JP3484621B2 - Power storage system using secondary battery - Google Patents

Description

Detailed Description of the Invention TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to a power storage system using a secondary battery, and in particular, it is suitable for charging a secondary battery when the overload region of the secondary battery is utilized to the maximum for the purpose of system stabilization control and the like. The present invention relates to a discharge control device.

[Prior art]

A secondary battery such as a sodium-sulfur battery (NaS battery) is installed in the power system of the power storage system to level the load (level the demand change of one day), suppress the fluctuation of the system frequency, As a technique used for multiple purposes such as system stabilization control at the time of a system fault, there is a system described in Japanese Patent Laid-Open No. 9-65588, for example.

In this system, the upper and lower limit values of the charge / discharge command are set according to the state of the electric power system and the state of electric power storage. When the system is in a normal state, attach importance to the efficiency of charging and discharging,
Set the upper and lower limits so that the operation is within the rating. When a system accident occurs, the upper and lower limits are widened while considering the amount of stored electricity so that the maximum output of power storage is used. According to this method, the effect of system control in an emergency can be enhanced.

[Problems to be Solved by the Invention]

In the method of the above-mentioned Japanese Laid-Open Patent Publication No. 9-65588, no specific study has been made as to what value the limit output of power storage should be set to. NaS
In a secondary battery such as a battery, there are limit points peculiar to the battery at the time of charging and discharging, so it is necessary to set a value in consideration of them.

When the secondary battery is charged, the battery voltage rises at the final stage of charging, so when the predetermined upper limit voltage is exceeded, charging is generally stopped or a so-called trickle charge protection method is generally used. is there. Prior arts relating to this type of floating charging include JP-A-55-58737, JP-A-57-16539, JP-A-59-500596 and JP-A-6-
There are those described in JP-A 1-136931, JP-A 5-137272 and the like.

However, since the predetermined upper limit voltage is set on the premise of charging at the rated current value, a large current charge for a very short time utilizing the overload region of the secondary battery which is the subject of the present invention. In the above, there is a possibility that the state of charge storage, internal resistance, etc. may change significantly, and the method using the above rated current value could not be applied to charging that makes maximum use of the overload region.

On the other hand, when the secondary battery is discharged, since the secondary battery has an internal resistance, when the discharge current is increased,
Battery voltage drops. Moreover, when the discharge current exceeds a certain value, the power does not increase even if the current is increased, and conversely decreases. In such a case, it is necessary to detect the maximum power point and limit the current so that it does not increase further.

The object of the present invention is to detect the charge limit and discharge limit of the secondary battery and protect them appropriately when the overload output region of the secondary battery is used for the purpose of system stabilization control and the like.
An object of the present invention is to provide a power storage system using a secondary battery that can be charged and discharged at maximum output.

[Means for Solving the Problems]

In order to achieve the above-mentioned object, the present invention is arranged between a secondary battery for storing electric power and a power system and a power converter for converting electric power when the secondary battery is charged or discharged. And a means for detecting the current of the battery, a means for detecting the voltage of the battery, and a control device for controlling the conversion operation of the power converter, for load leveling of the power system, frequency control, and system stabilization control. In a power storage system using a secondary battery, the control device includes means for detecting the discharge limit of the secondary battery, the discharge limit detection means, the battery power from the battery current and the battery voltage detected every predetermined time. We propose a power storage system that uses a secondary battery that is a means for calculating and determining whether or not the battery current and the battery power have increased, and limiting the discharge command when the battery power does not increase even if the battery current increases.

[0010] This invention also is directed, in order to achieve the above object, a power converting a secondary battery for storing electric power, the power at the time of charging or discharging of the secondary battery is disposed between the power system and a secondary battery A converter and means for detecting the battery current,
A power storage system that includes a means for detecting a voltage of a battery and a control device for controlling a conversion operation of a power converter, and uses a secondary battery for load leveling of a power system, frequency control, and system stabilization control. The device has a means for detecting the charge limit of the secondary battery, a means for detecting the discharge limit of the secondary battery, and an internal resistance value of the secondary battery based on the battery current and the battery voltage detected at every predetermined time. And an internal resistance calculating means for calculating the voltage rise value based on the battery current detected at every predetermined time and the internal resistance value calculated by the internal resistance calculating means, It is a means for comparing the value obtained by adding a predetermined margin voltage to the sum of the electric power and the calculated voltage rise value and the battery voltage detection value, and limiting the charging command when the battery voltage detection value is larger, and the discharge limit. When the detection means is at a predetermined time A means for calculating the battery power from the battery current and the battery voltage detected for each, determining whether the battery current and the battery power have increased, and limiting the discharge command when the battery power does not increase even if the battery current increases. A power storage system using a secondary battery is proposed.

