JP4680102B2 - Power converter - Google Patents

Power converter Download PDF

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JP4680102B2
JP4680102B2 JP2006061155A JP2006061155A JP4680102B2 JP 4680102 B2 JP4680102 B2 JP 4680102B2 JP 2006061155 A JP2006061155 A JP 2006061155A JP 2006061155 A JP2006061155 A JP 2006061155A JP 4680102 B2 JP4680102 B2 JP 4680102B2
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power
generator
output
voltage
current
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JP2007244068A (en
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毅 古賀
正英 川村
和繁 杉本
光司 松本
裕司 進藤
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川崎重工業株式会社
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Description

  The present invention relates to a power conversion device used for a microgrid (small power distribution network) or the like.

  In recent years, there has been an increasing interest in power supply systems that use distributed power sources such as gas engine generators and fuel cells. For example, in a specific area, a system called a microgrid has been proposed that uses the above-described power generation device called a distributed power source and supplies power from the power generation device to a plurality of loads. In such a microgrid, in addition to the above-described power generation device, a power storage device including a secondary battery is connected to the internal power system in order to compensate for fluctuations in generated power and load fluctuations of the power generation device. Are often configured. Moreover, about the microgrid, the form operate | moved independently with a commercial power system and the form operate | moved in connection with a commercial power system are considered. In a system using such a distributed power source, it is important to realize a stable power supply.

  For example, Patent Documents 1, 2, and 3 disclose a configuration that includes a power generation device and a power storage device that are linked to a commercial power system.

  Furthermore, Patent Document 2 discloses a technique for suppressing power oscillation and power fluctuation of an internal power system at the time of transition to independent operation by detecting effective power of a load and controlling charge / discharge of a power storage device. Has been.

  Patent Document 3 discloses a technique for detecting a generator output, load power, and the like in a private power generation facility, and controlling the generator output and the output from the secondary battery according to the power demand of the load. Yes.

  Patent Document 4 discloses a reactive power compensator that compensates reactive power generated by a load connected to an electric power system with a voltage-type self-excited inverter, and detects the load current, thereby converting it into a three-phase unbalanced component of the load current. A technique for suppressing the voltage fluctuation of the electric power system generated due to this is disclosed.

Further, Patent Document 5 describes an active filter having a configuration in which a plurality of filters are combined and selectively functioned by a switch to detect a load current, a harmonic current of the load current, a three-phase unbalanced component, and the like. A technique for compensating for the above is disclosed.
JP 2004-064810 A JP 2004-147445 A JP 2001-112176 A JP-A-7-67255 JP-A-8-65892

  The power storage device used for the microgrid includes a power storage unit such as a secondary battery, and a power conversion device using a current-type inverter that charges and discharges the power of the power storage unit with respect to the power system. However, in general power converters, current-type inverters are controlled to output in accordance with a constant command value regardless of the state of the power system. There is a problem that the burden on the power generation device increases.

  Patent Document 1 does not disclose a technique for solving the above problems.

  Although it is considered that the above-described problems can be solved to some extent by using the techniques of Patent Documents 2 and 3, it is necessary to detect the effective power of the load and the like, and a detection means for that purpose is required.

  Further, it is considered that the above-described problems can be solved to some extent by using the techniques of Patent Documents 4 and 5. However, Patent Documents 4 and 5 disclose a dedicated device for solving a specific problem. It is necessary to install the device separately. Also in the apparatus, means for detecting the load current is necessary.

  The present invention has been made to solve the above-described problems, and is used in an electric power storage device, and bears a harmonic component and an unbalanced portion of the load current without separately providing a detection means such as a load current. An object of the present invention is to provide a power converter that can perform the above-described process.

