JP2018143052A - Converter control device and converter control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new technique for suppressing a return-wire current higher harmonic.SOLUTION: A deficit voltage calculation part 34 calculates deficit voltage vbeing a deficit with respect to predetermined voltage which is based on an AC side voltage command value vof DC stage voltage v, and a deficit current calculation part 38 calculates a deficit current ibeing an AC side current generated by a deficit voltage vquantity. An AC side current adjustment part 39 subtracts a deficit current iquantity from an AC side current iof a converter and outputs the subtraction result to a current control system artithmetic operation part 32. The current control system calculation part 32 generates the AC side voltage command value vusing the AC side current ifrom which the deficit current iquantity is subtracted.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a control device for a converter in an electric vehicle capable of traveling in an AC section provided with a storage battery connected to a DC intermediate circuit between a converter and an inverter.

  In an electric vehicle that can travel in an AC section, a technology that controls storage of electricity by connecting a storage battery to a DC intermediate circuit (also called a DC stage) between the converter and the inverter in a chargeable / dischargeable manner has been researched and developed. Yes. For example, the hybrid overhead line mode described in Patent Document 1 that uses AC power from an overhead line and the output of a battery (storage battery) corresponds to this technique.

  By connecting the storage battery to the DC intermediate circuit, the storage battery assists the power necessary for powering, or the storage battery stores the regenerative power, thereby reducing environmental load and running costs.

Japanese Patent Application Laid-Open No. 2014-64397

  In the electric vehicle described above, when the voltage of the DC intermediate circuit (hereinafter referred to as “DC stage voltage”) decreases and the converter enters an overmodulation operation (also referred to as an overmodulation mode), the AC side current of the converter Waveform distortion may worsen, and the harmonics of the retrace current may appear greatly. As a technique for suppressing this return current harmonic, a method of injecting reactive power into the train line is conceivable, but since the effective current value increases, consideration should be given to the influence on the feeder system and the temperature rise of the trolley line. There is a need. Therefore, a technique for suppressing the return current harmonic by a method other than the reactive power injection method is desired.

  The present invention has been devised to provide a new technique for suppressing the return current harmonic, and more specifically, to reduce the deterioration of the waveform distortion of the AC side current of the converter. It was devised as a purpose.

The first invention for solving the above problems is:
In a DC intermediate circuit between the converter (for example, the converter 40 in FIG. 1), an inverter (for example, the inverter 50 in FIG. 1) for driving and controlling a main motor (for example, the main motor M in FIG. 1), and the inverter. In an electric vehicle (for example, electric vehicle 1 in FIG. 1) that travels in an AC section including a storage battery (for example, storage battery 60 in FIG. 1) connected in a chargeable / dischargeable manner, an alternating current for controlling the power conversion operation of the converter. A converter control device (for example, the converter control device 30 in FIGS. 1 and 2) that generates a side voltage command value using an AC side current detection value and controls the converter,
A deficient voltage calculation unit (for example, deficient voltage calculation in FIG. 2) that calculates a deficient voltage that is a deficiency of a voltage of the DC intermediate circuit (hereinafter referred to as “DC stage voltage”) with respect to a predetermined voltage based on the AC side voltage command value. Part 34),
A deficient current calculation unit (for example, deficient current calculation unit 38 in FIG. 2) that calculates a deficient current that is an AC side current due to the deficient voltage in power conversion of the converter;
An AC-side current adjustment unit (for example, an AC-side current adjustment unit 39 in FIG. 2) that subtracts the missing current from the AC-side current detection value obtained by detecting the AC-side current of the converter;
And a converter control device that generates the AC side voltage command value using the AC side current detection value subtracted by the deficient current by the AC side current adjustment unit.

As another invention,
In an electric vehicle that travels in an AC section comprising a converter, an inverter that drives and controls a main motor, and a storage battery that is connected to a DC intermediate circuit between the converter and the inverter in a chargeable / dischargeable manner, the electric power of the converter A converter control method for controlling the converter by generating an AC voltage command value for controlling a conversion operation using an AC current detection value,
Calculating a deficient voltage that is an insufficient amount of a voltage of the DC intermediate circuit (hereinafter referred to as “DC stage voltage”) with respect to a predetermined voltage based on the AC voltage command value;
Calculating a deficit current that is an AC side current due to the deficit voltage in power conversion of the converter;
Subtracting the deficient current from the AC side current detection value that has detected the AC side current of the converter;
Generating the AC side voltage command value using the AC side current detection value subtracted by the missing current;
It is good also as comprising the converter control method containing these.

