JP5361350B2 - Electric vehicle power converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power conversion device for an electric car capable of obtaining an excellent harmonic spectrum suppression effect thanks to carrier frequency dispersion of a converter and allowing simulation of the harmonic spectrum dispersion effect. <P>SOLUTION: When changing a carrier frequency of a converter, a carrier frequency calculation part 16 determines the carrier frequency by referencing a predetermined carrier frequency pattern 26 according to a cycle count value of an AC power source waveform. A plurality of carrier frequency pattern 26 are prepared, and a frequency of each frequency pattern changes at random in a pseudo manner. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a power converter for an electric vehicle that converts AC power supplied from an overhead wire into DC power using a converter, converts the DC power into AC power using an inverter, and drives a motor.

  In an AC train system, single-phase AC applied to an overhead wire is AC / DC converted by a PWM converter, and power is supplied to an inverter and a main motor that is a load thereof. As a PWM converter control method, a PWM control method that performs pulse width modulation control by comparing a triangular wave carrier with a constant frequency and a modulated wave is widely applied. However, a harmonic component of a specific frequency generated by a certain carrier frequency may return to the return line (overhead line and rail), and may cause an inductive failure in the feeder system and communication line.

  As a technique for dealing with the above problem, a PWM method has been proposed that disperses the harmonic spectrum by changing the carrier frequency to various frequencies without making the carrier frequency constant so as not to generate a harmonic component of a specific frequency. Yes.

The above known techniques are disclosed in Patent Document 1, Patent Document 2, and the like. Patent Document 1 merely describes a general theory about making the carrier frequency of the PWM converter variable. Patent Document 2 is characterized by using different carrier frequencies.
Japanese Patent Laid-Open No. 9-14165 JP 2006-67638 A

  In the prior art, an effect of carrier frequency dispersion can be obtained, but there is a problem that the current harmonic spectrum dispersion effect cannot be simulated (preliminary evaluation) because frequency change is not reproducible.

  An object of the present invention is to provide an electric vehicle power conversion device that can obtain an excellent harmonic spectrum suppression effect due to carrier frequency dispersion of a converter and can simulate the harmonic spectrum dispersion effect.

  The present invention has been made in view of the above-described conventional problems, and when changing the carrier frequency of the PWM converter, refer to a predetermined carrier frequency pattern according to the period count value of the AC power supply waveform. A carrier frequency is determined. A plurality of carrier frequency patterns are prepared, and the frequency in each frequency pattern changes pseudo-randomly.

  An excellent harmonic spectrum suppression effect can be obtained, the current harmonic spectrum dispersion effect can be evaluated in advance, and an optimum carrier frequency can be selected according to the purpose. In addition, since there is reproducibility, analysis at the time of trouble can be made easier than just a random carrier distribution method.

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

   FIG. 1 is a block diagram showing a schematic configuration of a first embodiment of a PWM converter control device according to the present invention.

   The pantograph 1 and the wheels 2 collect the single-phase alternating current supplied from the substation and applied to the overhead line. A converter 4 is connected to the pantograph 1 through the main transformer 3, and a smoothing filter capacitor 5 and a VVVF inverter 6 that drives the main motor 7 are connected to the DC side of the converter 4. Here, the load of the converter is the inverter 6 and the main motor 7.

   The converter control part 11 controls the conduction | electrical_connection state of the switching element which comprises a converter switching circuit. The input of the converter control unit 11 is detected by the voltage detector 8, the overhead line voltage V 1 detected by the voltage detector 10, the output current Ic that is the AC side current of the converter detected by the current detector 9, and the voltage detector 8. This is the filter capacitor voltage Vdc.

   The current control unit 18 performs converter current control, which is a well-known technique, and controls the converter output voltage command Vc * so that the deviation between the filter capacitor voltage Vdc and the DC voltage command Vdc * that is the target value becomes zero. .

