JP4164975B2 - Power supply system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a power feeding system in which an inverter that receives power from a storage battery and a power system cooperate to feed power to a load.
[0002]
[Prior art]
As a system for leveling daytime and nighttime power demand, pumped-storage power generation has been known, but recently, instead of this, practical use of a power supply system that stores nighttime power in a storage battery and uses it during the daytime Is being considered. The reason for this is that pumped-storage power generation can only be installed at a power plant, but a system using a storage battery can be reduced in size, so it can be installed in factories and general households, and as a result, the power system (for example, AC100V commercial) This is because the power can be uninterrupted when a power failure occurs.
[0003]
FIG. 7 shows an example in which a power supply system using a storage battery is installed in a general home. This system includes a bidirectional inverter 2 (hereinafter simply referred to as “inverter 2”) connected to the storage battery 1. The output is connected to a common connection point between the electric power system 4 (for example, AC 100V commercial power supply) and the load 3 (for example, a load group including a television, an air conditioner, a refrigerator, and the like). In the nighttime, the inverter 2 is forward-converted (converted from alternating current to direct current) to store the received power from the power system 4 in the storage battery 1, while in the daytime, the inverter 2 is reverse-converted to the storage battery. The output of 1 is converted into AC power, and the load 3 is fed in cooperation with the power system 4.
[0004]
[Problems to be solved by the invention]
However, in the above power feeding system, the inverter 2 outputs AC power without monitoring the received power from the power system 4, and therefore a situation may occur in which the output of the inverter 2 flows backward to the power system 4.
[0005]
In addition, the above power supply system needs to have specifications that correspond to the power demand of each household for practical use. However, if multiple types of inverters and storage batteries with different capacities are prepared, versatility is impaired and manufacturing costs are reduced. Becomes higher. For this reason, as shown in FIG. 8, the AC power supply device 5 provided with the storage battery 1 and the inverter 2 is provided in a desired number (two in the figure), and these are connected in parallel to the power system 4 to each general household. A configuration corresponding to each power demand can be considered. Further, in this case, from the viewpoint of versatility, a configuration in which each AC power supply device 5 individually controls the conversion power by the inverter 2 is preferable to controlling all the inverters 2 with a single control circuit.
[0006]
Therefore, the inventor of the present application detects the received power from the power system 4 and imports it into each AC power supply device 5, 5, so that each AC power supply device 5, 5 becomes the predetermined reference power. A configuration for controlling the conversion power of each of the inverters 2 and 2 was examined. However, even if the reference received power is set in the same manner, the power actually output from the inverters 2 and 2 may not match due to variations in the characteristics of the inverters 2 and 2 (see FIG. 6). Specifically, when the conversion power of each inverter is controlled in order to prevent the storage battery power from flowing into the grid, the value of the received power is distributed to each inverter in a lump. A difference occurs in the converted power of each inverter due to an error in the set value of the received power. For example, an inverter having a slightly large set value first reduces the conversion power, and in an extreme case, an inverter that converts power and an inverter that does not convert at all are generated. When such a state occurs, there is a problem in that a difference occurs in the charge / discharge amount of the storage battery connected to each inverter, resulting in a difference in the storage battery life.
In addition, there is a problem that reliability of the inverter is lowered because an inverter with constantly large conversion power is generated.
[0007]
The present invention has been made in view of the above circumstances, and prevents reverse power flow from the inverter to the power system, and when a plurality of AC power supply devices are provided, increases the life and reliability of each of the power supply devices. The purpose is to provide a power supply system that can be used.
[0008]
A power supply system according to claim 1 is configured to connect a plurality of AC power supply devices including a storage battery and an inverter that receives power from the storage battery in parallel to a common connection point between a power system and a load connected thereto, and the AC power supply device In a power feeding system that cooperates with the power system to supply power to a load, the power system includes a system power detection unit that detects received power received from the power system, and each AC power supply device receives power output from the inverter. an inverter output power detecting means for detecting said receive a detection signal from the inverter output power detecting means, the greater the power inverter output is reduced, the reference changing means for changing reduced criteria received power, the system power detecting means When the detection signal is received, the output power from the inverter is reduced when the received power is smaller than the reference received power, and the previous When the received power is larger than the reference reception power is power supply system is characterized in that an inverter output control means for controlling said inverter to increase the output power from the inverter.
