Reactive power compensation device, air conditioning system and controller

Abstract

The present invention provides a reactive power compensation device that determines reactive power based on wire information relating to the specifications of the wires between the power receiving point, which receives power from the power system within the premises, and the reactive power compensation device. [Solution] A reactive power compensation device installed on the premises of a consumer that receives power from a power grid, comprising a control unit and a supply unit that outputs reactive power, wherein the control unit determines the reactive power based on the voltage at the receiving point estimated from wire information relating to the specifications of the wires between the power receiving point on the premises that receives power from the power grid and the reactive power compensation device, and the voltage at the end of the reactive power compensation device.

Description

Technical Field

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[0004] , , , , ,

[0001] The present disclosure relates to a reactive power compensation device, an air conditioner, and a controller.

Background Art

[0002] Patent Document 1 describes an air conditioner including voltage information acquisition means for acquiring voltage information regarding an input voltage input to the device itself, supply means for supplying fundamental wave reactive power to a power reception point of the input voltage in the device itself, and control means for controlling the supply means. The control means has a first supply mode in which fundamental wave reactive power is supplied from the supply means to the power reception point according to the magnitude of the input voltage specified from the voltage information acquired by the voltage information acquisition means.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When performing reactive power output (Volt-Var control) using consumer equipment or the like, a difference occurs between the power reception point voltage that is originally desired to be controlled and the self-terminal voltage of the reactive power compensation device due to the impedance of the distribution line within the consumer premises from the power reception point from the power grid to the reactive power compensation device and the output reactive power. When the length of the in-premises distribution line is long, for example, since it may seem that the voltage is adjusted when viewed from the self-terminal voltage, there is a margin in the supply capacity of reactive power sufficient to control the power reception point voltage that is originally desired to be controlled, yet the reactive power output stops increasing, the voltage regulation effect deteriorates, and there is a risk of outputting reactive power of the opposite polarity depending on the characteristics of the Volt-Var curve.

[0005] This disclosure aims to provide a reactive power compensation device that determines reactive power based on wire information relating to the specifications of the wires between the power receiving point, which receives power from the power system within the premises, and the reactive power compensation device. [Means for solving the problem]

[0006] The reactive power compensation device in the first aspect is a reactive power compensation device installed on the premises of a consumer that receives power from a power system, and comprises a control unit and a supply unit that outputs reactive power, wherein the control unit determines the reactive power based on wire information relating to the specifications of the wires between the power receiving point on the premises that receives power from the power system and the reactive power compensation device. In this case, since the wire information can be reflected in the reactive power compensation control, the influence of the premises distribution lines can be reduced. In the second aspect of the reactive power compensation device, the control unit sets the wire information and determines the reactive power based on the wire information. In this case, the wire information of the in-house power distribution lines can be reflected in the reactive power compensation control, thereby reducing the influence of the power distribution lines. In the third aspect of the reactive power compensation device, the control unit acquires voltage information relating to the input voltage input to the reactive power compensation device, acquires current information relating to the current flowing through the power line, estimates the voltage difference between the voltage at the power receiving point and the input voltage from the power line information and the current information, and determines the reactive power based on the voltage information and the voltage difference. In this case, the output from the reactive power compensation device can suppress the influence of voltage differences due to the on-site power distribution lines. The reactive power compensation device in the fourth aspect is such that the control unit, when the voltage difference becomes greater than a preset upper limit, sets the voltage difference to be less than or equal to the upper limit, and when the voltage difference becomes less than a preset lower limit, sets the voltage difference to be greater than or equal to the lower limit. In this case, it is possible to prevent the voltage difference from becoming an abnormal value and making normal Volt-Var control impossible. In the fifth aspect of the reactive power compensation device, the wire information includes information regarding the length of the wire. In this case, the reactive power compensation device can calculate the resistance or reactance of the distribution line from the length of the wire. The reactive power compensation device in the sixth aspect includes either reactive current information or active current information in the current information. In this case, reactive power can be controlled based on the difference between reactive current and active current. In the seventh aspect of the reactive power compensation device, the control unit calculates a correction voltage from the voltage information and the voltage difference, and the supply unit outputs reactive power based on the correction voltage. In this case, appropriate reactive power compensation control can be achieved by performing Volt-Var control that takes the voltage difference into consideration. In the eighth aspect of the reactive power compensation device, the control unit calculates the correction voltage by reducing the magnitude of the voltage difference so that the input voltage does not exceed a predetermined upper or lower limit. In this case, reactive power compensation control can be performed so that the input voltage falls within an appropriate range. The reactive power compensation device of the ninth aspect is a reactive power compensation device in which loads are connected in parallel, and includes a detection unit for detecting the load current flowing through the loads, and the supply unit outputs a current for compensating for harmonics contained in the load current and a fundamental wave reactive current for adjusting the voltage at the power receiving point. In this case, it is possible to detect the load current flowing through the loads and control to compensate for the harmonics of the load current. The air conditioning system according to the tenth aspect comprises the load and the reactive power compensation device. In this case, an air conditioning system can be provided that can suppress the effects of voltage differences due to the in-house power distribution lines by output from the reactive power compensation device. The controller of the eleventh aspect is a controller for a reactive power compensation device installed on the premises of a consumer that receives power from a power system, wherein wire information regarding the specifications of the wires between the power receiving point on the premises and the reactive power compensation device is set, and information regarding the wire information is transmitted to the reactive power compensation device. In this case, a controller can be provided that controls a reactive power compensation device that reflects the premises distribution line information in the reactive power compensation control. In the controller of the twelfth aspect, the wire information includes information about the length of the wire. In this case, it is easy to set the length of the wire, and the resistance or reactance of the distribution line can be calculated from the length of the wire. The controller in the 13th aspect calculates the resistance or reactance value of the wire from the wire information. In this case, the resistance or reactance value of the wire calculated from the wire information can be calculated. [Brief explanation of the drawing]

