JP6831565B2 - Single-phase pseudo-synchronization power inverter and its controller - Google Patents

Description

The present invention relates to a technique of converting a DC voltage into a single-phase AC voltage and giving a pseudo-synchronization power to an inverter that supplies single-phase AC power to an electric power system.

In the power system, the inertia of the synchronous machine plays an important role for the stable operation of the system. That is, the synchronous machine contributes to the stable operation of the electric power system by operating in synchronization with the electric power system by the synchronization power.

On the other hand, renewable energies such as photovoltaic power generation systems are being introduced into electric power systems. Basically, renewable energy is converted into AC power by an inverter and supplied to the power system. In the future, it is expected that a large number of power electronics devices (for example, single-phase inverters) that convert renewable energy into AC power will be connected to the power system. However, such power electronics devices, unlike synchronous machines, inherently have no inertia or synchronization force. Therefore, there is a concern that the synchronization power in the power system will decrease as the number of power electronics devices increases. Therefore, a method has been proposed in which a power electronics device is made to simulate the behavior of a synchronous machine to stabilize a power system in which the synchronization power is reduced (see, for example, Non-Patent Documents 1 and 2).

A pseudo-synchronization force inverter that has the function of synchronizing with the system based on the sway equation of the synchronous machine can contribute to system stabilization by generating synchronization force, but due to its characteristics, it can also be used as a system even in a steady state. We are constantly giving and receiving power. Therefore, the vibration component of the secondary system is superimposed on the voltage and current according to the dynamic characteristics of the sway equation, and PI (Proportional + Integral) in the rotating coordinate system used in many conventional pseudo-synchronization force inverters. In control, it is difficult in principle to make the deviation from the command value zero. On the other hand, in PR (Proportional + Resonance) control in the stationary coordinate system, it is relatively easy to set the deviation to 0, and even in the previous research, PR control was used to synchronize with a single-phase electric vehicle charger. Attempts have been made to have (see, for example, Non-Patent Document 3).

Keita Noguchi, Yutaka Sasaki, Yoshifumi Zoka, Naoto Toshino, "System Stabilization Control Using Synchronous Power Inverter", 2013 Proceedings of the China Chapter of the Electrical and Information Society, pp. 67-68, 2013 Shinya Sekizaki, Yuki Nakamura, Yutaka Sasaki, Yoshifumi Zoka, Naoto Toshino, "Construction of System Stabilization Experimental Environment by Inverter", 2014 Proceedings of the China Chapter of the Electrical and Information Society CD-ROM, pp .. 59-60, 2014 Jon Are Suul, Salvatore D'Arco, and Giuseppe Guidi, “Virtual Synchronous Machine-Based Control of a Single-Phase Bi-Directional Battery Charger for Providing Vehicle-to-Grid Services”, IEEE Trans. Ind. App., Vol. 52, No. 4, pp. 3234-3244, 2016

The control system disclosed in Non-Patent Document 3 is composed of a double loop of a current control system for protecting the inverter from overcurrent and a voltage control system for maintaining the voltage of the power system at a desired value. However, in general, it is difficult to tune the parameters of a control system having such a multi-loop. In addition, when the inverter output voltage command value is calculated from the inverter internal voltage phase obtained by the sway equation and the actual inverter output voltage is made to follow this, the inverter output voltage is synchronized due to the characteristics of the voltage major loop and the current minor loop. It does not always faithfully reproduce the dynamic characteristics of. In particular, when designing multiple pseudo-synchronization power inverters in a coordinated manner for power system stabilization, multi-loops for voltage and current control can degrade performance, and multi-loops can be defeated from the control system. It is important to eliminate as much as possible.

In view of the above problems, it is an object of the present invention to provide a single-phase pseudo-synchronization power inverter having no multi-loop by a current control system and a voltage control system and a controller thereof.

The controller according to one aspect of the present invention is an inverter controller that converts a DC voltage into a single-phase AC voltage and supplies single-phase AC power to the power system, and is an inverter from the output current of the inverter and the voltage of the power system. The active power output calculation unit that calculates the active power output of, the governor unit that controls the governor command value for droop control of the inverter so that the output frequency of the inverter becomes the target frequency, and the effective voltage of the power system is the target voltage. Based on the regulator section that controls the effective voltage command value of the inverter so that it becomes, and the sway equation of the synchronous machine, the output voltage phase of the inverter is calculated from the active power output of the inverter and its command value, target frequency, and governor command value. An inverter based on the output voltage phase calculation unit to be calculated, the output voltage command value calculation unit that calculates the output voltage command value of the inverter from the effective voltage command value of the inverter and the output voltage phase of the inverter, and the output voltage command value of the inverter. It is provided with a PWM signal generation unit that generates a PWM signal for controlling the switching element in the above, and an overcurrent protection unit that limits the output voltage command value of the inverter when an overcurrent occurs in the inverter.

