Control device, power converter, control method

Abstract

This technology provides the ability to appropriately control the AC current as seen from the power conversion unit. [Solution] A control device 46 according to one embodiment of the present disclosure includes a power conversion unit 42 and an AC filter 50 connected to the other end of the power conversion unit 42. The control device 46 controls a power system 1 that supplies power in at least one direction, from AC to DC and from DC to AC, through the power conversion unit 42 and the AC filter 50, so that the measured value of the current at the interconnection point GCP downstream of the AC filter 50, as seen from the power conversion unit 42, follows a command value. The control device 46 predicts the current at the interconnection point GCP at a predetermined future time based on the measured value or command value of the voltage at the other end of the power conversion unit 42, the measured value of the current at the interconnection point GCP, and the circuit constants of the AC filter 50, and controls the power conversion unit 42 based on the predicted value of the current at the interconnection point GCP at the predetermined time and the command value.

Description

[Technical Field]

[0001] This disclosure relates to control devices, etc. [Background technology]

[0002] Conventionally, a technique is known for controlling a power conversion unit (e.g., an inverter) that performs power conversion between DC at one end and AC at the other end, and an AC filter unit (e.g., an LCL filter) connected to the other end of the power conversion unit, so that the current at a predetermined point in the power path downstream of the AC filter unit (e.g., a connection point) as seen from the power conversion unit follows a command value (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2013-505688 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] However, there is room for improvement in the current control described above.

[0005] Therefore, in light of the above issues, the objective is to provide a technology that can appropriately control the AC current as seen from the power conversion unit. [Means for solving the problem]

[0006] To achieve the above objective, in one embodiment of this disclosure, A power system comprising a power conversion unit that performs power conversion between DC at one end and AC at the other end, and an AC filter unit connected to the other end of the power conversion unit, wherein the power system supplies power in at least one direction, from AC to DC and from DC to AC, through the power conversion unit and the AC filter unit, is a control device that controls the power conversion unit so that the measured current at a predetermined point in the AC power path downstream of the AC filter unit, as seen from the power conversion unit, follows a command value. Based on the measured voltage or command value at the other end of the power conversion unit, the measured current at the predetermined location, and the circuit constants of the AC filter unit, the current at the predetermined location at a predetermined future time is predicted. Based on the predicted value and command value of the current at the predetermined location at the predetermined time, the power conversion unit is controlled. A control device is provided.

[0007] In other embodiments of this disclosure, A power conversion unit that performs power conversion between DC at one end and AC at the other end, the power conversion unit having an AC filter unit connected to the other end, A power system that supplies power in at least one direction, from AC to DC and from DC to AC, through the power conversion unit and the AC filter unit, comprises a control unit that controls the power conversion unit so that the measured current at a predetermined point in the AC power path downstream of the AC filter unit, as seen from the power conversion unit, follows a command value. The control unit, Based on the measured voltage or command value at the other end of the power conversion unit, the measured current at the predetermined location, and the circuit constants of the AC filter unit, the current at the predetermined location at a predetermined future time is predicted. Based on the predicted value and command value of the current at the predetermined location at the predetermined time, the power conversion unit is controlled. A power converter is provided.

[0008] Furthermore, in yet another embodiment of this disclosure, A power system comprising a power conversion unit that performs power conversion between DC at one end and AC at the other end, and an AC filter unit connected to the other end of the power conversion unit, wherein the power system supplies power in at least one direction, from AC to DC and from DC to AC, through the power conversion unit and the AC filter unit, and a control method for controlling the power conversion unit so that the measured current at a predetermined point in the AC power path downstream of the AC filter unit, as seen from the power conversion unit, follows a command value. Based on the measured voltage or command value at the other end of the power conversion unit, the measured current at the predetermined location, and the circuit constants of the AC filter unit, the current at the predetermined location at a predetermined future time is predicted. Based on the predicted value and command value of the current at the predetermined location at the predetermined time, the power conversion unit is controlled. A control method is provided. [Effects of the Invention]

[0009] According to the above embodiment, the AC current as seen from the power conversion unit can be appropriately controlled. [Brief explanation of the drawing]

[0010] [Figure 1] This is a diagram showing an example configuration of a power system. [Figure 2] This diagram shows an example configuration of a power conversion unit. [Figure 3] This diagram illustrates the phase relationship between voltage and current in a power system. [Figure 4] This is a control block diagram showing the functional configuration of an example of a control device. [Figure 5] This diagram illustrates an example of a power supply system control method. [Figure 6] This is a control block diagram showing an example of the functional configuration of a current control unit. [Figure 7] This is a control block diagram showing an example of the functional configuration of the correction value generation unit. [Figure 8] This figure shows an example of a method for generating manipulated variables in the manipulated variable generation unit. [Figure 9]This diagram illustrates the admittance characteristics related to the interconnection point current. [Figure 10] This diagram illustrates the admittance characteristics related to the interconnection point current. [Figure 11] This figure shows an example of the time variation of the interconnection point current and the on / off state of the semiconductor switch in the power conversion section. [Figure 12] This is a timing chart diagram showing an example of the processing flow of a control device. [Figure 13] This is a control block diagram showing a control device related to a comparative example. [Figure 14] This is a time chart diagram showing the first example of the simulation results of current control by a control device related to a comparative example. [Figure 15] This is a time chart diagram showing a second example of the simulation results of current control by the control device relating to the comparative example. [Figure 16] This is a time chart diagram showing a third example of the simulation results of current control by a control device related to the comparative example. [Figure 17] This is a time chart diagram showing the fourth example of the simulation results of current control by a control device related to the comparative example. [Figure 18] This is a time chart diagram showing a first example of the simulation results of current control by the control device according to the embodiment. [Figure 19] This is a time chart diagram showing a second example of the simulation results of current control by the control device according to the embodiment. [Figure 20] This is a control block diagram showing the functional configuration of another example of a control device. [Modes for carrying out the invention]

[0011] The embodiments will be described below with reference to the drawings.

[0012] [Power System Configuration] The configuration of the power system 1 according to this embodiment will be described with reference to Figures 1 to 3.

[0013] Figure 1 shows the configuration of an example of power system 1. Figure 2 shows the configuration of an example of a power conversion unit. Figure 3 is a diagram illustrating the phase relationship between voltage and current in power system 1.

[0014] As shown in Figure 1, the power system 1 includes a power supply system 10 and a power grid 20.

[0015] Power system 1 exchanges power between power supply system 10 and power grid 20.

[0016] In power system 1, the exchange of power between the power supply system 10 and the power grid 20 is, for example, a bidirectional exchange of power. Alternatively, the exchange of power between the power supply system 10 and the power grid 20 may consist only of power supply from one to the other, such as power supply only from the power supply system 10 to the power grid 20, or power supply only from the power grid 20 to the power supply system 10.

[0017] The power supply system 10 includes a DC power supply 30, a power converter 40, and an AC filter 50.