In order to solve the above-described problems, a power converter according to the present invention converts DC power of a secondary battery into AC power, outputs the AC power to an output line connected to the AC circuit, and outputs the output line from the AC circuit. A power conversion unit capable of converting AC power input via DC into DC power and storing it in the secondary battery, and a control unit for controlling the power conversion unit. Assuming that a virtual power generation device that is a power generation device is provided in advance instead of the power conversion unit and the secondary battery, and an output line of the power conversion unit is an output line of the virtual power generation device, Based on the voltage of the output line of the power conversion unit, a current value to be output by the virtual power generation device is calculated, a virtual power generation device model unit that determines the calculated current value as a current command value, and a current corresponding to the current command value Current to output to the output line And a power converter control unit for controlling the power converting unit by fed back control, the virtual power generating device model unit, the virtual power plant, the AVR controlling the generator, a field voltage of the generator, Assuming that the motor is configured to include a prime mover that drives the generator and a governor that controls the amount of fuel supplied to the prime mover, the input / output relationships of the assumed generator, AVR, prime mover, and governor are as follows: The generator model, the AVR model, the prime mover model, and the governor model are defined. The AVR model includes a voltage of the output line of the power converter, a reactive power command value given from the outside, and a voltage command value of the output line. And the governor model is configured to calculate an angular velocity of the generator calculated by the prime mover model and an externally applied value. The fuel supply amount to the prime mover is calculated based on at least the active power command value of the generated active power command value and the angular velocity command value of the generator, and the prime mover model is the governor model. The angular velocity and the phase angle of the generator are calculated based on the fuel supply amount calculated to the prime mover and the electric torque of the generator calculated by the generator model, The machine model includes the output line voltage of the power converter, the field voltage of the generator calculated by the AVR model, and the angular velocity and phase angle of the generator calculated by the prime mover model. Based on this, the straight axis current value and the horizontal axis current value output from the generator are calculated, and the calculated straight axis current value and horizontal axis current value are determined as the current command value.

  Here, when the current value (current command value) to be output by the virtual power generation device calculated by the virtual power generation device model unit is a negative current value, the virtual power generation device is in the operation area as an electric motor and is input. The secondary battery is charged with the electric power.

  According to this configuration, the current value to be output by the virtual power generator is calculated based on the voltage of the output line connected to the AC circuit, in other words, based on the voltage of the AC circuit, and the current command value is supported. Since the power conversion unit is controlled so as to output the current to be output, the current output from the power conversion unit is controlled in the same manner as the current output from the normal power generator. Therefore, even if a load and a power generation device are connected to the AC circuit, and the load current contains a harmonic component or an unbalanced state occurs, the power conversion device, as a result, has the same harmonics as the power generation device. Since the wave current and the unbalanced current are output, the harmonic component and the unbalanced component can be borne together with the power generator, and the burden on the power generator can be reduced. Further, in this case, a means for detecting the voltage and current of the output line of the power conversion unit is necessary, but such a detection means is provided as an internal component of the power converter and is connected to a load connected to the AC circuit. It is not necessary to separately provide the current and power detection means.

  According to this configuration, the output of the power conversion device can be controlled in the same manner as the output of the power generation device having the generator and the prime mover, and the AVR and governor that controls them.

  In addition, when the AC circuit to which the output line of the power conversion unit of the power conversion device of the present invention is connected is connected to the circuit of the large-scale power system through the circuit breaker, the circuit breaker is closed and the AC circuit is closed. Even when the electric circuit is connected to the electric circuit of the large-scale power system (connected state), the circuit breaker is opened and the AC circuit is disconnected from the electric circuit of the large-scale power system (connected) Even in the cut-off state, in the power conversion device of the present invention, the current output from the power conversion unit is controlled in the same way as the current output from the normal power generation device. It is possible to stabilize the power quality of the own system (AC circuit). Further, even when transitioning from the connected state to the disconnected state, it is possible to stabilize the power quality of the own system in a transient manner in cooperation with a normal power generator.

  The present invention has the above-described configuration, and in the power conversion device used in the power storage device, the load current harmonic component and the unbalanced component are borne without separately providing a load current detection means. There is an effect that can be. In addition, it can be handled without switching control methods, etc., even when connected to a large-scale power system, in the case of a connection disconnection state, or when shifting from the connection connection state to the connection disconnection state. There is an effect. Further, for example, by setting each command value input to the AVR model and the governor model and the internal setting values of the AVR model, the governor model and the prime mover model to be adjustable, they are adjusted based on the knowledge of the power generator. There is an effect that it becomes possible.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a circuit diagram showing a configuration example of a microgrid (small-scale power distribution network) using the power conversion device according to the embodiment of the present invention.

