JPS6117233B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power supply system for a linear motor, and more particularly to a device for reducing harmonic components of a power supply side current of a power converter using an efficient filter configuration.

A power converter with variable frequency output is used as a power supply system for the linear motor of a superconducting magnetic levitation type ultrahigh-speed railway.

As a power supply system, there are two methods: one is to supply power directly from a commercial frequency AC power supply to the propulsion coil on the orbit side via a power converter, and the other is to supply power to the propulsion coil on the orbit side from a dedicated AC generator via a power converter. However, in any case, it is well known that the AC input current of the power conversion device is amplitude-modulated by the output current and contains many fractional harmonics and harmonics in addition to the fundamental wave.

Frequency f of harmonic current generated by the power converter
_h is generally expressed as follows.

f _h = kf _i ±2nf _p …(1) where, f _i : power supply frequency, f _p : output frequency,
k: 1 and 6m±1, m=1, 2,..., n:
0, 1, 2,... In a power conversion device, as is known from the second term on the right side of equation (1), harmonics of irregular numbers of the power supply frequency appear, and the output frequency f _p changes depending on the speed of the traveling object. Therefore, it is necessary to consider that the frequency spectrum of harmonics changes continuously.

When a dedicated AC generator is used as an AC power source for a power conversion device, the operating limit of the AC generator is when a current with a harmonic frequency f _h shown by equation (1) flows into the AC power source when the power conversion device is operating. The rotor is the part that has the greatest influence on the power supply frequency, and the rotor also regulates the resistance to the negative phase component of _the fundamental wave current of the power supply frequency. It is expressed as an equivalent negative sequence current that can be converted at the same level as the phase current, and the conversion is obtained assuming that the sum of losses due to each harmonic current is equal to the loss due to negative sequence current. That is, However, K: constant, f _h : harmonic frequency, f _p :
Fundamental frequency, I _h : Harmonic current, f′ _p : Frequency of anti-phase component (generally twice the fundamental frequency f _p ),
I′ _p : Negative sequence current (=I′ _peq ) In the equation, equations (2) and (3) are equal and
Substituting f′ _p into each equation (2) and (3) and rearranging, we get From the formula, the equivalent negative sequence current I′ _peq is It is expressed as

On the other hand, when a commercial frequency is used as the AC power source for a power conversion device, if the current at the harmonic frequency f _h shown in equation (1) flows into the AC power source when the power conversion device is operating, it will cause an inductive disturbance in communication lines, etc. occurs, and the equivalent damage current J _p shown by the following equation is used as a relational expression to consider this. That is, Here, S _o is a noise evaluation coefficient of voltage at frequency _fo , and I _o is a current component at frequency _fo .

In other words, disturbances due to harmonic currents on the AC power supply side that occur during the operation of a power converter are evaluated by the equivalent negative sequence current when a dedicated alternator is used as the AC power supply, and by the equivalent negative sequence current when a commercial frequency is used as the AC power supply. Evaluated by disturbance current.

The inventors analyzed the frequency spectrum of continuous harmonics from the current waveform on the power supply side of the power converter when the linear motor was running with a constant current command signal and calculated the equivalent disturbance current J _p using a large-scale power converter. As a result of calculation, as shown in FIG. 1, the characteristic is large in the low speed range and high speed range, and minimum in the medium speed range.

Here, the reason why the equivalent disturbance current J _p becomes large in the low speed range is because the back electromotive force of the linear motor is small, so the current supplied from the AC power supply to the power converter increases, and each harmonic current increases accordingly. Also, the reason why the equivalent disturbance current J _p became large in the high-speed range was because the sideband currents of the fundamental frequency and integer harmonics became large due to the influence of the back electromotive force of the linear motor. be.

In order to reduce the current at the harmonic frequency f _h shown in equation (1), it is necessary to connect a high-order reduction filter, such as the one shown in Figure 2, which is used in DC transmission systems, to the AC power source. However, there are drawbacks such as the fact that it is uneconomical to connect the high-order reduction filter shown in FIG. 2 to the operating state where the traveling body straddles two propulsion coils with the characteristics shown in FIG. 1.