   The phase estimation unit 15 calculates the phase θs of the power supply voltage V1 based on the overhead line voltage (hereinafter referred to as power supply voltage) V1 detected by the voltage detector 10 by a well-known single-phase PLL technique. In this embodiment, the zero point of θs is defined as a zero cross point at which the power supply voltage is changed from negative to positive.

The carrier frequency calculation unit 16 calculates the carrier frequency fc * based on the phase θs and the carrier phase θcar calculated by the subsequent carrier phase calculation unit 20. Based on the carrier frequency fc *, the carrier phase calculation unit 20 calculates the carrier phase θcar as shown in Equation (1).

   The carrier triangular wave generator 17 generates a triangular wave carrier based on the carrier phase θcar. The comparator 19 generates a gate to the converter 4 by triangular wave comparison PWM control so that an AC output voltage of the converter 4 that matches the converter output voltage command value Vc * is obtained.

   In the current PWM converter, the carrier frequency fc * is generally constant. The output current includes a large ripple of the carrier frequency component as shown in FIG. 5, which will be described later, and causes a noise of the main transformer.

   Here, the main part of the present embodiment is in the carrier frequency calculation unit 16. Details thereof will be described below.

   FIG. 2 shows the configuration of the carrier frequency calculation unit 16. The carrier count calculation unit 25 receives the phase θs of the power supply voltage and the phase θcar of the carrier triangular wave, and generates a pattern cycle count N and a carrier count M.

   The carrier frequency calculation unit 16 selects a carrier frequency pattern based on the pattern cycle count N, and selects and outputs the carrier frequency fc * stored in the carrier pattern for each carrier period based on the carrier count M. .

   FIG. 3 is a diagram showing signal waveforms at various parts. 3A is a voltage waveform of the AC power supply voltage V1 supplied from the overhead wire, and FIG. 3B is a diagram showing the relationship between the phase θs and the pattern cycle count N. FIG. 3C shows the relationship between the phase θcar and the carrier count M, and FIG. 3D shows the carrier triangular wave Vt.

For example, the pattern cycle count N can be calculated as in equation (2).

Further, the carrier count M can be calculated as shown in Equation (3).

   Here, floor () is a function for rounding down decimals to an integer. MM is the number of carrier triangular waves in one cycle of θs. Further, it is assumed that the power supply voltage phase θs and the carrier triangular wave phase θcar exist in a region of 0 [deg] or more and less than 360 [deg].

   The carrier frequency calculation unit 16 stores carrier frequency pattern tables 26a, 26b, 26c... Corresponding to the pattern cycle count N. A carrier frequency pattern table 26 corresponding to the pattern cycle count N generated by the carrier count calculation unit 25 is referred to.

   Each carrier frequency pattern table 26 stores a carrier frequency fc * corresponding to the carrier count M. The carrier frequency fc * varies pseudo-randomly in one carrier frequency pattern table 26. Carrier frequency data corresponding to the carrier count M calculated by the carrier count calculation unit 25 is output as the carrier frequency fc * at that time. The frequency pattern in the carrier frequency pattern table 26 is obtained by extracting the optimized carrier frequency pattern from the operation simulation of the power conversion device.

   As described above, in the first embodiment, the phase θs of the power supply voltage and the phase θcar of the carrier triangular wave, and the carrier frequency fc * with respect to values (referred to as pattern cycle count and carrier count in this embodiment) are calculated in advance. In the actual operation, the carrier frequency fc * is selected with reference to the table for each carrier triangular wave period.

   By calculating the carrier frequency pattern in advance and storing it as table data, the carrier frequency calculation unit 16 creates the carrier frequency pattern table 26 for each carrier triangular wave period according to the pattern cycle count N and the carrier count M. Referring to, the carrier frequency is set. Therefore, as an effect, the carrier frequency calculation unit 16 can immediately set the carrier frequency fc *, and can change the converter carrier triangular wave frequency for each period of the carrier triangular wave.