[0018] The power supply system 10 uses a power converter 40 to exchange power between the DC power supply 30 and the power grid 20. For example, as shown in Figure 1, current flows between the power converter 40 and the power grid 20 through the reactor 50L1, filter capacitor 50C, and reactor 50L2 of the AC filter 50, the line resistor 60, and the line impedance 70.

[0019] The power system 20 supplies alternating current (AC) power to electrical loads not shown. The AC power of the power system 20 is, for example, single-phase AC. Alternatively, the AC power of the power system 20 may be three-phase AC.

[0020] The DC power supply 30 is electrically connected to one end of the power converter 40 by a DC link.

[0021] The DC power supply 30 is, for example, a grid battery. The grid battery is, for example, a liquid lithium-ion battery or an all-solid-state battery.

[0022] Furthermore, the DC power supply 30 may be a wind turbine included in the wind power generation system as the power supply system 10. The wind turbine as the DC power supply 30 includes a wind turbine, a generator (for example, a PM (Permanent Magnet) type synchronous generator) mechanically connected to the wind turbine by a rotating shaft, and a power converter that converts the AC power output by the generator into DC power. In this case, the exchange between the power supply system 10 and the power grid 20 is limited to the supply of power from the power supply system 10 to the power grid 20.

[0023] Furthermore, the DC power supply 30 may be, for example, a photovoltaic generator (specifically, a solar panel) included in a photovoltaic power generation system as the power supply system 10. In this case, the interaction between the power supply system 10 and the power grid 20 is limited to the supply of power from the power supply system 10 to the power grid 20.

[0024] The power converter 40 is electrically connected at one end to the DC power supply 30 via a DC link, and at the other end to the power system 20 via an AC filter 50. The power converter 40 performs power conversion between the DC power supply 30 and the AC power system 20.

[0025] Specifically, when power is supplied from the power supply system 10 to the power grid 20, the DC is converted to AC of the desired voltage (specifically, voltage amplitude) and frequency and output to the power grid 20 via the AC filter 50. Also, when power is supplied from the power grid 20 to the power supply system 10, the AC is converted to DC and supplied to the DC power supply 30 via the DC link.

[0026] The power conversion device 40 includes, for example, a power conversion unit 42 capable of converting DC power to AC power of a desired voltage and frequency, or AC power to DC power, a drive circuit 44 for driving the power conversion unit 42, and a control device 46.

[0027] For example, as shown in Figure 2, the power conversion unit 42 includes a DC link 42A and an inverter circuit 42B.

[0028] The DC link 42A is connected at one end to the DC power supply 30 and at the other end to the inverter circuit 42B. The DC link 42A includes a positive line 42PL, a negative line 42NL, and a smoothing capacitor 42C.

[0029] The positive line 42PL is a power line connected to the positive terminal of the DC power supply 30. The negative line 42NL is a power line connected to the negative terminal of the DC power supply 30. The smoothing capacitor 42C is electrically connected between the positive line 42PL and the negative line 42NL to smooth the DC of the DC link 42A.

[0030] Furthermore, a DC smoothing reactor may be provided in either the positive line 42PL or the negative line 42NL.

[0031] The inverter circuit 42B performs power conversion between the DC of the DC link 42A at one end and the AC at the other end.

[0032] For example, as shown in Figure 2, the inverter circuit 42B is a single-phase full-bridge inverter circuit that includes two sets of switch legs of upper and lower arm semiconductor switches (also called "switching elements") 42SW connected in series between the positive line 42PL and the negative line 42NL. In addition, for example, each semiconductor switch 42SW is connected in parallel with a recirculating diode (also called a "freewheeling diode") 42FD whose cathode is on the positive line side and whose anode is on the negative line side.

[0033] Furthermore, the inverter circuit 42B may be a half-bridge inverter circuit. Also, for example, if the AC of the power system 20 is three-phase AC, the inverter circuit 42B is configured as a three-phase inverter that performs power conversion between DC on one end and three-phase AC on the other end.

[0034] The drive circuit 44, under the control of the control device 46, drives the semiconductor switch 42SW of the inverter circuit 42B to turn on and off. For example, the drive circuit 44 is a known gate drive circuit.

[0035] The AC filter 50 allows the AC output from the power converter 40 and the AC supplied (input) from the power grid 20 to the power supply system 10 to pass through, attenuating unwanted frequency components (e.g., harmonic components). For example, the AC filter 50 is an LCL filter that includes reactors 50L1 and 50L2 of the power converter 40 and a filter capacitor 50C provided between reactors 50L1 and 50L2. Alternatively, the AC filter 50 may be another type of filter, such as an LC filter.

[0036] The control device 46 controls the power converter 40 to facilitate the exchange of power between the power supply system 10 (specifically, the DC power supply 30) and the power grid 20. Specifically, the control device 46 controls the power converter 42, which acts as the main circuit for performing power conversion between the DC power supply 30 and the AC power grid 20.

[0037] For example, as shown in Figure 1, the control device 46 is built into the power converter 40. Alternatively, the control device 46 may be a PLC (Programmable Logic Controller), edge controller, edge server, etc., installed in the same facility as the power converter 40. Alternatively, the control device 46 may be a server device (for example, an on-premise server or a cloud server) installed in a different location from the facility where the power converter 40 is installed.

[0038] For example, as shown in Figure 3, the voltage V of each part on the AC side of the power supply system 10 B ,V C ,V D The current I in each part B ,I C ,I D It is determined by the impedance of each part.

[0039] Voltage V Bis the voltage of the line between the power conversion device 40 and the AC filter 50, and corresponds to the voltage at the other end of the power conversion device 40 (also referred to as "output voltage"). Current I B is the current of the line between the power conversion device 40 and the AC filter 50, and corresponds to the current at the other end of the power conversion device 40 (also referred to as "output current"). When the current at the other end of the power conversion device 40 is a positive value, as shown in the figure, it is the current flowing from the power conversion device 40 to the power system 20. When the value is negative, contrary to the figure, it is the current flowing from the power system 20 to the power conversion device 40. Voltage V C corresponds to the voltage of the filter capacitor 50C. Current I C corresponds to the current of the filter capacitor 50C. When the current of the filter capacitor 50C is a positive value, as shown in the figure, it is the current flowing out from the line between the power conversion device 40 and the power system 20. When the value is negative, contrary to the figure, it is the current flowing into the above line. Voltage V D corresponds to the voltage of the connection point GCP between the power supply system 10 and the power system 20 (hereinafter, may be referred to as "connection point voltage"). Current I D corresponds to the current of the connection point GCP (hereinafter, may be referred to as "connection point current").

[0040] [Functional Configuration of the Control Device] In addition to FIGS. 1 to 3, refer to FIGS. 4 and 5 to describe the functional configuration of the control device 46.

[0041] FIG. 4 is a control block diagram showing an example of the functional configuration of the control device 46. FIG. 5 is a diagram for explaining an example of the control method of the power supply system 10.

[0042] As shown in FIG. 4, the control device 46 includes, as functional units, a measurement unit 460, a current command generation unit 461, a current control unit 462, a voltage command generation unit 463, and a drive signal generation unit 464.

