JP2007318930A - Interconnection power generation system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the quality of power supplied to a load in an interconnection power generation system where a generation power system including an AC generator and a commercial power system are interconnected by suppressing output variation of the generation power system resulting from voltage disturbance. <P>SOLUTION: A phase shift occurring between an output voltage applied to a load 4 and an output current from a generation power system 3 is corrected by inserting a voltage source 8 into the main line route 6 of the generation power system 3 and imparting a compensation voltage from the voltage source 8 to the main line route 6. More specifically, a compensation voltage (V<SB>C</SB>) is imparted to the voltage generated from the AC generator such that the phase of a voltage (V<SB>L</SB>) flowing through an interconnection reactor 7 provided in the main line route 6 delays by 90° behind the phase of a voltage (V<SB>S</SB>) from a commercial power system 1. Since the phase of the output voltage applied to the load 4 matches the phase of the output current from the generation power system 3, high quality power can be supplied to the load 4. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a grid-connected power generation system in which a power generation system including an AC generator driven by an internal combustion engine such as a diesel engine and a commercial power system are linked to each other. The present invention relates to a technology for improving the quality of power supplied to a load by suppressing output fluctuations of a generated power system.

  Conventionally, a power generation system called a “grid-connected power generation system” in which a power generation system including a distributed generator is connected to a commercial power system supplied from an electric power company is known. Distributed generators applied to this grid-connected power generation system include solar generators and prime movers. Especially, generators for large and medium-scale power generation systems such as factories and buildings include gas engines, An AC generator driven by an internal combustion engine such as a diesel engine or a gas turbine is applied.

  However, in an alternator driven by this type of internal combustion engine, pulsation torque (unevenness of rotation) may occur due to structural problems and imperfect control system, and pulsation torque must be completely eliminated. It is also difficult. For this reason, voltage fluctuation occurs in the output of the generator, and as a result, the output from the generated power system may fluctuate.

In order to solve this problem, in Patent Document 1, a reactor is inserted in the path from the output end of the diesel generator to the interconnection point of the power system, thereby suppressing the voltage fluctuation of the diesel generator and generating power. The output from the power system is stabilized.
JP-A-10-257777

  However, it is difficult to stabilize the output from the generated power system by effectively eliminating the voltage fluctuation of the generator with only the reactor as in Patent Document 1, and in order to improve the quality of the power supplied to the load. There was a limit.

  The present invention has been made in order to solve the above-described problems. In a grid-connected power generation system in which a power generation system including an AC generator and a commercial power system are interconnected, an AC generator An object of the present invention is to effectively suppress the output fluctuation of the generated power system caused by the fluctuation of the generated voltage of the power supply and to improve the quality of the power supplied to the load.

  According to the first aspect of the present invention, a generated power system including an AC generator and a commercial power system are interconnected via a transformer, and output power from the generated power system is connected to commercial power from the commercial power system. In a grid-connected power generation system that superimposes and supplies the load to the load, a voltage for making the phase of the load voltage applied to the load and the phase of the output current from the generated power system the same phase in the main line of the generated power system A source is inserted.

  According to a second aspect of the present invention, the voltage source converts a compensation transformer that is branched and connected from the commercial power system, and converts AC power transformed by the transformer into DC power. An AC / DC converter, a DC / AC converter that generates DC power supplied from the AC / DC converter as a compensation voltage, and control means for controlling the DC / AC converter may be included. .

  According to a third aspect of the present invention, the voltage source converts a compensating alternating current generator arranged in parallel with the alternating current generator, and alternating current power from the compensating alternating current generator to direct current power. An AC / DC converter, a DC / AC converter that generates DC power supplied from the AC / DC converter as a compensation voltage, and control means for controlling the DC / AC converter may be included. .

  5. The AC / DC converter for converting the voltage source into DC power branched and connected from the output of the transformer of the commercial power system, and the AC / DC converter. It is possible to include a direct / alternating current converter that generates direct-current power supplied from a compensation voltage, and a control unit that controls the direct / alternating current converter.

