JP2021058034A - Power control device and power control method, and power supply equipment - Google Patents

Abstract

To provide a power control device and a power control method capable of improving the operation efficiency of power supply equipment, and power supply equipment.SOLUTION: In a photovoltaic power generation system, a power control device 104 is for controlling the output power of multiple power converters 106 that are connected to multiple power sources and connected to a power system 102. In order that the multiple power converters 106 output the desired total reactive power, the power control device 104 controls the reactive power output by the power converter 106 depending on the apparent power output by the power converter 106.SELECTED DRAWING: Figure 1

Description

The present invention relates to a power control device and a power control method for controlling a power supply facility connected to a power system via a plurality of power conversion devices, and a power supply facility using the power control device.

In recent years, power supply equipment equipped with renewable energy power generation devices such as wind power generation devices and solar power generation systems and power storage devices has become widespread. These power supply facilities supply power to the load and are connected to the power system via the power conversion device, and include a plurality of power conversion devices according to the amount of power that can be output.

In the power supply equipment connected to the power system, the output of reactive power is controlled in order to stabilize the power system. At this time, the amount of invalid power required to be output as the power supply facility is distributed to the plurality of power conversion devices.

The technique described in Patent Document 1 is known as a power control technique for allocating an amount of invalid power to a plurality of power conversion devices.

In the technique described in Patent Document 1, among a plurality of power conversion units (PCS) to which a plurality of power storage units are connected, an object for outputting active power by satisfying predetermined conditions (SOC, charge capacity, etc.). The generated power conversion unit is preferentially output the reactive power.

Japanese Unexamined Patent Publication No. 2018-191486

In the above-mentioned conventional power control technique, the apparent power output by the plurality of power conversion units increases. Therefore, the power loss in the power supply equipment increases, and the operating efficiency of the power supply equipment decreases.

Therefore, the present invention provides a power control device and a power control method capable of improving the operating efficiency of the power supply equipment, and a power supply equipment.

In order to solve the above problems, the power control device according to the present invention controls the output power of a plurality of power conversion devices connected to a plurality of power sources and connected to a power system, and controls a plurality of power sources. In order for the conversion device to output the desired total negative power, the negative power output by the power conversion device is controlled according to the apparent power output by the power conversion device.

In order to solve the above problems, the power supply facility according to the present invention includes a plurality of power sources, a plurality of power conversion devices to which the plurality of power sources are connected and connected to the power system, and a plurality of power conversion devices. The power control device includes a power control device that controls the output power, and the power control device depends on the apparent power output by the power conversion device in order for the plurality of power conversion devices to output the desired total negative power. , Controls the invalid power output by the power converter.

In order to solve the above problems, the power control method according to the present invention is a method of controlling the output power of a plurality of power conversion devices connected to a plurality of power sources and connected to a power system, and is a method of controlling a plurality of powers. In order for the conversion device to output the desired total negative power, the negative power output by the power conversion device is controlled according to the apparent power output by the power conversion device.

According to the present invention, the increase in apparent power is suppressed. This improves the operating efficiency of the plurality of power converters. In addition, the operating efficiency of the power supply equipment is improved.

Issues, configurations and effects other than those described above will be clarified by the description of the following embodiments.

It is a block diagram of the solar power generation system which is Example 1. FIG. It is a block diagram of the power conversion apparatus in this Example 1. It is a functional block diagram which shows the structure of the system control unit 104. It is a functional block diagram which shows the structure of the system power command setting unit 302. It is a functional block diagram which shows the structure of the electric power command distribution part 303. It is a functional block diagram which shows the structure of the active power command distribution part 501. It is a functional block diagram which shows the structure of the reactive power command distribution part in the comparative example. It is explanatory drawing of the calculation means of the reactive power margin in the comparative example. It is a flowchart which shows the outline of the process in the reactive power command distribution part in Example 1. FIG. It is a functional block diagram which shows the structure of the reactive power command distribution part in Example 1. FIG. It is a functional block diagram which shows one configuration example of a priority-based invalid power command distribution part 903. It is a functional block diagram which shows the other structural example of the priority-based invalid power command distribution part 903. It is a vector figure which shows an example of the output voltage vector of an Example (FIG. 11) and a comparative example. It is a vector figure which shows an example of the output voltage vector of an Example (FIG. 12) and a comparative example. It is a flowchart which shows the outline of the process in the reactive power command distribution part in Example 2. FIG. It is a functional block diagram which shows the structure of the reactive power command distribution part in Example 2. FIG. It is a functional block diagram which shows the structure of the active power base invalid power command setting part in Example 2 (FIG. 16). It is a functional block diagram which shows the structure of the reactive power output limiter in Example 2 (FIG. 16). FIG. 5 is a functional block diagram showing a configuration example of a priority-based reactive power command distribution unit in the second embodiment (FIG. 16). It is a functional block diagram which shows the other structural example of the priority-based invalid power command distribution part 1405. It is a vector figure which shows an example of the output voltage vector of an Example (FIG. 19) and a comparative example. It is a vector figure which shows an example of the output voltage vector of an Example (FIG. 20) and a comparative example.

First, an outline of a photovoltaic power generation system, which is an embodiment of the present invention, will be described.

The system control unit, which is a power control device in the present embodiment, controls the output power of a plurality of power conversion devices. The power conversion device outputs the generated power of the solar cell, which is a power source, to the interconnection point with the power system. The system control unit controls a plurality of power conversion devices so as to output ineffective power according to the apparent power output by the power conversion device. The system control unit distributes the total reactive power output by the plurality of power conversion devices to each power conversion device, and preferentially distributes the power conversion device having a large apparent power. For example, the system control unit sets a priority according to the apparent power, and controls the reactive power output by each power conversion device based on the set priority.

