Patent Description:
A power system may be equipped with a direct current power source such as a solar power module or a storage battery and connected to commercial power supplied from a grid. Such power systems are known to include a power converter device (power conditioner) for converting power from direct current to alternating current (or from alternating current to direct current). A noise filter can be provided to the power converter device at the input side and the output side respectively where direct current power and alternating current power are supplied to minimize conduction noise, such as common mode noise or normal mode noise.

A typical noise filter may be configured from a passive element as illustrated in <FIG>. Specifically, a noise filter may be constituted by a reactor (CMC: common mode coil) functioning as a common mode filter and a capacitor (Cx1, Cy1, Cy2) provided at the input side and a capacitor (Cx2, Cy3, Cy4) provided at the output side of the aforementioned reactor. The capacitor Cx1 provided at the input side and the capacitor Cx2 provided at the output side of the reactor function as an X-capacitor connected between a power lines and suppress normal mode noise. The capacitors Cy1 and Cy2 provided at the input side, and the capacitors Cy3 and Cy4 provided at the output side of the reactor connect the power lines and a frame ground (FG), which is a reference potential, and serve as a Y-capacitor that releases the common mode noise current of the power lines to the reference potential on the FG, etc. The reactor, the Y capacitor provided at the input side and the Y capacitor provided at the output side of the aforementioned reactor constitute an LC filter.

In a passive filter constituted by this kind of passive element, when a large amount of power is being converted (e.g., on the order of several kilowatts), the thickness of the wiring in a reactor increases because the current flowing through the reactor constituting the passive filter is relatively larger. When the wiring in the reactor is relatively thicker, the noise filter including a reactor such as a CMC also increases in size, and the power converter device that includes the aforementioned noise filter in its configuration must also necessarily increase in size. From the desire to have smaller power converter devices, a recent trend is hybridization by combining a passive filter configured from a passive element with an active filter; and noise filters that can be downsized while controlling size are becoming mainstream.

However, an active filter can include an active element in the configuration such as an operational amplifier or a transistor; therefore, the active filter tends to fail more easily compared to a passive filter configured from a passive element. Consequently, when the active filter fails, essentially, there is a relative increase in the conduction noise that should be reduced by the noise filter. In cases where the power converter device continues to operate while, for instance, the active filter has failed, the conduction noise with respect to machines connected to and operating with the aforementioned power converter device can propagate to surrounding machines, causing the aforementioned machines to malfunction, etc..

The following patent documents are among the related art documents that disclose features pertaining to the features described in the present specification.

In view of the foregoing, the present invention provides a technology for detecting a failure of a noise filter that includes an active filter in the configuration thereof and allows for preventing transmission of conduction noise to surrounding machines.

A noise filter according to the present invention for addressing the above-mentioned problems includes the features specified in claim <NUM>.

Hereby, the behavior of a power source module may be monitored via active filter that is connected to a power-receiving terminal of a power line for an alternating-current power supplied to a power converter device from an alternating-current power grid or a direct-current power source interconnected with the alternating-current power grid, or for a direct-current power supplied from the direct-current power and a failure (abnormality) or normal operation of the aforementioned active filter may be diagnosed. The present invention is capable of detecting the failure of a noise filter that includes an active filter in its configuration.

In the present invention, when diagnosing that an abnormality occurred in the circuit operation of the active filter circuit that includes the active element on the basis of the variation in the state of the drive power, the controller may suspend the operation of the power converter device. Thus, if the active filter is diagnosed as having failed, the operation of the power converter device having the noise filter in the configuration thereof can be suspended. The present invention prevents the conduction noise that would accompany a failure of the active filter from propagating to surrounding machines.

In the present invention, when diagnosing that the circuit operation of the active filter circuit that includes the active element is normal on the basis of the variation in the state of the drive power, the controller may continue the operation of the power converter device. Thus, when the filter is diagnosed as being in normal operation, the power converter device continues to operate, thus improving the working rate of the aforementioned power converter device, and the harmonic component in the conduction noise propagating to the power line can be reduced via the aforementioned active filter.

In the present invention, the power source module includes a positive power source for generating a positive-side voltage and a negative power source for generating a negative-side voltage. The controller monitors the variation in the state of the drive power supplied from the power source module on the basis of at least any one current of a first current flowing from the positive power source of the power source module to a reference potential, a second current flowing from a negative power source in the power source module to a reference potential, and a third current flowing from a connection point for connecting the negative-side electrode of the positive power source and the positive-side electrode of the negative power source to a reference potential. Thus, the variation in the state of the drive power supplied from the power source module on the basis of any one current of a first current (Ip) flowing from the positive power source of the power source module to a reference potential, a second current (In) flowing from a negative power source in the power source module to a reference potential, and a third current (lg) flowing from a connection point for connecting the negative-side electrode of the positive power source and the positive-side electrode of the negative power source to a reference potential can be monitored.

The controller may diagnose an abnormality in the circuit operation of a circuit including the active element of the active filter circuit on the basis of a first current flowing from the positive power source of the power source module to a reference potential or a second current flowing from a negative power source in the power source module to a reference potential, and a third current flowing from a connection point for connecting the negative-side electrode of the positive power source and the positive-side electrode of the negative power source to a reference potential. Hereby, the noise filter is capable of increasing the diagnostic reliability of a failure diagnosis.

In the present invention, the controller may determine that the circuit operation of the circuit including the active element of the active filter circuit is normal when the first current or the second current is at or above a first threshold and is at or below a second threshold that is greater than the first threshold. A failure diagnosis is hereby possible by using that the first current or the second current is within a predetermined range (a range of at or above a first threshold and at or below a second threshold).

