Power conversion device and control method for power conversion device

Abstract

The present invention reduces power loss during autonomous operation of a power conversion device provided with a power storage device.　This power conversion device is provided with a power storage device. The power conversion device comprises: an operation determination unit that determines whether the power conversion device is in an autonomous operation state or not; a power calculation unit that calculates power stored or output by the power storage device and determines whether or not power is stored in the power storage device; an active power command value setting unit that receives an active power value and determines an active power command value from the received value and the active power calculated by the power calculation unit; and a main circuit that outputs power on the basis of the active power command value determined by the active power command value setting unit. When the operation determination unit determines that the power conversion device is in the autonomous operation state, the active power command value setting unit changes the active power command value to an active power command value that does not store power in the power storage device when the power calculation unit detects power stored in the power storage device.

Description

Power conversion device and control method for power conversion device

[0001] The present invention relates to a power conversion device and a control method for a power conversion device.

[0002] A power supply system consisting of a plurality of power generation facilities including a power storage facility having a power storage device and a power converter, the power supply system having a voltage measurement means for measuring the voltage of the power supply system, a frequency measurement means for measuring the frequency of the power supply system, a power measurement means for measuring active power and reactive power at an output terminal of the power storage facility, and a system control device, the system control device comprising: a first proportional calculator for proportionally calculating a deviation between an active power command value and the active power measured by the power measurement means; a frequency command value calculation unit having a first adder for calculating a frequency command value by adding a reference frequency to an output of the first proportional calculator; There is a power conversion device for a combined power generation system that includes an internal phase difference angle calculation unit that calculates an internal phase difference angle by integrating the deviation between a command value and the frequency measured by the frequency measurement means, an internal electromotive voltage command value calculation unit that has a second proportional calculator that proportionally calculates the deviation between a reactive power command value and the reactive power measured by the power measurement means, and a second adder that calculates an internal electromotive voltage command value by adding a reference voltage to the output of the second proportional calculator, and a current command value calculation unit that calculates a command value for an output current of the power converter from the internal phase difference angle, the internal electromotive voltage command value, and the voltage measured by the voltage measurement means, and outputs the command value for the output current to control the power converter (Patent Document 1).

[0003] WO13 / 008413

[0004] The power conversion device for a combined power generation system described above supplies a power converter that does not require a change in control method when interconnected to a grid, thereby making it possible to build an independent power supply system that is easy to handle.

[0005] However, while the power conversion device for the combined power generation system outputs active power according to the command value during grid-connected operation, the output of the power conversion device for the combined power generation system during independent operation is determined by the power consumption of the load.Therefore, when switching from grid-connected operation to independent operation, if independent operation is started using the command value of the active power during grid-connected operation, the actual active power output by the power conversion device for the combined power generation system will deviate from the command value.

[0006] When multiple power conversion devices for a combined power generation system are operated in parallel, there is a problem that charging power conversion devices for the combined power generation system and discharging power conversion devices for the combined power generation system are mixed together, resulting in losses due to the exchange of power between the power conversion devices for the combined power generation system.

[0007] An object of the present invention is to provide a power conversion device that includes a power storage device and that reduces power loss during stand-alone operation.

[0008] An object of the present invention is achieved by a power conversion device equipped with a power storage device, the power conversion device comprising: an operation determination unit that determines whether the power storage device is in an autonomous operation state; a power calculation unit that calculates the power stored or output by the power storage device and determines whether power is being stored in the power storage device; an active power command value setting unit that receives an active power value and determines an active power command value from the received value and the active power calculated by the power calculation unit; and a main circuit that outputs power based on the active power command value determined by the active power command value setting unit, wherein when the operation determination unit determines that the power storage device is in an autonomous operation state, the active power command value setting unit changes the active power command value to one that does not store power in the power storage device when the power calculation unit detects that power is being stored in the power storage device.

[0009] According to the present invention, it is possible to reduce power loss during stand-alone operation of a power conversion device equipped with a power storage device.

[0010] FIG. 1 is a block diagram showing the configuration of a power conversion device according to a first embodiment of the present invention. FIG. 2 is a diagram showing the configuration of a phase command generating unit according to the first embodiment of the present invention. FIG. 3 is a diagram showing the relationship between an active power command value, active power, and an angular frequency change amount command according to the first embodiment of the present invention. FIG. 4 is a block diagram showing a system configuration according to the first embodiment of the present invention. FIG. 5 is a graph showing the relationship between an active power command value, active power, and an angular frequency change amount command in the system configuration example according to the first embodiment of the present invention. FIG. 6 is a flowchart of a method for updating an active power command value of the power conversion device according to the first embodiment of the present invention. FIG. 7 is a graph showing the time change of active power and the time change of the angular frequency change amount command in the power conversion device according to the first embodiment of the present invention. FIG. 8 is a graph showing the relationship between the active power command value, active power, and the angular frequency change amount command when the load power consumption fluctuates in the system configuration example according to the first embodiment of the present invention. FIG. 9 is a block diagram showing the configuration of a power conversion device according to a second embodiment of the present invention. FIG. 10 is a block diagram showing a system configuration according to the second embodiment of the present invention. FIG. 11 is a graph showing the relationship between the active power command value, angular frequency command, and update determination angular frequency in the system configuration example according to the second embodiment of the present invention. FIG. 12 is a flowchart of a method for updating an active power command value of the power conversion device according to the second embodiment of the present invention. FIG. 13 is a graph showing the relationship between the active power command value, active power, and the angular frequency change amount command in the system configuration example according to the second embodiment of the present invention. Graph showing the relationship between an active power command value, active power, and an angular frequency change amount command in an example of a system configuration according to a second embodiment of the present invention. Graph showing the relationship between an active power command value, an angular frequency command, and an angular frequency for update determination in a third embodiment of the present invention. Graph showing the relationship between an active power command value, active power, and an angular frequency change amount command in a third embodiment of the present invention. Graph showing the relationship between an active power command value, active power, and an angular frequency change amount command in a third embodiment of the present invention. Block diagram showing a system configuration according to a fourth embodiment of the present invention.

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the following examples. Those skilled in the art will be able to make various additions and modifications within the scope of the present invention.

[0012] FIG. 1 shows an example of the configuration of a power conversion device according to a first embodiment of the present invention.