Here, inconsistencies in operating states occur between a plurality of power conversion devices under various conditions. As an example, in a residential photovoltaic system, multiple solar panels installed on the roof are oriented in different directions. When such a plurality of solar cell panels are connected to a plurality of power conversion devices, the operating state differs between the plurality of power conversion devices. As another example, in the application to a microgrid (small-scale power supply network by distributed power supply), the solar cell panel and the power conversion device are installed in a remote place. Therefore, a plurality of different photovoltaic power generation states occur at the same time. Therefore, the operating state and operating limit may differ depending on the power conversion device.

Therefore, the system control unit controls the output power within the range of the effective and ineffective power that the output is allowed in each power conversion device.

Further, the system control unit in the present embodiment operates as a regulator for adjusting the power distribution to a plurality of power conversion devices, and sets a total power command for a photovoltaic power generation system including the plurality of power conversion devices. The system control unit sets a power command for each power conversion device, and at this time, the total power command is distributed to each power conversion device.

Here, the distribution of the power command is to determine the power command to each power conversion device, and these power commands result in the same total output power as the total power command. However, the combination of power commands for each power converter may differ depending on the means of power command distribution. Even if the same total output power as the target total power command is output, the total amount of apparent power of these power converters can increase depending on the combination of power commands for each power converter.

Therefore, the system control unit in the present embodiment suppresses an increase in the total apparent power of the plurality of power conversion devices. For example, the system control unit minimizes the total apparent power of the plurality of power converters. By suppressing the increase in the total apparent power, the increase in the power conversion loss is prevented, and the operating efficiency of the power conversion device and the photovoltaic power generation system is improved.

As described above, the system control unit, that is, the power control device in the present embodiment distributes the total reactive power to the plurality of power conversion devices according to the apparent power output by the power conversion device. In addition, this power control device preferentially distributes the reactive power to the power conversion device having a large apparent power. This prevents an increase in power conversion loss and improves the operating efficiency of the photovoltaic power generation system.

Hereinafter, embodiments of the present invention will be described with reference to the following Examples 1 and 2 with reference to the drawings. In each figure, those having the same reference number indicate the same constituent requirements or constituent requirements having similar functions.

FIG. 1 is a block diagram of a photovoltaic power generation system according to a first embodiment of the present invention.

The photovoltaic power generation device 101 includes a plurality of power conversion devices 106 (three in FIG. 1) to which a solar cell is connected. The power conversion device 106 converts the DC power generated by the solar cell into AC power. The photovoltaic power generation device 101 outputs the total output power (P _gen : total active power, Q _gen : total reactive power) of the plurality of power conversion devices 106 as its own output power.

The photovoltaic power generation device 101 is connected to the load 103 and is connected to the power system 102. Load 103 _{(P L:} active power, _{Q L:} reactive power), the power from the photovoltaic device 101 and the electric power system 102 is supplied _{(P s:} active power, _{Q s:} reactive power). The power system 102 is, for example, an AC power system that serves as a commercial AC power source.

The system control unit 104 receives a (power supply) command from the system operator 105 for controlling the total output of the plurality of power conversion devices 106, and collects information on the operating state from each power conversion device 106. Further, the system control unit 104 acquires information on the system voltage and the system current by the sensor 107. Then, the system control unit 104 creates a command for controlling each power conversion device 106 in response to a (power supply) command from the system operator 105 while using this information.

In this way, the system control unit 104 constitutes a so-called SCADA (Supervisory Control And Data Acquisition: monitoring control system). In the first embodiment, the system control unit 104 is composed of a computer system, and the computer system functions as a power control device by executing a predetermined program.

FIG. 2 is a configuration diagram of the power conversion device 106 in the first embodiment.

The power converter 106 includes a power converter 202 including a main circuit having an inverter circuit, and a converter control unit 201 that controls the output power of the power converter 202.

The power converter 202 converts the DC power generated by the solar cell panel 203 into AC power by the inverter circuit, and outputs the DC power via the grid interconnection transformer. In the first embodiment, the power semiconductor switching element constituting the main circuit of the power converter 202 is an IGBT (Insulated Gate Bipolar Transistor), but other power MOSFETs (Metal Oxide Semiconductor Field Effect Transistor) and the like are used. A power semiconductor switching element may be applied.

The converter control unit 201 and the system control unit 104 exchange information with each other by communication. In the first embodiment, the active power Pgen (x) and the reactive power Qgen (x) output by each power converter 106 by photovoltaic power generation are sent from the converter control unit 201 to the system control unit 104 as information. .. Further, the active power command Plim (x) and the reactive power command Quref (x), which are output power commands for the power converter 106, are sent from the system control unit 104 to the converter control unit 201 as information.

The output of the power conversion device 106, that is, the AC side, is connected to the output (AC side) of another power conversion device 106 (not shown in FIG. 2). That is, the outputs (AC side) of the plurality of power conversion devices 106 are commonly connected. As a result, the plurality of power conversion devices 106 are connected in parallel and multiplex to form the photovoltaic power generation device 101 (FIG. 1).

FIG. 3 is a functional block diagram showing the configuration of the system control unit 104.

The system control unit 104 creates an output power command for the solar power generation device 101 (FIG. 1), that is, a total active power command Plim and a total disabled power command Quref, which are total output power commands of a plurality of power conversion devices. The command setting unit 302, the total active power command Plim, and the total dead power command Quref are distributed to each power conversion device 106, and the active power command Plim (x) and the negative power command Quref (x) for each power conversion device 106 are assigned. It includes a power command distribution unit 303 to be created.

The system power command setting unit 302 acquires information from the sensor 107 and the converter control unit 201 and a (power supply) command from the system operator 105 via the input / output interface 301, and based on these commands and information, the system power command setting unit 302 obtains information. Create Total Active Power Directive Plim and Total Reactive Power Directive Quref.