In the present invention, the controller may determine that the circuit operation of the circuit including the active element of the active filter circuit is normal when the third current is at or above a third threshold and is at or below a fourth threshold that is greater than the third threshold. A failure diagnosis is hereby possible by using that the third current is within a predetermined range (a range of at or above a third threshold and at or below a fourth threshold).

The present invention may further include a passive filter for a power line which is supplied the alternating-current power supplied to a power converter device from an alternating-current power grid or a direct-current power source interconnected with the alternating-current power grid or is supplied from the direct-current power source on the power converter device side for reducing the common mode noise propagating to the power line. Hereby, it is possible to implement a hybrid noise filter in which the passive filter is capable of minimizing the common mode noise, and the active filter is capable of minimizing the harmonic component in the conduction noise.

The present invention detects a failure of a noise filter that includes an active filter in the configuration thereof and prevents transmission of conduction noise to surrounding machines.

An example application of the present invention is described below with reference to the drawings. <FIG> is a block diagram of a power system <NUM> provided with a power converter device <NUM> that employs a noise filter <NUM> of an example application of the present invention. <FIG> provides an example of the resource configuration of a grid-connectable power system which interconnects a DC power supply <NUM> that supplies direct-current power and a commercial power grid <NUM> (also referred to as "grid" below) that supplies alternating current power.

The power converter device <NUM> includes in the configuration thereof a DC-DC converter 102b and an inverter 102c for converting direct-current power supplied from the DC power supply <NUM> to alternating-current power synchronized with the power supplied from the grid, or converting the alternating-current power supplied from the grid to direct-current power synchronized with the power supplied from the DC power supply <NUM>. The power converter device <NUM> also includes in the configuration thereof a DCF 102a and an ACF102d, also called a noise filter, for minimizing the conduction noise (common mode noise or normal mode noise) derived from a conversion process from direct-current power to alternating-current power or alternating-current power to direct-current power (boost/buck conversion, frequency conversion, etc.). The DCF 102a inside the noise filter is provided at the input-output end parts on the DC power supply <NUM> side of a power converter unit <NUM>, and the ACF 102d is provided at the input-output end parts on the grid side <NUM> of the power converter unit <NUM>. The DCF 102a and ACF 102d have different voltage specifications, current specifications, or the like in accordance with the difference in direct current and alternating current; however, the constituent parts making up the respective circuits may be roughly the same.

<FIG> is a block diagram illustrating a resource circuit configuration of a noise filter <NUM> according to the first embodiment of the present invention. As illustrated in <FIG>, the noise filter <NUM> according to the example application of the present invention is configured as a hybrid noise filter that combines a passive filter <NUM> and an active filter <NUM>. The passive filter <NUM> in the noise filter <NUM> may be provided at the noise source (the power converter circuit (the DC-DC converter 102b, the inverter 102c, etc.)), and minimizes the common mode noise current that propagates on the power line connected to the terminals 20a, 20B. The active filter <NUM> according to the example application of the present invention is connected to the terminal 20c and the terminal 20d of the power line at the power-source side (DC power supply <NUM>, grid <NUM>) of the passive filter <NUM> that is supplying direct-current or alternating-current power; the active filter <NUM> detects the high frequency component in the conduction noise propagating to the aforementioned power line and functions to reduce the harmonic current corresponding to the aforementioned high frequency component. The active filter <NUM> includes active elements such as an operational amplifier 13a, a transistor TR1, a transistor TR2, etc., in the circuit configuration thereof.

The active filter <NUM> of the example application of the present invention includes as a configuration element, a dual power module provided with a positive power source P1 which supplies a positive voltage (Vp) power and a negative power source P2 which supplies a negative voltage (Vn) power for driving the above-described active element. The noise filter <NUM> according to the example application of the present invention is provided with an abnormality detector unit <NUM> for monitoring the behavior of the power which supplies operative power to the active elements, etc., in the active filter <NUM>, and measuring the current of the power that is supplied from the above-described dual power source module to the active element, etc., making up the active filter <NUM>. Specifically, as illustrated in <FIG>, the current (Ip) flowing from the positive power source P1 to a reference potential FG and the current (In) flowing from the negative power source P2 into the reference potential FG. The current (lg) flowing from a connection point that connects the negative-side electrode of the positive power source P1 and the positive-side electrode of the negative power source P2 into the reference potential FG is also measured.

As illustrated in <FIG>, when an open-circuit fault or a short-circuit fault occurs in the circuit configuration which includes the active filter <NUM>, the currents Ip, In, Ig supplied from the dual power source module to the active elements etc. change significantly. An abnormality in the aforementioned active filter <NUM> may be diagnosed by monitoring the behavior of the power by measuring at least two among three of the currents, that is, the current Ig, and current In or current Ip in the active filter <NUM> according to the example application of the present invention.

<FIG> shows an example table presenting a condition for a failure assessment of the currents Ip, In, Ig respectively with regard to failure diagnosis points in the active filter <NUM>. At least the current Ig and current In, or current Ip are measured in the noise filter <NUM> according to the example application of the present invention via a current measuring function <NUM> in the abnormality detector unit <NUM>. The abnormality diagnosis function <NUM> in the abnormality detector unit <NUM> diagnoses a failure of the active filter <NUM>, where an assessment condition is that each of the currents measured is within a predetermined threshold value. If the active filter <NUM> is diagnosed as being normal in the noise filter <NUM> according to the example application of the present invention, the power converter device <NUM> having the noise filter <NUM> included in the configuration thereof continues to operate. Whereas, if the active filter <NUM> is diagnosed as having failed, the operation of the power converter device <NUM> having the noise filter <NUM> in the configuration thereof is suspended. Consequently, the noise filter <NUM> according to the example application of the present invention detects the failure of the noise filter that includes an active filter in the configuration thereof, and makes it possible to prevent conduction noise from propagating to surrounding machines.