  In general, a microgrid is configured by connecting a power generation device including a distributed power source such as a gas engine generator or a fuel cell, a load, and a power storage device to a distribution line of the microgrid. Further, the load fluctuates due to expansion or replacement. In FIG. 1, a gas engine generator 10, a load 11, and a power storage device PS are connected to a distribution grid (AC circuit) 9 of a microgrid. In addition, the microgrid is provided with a microgrid control device 14 that manages and manages the microgrid in the area of the microgrid based on the setting of the operator operating the microgrid. Each of the power storage device PS, the gas engine generator 10 and the load 11 connected to the distribution line 9 of the microgrid is provided with a monitoring unit (measuring device for power etc .: not shown) for monitoring each situation. These monitoring units and the microgrid control device 14 can transmit and receive via a signal line (not shown), for example. The microgrid control device 14 receives the monitoring status (measured value) from each monitoring unit, and commands the output power target value and the like to the power storage device PS and the gas engine generator 10 according to the monitoring status. Send value. These command values are set (programmed) by the operator so as to be determined according to the monitoring status of each monitoring unit.

  In addition, the microgrid is operated independently of the commercial power system (large-scale power system) without being connected to the commercial power system (hereinafter referred to as “independent form”) and connected to the commercial power system. There is a form (hereinafter referred to as “interconnected form”). In the case of the interconnected form, the microgrid distribution line 9 is connected via a circuit breaker 15 to a distribution line 16 that is an electric path of a commercial power system. Even in the case of this interconnected form, when an abnormality or the like occurs in the commercial power system, the circuit breaker 15 is opened and the state is the same as in the independent form. The opening / closing of the circuit breaker 15 is controlled by, for example, a commercial power system control system (not shown). In the following, it is assumed that the system is operated in an independent form unless it is referred to as an interconnected form.

  The power storage device PS is connected to a distribution line 9 of a microgrid via a transformer 8. The power conversion device PC of the present embodiment constitutes a power storage device PS together with the secondary battery 1 such as a nickel metal hydride battery. Here, the power conversion device PC is output from the voltage sensor (voltage measurement PT) 2 that detects the voltage Vs of the secondary battery 1, the power conversion unit 3 that converts direct current into alternating current, and the power conversion unit 3. A current sensor (PT for current measurement) 4 that detects output currents ia, ib, ic of each of the three phases (a phase, b phase, c phase), an output reactor 5, and each phase (a phase, b phase) , C-phase) output voltage va, vb, vc, voltage sensor (voltage measurement PT) 6, filter capacitor 7, and control unit 12.

  The power conversion unit 3 includes six switching elements 3a to 3f each including a diode connected in antiparallel. The power conversion unit 3 is formed of a semiconductor element, and IGBTs are used for the switching elements 3a to 3f, for example. The control unit 12 outputs a control signal group Sc composed of control signals input to the control terminals (for example, the gate terminals of the IGBTs) of the respective switching elements 3a to 3f to the power conversion unit 3, and each switching element 3a to 3f is output. By performing the on / off operation, the power conversion unit 3 functions as an inverter, the DC power of the secondary battery 1 is converted into AC power and output, and the power conversion unit 3 functions as a rectifier. AC power input from 9 through the transformer 8 or the like is converted to DC power and stored in the secondary battery 1.

  The control unit 12 includes a virtual power generation device model unit 13 and a control signal generation unit (power conversion control unit) 20 that controls the power conversion unit 3 by current feedback control. The virtual power generation device model unit 13 assumes that a power generation device (virtual power generation device) is connected to the microgrid distribution line 9 in advance instead of the power storage device PS, and the assumed virtual power generation device should output. The current value is calculated, and the current value is given to the control signal generation unit 20 as a current command value (Id-ref, Iq-ref). The control signal generator 20 controls the switching elements 3a to 3f of the power converter 3 so that a current corresponding to the current command value (Id-ref, Iq-ref) is output from the power converter 3. Control signal group Sc is generated and output. That is, the control unit 12 controls the power conversion unit 3 so that the output current of the power conversion unit 3 is the same as the output current (calculated value) of the virtual power generator.

  The virtual power generator model unit 13 controls the generator, the AVR that controls the field voltage of the generator, the engine that drives the generator (the prime mover), and the fuel flow rate that is supplied to the engine. A generator model 30, an AVR model 70, and an engine model that define input / output relationships of the assumed generator, AVR (automatic voltage regulator), engine, and governor. (Motor model) 60 and governor model 80 are included. That is, the generator model 30 is a calculation unit that calculates an output with respect to the input of the generator, the AVR model 70 is a calculation unit that calculates an output with respect to the input of the AVR, and the engine model 60 is an output with respect to the input of the engine. The governor model 80 is a computing unit that computes the output for the governor input.