  According to the first aspect of the invention, when the DC stage voltage becomes insufficient with respect to the predetermined voltage based on the AC-side voltage command value that is a command value for controlling the converter, A certain missing voltage is calculated, and the missing current corresponding to this missing voltage is subtracted from the detected value of the AC side current. Then, the AC side voltage command value is generated by using the AC side current after being subtracted (virtual current having no defect), and the converter is controlled. As a result, control is performed in a state where the shortage of the DC stage voltage is allowed, and even if the converter is overmodulated and waveform distortion occurs in the AC side current, excessive response of the current control system is prevented. Therefore, it is possible to reduce the deterioration of the waveform distortion. Moreover, since the deterioration of the waveform distortion of the AC side current can be reduced, the retrace current harmonic can be suppressed.

The second invention is the first invention, wherein
When the DC stage voltage is not insufficient with respect to the predetermined voltage, the missing voltage calculation unit calculates the missing voltage as zero,
It is a converter control device.

  According to the second invention, when the DC stage voltage is not insufficient, the detected value of the AC side current is not reduced (subtracted). Therefore, it is not necessary to selectively control whether or not to perform missing voltage calculation or missing current subtraction according to the operation control mode of the converter such as whether or not an overmodulation operation is being performed. That is, regardless of the operation control mode of the converter, it is possible to keep the calculation of the missing voltage and the subtraction of the missing current continuously, and the control is simplified.

The third invention is the first or second invention, wherein
The missing current calculation unit calculates the missing current by calculating an AC side current of the converter generated by the missing voltage component by the converter based on the specifications of the main transformer.
It is the converter control apparatus of 1st or 2nd invention.

  According to the third aspect of the invention, based on the specifications of the main transformer, the AC side current generated by the missing voltage component that is the DC side voltage can be calculated as the missing current.

The figure which shows the circuit structure of the principal part which comprises an electric vehicle. The figure which shows the structure of the calculation block (functional block) of a converter control apparatus. The figure which shows the structure of the calculation block (functional block) of a missing voltage calculation part. The figure which shows the waveform of the result of having simulated the circuit operation | movement at the time of an overmodulation driving | operation.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In the following, an embodiment in which the present invention is applied to an AC electric vehicle will be described as an example. However, the present invention can be applied to any electric vehicle that can travel in an AC section. It is also possible to apply to the AC / DC electric vehicle. In addition, in order to simplify the explanation, a case where the converter is operated in the forward direction (when AC power from the overhead line is converted into DC power) will be described, but a case where the converter is operated in the reverse direction (for example, regenerative power or storage battery output power) Of course, it is also possible to apply this embodiment to the case where DC power is converted to AC power in order to return to the overhead line.

  FIG. 1 is a diagram showing a circuit configuration of a main part constituting the electric vehicle 1 of the present embodiment. The electric vehicle 1 includes a main transformer 20, a converter control device 30, a converter 40, an inverter 50, an inverter control device (not shown), a storage battery 60, and a main motor M.

The main transformer 20 is located between the pantograph P that receives AC power from the overhead line CT and the wheel W that is in contact with the rail R and plays a role of flowing a return current, and transforms the overhead power received by the pantograph P. And output to the converter 40. The secondary voltage of the main transformer 20 as an output becomes the AC side voltage of the converter 40, and the secondary current of the main transformer 20 becomes the AC side current _ic of the converter 40.

  The turns ratio of the primary winding 21 and the secondary winding 22 and the specifications of the main transformer 20 such as resistance and inductance are determined in advance. As a model formula representing the equivalent circuit of the entire main transformer 20, The main transformer model 381 (see FIG. 2) is set.

In this embodiment, the converter 40 is a PWM (Pulse Width Modulation) converter. Based on the gate pulse signal PS input from the converter control device 30, the power conversion operation is executed by the PWM operation for turning the gate ON / OFF. The operation mode of the converter 40 includes at least a rectangular wave operation mode and an overmodulation operation mode, and the overmodulation operation mode is employed when the DC stage voltage v _dc becomes a low voltage state equal to or lower than a predetermined voltage. The The gate pulse signal PS is a signal corresponding to the operation mode, and is generated by the converter control device 30. That is, the converter control device 30 selects the operation mode of the converter 40, and generates and outputs the gate pulse signal PS corresponding to the selected operation mode.