[0007] [Figure 1] This figure shows an example of a voltage regulation system according to this embodiment. [Figure 2] This diagram shows the difference between the voltage at the power source and the voltage at the end of the circuit in Volt-Var control. [Figure 3] This figure shows the difference between the voltage at the point of power supply and the voltage at the end of the circuit when the Volt-Var characteristic is steep and the voltage drop is large. [Figure 4] This diagram shows the functional configuration of the reactive power compensation device according to this embodiment. [Figure 5] (A) is a diagram illustrating the estimation of the voltage difference in the case of leading reactive power, and (B) is a diagram illustrating the estimation of the voltage difference in the case of lagging reactive power. [Figure 6] This figure shows the relationship between the point-of-charge voltage and the value supplied as a reactive power index in Volt-Var control. [Figure 7] This diagram shows the flow of the control process up to the point where reactive power is output. [Figure 8] This diagram shows that the voltage difference is set within a predetermined range. [Figure 9] This figure shows several example configurations of reactive power compensation devices. [Modes for carrying out the invention]

[0008] Voltage regulation in power distribution systems is currently carried out using high-capacity reactive power compensation devices such as step voltage regulators (SVRs) that switch transformer taps, static var compensators (SVCs) that adjust voltage by controlling reactive power, and static synchronous compensators (STATCOMs). Because these devices are expensive, there is a demand for cheaper voltage regulation methods, and approaches that incorporate reactive power regulation functions into distributed power sources and consumer equipment have been proposed. Examples include smart inverters and active filters (AFs) for air conditioners.

[0009] When controlling grid voltage by reactive power adjustment, the voltage adjustment effect varies depending on where the reactive power is injected. Therefore, in order to efficiently control grid voltage, a centralized control system can be considered in which the voltage, power flow, etc. at various points are taken into consideration, and the amount of reactive power that should be output from each compensation device is calculated, and output instructions are issued to the reactive power compensation devices. However, implementing a centralized control system requires significant investment because it necessitates the construction of infrastructure such as sensors to obtain information from the power distribution system and communication lines to send commands to each reactive power compensation device. Therefore, as a low-cost method for voltage regulation, Volt-Var control, which outputs reactive power based on preset characteristics derived from the terminal voltage, has been proposed.

[0010] When performing reactive power output (Volt-Var control) using household appliances or the like, a difference occurs between the receiving-end voltage that is originally to be controlled and the self-end voltage of the reactive power compensation device due to the impedance of the distribution line within the customer's premises from the power receiving point from the power grid to the reactive power compensation device and the output reactive power. In cases where the length of the internal distribution line is long, etc., it may appear that the voltage is adjusted when viewed from the self-end voltage. In this case, there is a risk that reactive power will no longer be output even though there is a margin in the supply capacity of reactive power sufficient to control the receiving-end voltage that is originally to be controlled. Furthermore, the voltage regulation effect deteriorates, and depending on the characteristics of the Volt-Var curve, there is a risk of outputting reactive power of the opposite polarity.

[0011] It is considered that accurate voltage regulation becomes possible if the receiving-end voltage is detected and reactive power can be output based on the receiving-end voltage. However, if there is no voltage sensor for detecting the receiving-end voltage or if there is no communication network between the receiving point and the reactive power compensation device, a system construction is required, leading to an increase in cost. In particular, when trying to introduce a reactive power compensation system into an existing building or the like, it may be difficult to construct a voltage sensor or a communication network later. Therefore, the inventors have developed a reactive power compensation device that can adjust the voltage by outputting reactive power at the self-end while using the measured value of the self-end voltage of the reactive power compensation device. Hereinafter, embodiments will be described in detail with reference to the accompanying drawings.

[0012] <0000T89><Configuration of Voltage Regulation System> FIG. 1 is a diagram showing an example of a voltage regulation system 1 according to the present embodiment. The voltage regulation system 1 includes a power grid 10 and a customer facility 20. The customer facility 20 includes a power receiving and transforming facility 22, an internal distribution line 24, a reactive power compensation device 30, and a load 40. The customer facility 20 is connected to the power grid 10 via the power receiving and transforming facility 22. The power receiving and transforming facility 22 is connected to the reactive power compensation device 30 and the load 40 via the internal distribution line 24. In FIG. 1, as an example, the reactive power compensation device 30 and the load 40 are connected in parallel to the internal distribution line 24.

[0013] The voltage at the power receiving point RP is referred to as the power receiving point voltage Vs. In the voltage regulation system 1, a device for directly measuring the power receiving point voltage Vs is not provided. The reactive power compensation device 30 is referred to as the self-device, and the input terminal of the reactive power compensation device 30 is referred to as the self-terminal OP. The voltage at the self-terminal OP is referred to as the self-terminal voltage Vr, and the current flowing from the self-terminal OP of the reactive power compensation device 30 into the reactive power compensation device 30 is referred to as the current Icom. As shown by the arrow in FIG. 1, the current Ir is positive in the direction flowing into the self-terminal OP. The current flowing through the load 40 is referred to as the load current Iload. As shown by the arrow in FIG. 1, the load current Iload is positive in the direction flowing into the load 40. The impedance of the in-facility distribution line 24 is defined as the distribution line impedance Z (= R + jX), and the current flowing through the in-facility distribution line 24 is referred to as the current Ir. Here, "in-facility" means including within the customer facility 20 and the site of the customer including the customer facility 20. The "in-facility distribution line" is an electric wire arranged in the in-facility for transmitting electricity, and refers to an electric wire on the downstream side of the power receiving point.

