JP2008005651A - Power supply device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply device which can reduce rotational variation even if an engine is driven in a low rotational region, can maintain high energy total efficiency by controlling the RPM of the engine in a wide electric load range, has high reliability and easy configuration, and is excellent in economical efficiency. <P>SOLUTION: The power supply device 1 includes the engine 2, a power generator 3, a converter 4, and an inverter 7. The converter 4 consists of a bridge circuit 5 formed of a plurality of switching elements S1-S6 controllable to be opened/closed; and a gate control unit 6 for opening and closing the switching elements S1-S6 more frequently than a frequency of a power generator side AC power and at variable time intervals, and executing boosting and regenerating control for shifting the bridge circuit 5 to a short circuit state and an output state. In the short circuit state, at least some output lines (35U and 35V) of the power generator 3 are short-circuited, and in the output state, the output lines (35U and 35V) are connected to the inverter 7. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an engine-driven distributed power supply, and more particularly to a power supply that operates a single cylinder gas engine in a wide output range.

  In recent years, the development of distributed power supply devices aimed at saving energy and reducing carbon dioxide emissions has been promoted, and it is considered that the introduction to power consumption areas such as offices and apartment buildings will rapidly progress in the future. The distributed power supply uses natural energy power sources such as solar cells and wind power generators, and fossil fuel type power sources such as gas turbine generators and gas engine generators. Generally, a power conversion unit is provided. In addition, by connecting with a commercial power system, power that is insufficient is received, or surplus power is transmitted in reverse power. The applicant of the present application discloses a small and highly economical system interconnection system that interconnects a plurality of distributed power sources in a system. The system of Patent Document 1 includes a plurality of DC-side converters that are connected to each of the distributed power sources in a one-to-one manner and output DC power, and an AC-side converter that converts DC power to AC power and links it to an AC system. And an output current on the AC side is determined by a DC voltage at a connection point where DC power is superimposed.

Patent Document 2 discloses an example of a gas engine power generation facility linked to a power system. The facility of Patent Document 2 controls the fuel of the gas engine in accordance with the power demand, controls the generator at a variable speed by an AC / DC converter, and follows the sudden change in load by the inertia energy of the gas engine generator. It is said that the rotational speed is adjusted with respect to the operating state and gas fuel component change. The gas engine generator is often used as a cogeneration apparatus that can effectively use not only electric energy but also heat energy, and is expected to be applied to general households.
JP 2003-250222 A JP-A-2005-245105

  By the way, when a gas engine generator is applied to a cogeneration apparatus that can be used even in ordinary homes, the rated power output is a small output of about 1 kW, and the engine is a single cylinder. However, in a single-cylinder gas engine, the deceleration action during the compression stroke and the acceleration action during the combustion process are output directly as rotation irregularities, so that a large vibration is generated particularly in the low rotation range, which is practical. There wasn't. In the case of an engine having a plurality of cylinders, the operation timings of the respective cylinders are shifted, so that the rotation unevenness cancels out and does not become a big problem, but it is difficult to apply in terms of economy. Even if the configuration of Patent Document 2 is applied, it was considered insufficient as a countermeasure for use in a low rotation range at a light load.

  As a countermeasure against this, it is conceivable to attach a flywheel and mechanically absorb the rotation unevenness by inertia energy, but the apparatus becomes large in weight and the cost also increases. In addition, there is an example in which constant speed rotation is performed in a high speed range of about 2000 rotations per minute without a flywheel, and surplus power is used as a heat source at a light load, but the energy unit price of the heat source is high. After all, it is preferable that the generated exhaust heat can be recovered while operating with high overall energy efficiency while controlling the power generation output following the electric load. Furthermore, it is necessary to have a simple configuration suitable for miniaturization and small output and sufficient reliability.

  The present invention has been made in view of the above background, and even when a single-cylinder engine is operated in a low speed range, there is little rotation unevenness, and the engine speed is controlled in a wide electric load range to maintain high overall energy efficiency. In addition, a power supply device that is highly reliable, simple, and economical is provided.

  The power supply device of the present invention includes an engine controlled to be variable in rotation speed, a generator that is driven by the engine and outputs power generation side AC power, a converter unit that converts the power generation side AC power to DC power, An inverter unit that converts DC power into load-side AC power and supplies the electrical load to the electrical load, wherein the converter unit includes a bridge circuit formed by a plurality of switching elements that can be controlled to open and close, A gate control unit that performs boost regeneration control that opens and closes the switching element more frequently than the frequency of the power generation side AC power and variably in time interval, and causes the bridge circuit to transition between a short circuit state and an output state, In the short-circuit state, at least a part of the output lines of the generator is short-circuited, and in the output state, the output lines are connected to the inverter unit. The engine may be a single cylinder gas engine for a cogeneration system. Furthermore, the gate control unit may control the duration of the short circuit state and the output state by a pulse width control method.