  The control unit 12 is configured by a calculation device such as a microcomputer, and the virtual power generation device model unit 13 and the control signal generation unit 20 are functions realized by executing software built in the calculation device. It is.

  As shown in FIG. 1, when only the power storage device PS, the gas engine generator 10 and the load 11 are connected to the microgrid distribution line 9, the effective power generated by the gas engine generator 10 is the load 11. When the effective power consumed in the battery is exceeded, the amount exceeding the effective power is charged in the secondary battery 1 of the power storage device PS. In this case, the power conversion unit 3 functions as a rectifier.

  Next, the configuration of the control unit 12 will be described in detail with reference to FIG. FIG. 2 is a block diagram illustrating a detailed configuration of the control unit 12. Hereinafter, an adder, a subtracter, and an adder / subtractor are referred to as an adder / subtracter without distinction.

  In addition to the generator model 30, the engine model 60, the AVR model 70, and the governor model 80, the control unit 12 includes a power calculation unit, an effective voltage calculation unit, and an angular velocity ratio calculation unit, which are not shown. The power calculation unit inputs the output currents ia, ib, ic detected by the current sensor 4 and the output voltages va, vb, vc detected by the voltage sensor 6, and calculates the active power Pg and the reactive power Qg from them. Then, the calculated active power Pg is output to the governor model 80, and the reactive power Qg is output to the AVR model 70. Here, the power calculation unit may be configured to input the current command values Id-ref and Iq-ref output from the generator model 30 instead of the output currents ia, ib, and ic. In this case, the power calculator generates a three-phase current signal (referred to as ia-v, ib-v, and ic-v) by performing dq inverse transformation on the current command values Id-ref and Iq-ref, The active power Pg and the reactive power Qg are calculated from the three-phase current signals ia-v, ib-v, ic-v and the output voltages va, vb, vc. The effective voltage calculation unit receives the output voltages va, vb, vc detected by the voltage sensor 6, calculates the effective voltage Vg from them, and outputs it to the AVR model 70. The angular velocity ratio calculation unit inputs the generator angular velocity ωe, which is the output of the engine model 60, calculates the angular velocity ratio ωe / 2πf, and outputs it to the governor model 80. Here, f is a reference (rated: for example, 50 Hz) frequency, and 2πf is a reference (rated) angular velocity (fixed value). This angular velocity ratio calculation unit may be included in the governor model 80.

  In the governor model 80, the active power command value Pref and the angular velocity command value ωref are input from the external microgrid control device 14, the effective power Pg calculated by the power calculating unit is input, and the angular velocity ratio calculating unit calculates The angular velocity ratio ωe / 2πf thus input is input. The adder / subtractor 81 outputs a value obtained by subtracting the active power Pg from the active power command value Pref to the droop block 82. In the droop block 82, a value obtained by performing a predetermined operation on the output of the adder / subtractor 81 according to the droop set value is output to the adder / subtractor 85. The angular velocity ratio ωe / 2πf is input to the adder / subtractor 85 and the first-order lag calculation block 83. One of the angular velocity command value ωref and the output of the first-order lag calculation block 83 is selected by the switching circuit 84 and input to the adder / subtractor 85. The adder / subtractor 85 adds the output of the droop block 82 and the output of the switching circuit 84, and outputs a value obtained by subtracting the angular velocity ratio ωe / 2πf from the added value to the PI control block 86. In the PI control block 86, the fuel flow rate F is calculated from the output of the adder / subtractor 85 and output to the engine model 60.

In the engine model 60, the fuel flow rate F is input from the governor model 80 and the electric torque Te is input from the generator model 30. In the engine characteristic block 61, the fuel flow rate F is input, and the engine torque Tm is calculated in consideration of the response delay of the engine and output to the adder / subtractor 62. In the adder / subtractor 62, a value obtained by subtracting the electric torque Te input from the generator model 30 and the output value of the damping block 65 from the output value (engine torque Tm) of the engine characteristic block 61 is output to the unit inertia constant block 63. To do. The unit inertia constant block 63 calculates a generator angular velocity ωe by performing a predetermined calculation process using the unit inertia constant M 0 , outputs it to the integrator 64 and the damping block 65, and generates the generator model 30 and the angular velocity ratio. Output to the calculator. In the damping block 65, a predetermined calculation process is performed using the damper coefficient D 0 , and the output is input to the adder / subtractor 62. The integrator 64 calculates the generator internal phase angle θm from the input generator angular velocity ωe and outputs it to the generator model 30 and the control signal generator 20.