  According to a fifth aspect of the present invention, the voltage source is supplied from the AC / DC converter, and an AC / DC converter that is branched and connected from the output of the AC generator to convert it to DC power. It is possible to include a DC / AC converter that generates DC power as a compensation voltage, and a control unit that controls the DC / AC converter.

  According to a sixth aspect of the present invention, the voltage source serves as both a direct / alternating current converter and an AC / DC converter, and a direct current capacitor connected to the direct / alternating current converter, And a control means for controlling the AC converter.

  In this invention of Claim 1, a voltage source is inserted in the main line path | route of a generated electric power system, and the compensation voltage is provided with respect to a main line path | route from this voltage source, The load voltage concerning load and a generated electric power system | strain It was made possible to correct the phase shift caused between the output current from the output current. Specifically, the phase of the voltage applied to the interconnection reactor provided in the main line path is advanced by 90 ° with respect to the phase of the load voltage (voltage output from the commercial power system 1 via the transformer 2). As described above, the compensation voltage is applied to the generated voltage from the AC generator (see FIG. 1B). Thereby, since the phase of the load voltage applied to the load and the phase of the output current from the generated power system can be made the same phase, high-quality power can be supplied to the load.

  When the power supply to the voltage source is performed from the commercial power system as in the present invention described in claim 2, the commercial power system is stable without being affected by the voltage fluctuation of the AC generator. Since power supply can be received, a stable compensation operation by the voltage source is ensured, and a grid-connected power supply system with excellent reliability can be obtained.

If the power supply to the voltage source is performed from the compensating AC generator as in the third aspect of the present invention, the compensating AC is not affected by the voltage fluctuation of the alternating current generator. A stable power supply can be received from the generator. As a result, a stable compensation operation by the voltage source is ensured, and a grid-connected power supply system with excellent reliability can be obtained. Even when the commercial power system is in a power failure state, it is also superior in that it can receive a power supply from the compensating AC generator and perform a stable compensation operation.
Moreover, since the system form of Claim 2 was provided with two transformers, it is disadvantageous in that a large space is required for installing these transformers. On the other hand, according to the system configuration according to claim 3, the transformer for compensation can be eliminated and the number of transformers can be reduced to one. Therefore, compared to the system configuration according to claim 2, It is excellent in that the installation space for the transformer is small and the system can be made compact.

As described in claim 4, when a branch path is provided in the main line route through the transformer, and the commercial power applied through the branch path is used as the supply power to the voltage source, the influence of the voltage fluctuation of the AC generator Therefore, a stable power supply can be received from the commercial power system, so that a stable compensation operation by the voltage source is ensured, and a grid-connected power supply system with excellent reliability can be obtained.
Further, since the number of transformers can be reduced as compared with the system configuration according to the second aspect, the installation space for the transformer can be reduced as compared with the second aspect, and the system can be made compact. Further, it is not necessary to separately provide a dedicated generator for compensation as in the third aspect, and the total cost of the system can be reduced by reducing the number of components of the system.

  As in the present invention described in claim 5, when a branch path is provided in the main line route, and the generated power from the AC generator applied through this branch path is used as the power supplied to the voltage source, the claim 2 is described. Since the number of transformers can be reduced as compared with the system form, the installation space for transformers can be reduced, and the system can be made compact. Further, it is not necessary to separately provide a dedicated generator for compensation as in the third aspect, and the total cost of the system can be reduced by reducing the number of components of the system.

  According to the present invention as set forth in claim 6, in addition to being able to eliminate the compensating transformer, the AC generator, etc., the AC power for converting the AC power of these transformers and the AC generator into DC power is used. Since the / DC converter can be eliminated, the system can be made more compact and the overall cost of the system can be reduced as compared with the system forms of claims 2 to 5.

FIG. 1 is a system configuration diagram showing an outline of a grid-connected power generation system according to the present invention.
As shown in FIG. 1, this power generation system includes a commercial power system 1 that transforms a voltage supplied from commercial power into a desired voltage by a transformer 2 and supplies power to the commercial power system 1. It is comprised with the electric power grid | system 3. The commercial power from the commercial power system 1 and the output power from the generated power system 3 are superimposed and then applied to the load 4.