  An object of the present invention is to improve the practical performance as a distributed power supply device by reducing rotation unevenness in a low rotation range of a single cylinder gas engine and maintaining high overall energy efficiency in a wide electric load range, As a means, the main purpose is to apply boost regeneration control to the generator output. The present invention can be realized by improving the direct current side converter (converter unit) based on the inverter disclosed in Patent Document 1 disclosed by the present applicant.

  First, the configuration and control method of the power supply device of the present invention will be described.

  The engine used in the present invention operates at a different rotational speed, and a single cylinder gas engine for a cogeneration system is a good example. The engine output shaft can be coupled to the generator rotor and can rotate together to drive the generator. For example, a three-phase machine can be used as the generator, and there is no restriction such as the number of poles. The output terminal of the generator can be connected to the converter unit by an output line. The frequency of the power generation side AC power to be output is determined depending on the engine speed and is not particularly limited.

  The converter unit can be formed by a bridge circuit for AC / DC conversion and a gate control unit, and converts power generation side AC power output from the generator into DC power. The bridge circuit can be formed, for example, by connecting each of the three output lines from the generator to the positive terminal and the negative terminal via a switching element. As the total of six switching elements, ones having specifications that are controlled to be opened and closed by a gate signal from a gate control unit can be used. And direct-current power can be output by connecting a positive electrode terminal and a negative electrode terminal to an inverter part.

  The inverter unit includes, for example, a stabilization capacitor provided on the DC input side, a bridge circuit for orthogonal transformation using a switching element, a smoothing filter provided on the AC output side, and a gate control unit that controls opening and closing of the switching element. And can be formed. The load-side AC power output from the inverter unit can have a commercial frequency. For example, the load-side AC power may be supplied as a single-phase three-wire system to an electric load on the premises, or may be linked to a commercial power system. .

  Further, as a cogeneration apparatus that obtains not only an electric output but also a heat output, an exhaust heat recovery unit that recovers exhaust heat of the engine and supplies it to a heat load may be provided.

  In the present invention, boost regeneration control is performed in the converter unit. That is, the switching element is opened and closed frequently and variably in time intervals to change the bridge circuit between a short circuit state and an output state. For example, when the three-phase output of the generator is U-phase, V-phase, and W-phase, the U-phase output line and the V-phase output line are short-circuited in the phase range of 120 ° where the U-phase voltage is higher than the V-phase voltage Repeat the transition to the state and output state. In the short circuit state, the U-phase output line and the V-phase output line are short-circuited in the bridge circuit, and a short circuit including the U-phase winding and the V-phase winding is formed. In the output state, the U-phase output line is connected to the positive terminal and the V-phase output line is connected to the negative terminal.

  In the next 120 ° phase range, the same boost regeneration control is performed for the V phase and the W phase, and in the next 120 ° phase range, the same boost regeneration control is performed for the W phase and the U phase. Also, returning to the original state, the boost regeneration control for the U phase and the V phase is performed.

  The above-described boost regeneration control can be performed by, for example, a pulse width control type gate control unit. That is, a triangular wave output unit that outputs a triangular wave with a constant peak value and frequency to the gate control unit, a level output unit that adjusts and outputs a slice level according to the rotational speed of the generator, and a slice level is subtracted from the triangular wave A comparison unit and a gate output unit that outputs a gate signal to each switching element based on the subtracted result can be provided. By making the triangular wave frequency about two orders of magnitude greater than the output frequency of the generator-side AC power, the transition between the short circuit state and the output state can be repeated many times within the 120 ° phase range. In addition, the gate output unit outputs a gate signal that makes the bridge circuit short-circuited when the subtraction result is positive, and outputs a gate signal that makes the bridge circuit output when the result is negative. It can be configured.

  Next, the operation and action of the power supply device of the present invention configured and controlled as described above will be described.

When the engine is rotated and the generator is driven, a substantially sinusoidal AC side output power is output to the output line of the generator at a frequency corresponding to the rotational speed. On the other hand, in the bridge circuit of the converter unit, the short circuit state and the output state are repeatedly changed by the boost regeneration control. Here, in the short-circuit state, the AC side output power has no place to go, and a short-circuit current flows in the short-circuit circuit to form electric energy, most of which is temporarily in the form of electromagnetic energy EG in the inductance L of the generator winding. Accumulated in. The magnitude of the electromagnetic energy EG can be obtained by the following equation, assuming that the final value I of the short circuit current gradually increases with the short circuit state duration T.
EG = (1/2) ・ L ・ I ・ I

Next, when the bridge circuit transitions to the output state, a DC voltage V represented by a time derivative of the short-circuit current final value I is induced between the positive terminal and the negative terminal that are the outputs of the converter unit as shown in the following equation. Is done.
V = (− L) · (dI / dt)

  That is, at the moment when the short circuit is opened and connected to the inverter unit, the short circuit current final value I rapidly decreases and a large DC voltage V is generated. Due to the DC voltage V, the temporarily stored electromagnetic energy EG is output to the inverter unit in the form of DC power.