In the present invention, when charging the battery, the voltage rise value is calculated from the battery current and the battery internal resistance value measured at each time point, and a predetermined margin voltage is added to the sum of the battery electromotive force and the voltage rise value. The charging limit detecting means for limiting the charging command is provided when the detected battery voltage value becomes larger than the actual battery voltage detected value.

An internal resistance calculating means for calculating the internal resistance value of the battery at each point in time from the battery current and the battery voltage is provided.

At the time of discharging the battery, the battery power is calculated from the battery current and the battery voltage, and it is determined whether the battery current and the battery power have increased. If the battery current has increased but the battery power has not increased, Discharge limit detection means for determining the discharge limit and limiting the discharge command is provided.

As a result, it is possible to prevent the secondary battery from being destroyed due to overcharge during charging, to prevent the current from increasing beyond the maximum power during discharging, and to perform control that makes the best use of the charging / discharging ability of the secondary battery. It becomes possible and the effect of system stabilization can be enhanced.

DETAILED DESCRIPTION OF THE INVENTION

Next, an embodiment of a power storage system using a secondary battery according to the present invention will be described with reference to FIGS.

FIG. 1 is a block diagram showing a system configuration of an embodiment of a power storage system according to the present invention using a NaS battery as a secondary battery. The power storage system of the present embodiment includes a secondary battery module 11, a power converter 12, and a control device 13, and via a power conversion transformer 14,
It is connected to the power grid.

The secondary battery module 11 is connected in series and / or
Or it consists of multiple NaS batteries interconnected in parallel. The power converter 12 is configured by using a semiconductor element such as an IGBT or a diode and converts DC power into AC power or AC power into DC power. The control device 13 creates a control signal for setting a predetermined charging power or discharging power, or creates a control signal for stabilizing the system in the event of a system fault, and outputs the control signal to the power converter 12.

The control device 13 mainly comprises a power control section 32.
A current control unit 31, a pulse generation unit 34, and a system stabilization control unit 33.

FIG. 2 shows a power control unit (APR: AutomaticPo).
2 is a block diagram showing an example of the configuration of the werRegulator) 32. FIG. The voltage calculator 26 calculates the d-axis voltage detection value Vd1 and the q-axis voltage detection value Vq1 from the output of the AC voltage detecting means 21. The current calculator 27 calculates the d-axis current detection value Id1 and the q-axis current detection value Iq1 using the output of the AC current detection means 22. The power calculator 28 calculates the power detection value P1 based on the outputs of the voltage calculator 26 and the current calculator 27. The power control unit 32 (APR) compares the command value of the charging / discharging power with the detected value of the actual charging / discharging power, and creates a current command value for the power converter 12 so as to eliminate the difference.
More specifically, the difference between the command value P0 of the charging / discharging power and the detected power value P1 is obtained and proportionally integrated to remove the offset amount, and the d-axis current command value Id0 is created.

FIG. 3 shows a current controller (ACR: Automatic Cu).
3 is a block diagram showing an example of a configuration of a rrentRegulator) 31. FIG. The current control unit 31 (ACR) compares the current command value output by the power control unit 32 with the actual current detection value output by the current calculation unit 27, and outputs the current to the power converter 12 so as to eliminate the difference. Create an output voltage command value.

Specifically, as shown in FIG. 3, the difference between the d-axis current command value Id0 and the d-axis current detection value Id1 is calculated, proportionally integrated, and the non-interference term from the q-axis current detection value Iq1 is calculated. In addition, by adding the d-axis voltage detection value Vd1 as a feedforward term,
The d-axis voltage command value Vdh. The q-axis voltage command value Vqh is also created similarly to the d-axis. However, in this embodiment, since the reactive power control is not performed, the q-axis current command value Iq0 is zero.

The pulse generating section 34 determines the d-axis voltage command value Vdh.
And q-axis voltage command value Vqh are converted into three-phase voltage command values,
A PWM (Pulse Width Modulation) gate pulse signal to the power converter 12 is created.

FIG. 4 is a block diagram showing an example of the configuration of the system stabilization control unit 33. The system stabilization control unit 33
Create a charging / discharging command so as to suppress system sway caused by an accident. More specifically, the frequency calculator 25
Calculates the system frequency detection value f based on the output of the AC voltage detecting means 21. The system stabilization controller 33 uses the system frequency detection value f as an input signal, cuts high frequencies with a low-pass filter, cuts low frequencies with a reset filter, performs phase compensation and gain compensation, and outputs a control command. . The control command is added to the charge / discharge command value.

