JPH09223515A - Secondary battery system to cope with peak electric power - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a system effective in a measure against peak electric power of an electric power system by eliminating uselessness of a conventional secondary battery system. SOLUTION: Integrated electric energy of one day of electric power used by exceeding an electric power value by subtracting AC output capacity of an electric power converter 2 from a peak value of electrice power used in an electric power system 4 and a value by multiplying storage electric energy capacity of a secondary battery by D.C-A.C conversion efficiency of the electrice power converter 2, are made to almost coincide with each other. Or the relationship between the integrated electric energy and AC output is found by using a pattern with the lapse of time of electric power in the past annual electric power peak generating days, and when the integrated electrice energy is equal to the value by multiplying the storage electric energy capacity of the secondary battery 1 by the orthogonal conversion efficiency of the electric power converter 2, AC output capacity of the electric power converter 2 is made larger than a value of AC output calculated from this relationship.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary battery system which is effective as a measure against peak power in a power system.

[0002]

2. Description of the Related Art As a load leveling measure for a power system, a secondary battery system such as a sodium-yellow-yellow battery using sodium for a negative electrode and sulfur for a positive electrode is used to store nighttime power with a small amount of power consumption. , A load leveling system that emits power during the daytime when power consumption is high,
It is known, as can be found in the publication "Energy Storage System", pages 61-81, published by the Resource Society in 1992. On the other hand, in the recent power situation, the effect of the peak power value required during a specific time zone during the daytime is large, and the capacity of the power generation equipment, the power transmission equipment, and the substation equipment to be equipped is determined according to this peak power value. Therefore, it is necessary to invest excessive power generation equipment, power transmission equipment, and substation equipment with respect to the average power used, and in order to avoid this, peak power measures are urgently needed. However, in the conventional secondary battery system for load leveling, the balance between the output capacity of the power converter and the stored power capacity of the secondary battery is improper, and the secondary battery system is relatively used for peak power measures. There was nothing suitable for this purpose, because the amount of stored electricity was too large, the system became large, and waste was generated.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a secondary battery system which is effective as a measure against peak power in an electric power system, except for the above-mentioned drawbacks of the prior art.

[0004]

In order to achieve the above object, the first invention is a peak power secondary battery system connected to a power system via a power converter and used in the power system. The daily integrated electric energy of the electric power used exceeding the electric power value obtained by subtracting the AC output capacity of the electric power converter from the peak value of electric power, and the stored electric energy capacity of the secondary battery are orthogonal to the electric power converter. It is characterized in that the value obtained by multiplying the conversion efficiency is substantially matched. Further, in the peak power secondary battery system, a relationship between the AC output capacity and the integrated electric energy obtained by variably determining the AC output capacity using a temporal pattern of electric power on a past annual power peak occurrence day. And the required value of the AC output capacity in the electric power system, the integrated electric energy is calculated.

A second aspect of the present invention is a peak power secondary battery system connected to a power system via a power converter, wherein the power consumption is measured by using a temporal pattern of power on the day of the past annual power peak. The relationship between the daily integrated power amount of the power used exceeding the power value obtained by subtracting the AC output of the power converter from the peak value of the power of the grid and the AC output is obtained, and the integrated power amount is calculated. Is equal to the storage power capacity of the secondary battery multiplied by the orthogonal conversion efficiency of the power converter, the AC output capacity of the power converter than the value of the AC output calculated from the relationship. It is characterized by making it larger.

The power system considered here means the entire power system connected by the power network or a local power system such as one substation. In addition, when installing multiple secondary battery systems in the target power system, the total AC output capacity of the power converters that make up the secondary battery system and the total stored power capacity of the secondary battery Should satisfy the relationship of the present invention.

According to the first aspect of the present invention, the daily integrated electric energy of the electric power used exceeding the electric power value obtained by subtracting the AC output capacity of the electric power converter from the peak value of the electric power of the electric power system, and the storage of the secondary battery The value obtained by multiplying the electric energy capacity by the orthogonal conversion efficiency of the electric power converter is substantially matched. For this reason, the AC output capacity of the power converter and the stored power capacity of the secondary battery are just the necessary and sufficient amounts to support peak power, and the AC output capacity and the stored power capacity of the peak power compatible secondary battery system are exceeded. It can be used without any shortage, and the power peak used when exceeding the power value obtained by subtracting the AC output capacity of the power converter from the peak value of the power can be covered by the stored power amount from the secondary battery.

