JP5198232B2 - Power converter - Google Patents

Description

  The present invention relates to a power conversion device, and in particular, is a device devised to suppress noise emission due to a change or fluctuation in carrier frequency when switching control of a plurality of converters.

  In an AC train system, single-phase AC applied to an overhead wire is AC / DC converted by a pulse width modulation (PWM) converter, and electric power is supplied to an inverter and a main motor as a load thereof. The PWM converter control method generates a pulse width modulated wave signal by comparing a triangular wave carrier having a constant frequency and a modulated wave (sine wave), and controls the switching element of the PWM converter based on the pulse width modulated wave signal. The so-called PWM control method is widely applied. However, when one group of the plurality of converters is opened, unnecessary harmonic components generated by a certain carrier frequency as a train increase, which may cause inductive disturbances to the feeder system and the communication line.

  As a countermeasure technique to solve such problems, PWM control that disperses the harmonic spectrum by changing the carrier frequency to various frequencies without making the carrier frequency constant so as not to generate unnecessary harmonic components. A law has been proposed.

There are Patent Documents 1, 2, and 3 as documents showing the above technique. Patent Document 1 merely describes a general theory about making the carrier frequency of the PWM converter variable. Patent Document 2 describes that the carrier frequency is changed with time. Patent Document 3 describes using different carrier frequencies. At this time, the continuously changing carrier frequency is calculated based on the absolute value of the power supply voltage.
Japanese Unexamined Patent Publication No. 9-140165 Japanese Patent Laid-Open No. 2004-312922 JP 2006-67638 A

  Even if the above-described conventional technique is employed, an unnecessary harmonic signal may be generated from the periphery of the power converter. The inventor of the present invention has noticed that there are generation factors of unnecessary harmonic signals that cannot be suppressed by the conventional technique.

    Accordingly, the object of the present invention has been made in view of the above circumstances. When the carrier frequency of the PWM control converter is made variable, the operation states of a plurality of converters are discriminated, and the carrier frequencies set in advance according to the states. It is in providing the power converter device which can suppress generation | occurrence | production of an unnecessary harmonic component by using.

According to one embodiment, a PWM that controls a plurality of converters that convert alternating current into direct current, and a pulse width modulation output that is generated by comparing a triangular wave carrier and a modulated wave with a switching operation of a plurality of switching elements of the plurality of converters. A control unit, and a carrier frequency calculation unit that changes a carrier frequency of the triangular wave carrier in accordance with each operation state of the plurality of converters, the output power of the inverter in accordance with the state determination result of the plurality of converters A carrier frequency calculation unit that changes the carrier frequency of the converter that is not abnormal .

  According to said means, according to each operation state of a some converter, a carrier frequency can be changed, a harmonic can be set and generation | occurrence | production of an unnecessary harmonic can be suppressed.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of a first embodiment of the present invention. FIG. 2 is a diagram showing a basic configuration example of the converter 14a of FIG. FIG. 3 is a diagram illustrating a configuration example of the carrier frequency calculation unit 116 of FIG.

  It demonstrates from FIG. In the figure, one system of the converter 14a is shown with a reference numeral, but there are a plurality of converter systems. The single-phase alternating current supplied from the substation and applied to the overhead line is collected through the system from the pantograph 10 to the wheel 12. A converter 14a is connected to the main transformer 13 of the current collection path. Further, a smoothing filter capacitor 15a and a VVVF inverter 16a for driving the main motor 17a are connected to the DC side terminal of the converter 14a. Here, the load of converter 14a is inverter 16a and main motor 17a.

  Converter 14a is controlled by converter control unit 111. The converter control unit 111 controls the conduction state of the switching element used in the converter switching circuit.

  The input of the converter control unit 111 is detected by the overhead voltage Vs detected by the voltage detector 100, the output current Is which is the AC side current of the converter 14a detected by the current detector 19a, and the voltage detector 18a. This is the terminal voltage Vd of the filter capacitor 15a.

In the converter control unit 111, the voltage control calculation unit 113 receives the voltage Vd of the filter capacitor 15a. The voltage control calculation unit 113 outputs a current Isref having an amplitude corresponding to, for example, a difference between the voltage Vd and a DC command reference voltage Vdref that commands a target value. This change in current Isref corresponds to the change in voltage Vd. The current Isref is input to the current control calculation unit 114 as a reference current. Where Isref = (Kpdc + Kidc / s) × (Vdref−Vd)
Kpdc: DC voltage control proportional gain Kidc: DC voltage control integral gain s: Laplace operator.