[0013] The power conversion device 1 includes a main circuit 2 which is a power supply unit, a control unit 3 which controls the power and phase to be supplied, and an AC filter 4 which adjusts the waveform of the power to be supplied. The main circuit 2 is, for example, a three-phase full-bridge inverter, and the AC end of the main circuit 2 is connected to an AC system 5 and an AC load 6 via the AC filter 4 and a private line 52. The AC system 5 is, for example, 50 Hz, three-phase 200 V, and the AC load 6 is, for example, equipment owned by a consumer, such as an air conditioner.

[0014] The AC load 6 is shown as a single unit, but in reality, multiple AC loads may be connected. The AC filter 4 is made up of an inductor and an X capacitor. A connection point relay 51 is installed at the connection point of the AC system 5 so that the power conversion device 1 and the AC load 6 can be disconnected from the AC system 5.

[0015] The DC end of the main circuit 2 is connected to a power storage device 7. The power storage device 7 is, for example, a secondary battery such as a lithium ion battery, a nickel-metal hydride battery, or a lead-acid battery, or a capacitor. Note that the power storage device 7 may also be a device that can store energy in a form other than electrical power, such as a compressed air energy storage (CAES), pumped storage power generation, gravity power generation, or a flywheel, or a device that converts that energy into electrical power.

[0016] A voltage meter 21 is installed on the AC system 5 and AC load 6 side of the AC filter 4, and a current meter 22 is installed on the main circuit 2 side of the AC filter 4. The control unit 3 obtains a measured AC voltage Vout from the voltage meter 21 and a measured AC current Iout from the current meter 22.

[0017] The control unit 3 includes a power calculation unit 31, a phase command generation unit 32, an active power command value setting unit 33, a reactive power command generation unit 34, a reactive power control (AQR) unit 35, and a main circuit control unit 36.

[0018] The power calculation unit 31 calculates the active power Pout (in this embodiment, the power flow that charges the DC power supply 7 is taken as positive) and the reactive power Qout (in this embodiment, the delay is taken as positive) output by the power conversion device 1 from the measured AC voltage value Vout and the measured AC current Iout.

[0019] The phase command generating unit 32 generates a phase command θref using the active power Pout calculated by the power calculating unit 31 and the active power command value Pref output by the active power command value setting unit 33 .

[0020] 2 shows an example of the configuration of the phase command generating unit in the first embodiment of the present invention. In the phase command generating unit 32, first, the active power command value Pref and the active power Pout are input to a subtractor 321 to obtain the deviation Pout-Pref.

[0021] This is input to a proportional controller 322 with a gain Kp, which calculates an angular frequency change command Δωref'. This is illustrated in Figure 3, where the angular frequency change command Δωref' is determined by droop control to which the deviation of the active power is input. The gradient of the droop characteristic of this active power - angular frequency change command is the gain Kp,

[0022] When Pout<Pref, Δωref'<0, and lowering the angular frequency increases Pout (increases charging power or decreases discharging power). When Pout>Pref, Δωref'>0, and decreases Pout (decreases charging power or increases discharging power).

[0023] In this embodiment, this angular frequency change amount command Δωref′ is not used as is, but is input to a virtual inertia imparting filter 323 .

[0024] The virtual inertia imparting filter 323 is, for example, a first-order lead-lag filter, and by determining its time constant using the unit inertia constant and unit damping constant of the synchronous generator, it outputs an angular frequency change command Δωref in which the inertia of the synchronous generator is virtually imparted to Δωref'.

[0025] This virtual inertia imparting filter 323 gently changes Δωref′, which would otherwise change in a step-like manner instantaneously when the deviation Pout-Pref changes in a step-like manner, thereby achieving an angular frequency change with inertia.

[0026] This post-inertia angular frequency change amount command Δωref and the reference angular frequency ω0 (in this embodiment, the reference frequency is set to 50 Hz and 2π×50 rad / s) are input to an adder 324 to obtain an angular frequency command ωref. The angular frequency command ωref is then input to an integrator 325 for integration, thereby generating a phase command θref. The generated phase command θref is output to the main circuit control unit 36.

[0027] The active power command value setting unit 33 can receive the active power value Pref' via wired or wireless communication from a higher-level command device 8 (e.g., an energy management system) of the power conversion device 1 that is external to the power conversion device 1. At this time, the active power command value setting unit 33 uses the received active power value Pref' to output it to the phase command generating unit 32 as the active power command value Pref. The reception frequency can be set arbitrarily, for example, every minute. Aperiodic reception is also possible.

[0028] A reactive power command generation unit 34 generates a reactive power command Qref by multiplying a deviation V0-Vout between a rated voltage V0 (for example, 200 V) and a measured AC voltage Vout by a proportional gain Kq (Kq>0). Then, a reactive power control (AQR) unit 35 generates a voltage command Vref by PI control of a deviation Qref-Qout between this reactive power command Qref and the reactive power Qout calculated by the power calculation unit 31. The generated voltage command Vref is output to a main circuit control unit 36.

[0029] The main circuit control unit 36 ​​generates gate signals for the switching elements of the main circuit 2 by PWM (Pulse Width Modulation) control using the phase command θref and the voltage command Vref, and drives the main circuit 2 .

[0030] As a result, the power conversion device 1 can operate in a grid-connected state with virtual inertia. Since the power conversion device 1 is driven using the phase command θref and the voltage command Vref, the power conversion device 1 operates as a voltage source and can operate independently when the AC grid 5 is disconnected.

[0031] 4 is a block diagram showing an example of a system configuration of a power conversion device according to a first embodiment of the present invention. In this embodiment, a power conversion device 101 and a power conversion device 102 are connected in parallel to an AC load 6 via a private line 52.

[0032] In this embodiment, the AC load 6 is a load that does not generate regeneration as a whole, and the power consumption is Pload (Pload>0). The configurations of the power conversion device 101 and the power conversion device 102 are the same as that of the power conversion device 1. It is also assumed that the gains Kp and Kq used in the power conversion device 101 and the power conversion device 102 are the same.

[0033] The upper command device 8 of the power conversion device communicates with the power conversion device 101 and the power conversion device 102, and transmits Pref1' (Pref1' > 0) as the active power value Pref' to the power conversion device 101, and Pref2' (Pref2' > Pref1') as the active power value Pref' to the power conversion device 102.

[0034] Then, the active power command value setting units 33 of the power conversion devices 101 and 102 generate active power command values ​​Pref1 and Pref2, respectively.