[0014]
[Action and effect of the invention]
In the power supply system of the present invention , when a difference occurs in the output from each inverter due to variations in the characteristics of the inverter, the inverter output power detection means provided in each inverter detects the output from each inverter, and the detection result Accordingly, the reference changing unit changes the reference received power in each inverter, so that the reference received power is set differently for each AC power supply device, and variations in output from each inverter can be eliminated.
[0015]
In the present invention, since the reference changing unit is configured to reduce the reference received power as the power output from the inverter decreases, the reference received power related to the inverter having the lower output power among the plurality of AC power supply devices. Is reduced by the reference changing means. As a result, the output from the inverter increases and the received power from the power system decreases. Then, in the inverter having a large output power, it is determined that the received power from the power system is smaller than the reference received power, and the output from the inverter is lowered. That is, while the output from the inverter with the low output power increases, the output from the inverter with the high output power decreases and the output from each inverter is balanced.
[0016]
As described above, according to the present invention, even in a power supply system including a plurality of inverters, the outputs of the AC power supply devices are balanced to suppress the difference in the life of the storage batteries provided in the AC power supply devices. Reliability can be improved.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
<Reference example>
First , a power supply system according to a reference example that is a reference for understanding the present invention will be described with reference to FIGS. 1 to 3. In this system, the output of a bidirectional inverter 7 (hereinafter simply referred to as “inverter 7”) connected to the storage battery 1 is connected to a common connection point between the power system 4 and the load 3, and the inverter 7 is connected at night. In forward conversion, the power received from the power system 4 is stored in the storage battery 1, while in the daytime, the inverter 7 is operated in reverse conversion to convert the output of the storage battery 1 into AC power. To supply power to the load 3.
[0018]
For example, the inverter 7 is provided with an inverter output control circuit 7 </ b> A including a CPU 15. A command value is passed from the CPU 15 to the inverter drive circuit 8 to cause the inverter 2 to output predetermined power.
[0019]
In the middle of the output line from the power system 4 to the load 3, a power measuring device 6 is connected. The power measuring device 6 includes, for example, a voltmeter and an ammeter, and the product of these measured values is used as the power. Is calculated, for example, as digital data, and provided to the CPU 15.
[0020]
In the inverter output control circuit 7A, the minimum power supplied from the power system 4 is set to a predetermined value (for example, 100 W) in advance as the reference received power W3, and this is written in the ROM 15A connected to the CPU 15, for example. Further, the reference power to be output to the inverter 7 is determined (for example, 400 W), and a value (500 W = 100 W + 400 W) obtained by adding the reference power and the reference received power W3 is set as the inverter output starting received power W1. is there. Further, the inverter output stop output power W2 as a reference value for determining whether or not to stop the output from the inverter 7 is set so that W2 + W3 is smaller than the inverter output start received power W1 (400W). ing.
[0021]
Each reference value (W1, W2, W3) described above is stored in a ROM 15A connected to the CPU 15 as a specific power value summarized below.
・ Inverter output starting received power W1 = 500 [W]
・ Inverter output stop output power W2 = 300 [W]
・ Reference received power W3 = 100 [W]
[0022]
Then, the CPU 15 compares the reference values (W1, W2, W3) with the actually measured received power P1 and inverter output power P2 according to the flow shown in FIG. 2, and is output from the inverter 7 as follows. Control power.
[0023]
That is, in the power supply system of this reference example , when the charging mode is switched to the discharging mode, the received power measuring device 6 detects the received power P1 from the power system 4, and the received power P1 as the detection result is the power monitoring circuit. 30 is taken in by the CPU 15 provided in the system 30. In addition, the inverter 7 has not started yet at the time of switching from the charge mode to the discharge mode.
[0024]
When receiving the received power P1, the CPU 15 determines whether or not the received power P1 is larger than the inverter output starting received power W1 (= 500 W), as shown in STEP1 of FIG. Since the inverter 7 is not outputting at this time, the received power P1 becomes the magnitude of the load power itself, and as a result, it is determined whether or not the load power is equal to or higher than the inverter output starting received power W1 (= 500 W).