[0043] Some or all of the functions of each part of the control device 46 are realized solely by hardware, such as electrical circuits or electronic circuits. Alternatively, some or all of the functions of each part of the control device 46 may be realized by a combination of hardware and software, such as a program, and auxiliary storage devices, memory devices, and processors corresponding to the program's installation destination, load destination, and execution unit. Examples of auxiliary storage devices include HDDs (Hard Disk Drives), SSDs (Solid State Drives), EEPROMs (Electrically Erasable Programmable Read Only Memory), and flash memory. Examples of memory devices include SRAMs (Static Random Access Memory) and DRAMs (Dynamic Random Access Memory). The processor includes, for example, a CPU (Central Processing Unit). The processor may also include, for example, a GPU (Graphics Processing Unit), an FPGA (Field Programmable Gate Array), and an ASIC (Application Specific Integrated Circuit).

[0044] The measuring unit 460 measures the interconnection point voltage V D Measured value (hereinafter referred to as "interconnection point voltage measurement value") V D_m and interconnection point current I D Measured values ​​(hereinafter referred to as "interconnection point current measurement values") I D_m Obtain it.

[0045] For example, the measuring unit 460 measures the interconnection point voltage V D A voltage sensor that detects the interconnection point current I D Based on the detection signal acquired from the current sensor that detects the current, the interconnection point voltage measurement V D_m and interconnection point current measurement value I D_m The measurement unit 460 calculates the interconnection point voltage measurement value V from the control device on the power system 20 side. D_m and interconnection point current measurement value I D_m You may obtain it.

[0046] The current command generation unit 461 receives the interconnection point voltage measurement value V output from the measurement unit 460. D_m or interconnection point current measurement I D_m Based on this, the interconnection point current I D The command value (hereinafter referred to as the "connection point current command value") I D * Generates.

[0047] For example, as shown in Figure 5, the interconnection point voltage V D and the interconnection point current I D Based on this, the active power P and reactive power Q exchanged between the power supply system 10 and the power grid 20 are determined, and the interconnection point voltage V D and the interconnection point current I D The phase angle θ corresponds to the phase difference with respect to the phase difference. D The cosine of cosθ D This is the power factor. Therefore, for example, the current command generation unit 461 adjusts the interconnection point current command value I by power factor control so that the power factor becomes a desired value. D * The current command generation unit 461 also performs active power control to adjust the active power P to a desired state, reactive power control to adjust the reactive power Q to a desired state, or interconnection point voltage V D The interconnection point current command value I is adjusted to a constant value by constant voltage control, etc. D * You may generate this.

[0048] The current control unit 462 measures the interconnection point current measurement I D_m And, the interconnection point current command value I D * Based on this, the interconnection point current I D It controls the current control unit 462, which measures the interconnection point current measurement I D_m The interconnection point current command value I D * The interconnection point current I is made to follow suit. D Generates the manipulated variable ΔV.

[0049] The voltage command generation unit 463 adds the manipulated variable ΔV to the measured value of the interconnection point current VD_m, thereby generating the interconnection point voltage V BThe command value (hereinafter referred to as "voltage command value") V B * This generates (see formula 1).

[0050]

number

[0051] The drive signal generation unit 464 generates the interconnection point voltage command value V B * Based on this, a drive signal for driving the power conversion unit 42 is generated and output to the drive circuit 44. For example, the drive signal generation unit 464 generates and outputs a rectangular pulse signal (i.e., a PWM signal) corresponding to the carrier period Tc by PWM (Pulse Width Modulation) conversion.

[0052] [Functional configuration of the current control unit] In addition to Figures 1 to 5, the functional configuration of the current control unit 462 will be explained with reference to Figures 6 to 8.

[0053] Figure 6 is a control block diagram showing an example of the functional configuration of the current control unit 462. Figure 7 is a control block diagram showing an example of the functional configuration of the correction value generation unit 4622. Figure 8 is a diagram showing an example of the method for generating the manipulated variable of the manipulated variable generation unit 4626.

[0054] As shown in Figure 6, the current control unit 462 includes, as functional units, a current prediction unit 4621, a correction value generation unit 4622, a current prediction value correction unit 4623, a current command prediction unit 4624, a target deviation calculation unit 4625, and an manipulated variable generation unit 4626.

[0055] The current prediction unit 4621 measures the interconnection point voltage V D_m And the voltage command value V generated in the previous control cycle B * Based on the circuit constants of the circuit including the AC filter 50 between the power conversion unit 42 and the interconnection point GCP, the interconnection point current I at a predetermined point in the future is calculated. D It predicts the current. Specifically, the current prediction unit 4621 predicts the current over a predetermined period T from the most recent sample time t.p The time advanced by that amount (t+T p ) Interconnection point current I D Predicted value (hereinafter referred to as "predicted current value at the interconnection point") I D_est (t+T p ) is calculated.

[0056] The most recent sample time t is the most recent interconnection point voltage measurement V obtained by the measurement unit 460. D_m and interconnection point current measurement value I D_m This refers to the measurement time. A predetermined period T. p This is, for example, an integer multiple of the carrier period Tc of the PWM conversion in the drive signal generation unit 464, which corresponds to the control period of the current control unit 462. Also, a predetermined period T p This may be defined independently of the carrier period Tc. For example, a predetermined period T p This can be set to any value between 0 (zero) and the carrier period Tc.

[0057] The correction value generation unit 4622 uses the most recent interconnection point current measurement I D_m (t) and the previously generated predicted interconnection point current I at sample time t. D_est Based on (t), time (t+T p Predicted current value at the interconnection point I D_est (t+T p Error correction value e for correcting ) D Generates.

[0058] For example, as shown in Figure 7, the correction value generation unit 4622 includes an error calculation unit 4622A and a filter 4622B.

[0059] The error calculation unit 4622A calculates the interconnection point current measurement I D_m (t) and the predicted current value at the interconnection point I D_est Calculate the error δ(t) with (t) (see Equation 2).

[0060]

number

[0061] Filter 4622B is applied to the error δ(t), and the result of multiplying the error δ(t) by filter 4622B is the error correction value e D It will be output as (t).

[0062] Filter 4622B is used, for example, to measure the interconnection point current I D_m It is applied to the error δ(t) for the purpose of suppressing the effects of noise (e.g., harmonic components) contained in the signal and to prevent the excitation of the resonance point of admittance Y1, which will be described later.

[0063] For example, filter 4622B is a discrete first-order lag filter (see Equation 3).

[0064]

number

[0065] Equation 3 is the filter time constant T. f and sampling time T s The relationship between the input u, the internal state x, and the output y is expressed using this formula.

[0066] Furthermore, filter 4622B may be of any other type, provided that the above objectives can be achieved.

[0067] The current prediction value correction unit 4623 calculates the error correction value e D Based on this, the current prediction value I D_est (t+T p ) corrects the current prediction value I. For example, as shown in Figure 6, the current prediction value correction unit 4623 corrects the current prediction value I D_est (t+T p ) with error correction value e D By adding (t), the corrected predicted interconnection point current value (hereinafter referred to as "corrected interconnection point current value") I D_est_c (t+T p ) obtain.