According to this configuration, the output voltage command value of the inverter based on the sway equation of the synchronous machine is calculated in the control system consisting of the active power output calculation unit, the governor unit, the regulator unit, the output voltage phase calculation unit, and the output voltage command value calculation unit. Then, based on the output voltage command value of the inverter, a PWM control signal for controlling the switching element in the inverter is generated. Here, the overcurrent protection unit that protects the inverter from overcurrent is provided in parallel with the PWM signal generation unit that generates the PWM signal, so that the current control system for protecting the inverter from overcurrent and the current control system A multi-loop is not formed by the voltage control system for maintaining the voltage of the power system at a desired value.

Specifically, the overcurrent protection unit detects the overcurrent of the output current of the inverter, the filter that extracts the frequency component of the output frequency band of the inverter from the output current of the inverter, and the output value of the filter. It has a limiter that limits the upper and lower limits of the limiter and a deviation amplification unit that amplifies the deviation between the output value of the limiter and the output current of the inverter, and the overcurrent detection unit detects the overcurrent of the output current of the inverter. At that time, the output value of the deviation amplification unit is added to the output voltage command value of the inverter, and the PWM signal generation unit pulses based on the output voltage command value of the inverter to which the output value of the deviation amplification unit is added. It generates a modulated signal.

According to this configuration, since the calculation with a delay is not performed on the output current of the inverter, overcurrent protection can be performed at high speed when an overcurrent occurs in the inverter.

Specifically, the active power output calculation unit calculates the α-axis component and β-axis component of the inverter output current from the output current of the inverter, and the first αβ-axis component calculation unit, and the voltage of the power system of the power system. The second αβ-axis component calculation unit that calculates the α-axis component and β-axis component of the voltage, the α-axis component and β-axis component of the output current of the inverter, and the α-axis component and β-axis component of the voltage of the power system of the inverter It has a single-phase power calculation unit that calculates the active power output.

According to this configuration, the single-phase active power output of the power system can be easily calculated from the output current of the inverter and the voltage of the power system.

The single-phase pseudo-synchronization power inverter according to one aspect of the present invention has the above controller and a plurality of switching elements, and converts a DC voltage into a single-phase AC voltage by switching operations of the plurality of switching elements. It is equipped with an inverter, and a plurality of switching elements in the inverter are controlled by a PWM signal output from the controller.

As described above, according to the present invention, it is possible to eliminate the multi-loop due to the current control system and the voltage control system in the controller of the single-phase pseudo-synchronization power inverter. This facilitates parameter tuning of the single-phase pseudo-synchronization force inverter, and facilitates cooperative design especially when a plurality of single-phase pseudo-synchronization force inverters are connected for power system stabilization.

Schematic diagram of a power supply device including a single-phase pseudo-synchronization force inverter according to an embodiment of the present invention. Diagram showing a model of a single-phase pseudo-synchronization force inverter Single-phase pseudo synchronization force Inverter controller control block diagram SOGI-QSG control block diagram Control block diagram of overcurrent protection unit Diagram showing a simulation model of a single-phase pseudo-synchronization force inverter Graph of inverter frequency during independent operation Graph of inverter active power output during independent operation Graph of inverter output voltage during independent operation Graph of inverter output current during independent operation Graph of inverter frequency at the time of failure Graph of inverter output voltage at the time of failure Graph of inverter output current at the time of failure

Hereinafter, embodiments will be described in detail with reference to the drawings as appropriate. However, more detailed explanation than necessary may be omitted. For example, detailed explanations of already well-known matters and duplicate explanations for substantially the same configuration may be omitted. This is to avoid unnecessary redundancy of the following description and to facilitate the understanding of those skilled in the art.

It should be noted that the inventors provide the accompanying drawings and the following description in order for those skilled in the art to fully understand the present invention, which are intended to limit the subject matter described in the claims. is not it. In addition, the dimensions, thickness, detailed shape of details, etc. of each member drawn in the drawing may differ from the actual ones.

