JP2005328622A - Power supply system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply system which is equipped with a distributed power unit where an autonomous distribution control system is applied. <P>SOLUTION: This power supply system performs autonomous distribution control for the balance between demand and supply and the economic operation of a system, by arranging an AFC controller capable of adjustment of the target frequency for each power generation facility, and adjusting the AFC setting frequency in the local by means of the controller provided in each generator, based on the system information or power generation information obtained in the local without using a communication circuit. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a power generation system including a distributed power supply device, and more particularly to a power supply system to which an autonomous distributed control system is applied.

  In order to achieve economic operations such as maintaining power quality such as frequency and voltage and saving fuel for power generation in a power system that generally connects multiple power generators, the output sharing according to the power supply / demand balance of the system and the unit price of power generation (Load sharing) is required, and it is necessary to accurately grasp the operating status of the power generation facilities that are connected.

  For this reason, as with large-scale power systems, remote islands and independent small-scale systems in developing countries require a communication line for grasping the operating status of power generation facilities and transmitting control signals. An inexpensive control method is required.

  In addition, in order to perform stable operation against load fluctuations, it is necessary for the connected power supply to perform load sharing according to capacity. However, a power source using an inverter such as a photovoltaic power generation or a storage battery has only a method of operating at a constant frequency or a constant output, and there is no method capable of sharing a load in cooperation with other distributed power sources forming a small scale system.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a power supply system that performs autonomous distributed control in order to enable stable power supply with low frequency fluctuation and low cost without causing inconvenience such as a power failure.

  According to the first aspect of the present invention, an AFC control device capable of adjusting the target frequency is provided in each power generation facility, and the supply and demand of the system obtained from the information obtained by the control circuit provided in each power generation facility and the system frequency. It is characterized in that economic operation and supply-demand balance control are performed by adjusting the target frequency of the self-end AFC control device based on the balance information.

  According to the first aspect of the present invention, by using the AFC target frequency for control, a deviation amount from the target value of the system frequency is slightly increased, but communication equipment for system control becomes unnecessary, and power quality is reduced. It is possible to provide an inexpensive power supply system suitable for a small-scale system that balances maintenance and economic burden distribution. Further, by smoothing the detected system frequency with an AFC circuit, it is possible to prevent the power generation equipment from repeatedly repeating start and stop and output fluctuation due to frequency fluctuations accompanying steep load fluctuations peculiar to small-scale systems. .

  According to the second aspect of the present invention, each power generation facility is provided with an AFC control device, each target frequency is set to the same value, and the time response of the control function of the control block of the own end AFC control device is determined according to the unit price of power generation. Thus, the economic operation and the supply-demand balance control are performed based on the information obtained on its own and the supply-demand balance information obtained from the system frequency.

  According to the second aspect of the present invention, even if the number of generators to be controlled increases, each target frequency is set to the same value, so that deviation of the system frequency from the target frequency can be suppressed, and the economy can be reduced. Therefore, it becomes possible to supply high quality power. In addition, the addition of the generator is easy because the adjustment and construction of existing equipment is not required just by adjusting the control function of the generator.

  According to a third aspect of the present invention, there is provided an inverter circuit for converting direct current power into alternating current power by a switching action, and a distributed power source that operates to supply power at a target frequency to the grid interconnection by the switching action of the inverter circuit. A power supply system having a device, wherein the inverter circuit operates to reduce an output frequency of the distributed power supply device in accordance with an increase in load of the interconnection system.

  In the power generation system according to claim 3, the distributed power supply device is a distributed power supply device that operates to supply power of a target frequency to the grid interconnection, and the inverter circuit of the distributed power supply device has a load of the interconnection grid. Since it operates to decrease or increase the output frequency of the distributed power supply autonomously according to the increase or decrease, the distributed power supply can be used even when a distributed power supply such as diesel power generation is combined. It is possible to share the increase and decrease of the load with the device, and the coordinated operation enables stable power supply for grid interconnection.

  According to a fourth aspect of the present invention, an inverter circuit for converting DC power into AC power by a switching action is provided, and power having a frequency corresponding to the grid frequency is supplied to the grid by the switching action of the inverter circuit. A power supply system having a distributed power supply device that operates as appropriate, wherein the inverter circuit operates to decrease the output power of the distributed power supply device in response to an increase in the interconnection system frequency. And

  According to a fourth aspect of the present invention, the distributed power supply device is a distributed power supply device that operates to supply electric power having a frequency corresponding to the interconnection system frequency to the interconnection system, and the inverter circuit of the distributed power supply device Is operated to autonomously reduce or increase the output power of the distributed power supply according to the increase or decrease of the grid power frequency, for example, when combined with a distributed power supply such as diesel power generation Even if it exists, it can share the fluctuation | variation suppression of a system frequency with this distributed power supply device, and the stable electric power supply of a grid connection is attained by the cooperative operation.

  According to the present invention, without providing an expensive communication line as in the existing power system, based on the information obtained at the own end of each generator, the economy by the frequency sharing of the system and the output sharing according to the unit price of power generation Operation can be realized. In addition, a power source using an inverter can be operated in cooperation with other power sources for system frequency fluctuations and output fluctuations.

  The features of the present invention will be described in detail below with reference to the illustrated embodiments.

<Embodiment 1> Stand-alone type FIG. 1 is a block diagram schematically showing an example in which a power generation system according to the present invention is applied to a stand-alone inverter. In the illustrated example, the power generation system 10 is a distributed power system in which each of the DC power source 11 including a power storage device and the AC power source 12 including a diesel generator is a distributed power source. A load 14 is connected to the system bus 13 of this distributed power supply system, that is, the power generation system 10.

  The DC power source 11 is connected to the system bus 13 via the inverter circuit 15, and the DC power of the DC power source 11 is converted into AC power by the switching action of the inverter circuit 15, and the load 14 passes through the system bus 13. To be supplied. The load 14 is supplied with AC power from the AC power source 12 via the system bus 13.

The inverter circuit 15 is controlled in operation by a control signal from the control circuit 16. The control circuit 16 basically receives an instruction signal of the target frequency f ₀ via the adder 17, thereby converting the DC power of the DC power source 11 into AC power at a frequency that matches the target frequency f _0. Operates to switch.

In order to correct the instruction signal of the target frequency f ₀ to the control circuit 16 according to the output power of the inverter circuit 15, the frequency detector 18 that detects the frequency from the output voltage of the inverter circuit 15, and the output of the inverter circuit 15 From the output power detection unit 19 for obtaining the output power of the inverter circuit 15 from the current and the output voltage, the AFC (automatic frequency control) unit 20 for suppressing the deviation from the target frequency f _0, and the PI (proportional integration) circuit, for example. The average value circuit unit 21 is provided.

A detection signal from the frequency detector 18 is input to the comparator 22, and a deviation from the target frequency f ₀ obtained by the comparator is input to the AFC unit 20. The AFC unit 20 basically outputs a control signal such that the aforementioned deviation becomes zero. Further, the output power detection unit 19 outputs a control signal corresponding to increase / decrease in output power from the inverter circuit 15 to the system bus 13. A difference between the control signal from the AFC unit 20 and the control signal from the output power detection unit 19 is obtained by the comparator 23, and the difference passes through the average value circuit unit 21, so that the equalized correction control signal is obtained. The switching operation of the inverter circuit 15 is controlled by the target value control signal (f ₀ ) added to the target frequency f ₀ by the adder 17 and corrected by the correction control signal.

  The control signal output from the output power detector 19 acts so as to decrease or increase the switching frequency of the inverter circuit 15, that is, the output frequency of the distributed power supply device, when the output power to the system bus 13 increases or decreases. To do. When the system frequency decreases or increases, the output of the AFC unit 20 increases or decreases after a predetermined output delay time by the AFC unit 20, and the output frequency recovers to the target frequency.

FIG. 2A and FIG. 2B are graphs showing the drooping characteristics of the generator output-frequency. Each horizontal axis represents a load, and the left vertical axis of each graph represents the AC power source 12. The output frequency of a certain diesel generator G1 and the right vertical axis of each graph indicate the output frequency of a power storage device G2 including the DC power source 11 and the inverter circuit 15, respectively. FIG. 2A shows the drooping characteristics of the diesel generator G1 and the power storage device G2 at a certain load, and the output frequency indicated by the intersection of the characteristic line g1 of the diesel generator G1 and the characteristic line g2 of the power storage device G2 ( f ₀ ) and the load sharing ratio (G1: G2).

