Power conversion device and program

Abstract

This electric power conversion device comprises a conversion unit, a grid-forming control unit, a grid-following control unit, a modulation unit, a switching unit, and an initial-value-adjusting unit. Upon receiving a switching signal instructing a switch from grid-following control to grid-forming control, a command value output unit outputs a grid-following amplitude command value indicating a target value for an amplitude calculated by grid-following control, and a grid-following phase command value indicating a target value for a phase calculated by grid-following control. When switching from grid-following control to grid-forming control, the initial-value-adjusting unit sets an initial value of the target value for the amplitude in grid-forming control to the grid-following amplitude command value, and sets the initial value of the target value for the phase in grid-forming control to the grid-following phase command value.

Description

[Technical field]

[0001] An embodiment of the present invention relates to a power conversion device and a program. [Background technology]

[0002] In recent years, the use of inverter power supplies that convert DC power output from power sources such as generators and storage batteries that use renewable energy into AC power and output it has been increasing. Known control methods for inverter power supplies include the grid forming (GFM) type and grid following (GFL) type. Grid forming control (hereinafter referred to as GFM control) is a control that maintains the amplitude and phase of the output voltage of the inverter power supply at a predetermined set value. Grid following control (hereinafter referred to as GFL control) is a control that makes the amplitude and phase of the output voltage of the inverter power supply follow the amplitude and phase of the voltage of a predetermined power grid. The above-mentioned GFM control and GFL control may be switched depending on the usage status of the inverter power supply, etc. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2015 / 070493 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the conventional technology, when switching from GFL control to GFM control, the phase and amplitude of the output voltage may fluctuate significantly, which may cause the operation of the inverter power supply to become unstable.

[0005] An object of the present invention is to provide a power conversion device and a program capable of improving stability when switching between control methods. [Means for solving the problem]

[0006] A power conversion device according to an embodiment includes a conversion unit, a system formation control unit, a system tracking control unit, a modulation unit, a switching unit, and an initial value adjustment unit. The conversion unit converts DC power output from a power source into AC power and outputs the AC power. The system formation control unit generates a first modulation command for changing the amplitude and phase of the output voltage by system formation control that maintains the amplitude and phase of the output voltage from the conversion unit at a predetermined set value. The system tracking control unit generates a second modulation command for changing the amplitude and phase of the output voltage by system tracking control that makes the amplitude and phase of the output voltage follow the amplitude and phase of a system voltage that is a voltage of a predetermined power system. The modulation unit changes the amplitude and phase of the output voltage based on the first modulation command or the second modulation command. The switching unit switches the input to the modulation unit so that either the first modulation command or the second modulation command is input to the modulation unit in response to a switching signal. When receiving a switching signal instructing switching from grid tracking control to grid formation control, the command value output unit outputs a grid tracking amplitude command value indicating a target value of the amplitude calculated by the grid tracking control and a grid tracking phase command value indicating a target value of the phase calculated by the grid tracking control. When switching from grid tracking control to grid formation control, the initial value adjustment unit sets an initial value of the target value of the amplitude in the grid formation control to the grid tracking amplitude command value and sets an initial value of the target value of the phase in the grid formation control to the grid tracking phase command value. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a block diagram illustrating an example of a configuration of a power system according to an embodiment. [Diagram 2] FIG. 2 is a block diagram illustrating an example of a hardware configuration of the power conversion device according to the embodiment. [Diagram 3] FIG. 3 is a block diagram illustrating an example of a functional configuration of a power conversion device according to an embodiment. [Figure 4] FIG. 4 is a control block diagram showing an example of processing in the GFM control unit and GFL control of the embodiment. [Diagram 5]FIG. 5 is a flowchart illustrating an example of processing performed when switching from GFL control to GFM control in the power conversion device of the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, embodiments will be described with reference to the drawings.

[0009] 1 is a block diagram showing an example of a configuration of a power system 1 according to an embodiment. The power system 1 includes an inverter power supply 11, a transformer 12, and a power grid 13. The power system 1 may be, for example, a so-called microgrid system that configures an independent power grid 13 using distributed power sources including a plurality of power sources such as the inverter power supply 11.

[0010] The inverter power supply 11 includes a power supply 20 and a power conversion device 21. The power supply 20 is a unit that outputs DC power, and may be, for example, a generator that uses renewable energy (for example, solar power, wind power, etc.), a storage battery, etc. The power conversion device 21 is a device that converts DC power output from the power supply 20 into AC power and outputs it. Note that multiple power supplies 20 may be connected to one power conversion device 21.

[0011] The power conversion device 21 of this embodiment has a function of appropriately switching between GFM control (system formation control) for maintaining the amplitude and phase of the output voltage at predetermined set values, and GFL control (system tracking control) for making the amplitude and phase of the output voltage track the amplitude and phase of the voltage of the power system 13.