A noise filter in a power converter device according to an embodiment of the present invention is described in detail below with reference to the drawings.

<FIG> is a block diagram illustrating a schematic configuration of a power system <NUM> installed on a customer's premises. The power system <NUM> illustrated in <FIG> is a grid-connected system that interconnects a DC power supply <NUM> which supplies direct-current power and a commercial power grid <NUM> (also referred to as "grid" below), which supplies alternating-current power. The power system <NUM> is provided with a power converter device <NUM> (power conditioner) for converting the direct-current power supplied from a DC power supply <NUM> such as a solar power module, storage battery, an EV, etc., to a predetermined alternating-current power (e.g., single-phase, three-wire, <NUM>/100V). The predetermined alternating-current power converted by the power converter device <NUM> is supplied to a lighting installation, load, or the like (not shown) provided on a customer's premises, or is supplied to an interconnected grid <NUM>. The power converter device <NUM> converts the alternating-current power supplied from the grid <NUM> to a predetermined direct-current power. The direct-current power converted by the power converter device <NUM> is supplied to a connected storage battery or EV, etc., as the DC power supply <NUM>.

The power converter device <NUM> includes in the configuration thereof a DC-DC converter 102b and an inverter 102c for converting direct-current power supplied from the DC power supply <NUM> to alternating-current power synchronized with the power supplied from the grid, or converting the alternating-current power supplied from the grid to direct-current power synchronized with the power supplied from the DC power supply <NUM>. The power converter device <NUM> also includes in the configuration thereof a DCF 102a and an ACF102d, also called a noise filter, for minimizing the conduction noise (common mode noise or normal mode noise) produced in a conversion process from direct-current power to alternating-current power or alternating-current power to direct-current power (boost/buck conversion, frequency conversion, etc.). The DCF 102a inside the noise filter is provided at the input-output end parts on the DC power supply <NUM> side of a power converter unit <NUM>, and the ACF 102d is provided at the input-output end parts on the grid side <NUM> of the power converter unit <NUM>. The DCF 102a and ACF 102d have different voltage specifications, current specifications, or the like in accordance with the difference in direct current and alternating current; however, the constituent parts making up the respective circuits may be roughly the same. The DCF 102a and the ACF 102d are jointly referred to as simply the "noise filter".

<FIG> is a block diagram illustrating a resource circuit configuration of a noise filter <NUM> according to the first embodiment of the present invention. The noise filter <NUM> illustrated in <FIG> is a hybrid noise filter, which includes a passive filter <NUM> and an active filter <NUM> in the configuration thereof. The active filter <NUM> detects the high-frequency component in the conduction noise propagating to the power line and functions to reduce the harmonic current corresponding to the aforementioned high-frequency component. The size of the noise filter <NUM> according to this embodiment can be minimize even when performing power conversion on the order of several kilowatts by combining a passive filter <NUM> configured from a passive element and an active filter <NUM> that includes an active element in the circuit configuration with an operational amplifier, a transistor, or the like. The noise filter <NUM> according to this embodiment may further includes an abnormality detector unit <NUM> for the purpose of monitoring the behavior of the power supplied as operation power with respect to the active element, etc., in the active filter <NUM> etc. The abnormality detector unit <NUM> measures the current of the power supplied to the active element, etc., in the noise filter <NUM> that is energized and an energized state for example. The abnormality detector unit <NUM> diagnoses an abnormality of the active filter <NUM>, which includes an active element, etc., on the basis of variation in the state of the current measured.

The passive filter <NUM> is provided on the noise-generating side of the power converter device <NUM> in the noise filter <NUM> according to the present embodiment. For example, when the noise filter <NUM> is functioning as the DFC 102a illustrated in <FIG>, the power line connecting the DC-DC converter 102b and the DFC 102a in the power converter device <NUM> is connected to the terminal 20a, 20b of the passive filter <NUM>. The power line that connects the aforementioned DFC and the DC power supply <NUM>, which is a direct-current power source, is connected to the terminal 20c, 20d of the passive filter <NUM>. Whereas, when the noise filter <NUM> is functioning as the AFC 102d illustrated in <FIG>, the power line joining the inverter 102c in the power converter device <NUM> and the AFC 102d is connected to the terminals 20a, 20b of the passive filter <NUM>. The power line joining the aforementioned AFC and the grid <NUM>, which is the alternating-current power source, is connected to the terminals 20c, 20d of the passive filter <NUM>.

The passive filter <NUM> is constituted by a reactor CMC, which is a passive element, capacitors (C1, C2) that are provided on the noise source side, and capacitors (C3, C4) that are provided on the direct-current power source side (DC power supply <NUM>) or alternating-current power source side (grid <NUM>). The capacitors C1 and C2, which are provided on the noise source side, and the capacitors C3 and C4, which are provided on the direct-current or alternating-current power source side are connected to the power lines and the frame ground (FG), etc., which is the reference potential and serve as a Y capacitor that is for allowing the common mode noise current propagating to the power lines to escape to the FG, etc. The reactor CMC and the aforementioned Y capacitor provided on the noise source side and the Y capacitor provided at the power source constitute an LC filter.

