Power conversion device

Abstract

To provide a power conversion device with a circuit for generating 105 V without enlarging a transformer used to change the output voltage of a PCS to 210 V.SOLUTION: The power conversion device includes a PCS 2 that converts externally supplied DC power into three-phase AC power and a three-phase transformer 3 that converts the AC power output from the PCS into 210 V. The three-phase transformer 3 is configured of a primary winding 31 connected to the PCS 2 in a star configuration, and a secondary winding 32 connected in a delta configuration. An autotransformer 8 is connected between two of the three poles on the secondary side, and transforms 210 V into 105 V. The autotransformer 8 thus generates 105 V single-phase power.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a power conversion device including a PCS that converts DC power into AC power and a transformer that changes the output voltage of the PCS.

Background Art

[0002] Since the power generated by a solar cell is DC, when connecting to commercial power, it is converted into AC power using a power conditioner (PCS) equipped with an inverter, and further stepped up or down using a transformer. Therefore, the PCS and the transformer are often installed integrally, and a power conversion device integrating both has been proposed (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Since both the PCS and the transformer are devices that generate heat, a cooling device such as a fan is required for the power conversion device equipped with these, and various measuring devices are also installed. Therefore, in order to secure these power supplies, in Patent Document 1, a transformer that steps down the 440V output of the PCS to 210V is provided with a tertiary winding to generate a 105V voltage for countermeasures. As a result, since a tertiary winding is provided in the transformer to generate 105V, the transformer has become large. In addition, since the tertiary winding has a special winding method, the cost has become high.

[0005] In order to avoid increasing the size and cost of this transformer, in the power conversion device, instead of generating 105V, a configuration can be considered in which the device receives a 105V supply from high-voltage power receiving equipment such as a cubicle. Since the high-voltage power receiving equipment is provided with a 105V power source for operating instruments, there is no need for a device that newly generates a 105V voltage. However, since the PCS is arranged near distributed power sources such as solar power generation facilities, the power conversion device will inevitably be installed in such a location. Therefore, in order to receive a 105V supply from the high-voltage power receiving equipment, it was troublesome because wiring work was required between the high-voltage power receiving equipment and the power conversion device.

[0006] Therefore, in view of such problems, an object of the present invention is to provide a power conversion device provided with a circuit for generating 105V without increasing the size of a transformer that changes the output voltage of the PCS to 210V.

Means for Solving the Problem

[0007] In order to solve the above problems, the configuration of the present invention is a power conversion device including a power conditioner that converts DC power input from the outside into three-phase AC power, and a three-phase transformer that changes the AC power output by the power conditioner to 210V, wherein a single-winding transformer that transforms 210V to 105V is connected between two of the three secondary-side poles, and a single-phase power of 105V is generated by the single-winding transformer. According to this configuration, by connecting a single-winding transformer between two poles of the three-phase transformer to obtain 105V, there is no need to provide a new winding in the three-phase transformer. Therefore, there is no need to provide a new winding in the three-phase transformer itself, and there is no need to increase the size of the three-phase transformer. Note that the 105V mentioned here is a convenient way to represent 101±6V as defined in the Electricity Business Act with a single numerical value, and does not exclude 95V or 107V.

[0008] Another aspect of the present invention is that, in the above configuration, the secondary side of a step-down transformer that converts the high voltage of high-voltage power receiving equipment to low voltage is connected to the secondary side that outputs 210V of a three-phase transformer. The step-down transformer is formed such that the secondary winding is delta-connected and one of the three poles on the secondary side is grounded, and one of the two poles to which a single-winding transformer is connected is the grounded pole of the step-down transformer, and the secondary-side voltage is drawn from between the grounded pole and the middle position of the winding of the single-winding transformer. According to this configuration, since the single-winding transformer is connected to the grounded pole on the step-down transformer side, it is possible to achieve alignment with the step-down transformer and generate a stable voltage.

