Patent Application
20200170088
Not Applicable.
The present invention relates generally to electrical circuits and, more particularly, to electrical circuits for controlling Voltage to a load.
As is known in the art, there are a variety of circuits that limit the energy delivered to a load. For example, dimming circuits for lighting applications adjust the brightness of a light source. Exemplary power control, dimming, and/or feedback circuits are shown and described in U.S. Pat. Nos. 5,686,799; 5,691,606; 5,798,617; 5,955,841; and 7,099,132 all of which are incorporated herein by reference.
However, known power control/dimmer circuits typically operate out of a source of constant voltage supply.
There are applications where, especially in the Power Generation field in general and in the Green Power Generation field in particular, where the generated Voltage is not constant but depends on the electrical Load. As the load gets lighter, the generated Voltage increases, sometimes to unacceptable levels, transients or peaks.
The present invention provides a voltage management circuit that eliminates the over-voltage, transients and peak-voltages by electronically switching or adjusting the electric load, in a system or application where the generated supply voltage is variable.
Such an example is a Green Power Generation application, where energy is extracted from a natural gas pipe line under pressure, by passing the stream of natural gas through an Air-Motor connected to an Electric Generator, or a Motor-Gen group.
An electric load is connected to this Motor-Gen group, for supplying the energy needs of remote natural gas distribution and control centers in the field, that otherwise do not have access to any off the grid power lines.
While the invention is primarily shown and described in conjunction with circuits connected to a Motor-Gen group for energizing electric loads, it is understood that the invention is applicable to circuits for energizing loads in general in which it is desirable to provide voltage control, as well as overvoltage and consequently current surge protection.
In one aspect of the invention, a voltage control circuit includes a switching element coupled between one end of the electric load and one end of a control impedance. A voltage control circuit biases the switching element to a non-conductive state for a portion of an AC half cycle during which a peak voltage of the AC half cycle occurs when a voltage across the first and second rails is smaller than a predetermined threshold. Conversely, the voltage control circuit biases the switching element to a conductive state for a portion of an AC half cycle whenever the voltage of the AC half cycle occurs when a voltage across the first and second rails is higher than a predetermined threshold.
In another aspect of the invention, the circuit includes a voltage transient sensing circuit coupled to the voltage control circuits for providing current surge and over voltage protection.
The invention will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings, in which:
A switching element (131) is part of the Switching Circuit and a voltage control circuit (132) is coupled across the switching element.
In general, the voltage control circuit (132) selects conduction and non-conduction regions for the switching element (131) such that the control impedance Rc (140) is connected to or disconnected from the load impedance Rld in a dynamic fashion, for parts of the voltage cycles. This way, the static control impedance Rc effectively becomes a dynamic impedance, operating between two extreme values, the two value limits being given by the continuous connection or continuous disconnection between Rc and Rld, operated by the switching element.
The switching element (131) is shown as a TRIAC (TR), having three terminals A1, G and A2. It will be readily understood by one of ordinary skill in the art that a wide
variety of switching devices, like Bipolar Junction Transistors (BJTs) or Field Effect Transistors (FETs), can be used in other embodiments to meet the requirements of this particular application. A voltage divider made out of two impedances R1, R2 and a Potentiometer P is connected between terminals A1 and A2 of the switching element TR, with a Diac (D1) connected between the mid-point of the voltage divider R1 and R2 connected to the Potentiometer P, and Triac terminal G.
A capacitor C1, or any other suitable impedance, could optionally be connected across resistor R2 and potentiometer P, to help detect the voltage transients and consequently operate the switching element to direct the transient energy into the Transient Suppression Element Rz, as part of the control impedance (140).
As the circuit operates to connect and energize the control impedance Rc, the switching element 131 is biased to the conductive state by a potential applied to the gate terminal G by the instantaneous voltage developed across impedance R1, which in turn fires the Diac D1, whenever this voltage reaches the Diac's breakdown voltage, which defines a threshold voltage (Vth) between the two Input Terminals.
This causes the switching element to transition to the conductive state and naturally stay in that state, in case the switching element is a Triac, until the end of the voltage half-cycle. At the end of the half-cycle the switching element will naturally turn OFF (non-conductive state), repeating the scenario described above for the next half-cycle.
