JPS5926189B2 - Inverter control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inverter control circuit, and in particular to constant voltage control of load end voltage and active power sharing control in parallel operation of an inverter and another power source with extremely low internal impedance. It is.

Conventionally, an inverter and an AC power source other than the inverter with low internal impedance, such as a commercial power source, for example, have not been connected at their output ends and operated in parallel to supply power to a common load.

The reason for this is that if the system impedance between the two AC power supplies is small, cross currents due to voltage and phase differences between the two power supply voltages are large and dangerous to the inverter. This invention was made in view of the above points, and a reactor is inserted between the output end of the inverter and the other AC power source, and voltage fluctuations of the other AC power source are handled by the presence of the reactor and from the inverter. The inverter voltage is controlled so that the load terminal voltage becomes constant by supplying reactive power to the common load, and the inverter voltage position is controlled so that the active power deviation of the two AC power sources becomes constant. An object of the present invention is to provide an inverter control circuit that can supply voltage power.

An embodiment of the present invention shown in the drawings will be described below.

In the figure, 1 is a commercial power supply, 2 is a DC power supply, 3 is an inverter, 4 is a load, 5 is a reactor, 6, 1 is a current transformer, 3
0 is an oscillator, 31 is a gate control circuit, 10 is a voltage detection circuit, 11, 20 and 23 are adders, 21 is a multiplier, 22
is a filter, 24 is an active power deviation reference source, 12 is a voltage reference source, VL is a load end voltage signal, Vref is a voltage reference signal, and ev is the load end voltage signal VL and the voltage reference signal Vre.
f deviation signal, VL is the load end voltage instantaneous value signal, il is the inverter current instantaneous value signal, is is the commercial power supply current instantaneous value signal, iD is the deviation between the inverter current instantaneous value signal il and the commercial power supply current instantaneous value signal is The signal PD is an active power deviation instantaneous value signal, PD is an active power deviation signal, Pref is an active power deviation reference signal, and E is a deviation signal between the active power deviation signal PD and the active power deviation reference signal Pref. The manner in which the inverter voltage and its phase are manipulated in the inverter control circuit configured as described above will be described below.

Inverter voltage manipulation is performed by the following known method.

First, the load end voltage signal V detected by the voltage detection circuit 10
L and the voltage reference signal Vref produced by the voltage reference source.
Then, the adder 11 generates a deviation signal Ev between the load end voltage signal VL and the voltage reference signal Vref, and the inverter voltage is controlled by the inverter voltage operating section of the inverter gate control circuit 31 based on this deviation signal e. Due to this operation and the presence of the reactor 5, it is possible to control the load end voltage to be kept constant against fluctuations in the commercial power supply voltage. The reason why the control can be performed as described above is as follows.

Figure 2 is a block diagram showing the main circuit power consumption extracted from Figure 1, and Figure 3 explains the effect of the output impedance (inductive reactance) of the reactor and inverter on commercial power supply voltage fluctuations. FIG. 3A is a vector diagram when the commercial power supply voltage is lower than the specified voltage, and FIG. 3B is a vector diagram when the commercial power supply voltage is higher than the specified voltage. In Figures 2 and 3, V
s is the commercial power supply voltage, VI is the inverter induced voltage, and the vertical
is the reactor voltage, VX2 is the voltage due to the inductive reactance of the inverter, VL is the load end voltage, and Ix is the cross current. For example, when the commercial current voltage Vs is lower than the specified voltage as shown in the vector diagram shown in FIG. Dimension X shown in flow diagram 3
There is a voltage increase effect of 1.

In other words, VL=VS+VXl. Here, the purpose of the control is to keep the load end voltage absolute value 1VL1 constant, and as shown in FIG. 3a, 1L1-constant control is possible by setting ψX1 to an appropriate amount with respect to the change in Vs.

It will be explained below that X1 can be further adjusted by controlling the inverter induced voltage VI. When the impedance of the reactor 5 is LXl and the inverter output impedance is LX2, the b dimension is determined by the cross current 1x flowing due to the VXl power difference and the impedance LXl.
L ゜ ゜ ゜ ゜ ゜ ゜ ゜ ゜ ゜ ゜ ゜ L -type -sidewalk 1X can be obtained by assuming a determined B2 type by voltage difference and impedance LXL + LX2 to 1 type.

In the LXl 3 formula, is a constant, so a certain quotient 1--. ．． It can be seen that the desired reactor voltage X1 can be obtained by controlling the inverter induced voltage V1 with respect to the power supply voltage Vs for 4- and 7-.