The power command distribution unit 303 uses system power based on the active power Pgen (x) and the ineffective power Qgen (x) output by each power converter 106 acquired from the converter control unit 201 via the input / output interface 301. The total active power command Plim and the total ineffective power command Quref created by the command setting unit 302 are distributed to each power conversion device 106, and the active power command Plim (x) and the ineffective power command Quref (x) for each power conversion device 106 are distributed. To create.

The data of Plim, Quref (x), Plim (x) and Quref (x) are recorded in the database 304 (DB). These data stored in the database 304 (DB) are displayed on the display device of the monitor 305. In addition, the database 304 (DB) stores data related to the installation state (installation direction, etc.) of the solar panel and the output range of the allowable active power and invalid power of each power conversion device, and is stored in the power command distribution unit. 303 can refer to these data. The database 304 (DB) is stored in a storage device such as a semiconductor memory or a magnetic memory.

FIG. 4 is a functional block diagram showing the configuration of the system power command setting unit 302.

The system operator 105 gives the delay power factor PF_lag and the advance power factor PF_lead at the grid interconnection points as control targets. Power factor control is required when the photovoltaic power generation device 101 generates active power to be supplied to the load 103, and the active power received by the load 103 from the power system 102 is reduced by that amount. In this state, the power factor of the power received from the power system 102 decreases, and therefore the system power command setting unit 302 is applied to maintain the power factor of the power received from the power system 102. The power factor is maintained by controlling the reactive power of the plurality of power converters 106.

Therefore, the system power command setting unit 302 uses the total unit 406 from the information of the active power Pgen (x) and the reactive power Qgen (x) in each power converter (x) received from the converter control unit 201. Then, the total active power value Pgen and the total active power value Qgen are calculated. Further, the system power command setting unit 302 uses the power calculation unit 401 to obtain the active power Ps and the active power Qs received from the power system 102 based on the information (system voltage Vs, system current Is) from the sensor 107. calculate.

Based on the active power calculation value Ps_cal and the power factor limit value (lower limit value) PF_lag (delay power factor) and PF_lead (advance power factor) given by the system operator 105, the system power command setting unit 302 sets the reactive power limit value. The calculation unit 402 is used to calculate the reactive power limit values Qulim_lag (delay) and Qulim_lead (advance) at the grid interconnection points for satisfying the power factor limit value. Further, based on the total active power value Pgen and the total reactive power value Qgen, and the active power calculated value Ps_cal and the reactive power calculated value Qs_cal, the system power command setting unit 302 uses the load power estimation unit 403 to make the load 103. The estimated active power PL_cal and the estimated active power QL_cal are calculated.

The difference between the estimated reactive power value QL_cal of the load 103 and the reactive power limit value Qlim_lag at the grid interconnection point is calculated by the subtractor. Further, the difference between the estimated reactive power QL_cal of the load 103 and the reactive power Qlim_lead is calculated by the subtractor.

The difference value between the ineffective power estimated value QL_cal and the ineffective power limit value Qulim_lag is limited to a value of zero or more and Qmax or less by the limiter. Further, the difference value between the ineffective power estimated value QL_cal and the ineffective power limit value Qlim_lead is limited to a value of −Qmax or more and zero or less by the limiter. Here, Qmax is the maximum value (upper limit value) of the total reactive power that can be output by the plurality of power conversion devices.

The outputs of each of the above-mentioned limiters are added by an adder to create a total reactive power command value Quref for a plurality of power conversion devices 106. The total reactive power command value Quref is sent to the power command distribution unit 303 via the interface.

Further, the total reactive power command value Quref is input to the active power upper limit value calculation unit 404. The active power upper limit value calculation unit 404 calculates the total active power upper limit value Pmax that can prevent the overload of the power conversion device based on the total reactive power command value Qref. The active power upper limit value calculation unit 404 calculates Pmax after limiting the input Qref to the range of −Qmax ≦ Qref ≦ Qmax.

The active power upper limit value Pmax is set in the limiter in the reverse power flow suppression unit 405. The reverse power flow suppression unit 405 generates the reverse power flow of the active power while the plurality of power conversion devices output the total reactive power QReff based on the calculated active power Ps_cal of the power system 102 and the estimated active power PL_cal of the load 103. The total active power command value Plim, which is also the total active power limit for not causing it, is calculated and created. The total active power command value Plim is sent to the power command distribution unit 303 via the interface.

FIG. 5 is a functional block diagram showing the configuration of the power command distribution unit 303. It is assumed that the photovoltaic power generation device 101 includes three power conversion devices (x) (x = 1, 2, 3: the same applies hereinafter).

The power command distribution unit 303 has an active power command distribution unit 501 and an inactive power command distribution unit 502.

The active power command distribution unit 501 includes the total active power command value Plim, the active power (Pgen (1), Pgen (2), Pgen (3)) and the reactive power (Qgen (1)) output by each power conversion device. , Qgen (2), Qgen (3)) to create active power command values (Plim (1), Plim (2), Plim (3)) for each power converter. That is, the active power command distribution unit 501 distributes the total active power command value Plim to each power conversion device 106, and the active power command value (Plim (1), Plim (2), Plim) for each power conversion device 106. (3)) is created.

In addition, the reactive power command distribution unit 502 includes the total reactive power command value Quref, the active power (Pgen (1), Pgen (2), Pgen (3)) output by each power conversion device, and the reactive power (Qgen (Qgen (1)). Based on one or both of 1), Qgen (2), and Qgen (3), the reactive power command values (Qref (1), Qref (2), Qref (3)) for each power conversion device are created. That is, the reactive power command distribution unit 502 distributes the total reactive power command value Qref to each power conversion device 106, and the reactive power command value (Qref (1), Qref (2), Qref) for each power conversion device 106. (3)) is created.

FIG. 6 is a functional block diagram showing the configuration of the active power command distribution unit 501.