1. 1. Outline of Power Supply Device FIG. 1 is a schematic view of a power supply device including a single-phase pseudo-synchronization force inverter according to an embodiment of the present invention. The power supply device 100 includes a power storage device 10, a DC / DC converter 20, a single-phase pseudo-synchronization power inverter 30, a reactor 40, and an isolation transformer 50.

The power storage device 10 is a device that stores electric power generated by renewable energy such as sunlight and wind power. The power storage device 10 can be composed of a lithium ion capacitor, an electric double layer capacitor, or the like. The DC / DC converter 20 receives electric power from the power storage device 10 and converts it into an arbitrary DC voltage for output. The single-phase pseudo-synchronization power inverter 30 converts the DC voltage supplied from the DC / DC converter 20 into a single-phase AC voltage. The AC voltage output from the single-phase pseudo-synchronization power inverter 30 is connected to an external power system via a grid interconnection filter 40 and an isolation transformer 50.

In this way, the power supply device 100 does not have a synchronous machine, but the single-phase pseudo-synchronization power inverter 30 simulates the behavior of the synchronous machine, thereby enabling interconnection to an arbitrary power supply system including a microgrid. ing.

2. 2. Basic control system of single-phase pseudo-synchronization power inverter 2.1 Basic circuit configuration The single-phase pseudo-synchronization power inverter 30 includes an inverter 31 and a controller 32. The inverter 31 has an IGBT (Insulated Gate Bipolar Transistor) 311 as a plurality of switching elements. When these IGBTs 311 are switched, the DC voltage supplied from the DC / DC converter 20 is converted into a single-phase AC voltage. The controller 32 feeds back the output current of the inverter 31 and the secondary side voltage of the isolation transformer 50, that is, the voltage of the power system to generate a PWM (Pulse Width Modulation) signal to switch and control each IGBT 311 in the inverter 31.

FIG. 2 is a diagram showing a model of the single-phase pseudo-synchronization force inverter 30. The single-phase pseudo-synchronization power inverter 30 can be regarded as a synchronous machine in which a pseudo-rotor, which is a virtual rotor, rotates to generate single-phase AC power. Now, assuming that the effective voltage value of the power system (Grid) is V ^grid and the angular frequency is ω, the voltage of the power system at time t is represented by v ^grid = √2V ^grid · sin (ωt). On the other hand, when the effective voltage value of the single-phase pseudo synchronizing power inverter 30 and ^{V inv,} the output voltage of the single-phase pseudo synchronizing power inverter 30 at time t is given by ^{v inv = √2V inv · sin (} ωt + θ diff) .. That is, the pseudo-rotor angle θ _inv is advanced by θ _diff from ωt.

FIG. 3 is a control block diagram of the controller 32 of the single-phase pseudo-synchronization force inverter 30. The controller 32 includes an active power output calculation unit 33, a governor unit 34, a regulator unit 35, an output voltage phase calculation unit 36, an output voltage command value calculation unit 37, a PWM signal generation unit 38, and an overcurrent protection unit. It has 39 and.

Active power output calculation section 33 calculates an active power output _{P e} of the inverter 31 from voltage ^{v grid} of the output current ^{i inv} and power system of the inverter 31.

The governor unit 34 controls the governor command value P _gov for droop control of the inverter 31 so that the output frequency ω _inv of the inverter 31 becomes the target frequency ω _ref .

The regulator unit 35 controls the effective voltage command value ^Vinv of the inverter 31 so that the effective voltage V ^grid of the power system becomes the target voltage V ^{grid *} .

Output voltage phase calculation section 36, based on the swing equation of the synchronous machine, the active power output _{P e} and the command value _{P m} of the inverter 31, the target frequency omega _ref, and the governor command value output voltage phase from the _{P gov} inverter 31 Calculate θ _inverter .

The output voltage command value calculation unit 37 calculates the output voltage command value √2V ^inv · sin (θ _inv ) of the inverter 31 from the effective voltage command value V ^inv of the inverter 31 and the output voltage phase θ _inv of the inverter 31.

The PWM signal generation unit 38 generates a PWM signal for controlling the switching element 311 in the inverter 31 based on the output voltage command value v ^* of the inverter 31.

