JP6006637B2 - Power conversion control device - Google Patents

Description

  The present invention relates to a power conversion apparatus having a single control method that enables both an interconnected operation that operates in conjunction with an electric power system and an independent operation that operates independently from the electric power system.

  In recent years, there has been an increasing interest in distributed power supply systems that use direct current generators such as solar power generation. Such a system includes a power conversion device that converts DC power into AC power. A general power conversion device that operates in conjunction with an electric power system has an interconnection operation function, but cannot perform independent operation independently of the electric power system. The present applicants recently developed a control method for a power converter having characteristics equivalent to a generator, and supplies stable power not only during grid operation but also during stand-alone operation. It has been proposed to realize a non-instantaneous transition to (see, for example, Patent Document 1).

  Further, in Patent Document 2, when additional injection reactive power having a predetermined phase when the already injected reactive power balances with the load reactive power is additionally injected for a certain period, the above-mentioned certain period after the additional reactive power injection The phase of the already injected reactive power is determined based on the sign of the system frequency deviation after a shorter period of time, and the phase of the already injected reactive power from the sign of the system frequency deviation at the time of determination is When the phase is opposite to the determined phase, the additional injection reactive power of the phase corresponding to the sign of the system frequency deviation is injected again for a certain period, and the sign of the system frequency deviation at the time of determination When the phase of the pre-injected reactive power is the same as the predetermined phase of the additional reactive power, it is added in the same phase for the remaining period after the additional reactive power is injected. It is disclosed to detect the isolated operation by continuing injection of the incoming reactive power.

JP 2007-244068 A JP 2011-55678 A

  By the way, when the system is opened due to an upper system accident, work, etc., if the single operation is continued without being disconnected from the power generation facility system, the system that should be essentially no voltage will be charged, In order to raise security and supply reliability problems, the power generator is required to reliably prevent isolated operation. In addition, when the output of the power generation system and the load are in a state of power balance, it is not easy to detect that the system has been opened. Stopping is required, and the requirements differ depending on whether the generator is a generator or a power converter.

  However, since the power conversion device having the control method invented by the applicant in Patent Document 1 has characteristics equivalent to a generator while being a power conversion device, an isolated operation detection method suitable for such a power conversion device is Does not exist. That is, as with a general power conversion device that operates in conjunction with the power system, if a detection method that directly manipulates the phase component of the current command value is employed, interference with components other than the frequency increases. This inherently impairs the characteristic of the power conversion device that shifts to a self-sustained operation without instantaneous interruption after detecting an isolated operation. On the other hand, when a detection method for directly operating reactive power as in the case of a generator is adopted for a virtual generator, high-speed isolated operation detection required for a power converter cannot be satisfied.

  In order to shift to independent operation after detecting isolated operation in the conventional technology, it is necessary to switch the system or equip the dedicated device, and the conventional technology that can shift to independent operation without instantaneous interruption without providing a dedicated device in a single system Did not exist.

  The present invention has been made to solve the above-described problems.It detects an isolated operation caused by an upper system fault or the like during grid connection at high speed, and shifts to a self-sustained operation without instantaneous interruption. It is an object of the present invention to provide a power conversion control device that enables continuous operation.

  In order to solve the above problems, a power conversion control device according to an aspect of the present invention is connected to the system-side circuit breaker in a power conversion device used by being connected or disconnected by a power system and a system-side circuit breaker. A power conversion control device that controls a power converter that is connected to the disconnected switch via an output line and converts DC power input from a DC power supply unit to AC power and outputs the AC power to the output line. The virtual power based on the deviation of the active power output from the power converter with respect to the active power command, the virtual generator speed drooping characteristic, and the deviation of the angular speed of the AC voltage output from the power converter from a predetermined angular speed. A governor model unit for calculating an internal phase difference angle between a typical generator and the output line, a deviation of reactive power output by the power converter with respect to a reactive power command, and a voltage drooping characteristic of the virtual generator And an AVR model unit that calculates an absolute value of an internal induced voltage of the virtual generator based on a deviation of an AC voltage output from the power converter with respect to a predetermined voltage, and an internal phase difference angle calculated by the governor model unit , Based on the absolute value of the internal induced voltage calculated by the AVR model unit, the internal impedance of the virtual generator combined with the virtual impedance and the real impedance, and the AC voltage output from the power converter A generator model unit that calculates a command value of a current corresponding to an armature current of a generator, and a PWM signal that converts the current command calculated by the generator model unit into a PWM signal and outputs the PWM signal to the power converter Based on the electrical fluctuations of the generator and the output line, the amount of operation is determined for each control cycle that matches the frequency of the AC voltage transmitted on the output line. Is applied to the internal phase difference angle calculated by the control unit, and when the resulting fluctuation in the angular velocity is equal to or greater than a first predetermined value, the isolated operation is actively detected, and then the disconnecting switch is opened. An isolated operation detection unit configured to shift the power conversion device to the independent operation.

  Here, “operation amount” means an active fluctuation amount, and “giving an operation amount to the internal phase difference angle” means giving an active fluctuation amount to the internal phase difference angle.