The present invention eliminates the above-mentioned drawbacks and provides at least two
a first filter for reducing harmonic current on the AC power source side when two power converters operate alternately to sequentially supply power to multiple sections of propulsion coils via a switch;
A second filter for reducing harmonic current on the AC power source side when at least two power converters operate simultaneously and supply power to different propulsion coils when the traveling body is running astride two propulsion coils; , the first filter is always operated,
The second filter operates only when controlling the power supply switching to the propulsion coil, thereby providing an economical and efficient power supply system for a linear motor that can reduce harmonic current on the AC power supply side. purpose.

Hereinafter, the present invention will be explained in detail based on specific examples.

Figure 3 is a configuration diagram of a power supply system for a linear motor in which the present invention is implemented, and the propulsion coils of the linear motor are propulsion coil units for each section LM _o-1 , LM _o , LM _o+1.
divided into switches SW _o-1 , SW _o , SW _o+1 respectively.
The feeders 3 and 4 are connected to the feeders 3 and 4 in a sequentially and alternately repeated manner.

Power converters CC ₁ and CC ₂ are connected to each feeder, and the primary sides of transformers T ₁ and T ₂ and AC power supply 7 are connected to each feeder.
The first filter 11 and the second filter 12 described above are connected between the two filters.

Operate one of the power converters CC ₁ and CC ₂ by a signal from the switch opening/closing command 6 so as to supply power only to the propulsion coil where the traveling body 1 carrying the field magnet 2 is present; In addition, the signal from the position detector 5 that detects the position of the traveling object 1 is used to operate one of the power converters CC ₁ and CC ₂ and to determine which propulsion coil is to be supplied with power. It is a power supply system.

8 issues a command to close the switching device 21 when each of the power converters CC ₁ and CC ₂ issues a gate start command, and when each of the power converters CC ₁ and CC ₂ issues a gate block command. An opening/closing command circuit for the switching device 21 issues a command to open the switching device 21. Reference numeral 10 denotes a cross guiding wire installed on the track, and a receiver is provided at one end of the crossing guide wire to receive the signal from the transmitter and antenna mounted on the traveling body 1. It receives a frequency signal and detects the relative position of the field mounted on the traveling body 1 and the propulsion coil.

Next, to explain the operation of the circuit shown in Fig. 3, when the tip of the traveling body 1 is at the position t ₁ , power is supplied to the propulsion coil LM _o into which the traveling body 1 will next enter in response to a command from the position detector 5. The power converter CC ₂ is activated and the switching device 21 is closed by the opening/closing command circuit 8, and when the traveling body 1 advances and its tip reaches the position t ₂ , the traveling body 1 is completely connected to the propulsion coil LM _{o -1}
, the power converter CC ₁ that has been supplying power to the propulsion coil LM _o-1 is stopped, and the switching device 21 is opened by the switching command circuit 8.

That is, until just before the traveling body 1 enters the next propulsion coil, only one of the power converters CC ₁ and CC ₂ is operating, so at this point the first filter 11, which is always connected, is in operation. The harmonic current of the AC power source 7 is reduced so that the equivalent disturbance current J _p becomes below the permissible value, and the period from when the traveling object 1 enters the next propulsion coil to when it completely exits the previous propulsion coil. The power converters CC ₁ and CC ₂ are operated simultaneously to supply power to different propulsion coils, thereby eliminating fluctuations in the propulsion force when the traveling object 1 runs astride two propulsion coils, and at the same time reducing the current AC current. The harmonic current caused by the increase in the current supplied from the power source 7 is reduced by the second filter 12, and the equivalent disturbance current J _p is set to be below the allowable value, so that the traveling body 1 completely removes the previous propulsion coil. At the time of exit, the power conversion device that was feeding power to the previous propulsion coil is stopped, and the second filter 12 is disconnected from the AC power source 7 to reduce the overall filter capacity.

As described above in detail, according to the embodiment shown in FIG. , the running body is 2
a second filter for reducing harmonic current on the AC power source side when at least two power converters operate simultaneously and feed power to different propulsion coils when traveling across two propulsion coils; The first filter is operated all the time, and the second filter is operated only when controlling the power supply switching to the propulsion coil.This is an economical and efficient filter that reduces harmonic current on the AC power supply side and eliminates equivalent interference. This has the effect of lowering the current below the allowable value.

