converting DC to DC and supplying it to an overhead line; and an inverter control means for PWM-controlling the inverter, the AC side power line of the inverter and the induction motor And a primary winding connected to a portion of the AC side power line of the inverter that is closer to the inverter side than the secondary winding, and at least during braking, the induction motor A voltage addition transformer for boosting the regenerative voltage is provided.

  In this power control apparatus, as shown in FIG. 7 of the embodiment, when a voltage addition transformer is connected and the motor voltage is boosted from the inverter voltage, the V / F constant region is expanded by the increased voltage. be able to. The relationship between the inverter current and the motor current is an inverse ratio of the inverter voltage and the motor voltage. Since the inverter has the capability of flowing the maximum current shown in FIG. 11, if the winding ratio of the transformer is set so as to maintain the maximum current during regeneration in the entire speed range, the characteristics shown in FIG. 8 can be obtained, for example. .

  The constant torque region is slightly widened, and the speed region that is not subject to the restriction of the stationary torque is widened by increasing the motor voltage. In FIG. 11, the torque in the high speed range is affected by the stalling torque of the motor, and thus the speed is greatly reduced. However, in the characteristics of FIG. 8, the region not affected by the stalling torque is widened. Since a constant power region can be used, the torque in the high speed region is less decreased than in FIG. 11, and the braking characteristics in the high speed region can be improved.

  According to the first aspect of the present invention, the power control apparatus for a railway vehicle includes a three-phase induction motor for driving driving, a variable voltage / variable frequency type first inverter, and inverter control means. A variable voltage / variable frequency type second inverter connected in parallel to the first inverter with respect to the overhead wire, a secondary winding between the AC power line of the first inverter and the motor, and the AC side of the second inverter Including a primary winding connected to the power line and at least a voltage addition transformer for increasing the regenerative voltage of the motor during braking, and the inverter control means is decelerated from the high speed side to a predetermined speed during regeneration. Activates the first and second inverters.

  Therefore, the regenerative voltage is increased through the voltage addition transformer by the amount of operation of the second inverter until the speed is reduced from the high speed side to a predetermined speed, and the regenerative power can be increased with a constant braking torque. Therefore, since the braking torque of the induction motor can be kept constant during braking while the railway vehicle is running at high speed, the regenerative brake can be applied with this braking torque kept constant, and the braking performance is greatly improved. be able to.

  Since the regenerative voltage increases as much as the second inverter is operated, the regenerative rate (recovery rate) of the regenerative voltage regenerated on the overhead wire can be greatly improved. In this case, the second inverter may not be an expensive inverter using a special high-voltage and large-capacity switching element, and can be configured at low cost.

  Brake performance is improved by such improved braking torque characteristics, so regenerative braking can be effectively applied without using dynamic brakes or mechanical brakes until the vehicle speed of railway vehicles reaches low speeds. Therefore, it is possible to realize an ideal railway vehicle that can exhibit energy saving during regeneration.

  Moreover, the inverter control means operates only the first inverter when decelerating at a vehicle speed below a predetermined speed, and simultaneously controls the second inverter to short-circuit the primary winding of the voltage addition transformer. Therefore, the voltage drop due to the transformer is not caused, so that the braking operation by the first inverter is not adversely affected.

  According to the second aspect of the present invention, the inverter control means operates only the first inverter until it accelerates to the set speed during acceleration traveling, and simultaneously controls the second inverter to control the voltage adding transformer 1. Since the voltage drop due to the transformer is not caused by short-circuiting the secondary winding, the good acceleration performance by the first inverter is not adversely affected. And since the inverter control means operates the first and second inverters when accelerating at a speed higher than the set speed, the voltage supplied to the induction motor can be increased by an amount corresponding to the operation of the second inverter and the transformer. And acceleration can be significantly improved. Other effects similar to those of the first aspect are obtained.

  According to the invention of claim 3, the inverter control means operates the first inverter and the second inverter over the entire speed range during regeneration and acceleration travel. Instead of giving different control signals to the first inverter and the second inverter, it is only necessary to give the same control signal to the first inverter and the second inverter at the same time from the start of traveling.

Further, in claims 1 and 2, a signal is given to the gate of the second inverter so as not to cause a voltage drop of the voltage addition transformer during the operation of the first inverter, and the winding is short-circuited. Whereas it is necessary to allow a short-circuit current to flow, according to claim 3, there is no need for such short-circuit control, and rational regenerative control and acceleration control are possible.
Moreover, as described above, when viewed from the three-phase induction motor side, the power supply voltage is supplied with, for example, a drive voltage that is 1.4 times higher, for example, a single element composed of a semiconductor element having a withstand voltage that is 1.4 times higher. It can be configured equivalent to a power control device driven by a VVVF inverter.

