JP7537813B2 - Jet fan drive power supply circuit system using 18-phase rectifier circuit with non-insulated transformer - Google Patents

Description

This invention relates to a power supply circuit system for driving jet fans which achieves cost reduction, miniaturization, and reduction in transformer loss by adopting a power supply using a non-insulated transformer as the transformer used for the DC power supply of an inverter for driving jet fans in road tunnels.
In particular, the present invention relates to a power supply circuit system for driving a jet fan that combines rectifier circuits for three inverters.

In road tunnels, natural ventilation and traffic ventilation alone are insufficient to exhaust exhaust gases from automobiles inside the tunnel, so forced ventilation is carried out using jet fans and exhaust fans installed inside the tunnel.
In Japan, the so-called "longitudinal ventilation method" is widely used. The "longitudinal ventilation method" is a ventilation method that uses the entire cross section of the tunnel as a ventilation duct. The ventilation equipment used includes jet fans that create a longitudinal air flow along the road tunnel, and large exhaust fans that draw air from the middle of the tunnel to the top of the mountain, and these are appropriately combined to exhaust the air from the tunnel.

Jet fan motors are usually around 20kW to 50kW, with 4 to 8 poles and 400V induction motors. Exhaust fans also have a larger capacity of around 100kW to 500kW and often use induction motors as well.

In road tunnels, the commercial power supply voltage is 400V, and the step-down transformers used to step down from 6,600V to 400V are often prepared at substations and shared with other electrical equipment such as lighting, meaning that the tunnels can be used as is at 400V.

In short tunnels, jet fans may be installed in one location, either at the entrance or exit, but in long-distance tunnels, multiple jet fans will be installed in multiple locations. Conventional ventilation control using jet fans in longitudinal ventilation systems was once dominated by control of the number of jet fans in operation by switching each one on and off depending on the desired ventilation volume, but in recent years, ventilation control using inverters has been attracting attention.

Automobile tunnels are equipped with various electronic devices and AM radio broadcasts for environmental measurement and safety purposes, and since these delicate electronic devices are vulnerable to noise, it is extremely difficult to implement EMI countermeasures when using inverters. For this reason, there are only a few manufacturers worldwide that have put inverter-driven jet fans into practical use, and in Japan, only the applicant and others have been using them in several dozen tunnels for the past few years.

EMI countermeasures for inverter-driven jet fans require measures against harmonics on the inverter output side and on the power supply side, and the inventors of the present invention have described the former measures in JP 2013-069183 A. The present invention is concerned with the latter measures against harmonics on the power supply side.

Inverters require a DC power source, and usually a PWM converter or rectifier circuit is used. Recently, PWM converters have been widely used for general purposes, but they are complex, expensive, and large in size, and they generate a lot of EMI due to high-frequency switching, so they are not suitable for automobile tunnels, which are sensitive to noise. In addition, losses are two to three times greater than with rectifier circuits, so the applicants have adopted rectifier circuits for driving ventilation fans that do not require regenerative braking.

When a rectifier circuit is used, a single three-phase bridge rectifier circuit produces a large number of low-order harmonics such as the 5th, 7th, 11th, 13th, 17th, and 19th harmonics, so it is essential to use a multi-phase rectifier circuit to reduce these harmonics.
Several to several dozen jet fans are installed in one tunnel, and they are installed in two or three electrical rooms, and the jet fans are driven from the inverters via long cables of several hundred meters to about 1 km. In this case, the inverters in the same electrical room operate at the same frequency, so the required DC power is the same. Therefore, it is an environment in which a so-called "combined multi-phase rectifier circuit" can be configured to reduce harmonics. Therefore, the applicants have adopted the "combined 12-phase rectifier circuit" (FIG. 15), "single 12-phase rectifier circuit" (FIG. 16), and a circuit combining the "combined 12-phase rectifier circuit" and the "single 12-phase rectifier circuit" (FIG. 17) in Patent Document 2, JP Patent Publication No. 2018-87423 to reduce harmonics.

JP 2013-069183 A JP 2018-087423 A JEM_TR201:2007, page 10 Figure 2

In the "combined 12-phase rectifier circuit" using a general insulating transformer in the prior art, it is common to use an insulating transformer with a primary side of Δ and a secondary side of ΔY as shown in Fig. 13 to create power sources U1, V1, and W1 with a 15° phase lead and power sources U2, V2, and W2 with a 15° phase lag. However, since the insulating transformer has a 100% self-capacity, it is large and expensive.
Therefore, as described above, the inventors have taken advantage of the environmental condition that the commercial power supply voltage used in road tunnels can be used as is at 400V, and have proposed a combined 12-phase rectifier circuit using a non-isolated transformer with low self-capacity, as shown in Figure 15.

