Patent Description:
For electrical power generation, a generator may be regulated by a pulse width modulated (PWM) control signal in response to a feedback signal that is based on the output of the generator. The output of the generator, and thus the feedback signals used to regulate the output, may be susceptible to transient conditions experienced by the generator. Such transient conditions may cause a change in a voltage, current, or both of an output of a generator. Due to the changes of the output of the generator, the PWM control signal used to regulate the generator may also experience distortion as a result of transient conditions. Such distortion of the PWM control signal may cause false voltage compensation that results in an undesired increase or decrease in output voltage regulation. Further, the distortion of the PWM control signal may result in unnecessary complication of fault detection and protection circuits associated with the generator. <CIT> describes an alternating current power source apparatus comprising: an AC generator having a field coil which is driven by an engine; a first rectifier having one or more thyristors which rectify the AC output of the AC generator; a second rectifier having one or more thyristors which is connected in parallel to said first rectifier to give the output having a polarity reverse to the polarity of the output of said first rectifier; an AC driving load connected to said first and second rectifiers; a voltage control device for controlling the output voltage of said generator to a predetermined value by controlling a field current passing through said field coil; an oscillator for oscillating at a desired frequency; and a gate signal generating circuit which is controlled by the output of said oscillator so as to feed a turn-on signal alternately to said gate circuit of said first rectifier and said gate circuit of said second rectifier. <CIT> discloses a dual-output automobile generator in which three positive terminals are connected together in parallel to be the positive output of the generator and full-wave rectification is applied. <CIT> discloses a circuit for association with the regulator of an electrical generator, especially an AC generator, and serving to smooth the voltage supplied by the electric generator. The circuit includes a compensation device consisting of at least one active semiconductor switching element, usually a transistor, and so connected to the regulator input as a supplement thereto that the generator output voltage is smoothed by a compensation voltage whose own ripple or oscillatory component is in opposite phase to the generator voltage. <CIT> discloses methods and apparatus for producing current with a desired output frequency from one or more fixed or variable speed alternators, by varying a saturation level of a portion of the alternator(s) based on a output frequency desired.

The invention is defined by the features of device claim <NUM> and method claim <NUM>. The dependent claims recite advantageous embodiments of the invention.

The terms "disclosure," "the disclosure," "this disclosure" and "the present disclosure" used in this patent are intended to refer broadly to all of the subject matter of this patent and the patent claims below. Embodiments of the subject matter covered by this patent are defined by the claims below, not this summary. This summary is a high-level overview of various aspects of the subject matter of the present disclosure and introduces some of the concepts that are further described in the Detailed Description section below.

According to a first aspect of the invention there is provided a system according to claim <NUM>.

According to a second aspect of the invention there is provided a method according to claim <NUM>. The system may also include a first conditioning filter that filters the positive rectified ripple signal to output a filtered positive rectified ripple signal and a second conditioning filter that filters the negative rectified ripple signal to output a filtered negative rectified ripple signal. The filtered positive rectified ripple signal and the filtered negative rectified ripple signal may summed to output a differential ripple signal. Additionally, the system may include regulator that controls the output of the polyphase generator with a field control signal based on summing of the differential ripple signal and a reference voltage.

The subject matter of embodiments of the present disclosure is described here with specificity to meet statutory requirements, but this description is not necessarily intended to limit the scope of the claims. The claimed subject matter may be embodied in other ways, may include different elements or steps, and may be used in conjunction with other existing or future technologies. This description should not be interpreted as implying any particular order or arrangement among or between various steps or elements except when the order of individual steps or arrangement of elements is explicitly described.

Certain aspects and examples of the disclosure relate to a transient condition resilient ripple blender ("ripple blender") used to control operation of a polyphase generator. The polyphase generator may be used to generate electrical power used in aircraft electrical systems. Control of the polyphase generator may be affected by transient conditions experienced by the polyphase generator. For example, a regulator of a polyphase generator may rely on feedback signals produced from an output of the polyphase generator and used to provide control signals to the generator. Should the feedback signals be sensitive to transient conditions of the polyphase generator, the regulator may provide distorted control signals to the polyphase generator resulting in a further distorted output. As used herein, the term "transient condition" may refer to any condition that results in a change in a steady-state condition of voltage, current, or both of an output of a generator.

To avoid the effects of transient conditions on the control of the polyphase generator, the ripple blender described below with respect to <FIG> outputs a differential ripple between positive and negative outputs of a bridge rectifier. The differential ripple negates the effects of the transient conditions, and is provided to the regulator of the polyphase generator as the feedback signal. By avoiding effects of transient conditions on the feedback signal, adverse effects of the transient condition on the control of the generator may also be avoided.