Effects of the Invention

[0009] According to the present invention, by connecting a single-winding transformer between two poles of a three-phase transformer to obtain 105V, it is not necessary to provide a new winding in the three-phase transformer. Therefore, it is not necessary to provide a new winding in the three-phase transformer itself, and it is not necessary to increase the size of the three-phase transformer.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments embodying the present invention will be described in detail with reference to the drawings. FIGS. 1 and 2 show a first form of a power conversion device according to the present invention. FIG. 1 is an explanatory diagram including the device at the connection destination, and FIG. 2 is an explanatory diagram with the windings of the transformer extracted. In FIG. 1, 2 is a PCS (Power Conditioner) that converts DC power into three-phase AC power, 3 is a three-phase transformer that changes the AC voltage output by the PCS 2, 4 is a solar panel, 5 is a step-down transformer of high-voltage power receiving equipment (not shown), 6 is a load with a power supply difference, 7 is a power system to which a high voltage such as 6600V is applied, and 8 is a single-winding transformer. The power conversion device 1 converts the DC power generated by the solar panel 4 into three-phase AC power and links it to the output of the high-voltage power receiving equipment.

[0012] The power conversion device 1 is composed of a PCS 2, a three-phase transformer 3, and a single-winding transformer 8. The DC power output by the solar panel 4 is converted into three-phase power by the PCS 2. Then, it is changed to a voltage that matches the voltage output from the high-voltage power receiving equipment in the three-phase transformer 3. Specifically, the PCS 2 generates and outputs a three-phase AC of 440V, and the three-phase transformer 3 steps down 440V to 210V, which is equal to the secondary-side voltage of the step-down transformer 5, and outputs it. Incidentally, the step-down transformer 5 steps down, for example, 6600V to 210V. Also, the PCS 2 generates an AC voltage whose phase matches the voltage output by the step-down transformer 5.

[0013] In the step-down transformer 5, the primary winding 51 is delta-connected, and the secondary winding 52 is star-connected. The neutral point M of the star-connected secondary winding 52 is the grounding point Q and is grounded. On the other hand, in the three-phase transformer 3, the primary winding 31 on the PCS 2 side is star-connected, and the secondary winding 32 is delta-connected. And, among the three poles (R pole, S pole, T pole) on the secondary side of the three-phase transformer 3, a single-winding transformer 8 for extracting 105V between the R pole and the S pole is connected. The single-winding transformer 8 is connected to the first lead wire L1 connected to the R pole and the second lead wire L2 connected to the S pole as shown in FIG. 1. Then, a 105V output section 9 is formed by the third lead wire L3 provided at the midpoint of the winding and the fourth lead wire L4 provided at the R pole common to the primary side of the single-winding transformer 8.

[0014] In this way, by connecting the single-winding transformer 8 between two poles of the three-phase transformer 3 to obtain 105V, it is possible to secure the power supply for the cooling fan or the like without providing a new winding in the three-phase transformer 3. And the configuration of connecting the single-winding transformer 8 to the three-phase transformer 3 can be made smaller and lower in cost than winding a new winding on the three-phase transformer 3 to generate 105V.

[0015] In addition, in the above embodiment, the single-winding transformer 8 is connected between the R pole and the S pole, but the poles between which the single-winding transformer 8 is connected are arbitrary, and it may be attached between the S pole and the T pole, for example. No matter which poles it is connected to, it can be made to match with the step-down transformer 5. This is because when the star-connected neutral point M of the secondary winding 52 of the step-down transformer 5 becomes the grounding point G, the center of the winding of the single-winding transformer 8 connected between two poles on the secondary side of the three-phase transformer 3 can be regarded as having the same potential as the neutral point M. One terminal on the secondary side of the single-winding transformer 8 that steps down 210V to half and outputs it is drawn out from the center of the winding.

[0016] Figs. 3 and 4 show a second embodiment of the power conversion device 1. Fig. 3 is a schematic diagram including the connection destination, and Fig. 4 is an explanatory diagram with the windings of the transformer extracted. Different from the above embodiment, this shows the case where the configuration of the step-down transformer 5 to which the power conversion device 1 is connected is different, and the primary winding 53 is star-connected and the secondary winding 54 is delta-connected. When the secondary winding 54 of the step-down transformer 5 is delta-connected in this way, the position for extracting 105V is different from that in the above embodiment and is limited. In addition, the winding form of the three-phase transformer 3 is the same as that in the above embodiment, the primary winding 31 is star-connected, and the secondary winding 32 is delta-connected. Hereinafter, the same components as those in the above embodiment are given the same reference numerals and the description thereof is omitted.