According to the invention of claim 4, since the voltage addition transformer is inserted between the inverter and the motor in order to expand the regeneration area by using the voltage and current capacity of the inverter as much as possible, the motor voltage corresponding to the winding ratio is reduced. Raised. The motor current is determined by the inverse ratio of the transformer with respect to the inverter current, and less current flows than the inverter current.
As a result, the motor voltage can be boosted higher than the inverter voltage during regeneration, and the V / F constant region can be expanded, and the region that is not restricted by the stalling torque can be expanded as much as the motor voltage is increased. Torque can be increased and braking characteristics at high speeds can be improved. In addition, although the acceleration torque during powering decreases as the current decreases, the V / F constant region is expanded, and even in the region where the acceleration torque decreases with the conventional method, the acceleration performance of powering is affected. Not receive.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  The railroad vehicle power control apparatus of this embodiment has a variable voltage / variable frequency type sub-inverter with respect to the overhead line in addition to a variable voltage / variable frequency main inverter capable of supplying three-phase alternating current to the induction motor. Connect in parallel with the inverter, connect the primary winding of the voltage addition transformer to the sub inverter and connect the secondary winding to the main inverter, and add the secondary winding voltage in series to the output voltage of the main inverter Thus, it is possible to improve the recovery rate of braking torque and regenerative power at the time of braking to decelerate from the high-speed running state of the railway vehicle, and to improve the acceleration performance at high-speed running.

  As shown in FIG. 1, an electric vehicle 2 that is a railway vehicle includes a pantograph 3 that collects direct current fed to an overhead line 1 from a substation (not shown) and a high-speed circuit breaker 5 and a filter reactor 6 that blocks high-frequency components. Is supplied to the DCLINK (feed line) 4 through the main inverter 7 (which corresponds to the first inverter) capable of VVVF control (variable voltage variable frequency control), and V (voltage) / F (frequency) is constant. It is designed to convert to three-phase alternating current. The induction motor 10 for three-phase alternating current is driven according to the voltage and frequency of the three-phase alternating current supplied from the main inverter 7 and the rotation frequency of the induction motor 10, and the electric vehicle 2 can be accelerated or decelerated. It is configured.

  Next, the power control device 18 that drives and controls the induction motor 10 during power running and supplies the regenerative power induced by the induction motor 10 during regeneration to the overhead wire 1 will be described.

  As shown in FIG. 1, the power control device 18 includes a main inverter 7, a sub inverter 8 (which corresponds to a second inverter), and a voltage addition that adds the output voltage of the sub inverter 8 to the output voltage of the main inverter 7. Three-phase transformer 9, a first voltage detector 12 for detecting overhead voltage, a second voltage detector 13 for detecting DCLINK voltage supplied to DCLINK 4, and AC power lines L 1, L 2 of main inverter 7 U1, V1 current detectors 14 and 15 for detecting the current of the inverter, U2 and V2 current detectors 16 and 17 for detecting the current of the AC power lines L4 and L5 of the sub inverter 8, and the main and sub inverters 7 and 8 Each includes an inverter control device 11 (which corresponds to inverter control means) that performs PWM control.

  Since the main inverter 7 is a general variable voltage / variable frequency type VVVF inverter in which six switching elements S1 to S6 are connected in a bridge shape, detailed description thereof is omitted. Similarly to the main inverter 7, the sub inverter 8 is an inverter having a configuration in which six switching elements S11 to S16 are connected in a bridge shape, and thus detailed description thereof is omitted. These switching elements S1 to S6 and S11 to S16 are made of IGBT (insulated gate bipolar transistor). In addition, each of the switching elements S1 to S6 and S11 to S16 is connected to a free wheel diode.

  The DC side input line 7A of the main inverter 7 is connected to the DCLINK4, and the DC side input line 8A of the sub inverter 8 is also connected to the DCLINK4. The sub-inverter 8 is connected in parallel with the main inverter 7 with respect to the overhead line 1. As shown in FIG. 1, the three-phase transformer 9 for voltage addition is provided between the main inverter 7 and the induction motor 10.

  The AC side power lines L1 to L3 of the main inverter 7 are respectively connected to the left terminals of the secondary windings Ua, Va, Wa of the three-phase transformer 9, and the secondary windings Ua, Va, Wa of the three-phase transformer 9 are connected. The power lines L7 to L9 of the induction motor 10 are connected to the right terminal, respectively. The AC side power lines L4 to L6 of the sub inverter 8 are respectively connected to the left terminals of the primary windings Ub, Vb, Wb of the three-phase transformer 9, and are connected to the primary windings Ub, Vb, Wb of the three-phase transformer 9. The right terminal is star-connected. Thus, the AC power lines L4 to L6 of the sub inverter 8 and the induction motor 10 are magnetically connected to the primary windings Ub, Vb, Wb of the three-phase transformer 9 and the secondary windings Ua, Va, Wa. Combined.

  The inverter control device 11 has an input / output interface and a microcomputer, and travel speed signals from a vehicle speed sensor (not shown), detection voltages of the first and second voltage detectors 12 and 13, and U1 for the main inverter 7. , Receiving the detection current of the V1 current detectors 14 and 15 and the detection current of the U2 and V2 current detectors 16 and 17 for the sub inverter 8, and based on the driving operation or braking operation of the master controller operated by the driver, Each of the switching elements S1 to S6 of the main inverter 7 and each of the switching elements S11 to S16 of the sub inverter 8 are PWM-controlled according to the operating state.

Next, the operation of the power control device 18 configured as described above will be described.
First, for convenience of explanation, an acceleration operation at the time of power running in which the master controller is traveled by the driver and the electric vehicle 2 travels at an accelerated speed will be described with reference to FIG. However, in FIG. 2, the torque, power, current, and voltage of the electric motor are expressed with the maximum value at the time of power running in the conventional method (see FIG. 10) as 100%.