  In the present invention, the electrical energy output from the generator output terminal is equivalent to the conventional one, but the DC voltage V is made higher than the conventional rectified voltage by intermittently outputting the electrical energy to the inverter unit in the converter unit. be able to.

  Next, a mode capable of reducing the rotation unevenness in the engine low rotation range will be described.

  The gate control unit shortens the duration of the short-circuit state when the engine speed temporarily decreases, and extends the duration of the short-circuit state when the engine speed temporarily increases. It is preferable to do. For example, a rotation speed detection sensor can be provided on the output shaft of the engine to detect the rotation speed, and the gate control section can be configured to change the slice level of the level output section in response to increase or decrease of the engine rotation speed. In place of the rotation speed detection sensor, the rotation speed may be obtained based on a temporal change in the generator output voltage.

  In the above-described aspect, for example, when the rotation speed of the output shaft is temporarily reduced due to the force required to compress the fuel gas in the compression stroke of the engine, the slice level can be changed to be higher. When the slice level is changed to a higher value, the time zone in which the result when the slice level is subtracted from the triangular wave in the comparison unit is positive is shortened, and the duration T in which the bridge circuit is short-circuited is shortened. Then, the final value I at which the short-circuit current reaches and the DC voltage V obtained by differentiating the same decrease, and the electromagnetic energy EG output from the converter unit to the inverter unit decreases. If this is viewed from the engine side, the decrease in the rotational speed of the output shaft is mitigated corresponding to the decrease in the load torque.

  Conversely, when the output shaft is energized in the combustion process of the engine and the rotational speed temporarily increases, the slice level can be changed low. Then, conversely, the duration T of the short circuit state is extended, and the output electromagnetic energy EG increases. If this is seen from the engine side, it corresponds to an increase in the load torque, and an increase in the rotational speed of the output shaft is mitigated.

  As described above, according to the aspect in which the engine speed is detected and the duration T of the short-circuit state of the bridge circuit is adjusted according to the change, the generator is configured to reduce the temporary change in the engine speed. The output side electric circuit performs a compensation operation. This can also be called an electric flywheel function, and has a function equivalent to that of a mechanical flywheel that absorbs rotational unevenness by conventional inertial energy. In the present invention, the apparatus can be miniaturized without the need for a mechanical flywheel. Furthermore, since the bridge circuit of the converter unit is originally necessary for rectification, the present invention only requires an advanced gate control unit, and the economic efficiency is remarkably improved as compared with the cost of the flywheel.

  Next, the aspect provided with the protection function with respect to the overvoltage of the power supply device of this invention is demonstrated.

  The gate control unit can select a motor drive mode for controlling the bridge circuit to excite the generator according to a rotation phase and drive it as a motor, and a generator regeneration mode for performing the boost regeneration control. You may make it have. Further, it is preferable that the gate control unit selects the motor driving mode when a DC voltage of an output of the converter unit exceeds a specified value.

  In the present invention, the DC voltage V output from the converter unit is set higher than the conventional rectified voltage for operation. Furthermore, it cannot be said that there is no possibility that the DC voltage V will rise excessively due to a reduction in the electric power load in the commercial power system or the premises connected to the engine or a transient excessive output of the engine. The DC voltage V is the operating voltage of the converter unit and the inverter unit, and it is preferable to provide a protective function in order to safely use the stabilizing capacitor and the switching element in the circuit at a voltage lower than a specified value. However, providing a dedicated protection circuit is not preferable because it increases the number of parts, complicates the circuit, and increases the cost. Instead, countermeasures can be taken by providing the gate controller with a motor drive mode.

  In short, the motor drive mode is to reduce the DC voltage V by returning electrical energy to mechanical energy by temporarily driving the generator as a motor. In order to realize this, a monitoring function of the DC voltage V and a timing control function of detecting the rotational phase of the rotor of the generator and exciting the generator from the converter unit are required. These two functions can be performed by the gate controller.

  For example, when the DC voltage V is detected by a DC voltage detection circuit provided between the positive electrode terminal and the negative electrode terminal and compared with a specified value by the gate control unit, the generator regeneration mode is driven by the motor. You can switch to mode. Further, the rotation phase detection of the generator rotor can be shared by a rotation speed detection sensor provided on the output shaft of the engine, or a method of obtaining from a change with time of the generator output voltage. In either case, the bridge circuit is controlled based on the positional relationship between the rotor and the stator, and the generator is excited with the DC voltage V. Then, the generator operates as a motor, consuming electric energy and increasing the rotation speed. The amount of electric energy consumed is a decrease in the DC voltage V, and the electric circuit is protected.

  As a result, even if the DC voltage V rises excessively, the gate control unit automatically shifts to the motor drive mode, and the protection function for returning the electric energy to mechanical energy and lowering the DC voltage V is activated. In order to realize this protection function, it is not necessary to add new parts, and it is possible to provide a protection function against overvoltage of the converter unit and the inverter unit economically with a simple circuit configuration.