FIG. 5 is a time chart showing an example of the operation of the system stabilization control unit 33 of FIG. The upper part shows the frequency fluctuation caused by the system fault, and the lower part shows the charge / discharge output of the secondary battery module 11 of the power storage system for coping with it. In FIG. 5, the battery power is positive on the discharge side and is controlled so that the battery is charged when the frequency is higher than the reference value and discharged when the frequency is lower than the reference value. At this time, the greater the change in battery power, the greater the effect of system control. Therefore, it is desirable to maximize the charge / discharge power of the secondary battery module 11. During steady operation, the charging and discharging efficiency of the secondary battery is prioritized, so charging and discharging will be within the battery rating, but in the event of a system failure,
Within the capacity of the power converter 12, that is, ± 4 in this example.
Maximum charge / discharge is performed within the range of 000 kW.

However, it is necessary to consider the charge limit and discharge limit of the secondary battery and set the current command limiter 44 so as not to exceed these limits. Next, the charge limit detecting means 41 and the discharge limit detecting means 42 for that purpose
The operation of will be described.

FIG. 6 is a flow chart showing an example of the detection procedure of the charge limit detection means 41. The charge limit detecting means 41 detects the charge limit by using the outputs of the battery voltage detecting means 23 and the battery current detecting means 24 and sets the lower limit Idmin of the d-axis current command value according to the detection procedure of FIG.

Step 101: First, it is checked whether the battery current Idc is being charged or discharged, depending on whether the battery current Idc is positive or negative. The battery current is defined as positive on the discharging side and negative on the charging side.

Step 102: If not charging, Idm
Let in be the lower limit value Id1 determined by the converter capacity.

Step 103: When charging, it is judged whether the battery voltage Vdc is higher than the upper limit voltage Vth defined by the formula ( 1 ) Vth = E0.Ns + Idc.r0.Ns + α (1).
To do. Here, E0 is a secondary battery electromotive force, r0 is a secondary battery internal resistance, Ns is the number of series of secondary batteries, and α is a margin voltage.

Step 104: If Vdc is larger than Vth, Idmin is set to the d-axis current detection value Id1 to prevent the charging current from further increasing.

In the prior art as well, the measure for overcharge protection was taken based on the rise of the battery voltage as described above.
Since the second term on the right side of the above is a constant value assuming rated charging, it was not possible to cope with overload operation.

On the other hand, as in this embodiment, when the battery current, the battery voltage, and the internal resistance are measured in real time, and the charging / discharging limit point is determined in consideration of the voltage increase due to the actual internal resistance, the Overcharge protection during load operation becomes possible.

The measurement of the battery voltage is not limited to one for the entire secondary battery module 11. When the battery voltage is high, the voltage may be detected at several points. In that case, the formula (1) may be determined for each detection voltage, and if any of the voltage detection values reaches the limit point, the control may be performed so as to limit the voltage.

FIG. 7 is a graph showing an example of the relationship between the discharge voltage and the battery voltage and the discharge power. Next, the discharge limit detection means 42 will be described. As shown in FIG. 7, as the discharge current increases, the voltage drop due to the internal resistance increases, and the discharge power decreases conversely when the discharge power exceeds a certain limit point. Therefore, check whether the battery current is increasing and whether the battery power is increasing,
It is determined whether or not the limit point is exceeded, and the current command limiter 44 is set.

FIG. 8 is a block diagram showing an example of the structure of the internal resistance calculating means. First, the output Vdci of the battery voltage detecting means 23 and the output Idci of the battery current detecting means 24 are respectively passed through a low pass filter to obtain the battery current Idc and the battery voltage Vdc, and the battery power Pdc is obtained from the product of them.

FIG. 9 is a flow chart showing an example of the detection procedure of the discharge limit detection means. The values Idcx and Pdcx obtained by passing the battery current Idc and the battery power Pdc shown in FIG. 8 through a delay element of, for example, about 10 ms are obtained, and the discharge limit is detected according to the detection procedure shown in FIG.

Step 111: First, it is checked whether or not the battery is being discharged depending on whether the battery current Idc is positive.

Step 112: If not discharging, Idm
Let ax be the upper limit value Idh determined by the capacity of the converter.

Step 113: When discharging, the battery current Idc is compared with the past value Idcx to check whether or not the current is increasing.

Step 114: If the current is increasing, check whether the battery power Pdc is larger than the past value Pdcx.

Step 115: If the battery power has not increased, it is judged that the discharge limit point has been exceeded, that is, as shown in FIG.
Of the d-axis current detection value I
Set to d1 to prevent further increase of discharge current.

During system stabilization control, as shown in FIG. 5, the charging / discharging near the limit is repeated in a short time. Therefore, if the charging / discharging limit detecting means as described above is provided, the secondary It is possible to perform control using the full overload region up to the limit performance of the battery, and enhance the system control effect.

