Control devices, power converters

Abstract

To provide a control device that can suppress power fluctuations in an inverter. [Solution] A control device for controlling an inverter connected to a power grid and having a virtual synchronous generator function, comprising: a first output unit that outputs a first phase of the output voltage of the inverter based on the active power from the inverter, a first command value, and the virtual synchronous generator function; a second output unit that outputs the amplitude of the output voltage based on the reactive power from the inverter and a second command value; a phase correction value output unit that outputs a phase correction value based on the circuit constants of the transmission and distribution lines between the inverter and the power grid and the first command value; an adder that outputs a second phase obtained by adding the phase correction value and the first phase; and a third output unit that outputs a control signal for controlling the inverter based on the amplitude of the output voltage and the second phase.

Description

[Technical Field]

[0001] The present invention relates to a control device and a power conversion device. [Background technology]

[0002] Some power conversion devices have the function of a virtual synchronous generator (also called a pseudo-synchronous generator) (see, for example, Patent Documents 1 to 3). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Patent Application No. 2019-176584 [Patent Document 2] Patent Application No. 2021-13207 [Patent Document 3] Patent Application No. 2024-60953 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] Incidentally, in power converters that function as typical virtual synchronous generators, fluctuations in the inverter's power occur when the command value of the active power changes. If the power fluctuation is large, it can cause a loss of synchronism, which can make the power system unstable.

[0005] The present invention has been made in view of the above-mentioned conventional problems, and aims to provide a control device and a power conversion device that can suppress power fluctuations in an inverter. [Means for solving the problem]

[0006] The first aspect of the present invention, which is the main aspect for solving the aforementioned problems, is a control device for controlling an inverter having a virtual synchronous generator function and connected to a power grid, comprising: a first output unit that outputs a first phase of the output voltage of the inverter based on the active power from the inverter, a first command value, and the virtual synchronous generator function; a second output unit that outputs the amplitude of the output voltage based on the reactive power from the inverter and a second command value; a phase correction value output unit that outputs a phase correction value from the circuit constants of the transmission and distribution lines between the inverter and the power grid and the first command value; an adder that outputs a second phase obtained by adding the phase correction value output and the first phase; and a third output unit that outputs a control signal for controlling the inverter based on the amplitude of the output voltage and the second phase.

[0007] A second aspect of the present invention, which is the main aspect for solving the aforementioned problems, is a power conversion device comprising an inverter connected to a power grid and a control device having a virtual synchronous generator function and controlling the inverter, wherein the control device includes: a first output unit that outputs a first phase of the output voltage of the inverter based on the active power from the inverter, a first command value and the virtual synchronous generator function; a second output unit that outputs the amplitude of the output voltage based on the reactive power from the inverter and a second command value; a phase correction value output unit that outputs a phase correction value from the circuit constants of the transmission and distribution lines between the inverter and the power grid and the first command value; an adder that outputs a second phase obtained by adding the phase correction value output and the first phase; and a third output unit that outputs a control signal for controlling the inverter based on the amplitude of the output voltage and the second phase. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a control device and a power conversion device that can suppress power fluctuations in an inverter. [Brief explanation of the drawing]

[0009] [Figure 1] This figure shows an example of a power converter 10a. [Figure 2] This is a diagram illustrating the active power between the power converter 10a and the power grid. [Figure 3] This is a diagram showing an example of a power conversion device 15. [Figure 4] This figure shows an example of active power and reactive power when the command value for active power is changed. [Figure 5] This figure shows an example of active power and reactive power when the command value for active power is changed. [Figure 6] This figure shows an example of a power converter 10b. [Modes for carrying out the invention]

[0010] This specification and the accompanying drawings make at least the following matters clear. Furthermore, identical or equivalent components, members, etc., shown in each drawing are denoted by the same reference numerals, and redundant explanations are omitted where appropriate.

[0011] =====Power converter 10a===== Figure 1 shows an example of the power converter 10a of this embodiment. The power converter 10a is a device that is connected to the power grid and exchanges power with the power grid. The power converter 10a is composed of an inverter 20 and a control device 21a.

