JP2003032895A - Method of measuring loss in tidal current controller, and its use - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a loss measuring method which detects the power loss in a tidal current controller by the measurement of power at one end of input ends or output ends. SOLUTION: In the method of measuring the loss in a tidal current measuring device, an asynchronous linkage device, a DC transmission system, or the forward converter of UPFC perform DC voltage constant control, and the side of an inverter at the end of its opposite number performs power constant control, and the forward converter operates to take in power being larger by the amount of total loss of the system than the power set in the inverter so as to keep the DC voltage constant. As a result, the total power loss of the system including higher harmonic loss is obtained by subtracting the value of the power to be transmitted to load from the measured value of the input power of a forward converter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a loss measuring method for a power flow control device and a method of using the loss measurement result for power setting, power cost determination and cost evaluation for power flow control.

[0002]

2. Description of the Related Art With the liberalization of electric power, wholesale and retail electric power companies such as IPPs and distributed power sources are entering the electric power system. In this way, when many electric power companies enter the electric power system, it becomes necessary to control the power flow of electric power. Therefore, introduction of a power flow control device is being considered.

For such a power flow control device, a device using power electronics technology such as FACTS, which has been developed as a system stabilizing device, is applied from the viewpoint of controllability, high speed, and improvement of stability. it can.

Asynchronous interconnection systems and DC power transmission systems convert AC to DC at the power transmission end and convert DC to AC at the load site directly or via a DC power transmission line to supply a predetermined amount of power to the load. In addition, high-speed phase shift adjuster (UPFC: Unified
The power flow controller) includes a converter and an inverter, and controls the phase and magnitude of the applied voltage of the series transformer inserted in series in the power transmission line to control the power flow. Since these power flow control devices are always used for power flow control, it is necessary that the device loss is low at all times. In addition, the power transmission loss of these devices needs to be grasped by the electric power command center, ISO, power transmission company, power generation company, etc. from the necessity of setting transmission power and paying charges.

The power flow control devices such as the asynchronous interconnection system, the DC power transmission system, and the UPFC to which the power electronics technology is applied are equipped with a converter for converting AC to DC and an inverter for converting DC to AC. Equipment losses are mainly caused by AC / DC converters and conversion transformers connected to the AC system.

Conventionally, this power loss is obtained by calculation from the resistance of each device and the flowing current, or both the power at the input end and the power at the output end are detected and the difference is obtained.

[0007]

In the method of calculating the power loss from the resistance of each device and the flowing current, the power loss due to the harmonic generated from the AC / DC converter of the power flow control device cannot be calculated. It was Further, in the method of detecting the input power and the output power of the prior art and obtaining the loss from the difference between them, it is necessary to have power detectors having the same accuracy at both the input end and the output end, and moreover, the detection data of the power detector. Need to be sent to the other end.

An object of the present invention is to provide a loss measuring method for detecting the power loss of a power flow control device by measuring the power at the input end or the output end.

Another object of the present invention is to detect the detected power loss information of the power flow control device through a general-purpose communication device such as the Internet or an intranet in a company to a power control center, ISO, power transmission company, IPP. , The method of delivering to distributed power supply companies, etc., and evaluating and determining power control and cost.

[0010]

According to a loss measuring method of a power flow measuring device of the present invention, a converter (forward converter) side of an asynchronous interconnection device, a DC transmission system or a UPFC performs a constant DC voltage control, and an inverter at the other end. The (inverse converter) side is performing constant power control, and the forward converter operates to take in power that is larger than the power set in the inverse converter by the total system loss in order to keep the DC voltage constant. Therefore, the total power loss of the system including the harmonic loss is obtained by subtracting the power setting value transmitted to the load from the measured value of the input power of the forward converter.

Further, in the loss measuring method of the power flow measuring device of the present invention, the forward converter side performs constant power control, the inverse converter side performs constant DC voltage control, and the inverse converter outputs from the output of the forward converter. Can output only a small amount of power corresponding to the system total loss, so obtain the measured output power on the inverse converter side that performs constant DC voltage control, and subtract the measured output power from the power set value transmitted to the load. Determine the total power loss of the system including harmonic loss.

The power loss information measured as described above is sent to a power control station, a power generation company, a consignment company, ISO, etc. via the Internet, and power dealing including loss of a power flow control device, operation, cost evaluation, etc. I do.