The described embodiments provide a ripple blender used in a generator control system. While the ripple blender and the generator control system are discussed for use in an aircraft, it is by no means so limited. Rather, embodiments of the ripple blender and the generator control system may be used in power generation systems of any type or otherwise as desired.

<FIG> is a schematic diagram of a transient condition resilient ripple blender circuit ("ripple blender circuit") <NUM>. The ripple blender circuit <NUM> includes a polyphase generator <NUM>. The polyphase generator <NUM> is depicted as a three-phase generator, however, the polyphase generator <NUM> may include more or fewer phases. The polyphase generator <NUM> outputs voltage signals of each phase of the polyphase generator <NUM> to a full-wave bridge rectifier <NUM> (e.g., a polyphase bridge rectifier). The full-wave bridge rectifier <NUM> rectifies the voltage signals output by the polyphase generator <NUM> and provides a positive rectified ripple signal at node <NUM> and a negative rectified ripple signal at node <NUM>.

In an example, a transient condition experienced at the polyphase generator <NUM> may result in a change in a steady-state condition of voltage, current, or both at an output <NUM> of the polyphase generator <NUM>. The positive rectified ripple signal and the negative rectified ripple signal output at the nodes <NUM> and <NUM>, respectively, may each be influenced by the transient conditions experienced at the polyphase generator <NUM>. That is, the transient condition experienced at the polyphase generator <NUM> may result in an abnormal output of the positive rectified ripple signal and the negative rectified ripple signal.

In an example, the positive rectified ripple signal and the negative rectified ripple signal may be provided to a conditioning filter 110a and a conditioning filter 110b, respectively. The conditioning filters 110a and 110b may be simple filters that remove noise from the positive rectified ripple signal and the negative rectified ripple signal. The conditioning filters 110a and 110b may be band pass filters that are tuned to pass the positive rectified ripple signal and the negative rectified ripple signal while blocking any noise of a frequency greater or less than the band pass range. Other filter types are also contemplated for use as the conditioning filters 110a and 110b. For example, the conditioning filters 110a and 110b may also be low pass filters or high pass filters depending on an expected frequency of a voltage ripple associated with the positive rectified ripple signal and the negative rectified ripple signal.

The filtered positive rectified ripple signal and negative rectified ripple signal may be provided to decoupling capacitors 112a and 112b in series with resistors 114a and 114b, respectively, prior to combining at node <NUM>. The decoupling capacitors 112a and 112b are used to decouple the full-wave bridge rectifier <NUM> from a feedback control loop <NUM>. For example, noise caused by circuit components associated with the full-wave bridge rectifier <NUM> and the conditioning filters 110a and 110b may be removed using the decoupling capacitors 112a and 112b, which reduces any effects of the noise on the feedback control loop <NUM>.

At the node <NUM>, the filtered positive rectified ripple signal and the filtered negative rectified ripple signal are added together to output a differential ripple signal (i.e., a total ripple signal) on the feedback control loop <NUM>. In an example, a pair of diodes <NUM> provide a ripple limiting function that limits a voltage output of the differential ripple to voltages between threshold voltages of the pair of diodes <NUM>. For example, when the differential ripple has a voltage greater than a threshold voltage of a forward biased diode <NUM>, the forward biased diode <NUM> is activated and the differential ripple voltage is pulled down to the threshold voltage of the forward biased diode <NUM>. Similarly, when the differential ripple has a negative voltage less than a threshold voltage of the reverse biased diode <NUM>, the reverse biased diode <NUM> is activated and the differential ripple voltage is pulled up to a negative threshold voltage of the reverse biased diode <NUM>.

To achieve a stable regulated output at the polyphase generator <NUM>, a pulse width modulated (PWM) control signal from a regulator <NUM> may control the output of the polyphase generator <NUM>. For the regulated output of the polyphase generator <NUM> to remain stable, a frequency of the PWM control signal may be proportional to a frequency of the output <NUM> of the polyphase generator <NUM>. Accordingly, the differential ripple, via the feedback control loop <NUM>, is combined with a reference voltage <NUM> to provide a frequency proportional to the frequency of the output of the polyphase generator <NUM> for use by the regulator <NUM>. The regulator <NUM> may use the frequency of the differential ripple to generate the PWM control signals at the appropriate frequency for control of the polyphase generator <NUM>. A combination of the feedback control loop <NUM> and the regulator <NUM> may collectively be referred to as a generator regulation feedback loop.