  Next, a mode in which an electrical failure of the generator can be detected will be described.

  Current detection means provided on the output line of the generator for detecting current, and failure determination means for determining an electrical failure of the generator based on the detected current information may be included. . As a current detection means, a current sensor can be provided on the output line of each phase of the generator. The current sensor preferably has a frequency characteristic that can sufficiently detect a transient current change due to frequent switching, and for example, a sensor using a Hall element can be applied. The current sensor may be installed in two phases to reduce the cost, and the third phase may be obtained by a current vector calculation.

  The failure determination means is means for determining the presence or absence of an electrical failure based on the current information of each phase. As the current information, in addition to the current waveform itself, the effective value, the peak value, and the like, it is also possible to use information obtained by appropriately processing the waveform. In addition, as a determination method, there are methods such as a size comparison with a specified value, a time change rate, and a balance check between phases. Thereby, it is possible to determine the disconnection failure of the generator winding, the partial short-circuit failure, or the failure in the output terminal or the output line. Further, a part of the converter unit failure can also be detected.

  Next, a comprehensive control method as the power supply device will be described.

  It is preferable that a comprehensive control unit that comprehensively controls the gate control unit and the engine is provided. The gate control unit controls the bridge circuit of the converter unit, and preferably includes a comprehensive control unit that comprehensively controls the entire power supply apparatus. The general control unit is located above the gate control unit of the converter unit and the inverter unit, and performs engine operation control, interconnection with an electric load, and control of the exhaust heat recovery unit in a cogeneration system. This is done in an organic manner.

  As a specific example, for example, consider the above-described excessive rise of the DC voltage V. At this time, the gate control unit can be configured to select the motor drive mode and report the situation to the general control unit. Then, the general control unit functions to suppress an increase in the engine and generator speeds by narrowing the fuel throttle of the engine and to return to normal operation in cooperation.

  When the electrical load is light, the general control unit controls the engine speed to decrease according to the electrical load, and the gate control unit appropriately maintains the DC voltage V of the converter unit output by the boost regeneration control corresponding to the generator output. be able to. Therefore, the engine can be efficiently operated at a high load factor by lowering the rotational speed, not at a low load factor with a constant rotational speed. Furthermore, high power generation efficiency can be maintained in a wide electric load range, and high total energy efficiency can be maintained in the cogeneration apparatus.

  According to the power supply device that performs the boost regeneration control by the converter unit of the present invention, the DC voltage of the output of the converter unit can be made higher than the conventional rectified voltage, so that the power generation efficiency can be improved. Further, according to the aspect of controlling the duration of the short circuit state of the bridge circuit of the converter unit according to the change of the engine speed, the rotation unevenness of the single cylinder engine in the low rotation range can be absorbed on the electric circuit side. The apparatus can be miniaturized without the need for a mechanical flywheel, the electric circuit is simple, and the economy is greatly improved.

  Furthermore, by having a motor drive mode in which the generator is temporarily driven as a motor, a protection function against an overvoltage of the electric circuit can be provided with a simple circuit configuration. In the aspect having the current detection means and the failure determination means, it is possible to detect an electrical failure of the generator.

  In the aspect provided with the integrated control unit, when the electrical load is light, the engine speed can be lowered to efficiently operate at a high load factor, and high power generation efficiency can be maintained over a wide electrical load range. The device can maintain a high overall energy efficiency.

  The best mode for carrying out the present invention will be described with reference to FIGS. FIG. 1 is a diagram illustrating a power supply device 1 according to an embodiment of the present invention. A broken line in FIG. 1 indicates a path of a gate signal used for control. The power supply device 1 according to the embodiment includes a single cylinder gas engine 2, a generator 3, a converter unit 4, and an inverter unit 7. Output terminals 79X and 79Y of the inverter unit 7 are connected to a commercial power system 9, and the system The power is supplied to the electrical load in 9.

  The output shaft 21 of the single cylinder engine 2 is coaxially coupled to the rotor 31 of the generator 3 so as to rotate integrally. The generator 3 is a three-phase machine and is formed by a rotor 31 and a stator 32. The stator 32 is provided with U-phase, V-phase, and W-phase windings 33U, 33V, and 33W in a star connection. Each phase output terminal 34U, 34V, 34W from which each phase winding 33U, 33V, 33W outputs the power generation side AC power is connected to each of the three-phase bridge circuit 5 of the converter unit 4 by each phase output line 35U, 35V, 35W. It is connected to the phase intermediate points 51U, 51V, 51W.