[0035] FIG. 5 is a graph showing the relationship between the active power command value, the active power, and the angular frequency change amount command in the system configuration example of the first embodiment of the present invention, and shows the droop characteristics of the power conversion device.

[0036] Here, Pref1=Pref1', Pref2=Pref2'. At this time, the relationship between the active power command value and the angular frequency change amount command is shown in Fig. 5. The circled point 0 is the operating point of the power conversion device 101 and the power conversion device 102 when they are operating in interconnected mode.

[0037] The droop characteristics of the power conversion device 101 are indicated by a solid line a, and the droop characteristics of the power conversion device 102 are indicated by a solid line b. The AC system 5 supplies only Pref1 and Pref2 to the power conversion device 101 and the power conversion device 102, respectively, and supplies only Pload to the AC load 6. In other words, if the power supplied by the AC system 5 is Pgrid, then Pgrid = Pref1 + Pref2 + Pload.

[0038] Here, if an accident, power outage, etc. occurs in the AC system 5, the interconnection point relay 51 opens, and the power conversion device 101 and the power conversion device 102 switch to independent operation within the private line 52 and supply power to the AC load 6.

[0039] At this time, regardless of the values ​​of Pref1 and Pref2, the power conversion devices 101 and 102 will output a total of the power consumption Pload of the AC load 6. That is, if the actual active powers of the power conversion devices 101 and 102 after transition to independent operation are Pout1 and Pout2, then Pout1 + Pout2 = -Pload.

[0040] Since the power conversion device 101 and the power conversion device 102 are operated in parallel in the isolated operation system, the angular frequency change amount command Δωref′ at the operating point after the transition to isolated operation takes a common value. Point 1 in Figure 5 is the operating point immediately after the transition to isolated operation.

[0041] The actual active powers of the power conversion device 101 and the power conversion device 102 at this operating point 1 are represented as Pout1_1 and Pout2_1. At the operating point 1, Pout1_1<0<Pout2_1 and Pout1_1+Pout2_1=-Pload, and the power conversion device 101 performs a discharging operation, and the power conversion device 102 performs a charging operation, supplying power to the AC load 6.

[0042] In this state, power can be supplied to the AC load 6, but power transfer occurs between the power conversion devices, which results in additional power conversion loss.

[0043] Therefore, control is performed so that power is supplied to the AC load 6 without power exchange between the power conversion devices 101 and 102. Since Pout1+Pout2=-Pload<0, at least one of the power conversion devices 101 and 102 needs to discharge. Therefore, by controlling the charging power conversion device so that it does not charge, power exchange between the power conversion devices 101 and 102 is prevented. In this embodiment, the charging power conversion device 102 is controlled.

[0044] FIG. 6 is a flowchart of a method for updating an active power command value of a power conversion device according to the first embodiment of the present invention.

[0045] With this method, the power conversion device no longer needs to receive an angular frequency command value from an external source to charge or discharge; instead, it changes the active power command value based on ωcheck and information on whether it is charging or discharging itself, making it possible to control the amount of charge and discharge.

[0046] The upper command device 8 may calculate an active power command value based on measured values ​​such as the charge / discharge amount for each power conversion device and the power consumption of the AC load, and transmit the calculated active power command value to each power conversion device. However, if the power consumption of the AC load changes frequently or if a large number of power conversion devices are connected, the upper command device 8 would need to have real-time processing capabilities, which is not practical.

[0047] Hereinafter, the power conversion device may be referred to as a PCS. Fig. 6 is executed at an operation period (e.g., 100 microseconds) in the control unit of the power conversion device that employs this method. Hereinafter, the control of the power conversion device 102 and changes in the operating points of the power conversion devices 101 and 102 will be described with reference to Figs. 5 and 6.

[0048] First, in step S6-2, the power conversion device receives a new active power value Pref′ from the higher-level command device 8 or the like, and then in step S6-6, the power conversion device updates the active power command value Pref to the new active power value Pref′. As a result of the update, the output of the power conversion device changes (step S6-7).

[0049] If a new active power value Pref' has not been received in step S6-2, the process proceeds to step S6-3, where an operation determination unit (not shown) provided in the power conversion device determines whether the power conversion device is in independent operation. For example, the determination may be made whether the power conversion device is in independent operation by an islanding operation detection method provided in the power conversion device, by receiving a contact signal or the like from the interconnection point relay 51, or by manual input or operation by the user of the power conversion device.

[0050] If the power conversion device is not operating in an autonomous mode, i.e., if it is operating in an interconnected mode, the process proceeds to step S6-7. If it is operating in an autonomous mode, the process proceeds to step S6-4, where the active power command value setting unit 33 determines whether the power conversion device is charging, i.e., whether the active power Pout actually being charged or discharged by the power conversion device is positive. If the power conversion device is not charging, the process proceeds to step S6-7. If the power conversion device is charging, the process proceeds to step S6-5.

[0051] Then, the active power command value setting unit 33 executes a change process to autonomously update the active power command value Pref by subtracting the active power Pout from the active power command value Pref. That is, the updated value Pref becomes the value Pref-Pout before the update process. As a result of the change process, the output of the power conversion device changes (step S6-7).

[0052] 5, at operating point 1, both power electronics devices 101 and 102 transition to step S6-3 and then to step S6-4. Power electronics device 101 is discharging and therefore transitions to step S6-7, but power electronics device 102 is charging and therefore transitions to step S6-5.

[0053] Then, the active power command value Pref2 is autonomously updated in the active power command value setting unit 33. During grid-connected operation, Pref2=Pref2', but in step S6-5, the active power command value setting unit 33 sets the active power command value Pref2 to Pref2'-Pout2_1.

[0054] The set active power command value Pref2 is sent to the phase command generator 32. The phase command generator 32 sends θref (phase command) to the main circuit controller 36 to control the active power output by the main circuit. As a result, the droop characteristic of the power conversion device 102 moves from line b to line c in Fig. 5, and the operating point of the power conversion device 102 transitions to point 2 in Fig. 5.

[0055] However, because the active power output of the power conversion device 102 changes from Pout2_1 to 0 [kW], Pout1 + Pout2 = Pout1_1 < -Pload. This is a state in which the power supplied from the power conversion device is large relative to the load power consumption, so the operating points move to a point where Pout1 + Pout2 = -Pload and the angular frequency change amount command Δωref' becomes a common value. The operating point of the power conversion device 101 transitions from point 1 to point 3 in Figure 5 (step S6-7), and the operating point of the power conversion device 102 transitions from point 2 to point 3 in Figure 5 (step S6-7).