In the combined 12-phase rectifier circuit using a non-insulated transformer proposed by the present inventor in Patent Document 2 (JP Patent Publication 2018-087423), as shown in Fig. 15, a non-insulated phase transformer is used to create power sources U1, V1, W1 with a phase lead of 15° and power sources U2, V2, W2 with a phase lag of 15° from three-phase power sources U, V, W. The rectifier circuit of inverter 1 is then connected to the power sources U1, V1, W1, and the rectifier circuit of inverter 2 is connected to the power sources U2, V2, W2. In this way, the fifth and seventh harmonics of rectifier circuit 1 and rectifier circuit 2 are eliminated (reference document JEM_TR201:2007, page 10, Figure 2).
The system shown in Fig. 15 is not a general prior art but a prior art of the present applicant and is an excellent system using a non-insulated transformer, but there is an issue that needs improvement: when the number of inverters is odd, it becomes uneconomical.

When configuring a "combined multi-phase rectifier circuit" with multiple inverters to reduce harmonics, if the number of inverters is an even number, 2N, it is possible to configure N sets of "combined 12-phase rectifier circuits." However, if the number of inverters is an odd number, 2N+1, there is one extra inverter, and the question arises as to what to do with its DC power supply.
As one solution to this problem, the present inventors have proposed a "combined 12-phase rectifier circuit" using a non-isolated transformer as shown in Fig. 15, a "single 12-phase rectifier circuit" using a non-isolated transformer as shown in Fig. 16, and a combination of a "combined 12-phase rectifier circuit (Fig. 15)" and a "single 12-phase rectifier circuit (Fig. 16)" as shown in Fig. 17. Combination patterns of the number of inverters and rectifier circuit systems when these systems are adopted are shown in Fig. 18(a).
However, this "single-unit 12-phase rectifier circuit" requires two diode bridges 50, a phase transformer 30, and two three-phase AC reactors 40 for one inverter, as well as an in-phase reactor 41 to suppress circulating current, making it complicated and economical. Therefore, when the number of inverters is odd, there is room for further improvement, and it has been necessary to develop a more economical rectifier circuit method.
In view of the above problems, the present inventor came up with the idea of an 18-phase rectifier circuit using a non-insulated transformer and developed the present invention.

Non-patent document 1, JEM_TR201:2007, describes 12-phase and 24-phase rectifier circuits, but not 18-phase rectifier circuits. The 18-phase rectifier circuit is not well known even in the power electronics industry, and it is thought that there have been almost no examples of it being put to practical use. Moreover, a new method has been invented to configure the 18-phase rectifier circuit using an economical non-isolated transformer with small self-capacity rather than an isolated transformer, and this method is used as a DC power source for a tunnel ventilation inverter.

Although there is no concrete example in the prior art, the following problem occurs even if it is assumed that an 18-phase rectifier circuit is constructed using an insulating transformer. The problem is that no concrete example of a transformer winding method is known when creating a three-phase power supply with phase differences of -20 degrees, 0 degrees, and +20 degrees. If the inventor were to assume it, it would be a staggered connection as shown in Figure 19(a). The ratio of each winding voltage of this assumed transformer is shown in Figure 19(b).
The vector diagram in Figure 19(b) shows the vector composition of the leading side U1 of the U phase, and the diagram of the lagging side U3 is omitted. If a and b are found with the phase voltage set to 1.0, they are as shown in [Equation 1].

[Equation 1]
acos(10)+bcos(50)=1.0
asin(10)=bsin(50)
From this simultaneous equation, a=0.884 and b=0.201 are obtained.

A combined 18-phase rectifier circuit using these insulating transformers has the configuration shown in FIG.
In the combined 18-phase rectifier circuit using the insulating transformer shown in FIG. 20, if the loads of the three inverters are approximately the same, the 5th, 7th, 11th, and 13th harmonics of the power supply current are eliminated, resulting in a waveform with little distortion.
However, assuming that an 18-phase rectifier circuit is constructed using an isolation transformer, an isolation transformer of the full capacity is required, which results in a disadvantage that the isolation transformer is heavy, large in size, and has a large loss, making it uneconomical.

In view of the above problems, the inventors have proposed an 18-phase rectifier circuit using a non-insulated transformer as a power source for a jet fan inverter, thereby solving the above problems.
The 18-phase rectifier circuit is a circuit method that is not well known in the power electronics industry, and it is believed that there are no practical examples of it. The object of the present invention is to provide a DC power supply device for a tunnel ventilation inverter that uses this 18-phase rectifier circuit, and that uses an economical non-isolated transformer with small self-capacity instead of an isolated transformer.