  The converter unit 4 is formed by a three-phase bridge circuit 5 and a gate control unit 6. The three-phase bridge circuit 5 receives power generation side AC power supplied to the phase intermediate points 51U, 51V, 51W, and outputs DC power with a DC voltage V to the positive terminal 53P and the negative terminal 53N. A circuit is constituted by the switching elements S1 to S6. That is, the U-phase intermediate point 51U and the positive electrode terminal 53P are connected via the switching element S1. Similarly, the V-phase intermediate point 51V and the positive terminal 53P are connected via the switching element S2, and the W-phase intermediate point 51W and the positive terminal 53P are connected via the switching element S3. Further, the U-phase intermediate point 51U and the negative electrode terminal 53N are connected via the switching element S4, the V-phase intermediate point 51V and the negative electrode terminal 53N are connected via the switching element S5, and the W-phase intermediate point 51W and the negative electrode terminal 53N are connected to the switching element S6. Are connected to each other. Each of the switching elements S1 to S6 is controlled to be opened and closed independently by a gate signal from the gate control unit 6, and is configured to be able to take a conduction state and a cutoff state.

  The inverter unit 7 includes a stabilization capacitor 71, a single-phase bridge circuit 72, a smoothing filter 75, and an inverter gate control unit 77. The inverter unit 7 receives DC power output from the converter unit 4 to the positive terminal 53P and the negative terminal 53N, and outputs single-phase load side AC power to the two output terminals 79X and 79Y of single-phase AC. is there. The stabilizing capacitor 71 is provided between the positive terminal 53P and the negative terminal 53N, and has a function of stabilizing by removing a ripple included in the DC voltage V output from the converter unit 4.

  The single-phase bridge circuit 72 is configured by four switching elements SA to SD. That is, the positive terminal 53P and the intermediate terminal 73X are connected via the switching element SA. Similarly, the positive terminal 53P and the intermediate terminal 73Y are connected via the switching element SB, and the negative terminal 53N and the intermediate terminal 73X are connected via the switching element SC. The negative terminal 53N and the intermediate terminal 73Y are connected to each other via the switching element SD. Each of the switching elements SA to SD is controlled to be opened and closed independently by a gate signal from the inverter gate control unit 77, and is configured to be able to take a conduction state and a cutoff state.

  The smoothing filter 75 is provided between the intermediate terminals 73X and 73Y and the output terminals 79X and 79Y. The smoothing filter 75 has a function of smoothing a rectangular wave-shaped intermediate AC output on the intermediate terminals 73X and 73Y side and outputting a sine wave-shaped load-side AC power from the output terminals 79X and 79Y.

  Next, a method and an operation of boost regeneration control by the gate control unit 6 of the power supply device 1 configured as described above will be described. 2A and 2B are diagrams for explaining a method of boost regeneration control, where FIG. 2A is a diagram showing a short-circuit state, FIG. 2B is a diagram showing a moment when a short-circuit state is changed to an output state, and FIG. 2C is an output state. FIG.

Consider a state in which a voltage V1 higher than that of the V-phase output terminal 34V is induced at the U-phase output terminal 34U of the generator. At this time, the gate control unit 6 performs control so as to repeat transition of the U phase and the V phase to the short circuit state and the output state. That is, as shown in FIG. 2A, in the short-circuit state, the two switching elements S1 and S2 are in a conductive state, the three-phase bridge circuit 5 is in a short-circuit state, and the U-phase output line 35U and the V-phase output line A short circuit is formed by 35V, V-phase winding 33V and U-phase winding 33U. Then, with respect to the voltage V1 in the short circuit, the inductance L1 of the V-phase winding 33V and the U-phase winding 33U brakes energization, and a short-circuit current that increases with the duration flows and becomes the final value I1. Eventually, the electrical energy output from the generator within the duration of the short circuit state is stored in the short circuit as electromagnetic energy EG1 expressed by the following equation.
EG1 = (1/2) · L1 · I1 · I1

Next, as shown in FIG. 2B, it is the moment of transition from the short circuit state to the output state. At this moment, the gate signal of the gate control unit 6 causes the switching element S2 to change from the conductive state to the cut-off state, the short circuit is opened, and the short-circuit current final value I1 is forcibly cut off. A large voltage V2 expressed by the following equation is induced between the point 51V.
V2 = (− L) · (dI1 / dt)

  At the next moment, as shown in FIG. 2C, the switching element S5 is turned on by the gate signal of the gate control unit 6, and the bridge circuit 5 is in the output state. That is, an output circuit is formed which enters the inverter unit 7 from the U-phase intermediate point 51U via the positive terminal 53P and returns from the negative terminal 53N to the V-phase intermediate point 51V. Then, the voltage V2 moves between the positive terminal 53P and the negative terminal 53N, and a direct current I2 corresponding to the accumulated electromagnetic energy EG1 is output.

  Next, when the switching element S1 is turned off and the switching S4 is turned on, a short circuit is formed by the two switching elements S4 and S5, and the electromagnetic energy EG is accumulated again. Next, when the switching element S4 is turned off and the switching S1 is turned on, an output circuit is formed by the two switching elements S1 and S5, and the direct current I2 corresponding to the electromagnetic energy EG is output again. This is repeated in a phase range of 120 ° in which a voltage V1 higher than that of the V-phase output terminal 39V is induced at the U-phase output terminal 39U. Then, the same control is performed for the V phase and the W phase in the next 120 ° phase range, and for the W phase and the U phase in the next 120 ° phase range, and the following is repeated.