Between the converter 40 and the inverter 50 is a DC voltage circuit portion, which is also called a DC stage or the like, but is called a DC intermediate circuit in this embodiment. The voltage of the DC intermediate circuit is referred to as DC stage voltage v _dc . The voltage output to the DC side by the forward operation of the converter 40 is the DC stage voltage v _dc , and this DC stage voltage v _dc becomes the input of the inverter 50.

The inverter 50 drives and controls the main motor M by converting the DC stage voltage v _dc into an AC voltage and supplying it to the main motor M during powering. In FIG. 1, the correspondence relationship between the inverter 50 and the main motor M is shown as a one-to-one relationship, but it may be configured to drive and control N (N ≧ 1) main motors M with one inverter 50. Of course.
During regenerative braking, the inverter 50 converts the regenerative power generated by the main motor M into a DC stage voltage v _dc and outputs it to the DC intermediate circuit.
Operation control of the inverter 50 is performed by an inverter control device (not shown).

The storage battery 60 is a secondary battery connected to the DC intermediate circuit so as to be chargeable / dischargeable. Regardless of the type, any secondary battery such as a lead-acid battery, a lithium-ion battery, or a large-capacity capacitor can be used. If the input / output voltage (hereinafter referred to as “storage battery voltage”) applied to the terminal of the storage battery 60 is higher than the DC stage voltage v _dc , the discharging operation is performed to supply power to the DC intermediate circuit, and if it is lower, the charging operation is performed. In addition, it is good also as providing the apparatus which controls whether the storage battery 60 is connected to a direct current | flow intermediate circuit, or disconnecting.

  The converter control device 30 is a control device that controls the power conversion operation of the converter 40, and starts the power conversion operation based on an operation command from the cab of the electric vehicle 1. The converter control device 30 is a kind of computer device configured with an electronic circuit. Arithmetic control of the converter control device 30 may be partly or entirely realized by software by arithmetic processing by a program, or part or all of the arithmetic control may be performed by an ASIC (Application Specific Integrated Circuit) or FPGA (Field Programmable Gate). It may be realized by an integrated circuit such as an (Array).

  The configuration of the calculation block (functional block) of the converter control device 30 is shown in FIG. The converter control device 30 includes a calculation unit 31, a missing voltage calculation unit 34, a missing current calculation unit 38, and an AC side current adjustment unit 39.

Detection values such as the DC stage voltage v _dc , the AC side current i _c , the overhead line voltage, and the storage battery current (input / output current applied to the terminals of the storage battery 60) are input to the calculation unit 31, and the AC side voltage command value v _{c_ref} is obtained. A gate pulse signal PS that generates and outputs the gate of the converter 40 is turned on and off.

The converter control device 30 is not directly applied / input with the DC stage voltage v _dc , the AC side current i _c , the overhead wire voltage, the storage battery current, etc., but a voltage sensor, a current sensor, etc. for detecting these values. The detected value is input. For convenience of explanation, although it is not specifically mentioned below that they are detected values, these voltages and currents input to the converter control device 30 are detected values. The electric vehicle 1 is appropriately provided with a voltage sensor, a current sensor, or the like that detects these values.

Calculation unit 31 includes a current control system computing unit 32 for generating the AC-side voltage command value v _{C_ref} using at least ac side current i _c, the gate pulse signal PS on the basis of the generated AC side voltage command value v _{C_ref} And a pulse signal generation unit 33 for generation. A conventional calculation process can be adopted as the calculation process related to the generation of the AC side voltage command value _{vc_ref} .

The pulse signal generation unit 33 generates a gate pulse signal PS that becomes PWM by comparing the AC side voltage command value _{vc_ref} with a given triangular wave pulse. Further, the pulse signal generation unit 33, when the DC stage voltage v _dc is in a low voltage state that is equal to or lower than a predetermined voltage, causes the converter 40 to perform overmodulation operation (also referred to as overmodulation PWM control). Generate PS.

The missing voltage calculation unit 34 calculates a missing voltage v _cs that is an insufficient amount of the DC stage voltage v _dc with respect to the “predetermined voltage based on the AC side voltage command value v _{c_ref} ”. When the missing voltage v _cs is calculated as a non-zero value, the converter is in an overmodulated operation.