In order to achieve the above object, the present invention provides a jet fan drive power supply circuit system using a combined 18-phase rectifier circuit that drives a jet fan in a road tunnel via an inverter, a non-insulated multi-phase transformer that converts a three-phase commercial power supply into six phases, the non-insulated multi-phase transformer having a leading circuit element that leads the phase of the three-phase commercial power supply by approximately 20 degrees and a lag circuit element that lags the phase of the three-phase commercial power supply by approximately 20 degrees; an auto-winding step-up transformer for regulating step-up that boosts the three-phase commercial power supply by an amount of regulated step-up while maintaining the phase of the three-phase commercial power supply; and three sets of diode three-phase bridge rectifier circuits that convert AC to DC based on the output of the non-insulated multi-phase transformer and the output of the auto-winding step-up transformer for regulating step-up, the three sets of diode three-phase bridge rectifier circuits having as their AC inputs the leading-phase three-phase power supply from the non-insulated multi-phase transformer, the lag-phase three-phase power supply from the non-insulated multi-phase transformer, and an in-phase three-phase power supply from the auto-winding step-up transformer for regulating step-up, respectively; and three sets of inverter circuits that convert the three DC output powers of the diode three-phase bridge rectifier circuits into three-phase AC with variable frequency and variable voltage.

The power supplies U1, W1, and V1 obtained by the above configuration, which have a 20 degree lead phase, the power supplies U2, V2, and W2 which are in-phase and have a phase of 0 degrees, and the power supplies U3, V3, and W3 which have a phase lag of 20 degrees, are each rectified by a diode three-phase bridge rectifier circuit, and the three obtained DC power supplies can be supplied to three fan drive inverters.

In the above configuration, the leading circuit element is a transformer winding arranged in a direction in which the phase leads the primary phase voltage, and the voltage of the winding advances the phase by 20 degrees.Similarly, the lag circuit element is a transformer winding arranged in a direction in which the phase lags the primary phase voltage, and the voltage of the winding delays the phase by 20 degrees.
A circuit configuration in which a transformer winding is provided in a direction that advances and delays the phase of such a primary phase voltage can be easily constructed using a non-isolated transformer having the configuration shown in Figures 4(a) and (b), making it possible to miniaturize the device.

Here, it is preferable that the regulated step-up voltage provided by the auto-winding step-up transformer for regulating step-up is approximately 6.4% higher than the voltage of the three-phase commercial power supply.
As can be seen from the transformer vector diagram shown in Figure 2, in a polyphase transformer, 1/cos(20) = 1.064, in other words, when the phase becomes ±20 degrees, the voltage increases by 6.4%, so the voltage when the phase difference is 0 degrees is also increased by 6.4% with a single winding to match this voltage value.

In other words, in the conventional technology using a primary Δ, secondary ΔY insulating transformer as shown in FIG. 13, there was a problem of an imbalance in current sharing caused by a slight difference in voltage between the leading and lagging sides of two sets of three-phase power sources. According to the present invention, however, a leading circuit element that leads the phase of the three-phase commercial power source by approximately 20 degrees and a lagging circuit element that delays the phase of the three-phase commercial power source by approximately 20 degrees are used to obtain the leading and lagging voltages of two sets of three-phase power sources, and the voltage of the single-winding step-up transformer for regulating step-up, which generates a regulated and boosted in-phase three-phase power source that is boosted by the amount of regulated step-up while maintaining the phase of the three-phase commercial power source, is adjusted to the same value, thereby preventing an imbalance in current sharing.

Furthermore, it is preferable to compensate for the AC reactor value connected to the auto-winding step-up transformer for regulating step-up so as to be larger than the AC reactor value connected to the non-insulated multi-phase transformer.
Since the self-capacity of the auto-winding step-up transformer for regulating step-up is smaller than the self-capacity of the non-isolated multi-phase transformer, its leakage inductance is also small. By compensating for the difference in leakage inductance, the harmonic currents of the leading phase three-phase power supply, lagging phase three-phase power supply, and in-phase three-phase power supply all become approximately the same, and the principle of the 18-phase rectifier circuit works effectively to reduce harmonics.

With the above-described configuration, the jet fan drive power supply circuit system of the present invention can use a non-insulated transformer, which can be made less expensive and smaller in size than when an insulating transformer is used.
When using an insulating transformer, there is a problem of imbalance in current sharing caused by a slight difference in voltage between the leading and lagging sides of two sets of three-phase power supplies. However, this invention can make the voltages the same. In other words, since the non-insulated multi-phase transformer is symmetrical in configuration, the voltages of the 20 degree leading phase power supply and the 20 degree lagging phase power supply are the same in principle. Since the output voltage of the non-insulated multi-phase transformer increases by 6.4%, the power supply with phase 0 degree is boosted by 6.4%, so the three voltages are made uniform by using an auto-step-up transformer. In addition, the difference in leakage inductance is also compensated for, so there is a design to prevent imbalance in current sharing.