When an overcurrent occurs in the inverter 31, the overcurrent protection unit 39 limits the output voltage command value v ^* of the inverter 31 to protect the inverter 31 from the overcurrent.

The model shown in FIG. 2 can be embodied by the controller 32 having the above configuration. Hereinafter, the operation of each block of the controller 32 will be described while showing the control system equations.

2.2 Sway equation The basic control system of the single-phase pseudo-synchronization force inverter 30 is based on the sway equation (1) of the three-phase synchronous machine.

In the equation (1), _Minv is a pseudo-inertia constant of the single-phase pseudo-synchronization force inverter 30, D _inv is a pseudo-dumping coefficient, P _m is a pseudo-machine input, and _Pe is an electric output. (1) formula is a differential equation representing the dynamic characteristic of the three-phase synchronous machine, when applying it to the single-phase pseudo synchronizing power inverter 30, the problem of how to handle the P _e arises. As will be described later, P _e is to vibrate at a frequency twice the fundamental frequency is a single-phase circuit, treated as a DC quantity with a stationary coordinate components. When P _e is treated as a DC amount, P _m and P _e match in the steady state, but when P _e changes due to disturbance, there is a difference between the two. The single-phase pseudo-synchronization force inverter 30 automatically synchronizes with the system while vibrating according to the positive and negative of the right side of the equation (1). The eigenvalues of the equation of state based on equation (1) can be arranged on the left half plane by appropriately setting the parameters, and at this time, it is possible to stably synchronize with the system.

2.3 Basic control system with governor Next, the basic control system with governor for maintaining the frequency will be described. The differential equation obtained by linearizing the equation (1) near the equilibrium point is solved to calculate the minute fluctuation amount Δθ _inv of the rotor angle θ _inv , and θ _inv is obtained. By linearizing Eq. (1) with the governor included, Eqs. (2) to (6) can be obtained.

Here, [Delta] [theta] _inv is small variation from the steady state of the pseudo rotor angle _{(= ω inv t), P} gov is governor _{output, K gov} is _{Gabanagein, T gov} the governor time constant, omega _ref inverter frequency command value , Ω _inv is the inverter frequency. Equations (4) and (5) that calculate the governor output using the frequency deviation as an input have a first-order lag characteristic, and can be expected to have the effect of stabilizing the control system.

The governor unit 34 calculates P _gov according to the equation (5), and the output voltage phase calculation unit 36 calculates θ _inv according to the equations (2) to (4) and (6).

2.4 calculating the active power output calculation section 33 of the single-phase active power, first calculates the output current _{i inv} the alpha axis component ^{i inv} _alpha and beta axis component ^{i inv} _beta inverter 31 from the output current ^{i inv} of the inverter 31 1 of αβ-axis component calculation unit 331, a second αβ-axis component calculation unit 332 for calculating the alpha-axis component of the voltage ^{v grid} of the power system ^{v grid} _alpha and beta axis component ^{v grid} _beta from the voltage ^{v grid} of power system ^{_{, i inv α, i inv β}} , v grid α, v and a single-phase power calculation unit 333 from the ^grid _beta calculates the active power output _{P e} of the inverter 31.

The static coordinate component is used to calculate the active power in the single-phase circuit. Conversion of voltage and current to a static coordinate system in a single-phase circuit can be realized by using the measured waveform as an α-axis component and generating a β-axis component orthogonal to the α-axis component. This is called SOGI-QSG (second order generalized integrator --quadrature signal generation). The transfer function of SOGI-QSG has a gain of 0 [dB] near the resonance frequency ω ₀ , an α-axis component phase of 0 [deg], and a β-axis component phase of −90 [deg]. With this characteristic, the SOGI-QSG can remove the harmonic component, and can obtain the α-axis component having the resonance frequency ω ₀ as the fundamental wave and the β-axis component orthogonal to the α-axis component. Assuming that the input signal is u, the α-axis component is u _α , and the β-axis component is u _β , the transfer function of SOGI-QSG can be expressed as equations (7) and (8).

(7) By setting ω ₀ in Eq. (8) to the frequency ω _{inv of} the single-phase pseudo-synchronization force inverter 30 obtained from the sway equation (ω _inv = ω ₀ ), the rest with ω _inv as the fundamental wave. Convert to a coordinate system.

