JPH0744785B2 - Control system for grid-connected inverter - Google Patents

Description

TECHNICAL FIELD The present invention relates to an active / reactive power control system for a voltage type self-excited inverter that is interconnected with a power system. In such a system, it responds stably and promptly to disturbances such as active and reactive power setting changes, grid disturbances, DC power supply fluctuations, etc., and the desired valid or invalid without adversely affecting the grid. Power control is desirable.

[Conventional technology]

FIG. 6 is a schematic diagram showing the basic configuration of the interconnection inverter system. In the figure, 21 is a DC voltage source, 22 is a voltage type self-excited inverter, 23 is a transformer, and 26 is a power system. This is shown in an equivalent model as shown in FIG.
It can be represented by 1 and impedance X. 30
Represents an equivalent model of the inverter and 31 represents an equivalent model of the power system.

Control of active power P and reactive power Q in such a system is performed as follows, for example. FIG. 8 is a block diagram showing a conventional example of an active / reactive power control system using an inverter. In the figure, 20a is an active power regulator (APR),
20b is a reactive power regulator (AQR), 2 is a firing angle calculator, 3 is an active power detector (PQ detector), 21 is a DC voltage source,
22 is a voltage type self-excited inverter, 23 and 24 are transformers, 25 is a current transformer, and 26 is a power system.

This, APR20a output and AQR20b of the output phase component with respect to the system voltage _S of the inverter output voltage _i, respectively (∠V _i) and the amplitude component (| V _i |) treated as in the based ignition angle calculator 2 which The ignition pulse to be given to the switching element of the inverter 22 is obtained and the control is performed. In addition, a dot "."

[Problems to be solved by the invention]

However, in the method as described above, | V _i | and ∠V _i do not correspond to P and Q one-to-one, but serve as both functions. Therefore, for example, by changing the setting of P or Q, ∠ V _i is affected, and a phenomenon occurs in which both P and Q change due to this change in ∠V _i . This becomes a problem as a disturbance of the system as the capacity of the grid-connected inverter progresses, and it becomes difficult to speed up the system responsiveness due to such mutual interference, which makes it impossible to control at high speed. Is occurring.

Therefore, it is an object of the present invention to provide a control method that makes it possible to control active and reactive power by making them non-interfering with each other, and that is stable, fast, and excellent in transient response characteristics.

[Means for solving problems]

An active current controller and a reactive current controller for adjusting each detected value of an active current component and a reactive current component of an inverter output current corresponding to active power and reactive power in a one-to-one manner so as to match each target value thereof; Predetermined adjustment calculation including at least differentiation so that the detected values iα, iβ of the active current component and the reactive current component of the inverter output current, which correspond one-to-one to the electric power and the reactive power, match the respective target values iα ^* , iβ ^* The active current controller and the reactive current controller that perform the above, and the calculator that receives the outputs of the active current controller and the reactive current controller as input and calculates the inverter output voltage target values Vα ^* and Vβ ^* are provided. The active current regulator, the reactive current regulator and the arithmetic unit are the following differential equations representing the relationship between the active current and the reactive current and the output voltage, (However, L and r are the inductance and resistance that represent the impedance between the inverter and the system, V _SS is the system voltage and S
The inverter output voltage target values Vα ^* and Vβ ^* are calculated based on the Laplace operator).

[Action]

The present invention relates to a control system of a voltage-type self-excited inverter that operates in cooperation with a grid to control active power and reactive power, and an active current component in which an output current of the inverter corresponds to active power and reactive power on a one-to-one basis. And consider it as a reactive current component,
An active current controller and a reactive current controller for controlling the active current and the reactive current are provided, and the outputs of these controllers are treated as control signals including the active or reactive current differentials or the differentials that have a linear correspondence relationship. , Active voltage and reactive power are separated by performing a simple calculation based on the relational expression between this output signal and the inverter output voltage to find the voltage target value to be output from the inverter, and controlling the inverter voltage based on this. It can be controlled independently.