FIG. 2B shows a graph with the load 14 increased. Since the output frequency of the inverter circuit 15 of the power generation system 10 decreases as the output power of the inverter circuit 15 increases, the characteristic line g1 of the diesel generator G1 and the characteristic line g2 of the power storage device G2 in the graph of FIG. As shown by the intersection with, the output frequency of the power storage device G2 is reduced to (f ₀ ′), and along with this reduction, the load sharing amount (G1) of the diesel generator G1 increases.

  On the other hand, FIG. 3A and FIG. 3B show graphs similar to FIG. 2A and FIG. 2B regarding the generator drooping characteristics of the conventional distributed system. As shown in FIGS. 3A and 3B, the load sharing amount of the diesel generator G1 does not change because the output frequency of the power storage device G2 does not change regardless of the change of the load 14 in the related art. Therefore, a large burden is placed on the power storage device G2 when the load increases.

  On the other hand, according to the power generation system 10 according to the present invention, as shown in the graphs of FIGS. 2A and 2B, the load sharing amount of the diesel generator G1 according to the increase in the load 14. As a result, the load sharing amount of the power storage device G2 can be reduced, so that the problem caused by the increased load on the power storage device G2 can be eliminated and stable power supply can be achieved.

The average value circuit unit 21 can be constituted by a PID (proportional integral derivative) control circuit or a low-pass filter instead of the PI control circuit. Further, the frequency detection unit 18 in FIG. 1 is used in the G1 (S) circuit shown in FIG. 7 for the third embodiment described later, and the AFC unit 20 in FIG. 1 is used in the G2 (s) circuit in FIG. , from the corresponding possible respectively to f ₀ of f ₀ any 7 in Figure 1, in examples 3 and 4 below these frequency detection unit 18 and the AFC portion 20 G1 (s) circuit and G2 ( s) Each can be applied to a circuit.

<Embodiment 2> Interconnection Type A power generation system 50 shown in FIG. 4 shows an example in which the power generation system according to the present invention is applied to a power storage interconnection type inverter.

  In the storage power generation system 50, the control circuit 16 for the inverter circuit 15 basically detects the phase of the output voltage of the inverter circuit 15 from the output voltage of the inverter circuit 15 and outputs a phase adjustment signal. 24 and an output setting circuit 25 that outputs an output instruction value signal. In the control circuit 16 of the power generation system 50, the output signal from the phase adjustment unit 24 and the output signal from the output setting circuit 25 are multiplied by the multiplier 26, and then the difference from the output current signal of the inverter circuit 15 by the comparator 27. This difference is subjected to smoothing and gain adjustment by the smoothing circuit unit 21, and the control signal formed by adding the output signal from the phase adjustment unit 24 by the adder 17 to the inverter circuit 15. To be supplied. This configuration is the same as that of the conventional power generation system, and the inverter circuit 15 is subjected to switching control in order to output the power of the frequency corresponding to the frequency of the system bus 13, that is, the frequency of the grid system, to the system bus 13.

In the storage power generation system 50, the control circuit 16 having the conventional configuration receives the output of the phase adjustment unit 24, and outputs a correction signal indicating a coefficient K that changes according to the deviation from the target frequency f ₀ from the output. A coefficient circuit 28 is provided. The correction coefficient circuit 28 calculates a correction coefficient K expressed by the following equation (1) using the output signal from the phase adjustment unit 24.

K = 1− (f−f ₀ ) / (δf ₀ ) (1)
Here, f indicates the output voltage frequency of the inverter circuit 15 obtained from the output signal of the phase adjustment unit 24.

  The coefficient K signal obtained by the correction coefficient circuit 28 is multiplied by each output from the output setting circuit 25 and the phase adjustment unit 24 by the multiplier 26, whereby the control signal to the inverter circuit 15 is corrected.

  By the correction signal from the correction coefficient circuit 28, the inverter circuit 15 decreases the output power from the power storage device G2 including the DC power source 11 and the inverter circuit 15 in accordance with the increase in the frequency of the system bus 13.

  As shown in the graphs of FIGS. 5 (a) and 5 (b), the output-frequency characteristics of the conventional distributed system are such that the output of the storage battery power generation device G2 does not change despite the change in load power. Therefore, a large burden was placed on the diesel power generator G1 when the load increased.

