JPS61295832A - Apparatus for cycle switch between inverter and commercial power source - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a synchronous switching device between an inverter and a commercial power source.

B5 Summary of the Invention The present invention provides a device that synchronizes switching to a load between an inverter and a commercial power source. By shifting the phase setting value of the inverter's phase-locked loop circuit so that the value becomes zero, and adjusting the output voltage of the inverter so that the reactive power becomes zero based on the reactive power detection signal of the commercial power supply, This is designed to suppress transient voltage fluctuations during switching.

C2 Problems to be solved by the conventional technology and the invention Generally, when power is supplied to a load using an inverter, when the inverter fails or is inspected, the inverter may switch to a commercial power source and power is supplied from the commercial power source to the load. . When instantaneously switching between an inverter and a commercial power source, the inverter undergoes load fluctuations between maximum no load and rated load, resulting in transient fluctuations in the inverter's output voltage. Figure 2 is a diagram showing voltage fluctuations when switching between the inverter and commercial power supply, and (i)
is the output voltage of the inverter, (ii) is the voltage of the commercial power supply,
(iii) indicates the voltage applied to the load, and represents a state in which the commercial power source is switched to the inverter at time t1, and the inverter is switched to the commercial power source at time t. As can be seen from the figure, transient fluctuations occur in the output voltage of the inverter during switching, and the extent of the transient voltage fluctuations is particularly large when switching from a commercial power source to the inverter.

Conventionally, measures have been taken to suppress such transient voltage fluctuations, such as increasing the capacity of the inverter, using a circuit to compensate for transient voltage fluctuations during switching, or switching on the phase using a thyrisk switch. A high-speed switch such as a thyrisk switch is required as a switching means, and even if such measures are taken, transient voltage fluctuations during switching are large.

The present invention has been made based on this background, and an object of the present invention is to provide a synchronous switching device between an inverter and a commercial power source that can suppress transient voltage fluctuations during switching to a small level by simple means. It is.

Means for Solving Problem D1 Compare the signal corresponding to the voltage phase of the commercial power supply and the signal corresponding to the output voltage phase of the inverter to detect the voltage phase difference between them, and, for example, detect the voltage phase difference and the phase setting. A phase-locked loop circuit that adds a frequency setting signal to the deviation from the signal and outputs a signal corresponding to one frequency and number of phases of the inverter from a voltage controlled oscillator based on this added value, and a voltage setting signal and voltage of the inverter. a matching circuit that extracts the deviation from the detection signal; an inverter control section that controls the inverter based on each signal from the matching circuit and the voltage-controlled oscillator; The mode is set to synchronous control mode in which the inverter is controlled while being ignored, and when power is transferred from the commercial power supply to the inverter, each power supply switch of the commercial power supply and inverter is closed, and the relevant power is set so that the active power of the commercial power supply becomes zero. The phase setting signal is shifted by an amount corresponding to the deviation between active power and zero power, and the voltage is set by an amount corresponding to the deviation between the reactive power and zero power so that the reactive power of the commercial power supply becomes zero. A switching control section is provided that switches to a power control mode for shifting the signal, switches from the power control mode to a synchronous control mode when the power burden is transferred from the commercial power source to the inverter, and opens a power supply switch for the commercial power source. .

83 action When the power supply command of the commercial power supply is input to the switching control unit, the power supply switch of the commercial power supply and the power supply switch of the inverter are respectively closed and opened, and the synchronous control mode is set, The inverter outputs the rated voltage in synchronization with the commercial power supply. When the inverter power supply command is input to the switching control section, the inverter power supply switch is closed and the mode is switched to the power control mode.

As a result, the commercial power source and the inverter are operated in parallel, and the phase and voltage of the inverter are controlled so that the active power and reactive power of the commercial power source become zero.

For example, when the current detection signal from the current detection section of the commercial power source becomes less than the set value, the mode is switched to the synchronous control mode by a switching command from the switching control section, and the power supply switch of the commercial power source is opened. Power is then supplied to the load by the inverter.

F. Embodiment FIG. 1 is a block circuit diagram showing an embodiment of the present invention.
2 is a commercial power supply, and 2 is an inverter such as CVCP.

3 is a load, 11 is a commercial power supply switch, 21 is an inverter power supply switch, T1 is a commercial power supply voltage detection unit, T
, is an inverter voltage detection section, and CT is a commercial power supply current detection section.