[0012] The AC power output from the inverter power supply 11 (power conversion device 21) is boosted by the transformer 12 and then output to the power system 13. Depending on the characteristics of the inverter power supply 11 and the power system 13, the transformer 12 may not be necessary.

[0013] 2 is a block diagram showing an example of a hardware configuration of the power conversion device 21 according to the embodiment. The power conversion device 21 illustrated here includes a power conversion circuit 31, a high-frequency filter circuit 32, and a control device 33 (an example of an information processing device).

[0014] The power conversion circuit 31 is a circuit that converts DC power output from the power source 20 into AC power, and may be configured using, for example, a converter circuit, a PWM (Pulse Width Modulation) circuit, etc. The high-frequency filter circuit 32 is a circuit (for example, a reactor) that performs high-frequency filtering (low-pass filtering) processing on the output of the power conversion circuit 31. The control device 33 is an integrated circuit that includes a CPU (Central Processing Unit), a memory, etc., and executes predetermined arithmetic processing and control processing according to a program stored in the memory. The control device 33 may be configured using an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), etc.

[0015] The power conversion circuit 31 changes the amplitude and phase of the output voltage based on a modulation command output from the control device 33. The control device 33 performs GFM control or GFL control based on a feedback signal of the output from the power conversion circuit 31, and controls the output power P out (Output voltage V S In the configuration illustrated here, the control device 33 generates a modulation command to change the amplitude and phase of the reactor current I L , the output current I from the high frequency filter circuit 32 S , the output voltage V from the high frequency filter circuit 32 S The active power and reactive power are calculated based on the above.

[0016] In addition, the control device 33 of the present embodiment has a function of switching between GFM control and GFL control in accordance with a predetermined condition, and a function of improving stability when switching from GFL control to GLM control (for example, the output voltage V SThe system has functions to suppress sudden fluctuations in the supply and demand.

[0017] 3 is a block diagram showing an example of a functional configuration of the power conversion device 21 of the embodiment. The power conversion device 21 of the present embodiment includes a conversion unit 101, a GFM control unit 102 (grid formation control unit), a GFL control unit 103 (grid tracking control unit), a modulation unit 104, and a switching unit 105. These functional components 101 to 105 can be configured, for example, by cooperation between hardware elements such as those illustrated in FIG. 2 and software elements such as a program that controls the control device 33.

[0018] The conversion unit 101 converts the DC power output from the power source 20 into AC power to generate an output power (effective output power) P out At this time, the output voltage V S The amplitude and phase of the signal are adjusted by the modulation section 104 .

[0019] The GFM control unit 102 controls the output voltage V S The GFM control is performed to maintain the amplitude and phase of the output voltage V at a predetermined set value. S The GFL control unit 103 generates a first modulation command for changing the amplitude and phase of the output voltage V S The GFL control is performed to make the amplitude and phase of the output voltage V follow the amplitude and phase of the voltage (system voltage) of a predetermined power system (for example, the power system 13). S A second modulation command is generated to change the amplitude and phase of the

[0020] The switching unit 105 switches the input to the modulation unit 104 in response to a switching signal output from a predetermined control mechanism so that either the first modulation command or the second modulation command is input to the modulation unit 104. The modulation unit 104 controls the output voltage V S The amplitude and phase of the signal are changed.

[0021] The GFM control unit 102 of this embodiment includes a voltage control unit 111, a phase control unit 112, and an initial value adjustment unit 113. The GFL control unit 103 of this embodiment includes a command value output unit 121.

[0022] The voltage control unit 111 controls the output voltage V S The phase control unit 112 generates an amplitude command indicating a target value of the amplitude of the output voltage V S The first modulation command is generated based on the amplitude command generated by the voltage control section 111 and the phase command generated by the phase control section 112.

[0023] When a switching signal instructing switching from GFL control to GFM control is received, the command value output unit 121 outputs to the initial value adjustment unit 113 a GFL amplitude command value (system tracking amplitude command value) indicating the target value of the amplitude calculated by the GFL control, and a GFL phase command value (system tracking amplitude command value) indicating the target value of the phase calculated by the GFL control.

[0024] When switching from GFL control to GFM control, the initial value adjustment unit 113 sets the initial value of the amplitude target value (amplitude command) in GFM control to the GFL amplitude command value, and sets the initial value of the phase target value (phase command value) in GFM control to the GFL phase command value.