[0056] The actual active powers of the power conversion device 101 and the power conversion device 102 at point 3 are represented as Pout1_3 and Pout2_3. At point 3, Pout1_3<0<Pout2_3 and Pout1_3+Pout2_3=-Pload, and the power conversion device 101 is discharging and the power conversion device 102 is charging, supplying power to the AC load 6. In this state, power can be supplied to the AC load 6, but power is being exchanged between the power conversion devices, resulting in a state similar to point 1.

[0057] Then, in steps S6-4 and S6-5, as at point 1, the power conversion device 102 detects that it is charging based on the value of Pout received from the power calculation unit 31, and the active power command value setting unit 33 autonomously updates the active power command value Pref2.

[0058] At this time, Pref2=Pref2′−Pout2_1−Pout2_3. In this way, similar to the transition from point 1 to point 2, the operating point of the power conversion device 102 further transitions from point 3. The point to which this transition is made is point 4. The droop characteristic of the power conversion device 102 at this time is line d in FIG.

[0059] Here, power conversion device 102 operates at point 4 and the active power output is 0 [kW], so Pout1 + Pout2 = Pout1_3 < -Pload. This is a state in which the power supplied from the power conversion device is large compared to the load power consumption, so the operating point of power conversion device 101 moves from point 3 in Fig. 5 and the operating point of power conversion device 102 moves from point 4 in Fig. 5 in accordance with the droop characteristics so that Pout1 + Pout2 = -Pload is established.

[0060] By repeating the above operation, the operating points of the power conversion device 101 and the power conversion device 102 each move to point 5. The droop characteristic of the power conversion device 102 at this time is shown by line e in Figure 5. If the actual active powers of the power conversion device 101 and the power conversion device 102 at point 5 are represented as Pout1_5 and Pout2_5, respectively, then Pout1_5<Pout2_5=0 [kW]. Furthermore, Pout1+Pout2=Pout1_5=-Pload.

[0061] Since the sum of the discharge power of power conversion device 101 and power conversion device 102 is equal to the load power consumption, the operating points of power conversion device 101 and power conversion device 102 each remain at point 5 and do not move according to the droop characteristics as described above.

[0062] At operating point 5, power conversion device 101 discharges and power conversion device 102 operates at 0 kW, so power can be supplied to AC load 6 without power exchange between power conversion devices 101 and 102.

[0063] As described above, the control of this embodiment is processed within the active power command value setting unit 33 of the power conversion device, and does not require the upper command device 8 of the power conversion device. Therefore, when the power conversion devices 101 and 102 transition to independent operation due to an accident, power outage, or the like occurring in the AC system 5, the control of this embodiment is executed even if communication with the upper command device 8 of the power conversion devices is interrupted.

[0064] 7 is a graph showing the time change of the active power of the power conversion device and the time change of the angular frequency change amount command in the first embodiment of the present invention. The horizontal axis represents time, and the origin is the time when the power conversion device 101 and the power conversion device 102 transition to independent operation.

[0065] In the waveform of the active power, the power conversion device 101 has a line f, and the power conversion device 102 has a line g. As described above, the angular frequency change amount command Δωref′ (line h) has a common value for the power conversion device 101 and the power conversion device 102.

[0066] The control in this embodiment is executed for each calculation cycle of the control units of the power conversion devices 101 and 102. This calculation cycle is often equal to or shorter than several hundred microseconds, and at this time, the active power Pout2_3 at the operating point 3 of the power conversion device 102 becomes very small.

[0067] Therefore, the locus of the operating point of the power conversion device 102 does not actually follow a sawtooth wave like point 1 ---> point 2 ---> point 3 ---> point 4 ---> ... in Figure 6, but follows a smooth locus from point 1 to point 5, and when the active power Pout2 of the power conversion device 102 becomes 0 [kW] at point 2, the frequency increases at Pout2 ≈ 0 [kW]. The locus of the operating point of the power conversion device 101 moves from point 1 to point 4, resulting in an overshooting locus.

[0068] 8 is a graph showing an example of the relationship between the active power command value, active power, and angular frequency change command when the load power consumption fluctuates in the example system configuration of Example 1 of the present invention. The droop characteristics of power conversion device 101 are represented by line i, and the droop characteristics of power conversion device 102 are represented by lines j and k. At operating point 5, the droop characteristics of power conversion device 101 are represented by line i, and the droop characteristics of power conversion device 102 are represented by line j.

[0069] After the operating points of the power conversion device 101 and the power conversion device 102 each shift to point 5 as described above, when the power consumption of the AC load increases to Pload2 (Pload2>Pload), the power conversion device 101 and the power conversion device 102 increase the discharge power to cover the load power consumption.

[0070] At this time, the operating points of the power conversion devices 101 and 102 move from point 5 in accordance with the droop characteristics to point 6 where Pout1+Pout2=-Pload2 and the angular frequency change amount command Δωref' has a common value. At this time, since both the power conversion devices 101 and 102 are discharging, the control for autonomously updating the above-mentioned active power command value is not performed.

[0071] On the other hand, after the operating points of the power conversion devices 101 and 102 each shift to point 5 as described above, when the power consumption of the AC load decreases to Pload3 (0 < Pload3 < Pload), the power conversion devices 101 and 102 reduce their discharge power and discharge the same amount of power as the load power consumption.

[0072] At this time, the operating points of power conversion devices 101 and 102 move from point 5 in accordance with the droop characteristics to point 7 where Pout1+Pout2=-Pload3 and the angular frequency change amount command Δωref' has a common value. If the actual active powers of power conversion devices 101 and 102 at point 7 are represented as Pout1_7 and Pout2_7, then at point 7, Pout1_7<0<Pout2_7.

[0073] That is, the power conversion device 101 performs a discharging operation, and the power conversion device 102 performs a charging operation to supply power to the AC load 6, and although power can be supplied to the AC load 6, power is being exchanged between the power conversion devices. Therefore, in the power conversion device 102, which is the power conversion device that is charging as described above, an update process is executed in step S6-5 to autonomously update the active power command value in the same manner as described above.

[0074] As a result, the operating point shifts to operating point 8 where Pout1=-Pload3, Pout2=0 [kW], and the angular frequency change amount command Δωref′ has a common value. The droop characteristic of the power conversion device 102 at this time is line k in FIG.

