JP2022034288A - Inverter device - Google Patents

Abstract

To eliminate a need for an output current detector of an inverter to reduce cost and size.SOLUTION: An inverter device that comprises an inverter 10 and a control circuit 40A and that is operated in cooperation, simulates a frequency stabilization function by inertia of a rotation body in a synchronous generator through pseudo synchronous generator control. In the inverter device, the control circuit 40A comprises: a generator rotation body simulation unit 43A that receives a voltage at a connection point between a reactor X and a power system 20 and performs simulated operation of a voltage phase for an inner electromotive force of the synchronous generator; and means 44 and 45 that generate a signal for driving the inverter 10 on the basis of the voltage phase θ. The generator rotation body simulation unit 43A has: coordinate conversion means 43f as q-axis voltage calculation means that calculates at least a q-axis voltage from a voltage at the connection point; means 43g of estimating an output effective power of the inverter 10 from the q-axis voltage, a reactance value X, and an output voltage command of the inverter 10; and means 43c and 43d that calculate the voltage phase θ by integrating the effective power.SELECTED DRAWING: Figure 1

Description

The present invention relates to an inverter device operated in connection with an electric power system, and more particularly to an inverter device that realizes a frequency stabilization function of a synchronous generator by pseudo-synchronous generator control.

In recent years, a large number of distributed power sources such as photovoltaic power generation devices have been connected to the power system, and the ratio of synchronous generators has decreased relatively, so that the stability of the power system tends to decrease.
As is well known, in a synchronous generator, the difference between the input driving force and the generated power is stored in the inertial energy of the rotating body, and this becomes the angular velocity of the rotating body, that is, the frequency of the output voltage. In other words, the inertia of the rotating body of the synchronous generator functions to stabilize the frequency of the power system.
On the other hand, inverter devices such as PCS (power conditioner system) that make up a distributed power source are controlled to follow the voltage of the power system at high speed, and maintain the output frequency independently like a synchronous generator. Does not have the ability to do.
Therefore, when the ratio of the synchronous generator in the electric power system becomes small, the frequency stabilization function by the synchronous generator does not work sufficiently, and there arises a problem that the fluctuation of the system frequency becomes large.

In view of the above points, a large number of conventional techniques have been provided in which the frequency stabilizing function of the synchronous generator is realized by the pseudo synchronous generator control of the inverter device.
6 and 7 show this type of inverter device, and for example, Patent Document 1 discloses a similar prior art.

In FIG. 6, 10 is a three-phase inverter that controls a pseudo-synchronous generator, 11 is a DC power source such as a solar cell module or a storage battery, and 12 is a DC / AC conversion that converts DC power into AC power by the operation of a semiconductor switching element. Part X is a reactor for smoothing connected to the interconnection line 21 between the inverter 10 and the power system 20, C is also a capacitor, and 30 is a synchronous generator as an AC power source.
The control circuit 40 that controls the inverter 10 includes a current detector 41 that detects the output currents I _a , I _b , and I _c (abbreviated as I _{a, b, c} if necessary) of the inverter 10, and an output voltage V. A voltage detector 42 that detects _a , V _b , V _c (also abbreviated as Va _{, b, c} ), a generator rotating body simulation unit 43, a sine wave calculation unit 44, and a PWM calculation unit 45. I have.
In the present specification, the inverter device including the inverter 10 and the control circuit 40 is referred to as an inverter device. In FIG. 6, V _inv and V _s are the voltages across the reactor X, respectively, and the voltage V _s is substantially equal to the voltages V _{a, b, and c} .

FIG. 7 is a configuration diagram of a generator rotating body simulation unit 43 in the control circuit 40.
In FIG. 7, the active power measuring unit 43a measures the active power P from the output currents I _{a, b, c} and the output voltages Va _{, b,} c of the inverter 10 and inputs them to the addition / subtraction means 43b. The output target value of the inverter 10, which is regarded as the input (driving force) of the simulated synchronous generator, and the output of the damper 43e, which will be described later, are also added to the addition / subtraction means 43b.
The output of the addition / subtraction means 43b is integrated by the first integration means 43c, and the angular velocity Δω of the rotating body of the simulated synchronous generator is calculated. M in the first integrating means 43c is a coefficient corresponding to the inertia of the rotating body of the synchronous generator.
The angular velocity Δω is input to the damper 43e that suppresses the vibration component and is integrated by the second integrating means 43d to calculate the voltage phase θ of the internal electromotive force of the simulated synchronous generator.