  According to the above configuration, even for an active operation for detecting an isolated operation, an operation amount for changing an angular velocity to an internal phase difference angle in a power conversion control device of a power conversion device having characteristics equivalent to a generator is provided. Then, the fluctuation of the angular speed of the AC voltage output from the power converter is amplified, and after the fluctuation of the resulting angular speed exceeds a predetermined value, the disconnection switch is opened and the power converter is shifted to the autonomous operation. Therefore, even after the isolated operation is detected, it is possible to continue the independent operation without impairing the characteristic that the power conversion device can essentially shift to the independent operation without instantaneous interruption. In addition, since the operation amount is given to the internal phase difference angle, there is no response delay that occurs when the operation amount is given to the reactive power, so that the high-speed isolated operation detection required for the power converter can be satisfied.

  The islanding detection unit detects an electrical variation of the output line to generate an electrical variation detection signal, and detects the passive islanding when the electrical variation is a predetermined amount or more, and then An electrical fluctuation detection unit configured to open the disconnection switch and shift the power converter to a self-sustaining operation, and a period in which an electrical fluctuation detection signal is input from the electrical fluctuation detection unit, An operation amount is given to the internal phase difference angle calculated by the governor model unit for each control cycle that matches the frequency of the AC voltage transmitted on the output line, and whether or not there is an electrical fluctuation, Is given to the internal phase difference angle calculated by the governor model unit an operation amount proportional to the fluctuation of the angular velocity of the AC voltage transmitted on the output line for each control cycle that matches the frequency of the AC voltage transmitted. The result When the fluctuation of the angular velocity of the vehicle is greater than or equal to a first predetermined value, an active isolated operation is detected, and then the disconnection switch is opened to shift the power conversion device to the independent operation. May be provided.

  In the electrical fluctuation detection unit, the case where the electrical fluctuation is in a predetermined mode means that, for example, when the AC voltage jumps as an electrical fluctuation (instantaneous large fluctuation), the ratio of harmonics is a predetermined value. It may be the case where the above is reached, or the case where the frequency or angular velocity fluctuates greatly.

  In the operation amount giving unit, the sign of the amount proportional to the fluctuation of the angular velocity is determined in a direction in which the fluctuation of the angular velocity increases. In addition, when it is determined that the fluctuation amount of the angular velocity obtained as a result is equal to or greater than a second predetermined value smaller than the first predetermined value, an operation amount for changing the angular velocity applied to the internal phase difference angle is further increased. You may be comprised so that it may become large.

  With the above configuration, the independent operation can be preferably continued even after the isolated operation is detected.

  The power conversion device or the power conversion control device calculates or measures the active power output from the power converter and outputs the active power to the governor model unit, and the invalidity output from the power converter. A reactive power detection unit that calculates or measures power and outputs it to the AVR model unit; an AC voltage output from the power converter is measured to calculate an effective value; these are calculated as the AVR model unit and the power generation unit A voltage detection unit that outputs to the machine model unit; and an angular velocity detection unit that calculates or measures an angular velocity of the AC voltage output from the power converter and outputs the angular velocity to the governor model unit.

  According to the present invention, an isolated operation that occurs due to an upper system fault or the like during grid connection is detected at high speed, and the power converter inherently detects an isolated operation and thus loses the characteristic of shifting to an independent operation without instantaneous interruption. It is possible to provide a power conversion control device that does not occur.

It is a block diagram which shows the structural example of the power conditioner system using the power converter device which concerns on Embodiment 1 of this invention. It is a block diagram which shows the structure of the power conversion control apparatus of the power converter device of FIG. It is a block diagram which shows the specific structural example of the power conversion control apparatus of FIG. It is a flowchart which shows an example of control in case the power converter device of FIG. 1 transfers to a self-sustained operation from a grid operation. It is a flowchart which shows an example of the electrical fluctuation detection process in the independent operation detection process of the power conversion control apparatus of FIG. It is a flowchart which shows an example of the operation amount provision process in the independent operation detection process of the power conversion control apparatus of FIG. It is a graph which shows the experimental result of the independent operation detection process at the time of providing the operation amount for changing an angular velocity to the electric current command value of a phase component as a comparative example. It is a graph which shows the experimental result of the independent operation detection process at the time of providing the operation amount for changing an angular velocity to an internal phase difference angle.

  Embodiments of the present invention will be described with reference to the drawings. Below, the same code | symbol is attached | subjected to the element which is the same or it corresponds through all the drawings, and the overlapping description is abbreviate | omitted.

(Embodiment 1)
FIG. 1 is a configuration diagram illustrating a configuration example of a power conditioner system using the power conversion device according to the first embodiment of the present invention. The power conditioner system is not particularly limited as long as it is a distributed power supply system including a DC power supply and a power converter.

[Constitution]
As shown in FIG. 1, a power conditioner system 200 is installed in a home, for example, through a power system 7 that is a substation bus of an electric power company, a system-side circuit breaker 8 (connection unit), and a transformer 9. It is connected. Opening and closing of the system side circuit breaker 8 is controlled by a control system (not shown) of the power system 7. The transformer 9 is, for example, a transformer disposed on a pillar.