In order to determine the AC output capacity of the power converter and the stored power capacity of the secondary battery, it is sufficient to use the temporal pattern of power on the past annual power peak occurrence day of the target power system. That is, the AC output capacity is made variable, and the daily integrated power amount of the power used that exceeds the power value obtained by subtracting the AC output capacity of the power converter from the peak power value of the power system from the aging pattern, and the AC output capacity. Then, the integrated power amount is calculated using this relationship and the required value of the AC output capacity in the power system, and the value obtained by dividing this value by the orthogonal conversion efficiency of the power converter is used as the secondary battery. The storage power capacity of

The relationship between the integrated electric energy and the AC output capacity changes depending on the life pattern, but does not change so much in Japan depending on the scale of the electric power system and the year, and the annual average of the electric power used in the electric power system. It was found that when the value is P (kW), the AC output capacity is p (kW), and the integrated electric energy is E (kWh), it is given by the following formula.

[0010]

## EQU00005 ## log (E / p) = (5/7) .log (p / P) +1.24. +-. 0.08 (Equation 5) Also, the same relationship applies to the annual amount of electric power used in the power system. When the peak value is P '(kW), the AC output capacity is p (kW), and the integrated electric energy is E (kWh), it is given by the following formula.

[0011]

[Equation 6] log (E / p) = (5/7) · log (p / P ′) + 1.455 ± 0.08 (Equation 6) Therefore, using these relational expressions, past performance and GNP The required storage capacity of the secondary battery can be obtained from the annual average value or the annual peak value of the electric power predicted from the growth of the electric power, and the AC output capacity of the power converter required in the system.

On the other hand, in the second invention, the relationship between the AC output of the power converter and the integrated power amount obtained by the same procedure as described above is used, and the orthogonal conversion of the power converter is converted into the stored power capacity of the secondary battery. The AC output capacity of the power converter is made larger than the value of the AC output obtained by assuming that the value obtained by multiplying the efficiency is equal to the integrated electric energy. For this reason, even if the peak power of the system becomes larger than expected, the AC output capacity of the converter has a margin, so the AC output should be maximized and the response time to the power peak should be shortened. It is possible to effectively deal with the deviation of the peak power from the prediction by means such as covering the shortage of the stored power capacity of the battery. In general, the AC output capacity of a power converter can be increased by changing the conversion element used and the cooling performance to a large extent, whereas the number of batteries must be increased in order to increase the storage power capacity of the secondary battery. It is necessary to increase the number of batteries and increase the size of the battery, and the former is more advantageous in terms of downsizing of the secondary battery system and economy.

The relationship between the AC output and the integrated electric energy is
When the annual average value of the power used in the power system is P (kW), the AC output is p '(kW), and the integrated power amount is E (kWh)

[0014]

[Equation 7] log (E / p ′) = (5/7) · log (p ′ / P) + 1.24 ± 0.08 (Equation 7) Alternatively, the annual peak value of the power used in the power system Is P '(kW), AC output is p' (kW), and integrated electric energy is E
When (kWh)

[0015]

(8) log (E / p ′) = (5/7) · log (p ′ / P ′) + 1.455 ± 0.08 ... (Equation 8)

Further, the secondary battery used in the present invention uses a sodium-yellow yellow battery using sodium and sulfur as active materials. Since the energy density is large, the system can be made compact and the output density is high. It is suitable for this purpose because it is large and suitable for peak power, because the long cycle life does not impair the reliability of the power system, there is no self-discharge, and the charge and discharge efficiency is high. . In particular, by repeating the discharge with a large amount of power, or by taking advantage of the characteristic of the sodium-yellow-yellow battery that characteristic deterioration does not easily occur even if the charge and discharge are repeated up to the rated value of the stored power capacity, the power consumption of For the first time, it is possible to rationally design the AC output capacity of the converter and the stored power capacity of the secondary battery according to the characteristics of the power system.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments.

