FLYWHEEL POWER SOURCE APPARATUS

Abstract: A flywheel power source apparatus of the invention can be additively used in a power source apparatus for a load such as computer, which is weak to momentary service interruption or large voltage variation and therefore requires the countermeasure. The flywheel power source apparatus comprises main circuit having a converter for converting AC power source output into DC output and a first inverter for converting the DC output of the con­ verter into AC output and supplying it to a load, a flywheel device supplied with power from the main circuit and driven for rotation, and a compensation circuit for supplying the stored energy based on the rotational force of the flywheel device to the first inverter of the main circuit. The flywheel power source apparatus is composed of a chopper circuit for controlling voltage of the compensation circuit, a second inverter circuit for controlling frequency of the compensation circuit, and first and second comparators for comparing outputs during outage of the power source and at normal state with reference values respectively and controlling the chopper circuit.

Description: The invention relates to a flywheel power source apparatus comprising a main circuit having a converter for converting AC (alternating current) power source output into DC (direct current) output and a first inverter for converting the DC output of the converter into AC output and supplying it to a load, a flywheel device supplied with power from the main circuit and driven for rotation, and a compensation circuit for supplying the stored energy based on the rotational force of the flywheel device to the first inverter of the main circuit. The invention particularly relates to a flywheel power source apparatus which is effective as power source for computers or the like, wherein continuous supply of power to a load is required during failures of a power source, and even when large voltage variations occur at the power source the voltage variation supplied to the load must be minimized. As computer technology has been significantly developed in recent years, computers are introduced in industrial field and other fields. In such a computer, if power supply to main components, particularly a processing unit, a memory unit or the like, is interrupted due to outage or large voltage variation, the processing until then may become entirely vain or the stored information may be lost. Consequently, in the prior art, a flywheel power source apparatus as shown in Fig. 1 or Fig. 2 is used as a power supply compensation means during service interruption or large voltage drop. The flywheel power source apparatus in Fig. 1 and Fig. 2 are disclosed in Japanese Laid-open No. 60-66632 and No. 60-197198, respectively. The fly wheel power source apparatuses utilize rotational energy of a flywheel rotating at a high speed, and converts the rotational energy into electric energy and supplies it to a computer or the like. Fig. 1 shows an example of a flywheel power source apparatus in the prior art. In Fig. 1, F designates a power source apparatus body. The power source apparatus body F comprises an auxiliary inverter 1, a converter 2, a changeover switch 3, a main circuit converter 4, a main circuit inverter 5, and a switching circuit 67 having a changeover switch 6 of main circuit S and a changeover switch 7 of direct voltage delivery circuit L. Numeral 8 designates AC (alternating current) power source, numeral 9 a load, and R a flywheel device. The flywheel device R is composed of a generator/motor unit and a flywheel. The flywheel device R normally rotates the flywheel by output of the auxiliary inverter in 30,000 (r.p.m.) for example, and during service interruption the device converts the rotational energy of the flywheel into electric energy and outputs it. Operation of the flywheel power source apparatus will now be described. The main circuit S composed of the main circuit converter 4 and the main circuit inverter 5 supplies AC power of constant voltage and constant frequency from the external power source 8 to the load 9 through the changeover switch 6. Then the changeover switch 3 for the compensation circuit P composed of the auxiliary inverter 1, the flywheel device R and the converter 2 is open, and the flywheel contained in the flywheel device R stores energy according to the high speed rotation by the auxiliary inverter 1. If an abnormal state occurs in the external power source 8 due to outage or the like, the changeover switch 3 controlled by an outage detecting means (not shown) is closed, and power generation is effected in the generator by the inertial energy of the flywheel of the flywheel device R. The AC power is converted into DC power by the converter 2, and the DC power is supplied through the inverter 5 and the changeover switch 6 to the load 9. When the changeover switch 7 is turned on, the changeover switch 6 is turned off. In the above constitution, however, since the converter 2 and the switch 3 are required at the output side of the flywheel device, the circuit constitution is complicated and the cost becomes high. In order to solve the above-mentioned problems, the applicant already proposed a flywheel power source apparatus, wherein an auxiliary inverter is connected between input/output terminal of a flywheel device and front side of an inverter to constitute main circuit. Fig. 2 is a block diagram of the flywheel power source apparatus, and like parts of Fig. 1 are designated by the same reference numerals. In Fig. 2, numeral 10 designates a transformer, and a primary winding 10a of the transformer 10 is connected through a switch 11 to AC power source 8. A secondary winding 10b of the transformer is connected through a converter 4 of main circuit S, a chopper circuit 12, a DC (direct current) filter 13, and a main circuit inverter 5 to a switching circuit 67. The secondary winding 10b is connected to a direct voltage delivery circuit L. Numeral 14 designates an auxiliary inverter, and an input stage of the auxiliary inverter 14 is connected to the joint between the converter 4 of the main circuit S and the