[0068] The current command prediction unit 4624 calculates the time (t+T p Current command value I D *(t + T p ) is predicted.

[0069] For example, the tie - point current command value I D * is usually defined by a sine - wave signal of the fundamental frequency f0 of the power system 20. In this case, the current command prediction unit 4624 advances the phase of the sine - wave signal by an amount corresponding to a predetermined period T p (= 2πf0·T p ) to predict the current command value I D * (t + T p ). Also, the current command prediction unit 4624 may simply obtain the current command value I D * (t + T p ) by means of zero - order hold or first - order hold, etc.

[0070] The target deviation calculation unit 4625 calculates and generates the target deviation e D * (t + T p ) as the difference between the tie - point current command value I D_est_c (t + T p ) and the corrected tie - point current predicted value I * (t + T p )(see Equation 4).

[0071]

Equation

[0072] The manipulated variable generation unit 4626 generates the manipulated variable ΔV based on the target deviation e * (t + T p ) and the control gain k p . For example, the manipulated variable generation unit 4626 generates the manipulated variable ΔV by multiplying the target deviation e * (t + T p ) by the control gain k p (see Equation 5).

[0073]

Equation

[0074] Furthermore, as shown in Figure 8, for example, a limiter is provided for the manipulated variable ΔV, and the manipulated variable generation unit 4626 generates a voltage V B To prevent the manipulated variable ΔV from deviating from a predetermined upper and lower limit, the manipulated variable ΔV may be restricted to a range that is less than or equal to the upper limit ΔVmax and greater than or equal to the lower limit ΔVmin.

[0075] [Overview of the current prediction unit] In addition to Figure 6, the overview of the current prediction unit 4621 will be explained with reference to Figures 9 and 10.

[0076] Figure 9 shows the interconnection point current I D This figure shows the characteristics of admittance Y1 with respect to the current I. D This is a diagram illustrating the characteristics of admittance Y2.

[0077] Specifically, Figure 9 includes Figures 9A and 9B. Figure 9A is the Bode plot of admittance Y1. Figure 9B is a diagram showing the step response of admittance Y1 and admittance Y1 multiplied by a first-order lag filter. Figure 10 includes Figures 10A and 10B. Figure 10A is the Bode plot of admittance Y2. Figure 10B is a diagram showing the step response of admittance Y2 and admittance Y2 multiplied by a first-order lag filter.

[0078] current I B ,I C ,I D , and voltage V C This can be expressed by the following equation 6, using the inductance L1 of reactor 50L1, the inductance L2 of reactor 50L2, the capacitance C of filter capacitor 50C, the resistance R2 of resistor 60, and the Laplace variable s.

[0079]

number

[0080] Rearranging equation 6, we get the interconnection point current ID This is expressed by the following equation 7.

[0081]

number

[0082] Furthermore, rearranging equation 7, we get the interconnection point current I D This can be expressed using admittances Y1 and Y2 in the following equation 8.

[0083]

number

[0084] Furthermore, by rearranging equation 8, the admittances Y1 and Y2 can be expressed in the following equation 9.

[0085]

number

[0086] Here, as shown in Figure 9A, the admittance Y1 has a maximum gain at frequency 0 (zero) and tends to decrease as the frequency increases. However, the resonant frequency f at which the gain of admittance Y1 rises sharply with respect to surrounding frequencies is... r1 It has.

[0087] Furthermore, as shown in Figure 9B, the step response of admittance Y1 is a response that gradually increases while accompanied by relatively small oscillations. The step response when admittance Y1 is multiplied by a first-order lag filter is a response that gradually increases, similar to the step response of admittance Y1, but with the oscillations suppressed compared to the step response of admittance Y1.

[0088] Furthermore, as shown in Figure 10A, the admittance Y2 has a minimum gain at frequency 0 (zero) and tends to increase as the frequency increases. However, the resonant frequency f at which the gain of admittance Y2 rises sharply with respect to surrounding frequencies is the resonant frequency f. r2 It has the following characteristics. In addition, the admittance Y2 is the resonant frequency f r2 At frequencies other than 0, the gain is less than 0 dB.

[0089] Furthermore, as shown in Figure 10B, the step response of admittance Y2 is a response that oscillates around 0 (zero) and does not have a DC component. When admittance Y2 is multiplied by a first-order lag filter, the step response has a lower gain (i.e., amplitude of oscillation) than the step response of admittance Y2 alone.

[0090] Considering the above characteristics of admittance Y2, the interconnection point voltage V D The frequency is the resonant frequency f r2 It is assumed to be sufficiently lower than the interconnection point current I in Equation 8. D The second term on the right-hand side of the equation representing can be ignored. Therefore, the interconnection point current I D This can be approximately expressed by the following equation 10.

[0091]

number

[0092] The current prediction unit 4621 predicts a predetermined period T from the sample time t based on equation 10. p The time advanced by that amount (t+T p ) Interconnection point current I D To predict.

[0093] [First example of a current prediction unit] Next, with reference to Figure 6, we will describe the first example of the current prediction unit 4621. Specifically, the predicted current value at the interconnection point I using the above formula 10 is described. D_est (t+T p The first example of how to perform the calculation of ) will be explained.

[0094] Rearranging equation 9 above, the admittance Y2 can be expressed in the following equation 11. .

[0095]

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[0096] Therefore, equation 10 can be expressed as equation 12 below, where U(s) is the input, Y(s) is the output, and G(s) is the transfer function.

[0097]

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[0098] Equation 12 can be transformed into a controllable standard form state-space model (i.e., a state equation) represented by the following equation 13, using state variables x1, x2, and x3.

[0099]

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[0100] Furthermore, the delay element D(s) having a time constant Td is defined by the following equation 14.

[0101]

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[0102] The delay element D(s) can be transformed into the state-space model (state equation) shown in equation 15 below.

[0103]

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[0104] The state-space model expressed in terms of the Laplace variable s in equation 13 is equivalent to the time-domain differential equation in equation 16 below.

[0105]

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[0106] The input u(t) is at a time (t+T) that has advanced by a predetermined period Tp from the sample time t. p Assuming that it is held in zero order until time (t+T), p The predicted value y(t+Tp) of the output y in ) is expressed by the following equation 17.

[0107]

number

[0108] For example, matrix A c ·T p The exponential function of (=exp(A) c ·T p )) is matrix A c It can be performed using spectral decomposition, Shur decomposition, etc., of matrix A. c This can also be calculated in advance.

[0109] Therefore, the current prediction unit 4621 uses equation 17 to determine the time (t+T p Predicted value of output y in ) y(t+T p Predicted value of interconnection point current I D_est (t+T p It is possible to calculate ).

[0110] [Second example of a current prediction unit] Next, with reference to Figure 6, a second example of the current prediction unit 4621 will be described. Specifically, the interconnection point current prediction value I using the above equation 10 will be explained. D_est (t+T p A second example of the calculation method for ) will be explained.