Here, let us examine the system interconnection inverter system as shown in FIG. 6 by using mathematical expressions.

Now, consider a grid-connected inverter system as shown in FIG. Here, the impedance between the inverter and the system is represented by an inductance L and a resistance r.
Then, with the system voltage _s as a reference, the inverter output voltage _i and the output current are α- as shown in FIG.
Treat as a vector on β coordinates. At this time, each α-β component is It is said. In the interconnection system represented as above, the relational expression between the inverter output voltage and the current can be obtained as follows by solving a predetermined differential equation.
In addition, P is a differential operator (d / dt).

If these are Laplace-transformed and shown, it will become like the following formula. Note that S is a Laplace operator.

Further, the active power P and the reactive power Q are calculated from the currents of the in-phase component and the quadrature component of the system voltage _S Becomes That is, i _α and i _β are active and reactive currents that correspond one-to-one to active and reactive power, respectively. Therefore, P, Q
The effective and reactive currents i _α and i _β may be controlled in order to control the current. Since these i _α and i _β are related to the inverter output voltage by the equation (4) ′, an arithmetic unit or current / voltage (I / V) conversion that actually develops this equation in the control system. If a device is installed and controlled, ideal control performance can be obtained. This arithmetic unit or I / V converter is, for example, as shown in FIG. 10, but 5a and 5b in the same figure are locations for performing differential operations, and it is difficult to actually perform this type of operations with high accuracy. In addition, 5a, 5b are differential calculators, 5c, 5d
Is a proportional calculator.

〔Example〕

The present invention has been made in view of such a viewpoint, and an embodiment thereof is shown in FIG. As is clear from the figure, this embodiment has an arithmetic unit (I / V converter) 1 indicated by a chain line.
It is characterized by the provision of.

That is, the target values i _α ^* , i _β ^* of the active current and the reactive current together with the detection values i _α , i _β obtained through the detector 3 are the active current regulator (ACR) 11a and the reactive current regulator (ACR). ) 11
It is input to b, and a predetermined adjustment operation is performed so that the target value and the detected value match. Then, the output signals S ₁ and S ₂ of these regulators are treated as control amounts including respective differentials linearly corresponding to active and reactive currents, as shown in the following equation.

Therefore, in the calculation unit indicated by the dotted line in the figure, the first-order lag element 13
By simple calculation of a, 13b and proportional elements 12a, 12b, the target values v _α ^* , v _β ^{* of} the inverter output voltage satisfying the relationship shown in the equation (4) ′ can be obtained.

This is shown below by mathematical expressions.

From the above, Holds, which is the same as the above equation (4) ′. Then, from the target value v _α ^* , v _β ^{* of} the output voltage obtained here, the ignition pulse to be supplied to the inverter is obtained by the ignition angle calculator 2, and the ignition pulse is given to the inverter 22 to obtain the voltage. Control is performed.

As a result, in this system, the active power and the reactive power can be controlled without being interfered with each other, and the control performance is significantly improved.

In the above embodiment, the outputs of the current regulators 11a and 11b are (6)
Although it is treated as the sum of the derivative and the proportion as in the equations (7), it can be treated as the control amount of only the derivative as follows.

S ₃ : Si _α ^* S ₄ : Si _β ^{* In} this case, the calculation unit in the subsequent stage is a proportional integrator as shown in Fig. 2.
It may be composed of 14a, 14b and integrators 15a, 15b.

If the resistance (r) of the impedance between the system and the inverter can be ignored, the signal as shown in Fig. 3 is generated.
Assuming that S ₅ and S ₆ are S ₅ : Si _α ^* S ₆ : Si _β ^* , the proportional computing units 16a and 16b and the integrators 17a and 17b form a computing unit.