"Predetermined voltage based on the AC-side voltage command value v _{C_ref"} also may the AC side voltage instruction value v _{C_ref,} voltage and that or subtracted by adding a constant value to the AC-side voltage command value v _{C_ref,} AC side voltage A voltage obtained by increasing or decreasing the command value v _{c_ref} by a certain percentage may be used.
In the present embodiment, for simplicity of description, the "predetermined voltage based on the AC-side voltage command value v _{C_ref"} as the AC-side voltage instruction value _v c_ref.

FIG. 3 shows the configuration of the calculation block of the missing voltage calculation unit 34. The missing voltage calculation unit 34 includes a first calculator 35 and a second calculator 36. The first computing unit 35 is a computing unit that calculates a reference value v _ct that is directly proportional to the AC side voltage command value v _{c_ref} . However, the upper limit value of the reference value v _ct is a value with the sign of the DC stage voltage v _dc as positive, and the lower limit value is a value with the sign of the DC stage voltage v _dc as negative. The second calculator 36 is a calculator that subtracts the reference value v _ct from the AC side voltage command value v _{c_ref} . The calculation result by the second calculator 36 is the missing voltage v _cs .

The operation of the missing voltage calculation unit 34 will be described more specifically. If the AC side voltage command value v _{C_ref} has not reached the limit value defined by the DC stage voltage v _dc, the value of the AC side voltage command value v _{C_ref} is a reference value v _ct in the first arithmetic unit 35 Therefore, the calculation result in the second calculator 36 is zero, and the deficient voltage v _cs is calculated and output with the deficiency of the DC stage voltage v _{dc with} respect to the AC side voltage command value v _{c_ref} being zero. On the other hand, if the AC side voltage command value v _{C_ref} has reached the limit value defined by the DC stage voltage v _dc, the value of the DC stage voltage v _dc is a reference value v _ct in the first arithmetic unit 35 For this reason, in the second computing unit 36, an insufficient voltage of the DC stage voltage v _{dc with} respect to the AC side voltage command value v _{c_ref} is calculated and output as a missing voltage v _cs .

If the “predetermined voltage based on the AC side voltage command value _{vc_ref} ” is a voltage obtained by adding or subtracting a constant value or a dead time error compensation value to the AC side voltage command value _{vc_ref} , FIG. In the calculation block, a constant value or a dead time error compensation value is added to or subtracted from the AC side voltage command value v _{c_ref} before the first calculator 35 and the second calculator 36 in the input stage of the missing voltage calculator 34. Then, an arithmetic unit to be corrected may be inserted.

Returning to FIG. 2, the missing current calculation unit 38 calculates the missing current i _cs that becomes an AC side current corresponding to the missing voltage v _cs in the power conversion of the converter 40. The missing current calculation unit 38 stores a functional expression indicating an equivalent circuit of the main transformer 20 based on the specifications of the main transformer 20 as the main transformer model 381. based on the vessel model 381, the converter 40 is an AC side current of the converter 40 caused by a deficiency voltage v _cs content, calculated as missing current i _cs.

Ac side current adjusting unit 39, the AC side current i _c, by adjusting the ac side current i _c by subtracting deficient current i _cs, and outputs the current control system computing unit 32. For convenience of explanation, it referred to AC-side current i _c of the adjusted and second ac side current i _c2.

As a result, the current control system calculation unit 32 enters a state in which the AC side voltage command value v _{c_ref} is generated using the second AC side current i _{c2 from} which the missing current i _cs is subtracted. In other words, by subtracting the missing current i _cs from the actual AC side current i _c and inputting it to the current control system computing unit 32, the current control system computing unit 32 is allowed to accept the missing current i _cs . The second AC side current i _c2 is a virtual current that does not include a missing component. In other words, it can be said that the current control system calculation unit 32 is in a fooled state.

Next, the effect of this embodiment is demonstrated.
FIG. 4 is a diagram showing waveforms as a result of circuit simulation of the main circuit operation of the electric vehicle 1 when the converter 40 performs overmodulation operation. From the top, (1) the AC side voltage of the converter (main transformer) (Secondary voltage), (2) AC side current i _c , (3) DC stage voltage v _dc , (4) AC side voltage command value v _{c_ref} . Moreover, the horizontal axis indicates the elapsed time, before the time t _a before to apply a control in the present embodiment, after the time t _a is after applying the control of this embodiment.

  The AC side voltage (main transformer secondary voltage) of the converter in FIG. 4A has the same sine wave waveform before and after applying the control of this embodiment.