[0012] The inverter 20 is a device that exchanges AC power with the interconnected power system via a three-phase transmission line 11 based on a PWM (pulse width modulation) signal. In this embodiment, the transmission line 11 includes transmission and distribution lines.

[0013] The control device 21a controls the output voltage V of the inverter 20 based on instructions from the central power dispatch center (hereinafter referred to as the "central power dispatch system" or simply "central power") which monitors the demand of the power grid, or from higher-level controllers, etc. PCS This is a device that controls the output voltage V. PCS This includes, for example, the three-phase AC voltage for each of the three phases of the transmission line 11.

[0014] The control device 21a includes a PQ calculation unit 30, a low-pass filter (LPF) 31, a virtual synchronous generator unit 32, a multiplication unit 33, a calculation unit 34, addition units 35 and 36, an AVR (Automatic Voltage Regulator) 37, an instantaneous voltage control unit 38, and a PWM circuit 39. In the control device 21a, blocks other than the PWM circuit 39 are realized by, for example, a digital signal processing circuit (DSP: Digital Signal Processor) included in the control device 21a executing a predetermined program.

[0015] At the position where the inverter 20 and the transmission line 11 are connected (hereinafter referred to as position A), the PQ calculation unit 30 measures the output voltage V PCS and the output current I PCS from the inverter 20, and calculates the active power P and the reactive power Q from the measurement results.

[0016] The low-pass filter 31 removes noise and the like from the command value P * of the active power P, and outputs it to the virtual synchronous generator unit 32 and the multiplication unit 33. Here, for the sake of convenience, the output from the low-pass filter 31 is also regarded as the command value P * .

[0017] The virtual synchronous generator unit 32 is a functional block that virtually simulates a synchronous generator (that is, a block with a virtual synchronous generator function). Based on the command value P * , it outputs the phase θ1 of the output voltage V PCS of the inverter 20. The virtual synchronous generator unit 32 includes addition units 50 and 52, and calculation units 51, 53, and 54. The virtual synchronous generator unit 32 in this embodiment corresponds to the "first output unit", the phase θ1 corresponds to the "first phase", and the command value P * corresponds to the "first command value".

[0018] The addition unit 50 is the command value P *The active power P obtained by the PQ calculation unit 30 and the output from the calculation unit 53 (described later) are subtracted, and the subtraction result is output to the calculation unit 51.

[0019] The calculation unit 51 multiplies the output from the adder 50 by a coefficient 1 / M (described later) and then integrates it over time from the time the initial value was given to the current time. Here, "M" is a value representing the inertia constant of the virtual synchronous generator. In this embodiment, the integration result of the calculation unit 51 is the output voltage V of the power converter 10a. PCS This is a value where the frequency ω is expressed in units of the nominal frequency ωn of the power system.

[0020] Here, the nominal frequency ωn of the power system is, for example, in Japan, 50Hz multiplied by 2π in eastern Japan and 60Hz multiplied by 2π in western Japan. Therefore, although the details will be described later, the calculation unit 53 calculates the output voltage V PCS If the frequency ω matches the nominal frequency, the value of ω / ωn[pu] becomes 1.0. Therefore, in this case, the summer 50 will have the command value P * The difference between this value and the active power P obtained by the PQ calculation unit 30 is then output.

[0021] The adder 52 outputs a value obtained by subtracting 1.0 from the value of ω / ωn, which is the output from the calculation unit 51. The calculation unit 53 multiplies the output from the adder 52 by a coefficient D and outputs the result. Here, "D" is a value that represents the braking constant of the virtual synchronous generator.

[0022] The calculation unit 54 multiplies the output ω / ωn from the calculation unit 51 by the nominal frequency ωn (=2πf0) and integrates. As a result, the calculation unit 54 obtains the output voltage V of the power converter 10a. PCS The phase θ1 will be output. In other words, the calculation unit 54 converts the active power P from the power converter 10a to the command value P * The phase θ1 that results in this will be calculated based on the feedback active power P.