FIG. 4 is a control block diagram of SOGI-QSG. Since ω _inv fluctuates dynamically, the value obtained from the sway equation is input as shown in FIG. Since the bandwidth of the transfer function of Eqs. (7) and (8) changes depending on the value of k, it is determined in consideration of the quick response and the harmonic component in the rest coordinate component calculation process. (7) .alpha..beta axis component of the voltage Vgrid of the electric power system calculated by using the equation (8), and the use of .alpha..beta axis component of the output current ^{i inv} of the inverter 31, the active power output _{P e} of the inverter 31 (9) It can be calculated by the formula.

The first αβ axis component calculation unit 331 calculates i ^inv _α and i ^inv _β according to equations (7) and (8), and the second αβ axis component calculation unit 332 calculates v ^grid _α according to equations (7) and (8). and ^v to calculate the ^grid _beta, single-phase power calculation unit 333 calculates a _{P e} according (9).

The first αβ-axis component calculation unit 331 and the second αβ-axis component calculation unit 332 can be configured by a bandpass filter instead of the SOGI-QSG.

2.5 Automatic voltage regulator (AVR)
From the pseudo-rotor angle θ _inv obtained from the sway equation, the virtual internal voltage v ^{inv *} of the single-phase pseudo-synchronization force inverter 31 is as shown in equation (10).

The effective voltage command value ^Vinv of the inverter 31 is adjusted by the automatic voltage regulator (AVR), that is, the regulator unit 35. That is, the single-phase pseudo-synchronization force inverter 30 has an AVR for maintaining the interconnection point voltage, and the AVR is simulated by a control block having a transfer function having a first-order lag with respect to the command value. Since it is assumed that the internal DC voltage of the inverter 31 is controlled at high speed by the DC / DC converter 20 attached to the inverter 31 and the power storage device 10 so as to follow the rated value, among the excitation systems of the synchronous machine, It can be designed by ignoring the part with a large time constant. Let V ^inv be the sum of the output V ^{avr of the} AVR and the voltage V ^grid of the detected power system. Equations (11) and (12) show the output V ^avr of the AVR and the accompanying change in V ^inv when the gain of the AVR is K _avr , the time constant is T _avr , and the voltage command value is V ^{avr *} .

The effective voltage V ^grid of the power system is calculated by Eq. (13) when the α-axis component of the measured interconnection point voltage is v _α and the β-axis component is v _β .

The regulator unit 35 calculates √2V ^inv , which is the maximum output voltage value of the inverter 31, according to the equations (10) to (13).

2.6 Inverter protection circuit Single-phase pseudo-synchronization power that outputs the voltage v ^{inv *} obtained from equation (10) based on the sway equation that simulates the dynamic characteristics of the synchronous machine. The inverter 30 has a synchronization power in a steady state. It is possible to contribute to system stabilization. However, unlike a synchronous machine having a mechanical structure, the inverter 31 has an allowable current i ^{lil that} can be obtained from the capacity of the converter. Is required.

In order to make the single-phase pseudo-synchronization power inverter 30 simulate the dynamic characteristics of the synchronous machine, the output voltage v ^{inv *} shown in Eq ^. Should be output. However, if there is a multi-loop of a current minor loop and a voltage major loop as in Non-Patent Document 3, it becomes an obstacle to simulate the dynamic characteristics of the synchronous machine. Therefore, in the present embodiment, such a multi-loop is eliminated and a PWM signal is generated instead. An overcurrent protection unit 39 is provided in parallel with the unit 38.

The overcurrent protection unit 39 has an output voltage command value of the inverter 31 √2V ^inv · sin (output from the output voltage command value calculation unit 37 in a steady state in which an overcurrent does not occur in the output current i ^inv of the inverter 31. θ _inv ) is directly input to the PWM signal generation unit 38 as the output voltage command value v ^* of the inverter 31. On the other hand, the overcurrent protection unit 39 outputs the output voltage command value √2V ^{inv of the} inverter 31 output from the output voltage command value calculation unit 37 when an overcurrent is flowing in the output current i ^inv of the inverter 31. The protection signal v ^prot is added to sin (θ _inv ) to limit the output voltage command value v ^* of the inverter 31 input to the PWM signal generation unit 38.