  In the AVR model 70, the reactive power command value Qref and the voltage command value Vref are input from the external microgrid control device 14, the reactive power Qg calculated by the power calculation unit is input, and the effective voltage calculation unit calculates it. The effective voltage Vg is input. The adder / subtractor 71 outputs a value obtained by subtracting the reactive power Qg from the reactive power command value Qref to the droop block 72. In the droop block 72, a value obtained by performing a predetermined operation on the output of the adder / subtractor 71 according to the droop set value is output to the adder / subtractor 73. The adder / subtractor 73 adds the output of the droop block 72 and the voltage command value Vref, and outputs a value obtained by subtracting the effective voltage Vg from the added value to the PI control block 73. In the PI control block 73, the field voltage Vf is calculated from the output of the adder / subtractor 73 and output to the generator model 30.

  In the generator model 30, the output voltage va, vb, vc detected by the voltage sensor 6, the field voltage Vf that is the output of the AVR model 70, the generator internal phase angle θm and the angular velocity that are the outputs of the engine model 60. ωe is input, the electric torque Te is output to the engine model 60, and the current command values Id-ref and Iq-ref are output to the control signal generation unit 20. The generator internal phase angle θm is input to the dq conversion block 31, and the angular velocity ωe is input to the matrix calculation blocks 32, 33, 40, and 43.

  The dq conversion block 31 obtains the d-axis voltage Vd and the q-axis voltage Vq by performing dq conversion on the output voltages va, vb, and vc, and the d-axis voltage Vd is obtained from the matrix operation blocks 32 and 33 and the adder / subtractor 46. The q-axis voltage Vq is output to the matrix calculation blocks 32 and 33 and the adder / subtractor 45. In the matrix calculation block 32, the d-axis voltage Vd and the q-axis voltage Vq are input, and the outputs are output to the adder / subtractors 41 and 42. In the matrix calculation block 33, the field voltage Vf, the d-axis voltage Vd, and the q-axis voltage Vq are input, and the outputs are input to the adders / subtractors 34, 35, and 36. The adders / subtracters 34, 35, and 36 add the outputs of the matrix calculation block 33 and the outputs of the matrix calculation block 43, respectively, and output the added values to the integrators 37, 38, and 39. The outputs of the integrators 37, 38, and 39 are input to the matrix operation blocks 40, 43, and 44, respectively. The output of the matrix operation block 40 is input to adders / subtractors 41 and 42. The outputs of the adders / subtractors 41 and 42 are input to the multipliers 48 and 49, respectively, and are input to the control signal generator 20 as current command values Id-ref and Iq-ref. The output of the matrix operation block 44 is input to adders / subtracters 45 and 46. The adder / subtracter 45 outputs a value obtained by subtracting one output of the matrix calculation block 44 from the q-axis voltage Vq to the matrix calculation block 47, and the adder / subtractor 46 outputs the other output of the matrix calculation block 44 from the d-axis voltage Vd. The subtracted value is output to the matrix calculation block 47. The two output values of the matrix operation block 47 are input to multipliers 48 and 49, respectively, and multiplied by the outputs of the adder / subtractors 41 and 42, respectively. The outputs of the multipliers 48 and 49 are input to the adder / subtracter 50, respectively. The adder / subtracter 50 subtracts the output of the multiplier 48 from the output of the multiplier 49 and outputs the value to the engine model 60 as the electric torque Te.

  The configuration of the generator model 30 is well known as described in, for example, the document “PAUL C. KRAUSE, et al: ANALYSIS OF ELECTRIC MACHINERY, IEEE Press (1995)”. Omitted.

  In the control signal generation unit 20, the battery voltage Vs detected by the voltage sensor 2, the output current ia, ib, ic detected by the current sensor 4, and the current command value Id-ref, which is the output of the generator model 30. Iq-ref and the generator internal phase angle θm that is the output of the engine model 60 are input, and the control signal group Sc is output to the power converter 3. The generator internal phase angle θm is input to the dq conversion block 21 and the dq inverse conversion block 28.