  The power conditioner system 200 includes, for example, a DC power source 101 that is a solar panel for solar power generation, a secondary battery 2 such as a nickel metal hydride battery, and a DC power source 101 that includes the DC power generator 1 and the secondary battery 2. A power converter 3 that converts the DC power input from AC into AC power and outputs it to the output line 30; a power conversion control device 4 that controls the operation of the power converter 3; and a disconnecting switch 5. I have. The power converter 3 and the power conversion control device 4 constitute a power conversion device 100.

  Although the power converter 3 is not specifically limited, For example, it is comprised with an inverter and an output filter. The power conversion control device 4 has a single operation transition detection function for detecting that the power converter 3 has been disconnected from the power system 7 and shifted to a single operation during the interconnected operation with the power system 7 and opens and closes for disconnection. The opening and closing of the device 5 is controlled. When the power conversion control device 4 detects the shift to the single operation, the power conversion control device 4 opens the disconnection switch 5 and switches the power conversion device 100 to the independent operation. In this way, the power conversion device 100 is connected to the power system 7 during the interconnected operation, and disconnected from the power system 7 during the independent operation and the independent operation. When the capacity of the specific load 6 is limited to the range of the rated capacity of the power converter 3, the specific load 6 is connected to the inverter side from the disconnecting switch 5 in the output line 30 as shown in FIG. Thus, the power conversion device 100 can continue the independent operation without stopping the power supply to the specific load 6 only by the operation of disconnecting the switch 5 even after the isolated operation is detected.

  FIG. 2 is a block diagram showing a configuration of the power conversion control device 4. As shown in FIG. 2, the power conversion control device 4 includes a generator model 21, a generator control unit model 15 including a governor model 19 and an AVR model 20, a PWM signal generation unit 16, and an isolated operation detection unit 17. Is mainly provided. The isolated operation detection unit 17 includes an electrical fluctuation detection unit 17a and an operation amount providing unit 17b.

  The power conversion control device 4 includes arithmetic devices such as a field-programmable gate array (FPGA), a programmable logic controller (PLC), and a microcontroller, and includes a generator control unit model 15, a PWM signal generation unit 16, an isolated operation detection unit. Reference numeral 17 denotes a function realized by executing a program incorporated in the arithmetic device. The active power detection unit 11, the reactive power detection unit 12, the voltage detection unit 13, and the angular velocity detection unit 14 are output current values and output voltages measured by a measurement device (not shown) connected to the output side of the power converter 3. Based on the values, the active power, reactive power, AC power voltage, and angular velocity output from the power converter 3 are measured or calculated.

  The generator model 21 is a model of a synchronous generator body. The generator control unit model 15 is a control model (calculation block) in which the function of the synchronous generator is modeled using predetermined calculation parameters. The generator control unit model 15 only needs to include a governor model and an AVR model, which are control models each modeling a governor that controls a synchronous generator and an AVR (automatic voltage regulator). As the generator model 21 and the generator control unit model 15, known ones can be used, for example, a Park model can be used.

In the present embodiment, the generator control unit model 15 includes variables (ω, E _f ), internal impedances, which are defined in the control program of the power conversion control device 4 and correspond to the rotor angular velocity and internal induced voltage of the generator. to the corresponding constant (r _{s, x),} corresponding to the variable (I _ref) to a command value of the armature _current, and the terminal voltage effective value to the corresponding variable has a (V _g), corresponding to the rotor angular velocity variables ( The control corresponding to the governor for determining ω) and the control corresponding to AVR for determining the absolute value of the variable (E _f ) corresponding to the internal induced voltage are constituted by logical expressions, and the terminal voltage and the internal induction are determined. phase difference between the voltage (internal phase angle ([Delta] [theta])), the difference between the absolute value of the induced voltage of the terminal voltage and the internal impedance (r _{s, x)} variable corresponding from the command value of the armature current ( I _ref ) is calculated. The governor control gives the power converter 3 a speed drooping characteristic, and the AVR control gives the power converter 3 a voltage drooping characteristic.

The variable I _ref corresponding to the armature current command value calculated by the generator control unit model 15 and the generator model 21 is used as a current command value (d-axis current command value I _{d_ref} and q-axis current command value I _{q_ref} ). By operating the power converter 3 (for example, an inverter), it becomes possible to handle the output current of the power converter 3 as a generator armature current and the output voltage of the power converter 3 as a generator terminal voltage. When the variable (ω) corresponding to the rotor angular velocity is changed, the phase difference Δθ between the terminal voltage effective value (V _g ) and the induced voltage (E _f ) changes, which is mainly effective during grid-connected operation. The power output changes, and the grid frequency changes mainly during independent operation.

In addition, when the induced voltage (E _f ) is increased, the difference between the absolute value of the terminal voltage effective value (V _g ) and the absolute value of the induced voltage (E _f ) changes, which is mainly invalid during grid connection operation. The power conversion device 100 can realize a behavior having the characteristics of a synchronous generator in which the power changes and the system voltage changes mainly during the independent operation. In addition to the variables, constants, and characteristics described above, actual generators have other characteristics such as transient characteristics, braking winding characteristics, asymmetry, and non-linearity. Even if the behavior having the above characteristics is realized by the inverter (power converter 3), it is apparent that the effectiveness of the present invention is not impaired as long as the above characteristics are included.

