JP2023019165A - Charge/discharge control device and charge/discharge control program - Google Patents

Abstract

[Problem] To discharge or charge electric power stored in a power storage unit in response to load fluctuations, especially increases or decreases in load that cannot be handled by private power generators, and control the amount of discharge and charge to be appropriate. . [Solution] When the load suddenly increases, the power storage section 12 starts discharging, and as the power generation amount of the power generation unit 10 increases, the discharge is gradually decreased, so that the power generation amount of the power generation section 16 increases. By forcibly terminating the discharge when the proportionally increasing rate of change in frequency falls below a predetermined threshold, the power generation amount is returned to the amount before the sudden load change caused by droop control. did. [Selection diagram] Figure 4

Description

The present invention relates to a charge/discharge control device and a charge/discharge control program for a power storage unit that assists in-house power generation.

Patent Document 1 describes a power generation unit that is normally connected to a commercial system and is driven by a prime mover independently from the commercial system when the commercial system fails, etc.; In a method for operating a private power generation facility equipped with a charge/discharge control device for controlling charge/discharge of a storage unit, when an increase in load is detected, the power storage unit outputs (discharges) the increased amount of load to the power storage unit. After that, the output of the power storage unit is gradually reduced at a speed below the allowable fluctuation load of the power generation unit, and when the output of the power storage unit becomes 0, the load sharing process is terminated. A method of operating a private power generation facility is described which is characterized by improving the load-throwing rate of the power generation facility. It should be noted that the same effect can be obtained even when the load is reduced.

Japanese Patent Application Laid-Open No. 2007-6595

However, in the conventional operating method, when an increase in load is detected, all the power temporarily stored in the power storage unit for the increase is discharged. In other words, the power storage unit needs to have a capacity capable of charging an amount corresponding to the load increase in advance.

Further, when the private power generator has a droop control function, the frequency during operation may deviate from the frequency set as the reference depending on the output of the private power generator. Due to this frequency deviation, the power generated by the in-house power generator is stabilized with less power than the required amount of power (occurrence of an offset corresponding to the frequency deviation). This offset will continue to discharge from the power storage unit.

The present invention discharges or charges the electric power stored in the electric power storage unit in response to load fluctuations, particularly an increase or decrease in the load that cannot be handled by the in-house power generator, and controls the amount of discharge/charge to be appropriate. An object of the present invention is to obtain a charge/discharge control device and a charge/discharge control program that can

The charge/discharge control device according to the present invention generates power by driving the prime mover, and when synthesizing the power generated by itself and the power generated by others, changes the target frequency according to the load of the power generation output of itself. a power generator having a droop control function that adjusts the load factor by increasing the load factor; In the device, the power storage unit is controlled when the amount of power required by the load changes to increase or decrease beyond a reference level, resulting in excess or deficiency in the amount of power generated by the power generation unit. , the power generation unit is discharged when the power generation is insufficient, and is charged when the power generation is excessive. a charging/discharging control unit that controls to end discharging or charging by the power storage unit when a corresponding predetermined condition is established.

According to the present invention, it is possible to meet the required load with only the amount of power generated by the power generation unit in a state where the target frequency that changes by the droop control function is stable and the power storage unit is not discharged or charged. As the predetermined condition, various means for avoiding the continuation of discharging can be used, such as the rate of change in frequency, change in charge/discharge switching frequency, predetermined time (timer), and the like.

The charge/discharge control device according to the present invention generates power by driving the prime mover, and when synthesizing the power generated by itself and the power generated by others, changes the target frequency according to the load of the power generation output of itself. a power generator having a droop control function that adjusts the load factor by increasing the load factor; In the device, the power storage unit is controlled when the amount of power required by the load changes to increase or decrease beyond a reference level, resulting in excess or deficiency in the amount of power generated by the power generation unit. The power generation unit discharges when power generation is insufficient and charges when power generation is excessive, and the rate of change in frequency during operation of the power generation unit falls below a predetermined value while the power is being discharged or charged from the power storage unit. a charge/discharge control unit that controls to terminate the discharge or charge from the power storage unit when the power storage unit is discharged or charged.