[0017] When the secondary winding 54 of the step-down transformer 5 is delta-connected, the 105V extraction position of the three-phase transformer 3 is determined by the grounding part thereof. That is, the connection poles of the single-winding transformer 8 are limited. Here, it will be described assuming that the S pole of the step-down transformer 5 is grounded. When the S pole is grounded, one of the poles to which the single-winding transformer 8 is connected becomes the S pole. And for the other pole, it can be either the T pole or the R pole. Here, the case where it is connected to the R pole will be described. As shown in FIG. 3, the single-winding transformer 8 is connected to a first lead wire L1 connected to the R pole and a second lead wire L2 connected to the S pole. And a 105V output section 9 is formed by a fifth lead wire L5 provided at the midpoint of the winding and a sixth lead wire L6 provided at the S pole. In this way, the single-winding transformer 8 generates and outputs a voltage of 105V, which is one-half of the inter-pole voltage (line voltage) of 210V.

[0018] Here, the reason why the connection poles of the single-winding transformer 8 are limited will be explained. Since the secondary winding 32 of the three-phase transformer 3 has an inter-pole voltage (line voltage) of 210V, by connecting a single-winding transformer 8 that steps down the voltage by one-half between the poles, 105V can be obtained. However, to achieve coordination with the step-down transformer 5, it is necessary to be based on the grounded pole. Therefore, the S pole is selected because the S pole is the grounding point G, and this S pole becomes one of the terminals of the 105V output section 9. The other connection destination is the R pole in the above form, but it can also be the T pole. It is possible to take out a 105V voltage without using the grounded pole, but it is difficult to achieve coordination with the step-down transformer 5.

[0019] In this way, when one of the three poles of the three-phase power output from the step-down transformer 5 of the high-voltage power receiving facility is the grounding pole, the single-winding transformer 8 is connected to the pole grounded on the step-down transformer 5 side, and by using that pole as one of the output terminals, coordination with the step-down transformer 5 can be achieved, and a stable voltage can be generated. And the configuration of connecting the single-winding transformer 8 to the three-phase transformer 3 can be made smaller and configured at a lower cost than winding a new winding around the three-phase transformer 3 to generate 105V.

[0020] FIG. 5 shows an external view of the single-winding transformer 8. As shown in FIG. 5, terminals for connecting wiring and the like are concentrated on the upper surface of the housing 35 of the single-winding transformer 8. Specifically, on the upper surface of the rectangular housing 81 that houses the single-winding transformer 8, there are arranged a primary-side terminal 82 for connecting to the three-phase transformer 3, a power outlet 9a that constitutes the 105V output section 9, a breaker 9b, a connection terminal 9c, and the like. Thus, since the 105V output section 9 that outputs a 105V voltage is concentrated on the upper surface of the housing 81 of the single-winding transformer 8 together with the primary-side terminal 82, the wiring work is easy.

[0021] In addition, in the above embodiment, the windings of the three-phase transformer 3 have the primary winding 31 in a star connection and the secondary winding in a delta connection, but the connection form of the windings is not limited to this form. It is only necessary that the output on the secondary side is 210V.

Explanation of Reference Numerals

[0022] 1... Power conversion device, 2... PCS (Power Conditioner), 3... Three-phase transformer, 5... Step-down transformer, 8... Single-winding transformer, 9... 105V output section, 31... Primary winding, 32... Secondary winding, 51... Primary winding, 52... Secondary winding, 53... Primary winding, 54... Secondary winding, M... Neutral point, G... Grounding point.

Claims

1. A power conversion device comprising a power conditioner that converts externally input DC power into three-phase AC power, and a three-phase transformer that changes the AC power output by the power conditioner to 210V, A single-winding transformer that transforms 210V to 105V is connected between two of the three poles on the secondary side, and single-phase power of 105V is generated by the single-winding transformer. The power conversion device is characterized by this.

2. The secondary side of a step-down transformer that converts the high voltage of high-voltage power receiving equipment to low voltage is connected to the secondary side that outputs 210V of the three-phase transformer, and the step-down transformer is configured such that the secondary winding is delta-connected and one of the three poles on the secondary side is grounded, One of the two poles to which the single-winding transformer is connected is the grounded pole of the step-down transformer, and the secondary voltage is drawn from the grounded pole and the middle position of the winding of the single-winding transformer. The power conversion device according to Claim 1 is characterized by this.

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