The governor model unit 19 includes a deviation of the active power P measured or calculated by the active power detection unit 11 with respect to the active power command P _ref, a control to give the above-mentioned speed drooping characteristics, and an angular speed reference value ω _ref (predetermined angular speed). The internal phase difference angle Δθ described above is calculated based on the deviation of the angular velocity ω measured or calculated by the angular velocity detector 14. The angular velocity reference value ω _ref may be input from the outside or may be held inside the governor model unit 19.

The AVR model unit 20 includes a deviation of the reactive power Q measured or calculated by the reactive power detection unit 12 with respect to the reactive power command Q _ref, a control for giving the above-described voltage drooping characteristic, and a voltage effective value reference value V _ref (predetermined The absolute value of the induced voltage (more precisely, the absolute value of the induced voltage) E _f is calculated based on the voltage effective value V _g measured or calculated by the voltage detector 13 with respect to (voltage). Note that the voltage effective value reference value V _ref may be input from the outside or may be held inside the AVR 20.

The generator model unit 21 includes the internal phase difference angle Δθ calculated by the governor model unit 19, the absolute value of the induced voltage E _f calculated by the AVR model unit 20, the internal impedance r _s , x, and the voltage detection calculation unit. The armature current command value I _ref (d-axis current command value I _{d_ref} and q-axis current command value I _{q_ref} ) is calculated based on the voltage effective value V _g measured and calculated in step 13.

The PWM signal generation unit 16 converts the armature current command value I _ref (d-axis current command value I _{d_ref} and q-axis current command value I _{q_ref} ) calculated by the generator model unit 21 into a PWM signal to convert power. To the device 3. Thereby, the power converter 3 outputs electric power according to the command value I _{ref of the} armature current. The PWM signal generation unit 16 controls, for example, the current control voltage output type power converter 3.

  The electrical fluctuation detection unit 17a passively detects an isolated operation when the electrical fluctuation of the output line 30 is greater than or equal to a predetermined amount, and then opens the disconnect switch 5 and the output line 30. If it is detected even if the electrical fluctuation is less than a predetermined amount, an electrical fluctuation detection signal is output to 17b.

  The manipulated variable applying unit 17b performs an active operation that amplifies the fluctuation of the angular velocity of the voltage of the output line 30 during the single operation, and performs the single operation when the resulting change in the angular velocity exceeds a predetermined amount. Active detection is performed, and then the disconnecting switch 5 is opened.

  FIG. 3 is a block diagram illustrating a specific configuration example of the power conversion control device 4 of FIG. As shown in FIG. 3, the power converter 3 includes an inverter and an output filter. The generator control unit model 15 includes a governor model unit 19 and an AVR model unit 20.

The governor model unit 19 calculates the deviation of the active power P measured or calculated by the active power detection unit 11 with respect to the active power command P _ref input from the outside, and performs control to give this deviation a speed drooping characteristic. Further, the angular velocity deviation is calculated by subtracting the angular velocity ω measured or calculated by the angular velocity detector 14 from the angular velocity reference value ω _ref input from the outside, and this is used to give the effective power deviation a velocity drooping characteristic. It is converted into a variation of the rotor angular speed of the virtual generator. Then, the internal phase difference angle Δθ is calculated by integrating the variation of the rotor angular velocity. The angular velocity reference value ω _ref is, for example, an angular velocity corresponding to a frequency of 60 Hz, and the velocity drooping characteristic has a frequency drop corresponding to 5% of the frequency 60 Hz, for example, when the rated active power is output.

The AVR model unit 20 calculates a deviation of the reactive power Q measured or calculated by the reactive power detection unit 12 with respect to the reactive power command Q _ref input from the outside, and performs control to give this deviation a voltage drooping characteristic. Further with respect to the effective voltage reference value V _ref input from the outside, calculates a voltage deviation by subtracting the effective voltage value V _g which is measured by the voltage detection unit 13, the voltage drooping characteristic it to the reactive power deviation Add to what you have. And to this, for example, by applying a voltage maintenance control by PI control, and calculates the absolute value of the internal induced voltage E _f of the virtual generator. The voltage effective value reference value V _ref is, for example, 202 V, and the voltage drooping characteristic has a voltage drop corresponding to 5% of the voltage 202 V, for example, when the rated reactive power is output.

The generator model unit 21 includes an internal phase difference angle Δθ calculated by the governor model unit 19, an absolute value of the induced voltage E _f calculated by the AVR model unit 20, and a voltage effective value V measured or calculated by the voltage detection unit 13. A current command I _ref corresponding to the armature current command value of the generator control unit model 15 is calculated based on _g , the internal impedance r _s , and x. This calculation is performed, for example, by a vector operation using a phasor diagram shown in the block 21 of FIG. The current command value I _{d_ref} and the current command value I _{q_ref} calculated by this calculation are output to the PWM signal generation unit 16.