  In FIG. 2, until the vehicle speed of the electric vehicle 2 reaches about 50 km / h (corresponding to the set speed), only the main inverter 7 is controlled by the inverter controller 11 as described in the section of the prior art based on FIG. Is controlled to operate. In this case, the inverter control device 11 controls the switching elements S11 to S16 of the sub inverter 8 that is not used to short-circuit the primary windings (Ub, Vb, Wb) of the three-phase transformer 9. Thereby, since the voltage drop of the secondary windings (Ua, Va, Wa) of the three-phase transformer 9 does not occur, the acceleration traveling by the main inverter 7 is not adversely affected.

  In other words, during low-speed travel where the vehicle speed reaches approximately 50 km / h, the current is constant in the three armature coils of the induction motor 10 and the voltage gradually increases with the voltage / frequency being constant. Constant (about 100%), power increases with increasing voltage. At the speed of 50 km / h, the 1-pulse mode is set. Thereafter, the main inverter 7 is at a constant voltage and only the frequency is changed.

  However, in order to accelerate the vehicle speed of the electric vehicle 2 to about 50 km / h or more, the inverter control device 11 controls the sub inverter 8 to operate simultaneously in the 3-pulse mode in addition to the main inverter 7. Next, the operation of the electric vehicle 2 during high speed traveling will be described with reference to FIG.

  4, the first sine modulated wave (UA phase, VA phase, WA phase) generated in the inverter control device 11 for the main inverter 7 and the inverter control device for the sub inverter 8. 11 shows a three-pulse mode second sine modulated wave (UB phase, VB phase, WB phase) generated at 11 and a triangular modulation wave CW for the synchronous three-pulse mode.

  Therefore, each first sine modulated wave of the UA phase, VA phase, and WA phase is one pulse because there is no intersection with the modulated wave CW for the synchronous three-pulse mode. The amplitude of the second sine modulated wave is smaller than the amplitude of the first sine modulated wave because the sub inverter 8 is in the pulse width control state of 3 pulses, and the second sine modulated wave (UB phase, VB phase, WB phase). ) Crosses the modulated wave CW at a plurality of locations. Therefore, the inverter control device 11 performs PWM control of the switching elements S1 to S6 of the main inverter 7 according to the intersections of the first sine modulated wave and the modulation wave CW, and the switching elements S11 to S16 of the sub inverter 8. Is PWM controlled according to the intersection of the second sine modulated wave and the modulated wave CW.

  Therefore, the potential of each connection point U1a, V1a, W1a of the main inverter 7 is a rectangular wave voltage having a width of 180 ° shown in FIG. Therefore, the potential difference between the connection points U1a-V1a, between the connection points V1a-W1a, and between the connection points W1a-U1a of the main inverter 7 is given, and a rectangular wave voltage having a 120 ° width shown in FIG. Is output. Further, the U1 phase voltage, the V1 phase voltage, and the W1 phase voltage, which are the difference potentials between the output point (U1 phase, V1 phase, W1 phase) potential from the main inverter 7 and the neutral point of the star-connected virtual load, are Output as shown.

  On the other hand, the potential at the connection points U2a, V2a, W2a of the sub inverter 8 is represented by a rectangular wave two-pulse train shown in FIG. Comparing the waveform of the sub-inverter 8 with the waveform of the main inverter 7, the main inverter 7 has one pulse of a rectangular wave, the intermediate portion is at zero potential, and this portion is an intersection of the modulated wave CW and the modulated wave of each phase. is connected with. If the output voltage of the sub-inverter 8 is controlled to increase, the zero potential width decreases, and finally the zero potential width becomes zero, which coincides with the first inverter and becomes a one-pulse waveform with a width of 120 °.

  Therefore, the illustrated rectangular wave voltage is output between the connection points U2a and V2a of the sub inverter 8, between the connection points V2a and W2a, and between the connection points W2a and U2a. Further, the U2 phase voltage, V2 phase voltage, W2 which is the difference potential between the output point (U2-phase, V2-phase, W2-phase) voltage from the sub inverter 8 and the primary winding neutral point of the three-phase transformer 9. The phase voltage is output as shown.

  The phase voltage of the sub-inverter 8 is a voltage stepped down to the secondary windings (Ua, Va, Wa) through the three-phase transformer 9 at a winding ratio (here, secondary / primary = 0.0). 4) Output and added to the phase voltage of the main inverter 7 to obtain the U-phase voltage, V-phase voltage, and W-phase voltage of the induction motor 10, respectively. And finally, as shown in the lowest stage of FIG. 4, the voltage between the U-phase and V-phase terminals, the voltage between V-phase and W-phase terminals, and the voltage between W-phase and U-phase terminals of the induction motor 10 are obtained.

  As shown in FIG. 4, the induction motor 10 is supplied to the induction motor 10 by the main inverter 7 between the U-phase and V-phase terminals, between the V-phase and W-phase terminals, and between the W-phase and U-phase terminals. An inter-terminal voltage is generated by adding 40% of the voltage generated by the sub inverter 8 to the original inter-terminal voltage. In FIG. 4, the amplitude of the superimposed voltage is described as “added voltage λE”. In this case, the ratio of the sub inverter 8 added to the main inverter 7 is that the winding ratio (secondary winding / primary winding) of the three-phase transformer 9 is λ, and the main inverter phase voltage is E. Then, the added voltage by the sub inverter 8 becomes λE in the final stage of the acceleration control, that is, in the state of one pulse.