The active power command distribution unit 501 proportionally distributes the total active power command value Plim according to the active power Pgen (x) output by each power conversion device, thereby causing the active power command value (Plim (1), Plim (Plim (1)). 2), Plim (3)) is created.

More specifically, as shown in FIG. 6, the active power command distribution unit 501 divides Pgen (x) (x = 1, 2, 3) by the sum of Pgen (x) (A / B: A). = Pgen (x), B = sum of Pgen (x)) is executed, and Plim (x) is calculated by multiplying the result of division by Plim.

Here, a comparative example will be described before the reactive power command distribution unit 502 in the first embodiment is described.

FIG. 7 is a functional block diagram showing the configuration of the reactive power command distribution unit in the comparative example.

As shown in FIG. 7, the reactive power command distribution unit 502 in this comparative example uses the reactive power margin calculation unit 901 and is based on Pgen (x) (x = 1, 2, 3). Calculates the margin Qmarg (x) of the reactive power that can be output by. In this comparative example, the margin of the reactive power is the upper limit of the reactive power that can be output when each power conversion device outputs the active power Pgen (x).

Further, as shown in FIG. 7, the reactive power command distribution unit 502 divides Qmarg (x) (x = 1, 2, 3) by the sum of Qmarg (x) (A / B: A = Qmarg (x). ), B = sum of Qmarg (x)), and the Qref (x) is calculated by multiplying the result of division by Qref.

FIG. 8 is an explanatory diagram of a means for calculating the reactive power margin in the comparative example.

On the PQ plane (P: active power, Q: reactive power), the power (for example, rated power) that the power converter can output in terms of performance (design) is represented by a semicircle.

On the semicircle in FIG. 8, the value of Q with respect to P = Pgen (x) is Qmarg (x). However, Qmarg (x) is limited by the maximum value of the reactive power that the power converter can output in terms of performance (design). That is, the range indicated by the thick line in the semicircle in FIG. 8 is the range of Qmarg (x). In this case, Qmarg (x) is represented by the equation (1). The reactive power command distribution unit 502 calculates Qmarg (x) using the equation (1).

As described above, in the comparative example, the ineffective power command distribution unit 502 sets the total ineffective power command value Quref to the ineffective power margin Qmarg (x), that is, each electric power according to the active power Pgen (x) of each power conversion device. The ineffective power command value Quref (x) is created by proportionally allocating according to the upper limit of the ineffective power output by the conversion device. Therefore, when the photovoltaic power generation device outputs the reactive power for system stabilization, the apparent power output by the power conversion device increases, and the power conversion loss increases. Therefore, the operating efficiency of the power conversion loss is lowered.

On the other hand, according to the reactive power command distribution unit in the first embodiment, it is possible to suppress an increase in the power conversion loss while distributing the Qref to each power conversion device.

Hereinafter, the reactive power command distribution unit in the first embodiment will be described.

FIG. 9 is a flowchart showing an outline of processing in the reactive power command distribution unit in the first embodiment.

When the process is started, the reactive power command distribution unit in the first embodiment first calculates the reactive power margin (step S1).

Next, the reactive power command distribution unit calculates the apparent power output by the power conversion device (step S2).

Next, the reactive power command distribution unit sets a priority for assigning the reactive power command to each power conversion device based on the apparent power calculated in step S2, and further sets a total reactive power command according to the set priority. Is distributed to each power converter (step S3).

FIG. 10 is a functional block diagram showing the configuration of the reactive power command distribution unit 502 in the first embodiment. The reactive power command distribution unit 502 shown in FIG. 10 executes the process shown in FIG. 9 described above.

As shown in FIG. 10, the ineffective power command distribution unit 502 includes an ineffective power margin calculation unit 901 that calculates an ineffective power margin for each of a plurality of power conversion devices included in the solar power generation device 101, and a plurality of power conversion devices. Based on the apparent power calculation unit 902 that calculates the apparent power for each and the calculated invalid power margin and the apparent power, the total negative power command QRef is distributed to each power conversion device, and the invalid power command of each power conversion device is distributed. It includes a priority-based invalid power command distribution unit 903 that creates a value.

The reactive power margin calculation unit 901 uses the same means as in the above comparative example (see FIG. 8 and equation (1)) to output the active power Pgen (x) of each power conversion device (x: x = 1, 2, 3). ), The reactive power margin Qmarg (x) of each power conversion device, that is, the upper limit of the reactive power that can be output with respect to Pgen (x) is calculated.

The apparent power calculation unit 902 calculates the apparent power Sgen (x) output by each power conversion device based on the active power Pgen (x) and the ineffective power Qgen (x) output by each power conversion device. As shown in the figure, the apparent power calculation unit 902 is a vector of "Sgen (x) = (Pgen (x) ² + Qgen (x) ² ) ^0.5 " (Pgen (x) and Qgen (x)). Sgen (x) is calculated using the relation (the magnitude of the sum).

The priority-based reactive power command distribution unit 903 sets the priority for assigning the total reactive power command Quref to each power conversion device based on the apparent power Sgen (x) as described below. Further, the priority-based reactive power command distribution unit 903 distributes the total reactive power command Qref to each power conversion device according to the set priority, and creates the reactive power command value Qref (x) for each power conversion device. To do.

FIG. 11 is a functional block diagram showing a configuration example of the priority-based reactive power command distribution unit 903. An example of specific means is described in the functional block.

The priority-based reactive power command distribution unit 903 uses the priority setting unit to set the priority for assigning the total reactive power command QReff to each power conversion device based on the apparent power Sgen (x). In FIG. 11, as an example, higher priority is set in descending order of magnitude of apparent power Sgen (x). That is, for the three power conversion devices Px (x = 1, 2, 3), when the magnitude of the apparent power Sgen (x) is Sgen (1)> Sgen (2)> Sgen (3), the priority is given. N (N: a natural number with higher priority in the order of N = 1, 2, 3 ...) Is set as power conversion device P1 = 1, power conversion device P2 = 2, power conversion device P3 = 3. ..