The PWM signal generation unit 16 converts the current command I _ref calculated by the generator model unit 21 into a PWM signal and outputs the PWM signal to the power converter 3. In the present embodiment, the PWM signal generation unit 16 receives the current of the power converter 3 measured by a current measurement unit (not shown) and the current command value I _ref that is the output of the generator model unit 21. The The PWM signal generator 16 obtains a d-axis current Id and a q-axis current Iq by performing dq conversion on the output current, and outputs them to the adder / subtractor. On the other hand, the adder / subtracter subtracts the d-axis current Id from the current command value I _{d_ref} from the generator model unit 21 and outputs the value to the PI control block. In the other adder / subtracter, the q-axis current Iq is subtracted from the current command value I _{q_ref} from the generator model unit 21 and the value is output to the PI control block. The output from each PI control block is d-q inversely converted and output to the PWM signal generation block. The PWM signal generation block generates a PWM signal that is PWM-processed and controls each switching element of the power converter 3 and outputs the PWM signal to the power converter 3.

  The angular velocity detector 14 measures or calculates the frequency of the AC voltage output from the power converter 3, estimates the system phase (angular velocity) based on the measured or calculated frequency, and determines the estimated angular velocity as the governor model 19 and Output to the isolated operation detection unit 17. In the present embodiment, the angular velocity detection unit 14 is included in the power conversion control device 4 (more precisely, its control program) as PLL control logic, but the phase conversion device is externally (hardened) to convert the power. It may be provided outside the control device 4.

  The voltage detector 13 measures the AC voltage output from the power converter 3. In the present embodiment, the voltage detection unit 13 measures the AC voltage output from the power converter 3 with a voltmeter (not shown), d-q converts this, and calculates the system voltage effective value. The voltage d-q converted and the system voltage effective value are output to the AVR model unit 20 and the generator model 21, respectively.

Electrical variation detecting unit 17a, when the fluctuation of the voltage effective value V _g which is measured and calculated by the voltage detection calculating unit 13 is a predetermined amount or more, and outputs an electrical variation detection signal to 17b. In addition to the voltage effective value V _g or the voltage effective value V _g , for example, when the variation in the angular velocity or the frequency measured or calculated by the angular velocity detection unit 14 is a predetermined amount or more, the single operation is passively performed. Then, the disconnecting switch 5 is opened.

  The operation amount providing unit 17b provides an operation amount for changing the angular velocity to the rotor angular velocity calculated by the governor model unit 19. In the present embodiment, in a period in which the electrical fluctuation detection signal generated by the electrical fluctuation detector 17a is input, a constant operation amount is generated for each control cycle that matches the frequency of the voltage of the output line 30. It is given to the internal phase difference angle Δθ calculated by the governor model unit 19 of the control unit model 15 and the output line 30 of the output line 30 at every control period that matches the frequency of the voltage of the output line 30 regardless of the presence or absence of the electrical fluctuation detection signal. An amount proportional to the change in the angular velocity of the voltage is given by the adder 25. As a result, when the fluctuation of the angular velocity is greater than or equal to a predetermined amount, the isolated operation is actively detected, and then the disconnecting switch 5 is opened.

  It should be noted that the value to which the operation amount giving unit 17b gives the operation amount for changing the angular velocity is the value before the calculation of the internal phase difference angle Δθ in the governor model unit 19, that is, the rotor angular velocity and system voltage of the virtual synchronous generator. It may be a value before integrating the difference in angular velocity. This is also because, as a result, an operation amount for changing the angular velocity is given to the internal phase difference angle Δθ.

[Operation]
Next, the operation of the power conversion apparatus 100 configured as described above will be described. FIG. 4 is a flowchart illustrating an example of control in the case where the power conversion apparatus 100 detects a single operation and shifts to a self-sustained operation.

  Referring to FIG. 1 to FIG. 3, it is assumed that the power conversion apparatus 100 performs a linked operation in linkage with the power system 7 shown in FIG. 1 (step 1). In this interconnection operation, the system side circuit breaker 8 is in a connected state. In the power conversion device 100, the disconnection switch 5 is in a connected state under the control of the power conversion control device 4.

  The power conversion device 100 detects an isolated operation that has occurred unintentionally in the grid interconnection operation (step 2). The electrical fluctuation detection unit 17a of the power conversion control device 4 monitors the voltage of the AC power transmitted through the output line 30. For example, when it detects that the voltage jumps (changes instantaneously), A dynamic fluctuation detection signal is generated and output to the operation amount assigning unit 17b. In addition to the voltage of the AC power, the electrical fluctuation detection unit 17a monitors, for example, the harmonic distortion factor and frequency, and the fluctuation amount of any of these electrical elements exceeds a predetermined amount. In addition, it is passively detected that the power conversion apparatus 100 (power converter 3) has shifted to the single operation. The manipulated variable providing unit 17b generates a fixed manipulated variable for each control cycle that matches the frequency of the AC voltage of the output line 30 during the period in which the electrical variation detection signal generated by the electrical variation detector 17a is input. It is given to the internal phase difference angle Δθ output to the machine model unit 21 and the AC voltage of the output line 30 is controlled at every control cycle that matches the frequency of the AC voltage of the output line 30 regardless of the presence or absence of the electrical fluctuation detection signal. An amount proportional to the fluctuation of the angular velocity is given to the internal phase difference angle Δθ output to the generator model unit 21. And if the fluctuation | variation of the angular velocity of the result of providing exceeds predetermined amount, the operation amount provision part 17b will detect actively that the power converter device 100 (power converter 3) shifted to independent operation.