The phase θs signal is input to the current control calculation unit 114. The current control calculation unit 114 multiplies the phase θs signal by the current Isref, and once creates a detection current Isdet having the frequency of the phase θs signal. Next, the current control calculation unit 114 outputs a control voltage Vcref corresponding to the amplitude difference between the output current Is on the AC side of the converter 14a and the detected current Isdet. Where Isdet = Isref × sin (θs)
Vcref = Kp × (Isdet−Isref)
It is.

The phase θs signal is input to the current calculation unit 114. The current calculation unit 114 multiplies the phase θs signal and the current Isref, and once creates a detection current Isdet having the frequency of the phase θs signal. Next, the current control calculation unit 114 outputs a control voltage Vcref corresponding to the amplitude difference between the output current Is on the AC side of the converter 14a and the detected current Isdet. Where Isdet = Isref × sin (θs)
Vcref = Kp × (Isdet−Isref)
It is.

  The current control calculation unit 114 performs converter current control, and the control voltage Vcref as the converter output voltage command is set so that the deviation between the voltage Vd of the filter capacitor 18a and the DC voltage command Vdref that is the target value becomes zero. To control. This control voltage Vcref is input to the PWM calculation unit 115. Further, the triangular wave carrier whose phase is controlled from the carrier phase calculation unit 117 is input to the PWM calculation unit 115.

  By the way, the carrier phase calculation unit 117 receives a signal having the carrier frequency fc from the carrier frequency calculation unit 116.

Based on the carrier frequency fc that is the output of the carrier frequency calculation unit 116, the carrier phase calculation unit 117 calculates the carrier phase θcar as shown in Expression (1).

 The carrier phase calculation unit 117 generates the triangular wave carrier corresponding to the carrier phase based on the carrier phase θcar and supplies it to the PWM calculation unit 115. The PWM calculation unit 115 generates a gate control signal to the converter by triangular wave comparison PWM control so that an output voltage matching the converter output voltage command value Vc is obtained from the converter.

   In a plurality of conventional PWM converters, the carrier frequency fc assigned to each is constant. However, since the carrier phase θcar has a phase difference as a knitting, when the converter is opened in one group, the ripple of the carrier frequency component becomes large in the output current, and there is a risk of causing inductive disturbance to the feeder system and communication line. is there.

   In other words, each carrier frequency and its carrier phase are normally set when multiple converters are operating normally. If one of the multiple converters is stopped for some reason, it operates with the remaining converters. Is done. In such a case, if the set carrier frequency is maintained, the harmonic component of the specific frequency increases, which may cause inductive interference to the feeder system and the communication line.

Therefore, the point of the present embodiment is that the carrier frequency calculation unit 116 generates carrier frequencies set in advance according to the states of a plurality of converters so that the above-described inductive disturbance can be suppressed. Details thereof will be described below.

   First, the converter state detection unit 200 detects a plurality of converter states, for example, stop states. The converter may be automatically shut down depending on the destruction of the element or the corresponding load condition. Converter open group number COVn from converter state detection unit 200 is input to carrier calculation unit 116 as information. At this stage, it is assumed that the converter 14a corresponding to the converter control unit 111 is operating normally.

   FIG. 2 shows a basic configuration example of the converter 14a. For example, an insulated gate bipolar transistor (hereinafter abbreviated as IGBT) is used. That is, the IGBTs 31 and 32 are connected in series, and the IGBTs 33 and 34 are connected in series. The series circuits are connected in parallel, the collectors of the IGBTs 31 and 33 are connected to the positive terminal of the filter capacitor 15a, and the emitters of the IGBTs 32 and 34 are connected to the negative terminal of the filter capacitor 15a. The gate circuits 41-44 are connected to the gate electrodes of the IGBTs 31-34, respectively, and the turn-on and turn-off timings of the transistors can be controlled. A control pulse is supplied from the PWM control calculation unit 115 to the gate circuits 41-44.