  Therefore, when the electric vehicle 2 travels at a high speed of 50 km / h or more, if the winding ratio λ = 0.4 of the three-phase transformer is set, the voltage supplied to the induction motor 10 is supplied by the main inverter 7. The voltage can be increased by up to 40% (output voltage E2: 40% in FIG. 2) with respect to the voltage (output voltage E1: 100% in FIG. 2).

  In this way, as shown in FIG. 2, the high-speed traveling region where the vehicle speed of the electric vehicle 2 is 50 km / h to about 70 km / h, that is, the acceleration region where “voltage V / frequency F is constant” is added by the sub inverter 8. In the voltage possible range, the voltage characteristic and the power characteristic extend linearly. For this reason, the torque characteristics that make the motor torque constant reach the high speed region, and the acceleration performance can be improved.

  However, in this case, the increase in voltage (superimposition λE) is “about 40%”. From another viewpoint, when the arrival time to the specified speed is determined, the constant torque region is high speed. When the time is extended, the arrival time is shortened. Therefore, if the arrival time is the same, the acceleration torque, that is, the motor current may be reduced by the amount of time shortened.

  Next, the regenerative braking operation at the time of braking when the electric vehicle 2 is braked by the driver in a high-speed acceleration traveling state of, for example, about 100 km / h will be described. However, in FIG. 3, the torque, power, current, and voltage of the electric motor are expressed with the maximum value at the time of conventional braking being 100%.

  In this case, as described above, when the electric vehicle 2 is running at high speed, the inverter control device 11 controls the frequency of the main inverter 7 with one pulse, and the sub inverter 8 is PWM-controlled. In the control of the inverters 7 and 8, the inverter control device 11 includes the voltage and current of the induction motor 10, the rotation speed, the overhead wire voltage detected by the first voltage detector 12, the overhead wire current, and the second voltage detector 13. The phase of the main and sub inverters 7 and 8 is controlled so that the actual deceleration calculated by the computer of the inverter control device 11 is matched based on the deceleration command from the master controller. To do.

  Therefore, in the case of braking in which the regenerative braking operation is performed in this manner, the inverter control device 11 also receives the deceleration command from the master controller and the first command until the vehicle speed is reduced to about 50 m / h (corresponding to a predetermined speed). 1. Actual reduction calculated based on the detected voltage from the second voltage detectors 12 and 13, the detected current from the U1 and V1 current detectors 14 and 15, and the detected current from the U2 and V2 current detectors 16 and 17. Necessary control signals are output to the main and sub inverters 7 and 8 so as to match the speed.

  However, as the sub inverter 8 decelerates from about 100 km / h high speed to about 50 km / h, the pulse mode is gradually changed from 1 pulse, 3 pulses, and 9 pulses to the opposite of powering. Thus, the pulse width is controlled from 100% to zero.

  As conditions before entering the regenerative brake, there are three cases: (a) during power running, (b) coasting (with excitation), and (c) coasting (without excitation). In cases (a) and (b), the main and sub inverters 7 and 8 are operating, and the rotating magnetic field of the electric motor 10 already exists. In the case (c), since the main and sub inverters 7 and 8 are not operated, the rotating magnetic field of the electric motor 10 does not exist. In this case, first, it is necessary to start up the main and sub inverters 7 and 8 at a frequency equal to the rotation frequency, apply a voltage to the electric motor 10, flow an excitation current, and generate a rotating magnetic field.

  Therefore, when a voltage is applied to cause the exciting current to flow through the current 0 by the main and sub inverters 7 and 8 and a magnetic field is generated, a brake command is given and the inverter frequency is lowered from the rotation frequency of the rotor. Then, a high regenerative voltage is induced in the zero armature coil by induction rotating at high speed. This regenerative voltage is opposed by the voltage of the sub-inverter 8 induced in the primary windings (Ub, Vb, Wb) of the three-phase transformer 9 inserted in series with the voltage of the main inverter 7, and both the inverters 7, 8 It is regenerated to overhead line 1 through.

  The voltage sharing of the sub-inverter 8 at the maximum speed is a value corresponding to the winding ratio of the transformer 9 (Ua turns / Ub turns, 0.4 in this embodiment) with respect to the DCLINK voltage. First, the sub-inverter 8 is controlled to lower the shared voltage to zero, and then controlled to zero speed by the main inverter 7 side.

  As explained in the prior art of FIG. 9, when the main inverter 7 is regenerated, the induction motor 10 generates a regenerative voltage of “about 110%”. On the other hand, at the time of regeneration of the present plan, the sub inverter 8 operates simultaneously with the main inverter 7, so that, as shown in the lowermost stage of FIG. The output voltage generated only by the main inverter 7 (output voltage E1: 110% in FIG. 3) is added to the “addition voltage λE (FIG. 3 Output voltage E2: 40%) ”can be generated, and a higher regenerative voltage of“ about 150% ”can be generated. Therefore, a regenerative voltage as large as about 150% is generated in the armature coil of the induction motor 10.

  Therefore, as shown in FIG. 3, the braking torque is approximately constant at approximately 100%, and the power can be increased to approximately the maximum of approximately 200%. As a result, the regenerative braking torque during high speed traveling at a vehicle speed of about 100 km / h can be kept constant at about 100%, so that regenerative full braking can be used in the entire speed range.