  On the other hand, by applying the power generation system 50 according to the present invention, the drooping characteristic similar to that shown in FIG. 2 can be obtained, thereby increasing the load sharing amount of the power storage device G2 (11, 15, 16). Therefore, the load sharing amount of the diesel generator G1 can be reduced, and problems due to the increased load on the diesel generator G1 can be eliminated, and stable power supply can be achieved.

  The output setting circuit 25 outputs an output instruction value corresponding to an output setting signal input from an external control circuit, or an output instruction for a constant DC voltage control or maximum output control as in a solar power generation system. There are cases where a value is output.

  As shown in FIG. 4, the abnormal frequency can be detected by the correction coefficient circuit 28. When the correction coefficient circuit 28 detects this abnormal frequency, the output setting circuit 25 stops the maximum output control or the like. It is possible to cause the output setting circuit 25 to output an operation lock signal.

  The output instruction value of the output setting circuit 25 is subtracted from the output signal of the AFC circuit of the third embodiment (see FIG. 12) or the AFC circuit of the fourth embodiment (see FIG. 15), which will be described later, and input to the multiplier 26 in FIG. Thus, Embodiments 3 and 4 can be applied.

<Example 3>
The burden sharing that minimizes the fuel consumption of the plurality of generators is distributed so as to be equal incremental fuel costs. In an electric power system composed of photovoltaic power generation (PV) or wind power generation, a diesel generator (DG), and a power storage device (Batt), a diesel generator ( It is most efficient to use the power charged at DG) last.

  The relationship of the energy cost according to the energy source of photovoltaic power generation (PV), a diesel generator (DG), and an electrical storage device (Batt) is shown in FIG.

  A small-scale power system composed of such a diesel generator (DG), photovoltaic power generation (PV), and power storage device (Batt). Each power generation facility is based on AFC control functions and own information. The control circuit shown in FIG. 7 for adjusting the AFC set frequency is provided, and each generator (based on self-end information such as the power generation output and the remaining capacity of the power storage device) and the supply and demand balance information obtained from the system frequency is provided. Each control circuit (DG, PV, Batt) cooperates by starting and stopping the relevant generator, automatically adjusting the set frequency of its own AFC, and starting and stopping the necessary power generation equipment and adjusting the output. Therefore, it is possible to adjust the supply and demand balance of the system, reduce the fuel consumption, and secure the maximum power supply.

  The AFC control controls the output of the generator so that the average value of the system frequency within a certain time or the value obtained by smoothing the system frequency with a low-pass filter becomes the set frequency.

  FIG. 7 shows an example of the AFC circuit of the AFC controlled generator.

G1 (s) shown in FIG. 7 indicates a transfer function such as an average value calculation circuit for obtaining the average value or a low-pass filter that passes the system frequency, and when the average value calculation circuit is used, a frequency for a certain time (Δt × n). The average value f _ave is displayed by equation (1) shown in FIG. When a first-order lag low-pass filter or the like is used, the transfer function G1 (s) is expressed by the equation (2) shown in FIG. The transfer function G2 (s) such as an integration circuit or a proportional integration circuit is expressed by the equation (3) shown in FIG. 7 when the integration circuit is used, and by the equation (4) shown in FIG. 7 when the proportional integration circuit is used. Indicated.

  The output instruction value shown in FIG. 7 is a control signal for output distribution. In the third embodiment, the average value of the AFC circuit output can be substituted, and is set to 0.

  As described above, the G1 (S) circuit and the G2 (s) circuit shown in FIG. 7 for the third embodiment correspond to the frequency detection unit 18 and the AFC unit 20 shown in FIG.

(Responding to reduced efficiency at low output of diesel generators)
When the output of photovoltaic power generation (PV) is large, or when the load is light and the power generation efficiency of the diesel generator (DG) is reduced, such as at midnight, the power storage device with the output of high power generation efficiency of the diesel generator (DG) in advance (Batt) is charged and electric power is supplied from the power storage device (Batt) instead of the diesel generator (DG), thereby saving fuel consumption.

  Coordinated control is possible by adjusting the AFC set frequency by each control circuit of the generator based on the state of each generator for output adjustment and start / stop of the power storage device (Batt) and diesel generator (DG) become.

  FIGS. 8 to 10 show graphs of output-frequency drooping characteristics showing the low output correspondence of a diesel generator (DG).