[0111] The relationship between the Laplace variable s and the discrete variable z is given by the sampling time T. s Using this, it can be expressed by the following SZ transformation formula 18.

[0112]

number

[0113] Equation 13 above is obtained by the sz transformation, where the discrete variable z and the sampling time T are... s Using this, it can be represented by the discrete state-space model in equation 19 below.

[0114]

number

[0115] Therefore, the current prediction unit 4621 calculates equation 19 over the sampling time T. s By numerically integrating over intervals, we can obtain the time (t+T p Predicted value of output y in ) y(t+T p Predicted value of interconnection point current I D_est (t+T p It is possible to calculate ).

[0116] [Third example of a current prediction unit] Next, with reference to Figure 6, a third example of the current prediction unit 4621 will be described. Specifically, the interconnection point current prediction value I using the above equation 10 will be explained. D_est (t+T p A third example of the calculation method for ) will be explained.

[0117] The state-space model in equation 13 above can be summarized as follows:

[0118]

number

[0119] Equation 20 can be transformed into the discrete state-space model of Equation 21 below.

[0120]

number

[0121] In this example, the discrete state-space model of equation 21 differs from the discrete state-space model of equation 19 in the second example above in that the second term of row Ad is the second term of the Taylor expansion. Furthermore, terms of order 3 or higher in the Taylor expansion may also be considered.

[0122] The current prediction unit 4621, similar to the second example described above, calculates the time (t+T) by numerically integrating equation 21 over the sampling time interval Ts. p Output Y in ) d Predicted value Y d (t+T p Predicted value of interconnection point current I D_est (t+T p It is possible to calculate ).

[0123] [Specific examples of control device processing operations] A specific example of the processing operation of the control device 46 will be described with reference to Figures 11 and 12.

[0124] Figure 11 is a diagram showing an example of the time variation of the interconnection point current ID and the on / off state of the semiconductor switch 42SW of the power conversion unit 42. Specifically, Figure 11 includes Figure 11A, which is a time chart diagram showing an example of the time variation of the interconnection point current ID, and Figure 11B, which is a time chart diagram showing the time variation of the on / off state of the semiconductor switch 42SW of the power conversion unit 42. Figure 12 is a timing chart diagram showing an example of the processing operation flow of the control device 46.

[0125] As shown in Figures 11 and 12, in this example, the measurement period Tm of the measurement unit 460 is shorter than the carrier period Tc (specifically, 1 / 5 of the carrier period Tc). Therefore, the measurement unit 460 measures the interconnection point voltage V during the carrier period Tc. D and interconnection point current I D This can be measured multiple times (5 times in this example).

[0126] On the other hand, as shown in Figure 11B, in this example, the control device 46 adjusts the duty cycle (conductivity) of the semiconductor switch 42SW by PWM control. In this case, the control device 46 updates the duty cycle for each carrier period Tc corresponding to the switching period of the semiconductor switch 42SW, thereby controlling the interconnection point current I D The interconnection point current command value I D * The current is controlled to follow the movement.

[0127] As shown in Figure 12, the control device 46 controls the drive of the power conversion unit 42 through the drive circuit 44 by a series of processes represented by white rectangles in the figure. The series of processes for controlling the drive of the power conversion unit 42 (hereinafter referred to as the "drive control process") is performed once for each carrier cycle Tc, and the result of the process is reflected in the update of the duty cycle described above.

[0128] In this example, the control device 46 performs a series of processes (for convenience, "error monitoring processes") that generate (specifically, calculate) an error correction value eD(t), starting from the processing of the measurement unit 460, which is performed at each measurement cycle Tm. Of the error monitoring processes performed multiple times (five times in this example) during the carrier cycle Tc, one is performed as part of the above-mentioned drive control process, and the others (the remaining four times in this example) are performed as processes independent of the above-mentioned drive control process (see the blacked-out processes in the figure). This allows the control device 46 to monitor the error correction value eD(t) from the time the duty cycle of the semiconductor switch 42SW is updated until the next time the duty cycle is updated. Therefore, it is possible to grasp sudden changes in the interconnection point current ID of the controlled object early, and for example, at the timing of the next duty cycle update, a calculation method for the manipulated variable ΔV to deal with the sudden change can be adopted. For example, the control device 46 can use the error correction value eD(t), or the target deviation e * (t+T p If the rate of increase of the absolute value of ) is equal to or exceeds a predetermined standard, the control gain kp is increased. Therefore, the control device 46 increases the interconnection point current I D The interconnection point current command value I D* This improves responsiveness to changes. Furthermore, the control device 46 may detect sudden changes and issue an alarm externally.

[0129] [Control device relating to comparative example] Referring to Figure 13, the control device 46C of the comparative example will be described.

[0130] Figure 13 is a control block diagram showing the functional configuration of the control device 46C according to the comparative example.

[0131] In the following description of the control device 46C in the comparative example, components that are the same as or corresponding to those in the control device 46 of this embodiment will be denoted by the same reference numerals.

[0132] As shown in Figure 13, the control device 46C differs from the control device 46 in this embodiment in that it includes a current control unit 462C instead of a current control unit 462.

[0133] The current control unit 462C includes a deviation calculation unit 4621C and an manipulated variable generation unit 4622C.

[0134] The deviation calculation unit 4621C calculates the interconnection point current command value I at the most recent sample time t. D * and interconnection point current measurement value I D_m Calculate the deviation.

[0135] The manipulated variable generation unit 4622C generates the interconnection point current command value I D * and interconnection point current measurement value I D_m The manipulated variable ΔV is generated by multiplying the deviation by the control gain (i.e., proportional gain).

[0136] [Simulation results of current control by the control device in the comparative example] Referring to Figures 14 to 17, a specific example of the simulation results of current control by the control device 46C in the comparative example will be explained.

[0137] Figures 14 to 17 are time charts showing the first to fourth examples of simulation results of current control by a control device related to a comparative example.

[0138] Specifically, Figure 14 shows the measured value of the interconnection point current I D_m This is a time chart diagram showing an example of the simulation results of current control by the control device 46C when no high-frequency suppression filter is applied, the control gain (proportional gain) is a relatively small value, and the voltage of the power system 20 does not contain harmonic components. Figure 15 shows the measured value of the interconnection point current I D_m This is a time chart diagram showing an example of the simulation results of current control by the control device 46C when no high-frequency suppression filter is applied, the control gain (proportional gain) is a relatively large value, and the voltage of the power system 20 does not contain harmonic components. Figure 16 shows the measured value of the interconnection point current I D_m This is a time chart diagram showing an example of the results of a current control simulation by the control device 46C when a high-frequency suppression filter is applied, the control gain (proportional gain) is a relatively small value, and the voltage of the power system 20 does not contain harmonic components. Figure 17 shows the measured value of the interconnection point current I D_m This time chart shows an example of the simulation results of current control by the control device 46C when no high-frequency suppression filter is applied, the control gain (proportional gain) is relatively small, and the voltage of the power system 20 contains harmonic components (specifically, the 5th harmonic).