According to the present invention, for example, by controlling the discharge of the power storage unit using the frequency fluctuation of the power generation unit, the target frequency that is changed by the droop control function is stabilized (the rate of change is less than a predetermined value), and the electric power is generated. The discharge or charge by the storage unit can be terminated and the power generation amount of the power generation unit alone can meet the required load. The rate of change of the frequency is directly related to the power generated by the power generation unit, and it is possible to accurately grasp the discharge end timing.

The same applies when the load decreases. After starting charging to the power storage unit, the charging of the power storage unit should be terminated in a state where the target frequency, which is changed by the droop control function, is stabilized (the rate of change is less than a predetermined value). Just do it.

In the present invention, the charge/discharge control unit reduces the rate of change of the frequency during operation of the power generation unit to a predetermined value or less on the premise that the frequency during operation of the power generation unit is equal to or greater than a predetermined threshold value. It is characterized by judging whether or not it has become.

For example, malfunction due to frequency hunting can be prevented. From a microscopic point of view, the frequency change rate may fluctuate greatly, so it is useful to set the operating frequency of the power generation unit to a predetermined threshold value or higher for so-called masking.

The present invention is characterized in that the discharge or charge by the power storage unit by the charge/discharge control unit is gradually decreased in proportion to the elapsed time from the point of time when the discharge or charge by the power storage unit is terminated, and the end state is reached.

For example, when the load increases, the load is gradually decreased at a constant rate of change, so that the power storage unit does not repeat discharge and discharge stop, and the power generation amount of the power generation unit gradually increases and gradually converges (power generation The power generation amount of the part = the required load). It can be handled with the minimum amount of discharge required.

The present invention is characterized in that the charge/discharge is stopped immediately when the charge/discharge control unit terminates the discharge or charge by the power storage unit.

For example, when the load is increased, if the discharge is terminated immediately, the difference between the power generation amount of the power generation unit and the load remains, and the discharge and discharge stop of the power storage unit are repeated several times, but the difference is Since it gradually converges (amount of power generated by the power generation unit=required load), the charge/discharge 0 (charge/discharge end) state can finally be achieved. At least, the amount of discharge can be reduced more than when discharging is continued.

A charge/discharge control program according to the present invention operates a computer as the charge/discharge control unit.

As described above, according to the present invention, the electric power stored in the electric power storage unit is discharged or charged in response to load fluctuations, particularly an increase or decrease in the load that cannot be handled by the in-house power generator, and an appropriate discharge amount is obtained.・The effect of being able to control the amount of charge can be obtained.

FIG. 3 is a functional block diagram for power generation/discharge control during grid isolation in the power generation system according to the present embodiment; FIG. 4 is a droop control function characteristic diagram applied to the power generation system according to the present embodiment; 4 is a flow chart showing a power generation/discharge control routine during grid isolation in the power generation system according to the present embodiment. (A) is a graph of power and frequency transition characteristics during grid isolation in the power generation system according to the present embodiment, and (B) is an enlarged view of the characteristics of the frequency change rate near the discharge end determination threshold. FIG. 4 is a frequency-change rate characteristic diagram for determining the discharge end time; FIG. 10 is a diagram of power and frequency transition characteristics during grid isolation according to a comparative example;

FIG. 1 is an overall configuration diagram of a power generation system provided with a power generation unit 10 and a power storage section 12 according to this embodiment.

The power generation unit 10 includes a prime mover 14 and a power generation section 16 that generates power by driving the prime mover 14 .

A gas engine, a gas turbine engine, a diesel engine, or the like can be used as the prime mover 14, and can be applied to a cogeneration system.

Also, the power storage unit 12 has a function of storing power, and may be any facility as long as it has a quick response characteristic. An ion capacitor, a lithium ion secondary battery, or the like can be used. Here, the quick response characteristic of the power storage unit 12 means, for example, the characteristic that the prime mover 14 can be charged and discharged in a shorter time than the output response time.

