Load balancing system for ups rectifiers

• US 4,114,048 A
• Filed: 07/18/1977
• Issued: 09/12/1978
• Est. Priority Date: 03/10/1976
• Status: Expired due to Term

• Current Assignee: Westinghouse Electric Corporation (Paramount Global (f/k/a ViacomCBS Inc.))
• Original Assignee: Westinghouse Electric Corporation (Paramount Global (f/k/a ViacomCBS Inc.))
• Inventors: Gemp, Robert S., Hull, Robert E.
• Primary Examiner(s): Schaffer, Robert K.
• Assistant Examiner(s): Ginsburg, Morris
• Application Number:
  US05/816,556
• Time in Patent Office: 421 Days
• Field of Search: 307/48, 307/44, 307/53, 307/51, 307/69, 307/54, 307/57, 307/23, 307/24, 307/66, 307/82, 307/55, 307/58, 363/37, 363/129, 363/130, 363/71, 363/82
• US Class Current: 307/53
• CPC Class Codes: H02J 3/46 Controlling of the sharing of output between the generators, converters, or transformers
• CPC Class Codes: H02J 3/48 Controlling the sharing of the in-phase component
• CPC Class Codes: H02J 9/062 for AC powered loads
• CPC Class Codes: H02M 5/4505 having a rectifier with controlled elements
• CPC Class Codes: H02M 7/162 in a bridge configuration
• CPC Class Codes: H02M 7/17 arranged for operation in parallel
• CPC Class Codes: H02M 7/493 the static converters being arranged for operation in parallel

Abstract

In order to maintain a balanced load between power rectifiers operating in parallel within an uninterruptible power system, individual closed loops are established for regulating the direct current voltage at the output of the rectifiers and an open loop generates a reference voltage for each of such regulations. An operational amplifier is used as a current source to develop a current representative of the load in a particular rectifier. Parallel current dissipating resistors between each rectifier line and a floating potential common to all rectifier lines generates a reference voltage which is proportional to the average of such current dissipations and represents the average rectifier load.

Claims

1. A system for supplying a load with alternating current from a plurality of adjustable direct current voltage sources with said plurality of voltage sources including a like plurality of rectifier means supplied with alternating current from a power supply common to all voltage sources for generating a corresponding direct current voltage and the system further including a like plurality of inverter means each associated with one of said rectifier means for supplying a corresponding alternating current to said load, comprising:

means associated with one of said voltage sources for sensing direct current supplied therefrom and for deriving a signal representative of said supplied direct current;

means associated with each of said voltage sources for deriving a reference signal representative of the average of the direct currents flowing from all of said sources;

means responsive to said current representative signal and to said reference signal for generating an error signal representative of a discrepancy between said current representative signal and said reference signal; and

means responsive to said error signal for adjusting the direct current voltage of said one source to compensate for said discrepancy.

2. In a system for supplying direct current to a load from a plurality of adjustable DC voltage sources, the combination:

of a network of parallel resistors, with each resistor being associated with a different one of said voltage sources and coupled between common first and second electrical connections, and of individual control circuits each connected between a different voltage source and a corresponding resistor of said network, wherein each of said control circuits comprises;

(a) first isolating means;

(b) current sensing means for providing a first signal representative of the current supplied to the load by the associated voltage source;

(c) means connected after said first isolating means and responsive to said current sensing means for providing through said resistor network a first individual current in proportionate amount to said representative signal to establish between said first and second connections with all similar first individual currents in other control circuits a voltage representing the average of all said first individual currents;

(d) a second isolating means;

(e) means connected to the resistor associated with that control circuit for providing through said second isolating means a second individual current in relation to said average voltage; and

(f) means responsive to said second individual current after said second isolating means and to said first representative signal for adjusting the voltage of the associated voltage source to compensate for any difference error between said first representative signal and said second individual current.

3. The system of claim 2 comprising means for disconnecting a selected voltage source from said load and for concurrently disconnecting the associated individual control circuit from one of said first and second electrical connections.