JPH0783555B2 - Photovoltaic power generator control method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a control method for a photovoltaic power generator that supplies power to a load together with an existing system power supply, and particularly, to suppress the frequency of controlling the number of operating system power supplies. The present invention relates to a method for controlling a photovoltaic power generation device that prevents a reduction in fuel efficiency of a system power supply.

[Prior Art] FIG. 4 is shown in, for example, Japanese Patent Application Laid-Open No. 58-175929 and Japanese Patent Application No. 62-62.
FIG. 15 is a block diagram showing a conventional solar power generation device having a grid-connected battery, which is described in, for example, the specification of JP-A-15213.

In the figure, (1) is a solar cell, (2) is a battery that is connected in parallel with the solar cell (1) to absorb the output fluctuation of the solar cell (1), and (3) is the output of the solar cell (1). shunt for detecting a current is, (4) the shunt for detecting a charge-discharge current I _B of battery (2), (5) the solar cell (1)
And an inverter that converts DC power supplied from the battery (2) into AC power, that is, inverter output P _I.

(6) is a control device for generating an inverter output command Pr to control the inverter output P _I on the basis of the solar cell output current Is and the charge-discharge current I _B, the solar cell output current Is and the charge-discharge current I _B a power converting means for obtaining a photovoltaic output Ps and charge-discharge electric power P _B from the charge and discharge current I and the measuring means for determining the held electrical quantity AH of the battery (2) on the basis of _B, a predetermined sampling period [Delta] T (seconds) for each Inverter output command Pr
And a calculation program for generating

Reference numeral (7) is an existing system power supply connected to the inverter (5), which is composed of, for example, a plurality of diesel generators connected in parallel and has an output capacity of several thousand KW. (8) is a load which is connected to the inverter (5) and the system power supply (7) and is supplied with the inverter output P _I and the system power supply output P _G , and (9) selects the load (8) from the system power supply (7) It is a feeder circuit breaker for disconnecting automatically.

The conventional solar power generation device is configured as described above,
If the system power supply (7) is relatively small and not so large compared to the capacity of the inverter (5), the inverter output
It is necessary to avoid the disturbance (effect of voltage or frequency) of the system power supply (7) due to the fluctuation of P _I. Therefore, even if the solar cell output Ps fluctuates due to solar radiation fluctuation, the inverter output P _I is controlled gently.

At this time, the difference between the solar cell output Ps and the input power of the inverter (5) (corresponding to the inverter output P _I ) is absorbed by the charge / discharge power P _B of the battery (2), but Inverter output P is generally used to reduce capacity.
_I is controlled so as to follow the solar cell output Ps on average. In fact, the inverter output P _I is the input power P _IN ,
If the inverter efficiency is η _I [%], it can be expressed as P _I = P _IN × η _I / 100, but here, for simplification of explanation, the inverter efficiency η _I is 100%, that is, P _I ≈ _Set to P _IN .

Next, referring to the flow chart of FIG.
A control method of the conventional solar power generation device shown in the figure will be described.

The control device (6) initializes the inverter output command Pr to 0 (step S1), then obtains the solar cell output Ps based on the solar cell output current Is detected by the shunt (3), and determines the solar cell output Ps. The inverter output command Pr corresponding to the solar cell output Ps is calculated by integrating the output deviation (Ps-Pr) between the output Ps and the inverter output command Pr with the time constant Tc (10 to 20 minutes).

That is, the output command deviation ΔPr is calculated from the formula that is obtained by multiplying the output deviation (Ps-Pr) by the small value (ΔT / Tc), ΔPr = (Ps-Pr) · ΔT / Tc (step S2). Is added to the initially set inverter output command Pr (step S3), and further multiplied by the correction factor F (step S4), and this is output to the inverter (5) as the final inverter output command Pr.

In this case, shunt (4) charge-discharge current I possess electrical quantity AH of the battery (2) based on _B are measured at regular time intervals from the correction factor F used in step S4 is held electric quantity When AH is above a predetermined management level, it is set large (discharging tendency), and when it is below the management level, it is set small (charging tendency).