Now, in the above explanation, the case where s is lower than the predetermined voltage has been described, but even when the voltage is high, the same constant control of the load voltage 1Wi is possible by controlling the inverter voltage.

In this case, -1x is a lagging current with respect to Vs, and VXl is a voltage drop effect, as shown in FIG. 3b. That is, the third
From the vector diagram in the figure, it can be seen that by operating the inverter induced voltage VI, the load end voltage is equal to the fluctuation of the commercial power supply voltage Vs.
It can be seen that control can be performed to a fixed value of 1VL].

Next, the inverter voltage phase is manipulated by first using the inverter current instantaneous value signal 11 and the commercial power supply frost flow instantaneous value signal 1s and using the adder 20VC to generate a deviation signal 1 between the inverter current instantaneous value signal 11 and the commercial power supply current instantaneous value signal 1s.

Create b, and from this and the load end voltage instantaneous value signal VL, multiplier 2
1, the active power deviation instantaneous value signal P. From this active power deviation instantaneous value signal PD, the average value signal ♂ is made by the FILNO 22, and this and the active power deviation reference value signal Pre
An adder 23 generates a deviation signal E from f, and by controlling the frequency of the oscillator 30 using this deviation signal e, the inverter voltage phase is controlled by p.

Through this operation, the phase difference between the in-part voltage and the commercial power supply voltage is maintained at an appropriate value so that the active power deviation PD from the inverter and the commercial power supply remains constant despite changes in the frequency and phase of the commercial power supply voltage as well as load fluctuations. The inverter voltage phase force is maintained until it becomes . Here, the reason why the active power sharing can be controlled by the voltage phase difference between the inverter 3 and the commercial power source 1 is that the impedance between the power sources is a reactance component. The reason why the control can be performed as described above is as follows. FIG. 4 is a vector diagram for explaining the reason why active power sharing can be controlled by voltage phase difference when the impedance between the power sources is inductive reactance. In FIG. 4, ψ is the voltage phase difference. Portions with the same reference numerals as in FIGS. 2 and 3 indicate the same parts. As can be seen from the Betator diagram shown in Figure 4, Fx has a 900 lag current with respect to vertical X1+8●, and -1x has almost the same direction as vertical s. It will be sent out. In other words, active power sharing can be controlled by controlling the inverter voltage phase.
In the above, the case where the active power required by the load is supplied from both the inverter 13 and the commercial power supply 1 has been described. It is also possible to not supply active power from the part 3 to the load, but instead to supply power from the inverter 3 to the DC power supply 2.

At this time, for example, if the DC power source 2 is a battery, constant voltage power can be supplied to the load while charging the battery. Further, as described above, the present invention is applicable not only to parallel operation of an inverter and a commercial power source, but also to parallel operation of an inverter and a generally uncontrollable power source. As described above, according to the present invention, it is possible to operate an inverter in parallel with another alternating current power source with low impedance, and the range of applications of the inverter can be expanded and various power supply systems can be configured.

[Brief explanation of the drawing]

Fig. 1 is a plotter diagram showing one embodiment of the present invention, Fig. 2 is a plotter diagram showing the main circuit electrical quantity extracted from a part of Fig. Figure 3a is a vector diagram for explaining the effect of commercial power supply voltage (reaction) on commercial power supply voltage fluctuations. FIG. 4, which is a vector diagram for a higher case, is a block diagram for explaining the reason why active power sharing control can be performed by voltage phase difference when the impedance between the power sources is a conductive rearnonce. In the figure, 1 is a commercial power supply, 3 is an in-part, 5 is a reactor, 6 and 7 are current transformers, 10 is a voltage detection circuit, 11,
20 and 23 are adders, 21 is a multiplier, 22 is a pool, 24 is an active power deviation reference source, 30 is an oscillator, and 31 is a gate control circuit.

Claims (1)

[Claims] 1. A reactor that connects the output side of an inverter that has inductive reactance as output impedance and the output side of another AC power source with low internal impedance, such as a commercial power source, and a voltage signal at the connection point between this reactor and the above inverter. an adder comprising a voltage detection circuit for detecting and a voltage reference source, and for detecting a deviation between an instantaneous value signal of the output current of the inverter and an instantaneous value signal of the output current of the AC power supply; The voltage detection circuit comprises an active power deviation detection means and an active power deviation reference signal source, each comprising a multiplier that multiplies the voltage instantaneous value signal at the connection point and a filter that averages the output signal of the multiplier. The voltage and voltage phase of the inverter are controlled by a deviation signal between the output signal and the output signal of the voltage reference source, and a deviation signal between the output signal of the active power deviation detection means and the output signal of the active power deviation reference source. An inverter control circuit characterized by: