JPH03124267A - Controller of inverter for interlocking and individual operation - Google Patents

Abstract

PURPOSE:To restrain effects on a load and a control system by a method wherein the output of a constant voltage control system upon individual operation is made zero and the output is added with a preset value while a control system is switched instantaneously from effective/ineffective power control into a constant voltage control by a switch simultaneously with the system parallel-off. CONSTITUTION:When an inverter is released from a system and the operation of the same is shifted from interlocking operation into individual operation, the output of a voltage control device 7 is added with a control amount corresponding to 50% load operation upon the individual operation, for example, by an initial setter 4 whereby the fluctuation becomes a value corresponding to the 50% load fluctuation at maximum to a constant voltage control system and non-instantaneous switching of a control system is permitted when the control system is switched by switches 8A, 8B, 9, 16 and the like. In this case, the output of the voltage control device 7 is reduced into zero. According to this method, effects on the load and the control system can be minimized.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention generates alternating current voltage using an independent direct current power source as a supply source, and is connected to a power system (also simply referred to as a power system) and connected to the power system. A control device for a voltage-type automatic inverter that performs both grid-connected operation in which power is transferred and received, and stand-alone operation in which it is disconnected from the grid and supplies power to the load independently, and in particular, it is capable of disconnecting from the grid without momentary interruption. The present invention relates to an inverter control device.

[Conventional technology]

Conventionally, at the time of this kind of grid disconnection, it is known to first stop the inverter, put it in an independent state, and then restart the constant voltage control system.

[Problem to be solved by the invention]

However, in such a system, an instantaneous power outage occurs in the load whose power source is the inverter, and the control system ends up starting from zero. That is, there is a problem in that it is not possible to shift from active power (P)/reactive power (Q) control during interconnected operation to constant voltage control during isolated operation without momentary interruption.

Therefore, the objects of this invention are: i) In particular, to switch from grid-connected operation to isolated operation without momentary interruption.

ji) At that time, do not stop power supply to the load.

iii) Similarly, the impact on the load and control system should be minimized.

etc.

[Means to solve the problem]

Interconnected operation involves generating AC voltage from an independent power source and transmitting it to the power grid to control active and reactive power to transfer power to and from the grid, and constant voltage control for the load. In an inverter control device that is capable of both islanding and power supply, the output of the constant voltage control system when it is alone is set to zero, and a preset value is added to that output. At the same time as disconnection, a switch activates the control system, instantly switching from reactive power control to constant voltage control. In addition, in order to prevent the inverter output from generating overvoltage when the grid is disconnected, the output of the reactive power control system is set to zero before the grid is disconnected, and a predetermined bias amount is added to the output to make it ineffective. The amount of power control may be forcibly reduced to zero (or even the latter may be performed independently).

[Effect]

When disconnecting from the grid and transitioning from interconnected operation to isolated operation, for example, by adding an initial setting amount equivalent to 50% load when isolated to the output of the constant voltage control system for isolated operation,
This prevents the constant voltage control system from starting from zero, allowing the constant voltage control system to receive only ±50% load fluctuations at most, reducing disturbances to the control system, and switching from grid-connected operation to independent operation. It is possible to switch to operation without momentary interruption. At this time, if the load amount at the time of individual operation is known in advance, by adjusting the above-mentioned addition value to this amount (load equivalent amount), it is possible to perform switching with less shock. Note that switching of the control system is performed at the same time as disconnection.

〔Example〕

FIG. 1 is a system configuration diagram showing an embodiment of the present invention. In the same figure, ■ is an active power (P) setting device, 2 is a reactive power (Q) setting device, 3 is an output voltage (Vj) setting device, and 4 is an output voltage (Vj) setting device.
is the initial setting device, 5 is the active power controller (APR), 6
is a reactive power controller (AQR), 7 is a voltage controller
(AVR), 8A.

8B, 9 and 16 are switches, 1o is a pulse amplifier (
PA), 11 is a DC power supply, 12 is a voltage type automatic inverter, 13 is a transformer, 14 is a reactor, 15 is a load,
17 is a power system, 18 is a transformer (PT), I9 is a current transformer (CT), and 20 is an active 2 reactive power detector.