1 is a diagram showing a circuit configuration centered around a non-insulated multi-phase transformer 110 in a jet fan drive power supply circuit system 100 of the present invention. FIG. This is a vector diagram focusing on the phase of voltage. 13 is a diagram showing the relationship between a voltage having a phase lead of approximately 20 degrees and a voltage having a phase lag of approximately 20 degrees with respect to a phase voltage. FIG. FIG. 2 is a diagram showing a vector relationship diagram of the windings of the non-isolated transformer 110. FIG. 1 is a diagram showing a vector diagram of two sets of three-phase power supplies with a phase difference of approximately 20 degrees. 1 is a diagram showing a configuration example of a power supply circuit system for driving a jet fan according to the present invention; FIG. 1 is a diagram showing a two-level inverter in a three-phase bridge inverter. FIG. 1 is a diagram showing a three-level inverter TYPE 1. FIG. 1 is a diagram showing a three-level inverter TYPE 2. FIG. 2 is a diagram showing an input power supply current and its frequency components. FIG. 1 is a diagram showing an input power supply current and its frequency components to a rectifier circuit of one jet fan when driven by a combined 12-phase rectifier circuit in the prior art. FIG. 1 is a diagram showing an input power supply current and its frequency components to a rectifier circuit of one jet fan when driven by the 18-phase rectifier circuit of the present invention. FIG. 1 is a diagram showing an example of the configuration of a typical combined 12-phase rectifier circuit using an isolation transformer according to the prior art. FIG. 1 is a diagram showing an example of the configuration of a typical single-machine 12-phase rectifier circuit using an isolation transformer according to the prior art. FIG. 1 is a diagram showing an example of the configuration of a combined 12-phase rectifier circuit using a non-isolated transformer described in Patent Document 2 (JP 2018-087423 A). FIG. 1 is a diagram showing an example of the configuration of a single-machine 12-phase rectifier circuit using a non-isolated transformer described in Patent Document 2 (JP 2018-087423 A). FIG. 1 is a diagram showing a three-inverter DC power supply system according to the prior art described in Patent Document 2 (JP 2018-087423 A). 1A is a diagram showing a combination of the number of inverters and the rectifier circuit type when a combined 12-phase rectifier circuit and a single 12-phase rectifier circuit are combined, and (b) is a diagram showing a combination of the number of inverters and the rectifier circuit type when a combined 18-phase rectifier circuit of the present invention is used, a conventional combined 12-phase rectifier circuit, and a single 12-phase rectifier circuit are used. FIG. 1 is a diagram showing a combined 18-phase rectifier circuit using an isolation transformer according to the prior art. FIG. 1 is a diagram showing a power supply circuit system 10 for driving a jet fan using a combined 18-phase rectifier circuit using an insulating transformer according to the prior art.

Hereinafter, an embodiment of the power supply circuit system for driving a jet fan of the present invention will be described with reference to the drawings. However, it goes without saying that the scope of the present invention is not limited to the specific applications, shapes, numbers, etc. shown in the following embodiments.

FIG. 1 is a diagram showing a circuit configuration centered around a non-insulated multi-phase transformer 110 in a power supply circuit system 100 for driving a jet fan according to the present invention.
As shown in FIG. 1 , a three-phase commercial power supply 200 is used as an input power supply, and three input lines are connected to a U-phase terminal, a V-phase terminal, and a W-phase terminal of a non-insulated multi-phase transformer 110, respectively.

Here, the non-insulated multi-phase transformer 110 is provided with a coil 111 between UV, a coil 112 between VW, and a coil 113 between WU as primary coils.
The non-insulated multi-phase transformer 110 has, as secondary coils, a leading circuit element 114U1 for the U phase, a lag circuit element 114U3 for the U phase, a leading circuit element 114V1 for the V phase, a lag circuit element 114V3 for the V phase, a leading circuit element 114W1 for the W phase, and a lag circuit element 114W3 for the W phase.

To configure an 18-phase rectifier circuit, three sets of three-phase power supplies are required: one with a phase delay of 20 degrees, one with a phase difference of 0 degrees, and one with a phase lead of 20 degrees.
This transformer has a Δ winding on each of the three legs of a three-legged core, and its secondary windings are U1-U3, V1-V3, and W1-W3, each with a center tap, as shown in Figure 1. When the center tap of winding U1-U3 is connected to the U phase as shown in the figure, a voltage with a 20° leading phase is obtained at terminal U1, and a voltage with a 20° lagging phase is obtained at terminal U3.
1, each of the lead circuit element 114U1, lead circuit element 114V1, and lead circuit element 114W1 is a secondary coil that leads the phase of each phase of the three-phase commercial power supply 200 by approximately 20 degrees. Also, each of the lag circuit element 114U3, lag circuit element 114V3, and lag circuit element 114W3 is a secondary coil that lags the phase of each phase of the three-phase commercial power supply 200 by approximately 20 degrees.

Here, the conditions for the secondary coil to advance the phase of each phase of the three-phase commercial power supply 200 by approximately 20 degrees and the conditions for the secondary coil to lag the phase by approximately 20 degrees will be described.
As an example, the U-phase will be described below, with the V-phase and W-phase being considered in the same manner.