[0014] The reactive power compensation device 30 performs voltage drop compensation and reduction of voltage fluctuation range by continuously adjusting the reactive power from lag to lead. The reactive power compensation device 30 broadly includes devices including the function of outputting reactive power or reactive current in addition to SVC (Static Var Compensator) and STATCOM (Static Synchronous Compensator)). For example, the reactive power compensation device includes a power conditioner (PCS (Power Conditioning System)) including a reactive power compensation function, a battery system, a synchronous generator, and the like. The load 40 is a power consumption facility installed in a customer such as a house or a business office, and receives power supply via a distribution line. In FIG. 1, since the load 40 is arranged in parallel with the reactive power compensation device 30, the current flowing through the distribution line changes due to the load current Iload component. The phase between the current and the voltage changes depending on the presence or absence of the load current Iload.

[0015] The reactive power compensation device 30 measures the terminal voltage Vr input to itself, as well as the current Ir and power factor φr flowing into it from the premises distribution line 24. Measuring the current Ir and power factor φr is equivalent to measuring the reactive current and the active current. Terminal OP is the position just before the current from the power system enters the reactive power compensation device 30. The terminal voltage is the voltage input to the reactive power compensation device 30, and is therefore sometimes referred to as the input voltage.

[0016] Due to the influence of the distribution line impedance Z of the in-house distribution line 24 from the power receiving point RP, which is the connection point between the power system 10 and the customer facility 20, to the terminal OP of the reactive power compensation device 30, a difference (voltage fluctuation) occurs between the power receiving point voltage Vs and the terminal voltage Vr.

[0017] Figure 2 illustrates the difference between the point-of-reception voltage Vs and the on-end voltage Vr in Volt-Var control. Normally, when the point-of-reception voltage Vs is known, control is performed to output a reactive power index Qs corresponding to the value of the point-of-reception voltage Vs on the Volt-Var characteristic curve L. However, if the value of the point-of-reception voltage Vs is unknown, and Volt-Var control is attempted using the on-end voltage Vr without estimating the point-of-reception voltage Vs, then control will be performed using the reactive power index Qr corresponding to the on-end voltage Vr. In Figure 2, Qs is larger than Qr, so control is performed using the smaller value of Qr instead of the value of Qs, which is the reactive power index that should ideally allow control. Thus, when Volt-Var control is performed based on the on-end voltage, the output from the reactive power compensation device may be unnecessarily suppressed by the difference between Qs and Qr due to the influence of the distribution line impedance within the premises.

[0018] Figure 3 shows the difference between the receiving point voltage Vs and the on-end voltage Vr when the Volt-Var characteristic is steep and the voltage drop is large. Figure 3 is an example where the Volt-Var characteristic is even steeper than in Figure 2 and the voltage drop from the receiving point voltage to the on-end voltage is large. Normally, control is performed using the reactive power index Q corresponding to the receiving point voltage Vs on the Volt-Var characteristic curve L. However, when the Volt-Var characteristic is steep and the voltage drop is large due to the impedance of the distribution lines within the premises, the on-end voltage Vr becomes negative, and the corresponding reactive power index Qs also becomes a negative value. In this case, the control would output a negative reactive power index Qr instead of the positive reactive power index Qs that should be output. Thus, if Volt-Var control is performed using the on-end voltage Vr as is, there is a risk of outputting reactive power of the opposite polarity depending on the characteristics of the Volt-Var curve and the magnitude of the distribution line impedance.

[0019] If the voltage output to the point of power reception could be adjusted based on the point of power reception voltage Vs, accurate voltage adjustment would be possible. However, installing a device to directly measure the point of power reception voltage Vs would impose an infrastructure burden. In the voltage adjustment system 1 according to this embodiment, the compensation current Icom is adjusted by estimating the point of power reception voltage Vs based on the terminal voltage Vr of the reactive power compensation device 30.

[0020] The reactive power compensation device 30 adjusts the voltage input to the customer's premises by supplying power constituting the fundamental wave reactive power to its own terminal OP according to the magnitude of the estimated receiving point voltage Vs. An example of how the reactive power compensation device 30 adjusts the receiving point voltage Vs is described below. When the reactive power compensation device 30 supplies leading reactive power to its own terminal OP, the voltage at the receiving point RP rises. Conversely, when the reactive power compensation device 30 supplies lagging reactive power to its own terminal OP, the voltage at the receiving point RP drops. In this way, the voltage at the receiving point RP is adjusted by the reactive power compensation device 30 supplying leading or lagging reactive power to its own terminal OP. In addition, as the voltage at its own terminal OP is adjusted, the receiving point voltage Vs upstream of the terminal OP is also adjusted. Leading reactive power is reactive power in which the phase of the current leads the phase of the voltage. Lagging reactive power is reactive power in which the phase of the current lags the phase of the voltage.

[0021] Figure 4 shows the functional configuration of the reactive power compensation device 30 according to this embodiment. The reactive power compensation device 30 includes an acquisition unit 331, a storage unit 332, a measurement unit 333, a supply unit 334, a control unit 335, a display unit 336, and the like.

[0022] The acquisition unit 331 acquires, for example, information regarding the specifications of the wires of the in-house power distribution line 24. "Wire information regarding wire specifications" (also simply called wire information) is information that allows for the estimation of the resistance component R or reactance component X of the wire, or the resistance component R or reactance component X of the wire. However, it is not always necessary to have both the resistance component R and the reactance component X of the wire; information on only one component is sufficient. Furthermore, since the resistance component R or reactance component X of the wire can be estimated from the wire length, wire diameter, wire type, etc., the wire length, wire diameter, and wire type are also included in the information regarding the wire specifications. In addition, if the wire type and wire diameter are known, the resistance value [Ω / km] and reactance value [Ω / km] per unit length can be determined. For this reason, this information may be stored in advance in the storage unit 332, and the resistance component R or reactance component X of the wire may be calculated from the length information acquired by the acquisition unit 331.