[0013]

DETAILED DESCRIPTION OF THE INVENTION The details of the present invention will be described below with reference to the drawings.

(Embodiment 1) An asynchronous interconnection system or a DC power transmission system to which this embodiment is applied will be described. Figure 1
The DC power transmission system of this embodiment is shown in FIG. In this embodiment,
A case where the tidal current flows from left to right in FIG. 1 will be described. In FIG. 1, reference numerals 14 and 24 are AC systems, 13 and 23 are AC buses,
3 is an AC interconnection line that connects two AC systems, and 1 is an IGB
A forward converter (converter) of a self-exciting converter that converts alternating current to direct current, which is composed of a self-extinguishing element such as T, 2 is an inverse converter (inverter) of a self-exciting converter that converts direct current to alternating current,
Reference numerals 11 and 21 are DC capacitors for smoothing DC voltage, reference numerals 12 and 22 are conversion transformers, and reference numerals 30a and 30b are DC transmission lines. Reference numeral 100 is a power flow command station that commands the power flow power of the power flow control device, 200 is a control device that controls the forward converter 1, and 300 is a control device that controls the inverse converter 2. Reference numeral 201 is an AC current transformer that detects the current flowing through the forward converter 1, 202 is an AC voltage transformer, and 203 is a power transformer that detects the input power of the forward converter 1. Code 4
Reference numeral 00 is an all-power command center (control station) that controls the power flow of all systems, 500 is an ISO, a power transmission company, etc., and 600 is a general-purpose communication network such as the Internet or an intranet.

The asynchronous interconnection system is the same as the DC transmission system shown in FIG. 1 except that the DC transmission lines 30a and 30b are not provided.

First, it will be described that the power flow between the AC systems 14 and 24 can be arbitrarily controlled with the configuration of FIG. The power flow between the AC systems 14 and 24 is performed by adjusting the phase difference between the voltages of the AC systems 14 and 24. AC system 14 to AC system 24
When the phase of is advanced by θ, it becomes the following formula.

P = V1V2sin (θ) / X where V1 is the voltage of the AC system 14 and V2 is the AC system 2
4 is the voltage, X is the impedance of the transmission line interconnecting the AC systems 14 and 24, and P is the power.

However, if there is a DC interconnection device, it is possible to flow electric power in any direction and at high speed according to the power setting value of the DC interconnection device regardless of the phase difference between the AC systems 14 and 24. . However, when the tidal current flows through the tidal current interconnection device, the phase difference of the AC system changes, so the tidal current can be transiently adjusted by the tidal current controller, but if the phase difference between the AC systems is not adjusted steadily, Does not change.

Next, in this embodiment, the loss of the power flow control device can be obtained by measuring only the input power on the side of the forward converter 1.
Will be explained. FIG. 2 shows the relationship between the active power and the DC voltage characteristics of the forward converter and the inverse converter of the DC interconnection device. The forward converter and the inverse converter are given constant power control characteristics and constant DC voltage control characteristics, and the power setting value of the forward converter is set to the value at which the converter capacity is full, and the DC voltage setting value is the specified value. Vdre
Set to f. The DC voltage set value of the reverse converter is set to a value having a margin larger than the set value of the forward converter, for example, a value lower by about 10% of the rating, and the power set value is set to a value Pd required by the load.
Set to ref.

The operating point thus set is the intersection of the forward converter characteristic and the inverse converter characteristic shown in FIG. With the above characteristics, the input power of the forward converter becomes larger than the amount of power set in the inverse converter in order to keep the DC voltage constant by the loss of the power flow control device. In other words, when the power of the forward converter is lower than this value, the DC voltage is lower than the specified value, and when it is higher, the DC voltage is higher and the DC voltage becomes equal to the specified voltage.

Therefore, it is possible to obtain the total loss including the harmonic loss of the power flow control device by measuring only the input power of the converter controlling the DC voltage. That is, as shown in FIG. 3, the total loss can be obtained by subtracting the power set value of the load from the input power. In FIG. 3, the reason why the absolute value of the difference between the measured power value and the load power command value is calculated is that the loss will be positive in the measured power value as described above depending on the power flow direction of the power flow control device, and will be described later. This is because there are cases where it appears negative.

By transmitting the electric power loss information obtained above to all electric power command centers, electric power transmission companies, ISOs, etc. by a general-purpose communication device such as the Internet, intranet, etc., it is possible to balance the power flow of all systems. It becomes possible to transmit power to the load and calculate the transmission cost in consideration of power loss.