[0025] FIG. 4 is a control block diagram showing an example of processing in the GFM control unit 102 and the GFL control 103 of the embodiment. In the voltage control unit 111, a reactive power command value Q ref to reactive power output value Q out The amplitude command offset value V is calculated by QV droop control for the value obtained by subtracting offset Calculate the reference amplitude setting value V set and amplitude command offset value V offset The first amplitude setting value V1 is calculated by adding the above. sdThe second amplitude setting value V2 is calculated by an automatic voltage regulator (AVR) for the value obtained by subtracting V from V. The first amplitude setting value V1 and the second amplitude setting value V2 are added together to calculate the inverter output d-axis amplitude command value V dref_GFM (An example of the amplitude target value in GFM control) is calculated. In addition, the inverter output q-axis amplitude command value V qref_GFM (an example of a target value of amplitude in GFM control) is 0 under normal circumstances (for example, when GFM control is being executed in a predetermined stable state).

[0026] In the phase control unit 112, the active power command value P ref to the effective power output value P out The frequency ω1 is calculated by Pf droop control or VSG (Virtual Synchronous Generator) control for the value obtained by subtracting ω1. The deviation Δω between the frequency ω1 and the reference frequency ω0 of the inverter output voltage frequency m Calculate the deviation Δω m The inverter output voltage frequency ω m By integrating with the transfer function 1 / S of the integral element, the inverter output voltage phase θ GFM (An example of the target value of the phase in GFM control) is calculated, where s is the Laplace operator.

[0027] Inverter output d-axis amplitude command value V dref_GFM , inverter output q-axis amplitude command value V qref_GFM , and the inverter output voltage phase θ GFM Based on this, the inverter output voltage command value V ref_GFM The GFL control unit 103 generates an inverter output voltage command value V ref_GFL The switching unit 105 generates an output voltage V S The input to the PWM120 that modulates the inverter output voltage command value V ref_GFM Or inverter output voltage command value Vref_GFL Switch so that one of the two is input.

[0028] When a switching signal instructing switching from GFL control to GFM control is received, the command value output unit 121 outputs a PLL phase θ PLL and the inverter output d-axis amplitude command value V as the GFL amplitude command value. dref_GFL and inverter output q-axis amplitude command value V qref_GFL and is output to the initial value adjustment unit 113. PLL can be obtained, for example, from the output of a PLL circuit. dref_GFL and inverter output q-axis amplitude command value V qref_GFL For example, the inverter output voltage command value V ref_GFL PLL phase θ PLL It can be obtained by dq transformation using

[0029] As shown in FIG. 4, the initial value adjustment unit 113 adjusts the inverter output d-axis amplitude command value V dref_GFM The switch unit 151 corresponds to the inverter output q-axis amplitude command value V qref_GFM and the inverter output voltage phase θ GFM When switching from GFL control to GFM control, each of the switch units 151 to 153 changes from the state shown by the solid line to the state shown by the dashed line. As a result, when switching from GFL control to GFM control, the inverter output voltage phase θ GFM The initial value of the PLL phase θ PLL is set, and the inverter output d-axis amplitude command value V dref_GFM The inverter output d-axis amplitude command value V dref_GFL is set, and the inverter output q-axis amplitude command value V qref_GFM The inverter output q-axis amplitude command value V qref_GFL is set.

[0030] According to the above configuration, when switching from GFL control to GFM control, GFM control is started with the amplitude command value and phase command value in GFL control as initial values, thereby making it possible to suppress abrupt fluctuations in the output voltage when GFM control starts.

[0031] In this embodiment, the inverter output d-axis amplitude command value V dref_GFL and inverter output q-axis amplitude command value V qref_GFL The filter unit 155 is provided to perform a filter process on the amplitude target value. The filter unit 155 may be, for example, a first-order lag filter, a rate limiter, etc. This makes it possible to suppress abrupt fluctuations in the target value of the amplitude after switching to the GFM control.

[0032] 5 is a flowchart showing an example of processing when switching from GFL control to GFM control in the power conversion device 21 of the embodiment. The initial value adjustment unit 113 determines whether GFL control is being executed (whether a second modulation command is input to the modulation unit 104) (S101), and ends this routine if GFL control is not being executed (S101: No). If GFL control is being executed (S101: Yes), the initial value adjustment unit 113 determines whether a switching signal to switch to GFM control has been received (S102), and ends this routine if a switching signal to switch to GFM control has not been received (S103: No).

[0033] When a switching signal to GFM control is received (S102: Yes), the command value output unit 121 outputs the GFL amplitude command value (the inverter output d-axis amplitude command value V dref_GFL and inverter output q-axis amplitude command value V qref_GFL ) and GFL phase command value (inverter output voltage phase θ GFL ) to the initial value adjustment unit 113 of the GFM control unit 102 (S103). The initial value adjustment unit 113 adjusts the acquired GFL amplitude command value to the GFM amplitude command value (the inverter output d-axis amplitude command value V dref_GFM and inverter output q-axis amplitude command value V qref_GFM ) and the acquired GFL phase command value is set as the initial value of the GFM phase command value (inverter output voltage phase θGFM ) as the initial value (S104). Then, the voltage control section 111 and the phase control section 112 of the GFM control section 102 start the GFM control based on the initial value set as described above (S105).