[0023] The acquisition unit 331 acquires wire information. For example, the acquisition unit 331 acquires wire information entered by the user on the user interface of the touch panel display, which acts as the display unit 336. Alternatively, the acquisition unit 331 can acquire wire information that has been pre-stored in the storage unit 332. The acquisition unit 331 can also acquire wire information by selecting from a plurality of pre-set wire information sets using a DIP switch or the like. Furthermore, the acquisition unit 331 can also acquire wire information stored externally via communication. Furthermore, the acquisition unit 331 may also acquire voltage and current information measured by the measurement unit 333.

[0024] The storage unit 332 stores information. The storage unit 332 is implemented by a storage device such as a ROM (Read Only Memory), an HDD (Hard Disk Drive) used for storing programs and various setting data, a RAM (Random Access Memory) used as a work area during calculations, or a semiconductor memory. The information stored in the storage unit 332 includes the wire information of the in-house power distribution line 24, voltage information related to the input voltage input to the reactive power compensation device 30, current information related to the current flowing through the wires of the in-house power distribution line 24, and Volt-Var characteristic information.

[0025] The measurement unit 333 is a sensor capable of measuring voltage, current, and power factor, similar to a multi-function energy meter. The sensor in the measurement unit 333 measures the voltage Vr at its own end, the current Ir flowing into the device from the premises power distribution line 24, and the power factor φr. In other words, the measurement unit 333 can measure reactive power, active power, reactive current, active current, etc. The measurement unit 333 does not necessarily have to be located inside the reactive power compensation device 30; it may be located outside. Furthermore, the measurement unit 333 does not necessarily have to be a sensor; it may be a device that can acquire the voltage Vr at its own end, the current Ir, etc., within a microcontroller.

[0026] The measurement unit 333 detects voltage and current at predetermined intervals. The predetermined interval can be any time, but for example, it may be 1 hour. The measurement unit 333 may also have a function to manage time, such as a real-time clock (RTC). Furthermore, the measurement unit 333 may measure the compensation current Icom flowing from its own terminal OP to the reactive power compensation device 30 and the load current Iload flowing to the load 40.

[0027] The supply unit 334 supplies current near its own terminal OP as a means of supplying current. The supply unit 334 supplies current and other components that constitute reactive power determined by the control unit 335.

[0028] The control unit 335 controls the processing of the reactive power compensation device 30, including acquiring information from the acquisition unit 331, storing information in the storage unit 332, controlling the supply unit 334, and determining the amount of reactive power to output. The control unit 335 realizes the various functions in this embodiment using a processor (CPU (Central Processing Unit)) or a CPU used in various devices connected thereto. The operation of the aforementioned processor is not limited to a single processor, but may be performed by multiple processors working together.

[0029] The control unit 335 estimates the voltage at the power receiving point RP (power receiving point voltage Vs) based on wire information relating to the wire specifications of the in-premises distribution line 24 between the power receiving point RP, which receives power from the power system 10 within the premises, and the reactive power compensation device 30. As described above, the wire information is pre-set information such as the resistance component R or reactance component X of the wire, or information that can estimate them. Based on the estimated power receiving point voltage Vs, the control unit 335 performs Volt-Var control. Volt-Var control refers to voltage control performed by outputting reactive power in response to voltage fluctuations at the point to be controlled, based on a pre-set Volt-Var curve where the horizontal axis represents voltage (Volt) and the vertical axis represents reactive power (Var). The Volt-Var curve will be explained later.

[0030] Furthermore, the control unit 335 causes the acquisition unit 331 to acquire voltage information related to the input voltage (called the terminal voltage Vr) input to the reactive power compensation device 30, and current information related to the current flowing through the wires. Next, the control unit 335 estimates the voltage difference ΔV, which is the voltage fluctuation between the power receiving point voltage Vs and the terminal voltage Vr, from the aforementioned wire information and current information. The control unit 335 determines the reactive power based on the terminal voltage Vr and the voltage difference ΔV.

[0031] (Estimation of the voltage Vs at the point of power reception) Figures 5(A) and 5(B) are voltage vector diagrams illustrating the estimation process of the power receiving point voltage Vs performed by the control unit 335. Figure 5(A) illustrates the estimation of the voltage difference in the case of leading reactive power, and Figure 5(B) illustrates the estimation of the voltage difference in the case of lagging reactive power.

[0032] In Figures 5(A) and (B), the vector of the on-end voltage Vr and the vector of the receiving point voltage Vs do not coincide. This is because, from the receiving point RP, which is the connection point between the power system 10 and the consumer facility 20, to the on-end OP of the reactive power compensation device 30, there is a difference between the receiving point voltage Vs and the on-end voltage Vr due to the impedance Z of the in-house distribution line 24. Figure 5(A) shows the case of leading reactive power, where the phase of the current Ir leads the on-end voltage Vr. Figure 5(B) shows the case of lagging reactive power, where the phase of the current Ir lags behind the on-end voltage Vr.