The priority-based reactive power command distribution unit 903 is based on, for example, FIG. 11 based on the priority (P1 = 1, P2 = 2, P3 = 3) and the reactive power margin Qmarg (x) set by the priority setting unit. By the means described in the inside, the total reactive power command value Qref is distributed to each power conversion device to create the reactive power command value Qref (x).

When the sum of the reactive power margins (Qtpp (3)) of the power converters P1, P2, and P3 is larger than the total reactive power command value Quref, the value of the reactive power margin Qmarg (x) of each power converter is each power. It is assigned as the reactive power command value Quref (x) for the converter.

If Qtpp (3) is not larger than Qref, but the sum of the reactive power margins (Qtpp (2)) of the power converters P1 and P2 is larger than the total reactive power command value Qref, the two units are in descending order of priority. The value of Qmarg (x) is assigned as Qref (x) to the power converters P1 and P2 of. The residual Qref (Qref-Qtpp (2)) is assigned as the Qref (x) to the power converter P3 having the lowest priority.

If Qtpp (2) is not greater than Qref, but the sum of the reactive power margins of the power converter P1 (Qtpp (1) (= Qmarg (P1))) is greater than the total reactive power command value Qref, the priority The value of Qmarg (x) is assigned as Qref (x) to the power converter P1 having the highest value. The residual Qref (Qref-Qtpp (1)) is assigned as the Qref (x) to the power conversion device P2 having the next highest priority. Qref is not assigned to the power conversion device P3 having the lowest priority, and Qref (x) becomes zero.

In any of the above cases, that is, when the Qref is smaller than Qtpp (1), all of the Qrefs are assigned as the Qref (x) to the power converter P1 having the highest priority.

In this way, for each power conversion device, the priority of Qref allocation is increased according to the magnitude of the apparent power, and the Qmarg (x) that each power conversion device can output from the power conversion device with the higher priority. Since Qref (x) is assigned up to the upper limit, an increase in the apparent power of the power conversion device due to the invalid power control can be suppressed.

FIG. 12 is a functional block diagram showing another configuration example of the priority-based reactive power command distribution unit 903.

In this configuration example as well, Qref (x) is assigned according to the magnitude of the apparent power Sgen (x) of each power conversion device, but the priority-based invalid power command distribution unit 903 of this configuration example is Sgen (x). ) Is multiplied by the proportional gain (proportional constant) to calculate Qref (x). The multiplication value of Sgen (x) and the proportional gain (proportional constant) is output as Qref (x) via a limiter having −Qmarg (x) and Qmarg (x) as the lower limit value and the upper limit value, respectively. ..

Here, the priority-based reactive power command distribution unit 903 reduces the calculated sum of Qref (x) and the difference between Qref (Qref- (sum of Qref (x))), that is, Qref (x). Adjust the magnitude of the proportional gain so that the sum of the above matches the Qref. As a result, Qref is substantially assigned to each power converter according to the ratio of the apparent power Sgen (x) of each power converter to the total apparent power (total of Sgen (x)) of the plurality of power converters. Proportional distribution.

In this way, Qref is distributed to each power conversion device according to the magnitude of the apparent power, and Qmarg (x) that can be output by each power conversion device is set as a limit value for each power conversion device. Since Qref (x) is assigned, the increase in apparent power of the power conversion device due to the invalid power control can be suppressed.

FIG. 13 is a vector diagram showing an example of the output voltage vector of the present embodiment (FIG. 11) and the comparative example. The configuration of the priority-based reactive power command distribution unit is the configuration shown in FIG.

As shown in FIG. 13, the magnitude of the apparent power in the target total power command 1300 (the vector sum of the total active power command Pim and the total reactive power command Quref) is 2.3324 pu (per unit). On the other hand, the total sum of the apparent power Sgen (x) in the power commands 1301, 1302, 1303 (the sum of the active power command Pim (x) and the ineffective power command Quref (x) vectors) of each power conversion device in the comparative example is 2. It is 3767pu, and the total apparent power in the power commands 1301A, 1302A, and 1303A of each power conversion device in this embodiment (FIG. 11) is 2.3543. As described above, according to the present embodiment (FIG. 11), it is possible to suppress an increase in total apparent power due to reactive power control.

FIG. 14 is a vector diagram showing an example of the output voltage vector of the present embodiment (FIG. 12) and the comparative example. The configuration of the priority-based reactive power command distribution unit is the configuration shown in FIG.

Similar to the case of FIG. 13, the magnitude of the apparent power in the target total power command 1300 is 2.3324 pu, and the total apparent power in the power commands 1301, 1302, 1303 of each power converter in the comparative example is 2.3767 pu. Is. On the other hand, the total apparent power in the power commands 1301B, 1302B, and 1303B of each power conversion device in this embodiment (FIG. 12) is 2.3394. As described above, according to the present embodiment (FIG. 12), it is possible to suppress an increase in the total apparent power due to the control of the reactive power.

As described above, according to the first embodiment, with respect to the active power value output by each power conversion device according to the magnitude of the apparent power output by each power conversion device for a plurality of power conversion devices. Since the total power conversion command value is distributed within the range of the power conversion device that can output the power conversion device, the increase in the apparent power of the power conversion device due to the power conversion device control can be suppressed. As a result, the increase in power conversion loss can be suppressed, so that the operating efficiency of the photovoltaic power generation device is improved.

Next, the photovoltaic power generation system according to the second embodiment of the present invention will be described. In the following, the points different from those of the first embodiment will be mainly described.

FIG. 15 is a flowchart showing an outline of processing in the reactive power command distribution unit in the second embodiment.