[0139] More specifically, Figures 14, 16, and 17 show the measured values ​​of the interconnection point current I over a relatively short time range. D_m , interconnection point current command value I D * , and the time variation of the manipulated variable ΔV are shown. Also, Figure 15 shows the measured value of the interconnection point current I over a relatively long time range. D_m , interconnection point current command value I D * This also shows the time evolution of the manipulated variable ΔV.

[0140] For example, as shown in Figure 14, when the control gain of the manipulated variable generation unit 4622C is relatively small, the interconnection point current measurement value I D_m The interconnection point current command value I D * It is not following the target at all, resulting in a relatively large control deviation.

[0141] Furthermore, for example, as shown in Figure 15, when the control gain of the manipulated variable generation unit 4622C is relatively large, the interconnection point current measurement value I D_m It has become divergent and unstable.

[0142] Furthermore, as shown in Figure 16, for example, the connected point current measurement value I input to the deviation calculation unit 4621C D_m When a high-frequency suppression filter is applied, the measured value of the interconnection point current I is different from the case in Figure 14. D_m The amplitude is the interconnection point current command value I D * It has increased to the same level as the interconnection point current command value I D * A phase lag occurs in relation to this.

[0143] Thus, in the current control using the control device 46C in the comparative example, instability occurs due to the control gain (proportional gain), and tracking errors occur. As a result, a problem may arise in that the original capacity of the power converter 40 cannot be fully utilized.

[0144] Furthermore, for example, as shown in Figure 17, if the voltage of the power system 20 contains harmonic components (5th harmonic), the measured value of the interconnection point current I D_m The signal contains superimposed harmonic components, and these harmonic components are not being adequately suppressed.

[0145] [Results of current control simulation using the control device according to the embodiment] Referring to Figures 18 and 19, a specific example of the simulation results of current control by the control device 46 according to this embodiment will be described.

[0146] Figures 18 and 19 are time charts showing the first and second examples of simulation results of current control by the control device 46 according to the embodiment.

[0147] Specifically, Figure 18 is a time chart showing an example of the simulation results of current control by the control device 46 when the voltage of the power system 20 does not contain harmonic components. Figure 19 is a time chart showing an example of the simulation results of current control by the control device 46 when the voltage of the power system 20 contains harmonic components (specifically, the 5th harmonic).

[0148] For example, as shown in Figure 18, the manipulated variable ΔV changes in a stepwise manner with each carrier period Tc, and as a result, the interconnection point current measurement I D_m The interconnection point current command value I D * It tracks the signal accurately, with virtually no amplitude deviation or phase lag.

[0149] Also, the predicted value of the interconnection point current I D_est And, the measured value of the interconnection point current I D_m Although there is a slight discrepancy between the two, as described above, this is corrected by the current prediction value correction unit 4623, thus suppressing its effect.

[0150] Furthermore, as shown in Figure 19, for example, distortion occurs in the waveform of the manipulated variable ΔV, indicating that it is operating to suppress harmonics. As a result, the measured value of the interconnection point current I D_m The interconnection point current command value I D * It follows the pattern and is able to suppress harmonic components.

[0151] Thus, the control device 46 according to this embodiment is different from the control device 46C according to the comparative example. Interconnection point current measurement value I D_m The interconnection point current command value I D * This significantly improves responsiveness to changes, suppression of harmonic components, and stability of current control.

[0152] [Other embodiments] Other embodiments will be described with reference to Figure 20.

[0153] Figure 20 is a control block diagram showing the functional configuration of another example of the control device 46.

[0154] The embodiments described above may be modified or altered as appropriate. Hereinafter, examples of modifications or alterations to the embodiments described above will be referred to as "modified examples" for convenience.

[0155] For example, in the embodiment described above, the current prediction unit 4621 uses the voltage command value V generated in the previous control cycle. B * Instead, voltage V B The measured value (hereinafter referred to as "voltage measurement value") V B_m You may use the voltage measurement V. B_m Since a relatively large amount of switching noise from the semiconductor switch 42SW of the power conversion unit 42 is superimposed, it is desirable to apply a noise filter or the like.

[0156] Furthermore, in the above embodiment, the correction value generation unit 4622 and the current prediction value correction unit 4623 are omitted, and the target deviation calculation unit 4625 receives the interconnection point current prediction value I output from the current prediction unit 4621. D_est (t+T p Based on this, the target deviation e * (t+T p You may also perform the calculation )

[0157] Furthermore, in the embodiments and modifications described above, for example, as shown in Figure 20, the measured value of the interconnection point current I D_m and interconnection point current command value I D * Instead, current I B Measured values ​​(hereinafter referred to as "current measurement values") I B_m , and current I B The command value (hereinafter referred to as "current command value") I B * You may also use this. In this case, current I C Measurement value I C_m and command value I C* From the relationship of the following mathematical formula 22 including D_m and the tie-point current command value I D * the tie-point current measured value I is estimated.

[0158] [Function]

[0159] [Action] The control device, power conversion device, and control method according to this embodiment will be described.

[0160] In the first aspect of this embodiment, there is provided a power conversion unit that performs power conversion between DC on one end side and AC on the other end side, and an AC filter unit connected to the other end of the power conversion unit, and for a power system that performs power supply in at least one direction from AC to DC and from DC to AC through the power conversion unit and the AC filter unit, a control device is provided that controls the power conversion unit so that the measured value of the current at a predetermined location in the AC power path after the AC filter unit, as viewed from the power conversion unit, follows the command value. The control device is, for example, the above-described control device 46. The power conversion unit is, for example, the above-described power conversion unit 42. The AC filter unit is, for example, the above-described AC filter 50. The power system is, for example, the above-described power system 1. The predetermined location is, for example, the above-described tie-point GCP. The measured value of the current at the predetermined location is, for example, the above-described current measured value I D_m is. The command value of the current at the predetermined location is, for example, the above-described current command value I D * is. Specifically, the control device predicts the current at the predetermined location at a future predetermined time based on the measured value or command value of the voltage at the other end of the power conversion unit, the measured value of the current at the predetermined location, and the circuit constants of the AC filter unit. The measured value of the voltage at the other end of the power conversion unit is, for example, the above-described voltage measured value V B_m is. The command value of the current at the other end of the power conversion device is, for example, the above-described voltage command value V B *The predetermined time point is, for example, a time (t+T) that is advanced by a predetermined period Tp from the latest sample time t. p The circuit constants of the AC filter section are the inductance L1 of the reactor 50L1, the inductance L2 of the reactor 50L2, and the capacitance C of the filter capacitor 50C. The control device controls the power conversion section based on the predicted value and command value of the current at the predetermined location at the predetermined time.

[0161] For example, an Automatic Current Regulator (ACR) is known that controls the power conversion section by multiplying the deviation between the measured value and the commanded value of the current at a predetermined point in the power path downstream of the AC filter section by a proportional gain. While the ACR is relatively simple and easy to implement, the proportional gain can amplify high-frequency components included in the measured current, potentially destabilizing the current control or generating excessive noise in the current at the predetermined point.