  The generated power system 3 includes an engine generator (alternator) 5, a connected reactor 7 formed on the main line 6 from the output end of the engine generator 5 to the transformer 2, and the main line 6 And a voltage source 8 inserted in. The voltage source 8 applies a compensation voltage to the main line 6, thereby converting the output current from the generated power system 3 into a load voltage (voltage output from the commercial power system 1 via the transformer 2). It is installed for the purpose of achieving the same phase.

Here, a method for compensating the output current by the compensation voltage applied from the voltage source 8 will be described with reference to FIGS.
FIGS. 2A and 2B show the phase states of current and voltage when the engine generator 5 is in a normal state where no voltage fluctuation occurs. In the figure, V _G is the generator voltage from the generator 5 driven by the engine 9, V _S is the load voltage (commercial power voltage is output through the transformer 2 from the system 1) V _L is interconnection reactor 7 in the voltage generated, I _S denotes a current flowing in the power generation system 3.

As shown in FIG. 2B, when the engine generator 5 is in a normal state with no voltage fluctuation, the output current (I _S ) and the load voltage (V _S ) are in phase, and the engine generator 5 The generated voltage (V _G ) is the sum of the load voltage (voltage output from the commercial power system 1 via the transformer 2) (V _S ) and the voltage (V _L ) generated in the interconnection reactor 7, The voltage (V _L ) generated in the system reactor 7 has a phase advanced by 90 ° from the load voltage (V _S ). That is, (V _L ) and (V _S ) are orthogonal to each other.

This state is expressed as follows.
・ V _L = V _G -V _S
・ I _S = V _L / jX _L ((jX _L ) is the interconnected reactance)

From this state, as shown in FIG. 3B, it is assumed that a voltage fluctuation occurs in the generated voltage (V _G ) from the engine generator 5 due to some factor. When the power generation voltage (V _G ) varies in this way, the voltage (V _L ) generated in the interconnection reactor 7 also fluctuates, and the phase orthogonal to the voltage (V _L ) generated in the interconnection reactor 7 The phase of the output current (I _S ) also changes, and the phase of the load voltage (voltage output from the commercial power system 1 via the transformer 2) (V _S ) does not match, resulting in a problem such as power factor reduction Invite. This means that the power quality of the grid-connected power generation system is degraded.

A specific example is shown in FIG. Assume that the generated voltage (V _G ) has increased by about 5%. When the voltage fluctuation occurs in the generated voltage (V _G ) in this way, as shown in FIG. 4A, the phase of the output current (I _S ) of the generated power is shifted. In other words, a deviation occurs between the amplitude and phase of the output current (I _S ) of the generated power and the ideal value of the amplitude and phase of the current (I _S ^* ) to be supplied to the load.

Therefore, in the grid-connected power generation system according to the present invention, as shown in FIG. 1, the output current (V _C ) is applied by inserting a voltage source 8 into the main line 6 (in series connection) and applying a compensation voltage (V _C ). The phase shift generated between I _S ) and the load voltage (V _S ) is corrected. Here, as shown in FIG. 1 (b), a sinusoidal compensation voltage (V _C ) is applied to the generated voltage (V _G ) from the engine generator 5 (see FIG. 5 (b)). phase of the voltage generated by the system reactor 7 _{(V L)} is, advances 90 ° the phase of the load voltage _{(V S),} the load voltage _{(V S)} and the output current _{(I S)} is the same phase (Fig. 5 (a)).

Specifically, since the following equation is established, the instantaneous value (i _S ) of the output current is detected, and from the error with the instantaneous value (i _S ^* ) of the current to be supplied to the load, the interconnection reactor 7 The instantaneous value (v _L ) of the voltage that must be generated is obtained, and the load voltage (voltage output from the commercial power system 1 via the transformer 2) is calculated from the instantaneous value (v _G ) of the generated voltage from the engine generator 5. The instantaneous value (v _C ) of the compensation voltage can be calculated by subtracting the instantaneous value (v _S ) and the instantaneous value (v _L ) of the voltage that must be generated by the interconnection reactor 7. Here, a control gain such as proportional to proportional + integral element can be applied to α.
・ V _L = α (i _S ^* −i _S )
・ V _C = v _G -v _S -v _L

By applying the instantaneous value (v _C ) of the compensation voltage obtained as described above to the main line 6, the instantaneous value (i _S ) of the output current of the generated power system 3 and the instantaneous value (v _{S of the} load voltage). ) In phase with each other, and high-quality power can be supplied to the load 4.