  Here, the gate control unit 5 can control and adjust the duration of the short circuit state by shifting the timing of the gate signal. That is, by extending the short-circuit state, the short-circuit current final value I1, the electromagnetic energy EG1, and the voltage V2 can be increased. This means that when viewed from the engine 2 side, the load torque increases instantaneously. Conversely, by shortening the short circuit state, an effect equivalent to instantaneously reducing the load torque occurs. Therefore, the rotation unevenness can be reduced by detecting the rotation speed change of the engine 2 and controlling the duration of the short-circuit state so as to compensate for the change.

  Next, a detailed block configuration and operation of the power supply device 1 according to the embodiment will be described with reference to FIG. A broken line in FIG. 3 indicates a flow of a gate signal or a signal used for control. In FIG. 3, in addition to the configuration of FIG. 1, current sensors 37U and 37W are provided on the U-phase output line 35U and the W-phase output line, respectively. In addition, a voltage dividing circuit 55 is provided in the converter unit 4 to receive the voltages of the phase intermediate points 51U, 51V, 51W. Between the positive terminal 53P and the negative terminal 53N, two resistance elements R1 having the same resistance value are inserted in series, and similarly, two capacitance elements C1 having the same capacity are inserted in series, and their intermediate points are coupled. Thus, the reference potential E of the voltage dividing circuit is set. The voltage dividing circuit 55 detects the voltage of each phase output terminal 34U, 34V, 34W of the generator 3 via each phase intermediate point 51U, 51V, 51W.

  In addition, a DC voltage detection circuit 53D that detects a DC voltage V between the positive terminal 53P and the negative terminal 53N that is an output of the converter unit 4 is provided in the inverter unit 7. An instrument transformer 73P is provided between the intermediate terminal 73Y and the filter 75. Further, between the smoothing filter 75 of the inverter unit 7 and the output terminals 79X and 79Y, an instrument transformer 78P for detecting voltage information of the load side AC power and the inverter unit 7 are disconnected from the commercial power system 9. The relay 78R is provided.

  The gate control unit 6 of the converter unit 4 and the inverter gate control unit 77 of the inverter unit 7 are configured on a common electronic circuit board 61 and are operated by a common CPU 68. The CPU 68 exchanges information with a general control unit (not shown) and performs control in cooperation. The CPU 68 takes in the information of the DC voltage detection circuit 53D and controls the relay 78R.

  Next, functional blocks in the gate control unit 6 of the converter unit 4 will be described in detail. The current confirmation unit 601 in the gate control unit 6 takes in the detection signals of the two current sensors 37U and 37W, and confirms whether or not it matches the predetermined instruction current value transmitted from the general control unit to the CPU 68. . At this time, the V-phase current that is not directly detected is also obtained by the current vector calculation.

  On the other hand, the sensorless position detection unit 611 takes in the detection signal of the voltage dividing circuit 55. Since this detection signal corresponds to the three-phase output voltage of the generator 3, the rotational speed and phase of the rotor 31 can be indirectly detected from the rate of change. Further, an oscillation circuit 612 is provided in the gate control unit 6, and the oscillation frequency is controlled by the CPU 68. That is, the oscillation frequency of the oscillation circuit 612 is controlled so as to coincide with the rotational speed commanded to the engine 2 by the general control unit. The phase comparison unit 613 compares signals from the sensorless position detection unit 611 and the oscillation circuit 612 to confirm whether the rotor 31 is actually rotating at the target rotation speed. The F / V unit 614 converts the rotational speed signal of the sensorless position detection unit 611 into a voltage amount, and the dF / dt unit 615 obtains the rotational speed change rate equivalent amount DF by a voltage amount differentiation circuit. .

  The regeneration / drive amount instruction unit 621 is a part that switches between the generator regeneration mode and the motor drive mode and outputs a slice level SL of the pulse width control method with reference to various signals. The regeneration / drive amount instruction unit 621 receives the output signal of the DC voltage detection circuit 53 and switches to the motor drive mode when the magnitude of the DC voltage V output from the converter unit 4 exceeds a specified value. The output is controlled to be turned on / off by an output command from the general control unit.

  The regenerative / drive amount instruction unit 621 takes in the change rate equivalent amount DF of the rotation speed from the dF / dt unit 615 and controls to change the slice level SL. Specifically, the slice level SL is increased when the change rate equivalent amount DF takes a negative value, that is, when the rotational speed of the engine 2 is decreasing. Then, when the change rate equivalent amount DF takes a positive value, the slice level SL is decreased, and when the change rate equivalent amount DF is 0, the slice level SL is maintained at present.

