JPS5849100A - Power converting system - Google Patents

Abstract

PURPOSE:To perform power conversion while utilizing the merits of a separately-excited inverter by providing a motor coil and a generator coil at a stator between the inverter and a power system and connecting a synchronous machine having a damper and a field coil to a rotor. CONSTITUTION:In starting, the prescribed field current is supplied to the field coil 85 of a synchronous machine 8, a chopper 2 and an inverter 3 are controlled by a commutation signal from a position detector 9, and a current is flowed to the motor coil 81 of the machine 8. When the speed of the machine 8 reaches the 5-10% of the rated speed of the machine 8, the machine 8 is accelerated by the operation of a commutatorless motor. The current by a chopper 2 and the field current of the machine 8 are regulated so that the voltage and the frequency of the power system 7 coincide, and an AC breaker 6 is closed. Thereafter, the effective power is controlled by the chopper, and the reactive power is controlled by the field of the machine. The harmonic field in the machine is absorbed by a damper 83.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power conversion system 1 in which DC power is replaced with AC power (2) by inverter C2, and power grid C=interconnected power conversion system 1;

To deal with the oil crisis in nearby cities, plans such as large-scale photovoltaic power generation, fuel cell power generation, and secondary battery power storage systems are being developed. The development of interconnected systems is being promoted.

FIG. 1 shows a system block diagram of the above conventional system. 1 is a DC power source for solar cell arrays, fuel cells, secondary batteries, etc., and 02 is a DC-DC that controls this voltage change to a predetermined voltage. A 6-inch tube is generally used as a converter. 3I is an inverter that converts DC power to AC power, and 4 is a transformer that transforms the AC side voltage of the inverter 3 to the voltage C of the power system 7. The electric power to be handled is several IQQff or more. Therefore, a thyristor is used as the switching element 1 that constitutes the inverter. 5 is a power filter that absorbs harmonics generated by the inverter 3, and 6 is an AC cutoff. It is a vessel.

As is well known, there are two types of inverter C=, a separately excited type and an automatic type, each with their own advantages and disadvantages (= opposite relationship C: Yes). The biggest advantage is that the inverter can be configured at a low cost because it is carried out at a low cost. However, the disadvantage is that the inverter cannot be started and operated when the connected grid capacity is relatively small or in the event of a power outage. .

On the other hand, in the case of an automatic type, the commutation of the inverter is carried out by its own commutation circuit, so the advantage is that it can be started and operated independently without depending on the connected grid voltage. Since the type inverter includes a commutation circuit, it has the disadvantage of a complicated configuration and high price.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a power conversion system having a configuration that takes advantage of the advantages of separately excited inverters and eliminates their disadvantages.

FIG. 2 is a system block diagram showing one embodiment of the present invention. Elements having the same reference numerals as in FIG. 1 indicate the same elements. Second
In the figure, 3 is a separately excited inverter, 8 is a synchronous machine connected between the inverter 3 and the power system 7, and 9 is a position detector.

FIG. 3 is an embodiment showing the details of the configuration of the synchronous machine 8 used in the present invention. Reference numeral 81 indicates a motor winding, 82 a generator winding, and slots in the stator core that serve as a common magnetic path for each. 1
: The armature windings are wound, the number of turns of each corresponds to the transformer 46 shown in FIG. 1, and the wires are connected in a star shape.

Reference numeral 85 denotes a rotor 84 (two-wound field winding), to which a field current is supplied via a slip ring from a field control device (not shown).

Reference numeral 83 denotes a rotor 84 (two dampers are provided, which are arranged on the surface of the rotor 84, and have a structure similar to that of a squirrel cage induction motor.

FIG. 4 shows an example of the circuit configuration of the chopper 2 and the inverter 3. The chopper 2 is provided with a positive and negative DC circuit, a switch using, for example, a thyristor as a switching element, and a diode DIID1 connected as a ζ bridge as shown in the figure. DCL is a current smoothing DC reactor. As shown in the figure, the inverter 3 has a passive configuration in which 26 Iristors are connected in a 6-phase grates connection.