[0023] The multiplication unit 33 calculates the command value P of the active power P. *The coefficient X is multiplied by the output voltage V, and the calculation unit 34 outputs the arcsine value of the multiplication result from the multiplication unit 33. Here, "X" is a value that represents the reactance of the transmission line 11 between the power converter 10a and the power system, as shown in Figure 2. In the upper part of Figure 2, the output voltage V is located at position A where the power converter 10a and the transmission line 11 are connected. PCS It also states that at location B where the power transmission line 11 and the power system are connected, the system voltage V of the system is described. SYS This is described. Furthermore, in this embodiment, the reactance of the transmission line 11 between the power system and the transmission line is used, but any "circuit constant" of the transmission line 11 between the power system and the transmission line 11, such as the impedance of the transmission line 11 (including not only the resistance of the transmission line itself but also parasitic capacitance), would suffice.

[0024] Furthermore, the lower part of Figure 2 shows the active power P and the output voltage V, which includes information on amplitude and phase. PCS and system voltage V SYS A schematic diagram illustrating the relationship is shown. Here, the active power P from the power converter 10a is given by equation (1). P=(|V PCS |·|V SYS |·sin(Δθ)) / X···(1) Note that in equation (1), |V PCS | is the output voltage V PCS This is the amplitude (magnitude) of |V SYS | represents the system voltage V SYS The amplitude (magnitude) is such that Δθ is the output voltage V PCS and system voltage V SYS This is the phase difference. Also, X is the reactance of the transmission line 11 as described above.

[0025] In equation (1), |V PCS | and |V SYS If we set | and to 1.0[pu], which represent their respective ratings, then equation (1) becomes equation (2). P·X=sin(Δθ)···(2)

[0026] From equation (2), we obtain the following equation (3). Δθ = sin -1 (P·X)···(3) Therefore, for example, in order for the power converter 10a to output active power P, the output voltage V PCS and system voltage V SYS The phase difference Δθ must satisfy the relationship in equation (3).

[0027] The multiplication unit 33 in Figure 1 controls the command value P * The coefficient X is multiplied to the value, and the calculation unit 34 outputs the arcsine value of the multiplication result from the multiplication unit 33. Therefore, the multiplication unit 33 and the calculation unit 34 determine that the power converter 10a has command value P as active power P. * The phase θ2 required to output the result will be calculated based on equation (3). Note that the arcsine value corresponds to the "phase correction value," and the multiplication unit 33 and the calculation unit 34 correspond to the "phase correction value output unit."

[0028] Here, the multiplication unit 33 and the calculation unit 34 of this embodiment calculate the active power P to the command value P * Output voltage V PCS The phase θ2 is output via a so-called feedforward path, without going through the feedback path in Figure 1 (the path from the PQ calculation unit 30 to the virtual synchronous power generation unit 32). As will be described in detail later, this allows the power converter 10a to output the command value P * When the value changes, the active power P can be changed immediately.

[0029] The addition unit 35 adds the phase θ1 from the virtual synchronous power generation unit 32 and the phase θ2 from the calculation unit 34, and the resulting phase θ * The output is calculated by adding the reactive power Q from the PQ calculation unit 30 and the command value Q for the reactive power Q. * The difference between this and is calculated. Note that the phase θ2 from the calculation unit 34 in this embodiment corresponds to the "arcsine value", and the phase θ * This corresponds to the "second phase."

[0030] The AVR37 has reactive power Q and command value Q. * Based on the difference, the output voltage V of the power converter 10a PCS Amplitude |V PCS *Outputs |. Note that the command value Q in this embodiment * This corresponds to the "second command value," and AVR37 corresponds to the "second output unit."