chopper circuit 12, and an output stage thereof is connected to input/output terminal of a flywheel device R. The auxiliary inverter 14 and the flywheel device R constitute a voltage compensation circuit P. Numeral 15 designates a switch connected between the switching circuit 67 and the load 9. Operation of the flywheel power source apparatus of Fig.2 will now be described. At normal state, output of the AC power source 8 is supplied to the primary winding 10a of the transformer 10 through the switch 11. Output obtained from the secondary winding 10b of the transformer 10 is converted into DC voltage by the converter 4 and further converted into a constant voltage by the chopper circuit 12, and then ripple of the DC output is removed by the DC filter 13. The DC output from the DC filter 13 is supplied to the inverter 5 and converted into AC by the inverter 5, and the AC output is shaped into sinusoidal wave by an AC filter (not shown) and then supplied through the switching circuit 67 and the switch 15 to the load 9. On the other hand, the DC output from the converter 4 is converted into high frequency A.C. by the inverter 14, thereby the flywheel device R is rotated at a high speed and stores energy. If abnormal state such as outage or voltage reduction of the power source 8 occurs, output of the converter 4 is reduced. Then the rotational energy stored by rotation of the flywheel device R is released as electric energy, and output voltage accompanying with the release is supplied to the auxiliary inverter 14. The AC voltage supplied to the auxiliary inverter 14 is converted into DC and supplied through the auxiliary inverter 14 to front stage of the chopper circuit 12 of the main circuit S. Output supplied from the flywheel device R to the front stage of the chopper circuit 12 is supplied through the DC filter 13, the inverter 5, the switching circuit 67 and the switch 15 to the load 9. In the above-mentioned flywheel power source apparatus in the prior art, however, since the auxiliary inverter 14 only is installed between the main circuit S and the flywheel device R, one auxiliary inverter must control voltage and frequency simultaneously and therefore the power control by the inverter is complicated. Since the chopper circuit 12 installed in the main circuit S is normally operated, it must be designed as continuous rating. Further, since ripple is produced in the output of the chopper circuit 12, the DC filter 13 must be installed at the output stage of the chopper circuit 12 as above described, thereby the constitution is complicated and the cost becomes high. From JP-A-60-210200, a flywheel power source apparatus is known being similar to that as described in connection with figure 2. The flywheel device is held in motion by electric power delivered directly from the main A.C. power source through a converter and an inverter, whereas the output power of the flywheel device is delivered through a converter, a chopper and a D.C. filter to the main circuit. Finally, US-A-4,065,711 relates to a chopper assistant uninterruptible power supply which uses a bilateral chopper between an A.C. circuit comprising an inverter and a storage battery. It is an object of the invention to provide a flywheel power source apparatus containing a compensation circuit for supplying stored energy of a flywheel device to the main inverter, which is simple in construction and which has a relatively low rating as compared with the main circuit. According to the invention, a flywheel power source apparatus as defined above is characterized in that said compensation circuit is composed of a chopper circuit for controlling voltage in the supply power from the converter to the flywheel device at normal state and in the supply power from the flywheel device to the first inverter during service interruption; a second inverter circuit for controlling frequency in the supply power at normal state and the supply power during service interruption; a first comparator for controlling the chopper circuit based on output of the flywheel device during service interruption; and a second comparator for controlling the chopper circuit based on output of the converter at normal state. Preferred embodiments are defined in the dependent claims. Fig. 1 is a block diagram of an example of a flywheel power source apparatus in the prior art; Fig. 2 is a block diagram of another example of a flywheel power source apparatus in the prior art; Fig. 3 is a block constitution diagram of a flywheel power source apparatus as an embodiment of the invention; Fig. 4 is a detailed circuit diagram of a flywheel power source apparatus shown in Fig. 3; and Fig. 5 is a detailed circuit diagram of a voltage compensation circuit P shown in Fig. 4. Preferred embodiments of a flywheel power source apparatus according to the invention will now be described in detail referring to the accompanying drawings. Fig. 3 is a block constitution diagram illustrating an embodiment of the invention, and like parts to Fig. 1 or Fig. 2 are designated by the same reference numerals and an overlapping description shall be omitted. A capacitor C is connected in parallel at a front stage of an inverter 5 installed in the main circuit S in Fig. 3. A voltage compensation circuit P and a flywheel device R in series connection to each other are connected to a joint between the capacitor C and a converter 4. The voltage compensation circuit P is composed of a chopper 16 at side of the main circuit S and an inverter 17 connected in series. The chopper 16 is controlled according to comparison results 22, 23 of a first comparator 18 comparing reference value REF 1 with a speed detection value 20 of the flywheel device R and a second comparator 19 comparing reference value REF 2 for the DC output voltage of the converter 4 of the main circuit S with a voltage output value 21 of the chopper 16, respectively. Fig. 4 and Fig. 5 are detailed circuit diagrams of the flywheel power source apparatus shown in Fig. 3, and like parts in Fig. 3 are designated by the same reference numerals. In Fig. 4, a reactor 31 and a current transformer 32 are arranged between the chopper 16 and