  In the following first to fifth embodiments, a specific configuration of the power supply 8 and control is shown.

(First embodiment)
FIG. 6 is a circuit configuration diagram of the grid-connected power generation system according to the first embodiment (corresponding to claim 2). The power source 8 therefor includes a coil 10a disposed on the main line 6, a coil 10b connected to the output side of the DC / AC converter 17, and a predetermined voltage output to the coil 10b to provide a compensation voltage (V _C ). A DC / AC converter (inverter) 17 for generating the DC / AC converter 17, a controller 11 for controlling the DC / AC converter 17, an AC / DC converter (converter) 12 for applying a DC current to the DC / AC converter 17, And a DC capacitor 13 that stabilizes the electric power applied to the DC / AC converter 17. The coil 10a and the coil 10b constitute a transformer so that a desired voltage can be obtained. Moreover, it is also possible to substitute the coil 10a instead of the interconnection reactor 7 arranged on the main line route 6.
In order to supply power to the DC / AC converter 17, a branch path 15 is connected in parallel from the commercial power system 1, and a compensation transformer 16 is connected to the branch path 15 to transform it to a desired voltage. The AC / DC converter 12 converts the transformed power from AC power to DC power. Alternatively, the compensation transformer 16 and the transformer 2 may have the same iron core, and a tertiary winding may be added to the transformer 2 to supply AC power to the AC / DC converter 12.

The controller 11 includes the DC / AC converter 17, a voltage sensor 20 for detecting an instantaneous value (v _G ) of the generated voltage from the generated power system 3, a load voltage (the commercial power system 1 to the transformer 2). A voltage sensor 21 for detecting an instantaneous value (v _S ) of a voltage output through the main line 6 and a current sensor 22 for detecting an instantaneous value (i _S ) of a current flowing through the main line 6 are connected. . The memory 18 connected to the controller 11 stores a program for controlling the controller 11 and the like.
In such a configuration, the controller 11 uses the detected values from these sensors 20, 21, and 22, and the instantaneous value of the compensation voltage to be applied to the main line 6 in the procedure described above ( v _C ) is calculated, and the output of the DC / AC converter 17 is controlled based on the calculated value so that the instantaneous value (v _C ) of the compensation voltage is obtained.

  As described above, when the power supply to the voltage source 8 is performed from the commercial power system 1, stable power supply from the commercial power system 1 can be achieved without being affected by the voltage fluctuation of the engine generator 5. Can receive. Thereby, a stable compensation operation by the voltage source 8 is ensured, and a grid-connected power supply system with excellent reliability can be obtained.

(Second embodiment)
FIG. 7 shows a grid-connected power generation system according to the second embodiment of the present invention (corresponding to claim 3). In this system, a compensation AC generator 25 is provided separately from the engine generator 5 of the generated power system, and power supply to the voltage source 8 is performed from the compensation AC generator 25. This is different from the previous first embodiment. Other than that, since it is substantially the same as the first embodiment, the same members are denoted by the same reference numerals, and the description thereof is omitted.
That is, in order to supply power to the direct / alternating current converter 17, a compensating alternating current generator 25 is provided in parallel instead of the commercial power system 1, and the alternating current generator 25 is combined with the engine generator 5 and the engine 9. To supply the AC power from the AC generator 25 to the AC / DC converter 12.

  Thus, when the power supply to the voltage source 8 is performed from the compensating AC generator 25, stable power is supplied from the AC generator 25 without being affected by the voltage fluctuation of the engine generator 5. Can be supplied. Thereby, a stable compensation operation by the voltage source 8 is ensured, and a grid-connected power supply system with excellent reliability can be obtained.