[0034] According to the above embodiment, when switching from GFL control to GFM control, GFM control is started with the amplitude command value and phase command value in GFL control as initial values. This makes it possible to suppress abrupt fluctuations in the output voltage when GFM control starts, and improves the stability of the operation of the inverter power supply when switching the control method.

[0035] The program for realizing the functions of the power conversion device 21 in the above-described embodiment is provided mainly by being pre-installed in a storage device provided in the power conversion device 21, but is not limited thereto, and may be provided by being recorded in an installable or executable format on a computer-readable recording medium such as a CD-ROM, a flexible disk (FD), a CD-R, or a DVD (Digital Versatile Disc). In addition, the storage medium is not limited to a medium independent of a computer or an embedded system, but also includes a storage medium in which a program transmitted via a LAN, the Internet, or the like is downloaded and stored or temporarily stored.

[0036] In addition, the above program may be configured to be stored on a computer connected to a network such as the Internet and provided by being downloaded via the network, or may be configured to be provided or distributed via a network such as the Internet.

[0037] Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0038] 1...power system, 11...inverter power supply, 12...transformer, 13...power system, 20...power supply, 21...power conversion device, 31...power conversion circuit, 32...high frequency filter circuit, 33...control device, 101...conversion section, 102...GFM control section, 103...GFL control section, 104...modulation section, 105...switching section, 111...voltage control section, 112...phase control section, 113...initial value adjustment section, 120...PWM, 121...command value output section, 151, 152, 153...switch section, 155...filter section

Claims

1. A conversion unit that converts DC power output from a power source into AC power and outputs the AC power; a system configuration control unit that generates a first modulation command for changing the amplitude and phase of the output voltage from the conversion unit through a system configuration control that maintains the amplitude and phase of the output voltage from the conversion unit at predetermined set values; a grid tracking control unit that generates a second modulation command for changing the amplitude and phase of the output voltage by grid tracking control that causes the amplitude and phase of the output voltage to follow the amplitude and phase of a grid voltage that is a voltage of a predetermined power grid; a modulation unit that changes the amplitude and phase of the output voltage based on the first modulation command or the second modulation command; a switching unit that switches an input to the modulation unit so that either the first modulation command or the second modulation command is input to the modulation unit in response to a switching signal; a command value output unit that outputs, when the switching signal instructing switching from the grid tracking control to the grid formation control is received, a grid tracking amplitude command value indicating a target value of amplitude calculated by the grid tracking control and a grid tracking phase command value indicating a target value of phase calculated by the grid tracking control; an initial value adjusting unit that, when switching from the grid tracking control to the grid formation control, sets an initial value of an amplitude target value in the grid formation control to the grid tracking amplitude command value and sets an initial value of a phase target value in the grid formation control to the grid tracking phase command value; A power conversion device comprising:

2. the initial value adjustment unit includes a filter unit that performs a predetermined filtering process on the grid tracking amplitude command value output from the command value output unit. The power conversion device according to claim 1 .

3. The filter unit is a first-order lag filter. The power conversion device according to claim 2 .

4. The filter unit is a rate limiter. The power conversion device according to claim 2 .

5. An information processing device controls a conversion unit that converts DC power output from a power supply into AC power and outputs the AC power, generating a first modulation command for varying the amplitude and phase of the output voltage from the converter by a system formation control for maintaining the amplitude and phase of the output voltage at a predetermined set value; a process of generating a second modulation command for changing the amplitude and phase of the output voltage by a system tracking control for making the amplitude and phase of the output voltage follow the amplitude and phase of a system voltage, which is a voltage of a predetermined power system; A process of varying the amplitude and phase of the output voltage based on the first modulation command or the second modulation command; a process of switching an input to a modulation unit so that either the first modulation command or the second modulation command is input to the modulation unit that changes the amplitude and phase of the output voltage in response to a switching signal; a process of outputting, when the switching signal instructing switching from the grid tracking control to the grid formation control is received, a grid tracking amplitude command value indicating a target value of amplitude calculated by the grid tracking control and a grid tracking phase command value indicating a target value of phase calculated by the grid tracking control; a process of setting an initial value of an amplitude target value in the grid formation control to the grid tracking amplitude command value and setting an initial value of a phase target value in the grid formation control to the grid tracking phase command value when switching from the grid tracking control to the grid formation control; A program that executes the following.

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