Here, when the load power is small, the received power P1 becomes smaller than the inverter output starting received power W1, and the process proceeds to STEP 2 where the output of the inverter 7 is stopped (load = 0 to 0 in the graph of FIG. 3). 500W reference).
[0025]
On the other hand, when the load power is large, the received power P1 becomes larger than the inverter output start received power W1, and the process proceeds to STEP 3 where the inverter 7 outputs.
Along with this, the inverter output power P2 output from the inverter 7 is detected and taken into the CPU 15. Then, the CPU 15 determines whether or not the inverter output power P2 is larger than the inverter output stop output power W2 (= 300 W) in STEP4 of FIG. 2, and the output power of the inverter 7 is greater than the inverter output stop output power W2. When it is larger, the process proceeds to STEP 6 and it is determined whether or not the received power P1 is larger than the reference received power W3 (= 100 W). When the received power P1 is larger than the reference received power W3 (= 100 W), the output power of the inverter 7 is increased (STEP 7). When the received power P1 is smaller, the output power of the inverter 7 is decreased (STEP 8). Control is performed to match W3 (= 100 W).
When the inverter output reaches the maximum output of the inverter, the inverter output becomes constant at the maximum output, and the received power increases.
[0026]
If the CPU 15 determines in STEP 4 that the output power of the inverter 7 is smaller than the inverter output stop output power W2, the CPU 15 proceeds to STEP 5 and stops the output of the inverter 7 (STEP 5).
[0027]
As described above, according to the power supply system of the present reference example , the received power from the power system 4 becomes a constant value (= 100 W) from when the inverter 7 is started until the output from the inverter 7 becomes maximum. In other words, when the inverter 7 outputs power, the power system 4 always outputs power that is equal to or higher than the reference received power W3 (= 100 W). A situation where the system 4 receives power from the inverter 7 and reversely flows is reliably prevented.
[0028]
<Embodiment>
A power supply system according to an embodiment of the present invention is shown in FIG. 4 and includes a pair of AC power supply devices 21 and 21. These AC power supply devices 21 and 21 have the same configuration, and are provided with the output of the inverter 7 connected to the storage battery 1 connected to a common connection point between the power system 4 and the load 3, in cooperation with the power system 4. Power is supplied to the load 3.
Each inverter 7 is provided with an inverter output control circuit 10 having a CPU 16, and a command value is passed from the CPU 16 to the inverter drive circuit 8 to cause the inverter 2 to output predetermined power.
[0029]
Further, in the middle of the output line from the power system 4 to the load 3, a power measuring device 6 having the same configuration as that of the reference example is connected. The output of the power measuring device 6 is converted into digital data and taken into the CPU 16. Yes. Further, a power measuring device 9 is connected to an output portion from the inverter 7 in each AC power supply device 21. The power measuring device 9 is also provided with a voltmeter and an ammeter, and the measured values thereof. Is calculated as electric power. And the output of this electric power measuring device 9 is also made into digital data, and is taken in into CPU16.
[0030]
The ROM 16A connected to the CPU 16 of each AC power supply device 21, 21 stores predetermined reference values (W1, W2, refer to reference examples ) summarized below.
・ Inverter output starting received power W1 = 500 [W]
・ Inverter output stop output power W2 = 300 [W]
[0031]
Here, in the reference example , the reference received power W3 is also fixed to a predetermined value (= 100 [W]) and stored in the ROM. However, in this embodiment, the CPU 16 detects the inverter detected by the power meter 9. The reference received power is changed one by one based on the output of No.7. Therefore, a data table in which inverter output power and reference received power are associated in advance is recorded in the ROM 16A. In this data table, the value of each inverter output power and the value of each reference received power are set so as to satisfy the relationship established between the inverter output power and the reference received power as shown in the graph of FIG. ing.
The set value of the reference received power is preferably set to be 3 to 5% of the power that can be received from the power system 4 or the contract power. In addition, the difference between the set values of the two inverters is an error, and the resulting error appears when the apparatus is configured to be the same.
[0032]
Next, the operation of the present embodiment configured as described above will be described.
The power feeding system of this embodiment is also in the charging mode at night, and charges both storage batteries 1 and 1 provided in both AC power supply devices 21 and 21 with the received power from the power system 4.