Then, it is determined whether or not a predetermined sampling period ΔT has passed (step S5), and when the sampling period ΔT has passed, the process returns to step S2 and steps S2 to S4 are repeated to calculate the next inverter output command Pr. Control the inverter output P _I.

By repeating the above operation, the inverter output command
Pr gradually approaches an appropriate value according to the solar cell output Ps.

In this way, the inverter output P _I is controlled to follow the solar cell output Ps gently and averagely by the time constant Tc.
Further, the amount of electricity AH possessed by the battery (2) is controlled so as to be equal to a predetermined management level on average, so that even if the battery (2) has a relatively small capacity, it is overcharged or overdischarged. It is possible to prevent the disturbance of the system power supply (7) due to the fluctuation of the inverter output P _I.

On the other hand, in the existing system power source (7), the power generation efficiency is generally affected by the load factor R, and particularly in the case of a diesel generator, for example, as shown in FIG. Becomes extremely low. Therefore, the generator, that is, the system power source (7) is composed of a plurality (N) of units, and the load factor R is the upper limit of the specified load factor due to the seasonal variation and time variation of the required power (load power) P _L of the load (8). When it becomes R _H or more, the system power supply (7) is additionally activated, and conversely, when it becomes the lower limit specified load factor R _L or less, the system power supply (7) is decelerated and stopped. Further, the unlikely event that control of the number of operating units of the system power source (7) to the rapid increase of the load power P _L can not completely follow the
Feeder circuit breaker (9) according to a predetermined priority order
Part of the power is temporarily cut off to avoid overloading the system power supply (7).

[Problems to be Solved by the Invention] As described above, the conventional method for controlling the solar power generation device avoids the disturbance of the system power supply (7) based only on the solar cell output Ps and the stored electricity amount AH. Therefore, the inverter output P _I will be controlled regardless of the load power P _L, the operating capacity of the system power supply (7), and the operating status of the system power supply (7) such as the load factor R. There was a point.

(I) Depending on the operating status of the grid power supply (7), the grid power supply capacity does not decrease with the increase in the inverter output P _I of the photovoltaic power generator, and the load factor R decreases, resulting in fuel consumption of the grid power supply (7). The effect G is reduced.

(Ii) Due to the battery capacity, the inverter output P _I is controlled to follow the solar radiation fluctuation on average, so it may vary depending on the solar radiation fluctuation and the load fluctuation, or even if the load (8) does not vary. Depending on the change in the inverter output P _I, the frequency of controlling the number of operating system power supplies (7) increases, and the auxiliary machine power for the system power supply device also increases.

(Iii) If the inverter output P _I increases when the load (8) is seasonally light and the system power supply (7) has the minimum operating capacity, the load factor R further decreases and the system power (7) becomes lighter. The load limit may be exceeded.

The present invention has been made to solve the above problems. Even if a solar power generation system having a relatively large capacity is installed in relation to the existing system power supply capacity, the frequency of operating unit control increases and An object of the present invention is to obtain a control method for a photovoltaic power generation device that can avoid load operation and prevent reduction in fuel efficiency of a system power supply.

[Means for Solving Problems] A method for controlling a photovoltaic power generator according to the present invention determines an inverter output P _I based on operation information J indicating a system power supply output P _G and a system power supply operating number n. Execute the control sequence to control, and output the solar cell as the control sequence.
The first step of obtaining the _first inverter output command Pr ₁ based on Ps and the amount of electricity AH possessed by the battery, and the start output set value P _GH and the system for additionally starting the system power supply for each operating number of system power supplies A second step of obtaining a final inverter output command Pr based on the stop output set value P _{GL at} which the power supply is reduced and stopped, and the second step includes the system power supply output P _G
Is above the non-starting output level P _{HL which is} lower than the starting output set value P _GH by the specified control width ΔP, the inverter output command P
The step of controlling r in the increasing direction from the first inverter output command Pr ₁ by the system power supply output deviation P _G r, and the system power supply output P _G is higher than the stop output set value P _GL by the specified control width ΔP. When the output level is below the stop output level P _LL , the inverter output command Pr is controlled to decrease from the first inverter output command Pr ₁ by the system power supply output deviation P _G r ′ and the system based on the operation information J. Find the load factor R of the power supply,
And a step of limiting the inverter output P _I in accordance with the load ratio R to the maximum inverter output P _IMAX, based on the number of operating units n and the system power output P _G of the system power source, the maximum inverter output P _IMAX, P _IMAX = R _HH · Q · n-P _G (However,
R _HH : Allowable load factor of system power supply, Q: Capacity of one system power supply)
And the final inverter output command Pr is Pr> P
_{If IMAX} , set the inverter output command Pr to Pr = P
_{In addition} to limiting to _IMAX , the system power output P _G is P _G ＞ R _LL・
Q (where, R _LL: minimum acceptable load factor of the system power source) so that the, the maximum inverter output _{P IMAX, P IMAX = P G} + P I -R LL
・ Limited to Q.