[0075] The control example in this embodiment described above is performed immediately after transition to independent operation due to, for example, an accident, power outage, or the like occurring in the AC system 5. After a certain amount of time has passed since transition to independent operation, the upper command device 8 of the power conversion devices can generate an optimal active power value Pref′ for each power conversion device during independent operation and transmit it to each power conversion device.

[0076] When the active power command value setting unit 33 of each power conversion device receives a new active power value Pref'' from the upper command device 8 of the power conversion device, it resets the autonomous update of the active power command value Pref that had been performed up to that point, sets Pref = Pref'', and can perform operation in accordance with the upper command device 8 of the power conversion device.

[0077] In this embodiment, the case where two power conversion devices are used has been described, but the number of power conversion devices is not limited to two. If three or more power conversion devices are connected, the above-described control may be performed on the third and subsequent power conversion devices. If there is only one power conversion device, the power conversion device can supply power to the load by discharging, so the power conversion device does not perform charging during standalone operation. Therefore, this control is not performed, but having this control program does not affect other operations.

[0078] In this embodiment, the same parts as those in the first embodiment will not be described as necessary.

[0079] 9 shows a configuration example of a power conversion device according to a second embodiment of the present invention. In this example, the active power command value setting unit 33 receives the update determination frequency fcheck or the update determination angular frequency ωcheck together with the active power value Pref′ via wired or wireless communication from a higher-level command device 8 of the power conversion device (for example, an energy management system, not shown in FIG. 9 ) that is external to the power conversion device 1.

[0080] When the update determination frequency fcheck is received, the active power command value setting unit 33 can obtain the update determination angular frequency ωcheck=2π×fcheck by calculation.

[0081] 10 is a block diagram showing an example of a system configuration according to a second embodiment of the present invention. In this embodiment, an AC generator 9 (e.g., a private power generating facility such as a diesel generator) is connected to the AC ends of a power conversion device 101 and a power conversion device 102 via a private line 52 in addition to an AC system 5 and an AC load 6.

[0082] In this embodiment, the AC load 6 is a load that consumes power Pload (Pload>0) and does not generate regeneration. The configurations of the power conversion devices 101 and 102 are the same as that of the power conversion device 1. Also, the power conversion devices 101 and 102 are assumed to use the same values ​​for the gains Kp and Kq.

[0083] The AC generator 9 is connected to the power conversion device 101, the power conversion device 102, and the AC load 6 side of the interconnection point relay 51 of the AC system 5, and is electrically connected to the power conversion device 101, the power conversion device 102, and the AC load 6 even when the AC system 5 is disconnected by the interconnection point relay 51.

[0084] In this embodiment, the AC generator 9 is directly connected to the power converter 101, the power converter 102, and the AC load 6, but may be connected via a transformer or the like.

[0085] It is assumed that the upper command device 8 of the power conversion devices communicates with the power conversion devices 101 and 102, and transmits Pref1' (Pref1'>0) as the active power value Pref' to the power conversion device 101, and transmits Pref2' (Pref2'>Pref1') as the active power value Pref' to the power conversion device 102. Then, the active power command value setting units 33 of the power conversion devices 101 and 102 respectively generate active power command values ​​Pref1 and Pref2.

[0086] In the first embodiment, the active power command values ​​Pref1 and Pref2 were changed according to Fig. 6. On the other hand, in the present embodiment in which the AC generator 9 is connected, the active power command values ​​Pref1 and Pref2 are changed using the angular frequency command value ωref (the sum of the reference angular frequency and the angular frequency change amount command Δωref') of the power conversion device and the update determination angular frequency ωcheck in addition to these operating conditions. The reference angular frequency is set to 2π × 50 rad / s, as in the first embodiment.

[0087] FIG. 11 is a graph showing an example of the relationship between the active power command value, the angular frequency command, and the update determination angular frequency in the example of the system configuration according to the second embodiment of the present invention.

[0088] The initial values ​​of the active power command values ​​Pref1 and Pref2 are Pref1' and Pref2', respectively. At this time, the droop characteristics of the power conversion device 101 are as shown by line 1, and the droop characteristics of the power conversion device 102 are as shown by line m.

[0089] Here, among the angular frequency command values ​​when Pout = 0 for each power conversion device, i.e., the angular frequency command values ​​corresponding to the intercepts of the vertical axis (angular frequency command axis) in the droop characteristics of each power conversion device, the angular frequency command value closest to the reference angular frequency, which is the origin of the graph, becomes the angular frequency ωcheck for update judgment.

[0090] 11, since Pref2'>Pref1', the intercept of the vertical axis (angular frequency command axis) of each droop characteristic that is closest to the reference angular frequency is the intercept of the power conversion device 101. Therefore, the update determination angular frequency ωcheck in this embodiment is the angular frequency command value when Pout=0 for the power conversion device 101.

[0091] In this embodiment, during grid-connected operation, the upper command device 8 of the power conversion devices determines the update determination angular frequency ωcheck and transmits it to each of the power conversion devices 101 and 102. In this embodiment, the power conversion devices 101 and 102 do not communicate with each other, and therefore cannot know each other's active power command value Pref. Furthermore, although not described in the present invention, the droop characteristics (the slopes in FIG. 11 ) of each device may also be different, and the update determination angular frequency ωcheck cannot be calculated independently. Therefore, the update determination angular frequency ωcheck is obtained from the upper command device 8. However, if the power conversion devices in the system are configured to be able to exchange information with each other, they can share information about Pref and the droop characteristics to autonomously calculate the update determination angular frequency ωcheck and operate accordingly.

[0092] Since the upper command device 8 of the power conversion devices transmits the active power values ​​Pref1′ and Pref2′ to the power conversion devices 101 and 102, respectively, if the gains Kp of the power conversion devices 101 and 102 are known, it is possible to determine the update determination angular frequency ωcheck and transmit this to the power conversion devices 101 and 102. The active power command value setting units 33 of the power conversion devices 101 and 102 generate the active power command values ​​Pref1 and Pref2 using the received update determination angular frequency ωcheck.

[0093] FIG. 12 is a flowchart of a method for updating an active power command value of a power conversion device according to the second embodiment of the present invention.

[0094] Steps S12-1, S12-2, S12-3, S12-11, and S12-12 in Fig. 12 are the same as steps S6-1, S6-2, S6-3, S6-6, and S6-7 in Fig. 6 of Example 1. Steps S12-4 to S12-10 will be mainly described below.