For as long as the Load Voltage (Vld) is less than the set Threshold Voltage (Vth) (Vld<Vth), the switching element TR (131) remains in a non-conductive state, keeping the Control Impedance (140) electrically disconnected from the Load Impedance Rld. This load voltage (VRld) is reflected in the 2.A waveform representation in
Whenever the Load Impedance becomes lighter, like in situations when electric consumers get disconnected, the Load Voltage (Vld) tends to increase, primarily because of the Generator Internal Impedance (Rg). Whenever this instantaneous Load Voltage tends to exceed the Threshold Voltage (Vth), the switching element TR will switch into a conductive state, connecting the control impedance (Rc) in an electrical connection with the Load Impedance (Rld). Even though, in this particular embodiment, the two impedances are electrically connected in parallel, it will be readily understood by one of ordinary skill in the art that a wide variety of electrical connections can be devised, in order to achieve a similar effect.
By means of instantaneously connecting the control impedance (Rc) to the load impedance (Rld), the electric generator effectively gets instantaneously ‘loaded’ during the portion of the half cycle when the two impedances are connected together, and the voltage across the load impedance (Rld) is effectively clamped or controlled, staying in the range of the threshold voltage (Vth). This is reflected in the 2.B waveform representation in
Since the voltage control circuit (132) selects conduction and non-conduction regions of each half-cycle for the switching element (131), the control impedance Rc (140) is connected to or disconnected from the load impedance Rld in a dynamic fashion, for parts of the voltage cycles. This way, the static control impedance Rc effectively becomes a dynamic impedance, with an effective value determined by the duration of electrical connection between Rc and Rld, throughout the voltage cycle.
Ideally, the Control Impedance (140) should be close in value to the nominal Load Impedance (120), in order to be able to perform an effective voltage control in the extreme case of all consumers (Load Impedance) being disconnected or removed.
Usually this energy is being lost in the process of decompressing high pressure natural gas, decompression required for local natural gas distribution.
High Pressure natural gas pipe (60) (Gas H.P.) usually passed through a pressure regulator (70) (P.R.), into a Medium Pressure gas pipe (80) (Gas M.P.), then into a Motor-Gen group (110), made out of at least one Air-Motor (111) (A.M.) and at least one Electric-Generator (112) (E.G.), mechanically coupled together.
This whole assembly is contained in an explosion proof cylinder (114), whenever the natural gas is the agent that operates the Motor-Gen group. Medium Pressure gas flowing through the gas pipe inside the cylinder, connected to the Air-Motor (A.M.), rotates the rotor inside the A.M., generating enough torque to mechanically operate the Electric-Generator (E.G.), which in turn generates enough electricity to energize the Load Impedance (Rld).
After decompression, i.e. the gas transferred part of its energy by conversion into electricity, the resulting Low Pressure flow of gas (Gas L.P.) is directed to the local users via the low pressure pipe (90).
The electric wires from the Electric-Generator pass through the Pressure-Barrier(s) (113) (P.B.), from the Medium-Pressure environment inside the cylinder to the Ambient Pressure environment of the HOT and GND Load Terminals, connecting to the Load Impedance (L.I.) (120), Switching Circuit (130) (S.C.) and Control Impedance (Rc).
In the extreme case of all consumers (Load Impedance) being disconnected for an extended period of time, the Control Impedance Rc will be fully switched-in, as a replacement to the disconnected Load Impedance, thus keeping the circuit voltage within reasonable limits, close to the threshold voltage Vth. However, in this particular situation, in order to avoid unnecessary power dissipation across the Control Impedance Rc, the Gas Medium Pressure (Gas M.P.) could be diminished by means of an additional control, performed by means of properly operating the Pressure Regulator (P.R.). This additional control line is shown in
It is understood that the Load-Switch Voltage Control circuit shown and described above has a wide variety of applications including, but not limited to, power voltage regulators and stabilizers.
One skilled in the art will appreciate further features and advantages of the invention based on the above-described embodiments. Accordingly, the invention is not to be limited by what has been particularly shown and described, except as indicated by the appended claims.
Typical components values, for a 1000W/220V application are:
Voltage Threshold Vth=232V
R1=6.49 kOhm/0.25 W
R2=27.4 kOhm/1 W
P=10.0 kOhm/0.5 W
C=1.0nF/1kV
TR=BTA06 6A/800V (Triac)
D1=DB-32 (32V Diac)
Rc=50 Ohm/1000 W
Rz=MOV/270 Vrms
