JPH0640702B2 - Power supply system - Google Patents

Description

The present invention relates to a power supply system, and more particularly to a power supply system that converts a DC voltage into an AC voltage by using an inverter and outputs the AC voltage to an AC power system.

[Prior art]

This type of conventional power supply system is published by the Institute of Electrical Engineers of Japan, "The Institute of Electrical Engineers of Japan, Semiconductor Power Conversion Study Group, S
PC-85-76-86, November 15, 1985 ", the direct power voltage is converted into an alternating voltage by controlling the chip and the inverter or the PWM inverter by the active power control circuit and the reactive power control circuit. It is configured to convert and supply this to the AC power system.

[Problems to be solved by the invention]

However, these power supply systems do not consider control of the interconnection switch for connecting the inverter output circuit to the AC power system and control for protecting the inverter when the AC power system is abnormal.

Therefore, an object of the present invention is to provide a power supply system that can easily control the interconnection switch and can stably control the inverter against an abnormality in the AC power system.

[Means for solving problems]

In order to achieve this object, the present invention provides an inverter that is interconnected via a interconnection circuit including an impedance between the system and an interconnection switch, and a system voltage value in response to the system voltage and the inverter output voltage. Voltage control means for controlling the inverter so that the value obtained by correcting the voltage drop of the impedance of the interconnection circuit when the interconnection switch is open is used as the inverter output voltage value, and in response to the system voltage phase. Phase control means for controlling the inverter so that the phase obtained by correcting the phase difference generated in the impedance of the interconnection circuit when the interconnection switch is opened to the system voltage phase is the inverter output voltage phase. In the power supply system, the voltage control means is responsive to the reactive power detection signal and the reactive power set value obtained from the system voltage and the inverter output current. Pressure automatic control device that controls the reactive power by giving a voltage deviation signal between the output voltage and the inverter output voltage, and the phase control in response to the active power detection signal and active power set value obtained from the system voltage and the inverter output current. Means for applying a phase deviation signal between the system voltage and the inverter output voltage to the means to control active power, and an interconnection system for controlling the interconnection switch by setting the voltage deviation signal and the phase deviation signal to 0 A control circuit is provided.

[Action]

The voltage control means and the phase control means operate the inverter in response to the system voltage value, the system voltage phase, the system power voltage and the reactive power detection value and active power detection value obtained from the inverter output current, the reactive power setting value and the active power setting value. Since the feedback control is performed, stable inverter control can be realized in response to the voltage change of the system. Further, the interconnection control circuit controls the interconnection switch by setting the deviation between the inverter and the system to 0, thereby preventing the occurrence of the disturbance during interconnection.

[Embodiment] An embodiment of the present invention will be described with reference to the drawings.

In the drawing, an output circuit of a PWM inverter 2 for converting a DC voltage from a DC power source 1 such as a solar cell or a battery into an AC voltage is an interconnection circuit 3 having series reactances X ₁ and X ₂ and an admittance Y and an output current detector. 4 and the interconnection switch 5 are sequentially connected to the AC power system 6. In order to control the active power output and the reactive power output of the inverter 2, an inverter voltage detector 7 that detects the output voltage V ₁ of the inverter 2 and a grid voltage detector 8 that detects the voltage _VL of the AC power grid 6. And an active power detector 9 for detecting the active power output P by inputting the current signal from the output current detector 4 and the voltage signal from the grid voltage detector 8 and a reactive power detector for detecting the reactive power output Q. An active power control circuit 11 for inputting a voltage signal from the grid voltage detector 8, an active power detection signal from an active power detector 9, and an active power set value P _ref and outputting a phase control signal; From the voltage signal from the inverter voltage detector 7, the voltage signal from the grid voltage detector 8, the reactive power detection signal from the reactive power detector 10, the reactive power set value Q _ref, and the active power control circuit 11. And a reactive power control circuit 12 that outputs an inverter control signal.

The active power control circuit 11 inputs the deviation between the active power detection signal from the active power detector 9 and the active power set value P _ref , and outputs a phase deviation signal δ; Phase control circuit 1 that outputs a control signal
4 is provided. The phase control circuit 14 divides the variable frequency oscillator 15 that oscillates so that the inverter output frequency becomes substantially equal to the power system frequency when the input voltage is 0, and allocates the output of the oscillator 15 to each phase of the inverter 2. The output frequency of the inverter 2 is determined, and the output phase thereof is a ring counter 16 which outputs a phase control signal equal to the inverter output phase, the ring counter output of a phase equal to the inverter output phase, and the voltage from the grid voltage detector 8. A phase difference detector 17 is provided which detects a phase difference between signals and gives a control signal to the oscillator 15 so that the phase difference becomes equal to the phase difference generated in the interconnection circuit 3. The oscillator 15 has a phase difference detector. The control signal from 17 and the deviation of the phase deviation signal δ from the active power automatic regulator 13 are input.

The reactive power control circuit 12 includes the reactive power detector 10
And a reactive power automatic adjuster 18 that outputs a voltage deviation signal ΔV by inputting the deviation between the reactive power detection signal from the above and the reactive power set value Q _ref , and a voltage control circuit 19 that outputs the inverter control signal. The automatic voltage regulator 20 of the voltage control circuit 19 uses the coefficient unit 21 to input k = to the voltage signal from the inverter voltage detector 7 and the voltage signal from the system voltage detector 8.
The voltage so that the deviation from the signal corrected by (1-X ₁ Y) becomes 0, and the inverter output voltage V ₁ changes in accordance with the voltage deviation signal ΔV from the reactive power automatic regulator 18. Output a control signal. And pulse width modulator 2
2 outputs an inverter control signal for controlling the output voltage value of the inverter 2 and its phase in response to the voltage control signal from the automatic voltage regulator 20 and the phase control signal from the ring counter 16.