The active filter <NUM> according to this embodiment is connected to the terminal 20c and the terminal 20d of the power line on the power source side (DC power supply <NUM>, grid <NUM>) supplying the direct-current or alternating-current power for the passive filter <NUM>. The active filter <NUM> includes a circuit configuration that serves as a filter power source <NUM>, a detector unit <NUM>, an amplifier unit <NUM>, and an injector unit <NUM>. The filter power source <NUM> is a dual power source module including a positive power source P1 that supplies power of a positive voltage (Vp) and a negative power source P2 that supplies power of a negative voltage (Vn) as constituent elements therein. The connection point that connects the negative-side electrode of the positive power source P1 and the positive-side electrode of the negative power source P2 is grounded at the frame ground (FG), etc., which is a reference potential.

The detector unit <NUM> in the active filter <NUM> detects the high-frequency component in the conduction noise that propagates to the power line on the power source side (DC power supply <NUM>, grid <NUM>) of the passive filter <NUM> which is combined with the aforementioned filter. The high-frequency component detected is output to the amplifier unit <NUM>. One end of the capacitor C5 constituting the detector unit <NUM> is connected to the terminal 20c of the power line and one end of the capacitor C6 is connected to the terminal 20d of the power line. The other end of the capacitor C5 which is connected to the terminal 20c and the other end of the capacitor C6 which is connected to the terminal 20d are connected to the reference potential (FG, etc.) through a resistor R1. The capacitor C5 and the resistor R1 constitute a high pass filter (HPF) that transmits the high-frequency component in the conduction noise propagating to the power line to which the terminal 20c is connected; the capacitor C6 and the resistor R1 constitute a high pass filter (HPF) that transmits the high-frequency component in the conduction noise propagating to the power line. The high-frequency component of the conduction noise, which is transmitted by the high pass filter, passes through a capacitor C7 and resistor R2, which are connected in series, and is output to the amplifier unit <NUM> as a voltage fluctuation responsive to the aforementioned high-frequency component.

The amplifier unit <NUM> includes in the configuration thereof an operational amplifier 13a, and active elements, that is, an NPN transistor TR1 and a PNP transistor TR2. The operational amplifier 13a is supplied a positive voltage (Vp) power and negative voltage (Vn) power from the filter power source <NUM> as the drive power. The collector of the transistor TR1 is similarly supplied a positive voltage (Vp) power from the filter power source <NUM> as the drive power, and the collector of the transistor TR2 is similarly supplied the negative voltage (Vn) power from the filter power source <NUM> as the drive power.

The voltage fluctuation in accordance with the high-frequency component output from the detector unit <NUM> enters the inverting input terminal <NUM> of the operational amplifier 13a. A voltage enters the non-inverting input terminal <NUM> of the operational amplifier 13a, the voltage serves as a reference for differential operation and is connected to the reference potential FG via the resistor R3. The operational amplifier 13a amplifies the voltage difference between the current fluctuation that entered the inverting input terminal <NUM> and the reference voltage that entered the non-inverting input terminal <NUM> and outputs the result to the output terminal <NUM>. The diodes D1, D2 are connected to the inverting input terminal <NUM> of the operational amplifier 13a to protect the aforementioned operational amplifier 13a from input over-voltage. The voltage difference output from the output terminal <NUM> passes through a resistor <NUM> and enters the base of the transistors (TR1, TR2) to which an emitter is mutually connected, to amplify the current. The base of the transistor TR1 is connected to the anode of a diode D3 and the base of the transistor TR2 is connected to the cathode of a diode D4. The voltage difference output from the output terminal <NUM> is connected to the cathode side of the diode D3 and to the anode side of the diode D4. A positive voltage (Vp) is applied to the anode side of the diode D3 via a resistor R5 and a negative voltage (Vn) is applied to the cathode side of the diode D4 via a resistor R6. The voltage fluctuation of the voltage difference causes the current between the emitter/base of the transistors TR1, T1 to change, while at the collector/emitter, a collector current in accordance with the amplification level of the aforementioned transistors is output as a harmonic current. The harmonic current output from the emitters of the transistors TR1 and TR2 is fed back and input to the inverting input terminal <NUM> of the operational amplifier 13a via a low pass filter configured from a resistor R7 and a capacitor C8. As a result, the output current of the active filter <NUM> is controlled so that the active filter <NUM> reduces the harmonic current in the current flowing in the power line to which the terminals 20c, 20d are connected in accordance with the harmonic current fed back and input to the inverting input terminal <NUM>.

The output current that is output from the emitters of the transistors enters the injector unit <NUM>. The output current that enters the injector unit <NUM> is injected via a resistor R8 and a capacitor C9 into the power line to which the terminal 20c is connected, and is injected via the resistor R8 and a capacitor C10 into the power line to which the terminal 20d is connected.

The abnormality detector unit <NUM> is control module having a current measuring function <NUM> and an abnormality diagnosing function <NUM>. A control microprocessor is a typical example of what may serve as the abnormality detector unit <NUM>. The abnormality detector unit <NUM> monitors the behavior of the positive voltage (Vp) and the negative voltage (Vn) supplied to the active elements from the filter power source <NUM> to cause the active filter <NUM> to function, and diagnoses any abnormality in the aforementioned active filter.

<FIG> is a diagram for describing with regard to monitoring the current supplied as the drive power from the filter power source <NUM> to drive the active elements. As illustrated in <FIG>, the behavior of current supplied from the filter power source <NUM> to the active elements can be monitored, for instance, by measuring the current (Ip) flowing from the positive power source P1 to the reference potential FG and the current (In) flowing from the negative power source P2 into the reference potential FG. The behavior of the current supplied to the active elements can also be monitored by measuring the current (lg) flowing from the connection point that connects the negative-side electrode of the positive power source P1 and the positive-side electrode of the negative power source P2 into the reference potential FG.