   In this embodiment, the carrier frequency fc * is selected for “every carrier triangular wave cycle”. However, even if “every 1 / N times the carrier cycle”, the carrier frequency fc * is set every “cycle that is N times the carrier cycle”. You may choose.

FIG. 4 shows a modification of the first embodiment, in which NN different carrier patterns determined in advance are sequentially applied for each power supply voltage period, and are set to be repeated after the NN period.

   Here, NN is the total number of pattern tables.

   The effect of this modification is that it is not necessary to create a large number of carrier frequency patterns by sequentially applying NN different frequency patterns determined in advance for each cycle of the power supply voltage and repeating it for each cycle of the power supply voltage NN. The design load can be reduced.

   Next, a method for setting a carrier frequency pattern, that is, a method for setting the carrier frequency pattern table 26 will be described.

   In this embodiment, the carrier frequency is set to be constant within one period of the carrier triangular wave. For example, the carrier count M is generated as in Expression (3), the carrier frequency pattern table is referenced for each carrier triangular wave period, and the same carrier frequency is used within one carrier triangular wave period.

   This effect is that since the frequency does not change within one cycle of the carrier triangular wave, the control disturbance is reduced, and stable and high-performance converter characteristics can be maintained.

In this embodiment, the carrier frequency is set so that the number of switching of the carrier triangular wave frequency is the same in each cycle of the power supply voltage V1. In order to satisfy this condition, the total period of the triangular wave within one period of the power supply voltage must be constant. Therefore, the setting of the carrier frequency needs to satisfy Expression (5). Here, T is the power cycle [sec].

   This effect is that the carrier triangular wave frequency and the power supply voltage can be synchronized in any one power supply voltage cycle, so that the carrier triangular wave and the power supply voltage can be synchronized, and stable and high-performance converter characteristics can be maintained.

   In the present embodiment, when the carrier frequency pattern table is created, the carrier frequency average value within the J (J = 1, 2, 3,...) Period of the power supply voltage is set to be substantially constant. Yes.

In order to satisfy the above condition, the setting of the carrier frequency needs to satisfy Expression (6) in an arbitrary J-th period. Here, MM is the number of pulses of the carrier triangular wave within one cycle of the power supply voltage. fc * ave is a carrier frequency average value within one cycle of the power supply voltage.

   This effect is because the average value of the carrier triangular wave frequency within one cycle of the power supply voltage is the same within any J-th cycle of the power supply voltage, so that when the carrier frequency is varied, the heat generation of the converter due to an excessively high frequency can be suppressed. And maintain high-performance converter characteristics.

   Further, in the present embodiment, when the carrier frequency pattern is created, the carrier frequency satisfies the condition that the average value of the carrier frequency in the J-th cycle of the power supply voltage is constant, and the carrier frequency is within the range of the upper limit / lower limit frequency. The frequency is set to be arbitrarily distributed.

   For example, a carrier frequency pattern is generated as shown in Equation (7).

fc * 1 = fc * ave + α
fc * 2 = fc * ave + β
...
fc * n = fc * ave + γ (7)
(Lower limit frequency <α, β, γ <upper limit frequency)
Here, α, β, and γ are arbitrary values and are within the range of the upper and lower frequency limits. fc * 1 to fc * n are data that fit in the carrier triangular wave pattern.

The effect of this embodiment is that by determining the upper and lower limits of the carrier frequency, the use of a carrier frequency that is too low or too high can be avoided, and when the carrier frequency is made variable, the heat generation of the converter is suppressed. The effect is further enhanced.
As an application example of the present embodiment, an optimal carrier frequency pattern suitable for the purpose is extracted in advance using means such as simulation, and a carrier frequency pattern table referred to during operation is generated.

   For example, when aiming to reduce the peak level of harmonics, create multiple carrier frequency patterns in advance and evaluate the reduction effect of each carrier frequency pattern by harmonic analysis simulation. Select an excellent pattern.

   This effect is that high-performance converter characteristics can be maintained by applying the most effective pattern suitable for the purpose.