  Since the winding ratio (transformation ratio) of the three-phase transformer 9 is λ, if the current flowing through the main inverter 7 is I, the current flowing through the sub-inverter 8 may have a current capacity of λI. Does not need to be composed of a high-voltage and large-capacity switching element, the production cost of the sub-inverter 8 is reduced, energy saving is expected, and the main inverter 7 should be an economically advantageous conventional inverter. Can do.

  In addition, since the regenerative braking performance is improved by the improved torque characteristics as described above, the regenerative braking is effectively operated without using the mechanical brake until the vehicle speed of the electric vehicle 2 reaches a low speed. Therefore, the ideal electric vehicle 2 that can exhibit energy saving when using the regenerative brake can be realized. Further, the frequency and time of use of the mechanical brake are significantly reduced, and the maintenance work is simplified.

  Thereafter, when the vehicle speed is reduced to about 50 km / h and the voltage component by the sub-inverter 8 becomes zero, as shown in FIG. 3, only the main inverter 7 is controlled by the inverter control device 11 as in the conventional case. PWM control is performed, and the traveling speed is gradually reduced. At this time, the inverter control device 11 controls the switching elements S11 to S16 of the sub inverter 8 that is not used to short-circuit the primary windings (Ub, Vb, Wb) of the three-phase transformer 9.

  As a result, no voltage drop occurs in the secondary windings (Ua, Va, Wa) of the three-phase transformer 9, so that the braking operation by the main inverter 7 is not adversely affected. After that, the pulse mode of the main inverter 7 is gradually changed from synchronous 1 pulse, 3 pulse, 9 pulse to asynchronous, contrary to power running, and the pulse width is controlled according to deceleration so that the pulse width becomes 100% to zero. Is done. However, after the traveling speed of the electric vehicle 2 is reduced to, for example, 5 km / h or less, the electric vehicle 2 is switched to a mechanical brake.

  As described above, the three-phase induction motor 10 for driving and driving, the variable voltage / variable frequency main inverter 7, the secondary windings (Ua, Va, Wa) of the three-phase transformer 9, and the inverter control device 11. And a variable voltage / variable frequency type sub-inverter 8 and primary windings (Ub, Vb, Wb) of a three-phase transformer 9, and the inverter control device 11 has a predetermined speed from the high speed side during regeneration. Since the main and sub inverters 7 and 8 are operated until the speed is reduced, the regenerative voltage becomes higher by the increment (about 40% that is λE) that the sub inverter 8 is operated until the speed is reduced from the high speed side to the predetermined speed. The regenerative power can be increased with a constant braking torque. Therefore, since the braking torque of the induction motor 10 can be kept constant during braking while the electric vehicle 2 is traveling at a high speed, the regenerative brake can be applied with the braking torque kept constant, and the braking performance is remarkably improved. Can be increased.

  In addition, since the regenerative voltage is increased by the increase (about 40%) of operating the sub inverter 8, the regenerative rate (recovery rate) of the regenerative voltage regenerated on the overhead wire 1 can be greatly improved. In this case, the sub-inverter 8 may not be an expensive inverter using a special high-voltage and large-capacity switching element, and can be configured at low cost.

  Furthermore, since the braking performance is improved by the improved braking torque characteristics, the regenerative braking can be effectively applied without using the mechanical brake until the vehicle speed of the electric vehicle 2 becomes low. Therefore, it is possible to realize an ideal electric vehicle 2 that can realize an energy-saving and economical inverter and can also exhibit energy saving during regeneration.

  Further, the inverter control device 11 controls only the main inverter 7 and simultaneously controls the sub-inverter 8 to short-circuit the primary winding of the voltage addition transformer until the set speed is accelerated during acceleration traveling. Therefore, the voltage drop due to the secondary winding is not caused, so that the good acceleration performance by the main inverter 7 is not adversely affected.

  On the other hand, during high speed acceleration during acceleration, the drive voltage supplied to the induction motor 10 is increased by about 40% as much as the sub inverter 8 is operated, the voltage characteristics and power characteristics are improved, and the motor torque is kept constant. As a result, the torque characteristic of the motor reaches the high speed region, and the acceleration performance can be remarkably improved.

  From another point of view, if the acceleration time up to the same speed may be the same, the acceleration torque in the high speed region due to the use of the sub inverter 8 becomes large, so the acceleration time until the set speed is reached. Therefore, the acceleration torque, that is, the motor current and the inverter current can be reduced accordingly.

Next, a modified embodiment in which the above embodiment is partially modified will be described.
1) First modification: The winding ratio λ of the secondary winding / primary winding of the three-phase transformer 9 is not limited to 0.4, and a desired number of windings should be used. Also good.

2) Second modification: The predetermined speed at the time of regeneration and the set speed at the time of acceleration traveling are not limited to 50 km / h, but are appropriately changed according to the operating characteristics of the sub inverter 8 and the configuration of the three-phase transformer 9. Is possible.

3) Third modification: It is not necessary to separate the main and sub inverters 7 and 8 from the main inverter 7 in the low speed region and the sub inverter 8 in the low speed region. Thus, a method of simultaneously operating from a low speed to a maximum speed may be adopted.