The behavior of the filter power source <NUM> may also be monitored, for instance, by measuring the positive voltage (Vp) and the negative voltage (Vn). The characteristics of the dual power-source module employed by the filter power source <NUM> may be configured so that, for instance, the power source reduces the voltage at the time of failure by increasing the current flowing to the reference potential (FG) side. The current waveform of the current (lg) flowing from the connection point that connects the negative-side electrode of the positive power source P1 and the positive-side electrode of the negative power source P2 into the reference potential FG side may also be established as a parameter to be monitored; for example, the failure of the active filter <NUM> can be detected under the condition of monitoring a current waveform where the DC component and not the AC component is the main constituent.

Within the circuit configuration of the active filter <NUM>, the amplifier unit <NUM>, which includes the operational amplifier 13a and the transistors (TR1, TR2), which are active elements, can be said to be a location tends to fail. The injector unit <NUM> injects the output current controlled by the active filter <NUM> to reduce the harmonic current into the power line; even when configured with passive elements, the injector unit <NUM> can be said to be a location with a high level of impact on surrounding machines when there is a failure. Accordingly, the abnormality detector unit <NUM> in the noise filter <NUM> measures the currents Ip, In, Ig from the filter power source <NUM> via the current measuring function <NUM>. The abnormality detector unit <NUM> diagnoses an abnormality in the active filter <NUM> using the abnormality diagnosing function <NUM> on the basis of the each of the currents measured via the current measuring function <NUM> with the amplifier unit <NUM> and the injector unit <NUM> as the primary targets thereof.

The variation in current that accompanies a failure in the active filter <NUM> is described next with references to <FIG>. <FIG> is one example of a graph modeling a variation in current when the injector unit <NUM> in the active filter <NUM> undergoes an open-circuit fault (disconnected state). As an example of an open-circuit fault in the injector unit <NUM>,the resistor R8 may be damaged due to over-current. The vertical axis of the simulation graph in <FIG> represents the current (mA), and the horizontal axis represents the time (µsec). In <FIG>, the graphs shown in dotted line represent the change in the current during normal operation, and the graphs shown in solid lines represent the change in the current during a failure. The properties of the vertical axis and horizontal axis of the graphs indicating the variation in current in <FIG>, the display properties of the graphs are the same with regard to <FIG>.

When a failure occurs due to open-circuit damage of the injector unit <NUM>, the currents Ip and In flowing to the filter power source <NUM> are in a state in which the fluctuation band due to the AC component of is roughly zero and a fixed current continues to be measured. Similarly, in the current Ig, the fluctuation band due to the AC component is roughly zero, and the current flowing to the reference potential FG is roughly zero. As illustrated by the dotted line, the fluctuation band of the current Ig during normal operation is relatively large compared to the fluctuation band of the currents Ip, In during normal operation. Therefore, it is possible to detect an open-circuit fault in the injector unit <NUM> while the power converter device <NUM> is operating, on the basis of the fluctuation band of the current Ig measured from the filter power source <NUM>. However, as illustrated by the solid line, when there is a failure, the currents Ip and In are in a constant current state in which the fluctuation band due to the AC component is roughly zero; therefore, it is possible to detect an open-circuit fault of the injector unit <NUM> with measuring this constant current state as a condition therefor.

<FIG> is one example of a graph modeling a variation in current when the positive voltage (Vp) of the operational amplifier 13a making up the amplifier unit <NUM> in the active filter <NUM> experiences a short-circuit fault. As illustrated in <FIG>, during normal operation, the current Ip changes to near -<NUM> mA including the fluctuation band due to the AC component and the current Ig changes to near <NUM> mA including the fluctuation band due to the AC component. When a short-circuit fault occurs, the currents Ip and Ig change while making a large shift toward the negative current (approximately <NUM> mA in the example illustrated). In contrast, although the current In deteriorates slightly before and after the failure, the current In changes near <NUM> mA including the fluctuation band due to the AC component. Accordingly, it is possible to detect a short-circuit fault on the positive voltage (Vp) side of the operational amplifier 13a on the basis of the variation in state of the currents Ip, Ig measured from the filter power source <NUM> in the power converter device <NUM>.

<FIG> is one example of a graph modeling a variation in current when the transistors (TR1, TR1)making up the amplifier unit <NUM> in the active filter <NUM> experiences a short-circuit fault. As illustrated in <FIG>, during normal operation, the currents change near <NUM> mA including the fluctuation band due to the AC component. However, when a short-circuit fault occurs, the current Ip makes a large shift toward the negative current side (approximately <NUM> mA in the example illustrated) and the current In makes a large shift toward the positive current side (approximately <NUM> mA in the example illustrated). Note that, the current In changes near <NUM> mA including the fluctuation band due to the AC component even in when a failure occurs. Accordingly, it is possible to detect a short-circuit fault of the transistors (TR1, TR2) making up the amplifier unit <NUM> on the basis of the variation in the state of the currents Ip, In measured from the filter power source <NUM> in the power converter device <NUM>.

<FIG> illustrates the results of running a simulation with regard to an open-circuit fault and a short-circuit fault (short), which are causes of failure, with respect to the amplifier unit <NUM> and injector unit <NUM> respectively in the active filter <NUM>. <FIG> shows one example of a table presenting a condition for a failure assessment of the currents Ip, In, Ig respectively with regard to failure diagnosis points in the active filter <NUM>.