  From here, the isolated operation detection process of the power converter 100 will be specifically described with reference to the flowcharts of FIGS. 5 and 6. The power conversion device 100 detects an isolated operation by monitoring electrical fluctuations in the output line 30 of the power converter 3. In this embodiment, as described above, an algebraic virtual generator is used.

  FIG. 5 is a flowchart illustrating an example of an electrical variation detection process in the isolated operation detection process. As shown in FIG. 5, for example, when detecting a voltage jump in the output line 30 of the power converter 3, the electrical fluctuation detection unit 17 a passively detects an isolated operation or destroys the power balance (step Operation) command signal is generated. That is, for example, the electrical fluctuation detection unit 17a monitors the voltage of the output line 30 of the power converter 3 via the voltage detection unit 13 (step 13), and the voltage jumps (changes momentarily greatly). As a result, when the fluctuation of the voltage exceeds the first predetermined value, the electric islanding operation is passively detected (step 12). When the voltage fluctuation is less than the first predetermined value and the voltage fluctuation is greater than or equal to the second predetermined value (step 14), an electrical fluctuation detection signal is generated and input to the manipulated variable applying unit 17b (step 15). ). Further, when the state where the voltage fluctuation is less than the second predetermined value continues for a predetermined period (step 16), the output of the electrical fluctuation detection signal is stopped (step 17).

Further, for example, the electrical fluctuation detection unit 17a monitors the angular velocity of the output line 30 of the power converter 3 via the angular velocity detection unit 14 (step 11), and the fluctuation of the angular velocity exceeds a predetermined amount. In this case, the isolated operation is passively detected (step 12).
The operation amount providing unit 17b feeds back the fluctuation of the angular velocity of the voltage of the output line 30 and performs an active operation that amplifies the fluctuation of the angular velocity during the single operation. That is, the operation amount providing unit 17b performs, for example, the following processing for each cycle of the predetermined frequency of the power system 7 in the power conversion control device 4 of the power conversion device 100. The value to be fed back is the angular velocity variation Δω, but may be the frequency variation ΔF. The parameter to be actively operated is the internal phase difference angle Δθ calculated by the governor model unit 19 of the generator control unit model 15.

FIG. 6 is a flowchart illustrating an example of an operation amount providing process in the isolated operation detection process. 6, first, the operation amount adding portion 17b subtracts the predetermined period before the angular velocity omega ₂ from the angular velocity omega ₁ of the current cycle, to update the angular speed variation [Delta] [omega ₁ (step 18). For example, in the case of the present embodiment, the fixed period is two periods.

Next, the operation amount adding unit 17b, the absolute value of [Delta] [omega ₁ | [Delta] [omega ₁ | comparing a first predetermined value [Delta] [omega _det as the isolated operation detection determining threshold (step 19). The absolute value of [Delta] [omega ₁ | [Delta] [omega ₁ | often higher than the first predetermined value _{Δω det (| Δω 1 | ≧} Δω det), determines that it has detected the isolated operation, the control is terminated (step 20).

On the other hand, the absolute value of [Delta] [omega ₁ | [Delta] [omega ₁ | case is less than the first predetermined value _{Δω det (| Δω 1 | <} | Δω det |), firstly, an electrical variation detecting signals generated by the electrical variation detecting unit 17a Is determined (step 22). When the electrical fluctuation detection signal is received, a constant step operation amount θ _{inj_step} is given to the internal phase difference angle Δθ (step 21), and the output line 30 is output regardless of the presence or absence of the electrical fluctuation detection signal. A constant manipulated variable θ _{int_inj} proportional to the change in the angular velocity of the AC voltage is _applied to the internal phase difference angle Δθ (step 27).

The calculation of the constant operation amount θ _{int_inj} is performed according to the following procedure. The signs of the proportional coefficients K ₁ and K ₂ determine whether or not the current cycle is the first step operation amount giving step when the electrical fluctuation detection signal is received (step 23), and the current cycle is the step operation. When the amount is given for the first time, the signs of the proportional coefficients K ₁ and K ₂ are made the same as the above-mentioned constant step operation amount θ _{inj_step} (step 24). Applying second and subsequent current cycle step manipulated variable, or, if the electrical variation detecting signal is not input, it is determined whether the slope of [Delta] [omega ₁ is attenuated (step 28), the [Delta] [omega ₁ Only when the inclination is attenuated, the signs of the proportional coefficients K ₁ and K ₂ are reversed (step 29).

If | Δω ₁ | is less than the second predetermined value ω _Klim that is a stepwise threshold based on the determination of the magnitude of the constant operation amount (step 25), the change in angular velocity is small, so the proportional coefficient K ₁ and the angular velocity fluctuation amount If Δω ₁ | is multiplied by Δω ₁ (step 26) and if | Δω ₁ | is equal to or greater than the second predetermined value ω _Klim , the change in angular velocity is large, so the sum of proportional coefficients K ₁ and K ₂ (K ₁ + K ₂ ) _Is multiplied by the angular velocity fluctuation amount Δω ₁ (step 30) to _obtain a constant operation amount θ _{int_inj} for the internal phase difference angle Δθ.