FIG. 4 shows the setting of the power command value in consideration of the loss. The power command value may be the power command value of the power flow controller, which is the power required for the load system plus the loss of the power flow controller, or may be the set value of the generated power on the power transmission side. It is required that all electric power command centers have this function.

On the other hand, with respect to the cost, since the loss amount of the power flow control device under the power flow condition is obtained, whether the loss power amount is added to the power generation cost, the power transmission cost, or the power receiving side cost, If it is decided which one to use, it can be decided based on the unit price of electric power. For cost evaluation considering loss, a dedicated program is used to
It can be calculated at SO, power plants, etc.

FIG. 5 shows a general control block of a self-excited converter that realizes the control characteristics of the forward converter and the inverse converter shown in FIG. Reference numeral 211 denotes a constant active power control circuit, 212
2 is a DC voltage constant control circuit, and 213 is a signal selection circuit.
The output signals of the active power constant control circuit and the constant DC voltage control circuit are selected so as to have the characteristics of each converter shown in Fig. 4, and this signal is the active power of the AC output of the self-excited converter or the DC output or the input DC voltage. Controls the phase of the AC output voltage to bring the voltage to a specified value (setting value). Reference numeral 214 is a constant reactive power control circuit that controls the magnitude of the output voltage of the self-excited converter to control the reactive power flowing in the grid. Reference numeral 215 represents a converter control unit for performing non-interference control of active power and reactive power. A commonly used configuration control block is shown in FIG.

In FIG. 6, reference numeral 215a denotes a command value for controlling the active power or DC voltage of the higher active power control circuit or DC voltage control circuit to a specified value, and is extracted from the AC current by dq conversion. A real current (d-axis current) control circuit 215 for controlling the real current to this command value
b receives a command value for controlling the reactive power of the upper reactive power control circuit to a specified value, and the imaginary current (q-axis) for controlling the imaginary current extracted from the alternating current by dq conversion to this command value. The (current) control circuit, IX, represents multiplication of the impedance of the transformer for conversion, and cancels interference due to the impedance drop of the real current or the imaginary current to realize non-interference control of the real current and the imaginary current. Here, the dq conversion is performed using the sine and cosine function values of the phase difference β between the system voltage and the converter output voltage. Reference numeral 215e is dq
A two-axis inverse conversion circuit 215f for converting the axis component into a fixed coordinate αβ coordinate system, and a three-phase conversion circuit 215f for converting the αβ coordinate system into the original AC voltage reference values Va21, Vb21, Vc21 of the three-phase rotation coordinate system. A PWM pulse generation circuit 215g creates a PWM pulse of a self-excited converter from a triangular wave serving as a pulse carrier and this AC voltage reference value. With this circuit configuration, the real current (active power) and the imaginary current (reactive power) can be independently controlled without interference.

(Second Embodiment) In the first embodiment, the case where the direction of the tidal current flows from left to right in the figure has been described. In the present embodiment, the power flow direction is opposite to that of the first embodiment, the forward converter is an inverse converter, and the inverse converter is a forward converter, and constant power control is performed on the forward converter side. , Inverter side performs constant DC voltage control. In this case, the output of the inverse converter can only be smaller than the output of the forward converter by the total system loss. This is smaller than the output by the loss,
When a large amount of power is output, the DC voltage decreases, and when a smaller amount of power is output than when the output is smaller, the DC voltage increases, so that the DC voltage becomes a specified value with the power obtained by subtracting the loss. Therefore, if the output power is measured on the side of the inverse converter that performs constant DC voltage control, the total loss of the system including the harmonic loss can be obtained by subtracting this measured value from the power setting value of the forward converter.

Similar to the above, the obtained power loss information is sent to all power control stations, power generation companies, consignment companies, ISO, etc. via the Internet or intranet, and power dealing including loss of the power flow control device, operation, and cost. Can make decisions and evaluations.

(Embodiment 3) FIG. 7 shows this embodiment. Figure 1
In the above, the power flow control device uses a self-excited converter, but the present embodiment is a power flow control device using an asynchronous interconnection system or a DC power transmission system using a separately excited converter. Similar to FIG. 1, the power flow between the two AC systems can be controlled by the configuration of FIG. 7.