When the process is started, the invalid power command distribution unit in the second embodiment first sets a provisional invalid power command for each power conversion device based on the active power output by each power conversion device (step S10).

Next, the reactive power command distribution unit corrects the initial value of the reactive power command set in step S10 based on the output power limit value (step S20).

Next, the reactive power command distribution unit calculates the reactive power margin when outputting the reactive power corresponding to the modified reactive power command obtained in step S20 (step S30).

Next, the reactive power command distribution unit calculates the apparent power output by the power conversion device (step S40).

Next, the reactive power command distribution unit sets a priority for assigning the reactive power command to each power conversion device based on the apparent power calculated in step S40, and further sets a total reactive power command according to the set priority. Is distributed to each power converter (step S50).

FIG. 16 is a functional block diagram showing the configuration of the reactive power command distribution unit 502 in the second embodiment. The reactive power command distribution unit 502 shown in FIG. 10 executes the process shown in FIG. 15 described above.

As shown in FIG. 10, the ineffective power command distribution unit 502 includes an active power-based invalid power command setting unit 1401 for setting a provisional inactive power command, and an ineffective power output limiter 1402 for modifying the provisional inactive power command. , The invalid power margin calculation unit 1403 that calculates the invalid power margin based on the modified invalid power command output by the invalid power output limiter 1402, and the apparent power calculation unit 1404 that calculates the apparent power based on the modified invalid power command. Priority-based disabled power command distribution unit 1405 that distributes the total disabled power command Quref to each power converter and creates the disabled power command value of each power converter based on the disabled power margin and apparent power to be generated. To be equipped.

The active power base invalid power command setting unit 1401 is a provisional invalid power command value of each power conversion device based on the active power Pgen (x) output by each power conversion device (x: x = 1, 2, 3). Set Qref_idea (x).

The invalid power output limiter 1402 modifies the Qref_idea (x) based on the output power limit value (Qmarg (x) in FIG. 18) described later, and outputs the modified invalid power command QRev (x).

The reactive power margin calculation unit 1403 calculates the reactive power margin Qmarg0 (x) of each power conversion device used by the priority-based reactive power command distribution unit 1405, which will be described later, based on Qrev (x) and Pgen (x).

The apparent power calculation unit 1404 is based on Pgen (x) and Qrev (x), and when each power conversion device outputs Pgen (x) and Qrev (x), the apparent power Srev (x) of each power conversion device is used. Is calculated.

As shown in the figure, the apparent power calculation unit 902 is a vector of "Srev (x) = (Pgen (x) ² + Qrev (x) ² ) ^0.5 " (Pgen (x) and Qrev (x)). The Srev (x) is calculated using the relation (the magnitude of the sum).

The priority-based reactive power command distribution unit 1405 sets the priority for assigning the total reactive power command Queff to each power conversion device based on the apparent power Srev (x) as described below. In the second embodiment, the priority-based reactive power command distribution unit 1405 sets the difference Qdiff (Qref- (sum of Qrev (x))) between the total reactive power command Qref and the sum of Qrev (x). Distribute to each power converter. Further, the priority-based invalid power command distribution unit 1405 distributes the Qdiff to each power conversion device according to the set priority, and outputs the difference distribution value Qdiff (x) to each power conversion device.

The reactive power command distribution unit 502 in the second embodiment sets the sum of the Qdiff (x) output by the priority-based reactive power command distribution unit 1405 and the Qrev (x) output by the reactive power output limiter 1402, respectively. It is output as an invalid power command value Quref (x) for the power converter.

FIG. 17 is a functional block diagram showing the configuration of the active power-based reactive power command setting unit 1401 in the second embodiment (FIG. 16).

The active power-based reactive power command setting unit 1401 distributes the QRef proportionally according to the magnitude of the active power Pgen (x) output by each power converter, thereby providing a provisional reactive power command value for each power converter. Calculate Qref_idea (x).

More specifically, as shown in FIG. 17, the active power-based reactive power command setting unit 1401 divides Pgen (x) (x = 1, 2, 3) by the sum of Pgen (x) (A /). B: A = Pgen (x), B = Pgen (x) sum)), and by multiplying the result of division by the total reactive power command Qref, the provisional reactive power command value Qref_idea for each power converter ( x) is calculated.

FIG. 18 is a functional block diagram showing the configuration of the reactive power output limiter 1402 in the second embodiment (FIG. 16).

The reactive power output limiter 1402 uses the reactive power margin calculation unit to calculate the reactive power margin Qmarg (x) as an invalid power limit value set in the limiter unit for correcting the Qref_idea (x).

The reactive power margin calculation unit uses the means shown in FIG. 8 and equation (1) above to obtain the reactive power margin Qmarg (x) of each power conversion device based on the active power Pgen (x) output by each power conversion device. That is, the upper limit of the reactive power that can be output with respect to Pgen (x) is calculated. The reactive power margin calculation unit sets the calculated Qmarg (x) in the limiter as a limit value.

The reactive power output limiter 1402 limits the provisional reactive power command value Quref_idea (x) to a value of −Qmarg (x) or more and Qmarg (x) or less by the limiter unit, and corrects the limited value. Output as command QRev (x). Therefore, Qrev (x) is represented by the equation (2).

Here, the operation of the reactive power margin calculation unit 1403 in the second embodiment (FIG. 16) will be described.

As will be described next, the reactive power margin calculation unit 1403 is a means different from the calculation means in the reactive power margin calculation unit in the reactive power output limiter 1402, that is, the means shown in FIG. The margin Qmarg0 (x) is calculated.

First, in the reactive power margin calculation unit 1403, the reactive power margin calculation unit is Qmarg (x) based on the active power Pgen (x) output by each power conversion device by the means shown in FIG. 8 and the formula (1) described above. ) Is calculated. Instead of calculating the Qmarg (x), the Qmarg (x) calculated by the reactive power output limiter 1402 may be used.