[0031] The instantaneous voltage control unit 38 controls the instantaneous value of the three-phase output voltage of the power converter 10a, with a phase θ * And, amplitude |V PCS * An instruction to set the phase θ is output to the PWM circuit 39. As a result, the PWM circuit 39 outputs a PWM signal corresponding to the above instruction, and the instantaneous value from the inverter 20 is phase θ. * And, amplitude |V PCS * |The voltage V PCS This will result in the output. In this embodiment, the instantaneous voltage control unit 38 and the PWM circuit 39 correspond to the "third output unit," and the PWM signal corresponds to the "control signal."

[0032] Here, we will describe a typical power converter that can be used as a point of comparison when explaining the operation of the power converter 10a.

[0033] =====Power converter 15===== Figure 3 shows an example of a typical power converter 15. The power converter 15 comprises an inverter 20 and a control device 25. The control device 25 comprises a PQ calculation unit 30, a low-pass filter 31, a virtual synchronous power generation unit 32, an adder 36, an AVR 37, an instantaneous voltage control unit 38, and a PWM circuit 39.

[0034] The control device 25 in Figure 3 has the same configuration as the control device 20a in Figure 1, except for the multiplication unit 33, the calculation unit 34, and the addition unit 35. Therefore, the control device 25 controls the command value P of the active power P. * When this changes, the output voltage V is determined based on the feedback path (PQ calculation unit 30 → virtual synchronous power generation unit 32). PCS Phase θ * (Here, θ * Output =θ1).

[0035] <<<Operation of power converters 10a and 15>>> Figure 4 shows the command value P of the active power P at time t=0. * This figure shows the waveforms of the active power P and reactive power Q of power converters 10a and 15, respectively, when the power is increased from 0.5[pu] to 1.0[pu]. Here, the active power P and reactive power Q are labeled as the measured value P (solid line) and the measured value Q (dotted line), respectively. The upper part of Figure 4 shows the active power P and reactive power Q of a typical power converter 15, and the lower part of Figure 4 shows the active power P and reactive power Q of the power converter 10a of this embodiment.

[0036] Here, the reactance X of the transmission line 11 is assumed to be 0.1 [pu], the number of inertia points M is assumed to be 5.0 [s], and the damping constant D is assumed to be 100. Note that a reactance X of 0.1 [pu] means that when a reactive power Q equivalent to 0.1 [pu] is supplied to the reactance X, the output voltage V PCS This means that it decreases by 0.1 [pu]. Also, in the upper and lower panels of Figure 4, the low-pass filter 31 has a time constant T from left to right. LPF However, these are first-order lag filters with values ​​of 0.0, 0.010, and 0.025.

[0037] Here, at time t=0, the command value P of the active power P is * The power is increased from 0.5[pu] to 1.0[pu]. As shown in the upper part of Figure 4, in the power converter 15, a relatively large power fluctuation occurs in the active power P, and then it gradually converges to the target value (1.0[pu]). On the other hand, as shown in the lower part of Figure 4, in the power converter 10a, there is almost no power fluctuation in the active power P, and the active power P also immediately converges to the target value (1.0[pu]).

[0038] Regarding reactive power Q, while some power fluctuations occur in power converter 15, almost no power fluctuations occur in power converter 10a.

[0039] Figure 5 shows the command value P of the active power P at time t=0. *This figure shows the waveforms of the active power P and reactive power Q of power converters 10a and 15, respectively, when the power is reduced from 1.0 [pu] to 0.5 [pu]. Here, the active power P and reactive power Q are indicated as the measured value of P (solid line) and the measured value of Q (dotted line), respectively. The upper part of Figure 5 shows the active power P and reactive power Q of a typical power converter 15, and the lower part of Figure 5 shows the active power P and reactive power Q of the power converter 10a of this embodiment.

[0040] In Figure 5, the reactance X, inertia points M, damping constant D, and time constant T of the low-pass filter 31 are also shown. LPF The conditions described above are the same. As shown in the upper part of Figure 5, in the power converter 15, a relatively large power fluctuation occurs in the active power P, and then it gradually converges to the target value (0.5 [pu]). On the other hand, as shown in the lower part of Figure 5, in the power converter 10a, there is almost no power fluctuation in the active power P, and the active power P also immediately converges to the target value (0.5 [pu]).