  Further, since the system configuration according to the first embodiment includes the two transformers 2 and 16, there is a disadvantage in that a large space is required for installing these transformers 2 and 16 (see FIG. 6). . On the other hand, according to the system configuration according to the second embodiment, since a desired voltage can be generated by the AC generator 25, the compensation transformer 16 is eliminated and the number of transformers is reduced to one. Compared to the system configuration according to the first embodiment, the installation space for the transformer is small, and the system can be made compact.

  Further, in the system configuration according to the first embodiment, when the power supply from the commercial power system 1 is stopped, that is, when a power failure occurs, the power supply from the commercial power system 1 cannot be received, and the direct current When there is no more power stored in the capacitor 13, the compensation operation by the voltage source 8 cannot be performed. On the other hand, according to the system configuration according to the present embodiment, even when the commercial power system 1 is in a power failure state, a stable compensation operation is performed by receiving power supply from the compensating AC generator 25. It can be carried out.

(Third embodiment)
FIG. 8 shows a grid-connected power generation system according to a third embodiment of the present invention (corresponding to claim 4). In this system, a branch path 26 is provided on the output side of the transformer 2 and connected to the AC / DC converter 12, and commercial power from the commercial power system 1 via the branch path 26 is supplied to the voltage source 8. This is different from the previous first embodiment in that the supplied power is used. Other than that, since it is substantially the same as the first embodiment, the same symbols are attached to the same members, and the description thereof is omitted.

  According to the system configuration of the third embodiment, the transformer 16 that is an essential component in the first embodiment can be eliminated, and the number of transformers can be reduced compared to the first embodiment. Compared to the system configuration according to the first embodiment, the system can be made more compact and lower in cost. Further, it is not necessary to separately provide a dedicated generator 25 for compensation as in the second embodiment, and in this respect as well, the number of components of the system can be suppressed and the cost can be reduced.

(Fourth embodiment)
FIG. 9 shows a grid-connected power generation system according to a fourth embodiment of the present invention (corresponding to claim 5). In this system, the branch path 27 is branched from the output of the engine generator 5 of the generated power system, and the generated power from the engine generator 5 via this branch path is supplied to the AC / DC converter 12 to generate a voltage. The point that voltage is generated in the source 8 is different from the first embodiment. Other than that, it is substantially the same as the first embodiment and so on, and therefore, the same members are denoted by the same reference numerals and the description thereof is omitted.

  According to the system configuration of the fourth embodiment, the number of transformers can be reduced compared to the first embodiment, so that the transformer installation space is small compared to the system configuration according to the first embodiment. The system can be made compact. Further, unlike the second embodiment, there is no need to separately provide a dedicated generator 25 for compensation, and there is an advantage that the total cost of the system can be reduced by suppressing the number of components of the system.

(5th Example)
FIG. 10 shows a grid-connected power generation system according to the fifth embodiment of the present invention. Such a system includes a direct / alternating current converter 17 that also serves as an AC / DC converter, a direct current capacitor 13 connected to the direct / alternating current converter 17, and a controller 11 that controls the direct / alternating current converter 17. This is different from the first embodiment. Other than that, it is substantially the same as in the first embodiment and the like, and the same members are denoted by the same reference numerals and the description thereof is omitted.

In this system, when the engine generator 5 is in a normal state with no voltage fluctuation, the direct / alternating converter 17 transforms the output power of the engine generator 5 from the coil 10a through the coil 10b to the direct / alternating converter 17. Is converted to direct current and held at the voltage of the direct current capacitor 13. When the controller 11 determines that voltage fluctuation has occurred, the DC / AC converter 17 outputs a predetermined voltage while the DC / AC converter 17 keeps the voltage of the DC capacitor 13 constant. The compensation voltage (V _C ) is applied to the main line 6 from 10b.

  According to the grid-connected power generation system according to the fifth embodiment configured as described above, the transformer 16 (see FIG. 1 and the like) for supplying power to the voltage source 8 and the generator 25 (see FIG. 7). Etc. can be completely abolished, so that the system can be made compact and the cost can be reduced. In addition, since the AC / DC converter 12 (see FIG. 1 and the like) for supplying DC power to the direct / AC converter 17 can be eliminated, the components of the system can be reduced in this respect as well. The overall cost can be reduced.