As described above, in short, according to the present invention, the target values i
Target value of the inverter output voltage v _α ^* , v _β from _α ^* , i _β ^*
When determining ^* , active and reactive current regulators are provided and they are differentiated, and v _α ^* , v is output from the regulator output signal.
_{Since β} ^* is obtained by calculation, high-performance control can be achieved with a simple control circuit that does not include differentiation in the calculation section.

In addition, the target values i of the active and reactive currents not mentioned above
Regarding the method of calculating _α ^* , i _β ^* , for example, as shown in FIG. 4, it functions so that the set values (P ^* , Q ^* ) of active power and reactive power and the detected values (P, Q) match. Active power controller 20a
And reactive power controller 20b are provided to enable these outputs,
The target values i _α ^* and i _β ^{* of the} reactive current may be set. If the system voltage fluctuation is small, i _α ^* , i _β ^* may be simply obtained by the proportional calculators 32a and 32b as shown in FIG.

〔The invention's effect〕

According to the present invention, focusing on the active current component and the reactive current component of the inverter output current, which correspond one-to-one to the active power and the reactive power, and theoretically analyzing the interconnected inverter system from these target values. Since the target value of the voltage to be output from the inverter is calculated by the calculation that satisfies the relational expression between the output current and the output voltage, and the inverter output voltage is adjusted based on this, the active power and the reactive power are The non-interference can be controlled, and the transient response performance can be greatly improved.

In the calculation for obtaining the output voltage target value,
Since the regulators for the active current and the reactive current are used to perform the differential operation, simplification of the actual arithmetic circuit is achieved. Furthermore, the provision of active and reactive current regulators can limit the output overcurrent in advance,
As a result, a good effect can be expected in terms of safety.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a main part configuration diagram showing another embodiment of the present invention, and FIG. 3 is a main part configuration diagram showing still another embodiment of the present invention. , Fig. 4 is valid,
Block diagram showing the method of deriving the reactive current.
A block diagram showing another method of deriving the reactive current, FIG. 6 is a schematic diagram showing the basic configuration of a grid-connected inverter system, FIG. 7 is an equivalent block diagram of FIG. 6, and FIG. FIG. 9 is a configuration diagram showing a conventional example of a power control system, FIG. 9 is an explanatory diagram for explaining the principle of the present invention, and FIG. 10 is a current / voltage (I) for obtaining a voltage target value based on the principle of the present invention. It is a block diagram which shows / V) conversion device. Reference numeral 1, 5 …… Calculation device (V / I conversion device), 2 …… Ignition angle calculator, 3 …… Detector, 5c, 5d, 12a, 12b, 16a, 16b, 32a, 32b…
… Proportional calculator, 5a, 5b …… Derivative calculator, 11a, 11b …… Current regulator, 13a, 13b …… First-order lag element, 14a, 14b …… Proportional integral element, 15a, 15b, 17a, 17b …… Integral element, 20a, 20b …… Power controller, 21 …… DC voltage source, 22 …… Voltage type self-excited inverter, 23,24 …… Transformer, 25 …… Current transformer, 26 …… Power system, 30 …… Inverter equivalent model, 31 …… Electric power system equivalent model.

Claims (1)

[Claims] 1. In a grid-connected inverter that is connected to a power system to control active power and reactive power, an active current component and a reactive current component of an inverter output current that correspond one-to-one to the active power and the reactive power. Each detected value i of
an active current controller and a reactive current controller that perform a predetermined adjustment calculation including at least differentiation to match α and iβ with their respective target values iα ^* and iβ ^* , and outputs of the active current controller and the reactive current controller Is provided as an input, and a computing unit for computing the inverter output voltage target values Vα ^* and Vβ ^* is provided, and the active current regulator, the reactive current regulator, and the computing unit are the relation between the active current and the reactive current and the output voltage. The differential equation (However, L and r are the inductance and resistance that represent the impedance between the inverter and the system, V _SS is the system voltage and S
Is a Laplace operator), and calculates the inverter output voltage target values Vα ^* , Vβ ^* based on the above equation, and controls the inverter output voltage based on the output of the computing unit. .