  As described above, in the operation amount providing unit 17b, the power conversion control device 4 amplifies the change in the angular velocity of the AC voltage during the independent operation by providing the operation amount for changing the angular velocity to the internal phase difference angle. When the variation in the angular velocity as a result of the application exceeds a predetermined amount, the single operation is actively detected.

  Incidentally, the amount of change in the angular velocity of the AC voltage is extremely small and can be ignored except during single operation, so even if an operation amount obtained by multiplying this by a proportional coefficient is added to the internal phase difference angle Δθ, the variation in the angular velocity of the AC voltage increases. There is no going.

  When the single operation detection unit 17 of the power conversion control device 4 detects the single operation actively or passively, in order to stop the supply of power from the distributed power source side to the commercial system side, a disconnection switch 5 is disconnected (step 3). The isolated operation detection unit 17 opens the disconnection switch 5 to shift the power conversion device 100 to the independent operation.

  As described above, after the isolated operation is detected on the distributed power source side, it is possible to continue the independent operation without stopping the power supply to the specific load connected in the independent system even after being disconnected from the power system 7. Yes (step 4).

  Since the power conversion device 100 according to the present embodiment has characteristics equivalent to a generator as described above, even when the system side is shut off, the power conversion apparatus 100 essentially has characteristics of shifting to independent operation without instantaneous interruption after detection of isolated operation. In addition, in the isolated operation detection unit 17 of the present embodiment, the manipulated variable applying unit 17b operates the internal phase difference angle Δθ, so that the angular velocity of the AC power voltage output from the power converter 3 is reduced. Only the fluctuation is amplified and the fluctuation of the voltage is suppressed, and even after detecting the single operation at high speed by the active detection method, it does not impair the essential characteristics of the above power converter, and it is independent operation without interruption. It becomes possible to shift to.

(Verification experiment)
The present inventors conducted an experiment under certain conditions in order to verify the effect when the above-described islanding detection process is executed. In this experiment, a configuration similar to a general power conversion control device that gives an operation amount for changing the angular velocity to the command value of the current phase component is used as a comparative example, and compared with the experimental result obtained by the first embodiment. The experimental results obtained by the examples are compared. In this experiment, in order to verify active detection at the time of power balance, which is most difficult to detect in isolated operation, passive detection and provision of step operation amount are invalidated.

FIG. 7 is a graph showing an experimental result of the isolated operation detection process when the operation amount I _{q_inj} for changing the angular velocity is given to the command value of the current phase component as a comparative example.

The upper graph of FIG. 7 shows the time change of the current periodic angular velocity ω1, the middle graph of FIG. 7 shows the time change of the angular velocity fluctuation amount Δω1, and the lower graph of FIG. 7 shows the time change of the system voltage effective value Vg. Show. In each graph, the time axis is common, and the thick line indicates the manipulated _variable I _{q_inj} .

  As shown in the graph of FIG. 7, in the isolated operation detection process in which the operation amount for changing the angular velocity is added to the command value of the current phase component and the amplification operation is performed, the time until the isolated operation is detected starts the experiment. About 0.5 seconds. Further, as shown in the lower part of FIG. 7, the system voltage effective value Vg from the start of the experiment to the detection of the isolated operation tends to increase, and the system voltage shows a sign that the fluctuation becomes large. That is, in the isolated operation detection process of the comparative example, interference with components other than the frequency becomes large, and the power converter inherently has a characteristic of shifting to independent operation without instantaneous interruption after detecting the isolated operation. .

  On the other hand, FIG. 8 is a graph showing an experimental result of the isolated operation detection process when an operation amount for changing the angular velocity is given to the internal phase difference angle Δθ.

The upper graph of FIG. 8 shows the time change of the current periodic angular velocity ω1, the middle graph of FIG. 8 shows the time change of the angular velocity fluctuation amount Δω1, and the lower graph of FIG. 8 shows the time change of the system voltage effective value Vg. Show. In each graph, the time axis is common, and the thick line indicates the manipulated _variable θ _{int_inj} .

  As shown in the graph of FIG. 8, when an amplification operation is performed by giving an operation amount for changing the angular velocity to the internal phase difference angle Δθ, the time until the isolated operation is detected is about 0.3 seconds from the start of the experiment. In comparison with the comparative example, it is shown that it is possible to realize an isolated operation detection that is faster than the isolated operation detection. Furthermore, as shown in the lower part of FIG. 8, the effective system voltage value Vg from the start of the experiment to the detection of the isolated operation is almost constant as compared with the comparative example in the lower part of FIG. 7. This makes it possible to suppress fluctuations in the output voltage even after detecting an isolated operation that has occurred due to an upper system fault during grid connection at a high speed using an active method. It has been demonstrated that this is possible. In addition, if this method is used, there is no interference or cancellation with other devices, and the power conversion device has characteristics such as a generator phase. Therefore, power having characteristics equivalent to other generators or similar generators. There is no loss of the characteristic that the microgrid can be expanded by connecting the conversion devices in parallel without limitation.

  In the above embodiment, the power conversion control device is configured to perform both passive islanding detection and active islanding detection. However, passive islanding detection processing (steps 12 to 12 in FIG. 5) is performed. 13) may be omitted.