In FIG. 7, the case where the direction of the tidal current flows from left to right in the figure will be described. In FIG. 7, reference numeral 3 is a forward converter (converter) of a separately excited converter including elements such as a thyristor that can control only the ON time, and 4 is an inverse converter (inverter) of the separately excited converter. Is a DC reactor that smoothes DC current, 301 is an AC current transformer that detects the current flowing in the inverse converter 1, 302 is an AC voltage transformer, and 303 is a power transformer that detects the output power of the inverse transformer 2. .

In this embodiment, the forward converter controls the active power, and the inverse converter controls the DC voltage to be constant. FIG. 8 shows the relationship between the DC current and DC voltage of the forward converter and the inverse converter at this time. The forward converter is provided with a direct current setting value Idref for transmitting active power required for the load, and has a constant direct current control characteristic. On the other hand, the inverse converter has a constant DC voltage control characteristic for maintaining the DC voltage at a specified value Vdref,
As a backup operation when the AC voltage drops, a direct current constant control characteristic having a current setting value is given to a value smaller than the current setting value Idref of the forward converter by a current margin ΔId.

When the forward converter and the inverse converter have such characteristics, the operating point is the intersection of the two characteristics. The forward converter operates to keep the active power required for the load constant,
Since the inverse converter performs constant DC voltage control, when the active power is measured on the inverse converter side, the power that is smaller by the loss is measured. If the reverse converter measures more power than this, the DC voltage will drop below the specified value, and if less power is measured the DC voltage will increase. Therefore, when the DC voltage is maintained at the specified value, the output power measured on the inverse converter side is smaller than the power set value on the forward converter side by the amount of loss. In order to extract a predetermined active power with the inverse converter, it is necessary to set the power setting value of the forward converter (DC current setting value x DC voltage) to a power setting value larger by the total loss of the system.

By measuring only the output power on the side of the inverse converter performing the constant DC voltage control and subtracting this measured value from the power setting value, the total loss of the power flow control system including the harmonic loss can be obtained. It will be. Information on the obtained loss can be sent to a power generation company, a consignment company, ISO, etc. using a communication device such as the Internet to perform power dealing including the loss of the power flow control device, operation and cost evaluation.

(Embodiment 4) This embodiment is shown in FIG. Figure 1
7 shows a power flow control device using a self-excited converter, and FIG. 7 shows a power flow control device using a separately excited converter. In this embodiment, the voltage phase of the series transformer inserted in series in the transmission line is The tidal current flowing through the track is controlled by changing it.

The voltage phase is produced by the forward converter and the inverse converter of the same self-exciting converter as in FIG. The same numbers as in the previous figures represent the same functions, so only different new ones will be described. Reference numeral 29 in FIG. 9 is a series transformer that is inserted in series in the transmission line, and the primary side of the transformer is excited by the inverse converter 2.

It is known that the magnitude and phase of the output voltage of the inverse converter can be controlled to control the effective and ineffective power flows. Also in this embodiment, the forward converter 1 controls the DC voltage to be constant, and the inverse converter 2 controls the active power to be constant. Similar to the description of FIG. 1, from the current and voltage flowing through the forward converter,
When the active power flowing here is determined, this value is measured as the power that is larger by the amount of system loss. Therefore, the total power loss of the system including the harmonic loss can be obtained by subtracting the power setting value.

The obtained power loss data is sent to a power generation company, a consignment company, ISO, etc. using a communication device such as the Internet, and power dealing including loss of the power flow control device, operation and cost evaluation can be performed.

[0038]

According to the present invention, the total system loss including the harmonic loss of the power flow control device can be obtained by measuring only the active power flowing in the converter that performs the constant DC voltage control. In addition, this loss is transferred to a power generation company, a power control station, a power transmission company, I through a general-purpose low-cost communication device such as the Internet or an intranet.
It is possible to send to SO etc., and deal with power including the loss of the power flow control device, operation and cost evaluation.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a loss measuring method and a using method of a power flow control device according to a first embodiment.

FIG. 2 is a diagram showing the characteristics of active power and DC voltage of the self-excited converter of the first embodiment.

FIG. 3 is an explanatory diagram of a loss measuring method according to the first embodiment.

FIG. 4 is an explanatory diagram of a power command value creation method according to the first embodiment.

FIG. 5 is a block diagram of a control unit of the self-excited converter according to the first embodiment.