The waveform of the DC stage voltage v _dc in FIG. 4 (3) is also temporarily disturbed until stable operation immediately after the start of circuit simulation and immediately after the control of this embodiment is applied. In the stable period before and after applying this control, the waveform is almost the same with the voltage oscillation within a certain voltage fluctuation range. That is, it can be said that the conditions of the overmodulation operation were the same before and after applying the control of the present embodiment.

It should be noted that the AC side current i _c in FIG. 4 (2) and the AC side voltage command value v _{c_ref} in FIG. 4 (4).
First, by applying the control according to the present embodiment, the current control system calculation unit 32 is in a state in which the missing current i _cs is allowed. That is, the AC side voltage command value v _{c_ref} is generated using the second AC side current i _c2 obtained by subtracting the missing current i _cs instead of the actual AC side current i _c . For this reason, the amplitude of the AC side current i _c shown in FIG. 4 (2) is substantially the same before and after applying the control according to the present embodiment, but the AC side voltage command value v _{c_ref} shown in FIG. The amplitude is greatly different before and after applying the control according to the present embodiment.

Next, regarding the AC side current _ic in FIG. 4B, before the control according to the present embodiment is applied, the distortion of the waveform is large and it is difficult to say that it is a smooth vibration waveform. Since extreme values are seen in addition to the maximum and minimum values, the content of higher-order harmonics is large. This state is considered to be a state in which the converter 40 is excessively oscillating with respect to the distorted current.

  On the other hand, after applying the control according to the present embodiment, the distortion of the waveform is clearly smaller than that before applying, and the shape is approaching a smooth shape. Moreover, since the extreme value other than the maximum value and the minimum value does not appear clearly, it can be said that the content rate of higher-order harmonics is reduced.

  Therefore, by applying the control of the present embodiment, it is possible to effectively reduce the deterioration of the waveform distortion of the AC side current that occurs during the overmodulation operation of the converter 40. Moreover, since reducing the deterioration of the waveform distortion of the AC side current leads to suppression of the return current harmonic, according to the present embodiment, it is possible to suppress the return current harmonic.

  As mentioned above, although an example of the embodiment to which the present invention is applied has been described, it is needless to say that the form to which the present invention can be applied is not limited to the above-described embodiment.

DESCRIPTION OF SYMBOLS 20 Main transformer 30 Converter control apparatus 31 Calculation part 34 Missing voltage calculation part 38 Missing current calculation part 39 AC side current adjustment part 40 Converter 50 Inverter 60 Storage battery M Main motor

Claims (4)

In an electric vehicle that travels in an AC section comprising a converter, an inverter that drives and controls a main motor, and a storage battery that is connected to a DC intermediate circuit between the converter and the inverter in a chargeable / dischargeable manner, the electric power of the converter A converter control device for controlling the converter by generating an AC side voltage command value for controlling a conversion operation using an AC side current detection value,
A missing voltage calculation unit that calculates a missing voltage that is an insufficient amount of the voltage of the DC intermediate circuit (hereinafter referred to as “DC stage voltage”) with respect to a predetermined voltage based on the AC voltage command value;
A deficient current calculation unit that calculates a deficient current that is an alternating current due to the deficient voltage in power conversion of the converter;
An AC side current adjustment unit that subtracts the amount of missing current from the AC side current detection value obtained by detecting the AC side current of the converter;
And a converter control device that generates the AC side voltage command value using the AC side current detection value subtracted by the deficient current by the AC side current adjustment unit. When the DC stage voltage is not insufficient with respect to the predetermined voltage, the missing voltage calculation unit calculates the missing voltage as zero,
The converter control device according to claim 1. The missing current calculation unit calculates the missing current by calculating an AC side current of the converter generated by the missing voltage component by the converter based on the specifications of the main transformer.
The converter control device according to claim 1 or 2. In an electric vehicle that travels in an AC section comprising a converter, an inverter that drives and controls a main motor, and a storage battery that is connected to a DC intermediate circuit between the converter and the inverter in a chargeable / dischargeable manner, the electric power of the converter A converter control method for controlling the converter by generating an AC voltage command value for controlling a conversion operation using an AC current detection value,
Calculating a deficient voltage that is an insufficient amount of a voltage of the DC intermediate circuit (hereinafter referred to as “DC stage voltage”) with respect to a predetermined voltage based on the AC voltage command value;
Calculating a deficit current that is an AC side current due to the deficit voltage in power conversion of the converter;
Subtracting the deficient current from the AC side current detection value that has detected the AC side current of the converter;
Generating the AC side voltage command value using the AC side current detection value subtracted by the missing current;
Including a converter control method.