  Moreover, in the said embodiment, although the power conversion control apparatus was set as the structure provided with the generator model 21, and the generator control part model 15 containing the governor model 19 and the AVR model 20, The present invention is not limited to such a configuration as long as a control model in which the governor, the AVR, and the generator main body are modeled is provided.

  From the foregoing description, many modifications and other embodiments of the present invention are obvious to one skilled in the art. Accordingly, the foregoing description should be construed as illustrative only and is provided for the purpose of teaching those skilled in the art the best mode of carrying out the invention. The details of the structure and / or function may be substantially changed without departing from the spirit of the invention.

  INDUSTRIAL APPLICABILITY The present invention can be used for a power conversion device having an interconnected operation function that operates in conjunction with an electric power system.

DESCRIPTION OF SYMBOLS 1 DC power generator 2 Secondary battery 3 Power converter 4 Power conversion controller 5 Disconnection switch 6 Specific load 7 Power system 8 System side circuit breaker 9 Transformer 10 General load 11 Active power detection part 12 Reactive power detection part DESCRIPTION OF SYMBOLS 13 Voltage detection part 14 Angular velocity detection part 15 Generator control part model 16 PWM signal generation part 17 Isolated operation detection part 17a Electrical fluctuation detection part 17b Operation amount provision part 19 Governor model part 20 AVR model part 21 Generator model part 100 Electric power Converter 101 DC power supply 200 Power conditioner system

Claims (5)

In the power conversion device used by being connected or disconnected by the power system and the system side circuit breaker, it is connected to the disconnecting switch connected to the system side circuit breaker via the output line and inputted from the DC power supply unit. A power conversion control device that controls a power converter that converts DC power into AC power and outputs the power to the output line,
Based on the deviation of the active power output by the power converter with respect to the active power command, the speed drooping characteristics of the virtual generator, and the deviation of the angular speed of the AC voltage output by the power converter from the predetermined angular speed A governor model unit for calculating an internal phase difference angle between the generator and the output line;
The virtual power generation based on the deviation of the reactive power output from the power converter with respect to the reactive power command, the voltage drooping characteristic of the virtual generator, and the deviation of the AC voltage output from the power converter with respect to a predetermined voltage An AVR model part for calculating the absolute value of the internal induced voltage of the machine,
Based on the internal phase difference angle calculated by the governor model unit, the absolute value of the internal induced voltage calculated by the AVR model unit, the internal impedance of the virtual generator, and the AC voltage output by the power converter. A generator model unit that calculates a command value of a current corresponding to the armature current of the virtual generator;
A PWM signal generation unit that converts the current command calculated by the generator model unit into a PWM signal and outputs the PWM signal to the power converter;
Based on the electrical fluctuation of the output line, an operation amount is given to the internal phase difference angle calculated by the governor model unit for each control period that matches the frequency of the AC voltage transmitted on the output line, and the result Independent operation detection configured to detect an active islanding operation when the fluctuation of the angular velocity of the vehicle is greater than or equal to a first predetermined value, and then open the disconnect switch and shift the power conversion device to an autonomous operation And
A power conversion control device. The islanding detection unit detects an electrical variation of the output line to generate an electrical variation detection signal, and detects the passive islanding when the electrical variation is a predetermined amount or more, and then An electrical fluctuation detector configured to open the disconnection switch and shift the power converter to a self-sustaining operation;
In the period in which an electrical fluctuation detection signal is input from the electrical fluctuation detection unit, the internal amount calculated by the governor model unit for the control period corresponding to the frequency of the AC voltage transmitted on the output line. In addition to being given to the phase difference angle, regardless of the presence or absence of the electrical fluctuation, it is proportional to the fluctuation of the angular velocity of the AC voltage transmitted on the output line at every control cycle that matches the frequency of the AC voltage transmitted on the output line. The manipulated variable is given to the internal phase difference angle calculated by the governor model unit, and the active islanding operation is detected when the resulting fluctuation of the angular velocity is equal to or greater than a first predetermined value, and then the disconnection The power conversion control device according to claim 1, further comprising: an operation amount providing unit configured to open a switch to shift the power conversion device to a self-sustained operation. 3. The power conversion control device according to claim 2 , wherein the operation amount assigning unit is configured to determine a sign of an operation amount proportional to the fluctuation of the angular velocity in a direction in which the fluctuation of the angular velocity increases. The operation amount for changing the angular velocity to be given to the internal phase difference angle when it is determined that the fluctuation of the angular velocity as a result of the addition is greater than or equal to a second predetermined value smaller than the first predetermined value. There is configured to be larger, the power conversion control apparatus according to claim 2 or 3.   The power conversion device or the power conversion control device measures or calculates the effective power output from the power converter and outputs the active power to the governor model unit, and the invalidity output from the power converter. Reactive power detection unit that measures or calculates power and outputs it to the AVR model unit; and measures and calculates voltage output from the power converter and outputs it to the AVR model unit and generator model unit 5. A voltage detection unit that performs measurement, and an angular velocity detection unit that measures or calculates an angular velocity of an AC voltage output from the power converter and outputs the measured angular velocity to the governor model unit. 6. The power conversion control device described in 1.

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