[0095] FIG. 13 is a graph showing Example 1 of the relationship between the active power command value, the active power, and the angular frequency change amount command in the example of the system configuration according to the second embodiment of the present invention.

[0096] In this example, an AC generator and two power conversion devices that charge the generator were operating in grid-connected mode at point 0, but due to a transition to independent operation, they have moved to point 1, with power conversion device 101 discharging and power conversion device 102 charging.

[0097] Note that the power storage device 7 connected to the power conversion device may be assumed to be chargeable, and if the power storage device 7 subsequently becomes fully charged, the power conversion device may be controlled not to charge the power storage device 7. That is, in Fig. 12, if the power storage device 7 is fully charged, a determination is made before S12-2 as to whether it is fully charged, and if it is fully charged, the process proceeds to S12-6, and if it is not fully charged, the process from S12-2 onwards continues. With this configuration, it is possible to prevent a fully charged power conversion device from being charged, and to discharge the power storage device when necessary.

[0098] The AC generator 9 outputs a constant power, and in FIG. 13, the characteristics of the AC generator 9 are shown by line n.

[0099] It is assumed that the power conversion devices 101 and 102 have received charging commands (Pref1', Pref2'>0) from the upper command device 8 of the power conversion devices during grid-connected operation, and the flow after transitioning to independent operation (S12-3: Yes) will be described.

[0100] 13, when Pref1', Pref2'>0, the value of the update determination angular frequency ωcheck is less than the reference angular frequency 2π × 50. Therefore, when the process proceeds to step S12-4 in FIG.

[0101] As in the description of the first embodiment, it is assumed that the operating points of the power conversion devices 101 and 102 have shifted to point 1 in FIG. 13 due to the shift to isolated operation.

[0102] Because the angular frequency command value ωref at point 1 is smaller than the update determination angular frequency ωcheck, step S12-5 returns No, and the process proceeds to step S12-6. In FIG. 13 , only the power conversion device 102 is charging at this time. Therefore, in step S12-7, the active power command value setting unit 33 of the power conversion device 102 executes a change process to change the active power command value Pref, and the changed active power command value Pref is sent to the phase command generation unit 32. This change process is performed by dividing the pre-update Pref by the updated Pout to calculate a new Pref, as in the first embodiment. The phase command generation unit 32 sends θref (phase command) to the main circuit control unit 36 ​​to control the active power output by the main circuit. As a result, the droop characteristic of the power conversion device 102 moves from line p to line q in FIG. 13 , and the operating point of the power conversion device 102 transitions to point 2 in FIG. 13 .

[0103] On the other hand, since the power conversion device 101 is discharging, the process transitions from step S12-6 to step S12-12.

[0104] By the above steps, when the active power output of the power conversion device 102 becomes 0 [kW] and the sum of the discharge powers of the AC generator 9, power conversion device 101, and power conversion device 102 becomes larger than the load power consumption, the sum of these discharge powers moves to a point where it is equal to the load power consumption and the angular frequency command ωref has a common value. As a result, the operating point of the power conversion device 101 shifts from point 1 to point 3 in Fig. 13, and the operating point of the power conversion device 102 shifts from point 2 to point 3 in Fig. 13.

[0105] At point 3, the angular frequency command value ωref is lower than the update determination angular frequency ωcheck, so the No branch is taken again in step S12-5 in FIG.

[0106] Subsequently, at operating point 3, the power conversion device 101 is discharging and the power conversion device 102 is charging, so processing to change the active power command value Pref of the power conversion device 102 is executed in step S12-7 of Fig. 12. Since the power conversion device 101 is discharging, processing to change the active power command value Pref1 is not executed.

[0107] Thereafter, as in the description of the first embodiment, the operating point of the power conversion device 102 shifts to point 4 and then to point 5. At this time, the droop characteristic of the power conversion device 102 shifts to line s via line r in FIG. 13 .

[0108] At operating point 5, power conversion device 101 discharges and power conversion device 102 operates at 0 kW, so power can be supplied to AC load 6 without power exchange between power conversion device 101 and power conversion device 102.

[0109] Next, a case will be described where the power consumption of the AC load 6 changes after the operating point has shifted to point 5. If the power consumption of the AC load 6 increases, the sum of the discharge powers of the AC generator 9, the power conversion device 101, and the power conversion device 102 becomes smaller than the load power consumption. At this time, the operating point shifts to a point where the sum of these discharge powers is equal to the load power consumption and the angular frequency command ωref has a common value.

[0110] This operating point is represented as point 6 in Fig. 13. Here, the angular frequency command value ωref at operating point 6 is lower than that at operating point 5, and step S12-5 in Fig. 12 is set to No. Then, since both power conversion device 101 and power conversion device 102 are discharging, the process of changing the active power command value in step S12-7 in Fig. 12 is not performed, and the operating point is stabilized at point 6.

[0111] Next, a case where the power consumption of the AC load 6 decreases will be described. The AC load 6 moves to a point where the sum of the discharge powers of the AC generator 9, the power converter 101, and the power converter 102 is equal to the load power consumption and the angular frequency command ωref has a common value.

[0112] This operating point is represented as point 7 in Fig. 13. Operating point 7 is the point where the AC load 6 becomes light and the constant power output of the AC generator 9 is excessively supplied.

[0113] In this case, the power conversion devices 101 and 102 may perform charging operations. Since the angular frequency command value ωref at the operating point 7 is higher than the update determination angular frequency ωcheck, the Yes branch is taken in step S12-5 in FIG. 12. Therefore, the operating point is stabilized at point 7.

[0114] The operations of the power conversion devices 101 and 102 when the power consumption of the AC load 6 changes after the operating point shift in Example 2 can be similarly implemented in Example 1 as long as the upper command device 8 of the power conversion devices transmits the update determination angular frequency ωcheck to each of the power conversion devices 101 and 102.

[0115] Although the AC load 6 has been described as a load that does not generate regeneration, it may be a regenerative load, in which case the power conversion device will follow the operation when the power consumption of the AC load 6 has decreased as described above. In addition, in a configuration similar to that of Example 1 that does not include the AC generator 9, the operation of the power conversion device can be appropriately controlled by following this example while the AC load 6 is regenerating.

[0116] Next, FIG. 14 is a graph showing the relationship between the active power command value, the active power, and the angular frequency change amount command in the system configuration example of the second embodiment of the present invention.