The interconnection control circuit 23 controls the opening / closing of the interconnection switch 5, and when the interconnection switch 5 is opened / closed, the phase deviation signal δ output from the active power automatic regulator 13 and invalid The voltage deviation signal ΔV output from the automatic power regulator 18 is configured to be zero. Note that this control is performed by setting the active power set value R _ref and the reactive power set value Q.
_It may be performed by a setting circuit that generates _ref .

The output relational expression of the control system with the above configuration is Therefore, when δ = 0, V ₁ = V _L (1-X ₁ Y), P =
Q = 0.

When δ is small, sin δ≈δ and cos δ≈1. Becomes

By the way, the inverter 2 is controlled by the voltage control circuit 19 so that V ₁ = (1−X ₁ Y) V _L −ΔV, and ΔV << (1−X ₁ Y) V _L Therefore, the active power output P and the reactive power output Q can be controlled by the phase deviation signal δ and the voltage control signal ΔV, that is, the active power setting value P _ref and the reactive power setting value Q _ref .

〔The invention's effect〕

 As described above, according to the present invention, the following effects can be obtained.

a: When opening / closing the interconnection switch for interconnection, the interconnection control circuit controls the active power automatic regulator and the reactive power automatic regulator to control the phase deviation signal δ and the power deviation signal ΔV.
If 0 is set to 0, the voltage value and phase of the inverter and the AC power system match (match) with each other, and the interconnection can be interrupted without causing disturbance. Therefore, a circuit for opening and closing the interconnection switch while monitoring the voltage value and the phase on both sides of the interconnection switch to turn on the interconnection switch becomes unnecessary.

b: Active voltage output P by adding voltage deviation ΔV
With respect to the disturbance that gives a, it can be easily reduced by adding a correction to the active power control. That is, Since it is sufficient for V _L in this equation to have a rated voltage (constant value), it can be simplified to δ = δ _o (1 + k ₂ ΔV).

c: voltage of the AC power system is response speed phase control means and voltage control means so as to be a _{V 1 = {V L (1} -X 1 Y) -ΔV} e j δ fluctuates.

Each of the active power output P and the reactive power output Q is detected by a detector, which has a delay of 0.1 second or more.
However, since the voltage value and the phase are detected within one cycle, the output voltage value and the phase of the inverter respond quickly to the fluctuation of the system voltage. Therefore, even if an accident occurs in the AC power system and the voltage value and the phase suddenly change, it is possible to stably follow this.

d: Generally, the system voltage value is often lowered in the case of an abnormality in the AC power system, but in the present control system, the phase deviation signal δ and Responsive to reduce the active power output P and the reactive power output Q in order to keep the voltage deviation signal ΔV constant. Therefore, if the active power set value P _ref and the reactive power set value Q _ref or the phase difference signal δ and the voltage deviation signal ΔV are made small by another protection detection circuit, the overload of the inverter at the time of abnormality can be prevented. You can

e: If the inverter 2 is prevented from being overloaded even when the system is abnormal as described above, the operation of the inverter can be interrupted even when the system is abnormal, and thus the output operation is returned to without any trouble at the time of restoration. be able to.

[Brief description of drawings]

The figure is a block diagram of the power supply system according to the present invention. 1 ... DC power supply, 2 ... PWM inverter, 3 ... interconnection circuit, 5 ... interconnection switch, 6 ... AC power system, 9 ...
Active power detector, 10 ... Reactive power detector, 11 ... Active power control circuit, 12 ... Reactive power control circuit, 13 ...
Active power automatic regulator, 14 ... Phase control circuit, 18 ...
Automatic reactive power regulator, 19 ... Power control circuit, 23 ...
Interconnection control circuit.

Claims (1)

[Claims] Claim: What is claimed is: 1. An inverter that is interconnected via a interconnection circuit including an impedance between the system and the interconnection switch, and the interconnection switch is opened to the system voltage value in response to the system voltage and the inverter output voltage. Voltage control means for controlling the inverter so that the value obtained by correcting the voltage drop of the impedance of the interconnection circuit during the operation is set as the inverter output voltage value, and the system voltage phase is adjusted to the system voltage phase in response to the system voltage phase. A power supply system comprising: phase control means for controlling the inverter so that the phase obtained by correcting the phase difference generated in the impedance of the interconnection circuit when the interconnection switch is opened is set as the inverter output voltage phase. In response to the reactive power detection signal and the reactive power set value obtained from the system voltage and the inverter output current, A reactive power automatic regulator that controls the reactive power by giving a voltage deviation signal from the output voltage, an active power detection signal obtained from the system voltage and the inverter output current, and a system to the phase control means in response to the active power set value. An active power automatic adjuster for controlling active power by giving a phase deviation signal between a voltage and an inverter output voltage; and an interconnection control circuit for controlling the interconnection switch by setting the voltage deviation signal and the phase deviation signal to 0. A power supply system characterized by being provided with.