  The dq conversion block 21 obtains a d-axis current Id and a q-axis current Iq by performing dq conversion on the output currents ia, ib, and ic, and outputs them to the adders / subtracters 22 and 23, respectively. The adder / subtracter 22 subtracts the d-axis current Id from the current command value Id-ref from the generator model 30 and outputs the value to the PI control block 24. The output of the PI control block 24 is multiplied by the battery voltage Vs by the multiplier 26 and input to the dq inverse conversion block 28. The adder / subtracter 23 subtracts the q-axis current Iq from the current command value Iq-ref from the generator model 30 and outputs the value to the PI control block 25. The output of the PI control block 25 is multiplied by the battery voltage Vs by the multiplier 26 and output to the dq inverse conversion block 28. In the dq inverse conversion block 28, the outputs of the multipliers 26 and 27 are dq inversely converted and output to the PWM signal generation block 29. The PWM signal generation block 29 generates and outputs a control signal group Sc for controlling the switching elements 3 a to 3 f of the power conversion unit 3 by performing PWM processing on the output of the dq inverse conversion block 28.

  Hereinafter, a simulation performed to verify the effect in the present embodiment will be described.

  In the simulation, a 200 kVA generator having the following Park constant was assumed as a generator represented by the generator model 30.

(Park constant of generator model)
d-axis synchronous reactance: Xd = 2.05
q-axis synchronous reactance: Xq = 1.94
d-axis transient reactance: Xd ′ = 0.22
d-axis next-order transient reactance: Xd ″ = 0.17
q-axis order transient reactance: Xq ″ = 0.17
Reverse phase reactance: X2 = 0.17
Zero-phase reactance: X0 = 0.09
Opening time constant: Td0 ′ = 6.3
d-axis transient time constant: Td ′ = 0.7
d-axis transient time constant: Td ″ = 0.03
Armature time constant: Ta = 0.25
The Park constant is for designating the characteristics of the generator, and the above-mentioned Park constant is described in, for example, the document “Shinji Moriyasu: Practical Electrical Equipment, Morikita Publishing (2000)”.

  In the simulation, the grid (microgrid distribution line 9) includes a power storage device PS, a 350 kW gas engine generator 10 (hereinafter abbreviated as “generator 10”), a load, as shown in FIG. 11 is connected, and the microgrid is operated in an independent form. In the governor model 80, the input of the switching circuit 84 can be switched by the user. In the following, it is assumed that the input of the switching circuit 84 is connected to the first-order lag calculation block 83. A configuration in which the angular velocity command value ωref is not input, the switching circuit 84 is not provided, and the output of the first-order lag calculation block 83 is directly input to the adder / subtractor 85 is also possible.

  First, a simulation result when a step load is applied to the system is shown in FIG. FIG. 3A shows a response waveform of the active power with respect to the step load, and FIG. 3B shows a response waveform of the system frequency with respect to the step load.

  In FIG. 3A, the active power consumed by the load when the step load is applied to the system (microgrid distribution line 9) from 1 second to 7 seconds with reference to a certain time, The active power to be output and the change with time of the active power output from the power converter PC are shown. First, from the steady state in which the generator 10 supplies all of the active power 100 kW consumed by the load 11, a step load is applied at 1 second, and when the active power of the load increases, the increase is shared. Thus, the active power output from the power converter PC increases as the active power of the generator 10 increases. Thereafter, the active power of the generator 10 gradually increases and the active power of the power conversion device PC gradually decreases. When the step load disappears at 7 seconds and the active power of the load returns to 100 kW, the active power of the generator 10 and Both the effective power of the power converter PC decreases. Thereafter, the active power of the generator 10 gradually decreases so as to converge to 100 kW, and the effective power of the power converter PC gradually increases so as to converge from a negative value to 0 kW. Here, the negative value of the active power of the power conversion device PC means that the virtual power generation device assumed in the virtual power generation device model unit 13 is in the operation area as an electric motor. In this case, the power conversion unit 3 operates as a rectifier, and the secondary battery 1 is charged with electric power.

  Next, in FIG. 3B, when the droop of the governor model 80 (the droop set value of the droop block 82) is set to 3%, when it is set to 5%, and there is no power storage device PS. Each case is simulated, and the change over time in the system frequency (frequency of the distribution line 9 of the microgrid) when a step load is applied between 1 second and 7 seconds with respect to a certain time is shown. From FIG.3 (b), when there is no power storage device PS, the fluctuation | variation of a system frequency is large, but when a power storage device PS exists (droop is 3%, 5%), the fluctuation | variation of a system frequency is suppressed. You can see that it is made. Furthermore, it can be seen that fluctuations in the system frequency can be suppressed more when the set value of the droop of the governor model 80 is 3% than when the droop setting value is 5%. Since the fluctuation of the system frequency is preferably within ± 0.2 Hz with respect to the reference frequency (50 Hz), in this embodiment, the droop of the governor model 80 may be set to 3%. In the simulation here, the droop of the AVR model 70 (the droop setting value of the droop block 72) is a constant value of 5%, for example.