[0041] Regarding reactive power Q, while some power fluctuations occur in power converter 15, almost no power fluctuations occur in power converter 10a.

[0042] Thus, in the power converter 10a of this embodiment, the multiplication unit 33 and the calculation unit 34 convert the active power P to the command value P * Output voltage V PCS The phase θ2 is output via a so-called feedforward path, without going through the feedback path (PQ calculation unit 30 → virtual synchronous power generation unit 32 path). As a result, the power converter 10a outputs the command value P of the active power P. * When the value changes, the active power P is immediately set to the command value P. * This can be achieved. As a result, by using the power conversion device 10a of this embodiment, power fluctuations of both active power P and reactive power Q can be suppressed, and thus the occurrence of step-out can also be suppressed.

[0043] =====Power converter 10b (other embodiments)===== Figure 6 shows an example of the power converter 10b of this embodiment. The power converter 10b comprises an inverter 20 and a control device 21b. The control device 21b comprises a PQ calculation unit 30, a low-pass filter (LPF) 31, a virtual synchronous power generation unit 32, a multiplication unit 33, a calculation unit 34, an addition unit 35, 36, an AVR (Automatic voltage regulator) 37, an instantaneous voltage control unit 38, a PWM circuit 39, and a division unit 40.

[0044] Comparing control device 21b and control device 21a, they are the same except for the division unit 40, so here we will explain the division unit 40. Here, in equation (1), |V PCS | and |V SYS |of which, |V SYS If we set | to the rated value of 1.0[pu], then equation (1) becomes equation (4). Δθ = sin -1 (P·X / |V PCS |)···(4)

[0045] The division unit 40, together with the multiplication unit 33 and the arithmetic unit 34, is a functional block for realizing equation (4), and the output from the multiplication unit 33 is |V PCS Divide by |. In this embodiment, the output voltage V PCS The amplitude is the measured value at position A (i.e., the measured |V) measured by the PQ calculation unit 30. PCS The value of | and the calculated value output from the AVR37 (i.e., |V PCS * There are two types: |) and

[0046] The division unit 40 of this embodiment calculates the measured value at position A (i.e., the measured |V PCS Using the value of |, we get P·X / |V in equation (4). PCS The division unit 40 performs calculations on |, but is not limited to this. For example, the division unit 40 calculates the value output from the AVR37 (i.e., |V PCS * Using |, P·X / |V in equation (4) PCS You may also perform the | operation.

[0047] Even when using the control device 21b including such a division unit 40, the phase θ2 of the output voltage V * set to the command value P PCS of the active power P can be output through the feed-forward path (the path of the multiplication unit 33 → division unit 40 → calculation unit 34). As a result, similar to the power conversion device 10a, when the command value P * of the active power P changes, the power conversion device 10b can immediately set the active power P to the command value P * while suppressing the power fluctuations of both the active power P and the reactive power Q.

[0048] =====Others===== In the control device 21b of the power conversion device 10b in FIG. 6, the division unit 40 uses |V PCS | and |V SYS |, and sets |V SYS | to 1.0 [pu] which is the rated value, but it is not limited to this. The division unit 40 may also actually measure the value of |V SYS |, for example, obtained from the medium supply, and calculate P·X / (|V PCS |·|V SYS |). Thus, even when P·X is divided by the product of the amplitude of the output voltage V PCS and the amplitude of the system voltage V SYS , the phase θ2 of the output voltage V PCS can be output through the feed-forward path, so the same effect as the power conversion device 10a of the present embodiment can be obtained.

[0049] ed=====Summary===== As described above, the power conversion devices 10a and 10b of the present embodiment have been explained. The power conversion device 10a can immediately set the active power P to the command value P * while suppressing the power fluctuations of both the active power P and the reactive power Q when the command value P * of the active power P changes. Therefore, when using such a power conversion device 10a, out-of-step can be prevented.