FIG. 5 is a control block diagram of the overcurrent protection unit 39. Overcurrent protection unit 39, an overcurrent detection unit 391 for detecting an overcurrent of the output current ^{i inv} of the inverter 31, a filter 392 for extracting a frequency component of the output frequency band of the inverter 31 from the output current ^{i inv} of the inverter 31 , A limiter 393 that limits the upper and lower limits of the output value of the filter 392, and a deviation amplification unit 394 that amplifies the deviation between the output value of the limiter 393 and the output current i ^inv of the inverter 31 are provided. When the detection unit 391 detects an overcurrent of the output current i ^inv of the inverter 31, the output value v ^prot of the deviation amplification unit 394 is added to the output voltage command value √2V ^inv · sin (θ ^inv ) of the inverter 31. The PWM signal generation unit 38 generates a pulse modulation signal based on the output voltage command value v ^* of the inverter 31 to which the output value v ^prot of the deviation amplification unit 394 is added.

2.6.1 Extraction of fundamental wave component The output current i ^inv of the inverter 31 measured by the sensor contains a harmonic component, and when a failure occurs on the power system side, the i ^inv may also contain a transient component. Therefore, a filter 392 composed of SOGI-QSG is used to extract a positive / negative symmetric sine wave signal having a frequency component equal to the inverter output frequency ω _inv, and this is limited via a limiter 39 to obtain an output current command value. ^Let i ^{inv *} . As a result, the output current command value i ^{inv *} is always a sine wave regardless of the fluctuation of the output current i ^inv of the inverter 31. The reason for using SOGI-QSG filter 392, to remove the harmonic component and positive-negative asymmetrical component from the AC waveform i ^inv measured, in order to stabilize the control system.

The filter 392 can also be configured with a bandpass filter instead of the SOGI-QSG.

2.6.2 Current feedback using direct AC waveform For the output current command value i- ^{invert *} , which is a sinusoidal wave, the AC waveform i- ^invert detected by the sensor is compared with the direct command value i- ^{inv *,} and the deviation is K- _prot. The doubled value is added to the output voltage command value √2V ^inv · sin (θ ^inv ) of the inverter 31 output from the output voltage command value calculation unit 37. In this method, since the AC waveform ^inv detected by the sensor is not calculated with a delay such as a filter, high-speed overcurrent protection is possible even for a momentary failure.

2.6.3 Parallelization of inverter protection circuit The feature of this control system is a parallel structure in which the protection circuit operates only when a failure occurs without disturbing the dynamic characteristic (10) of the synchronous machine in the steady state. The overcurrent detection unit 391 shown in FIG. 5 outputs "1" when the output current i ^inv of the inverter 31 exceeds the inverter allowable current i ^lim , and outputs "0" when the i ^inv is ^less than i ^lim. It acts as a trigger. Only when "1" is output from the overcurrent detection unit 391, the output voltage command value v ^* of the inverter 31 is suppressed at high speed, and the output voltage v ^inv of the inverter 31 is obtained from the sway equation in other steady states. It becomes v ^{inv *} . As a result, the factors that hinder the dynamic characteristics of the synchronous machine are eliminated. The operations in the above protection circuit are shown in equations (14), (15), and (16).

In equation (14), the sum of the output voltage command value √2V ^inv · sin (θ _inv ) of the inverter 31 output from the output voltage command value calculation unit 37 and the protection signal v ^prot output from the overcurrent protection unit 39 is ^Indicates that the inverter output is v ^* . Equation (15) represents that the protection signal v ^prot is output only when the trigger of the overcurrent detection unit 391 is turned on. Equation (16) shows that i ^{inv *} is obtained with the inverter allowable current i ^lim as a limiter for the sine wave obtained by using SOGI-QSG.

3. 3. Numerical simulation Next, the numerical simulation result of the single-phase pseudo-synchronization force inverter 30 according to the present embodiment will be described. FIG. 6 is a diagram showing a simulation model of the single-phase pseudo-synchronization force inverter 30. Three single-phase pseudo-synchronization power inverters 30 are connected in parallel to the infinity bus (3-phase, 6600 [V], 60 [Hz]), and all three have the same parameters and are connected to the same phase. .. Single-phase pseudo-synchronization force The DC link portion of the inverter 30 is simulated by the DC voltage source _VDC . The single-phase pseudo-synchronization power inverter 30 is connected to the infinity bus via a filter and a transformer, has a transformation ratio of 400/6600, and the filter is composed of a resistor R and an inductance L. There is a line R _line + jX _line between the inverter interconnection point and the infinity bus. A three-phase load (resistor R _load ) is connected to the simulation model, and its size is set to a size that allows the frequency to be maintained by the single-phase pseudo-synchronization force inverter 30 even during independent operation. The simulation was started after synchronizing the three single-phase pseudo-synchronization power inverters 30 with the infinity bus, and at t = 0.0 [s], the single-phase pseudo-synchronization power inverter using a switch from the infinity bus. The 30 is separated and the operation is started independently. Then, a three-phase ground fault occurs on the line at t = 2.0 [s], and it is verified whether the constructed control system operates normally. The three-phase ground fault shall be eliminated at t = 2.05 [s]. The simulation conditions are shown in Table 1.