FIG. 8 shows a state in which the diesel generator (DG) is operating in AFC at a constant output P _{DGL and} at a constant frequency f _DG0 . When the output is lower than the constant output P _DGL, the control circuit of the diesel generator (DG) shifts to governor operation (GOV), or the AFC set frequency of the diesel generator (DG) is increased, and the system frequency is increased. Here, f _DG · _AFC and f _DG · _o represent the AFC set frequency and the target frequency of the diesel generator (DG), respectively. f _DG · _on and f _DG · _off indicate the operation start frequency and operation stop frequency of the diesel generator (DG), respectively. f ′ _DG · _on indicates the AFC set frequency of the power storage device (Batt) for prompting the start of the diesel generator (DG). Further, P _DG represents the active power of the diesel generator (DG), and P _L represents the load.

FIG. 9 and FIG. 10 are graphs of drooping characteristics showing a low output correspondence state. f _B · _AFC indicates the AFC set frequency of the power storage device (Batt), f _B · _on , f _B · _L and f _B · _H are the operation start frequency of the power storage device (Batt) and diesel for charging the storage battery, respectively. The power storage device AFC set frequency for prompting an increase in the output of the generator (DG) and the power storage device AFC set frequency for prompting the disconnection of the diesel generator (DG) are shown. Further, f _PV · _max indicates a photovoltaic power generation AFC set frequency for suppressing an increase in system frequency when the storage battery is fully charged and surplus solar power cannot be charged.

As shown in FIGS. 9 and 10, when the control circuit of the power storage device (Batt) grasps that the load is lightened by the increase in the system frequency, the power storage device (Batt) is activated. When the remaining capacity of the power storage device (Batt) is lower than a preset value, the control circuit of the power storage device (Batt) sets the AFC set frequency f _B · _{AFC at its end} to f _B · _L that charging is required. To the diesel generator (DG), and urge the diesel generator (DG) to operate at maximum output. When the required amount of charging is completed, the control circuit of the power storage device (Batt) increases the AFC set frequency f _B · _AFC of the power storage device (Batt) to f _B · _H. Due to the increase in the AFC set frequency of the power storage device (Batt), the system frequency becomes _{equal to} or higher than the set frequency f _DG · _{OFF for} disconnecting the diesel generator (DG), and the diesel generator (DG) is disconnected.

When the load increases and the fuel consumption can be reduced by direct supply from the diesel generator (DG), f _B · _AFC is lowered, the diesel generator (DG) is started, and the power storage device (Batt ) Stop power supply from.

In addition, when the power generation amount of photovoltaic power generation (PV) is large and the power storage device (Batt) is in a fully charged state although the diesel generator (DG) is stopped, the power storage device (Batt) By increasing the AFC frequency, the system frequency can be maintained at f _PD · _max in the AFC of photovoltaic power generation (PV).

(For peak load)
When it can be predicted from the load curve given in advance that the power generation capacity of the diesel generator (DG) will be insufficient, the required amount of power is charged in the power storage device (Batt) in advance, and the diesel generator (DG) is Necessary power can be supplied by rated operation and discharging of the power storage device (Batt).

FIG. 11 is a graph of output-frequency drooping characteristics showing a state corresponding to a peak load. When the control circuit of the power storage device (Batt) predicts that the storage capacity of the power storage device (Batt) corresponding to the peak load is insufficient from the load curve, the AFC set frequency of the power storage device (Batt) is set to the diesel generator (DG). The diesel generator (DG) is started by lowering the starting frequency f _DG · _ON , and the diesel generator (DG) is operated at its maximum efficiency output by lowering it from the AFC set frequency f _DG · _ON. To charge the required power. If the required amount of power can be charged, the control circuit of the power storage device (Batt) stops charging without changing the AFC set frequency, and continues parallel operation with the diesel generator (DG). When the load increases and a load exceeding the rated capacity of the diesel generator (DG) is applied, the frequency cannot be maintained by the AFC of the diesel generator (DG), and the system frequency decreases. When the frequency is equal to or lower than the AFC set frequency of the power storage device (Batt), the shortage of power generation is supplied from the power storage device (Batt), and the system frequency is maintained at the AFC set value of the power storage device (Batt). This situation is shown in the generator drooping characteristic graph of FIG. From the peak load to the midnight low load, the power storage device (Batt) is stopped after waiting in the state of 12 in FIG. 11 to detect the load drop, and the state shifts to the state (1) of FIG.