[Operation] In the present invention, the load factor of the system power supply is detected based on the operation information, and the start output set value and the stop output are set based on the specified load factor and corresponding to the additional start and the reduction stop of the system power supply. By correcting the inverter output command that follows the solar cell output at the set value, the inverter output is controlled in coordination with the operating number (load factor) of the system power source, and the load factor of the system power source becomes the specified load factor. While maintaining the average load factor of the system power supply, the amount of power generation is reduced without significantly reducing the average load factor of the system power supply, and the fuel efficiency of the system power supply is improved.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings. First
The figure is a block diagram showing a photovoltaic power generator according to an embodiment of the present invention, and (1) to (5) and (7) to (9) are the same as those described above.

(10) is a current transformer that detects the output current I _G of the system power supply (7), (11) is a power converter that converts the system power output current I _G to system power output P _G , and (12) is the system power A transmitter that outputs operation information J based on the output P _G and the operating number n of the system power supply (7), and a receiver (13) that outputs control information C based on the operation information J.

(6A) is a corresponding control device (6), the battery current I _B, based on the solar cell current Is and the control information C and outputs an inverter output command Pr.

Next, an embodiment of the control method according to the present invention using the photovoltaic power generator of FIG. 1 will be described with reference to the flowchart of FIG. 2 and the explanatory view of FIG.

First, both the inverter output commands Pr and Pr ₁ are initially set to 0 (step S11), and then the output command deviation ΔPr between the solar cell output Ps and the first inverter output command Pr ₁ is calculated as ΔPr = (Pr−Pr ₁ ) ・ T ₁ However, T ₁ = ΔT / Tc ₁ ΔT: Sampling cycle (several seconds) Tc ₁ : Calculation from time constant (about 10 to 20 minutes) (step S12).

Next, this output command deviation ΔPr is added to the initially set inverter output command Pr ₁ (step S13), and the correction factor F is further added.
Multiplied by (step S14), and outputs the result as the first inverter output command Pr ₁ to the inverter (5). In this case, measures the held electrical quantity AH of the battery (2) on the basis of the charge-discharge current I _B, because it adjusts the correction factor F in accordance with the held electric quantity AH in the same manner as described above, the inverter (5) The output becomes gentle due to the time constant Tc ₁ , and the solar cell output Ps
The following control is performed on average.

The above steps S11 to S14 constitute a first step for obtaining the _first inverter output command Pr1 based on the solar cell output Ps and the stored electricity amount AH of the battery (2).

Here, the load power P _L is the first inverter output command Pr ₁
Is supplied by the inverter output P _I and the system power supply output P _G , which correspond to P _L = P _G + P _I. Therefore, if the inverter output P _I is controlled according to the fluctuation of the load power P _L , the system power supply output P _G can be made constant.

In addition, a system power supply (7) consisting of multiple diesel generators
If the upper limit specified load factor R _H is exceeded due to an increase in the load power P _L or a decrease in the inverter output P _I, an additional start is performed, and conversely, a decrease in the load power P _L or an increase in the inverter output P _I causes a lower limit If the load factor _falls below the specified load factor R _{L, the} load will stop decreasing. Therefore, based on the capacity Q of one unit of the system power supply (7) and the operation information J indicating the number of operating units n, the start output set value P _GH additionally started for each operating unit n and the stop output to be reduced and stopped. The set value P _GL can be known. That is, if the maximum number of operating system power supply (7) and _{N, P GH = R H ·} Q · n (n = 1~N-1) P GL = R L · Q · n (n = 2~N ) Is represented. In addition, the non-starting output level that is not additionally started is lower than the starting output set value P _GH by the specified control width ΔP and P
_{If it is HL} (see FIG. 3), it can be expressed as P _HL = P _GH −ΔP.