Here, each CPU 16 provided in each AC power supply device 21 takes in values of received power and inverter output power detected by the power measuring devices 6 and 9, and these are shown in FIG. 2 as in the first embodiment. According to the flow, the output from the inverter 7 is controlled by comparing with the inverter output start received power W1, the inverter output stop output power W2, and the reference received power.
[0033]
By the way, the relationship between the inverter output power and the reference received power may differ depending on the inverter due to an error when setting the set value of the reference received power, variation in inverter circuit characteristics, or the like. Also in this embodiment, as shown in FIG. 5, an error occurs in two inverters. However, in the present embodiment, the reference received power set for both inverters 7 and 7 is changed one by one according to the inverter output power. That is, the CPU 16 receives the detection signal as the inverter output power from the power meter 9 and extracts the reference received power corresponding to the detection signal from the preset data table. Then, the output from the inverter 7 is controlled so that the received power from the power system 4 does not fall below the reference received power. Thereby, the dispersion | variation in the output from each inverter 7 can be eliminated.
[0034]
As described above, according to the present embodiment, even in a power supply system including a pair of inverters 7 and 7, the outputs of the inverters are balanced to suppress the difference in life of the storage batteries 1 and 1, and Can be improved.
[0035]
As a control method by the CPU 16, for example, a method of reducing the reference received power as the power output from the inverter 7 decreases may be employed. According to this method, when the output power from one inverter 7 is small, the reference received power for the inverter 7 is reduced by the CPU 16, and as a result, the output from the inverter increases. As a result, the received power from the power system 4 decreases, and when the other inverter 7 having a large output power is determined that the received power from the power system 4 is smaller than the reference received power, the output from the inverter 7 is Be lowered. As a result, the output from the inverter 7 whose output power is small increases, while the output from the inverter 7 whose output power is large decreases, and the outputs from the inverters 7 and 7 are balanced.
[0036]
<Other embodiments>
The present invention is not limited to the above-described embodiment. For example, the embodiments described below are also included in the technical scope of the present invention, and various other than the following are within the scope not departing from the gist. It can be changed and implemented.
(1) In the reference example and the embodiment , information on the reference received power and the reference output power is stored and set in the ROM, but may be set, for example, as an output voltage value of the voltage dividing circuit.
[0037]
(2) Although the power supply system of the reference example and the embodiment is configured to charge the storage battery 1 at night by the inverter 7, the present invention may be applied to a power supply system that does not have a function of charging the storage battery. .
[Brief description of the drawings]
[1] embodiment of the present block diagram showing a power supply system of a reference example of the invention Figure 2 is a graph Figure 4 showing the relationship between the flow chart showing the operation [3] received power and the inverter output and the load power present invention FIG. 5 is a graph showing variations in inverter characteristics. FIG. 6 is a graph showing variations in inverter characteristics. FIG. 7 is a block diagram showing a conventional power supply system. Block diagram showing power supply system with AC power supply
DESCRIPTION OF SYMBOLS 1 ... Storage battery 3 ... Load 4 ... Electric power system 6 ... Electric power measuring device (system electric power detection means)
7: Inverter 7A, 10: Inverter output control circuit (inverter output control means)
9 ... Electric power meter (Inverter output power detection means)
15 ... CPU (inverter output control means)
16 ... CPU (inverter output control means, reference change means)
20, 21 ... AC power supply device P1 ... received power W3 ... reference received power

Claims (1)

A plurality of AC power supply devices including a storage battery and an inverter that receives power from the storage battery are connected in parallel to a common connection point between the power system and a load connected to the power system, and the AC power supply device and the power system cooperate with each other. In a power supply system that supplies power to a load,
System power detection means for detecting the received power received from the power system,
In each AC power supply device,
Inverter output power detection means for detecting the power output by the inverter;
Receiving a detection signal from the inverter output power detecting means, the greater the power inverter output is reduced, receiving a reference changing means for changing reduced criteria received power, a detection signal from the system power detecting means, the received power An inverter output that controls the inverter to reduce output power from the inverter when the power is smaller than the reference received power, and to increase output power from the inverter when the received power is greater than the reference received power And a power supply system.

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