[0033] While the terminal voltage Vr and current Ir can be obtained from the measurement unit 333, there is no device to directly measure the power receiving point voltage Vs. Therefore, the control unit 335 estimates the power receiving point voltage Vs based on the wire information regarding the specifications of the wires of the in-house power distribution line 24. The estimated power receiving point voltage Vs is also called the "corrected voltage" in the sense that it is a corrected version of the terminal voltage. First, the control unit 335 estimates the voltage difference ΔV between the terminal voltage Vr and the power receiving point voltage Vs due to the impedance Z of the in-house power distribution line 24 using equation (1), based on the resistance component R [Ω] and reactance component X [H] of the wires and the current Ir [A] measured by the measurement unit 333. ΔV = Ir × Z = RIr + jXIr … (1) Here, j is the imaginary unit. Next, the voltage at the point of power reception Vs (corrected voltage) is estimated using equation (2). Vs = Vr + ΔV … (2) As can be seen from the vector diagrams in Figures 5(A) and (B), starting from the vector of the on-end voltage Vr, if you move parallel to the current vector by the voltage of the resistance component and then move perpendicular to that by the voltage of the reactance component, you will get the vector of the receiving point voltage Vs.

[0034] Furthermore, as can be seen from Figures 5(A) and (B), in the case of leading reactive power, the effective power value of the receiving point voltage Vs is smaller than that of the on-end voltage Vr, and in the case of lagging reactive power, the effective power value of the receiving point voltage Vs is larger than that of the on-end voltage Vr. The control unit 335 estimates the receiving point voltage Vs by adding the estimated voltage difference ΔV to the measured on-end voltage Vr. If no correction is needed, ΔV is zero, and the on-end voltage Vr and the receiving point voltage Vs are equal.

[0035] (Determination of reactive power output) Figure 6 shows the relationship between the voltage at the point of power reception Vs and the value determined by the control unit 335 as a reactive power index. In Figure 6, the vertical axis represents the reactive power index, and the horizontal axis represents the voltage at the point of power reception Vs. Figure 6 also shows the Volt-Var curve L. The Volt-Var curve L is a line that defines the relationship between the voltage at the point of power reception Vs and the value determined by the control unit 335 as a reactive power index. The reactive power index is an index relating to the fundamental wave reactive power supplied by the supply unit 334 of the reactive power compensation device 30. The reactive power index includes the fundamental wave reactive power supplied by the supply unit 334. Additionally, the reactive power index includes the reactive current supplied by the supply unit 334.

[0036] Furthermore, the Volt-Var curve L defines two reactive power indices: a lagging reference index Qa and a leading reference index Qb. The lagging reference index Qa is the reference index for lagging reactive power or the reactive current that constitutes lagging reactive power. The leading reference index Qb is the reference index for leading reactive power or the reactive current that constitutes leading reactive power.

[0037] Furthermore, the Volt-Var curve L defines the following values ​​for the receiving point voltage Vs: the rated value Va, the unnecessary upper limit Vb, the lagging maximum value Vc, the unnecessary lower limit Vd, and the leading maximum value Ve. The rated value Va is the rated value of the point-of-reception voltage Vs. In this embodiment, the rated value Va is determined by the user of the voltage regulation system 1. The rated value Va may be any value, but for example, it is 202V.

[0038] The unnecessary upper limit Vb is the upper limit of the input voltage at which the control unit 335 determines that the supply of fundamental wave reactive power by the supply unit 334 is unnecessary. The unnecessary upper limit Vb can be any value, but for example, it is 5% higher than the rated value Va. The maximum delay value Vc is the maximum fundamental wave reactive power that the supply unit 334 can supply as delayed reactive power. The input voltage is determined by the control unit 335 to supply power to the power supply unit 334. The maximum delay value Vc can be any value, but for example, it is 10% higher than the rated value Va.

[0039] The unnecessary lower limit Vd is the lower limit of the input voltage at which the control unit 335 determines that the supply of fundamental wave reactive power by the supply unit 334 is unnecessary. The unnecessary lower limit Vd can be any value, but for example, it is 5% lower than the rated value Va. Note that the ratio of the unnecessary upper limit Vb and the unnecessary lower limit Vd to the rated value Va may be different. The leading maximum value Ve is the input voltage at which the control unit 335 determines that the supply unit 334 should supply the maximum fundamental reactive power that it can supply as leading reactive power. The maximum lead value Ve can be any value, but for example, it may be 10% lower than the rated value Va. Note that the ratio of the maximum lag value Vc to the maximum lead value Ve may differ.

[0040] In the Volt-Var curve L, the reactive power index corresponding to the coordinate where the input voltage is above the unwanted lower limit Vd and below the unwanted upper limit Vb is shown as 0%. This means that when the input voltage is above the unwanted lower limit Vd and below the unwanted upper limit Vb, the control unit 335 does not allow the supply unit 334 to supply fundamental reactive power. On the other hand, when the input voltage is below the unwanted lower limit Vd or above the unwanted upper limit Vb, the control unit 335 allows the supply unit 334 to supply fundamental reactive power.

[0041] Furthermore, if the estimated power receiving point voltage Vs is greater than or equal to the maximum lagging value Vc, the control unit 335 determines the reactive power index to be the lagging reference index Qa. In other words, if the estimated power receiving point voltage Vs is greater than or equal to the maximum lagging value Vc, the control unit 335 decides to have the supply unit 334 supply the maximum fundamental wave reactive power that it can supply as lagging reactive power. Furthermore, if the estimated power receiving point voltage Vs is greater than the unnecessary upper limit Vb and less than the maximum lag value Vc, the control unit 335 determines the reactive power index as a ratio to the lag reference index Qa that is greater than 0% and less than 100%. In this case, the control unit 335 determines a reactive power index that is a larger ratio to the lag reference index Qa the larger the estimated power receiving point voltage Vs is.