Therefore, this non-starting output level P _HL is compared with the actual system power supply output P _G (step S15). If P _G ≧ P _HL , the process proceeds to step S20 and the system power supply output deviation P
Initialize _G r (= P _G −P _HL ) to 0.

Next, this system power supply output deviation P _G r is integrated with the time constant Tc ₂ (several seconds), and the corrected output deviation ΔP _G r is calculated as ΔP _G r = (P _G −P _HL ) T ₂ where T ₂ = Obtained from ΔT / Tc ₂ (step S21), this corrected output deviation ΔP _G r is added to the system power supply output deviation P _G r (step S22). Then, by adding the obtained system power source output deviation P _G r to the first inverter output command Pr ₁ (step S23), this is the final inverter output command Pr.

That is, the inverter output command Pr, rather than the first inverter output specification Pr ₁ based on solar cell output Ps (solar radiation) follow, is controlled in an increasing direction by the system power supply output deviation P _G r min. As a result, even if the load power P _L temporarily increases, the grid power supply output P _G is maintained below the non-starting output level P _HL, so the grid power supply (7) is not additionally started and the high load factor R It is possible to prevent the increase of the control frequency of the operating number n while being maintained at.

In this case, the inverter output P _I increases as the load power P _L increases from the output during solar radiation follow-up, so that the stored electricity amount AH of the battery (2) gradually decreases. For this reason,
Although not shown in the flow chart of FIG. 2, when the amount of stored electricity AH is less than or equal to a specified value, and when the amount of increase in load power P _L is large and the inverter output P _I is greater than or equal to the specified value, Stop the control and give the final inverter output command
Match Pr with the first inverter output command Pr ₁ and return to solar radiation follow-up control.

On the other hand, when it is determined in step S15 that P _G <P _HL , the process proceeds to step S30, where the system power supply output P _G is higher than the stop output set value P _GL by the specified control width ΔP and the non-stop output level P _G is not stopped. _LL (= P _GL + Δ
P [see FIG. 3]). When P _G ≦ P _LL , the system power supply output deviation P _G r ′ (= P _LL −P _G ) is set to 0.
(Step S31), and the system power supply output deviation P _G r ′ is integrated with the time constant Tc ₂ as described above, and the corrected output deviation ΔP
_G r ′ is obtained from ΔP _G r ′ = (P _LL −P _G ) · T ₂ (step S32).

Next, the corrected output deviation ΔP _G r ′ is added to the system power supply output deviation P _G r ′ (step S33), and the obtained system power supply output deviation P P r
_G r ′ is subtracted from the first inverter output command Pr ₁ (step S34), and this is used as the final inverter output command Pr.

That is, the inverter output command Pr is controlled in the decreasing direction by the system power supply output deviation P _G r ′ from the solar radiation following inverter output command Pr ₁ . As a result, even if the load power P _L is temporarily reduced, the system power supply output P _G is maintained above the non-stop output level P _LL, so the system power supply (7) is not reduced and stopped, and It is possible to suppress an increase in control frequency.

In this case, since the inverter output P _I decreases from the output during solar radiation following as the load power P _L decreases, the stored electricity amount AH of the battery (2) gradually increases. Therefore, although not shown in the flow chart of FIG.
When AH is above the specified value and when the amount of decrease in load power P _L is large and the inverter output P _I is below the specified value, the above control is stopped and the final inverter output command Pr
To the first inverter output command Pr ₁ to return to the solar radiation follow-up control.

Further, in step S30, i.e., P _G> P _LL, even if it is determined that _{P HL> P G> P LL} , an inverter output command Pr to match a first inverter output command Pr ₁ returns to the solar tracking control (Step S40).