The above explanation is based on the case where a commercial frequency is used as the AC power source 7, but when a dedicated AC generator is used as the AC power source 7, the equivalent negative sequence current I' _peq will have the same characteristics as shown in Figure 1. It goes without saying that the circuit shown in FIG. 3 can reduce the equivalent negative sequence current _I'peq .

In the embodiment shown in FIG. 3, a first filter that is always activated regardless of the current command signal and the speed of the traveling object;
We have described a circuit configuration that is installed with a second filter that operates only when switching sections to reduce the harmonic current on the AC power supply side when the power converter is operating. The equivalent disturbance current changes approximately in proportion to the magnitude of the signal, and if the capacity of the first and second filters is set at the rated current of the current command signal, the first and second filters will change in proportion to the rated current of the current command signal. Problems arise, such as the capacity of each filter becomes large.

An embodiment for solving this problem is shown in FIG. 4, in which 30 is a speed detection device for detecting the speed of the traveling object 1, 31 to 33 are subtracters, and 40 is a subtracter 3.
I _f is the current value of the current command signal, I _p is the reference current, and 50 is an OR circuit that outputs an output when either one or both of 1 and 32 outputs an output. 9 is an AND circuit that outputs an output when it outputs an output, and does not output otherwise; 9 is an AND circuit that issues a command to close the switching device 22 when the AND circuit 50 outputs an output; A switching command circuit of the switching device 22, which issues a command to open the switching device 22 when the switching device 22 does not output an output, V
_o1 is the reference voltage when the speed V of the traveling object 1 is V ₁ , V
_o2 is the reference voltage when the speed V of the traveling object 1 is _V2 ,
d ₁ and d ₂ are diodes, and 13 is a filter that connects or disconnects from the AC power source 7 by opening and closing the switchgear 22.Other symbols are shown with the same symbols as the circuit in Figure 3, so explanations will be omitted. .

Next, the operation of the circuit shown in FIG. 4 will be explained.

As shown in the characteristic shown by the solid line in FIG. 1, the filter 11 has an equivalent disturbance current J _p or an equivalent negative sequence current when the speed V of the traveling object 1 is in the speed range of V ₁ to _{V 2} .
If I′ _peq can be made below the allowable value and the current value I _f is the rated current, but the speed V of the traveling object 1 is within the speed range of V ₁ to V ₂ , the equivalent disturbance current J _p or the equivalent negative sequence current I′ _peq
Similarly to the circuit shown in FIG. 3, the filter 12 has a capacitance such that the equivalent disturbance current J _p or the equivalent negative sequence current I' _peq due to the increase in the power supply current at the time of cross-section is The current value _If is set at the rated current.

On the other hand, the filter 13 detects that the speed V of the traveling body 1 is V ₁
or below or above V ₂ , and when the current value I _f is 50% or more of the rated current, the equivalent disturbance current J _p or the equivalent negative sequence current I' _peq in the shaded range in the characteristics in Figure 1.
Set the capacity to a level that keeps it below the allowable value.

To explain the operation of the circuit shown in FIG. 4 in setting the capacity of each of the traveling bodies 11 to 13 as described above, if 50% of the rated current is given as the reference current I _{p ,} the current value I _f is the rated current
If it is less than 50%, the subtracter 33 does not output an output, so even if the OR circuit 40 outputs an output, the AND circuit 50 does not output an output, so the opening/closing command circuit 9 opens the switching device 22. issue a command to do so.

In this state, it is safe because the constantly operating filter 11 reduces the equivalent disturbance current J _p or the equivalent negative sequence current I' _peq to a permissible value or less.

In this state, when the traveling body 1 enters a section crossing between two propulsion coils, the opening/closing device 21 is closed by the output of the opening/closing command circuit 8, so the filter 12 is connected to the AC power source 7, J due to the increase in current of power supply 7
It is safe because the increase in _p or I' _peq is suppressed by the filter 12 to keep J _p or I' _peq below the allowable value.