   FIG. 3 shows the configuration of the carrier frequency calculation unit 116. In the fc selection table 118, fc is switched according to the group opening number COVn of all converters. As a knitting, in an converter composed of all n groups, an fc output pattern from 0 to n-1 of the number of open converters is set in advance and is selected by the number of open groups of converters COVn. The selected fc is a carrier frequency calculated so as to suppress the above-described inductive failure with respect to the current number of normally used converters.

In the AC train system, a component of an integer multiple (synchronization) of the power supply frequency can be allowed due to restrictions on current harmonics flowing out from the converter 14a to the overhead line (there is a track circuit that controls the signal system). N in (2) may be the number of open converter groups.

 However, T is the period [sec] of the power supply voltage, and t0 is an arbitrary time [sec]. Since t0 is an arbitrary time, for example, it may be considered as a time [sec] when the power supply voltage crosses zero.

  According to the above-described embodiment, it is possible to suppress the generation of unnecessary harmonics by setting the harmonics by changing the carrier frequency in accordance with the operation states of the plurality of converters.

  The present invention is not limited to the above embodiment. FIG. 4 shows another embodiment of the present invention. A description of the same parts as those in FIG. 1 will be omitted, and different parts will be described. In this embodiment, the output current Is, which is the current on the AC side of the converter 14a detected by the current detector 19a, is also input to the carrier frequency calculation unit 116.

  The carrier frequency calculation unit 116 at this time has a configuration as shown in FIG. Generally, the power limit of the inverter is determined by the output current Is detected by the converter input current detector 19a. If the inverter power limit is not limited without changing the converter open group number, the converter switching loss increases. Therefore, the converter open group number COVn is further added to the Is as the inverter power limit condition. The fc selection table 118 is used in which the value of fc increases as the value of Is increases and as the value of COVn increases.

For example, for Is (m), m and K are arbitrary integers.
Km ≦ Is (m) ≦ K (m + 1) (3)
A value that satisfies Here, since n and m are positive integers, n in equation (2) may be replaced with n + m as in equation (4).

 Therefore, this idea is to change the carrier frequency of the converter in which the output power of the inverter is not abnormal according to the determination results of the states of the plurality of converters.

  In normal operation, when switching from a certain carrier frequency to a specific carrier frequency, the converter switching loss increases, but since the loss is suppressed by limiting the inverter power from the above, increasing the converter carrier frequency Can do.

Moreover, the harmonic component of a specific frequency can be suppressed by raising the converter carrier frequency.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.

It is a configuration explanatory view showing an embodiment of the present invention. It is a figure which shows the basic structural example of the converter of FIG. It is a figure which shows the structural example of the carrier frequency calculating part 116 of FIG. It is composition explanatory drawing which shows other embodiment of this invention. FIG. 5 is a diagram illustrating a configuration example of a carrier frequency calculation unit 116 in FIG. 4.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Pantograph, 12 ... Wheel, 13 ... Main transformer, 14a ... Converter, 15a ... Filter capacitor, 16a ... VVVF inverter, 17a ... Main motor, 18a ... Voltage detector, 19a ... current detector, 100 ... voltage detector, 111 ... converter control unit, 112 ... phase calculation unit, 113 ... voltage control calculation unit, 114 ... Current control calculation unit, 115 ... PWM calculation unit, 116 ... carrier frequency calculation unit, 117 ... carrier phase calculation unit, 200 ... converter state detection unit.

Claims (2)

A plurality of converters for converting alternating current to direct current;
A PWM controller that controls a switching operation of a plurality of switching elements of the plurality of converters by a pulse width modulation output generated by comparing a triangular wave carrier and a modulated wave;
A carrier frequency calculation unit that changes a carrier frequency of the triangular wave carrier according to each operation state of the plurality of converters, and according to a state determination result of the plurality of converters, and the output power of the inverter is not abnormal A carrier frequency calculation unit for changing the carrier frequency of the converter;
The power converter characterized by having. A plurality of converters for converting alternating current to direct current;
A PWM controller that controls a switching operation of a plurality of switching elements of the plurality of converters by a pulse width modulation output generated by comparing a triangular wave carrier and a modulated wave;
A carrier frequency calculation unit that changes a carrier frequency of the triangular wave carrier according to each operation state of the plurality of converters, the number of open converter groups indicating a state determination result of the plurality of converters and an AC side of the converter A carrier frequency calculator having a table for setting a plurality of set carrier frequencies corresponding to output current values;
The power converter characterized by having.

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