  The triangular wave generation circuit 622 automatically generates and outputs a triangular wave TW having a frequency that is about two orders of magnitude higher than the engine two revolutions. The comparator 623 subtracts the slice level SL output from the regenerative / drive amount instruction unit 621 from the triangular wave TW output from the triangular wave generation circuit 622, and determines whether it is positive or negative. The timing creation unit 624 creates timing for transitioning between the short circuit state and the output state of the bridge circuit 5 based on the positive / negative discrimination result of the comparator 623. The gate output unit 625 sends a gate signal to each of the switching elements S <b> 1 to S <b> 6 forming the bridge circuit 5 at a timing instructed by the timing generation unit 624.

  Here, a pulse width control method from the regeneration / drive amount instruction unit 621 to the gate output unit 625 will be described with reference to FIG. FIG. 4 is a diagram schematically illustrating the pulse width control method of the converter unit 4, where the horizontal axis indicates a common time axis t and the vertical axis indicates the output of each unit. As shown in FIG. 4, the output waveform of the comparator 623 is an intermittent waveform obtained by subtracting the slice level SL from the triangular wave TW. The timing creation unit 624 sets the positive time zone in the intermittent waveform as the duration T1 of the short circuit state. And the gate output part 625 sends out the gate signal which controls a conduction | electrical_connection state and interruption | blocking state with respect to each switching element S1-S6. In FIG. 4, the hatched time zone is in a conductive state.

  By this pulse width control, the bridge circuit 5 operates as described in FIG. That is, when the rotational speed of the engine 2 temporarily decreases, the regeneration / drive amount instruction unit 621 increases the slice level SL to SL2, and the duration T1 of the short-circuit state is shortened to T2 as shown in FIG. The Correspondingly, the gate signal of the gate output section changes and the stored energy EG decreases. When the slice level SL decreases, the reverse control is performed to increase the stored energy EG.

  In the motor drive mode, the phase windings 33U, 33V, and 33W are excited by the DC voltage V based on the phase of the rotor 31 detected by the sensorless position detector 611. Thereby, the rotor 31 can be urged by electric energy, and the rotational speed of the engine 2 output shaft 21 is increased.

  Next, the inverter gate control unit 77 will be briefly described. The output signal of the instrument transformer 78P is taken into the sine wave generation circuit 773 through the PLL unit (Phase-Locked-Loop unit) 772 from the synchronization control unit 771 in the inverter gate control unit 77. Thereby, the sine wave generating circuit 773 outputs a sine wave SIN having the same frequency and the same phase as the commercial power system 9. The amplitude SW of the sine wave SIN is adjusted by the amplifier 774 and the waveform correction unit 775 and is input to the comparator 776. On the other hand, the triangular wave generation circuit 777 in the inverter gate control unit 77 automatically generates a triangular wave TW 2 having a frequency higher than the commercial frequency and outputs the triangular wave TW 2 to the comparator 776.

  In the comparator 776, the triangular wave TW2 is subtracted from the sine wave SIN to obtain a positive time zone and set it as an output time zone, which is sent to the inverter gate controller 778. The inverter gate controller 778 sends gate signals to the four switching elements SA to SD so that the single-phase bridge circuit 72 operates only during the output time period. Although the control method of the inverter unit 7 is different from the converter unit 4, it is a kind of pulse width control and will be described with reference to FIG. 5.

  FIG. 5 is a diagram schematically illustrating the pulse width control method of the inverter unit 7, where the horizontal axis indicates a common time axis t and the vertical axis indicates the output of each unit. As shown in FIG. 5, the gate signal is output only in a time zone in which the sine wave SIN is higher than the triangular wave TW2. In the example of FIG. 5, the switching elements SA and SD are made conductive in three times in the first half cycle, and the switching elements SB and SC are made conductive in the next half cycle in three times. In addition, the duration of the conduction state is long near the peak value of the original sine wave. As a result, as shown in FIG. 5, the intermediate voltage VX of the output of the single-phase bridge circuit 72 induced between the intermediate terminals 73X and 73Y has a waveform in which three positive and negative rectangular waves are alternately generated. FIG. 5 is a schematic explanation, and since the frequency of the triangular wave TW2 is actually higher, more than three rectangular waves are output.

  When the intermediate voltage VX is insufficient, this is detected by the instrument transformer 73P, and the waveform correction unit 775 is controlled to increase the amplitude SW of the sine wave SIN. As a result, the positive output time zone is increased by subtracting the triangular wave TW2, and the number and duration of the gate signals can be increased.

  In the pulse width control method of the inverter unit 7, a plurality of rectangular waves can be output from the single-phase bridge circuit 72 per cycle. Therefore, compared to a simple method that outputs one positive and negative rectangular wave for each cycle, the design and manufacture of the filter 75 is facilitated, and the storm wave component is reduced when linked to the commercial power system 9. be able to.