Functions for controlling the prime mover 14 and the power generation section 16 will be mainly described below, but each block is not limited to the configuration, but is an example for describing the function.

As shown in FIG. 1 , a droop control section 18 is connected to the power generation section 16 and the prime mover 14 . A droop control unit 18 controls driving of the prime mover 14 (droop control).

More specifically, the droop control unit 18 acquires the output information of the power generation by the power generation unit 16, sets the target frequency based on a predetermined frequency-output characteristic diagram (see FIG. 2), and adjusts the target frequency to the set target frequency. Based on this, the driving of the prime mover 14 is controlled.

Droop control is a control for adjusting the target frequency according to the output and matching the frequency of another power generation system (including commercial power supply) to generate power. Backflow of electric power can be prevented.

The power generation unit 16 discharges the generated power through the output unit 20 and supplies the power to the multiple loads 22 .

Here, the power generation unit 10 includes a frequency detection section 24 , detects the frequency based on output information from the power generation section 16 acquired by the droop control section 18 , and sends the detected frequency to the control section 26 .

The control unit 26 controls the power generation amount of the power generation unit 16 based on the frequency (which varies depending on the load) detected by the frequency detection unit 24 .

On the other hand, the power storage unit 12 is charged with power from a charging power source (including the power generation system in FIG. 1, other power generation systems, commercial power, solar power generation, etc.) and stores power, and is a charge/discharge control device. 28 controls to supply power to multiple loads 22 .

By being connected to the control unit 26 of the power generation unit 10, the charge/discharge control device 28 acquires information related to power generation by the power generation unit, and also receives independent operation instruction information and load information (here, the premises frequency), It controls the power generation of the power generation unit 16 and the discharge of the power of the power storage unit 12 when a predetermined condition is satisfied. Predetermined conditions will be described later.

(Sudden load change)

Here, if the load applied to the prime mover 14 suddenly changes (for example, increases), the frequency of the generator 16 may exceed the limit frequency and the prime mover 14 may malfunction and stop. An example of such a rapid increase in load is a power outage. In the charge/discharge control device 28, for example, upon receiving a self-sustained operation instruction and, for example, when the premises frequency reaches the lower limit level (establishment of a predetermined condition), the above-mentioned "load rapid increase" is recognized, and the power generation unit 16 generates power. In order to compensate for the above, discharge control of the power storage unit 12 is performed.

In the following, the control of the charge/discharge control device 28 will be described by taking a sudden increase in load as an example. ), if the charging control of the power storage unit 12 is performed, it is possible to perform the same control as when the load suddenly increases.

The charge/discharge control device 28 instructs the power storage unit 12 to discharge when the frequency of the power generation unit 16 exceeds a predetermined limit frequency.

In addition, the charge/discharge control device 28 performs control to decrease the amount of discharge from the power storage unit 12 as the output of the prime mover 14 increases.

That is, in the charge/discharge control device 28, when an instantaneous load fluctuation (increase in this case) occurs, the rapid response characteristic of the power storage unit 12 is utilized to store power so as not to exceed the upper limit of the characteristic of the prime mover 14. It controls the discharge amount of the unit 12 .

Here, the power generation system used in the cogeneration system generally has a tolerance for load fluctuation characteristics (instantaneous load fluctuations), and cannot cope with instantaneous load fluctuations that exceed the characteristics during isolated operation due to system separation.

Therefore, in the present embodiment, when the load on the power generation unit 16 increases (or decreases), the frequency of the power generation unit 16 is detected, and based on the frequency determined from the allowable amount for the load fluctuation characteristics of the prime mover 14, the electric power By performing control to discharge (or charge) the storage unit 12, it is possible to prevent the engine 14 from abnormally operating and stopping due to an instantaneous load change.

By the way, the power generation unit 10 of the present embodiment includes the droop control section 18 as described above, and depending on the output of the power generation section 16, the target frequency is adjusted by the droop control, and the target frequency during operation after a rapid increase in load is adjusted. The frequency may deviate from the frequency to accommodate the total power consumption (power requirement) of the load.