FIG. 2 is a vector diagram focusing on the phase of the voltage.
FIG. 2A is a vector diagram in which a three-phase power supply input passes through a non-isolated transformer (phase difference ±20 degrees) and no particular voltage adjustment is made to 0 degrees.
FIG. 2B is a vector diagram showing a case where a three-phase voltage is obtained by passing a three-phase power supply input through a non-isolated transformer (phase difference of ±20 degrees) and adjusting and boosting it relative to 0 degrees.
In Figures 2(a) and 2(b), a vector diagram can be created by adding or subtracting a VW line voltage of an appropriate magnitude perpendicular to the U phase voltage to create a voltage that is in a ±20 degree relationship with the U phase phase voltage 1.
In this vector diagram, X is tan(20) = 0.364 for a phase voltage of 1.
Voltage OU1 leading the U-phase by approximately 20 degrees and voltage OU3 lagging the U-phase by approximately 20 degrees are both calculated as 1/cos20=1.064.
Therefore, if the voltage obtained by increasing the U-phase voltage by approximately 6.4% is taken as OU2, then OU2 = OU1 = OU3, and it is clear that the voltage imbalance in the U-phase is eliminated.
In the jet fan driving power supply circuit system 100 of the present invention, a single-winding transformer for adjusting and stepping up is provided to increase the U-phase voltage by 6.4% and adjust and step up the voltage at phase 0 degree.
The same is true for the other V and W phases.

This relationship for three phases is shown in Figure 3. By rearranging this, a vector relationship diagram of the windings of the non-insulated transformer 110 is shown in Figure 4(a).
The voltages U, V, and W at 0 degree phase are boosted by 6.4% by an autotransformer to become U2, V2, and W2. The vector diagram of these three sets of three-phase power sources is shown in FIG. 5. That is, it can be seen that 18 phase vectors with a phase difference of approximately 20 degrees are obtained. Note that the vector relationship diagram of the windings of the non-isolated transformer 110 may be the vector diagram of FIG. 4(b) using a hexagonal transformer with the same function. Although the operation of the hexagonal transformer is somewhat complicated, both have the same function.

In this way, in the power supply circuit system 100 for driving a jet fan of the present invention, three sets of three-phase power supplies with a phase of approximately 20 degrees are created, thereby forming a power supply circuit system for driving a jet fan using a combined 18-phase rectifier circuit.

Next, the overall configuration and each of the components of the jet fan driving power supply circuit system 100 of the present invention will be described in detail.
6 shows an example of the circuit configuration of the jet fan drive power supply circuit system 100 of the present invention. The configuration example of Fig. 6 is configured such that three-phase AC reactors 140-1, 140-2, and 140-3 are provided on the AC side of a diode three-phase bridge rectifier circuit 130.

As shown in Figure 6, the power supply circuit system 100 for driving a jet fan of the present invention comprises a three-phase commercial power supply 200, a non-isolated transformer 110, a single-winding step-up transformer 120 for regulated step-up, a diode three-phase bridge rectifier circuit 130, three-phase AC reactors 140-1, 140-2, 140-3, and an inverter circuit 160.

The commercial power source 200 is not particularly limited as a power receiving facility, but since a long-distance road tunnel requires a large amount of power due to the presence of not only the jet fan 400 but also numerous lighting and disaster prevention facilities, it receives power directly from the electric utility at extra high or high voltage and transforms it to supply electricity to the equipment in the facility. As will be described later, the voltage of the commercial power source 200 is already stepped down to a so-called 400V system, such as 400V, 440V, or 460V, when it is supplied to the power supply circuit system for driving the jet fan of the present invention, which is the tunnel facility.

Next, the non-isolated transformer 110 is shown using a symbol for easy understanding as the non-isolated transformer 110, but it is the same as the configuration example detailed in Figure 2. Explanation of it will be omitted here.

The auto-winding step-up transformer 120 for regulated step-up generates an in-phase three-phase power supply that is stepped up by an amount of regulated step-up while maintaining the phase of the three-phase commercial power supply.
In the power supply circuit system 100 for driving a jet fan of the present invention, an 18-phase rectifier circuit is used, and as shown in Fig. 1, a lead circuit element 114U1, a lead circuit element 114V1, and a lead circuit element 114W1 are provided to form a secondary coil that leads the phases of the U phase, V phase, and W phase by approximately 20 degrees, and a delay circuit element 114U3, a delay circuit element 114V3, and a delay circuit element 114W3 are provided to form a secondary coil that delays the phases of the U phase, V phase, and W phase by approximately 20 degrees, but since the voltage of each phase is 6.4% higher than the voltage obtained above, in order to suppress this difference, the input voltage of the phase 0 degree of each phase is boosted for voltage adjustment. By providing an auto-winding boost transformer 120 for voltage adjustment, the input voltage of each phase is boosted by 6.4%.