4 is a phase difference detection circuit, and the commercial power supply voltage detection section T
The voltage phase difference between the commercial power supply 1 and the inverter 2 is detected by comparing the upstream voltage detection signal with a signal corresponding to the output voltage phase of the inverter, for example, an output signal from a voltage controlled oscillator 5, which will be described later. 41 is a matching circuit, 4
Reference numeral 2 denotes a phase setter, and a matching circuit 41 matches the phase setting signal from the phase setter 42 and the signal corresponding to the voltage phase difference from the phase difference detection circuit 4, and extracts the deviation thereof.

Further, in a power control mode to be described later, an active power signal of the commercial power source 1 is inputted to the matching circuit 41, and a signal obtained by subtracting the active power signal from the deviation is outputted. 43 is a matching circuit, and 44 is a frequency setter. This matching circuit 43 adds the signal from the matching circuit 41 via the amplifier 45 and the frequency setting signal from the frequency setter 44. A voltage controlled oscillator 5 outputs a signal corresponding to the phase 1 frequency of the inverter based on the signal from the matching circuit 43.

In this embodiment, the loop from the phase difference detection circuit 4 to the voltage controlled oscillator 5 and its feedback loop constitute a phase-locked loop circuit (PLL circuit).

Reference numeral 6 denotes a power detection section, which determines the active power and reactive power of the commercial power supply l based on the current detection signal from the current detection section CT, the voltage detection section T, and the upstream voltage detection signal, and calculates the active power and reactive power corresponding to these, respectively. Outputs a power signal and a reactive power signal. 61 is a first matching circuit, 62 is a second matching circuit, and these matching circuits 61 and 62 convert the active power signal and reactive power signal from the power detection section 6 into signals corresponding to zero power, such as O Match it with ■ and take out the deviation. S purchase is a switch, the first
The active power signal from the matching circuit 61 via the amplifier 63 and the reactive power signal from the second matching circuit 62 via the amplifier 64 are simultaneously supplied and disconnected. This switch SW
is closed, the active power signal passes through the butt circuit 4
1 with negative polarity, and the reactive power signal is input with negative polarity into matching circuit 7, which will be described next. 67 is a matching circuit, 71 is a voltage setter, and matching circuit 7 includes an inverter voltage detection section T, The deviation between the voltage detection signal from the voltage setting device 71 and the voltage setting signal from the voltage setting device 71 is extracted, and when the switch SW is opened, a signal obtained by subtracting the reactive power signal from the deviation is extracted. 8 is an inverter control section, which matches the signal from the voltage controlled oscillator 5 with a matching circuit 7.
Based on the signal passed through the amplifier 72, the frequency, nine phases, and voltage of the inverter are controlled.

Reference numeral 91 denotes a comparator, which outputs an output signal when the current detection signal from the commercial power supply current detection section CT becomes equal to or less than a set value. Reference numeral 9 is a switching control unit, which connects the commercial power supply
The power supply switch 11.21 opens and closes in response to the power supply command of When power is transferred from power supply 1 to inverter 2, or vice versa, both power supply switches 11 and 21 are closed, and the switch SW is closed to set the power control mode, and the current detection unit CT It has a function of switching from the power control mode to the synchronous control mode and opening the power supply switch 11 of the commercial power supply when the current detection signal of the power source becomes less than a set value and an output signal is input from the comparator 91. .

Next, the operation of the device configured as described above will be described.

Assuming that a power supply command for the commercial power supply is now input to the switching control unit 9, the power supply switch 11 of the commercial power supply and the power supply switch 21 of the inverter are opened and closed, respectively, and the load 3 is connected to the commercial power supply 1. Power is supplied from. At this time, the switch SW is open and the inverter 2 is in the synchronous control mode. In this synchronous control mode, the inverter 2 is controlled ignoring the active power and reactive power of the commercial power source, that is, without being influenced by them. Therefore, the inverter 2 is operated at the rated voltage while being synchronized with the commercial power source 1 with the phase difference set by the phase setter 42.