4) Fourth modification: The inverter control device 11 may operate the main inverter 7 and the sub-inverter 8 simultaneously over the entire speed range during regeneration and acceleration travel. Here, the output voltage E1 of the main inverter 7 and the output voltage E2 of the sub inverter 8 when acceleration control is performed are shown in FIG. 2, respectively, and the output voltage E1 of the main inverter 7 and the output of the sub inverter 8 when regenerative control is performed. The voltage E2 is shown in FIG.

  The output voltage E1 of the main inverter 7 increases in proportion to the speed V1 from zero to the maximum voltage E1M (“100%” during power running in FIG. 2 and “110%” during regeneration in FIG. 3). The speed when the output voltage E1 of the main inverter 7 reaches the maximum voltage E1M is V1M, and the frequency is F1M. In the main inverter 7, the output voltage E1 is constant and only the frequency F1 changes. From this point, the sub inverter 8 starts to operate, and the output voltage E2 of the sub inverter 8 increases in proportion to the speed difference between the actual speed V and the maximum voltage speed V2M when the maximum voltage E2M is reached.

  After the output voltage E2 of the sub inverter 8 reaches the maximum voltage E2M, the output voltage E2 is constant and only the frequency F2 increases in proportion to the speed V2. The size of the voltage addition transformer 9 is the maximum voltage E2M of the output voltage E2 of the sub inverter 8, and the maximum voltage speed V2M when the maximum voltage E2M is reached, that is, the maximum frequency F2M at the maximum voltage speed V2M. It is determined by the ratio, that is, E2M / F2M. In the first and second aspects described above, the output voltage E2 of the sub-inverter 8 changes in proportion to the speed difference between the actual speed V and the maximum voltage speed V2M, not the actual speed V at that time.

  Therefore, the magnetic flux density of the voltage addition transformer 9 becomes maximum at the maximum voltage speed V2M. In the range where the speed is higher than the maximum voltage speed V2M, the field weakening region is obtained. Therefore, the voltage adding transformer 9 becomes a field weakening and the magnetic flux density is lowered. In the region where the speed is slower than the maximum voltage speed V2M, the output voltage E2 of the sub inverter 8 is changed in proportion to the speed difference between the actual speed V and the maximum voltage speed V2M, not the actual speed V at that time. At the maximum voltage speed V2M, the output voltage E2 = 0, and the magnetic flux density of the voltage addition transformer becomes zero.

  Therefore, the voltage addition transformer 9 can be used under the condition of E2 / F = E2M / F2M = constant, but it is used under a condition with a sufficient margin. The output voltage E2 can be used under the condition that the output voltage E2 is changed to “zero to E2M” in proportion to the change “0 to F2M” of the frequency F2. From another point of view, it is suggested that it can be used under the conditions of claim 3.

  Therefore, if a control method is adopted in which the main inverter 7 and the sub-inverter 8 are synchronized and controlled in operation over all speeds as in the fourth modification, the same gate signal is sent to the main inverter 7. Therefore, one inverter control means is provided, and gate drive circuits for operating the main inverter 7 and the sub inverter 8 are provided separately. Therefore, the inverter control means can be simplified.

  On the other hand, in the PWM control of the VVVF inverter, in general, a switching point between a triangular wave that is a modulated wave and a U-phase, V-phase, and W-phase sine wave having a phase difference of 120 degrees is obtained. When the sine wave of each phase is larger than the triangular wave for two IGBTs connected in series up and down so as to correspond to each phase, a gate signal is given to the IGBT above the corresponding phase. When the sine wave of each phase is smaller than the triangular wave, a gate signal is given to the lower IGBT. Therefore, the potential at the output terminal of the VVVF inverter is a rectangular wave voltage that changes between the DCLINK voltage and the zero voltage.

  In this case, since the crossing point with the triangular wave is different for each phase, different rectangular wave voltages are obtained at the output terminals of the respective phases. Therefore, the voltage of the difference between the U-phase rectangular wave and the V-phase rectangular wave of the VVVF inverter is applied between the U-phase and V-phase U-V terminals of the three-phase induction motor 10, and between the V-W terminals. The voltage of the difference between the rectangular wave of the V phase and the rectangular wave of the W phase is applied, and the voltage of the difference between the rectangular wave of the W phase and the rectangular wave of the U phase is applied between the W-U terminals.

  When the speed is zero, a voltage having a frequency corresponding to a slip frequency necessary for generating the acceleration torque required for the three-phase induction motor 10 is generated, and acceleration is performed at a constant V / F. In order to avoid torque pulsation in the low speed range, the modulation triangle wave uses an asynchronous triangle wave in the order of kHz, and switches to the synchronous method according to the acceleration. The number of pulses is sequentially changed from 9 pulse mode to 3 pulse mode to 1 pulse mode. Go down.

  That is, when the main inverter 7 and the sub-inverter 8 are operated simultaneously over the entire speed range during regeneration and acceleration, the main inverter 7 and the sub-inverter 8 are different as in the above-described embodiment. Instead of giving a control signal, the same control signal may be given simultaneously to the main inverter 7 and the sub-inverter 8 from the start of traveling.

  Further, in the above-described embodiment, during the operation of the main inverter 7, a signal is given to the gate of the sub inverter 8 so that the voltage drop of the voltage adding transformer 9 does not occur, and the winding is short-circuited. However, according to the fourth modification, there is no need for such short-circuit control, and rational regenerative control and acceleration control are possible. Therefore, the output voltage E1 of the main inverter 7 and the output voltage E2 of the sub-inverter 8 relating to regeneration are as shown in FIG. 6, and the output voltage E1 of the main inverter 7 and the sub-inverter 8 relating to acceleration (powering) The output voltage E2 is as shown in FIG.