As illustrated in <FIG>, the failure due to an open-circuit fault and short-circuit fault of the transistors (TR1, TR2) in the amplifier unit <NUM> can be diagnosed using a measurement value for a power Ip and a power In. The open-circuit fault with respect to the operational amplifier 13a in the amplifier unit <NUM> can be diagnosed using the measurement value of the power Ip or the power In; the short-circuit fault may be diagnosed using at least two measurement values among the currents Ip, In, Ig. An open-circuit fault and a short-circuit fault with respect to the injector unit <NUM> can be diagnosed using the measurement value of the power Ig. Accordingly, the abnormality detector unit <NUM> in a noise filter according to this embodiment is able to diagnose an abnormality in the active filter <NUM> using at least two measurement values (power Ig and power Ip or power In) among the currents Ip, In, Ig.

An open-circuit fault in the transistors (TR1, TR2) of the amplifier unit <NUM> is assessed as a failure of the aforementioned location under the condition that the power Ip or the power In measured is less than a threshold A. Meanwhile, a short-circuit fault in the transistors (TR1, TR2) of the amplifier unit <NUM> is assessed as a failure of the aforementioned location under the condition that the power Ip or the power In measured is greater than a threshold B.

An open-circuit fault with respect to the operational amplifier 13a of the amplifier unit <NUM> is assessed as a failure of the aforementioned location under the condition that the power Ip or the power In measured is less than a threshold A. Meanwhile, a short-circuit fault with respect to the operational amplifier 13a of the amplifier unit <NUM> is assessed as a failure of the aforementioned location under the condition that at least two of the powers Ip, In, Ig measured is greater than a threshold B. An open-circuit fault with respect to the injector unit <NUM> is assessed as a failure of the aforementioned location under the condition that the power Ig measured is less than a threshold C. Further, a short-circuit fault in the injector unit <NUM> is assessed as a failure of the aforementioned location under the condition that the power Ig measured is greater than a threshold D.

A short-circuit fault in the operational amplifier 13a needed the measurement values with respect to at least two powers among the power Ip, In, Ig; however, if the current measurement accuracy is sufficient, the failure of the aforementioned location can be detected with even a single current measurement using the variation in current during normal operation and during a failure of the current In as illustrated in <FIG>.

The timing for performing a failure assessment on the active filter <NUM> may be on start up of the power converter device <NUM>, and before starting operations for a power conversion process with respect to power supplied from an interconnected DC power supply <NUM> or grid <NUM>. The operation of the power converter device <NUM> can be suspended by detecting a failure in the active filter <NUM> at the aforementioned timing;
therefore, the conduction noise that could be generated due to a power conversion process can be prevented from propagating to surrounding machines that are interconnected.

After the operation of the power converter device <NUM> begins, an output current controlled to reduce the harmonic current is injected into the power line by the active filter <NUM> through the injector unit <NUM>. Accordingly, the timing for failure assessment of the aforementioned injector unit <NUM> may be after the start of operation of the power converter device <NUM>. Performing the failure assessment of the injector unit <NUM> during operation essentially prevents the harmonic current in the conduction noise on the power line being reduced by the active filter <NUM> from propagating to surrounding machines while the harmonic current is not being reduced due to the failure of the injector unit <NUM>. If no failure is detected for the injector unit <NUM>, the abnormality detector unit <NUM> may skip the failure assessment of the injector unit <NUM> after operation begins.

<FIG> is a flowchart illustrating one example of failure diagnosis processing for the noise filter of the present embodiment. The failure diagnosis of the noise filter <NUM> in the flow in <FIG> is performed using two of the currents among the current Ig, and current Ip or current In. First, when the power converter device <NUM> is started, the noise filter <NUM> of this embodiment is energized and the filter power source <NUM> energizes the amplifier unit <NUM>. When the current measuring function <NUM> in the abnormality detector unit <NUM> acquires measurement values of two of the currents (Ig, and Ip or In) that are t be measured from filter power source <NUM> that is now energized, and processing continues to step S102. It is determined in step S102 whether the current Ip or the current In measured are within a range from the threshold value A to the threshold value B. If the current Ip or the current In measured are within a range from the threshold value A to the threshold value B (step S102, "YES"), processing continues to step S103 and operation of the power converter device <NUM> begins. Whereas, if the current Ip or the current In measured are outside the range from the threshold value A to the threshold value B (step S102, "NO"), processing continues to step S106 and the failure of the noise filter <NUM> is diagnosed. The power converter device <NUM>, which includes a noise filter <NUM> in the configuration thereof, suspends the operation of the aforementioned power converter device <NUM> if the abnormality diagnosing function <NUM> determines there is a failure.

After operations starts, it is determined in step S104 whether the current Ig measured is within range from a threshold value C to a threshold value D. If the current Ig measured is within the range from the threshold value C to the threshold value D (step S104, "YES"), processing continues to step S105 and the noise filter <NUM> is determined to be in normal operation. The operation continues for the power converter device <NUM> that includes the noise filter <NUM> in the configuration thereof. Whereas, if the current Ig measured is outside the range from the threshold value C to the threshold value D (step S104, "NO"), processing continues to step S106 and the failure of the noise filter <NUM> is diagnosed. The power converter device <NUM> suspends the operation of the aforementioned power converter device <NUM> that was started in step S103. Once the processing in steps S105, S106, the present routine ends for the time being.