[0042] Furthermore, if the estimated receiving point voltage Vs is less than or equal to the leading maximum value Ve, the control unit 335 determines the reactive power index to be the leading reference index Qb. In other words, if the input voltage is less than or equal to the leading maximum value Ve, the control unit 335 decides to have the supply unit 334 supply the maximum fundamental wave reactive power that it can supply as leading reactive power. Furthermore, if the estimated receiving point voltage Vs is less than the unnecessary lower limit Vd and greater than the leading maximum value Ve, the control unit 335 determines the reactive power index as a ratio to the leading reference index Qb that is greater than 0% and less than 100%. In this case, the control unit 335 determines a reactive power index that is a larger ratio to the leading reference index Qb the smaller the estimated receiving point voltage Vs is.

[0043] Figure 7 shows the flow of the control process until reactive power is output. The control unit 335 shown in Figure 4 starts the reactive power compensation process (START). First, the control unit 335 acquires pre-set wire information (S100). Next, the control unit 335 acquires voltage information related to the terminal voltage (S200). Then, the control unit 335 acquires current information flowing through the wires of the in-house power distribution line 24 (S300). Furthermore, the control unit 335 calculates the voltage difference based on the wire information and current information and estimates the power receiving point voltage (S400). Next, the control unit 335 controls the supply unit 334 to perform Volt-Var control based on the estimated power receiving point voltage (S500). The control unit 335 acquires information related to the terminal voltage again (S600). Furthermore, the control unit 335 determines whether the terminal voltage exceeds the limit value (S700). If it is determined that the terminal voltage exceeds the limit value (YES in S700), the control unit 335 reduces the voltage difference and estimates the voltage at the point of reception (S800). If it is determined that the terminal voltage does not exceed the limit value (NO in S700), the control unit 335 estimates the voltage at the point of reception based on the calculated voltage difference (S900). The control unit 335 controls the supply unit 334 to perform Volt-Var control based on the estimated voltage at the point of reception (S1000). After the above processing, the reactive power compensation process is completed (END).

[0044] The reactive power compensation device according to this embodiment corrects the reference voltage for Volt-Var control based on wire information regarding the specifications of the wires in the premises distribution line. This reduces the influence of voltage differences due to distribution line impedance, enabling the desired reactive power output at the point of power reception. Furthermore, the reactive power compensation device according to this embodiment estimates the point of power reception voltage using the above-mentioned wire information and the terminal voltage input to the reactive power compensation device, and performs Volt-Var control based on the estimated point of power reception voltage. According to the above control process, the output from the reactive power compensation device is not unnecessarily suppressed.

[0045] Furthermore, compared to installing voltage sensors and communication networks at the point of power reception, the reactive power compensation device according to this embodiment can be implemented at a lower cost. Even when introducing this system later into existing buildings, the reactive power compensation device according to this embodiment is easy to install.

[0046] Figure 8 shows that the voltage difference ΔV is set within a predetermined range. The control unit 335 sets the voltage difference to a value less than or equal to the upper limit ΔV_max if the voltage difference ΔV is greater than the preset upper limit ΔV_max. The control unit 335 sets the voltage difference ΔV to a value greater than or equal to the lower limit ΔV_min if the voltage difference ΔV is less than the preset lower limit ΔV_min. In the Volt-Var characteristics, the reactive power index Qs_max corresponds to the upper limit Vs_max, and the reactive power index Qs_min corresponds to the lower limit Vs_min. When the control unit 335 sets the voltage difference value to a value less than or equal to the upper limit ΔV_max, it sets the reactive power index to a value less than or equal to Qs_max. Also, when the control unit 335 sets the voltage difference value to a value greater than or equal to the lower limit ΔV_min, it sets the reactive power index to a value greater than or equal to Qs_min. Thus, if the voltage difference is calculated to be an extremely large or extremely small value, the reactive power index will also be set to fall within a certain range in order to set the voltage difference within a certain limit.

[0047] If there is a malfunction in the current sensor or an error in the setting of wire information regarding the specifications of the wires, the estimated voltage difference will be an abnormal value, making normal Volt-Var control impossible. Therefore, a limit value can be set in advance for the voltage difference so that the estimated result does not exceed this value. Depending on the characteristics of Volt-Var control, the limit value may be set so that it does not exceed the dead band width, for example, so that an output of reverse polarity does not occur when controlling with the terminal voltage. Thus, it is possible to prevent abnormal voltage differences that would prevent normal Volt-Var control from occurring.

[0048] In the example shown in Figure 8, it was explained that the voltage difference is set to fall within a predetermined range. In addition, upper and lower limits may also be predetermined for the terminal voltage, which is the input voltage of the reactive power compensation device, and the voltage difference may be reduced to estimate the power receiving point voltage so as not to exceed the upper and lower limits.

[0049] For example, if lagging reactive power is output to lower the voltage, the terminal voltage Vr will decrease relative to the receiving voltage Vs. If the voltage difference ΔV is estimated from the wire information and current information, and the terminal voltage is corrected (equivalent to estimating the receiving voltage) to perform Volt-Var control, the terminal voltage may rise or fall excessively, especially if the in-house power distribution lines are long and have high impedance. Therefore, upper and lower limits for the terminal voltage (input voltage) are set in advance. If, as a result of performing Volt-Var control after correcting the terminal voltage, the measured result of the terminal voltage (input voltage) exceeds the upper or lower limit, the magnitude of the voltage difference is reduced and a correction voltage is calculated. Alternatively, if it is expected that the terminal voltage (input voltage) will exceed the upper or lower limit, the magnitude of the voltage difference may be reduced so that the terminal voltage (input voltage) does not exceed the predetermined upper or lower limit, and a correction voltage is calculated.

[0050] The terminal voltage, correction voltage, and voltage difference data are stored as historical information in the storage unit 332. Therefore, the terminal voltage after voltage control can be estimated from past data of terminal voltage, correction voltage, and voltage difference. If the control unit 335 anticipates that the estimated terminal voltage (input voltage) will exceed an upper or lower limit, it calculates the correction voltage by setting it to a voltage difference magnitude that is predicted not to exceed a predetermined upper or lower limit.