Its main circuit is a DC power supply 11, a voltage type automatic inverter 12
, a transformer 13, a reactor 14, etc., and a load 15
and supplies power to the power grid 17. Further, the switch 16 opens and closes the electric circuit between the inverter 12 and the system. That is, when the switch 16 is in the closed state (when connected to the grid), the active power and reactive power detected via the active and reactive power detector 20 are transferred to the active power setter 1. When the active power control device 5 and the reactive power control device 6 are selected by the switches 8A and 8B, and the switch 16 is in the open state. (During independent operation), the switch 9 selects the voltage control device 7 that controls the inverter output voltage (Vi) obtained via the transformer 18 to match the value set by the setting device 3. Note that the output of each control device is given to an inverter 12 via a pulse amplifier 10.

Furthermore, in this embodiment, the output of the voltage control device 7 during grid-connected operation is set to 50, for example, by the setting device
By adding the control amount for the % load operation sum, when switching the control system using switches 8A, 8B, 9, and 16, etc., the fluctuation equivalent to at most 50% load fluctuation for the constant voltage control system can be reduced. This makes it possible to switch control systems without momentary interruption. Note that at this time, the output of the voltage control device 7 is narrowed down to zero by an appropriate means (not shown).

FIG. 2 is a block diagram of main parts showing another embodiment of the present invention.

This is to forcibly remove the controlled amount of reactive power before disconnecting the grid, and Figure (A) shows an example in which a switch 21 is provided at the output of the reactive power control device 6 to disconnect it. The figure (b) shows an example in which the output of the reactive power control device 6 is narrowed down to "0" by the switch 22. Then, by applying a bias such that the control amount of reactive power becomes zero to the output of the reactive power control device 6 via an adder as shown in FIGS. This prevents inverter output overvoltage and undervoltage from occurring when the inverter is disconnected from the grid.

〔Effect of the invention〕

According to this invention, not only is it possible to switch from a grid-connected operating state to an isolated operating state without a momentary interruption, but there is also the advantage that the effect on the load and control system can be minimized at that time. .

[Brief explanation of drawings]

FIG. 1 is a system configuration diagram showing one embodiment of the invention, and FIG. 2 is a main part configuration diagram showing another embodiment of the invention. Code explanation 1... Active power (P) setting device, 2... Reactive power (Q
) setting device, 3...output voltage (Vi) setting device, 4...
Initial setting device, 5... Active power control device, 6... Reactive power control device, 7... Voltage control device, 8A, 8B, 9
．． 16...Switch, 10...Pulse width meter (PA
), 11... DC power supply, 12... Voltage type self-excited inverter, 13... What lance, 14... Reactor I, 15... Load, 17... Power system, 18... ...Transformer (PT), 19...Current transformer (CT), 20...
Active and reactive power detector.

Claims (1)

[Scope of Claims] 1) Grid-connected operation in which AC voltage is generated based on an independent power source, which is connected to the power grid, controls active power and reactive power, and transfers power to and from the grid. In an inverter control device that is capable of both stand-alone operation in which power is supplied independently by performing constant voltage control on the load, the output of the constant-voltage control system during stand-alone operation is set to zero, and the output is set in advance to that output. A grid interconnection system characterized in that the control system is activated by a switch at the same time as the grid is disconnected, and instantaneously switches from reactive power control to constant voltage control.
Control device for inverter for standalone operation. 2) In order to prevent the output of the inverter from generating an overvoltage when the grid is disconnected, the output of the reactive power control system is set to zero before the grid is disconnected, and a predetermined bias amount is added to the output to control the reactive power control amount. 2. The control device for an inverter for interconnection and independent operation according to claim 1, wherein the inverter is forcibly set to zero. 3) Grid-connected operation, in which AC voltage is generated from an independent power source, which is connected to the power grid, controls active power and reactive power, and transfers power to and from the grid, and constant voltage to the load. In an inverter control device that is capable of both isolated operation and independent power supply, the output of the reactive power control system is controlled before grid disconnection so that the inverter output does not generate overvoltage during grid disconnection. What is claimed is: 1. A control device for an inverter for grid-connected or isolated operation, characterized in that the control amount of reactive power is forcibly reduced to zero by adding a predetermined bias amount to the output thereof.