Due to this frequency shift, the generated power of the power generation unit 16 is stabilized at a small amount of generated power with respect to the required amount of power (occurrence of an offset corresponding to the frequency shift (see FIG. 6)).

Due to this offset, the electric power storage unit 12 continues to discharge. For example, the electric power stored in the electric power storage unit 12 temporarily becomes 0 (storage amount 0), and a subsequent discharge request can be quickly responded to. It may lead to a situation that cannot be done.

Therefore, in the present embodiment, in the control for decreasing the amount of discharge from the power storage unit 12 as the output of the prime mover 14 increases, attention is focused on the frequency that increases in proportion to the increase in the amount of power generated by the power generation unit 16. A decrease in the frequency change rate that occurs when the power generation unit 16 attempts to stabilize the power generation amount based on the target frequency is monitored. ≤ Rs), discharge from the power storage unit 12 is terminated (see FIGS. 4 and 5, details will be described later).

When the discharge from the power storage unit 12 ends, the power generation unit 16 continues power generation corresponding to the load, and as a result, the power of the power generation unit 16 can cover the power consumption of the load. In addition, the target frequency gradually returns to the default value before the power failure according to the power generation of the power generation unit 16, so that the control state before the power failure is restored thereafter.

The operation of this embodiment will be described below.

(Discharge control during sudden load increase)

FIG. 3 is a flow chart showing a power generation/discharge control routine during grid isolation when the load of the power generation unit 16 suddenly increases.

When the power generation/discharge control during system isolation based on the instruction for isolated operation is started, in step 100, when the in-plant frequency reaches the lower limit level, the power storage unit 12 starts discharging, and the process proceeds to step 102.

At step 102, it is determined whether or not the in-plant frequency has returned to the rate-of-change determination frequency or higher. Specifically, it is determined whether or not it is within the range shown in the dotted circle frame in FIG. 4(A). That is, step 102 is a so-called masking measure for not capturing the rate of change in frequency fluctuation due to noise or the like during the period when it takes a considerable amount of time for the frequency to stabilize.

If a negative determination is made in step 102 , the process proceeds to step 104 . A step 104 determines whether or not a predetermined period of time has elapsed, and returns to the step 102 if a negative determination is made. Further, if the determination in step 104 is affirmative, it is assumed that there is another reason why the in-plant frequency does not return to the rate-of-change determination frequency or higher (for example, insufficient remaining capacity of the power storage unit 12), and the process proceeds to step 120. , an error is reported, and this routine ends.

On the other hand, if the determination in step 102 is affirmative, the process proceeds to step 106 to determine whether or not the determination period (periodic calculation period set by i on the horizontal axis in FIG. 5) has elapsed. stand by.

Here, if the determination in step 106 is affirmative, the process proceeds to step 108 to calculate the rate of change Ri of the local frequency.

In the next step 110, the change rate threshold value Rs stored in advance is read, and the process proceeds to step 112 to compare the calculated change rate Ri and the threshold value Rs (Ri:Rs).

If it is determined that Ri>Rs in the comparison at step 112, it is determined that the rate of change Ri is not the discharge end time, the process returns to step 106, and the above steps are repeated. That is, the calculation of the rate of change Ri and the comparison with the threshold value Rs are repeated every fixed time i.

Further, when it is determined that Ri≦Rs in the comparison at step 112 , it is determined that the change rate Ri is the discharge end time, and the process proceeds to step 114 .

At step 114, discharging from the power storage unit 12 is terminated.

It is preferable that this discharge termination control be gradually terminated while maintaining the rate of change when the discharge power decreases. The discharge may be controlled so as to decrease the amount of discharge based on the rate of change Ri after crossing the threshold value shown in FIG. Discharge may be terminated immediately when Ri≤Rs. Useless discharge can be suppressed more than when there is no .