   5 to 7 are diagrams showing a return current during operation of the converter.

   FIG. 5 shows measured values of the retrace current when a conventional converter control device with a constant carrier frequency (500 Hz) is operated. As can be seen from this figure, ripples are generated in the spectrum of 1000 Hz, 2000 Hz, and the like. These ripples indicate harmonic components of a carrier signal having a frequency of 500 Hz. These harmonic components degrade the signal quality of, for example, an ATC signal transmitted through the rail. Incidentally, the ripple near 4500 Hz is a ripple generated from the auxiliary power converter of the electric vehicle.

   FIG. 6 shows measured values of the retrace current when the converter control apparatus according to the first embodiment of the present invention is operated. As can be seen from this figure, the generation of ripple, which is a harmonic component of the carrier signal, which has conventionally occurred is effectively suppressed.

FIG. 7 shows a simulation result of the retrace current when the converter control apparatus according to the first embodiment is operated. As can be seen from this figure, this simulation result almost faithfully reproduces the actual retrace current characteristic of FIG. As described above, the carrier frequency change of the converter control device according to the present invention is reproducible, and thus a highly accurate simulation is possible.
(Second implementation state)
Next, a second embodiment of the present invention will be described. FIG. 8 is a block diagram showing a schematic configuration of the second embodiment of the present invention. FIG. 8 shows the configuration of one locomotive.

   On the secondary side of the main transformer 3, the same electric vehicle control device as in the first embodiment is connected in parallel. Each converter control unit 11 receives the total number K and the location address Kx of its own device as “K, Kx”.

   In each electric vehicle control device 30, the carrier frequency calculation unit 16 refers to the same carrier frequency pattern.

   The carrier phase calculation unit 20 calculates the phase of the carrier triangular wave of each switching circuit according to the total number K of electric vehicle control devices 20 and the location address Kx.

For example, the phase θcark of the carrier triangular wave is determined as in the following equation.

   Here, fc * is the carrier frequency of the converter switching circuit, K is the total number of power converters in parallel, and kx is the x-th power converter (x = 1 to K).

   The carrier frequency generation unit 17 of each converter control unit 11 generates each carrier triangular wave according to the carrier frequency fc * that is the output of the carrier frequency calculation unit 16 and the carrier triangular wave phase θcark.

   With the above configuration, the phase of the carrier triangular wave of each carrier triangular wave generator 17 is sequentially shifted, that is, shifted in accordance with the number of electric vehicle control devices, while making the carrier frequency of the converter switching circuit variable. For this reason, the peak level of the harmonics of the output current of the converter 4 can be further reduced, and an electric vehicle drive device with improved device performance can be provided.

(Third implementation state)
FIG. 9 is a block diagram showing a schematic configuration of the third embodiment of the present invention. The configuration of the main circuit is the same as that of the first embodiment of FIG.

   The driving situation determination unit 27 outputs a carrier frequency switching signal according to the driving situation.

   In a normal state, the switch 28 selects the position “0” in accordance with the output “0” of the driving condition determination unit 27, and the output fc * of the carrier frequency calculation unit 16 is input to the carrier phase calculation unit 20.

   When the driving situation changes, the output of the driving situation judgment unit 27 is switched to “1”, and the switch 28 selects position 1. The input to the carrier phase calculation unit 20 is switched to a high carrier frequency fc **. The time when the driving situation changes is, for example, when the driving state changes from the running state to the stopped state. When the vehicle is stopped, almost no current flows through the converter, so the carrier frequency is set to a high frequency fc ** to reduce noise and the like.

   In addition, this driving situation includes a case where a unit cut has occurred in one vehicle (for example, one of the two converters has failed). In this case, during normal operation, for example, the triangular wave carriers of the two converters are generated at a constant frequency and with phases shifted from each other. When the unit cut occurs, the normal one converter is operated and the operation is continued, but the triangular wave carrier is generated periodically and randomly changing as in the first embodiment. As a result, even when only one converter is operated and the operation is continued, the ripple of the return current and the noise of the inverter can be kept low.