  Next, FIG. 4 shows a simulation result when a harmonic load is present. FIG. 4 shows waveforms of the output current, the load current, and the output current of the power generator 10 when a harmonic load is present, and all show the a-phase current waveform. Note that the b-phase and c-phase current waveforms are the same except that the phases are different, and are not shown. As shown in FIG. 4, harmonic components are included in the output of the power conversion device PC, and the harmonic components of the load current can be shared between the output of the generator 10 and the output of the power conversion device PC. I understand.

  Next, a simulation result when an unbalanced load exists is shown in FIG. Fig.5 (a) shows the waveform of the load current when an unbalanced load exists, and FIG.5 (b) shows the waveform of the output current of the power converter device PC in the same case. 5A and 5B, an unbalanced current can be output from the power converter PC to the unbalanced load. Therefore, it can be seen that the unbalanced portion of the load current can be shared by the output of the generator 10 and the output of the power conversion device PC.

  From the above simulation results, when the microgrid is operated in an independent form, even if the load current includes a harmonic component or a three-phase unbalanced state occurs, the power conversion device PC is connected to the gas engine generator 10 or the like. Since harmonic currents and unbalanced currents are output in the same way as ordinary power generators, harmonic components and unbalanced components can be borne with normal power generators, and the burden on the power generators can be reduced. . In this way, it is possible to stabilize the power quality of the own system in cooperation with a normal power generator. In the present embodiment, detection means for the voltage sensor 2, the current sensor 4, and the voltage sensor 6 are necessary, but such detection means is provided as an internal component of the power conversion device PC. There is no need to provide a separate load current or power detection means connected to the distribution line 9.

  In addition to the case where the microgrid is operated in an independent form as described above, there is a case where the microgrid is operated in an interconnected form connected to a commercial power system. In the case of this interconnection form, the microgrid distribution line 9 is connected to the distribution line 16 of the commercial power system via the circuit breaker 15. Here, the normal state in which the circuit breaker 15 is closed (hereinafter referred to as “connected state”), an abnormality or the like occurs in the commercial power system, and the circuit breaker 15 is opened and disconnected from the commercial power system. There is a state (hereinafter referred to as “interconnection interruption state”). In the power conversion device PC of the present embodiment, since the control unit 12 includes the virtual power generation device model unit 13, it is possible to perform frequency control and voltage control similar to those of an actual power generation device, and in an interconnected connection state. In both cases, the operation of the power conversion device PC is the same as in the case where the power conversion device PC is operated in an independent form, and it is possible to stabilize the power quality of the own system in cooperation with a normal power generation device. It becomes possible. Further, even when shifting from the connected state to the disconnected state, it is possible to stabilize the power quality of the own system in a transient manner in cooperation with a normal power generator.

  As described above, in the power conversion device PC according to the present embodiment, when the microgrid is operated in the interconnected form, the same control method is used in the interconnected connection state and in the interconnected disconnection state. There is no need to switch the control method as in the power converter used in the storage device. Further, it is not necessary to detect the state of the system in order to switch the control method.

  In addition, when the microgrid is operated in an independent form, or when the connection is cut off in the operation in the connected form, the operation of the normal power generator in the microgrid is stopped, and the power storage device PS is used alone. Even in the case of operating with the power storage device PS, it is possible to operate alone without switching the control method.

  In addition, the control device 14 that manages and manages the microgrid can handle the power storage device PS in the same manner as a normal power generation device, and the control by the microgrid control device 14 becomes easy. In addition, for the user, the power storage device PS can be handled in the same manner as a normal power generation device, and its behavior can be predicted and adjustment is easy. In this case, for example, the droop setting value of the AVR model 70, the droop setting value of the governor model 80, the unit inertia constant of the engine model 60, and the like can be adjusted by the user. Further, the voltage command value Vref of the AVR model 70 and the angular velocity command value ωref of the governor model 80 are input from the microgrid control device 14, but the voltage command value Vref and the angular velocity command value ωref are adjusted by the user. It is good also as a possible structure. Here, for the adjustment of the angular velocity command value ωref by the user, the input of the switching circuit 84 may be switched to the angular velocity command value ωref, and a desired value may be input as the angular velocity command value ωref. For example, when the microgrid is operated in an independent form, the voltage command value Vref and the angular velocity command value ωref can be set to desired values, and the output voltage and the frequency can be kept constant.