Next, I will explain its operation.
First, the AC breaker 6 is opened, and the field winding 85 of the synchronous machine 8 is opened.
6; Supply a predetermined field current. Now turn on switch S,,S, of chopper 2; then, DC power supply 1
A current flows at a rise point determined by the magnetic pressure of the magnetic field and the inductance of the DC reactor DCL, and this current is controlled by a control circuit (not shown) between the predetermined upper and lower limits of the switch si.
- This current passes through the inverter 3 to the motor winding 81 of the synchronous machine 8 (two currents, the rotor 84 of the synchronous machine 8 starts rotating, but the commutation phase of the inverter 3 Synchronize and switch 8m and 8.1 at the same time each time.
2. Turn off for a short time. This operation and the turning-on operation of each side risk of the inverter 3 are performed by the commutation signal of the position detector 9. During this off-period:;, ~current flows through the diode Dll
It flows rapidly (
: becomes zero, the si risk of the inverter 3 is also turned off, and υ commutation becomes possible.

Since the induced voltage in the motor winding 81 of the synchronous machine 8 is proportional to the rotational speed (2), commutation (motor commutation) due to this voltage (:) is possible at a rated speed of 5 to 1016, so this speed C double From 19 onwards, the chopper 2 receives the current control only by the switch 51 (C=S), and transmits the commutation signal from the position detector 9 to a detector (not shown) using the generator winding voltage (2 switches, inverter 3 Set the commutation advance angle to a predetermined value (for example, 45°)
Then, synchronous Ii & 8 is accelerated by non-commutator motor operation. Then, the current by the chopper 2 and the field current of the synchronous ImB are adjusted so that the voltage and frequency of the power system 7 shown in FIG. 2 match the voltage and frequency of the generator winding 82 of the synchronous machine 8, AC is interrupted and interrupt Ia6 is input to cause synchronous parallel entry.

Thereafter, when power from the DC power source 1 is sent to the system 7, the active power is controlled by the chopper and the reactive power is controlled by the synchronous machine field.

In this case, from the inverter 3 to the motor winding 81 of the synchronous machine 8
(The current waveform that flows is a so-called 120-degree energized square wave, but the harmonic magnetic field in the synchronous machine is absorbed by the damper 83 (2), so the voltage waveform of the generator winding 82 is relatively good. It becomes a sine wave.

From the above explanation, it is easy to see that even if grid 7 has a power outage, it can continue operating as a non-commutator motor-generator device (
I hope you understand.

The features of the power conversion system according to the present invention C2 are as follows≦
The two are grouped together.

(1) Synchronize commutation energy of passive inverter 3 @S
Supplied from.

(2) The motor winding 81 and the generator winding 82 also serve as an insulation transformer.

(3) The damper 83 also serves as a harmonic filter.

(4) When parallel to the grid, lead/lag reactive power control can be performed using field control.

(5) In the event of a grid power outage, load E power can be supplied through independent operation.

(6) System 6: Unrelated (Able to start and accelerate) When using a secondary battery as a DC power source, a charging mode is required, but in this case, switch 81181 of the tilt circuit shown in Charging can be easily performed by turning off the passive inverter 3, switching the passive inverter 3 to phase conversion mode, and controlling the current with the gate phase side leg.

[Brief explanation of the drawing]

FIG. 1 is a system block diagram of a conventional power conversion system, FIG. 2 is a system block diagram showing an embodiment of the present invention, FIG. 3 is an internal configuration diagram of the windings of the synchronous machine shown in FIG. 4 is a circuit configuration diagram of the chopper and inverter shown in FIG. ...Synchronous machine 9...Position detector

Claims (3)

[Claims] (1) A DC power source such as a solar cell array, a fuel cell, or a secondary battery, a chopper circuit that is supplied with power from this DC power source and bridge-connected a switch element and a diode, and DC power is supplied from this chopper circuit. a separately excited inverter, and a synchronous machine having a stator with a motor winding and a generator winding, and a rotor with a damper and a field winding; A power conversion system characterized in that an AC side of an inverter is connected, and the generator winding is connected to a power system 6 via an AC breaker. (2) The power conversion system according to claim 1, wherein the power conversion system operates as a non-commutator motor-generator device during a power outage. (3) The DC power source includes an acoustic secondary battery, turns off the switching element of the chopper circuit, and switches the passive inverter to forward conversion mode for phase control (secondary control of charging from the power system to the secondary battery). Power conversion system 0 according to claim 1 characterized in