The above steps S15 to S40 are the second step for obtaining the final inverter output command Pr based on the start output set value P _GH and the stop output set value P _GL for each operating unit n of the system power supply (7). I am configuring.

Then, after each of steps S23, S34 and S40, it is determined whether or not a predetermined sampling period ΔT has elapsed (step
S50), when only the sampling period ΔT has elapsed, the process returns to step S12 and repeats steps S12 to S40 to calculate the next inverter output command Pr and control the inverter output P _I.

Needless to say, the above control sequence is executed by the program in the control device (6A), and all variables used in the control sequence are input into the control device (6A) before the program starts.

Although the above description does not consider the failure stop of the inverter (5), the inverter (5) stops due to some trouble when the load power P _L is shared by the system power output P _G and the inverter output P _I. In this case, the control of the number n of operating system power supply (7) cannot be fully followed, the load factor R increases rapidly, and the system power supply (7) may be temporarily overloaded depending on the inverter output P _I before the stop. There is. Therefore, in order to prevent this, the maximum inverter output during operation control is based on the number n of operating system power supplies (7) and the system power supply output P _G.
The _{P IMAX, P IMAX = R HH} · Q · n-P G However, R _HH: determined by allowable load factor of the system power source (7), limiting the inverter output P _I.

That is, when the final inverter output command Pr obtained according to FIG. 2 is Pr> P _IMAX , Pr = P _IMAX may be set. As a result, even if the inverter (5) stops, the system power supply (7) will not be overloaded.

If the load (8) is light seasonally and the system power supply (7) is at the minimum operating capacity, monitor the system power supply output P _G , P _G > R _LL · Q where R _LL : system limiting the inverter output P _I to be the minimum acceptable load factor of the power supply (7), the maximum inverter output P _IMAX, by which to limit the _{P IMAX = P G + P I} -R LL · Q, the system power supply (7 ) It is possible to prevent the light load operation.

When the photovoltaic power generation device including the solar cell (1) and the existing grid power supply (7) are relatively long distances, the operation information J from the transmitter (12) to the receiver (13) is used. May be transferred, for example, via a telephone line or a wireless device.
On the contrary, when the distance between the photovoltaic power generator and the system power supply (7) is relatively short, the transmitter (12) and the receiver (13)
Is omitted, the signal line is laid, and the operation information J is set to the control device (6
You may enter it directly in A).

[Effects of the Invention] As described above, according to the present invention, the inverter output can be efficiently output according to the load factor of the system power supply based on the operation information J representing the system power supply output P _G and the operating number n of the system power supply. The first step of controlling the P _I and obtaining the first inverter output command Pr ₁ based on the solar cell output Ps and the stored electricity amount AH of the battery as a control sequence, and the system power supply for each operating number of system power supplies. Includes a second step of obtaining a final inverter output command Pr based on the start output set value P _GH additionally started and the stop output set value P _GL at which the system power supply is reduced and stopped, and the second step includes , When the system power supply output P _G is at or above the non-starting output level P _{HL which is} lower than the starting output set value P _GH by the specified control width ΔP, the inverter output command Pr is output from the first inverter output command Pr ₁ to the system power supply output. Increase direction by deviation P _G r And the power supply output P
_{If G} is below the non-stop output level P _{LL, which is} higher than the stop output set value P _GL by the specified control width ΔP, the inverter output command P
The step of controlling r in the decreasing direction from the first inverter output command Pr ₁ by the system power supply output deviation P _G r ′, and the load factor R of the system power source is obtained based on the operation information J. Depending on the inverter output P _{I the} maximum inverter output P
And a step of limiting the _IMAX, based on the number of operating units n and the system power output P _G of the system power source, the maximum inverter output
The _{P IMAX, P IMAX = R HH} · Q · n-P G ( where, R _HH: line power permissible load factor, Q: the system power source 1 cars capacity) determined by a final inverter output command Pr is , Pr> P _IMAX , the inverter output command Pr is limited to Pr = P _IMAX , and the system power supply output P _G is P _G > R _LL · Q (where R _{LL is} the minimum of the system power supply. The maximum inverter output P _IMAX is limited to P _IMAX = P _G + P _I −R _LL · Q so that the load factor of the system power supply can be kept high and fuel efficiency is also improved. There is an effect that it is possible to obtain a control method of a photovoltaic power generation device that can improve and suppress an increase in the number of operating units control. Further, even if the inverter fails and stops, the system power supply does not become overloaded, and further, in the case of a light load, a method of controlling a photovoltaic power generation device that can prevent light load operation of the system power supply can be obtained. There is.