  In the first to fifth embodiments, even when the voltage of the commercial power system fluctuates, the output current from the generated power system can be compensated to an ideal value. On the other hand, when the load power fluctuates due to load fluctuations, the engine speed governor or other engine speed control mechanism is controlled to supply power stably or supply the shortage from the commercial power source 1. Like to do. For this reason, the voltage source 8 of the present invention can be a small-capacity converter, so that sufficient power can be supplied from the DC capacitor 13. By compensating at the initial stage of fluctuation, the fluctuation does not gradually increase (the fluctuation is amplified), and high-quality power can be obtained.

(A) is a block diagram of the grid connection electric power generation system which concerns on this invention, (b) is a figure for demonstrating the compensation method of an output current. (A) (b) are views for explaining a method of compensating the output current by the grid interconnection power generation system according to the present invention, the state when the power generation voltage (V _G) is in no normal state of voltage fluctuation Is shown. (A) (b) are views for explaining a method of compensating the output current by the grid interconnection power generation system according to the present invention, showing a state in which the power generation voltage (V _G) produced a voltage fluctuation. (A) is a diagram showing a phase state of the output current before compensation is a diagram showing a (b) is (without granting) state of the compensation voltage (V _C). (A) is a diagram showing a phase state of the output current after compensation is a diagram showing a (b) the compensation voltage (V _C). It is a figure which shows the structure of the grid connection electric power generation system which concerns on 1st Example of this invention. It is a figure which shows the structure of the grid connection electric power generation system which concerns on 2nd Example of this invention. It is a figure which shows the structure of the grid connection electric power generation system which concerns on 3rd Example of this invention. It is a figure which shows the structure of the grid connection electric power generation system which concerns on 4th Example of this invention. It is a figure which shows the structure of the grid connection electric power generation system which concerns on 5th Example of this invention.

Explanation of symbols

1 Commercial Power System 2 Transformer 3 Power Generation System 4 Load 5 AC Generator (Engine Generator)
6 main route 8 voltage source 11 control means (controller)
12 AC / DC converter 13 DC capacitor 17 DC / AC converter 25 AC generator 26 Branch 27 Branch

Claims (6)

A system in which a power generation system including an AC generator and a commercial power system are interconnected via a transformer, and the output power from the generated power system is superimposed on the commercial power from the commercial power system and supplied to the load. In the grid power generation system,
A grid-connected power generation system, wherein a voltage source for inserting the phase of the load voltage applied to the load and the phase of the output current from the generated power system in the same phase is inserted in the main line of the generated power system .   The voltage source is a compensation transformer branched and connected from the commercial power system, an AC / DC converter for converting AC power transformed by the transformer into DC power, and the AC / DC The grid-connected power generation system according to claim 1, further comprising: a direct / alternating current converter that generates DC power supplied from the converter as a compensation voltage; and a control unit that controls the direct / alternating current converter.   The voltage source is a compensating AC generator arranged in parallel with the AC generator, an AC / DC converter for converting AC power from the AC generator for compensation into DC power, and the AC / DC The grid-connected power generation system according to claim 1, further comprising: a direct / alternating current converter that generates DC power supplied from the converter as a compensation voltage; and a control unit that controls the direct / alternating current converter.   The voltage source generates an AC / DC converter that converts the DC power branched and connected from the output of the transformer of the commercial power system, and DC power supplied from the AC / DC converter as a compensation voltage. 2. The grid-connected power generation system according to claim 1, further comprising: a direct / alternating current converter that performs control and a control unit that controls the direct / alternating current converter.   The voltage source is connected to the output of the AC generator and connected to the AC / DC converter for converting into DC power, and the DC / DC converter for generating DC power supplied from the AC / DC converter as a compensation voltage. The grid-connected power generation system according to claim 1, comprising an AC converter and control means for controlling the direct / AC converter.   The voltage source serves as both a direct / AC converter and an AC / DC converter, and includes a DC capacitor connected to the DC / AC converter and control means for controlling the DC / AC converter. The grid-connected power generation system according to claim 1.

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