Returning to FIG. 6, the sine wave calculation unit 44 generates a sine wave voltage command V ^* _{a, b, c} using the voltage phase θ, a predetermined frequency, and an amplitude value, and outputs the voltage command V * a, b, c to the PWM calculation unit 45. The PWM calculation unit 45 compares the voltage commands V ^* _{a, b, and c} with the carrier to generate a pulse signal, and the pulse signal causes the semiconductor switching elements of the upper and lower arms of each phase of the DC / AC conversion unit 12 of the inverter 10 to generate a pulse signal. Driven.

In this conventional technique, when the phase of the output voltage of the inverter 10 is ahead of the phase of the system voltage, the inverter 10 outputs active power to the power system 20, and when the phase is delayed, the inverter 10 is connected to the power system 20. As a result of controlling the frequency and phase of the output voltage of the inverter 10 so as to absorb the active power, a so-called synchronization force works, and even when the ratio of a strong power source such as a synchronous generator to the power system 20 is small. The system frequency can be maintained at a predetermined value.

Japanese Unexamined Patent Publication No. 2007-318833 ([0024] to [0033], FIG. 1, etc.)

In the above-mentioned conventional technique, the active power measuring unit 43a in the generator rotating body simulating unit 43 measures the output currents _{Ia, b, c} of the inverter 10 by using the current detector 41 in order to measure the active power P. I had to do it.
As a result, there is a problem that the cost increases and the size of the entire device is increased.

Therefore, an object of the present invention is to provide an inverter device that eliminates the need for an output current detector of an inverter and enables cost reduction and miniaturization.

In order to solve the above problems, the invention according to claim 1 includes an inverter that converts DC power into AC power and a control circuit that controls a semiconductor switching element of the inverter, and operates in connection with a power system. It is an inverter device that is used.
In an inverter device that can simulate the frequency stabilization function due to the inertia of the rotating body of the synchronous generator connected to the power system by controlling the pseudo synchronous generator.
The control circuit is
A generator rotating body simulation unit that simulates the voltage phase of the internal electromotive force of the synchronous generator by inputting the voltage at the connection point between the reactor on the output side of the inverter and the power system.
A means for generating a drive signal of the semiconductor switching element based on a voltage command generated using the voltage phase is provided.
The generator rotating body simulation unit is
A q-axis voltage calculation means that calculates the q-axis voltage based on the input voltage of the connection point, and
An active power estimation means for estimating the active power output from the inverter by using the q-axis voltage, the reactance value of the reactor, and the output voltage command of the inverter.
A voltage phase calculation means that integrates the estimated active power to calculate the voltage phase, and
It is characterized by having.

The invention according to claim 2 is the inverter device according to claim 1.
The q-axis voltage calculation means is a coordinate conversion means for converting the voltage at the connection point from a static coordinate system to a rotating coordinate system to calculate at least the q-axis voltage, and the coordinate conversion means uses the voltage phase. It is characterized by performing coordinate transformation.

The invention according to claim 3 is characterized in that, in the inverter device according to claim 1 or 2, the output voltage command of the inverter is fixed by a unit voltage.
The invention according to claim 4 is characterized in that, in the inverter device according to claim 1 or 2, the active power estimation means sets the output voltage command of the inverter to an arbitrary variable voltage.

In the invention according to claim 5, in the inverter device according to any one of claims 1 to 4, the difference between the output of the active power estimation means and the output target value is input to the voltage phase calculation means. It is a feature.

The invention according to claim 6 is characterized in that, in the inverter device according to any one of claims 1 to 5, a damper for suppressing a vibration component generated by the operation of the voltage phase calculation means is provided. ..

In the invention according to claim 7, in the inverter device according to any one of claims 1 to 6, the integrated amount in the voltage phase calculation means includes the initial angular velocity of the rotating body of the simulated synchronous generator. It is characterized by.

According to the present invention, the output active power of the inverter is estimated from the voltage on the output side of the reactance component without detecting the output current of the inverter, and the pseudo-synchronous generator control is performed, thereby eliminating the need for a current detector and costing. It is possible to stabilize the system frequency while reducing the amount of power and reducing the size of the entire device.

It is a block diagram of the inverter device which concerns on 1st Embodiment of this invention. It is a block diagram of the generator rotating body simulation part in FIG. It is a vector diagram of the input / output voltage of the reactor of FIG. It is a block diagram of the inverter device which concerns on 2nd Embodiment of this invention. It is a block diagram of the generator rotating body simulation part in FIG. It is a block diagram of the inverter device which shows the prior art. It is a block diagram of the generator rotating body simulation part in FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram of an inverter device according to a first embodiment of the present invention, the same parts as those in FIG. 6 are designated by the same reference numerals, and the parts different from those in FIG. 6 will be mainly described below. ..