  Therefore, when viewed from the three-phase induction motor 10 side, the drive voltage is 1.4 times higher than the power supply voltage and is driven by a single VVVF inverter composed of a semiconductor element having a withstand voltage 1.4 times higher. The power control device can be configured equivalently.

Next, a second embodiment of the present invention will be described with reference to FIGS.
As shown in FIG. 7, the power control apparatus 18A for the railway vehicle omits the sub inverter 8 and the current detectors 16 and 17 in the power control apparatus 18 of the above embodiment, and is one of the voltage addition transformer 9A. Since the connection portions of the next windings Ub, Vb, and Wb are changed, the same reference numerals are given to the same components as those in the above-described embodiment, the description thereof is omitted, and different configurations will be described.

  The ends of the primary windings Ub, Vb, Wb of the voltage addition transformer 9A are on the inverter 7 side of the secondary windings Ua, Va, Wa of the AC power lines L1, L2, L3 of the inverter 7. Are connected to each part. The voltage addition transformer 9A includes primary windings Ub, Vb, Wb and secondary windings Ua, Va, Wa, and is used to boost the regenerative voltage of the induction motor 10 at least during braking (regeneration). Is.

The voltage addition transformer 9A in FIG. 7 is equivalent to the autotransformer shown in FIG. 7-1 and will be described based on this autotransformer. The three-phase winding of the transformer 9A is star-connected, the intermediate tap of the transformer 9A is connected to the AC side power lines L1, L2, L3 of the inverter 7, and the power lines L7, L8, L9 of the electric motor 10 are Connected to the output terminal of 9A, the motor voltage is boosted at a winding ratio of (Ua turns + Ub turns) / Ub turns (1.4 in this embodiment).
The control method for controlling the inverter 7 by the inverter control device 11 is the same as that in the above embodiment, so that the description thereof is omitted.

  In this power control device 18A, when a voltage addition transformer 9A is connected as shown in FIG. 7 and the motor voltage is boosted from the inverter voltage during regeneration, the V / F constant region is expanded by the amount of the increased voltage. be able to. The relationship between the current of the inverter 7 and the motor current is an inverse ratio of the inverter voltage and the motor voltage. Since the inverter has the capability of flowing the maximum current of the motor current of FIG. 11 (in the conventional technology, the motor current = inverter current because there is no transformer 9A), the above-mentioned maximum current is maintained during regeneration in the entire speed range. If the turns ratio of the transformer 9 is set to, the characteristics shown in FIG. 8 can be obtained, for example. The winding ratio may be set to secondary / primary = 0.4, but is not limited to this.

  The constant torque region is slightly widened, and the speed region that is not subject to the restriction of the stationary torque is widened by increasing the motor voltage. In FIG. 11 according to the prior art, the torque in the high speed range is affected by the stalling torque of the electric motor 10 and thus greatly decreases with respect to the speed. However, in the characteristics of this embodiment shown in FIG. Since the region not affected by the torque is widened and a constant power region can be used, the torque in the high speed region is less reduced than in FIG. 11, and the braking characteristics in the high speed region can be improved.

  According to the power control device 18A, since the voltage addition transformer 9A as described above is provided between the AC power lines L1, L2, L3 of the inverter 7 and the induction motor 10, the motor voltage 10 is set at least during regeneration. The voltage can be boosted above the inverter voltage, and the V / F constant region can be expanded. As the electric motor voltage is increased, the region not restricted by the stationary torque can be expanded, the torque in the high speed region can be increased, and the brake characteristics in the high speed region can be improved.

  That is, if the three-phase output voltage of the inverter 7 is applied to the intermediate tap of the voltage addition transformer 9A, which is the above-described autotransformer, a voltage multiplied by the winding ratio is generated at the output terminal of the transformer 9A. This voltage becomes the terminal voltage. In a coasting state without excitation, if a three-phase AC voltage having a frequency equal to the rotation frequency is applied to the motor 10 by the inverter 7, an excitation current flows through the armature winding to generate a rotating magnetic field.

  When the inverter frequency is equal to the rotation frequency of the electric motor 10, the rotation speed of the rotating magnetic field generated in the gap between the armature and the rotor of the electric motor 10 by the rotor of the electric motor 10 and the inverter 7 is equal, and the rotor and the rotating magnetic field Since the relative speed is zero and the magnetic flux does not cut through the rotor winding, no induced electromotive force (speed electromotive force) is generated in the winding, and only an excitation current corresponding to the voltage applied to the motor 10 flows.

  When there is a regeneration command, the frequency of the inverter 7 is set to a value lower than the rotation frequency of the rotor, the rotor winding is cut at a frequency that is the difference between the inverter frequency and the rotation frequency, and the frequency difference ( A voltage proportional to the slip frequency, slip <0 during regeneration, slip> 0 during power running) is generated, and current flows through the rotor winding (secondary winding). A force acts between the current and the magnetic field in the air gap, and acts in the direction of decreasing the rotation (deceleration braking force).