FIG. 6 is a block diagram of a converter control unit of the self-excited converter according to the first embodiment.

FIG. 7 is an explanatory diagram of a method of measuring loss and a method of using the power flow control device according to the third embodiment.

FIG. 8 is a diagram showing characteristics of a DC current and a DC voltage of a separately excited converter according to a third embodiment.

FIG. 9 is an explanatory diagram of a method of measuring loss and a method of using the power flow control device according to the fourth embodiment.

[Explanation of symbols]

1 ... Forward converter (converter) of self-excited converter, 2 ... Inverse converter (inverter) of self-excited converter, 3 ... AC interconnection line,
11, 21 ... DC capacitor, 12, 22 ... Conversion transformer, 13, 23 ... AC bus bar, 14, 24 ... AC system, 2
9 ... Series transformer, 30a, 30b ... DC transmission line, 100
… Power flow command station, 200… Control devices 1, 201, 301…
AC current transformer, 202, 302 ... AC voltage transformer, 2
03 ... Power transformer, 211 ... Active power constant control circuit, 2
12 ... DC voltage constant control circuit, 213 ... Signal selection circuit,
214 ... Constant reactive power control circuit, 215 ... Converter control unit, 215a ... Real current (d-axis current) control circuit, 215b
... imaginary current (q-axis current) control circuit, 215e ... 2-axis inverse conversion circuit, 215f ... 3-phase conversion circuit, 215g ... PWM pulse generation circuit, 300 ... Control device 2, 303 ... Power transformer, 400 ... Full power command Office, 500 ... ISO, power transmission company, etc. 600 ... Communication network.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shigeyuki Sugimoto             20-1 Kitakousan, Otakamachi, Midori-ku, Nagoya-shi, Aichi               Chubu Electric Power Co., Inc. (72) Inventor Shigeaki Ogawa             20-1 Kitakousan, Otakamachi, Midori-ku, Nagoya-shi, Aichi               Chubu Electric Power Co., Inc. F-term (reference) 5G066 CA04 CA10                 5H420 BB15 CC05 DD04 EA04 EA10                       EA29 EA45 EB09 EB23 FF03                       FF04 FF06 FF22 FF25 GG01

Claims (5)

[Claims] 1. A loss measuring method for a power flow control device comprising a forward converter for converting alternating current to direct current and an inverse converter for converting direct current to alternating current, wherein the power flow controller controls the direct current voltage to be constant. The measured value of the active power of the converter is subtracted from the power setting value of the load to obtain the total loss power of the power flow control device including the harmonic loss. Loss measurement method. 2. A loss measuring method for a power flow control device having a forward converter for converting alternating current to direct current and an inverse converter for converting direct current to alternating current, comprising: a forward converter for setting a direct current voltage of the power flow control device. From the measurement of active power, the active power setting value of the power flow control device is subtracted to obtain the total loss power of the power flow control device including the harmonic components of the power flow control device. Measuring method. 3. A loss measuring method for a power flow control device comprising a forward converter for converting alternating current to direct current and an inverse converter for converting direct current to alternating current, wherein the reverse converter for setting direct current voltage of the power flow controlling device. Loss of the power flow control device, characterized in that the active power measurement value is subtracted from the active power setting value of the power flow control device to obtain the total loss power of the power flow control device including the harmonic components of the power flow control device. Measuring method. 4. A method of using power loss information of a power flow controller having a forward converter for converting AC to DC and an inverse converter for converting DC to AC, wherein the power loss information is the power controller. Is information obtained by subtracting the measured value of the active power of the converter for controlling the DC voltage to be constant from the power setting value of the load to obtain the total loss power of the power flow control device including the harmonic loss, Power loss of a power flow controller characterized in that power loss information is distributed to a power control center, ISO, etc. using communication means such as the Internet and an intranet, and power flow control is performed using the signal distributed at the power control center. How to use the information. 5. A method of using power loss information of a power flow controller having a forward converter for converting AC to DC and an inverse converter for converting DC to AC, wherein the power loss information is the power controller. Is information obtained by subtracting the measured value of the active power of the converter for controlling the DC voltage to be constant from the power setting value of the load to obtain the total loss power of the power flow control device including the harmonic loss, Power of a power flow control device characterized in that power loss information is distributed to ISO, a power transmission company and a power generation company using communication means such as the Internet and an intranet, and cost determination and evaluation are performed using the distributed information. How to use loss information.