As heretofore described, the behavior of the filter power source <NUM> in the active filter <NUM> making up the noise filter <NUM> is monitored and the failure or normal operation of the aforementioned active filter <NUM> is diagnosed. If the active filter <NUM> is diagnosed as being normal in this embodiment, the power converter device <NUM> having the noise filter <NUM> included in the configuration thereof continues to operate. Whereas, if the active filter <NUM> is diagnosed as having failed, the operation of the power converter device <NUM> having the noise filter <NUM> in the configuration thereof can be suspended. This embodiment detects a failure of a noise filter that includes an active filter in the configuration thereof and prevents the conduction noise from propagating to surrounding machines.

The current Ip flowing from the positive power source P1 into the reference potential FG, the current In flowing from the negative power source P2 into the reference potential FG, and the current Ig flowing from a connection point connecting the negative-side electrode of the positive power source P1 and the positive-side electrode of the negative power source P2 into the reference potential FG can be measured in this embodiment to serve as information for monitoring the behavior of the filter power source <NUM>. The open-circuit fault and short-circuit fault in a circuit configuration that includes an active element in an active filter <NUM> may be diagnosed on the basis of a variation in the state of measured values by measuring the current Ip or the current In. The open-circuit fault and short-circuit fault in a circuit configuration that does not include an active element in an active filter <NUM> may be diagnosed on the basis of a variation in the state of measured values by measuring the current Ig. Accordingly, this embodiment allows for assessing the open-circuit fault or short-circuit fault of a circuit configuration that does not include active elements by measuring at least two of the currents among the current Ig, and the current Ip or the current In; therefore, this embodiment improves the assessment accuracy of a failure diagnosis.

The timing for performing a failure assessment on the active filter <NUM> in this embodiment may be on start up of the power converter device <NUM>, and before starting operations for a power conversion process with respect to power supplied from an interconnected DC power supply <NUM> or grid <NUM>. [error] A failure in the active filter <NUM> can be diagnosed prior the start of operation of a power converter device <NUM> that includes the noise filter <NUM> in the configuration thereof; therefore, it is possible to prevent the conduction noise that could be generated from a power conversion process from propagating to surrounding machines that are interconnected. This embodiment prevents a power converter device <NUM> from operating with a failed active filter <NUM> before it happens.

In this embodiment, failure assessment of the active filter <NUM> is possible event after the operation of the power converter device <NUM> has started. Therefore, this essentially prevents the harmonic current in the conduction noise on the power line, which is reduced by the active filter <NUM> from propagating while not reduced due to the failure of the active filter <NUM>, and negatively impacting the operation of surrounding machines. This embodiment prevents a power converter device <NUM> from continuing to operate with a failed active filter <NUM>.

<FIG> is a block diagram illustrating a resource configuration of a noise filter <NUM> according to a second embodiment. In the first embodiment the active filter <NUM> of the noise filter <NUM> is provided with a noise filter power source <NUM> as a drive power source for the active elements, and is configured to measure currents Ip, In, Ig from the aforementioned power source with respect to a failure diagnosis. In the second embodiment the noise filter <NUM> is provided with an AF circuit <NUM> that is configured from a detector unit <NUM>, an amplifier unit <NUM>, and extractor unit <NUM> to serve as the active filter. The second embodiment is configured so that an externally provided AF power source <NUM> supplies positive voltage (Vp) and negative voltage (Vn) to the AF circuit <NUM>. Thus, a configuration may be adopted wherein the driving power source for the active element is provided externally. The currents Ip, In that are supplied from the AF power source <NUM> to the AF circuit <NUM> are measured with a control microprocessor <NUM> in the power converter device <NUM>. Even with this configuration, similarly to the first embodiment, the behavior of the AF power source <NUM> that supplies the AF circuit <NUM> is monitored, and a failure or normal operation is diagnosed for the noise filter <NUM>, which includes the aforementioned AF circuit.

The control microprocessor <NUM> in the power converter device <NUM> performs failure diagnosis of the AF circuit <NUM> on the basis of two of the currents among the currents Ip, In, Ig measured. The control microprocessor <NUM> is capable of suspending the functions of a power converter circuit 2b when the AF circuit <NUM> is diagnosed to be in a state of failure. The power source 2a illustrated in <FIG> corresponds to the DC power supply <NUM> and grid <NUM> in the first embodiment, and the power converter circuit 2b corresponds to the DC-DC converter 102b and the inverter 102c in the first embodiment. The power converted by way of the power converter circuit 2b is supplied to a load 2c connected to the aforementioned power converter device.

The noise filter <NUM> according to this embodiment does not include the filter power source <NUM> and the abnormality detector unit <NUM> in the circuit configuration thereof; therefore, compared to the noise filter <NUM> in the first embodiment, the noise filter <NUM> can have a relatively small footprint and makes it possible to cut production costs by reducing the number of parts. The control microprocessor <NUM> can be made to perform the functions of the abnormality detector unit <NUM>, making it possible to reduce the power consumption of the power converter device <NUM>.

<FIG> is a block diagram illustrating a resource configuration of a noise filter <NUM> according to a modification example of the second embodiment which is not part of the claimed invention. The second embodiment is configured so that the current Ip of the positive power, the current In of the negative power, and the current Ig flowing into the reference potential FG that are supplied from the AF power source <NUM> to the AF circuit <NUM> are measured with the control microprocessor <NUM> in the power converter device <NUM>. Therefore, the reference potential with respect to failure detection needs to be the ground of the control microprocessor <NUM>. The modification example is further provided with an AF isolated power source 50b for supplying power to the AF circuit, and a driving power source 50a for supplying power to the aforementioned isolated power source. A transformer is one example of the AF isolated power source 50b; the transformer converts the power from the driving power source 50a that enters the primary side, and outputs the converted power (power of the AF circuit <NUM>) to the secondary side. In the modification example is configured so that the control microprocessor <NUM> in the power converter device <NUM> measures the current la supplied to the AF isolated power source 50b. When an open-circuit fault or a short-circuit fault occurs in the AF circuit <NUM>, the state of the power varies for the power supplied from the AF isolated power source 50b compared to during a normal operation. The power state of the power supplied to the primary side of the AF isolated power source 50b from the driving power source 50a varies in accordance with the power state of the secondary side; therefore, the current la supplied to the aforementioned AF isolated power source 50b also varies. Even with this configuration, similarly to the first embodiment, the behavior of the AF isolated power source 50b that supplies the AF circuit <NUM> is monitored, and a failure or normal operation is diagnosed for the noise filter <NUM>, which includes the aforementioned AF circuit.