   Thus, by switching the carrier frequency of the present embodiment, the carrier frequency suitable for the purpose can be selected according to the operating conditions, the harmonic peak level of the output current of the converter 4 can be reduced, and the noise can be reduced. The performance of the electric vehicle drive device can be improved.

  The above description is an embodiment of the present invention, and does not limit the apparatus and method of the present invention, and various modifications can be easily implemented.

It is a block diagram which shows schematic structure of 1st Example of the PWM converter control apparatus by this invention. 3 is a diagram illustrating a configuration of a carrier frequency calculation unit 16. FIG. FIG. 4 is a diagram illustrating signal waveforms of respective units of the converter control unit 11. It is a figure which shows the modification of 1st Example of this invention. It is a figure which shows the actual value of the retrace current at the time of operating the conventional converter control apparatus of constant carrier frequency (500Hz). It is a figure which shows the actual value of the return current at the time of operating the converter control apparatus by 1st Example of this invention. It is a figure which shows the simulation result of the retrace current at the time of operating the converter control apparatus by the said 1st Example. It is a block diagram which shows schematic structure of 2nd Example of this invention. It is a block which shows schematic structure of 3rd Example of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Pantograph, 2 ... Wheel, 3 ... Main transformer, 4 ... Converter, 5 ... Filter capacitor, 6 ... Inverter, 7 ... Electric motor, 8 ... Filter capacitor voltage detector, 9 ... Converter input current detector, 10 ... Overhead wire Voltage detector, 11 ... converter control unit, 15 ... phase estimation unit, 16 ... carrier frequency calculation unit, 17 ... carrier triangular wave generator, 18 ... current control, 19 ... comparator, 20 ... carrier phase calculation unit, 25 ... carrier Count calculation unit, 26... Carrier frequency pattern, 27... Driving condition determination unit, 28.

Claims (10)

A converter that converts alternating current to direct current,
A carrier frequency calculation unit for calculating the carrier frequency of the converter;
A triangular wave carrier generated based on the carrier frequency calculated by the carrier frequency calculation unit, and a converter control unit that performs pulse width modulation control of the converter by comparing the modulation wave;
The carrier frequency calculation unit calculates a carrier frequency with reference to a predetermined frequency pattern for each period of a triangular wave carrier.   The carrier frequency calculation means sequentially applies different frequency patterns determined in advance for each period of the AC side voltage of the converter, and repeatedly applies the different frequency patterns for every N periods. 1. The power conversion device according to 1.   The power conversion device according to claim 1, wherein the carrier frequency calculated by the carrier frequency calculation means is constant within one period of the triangular wave carrier.   The power conversion device according to claim 1, wherein the number of switching carrier frequencies calculated by the carrier frequency calculating means is constant within each period of the AC side voltage of the converter.   The average carrier frequency of the carrier frequency calculated by the carrier frequency calculating means is constant within an arbitrary N (N = 1, 2, 3,...) Period of the AC input side voltage of the converter. The power conversion device according to claim 1.   6. The power conversion apparatus according to claim 5, wherein the carrier frequency calculated by the carrier frequency calculation means changes within a predetermined upper limit frequency and a predetermined lower limit frequency.   The power conversion device according to claim 1, wherein an optimized carrier frequency pattern is extracted from the operation simulation of the power conversion device as the predetermined frequency pattern.   The said power converter device comprises two or more sets of a converter, a carrier frequency calculating part, and a converter control part, The phase of the triangular wave carrier produced | generated in the said converter control part has shifted | deviated mutually. Power conversion device. The power conversion device according to claim 1, wherein the carrier frequency calculation unit switches the carrier frequency to a higher carrier frequency according to a driving situation of the electric vehicle . The power conversion device according to claim 9, wherein the carrier frequency calculation unit switches the carrier frequency to a higher carrier frequency than when traveling when the electric vehicle is stopped.

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