[0050] Furthermore, as shown in the power converter 10b of Figure 6, the control device 21b may also include a division unit 40. Even in this case, the control device 21b outputs the phase θ2 via a feedforward path, thereby suppressing power fluctuations.

[0051] Furthermore, the division unit 40 of the power converter 10b determines the output voltage V at position A. PCS The measured value (i.e., the measured |V PCS You may also use the value of |. In such cases, the active power P is the command value P * This allows for the output of a more accurate phase θ2.

[0052] Furthermore, the division unit 40 of the power converter 10b calculates the value output from the AVR37 (i.e., |V PCS * You may also use |). In such cases, the active power P is the command value P * This allows for the output of a more accurate phase θ2.

[0053] Furthermore, the division unit 40 of the power converter 10b controls the output voltage V PCS The amplitude and the system voltage V SYS The output of the multiplication unit 33 may be divided by the product of the amplitude. In such a case, the active power P is the command value P * This allows for the output of a more accurate phase θ2.

[0054] The embodiments described above are provided to facilitate understanding of the present invention and are not intended to limit its interpretation. Furthermore, the present invention may be modified or improved without departing from its spirit, and it goes without saying that the present invention includes equivalents thereof. [Explanation of symbols]

[0055] 10a, 10b, 15 Power converter 11 Power transmission lines 20 Inverters 21a, 21b, 25 Control device 30 PQ calculation unit 31 Low-pass filter 32 Virtual Synchronous Power Generation Unit 33 Multiplication part 34,51,53,54 Arithmetic unit 35,36 Addition section 37 AVR 38 Instantaneous Voltage Control Unit 39 PWM circuit 50, 52 Addition section

Claims

1. A control device that has a virtual synchronous generator function and controls an inverter connected to a power grid, A first output unit outputs a first phase of the output voltage of the inverter based on the active power from the inverter, a first command value, and the virtual synchronous generator function, A second output unit outputs the amplitude of the output voltage based on the reactive power from the inverter and a second command value, A phase correction value output unit that outputs a phase correction value from the circuit constants of the transmission and distribution lines between the inverter and the power system and the first command value, An adder that outputs a second phase obtained by adding the phase correction value and the first phase, A third output unit outputs a control signal for controlling the inverter based on the amplitude of the output voltage and the second phase, A control device equipped with the following features.

2. A control device according to claim 1, The phase correction value output unit is, A multiplication unit that multiplies the circuit constant by the first command value, A calculation unit that calculates the arcsine value of the product of the circuit constant and the first command value and outputs it as the phase correction value, A control device including a control device.

3. A control device according to claim 2, The unit comprises a division unit that divides the multiplication result by the amplitude of the output voltage, The aforementioned arithmetic unit, The arcsine value of the division result obtained by dividing the multiplication result by the amplitude of the output voltage is calculated. Control device.

4. A control device according to claim 3, The division unit is, Divide by the amplitude of the measured output voltage. Control device.

5. A control device according to claim 3, The division unit is, Divide by the amplitude of the output voltage output by the second output unit. Control device.

6. A control device according to any one of claims 3 to 5, The division unit is, The result of the multiplication is divided by the product of the amplitude of the output voltage and the amplitude of the power system voltage. The aforementioned arithmetic unit, The arcsine value of the division result obtained by dividing the multiplication result by the product is calculated. Control device.

7. A power conversion device comprising an inverter connected to a power grid and a control device having a virtual synchronous generator function and controlling the inverter, The control device is A first output unit outputs a first phase of the output voltage of the inverter based on the active power from the inverter, a first command value, and the virtual synchronous generator function, A second output unit outputs the amplitude of the output voltage based on the reactive power from the inverter and a second command value, A phase correction value output unit that outputs a phase correction value from the circuit constants of the transmission and distribution lines between the inverter and the power system and the first command value, An adder that outputs a second phase obtained by adding the phase correction value and the first phase, A third output unit outputs a control signal for controlling the inverter based on the amplitude of the output voltage and the second phase, A power conversion device that includes a power converter.

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