In FIG. 1, 40A is a control circuit of an inverter 10, and voltage detection values Va _{, b, c} from a voltage detector 42 connected to an interconnection line 21 are used in a generator rotating body simulation unit 43A inside the control circuit. Only have been entered. That is, in this embodiment, the current detector 41 in FIG. 6 is not required.
The generator rotating body simulation unit 43A calculates the voltage phase θ of the internal electromotive force of the simulated synchronous generator by inputting the voltage detection values Va _{, b, and c} , and outputs the voltage phase θ to the sine wave calculation unit 44.

FIG. 2 is a block diagram of the generator rotating body simulated unit 43A of FIG.
The three-phase voltage detection values Va _{, b, and c} are input to the coordinate conversion means 43f as the q-axis voltage calculation means in the claims. In this coordinate conversion means 43f, the voltage detection values Va _{, b, c} , which are the three-phase quantities of the static coordinate system, that is, the output side voltage V of the reactor X, are used by using the voltage phase θ output from the integration means 43d described later. _s is coordinate-converted into d-axis voltage V _d and q-axis voltage V _q , which are two-phase quantities in the rotational coordinate system, and output.
In this embodiment, the d-axis voltage V _d and the q-axis voltage V _q are obtained using the coordinate conversion means 43f. For example, "vector control and AC machine drive dynamics" (DW Novotny, TA Lipo). Written in Equations 2.8.1, 2.8-2, etc. in "Conversion to 2.8 Rotational Coordinates" (p.60-p.67), published by Denki Shoin Co., Ltd., September 10, 2001. Using the method of converting the variable of the three-phase quantity into the variable on the d-axis and q-axis, the voltage detection values Va _{, b, and c} are converted into the d-axis voltage V _d and the q-axis voltage V _q , and the q-axis thereof. The voltage V _q may be used in the calculation after Equation 2 described later. In this case, the means for converting the voltage detection values Va _{, b, c} into the q-axis voltage V _q based on the above equation 2.8-1 or the like corresponds to the q-axis voltage calculation means in the claims.

Here, FIG. 3 is a vector diagram of the voltages V _inv and V _s across the reactor X, and δ is the phase difference of V _inv and V _s . In FIG. 3, the voltage V _inv , that is, the output voltage of the inverter 10 is in phase with the d-axis voltage V _d , which is an active power component.
Assuming that the reactor X does not contain a resistance component and has only a pure reactance component (the reactance value is also X), the active power P supplied from the inverter 10 to the reactor X is expressed by Equation 1.
[Formula 1]
P = (Vs · V _inv / X) _sinδ
The relationship of this formula 1 is described in, for example, [0010] of JP-A-5-80867 and [0027] of JP-A-2001-45662.

By substituting the relation of V _q = V _s · sin δ into the formula 1, the formula 2 is obtained, and when the voltage V _inv is set to the fixed value of 1 [pu] by the output voltage command, the formula 3 is obtained.
[Formula 2]
P = V _q · V _inv / X
[Formula 3]
P = V _q / X

Returning to FIG. 2, by inputting the _q -axis voltage Vq output from the coordinate conversion means 43f into the coefficient multiplying means 43g and multiplying by (1 / X), the above-mentioned equation 3 is calculated. That is, in FIG. 7 of the prior art, the active power P was calculated from the voltages Va _{, b, c} and the currents I _{a, b, c,} but in FIG. 2 according to the first embodiment, the voltages Va _{, b} . The active power P is estimated by the calculation of the equation 3 using the q-axis voltage V _q obtained by converting the coordinates _{of and c} and the reactance value X.

The estimated active power value P is input to the addition / subtraction means 43b together with the output target value and the output of the damper 43e that suppresses the vibration component of the angular velocity Δω, as in FIG. The output of the addition / subtraction means 43b is integrated by the first integration means 43c, and the angular velocity Δω of the rotating body of the simulated synchronous generator is calculated. This angular velocity Δω is input to the second integrating means 43d via the addition / subtraction means 43h, and the voltage phase θ of the internal electromotive force of the simulated synchronous generator is calculated.
In FIG. 2, the coefficient multiplying means 43g constitutes an active power estimation means within the claims, and the first and second integrating means 43c, 43d constitute a voltage phase calculating means within the claims.