[0162] Furthermore, when controlling the power conversion section using PWM control, for example, the duty cycle of the semiconductor switch is often controlled for each switching cycle (i.e., the carrier cycle) of the power conversion section. In this case, the current command value at the start of switching of the semiconductor switch is coded to the duty cycle in the time direction for one switching cycle. Therefore, a control delay equal to the switching cycle inevitably occurs. In particular, when increasing the voltage of the power conversion section to reduce transmission losses, for example, there is a tendency to lengthen the switching cycle in order to suppress switching losses, which makes the control delay more pronounced. As a result, the phase margin decreases, and current control may become unstable.

[0163] In contrast, in this example, the control device can control the power conversion unit based on the predicted value and command value of the current at a predetermined point in the power path downstream of the AC filter unit at a predetermined future time. Therefore, the control device can suppress problems caused by high-frequency components included in the measured current and control delays, thereby stabilizing the quality of the AC power. Thus, the control device can appropriately control the current on the AC side as seen from the power conversion unit, i.e., the current at a predetermined point downstream of the AC filter unit.

[0164] Furthermore, in a second aspect of this embodiment, based on the first aspect described above, the control device may correct the predicted value of the current at the predetermined location at the predetermined time based on the latest measured value of the current at the predetermined location and the predicted value at the time corresponding to the latest measured value. The control device may then control the power conversion unit based on the corrected predicted value and command value of the current at the predetermined location at the predetermined time.

[0165] As a result, the control device can correct the predicted current value at a predetermined point in the future by considering the error between the latest measured value of the current at a predetermined point in the power path downstream of the AC filter and the predicted value at the point in time corresponding to the latest measured value predicted in the past. Therefore, the control device can more appropriately control the current on the AC side as seen from the power conversion unit, i.e., the current at the predetermined point downstream of the AC filter.

[0166] Furthermore, in a third aspect of this embodiment, based on the second aspect described above, a predetermined filter may be applied to the error between the latest measured value of the current at the predetermined location and the predicted value at the time corresponding to the latest measured value, and the predicted value of the current at the predetermined location at the predetermined time may be corrected based on the output of the predetermined filter.

[0167] As a result, the control device can suppress the influence of harmonic components included in the measured current at a predetermined point in the power path downstream of the AC filter section. Therefore, the control device can more appropriately control the current on the AC side as seen from the power conversion section, i.e., the current at a predetermined point downstream of the AC filter section.

[0168] Furthermore, in a fourth aspect of this embodiment, based on the third aspect described above, the measurement period for the current at the predetermined location may be shorter than the switching period of the power conversion unit. The control device may calculate the error between the latest measured value of the current at the predetermined location and the predicted value at the time corresponding to the latest measured value at a frequency higher than the switching period of the power conversion unit.

[0169] As a result, the control device can, for example, address a sudden change in the current at a predetermined point in the power path downstream of the AC filter unit if the error rapidly increases due to a sudden change in the timing of the drive control of the semiconductor switch of the power conversion unit between the timing of the drive control and the timing of the next drive control. Therefore, the control device can more appropriately control the current on the AC side as seen from the power conversion unit, i.e., the current at the predetermined point downstream of the AC filter unit.

[0170] Furthermore, in a fifth aspect of this embodiment, based on any one of the first to fourth aspects described above, the control device may predict the current at the predetermined location at a predetermined time based on a state-space model that represents the relationship between the current at the predetermined location, the voltage at the other end of the power conversion unit, and the voltage at the predetermined location, and which is expressed using the circuit constants of the AC filter unit.

[0171] This allows the control device to predict the current at a predetermined point in the power path downstream of the AC filter section at a predetermined point in the future.

[0172] Furthermore, in a sixth aspect of this embodiment, based on the fifth aspect described above, the control device may predict the current at the predetermined location at the predetermined time using numerical integration based on the state-space model.

[0173] This allows the control device to predict the current at a predetermined point in the power path downstream of the AC filter section at a predetermined point in the future.

[0174] Furthermore, in the seventh aspect of this embodiment, based on any one of the first to sixth aspects described above, the control device may control the power conversion unit so that the voltage at the other end of the power conversion unit follows a value obtained by adding an operation variable, which is the difference between the command value and the predicted value of the current at the predetermined location at the predetermined time, multiplied by a predetermined gain, and the measured value of the voltage at the predetermined location.

[0175] This allows the control device to appropriately control the current at a predetermined location downstream of the AC filter, i.e., on the AC side as seen from the power conversion unit.

[0176] Furthermore, in the eighth aspect of this embodiment, based on any one of the first to seventh aspects described above, the control device may estimate the measured value and command value of the current at the predetermined location based on the measured value and command value of the current at the other end of the power conversion unit.

[0177] As a result, the control device can appropriately control the current at a predetermined location downstream of the AC filter, i.e., on the AC side as seen from the power conversion unit, based on the measured value and command value of the current at the other end of the power conversion unit.

[0178] Furthermore, in a ninth aspect of this embodiment, a power conversion device is provided that includes a power conversion unit and a control unit. The power conversion device is, for example, the power conversion device 40 described above. The power conversion unit is, for example, the power conversion unit 42 described above. The control unit is, for example, the control unit 46 described above. Specifically, the power conversion unit is a power conversion unit that performs power conversion between DC on one end and AC on the other end, and an AC filter unit is connected to the other end. The AC filter unit is, for example, the AC filter 50 described above. The control unit also controls the power conversion unit to make the measured current at a predetermined location in the AC power path downstream of the AC filter unit, as seen from the power conversion unit, follow a command value, for a power system that supplies power in at least one direction, from AC to DC and from DC to AC, through the power conversion unit and the AC filter unit. The power system is, for example, the power system 1 described above. The predetermined location is, for example, the interconnection point GCP described above. The measured current at the predetermined location is, for example, the current measurement value I described above. D_m The command value for the current at the predetermined location is, for example, the current command value I described above. D * More specifically, the control unit predicts the current at a predetermined point in the future based on the measured value or command value of the voltage at the other end of the power conversion unit, the measured value of the current at the predetermined point, and the circuit constants of the AC filter unit. The measured value of the voltage at the other end of the power conversion unit is, for example, the above-mentioned measured voltage V B_m The command value of the current at the other end of the power converter is, for example, the voltage command value V mentioned above. B * The predetermined time point is, for example, a time (t+T) that is advanced by a predetermined period Tp from the latest sample time t. p The circuit constants of the AC filter section are the inductance L1 of the reactor 50L1, the inductance L2 of the reactor 50L2, and the capacitance C of the filter capacitor 50C. The control unit controls the power conversion section based on the predicted value and command value of the current at the predetermined location at the predetermined time.

[0179] As a result, the power conversion device exhibits the same operations and effects as the control device of the first aspect described above.

[0180] Also, for the power conversion device, assuming the ninth aspect, aspects similar to the second to eighth aspects of the control device can be realized.