That is, in the present invention, in the droop control in the power generation unit 10, the target frequency is changed, the power generation amount of the power generation unit 16 cannot obtain the amount of power required for consumption of the load 22, and the discharge of the power storage unit 12 continues. The main purpose is to prevent

Therefore, in addition to the main purpose, the control for the termination of the discharge is an additional control for a more stable power supply. , stepwise) can be applied as a means of terminating the discharge.

In the next step 116, it is determined whether or not a predetermined time has passed. This is done by predicting in advance the amount of time that the power generation unit 16 will stabilize (corresponding to the power consumption of the load 22), waiting until the predetermined time elapses (negative determination in step 116), and determining that the predetermined time has elapsed. When determined (affirmative determination in step 116), the process proceeds to step 118 to determine whether or not the power consumption of the load 22 and the power generated by the power generation section 16 match.

If the determination in step 118 is negative, the reason why the power consumption of the load 22 and the power generated by the power generation unit 16 do not match even after a predetermined period of time that is predicted to stabilize is due to, for example, droop control failure, etc. Since other abnormalities are conceivable, the routine proceeds to step 120 to perform error notification and terminate this routine.

On the other hand, if the determination in step 118 is affirmative, it is determined that the power generated by the power generation section 16 is normal, and this routine ends.

(Example)

FIG. 4 shows changes in the generated power of the power generation unit 16 and the discharge power from the power storage unit 12 based on load fluctuations (passage of time) when the power generation system of the present embodiment is used, and the frequency of the power generation unit 16. It is an example of a characteristic diagram showing the transition of .

The origin of the time axis (horizontal axis) indicates the time when a power failure or the like occurred and the load decreased. Although the power generation unit 16 generates power as the load increases sharply, the power generation unit output cannot cope with the load and the frequency also drops.

On the other hand, the charge/discharge control device 28 instructs discharge from the power storage unit 12 in accordance with the amount of power generated by the power generation unit 16 that is insufficient.

Thereafter, the power consumption of the load is maintained by gradually increasing the power of the power generation unit 16 and decreasing the amount of discharge from the power storage unit 12 when the frequency is restored (switched from decrease to increase). .

If the power generated by the power generation unit 16 reaches the power consumption of the load 22 as it is, the discharge of the power storage unit 12 will end. and the target frequency may be adjusted as the load increases.

As a result, as shown in the comparative example of FIG. 6, the generated power of the power generation unit 16 is stabilized at a small amount of generated power with respect to the required amount of power, and the discharge from the power storage unit 12 is continued. Note that the comparative example of FIG. 6 is a characteristic diagram when the load suddenly increases when the power generation system of the present embodiment is not used.

On the other hand, in the present embodiment, the frequency dependent on the power generation output of the power generation unit 16 focuses on the time zone in which the target frequency is stabilized, and as shown in FIG. Discharge from the power storage unit 12 is forcibly terminated at the time when the calculated change rate Ri≤threshold value Rs).

FIG. 5 is a characteristic diagram showing the transition of the rate of change Ri calculated at regular intervals within the circled frame in FIG. 4(B). It can be seen that the rate of change Ri gradually decreases after a predetermined period of time. Since this time is the time when the frequency reaches a stable level, the threshold value Rs is set to a rate of change that is presumed to be the level at which the frequency is stabilized.

When the calculated rate of change Ri crosses the threshold value Rs, the discharge from the power storage unit 12 is terminated.

As a result, the power output of the power generation unit 16 matches the power consumption of the load 22, and wasteful discharge from the power storage unit 12 can be suppressed.

(Charging control when the load suddenly decreases)

In the present embodiment, as an example of a sudden change in load, the control of discharging when the load suddenly increases has been described in detail. Since control according to the flowchart of FIG. 3 (for example, charging control based on monitoring of the rate of change of frequency) may be performed, detailed description of charging control when the load suddenly decreases is omitted here.

Note that, in the present embodiment, charge/discharge control based on monitoring of the frequency change rate has been described. More specifically, when the load suddenly increases, the power storage unit 12 starts to discharge, and as the power generation amount of the power generation unit 10 increases, the discharge is gradually reduced to reduce the power generation amount of the power generation unit 16. When the rate of change in the frequency, which rises in proportion to the increase, falls below a predetermined threshold, discharge is forcibly terminated, returning the amount of power generated before the sudden load change caused by droop control. It was configured.