Further, the reactive power margin calculation unit 1403 calculates Qmarg0 (x) by the means represented by the equation (3) based on the Qmarg (x) and the Qrev (x) output by the reactive power output limiter 1402. ..

Therefore, if Qdiff is zero and positive, that is, if the sum of Qrev (x) is equal to or less than Qref, then Qmarg0 (x) is the difference between Qmarg (x) and Qrev (x) (Qmarg (x)). −Qrev (x)). Further, when Qdiff is a negative value, that is, when the sum of Qrev (x) is larger than Qref, Qmarg0 (x) is the difference between −Qmarg (x) and Qrev (x) (−Qmarg (x) −. Qrev (x)).

FIG. 19 is a functional block diagram showing a configuration example of the priority-based reactive power command distribution unit 1405 in the second embodiment (FIG. 16).

The priority-based reactive power command distribution unit 1405 uses the priority setting unit to provide each power conversion device with the total reactive power command Qref and the total sum of the Qrev (x) based on the apparent power Srev (x). Set the priority for assigning the difference Qdiff. In FIG. 11, as an example, higher priority is set in descending order of magnitude of apparent power Srev (x). That is, for the three power conversion devices Px (x = 1, 2, 3), when the magnitude of the apparent power Srev (x) is Srev (1)> Srev (2)> Srev (3), the priority is given. N (N: a natural number with higher priority in the order of N = 1, 2, 3 ...) Is set as power conversion device P1 = 1, power conversion device P2 = 2, power conversion device P3 = 3. ..

The priority-based reactive power command distribution unit 1405 is based on, for example, FIG. 11 based on the priority (P1 = 1, P2 = 2, P3 = 3) and the reactive power margin Qmarg0 (x) set by the priority setting unit. By the means described in the inside, Qdiff is distributed to each power conversion device, and a difference distribution value Qdiff (x) for each power conversion device is created.

When the sum of the reactive power margins Qmarg0 (x) of the power converters P1, P2, and P3 (Qtpp (3)) is larger than Qdiff, the value of the reactive power margin Qmarg0 (x) of each power converter is the value of each power conversion. It is assigned as the difference distribution value Qdiff (x) for the device.

If Qtpp (3) is not larger than Qdiff, but the sum of the reactive power margins Qmarg0 (x) (Qtpp (2)) of the power converters P1 and P2 is larger than Qdiff, the two units are in descending order of priority. The value of Qmarg0 (x) is assigned to the power converters P1 and P2 as Qdiff (x). The residual Qdiff (Qdiff-Qtpp (2)) is assigned to the power converter P3 having the lowest priority as Qdiff (x).

If Qtpp (2) is not larger than Qdiff, but the sum of the reactive power margins of the power converter P1 (Qtpp (1) (= Qmarg0 (P1))) is larger than Qdiff, the power conversion with the highest priority. The value of Qmarg0 (x) is assigned to the vessel P1 as Qdiff (x). The residual Qdiff (Qdiff-Qtpp (1)) is assigned to the power conversion device P2 having the next highest priority as Qdiff (x). Qdiff is not distributed to the power conversion device P3 having the lowest priority, and Qdiff (x) becomes zero.

In any of the above cases, that is, when Qdiff is smaller than Qtpp (1), all of Qdiff is assigned as Qdiff (x) to the power converter P1 having the highest priority.

In this way, for each power conversion device, the priority of Qdiff allocation is increased according to the magnitude of the apparent power Srev (x), and each power conversion device can output from the power conversion device having a high priority. Since Qdiff (x) is assigned with Qmarg0 (x) as the upper limit, an increase in apparent power of the power conversion device due to invalid power control can be suppressed.

FIG. 20 is a functional block diagram showing another configuration example of the priority-based reactive power command distribution unit 1405.

In this configuration example as well, Qdiff is distributed according to the magnitude of the apparent power Srev (x) of each power conversion device, but the priority-based reactive power command distribution unit 1405 of this configuration example is assigned to Srev (x). Calculate Qdiff (x) by multiplying by the proportional gain (proportional constant). The multiplication value of Sgen (x) and the proportional gain (proportional constant) is Qdiff via a limiter having −Qmargd (x) and Qmargu (x) (see equation (3)) as the lower limit value and the upper limit value, respectively. It is output as (x).

Here, the priority-based reactive power command distribution unit 1405 reduces the difference between the calculated sum of Qdiff (x) and Qdiff (Qdiff− (sum of Qdiff (x))), that is, Qdiff (x). Adjust the magnitude of the proportional gain so that the sum of the above matches the Qdiff. As a result, Qdiff is substantially assigned to each power converter according to the ratio of the apparent power Srev (x) of each power converter to the total apparent power (total of Srev (x)) of the plurality of power converters. Proportional distribution.

In this way, for each power conversion device, Qdiff can be distributed to each power conversion device according to the magnitude of the apparent power, and each power conversion device can output −Qmargd (x) and Qmargu (x). Since Qdiff (x) is assigned to each power conversion device with (see equation (3)) as a limit value, an increase in apparent power of the power conversion device due to invalid power control can be suppressed.

FIG. 21 is a vector diagram showing an example of the output voltage vector of the present embodiment (FIG. 19) and the comparative example. The configuration of the priority-based reactive power command distribution unit 1405 is the configuration shown in FIG.

As shown in FIG. 21, the magnitude of the apparent power in the target total power command 2000 is 2.3324 p (per unit). On the other hand, the total apparent power in the power commands 1301, 1302, 1303 of each power conversion device in the comparative example is 2.3767pu, and the power commands 2001A, 2002A, of each power conversion device in this embodiment (FIG. 19). The total apparent power in 2003A is 2.3409. As described above, according to the present embodiment (FIG. 19), it is possible to suppress an increase in the total apparent power due to the control of the reactive power.