  Next, a circuit configuration for detecting an electrical failure of the generator 3 will be described with reference to FIG. FIG. 6 is a diagram for explaining a circuit for detecting an electrical failure of the generator 3 using the two current sensors 37U and 37W and the CPU 68 shown in FIG. 3, and FIG. (B) shows an example of a detected current waveform. As shown in FIG. 6A, the circuit is configured by connecting a V-phase current calculation unit 81, a selection switching unit 82, and a filter unit 83 in this order.

  The outputs of the current sensors 37U and 37W provided on the output lines 35U and 35W of the generator 3 are first input to the V-phase current calculation unit 81. Then, the U-phase current IU and the W-phase current IW are output as they are, and addition and sign inversion are performed by the operational amplifier 811 to generate and output a V-phase current IV. Next, the phase currents IU, IV, and IW are sequentially switched by the switching control unit 821 provided in the selection switching unit 82 and are output in a time-sharing manner. The time-divided output is smoothed by the filter unit 83 and input to the A / D input unit 681 of the CPU 68. In the CPU 68, the input is A / D converted and the respective phase smoothing currents IUe, IVe, and IWe are reproduced.

  FIG. 6B shows an example of the U-phase current waveform IU before passing through the filter unit 83 and the U-phase smoothed current waveform IUe after passing through. As shown in the figure, the smooth current waveform allows the CPU 68 to reliably determine an electrical failure, for example, a one-phase disconnection, which is an effect of the filter unit 83. It should be noted that various methods can be applied to the failure determination, and of course, a current sensor may be provided in the V phase.

It is a figure explaining the power supply device of the Example of this invention. FIG. 2 is a diagram for explaining a method for boost regeneration control in the embodiment of FIG. 1, (A) is a diagram showing a short circuit state, (B) is a diagram showing a moment when the short circuit state transitions to the output state, and (C) is an output signal. It is a figure which shows a state. It is a figure explaining the detailed block structure in the Example of FIG. In the Example of FIG. 1, it is a figure which illustrates typically the pulse width control system of a converter part. In the Example of FIG. 1, it is a figure which illustrates typically the pulse width control system of an inverter part. It is a figure explaining the circuit which detects the electrical failure of a generator using two current sensors and CPU which are shown by FIG. 3, (A) is a circuit structure, (B) is the detected electric current. An example of a waveform is shown.

Explanation of symbols

1: Power supply device 2: Single cylinder gas engine 21: Output shaft 3: Generator 31: Rotor 32: Stator
33U, 33V, 33W: U phase, V phase, W phase winding
35U, 35V, 35W: U phase, V phase, W phase output line
37U, 37W: U-phase, W-phase current sensor (current detection means)
4: Converter section 5: Three-phase bridge circuit
53P, 53N: Positive terminal, negative terminal (converter part output and inverter part input)
6: Gate control unit 68: CPU (also serves as failure determination means)
69: Electronic circuit board
625: Gate output unit 7: Inverter unit 71: Stabilizing capacitor
72: Single-phase bridge circuit
75: Filter for smoothing
77: Inverter gate control unit 81: V-phase current calculation unit 82: Selection switching unit 83: Filter unit 9: Commercial power system S1 to S6: Switching element SA to SD: Switching element V: DC voltage VX: Intermediate voltage of inverter unit SL: Slice level TW, TW2: Triangular wave SIN: Sine wave

Claims (8)

An engine controlled to be variable in rotation speed, a generator driven by the engine to output power generation side AC power, a converter unit for converting the power generation side AC power to DC power, and the DC power as load side AC power An inverter unit for converting to an electric load and supplying the electric load,
The converter unit includes a bridge circuit formed by a plurality of switching elements that can be controlled to open and close, and the switching circuit is opened and closed more frequently than the frequency of the power generation side AC power, and the bridge circuit is short-circuited. And a gate control unit that performs step-up regeneration control for transitioning between a state and an output state. In the short-circuit state, at least a part of the output lines of the generator is short-circuited, and in the output state, the output line is connected to the inverter unit. Connected to the
A power supply device characterized by that.   The power supply device according to claim 1, wherein the engine is a single-cylinder gas engine for a cogeneration system.   The power supply device according to claim 1, wherein the gate control unit controls a duration time of the short circuit state and the output state by a pulse width control method.   The gate control unit shortens the duration of the short-circuit state when the engine speed temporarily decreases, and extends the duration of the short-circuit state when the engine speed temporarily increases. The power supply device according to claim 1.   The gate control unit can select a motor drive mode for controlling the bridge circuit to excite the generator according to a rotation phase and drive it as a motor, and a generator regeneration mode for performing the boost regeneration control. The power supply device according to claim 1.   The power supply device according to claim 5, wherein the gate control unit selects the motor drive mode when a DC voltage of an output of the converter unit exceeds a specified value.   7. A current detection unit provided on the output line of the generator for detecting a current, and a failure determination unit for determining an electrical failure of the generator based on the detected current information. The power supply device described in 1.   The power supply device according to claim 1, further comprising a comprehensive control unit that comprehensively controls the gate control unit and the engine.

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