[0051] The reactive power compensation device according to this embodiment corrects the reference voltage for Volt-Var control based on wire information relating to the specifications of the distribution line wires. This reduces the influence of voltage differences due to the distribution line impedance Z, enabling the desired reactive power output at the point of reception. Furthermore, the reactive power compensation device according to this embodiment estimates the point of reception voltage using the above-mentioned wire information and the terminal voltage input to the reactive power compensation device, and performs Volt-Var control based on the estimated point of reception voltage. According to the above control process, the output from the reactive power compensation device will not output reactive power with the opposite polarity to what it should.

[0052] (Other embodiments) Figure 9 shows several configuration examples of a reactive power compensation device. In other forms of the reactive power compensation device, as shown in Figures 9(A) to (E), a power converter and a load are connected in series. The power converter is described as a device including the reactive power compensation device 30. In Figure 1, the reactive power compensation device 30 and the load 40 were arranged in parallel, but the reactive power compensation device of this disclosure can also be applied when the reactive power compensation device 30 and the load 40 are connected in series. As shown in Figures 9(A) and (B), capacitors and inductors may be connected to the power converter. The reactive power compensation device 30 included in the power converter includes not only devices that output only fundamental reactive power for voltage adjustment of the power system (AF, STATCOM, SVC, etc.), but also devices that can output fundamental reactive power for voltage adjustment of the system as part of their function. As shown in Figures 9(C) to (E), the reactive power compensation device in this embodiment may include a configuration of a PCS for distributed power supplies, a PWM converter, an air conditioner, and an active filter, all connected in parallel.

[0053] The current output from a reactive power compensation device includes a fundamental reactive current component for adjusting the grid voltage, as well as a load current or generated current component from distributed energy resources (DERs). However, since voltage fluctuations due to reactive currents are more effective than voltage drops due to active currents, not all current components are necessarily required to compensate for voltage differences due to distribution line impedance.

[0054] Figure 9(D) shows the configuration of a reactive power compensation device in which a power converter and a load are connected in series. A power converter, as an example of a conversion unit, includes an inverter (not shown) and a converter (not shown). The power converter converts the received power into power of a specific voltage and frequency using the inverter and converter. A power converter equipped with a PWM converter or matrix converter may supply fundamental reactive power to the power receiving point. A PWM converter is a converter that controls the waveform of the input current. A matrix converter is a converter that converts AC power of a specific frequency into AC power of a different frequency. Furthermore, the power converter may supply fundamental reactive power to the power receiving point according to the magnitude of the input voltage. In this case, the power converter can also be considered as a supply means for supplying fundamental reactive power.

[0055] Figure 9(E) shows the configuration of a reactive power compensation device in which a power converter and a load are connected in parallel. The load may be, for example, an air conditioner. A detection unit (not shown) detects the load current flowing through the load. A supply unit (not shown) of the reactive power compensation device outputs a current that compensates for harmonics contained in the load current and a fundamental wave reactive current for adjusting the voltage at the power receiving point.

[0056] The reactive power compensation device reduces harmonic currents by supplying a current that is out of phase with the harmonics in the load current, when harmonics are present in the load current. This suppresses the outflow of harmonic currents from the air conditioning system. The harmonic currents that the reactive power compensation device suppresses may be of any order. The supply unit outputs a combined current to compensate for the harmonics in the load current and a fundamental reactive current to adjust the voltage at the point of reception. The supply unit may determine the reactive power index from a value obtained by subtracting the required reduction current from the current capacity that the reactive power compensation device can supply.

[0057] Furthermore, the voltage regulation system 1 may include a controller that transmits wire information regarding the specifications of the in-house power distribution lines 24 to the reactive power compensation device 30. The wire information may include information regarding the length of the wires. Furthermore, a portion of the processing performed by the control unit 335 of the reactive power compensation device 30 may be performed by the controller. For example, the controller calculates the resistance or reactance value of the wire from the wire information such as the length of the wire that has been input, and transmits the resistance or reactance value to the reactive power compensation device 30.