On the other hand, when the _current If is 50% or more of the rated current and the speed V of the traveling object 1 is less than _V1 , the output voltage _Vo of the speed detection device 30 is lower than the reference voltage _Vo1 , so the subtracter 31 Since the current value I _f is larger than the reference current I _p , the subtractor 33 outputs an output, and the AND circuit 50 outputs an output, so the opening/closing command circuit 9 Since the switching device 22 is closed, the filter 13 is connected to the AC power supply 7, and J _p or I' _peq
It is safe because it is below the allowable value. In this state, when the traveling body 1 enters a section crossing between two propulsion coils, the opening/closing device 21 is closed by the output of the opening/closing command circuit 8, so that the filter 12 is connected to the AC power source 7, and J _p when crossing the section.
Alternatively, even if the switching device 21 is opened by the opening/closing command circuit 8 when the traveling body 1 moves to the next propulsion coil by reducing I′ _peq below the allowable value, the filters 11 and 1
2, it is safe because J _p or I′ _peq becomes less than the allowable value.

In this state, when the speed V of the traveling object 1 falls within the range of V ₁ to _{V 2} , the output voltage V _o of the speed detection device 30 is higher than the reference voltage V _o1 and lower than the reference voltage V _o2 , so the subtracter 31 Since both 32 and 32 do not output an output, the OR circuit 40 does not output an output.
Since the AND circuit 50 no longer outputs an output, the switchgear 22 is opened, but it is safe because the filter 11 and the filters 11 and 12 at the time of section crossing make J _p or I' _peq below the allowable value.

As described above in detail, according to the embodiment shown in FIG. a second filter for reducing harmonic current on the AC power source side when at least two power converters operate simultaneously and feed power to different propulsion coils when the vehicle is traveling across two propulsion coils; A third filter is provided for reducing harmonic current of the AC power supply when the vehicle is running at a speed below a certain speed or above a certain speed and a current command signal exceeds a certain current value, and the first filter is always operated. The second filter is operated only when controlling the power supply switching to the propulsion coil, and the third filter is operated only in a certain speed range of the traveling body and a certain current command signal range, which is economical and The highly efficient filter reduces the harmonic current of the AC power supply and has the effect of making the equivalent disturbance current or equivalent negative sequence current below the permissible value in all speed ranges of the traveling body and in all operating states of the power converter.

Furthermore, in the present invention, a case has been described in which the high-order reduction filter shown in FIG. 2 is used as a filter, and one filter is provided for each phase on the power supply side of the power converter. It goes without saying that the present invention is not limited to the above, and can also be applied to cases where various filter circuits or a plurality of filters are provided.

[Brief explanation of the drawing]

Figure 1 is an actual measurement characteristic diagram of the equivalent disturbance current with respect to the speed change of a linear motor when the current command signal is constant, Figure 2 is an explanatory diagram of a conventional high-order reduction filter, and Figure 3 is an example of an implementation of the present invention. FIG. 4 is a circuit diagram showing another embodiment of the present invention. 1... Traveling body, 2... Field, 3, 4... Feeder, 5
...Position detector, 6... Opening/closing command for switchgear, 7... AC power supply, 8, 9... Opening/closing command circuit for switchgear, 11-
13...Filter, 21, 22...Switching device, 30...
Speed detection device for the traveling body 1, 31 to 33...subtractor,
40...OR circuit, 50...AND circuit, CC ₁ ,
CC ₂ ...Power converter, LM _o-1 ~ _{LM o+1} ...Propulsion coil, SW _o-1 ~ _{SW o+1} ...Switch.

Claims (1)

[Claims] 1 A magnetic field is mounted on the running body, propulsion coils in multiple sections are installed on the track side, power feeding points are arranged at approximately equal intervals on the propulsion coils in the multiple sections, and one of these
Power is alternately supplied to the third power supply point and the remaining power supply points from different power converters via switches, and to the range where the traveling body exists, and the different power converters are connected to each other via transformers. In a power supply system for a linear motor connected to an AC power source, the AC power source includes a first filter comprising a capacitor, a reactor, and a resistor;
A switching device is connected to a second filter consisting of a capacitor, a reactor, and a resistor connected in series, and one of the power converters is generated just before the traveling body enters the next propulsion coil. Means for issuing a command to close the opening/closing device in synchronization with a gate start command; and a gate block command for the other of the power conversion devices that is generated when the traveling body has completely transferred to the next propulsion coil. and means for issuing a command to open the switching device in synchronization, and reducing harmonic components of the alternating current power supply current generated when power is supplied to the propulsion coil while sequentially switching the switching device. Linear motor power supply system.