FIG. 1 shows an example of the configuration of a peak power secondary battery system of the present invention. In the figure, 1 is a secondary battery in which one or more sodium-yellow-yellow batteries are assembled. Reference numeral 2 denotes a power converter, which is used to convert the DC power discharged from the secondary battery into AC, or conversely convert the AC power into DC to charge the secondary battery. Further, 3 is a transformer, which is used for voltage conversion in order to match the voltage between the power converter and the power system 4 and for separating the power converter from the system in a direct current manner. Further, 5 is a control / protection device, which is used for controlling the power converter and protecting the system. Also,
FIG. 2 shows an example of a temporal pattern of electric power on a day when an annual peak occurs in the electric power system.

In the first embodiment, when the AC output capacity of the power converter is equal to 6 in FIG. 2, for example, the integrated power amount 7 shown by the broken line in FIG. 2 and the stored power capacity of the secondary battery are converted into the power converter. The value obtained by multiplying the orthogonal transformation efficiency of is approximately matched. By doing so, the capacities of the power conversion device and the secondary battery can be used without excess or deficiency, and the peak power in the broken line portion of FIG. 2 can be covered by the amount of power stored in the secondary battery to effectively cut the peak power.

The required capacity of the power converter differs depending on the peak cut value of the power in the power system, but when the AC output capacity 6 of the power converter changes, the integrated power amount 7 naturally changes. 3 and 4 show this relationship, and FIG. 3 shows the integrated electric energy (E) / AC output capacity.
Fig. 4 shows the relationship between (p) and AC output capacity (p) / annual average value (P) of electric power, and Fig. 4 shows accumulated electric energy (E) / AC output capacity (p) and AC output capacity (p) / power This is the relationship with the annual peak value (P '). In addition, the broken line and the solid line in the figure show the variation range (about ± 20%) of the data for three years from 1992 to 1994 and the average value thereof. If this is expressed by a mathematical formula

[0021]

[Equation 9] log (E / p) = (5/7) · log (p / P) + 1.24 ± 0.08 (Equation 9) However, p and P are kW, E is kWh, or

[0022]

[Equation 10] log (E / p) = (5/7) · log (p / P ′) + 1.455 ± 0.08 (Equation 10) However, p and P ′ are kW and E is kWh. . Therefore, the annual average value P of electric power or the annual peak value P ′ of electric power is obtained from past cases and the growth rate of GNP, and the peak cut amount of electric power required in the electric power system and the AC output capacity of the power converter are calculated. And the value obtained by dividing the integrated electric energy E obtained by inserting these values into the above equation by the orthogonal conversion rate of the power converter may be used as the storage power capacity of the secondary battery.

Specifically, in an electric power system with an annual average power of about 30,000 kW and an expected peak power of about 60,000 kW, the AC output capacity of a power converter with an orthogonal conversion efficiency of 0.95 is set to 3,000 kW,
Storage capacity of sodium-yellow-yellow battery is about 16,600k
By setting Wh, it is possible to cover the electric power of about 57,000 kW, which is 3,000 kW cut from the peak electric power, with the amount of electric power stored in the sodium-yellow-yellow battery.

In the second embodiment, the relationship between the integrated electric energy E / AC output p'and the AC output p '/ annual average value P of the electric power shown in FIGS. 3 and 4, or the integrated electric energy E / AC output p'and AC output p '/ annual peak value P'of electric power are used, and the annual average value P of electric power or the annual peak value P'of electric power obtained in the same manner as in the first embodiment, and , The AC output p ′ is calculated from the integrated power amount E which is equal to the product of the stored power capacity of the secondary battery and the orthogonal conversion rate of the power converter, and the AC output capacity of the power converter is calculated from this AC output p ′. Is also getting bigger. As a result, even if the peak power of the grid becomes larger than expected, the AC output capacity of the power converter has a margin, so the AC output should be full and the response time to the power peak should be shortened. Deviations from the expected peak power can be easily dealt with by means such as covering the shortage of the stored power capacity of the secondary battery. In addition, reactive power processing can be performed by using the margin of the AC output capacity of the power converter. The relational expression between E / p 'and p' / P and the relational expression between E / p 'and p' / P 'are respectively

[0025]

Log (E / p ′) = (5/7) · log (p ′ / P) + 1.24 ± 0.08 (Equation 11) or

[0026]

[Equation 12] log (E / p ') = (5/7) .log (p' / P ') + 1.455 ± 0.08 (Equation 12) where p, p', P and P'are kW and E are given by kWh.