3.1 Independent operation Figures 7, 8, 9 and 10 show the frequency, active power output, and output voltage of the single-phase pseudo-synchronization power inverter 30 during independent operation (t = 0.0 [s] to), respectively. , And the graph of the output current. From FIG. 7, it can be confirmed that the frequency drops once at the transition to independent operation, but then the frequency converges to a constant value due to the effect of governor and damping. From this, it can be seen that the single-phase pseudo-synchronization force inverters 30 are strongly synchronized with each other. Further, from FIG. 8, the active power output is automatically increased from Pm = 1000 [W] in order to maintain the frequency. From FIGS. 9 and 10, it can be seen that the single-phase pseudo-synchronization force inverter 30 appropriately outputs a sinusoidal voltage and current.

3.2 When a line failure occurs Figures 11, 12 and 13 show the frequency, output voltage, and output current of the single-phase pseudo-synchronization force inverter 30 after t = 2.0 [s] when a ground fault has occurred, respectively. It is a graph of. From FIG. 11, it can be confirmed that the single-phase pseudo-synchronization force inverter 30 accelerates due to the failure and returns to the original frequency after the failure is removed. As can be seen from FIG. 12, an instantaneous voltage drop occurs between t = 2.0 [s] and t = 2.05 [s] where a ground fault has occurred, and the inverter output voltage drops significantly. doing. It can be confirmed from FIG. 13 that the current is suppressed in order to protect the single-phase pseudo-synchronization force inverter 30 even when such a severe instantaneous voltage drop occurs.

4. Effects / Advantages of the Embodiment As described above, the single-phase pseudo-synchronization force inverter 30 according to the present embodiment can eliminate the multi-loop due to the current control system and the voltage control system. This facilitates parameter tuning of the single-phase pseudo-synchronization force inverter 30. In particular, cooperative design becomes easy when a plurality of single-phase pseudo-synchronizing force inverters 30 are connected for power system stabilization.

Further, in the single-phase pseudo-synchronization power inverter 30 according to the present embodiment, the following advantages can be obtained by providing the overcurrent protection unit 39 for protecting the overcurrent of the inverter 31 in parallel with the PWM signal generation unit 38.
(1) The overcurrent protection unit 39 functions only when a power transmission line or the like fails, and does not interfere with the main circuit during normal operation.
(2) Since the overcurrent protection unit 39 does not interfere with the main circuit during normal operation, the stabilization design of the entire system becomes easy.
(3) An interconnection operation mechanism can be easily realized in microgrid construction.
(4) The independent design of the overcurrent control system is also easy, and the FRT (Fault Ride Through) design is easy.

In particular, the single-phase pseudo-synchronization power inverter 30 according to the present embodiment can be connected in large numbers when disconnected from the power system to construct an independent single-phase microgrid only by the inverter group. Then, in the single-phase pseudo-synchronization force inverter 30 according to the present embodiment, the overcurrent protection unit 39 that eliminates the multi-loop by the current control system and the voltage control system and protects the overcurrent of the output current of the inverter 31 is output. By adopting a configuration in which the voltage phase calculation unit 36 and the output voltage command value calculation unit 37 are not inserted in series but are provided in parallel with the PWM signal generation unit 38, overcurrent protection is realized without impairing the characteristics of the entire control system. can do. Due to this feature, the single-phase pseudo-synchronization force inverter 30 according to the present embodiment can greatly contribute to the system stabilization of the single-phase microgrid independent of the power system.

Further, in the present embodiment, the synchronous machine model is applied as the inverter model as shown in FIG. 2, but the inverter model applicable to the present invention is not limited to the synchronous machine model. In addition to the synchronous machine model, the present invention can apply any model having a high power system stabilizing effect.