<FIG>, <FIG> are examples of graphs modeling a variation in a current (la) on the primary side and accompanying the failure of the active filter <NUM> in the modification example. <FIG> shows the variation in current when the injector unit <NUM> in the active filter <NUM> suffers an open-circuit fault; <FIG> shows the variation in current when the positive voltage (Vp) side of the operational amplifier 13a in the amplifier unit <NUM> suffers a short-circuit fault; and <FIG> shows the variation in current when the transistors (TR1, TR2) in the amplifier unit <NUM> suffer a short-circuit fault. In <FIG>, the vertical axis represents the current (mA) and the horizontal axis represents time (µsec); the solid line shown in the graph is the change in the current when there is a failure.

As indicated by the dotted arrow in <FIG>, the current (la) on the primary side fluctuates within a band range of a predetermined band (roughly ±<NUM> mA in the example illustrated) when the injector unit <NUM> is operating normally. Whereas, as indicated by the solid arrow, the amplitude of the current (Ia) on the primary side is roughly <NUM> mA and failure standby consumption current flows when open-circuit damage of the injector unit <NUM> occurs. The standby consumption current at fault is a current defined, for example by the rating of the AF isolated power source 50b; in <FIG> this is approximately <NUM> mA.

Similarly, the primary side current (la), which changes and varies near approximately <NUM> mA when the positive voltage (Vp) side of the operational amplifier 13a in the amplifier unit <NUM> suffers a short-circuit fault as indicated by the dotted arrow in <FIG>, increases and changes to near approximately <NUM> mA as indicated by the solid arrow. Moreover, the primary side current (Ia), which changes and varies on the order of mA when the transistors (TR1, TR2) in the amplifier unit <NUM> suffers a short-circuit fault as indicated by the dotted arrow in <FIG>, increases and changes to near approximately <NUM> mA as indicated by the solid arrow.

Accordingly, even when using the AF isolated power source 50b, it is possible to diagnose the failure or normal operation of a noise filter that includes an AF circuit <NUM> on the basis of the current (la) by detecting the variation in the state of the aforementioned current (la), which is supplied from the driving power source 50a to the primary side of the AF isolated power source 50b.

The microprocessor <NUM> in the power converter device <NUM> may be made to perform a failure diagnosis of the AF circuit <NUM> on the basis of the current Ia supplied from the driving power source 50a to the AF isolated power source 50b using the ground, which is a reference potential, of the host device. The control microprocessor <NUM> is capable of suspending the functions of a power converter circuit 3b when the state of the AF circuit <NUM> is diagnosed to have suffered a failure. The power source 3a illustrated in <FIG> corresponds to the power source 2a in the second embodiment, and the power converter circuit 3b corresponds to the power converter circuit 2b. The power converted by way of the power converter circuit 3b is supplied to a load 3c connected to the aforementioned power converter device.

The present embodiment has the advantage that when the AF circuit <NUM> in the noise filter <NUM> fails, a diagnosis can be performed on the basis on only the measurement value for the current Ia supplied from the driving power source 50a to the AF isolated power source 50b. The control microprocessor <NUM> in the power converter device <NUM> that includes the noise filter <NUM> in the configuration thereof makes it possible to reduce the number of input points for measurement with regard to diagnosis; therefore, the available input points can be assigned to other control inputs.

Claim 1:
A noise filter comprising:
an active filter circuit (<NUM>) connectable to:
i) a power-receiving terminal (20c, 20d) of a power line for:
a) an alternating-current power supplied to a power converter device (<NUM>) from an alternating-current power grid (<NUM>); or
b) a direct-current power source interconnected with the alternating-current power grid (<NUM>), or
ii) a power-receiving terminal (20c, 20d) of a power line for a direct-current power supplied from the direct-current power source;
the active filter circuit (<NUM>) being configured to reduce a harmonic component of a conduction noise propagating to the power line and to output the reduced harmonic component to the power line;
a controller (<NUM>) configured to monitor a variation in a state of an input power entering a power source module (<NUM>, <NUM>) for generating drive power for an active element constituting the active filter circuit (<NUM>), or a variation in a state of the drive power supplied from the power source module (<NUM>, <NUM>), and to diagnose an abnormality of a circuit operation for a circuit including the active element of the active filter circuit (<NUM>) therein on the basis of a variation in the state of the input power or the variation in the state of the drive power,
wherein the power source module i (<NUM>, <NUM>) includes a positive power source (P1) configured to generate a positive-side voltage and a negative power source (P2) configured to generate a negative-side voltage,
wherein the controller (<NUM>) is configured to monitor the variation in the state of the drive power supplied from the power source module on the basis of at least any one current of a first current flowing from the positive power source of the power source module to a reference potential, a second current flowing from the negative power source in the power source module to the reference potential, and a third current flowing from a connection point for connecting a negative-side electrode of the positive power source and a positive-side electrode of the negative power source to the reference potential.