[0117] This is an example of a case where there is no need to change the active power command value of the power conversion device. The AC generator 9 and the two power conversion devices that are charging were operating in interconnected mode, but even after switching to stand-alone operation, the two power conversion devices continue to charge at point 1.

[0118] The angular frequency command value ωref of the power conversion device 101 and the power conversion device 102 when they transition to independent operation is closer to the reference angular frequency 2π × 50 than the update determination angular frequency ωcheck. For this reason, the decision at the branch in step S12-5 in Fig. 12 is Yes, and the process does not proceed to step S12-7, so the active power command values ​​Pref1 and Pref2 are not changed.

[0119] In this embodiment, the description of the same parts as those in the first embodiment will be omitted as appropriate. The configuration example of the power conversion device and the system configuration example in this embodiment are the same as those in Figs.

[0120] 15 is a graph showing the relationship between the active power command value, the angular frequency command, and the update determination angular frequency in Example 3 of the present invention. The droop characteristics of power conversion device 101 are represented by line t, and the droop characteristics of power conversion device 102 are represented by line u.

[0121] In the second embodiment, the upper command device 8 of the power electronics devices transmits an active power value to the power electronics devices 101 and 102 so as to charge the devices, but in this embodiment, it transmits an active power value to discharge the devices. That is, it is assumed that the upper command device 8 of the power electronics devices transmits Pref1' (Pref1'<0) as the active power value Pref' to the power electronics device 101 and Pref2' (Pref1'<Pref2'<0) as the active power value Pref' to the power electronics device 102.

[0122] Here, as in the second embodiment, the angular frequency command value for each power conversion device when Pout = 0, i.e., the angular frequency command value for which the droop characteristic of each power conversion device corresponds to the intercept of the vertical axis (angular frequency command axis), that is, the angular frequency command value closest to the reference angular frequency is set as the angular frequency for update determination ωcheck.

[0123] 15, since 0>Pref2'>Pref1', the intercept of the vertical axis (angular frequency command axis) of each droop characteristic that is closest to the reference angular frequency is the intercept of the droop characteristic of the power conversion device 102. Therefore, the update determination angular frequency ωcheck in this embodiment is the angular frequency command value when Pout=0 for the power conversion device 102.

[0124] FIG. 16 is a graph showing the relationship between the active power command value, the active power, and the angular frequency change amount command in the third embodiment of the present invention.

[0125] In this embodiment, during grid-connected operation, power is supplied to the AC load by the power of AC generator 9 and the discharge of two power conversion devices at the operating point of point 0, but when the system enters stand-alone operation, power conversion device 101 discharges at point 1 and power conversion device 102 charges. This is an example of a system. AC generator 9 outputs constant power.

[0126] 16, the characteristic of the AC generator 9 is line v. Also, it is assumed that the power conversion devices 101 and 102 have received a discharge command (Pref1′<Pref2′<0) from the upper command device 8 of the power conversion devices as described above.

[0127] In this embodiment, the method of updating the active power command value of the power conversion device is the same as in the second embodiment, and follows Fig. 12. In this embodiment, as shown in Figs. 15 and 16, the update determination angular frequency ωcheck is greater than the reference angular frequency 2π×50, so when the process proceeds to S12-4 in Fig. 12, the process branches to Yes.

[0128] As in the second embodiment, the transition of the operating point will be described with reference to Fig. 12 and Fig. 16. It is assumed that the operating points of the power conversion devices 101 and 102 have shifted to point 1 in Fig. 16 due to the transition to independent operation. Since the angular frequency command value ωref at operating point 1 is higher than the update determination angular frequency ωcheck, the process branches to No in step S12-8.

[0129] Then, since the power conversion device 101 is discharging (step S12-9: Yes), in step S12-10, the active power command value setting unit 33 of the power conversion device 101 executes a change process to increase the active power command value Pref, and the changed active power command value Pref is sent to the phase command generation unit 32. This change process is performed, as in the first embodiment, by dividing the pre-update Pref by the updated Pout (<0) to calculate a new Pref. The phase command generation unit 32 sends θref (phase command) to the main circuit control unit 36 ​​to increase the active power output by the main circuit. As a result, the droop characteristic of the power conversion device 101 moves from line w to line x in FIG. 16, and the operating point transitions to point 2 in FIG. 16.

[0130] Since the active power output of the power conversion device 101 becomes 0 [kW], the sum of the discharge powers of the AC generator 9, power conversion devices 101, and power conversion devices 102 decreases and becomes small relative to the load power consumption. Then, the operating point moves to a point where the sum of these discharge powers is equal to the load power consumption and the angular frequency command ωref has a common value. The operating point of the power conversion device 101 shifts from point 2 to point 3 in Fig. 16, and the operating point of the power conversion device 102 shifts from point 1 to point 3 in Fig. 16.

[0131] At the operating point 3, the angular frequency command value ωref is higher than the update determination angular frequency ωcheck, so the process branches to No again at step S12-8 in FIG.

[0132] Subsequently, at operating point 3, the power conversion device 101 is discharging and the power conversion device 102 is charging, so in step S12-10 of Fig. 12, the active power command value setting unit 33 of the power conversion device 101 changes the active power command value Pref, and the changed active power command value Pref is sent to the phase command generation unit 32. The phase command generation unit 32 sends θref (phase command) to the main circuit control unit 36, and changes the active power output by the main circuit. The active power command value setting unit 33 further updates the active power command value Pref1.

[0133] Thereafter, the transition of the operating point as described above is repeated according to Fig. 12. Eventually, the operating points of power conversion devices 101 and 102 move to point 4. At this time, the droop characteristic of power conversion device 101 is shown by line y in Fig. 16. The droop characteristic of power conversion device 102 does not move and is shown by line z in Fig. 16.

[0134] At operating point 4, the angular frequency command value ωref=the update determination angular frequency ωcheck, so the Yes branch is taken in step S12-8 in Fig. 12. Therefore, at this time, the processing from step S12-10 onwards is not performed, and the operating point stabilizes at point 4. At operating point 4, power conversion device 101 is discharging, and power conversion device 102 is at 0 kW, preventing a mixture of charging and discharging power conversion devices.

[0135] FIG. 17 is a graph showing the relationship between the active power command value, the active power, and the angular frequency change amount command in the third embodiment of the present invention.