<Example 4>
As described above, it is necessary to set a target frequency for each control target, and when the number of generators to be controlled increases, the finish of the system frequency deteriorates. Convergence cannot be expected.

  In order to improve this point, all generators are provided with AFC, their target frequencies are set to the same value, and one of the control functions G1 (s) and G2 (s) of the AFC control block of each generator By setting the time response of one or both individually according to the unit price of power generation, it is possible to achieve both economical output sharing and maintenance of power quality.

  The principle is as follows. That is, when the frequency drop occurs, the AFC response time is shortened so that the output set value is increased in a shorter time for a generator with a lower unit price, and conversely, when the frequency rise occurs, The higher the generator, the faster the AFC response so that the output set value can be reduced in a shorter time. Thereby, different response speeds are set when the frequency is increased and when the frequency is decreased.

FIG. 12 shows an example of the control block. Here, G1 (s) indicates a transfer function such as an average value calculation circuit for obtaining an average value with the system frequency as an input or a low-pass filter that passes the system frequency, as in the third embodiment shown in FIG. f _ave indicates the output of G1 (s), and G2 (s) is a transfer function such as an integration circuit or a proportional integration circuit. Further, as described above, the G1 (S) circuit and the G2 (s) circuit shown in FIG. 12 correspond to the frequency detection unit 18 and the AFC unit 20 shown in FIG. 1 when applied to the first embodiment. H _i is a gain circuit, and e _i1 and e _i2 indicate an input signal and an output signal to the gain circuit H _i , respectively. The input signal e _i1 to the gain circuit H _i is a deviation between the output f _ave of G1 (S) and the target frequency f ₀ .

FIG. 13 is a characteristic diagram of the Hi, and g _iG and g _iL indicate a gain (proportional coefficient) when e _i1 is positive and a gain (proportional coefficient) when e _i1 is negative, respectively.

The generator with lower unit price of power generation increases g _iL and decreases g _iG . When the frequency increases, the generator with the higher unit price of power generation increases _ei2 , and the generator output instruction value P _Gi0 is decreased more quickly to reduce the system frequency rise. On the other hand, when the system frequency is lowered, e _i2 becomes smaller as the generator has a lower unit price, and the generator output instruction value P _Gi0 is increased earlier to restore the system frequency. Since this adjustment is performed every time there is a fluctuation in the system frequency, a generator with a lower unit price of power generation shares more output, thereby achieving both maintenance of power quality and economic load distribution.

The unit price of the generator varies depending on the power generation situation. Efficiency increases near the rated output, and efficiency decreases at low output. By adjusting g _iL and g _iG according to this situation, more detailed economic operation becomes possible.

(Characteristic value setting simplification method and generator operation leveling measures)
If the time characteristics are adjusted as described above and the AFC response time is finely set for each power generation unit price of the generator, fine control is possible, but the setting becomes complicated. In order to reduce this complication, the generators connected to the grid can be classified into a plurality of groups for each unit price of power generation, and characteristic values can be set according to each group.

  However, even if the same value is set as the same group, a specific generator is always prioritized due to measurement error, setting error, etc., or conversely, it is always used last. Arise. In order to prevent this, the characteristic values are randomly changed in such a way that the measurement error and the setting error can be ignored in units of days or months, and the same group is operated equally.

FIG. 14 shows a generator group and a characteristic setting example. Each set characteristic value g _iGm and g _{iLm in the} table shown in FIG. 14 is finely adjusted using the following equation in units of days or months.

g _iGm = g _iGm0 + ε _G × rnd
g _iLm = g _iLm0 + ε _L × rnd
Here, g _iGm0 and g _iLm0 are the central values of g _iGm and g _iLm , and rnd is a random number from −1 to +1. Further, ε _G and ε _L are adjustment _ranges , which are sufficiently larger than the measurement error and the setting error, and are values where the adjusted g _iGm and g _iLm do not reverse the order of other groups.

(AFC competition prevention measures)
If there is a measurement error or a setting error in the AFC of each generator, the other generator may detect an increase in frequency when one generator detects a decrease in frequency due to the error. When such a situation occurs, contention occurs due to the reverse action control in which one generator increases the output and the other generator decreases the output. In order to prevent this competition, it is possible to provide a dead zone in consideration of AFC frequency measurement error and set value error.