  Further, since the power generation device assumed in the virtual power generation device model unit 13 of the power conversion device PC is a virtual power generation device, the controllable range with respect to frequency and voltage can be made wider than the actual power generation device.

  Further, since the power generation device assumed in the virtual power generation device model unit 13 of the power conversion device PC is a virtual power generation device, it is possible to control to output negative power, that is, to operate as an electric motor. Since the input electric power is charged in the secondary battery 1, there is no loss.

  Further, the generator parameters (Park constant) simulated by the generator model 30 of the virtual generator model unit 13 can be arbitrarily changed. At this time, even a value that cannot be set due to problems such as physical constraints and efficiency in an actual generator can be set in the generator model 30 and a generator that does not actually exist can be simulated. .

  The power conversion device according to the present invention is useful as a power conversion device used in a power storage device of a power supply system using a distributed power source such as a microgrid.

It is a circuit diagram which shows the structural example of the microgrid using the power converter device of embodiment of this invention. It is a block diagram which shows the detailed structure of the control part of the power converter device of embodiment of this invention. (A) is the response waveform figure of the active power with respect to the step load by simulation, (b) is the response waveform figure of the system frequency with respect to the same step load by simulation. It is a wave form diagram of the output current of a power converter device, load current, and the output current of a gas engine generator in case the harmonic load by simulation exists. (A) is a waveform diagram of a load current when an unbalanced load is present by simulation, and (b) is a waveform diagram of an output current of the power conversion device when an unbalanced load is present by the simulation. .

Explanation of symbols

PS power storage device PC power conversion device 1 secondary battery 2 voltage sensor 3 power conversion unit 4 current sensor 5 output reactor 6 voltage sensor 7 filter capacitor 8 transformer 9 microgrid distribution line 10 gas engine generator 11 load 12 control unit 13 Virtual generator model part 14 Micro grid controller 15 Circuit breaker 16 Distribution line 20 of commercial power system Control signal generator 30 Generator model 60 Engine model 70 AVR model 80 Governor model

Claims (1)

  1. Converting the DC power of the secondary battery into AC power, outputting to an output line connected to the AC circuit, and converting AC power input from the AC circuit through the output line into DC power, A power converter that can be stored in a secondary battery;
    A control unit for controlling the power conversion unit,
    The controller is
    Assuming that a virtual power generation device that is an imaginary power generation device is provided in advance instead of the power conversion unit and the secondary battery, and that the output line of the power conversion unit is the output line of the virtual power generation device, A virtual power generation device model unit that calculates a current value to be output by the virtual power generation device based on a voltage of an output line of the power conversion unit, and determines the calculated current value as a current command value;
    A power conversion control unit that controls the power conversion unit by current feedback control so as to output a current corresponding to the current command value to the output line ;
    The virtual power generator model unit controls the generator, the AVR that controls the field voltage of the generator, the prime mover that drives the generator, and the fuel supply amount to the prime mover. A generator model, AVR model, prime mover model, and governor model that define the input / output relationship of each of the assumed generator, AVR, prime mover, and governor.
    The AVR model is configured to calculate the field voltage of the generator based on the voltage of the output line of the power converter, the reactive power command value given from the outside, and the voltage command value of the output line. ,
    The governor model is based on an angular velocity of the generator calculated in the prime mover model, an active power command value given from the outside, and at least the active power command value of the angular velocity command value of the generator. Configured to calculate the fuel supply to the prime mover,
    The prime mover model calculates the angular velocity and phase angle of the generator based on the fuel supply amount to the prime mover calculated by the governor model and the electric torque of the generator calculated by the generator model. Configured to calculate,
    The generator model includes the voltage of the output line of the power converter, the field voltage of the generator calculated by the AVR model, and the angular velocity and phase angle of the generator calculated by the prime mover model. Based on the above, a power conversion device configured to calculate a direct axis current value and a horizontal axis current value output from the generator, and to determine the calculated direct axis current value and horizontal axis current value as the current command value .
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