[0136] 16, the position of the operating point 1 is different. That is, the power consumption of the AC load 6 is different, and it is assumed that the load is light.

[0137] The transition of the operating point will be described with reference to Fig. 12 and Fig. 17. It is assumed that the operating points of the power conversion devices 101 and 102 have shifted to point 1 in Fig. 17 due to the transition to independent operation. Since the angular frequency command value ωref at operating point 1 is higher than the update determination angular frequency ωcheck, the process branches to No in step S12-8.

[0138] Then, in step S12-10, the discharging power conversion device 101 increases the active power command value Pref1, which causes the droop characteristic of the power conversion device 101 to move from line a2 to line b2 in Fig. 16, and the operating point to transition to point 2 in Fig. 17.

[0139] Thereafter, the transition of the operating point as described above is repeated according to Fig. 12. Eventually, the operating points of power conversion devices 101 and 102 move to point 3 in Fig. 17. At this time, the droop characteristic of power conversion device 101 is line c2 in Fig. 16. The droop characteristic of power conversion device 102 does not move and is line d2 in Fig. 16.

[0140] At the operating point 3, the angular frequency command value ωref is greater than the update determination angular frequency ωcheck, so the No branch is taken in step S12-8 in Fig. 12. However, at the operating point 3, the power conversion device 101 is 0 kW, the power conversion device 102 is in a charging operation, and there is no power conversion device that discharges, so the processing in step S12-10 is not performed.

[0141] Fig. 18 shows an example of a system configuration according to a fourth embodiment of the present invention. In this configuration example, compared to the system configuration examples (Fig. 10) shown in the second and third embodiments, only one power conversion device (power conversion device 101) is used.

[0142] In this configuration example, the power conversion device 101 receives the update determination angular frequency ωcheck, as in the second and third embodiments. Then, the active power command value Pref1 is updated as necessary, as in the second and third embodiments.

[0143] In this configuration example, an AC generator 9 is connected in addition to the power conversion device 101, so depending on the output of the AC generator 9 and the power consumption of the AC load 6, the power supply and demand of the entire system can be balanced by charging the power conversion device 101.

[0144] Therefore, if the active power command value Pref1 is constantly updated so as not to charge the power conversion device 101 during stand-alone operation without using the update determination angular frequency ωcheck as shown in Example 1, the power supply will be excessive. Therefore, the active power command value Pref1 is updated using the update determination angular frequency ωcheck as in Examples 2 and 3.

[0145] In this embodiment, the update determination angular frequency ωcheck is the angular frequency command value when the power conversion device 101 has Pout=0, that is, the angular frequency command value corresponding to the intercept of the vertical axis (angular frequency command axis) in the droop characteristics of the power conversion device 101. In this embodiment as well, by following the flow of Fig. 12, it becomes possible to appropriately control the operation of the power conversion device.

[0146] 1, 101, 102...power conversion device, 2...main circuit, 3...control unit, 4...AC filter, 5...AC system, 6...AC load, 7...power storage device, 8...high-level command device for power conversion device, 9...AC generator, 31...power calculation unit, 32...phase command generation unit, 33...active power command value setting unit, 34...reactive power command generation unit, 35...reactive power control (AQR) unit, 36...main circuit control unit

Claims

1. A power conversion device connected to a power storage device, comprising: an operation determination unit that determines whether the power conversion device is in an independent operation state or a grid-connected operation state; a power calculation unit that calculates the power input and output of the power storage device; an active power command value setting unit that determines an active power command value from a received active power value and the active power calculated by the power calculation unit; and a main circuit that converts power based on the active power command value, wherein the active power command value setting unit is capable of executing a change process to change the active power command value to a value corresponding to the input and output of power of the power storage device in the independent operation state.

2. The power conversion device according to claim 1, wherein the change process is performed when the power storage device is storing power.

3. The power conversion device according to claim 1, wherein the active power command value setting unit receives an angular frequency for update determination from outside, and the change process is executed when the angular frequency for update determination is equal to or lower than a predefined reference angular frequency, the angular frequency command of the power conversion device is less than the angular frequency for update determination, and the power storage device is storing power.

4. A power conversion device as described in claim 1, wherein the active power command value setting unit receives an angular frequency for update determination from outside, and the change process is executed when the angular frequency for update determination is greater than a pre-specified reference angular frequency, the angular frequency command of the power conversion device is greater than the angular frequency for update determination, and the power storage device is outputting power.

5. A power conversion device according to any one of claims 1 to 3, wherein the change process is a process of changing the active power command value to a value that does not input power to the power storage device.

6. The power conversion device according to claim 1 or 4, wherein the change process is a process of changing the active power command value to a value at which the power storage device does not output power.

7. A power conversion device according to any one of claims 1 to 4, wherein the change processing is processing for calculating an active power command value after the change processing by subtracting the active power at the time of the change processing from the active power command value before the change processing.

8. A control method for a power conversion device connected to a power storage device, the control method for a power conversion device being capable of: determining whether the power conversion device is in an independent operation state or an interconnected operation state; calculating the power input and output of the power storage device; determining an active power command value from the received active power value and the active power calculated by a power calculation unit; and executing a change process to change the active power command value to a value corresponding to the input and output of power of the power storage device in the independent operation state.

9. The method for controlling a power conversion device according to claim 8, wherein the change process is executed when the power storage device is storing power.

10. A control method for a power conversion device as described in claim 8, wherein an angular frequency for update determination is received from outside, and the change process is executed when the angular frequency for update determination is equal to or lower than a pre-specified reference angular frequency, the angular frequency command of the power conversion device is less than the angular frequency for update determination, and the power storage device is storing power.

11. A method for controlling a power conversion device as described in claim 8, wherein an angular frequency for update determination is received from outside, and the change process is executed when the angular frequency for update determination is greater than a pre-specified reference angular frequency, the angular frequency command of the power conversion device is greater than the angular frequency for update determination, and the power storage device is outputting power.

12. A method for controlling a power conversion device according to any one of claims 8 to 10, wherein the change process is a process for changing the active power command value to a value that does not input power to the power storage device.

13. The method for controlling a power conversion device according to claim 8 or 11, wherein the change process is a process for changing the active power command value to a value at which the power storage device does not output power.

14. A method for controlling a power conversion device according to any one of claims 8 to 11, wherein the change processing is processing for calculating an active power command value after the change processing by subtracting the active power at the time of the change processing from the active power command value before the change processing.

Images