When an inverter power supply command is manually inputted to the switching control unit 9 in such a state, the power supply switch 21 of the inverter is closed while the power supply switch 11 of the commercial power supply remains closed, and the commercial power supply 1 and the inverter 2 are connected. are operated in parallel. At the same time, the switch SW is closed by the action of the switching control section 9, thereby switching from the synchronous control mode to the power control mode. In this power control mode, the signals from the first matching circuit 61 and the second matching circuit 62 are respectively input to the face matching circuit 41.7 with negative polarity. As a result, the phase setting signal shifts by an amount corresponding to the deviation between the active power and zero power so that the active power borne by the commercial power supply 1 side becomes zero, and the phase setting signal borne by the commercial power supply 1 side is shifted by an amount corresponding to the deviation between the active power and zero power. The voltage setting signal changes by an amount corresponding to the deviation between the reactive power and the zero power so that the reactive power becomes zero. In this way, the active power and reactive power supplied to the load are transferred to the inverter 2, and correspondingly, the active power and reactive power borne by the commercial power source I gradually become smaller and finally reach zero. In this way, the load-sharing power of the commercial power supply l becomes smaller, and the current detection signal from the current detection unit CT becomes less than the set value (represents a state in which all active and reactive power has been transferred to the inverter side). and comparator 9
1 outputs a predetermined signal, which opens the power supply switch 11 of the commercial power source and also opens the switch SW to switch from the power control mode to the original synchronous control mode. Thereafter, the inverter 2 is brought into normal operation in the synchronous control mode. Note that if the load shift is confirmed using the current value of the commercial power source as in the above embodiment, it will not be affected by the presence or absence of a load.

In addition, when switching in the opposite direction, that is, switching from the inverter 2 to the commercial power supply 1, the switching can be performed smoothly by performing the above operations in reverse. Since the load is applied to the commercial power source l, which has low impedance and small transient voltage fluctuations, it is possible to keep voltage fluctuations to a fairly small level even without using power control mode, so it is not necessary to use power control mode. .

G5 Effects of the Invention As described above, according to the present invention, when switching the power source from the commercial power source to the inverter in a system that constantly supplies power to the load from the inverter, the commercial power source and the inverter are operated in parallel, and the effective use of the commercial power source is achieved. Since the phase and voltage of the inverter are controlled so that the electric power and reactive power become zero, the amount of transferred electric power is gradually increased (or decreased) and the switching is performed smoothly. Transient voltage fluctuations during switching can be suppressed to a small level, and the circuits for active power control and reactive power control only need to interrupt the settings of the normal PLL circuit and AVR circuit, so special control circuits and controls are required. mode is no longer required. Furthermore, there is no need for a high-speed switch,
Therefore, switching using a switch such as an electromagnetic contactor is possible, and special measures such as increasing the capacity of the inverter are not required. Also, when controlling the commercial power supply and inverter in parallel, there is no need to turn off the PLL control loop, and the PLL control loop can be left as is.
Because the active power sharing between the inverter and the commercial power source can be controlled simply by giving a deviation to the phase setting signal for active power control, it is possible to reduce the number of additional circuits for parallel control, and further improve the voltage control used. The oscillator can also be of low precision.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, and Fig. 2 is a waveform showing changes in the inverter output voltage, commercial power supply voltage, and load voltage when the power source is switched by a conventional synchronous switching device. It is a diagram. l...Commercial power supply, 2...Inverter, 11.21.
...Power supply switch, 4...Phase difference detection circuit, 5...
Voltage controlled oscillator, 6...power detection section, T1. Tt・
...Voltage detecting section, CT... Current detecting section, 8... Inverter control section, 9... Switching control section, SW... Switch. Figure 1

Claims (1)

[Claims] In a device in which switching to a load is performed synchronously between a commercial power source and an inverter, a signal corresponding to the voltage phase of the commercial power source and a signal corresponding to the output voltage phase of the inverter are compared and compared with each other. A phase lock loop circuit that detects a voltage phase difference between the two and outputs a signal corresponding to the phase and frequency of the inverter from a voltage controlled oscillator based on a signal corresponding to the voltage phase difference, a phase setting signal, and a frequency setting signal. a matching circuit that extracts the deviation between the voltage setting signal and the voltage detection signal of the inverter; an inverter control section that controls the inverter based on the matching circuit and each signal from the voltage controlled oscillator; A synchronous control mode is used in which the inverter is controlled while ignoring the active power and reactive power of the commercial power source, and when power is transferred from the commercial power source to the inverter, each power supply switch of the commercial power source and the inverter is closed, and the commercial power source is The phase setting signal is shifted by an amount corresponding to the deviation between the active power and the zero power so that the active power becomes zero, and the difference between the reactive power and the zero power is shifted so that the reactive power of the commercial power source becomes zero. Switching to a power control mode in which the voltage setting signal is shifted by an amount corresponding to the deviation, switching from the power control mode to a synchronous control mode when the power burden is transferred from the commercial power source to the inverter, and closing the power supply switch of the commercial power source. A synchronous switching device for an inverter and a commercial power source, characterized in that it is provided with a switching control section that switches between an inverter and a commercial power source.