In this way, by providing a single-winding step-up transformer 120 for regulated step-up together with the non-isolated transformer 110, the voltage obtained by the 18-phase rectifier circuit becomes balanced as shown in Figure 5.

Next, the diode three-phase bridge rectifier circuit 130 is a rectifier circuit that converts AC voltage into DC voltage.
In this example, as shown in FIG. 6 , the diode three-phase bridge rectifier circuit 130 is configured to include three diode three-phase bridge rectifier circuits each having an regulated and boosted input three-phase power supply, a leading phase three-phase power supply, and a lagging phase three-phase power supply as inputs.

Next, the AC reactors 140-1, 140-2, and 140-3 will be described.
In the configuration example of FIG. 6 , a three-phase AC reactor 140-1 corresponding to a leading phase is provided between the leading phase three-phase power supply output of the non-insulated multi-phase transformer 110 and the diode three-phase bridge rectifier circuit 130, and similarly, a three-phase AC reactor 140-3 corresponding to a lagging phase is provided between the lagging phase three-phase power supply output of the non-insulated multi-phase transformer 110 and the diode three-phase bridge rectifier circuit 130, and further a three-phase AC reactor 140-2 corresponding to the regulated and boosted input three-phase voltage is provided.

The three-phase AC reactors 140-1, 140-2, and 140-3 suppress harmonics generated in the diode three-phase bridge rectifier circuit 130.
The reactance values of three-phase AC reactors 140-1, 140-2, and 140-3 are not limited, but may be, for example, about 3% to 5% in order to improve the power supply current waveform.

Here, a method for compensating for the difference in leakage inductance will be described.
In the combined 18-phase rectifier circuit of the present invention, the leakage inductance of the zero-phase regulated step-up autotransformer 120 is smaller than the leakage inductance of the non-isolated multi-phase transformer 110, so that the harmonic current increases, and if an imbalance occurs, harmonics may remain.
Therefore, the value of AC reactor 140-2 connected to auto-step-up transformer 120 for regulating step-up is made larger than the values of AC reactors 140-1 and 140-3 connected to non-isolated multi-phase transformer 110, thereby compensating for the leakage inductance of auto-step-up transformer 120 for regulating step-up.

The following will consider how large the value of AC reactor 140-2 connected to auto-winding step-up transformer 120 for regulated step-up should be.
For example, consider the case where a 60 Hz, 440 V, 50 kW motor (DC power is 60 kW, and the rectifier circuit's AC rated current is 83.6 A) is used.
The voltage of the secondary winding of the non-isolated multi-phase transformer 110 is tan(20) of 440/1.732 = 0.364. This results in a winding voltage of 92.47 V and a current rating of 83.6 A.
Therefore, the unit impedance Zpu = 92.47/83.6 = 1.106.
The unit inductance Lpu is Zpu/ω=1.106/377=2.93 mH.
Therefore, if the leakage inductance La of the non-insulated multi-phase transformer 110 is assumed to be 3%, then La = 2.93 x 0.03 = 88 μH.

Next, the voltage of the auto-step-up transformer 120 for regulating step-up is (440/1.732)×0.064=16.258V, and the current rating is 83.6A.
Therefore, the unit impedance Zpu = 16.258/83.6 = 0.194.
The unit inductance is Lpu = Zpu/ω = 0.194/377 = 0.000516H = 516 μH.
Therefore, assuming that the leakage inductance Lb of the regulated step-up auto-step-up transformer 120 is 3%, Lb=16 μH.

In this way, there is a difference of 72 μH between leakage inductance La of non-insulated multi-phase transformer 110 and leakage inductance Lb of auto-winding step-up transformer 120 for regulated step-up.
For example, assuming that the AC inductance Ls required for the rectifier circuit is 260 μH, AC reactor 140-1 and AC reactor 140-3 connected to non-isolated multi-phase transformer 110 may have Ls = 260 - 88 = 172 μH, while AC reactor 140-2 of auto-winding step-up transformer 120 for regulated step-up may be compensated for to be 72 μH higher, so that Ls = 260 - 16 = 244 μH.

In this way, by compensating for the AC reactor 140-2 of the single-winding step-up transformer 120 for regulated step-up so that it is larger than the AC reactor 140-1 and AC reactor 140-3 connected to the non-insulated multi-phase transformer 110, the AC inductances of the three rectifier circuits are aligned, and the harmonics become the same, allowing the harmonics to be efficiently reduced.