On the other hand, the trigger for forced discharge termination in the power storage unit 12 is not limited to the change rate of the frequency (in-plant frequency). In addition to the rate of change in frequency, a timer or the like may be used to simply end charging/discharging when a certain period of time elapses after starting charging/discharging. The fixed time may be uniquely determined according to the specifications of the power generation system, etc., or may be set in advance using a plurality of factors such as load fluctuation information, power generation capacity information, remaining amount information of the power storage unit 12, etc. The time may be set each time by a calculation program (including AI such as machine learning).

Also, the charging/discharging switching timing itself of the frequency-output characteristic of droop control may be changed. That is, when a predetermined condition that the power generation unit 16 can respond to the load power is satisfied during discharging (or charging) of power by the power storage unit 12, discharging (or charging) from the power storage unit 12 is terminated. should be controlled to

10 Power generation unit (private power generator)
REFERENCE SIGNS LIST 12 power storage unit 14 prime mover 16 power generation unit 18 droop control unit 20 output unit 22 load 24 frequency detection unit 26 control unit 28 charge/discharge control device

In the present invention, the charging/discharging control unit gradually reduces the discharging or charging in proportion to the elapsed time from the time when it is time to terminate the discharging or charging by the power storage unit to reach the termination state. It is characterized by

In the present invention, the charging/discharging control section is characterized in that the charging or discharging is stopped immediately at the time when the charging or discharging by the power storage section is finished.

Claims (6)

Droop control that adjusts the load factor by changing the target frequency according to the load of the self-generated output when generating power by driving the prime mover and synthesizing the power generated by itself and the power generated by others. A charge/discharge control device for controlling charge/discharge of the power storage unit in a private power generation device comprising a power generation unit having a function and an electric power storage unit capable of charging/discharging electric power,
When the amount of power required by the load increases or decreases beyond a reference level, and the amount of power generated by the power generation unit becomes insufficient or excessive, the power storage unit is controlled to increase or decrease the amount of power generated by the power generation unit. The battery is discharged when power generation is insufficient and charged when power generation is excessive, and the power generated by the power generation unit during the charging or discharging of the power from the power storage unit is a predetermined condition under which the power required by the load can be met. a charge/discharge control unit that controls to end the discharge or charge by the power storage unit when
A charge/discharge control device having Droop control that adjusts the load factor by changing the target frequency according to the load of the self-generated output when generating power by driving the prime mover and synthesizing the power generated by itself and the power generated by others. A charge/discharge control device for controlling charge/discharge of the power storage unit in a private power generation device comprising a power generation unit having a function and an electric power storage unit capable of charging/discharging electric power,
When the amount of power required by the load increases or decreases beyond a reference level, and the amount of power generated by the power generation unit becomes insufficient or excessive, the power storage unit is controlled to increase or decrease the amount of power generated by the power generation unit. The battery is discharged when power generation is insufficient, and charged when power generation is excessive. a charge/discharge control unit that controls to end discharging or charging from the power storage unit;
A charge/discharge control device having The charging/discharging control unit determines whether the rate of change of the operating frequency of the power generating unit has become less than or equal to a predetermined value on the premise that the operating frequency of the power generating unit is equal to or greater than a predetermined threshold value. 3. The charge/discharge control device according to claim 2, which determines. 4. The charge/discharge control unit according to any one of claims 1 to 3, wherein from the time when the discharge or charge by the power storage unit by the charge/discharge control unit is to be terminated, the power is gradually decreased in proportion to the elapsed time to reach the termination state. 2. The charge/discharge control device according to claim 1. 4. The charge/discharge control device according to any one of claims 1 to 3, wherein the charge/discharge control unit stops discharging immediately at the time when the charge/discharge control unit terminates discharging or charging by the power storage unit. the computer,
Operate as the charge/discharge control unit according to any one of claims 1 to 5,
Charge/discharge control program.

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