the inverter 17. A boosting chopper is composed of a transistor of CH1, a diode of CH2 of the chopper 16 and the reactor 31. A step-down chopper consists of a transistor of CH2, a diode of CH1 of the chopper 16 and the reactor 31. Operation of the flywheel power source apparatus will now be described. At normal state, the DC output voltage V1 of the converter 4 is converted into V2 by the step-down chopper composed of the transistor of CH2, the diode of CH1 of the chopper 16 and the reactor 31, and the voltage V2 is supplied to the flywheel device R through the inverter 17 thereby the flywheel device R is driven as motor. At this moment, the voltage V1 is normally established higher than the voltage V2. The speed detection value 20 of the flywheel device R by the driving and the speed reference value REF 1 are compared in the first comparator 18, and the output current of the chopper 16 is controlled based on the comparison result 22. Operation of the flywheel device at accelerating state, namely operation of the motor will now be described. The value of the voltage V2 is controlled and the flywheel device R is driven by the inverter for controlling the predetermined value of the current according to the transistor of CH2, the diode of CH1 of the chopper 16 and the reactor 31 at accelerating state. When the revolving speed of the flywheel device R approximates the speed by the reference value REF 1, the output current of the chopper 16 is controlled to be decreased in order to prevent boosting the revolving speed over the set value. In result, the revolving speed of the flywheel device R is maintained constant. During outage, the flywheel device R is operated as a generator by the stored energy, and the voltage V2 generated through the inverter 17 is converted into the voltage V1 by the boosting chopper and then supplied to the front stage of the inverter 5 of the main circuit S. The boosting chopper is composed of the transistor of CH1, the diode of CH2 of the chopper 16 and the reactor 31, and the chopper 16 is controlled to output the setting voltage (V1) according to the reference value REF 2. The voltage V1, i.e., the voltage output value 21 of the inverter 17 is compared with the voltage reference value REF 2 in the second comparator 19, and the chopper 16 is controlled based on the comparison result 23 and the voltage V1 is held constant. According to the invention as above described, the chopper circuit controlling the voltage only and the inverter circuit controlling the frequency only in series connection are installed in the voltage compensation circuit P including the flywheel device, thereby the inverter control can be simplified. Since the chopper circuit need not be installed within the main circuit, rating burden of the main circuit is reduced. Further, as the chopper circuit of the main circuit is obviated, a DC filter also may be omitted, thereby the circuit constitution is simplified and the cost is decreased.

Claims: A flywheel power source apparatus comprising a main circuit (S) having a converter (4) for converting AC (alternating current) power source output into DC (direct current) output and a first inverter (5) for converting the DC output of the converter (4) into AC output and supplying it to a load (9), a flywheel device (R) supplied with power from the main circuit (S) and driven for rotation, and a compensation circuit (P) for supplying the stored energy based on the rotational force of the flywheel device (R) to the first inverter (5) of the main circuit, characterized in that said compensation circuit (P) is composed of a chopper circuit (16) for controlling voltage in the supply power from the converter (4) to the flywheel device (R) at normal state and in the supply power from the flywheel device (R) to the first inverter (5) during service interruption; a second inverter circuit (17) for controlling frequency in the supply power at normal state and the supply power during service interruption; a first comparator (18) for controlling the chopper circuit (16) based on output of the flywheel device (R) during service interruption; and a second comparator (19) for controlling the chopper circuit (16) based on output of the converter (4) at normal state. A flywheel power source apparatus as set forth in claim 1, wherein said compensation circuit (P) comprising of the flywheel device (R), and the chopper circuit (16), the second inverter circuit (17) and the comparators (18,19) is connected to the joint between the converter (4) and the first inverter circuit (5). A flywheel power source apparatus as set forth in claim 1, wherein said first comparator (18) is connected between the chopper circuit (16) and the flywheel device (R) in parallel relation to the second inverter circuit (17). A flywheel power source apparatus as set forth in claim 1, wherein said second comparator (18) is connected between the chopper circuit (16) and the joint in parallel relation to the compensation circuit (P). A flywheel power source apparatus as set forth in claim 1, wherein said chopper circuit (16) is controlled based on comparison results of the first comparator (18) for comparing the rotational speed reference value (REF 1) of the flywheel device (R) with the speed detection value (20) of the flywheel device (R) and the second comparator (19) for comparing the voltage reference value (REF 2) of the DC output of the converter (4) with the power output value of the chopper circuit (16) respectively. A flywheel power source apparatus as set forth in claim 1, wherein a capacitor (C) is connected in parallel between the joint of the main circuit (S) and the compensation circuit (P) and the first inverter (5). A flywheel power source apparatus as set forth in claim 1, wherein a switching circuit (67) is installed at output side of the first inverter (5), and a direct voltage delivery circuit (L) is installed between the switching circuit (67) and the main circuit converter (4).

Inventors: KAJITA, TAKEYOSHI C/O MITSUBISHI DENKI K.K.
Applicants: MITSUBISHI DENKI KABUSHIKI KAISHA
Application year: 1986
Main classification: H02M5
IPC codes: H02J3, H02J15, H02M7, H02M11