Specifically, in an electric power system with an annual average power of about 90,000 kW and an expected peak power of about 180,000 kW, sodium-
The storage capacity of the yellow-yellow battery is 32,000 kWh, and the AC output capacity of the power converter with an orthogonal conversion efficiency of 0.95 is 14,000 kWh.
By setting W, the peak power can be cut by about 5% with the stored power capacity of the sodium-yellow-yellow battery, and at the same time, there is a margin of about 3% as peak power in the AC output capacity of the power converter. It can effectively deal with the increase of the power from the expected value.

[0028]

According to the first aspect of the present invention, it is possible to process the peak power of the power system by utilizing the capacities of the power converter and the secondary battery that compose the peak power secondary battery system without excess or deficiency. It will be possible. As a result, it is possible to effectively cut the peak of electric power, and it is possible to suppress investment in power generation equipment, power transmission equipment, and substation equipment that constitute the power system.

Further, according to the second invention, even if the peak power of the power system becomes larger than expected, it can be easily dealt with.

[Brief description of drawings]

FIG. 1 is a block diagram of a peak power secondary battery system of the present invention.

FIG. 2 is a characteristic diagram showing an example of a temporal pattern of electric power in the electric power system.

FIG. 3 is a characteristic diagram showing a relationship between an AC output capacity or an AC output and an integrated electric energy.

FIG. 4 is a characteristic diagram showing a relationship between an AC output capacity or an AC output and an integrated electric energy.

[Explanation of symbols]

1 ... Secondary battery, 2 ... Power converter, 3 ... Transformer, 4 ... Power system, 5 ... Control / protection device.

Claims (8)

[Claims] 1. In a secondary battery system for peak power, which is connected to a power system via a power converter, an AC output capacity of the power converter is subtracted from a peak value of power used in the power system. It is characterized in that the daily integrated electric energy of the electric power used in excess of the electric power value and the value obtained by multiplying the stored electric energy capacity of the secondary battery by the orthogonal conversion efficiency of the electric power converter are substantially matched. Rechargeable battery system for peak power. 2. The relationship between the AC output capacity and the integrated electric energy obtained by variably setting the AC output capacity using a temporal pattern of electric power on a past annual power peak occurrence day, according to claim 1. A peak power compatible secondary battery system in which the integrated power amount is calculated using the required value of the AC output capacity in the power system. 3. The method according to claim 2, wherein an annual average value of electric power used in the electric power system is P (kW), the AC output capacity is p (kW), and the integrated electric energy is E (kWh). The peak power correspondence secondary battery system whose relation is given by log (E / p) = (5/7) · log (p / P) + 1.24 ± 0.08 (Equation 1). 4. The electric power used in the electric power system according to claim 2, wherein an annual peak value of electric power is P '(kW), the AC output capacity is p (kW), and the integrated electric energy is E (kWh). At this time, the above-mentioned relationship is given by the following equation: log (E / p) = (5/7) · log (p / P ') + 1.455 ± 0.08 (Equation 2) Secondary battery for peak power system. 5. A secondary battery system connected to a power system via a power converter, using a temporal pattern of power on a past annual power peak occurrence date, from a peak value of power of the power system to the power The relationship between the daily integrated power amount of the power used exceeding the power value obtained by subtracting the AC output of the converter and the AC output is obtained, and the integrated power amount is the stored power amount of the secondary battery. When the capacity is equal to the value obtained by multiplying the orthogonal conversion efficiency of the power converter, the AC output capacity of the power converter is larger than the value of the AC output calculated from the relationship. Secondary battery system. 6. The method according to claim 5, wherein an annual average value of electric power used in the electric power system is P (kW) and the AC output is p ′.
(kW) and the integrated electric energy is E (kWh), the relationship is as follows: log (E / p ′) = (5/7) · log (p ′ / P) + 1.24 ± 0 0.08 ... (Equation 3) A secondary battery system corresponding to peak power. 7. The method according to claim 5, wherein an annual peak value of electric power used in the electric power system is P '(kW), the AC output is p' (kW), and the integrated electric energy is E (kWh). At this time, the above relation is expressed by the following equation: log (E / p ′) = (5/7) · log (p ′ / P ′) + 1.455 ± 0.08 ... (Equation 4) Secondary battery system. 8. The peak power secondary battery system according to claim 1, 2, 3, 4, 5, 6 or 7, wherein the secondary battery is a sodium-sulfur battery.