The initial angular velocity value ω ₀ input to the addition / subtraction means 43h in FIG. 2 is a voltage phase for coordinate conversion so that the input of the second integration means 43d has a predetermined value even when Δω = 0. It is for obtaining θ.
Further, the damper 43e may be provided on the path from the output side of the addition / subtraction means 43h to the addition / subtraction means 43b.

As described above, according to the first embodiment, the active power P of the inverter 10 can be estimated and the voltage phase θ can be obtained without detecting the output current of the inverter 10, and this voltage phase θ is used. The frequency of the power system 20 can be stabilized by the pseudo-synchronous generator control.

Next, the second embodiment of the present invention will be described with reference to FIGS. 4 and 5.
The difference between the control circuit 40B shown in FIG. 4 and the control circuit 40A of FIG. 1 is that the configuration of the generator rotating body simulation unit 43B and the output of the sine wave calculation unit 44 are input to the multiplying means 46 to output the inverter 10. It is a point to multiply by the absolute value | V _inv ^* | of the voltage command and input the result as the voltage command V ^* _{a, b, c} to the PWM calculation unit 45.
The configuration of the generator rotating body simulation unit 43B is as shown in FIG. 5. The multiplication means 43i is inserted between the coefficient multiplication means 43g and the addition / subtraction means 43b, and the output of the coefficient multiplication means 43g is multiplied by | V _inv ^* |. To obtain the estimated active power value P. Here, the coefficient multiplying means 43g and the multiplying means 43i constitute the active power estimation means within the scope of the claims.

According to this second embodiment, the above-mentioned [Formula 2] becomes the following formula 4.
[Formula 4]
P = V _q・ | V _inv ^* | / X
Therefore, the voltage phase θ can be obtained in the same manner as in the first embodiment by using the estimated active power P when the output voltage of the inverter 10 is set to a desired magnitude | V _inv ^* |, and the inverter 10 can be obtained. It is possible to stabilize the frequency of the power system 20 by controlling the pseudo-synchronous generator.

10: Inverter 11: DC power supply 12: DC / AC converter 20: Power system
21: Interconnection line 30: Synchronous generator 40A, 40B: Control circuit 42: Voltage detector 43A, 43B: Generator rotating body simulation unit 43b, 43h: Addition / subtraction means 43c, 43d: Integration means 43e: Damper 43f: Coordinate conversion Means 43g: Coefficient multiplication means 43i: Multiplication means 44: Sine wave calculation unit 45: PWM calculation unit 46: Multiplication means X: Reactor C: Condenser

Claims (7)

An inverter device that includes an inverter that converts DC power into AC power and a control circuit that controls the semiconductor switching element of the inverter, and is operated in connection with the power system.
In an inverter device that can simulate the frequency stabilization function due to the inertia of the rotating body of the synchronous generator connected to the power system by controlling the pseudo synchronous generator.
The control circuit is
A generator rotating body simulation unit that simulates the voltage phase of the internal electromotive force of the synchronous generator by inputting the voltage at the connection point between the reactor on the output side of the inverter and the power system.
A means for generating a drive signal of the semiconductor switching element based on a voltage command generated using the voltage phase is provided.
The generator rotating body simulation unit is
A q-axis voltage calculation means that calculates the q-axis voltage based on the input voltage of the connection point, and
An active power estimation means for estimating the active power output from the inverter by using the q-axis voltage, the reactance value of the reactor, and the output voltage command of the inverter.
A voltage phase calculation means that integrates the estimated active power to calculate the voltage phase, and
An inverter device characterized by having. In the inverter device according to claim 1,
The q-axis voltage calculation means is a coordinate conversion means that converts the voltage at the connection point from a static coordinate system to a rotational coordinate system to calculate at least the q-axis voltage, and the coordinate conversion means uses the voltage phase. An inverter device characterized by performing coordinate conversion. In the inverter device according to claim 1 or 2.
The active power estimation means is an inverter device characterized in that the output voltage command of the inverter is fixed by a unit voltage. In the inverter device according to claim 1 or 2.
The active power estimation means is an inverter device characterized in that the output voltage command of the inverter is an arbitrary variable voltage. In the inverter device according to any one of claims 1 to 4.
An inverter device characterized in that the difference between the output of the active power estimation means and the output target value is input to the voltage phase calculation means. In the inverter device according to any one of claims 1 to 5.
An inverter device provided with a damper for suppressing a vibration component generated by the operation of the voltage phase calculation means. In the inverter device according to any one of claims 1 to 6.
An inverter device characterized in that the integrated amount in the voltage phase calculation means includes the initial angular velocity of the rotating body of the simulated synchronous generator.

Images