Next, the inverter circuit 160 will be described.
The inverter circuit 160 is a device that converts rectified direct current into three-phase alternating current with variable frequency and voltage.
Several examples of the inverter circuit 160 are shown below.
Figure 7 shows the most commonly used three-phase bridge inverter, which is also called a two-level inverter.
If the DC circuit voltage is Ed, the phase voltage has two levels: Ed/2 and -Ed/2. Since IGBTs (insulated gate bipolar transistors) are suitable for driving jet fans of about 20 kW to 50 kW, all of the following inverters are illustrated as examples using IGBTs.
Figure 8 shows a three-level inverter (also called an NPC inverter) type 1. When using IGBTs with the same rating, this circuit can handle twice the DC voltage compared to a two-level inverter, and the output voltage is also twice as high. The phase voltage of the inverter has three levels, Ed/2, 0, and -Ed/2, so an excellent output voltage waveform with fewer harmonics can be obtained compared to a two-level inverter.
9 shows a three-level inverter, TYPE 2. This circuit has the disadvantage that it can only handle the same DC voltage as the two-level inverter, so there are few examples of it being put to practical use, but the output voltage is three levels, just like TYPE 1.
In the jet fan driving power supply circuit system 100 of the present invention, the inverter circuit 160 may be any of the inverter circuit 160a in FIG. 7, the inverter circuit 160b in FIG. 8, and the inverter circuit 160c in FIG.

Next, the excellent technical effects of the jet fan driving power supply circuit system 100 of the present invention will be verified.
The 18-phase rectifier circuit shown in Fig. 6 is applied to three jet fans (60 Hz, 440 V, 50 kW motor, DC power 60 kW, rectifier circuit AC rated current 83.6 A). In addition, a conventional combined 12-phase rectifier circuit shown in Fig. 13 is used as a conventional technique and applied to two of the same jet fans, and the technical effects of both are compared by simulation.

10 is a diagram showing the input power supply current and its frequency components, that is, the power supply current and its frequency components that are directly input when there is no action of a non-insulated transformer in front of the rectifier circuit of the jet fan.
Figure 10(a) shows the input power supply current waveform for one jet fan, and Figure 10(b) is an FFT image showing the frequency components of the input power supply current. FFT is the peak value. In the FFT image of Figure 10(b), the fundamental wave has been cut to expand the harmonics. The fundamental wave has an effective value of 81.4 A and a peak value of 105.5 A.
As shown in the FFT image of FIG. 10(b), the harmonics contained in the input current include all of the 5th, 7th, 11th, 13th, 17th, 19th, . . . harmonics.

Next, FIG. 11 is a diagram showing an input power supply current and its frequency components to a rectifier circuit of a jet fan when driven by a combination 12-phase rectifier circuit in the prior art.
Fig. 11(a) shows the input power supply current waveform for one jet fan obtained through a combined 12-phase rectifier circuit in the prior art, and Fig. 11(b) is an FFT image showing the frequency components of the power supply current for one jet fan. FFT is the peak value. In the FFT image of Fig. 11(b), the fundamental wave has also been cut to expand the harmonics. The fundamental wave has an effective value of 77.4 A and a peak value of 109.1 A.
When driven using a combinational 12-phase rectifier circuit according to the prior art, the distortion of the power supply current waveform is improved as shown in Fig. 11(a). As shown in Fig. 11(b), it can be seen that the fifth, seventh, and other harmonics are eliminated.

Next, FIG. 12 is a diagram showing the input power supply current and its frequency components to the rectifier circuit of a jet fan when driven by the 18-phase rectifier circuit of the present invention.
Fig. 12(a) shows the input power supply current waveform for one jet fan obtained through the 18-phase rectifier circuit of the present invention, and Fig. 12(b) is an FFT image showing the frequency components of the power supply current for one jet fan. FFT is the peak value. In the FFT image of Fig. 12(b), the fundamental wave has also been cut to expand the harmonics. The fundamental wave has an effective value of 81.4 A and a peak value of 115.1 A.
When driven using the 18-phase rectifier circuit of the present invention, the power supply current waveform becomes a current with much better distortion, as shown in Fig. 12(a).As shown in Fig. 12(b), it can be seen that not only the 5th and 7th harmonics but also the 11th, 13th harmonics are eliminated.

The jet fan driving power supply circuit system 100 of the present invention is used to drive a jet fan in a tunnel, and in many cases power is supplied to the jet fan via a long cable of 100 m to over 1000 m.
The long cable is not particularly limited, but may be a single-core CV cable, a multi-core CV cable, a CVT in which three single-core CV cables are twisted together, or even a shielded cable.
A jet fan is a device for ventilating the air inside a tunnel, and is equipped with an induction motor. In the future, a PMSM motor using a permanent magnet may also be used, but the structure of the jet fan is not particularly limited in the present invention, and various jet fans can be applied as long as they can be driven by an inverter. Jet fans are installed at appropriate intervals in long-distance road tunnels. The longer the tunnel, the more jet fans will be installed.