  FIG. 15 is a block diagram showing an example of an AFC circuit provided with such a dead zone, and FIGS. 16A and 16B are graphs showing examples of the dead zone, respectively.

FIG. 16A shows an example in which the output is zero when e _i0 is within ± ε, and an output proportional to the input is output when the output exceeds it. Further, FIG. 16 (b), e _i0 is set to zero output when within ± epsilon, when more than epsilon outputs e _i1 = e _i0 -ε, when the following -ε e _i1 = e _i0 An example of outputting + ε is shown. In any case, since the output is zero when e _i0 is within ± ε, by setting the value of ε to be more than the tolerance determined from the frequency measurement error and setting error of each generator AFC, The AFC of each generator can be prevented from competing.

  As described above, the AFC target frequency of all the generators is set to the same value, and the time response of one or both of the control functions G1 (s) and G2 (s) of the AFC control block of each generator is set. Can be started and stopped or the load sharing can be adjusted due to changes in the normal system frequency, which can slightly increase the response time. Even if a large number of generators are provided in parallel, the system frequency is improved. Even if the generators are added, if a generator group is selected, no special adjustment is required, so that expandability is enhanced. In addition, it is possible to prevent the bias of the operating generator and the competition between the generators due to the measurement error and the setting error by providing a fine adjustment of the set value periodically and a dead zone.

It is a block diagram which shows Example 1 of the electric power generation system which concerns on this invention. 2 (a) and 2 (b) are graphs showing changes in the load sharing amount accompanying an increase in the load of the power generation system shown in FIG. FIG. 3A and FIG. 3B are graphs showing changes in the load sharing amount accompanying an increase in the load of the conventional power generation system. It is a block diagram which shows Example 2 of the electric power generation system which concerns on this invention. 3 (a) and 3 (b) are graphs showing changes in the load sharing amount accompanying an increase in the load of another conventional power generation system. It is a graph which shows the energy cost according to energy source. It is a block diagram which shows an example of the AFC circuit which concerns on this invention. The graph (the 1) of the drooping characteristic of the generator which concerns on this invention is shown. The graph (the 2) of the drooping characteristic of the generator which concerns on this invention is shown. The graph (the 3) of the drooping characteristic of the generator which concerns on this invention is shown. The graph (the 4) of the drooping characteristic of the generator which concerns on this invention is shown. It is a block diagram which shows another example of the AFC circuit which concerns on this invention. 13 is a graph showing Hi characteristics of the AFC circuit shown in FIG. 12. It is explanatory drawing which shows the example of a characteristic setting of the time characteristic of an AFC circuit. It is a block diagram which shows another example of the AFC circuit which concerns on this invention. FIG. 16A and FIG. 16B are graphs showing Example 1 and Example 2 of the AFC dead zone shown in FIG. 15, respectively.

Explanation of symbols

10, 50 Power generation system 11 DC power source 12 AC power source 13 System bus 14 Load 15 Inverter circuit 16 Control circuit

Claims (4)

  Each power generation facility is provided with an AFC control device capable of adjusting the target frequency, and the target frequency of the AFC control device at its own end is adjusted based on information obtained at its own end and information on the supply and demand balance of the system obtained from the system frequency A power supply system that performs economic operation and supply-demand balance control.   Each power generation facility is equipped with an AFC control device, each target frequency is set to the same value, and the time response of the control function of the control block of its own AFC control device is individually set according to the unit price of power generation. An electric power supply system that performs economic operation and supply-demand balance control based on information obtained at the end and supply-demand balance information obtained from system frequency.   An electric power supply system having a distributed power supply device that is provided with an inverter circuit that converts DC power into AC power by a switching action, and that operates to supply power at a target frequency to an interconnection system by the switching action of the inverter circuit. The inverter circuit operates to reduce the output frequency of the distributed power supply device in accordance with an increase in the load of the interconnection system.   An inverter circuit that converts direct current power into alternating current power by a switching action is provided, and a distributed power supply device that operates to supply power of a frequency corresponding to the interconnection system frequency to the interconnection system by the switching action of the inverter circuit The power supply system according to claim 1, wherein the inverter circuit operates to reduce output power of the distributed power supply device in accordance with an increase in the interconnection system frequency.

Images