As for the internal resistance value used in the charge limit detecting means 41, it has been conventionally considered that a fixed value based on a value measured in a normal state may be basically used. If you expect some fluctuations in resistance, set a small fixed value,
This is because it is considered that the result of control will be hardened on the safe side.

However, in the overload region of the secondary battery as in the present invention, it is necessary to constantly calculate the internal resistance in order to transiently exert the maximum charge / discharge capacity. The internal resistance calculating means 42 calculates an actual internal resistance from the battery current and the battery voltage measured at every predetermined time, and outputs the internal resistance value to the charge limit detecting means 41. By constantly measuring and updating the internal resistance value in this way, charging and discharging can be performed with the maximum power according to the actual state of the secondary battery.

【The invention's effect】

According to the present invention, when the power storage system using the secondary battery is used for the purpose of stabilizing the system,
By detecting the charge limit and discharge limit of the secondary battery and controlling the charge and discharge with the maximum output of the secondary battery, the system stabilization effect can be further enhanced.

[Brief description of drawings]

FIG. 1 is a block diagram showing a system configuration of an embodiment of a power storage system according to the present invention using a NaS battery as a secondary battery.

FIG. 2 is a block diagram showing an example of a configuration of a power control unit (APR).

FIG. 3 is a block diagram showing an example of a configuration of a current control unit (ACR).

FIG. 4 is a block diagram showing an example of a configuration of a system stabilization control unit.

5 is a time chart showing an example of the operation of the system stabilization control unit of FIG.

FIG. 6 is a flowchart showing an example of a detection procedure of a charge limit detection means.

FIG. 7 is a graph showing an example of the relationship between battery voltage and discharge power with respect to discharge current.

FIG. 8 is a block diagram showing an example of a configuration of an internal resistance calculation means.

FIG. 9 is a flowchart showing an example of a detection procedure of a discharge limit detection means.

[Explanation of symbols]

11 Secondary battery module 12 Power converter 13 Control device 14 Power conversion transformer 21 AC voltage detection means 22 AC current detection means 23 Battery voltage detection means 24 Battery current detection means 25 Frequency calculation means 26 AC voltage calculating means 27 AC current calculation means 28 AC power calculation means 31 Current Control Unit (ACR) 32 Power control unit (APR) 33 System stabilization controller 34 Pulse generator 41 Charge limit detection means 42 Discharge limit detection means 43 Internal resistance calculation means 44 Current command value limiter

Continuation of front page (56) Reference JP-A-9-19073 (JP, A) JP-A-7-240235 (JP, A) JP-A-8-140285 (JP, A) JP-A-9-65588 (JP , A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) H02J 3/00-5/00 H02J ⁷ /00-7/12 H02J 7/34-7/36

Claims (2)

(57) [Claims] 1. A secondary battery for storing electric power, a power converter arranged between a power system and the secondary battery for converting electric power when the secondary battery is charged or discharged, and a current of the battery is detected. Means, a means for detecting the voltage of the battery, and a control device for controlling the conversion operation of the power converter, and the secondary battery for load leveling, frequency control, and system stabilization control of the power system. In the power storage system using the, the control device comprises a means for detecting the discharge limit of the secondary battery, the discharge limit detection means, the battery power from the battery current and the battery voltage detected every predetermined time. A power storage system using a secondary battery, which is a means for calculating and determining whether the battery current and the battery power have increased, and limiting the discharge command when the battery power does not increase even if the battery current increases. Beam. 2. A secondary battery which stores electric power, a power converter which is arranged between a power system and the secondary battery, and which converts electric power when the secondary battery is charged or discharged, and detects a current of the battery. Means, a means for detecting the voltage of the battery, and a control device for controlling the conversion operation of the power converter, and the secondary battery for load leveling, frequency control, and system stabilization control of the power system. In a power storage system using the, the control device, means for detecting the charge limit of the secondary battery, means for detecting the discharge limit of the secondary battery, the battery current and the battery detected every predetermined time An internal resistance calculating means for calculating an internal resistance value of the secondary battery based on a voltage, the charging limit detecting means, the battery current detected at every predetermined time and the internal resistance calculating means Resistance and If the battery voltage detection value is greater than the battery voltage detection value, the voltage increase value is calculated based on the battery electromotive force and the value obtained by adding a predetermined margin voltage to the sum of the battery electromotive force and the calculated voltage increase value. Is a means for limiting the charge command, the discharge limit detecting means calculates the battery power from the battery current and the battery voltage detected every predetermined time, to determine whether the battery current and the battery power has increased, A power storage system using a secondary battery, which is a means for limiting a discharge command when the battery power does not increase even if the battery current increases.