The advantages of introducing the jet fan drive power supply circuit system 100 of the present invention can be summarized as follows.
(1) Regarding 18-phase rectifier circuits that had not attracted much attention in the power electronics industry, we have provided a "combined 18-phase rectifier circuit" that uses a non-isolated transformer and an auto-step-up transformer for regulated step-up, thereby economically resolving the harmonic problems of rectifier circuits.
(2) In the combined 18-phase rectifier circuit, the sum of the self-capacity of the two required transformers is small, at approximately 21% of the through-capacity, making it compact and economical, and also reducing losses in the transformer.
(3) In jet fan drive, the cable length often exceeds 1000m, in which case the cable voltage drop at full load can reach 15V to 20V, causing a problem that the terminal voltage of the motor drops and the current increases. In the non-insulated transformer of the present invention, the voltage is 6.4% higher than the power supply voltage, so the DC voltage of the inverter is higher, and as a result, the output voltage can also be increased by 6.4%, which is convenient because it is possible to increase the inverter output voltage to compensate for the drop in the terminal voltage of the motor.
(4) If there are an odd number of jet fans, such as 3, 5, 7, or 9, and three of them are made into an 18-phase rectifier circuit, the remaining fans will be 0, 2, 4, or 6, which can be combined into a 12-phase rectifier circuit. Therefore, the uneconomical "single-unit 12-phase rectifier circuit using a non-isolated transformer" shown in Figure 16 will only be used when there is one inverter, as shown in Figure 18 (b), and the entire system can be designed economically.
(5) In the case of six or nine units, a combined 12-phase rectifier circuit can be used, but using an 18-phase rectifier circuit for all is advantageous as it reduces harmonics.

The above illustrates and describes a preferred embodiment of the configuration of the power supply circuit system for driving a jet fan of the present invention. However, it will be understood that various modifications are possible without departing from the technical scope of the present invention.

The power supply circuit system for driving a jet fan of the present invention can be applied to a ventilation control system for a long-distance road tunnel, in particular a ventilation control system that controls multiple jet fans installed in a long-distance road tunnel using inverter drive.

REFERENCE SIGNS LIST 100 Jet fan drive power supply circuit system 110 Commercial power supply Power supply transformer 110 Non-insulated multi-phase transformer 120 Auto-winding step-up transformer for regulated step-up 130 Diode three-phase bridge rectifier circuit 140 Three-phase AC reactor 160 Inverter circuit 200 Commercial power supply 300 Cable 400 Jet fan

Claims (4)

A jet fan driving power supply circuit system for driving a jet fan in a road tunnel by an inverter, comprising:
a non-insulated multi-phasing transformer for converting a three-phase commercial power supply into a six-phase power supply, the non-insulated multi-phasing transformer including a leading circuit element for leading the phase of the three-phase commercial power supply by approximately 20 degrees and a delay circuit element for delaying the phase of the three-phase commercial power supply by approximately 20 degrees;
an auto-winding step-up transformer for adjusting step-up, which steps up the voltage by an amount of step-up adjustment while maintaining the phase of the three-phase commercial power source;
three sets of diode three-phase bridge rectifier circuits for converting AC to DC based on the output of the non-isolated multi-phase transformer and the output of the auto-winding step-up transformer for regulating step-up, the three diode three-phase bridge rectifier circuits having as their AC inputs the leading phase three-phase power supply from the non-isolated multi-phase transformer, the lagging phase three-phase power supply from the non-isolated multi-phase transformer, and an in-phase three-phase power supply from the auto-winding step-up transformer for regulating step-up;
A power supply circuit system for driving a jet fan using a combined 18-phase rectifier circuit, comprising three sets of inverter circuits for converting the three DC output powers of the diode three-phase bridge rectifier circuit into three-phase AC with variable frequency and variable voltage. The leading circuit element of the non-insulated multi-phase transformer is a transformer winding provided to apply a voltage at right angles to a phase leading direction relative to a phase voltage of a power source, and the winding voltage leads the phase by 20 degrees;
The delay circuit element of the non-insulated multi-phase transformer is a transformer winding provided to apply a voltage at right angles in a direction in which the phase is delayed relative to the phase voltage of the power source, and the winding voltage delays the phase by 20 degrees;
2. The power supply circuit system for driving a jet fan according to claim 1, wherein 18-phase rectification is configured using two sets of three-phase power supplies, the phase of which is ±20 degrees relative to the power supply. A power supply circuit system for driving a jet fan using a combined 18-phase rectifier circuit as described in claim 1 or 2, characterized in that the regulated boost provided by the single-winding boost transformer for regulated boost is approximately 6.4% higher than the voltage of the three-phase commercial power supply. 4. A power supply circuit system for driving a jet fan using a combination 18-phase rectifier circuit as claimed in any one of claims 1 to 3, characterized in that an AC reactor value connected to the auto-step-up transformer for regulating step-up is made larger than an AC reactor value connected to the non-insulated multi-phase transformer, and compensation is performed so that harmonic currents of the leading phase three-phase power supply, the lagging phase three-phase power supply, and the in-phase three-phase power supply are approximately the same.

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