As described above, an embodiment has been described as an example of the technique in the present invention. To that end, the accompanying drawings and detailed description are provided.

Therefore, among the components described in the attached drawings and the detailed description, not only the components essential for solving the problem but also the components not essential for solving the problem in order to exemplify the above technology. Can also be included. Therefore, the fact that these non-essential components are described in the accompanying drawings or detailed description should not immediately determine that those non-essential components are essential.

Further, since the above-described embodiment is for exemplifying the technique of the present invention, various changes, replacements, additions, omissions, etc. can be made within the scope of claims or the equivalent scope thereof.

30 Single-phase pseudo-synchronization power inverter 31 Inverter 311 IGBT (switching element)
32 Controller 33 Active power output calculation unit 331 First αβ axis component calculation unit 332 Second αβ axis component calculation unit 333 Single-phase power calculation unit 34 Governor unit 35 Regulator unit 36 Output voltage phase calculation unit 37 Output voltage command value calculation Part 38 PWM signal generation part 39 Overcurrent protection part 391 Overcurrent detection part 392 Filter 393 Limiter 394 Deviation amplification part

Claims (9)

An inverter controller that converts DC voltage to single-phase AC voltage and supplies single-phase AC power to the power system.
An active power output calculation unit that calculates the active power output of the inverter from the output current of the inverter and the voltage of the power system.
A governor unit that controls a governor command value for droop control of the inverter so that the output frequency of the inverter becomes a target frequency.
A regulator unit that controls the effective voltage command value of the inverter so that the effective voltage of the power system becomes the target voltage.
An output voltage phase calculation unit that calculates the output voltage phase of the inverter from the active power output of the inverter, its command value, the target frequency, and the governor command value based on the sway equation of the synchronous machine.
An output voltage command value calculation unit that calculates the output voltage command value of the inverter from the effective voltage command value of the inverter and the output voltage phase of the inverter.
A PWM signal generator that generates a PWM signal for controlling a switching element in the inverter based on the output voltage command value of the inverter.
A controller provided with an overcurrent protection unit that limits the output voltage command value of the inverter when an overcurrent occurs in the inverter. The overcurrent protection unit
An overcurrent detector that detects the overcurrent of the output current of the inverter,
A filter that extracts the frequency component of the output frequency band of the inverter from the output current of the inverter,
A limiter that limits the upper and lower limits of the output value of the filter,
It has a deviation amplification unit that amplifies the deviation between the output value of the limiter and the output current of the inverter.
When the overcurrent of the output current of the inverter is detected by the overcurrent detection unit, the output value of the deviation amplification unit is added to the output voltage command value of the inverter.
The PWM signal generation unit, according to claim 1 and generates a pulse modulated signal based on the output voltage command value of the inverter output values of the deviation amplifier is added up controller. The controller according to claim 2, wherein the filter is composed of SOGI-QSG (second order generalized integrator-quadrature signal generation). The controller according to claim 2, wherein the filter is composed of a bandpass filter. The active power output calculation unit
A first αβ-axis component calculation unit that calculates the α-axis component and β-axis component of the output current of the inverter from the output current of the inverter, and
A second αβ-axis component calculation unit that calculates the α-axis component and β-axis component of the power system voltage from the voltage of the power system, and
Claims 1 to claim that include a single-phase power calculation unit that calculates the active power output of the inverter from the α-axis component and β-axis component of the output current of the inverter and the α-axis component and β-axis component of the voltage of the power system. Item 4. The controller according to any one of Item 4. The controller according to claim 5, wherein the first αβ-axis component calculation unit and the second αβ-axis component calculation unit are composed of SOGI-QSG (second order generalized integrator-quadrature signal generation). The fifth or sixth aspect of the present invention, wherein the regulator unit calculates an effective voltage command value of the inverter from the α-axis component and the β-axis component of the voltage of the power system calculated by the second αβ-axis component calculation unit. Controller. The controller according to any one of claims 1 to 7.
It has a plurality of switching elements, and includes an inverter that converts a DC voltage into a single-phase AC voltage by the switching operation of the plurality of switching elements.
A single-phase pseudo-synchronization power inverter in which the plurality of switching elements in the inverter are controlled by a PWM signal output from the controller. A single-phase microgrid in which a large number of single-phase pseudo-synchronization power inverters according to claim 8 are connected.

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