Further, because the differential ripple on the feedback control loop <NUM> is a combination of the positive rectified ripple signal and negative rectified ripple signal, the differential ripple, and thus the PWM control signals, are unaffected by transient conditions of the polyphase generator <NUM>. For example, combining the positive rectified ripple signal with the negative rectified ripple signal results in the differential signal that peaks and troughs above and below ground, respectively, in a stable manner (e.g., without skipping a wave period). Thus, the differential ripple provided to the feedback control loop <NUM> maintains a constant frequency for use by the regulator <NUM>. In contrast, the positive rectified ripple signal and the negative rectified ripple signal may include peaks or troughs during a transient condition that are too low or too high to be registered by a regulator voltage control loop as a transition to a new half cycle of the positive or negative rectified ripple signals. When the regulator voltage control loop misses such a transition, the frequency of the PWM control signal generated by the regulator <NUM> may be distorted resulting in false voltage compensation of the polyphase generator <NUM>.

In an example, the regulator <NUM> may control the PWM control signals provided to the polyphase generator <NUM> by switching a field metal-oxide-semiconductor field-effect transistor (MOSFET) (not shown) between an "on" state and an "off" state. The field MOSFET may provide field current to the polyphase generator <NUM> that is directly related to a voltage output by the polyphase generator <NUM>. Controlling the field MOSFET in the "on" state and "off' state in accordance with the PWM control signal proportional to an output frequency of the polyphase generator <NUM> provides stable operation of the polyphase generator <NUM>. In one or more examples, the field MOSFET may include any other suitable semiconductor switching device capable of providing the field current to the polyphase generator <NUM> based on the PWM control signals.

<FIG> is a graphical representation <NUM> of a voltage output over time from a three-phase generator (e.g., the polyphase generator <NUM>) experiencing a transient condition. The graphical representation <NUM> includes an abscissa <NUM> representing elapsed time and an ordinate <NUM> representing a voltage magnitude output by the three-phases of the polyphase generator <NUM>. Lines <NUM>, <NUM>, and <NUM> represent a first phase, a second phase, and a third phase of the voltage magnitude output of the polyphase generator <NUM>, respectively.

As mentioned above, a transient condition may be defined as any condition that results in a change in a steady-state condition of voltage, current, or both of an output of the polyphase generator <NUM>. As depicted in the graphical representation <NUM>, a transient condition occurs for approximately <NUM> between lines <NUM> and <NUM>. Using the ripple blender circuit <NUM> described above, effects of the transient condition on control of the polyphase generator <NUM> may be limited.

<FIG> is a graphical representation <NUM> of a voltage output over time of a positive ripple of a rectified output of a polyphase generator (e.g., a positive rectified ripple signal) and a blended output of the rectified output of the polyphase generator (e.g., a differential ripple signal combination of the positive rectified ripple signal and a negative rectified ripple signal). The graphical representation <NUM> includes an abscissa <NUM> representing elapsed time and an ordinate <NUM> representing a voltage magnitude value of the signals displayed in the graphical representation <NUM>. As illustrated, line <NUM> may represent the positive rectified ripple signal of the polyphase generator <NUM>, and line <NUM> may represent the differential ripple signal between the positive rectified ripple signal and a negative rectified ripple signal of the polyphase generator <NUM>.

The positive rectified ripple signal of line <NUM> and the differential ripple signal of line <NUM> each result from the three-phase voltage output of the polyphase generator <NUM> depicted in the graphical representation <NUM> of <FIG>. For example, the positive rectified ripple signal of line <NUM> represents a positive-side rectified signal of the three-phase voltage output by the polyphase generator <NUM>. With reference to <FIG>, the positive rectified ripple signal of line <NUM> may be measured at the node <NUM> of the ripple blender circuit <NUM>. The differential ripple signal of line <NUM> represents a combination of the positive rectified ripple signal and a negative rectified ripple signal. With reference to <FIG>, the differential ripple signal of line <NUM> may be measured at the node <NUM> of the ripple blender circuit <NUM>.

As in the graphical representation <NUM>, the graphical representation <NUM> depicts a transient condition that occurs for approximately <NUM> between lines <NUM> and <NUM>. The transient condition is evident by a change in a steady-state condition of the positive rectified ripple signal of line <NUM>. As discussed above with respect to <FIG>, the change in the steady-state condition of the positive rectified ripple signal may result in generation of a distorted PWM signal by the regulator <NUM> should the positive rectified ripple signal be fed to the feedback control loop <NUM>. In contrast, the transient condition has a much smaller effect on the differential ripple signal of line <NUM>. Thus, the use of the differential ripple signal on the feedback control loop <NUM> of the ripple blender circuit <NUM> may limit effects of the transient condition on control of the polyphase generator <NUM> by the regulator <NUM>.

