Electrical transmission or interconnection systems – Plural load circuit systems – Plural sources of supply
Patent
1983-04-06
1989-05-30
Jennings, Derek S.
Electrical transmission or interconnection systems
Plural load circuit systems
Plural sources of supply
307 34, 307 38, 263 96, 263136, H02J 110
Patent
active
048354082
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a power conversion circuit comprising a direct voltage source having two capacitors connected across it in series, and one object of the invention is to provide a particularly convenient arrangement for supplying power from such a circuit to a number of loads. In one example, the loads are the load windings of a multi-phase switched reluctance motor, but they could equally well be individual loads or even the primary windings of a power transformer.
If the source is a three-point source established by two batteries connected in series, the mid-point or the common point of the two portions of the source will be held at a fixed potential, but if the source is a direct voltage source with two capacitors connected across it in series, as defined above, then the voltage of the common point of the two capacitors will tend to wander if the load currents taken from the two portions of the source are not the same, and the effect can be cumulative.
SUMMARY OF THE INVENTION
According to the present invention, there are two load circuits each comprising one or more loads, the loads in one load circuit being connected to the common point of the capacitors and to one side of the direct voltage source through individual controlled semi-conductor switches, and the loads in the other load circuit being connected between the said common point and the other side of the direct voltage source through individual controlled semi-conductor switches, and there are control means to control the semi-conductor switches, and means responsive to the potential of the said common point which tend to maintain that potential at a desired value.
Thus, if the currents in the two load circuits are not the same, so that the potential of the common point starts to wander, then the currents in the individual load circuits can be adjusted to compensate. In particular, the invention employs the idea of using the control means to control the instants of firing and commutating the semi-conductor switches to tend to produce that current balance.
In some circumstances the control means to control the instants of firing and commutating the semi-conducting switches to produce current balance may at the same time be arranged such that the operating frequencies in the two load circuits, defined by the the number of rises and falls of current per second in each circuit, are the same. This has the advantage of reducing the acoustic noise produced in the total load.
There may be two separate means, one responsive to the total current in one of the said load circuits and the other responsive to the total current in the other circuit. The control means may then fulfil two functions in response to the outputs of the said separate means. Firstly, it may control the semiconductor switches supplying power to the two load circuits in such a manner that the total current in both load circuits together corresponds to the total power requirement of the load.
The average current and power in each of the load circuits could take a multiplicity of values so long as the combination meets the total power requirement, and this would generally result in a departure of the potential of the said capacitor common point from its desired level. The second function of the control means is to prevent, or correct for, this departure, as is the object of the invention, by adjusting the firing of the said semiconductor switches so that the average current flowing into the said common point from the first load is equal to the average current flowing out of the said common point to the second load.
Alternatively, the first control function may be to set the current in one load at a value corresponding to the power requirement of the load, the value of current in the other load being of little or no consequence from the viewpoint of load power but being adjusted according to the second control function so that the average current flowing into the said common point from the first load is equal to the average current flowing out of the said common point to the
REFERENCES:
patent: 3743924 (1973-07-01), Genuit et al.
patent: 3935528 (1976-01-01), Brenneisen et al.
patent: 4092509 (1978-05-01), Mitchell
patent: 4136382 (1979-01-01), Ricci
patent: 4255783 (1981-03-01), Messer
Davis Rex M.
Ray William F.
Jennings Derek S.
Tasc Drives Limited
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