FIG. 22 is a vector diagram showing an example of the output voltage vector of the present embodiment (FIG. 20) and the comparative example. The configuration of the priority-based reactive power command distribution unit 1405 is the configuration shown in FIG.

Similar to the case of FIG. 21, the magnitude of the apparent power in the target total power command 1300 is 2.3324 pu, and the total apparent power in the power commands 1301, 1302, 1303 of each power converter in the comparative example is 2.3767 pu. Is. On the other hand, the total apparent power in the power commands 2001B, 200B, 2003B of each power conversion device in this embodiment (FIG. 20) is 2.3394. As described above, according to the present embodiment (FIG. 20), it is possible to suppress an increase in total apparent power due to the control of reactive power.

As described above, according to the second embodiment, with respect to the active power value output by each power conversion device according to the magnitude of the apparent power output by each power conversion device for a plurality of power conversion devices. Since the total power conversion command value is distributed within the range of the power conversion device that can output the power conversion device, the increase in the apparent power of the power conversion device due to the power conversion device control can be suppressed. As a result, the increase in power conversion loss can be suppressed, so that the operating efficiency of the photovoltaic power generation device is improved.

The present invention is not limited to the above-described embodiment, and includes various modifications. For example, the above-described embodiment has been described in detail in order to explain the present invention in an easy-to-understand manner, and is not necessarily limited to the one including all the described configurations. Further, it is possible to add / delete / replace a part of the configuration of each embodiment with another configuration.

For example, the number of power conversion devices is not limited to three, and may be a plurality of power conversion devices.

Further, the above-mentioned system control device, that is, a power control device can be applied not only to a photovoltaic power generation device but also to other power supply devices such as a wind power generation device and a power supply device using a power storage device.

101 photovoltaic power generation equipment, 102 power system, 103 load,
104 system control unit, 105 system operator, 106 power converter,
107 sensor, 201 converter control unit, 202 power converter,
203 solar panel, 301 input / output interface,
302 System power command setting unit, 303 Power command distribution unit,
304 database, 305 monitor, 401 power calculation unit,
402 Reactive power limit value calculation unit, 403 Load power estimation unit,
404 Active power upper limit calculation unit, 405 Reverse power flow suppression unit, 406 Sum total unit,
501 Active Power Command Distributor, 502 Reactive Power Command Distributor,
901 Reactive power margin calculation unit, 902 Apparent power calculation unit,
903 Priority-based reactive power command distributor,
1401 Active power base Reactive power command setting unit,
1402 Reactive power output limiter, 1403 Reactive power margin calculation unit,
1404 Apparent power calculation unit, 1405 Priority-based reactive power command distribution unit

Claims (15)

In a power control device that controls the output power of multiple power converters that are connected to multiple power sources and connected to the power system.
Power control, characterized in that, in order for the plurality of power conversion devices to output a desired total negative power, the negative power output by the power conversion device is controlled according to the apparent power output by the power conversion device. apparatus. In the power control device according to claim 1,
A power control device characterized in that the reactive power is limited within a range that can be output with respect to the active power output by the power conversion device. In the power control device according to claim 1,
A power control device for distributing the desired total reactive power to the plurality of power conversion devices according to the apparent power. In the power control device according to claim 3,
A power control device characterized in that the larger the apparent power is, the more preferentially the desired total reactive power is distributed to the power conversion device. In the power control device according to claim 3,
A priority for distributing the total reactive power according to the apparent power is set for the plurality of power conversion devices.
A power control device characterized in that the reactive power is controlled according to the priority. In the power control device according to claim 1,
A power control device characterized in that the reactive power is controlled according to the ratio of the apparent power to the total apparent power output by the plurality of power conversion devices. In the power control device according to claim 1,
The command value of the reactive power is calculated by multiplying the apparent power by a predetermined proportional gain.
A power control device characterized in that the proportional gain is adjusted so that the sum of the command values of the reactive power for each of the plurality of power conversion devices matches the total reactive power. In the power control device according to claim 1,
Temporary ineffective power is set based on the active power output by the power conversion device, and the difference between the total of the provisional ineffective power of the plurality of power conversion devices and the total ineffective power is set for the plurality of power conversion devices. A power control device characterized by distribution. In the power control device according to claim 8,
A power control device characterized in that the larger the apparent power is, the more preferentially the difference is distributed to the power conversion device. In the power control device according to claim 8,
For the plurality of power conversion devices, a priority for distributing the difference according to the apparent power is set.
A power control device characterized in that the reactive power is controlled according to the priority. In the power control device according to claim 8,
A power control device characterized in that the reactive power is controlled according to the ratio of the apparent power to the total apparent power output by the plurality of power conversion devices. In the power control device according to claim 8,
The apparent power is multiplied by a predetermined proportional gain to calculate the distribution command value of the difference with respect to the power conversion device.
A power control device characterized in that the proportional gain is adjusted so that the sum of the distribution command values of the difference with respect to each of the plurality of power conversion devices matches the difference. With multiple power sources
A plurality of power converters to which the plurality of power sources are connected and connected to a power system, and
A power control device that controls the output power of the plurality of power conversion devices, and
In the power supply equipment equipped with
The power control device is
A power supply characterized in that, in order for the plurality of power conversion devices to output a desired total negative power, the negative power output by the power conversion device is controlled according to the apparent power output by the power conversion device. Facility. In the power supply equipment according to claim 13,
A power supply facility characterized in that the power source is a solar cell. In a power control method that controls the output power of multiple power converters that are connected to multiple power sources and connected to the power system.
Power control, characterized in that, in order for the plurality of power conversion devices to output a desired total negative power, the negative power output by the power conversion device is controlled according to the apparent power output by the power conversion device. Method.

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