<FIG> is a flow chart of a process <NUM> for regulating an output of the polyphase generator <NUM> using the ripple blender circuit <NUM>. As discussed above, the output of the polyphase generator <NUM> may be regulated by the regulator <NUM> using a PWM control signal. To maintain a stable regulated output signal of the polyphase generator <NUM>, the PWM control signal may include a frequency that is proportional to a frequency of the output of the polyphase generator <NUM>. To avoid effects of transient conditions experienced by the polyphase generator <NUM> on the regulation of the polyphase generator <NUM>, the ripple blender circuit <NUM> provides the differential ripple signal to the feedback control loop <NUM> used to regulate the generator <NUM>.

At block <NUM>, the process <NUM> involves providing an output of the polyphase generator <NUM> to a polyphase bridge rectifier (e.g., the full-wave bridge rectifier <NUM>). The full-wave bridge rectifier <NUM> rectifies the polyphase output of the polyphase generator <NUM> to a positive rectified ripple signal and a negative rectified ripple signal. Such signals may be noisy and are susceptible to distortion resulting from transient conditions experienced by the polyphase generator <NUM>.

At block <NUM>, the process <NUM> involves outputting the positive rectified ripple signal and the negative rectified ripple signal from the full-wave bridge rectifier <NUM>. In an example, the positive and negative rectified ripple signals may be provided to the conditioning filters 110a and 110b, respectively, to remove noise from the signals. Additionally, the positive and negative rectified ripple signals may be provided to the decoupling capacitors 112a and 112b to decouple the signals from potentially noisy circuitry of the full-wave bridge rectifier <NUM>.

At block <NUM>, the process <NUM> involves summing the positive rectified ripple signal and the negative rectified ripple signal. Summing the positive rectified ripple signal and the negative rectified ripple signal involves directing the two signals to a single node (e.g., the node <NUM>) within the ripple blender circuit <NUM>. The result of summing the positive rectified ripple signal and the negative rectified ripple signal is a total ripple signal (e.g., the differential ripple signal). The total ripple signal is provided from the node <NUM> to the feedback control loop <NUM>, and the total ripple signal is not susceptible to distortion from transient conditions experienced by the polyphase generator <NUM>. Because the total ripple signal is not susceptible to distortion from transient conditions, effects of the transient conditions on regulation of the output of the polyphase generator <NUM> based on the total ripple signal is limited.

At block <NUM>, the process <NUM> involves generating a field control signal based on the total ripple signal. The field control signal may be a PWM control signal used to control an output of the polyphase generator <NUM>. The PWM control signal may be generated by the regulator <NUM>. For example, the regulator <NUM> may control a duty cycle of the PWM control signal by transitioning a field MOSFET between an "on" state and an "off' state. Further, the regulator <NUM> may use a frequency of the total ripple signal to control a frequency of the PWM control signal to a frequency proportional to an output frequency of the polyphase generator <NUM>.

Thus, at block <NUM>, the process <NUM> involves regulating the output of the polyphase generator <NUM> with the field control signal. Because the field control signal uses a frequency of the total ripple signal, the polyphase generator <NUM> may be regulated by the field control signal with a frequency that is proportional to the frequency of the total ripple signal to achieve a stable regulated output by the polyphase generator <NUM>. Further, because the total ripple signal is not susceptible to transient conditions experienced by the polyphase generator <NUM>, distortion of the field control signal based on feedback to the regulator <NUM> affected by transient conditions is avoided.

Claim 1:
A system, comprising:
a polyphase generator (<NUM>);
a polyphase bridge rectifier electrically coupled to an output of the polyphase generator, wherein the polyphase bridge rectifier (<NUM>) is a full-wave bridge rectifier configured to output a positive rectified ripple signal with respect to a ground voltage and a negative rectified ripple signal with respect to the ground voltage, wherein the positive rectified ripple signal and the negative rectified ripple signal are summed to produce a total ripple signal with respect to the ground such that in use the total ripple signal (<NUM>) peaks and troughs above and below the ground voltage, respectively, in a stable manner without skipping a wave period and with equal positive and negative amplitudes; and
a generator regulation feedback loop configured to regulate the output of the polyphase generator with a field control signal, wherein the field control signal is based on summing the total ripple signal and a reference voltage.