[0058] <Effects> The reactive power compensation device 30 of this disclosure is installed on the premises of a consumer that receives power from a power system 10, and comprises a control unit 335 and a supply unit 334 that outputs reactive power. The control unit 335 determines the reactive power based on wire information relating to the specifications of the wires between the power receiving point RP on the premises, which receives power from the power system 10, and the reactive power compensation device 30. In this case, since the wire information on the premises can be reflected in the reactive power compensation control, the influence of the premises distribution lines can be reduced. Here, the control unit 335 sets the wire information and determines the reactive power based on the wire information. In this case, the wire information can be reflected in the reactive power compensation control, thereby reducing the influence of the power distribution lines. Furthermore, the control unit 335 acquires voltage information relating to the input voltage input to the reactive power compensation device 30, acquires current information relating to the current flowing through the power line, estimates the voltage difference ΔV between the voltage at the power receiving point RP and the input voltage from the power line information and the current information, and determines the reactive power based on the voltage information and the voltage difference ΔV. In this case, the output from the reactive power compensation device 30 can suppress the influence of voltage differences due to the in-house power distribution lines. Furthermore, the control unit 335 sets the voltage difference ΔV to be less than or equal to the upper limit if the voltage difference ΔV becomes greater than a preset upper limit, and sets the voltage difference to be greater than or equal to the lower limit if the voltage difference becomes less than a preset lower limit. In this case, it is possible to prevent the voltage difference from becoming an abnormal value and making normal Volt-Var control impossible. Furthermore, the wire information includes information regarding the length of the wire. In this case, the reactive power compensation device can calculate the resistance or reactance of the distribution line from the length of the wire. Furthermore, the current information includes either reactive current information or active current information. In this case, reactive power can be controlled based on the difference between reactive current and active current. Furthermore, the control unit 335 calculates a correction voltage from the voltage information and the voltage difference ΔV, and the supply unit outputs reactive power based on the correction voltage. In this case, appropriate reactive power compensation control can be achieved by performing Volt-Var control that takes the voltage difference ΔV into consideration. Furthermore, the control unit 335 calculates the correction voltage by reducing the magnitude of the voltage difference so that the input voltage does not exceed a predetermined upper or lower limit. In this case, reactive power compensation control can be performed so that the input voltage falls within an appropriate range. Furthermore, the reactive power compensation device 30, to which the load 40 is connected in parallel, includes a detection unit for detecting the load current flowing through the load 40, and the supply unit outputs a current that compensates for the harmonics included in the load current Iload, along with a fundamental reactive current for adjusting the voltage at the power receiving point RP. In this case, the load current Iload flowing through the load can be detected, and control can be performed to compensate for the harmonics of the load current Iload. Furthermore, the air conditioner of this disclosure includes the load 40 and the reactive power compensation device 30. In this case, the output from the reactive power compensation device 30 can provide an air conditioner that can suppress the effect of the voltage difference ΔV due to the in-plant power distribution line 24. Furthermore, the controller of this disclosure is a controller for a reactive power compensation device 30 installed on the premises of a consumer that receives power from a power system 10, and wire information regarding the specifications of the wires between the power receiving point RP on the premises that receives power from the power system 10 and the reactive power compensation device 30 is set, and information regarding the wire information is transmitted to the reactive power compensation device 30. In this case, a controller can be provided that controls the reactive power compensation device 30 which reflects the wire information in the reactive power compensation control. Furthermore, the wire information includes information regarding the length of the wire. In this case, it is easier to set the length of the wire, and the resistance or reactance of the distribution line can be calculated from the length of the wire. Furthermore, the resistance or reactance value of the wire is calculated from the wire information. In this case, the resistance or reactance value of the wire calculated from the wire information can be calculated.

[0059] Although embodiments have been described above, the technical scope of this disclosure is not limited to the embodiments described above. It is clear from the claims that combinations of two or more of the above embodiments, as well as various modifications or improvements to the above embodiments, are also included in the technical scope of this disclosure. Furthermore, the order in which each operation in the control unit is executed is not limited to the order described in each of the embodiments described above, but may be changed individually. [Explanation of Symbols]

[0060] 1...Voltage regulation system, 10...Power system, 20...Customer facilities, 22...Substation equipment, 24...In-house power distribution lines, 30...Reactive power compensation device, 40...Load, 331...Acquisition unit, 332...Storage unit, 333...Measurement unit, 334...Supply unit, 335...Control unit, 336...Display unit, RP...Power receiving point, OP...Local end, Vs...Power receiving point voltage, Vr...Local end voltage, ΔV...Voltage difference, Ir...Current, R...Resistance component, X...Reactance component, Z...Impedance, L...Volt-Var curve

Claims

1. A reactive power compensation device installed on the premises of a consumer that receives power from the power grid, It comprises a control unit and a power supply unit that outputs reactive power, The control unit determines the reactive power based on wire information relating to the specifications of the wires between the power receiving point that receives power from the power system within the premises and the reactive power compensation device. Reactive power compensation device.

2. The reactive power compensation device according to claim 1, wherein the control unit sets the wire information and determines the reactive power based on the wire information.

3. The control unit, The voltage information relating to the input voltage input to the reactive power compensation device is acquired, Obtain current information relating to the current flowing through the aforementioned electric wire, The voltage difference between the voltage at the power receiving point and the input voltage is estimated from the wire information and the current information. The reactive power is determined based on the voltage information and the voltage difference. The reactive power compensation device according to claim 1.

4. The control unit, If the voltage difference exceeds a preset upper limit, the voltage difference will be reduced to less than or equal to the upper limit. If the voltage difference falls below a preset lower limit, the voltage difference is set to be equal to or greater than the lower limit. The reactive power compensation device according to claim 3.

5. The aforementioned wire information includes information regarding the length of the wire. The reactive power compensation device according to any one of claims 1 to 4.

6. The current information includes either reactive current information or active current information. The reactive power compensation device according to claim 3 or 4.

7. The control unit, A correction voltage is calculated from the voltage information and the voltage difference. The supply unit outputs reactive power based on the correction voltage. The reactive power compensation device according to claim 3 or 4.

8. The control unit, The correction voltage is calculated by reducing the magnitude of the voltage difference so that the input voltage does not exceed a predetermined upper or lower limit. The reactive power compensation device according to claim 7.

9. A reactive power compensation device in which loads are connected in parallel, The system includes a detection unit that detects the load current flowing through the aforementioned load, The supply unit outputs a current that compensates for harmonics included in the load current and a fundamental reactive current for adjusting the voltage at the power receiving point. The reactive power compensation device according to any one of claims 1 to 4.

10. An air conditioning system having the load and the reactive power compensation device according to claim 9.

11. A controller for a reactive power compensation device installed on the premises of a consumer that receives power from the power grid, A controller that sets wire information relating to the specifications of the wires between the power receiving point that receives power from the power system within the premises and the reactive power compensation device, and transmits information relating to the wire information to the reactive power compensation device.

12. The controller according to claim 11, wherein the wire information includes information regarding the length of the wire.

13. The controller according to claim 12, which calculates the resistance value or reactance value of the electric wire from the electric wire information.

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