  At the same time, a magnetic field is generated in the gap by this current, and a current flows in the armature winding (primary winding) in a direction to cancel the magnetic field. Since this current is a current related to the torque of the electric motor 10, it is called a torque current and is distinguished from the aforementioned excitation current. The current that actually flows through the armature winding is a combination of the excitation current and the torque current. The torque current is in phase with the voltage applied to the motor, and the excitation current is delayed by π / 2 (90 degrees). Required by vector synthesis.

  In the case of power running, the inverter frequency is set higher than the rotation frequency (slip> 0), current flows in the direction opposite to the regeneration in the rotor winding, and the force acting between the magnetic field in the air gap also increases the rotation in the opposite direction. This is the direction force (acceleration force). The motor current is determined by the inverse ratio of the transformer 9A with respect to the inverter current, and a current smaller than the inverter current flows. Although the acceleration torque during powering decreases as the current decreases, the V / F constant region is expanded, and even in the region where the acceleration torque decreases with the conventional method, the acceleration performance of powering is affected. Absent.

  The present invention is not limited to the first and second embodiments described above, and those skilled in the art can add various modifications to the first and second embodiments without departing from the spirit of the present invention. The present invention includes those modifications.

1 is an electrical wiring diagram of an electric vehicle (railway vehicle) according to Embodiment 1 of the present invention. FIG. 4 is a characteristic diagram of motor torque, power, voltage, and current during acceleration. It is a characteristic line figure of electric motor torque at the time of braking, power, voltage, and current. It is a time chart which shows each voltage of a main and a sub inverter, and an induction motor. FIG. 10 is a diagram corresponding to FIG. 2 in a fourth modification. FIG. 10 is a diagram corresponding to FIG. 3 in a fourth modification. 6 is an electrical wiring diagram of an electric vehicle (railway vehicle) according to Embodiment 2. FIG. It is a circuit diagram of a voltage addition autotransformer as a voltage addition transformer. It is a characteristic diagram, such as an electric motor voltage at the time of braking, electric current, and braking force. It is a characteristic line figure of the motor torque at the time of the conventional braking, power, voltage, and current. It is the characteristic line figure of the motor torque at the time of the conventional acceleration, power, a voltage, and an electric current. It is a characteristic diagram, such as an electric motor voltage at the time of the conventional braking, an electric current, and braking force.

Explanation of symbols

1 Overhead line 2 Electric car (Railway)
7 Main inverter (first inverter)
8 Sub inverter (second inverter)
9, 9A Three-phase transformer 10 Induction motor 11 Inverter controller 18, 18A Power controller Ua, Va, Wa Secondary winding Ub, Vb, Wb Primary winding

Claims (4)

A three-phase induction motor for driving and a variable that can convert the direct current of the overhead wire into a three-phase alternating current and supply it to the induction motor during traveling, and convert the electric power regenerated by the induction motor to DC and supply it to the overhead wire during braking In a railway vehicle power control apparatus comprising a voltage / variable frequency type first inverter and inverter control means for PWM-controlling the first inverter,
A variable voltage / variable frequency type second inverter connected in parallel with the first inverter to the overhead line and controlled by the inverter control means;
A regenerative voltage of the induction motor at least during braking, comprising a secondary winding provided between the AC power line of the first inverter and the induction motor, and a primary winding connected to the AC power line of the second inverter. A voltage addition transformer for boosting the voltage,
The inverter control means operates the first and second inverters until decelerating from the high speed side to a predetermined speed during regeneration, and operates only the first inverter when decelerating at a vehicle speed below the predetermined speed. Electric power for a railway vehicle characterized in that when the inverter only operates, the second inverter is controlled to short-circuit the primary winding of the voltage addition transformer so as not to cause a voltage drop in the secondary winding. Control device.   The inverter control means operates only the first inverter until accelerating to the set speed during acceleration traveling, operates the first and second inverters when operating at the set speed or higher, and operates only the first inverter. 2. The railway vehicle according to claim 1, wherein a voltage drop of the secondary winding is prevented from occurring by sometimes controlling the second inverter to short-circuit the primary winding of the voltage addition transformer. Power control device. A three-phase induction motor for driving and a variable that can convert the direct current of the overhead wire into a three-phase alternating current and supply it to the induction motor during traveling, and convert the electric power regenerated by the induction motor to DC and supply it to the overhead wire during braking In a railway vehicle power control apparatus comprising a voltage / variable frequency type first inverter and inverter control means for PWM-controlling the first inverter,
A variable voltage / variable frequency type second inverter connected in parallel with the first inverter to the overhead line and controlled by the inverter control means;
A regenerative voltage of the induction motor at least during braking, comprising a secondary winding provided between the AC power line of the first inverter and the induction motor, and a primary winding connected to the AC power line of the second inverter. A voltage addition transformer for boosting the voltage,
The power control device for a railway vehicle, wherein the inverter control means operates the first inverter and the second inverter over the entire speed range during regeneration and acceleration travel. A three-phase induction motor for driving and a variable that can convert the direct current of the overhead wire into a three-phase alternating current and supply it to the induction motor during traveling, and convert the electric power regenerated by the induction motor to DC and supply it to the overhead wire during braking In a railway vehicle power control apparatus comprising a voltage / variable frequency type inverter and inverter control means for PWM controlling the inverter,
A secondary winding provided between the AC power line of the inverter and the induction motor, and a primary winding connected to a portion of the AC side power line of the inverter that is closer to the inverter than the secondary winding; And a voltage addition transformer for boosting the regenerative voltage of the induction motor at least during braking.