[Brief description of drawings]

FIG. 1 is a block diagram showing a solar power generation device to which an embodiment of the present invention is applied, FIG. 2 is a flow chart diagram for explaining an embodiment of the present invention, and FIG. 3 is an embodiment of the present invention. FIG. 4 is an explanatory diagram showing a system power supply operation according to an example, FIG. 4 is a block diagram showing a conventional solar power generation device, FIG. 5 is a flowchart diagram for explaining a control method of the conventional solar power generation device, and FIG. It is a characteristic view which shows the fuel efficiency of the system power supply with respect to a load factor. (1) …… Solar cell, (2) …… Battery (5) …… Inverter, (6A) …… Control device (7) …… System power supply, (8) …… Load Ps …… Solar cell output, AH …… Amount of electricity P _I …… Inverter output Pr ₁ …… First inverter output command Pr …… Final inverter output command P _G …… Grid power output, n …… Number of operating units J …… Operation information, P _GH …… Start output set value P _GL …… Stop output set value, ΔP …… Specified control width P _HL …… Non-start output level P _LL …… Non-stop output level P _G r, P _G r ′ …… Grid power supply Output deviation S11 to S14 ...... First step S15 to S40 ...... Second step S23 ...... Step to control in the increasing direction S34 ...... Step to control in the decreasing direction Incidentally, in the drawings, the same reference numerals indicate the same or corresponding parts. .

Claims (1)

[Claims] 1. A solar cell, a battery that absorbs fluctuations in the output of the solar cell, an inverter that converts DC power supplied from the solar cell and the battery into AC power, the solar cell output Ps, and the battery. Electricity AH
And a control device for generating an inverter output command Pr for controlling the output P _I of the inverter based on the above, and a photovoltaic power generation device for supplying the inverter output P _I to a load together with an existing system power supply output P _G In the control method described above, the control device executes a control sequence for controlling the inverter output P _I based on operation information J representing the system power supply output P _G and the operating number n of the system power supply, The control sequence includes a first step of obtaining a _first inverter output command Pr ₁ based on the solar cell output Ps and the amount of electricity AH of the battery, and the system power supply for each operating number of the system power supplies. The second step of obtaining the final inverter output command Pr based on the start output set value P _GH additionally started and the stop output set value P _{GL at} which the system power supply is reduced and stopped. In the second step, when the system power supply output P _G is a non-starting output level P _HL lower than the starting output set value P _GH by a specified control width ΔP or more, the inverter output command Pr is The step of controlling the inverter output command Pr _{1 of 1 in the} increasing direction by the system power supply output deviation P _G r, and the system power supply output P _G being higher than the stop output set value P _GL by the specified control width Δp Non-stop When the output level P _LL or less, the inverter output command Pr is controlled to decrease from the first inverter output command Pr ₁ by the system power supply output deviation P _G r ′, based on the operation information J. Find the load factor R of the system power source, and a step of limiting the inverter output P _I in accordance with the load ratio R to the maximum inverter output P _IMAX, into a number of operating units n and the system power output P _G of the system power source Based on The maximum inverter output _{P IMAX, P IMAX = R HH} · Q · n · P G However, R _HH: allowable load factor of the system power source Q: determined by the capability of one system power supply amount, the final inverter output command Pr is , Pr> P _IMAX , the inverter output command Pr is limited to Pr = P _IMAX, and the system power supply output P _G is P _G > R _LL · Q, where R _LL : system power supply as the lowest allowable load factor, the maximum inverter output P _IMAX, the control method of the photovoltaic power generation apparatus characterized by limiting the _{P IMAX = P G + P I} -R LL · Q.