[0181] As a result, the power conversion device exhibits the same operations and effects as the control devices of the second to eighth aspects described above.

[0182] Further, in the tenth aspect of the present embodiment, there is provided a control method for controlling a power conversion unit that performs power conversion between DC on one end side and AC on the other end side, and an AC filter unit connected to the other end of the power conversion unit, for a power system that supplies power in at least one direction from AC to DC and from DC to AC through the power conversion unit and the AC filter unit. The control is performed so that a measured value of a current at a predetermined location in the AC power path after the AC filter unit, as viewed from the power conversion unit, follows a command value. The power conversion unit is, for example, the power conversion unit 42 described above. The AC filter unit is, for example, the AC filter 50 described above. The power system is, for example, the power system 1 described above. The predetermined location is, for example, the connection point GCP described above. The measured value of the current at the predetermined location is, for example, the current measurement value I D_m is. The command value of the current at the predetermined location is, for example, the current command value I D * is. Specifically, in this control method, based on a measured value or a command value of the voltage at the other end of the power conversion unit, a measured value of the current at the predetermined location, and a circuit constant of the AC filter unit, the current at the predetermined location at a future predetermined time is predicted. The measured value of the voltage at the other end of the power conversion unit is, for example, the voltage measurement value V B_m is. The command value of the current at the other end of the power conversion device is, for example, the voltage command value V B *The predetermined time is, for example, a time (t+Tp) that is advanced by a predetermined period Tp from the latest sample time t. The circuit constants of the AC filter section are the inductance L1 of the reactor 50L1, the inductance L2 of the reactor 50L2, and the capacitance C of the filter capacitor 50C. In this control method, the power conversion section is controlled based on the predicted value and command value of the current at the predetermined location at the predetermined time.

[0183] As a result, this control method produces the same functions and effects as the control device of the first embodiment described above.

[0184] Furthermore, regarding the control method, based on the tenth embodiment described above, an embodiment similar to the second to eighth embodiments for the control device can be realized.

[0185] As a result, this control method produces the same functions and effects as the control devices of the second to eighth embodiments described above.

[0186] Although embodiments have been described in detail above, this disclosure is not limited to these specific embodiments, and various modifications and changes are possible within the scope of the gist described in the claims. [Explanation of Symbols]

[0187] 1. Power Systems 10 Power Systems 20 Power system 30 DC power supply 40 Power converter 42 Power Conversion Unit 42A DC link 42B Inverter Circuit 42C smoothing capacitor 42FD Circulation Diode 42NL Negative Line 42PL positive line 42SW Semiconductor Switch 44 Drive Circuit 46 Control device 46C Control Unit 50 AC filter 50C filter capacitor 50L1 Reactor 50L2 Reactor 60 resistors 70 Impedance 460 Measuring section 461 Current command generation section 462 Current Control Unit 463 Voltage Command Generation Unit 464 Drive signal generation unit 4621 Current prediction unit 4622 Correction Value Generation Unit 4622A Error calculation section 4622B filter 4623 Current Prediction Value Correction Unit 4624 Current Command Prediction Unit 4625 Target deviation calculation section 4626 Manipulated amount generation section

Claims

1. A power system comprising a power conversion unit that performs power conversion between DC at one end and AC at the other end, and an AC filter unit connected to the other end of the power conversion unit, wherein the power system supplies power in at least one direction, from AC to DC and from DC to AC, through the power conversion unit and the AC filter unit, is a control device that controls the power conversion unit so that the measured current at a predetermined point in the AC power path downstream of the AC filter unit, as seen from the power conversion unit, follows a command value. Based on the measured voltage or command value at the other end of the power conversion unit, the measured current at the predetermined location, and the circuit constants of the AC filter unit, the current at the predetermined location at a predetermined future time is predicted. Based on the predicted value and command value of the current at the predetermined location at the predetermined time, the power conversion unit is controlled. Control device.

2. Based on the latest measured value of the current at the predetermined location and the predicted value at the time corresponding to the latest measured value, the predicted value of the current at the predetermined location at the predetermined time is corrected. Based on the corrected predicted value and command value of the current at the predetermined location at the predetermined time, the power conversion unit is controlled. The control device according to claim 1.

3. A predetermined filter is applied to the error between the latest measured value of the current at the predetermined location and the predicted value at the time corresponding to the latest measured value, and the predicted value of the current at the predetermined location at the predetermined time is corrected based on the output of the predetermined filter. The control device according to claim 2.

4. The measurement period for the current at the predetermined location is shorter than the switching period of the power conversion unit. The error between the most recent measured value of the current at the predetermined location and the predicted value at the time corresponding to the most recent measured value is calculated at a frequency higher than the switching cycle of the power conversion unit. The control device according to claim 3.

5. A state-space model representing the relationship between the current at the predetermined location, the voltage at the other end of the power conversion unit, and the voltage at the predetermined location, wherein the current at the predetermined location at the predetermined time is predicted based on the state-space model, which is represented using the circuit constants of the AC filter unit. The control device according to any one of claims 1 to 4.

6. Based on the state-space model, numerical integration is used to predict the current at the predetermined location at the predetermined time. A control device according to claim 5.

7. The power conversion unit is controlled to make the voltage at the other end of the power conversion unit follow a value obtained by adding a predetermined gain to an operating variable, which is the difference between the command value and the predicted value of the current at the predetermined location at the predetermined time, and the measured value of the voltage at the predetermined location. The control device according to any one of claims 1 to 4.

8. Based on the measured current and command value at the other end of the power conversion unit, the measured current and command value at the predetermined location are estimated. The control device according to any one of claims 1 to 4.

9. A power conversion unit that performs power conversion between DC at one end and AC at the other end, the power conversion unit having an AC filter unit connected to the other end, A power system that supplies power in at least one direction, from AC to DC and from DC to AC, through the power conversion unit and the AC filter unit, comprises a control unit that controls the power conversion unit so that the measured current at a predetermined point in the AC power path downstream of the AC filter unit, as seen from the power conversion unit, follows a command value. The control unit, Based on the measured voltage or command value at the other end of the power conversion unit, the measured current at the predetermined location, and the circuit constants of the AC filter unit, the current at the predetermined location at a predetermined future time is predicted. Based on the predicted value and command value of the current at the predetermined location at the predetermined time, the power conversion unit is controlled. Power conversion device.

10. A power system comprising a power conversion unit that performs power conversion between DC at one end and AC at the other end, and an AC filter unit connected to the other end of the power conversion unit, wherein the power system supplies power in at least one direction, from AC to DC and from DC to AC, through the power conversion unit and the AC filter unit, and a control method for controlling the power conversion unit so that the measured current at a predetermined point in the AC power path downstream of the AC filter unit, as seen from the power conversion unit, follows a command value. Based on the measured voltage or command value at the other end of the power conversion unit, the measured current at the predetermined location, and the circuit constants of the AC filter unit, the current at the predetermined location at a predetermined future time is predicted. Based on the predicted value and command value of the current at the predetermined location at the predetermined time, the power conversion unit is controlled. Control method.

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